OCA Optical Adhesive and Method for Producing the Same

Abstract

The present invention discloses an OCA optical adhesive and a method for manufacturing the same. The optical adhesive is composed of one or more block copolymers. The method uses reversible addition-fragmentation chain transfer emulsion polymerization, and controls the types and supply order of monomers to prepare a block copolymer with controllable design. Then, one or more types of prepared block copolymers are mixed and a solution is formed into a film to obtain an OCA optical adhesive. The OCA optical adhesive manufactured by the present invention has the advantages of high elongation, high transparency, and low haze, and can effectively reduce the modulus and improve the peel strength on the premise of not affecting the resilience. Therefore, it has extremely great application potential in fields such as electronic display devices, wearable electronic devices, resistive touch panels, and smart optical devices.

Description

Technical Field

[0001] The present invention relates to the field of adhesives, and particularly to OCA optical adhesives and their manufacturing methods.

Background Art

[0002] In the modern information electronics industry, a display provides a window for users to operate a device, enables feedback and response to the device, and has become an important component of the HCI (Human-Computer Interaction) interface in modern electronic devices. The development of display technology and related materials is an important condition for the progress of advanced electronic devices. Optically Clear pressure sensitive Adhesive (OCA) is an important functional material widely used in display devices and is used for bonding transparent optical elements. The OCA is colorless and transparent, has a light transmittance of 90% or more, excellent adhesive strength, can be cured at room temperature, and has characteristics such as small curing shrinkage. In addition, the OCA has flexibility, high viscoelasticity, and the ability to reduce the refractive index difference by filling voids, thus contributing to the improvement of the clarity of image display. In order to reduce the mechanical feeling of the electronic display and improve the intimacy between the user and the device, the display has evolved from the conventional flat type display to a flexible arc-shaped display, a curved surface display, and ultimately a foldable display and a rollable display. Moreover, due to the needs for wearable and flexible electronic devices, people's interest in flexible displays is increasing day by day. The emergence of these new device forms poses new challenges to the performance of OCA optical adhesives. Conventional OCA has characteristics such as high modulus and strong adhesive performance. Therefore, during the folding process, the stress applied to the elongation stress layer of the panel increases, resulting in serious material fatigue in the material. As a result, the adhesive function is lost during actual use, leading to visual discomfort during the use process and significantly reducing the use experience and service life of foldable smartphones. Currently, the OCA optical adhesive used in foldable smartphones needs to have three performances: (1) high flexibility that can generate high shear strain and only generates small stress when deformed greatly, (2) high elasticity that can be quickly restored even when statically folded for a long time, and (3) high interfacial adhesiveness that prevents delamination between layers and peeling of the adhesive when subjected to a pressing action.

[0003] Currently, most of the OCA optical adhesives are manufactured by photoinitiated polymerization. First, by increasing the concentration of the initiator to improve the crosslinking density, the elasticity of the OCA optical adhesive can be improved. Second, by adding a functional monomer such as acrylic acid to the system to improve the cohesive force of the material, the elasticity of the OCA optical adhesive can also be improved. However, the main difficulty is that it is impossible to achieve a balance between fluidity and elasticity. In this case, although the modulus of the OCA optical adhesive is significantly improved, the extensibility decreases, making it difficult to apply to foldable smartphones.

[0004] In addition, by the UV casting method, an OCA optical adhesive with alternately distributed high crosslinking degree and low crosslinking degree is also manufactured. In this case, it is possible to reduce the modulus of the OCA optical adhesive to a certain extent and improve the peel strength of the material, but at the same time, the resilience of the material decreases.

[0005] Currently, as a method of balancing elasticity and flexibility, by adding 10 mol% of acrylic acid to the prepolymer of the adhesive, while improving the peel strength of the OCA optical adhesive with a film thickness of 100 μm to about 14 N / 25 mm, it is possible to set the glass transition temperature to -54.3 °C and the modulus to 27 kPa. However, when the elongation rate exceeds 300%, breakage occurs, so it is impossible to support the long-term use of the optical adhesive.

