Optical adhesive with low curing shrinkage and high thermal conductivity and preparation method thereof

Abstract

The application provides an optical adhesive with low curing shrinkage and high thermal conductivity and a preparation method thereof. Modified nanoparticles, a catalyst and a polymerization inhibitor are dispersed to form a prepolymer, the prepolymer, an active diluent and a photoinitiator are uniformly mixed to form a glue solution, and the glue solution is coated on a film and then cured by ultraviolet light to obtain the optical adhesive with low curing shrinkage and high thermal conductivity. The method is simple, reduces the oxygen inhibition during UV curing, reduces the curing shrinkage and improves the thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an optical adhesive with low curing shrinkage and high thermal conductivity, and its preparation method. Background Technology

[0002] With the development of the electronics industry, the requirements for displays are becoming increasingly stringent. The optical films in displays are bonded together with optical adhesives, which must meet requirements such as high light transmittance, no delamination, and no air bubbles.

[0003] Existing optical adhesives are mainly polyurethane or rubber-modified acrylic optical adhesives and silicone optical adhesives (Optoelectronics Technology, 2020, 40(04):251-257.). Among them, acrylic optical adhesives have a large curing shrinkage rate during UV curing, which can reach 1-3%. This leads to uneven edges of the bonded optical film and yellow spots on the display screen. In order to improve the heat dissipation efficiency of displays (such as mobile phones), optical adhesives also need to have a certain thermal conductivity.

[0004] Therefore, there is an urgent need to develop a new type of optical adhesive with excellent properties such as low curing shrinkage, rapid curing, high light transmittance and high thermal conductivity using a simple and quick method. Summary of the Invention

[0005] The first objective of this invention is to address the shortcomings in the field by establishing a low-cost and simple method for preparing optical adhesives that maintain high light transmittance while reducing curing shrinkage and improving thermal conductivity. This invention proposes a method for preparing optical adhesives with low curing shrinkage and high thermal conductivity.

[0006] A method for preparing an optical adhesive with low curing shrinkage and high thermal conductivity, employing the following technical solution:

[0007] Step (1) Nanoparticle modification

[0008] A titanate coupling agent is dissolved in toluene, and then nanoparticles and low molecular weight olefins are added. The mixture is stirred at 50-60℃ for 2-3 hours for modification. The product is washed with water and acetone in sequence, then dried and pulverized to obtain modified nanoparticles. The nanoparticles are one of zirconium dioxide, titanium dioxide, aluminum trioxide or aluminum nitride. The low molecular weight olefins are liquid styrene-butadiene rubber with a molecular weight of less than 1000 or C5-C9 cyclic olefins and their derivatives.

[0009] Step (2) Raw material dehydration

[0010] The modified nanoparticles, monomer A, catalyst, polymerization inhibitor, monomer B, reactive diluent, and photoinitiator are dehydrated and dried. Monomer A is one of toluene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate. The catalyst is an organotin catalyst. The polymerization inhibitor is one of p-hydroxyanisole, tert-butylhydroquinone, or di-tert-butylhydroquinone. Monomer B is one of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid, or glycidyl methacrylate.

[0011] Step (3), Preparation of prepolymer

[0012] 3-1 0.05-5 parts by weight (mass ratio) of the modified nanoparticles obtained in step (1) were ultrasonically dispersed in 100 parts by weight of monomer A, and kept at 35-45℃ under N2 atmosphere to obtain dispersion A;

[0013] 3-2 Dissolve and disperse the catalyst and polymerization inhibitor in 10-50 parts by weight of monomer B, and slowly drop it into dispersion A under N2 atmosphere. Stir and polymerize at 40-50℃ for 1.5-2.5h to obtain dispersion B;

[0014] 3-3 Then, the catalyst and polymerization inhibitor are dissolved and dispersed in 10-50 parts by weight of monomer B, and slowly dripped into dispersion B under N2 atmosphere, and stirred and polymerized at 60-70℃ for 1.5-2.5h;

[0015] Step (4) Preparation of optical adhesive

[0016] Mix 100 parts by weight of the prepolymer synthesized in step (3), 20-40 parts by weight of the reactive diluent, and 0.3-2 parts by weight of the photoinitiator evenly to form a glue solution, thereby obtaining an optical adhesive with low curing shrinkage and high thermal conductivity.

