Thermal shock resistant OCA optical pressure-sensitive adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, and discloses a thermal shock resistant OCA optical pressure-sensitive adhesive and a preparation method thereof. The pressure-sensitive adhesive is prepared from the following raw materials in parts by mass: 70 to 95 parts of prepolymer, 0.01 to 5 parts of cross-linking agent, 5 to 30 parts of thermal shock resistant substance and 0.01 to 2 parts of photoinitiator, the structure of the prepolymer is M1-ran-M2-ran-M3-ran-M4, M1, M2, M3 and M4 are comonomers, and M1 is composed of a hard monomer; m2 is composed of soft monomers; m3 is composed of functional monomers; m4 is composed of a multi-double-bond monomer; the content of the hard monomer in the prepolymer is 0-30%, the content of the soft monomer is 40-99.99%, the content of the functional monomer is 0-40%, and the content of the multi-double-bond monomer is 0.01-5%; the pressure-sensitive adhesive with good mechanical property and rebound resilience is obtained by utilizing the combined action of the multi-double-bond monomer, the cross-linking agent and the heat-resistant impact aid in the block copolymer, and the peel strength change is very small after multiple alternating temperature cycles.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly relates to a heat shock-resistant OCA optical pressure-sensitive adhesive and a preparation method thereof. Background Art

[0002] In modern technological applications, the efficient and stable fixation and easy disassembly of optical devices have become an important issue. However, the use of these optical devices at various ambient temperatures is often affected by temperature changes, resulting in a decrease in the bonding effect, a weakening of the peel strength, and even failure. Therefore, it is of great significance to develop an optical pressure-sensitive adhesive material that can maintain stability in a heat shock temperature environment.

[0003] CN 105694773 A discloses an optical pressure-sensitive adhesive and a preparation method thereof. The optical pressure-sensitive adhesive is composed of 5-30 parts by mass of a first acrylate copolymer solution, 2-10 parts by mass of a second acrylate copolymer solution, 50-90 parts by mass of a third acrylate copolymer solution, 2-10 parts by mass of a fourth acrylate copolymer solution, and 1-5 parts by mass of a curing agent; the number-average molecular weights and glass transition temperatures of the acrylate copolymers in the four acrylate copolymer solutions are not exactly the same. For the optical pressure-sensitive adhesive, through the physical mixing of acrylate copolymers with different molecular weights and different glass transition temperatures, it is beneficial to generate a synergistic effect among the copolymers; through the crosslinking of the curing agent with the same acrylate copolymer and the crosslinking of the curing agent with acrylate copolymers with different structures and properties, the curing efficiency of the optical pressure-sensitive adhesive is effectively improved.

[0004] However, there is no association between the curing agent and the copolymer itself, and the peel strength and heat shock resistance of the product are still insufficient.

[0005] CN 105950081A discloses a pressure-sensitive adhesive resistant to high and low temperature alternation and a preparation method thereof. The pressure-sensitive adhesive resistant to high and low temperature alternation includes 70-95 parts of a soft monomer, 2-20 parts of a hard monomer, 1-10 parts of a modified monomer, 1-30 parts of silicone oil, 0.1-1 part of an initiator, 0.05-1 part of a crosslinking agent, 50-200 parts of a solvent, and 1-30 parts of a tackifying resin. The preparation steps include first mixing the soft monomer, hard monomer, silicone oil, and the first part of the solvent, and heating to 80-90°C; then, dropping a mixed solution composed of an initiating monomer, the first part of the initiator, and the second part of the solvent, and reacting at 80-90°C for 2-4 h; then dropping a mixed solution composed of the second part of the initiator and the third part of the solvent, reacting at 80-90°C for 2-4 h, cooling, and mixing with the crosslinking agent and the tackifying resin. Similarly, it is difficult for the crosslinking agent to combine with the copolymer in a large range, and the mechanical properties and resilience of the product are also unknown. Summary of the Invention

