Modified castor oil-based light-cured polyurethane acrylate resin composition, OCA (optical clear adhesive) and preparation method of OCA

Abstract

The invention discloses a modified castor oil-based light-cured polyurethane acrylate resin composition, an OCA (Optical Clear Adhesive) and a preparation method of the OCA, and belongs to the technical field of optical adhesives. The light-cured polyurethane acrylate resin composition based on the modified castor oil comprises the following components in parts by weight: 55-70 parts of modified castor oil polyol; 20 to 35 parts by weight of an isocyano pentaerythritol triacrylate end-capping reagent; and 10-20 parts by weight of a reactive diluent. The light-cured polyurethane acrylate resin composition based on the modified castor oil is simple and convenient in process, low in odor and free of by-products in the preparation process, and an OCA (optical clear adhesive) prepared from the resin is high in light transmittance and excellent in high-temperature resistance, has high peel strength and permanent adhesion under a high-temperature condition, and can be widely applied to the fields of optical clear adhesive, optical clear adhesive and the like. The problems that a traditional OCA is low in peel strength and prone to edge warping at the high temperature are effectively solved.

Description

Technical Field

[0001] The present application relates to a modified castor oil-based photocurable polyurethane acrylate resin composition, an OCA optical adhesive and a preparation method thereof, and belongs to the technical field of optical adhesives. Background Art

[0002] Optically clear adhesive (OCA) is an adhesive used to bond different components between display touch screens. It is used in mobile phones, tablets, smart watches, car central control and other products. It has the characteristics of colorless transparency, visible light transmittance>90%, low haze, yellowing resistance, high bonding strength, and small curing shrinkage. In recent years, with the popularization of folding screen products, higher requirements have been placed on the performance of OCA. In particular, when flexible screens are used in high temperature environments, problems such as decreased bonding performance, blistering, and warping are very likely to occur. Therefore, OCA needs to have a certain high temperature resistance to ensure that the flexible folding screen fits completely and without defects.

[0003] Increasing the cross-linking degree of OCA film is one of the effective methods to improve its high temperature resistance. The patent with publication number CN117510751A discloses a high temperature resistant OCA optical adhesive and a preparation method thereof. The invention increases the cross-linking degree and improves the high temperature resistance by introducing isocyanate, aluminum acetylacetonate, and high temperature resistant silicone resin into the OCA network. However, the introduction of too much cross-linking agent affects the light transmittance of OCA optical adhesive. In addition, it can also be modified by grafting. The patent with publication number CN115353824A reports a high temperature and high humidity resistant OCA tape and a preparation method thereof. The invention introduces octadecyl methacrylate and double bond siloxane, which effectively improves the hydrophobicity of the OCA tape at high temperature, but the peeling force at high temperature is still not high.

[0004] Therefore, in order to solve the above technical problems, it is urgent to develop an OCA optical adhesive that has high light transmittance, excellent bonding performance and high temperature resistance. Summary of the invention

[0005] In order to cope with the application scenarios of folding screens in high temperature environments and overcome the problem of low peel strength of OCA optical adhesives under high temperatures in the prior art, the present application proposes a technical solution based on a modified castor oil photocurable polyurethane acrylate resin composition. The hydrophobicity and adhesion of the OCA adhesive film to the substrate are improved by introducing modified castor oil, and the cross-linking density of the OCA adhesive film is improved by introducing isocyanopentaerythritol triacrylate capping agent, thereby effectively improving the performance of the OCA optical adhesive under high temperature environments.

[0006] This application adopts the following technical solutions:

[0007] According to a first aspect of the present invention, a modified castor oil-based photocurable polyurethane acrylate resin composition is provided, wherein the modified castor oil-based photocurable polyurethane acrylate resin is prepared by reacting the following components in parts by weight:

[0008] 55-70 parts by weight of modified castor oil polyol;

[0009] 20 to 35 parts by weight of isocyanopentaerythritol triacrylate end-capping agent;

[0010] Active diluent 10 to 20 parts by weight.

