OCA optical cement and preparation method thereof

Abstract

The invention provides an OCA optical adhesive and a preparation method thereof. The optical adhesive comprises the following raw materials in parts by weight: 40-60 parts of modified acrylic resin, 20-30 parts of modified polyurethane resin, 15-25 parts of a solvent, 3-6 parts of a self-repairing agent, 2-4 parts of a self-lubricating agent, 1-3 parts of a cross-linking agent, 0.5-1.5 parts of an antioxidant and 0.2-0.8 part of an initiator. Wherein the self-repairing agent is prepared from stilbene, cyclodextrin and benzoin diethyl ether according to the mass ratio of (1.0 to 1.2) to (1.0 to 1.5) to (0.06 to 0.10). According to the invention, through initiation of benzoin diethyl ether in the self-repairing agent, cis-trans isomerization reaction of stilbene and cyclodextrin in the self-repairing agent and dynamic change of clathration and unclathration effects, self-repairing of micro cracks or defects in the OCA optical cement is realized, so that the flexibility and cohesion of the cement are improved; further, the bending performance and the peel strength of the adhesive are improved, so that the OCA optical adhesive has more excellent performance in adhesion and protection of optical devices.

Description

Technical Field

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

[0002] OCA optical adhesive, as a double-sided laminating tape designed for transparent optical components, stands out in many optical applications with its high cleanliness, excellent light transmittance, extremely low haze and strong adhesion. After curing, the refractive index of the adhesive layer of OCA optical adhesive can be highly similar to that of the bonded optical component, which effectively reduces the interface reflection and improves the overall optical performance. In addition, it exhibits stable bonding strength over a wide range of operating temperatures, and the shrinkage deformation after curing is extremely small, ensuring the precise positioning and long-term stability of the optical components. However, with the rise of foldable screen mobile phones, OCA optical adhesives have been posed with higher challenges. Foldable screen mobile phones need to undergo countless repeated bending, which places extremely high demands on the bending performance and peeling strength of the tape. Traditional OCA optical adhesives may experience problems such as debonding and peeling when facing such frequent bending scenarios, affecting the service life and user experience of the mobile phone. Therefore, the development of OCA optical adhesives with higher bending performance and higher peeling strength has become the key to meeting the needs of foldable screen mobile phones. Summary of the invention

[0003] In view of this, the present invention proposes an OCA optical adhesive and a preparation method thereof to solve the above problems.

[0004] The technical solution of the present invention is achieved in this way:

[0005] An OCA optical adhesive comprises the following raw materials in parts by weight: 40-60 parts of modified acrylic resin, 20-30 parts of modified polyurethane resin, 15-25 parts of solvent, 3-6 parts of self-repairing agent, 2-4 parts of self-lubricating agent, 1-3 parts of cross-linking agent, 0.5-1.5 parts of antioxidant, and 0.2-0.8 parts of initiator. The self-repairing agent is composed of diphenylethylene, cyclodextrin, and benzoin ethyl ether in a mass ratio of (1.0-1.2):(1.0-1.5):(0.06-0.10).

[0006] Further, the modified acrylic resin is prepared by the following method: adding a high molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1: (5-10), heating to 50-80°C, stirring and dissolving, and obtaining a high molecular weight polyacrylic acid resin solution. Adding a low molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1: (2-5) and stirring and dissolving to obtain a low molecular weight polyacrylic acid resin solution. Wherein, the molecular weight of the high molecular weight polyacrylic acid resin is 800,000-1,000,000 Da, and the molecular weight of the low molecular weight polyacrylic acid resin is 100,000-300,000 Da. The high molecular weight polyacrylic acid resin solution and the low molecular weight polyacrylic acid resin solution are mixed and stirred uniformly at a volume ratio of (55-60): (24-26) to obtain a mixed resin solution. Methyl methacrylate and azobisisobutyronitrile are added to the mixed resin solution, reacting at 60-90°C for 10-20 hours to obtain a reaction mixture. Wherein, the amount of methyl methacrylate added is 5-15% of the volume of the mixed resin solution, and the amount of azobisisobutyronitrile added is 0.2-0.4% of the volume of the mixed resin solution. After the reaction is completed, the reaction mixture is filtered through a Buchner funnel, and the filtered product is washed with ethanol 2-3 times, and then the washed product is placed in a vacuum drying oven and dried at 40-60° C. for 12-24 hours to obtain a modified acrylic resin.