[0006] Therefore, on the premise of improving the extensibility of the OCA optical adhesive without affecting the resilience, it is an urgent problem to be solved to research and develop a technology that improves the peel strength of the OCA optical adhesive and reduces the modulus of the material, so that the OCA optical adhesive has good balanced flexibility, modulus, and interfacial adhesiveness. Summary of the Invention Problems to be Solved by the Invention

[0007] In view of the defects of the prior art, the present invention provides a method for manufacturing an OCA optical adhesive with controllable structure. The method prepares a block copolymer with controllable design by reversible addition-fragmentation chain transfer emulsion polymerization, and forms a film of one or more block copolymer solutions, so as to effectively reduce the modulus and improve the peel strength on the premise of not affecting the resilience, and manufacture an OCA optical adhesive with high elongation, high transparency and low haze.

Means for Solving the Problems

[0008] The present invention is realized by the following technical means. The OCA optical adhesive is composed of a main matrix with a mass content of 20-100% and a reinforcing matrix with a mass content of 0-80%.

[0009] The structural formula of the main matrix is M1-b-M2-b-M3···-b-M j where j ranges from 3 to 11. Also, M1, M2, M3···M j are the comonomers of the block copolymer, and the number average molecular weight of the block copolymer of the main matrix is 80,000-800,000 g / mol. M1, M2, M3···M j are respectively selected from soft monomers, hard monomers or functional monomers. And the mass contents of the soft monomer, hard monomer and functional monomer in the block copolymer are 70-98%, 2-30% and 0-5% respectively.

[0010] The structural formula of the reinforcing matrix is N1 or N1-b-N2, and the number average molecular weight of the block copolymer of the reinforcing matrix is 100,000-400,000 g / mol. N1 is a soft monomer, and N2 is a hard monomer or a functional monomer. And the mass contents of the soft monomer, hard monomer and functional monomer in the block copolymer are 75-100%, 0-25% and 0-5% respectively.

[0011] Specifically, the hard monomer includes styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile, and vinyl acetate, and the range of its glass transition temperature is 60 to 150 °C. The soft monomer includes ethyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene-butene, and methacrylic acid, and the range of its glass transition temperature is -90 to -30 °C. The functional monomer includes methacrylic acid, acrylic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxy-1-methylethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, methacrylamide, N-(hydroxymethyl)acrylamide, glycidyl methacrylate, and maleic anhydride.

[0012] Specifically, the steps are as follows.

[0013] (1) Dissolve the amphiphilic polymer reversible addition-fragmentation chain transfer reagent in water, then add styrene, or styrene and methacrylic acid, and stir until uniformly mixed. Then, add the first initiator at 70 to 90 °C and react for 1 to 3 h to obtain a homopolymer. The homopolymer is stably dispersed in water in the form of particles to form a latex.

[0014] (2) Add a 10 wt% aqueous sodium hydroxide solution, then add isooctyl acrylate, or isooctyl acrylate and methacrylic acid, and then add water. Then, add the second initiator at 40 to 60 °C, react for 4 to 10 h in an oxygen-free environment, then add the hard monomer, and react for 5 to 10 h in an oxygen-free environment to obtain a polymer latex of the main substrate.

[0015] (3) After the reaction is completed, the polymer latex, 30 wt% hydrogen peroxide solution, and 7.5 wt% hydrochloric acid are placed in a beaker at a volume ratio of 2:1:2, stirred for 15 min until uniform, then heated to 50 °C and reacted for 1.5 - 3 h. Next, the precipitated product is washed with distilled water until neutral, dried, and then placed in a vacuum oven and vacuum dried at 120 °C for 5 - 20 h to finally obtain the main substrate.

[0016] (4) The amphiphilic polymer reversible addition-fragmentation chain transfer reagent is stirred and dissolved in water, then styrene, or styrene and methacrylic acid are added and stirred until completely dissolved. Then, after setting the water bath temperature to 70 - 90 °C, the first initiator is added and reacted for 1 - 3 h to obtain a homopolymer. The homopolymer is stably dispersed in water in the form of particles to form a latex.

[0017] (5) After adding a 10 wt% aqueous sodium hydroxide solution, isooctyl acrylate and water are added, and then the second initiator is added. Then, the temperature of the water bath is set to 40 - 60 °C, and the reaction time is set to 4 - 10 h under a vacuum environment to obtain the polymer latex of the reinforcing substrate.