[0011] Castor oil has a long carbon chain and polar ester bonds, which not only has good adhesion to most substrates, but also has high cohesive strength. The present application adopts modified castor oil polyol as one of the formula components, which can make the modified castor oil-based photocurable polyurethane acrylate resin composition applicable to OCA optical adhesive, so that the OCA optical adhesive has good bonding and high temperature resistance.

[0012] In the modified castor oil photocurable polyurethane acrylate resin composition, the isocyanopentaerythritol triacrylate capping agent can react with the modified castor oil polyol to generate a modified castor oil photocurable polyurethane acrylate resin composition with multiple double bonds capped, which can be used to participate in the subsequent photocuring of the OCA film.

[0013] Optionally, the modified castor oil polyol is prepared by reacting the following components in parts by weight:

[0014] 75-90 parts by weight of castor oil;

[0015] 10 to 25 parts by weight of low-molecular-weight diol;

[0016] Catalyst 0.002-0.004 parts by weight.

[0017] Optionally, the molar ratio of castor oil to small molecule diol in the preparation material of the modified castor oil polyol is 1:2.5-3.5.

[0018] Optionally, the molar ratio of castor oil to small molecule diol in the preparation material of the modified castor oil polyol is selected from any value of 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, or any range value therebetween.

[0019] Optionally, the small molecule diol is selected from at least one of ethylene glycol, 1,2-propylene glycol, dipropylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol and bisphenol A.

[0020] Castor oil is an ester of glycerol and ricinoleic acid. Through the ester exchange reaction between small molecule diols and castor oil, linear modified castor oil polyols are obtained. The modified castor oil polyols can react with isocyanopentaerythritol triacrylate capping agent to obtain double-bond terminated modified castor oil photocurable polyurethane acrylate resin.

[0021] The modified castor oil polyol prepared by the above technical scheme has an acid value of less than 2 mgKOH / g, a molecular weight of 500-1000, and a hydroxyl value of 112-224 mgKOH / g.

[0022] Optionally, the catalyst is selected from at least one of tetraisopropyl titanate, tetra-n-butyl titanate, tetra-tert-butyl titanate, stannous octoate, dibutyltin dilaurate, and bismuth laurate.

[0023] In the present application, the modified castor oil polyol is prepared by ester exchange reaction between castor oil and small molecule diol, and its molecular chain contains polar ester bonds, and the intermolecular force is strong, so the cohesion is high and the temperature is resistant. In this regard, the present invention adopts the above technical scheme to obtain a modified castor oil polyol with good adhesion to the substrate and high temperature resistance.

[0024] Alternatively, it is prepared by reacting pentaerythritol triacrylate and isocyanate trimer.

[0025] Optionally, the isocyanate trimer is selected from at least one of isophorone diisocyanate trimer, 2,4-toluene diisocyanate trimer and hexamethylene diisocyanate trimer.

[0026] Optionally, the reactive diluent is selected from at least one of butyl acrylate, n-pentyl acrylate, cyclotrimethylolpropane formal acrylate, trimethylolpropane triacrylate, ethoxyethoxyethyl acrylate, acryloylmorpholine, pentaerythritol triacrylate, N-vinyl pyrrolidone, tripropylene glycol diacrylate, N-vinyl caprolactam, and triethylene glycol diacrylate.

[0027] By adding active diluent during the reaction process, the viscosity of the modified castor oil photocurable polyurethane acrylate resin can be effectively reduced, which is beneficial to the uniform dispersion and reaction of the modified castor oil polyol and the isocyano pentaerythritol triacrylate capping agent.

[0028] According to the second aspect of the present application, there is provided a method for preparing the above-mentioned modified castor oil-based photocurable polyurethane acrylate resin composition, comprising the following steps:

[0029] A mixture containing modified castor oil polyol, isocyanate pentaerythritol triacrylate capping agent and active diluent is subjected to heating reaction I in an inert atmosphere to obtain the modified castor oil-based photocurable polyurethane acrylate resin composition.

[0030] Optionally, the conditions of the heating reaction I include: reaction temperature of 50-70° C., and reaction time of 5-7 h.

[0031] Optionally, the mixture comprises the following components in parts by weight:

[0032] 55-70 parts by weight of modified castor oil polyol;

[0033] 20 to 35 parts by weight of isocyanopentaerythritol triacrylate end-capping agent;

[0034] Active diluent 10 to 20 parts by weight.