[0017] Preferably, the titanate coupling agent is tetraisopropyl di(dioctylphosphite) titanate.

[0018] Preferably, the low molecular weight olefin is liquid styrene-butadiene rubber or 1,4-cyclohexadiene with a molecular weight of less than 1000.

[0019] Preferably, the nanoparticles are zirconium dioxide or aluminum nitride, with a size of 20-100 nm, and are added in an amount of 0.2-2 parts by weight.

[0020] Preferably, monomer A is isophorone diisocyanate or dicyclohexylmethane diisocyanate.

[0021] Preferably, the catalyst is one of dibutyltin dilaurate, di(dodecyl sulfide)dibutyltin, dibutyltin diacetate, and stannous octoate; more preferably, the catalyst is dibutyltin dilaurate or di(dodecyl sulfide)dibutyltin, and the amount of catalyst added in steps 3-2 and 3-3 is 0.1-0.5 parts by weight.

[0022] Preferably, the polymerization inhibitor is p-hydroxyanisole, and the amount of the catalyst and the polymerization inhibitor added in steps 3-2 and 3-3 is 0.02-0.1 parts by weight respectively.

[0023] Preferably, monomer B is 2-ethylhexyl methacrylate or glycidyl methacrylate, and the amount of monomer B added in steps 3-2 and 3-3 is 15-30 parts by weight, respectively.

[0024] Preferably, the reactive diluent is one of isobornyl methacrylate, ethylene glycol diacrylate, 2-hydroxydimethylacetylbenzene, or 1,6-hexanediol diacrylate; more preferably, the reactive diluent is isobornyl methacrylate.

[0025] Preferably, the photoinitiator is one of 4-acryloyloxybenzophenone, trimethylbenzoyl-diphenylphosphine oxide, dimethoxydiphenylethynyl ketone, trimethylbenzoyldiphenyloxyphosphate, or hydroxycyclohexylbenzophenone; more preferably, the photoinitiator is 4-acryloyloxybenzophenone or hydroxycyclohexylbenzophenone, and the amount of the photoinitiator added is 0.3-1 parts by weight.

[0026] The second objective of this invention is to provide an optical adhesive with low curing shrinkage and high thermal conductivity, which is prepared using the method described above.

[0027] The third objective of this invention is to provide an optical adhesive film prepared by coating the above-mentioned optical adhesive onto a substrate and then curing it with ultraviolet light.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. The method used in this invention uses a titanate coupling agent containing phosphoryloxy groups, which has antioxidant properties and can reduce oxygen inhibition during UV adhesive curing.

[0030] 2. The method employed in this invention can reduce the curing shrinkage rate of the prepared optical adhesive in multiple ways: by adjusting the content of acrylic acid segments in the prepolymer, the curing shrinkage rate is reduced; by controlling the molecular weight of the prepolymer, the prepolymer content in the optical adhesive before curing is increased, reducing the amount of reactive diluent used, thereby reducing the curing shrinkage rate; by grafting oligomers with cyclic side chains onto nanoparticles, the irregular structure of the oligomers can synergistically increase the free volume of the nanoparticles, change the degree of microphase separation during the curing of the optical adhesive, and at the same time act as stress concentration points, improving the stress unevenness during the curing of the optical adhesive, thereby reducing the curing shrinkage rate.

[0031] 3. The method used in this invention improves the thermal conductivity of the optical adhesive by adding nanoparticles.

[0032] 4. The optical adhesive prepared by the method of this invention does not contain VOCs, and the production process is relatively environmentally friendly.

[0033] 5. The method used in this invention is simple to operate and has good repeatability. Detailed Implementation

[0034] The invention will be more fully understood through the following detailed description. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary and the invention can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0035] This invention provides an optical adhesive with low curing shrinkage and high thermal conductivity, and a method for its preparation.

[0036] Example 1:

[0037] 0.1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 100 mL of toluene, and then 1 g of 30 nm zirconium dioxide and 2 g of 1,4-cyclohexadiene were added. The mixture was stirred at 50 °C for 3 h to obtain modified zirconium dioxide. The modified zirconium dioxide was washed successively with water and acetone, then dried and pulverized.

[0038] All raw materials were dried in a vacuum oven for 12 hours before use.