[0018] (6) After the reaction is completed, the polymer latex, 30 wt% hydrogen peroxide solution, and 7.5 wt% hydrochloric acid are placed in a beaker at a volume ratio of 2:1:2, stirred for 15 min until uniform, then heated to 40 - 60 °C and reacted for 1.5 - 3 h. Next, the precipitated product is washed multiple times with distilled water until neutral, dried, and then placed in a vacuum oven and vacuum dried at 120 °C for 5 - 20 h to finally obtain the reinforcing substrate.

[0019] (7) The main substrate and the reinforcing substrate are dissolved in a dispersion medium, and then coated, formed into a film, and dried in an argon gas environment to finally obtain the OCA optical adhesive.

[0020] Specifically, the structural formula of the amphiphilic polymer reversible addition-fragmentation chain transfer reagent is R-(M n1 -b-N n2 )-X.

[0021] R is an isopropionic acid group, an acetic acid group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group. M n1 Among them, M is a methacrylic acid monomer or an acrylic acid monomer unit, and n1 is the average degree of polymerization of M. Also, the range of n1 is 10 to 30. N n2 Among them, N is a styrene monomer, a butyl acrylate monomer, methyl acrylate, isooctyl acrylate, or a methyl methacrylate monomer unit, and n2 is the average degree of polymerization of N. Also, the range of n2 is 1 to 8. The X group is an alkyldithioester group or an alkyltrithioester group.

[0022] Furthermore, the dispersion medium is any one of ethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, and methyl propionate.

[0023] Specifically, the first initiator in steps (1) and (4) is any one of ammonium persulfate, potassium persulfate, hydrogen peroxide, and hydrogen peroxide derivatives. The second initiator in steps (2) and (5) is any one of 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane]2 hydrochloride, 2,2'-azobis(propane-2-carboxamidine) dihydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium bisulfate / potassium persulfate redox initiator, and sodium persulfate / ammonium persulfate redox initiator. Furthermore, the acrylic acid in steps (1) and (2) can be replaced with any one of other functional monomers.

Advantages of the Invention

[0024] The beneficial effects of the present invention are as follows.

[0025] (1) Block copolymers can be prepared as OCA optical adhesives by reversible addition-fragmentation chain transfer emulsion polymerization, allowing for controllable design. The soft segment of the block copolymer is formed by polymerization of a soft monomer, or a soft monomer and a functional monomer. The hard segment of the block copolymer is formed by polymerization of a hard monomer, or a hard monomer and a functional monomer. In addition, the glass transition temperature of the block copolymer does not change significantly compared to that of a homopolymer.

[0026] (2) The modulus of OCA optical adhesive can be significantly reduced by adding two blocks or homopolymers, and the glass temperature, cohesive strength and peel strength of OCA optical adhesive can be adjusted by introducing functional monomers.

[0027] (3) The use of a controllable living polymerization method that can be industrialized at low cost allows the synthesized block copolymers to be synthesized continuously and on a large scale, which is a simpler process and is advantageous for the customized production of OCA optical adhesives.

[0028] (4) The OCA optical adhesive produced by this method has the properties of flexibility, high transparency, high elongation, and high peel strength. It also has high recovery, with a recovery rate of over 95%. [Brief description of the drawings]

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0030] The following are specific examples of the present invention, and the technical means of the present invention will be further described. However, the present invention is not limited to these examples.

Examples

[0031] Preparation and Performance of Poly(styrene-b-isooctyl acrylate-b-styrene) Block Copolymer In this example, the material was prepared using the RAFT reversible addition-fragmentation chain transfer emulsion polymerization method. The specific steps were as follows.

[0032] Step 1: 1 part by mass of an amphiphilic polymer RAFT reagent (an amphiphilic polymer reversible addition-fragmentation chain transfer reagent) and 13 parts by mass of water were stirred until completely dissolved, and then 6 parts by mass of styrene was added, or 6 parts by mass of styrene and 1 part by mass of methacrylic acid were added. The addition of the methacrylic acid was to improve the adhesion between the monomers. Thereafter, stirring and mixing were carried out. Also, the structural formula of the amphiphilic polymer RAFT reagent was as follows.

[0033]

Chemical formula

[0034] Step 2: Add the above raw materials into a four-necked flask, introduce nitrogen and remove oxygen at room temperature for 0.5 h. Then, raise the temperature of the water bath to 70 °C, add an aqueous solution of potassium persulfate (dissolved 0.02 parts by mass of potassium persulfate in 12 parts by mass of water) as an initiator, and react for 1 h. Thereafter, slowly add an aqueous solution of sodium hydroxide (dissolved 1 part by mass of sodium hydroxide in 10 parts by mass of water), then add 90 parts by mass of isooctyl acrylate and 50 parts by mass of water, and then add 0.02 parts by mass of 2,2’-bis(2-imidazolin-2-yl)[2,2’-azobispropane] dihydrochloride and react for 2 h. Finally, add 7 parts by mass of styrene and react for 1.5 h to obtain a polymer latex.