[0007] Furthermore, the modified polyurethane resin is prepared by the following method: adding polytetrahydrofuran diol to a reaction kettle, heating to 110-130°C for reflux dehydration treatment, then cooling to 60-70°C, adding hexamethylene diisocyanate and dibutyltin dilaurate, and performing prepolymerization at 70-80°C to generate a polyurethane prepolymer with terminal isocyanate groups. The mass volume ratio of polytetrahydrofuran diol, hexamethylene diisocyanate, and dibutyltin dilaurate g / mL is (90-110): (40-60): (0.5-1.5). Then, 1,6-hexanediol is added to the polyurethane prepolymer with terminal isocyanate groups for chain extension reaction. The volume ratio of the polyurethane prepolymer with terminal isocyanate groups to 1,6-hexanediol is (1.0-1.5): (0.5-1.0), and the reaction is carried out for 1-2 hours to obtain a chain extension reaction product. The chain extension reaction product is cooled to 20-25° C., and solid impurities are filtered out using a filter, and then vacuum degassing is performed to obtain a modified polyurethane resin.

[0008] Furthermore, the solvent is isopropyl alcohol, isobutyl acetate or a combination thereof.

[0009] Furthermore, the cross-linking agent is one of xylylene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

[0010] Furthermore, the self-lubricant is polyimide nanofiber, and the particle size of the polyimide nanofiber is 20-80nm.

[0011] Furthermore, the antioxidant is one or a combination of triphenyl phosphite, dilauryl thiodipropionate, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

[0012] Furthermore, the initiator is one or a combination of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, methyl benzoylformate, benzoin dimethyl ether, and α-hydroxyisobutyl phenyl ketone.

[0013] Furthermore, a method for preparing an OCA optical adhesive comprises the following steps:

[0014] S1. Add the modified acrylic resin into the solvent, heat and stir to dissolve, and obtain solution I.

[0015] S2. Add the modified polyurethane resin into solution I and stir evenly to obtain solution II.

[0016] S3. Add antioxidant, self-repairing agent and self-lubricant to solution II, stir evenly to obtain solution III.

[0017] S4. Add initiator and cross-linking agent to solution III, stir evenly to obtain solution IV.

[0018] S5. Filter the solution with a filter to remove solid impurities, and then perform vacuum degassing to obtain OCA optical adhesive.

[0019] Further, S1 is heated to 60-80°C, the stirring speed is 200-400rpm, and the stirring time is 30-60min. S2 is stirred at a speed of 200-400rpm and a stirring time of 15-30min. S3 is stirred at a speed of 300-500rpm and a stirring time of 20-40min. S4 is stirred at a speed of 300-500rpm and a stirring time of 15-30min. In S5, the filter mesh aperture is 100-200μm, the vacuum degree of vacuum degassing treatment is -0.08~-0.1MPa, and the degassing time is 30-60min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention realizes self-repair of tiny cracks or defects in OCA optical adhesive by initiating benzoin ethyl ether in the self-repairing agent and the cis-trans isomerization reaction and dynamic changes of inclusion and deinclusion of distilbene and cyclodextrin in the self-repairing agent, thereby improving the flexibility and cohesion of the colloid, and then improving the bending performance and peel strength of the colloid, so that the OCA optical adhesive has more excellent performance in the bonding and protection of optical devices.

[0022] 2. The present invention forms a block copolymer with a unique structure by connecting the molecular chains of high molecular weight and low molecular weight polyacrylic resin in the form of blocks. The mutual coordination and synergy between the soft and hard segments endow the OCA optical adhesive with good flexibility and elasticity, while ensuring its high strength and heat resistance, so that it can maintain stable performance and reliability in various complex use environments. DETAILED DESCRIPTION

[0023] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0024] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0025] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0026] Example 1

[0027] An OCA optical adhesive comprises the following raw materials in parts by weight: 40 parts of modified acrylic resin, 20 parts of modified polyurethane resin, 15 parts of solvent, 3 parts of self-repairing agent, 2 parts of self-lubricating agent, 1 part of cross-linking agent, 0.5 parts of antioxidant, and 0.2 parts of initiator. Among them, the solvent is isopropanol, the self-repairing agent is composed of stilbene, cyclodextrin, and benzoin ethyl ether in a mass ratio of 1.0:1.0:0.06, the self-lubricating agent is polyimide nanofiber with a particle size of 20nm, the cross-linking agent is xylene diisocyanate, the antioxidant is dilauryl thiodipropionate, and the initiator is 1-hydroxycyclohexyl phenyl ketone.