[0006] In view of the problem that the existing OCA optical pressure-sensitive adhesive has poor heat shock resistance and is prone to failure in a repeatedly variable temperature environment, the present invention provides a cross-linked heat shock-resistant OCA optical pressure-sensitive adhesive. By the combined action of multi-double bond monomers in the block copolymer, a cross-linking agent, and a heat shock-resistant auxiliary agent, a pressure-sensitive adhesive with good mechanical properties and resilience is obtained. After multiple alternating temperature cycles, the change in peel strength is very small.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A heat shock-resistant OCA optical pressure-sensitive adhesive, by mass, comprises raw materials: 70-95 parts by mass of a prepolymer, 0.01-5 parts by mass of a cross-linking agent, 5-30 parts by mass of a heat shock-resistant substance, and 0.01-2 parts by mass of a photoinitiator; the heat shock-resistant substance includes one or more of an acrylic resin, an acrylate rubber, and a vinyl silicone resin;

[0009] The prepolymer has a structure of M1-ran-M2-ran-M3-ran-M4, where M1, M2, M3, and M4 are copolymer monomers, M1 is composed of hard monomers; M2 is composed of soft monomers; M3 is composed of functional monomers; M4 is composed of multi-double bond monomers; the content of hard monomers in the prepolymer is 0-30%, the content of soft monomers is 40-99.99%, the content of functional monomers is 0-40%, and the content of multi-double bond monomers is 0.01-5%;

[0010] The preparation method of the OCA optical pressure-sensitive adhesive includes the steps of dissolving the prepolymer in an inert diluent, adding a cross-linking agent, a heat shock-resistant substance, and a photoinitiator, mixing, coating, and photocuring to obtain the OCA optical pressure-sensitive adhesive.

[0011] In the present invention, a prepolymer with multi-double bond monomers in the outer end segment is used, and together with a cross-linking agent and a heat shock-resistant substance, it is photocured to obtain an OCA optical pressure-sensitive adhesive. Among them, the unsaturated double bonds in the prepolymer and the unsaturated double bonds in the heat shock-resistant substance are connected through a cross-linking agent by photocuring. The prepolymer is obtained by solution polymerization with a reversible addition-fragmentation chain transfer reagent, and its molecular weight and molecular structure have controllable characteristics, and the prepared optical adhesive has excellent performance. The heat shock-resistant substance has polar groups and can maintain excellent peel strength performance both at low temperature and high temperature. The two are combined with each other to obtain an OCA optical pressure-sensitive adhesive with excellent heat shock resistance, which can withstand rapid temperature changes without cracking or losing adhesion, thereby improving the reliability and stability of the device, and having good mechanical properties and resilience. After the OCA optical pressure-sensitive adhesive undergoes multiple alternating temperature (-50~90°C) cycles, the fluctuation degree of the peel strength is not large.

[0012] In the present invention, materials such as acrylic resin, acrylate rubber, and vinyl silicone resin used for heat-resistant impact substances, on the one hand, contain double bond structures that can crosslink with the prepolymer, and on the other hand, can provide viscosity for the optical adhesive, enabling it to still have strong peel strength at low and high temperatures. Without addition, it may cause delamination of the optical adhesive at low temperatures and creep of the adhesive layer at high temperatures, resulting in morphological changes.

[0013] Preferably, the content of the hard monomer in the prepolymer is 5 - 30%, the content of the soft monomer is 40 - 84.99%, the content of the functional monomer is 10 - 40%, and the content of the multi-double bond monomer is 0.01 - 5%; the total amount of each monomer is 100%.

[0014] The hard monomer includes any one or more of styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile, and vinyl acetate; the block glass transition temperature range formed by the hard monomer is 60 - 150 °C; the presence of the hard monomer is to supplement the deficiency of cohesive force when the molecular weight of the optical adhesive is low, the content of the functional monomer is low, or the degree of crosslinking is low.

[0015] The soft monomer includes any one or more of ethyl acrylate, 2-propylheptyl acrylate, octyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene-butene, and methacrylic acid; the block glass transition temperature range formed by the soft monomer is -90 - -30 °C; the soft monomer has a low glass transition temperature, and the prepared optical adhesive has low modulus and high flexibility.