[0035] Step 3: Put the polymer latex, 30 wt% hydrogen peroxide solution and 7.5 wt% hydrochloric acid into a beaker at a volume ratio of 2:1:2, stir for 15 min until uniform, then raise the temperature to 50 °C and react in an air environment for 1.5 h.

[0036] Step 4: After the reaction is completed, wash the precipitate product with distilled water multiple times until it becomes neutral, dry it, and then put it into a vacuum oven and vacuum dry at 120 °C for 12 h to finally obtain white polymer particles.

[0037] Step 5: Dissolve the polymer in butanone, then pour it into a polytetrafluoroethylene watch glass with a diameter of 12 cm to form a film. After most of the solvent has evaporated at room temperature, put it into a vacuum oven at 130 °C for continuous drying and annealing to prepare a polymer film with a thickness of about 0.8 - 1 mm.

[0038] Step 6: Dissolve the polymer in butanone and prepare an OCA optical adhesive film for peel strength test with a thickness of about 25 μm using a bar coater.

[0039] The characteristic evaluation of the molecular weight of the polymer was performed using a gel permeation chromatography Waters 1525 - 2414 - 717 GPC device. The eluent was tetrahydrofuran and calibrated with a narrow - distribution polystyrene standard.

[0040] Regarding the mechanical properties of the polymer, tests were conducted using a universal testing machine (Zwick / Roll Z020). Using standard - cut samples, the polymer film in step 4 above was cut into dumbbell - shaped test pieces. For the test method, GB16421 - 1996 was used, and the tensile speed was 30 mm / min. The tests for each sample were repeated at least 3 times.

[0041] Regarding the stress relaxation and recovery properties of the polymer, tests were conducted using DMA (TAQ800). The OCA optical adhesive film in step 4 above was cut into test pieces with a width of 5 mm and a length of 25 mm. Then, for the OCA optical adhesive, at strains of 100%, 200%, 300%, 400%, and 500% respectively, after stretching for 1 h, it was maintained at a stress of 0 MPa for 1 h, and the recovery curve was recorded.

[0042] Regarding the dynamic mechanical properties of the polymer, characteristic evaluation was performed using a rotational rheometer (HAAKE MARS 60). The above - mentioned polymer film was cut into circular test pieces with a diameter of 2 cm. The test frequency was 0.01 - 1 Hz, and the test temperature was 25 °C. During the test process, the loss factor tanδ of the material was recorded.

[0043] The peel strength of the polymer was tested using an adhesive shear strength tester (KJ - 1066A). The OCA optical adhesive film in step 5 above was cut into test pieces with a width of 25 mm and a length of approximately 300 mm. Also, for the test method, GB / T2792 - 2014 was used. The tests for each sample were repeated at least 3 times.

[0044] Figure 1 shows the GPC curves of the block copolymers obtained after the reaction of each block. Curve 1 in the figure is polystyrene (PSt), curve 2 is poly(styrene-b-isooctyl acrylate) (PSt-EHA), and curve 3 is poly(styrene-b-isooctyl acrylate-b-styrene) (PSt-EHA-PSt). As is clear from the drawing, as the number of blocks increased, the molecular weight of the polymer generally shifted to a higher molecular weight. This means that the product was a block copolymer. Also, the molecular weight of each block was 1.5W-22.5W-1.5W, respectively. Figure 2 is the mechanical property curve of the block copolymer. As is clear from the drawing, the polymer had a low modulus of 162.7 KPa, a low stress of 0.515 MPa, and a high elongation at break of nearly 1200%. Figure 3 is the stress relaxation recovery curve of the OCA optical adhesive. As is clear from the drawing, in the case of 100% elongation strain, the final deformation rate was only 4.55%. Also, in the case of 200% elongation strain, the final deformation rate was 5.07%, in the case of 300% elongation strain, the final deformation rate was 8.93%, in the case of 400% elongation strain, the final deformation rate was 11.58%, and in the case of 500% elongation strain, the final deformation rate was 17.05%. Figure 4 shows the shear dynamic mechanical properties of the OCA optical adhesive, with a storage modulus of only 26 KPa and a tanδ of only 0.2021.