[0028] The modified acrylic resin is prepared by the following method: adding a high molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:5, heating to 50°C, stirring and dissolving to obtain a high molecular weight polyacrylic acid resin solution. Adding a low molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:2 and stirring and dissolving to obtain a low molecular weight polyacrylic acid resin solution. Among them, the molecular weight of the high molecular weight polyacrylic acid resin is 800,000 Da, and the molecular weight of the low molecular weight polyacrylic acid resin is 100,000 Da. The high molecular weight polyacrylic acid resin solution and the low molecular weight polyacrylic acid resin solution are mixed and stirred evenly at a volume ratio of 55:24 to obtain a mixed resin solution. Methyl methacrylate and azobisisobutyronitrile are added to the mixed resin solution, reacted at 60°C for 20 hours, and a reaction mixture is obtained. Among them, the amount of methyl methacrylate added is 5% of the volume of the mixed resin solution, and the amount of azobisisobutyronitrile added is 0.2% of the volume of the mixed resin solution. After the reaction is completed, the reaction mixture is filtered through a Buchner funnel, and the filtered product is washed twice with ethanol. The washed product is then placed in a vacuum drying oven and dried at 40° C. for 24 hours to obtain a modified acrylic resin.

[0029] The modified polyurethane resin is prepared by the following method: adding polytetrahydrofuran diol to a reaction kettle, heating to 110°C for reflux dehydration treatment, then cooling to 60°C, adding hexamethylene diisocyanate and dibutyltin dilaurate, and performing prepolymerization at 70°C to generate a polyurethane prepolymer with terminal isocyanate groups. The mass volume ratio of polytetrahydrofuran diol, hexamethylene diisocyanate, and dibutyltin dilaurate g / mL is 90:40:0.5. Then, 1,6-hexanediol is added to the polyurethane prepolymer with terminal isocyanate groups for chain extension reaction. The volume ratio of the polyurethane prepolymer with terminal isocyanate groups to 1,6-hexanediol is 1.0:0.5, and the reaction is carried out for 2 hours to obtain a chain extension reaction product. The chain extension reaction product is cooled to 20°C, and solid impurities are filtered out using a filter, and then vacuum degassing is performed to obtain a modified polyurethane resin.

[0030] Example 2

[0031] An OCA optical adhesive comprises the following raw materials in parts by weight: 60 parts of modified acrylic resin, 30 parts of modified polyurethane resin, 25 parts of solvent, 6 parts of self-repairing agent, 4 parts of self-lubricating agent, 3 parts of cross-linking agent, 1.5 parts of antioxidant, and 0.8 parts of initiator. Among them, the solvent is isobutyl acetate, the self-repairing agent is composed of diphenylethylene, cyclodextrin, and benzoin ethyl ether in a mass ratio of 1.2:1.5:0.10, the self-lubricating agent is polyimide nano with a particle size of 80nm, the cross-linking agent is hexamethylene diisocyanate, the antioxidant is composed of triphenyl phosphite and 2,6-di-tert-butyl-4-methylphenol in a mass volume ratio of g / mL of 2:1, and the initiator is methyl benzoylformate.

[0032] The modified acrylic resin is prepared by the following method: adding a high molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:10, heating to 80°C, stirring and dissolving to obtain a high molecular weight polyacrylic acid resin solution. Adding a low molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:2 and stirring and dissolving to obtain a low molecular weight polyacrylic acid resin solution. Among them, the molecular weight of the high molecular weight polyacrylic acid resin is 1 million Da, and the molecular weight of the low molecular weight polyacrylic acid resin is 300,000 Da. The high molecular weight polyacrylic acid resin solution and the low molecular weight polyacrylic acid resin solution are mixed and stirred evenly at a volume ratio of 60:26 to obtain a mixed resin solution. Methyl methacrylate and azobisisobutyronitrile are added to the mixed resin solution, reacted at 90°C for 10 hours, and a reaction mixture is obtained. Among them, the amount of methyl methacrylate added is 15% of the volume of the mixed resin solution, and the amount of azobisisobutyronitrile added is 0.4% of the volume of the mixed resin solution. After the reaction is completed, the reaction mixture is filtered through a Buchner funnel, and the filtered product is washed with ethanol three times. The washed product is then placed in a vacuum drying oven and dried at 60° C. for 12 h to obtain a modified acrylic resin.