[0016] The functional monomer includes any one or more of methacrylic acid, acrylic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, N,N-dimethylaminoethyl methacrylate, methacrylamide, N-hydroxymethylacrylamide, glycidyl methacrylate, and maleic anhydride; appropriate functional monomers can improve the peel strength of the optical adhesive and supplement the problem of insufficient cohesive force.

[0017] The multi-double bond monomer includes 3-cyclohexene-1-ylmethyl acrylate and / or vinylacrylic acid. This monomer contains multiple double bonds and can initiate polymerization under the action of a photoinitiator, thereby crosslinking the prepolymers and crosslinking the unsaturated bonds of the prepolymer with the heat-resistant impact substances, stabilizing the heat-resistant impact performance of the material.

[0018] The prepolymer is prepared by reversible addition-fragmentation chain transfer solution polymerization; the molecular weight of the prepolymer is 0.1 - 100,000 g / mol.

[0019] The crosslinking agent contains one or more hydroxyl groups, carboxyl groups, ether bonds, aldehyde groups or carbonyl active groups. Preferably, the crosslinking agent includes one or more of 1,3-propanedithiol, 2-hydroxyethyl methacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, isobornyl acrylate.

[0020] The non-reactive diluent includes any one or more of acetone, toluene, ethyl acetate, ethyl acetate, xylene, ethyl pyruvate or n-butanol.

[0021] The wavelength of the photocuring is 300 - 400 nm, the energy is 1600 - 3000 mJ / cm 2 , and the photocuring time is 30 - 120 min.

[0022] The present invention also provides a preparation method of the heat-resistant shock OCA optical pressure-sensitive adhesive, which comprises the steps of:

[0023] Step 1, the soft monomer, hard monomer, 1 / 20 - 1 / 2 of the functional monomer, multi-double bond monomer, first initiator, small molecule reversible addition-fragmentation chain transfer reagent are dissolved in the reaction solvent and stirred until mixed, and the temperature of the system is raised to 60 - 90 °C and reacted for 5 - 15 h;

[0024] Step 2, the remaining functional monomer is added dropwise to the reaction solution in Step 1, the first initiator and the reaction solvent are added additionally, the dropping time is controlled within 1 - 10 h, and after the dropping is completed, the reaction is continued under heat preservation for 4 - 10 h;

[0025] Step 3, the first initiator and the reaction solvent are added dropwise to the reaction solution in Step 1, the dropping time is controlled to be 1 - 10 h, and after the dropping is completed, the reaction is continued under heat preservation for 2 - 10 h; after the system is naturally cooled, it is poured into a precipitant for precipitation, washed, dried in the air, and dried to obtain a prepolymer;

[0026] Step 4, the prepolymer is dissolved in the non-reactive diluent, the crosslinking agent, heat-resistant shock substance, photoinitiator are added and mixed, then coated and photocured to obtain the OCA optical pressure-sensitive adhesive.

[0027] The present invention adopts a chemical crosslinking method by photocuring between the prepolymer obtained by reversible addition-fragmentation chain transfer solution polymerization and the heat-resistant shock substance. First, the hard monomer, soft monomer, functional monomer, multi-double bond monomer, initiator and reaction solvent are mixed and polymerized to obtain a prepolymer. In order to enhance the alternating temperature resistance characteristics, the unsaturated double bonds in the heat-resistant shock substance and the unsaturated double bonds in the prepolymer are crosslinked under the action of a crosslinking agent and a photoinitiator, thereby obtaining a heat-resistant shock optical pressure-sensitive adhesive.

[0028] The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is: R-X; wherein, R is isopropyl acid group, acetic acid group, 2-cyanoacetic acid group or 2-aminoacetic acid group; the X group is an alkyl dithiocarbonate group or an alkyl trithiocarbonate group; the mass of the small molecule reversible addition-fragmentation chain transfer reagent is 1 / 100 - 1 / 10 of the total mass of the comonomers.