[0039] 0.3 g of modified zirconium dioxide was ultrasonically dispersed in 100 g of isophorone diisocyanate and kept at 35 °C under N2 atmosphere to obtain dispersion A. 0.2 g of dibutyltin dilaurate and 0.05 g of p-hydroxyanisole were dissolved and dispersed in 30 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 50 °C for 1.5 h to obtain dispersion B. After the addition was complete, 0.2 g of dibutyltin dilaurate and 0.05 g of p-hydroxyanisole were dissolved and dispersed in 30 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 60 °C for 2 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 534, a weight-average molecular weight of 1045, and a distribution ratio of 1.96.

[0040] Take 100g of prepolymer, 30g of isobornyl methacrylate, and 0.5g of hydroxycyclohexylbenzophenone, and mix them evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0041] The final optical adhesive had a curing shrinkage rate of 0.92%, a bond strength of 0.45 MPa, a thermal conductivity of 0.28 W / (m·K), and a light transmittance of 98.2%.

[0042] Example 2:

[0043] 0.5 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 500 mL of toluene, and then 5 g of 30 nm aluminum nitride and 10 g of liquid styrene-butadiene rubber were added. The mixture was stirred at 60 °C for 2 h to obtain aluminum nitride. The modified aluminum nitride was washed successively with water and acetone, then dried and pulverized.

[0044] All raw materials were dried in a vacuum oven for 12 hours before use.

[0045] 0.8 g of modified aluminum nitride was ultrasonically dispersed in 100 g of dicyclohexylmethane diisocyanate and kept at 45 °C under N2 atmosphere to obtain dispersion A. 0.1 g of bis(dodecylsulfide)dibutyltin and 0.02 g of tert-butylhydroquinone were dissolved and dispersed in 10 g of glycidyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 50 °C for 2.5 h to obtain dispersion B. After the addition was complete, another 0.1 g of bis(dodecylsulfide)dibutyltin and 0.02 g of tert-butylhydroquinone were dissolved and dispersed in 10 g of glycidyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 70 °C for 1.5 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 356, a weight-average molecular weight of 741, and a distribution of 2.08.

[0046] Mix 100g of prepolymer, 20g of isobornyl methacrylate, and 0.3g of 4-acryloyloxybenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0047] The final optical adhesive had a curing shrinkage rate of 0.78%, a bond strength of 0.45 MPa, a thermal conductivity of 0.31 W / (m·K), and a light transmittance of 98.2%.

[0048] Example 3:

[0049] 0.1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 100 mL of toluene, and then 1 g of 100 nm titanium dioxide and 2 g of 1,4-cyclohexadiene were added. The mixture was stirred at 60 °C for 2.5 h to obtain modified titanium dioxide. The modified titanium dioxide was washed successively with water and acetone, then dried and pulverized.

[0050] All raw materials were dried in a vacuum oven for 12 hours before use.

[0051] 0.2 g of modified titanium dioxide was ultrasonically dispersed in 100 g of hexamethylene diisocyanate and kept at 40 °C under N2 atmosphere to obtain dispersion A. 0.3 g of dibutyltin dilaurate and 0.1 g of p-hydroxyanisole were dissolved and dispersed in 30 g of glycidyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 40 °C for 2 h to obtain dispersion B. After the addition was complete, 0.3 g of dibutyltin dilaurate and 0.1 g of p-hydroxyanisole were dissolved and dispersed in 30 g of glycidyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 60 °C for 2 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 738, a weight-average molecular weight of 1489, and a distribution of 2.02.

[0052] Mix 100g of prepolymer, 40g of 1,6-hexanediol diacrylate, and 0.7g of hydroxycyclohexylbenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a doctor blade, and then cure the optical adhesive with ultraviolet light.

[0053] The final optical adhesive had a curing shrinkage rate of 1.15%, a bond strength of 0.43 MPa, a thermal conductivity of 0.25 W / (m·K), and a light transmittance of 98.2%.

[0054] Example 4:

[0055] 0.5 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 500 mL of toluene, and then 5 g of 50 nm zirconium dioxide and 10 g of liquid styrene-butadiene rubber were added. The mixture was stirred at 60 °C for 3 h to obtain modified zirconium dioxide. The modified zirconium dioxide was washed with water and acetone in sequence, then dried and pulverized.

[0056] All raw materials were dried in a vacuum oven for 12 hours before use.