[0035] By adopting the above technical scheme, the preparation process is simple, no solvent is needed, and the environment is environmentally friendly and pollution-free or less polluting. The prepared modified castor oil photocurable polyurethane acrylate resin can be used to prepare OCA optical adhesive.

[0036] Optionally, the preparation method of the modified castor oil polyol comprises the following steps:

[0037] A mixture containing castor oil, small molecule diol and a catalyst is subjected to a step-wise temperature increase reaction in an inactive atmosphere to obtain the modified castor oil polyol.

[0038] Optionally, the conditions of the step-wise temperature increase reaction include: heating to 120-130° C. and reacting for 1-2 hours, further heating to 170-180° C. and reacting for 1-2 hours, and finally heating to 210-220° C. and reacting for 2-3 hours.

[0039] Optionally, the mixture comprises the following components in parts by weight:

[0040] 75-90 parts by weight of castor oil;

[0041] 10 to 25 parts by weight of low-molecular-weight diol;

[0042] Catalyst 0.002-0.004 parts by weight.

[0043] The modified castor oil polyol is prepared by the above method without using solvent, and is environmentally friendly and pollution-free or less polluting. The synthesized modified castor oil polyol has good hydrolysis resistance and high temperature resistance. The molecular weight distribution of the resin can be adjusted by gradually increasing the temperature and reacting gradually to obtain a modified castor oil polyol with uniform structure and performance.

[0044] In the present application, the reaction is carried out in a closed reactor at a standard atmospheric pressure.

[0045] Optionally, the preparation method of the isocyanopentaerythritol triacrylate capping agent comprises the following steps:

[0046] The mixture containing isocyanate trimer and pentaerythritol triacrylate is heated in an inert atmosphere to carry out reaction II to obtain the isocyano pentaerythritol triacrylate capping agent.

[0047] Optionally, the conditions of the heating reaction II include: the reaction temperature is 50-60° C., and the reaction time is 4-6 hours.

[0048] Optionally, the molar ratio of the isocyanate trimer to pentaerythritol triacrylate is 1:2.

[0049] The isocyanoacrylate capping agent synthesized by the above method has good reactivity and high functionality, and is conducive to reacting with modified castor oil polyol.

[0050] The reactions in the steps of the method for preparing the modified castor oil photocurable polyurethane acrylate resin composition are all carried out in a closed container under a standard atmospheric pressure.

[0051] According to a third aspect of the present application, an OCA optical adhesive is provided, wherein the OCA optical adhesive is prepared by mixing the following components in parts by weight:

[0052] 98 to 99 parts by weight of a modified castor oil photocurable polyurethane acrylate resin composition;

[0053] 1 to 2 parts by weight of photoinitiator;

[0054] The modified castor oil photocurable polyurethane acrylate resin composition is selected from any one of the modified castor oil photocurable polyurethane acrylate resin compositions and the modified castor oil photocurable polyurethane acrylate resin composition prepared according to any one of the preparation methods.

[0055] By adopting the above technical solution, the prepared OCA optical adhesive has good properties such as light transmittance, bonding strength and high temperature resistance, and can be used in fields such as folding screens.

[0056] Optionally, the photoinitiator is selected from at least one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, benzil dimethyl ether, and 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone.

[0057] By adopting the above-mentioned photoinitiator, the curing rate of the modified castor oil photocurable polyurethane acrylate resin can be effectively improved and the curing time can be shortened.

[0058] Optionally, the preparation method of the OCA optical adhesive comprises the following steps: mixing modified castor oil photocurable polyurethane acrylate resin and a photoinitiator, and then coating and curing to obtain the OCA optical adhesive.

[0059] By adopting the above-mentioned preparation method, the operation is simple, the materials are evenly dispersed, the reaction is controllable, and the prepared OCA optical adhesive has good properties such as light transmittance, bonding strength and high temperature resistance.