[0029] The first initiator is any one or more of azobisisobutimidazoline hydrochloride, azobisisobutyramidine hydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium persulfate / potassium persulfate redox initiator and sodium persulfate / ammonium persulfate redox initiator.

[0030] The reaction solvent is dioxane;

[0031] The precipitating agent includes one or several of methanol, ethanol, acetone, methyl ethyl ketone, nitromethane, methyl phthalate, hexane, chlorohexane, ether, aliphatic hydrocarbon, aromatic hydrocarbon, ethyl acetate, dioxane, cyclohexanol, fatty alcohol, petroleum ether, cyclohexane, tetrahydrofuran and water.

[0032] The photoinitiator includes one or more of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, BASF IRGACURE 184, LUCIRIN TPO, IRGACURE 819, α-hydroxyacetophenone and dialkoxyacetophenone;

[0033] The molar mass of the first initiator is 1 / 50 - 1 of the molar mass of the small molecule reversible addition-fragmentation chain transfer reagent.

[0034] The total amount of the reaction solvent used is 1 - 10 times the total mass of all the comonomers. During the reaction process, the solid content of the system is maintained between 10% and 50%.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The heat-resistant OCA optical pressure-sensitive adhesive of the present invention utilizes the combined action of multi-double bond monomers, cross-linking agents and heat-resistant shock auxiliaries in the block copolymer to obtain a pressure-sensitive adhesive with good mechanical properties and resilience. Its core feature is that it can maintain and improve the peel strength after experiencing alternating environments after multiple alternating temperature cycles. The performance requirements of the adhesive should be stable at different temperatures, which can not only achieve firm bonding at low temperatures, but also be easily peeled off at high temperatures, so as to meet the requirements in various application scenarios, and provide a new solution for the stability and reliability of optical devices in diverse applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1GPC curve of the prepolymer prepared in Example 1.

[0038] Figure 2 Peeling strength result graph of the OCA optical pressure-sensitive adhesive prepared in Example 1 and Comparative Example 1.

[0039] Figure 3 DMA curve of the OCA optical pressure-sensitive adhesive prepared in Example 1.

[0040] Figure 4 Optical property graph of the OCA optical adhesive prepared in Examples 1-3 and Comparative Example 1. Detailed implementation mode

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Those skilled in the art who make modifications or equivalent replacements on the basis of understanding the technical solutions of the present invention, without departing from the spirit and scope of the technical solutions of the present invention, shall all be covered by the protection scope of the present invention.

[0042] The raw materials used in the following detailed implementation modes are all purchased from the market.

[0043] Example 1

[0044] A heat-resistant impact OCA optical pressure-sensitive adhesive, the raw material composition formula of which is: 70 parts by mass of prepolymer, 0.01 part by mass of 1,3-propanedithiol, 5 parts by mass of acrylic resin, 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone. In this example, the RAFT reversible addition-fragmentation chain transfer solution polymerization method and photocuring are used for material preparation, and the specific steps are as follows:

[0045] First step: Dissolve all 70 parts by mass of isooctyl acrylate, 10 parts by mass of styrene, 1 part by mass of acrylic acid, 1 part of 3-cyclohexene-1-methylene acrylate, 0.04 part by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 0.01 part by mass of a small molecule reversible addition-fragmentation chain transfer reagent in 100 parts by mass of dioxane and stir until evenly mixed, then heat up to 60°C. The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is as follows:

[0046]

[0047] Second step: Slowly dropwise add 20 parts by mass of acrylic acid, 0.04 part by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 50 parts by mass of dioxane, control the dropping time within 10 h, and continue to keep warm for 4 h after the dropping is completed.

[0048] Step 3: dropwise add the remaining 0.04 parts by mass of azobisisobutylimidazoline hydrochloride and 50 parts by mass of dioxane, control the dropping time to be 1 hour, and continue to keep warm for 10 hours after the dropping is completed.

[0049] Step 4: Cool the system naturally to about 50°C, slowly pour the solution into n-hexane to precipitate, repeatedly wash, stir and crush until it becomes fine sand, then put it into a mortar and dry it in a fume hood, and vacuum dry it at 35°C to obtain a flour-like yellow powder, which is the prepolymer.