[0033] The modified polyurethane resin is prepared by the following method: adding polytetrahydrofuran diol to a reaction kettle, heating to 130°C for reflux dehydration treatment, then cooling to 70°C, adding hexamethylene diisocyanate and dibutyltin dilaurate, and performing prepolymerization at 80°C to generate a polyurethane prepolymer with terminal isocyanate groups. The mass volume ratio of polytetrahydrofuran diol, hexamethylene diisocyanate, and dibutyltin dilaurate g / mL is 110:60:1.5. Then, 1,6-hexanediol is added to the polyurethane prepolymer with terminal isocyanate groups for chain extension reaction. The volume ratio of the polyurethane prepolymer with terminal isocyanate groups to 1,6-hexanediol is 1.5:1.0, and the reaction is carried out for 1h to obtain a chain extension reaction product. The chain extension reaction product is cooled to 25°C, and solid impurities are filtered out using a filter, and then vacuum degassing is performed to obtain a modified polyurethane resin.

[0034] Example 3

[0035] An OCA optical adhesive comprises the following raw materials in parts by weight: 50 parts of modified acrylic resin, 25 parts of modified polyurethane resin, 20 parts of solvent, 4.5 parts of self-repairing agent, 3 parts of self-lubricating agent, 2 parts of cross-linking agent, 1 part of antioxidant and 0.5 part of initiator. Among them, the solvent is composed of isopropanol and isobutyl acetate in a volume ratio of 1:1, the self-healing agent is composed of distilbene, cyclodextrin and benzoin ethyl ether in a mass ratio of 1.1:1.3:0.08, the self-lubricant is polyimide nanofiber with a particle size of 50nm, the cross-linking agent is isophorone diisocyanate, the antioxidant is composed of dilauryl thiodipropionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol) in a mass volume ratio of g / mL of 1:1:1, and the initiator is composed of 2-hydroxy-2-methyl-1-phenylacetone, methyl benzoylformate and benzoin dimethyl ether in a mass volume ratio of g / mL of 1:1:1.

[0036] The modified acrylic resin is prepared by the following method: adding a high molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:7.5, heating to 65°C, stirring and dissolving to obtain a high molecular weight polyacrylic acid resin solution. Adding a low molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:3.5 and stirring and dissolving to obtain a low molecular weight polyacrylic acid resin solution. Among them, the molecular weight of the high molecular weight polyacrylic acid resin is 900,000 Da, and the molecular weight of the low molecular weight polyacrylic acid resin is 200,000 Da. The high molecular weight polyacrylic acid resin solution and the low molecular weight polyacrylic acid resin solution are mixed and stirred evenly at a volume ratio of 58:25 to obtain a mixed resin solution. Methyl methacrylate and azobisisobutyronitrile are added to the mixed resin solution, reacted at 75°C for 15 hours, and a reaction mixture is obtained. Among them, the amount of methyl methacrylate added is 10% of the volume of the mixed resin solution, and the amount of azobisisobutyronitrile added is 0.3% of the volume of the mixed resin solution. After the reaction is completed, the reaction mixture is filtered through a Buchner funnel, and the filtered product is washed with ethanol three times. The washed product is then placed in a vacuum drying oven and dried at 50° C. for 18 h to obtain a modified acrylic resin.

[0037] The modified polyurethane resin is prepared by the following method: adding polytetrahydrofuran diol to a reaction kettle, heating to 120°C for reflux dehydration treatment, then cooling to 65°C, adding hexamethylene diisocyanate and dibutyltin dilaurate, and performing prepolymerization at 75°C to generate a polyurethane prepolymer with terminal isocyanate groups. The mass volume ratio of polytetrahydrofuran diol, hexamethylene diisocyanate, and dibutyltin dilaurate g / mL is 100:50:1. Then, 1,6-hexanediol is added to the polyurethane prepolymer with terminal isocyanate groups for chain extension reaction. The volume ratio of the polyurethane prepolymer with terminal isocyanate groups to 1,6-hexanediol is 1.2:0.7, and the reaction is carried out for 1.5 hours to obtain a chain extension reaction product. The chain extension reaction product is cooled to 22°C, and solid impurities are filtered out using a filter, and then vacuum degassing is performed to obtain a modified polyurethane resin.