[0060] The beneficial effects of this application include:

[0061] The present application is based on a modified castor oil photocurable polyurethane acrylate resin composition, which uses castor oil, a small molecule diol and a catalyst to prepare a modified castor oil polyol, and then uses the polyol to further prepare a modified castor oil photocurable polyurethane acrylate resin. In the preparation process, no solvent is used, no waste liquid is generated, and the environment is environmentally friendly and pollution-free or less polluting. The OCA optical adhesive prepared with the modified castor oil photocurable polyurethane acrylate resin has the advantages of good optical properties, bonding properties and high temperature resistance. In addition, the technical solution of the present application includes a one-step synthesis of an isocyano pentaerythritol triacrylate capping agent through pentaerythritol triacrylate and an isocyanate trimer. The capping agent has high reactivity and can react with the modified castor oil polyol, so that the prepared polyurethane acrylate resin has a terminal carbon-carbon double bond, giving the polyurethane acrylate resin good photocuring properties. DETAILED DESCRIPTION

[0062] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0063] The castor oil used in the examples was purchased from Fucheng County Huanyu Oil Co., Ltd.

[0064] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0065] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0066] Preparation Example 1 Obtaining Modified Castor Oil Polyol

[0067] Under nitrogen protection, 834.82 g of castor oil, 228.29 g of bisphenol A, and 0.03 g of tetrabutyl titanate were added to a reactor, stirred and heated to 120°C and reacted for 1 hour, then continued to heat to 170°C and reacted for 2 hours, and finally heated to 210°C and reacted for 2 hours, and then cooled and discharged to obtain modified castor oil polyol.

[0068] Preparation Examples 2-3

[0069] The same preparation method as in Preparation Example 1 was used, except that some raw material types, feed amounts and synthesis process parameters were different from those in Preparation Example 1 (as shown in Table 1), and the remaining experimental steps were consistent with those in Preparation Example 1.

[0070] Comparative Preparation Example 1 to obtain polyester polyol

[0071] Under nitrogen protection, 292.28 g of adipic acid, 684.86 g of bisphenol A and 0.03 g of tetra-n-butyl titanate were added to the reactor, stirred and heated to 120°C and reacted for 1 hour, then continued to heat to 170°C and reacted for 2 hours, and finally heated to 210°C and reacted for 2 hours, and then cooled and discharged to obtain polyester polyol.

[0072] Comparative Preparation Example 2

[0073] The same preparation method was used as in Comparative Preparation Example 1, except that some raw material types, feed amounts and synthesis process parameters were different from those in Preparation Example 1 (as shown in Table 1), and the remaining experimental steps were consistent with those in Comparative Preparation Example 1.

[0074] The types of raw materials, feed amounts and synthesis process parameters used in Preparation Examples 1-3 and Comparative Preparation Examples 1-2 are shown in Table 1:

[0075] Table 1 Raw materials, feed amounts and synthesis process parameters

[0076]

[0077] Example 1

[0078] (1) Preparation of isocyanopentaerythritol triacrylate capping agent

[0079] Under nitrogen protection, 50.46 g of hexamethylene diisocyanate trimer and 59.66 g of pentaerythritol triacrylate were added to the reactor, stirred and heated to 60°C, and kept warm for 4 hours to obtain 110.12 g of isocyano pentaerythritol triacrylate capping agent. After the reaction was completed, there was no need to discharge the material and the next step of synthesis was carried out directly.

[0080] (2) Preparation of modified castor oil photocurable polyurethane acrylate resin

[0081] Under nitrogen protection, 311.67 g of the modified castor oil polyol obtained in Preparation Example 1 and 50 g of active diluent butyl acrylate were directly added to the above-mentioned reactor containing 110.12 g of isocyanopentaerythritol triacrylate capping agent, stirred and heated to 60°C, reacted for 5 hours, cooled and discharged to obtain a modified castor oil photocurable polyurethane acrylate resin composition.

[0082] Embodiments 2 to 7

[0083] The preparation process of Examples 2 to 7 is the same as that of Example 1, except that, in the synthesis process of the isocyanopentaerythritol triacrylate end-capping agent in step (1), except for some raw material types, feed amounts and synthesis process parameters that are different from those in Example 1 (as shown in Table 2), the remaining experimental steps are the same as those in Example 1; in the preparation of the modified castor oil photocurable polyurethane acrylate resin composition in step (2), except for some raw material types, feed amounts and synthesis process parameters that are different from those in Example 1 (as shown in Table 2), the remaining experimental steps are the same as those in Example 1.