[0050] Step 5: Dissolve 70 parts by mass of the prepolymer in 75 parts by mass of ethyl acetate, add 0.1 parts by mass of 1,3-propanedithiol, 0.1 parts by mass of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone and acrylic resin (0-30 parts by mass) (0 part as comparative example 1, and the others are added with 5 parts, 15 parts and 30 parts respectively) and stir well, and then coat the heavy release film with a coating machine, with a wavelength of 300nm and an energy of 3000mJ / cm 2 , the photocuring time is 30 minutes, and finally the OCA optical pressure-sensitive adhesive film is obtained.

[0051] The molecular weight of the polymers was characterized by gel permeation chromatography (GPC) using a Waters 1525-2414-717 instrument with tetrahydrofuran as the eluent and calibration using narrow distribution polystyrene standards.

[0052] The peel strength of the polymer was tested by an adhesive shear strength tester (KJ-1066A). The OCA optical pressure-sensitive adhesive film in the fifth step was cut into strips with a width of 25 mm and a length of about 300 mm. The peel strength data was measured before and after 5 cycles of alternating temperatures (-40 to 80°C). The heating or cooling rate was 5°C / min. The test method adopted GB / T2792-2014, and the test of each sample was repeated at least three times.

[0053] Figure 1 This is the GPC curve of the prepolymer obtained after the reaction. It can be seen that the molecular weight is 40,000 g / mol and the molecular weight distribution is 4.5.

[0054] Figure 2 The peel strength data of this embodiment shows that when the film thickness is 25 μm, in the comparative example 1 without adding the heat-resistant shock material, the peel strength of the colloid decreases significantly after the alternating temperature. However, after adding the heat-resistant shock material, the peel strength of the OCA optical pressure-sensitive adhesive film does not decrease significantly after 5 times of the alternating temperature. With the increase of the added amount, the peel strength increases, which shows the stability of the peel strength under the alternating temperature environment.

[0055] Figure 3DMA curves of the acrylic resin without addition and with 5 parts addition in this example. It can be seen that after adding the heat shock resistant substance, as the temperature increases, the modulus of the optical adhesive does not decrease significantly.

[0056] Table 1 shows the properties of the optical adhesive after adding different parts by mass of acrylic acid. With the addition of acrylic resin, the properties such as modulus, stress, elongation at break, and strain recovery rate change little, mainly because there is no obvious change in the photoinitiator, crosslinking agent, and photocuring conditions in the formulation. The peel strength of the optical adhesive shows a slight increase, mainly because the polar monomer content in the heat shock resistant substance is relatively high, which can improve the peel strength. Compared with Comparative Example 1 without any heat shock resistant substance, adding different amounts of acrylic resin can improve the heat shock resistance of the optical adhesive.

[0057] Table 1 Properties of the optical adhesive prepared with different dosages of heat shock resistant substances

[0058]

[0059]

[0060] Example 2:

[0061] A heat shock resistant OCA optical pressure-sensitive adhesive, whose formulation is: 85 parts by mass of prepolymer, 0.01 - 2 parts by mass of 1,3-propanedithiol, 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 10 parts by mass of acrylic resin. In this example, the RAFT reversible addition-fragmentation chain transfer solution polymerization method and photocuring are used for material preparation. The specific steps are as follows:

[0062] First step: Dissolve 60 parts by mass of isooctyl acrylate, 10 parts by mass of 2-propylheptyl acrylate, 5 parts by mass of styrene, 2 parts by mass of acrylic acid, 1 part of 3-cyclohexene-1-ylmethylene acrylate, 0.04 part by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 0.01 part by mass of a small molecule reversible addition-fragmentation chain transfer reagent in 100 parts by mass of dioxane, stir until evenly mixed, and heat up to 60 °C. The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is as follows:

[0063]

[0064] Second step: Slowly dropwise add 15 parts by mass of acrylic acid, 0.04 part by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 50 parts by mass of dioxane. Control the dropping time within 10 h. After the dropping is completed, continue to keep warm for 4 h.