[0038] The OCA optical adhesive described in Examples 1-3 is prepared according to the following method, comprising the following steps:

[0039] S1. Add the modified acrylic resin into the solvent, heat to 70°C and stir at 300 rpm for 45 min to obtain solution I.

[0040] S2. Add the modified polyurethane resin to solution I, stir at 300 rpm for 24 min, and obtain solution II.

[0041] S3. Add antioxidant, self-repairing agent and self-lubricant to solution II, stir at 400 rpm for 30 min to obtain solution III.

[0042] S4, adding initiator and cross-linking agent to solution III, stirring evenly, to obtain solution IV. The stirring speed in S4 is 400 rpm, and the stirring time is 24 min.

[0043] S5. Filter the solution using a filter with a pore size of 150 μm to remove solid impurities, and then perform vacuum degassing treatment at a vacuum degree of -0.09 MPa for 45 minutes to obtain OCA optical adhesive.

[0044] Example 4

[0045] Compared with Example 3, Example 4 differs in that the OCA optical adhesive is prepared according to the following method, including the following steps:

[0046] S1. Add the modified acrylic resin into the solvent, heat to 60°C and stir at 200 rpm for 60 min to obtain solution I.

[0047] S2. Add the modified polyurethane resin to solution I, stir at 200 rpm for 30 min, and obtain solution II.

[0048] S3. Add antioxidant, self-repairing agent and self-lubricant to solution II, stir at 300 rpm for 40 min to obtain solution III.

[0049] S4, adding initiator and cross-linking agent to solution III, stirring evenly, to obtain solution IV. The stirring speed in S4 is 300 rpm, and the stirring time is 30 min.

[0050] S5. Filter the solution using a filter with a pore size of 100-200 μm to remove solid impurities, and then perform vacuum degassing treatment at a vacuum degree of -0.08 MPa for 60 minutes to obtain OCA optical adhesive.

[0051] Example 5

[0052] Compared with Example 3, Example 5 differs in that the OCA optical adhesive is prepared according to the following method, including the following steps:

[0053] S1. Add the modified acrylic resin into the solvent, heat to 80°C and stir at 400 rpm for 30 min to obtain solution I.

[0054] S2. Add the modified polyurethane resin to solution I, stir at 400 rpm for 15 min, and obtain solution II.

[0055] S3. Add antioxidant, self-repairing agent and self-lubricant to solution II, stir at 500 rpm for 20 min to obtain solution III.

[0056] S4, adding initiator and cross-linking agent to solution III, stirring evenly to obtain solution IV. In S4, the stirring speed is 300-500 rpm, and the stirring time is 15-30 min.

[0057] S5. Filter the solution using a filter with a pore size of 200 μm to remove solid impurities, and then perform vacuum degassing treatment at a vacuum degree of -0.1 MPa for 30 minutes to obtain OCA optical adhesive.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 3 is that the raw materials do not contain a self-healing agent.

[0060] Comparative Example 2

[0061] Compared with Example 3, the difference between this comparative example and Example 3 is that the self-healing agent is composed of dicyclodextrin and benzoin ethyl ether in a mass ratio of 1.3:0.08.

[0062] Comparative Example 3

[0063] The difference between this comparative example and Example 3 is that the mass ratio of diphenylethylene and benzoin ethyl ether is 1.1:0.08.

[0064] Comparative Example 4

[0065] The difference between this comparative example and Example 3 is that the raw material does not contain self-lubricant.

[0066] Comparative Example 5

[0067] The difference between this comparative example and Example 3 is that a high molecular weight polyacrylic acid resin is used instead of the modified acrylic acid resin.

[0068] Comparative Example 6

[0069] This comparative example is compared with Example 3, except that a low molecular weight polyacrylic acid resin is used instead of the modified acrylic acid resin.

[0070] Comparative Example 7

[0071] The difference between this comparative example and Example 3 is that no chain extension reaction is performed after the polyurethane prepolymer with isocyanate group is generated during the preparation of the modified polyurethane resin.