[0084] The types of raw materials, feed amounts and synthesis process parameters used in Examples 1 to 7 are shown in Table 2.

[0085] Table 2 Types of raw materials, feed amounts and synthesis process parameters in Examples 1 to 7

[0086]

[0087] Application Example 1 Preparation of OCA Optical Adhesive

[0088] 100 g of the modified castor oil photocurable polyurethane acrylate resin composition (from Example 1) and 1.5 g of the photoinitiator 1-hydroxycyclohexyl phenyl ketone were mixed, fully stirred, and then subjected to degassing, glue coating, and UV curing to obtain an OCA optical adhesive.

[0089] Application Examples 2 to 6

[0090] The difference between Application Examples 2 to 6 and Application Example 1 is that the types and amounts of some raw materials used are different from those in Application Example 1, and the rest of the experimental steps are the same as those in Application Example 1. The types and amounts of raw materials in Application Examples 1 to 7 are shown in Table 3:

[0091] Table 3 Types of raw materials and feed amounts in application examples 1 to 6

[0092]

[0093] The OCA optical adhesive prepared in Application Examples 1 to 6 was coated on a PET release film with a thickness of 0.1 mm and exposed to ultraviolet light with an energy of 1600 mJ / cm 2 The optical tape is cured under a UV lamp to obtain an optical tape.

[0094] Test Example 1

[0095] The optical adhesives prepared by the above-mentioned application examples 1 to 6 were tested for light transmittance, haze, bonding strength and (humidity) heat resistance using the following detection methods / test methods:

[0096] (1) Transmittance and haze: The transmittance and haze of transparent glass with a thickness of 1 mm were tested using a WGT-S transmittance / haze tester, and the test data were used as the blank sample. The OCA optical tapes prepared in Application Examples 1 to 6 were pasted on a glass sheet and the release film was removed. The transmittance and haze of the sample to be tested were tested, and the value of the sample was obtained by subtracting the value of the blank sample.

[0097] (2) Adhesive strength: The 180° peel strength of OCA optical tape was tested according to GB / T2792-1998.

[0098] (3) High temperature resistance test: After the OCA optical adhesives of application examples 1 to 6 were prepared according to GB / T2792-1998, they were placed in a constant temperature test box at 60°C to test the 180° peel strength of the samples. The test results and experimental data are shown in Table 4:

[0099] Table 4 Performance data of OCA optical adhesive before and after high temperature and high humidity test

[0100] Application Examples Light transmittance (%) Haze(%) Peel force (N / 25mm) High temperature test peeling force (N / 25mm) Application Example 1 92.4 0.09 12.9 4.3 Application Example 2 92.5 0.09 13.1 4.6 Application Example 3 93.1 0.08 12.7 4.3 Application Example 4 92.9 0.07 12.6 4.1 Application Example 5 80.1 1.9 11.7 2.2 Application Example 6 82.9 1.3 11.3 1.9

[0101] It can be seen from Application Examples 1 to 6 in combination with Tables 1 to 4 that the OCA optical adhesive prepared by adopting the present application has good optical, bonding and high temperature resistance properties.

[0102] Comparing Application Example 1 with Application Example 5, it is shown that the OCA optical adhesive prepared by the modified castor oil photocurable polyurethane acrylate resin prepared by this application and the photoinitiator under ultraviolet light irradiation has high temperature resistance. The main reason is that after the modified castor oil structure is introduced into the molecular structure of the OCA optical adhesive, the adhesion and cohesive strength of the OCA adhesive film are significantly improved, so the high temperature resistance of the OCA optical adhesive can be significantly improved. By comparing Application Example 1 with Application Example 2, it can be found that the presence of rigid benzene rings in modified castor oil significantly improves the high temperature resistance of the OCA optical adhesive. In addition, a large number of carbon-carbon double bonds are introduced at the ends of the modified castor oil photocurable polyurethane acrylate resin molecules to give the resin UV-curable properties, so that a cross-linked OCA optical adhesive film can be prepared, further improving the peel strength of the adhesive film.