[0065] Third step: Dropwise add the remaining 0.04 part by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 100 parts by mass of dioxane. Control the dropping time to be 1 h. After the dropping is completed, continue to keep warm for 10 h.

[0066] Step 4: Cool the system naturally to about 50°C, slowly pour the solution into ethanol to precipitate, repeatedly wash, stir and crush until it becomes fine sand, then put it into a mortar and dry it in a fume hood, and vacuum dry it at 35°C to obtain a flour-like yellow powder, which is the prepolymer.

[0067] Step 5: Dissolve 85 parts by mass of the prepolymer in 75 parts by mass of ethyl acetate, add 0-2 parts by mass of 1,3-propanedithiol (0 part is for comparative example 2, and the others are added with 0.01 parts, 0.05 parts, 1 parts and 2 parts respectively), 0.1 parts by mass of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, and 10 parts by mass of acrylic resin, stir well, and then coat the heavy release film with a coating machine, and cure with light at a wavelength of 300nm and an energy of 3000mJ / cm 2 , time is 30min, and finally the OCA optical pressure-sensitive adhesive film is obtained.

[0068] Table 2 shows the performance of OCA optical pressure-sensitive adhesives obtained by adding different weight parts of crosslinking agents. With the increase of crosslinking, the performance of the optical adhesive generally shows a trend of first optimizing and then decreasing, and the performance is excellent when the addition amount is 0.05 weight parts. This is because when the amount of crosslinking agent added is small, the light curing is insufficient, and the cohesion of the optical adhesive is insufficient, resulting in a decrease in the overall performance of the optical adhesive. When the amount of crosslinking agent added is large, the degree of crosslinking is too high, resulting in an increase in modulus, which leads to a decrease in the performance of the optical adhesive.

[0069] Table 2 Properties of optical adhesives prepared with different crosslinking agents

[0070]

[0071] Embodiment 3:

[0072] A heat-shock-resistant OCA optical pressure-sensitive adhesive, the formula of which is: 95 parts by mass of prepolymer, 0.1 parts by mass of 1,3-propanedithiol, 0.1 parts by mass of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, and 10 parts by mass of vinyl silicone resin, acrylic resin or acrylate rubber. This embodiment adopts RAFT reversible addition fragmentation chain transfer solution polymerization method and light curing to prepare the material, and the specific steps are as follows:

[0073] Step 1: Dissolve 60 parts by mass of isooctyl acrylate, 20 parts by mass of 2-propylheptyl acrylate, 10 parts by mass of octyl acrylate, 5 parts by mass of styrene, 3 parts by mass of methyl acrylate, 2 parts by mass of acrylic acid, 1 part of 3-cyclohexene-1-methylene acrylate, 0.04 parts by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 0.01 parts by mass of a small molecule reversible addition-fragmentation chain transfer agent in 100 parts by mass of dioxane, stir until evenly mixed, and heat up to 60 °C. The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer agent is as follows:

[0074]

[0075] Step 2: Slowly dropwise add 10 parts by mass of acrylic acid, 8 parts by mass of 2-hydroxyethyl acrylate, 0.04 parts by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 50 parts by mass of dioxane. Control the dropping time within 10 h. After the dropping is completed, continue to keep warm for 4 h.

[0076] Step 3: Dropwise add the remaining 0.04 parts by mass of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 100 parts by mass of dioxane, control the dropping time to be 1 h. After the dropping is completed, continue to keep warm for 10 h.

[0077] Step 4: Naturally cool the system to about 50 °C, slowly pour the solution into ethanol for precipitation, repeatedly wash, stir, and roll it into a fine sand shape, then put it into a mortar and dry it in a fume hood, and then vacuum dry it at 35 °C to obtain a yellow powder in the shape of flour, which is the prepolymer.