[0072] Performance test

[0073] The OCA optical adhesives prepared in Examples 1-5 and Comparative Examples 1-7 were subjected to bending performance tests, peel strength tests, and light transmittance tests, respectively, according to the following methods.

[0074] Bending performance test

[0075] The OCA optical adhesives prepared in Examples 1-5 and Comparative Examples 1-7 were coated on release films and cured. The coating thickness was 30 μm to form a protective film. The protective film was attached to a bending jig, and a dynamic bending machine was used to perform a bending performance test. The test temperature was 25°C, the bending radius R=1.0mm, and the bending angle was 180°. The bending performance tests were performed for 150,000, 200,000, and 250,000 times, respectively. The test was performed 150,000 times first. When the test reached 150,000 times, the experiment was stopped to observe whether the protective film cracked or fell off. If so, the number was recorded as 150,000 times. If the above phenomenon did not occur, the experiment was continued for 200,000 times. The experiment was performed progressively to 250,000 times according to the above method. If the above phenomenon did not occur during the 250,000 tests, it was recorded as >250,000 times. The test results are shown in Table 1.

[0076] Peel strength test

[0077] The OCA optical adhesives prepared in Examples 1-5 and Comparative Examples 1-7 were respectively coated on release films and cured to a coating thickness of 30 μm. The films were then cut into 10 cm × 5 cm sizes. The side not bonded to the release film was bonded to a steel plate with the same force and allowed to stand for 24 hours. The films were then tested according to the method in GB / T 2792-2014 “Test method for peel strength of adhesive tapes”. Each example and comparative example was tested 3 times and the average value was taken. The test results are shown in Table 1.

[0078] Light transmittance test

[0079] The OCA optical adhesives prepared in Examples 1-5 and Comparative Examples 1-7 were coated on release films and cured to a coating thickness of 100 μm, and then cut into discs of 50 mm in size. Three discs were prepared for each Example and Comparative Example, and the discs were placed in an environment of 23°C and 50% relative humidity, and tested after conditioning for 40 hours according to GB / T2918-1989. The test was conducted with reference to the method in GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics", and the average value was taken. The results are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] It can be seen from Table 1 that the OCA optical adhesives prepared in Examples 1-7 of the present invention have excellent bending performance, peeling strength and light transmittance.

[0084] By comparing Example 3 with Comparative Example 1, Example 3 adds a self-repairing agent composed of a specific ratio of diphenylethylene, cyclodextrin, and benzoin ethyl ether. When the OCA optical adhesive is subjected to external forces, such as bending or peeling, resulting in microcracks or defects, diphenylethylene undergoes a cis-trans isomerization reaction through external illumination and benzoin ethyl ether. This reaction is fast and reversible and can be carried out rapidly under illumination conditions. The cis configuration forms a stable inclusion complex with cyclodextrin, while the trans configuration is easily unencapsulated from cyclodextrin. When diphenylethylene is unencapsulated from cyclodextrin, the released molecules can migrate to cracks or defects. Due to the progress of the isomerization reaction, these molecules exist in different configurations, and they can fill in the cracks and form new interactions with the surrounding colloidal matrix. As the illumination continues, some diphenylethylene may isomerize again and transform into a configuration that is easier to be encapsulated with cyclodextrin. These molecules are reencapsulated with cyclodextrin to form a stable inclusion complex, thereby fixing the repair structure at the crack and enhancing the continuity of the colloid. Through the dynamic changes of the inclusion and deinclusion process, the intermolecular interactions in the colloid are adjusted and optimized. This dynamic adjustment enables the colloid to absorb and disperse stress more effectively when subjected to bending, thereby improving the flexibility of the colloid. The tiny cracks generated during the bending process can be repaired in time by the self-repair mechanism to prevent the expansion of the cracks and the destruction of the colloid, thereby maintaining the overall structure and performance of the colloid, thereby improving the bending performance. In addition, the self-repair mechanism strengthens the cohesion between the colloid molecules by repairing the tiny cracks and defects in the colloid, so that the colloid can resist greater external forces during the peeling process, thereby improving the peeling strength. By comparing Example 3 with Comparative Examples 2-3, it can be seen that the diphenylethylene and cyclodextrin in the self-repairing agent need to work together, and neither of them can be missing. The lack of any one of the components will destroy its self-repairing mechanism, thereby affecting the performance of the OCA optical adhesive. In addition, by comparing Example 3 with Comparative Examples 1-3, it can be seen that the addition of this self-repairing agent has very little effect on the light transmittance of the OCA optical adhesive, which can be ignored.