[0045] When the film thickness was 25 μm, the peel strength of the OCA optical adhesive film was 6.40 N / 25 mm.

Example

[0046] Preparation and Performance of Poly(styrene-b-isooctyl acrylate-b-styrene) Block Copolymer This example was basically the same as the steps of Example 1, but differed in that the part by mass of styrene was 1 and the part by mass of isooctyl acrylate was 18.

[0047] The characterization of the molecular weight of the polymer and the mechanical property test of the polymer in this example were similar to those of Example 1.

[0048] Figure 5 shows the shear dynamic mechanical properties in this example. The storage modulus was 45 KPa. In the case of 300% elongation strain, the sample broke after 47 minutes of maintenance. When the film thickness was 25 μm, the peel strength of the OCA optical adhesive film was 10.01 N / 25 mm.

Example

[0049] Mixing of triblock copolymer and poly(styrene-b-isooctyl acrylate) copolymer The preparation of the triblock copolymer in this example was the same as that in Example 1. Also, for the poly(styrene-b-isooctyl acrylate) copolymer, the material was prepared using the RAFT reversible addition-fragmentation chain transfer emulsion polymerization method. The specific steps were as follows.

[0050] Step 1: After stirring 1 part by mass of the amphiphilic polymer RAFT reagent and 13 parts by mass of water until completely dissolved, 6 parts by mass of styrene was added and stirred and mixed. The structural formula of the amphiphilic polymer RAFT reagent was as follows.

[0051]

Chemical formula

[0052] Step 2: The above raw materials were added to a four-necked flask, and nitrogen was introduced and oxygen was removed at room temperature for 0.5 h. Then, the water bath was heated to 70 °C, and an aqueous solution of potassium persulfate (prepared by dissolving 0.02 part by mass of potassium persulfate in 12 parts by mass of water) was added as an initiator and reacted for 1 h. Thereafter, an aqueous solution of sodium hydroxide (prepared by dissolving 1 part by mass of sodium hydroxide in 10 parts by mass of water) was slowly added, then 24 parts by mass of isooctyl acrylate and 50 parts by mass of water were added, and 0.02 part by mass of 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane] dihydrochloride was added and reacted for 2 h to obtain a polymer latex.

[0053] Step 3: The polymer latex, 30 wt% hydrogen peroxide solution, and 7.5 wt% hydrochloric acid were put into a beaker at a volume ratio of 2:1:2, stirred for 15 min until homogeneous, then heated to 50 °C and reacted in an air environment for 1.5 h.

[0054] Step 4: After the reaction was completed, the precipitated product was washed multiple times with distilled water until neutral, dried, and then placed in a vacuum oven and vacuum dried at 120 °C for 12 h to finally obtain white polymer particles.

[0055] Step 5: The particles of the triblock copolymer in Example 1 above and the diblock copolymer in this example were dissolved in butanone at ratios of 75 / 25, 50 / 50, and 25 / 75, then poured into a 12-cm-diameter polytetrafluoroethylene watch glass to form a film. After most of the solvent was volatilized at room temperature, it was placed in a vacuum oven at 130 °C for continuous drying and annealing to prepare a polymer film with a thickness of about 0.8 - 1 mm.

[0056] Step 5: The particles of the triblock copolymer in Example 1 above and the diblock copolymer in this example were dissolved in butanone at ratios of 75 / 25, 50 / 50, and 25 / 75, and then a OCA optical adhesive film for peel strength test with a thickness of about 25 μm was prepared by a bar coater.

[0057] The characterization of the molecular weight of the polymer in this example and the performance test of the polymer were similar to those in Example 1. Also, the molecular weight of each block was 1W - 4W respectively.

[0058] As is clear from the comparison of the peel strength performance when different ratios of diblock copolymers were added in Fig. 6, compared with the pure triblock copolymer, when the addition ratio of the diblock was halved, the peel strength improved from 6.40 N / 25 mm to 9.40 N / 25 mm. Fig. 7 shows stress relaxation recoverability. As is clear from the drawing, the recoverability did not change with the increase in the addition ratio of the diblock copolymer, and the final deformation rate was maintained at about 11% in all cases.