[0078] Step 5: Dissolve 95 parts by mass of the prepolymer in 85 parts by mass of ethyl acetate, add 0.1 parts by mass of 1,3-propanedithiol, 0.1 parts by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 10 parts by mass of vinyl silicone resin, acrylic resin or acrylate rubber, stir well, then coat on a heavy release film through a coating machine, and carry out photocuring with a wavelength of 300 nm and an energy of 3000 mJ / cm 2 , for a time of 30 min, and finally obtain an OCA optical pressure-sensitive adhesive film.

[0079] The molecular weight characterization of the polymer in this example and the test of the peel strength performance of the polymer are similar to those in Example 1.

[0080] Table 3 shows the performance of the optical adhesive prepared by adding different heat shock substances. Different heat-resistant substances have little effect on the performance of the optical adhesive. After alternating temperature, they can all maintain good peel strength performance.

[0081] Table 3 Performance of the optical adhesive with different heat shock substances added

[0082]

[0083]

[0084] Figure 4 Transmittance data for Examples 1 - 3 and Comparative Example 1, where Example 1 refers to the case when 5 parts of heat - shock - resistant substance are added, Example 2 refers to the case when 0.05 parts of cross - linker are added, and Example 3 refers to the case when vinyl silicone resin is added. The transmittance of each optical adhesive is greater than 99%, and it has good optical properties. The addition of the heat - shock - resistant substance does not affect the light transmittance of the colloid.

[0085] The above - mentioned examples are used to explain the present invention rather than limit the present invention. Any modification and change made within the spirit of the present invention and the scope of the claims fall within the protection scope of the present invention.

Claims

1. A heat-resistant shock OCA optical pressure-sensitive adhesive, characterized in that, By mass parts, it includes raw materials: 70 - 95 mass parts of prepolymer, 0.01 - 5 mass parts of crosslinking agent, 5 - 30 mass parts of heat shock resistant substance, 0.01 - 2 mass parts of photoinitiator; the heat shock resistant substance includes one or more of acrylic resin, acrylate rubber, vinyl silicone resin; The prepolymer structure is M1-ran-M2-ran-M3-ran-M4, where M1, M2, M3 and M4 are comonomers, M1 is composed of hard monomers; M2 is composed of soft monomers; M3 is composed of functional monomers; M4 is composed of multi-double bond monomers; the content of hard monomers in the prepolymer is 0 - 30%, the content of soft monomers is 40 - 99.99%, the content of functional monomers is 0 - 40%, and the content of multi-double bond monomers is 0.01 - 5%; The preparation method of the OCA optical pressure - sensitive adhesive includes the steps: dissolving the prepolymer in an inert diluent, adding a crosslinking agent, a heat shock resistant substance and a photoinitiator, mixing and then coating and photocuring to obtain the OCA optical pressure - sensitive adhesive.

2. The heat-shock resistant OCA optical pressure-sensitive adhesive according to claim 1, wherein The hard monomers include any one or more of styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile and vinyl acetate, and the block glass transition temperature range formed by the hard monomers is 60 - 150 °C; The soft monomers include any one or more of ethyl acrylate, 2 - propylheptyl acrylate, octyl acrylate, n - butyl acrylate, isobutyl acrylate, tert - butyl acrylate, isooctyl acrylate, n - butyl methacrylate, isobutyl methacrylate, tert - butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene - butene and methacrylic acid, and the block glass transition temperature range formed by the soft monomers is - 90 - - 30 °C; The functional monomers include any one or more of methacrylic acid, acrylic acid, itaconic acid, 2 - hydroxyethyl acrylate, 2 - hydroxypropyl acrylate, 2 - hydroxyethyl methacrylate, 2 - hydroxypropyl methacrylate, N, N - dimethylaminoethyl methacrylate, methacrylamide, N - hydroxymethylacrylamide, glycidyl methacrylate and maleic anhydride; The multi - double bond monomers include 3 - cyclohexene - 1 - methylene acrylate and / or vinyl acrylic acid.

3. The heat-resistant shock OCA optical pressure-sensitive adhesive according to claim 1, wherein The prepolymer is prepared by reversible addition - fragmentation chain transfer solution polymerization; the molecular weight of the prepolymer is 0.1 - 100,000 g / mol.