[0085] By comparing Example 3 with Comparative Example 4, the polyimide nanofibers in Example 3 can effectively reduce the friction between the colloid molecules when the colloid is subjected to external force, making the colloid easier to bend and less likely to break, and can also reduce the stress concentration of the colloid during the bending process, thereby improving the flexibility and bending performance of the colloid. At the same time, the polyimide nanofibers have extremely high specific surface area and aspect ratio, and they can form a large number of physical cross-linking points in the colloid, enhance the cohesive force of the colloid, help the colloid to improve the toughness and crack resistance of the colloid when subjected to external force, and also help to improve the peel strength.

[0086] By comparing Example 3 with Comparative Examples 5-6, Example 3 is modified to connect the molecular chains of high molecular weight and low molecular weight polyacrylic resins in the form of blocks, forming a block copolymer with a unique structure. The molecular chain of the high molecular weight polyacrylic resin is relatively long, the interaction force between the molecular chains is relatively strong, and the entanglement between the molecular chains is tighter, thereby forming a hard segment. The molecular chain of the low molecular weight polyacrylic resin is relatively short, the interaction force between the molecular chains is relatively weak, the degree of entanglement between the molecular chains is low, and the molecular chains are easily deformed, thus forming a soft segment. In the block copolymer, the hard segment, as a supporting structure, provides a stable skeleton and strength for the entire polymer. The soft segment gives the polymer flexibility so that it can adapt to changes in external stress. The soft segment in the block copolymer makes the optical adhesive have good flexibility and can adapt to various bends and deformations. In the bending process, the soft segment can absorb and disperse stress, reduce stress concentration, thereby avoiding the cracking and destruction of the optical adhesive. At the same time, the presence of the hard segment ensures that the optical adhesive will not lose strength during the bending process. The soft and hard structure enables the optical adhesive to effectively dissipate energy during the bending process, converting stress into heat or other forms of energy and releasing it, thereby improving the bending resistance of the optical adhesive. The soft and hard structure also enhances the cohesive force of the optical adhesive. During the peeling process, the interaction between the hard segment and the soft segment makes the optical adhesive more difficult to peel off, further improving the peeling strength.

[0087] By comparing Example 3 with Comparative Example 7, Example 3 adds 1,6-hexanediol to the polyurethane prepolymer with terminal isocyanate groups for chain extension reaction, which increases the length of the polyurethane molecular chain, weakens the interaction force between the molecular chains, and makes the movement of the molecular chains freer. This structural change gives the modified polyurethane resin higher flexibility, so that the OCA optical adhesive can better absorb and disperse stress when bent, reduce stress concentration, and thus improve the bending performance. The chain extension reaction also increases the flexibility of the molecular chain by introducing new chain segments, so that the OCA optical adhesive can be more easily deformed and restored to its original state when subjected to external forces, thereby improving its elasticity. In addition, the cross-linking points formed during the chain extension reaction enhance the interaction force between the polyurethane molecular chains and make the entanglement between the molecular chains tighter. This structural change helps to increase the adhesion between the OCA optical adhesive and the substrate, thereby increasing the peel strength.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An OCA optical adhesive, characterized in that: The invention comprises the following raw materials in parts by weight: 40-60 parts of modified acrylic resin, 20-30 parts of modified polyurethane resin, 15-25 parts of solvent, 3-6 parts of self-repairing agent, 2-4 parts of self-lubricating agent, 1-3 parts of cross-linking agent, 0.5-1.5 parts of antioxidant and 0.2-0.8 parts of initiator. The self-repairing agent is composed of diphenylethylene, cyclodextrin and benzoin ethyl ether in a mass ratio of (1.0-1.2):(1.0-1.5):(0.06-0.10).