Example

[0059] Mixing of triblock copolymer and poly(styrene-b-(isooctyl acrylate-r-acrylic acid)) copolymer The preparation of the triblock copolymer in this example was the same as in Example 1. Also, for the (styrene-b-isooctyl acrylate) copolymer, the material was prepared using the RAFT reversible addition-fragmentation chain transfer emulsion polymerization method. The specific steps were as follows.

[0060] Step 1: After stirring 1 part by mass of the amphiphilic polymer RAFT reagent and 13 parts by mass of water until completely dissolved, 6 parts by mass of styrene was added and stirred and mixed. The structural formula of the amphiphilic polymer RAFT reagent was as follows.

[0061]

Chemical formula

[0062] Step 2: Add the above raw materials into a four-necked flask, introduce nitrogen and remove oxygen at room temperature for 0.5 h. Then, heat the water bath to 70 °C, add an aqueous solution of potassium persulfate (prepared by dissolving 0.02 parts by mass of potassium persulfate in 12 parts by mass of water) as an initiator, and react for 1 h. Then, slowly add an aqueous solution of sodium hydroxide (prepared by dissolving 1 part by mass of sodium hydroxide in 10 parts by mass of water), and after adding 48 parts by mass of isooctyl acrylate, 1 part by mass of acrylic acid and 50 parts by mass of water, add 0.02 parts by mass of 2,2’-bis(2-imidazolin-2-yl)[2,2’-azobispropane] dihydrochloride and react for 2 h to obtain a polymer latex.

[0063] Step 3: Put the polymer latex, 30 wt% hydrogen peroxide solution and 7.5 wt% hydrochloric acid into a beaker at a volume ratio of 2:1:2, stir for 15 min until uniform, then heat to 50 °C and react in an air environment for 1.5 h.

[0064] Step 4: After the reaction is completed, wash the precipitated product with distilled water several times until it becomes neutral, dry it, then put it into a vacuum oven and vacuum dry at 120 °C for 12 h to finally obtain white polymer particles.

[0065] Step 5: Dissolve the particles of the triblock copolymer in Example 1 and the diblock copolymer in this example in butanone at a ratio of 50 / 50, and then use a bar coater to prepare an OCA optical adhesive film for peel strength test with a thickness of about 25 μm.

[0066] The characteristic evaluation of the molecular weight of the polymer and the mechanical property test of the polymer in this example were similar to those in Example 1.

[0067] Compared with Example 1, the peel strength of the block copolymer was improved to 12.21 N / 25 mm. That is, by introducing the functional monomer, the function of the OCA optical adhesive can be further improved.

[0068] The above embodiments do not limit the present invention but are for the purpose of explaining the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the scope of protection of the claims are all included in the scope of protection of the present invention.

Claims

1. It is composed of a main substrate with a mass content of 20 to 100% and a reinforcing substrate with a mass content of 0 to 80%. The structural formula of the main matrix is M １ -b-M ２ -b-M ３ ...-b-M ｊ where the value range of j is 3 to 11, and M １ , M ２ , M ３ ...M ｊ are comonomers of the block copolymer, the number average molecular weight of the block copolymer of the main matrix is 80,000 to 800,000 g / mol, and M １ , M ２ , M ３ ...M ｊ are each selected from a soft monomer, a hard monomer or a functional monomer, and the mass content ratios of the soft monomer, the hard monomer and the functional monomer in the block copolymer are 70 to 98%, 2 to 30% and 0 to 5% respectively, The structural formula of the reinforcing matrix is N １ or N １ -b-N ２ wherein the number average molecular weight of the block copolymer of the reinforcing matrix is 100,000 to 400,000 g / mol, N １ is a soft monomer, N ２ is a hard monomer or a functional monomer, and the mass content ratios of the soft monomer, hard monomer and functional monomer in the block copolymer are 75 to 100%, 0 to 25% and 0 to 5% respectively, and an OCA optical adhesive characterized by the above is provided.

2. The hard monomer includes styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile, and vinyl acetate, and the range of the glass transition temperature is 60 to 150 °C. The soft monomer includes ethyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene-butene, and methacrylic acid, and the range of the glass transition temperature is -90 to -30 °C. The functional monomer includes methacrylic acid, acrylic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxy-1-methylethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, methacrylamide, N-(hydroxymethyl)acrylamide, glycidyl methacrylate, and maleic anhydride. The OCA optical adhesive according to claim 1 is characterized by this.