4. The heat-shock resistant OCA optical pressure-sensitive adhesive according to claim 1, wherein, The crosslinking agent includes one or more of 1,3 - propanedithiol, 2 - hydroxyethyl methacrylate, 1,6 - hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, isobornyl acrylate.

5. The heat-resistant shock OCA optical pressure-sensitive adhesive according to claim 1, characterized in that, The photoinitiator includes one or more of 2 - hydroxy - 4′-(2 - hydroxyethoxy)-2 - methylpropiophenone, BASF IRGACURE 184, LUCIRIN TPO, IRGACURE 819, α - hydroxyacetophenone and dialkoxyacetophenone; The inert diluent includes any one or more of acetone, toluene, ethyl acetate, ethyl acetate, xylene, ethyl pyruvate or n - butanol.

6. The heat-resistant shock OCA optical pressure-sensitive adhesive according to claim 1, characterized in that, The wavelength of the photocuring is 300 - 400 nm, and the energy is 1600 - 3000 mJ / cm 2 , and the photocuring time is 30 - 120 min.

7. The preparation method of the heat-resistant shock OCA optical pressure-sensitive adhesive according to any one of claims 1-6, characterized in that, It will include the steps: Step 1: The soft monomer, hard monomer, 1 / 20 - 1 / 2 of the functional monomer, multi-double bond monomer, first initiator, and small molecule reversible addition-fragmentation chain transfer reagent are dissolved in the reaction solvent and stirred until mixed. The temperature of the system is raised to 60 - 90 °C and reacted for 5 - 15 h; Step 2: The remaining functional monomer is added dropwise to the reaction solution of Step 1, and the first initiator and reaction solvent are supplemented. The dropping time is controlled within 1 - 10 h. After the dropping is completed, the reaction is continued under heat preservation for 4 - 10 h; Step 3: The first initiator and reaction solvent are added dropwise to the reaction solution of Step 1. The dropping time is controlled to be 1 - 10 h. After the dropping is completed, the reaction is continued under heat preservation for 2 - 10 h; After the system is naturally cooled, it is poured into the precipitant for precipitation, washed, dried in air, and dried to obtain the prepolymer; Step 4: The prepolymer is dissolved in the non-reactive diluent, and the crosslinking agent, heat shock-resistant substance, and photoinitiator are added. After mixing, it is coated and photocured to obtain the OCA optical pressure-sensitive adhesive.

8. The preparation method of the heat-resistant shock OCA optical pressure-sensitive adhesive according to claim 7, characterized in that, The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is: R-X; wherein, R is isopropyl acid group, acetic acid group, 2-cyanoacetic acid group or 2-aminoacetic acid group; the X group is an alkyl dithiocarbonate group or an alkyl trithiocarbonate group; The mass of the small molecule reversible addition-fragmentation chain transfer reagent is 1 / 100 - 1 / 10 of the total mass of the copolymerizable monomers.

9. The preparation method of the heat-resistant shock OCA optical pressure-sensitive adhesive according to claim 7, wherein The first initiator is any one or more of 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methylpropionamidine) hydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium persulfate / potassium persulfate redox initiator, and sodium persulfate / ammonium persulfate redox initiator; The reaction solvent is dioxane; The precipitant includes one or several of methanol, ethanol, acetone, methyl ethyl ketone, nitromethane, methyl phthalate, hexane, chlorohexane, ether, aliphatic hydrocarbon, aromatic hydrocarbon, ethyl acetate, dioxane, cyclohexanol, aliphatic alcohol, petroleum ether, cyclohexane, tetrahydrofuran, and water.

10. The preparation method of the heat-resistant impact OCA optical pressure-sensitive adhesive according to claim 7, characterized in that, The molar mass of the first initiator is 1 / 50 - 1 times the molar mass of the small molecule reversible addition-fragmentation chain transfer reagent; The total amount of the reaction solvent used is 1 - 10 times the total mass of all the copolymerizable monomers.

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