2. An OCA optical adhesive as claimed in claim 1, characterized in that: The modified acrylic resin is prepared by the following method: adding a high molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:(5-10), heating to 50-80°C, stirring and dissolving to obtain a high molecular weight polyacrylic acid resin solution; adding a low molecular weight polyacrylic acid resin to acetone at a material-liquid ratio of 1:(2-5), stirring and dissolving to obtain a low molecular weight polyacrylic acid resin solution; the molecular weight of the high molecular weight polyacrylic acid resin is 800,000-1,000,000 Da, and the molecular weight of the low molecular weight polyacrylic acid resin is 100,000-300,000 Da; mixing the high molecular weight polyacrylic acid resin solution and the low molecular weight polyacrylic acid resin solution at a volume ratio of (55-60):(24-2 6) mixing and stirring evenly to obtain a mixed resin solution; adding methyl methacrylate and azobisisobutyronitrile to the mixed resin solution, reacting at 60-90° C. for 10-20 hours to obtain a reaction mixture, wherein the amount of methyl methacrylate added is 5-15% of the volume of the mixed resin solution, and the amount of azobisisobutyronitrile added is 0.2-0.4% of the volume of the mixed resin solution; after the reaction is completed, filtering the reaction mixture through a Buchner funnel, and washing the filtered product with ethanol for 2-3 times, and then placing the washed product in a vacuum drying oven, and drying it at 40-60° C. for 12-24 hours to obtain a modified acrylic resin.

3. An OCA optical adhesive as claimed in claim 1, characterized in that: The modified polyurethane resin is prepared by the following method: adding polytetrahydrofuran diol into a reaction kettle, heating to 110-130° C. for reflux dehydration treatment, then cooling to 60-70° C., adding hexamethylene diisocyanate and dibutyltin dilaurate, and performing prepolymerization reaction at 70-80° C. to generate a polyurethane prepolymer with terminal isocyanate groups, wherein the mass volume ratio of the polytetrahydrofuran diol, hexamethylene diisocyanate and dibutyltin dilaurate is (90-110) g / mL. :(40-60):(0.5-1.5); then, 1,6-hexanediol is added to the isocyanate-terminated polyurethane prepolymer to carry out a chain extension reaction, wherein the volume ratio of the isocyanate-terminated polyurethane prepolymer to 1,6-hexanediol is (1.0-1.5):(0.5-1.0), and the reaction is carried out for 1-2 hours to obtain a chain extension reaction product; the chain extension reaction product is cooled to 20-25°C, and a filter is used to filter out solid impurities, and then a vacuum degassing treatment is carried out to obtain a modified polyurethane resin.

4. An OCA optical adhesive as claimed in claim 1, characterized in that The solvent is isopropyl alcohol, isobutyl acetate or a combination thereof.

5. The OCA optical adhesive according to claim 1, characterized in that: The cross-linking agent is one of xylylene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

6. The OCA optical adhesive according to claim 1, characterized in that: The self-lubricant is polyimide nanofiber, and the particle size of the polyimide nanofiber is 20-80nm.

7. The OCA optical adhesive according to claim 1, characterized in that: The antioxidant is one or a combination of the following: triphenyl phosphite, dilauryl thiodipropionate, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

8. The OCA optical adhesive according to claim 1, characterized in that: The initiator is one or a combination of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, methyl benzoylformate, benzoin dimethyl ether, and α-hydroxyisobutyl phenyl ketone.

9. The method for preparing an OCA optical adhesive according to claim 1, characterized in that: The following steps are involved: S1, adding the modified acrylic resin to the solvent, heating and stirring to dissolve, to obtain solution I; S2, adding the modified polyurethane resin to solution I, stirring evenly, to obtain solution II; S3, adding antioxidant, self-repairing agent and self-lubricating agent to solution II, stirring evenly to obtain solution III; S4, adding an initiator and a cross-linking agent to solution III, stirring evenly to obtain solution IV; S5. Filter the solution with a filter to remove solid impurities, and then perform vacuum degassing to obtain OCA optical adhesive.

10. The method for preparing an OCA optical adhesive according to claim 9, characterized in that: In the S1, the temperature is heated to 60-80°C, the stirring speed is 200-400rpm, and the stirring time is 30-60min; in the S2, the stirring speed is 200-400rpm, and the stirring time is 15-30min; in the S3, the stirring speed is 300-500rpm, and the stirring time is 20-40min; in the S4, the stirring speed is 300-500rpm, and the stirring time is 15-30min; in the S5, the filter mesh aperture is 100-200μm, the vacuum degree of vacuum degassing treatment is -0.08 to -0.10MPa, and the degassing time is 30-60min.

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