[0103] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A modified castor oil-based photocurable polyurethane acrylate resin composition, characterized in that: The modified castor oil-based light-curable polyurethane acrylate resin comprises the following components in parts by weight: 55-70 parts by weight of modified castor oil polyol; 20 to 35 parts by weight of isocyanopentaerythritol triacrylate end-capping agent; Active diluent 10 to 20 parts by weight.

2. The modified castor oil-based photocurable polyurethane acrylate resin composition according to claim 1, characterized in that: The modified castor oil polyol is prepared by reacting the following components in parts by weight: 75-90 parts by weight of castor oil; 10 to 25 parts by weight of low-molecular-weight diol; Catalyst 0.002-0.004 parts by weight; Preferably, the small molecule diol is selected from at least one of ethylene glycol, 1,2-propylene glycol, dipropylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol and bisphenol A; Preferably, the catalyst is selected from at least one of tetraisopropyl titanate, tetra-n-butyl titanate, tetra-tert-butyl titanate, stannous octoate, dibutyltin dilaurate, and bismuth laurate.

3. The modified castor oil-based photocurable polyurethane acrylate resin composition according to claim 1, characterized in that: The isocyano pentaerythritol triacrylate capping agent is prepared by reacting pentaerythritol triacrylate and isocyanate trimer; Preferably, the isocyanate trimer is selected from at least one of isophorone diisocyanate trimer, 2,4-toluene diisocyanate trimer and hexamethylene diisocyanate trimer.

4. The modified castor oil-based photocurable polyurethane acrylate resin composition according to claim 1, characterized in that: The active diluent is selected from at least one of butyl acrylate, n-pentyl acrylate, cyclotrimethylolpropane formal acrylate, trimethylolpropane triacrylate, ethoxyethoxyethyl acrylate, acryloyl morpholine, pentaerythritol triacrylate, N-vinyl pyrrolidone, tripropylene glycol diacrylate, N-vinyl caprolactam, and triethylene glycol diacrylate.

5. The method for preparing the modified castor oil-based photocurable polyurethane acrylate resin composition according to any one of claims 1 to 4, characterized in that: The steps include: A mixture containing modified castor oil polyol, isocyanate pentaerythritol triacrylate capping agent and active diluent is subjected to heating reaction I in an inert atmosphere to obtain the modified castor oil-based photocurable polyurethane acrylate resin composition.

6. The preparation method according to claim 5, characterized in that: The conditions of the heating reaction I include: a reaction temperature of 50 to 70° C. and a reaction time of 5 to 7 hours.

7. The preparation method according to claim 5, characterized in that: The preparation method of the modified castor oil polyol comprises the following steps: A mixture containing castor oil, a small molecule diol and a catalyst is subjected to a step-wise temperature increase reaction in an inert atmosphere to obtain the modified castor oil polyol; Preferably, the conditions of the step-wise temperature increase reaction include: heating to 120-130° C. and reacting for 1-2 hours, further heating to 170-180° C. and reacting for 1-2 hours, and finally heating to 210-220° C. and reacting for 2-3 hours.

8. The preparation method according to claim 5, characterized in that: The preparation method of the isocyanopentaerythritol triacrylate end-capping agent comprises the following steps: The mixture containing isocyanate trimer and pentaerythritol triacrylate is heated in an inert atmosphere to perform reaction II to obtain the isocyano pentaerythritol triacrylate capping agent; Preferably, the conditions of the heating reaction II include: reaction temperature of 50-60° C., and reaction time of 4-6 h.

9. The preparation method according to claim 8, characterized in that: The molar ratio of the isocyanate trimer to pentaerythritol triacrylate is 1:

2.

10. An OCA optical adhesive, characterized in that: The OCA optical adhesive is prepared by mixing the following components in parts by weight: 98-99 parts by weight of modified castor oil photocurable polyurethane acrylate resin composition; 1 to 2 parts by weight of photoinitiator; The modified castor oil photocurable polyurethane acrylate resin composition is selected from the modified castor oil photocurable polyurethane acrylate resin composition according to any one of claims 1 to 4, and the modified castor oil photocurable polyurethane acrylate resin composition prepared by the preparation method according to any one of claims 5 to 8.

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