3. A method for manufacturing the OCA optical adhesive according to claim 1 or 2, (1) After dissolving the amphiphilic polymer reversible addition-fragmentation chain transfer reagent in water, add styrene, or styrene and methacrylic acid, stir until uniformly mixed, add the first initiator at 70 to 90 °C and react for 1 to 3 h to obtain a homopolymer. The homopolymer is stably dispersed in water in the form of particles to form a latex. (2) After adding a 10 wt% aqueous sodium hydroxide solution, add isooctyl acrylate, or isooctyl acrylate and methacrylic acid, then add water, add the second initiator at 40 to 60 °C, set the reaction time to 4 to 10 h in an oxygen-free environment, then add the hard monomer, and react for 5 to 10 h in an oxygen-free environment to obtain a polymer latex of the main substrate. (3) After the reaction is completed, the polymer latex, 30 wt% hydrogen peroxide solution, and 7.5 wt% hydrochloric acid are placed in a beaker at a volume ratio of 2:1:2, stirred for 15 min until homogeneous, then heated to 50 °C and reacted for 1.5 - 3 h. The precipitate product is washed with distilled water until neutral, dried, and then placed in a vacuum oven and vacuum dried at 120 °C for 5 - 20 h to finally obtain the main substrate. (4) The amphiphilic polymer reversible addition-fragmentation chain transfer reagent is stirred and dissolved in water, then styrene, or styrene and methacrylic acid are added, stirred until completely dissolved, the water bath is set at 70 - 90 °C, and then the first initiator is added and reacted for 1 - 3 h to obtain a homopolymer. The homopolymer is stably dispersed in water in particle form to form a latex. (5) After adding a 10 wt% aqueous sodium hydroxide solution, isooctyl acrylate and water are added, then the second initiator is added, the temperature of the water bath is set at 40 - 60 °C, and the reaction time is set at 4 - 10 h under a vacuum environment to obtain the polymer latex of the reinforcing substrate. (6) After the reaction is completed, the polymer latex, 30 wt% hydrogen peroxide solution, and 7.5 wt% hydrochloric acid are placed in a beaker at a volume ratio of 2:1:2, stirred for 15 min until homogeneous, then heated to 40 - 60 °C and reacted for 1.5 - 3 h. The precipitate product is washed multiple times with distilled water until neutral, dried, and then placed in a vacuum oven and vacuum dried at 120 °C for 5 - 20 h to finally obtain the reinforcing substrate. (7) A manufacturing method characterized by including the step of finally obtaining an OCA optical adhesive by dissolving the main substrate and the reinforcing substrate in a dispersion medium, and coating, forming a film, and drying in an argon gas environment.

4. The structural formula of the amphiphilic polymer reversible addition-fragmentation chain transfer reagent is R-(M ｎ１ -b-N ｎ２ )-X, and R is an isopropionic acid group, an acetic acid group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group, M ｎ１ wherein M is a methacrylic acid monomer or an acrylic acid monomer unit, n1 is the average degree of polymerization of M, the range of n1 is 10 to 30, N ｎ２ wherein N is a styrene monomer, a butyl acrylate monomer, methyl acrylate, isooctyl acrylate, or a methyl methacrylate monomer unit, n2 is the average degree of polymerization of N, the range of n2 is 1 to 8, and the X group is an alkyldithioester group or an alkyltrithioester group. The method for producing an OCA optical adhesive according to claim 5, characterized in that.

5. The manufacturing method of the OCA optical adhesive according to Claim 5, wherein the dispersion medium is any one of ethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, and methyl propionate.

6. The first initiators in the steps (1) and (4) are any one of ammonium persulfate, potassium persulfate, hydrogen peroxide and hydrogen peroxide derivatives, and the second initiators in the steps (2) and (5) are 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane]dihydrochloride, 2,2'-azobis(propane-2-carboxamidine)dihydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium bisulfate / potassium persulfate redox initiator and sodium persulfate / ammonium persulfate redox initiator, and the method for producing an OCA optical adhesive according to claim 5 is characterized in that it is any one of them.

7. The method for producing an OCA optical adhesive according to claim 5 is characterized in that the acrylic acid in the steps (1) and (2) can be replaced by any one of other functional monomers.

Images