[0057] 1 g of modified zirconium dioxide was ultrasonically dispersed in 100 g of isophorone diisocyanate and kept at 45 °C under N2 atmosphere to obtain dispersion A. 0.5 g of di(dodecyl sulfide)dibutyltin and 0.04 g of tert-butylhydroquinone were dissolved and dispersed in 15 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 40 °C for 2 h to obtain dispersion B. After the addition was complete, another 0.5 g of di(dodecyl sulfide)dibutyltin and 0.04 g of tert-butylhydroquinone were dissolved and dispersed in 15 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 70 °C for 2.5 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 826, a weight-average molecular weight of 1647, and a distribution ratio of 1.99.

[0058] Mix 100g of prepolymer, 20g of isobornyl methacrylate, and 0.3g of 4-acryloyloxybenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0059] The final optical adhesive had a curing shrinkage rate of 0.71%, a bond strength of 0.46 MPa, a thermal conductivity of 0.32 W / (m·K), and a light transmittance of 98.2%.

[0060] Example 5:

[0061] 1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 1000 mL of toluene, and then 10 g of 10 nm aluminum nitride and 20 g of 1,4-cyclohexadiene were added. The mixture was stirred at 50 °C for 2 h to obtain modified aluminum nitride. The modified aluminum nitride was washed successively with water and acetone, then dried and pulverized.

[0062] All raw materials were dried in a vacuum oven for 12 hours before use.

[0063] 3g of modified aluminum nitride was ultrasonically dispersed in 100g of hexamethylene diisocyanate and kept at 40℃ under N2 atmosphere to obtain dispersion A. 0.2g of dibutyltin dilaurate and 0.03g of p-hydroxyanisole were dissolved and dispersed in 20g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 50℃ for 2.5h to obtain dispersion B. After the addition was complete, 0.2g of dibutyltin dilaurate and 0.03g of p-hydroxyanisole were dissolved and dispersed in 20g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 60℃ for 2.5h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 617, a weight-average molecular weight of 1246, and a distribution ratio of 2.02.

[0064] Mix 100g of prepolymer, 30g of isobornyl methacrylate, and 0.7g of hydroxycyclohexylbenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0065] The final optical adhesive had a curing shrinkage rate of 0.89%, a bond strength of 0.47 MPa, a thermal conductivity of 0.35 W / (m·K), and a light transmittance of 98.1%.

[0066] Example 6:

[0067] 0.1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 100 mL of toluene, and then 1 g of 30 nm titanium dioxide and 2 g of liquid styrene-butadiene rubber were added. The mixture was stirred at 50 °C for 3 h to obtain modified titanium dioxide. The modified titanium dioxide was washed successively with water and acetone, then dried and pulverized.

[0068] All raw materials were dried in a vacuum oven for 12 hours before use.

[0069] 0.1 g of modified titanium dioxide was ultrasonically dispersed in 100 g of dicyclohexylmethane diisocyanate and kept at 35 °C under N2 atmosphere to obtain dispersion A. 0.4 g of di(dodecyl sulfide)dibutyltin and 0.05 g of tert-butylhydroquinone were dissolved and dispersed in 40 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 40 °C for 2 h to obtain dispersion B. After the addition was complete, 0.4 g of di(dodecyl sulfide)dibutyltin and 0.05 g of tert-butylhydroquinone were dissolved and dispersed in 40 g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 60 °C for 1.5 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 779, a weight-average molecular weight of 1563, and a distribution-to-weight ratio of 2.01.

[0070] Mix 100g of prepolymer, 40g of 1,6-hexanediol diacrylate, and 1g of 4-acryloyloxybenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a doctor blade, and then cure the optical adhesive with UV light.

[0071] The final optical adhesive had a curing shrinkage rate of 1.32%, a bond strength of 0.42 MPa, a thermal conductivity of 0.26 W / (m·K), and a light transmittance of 98.3%.

[0072] Example 7:

[0073] 0.1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 100 mL of toluene, and then 1 g of 100 nm zirconium dioxide and 2 g of 1,4-cyclohexadiene were added. The mixture was stirred at 60 °C for 2.5 h to obtain modified zirconium dioxide. The modified zirconium dioxide was washed successively with water and acetone, then dried and pulverized.

[0074] All raw materials were dried in a vacuum oven for 12 hours before use.

[0075] 0.05 g of modified zirconium dioxide was ultrasonically dispersed in 100 g of isophorone diisocyanate and kept at 40 °C under N2 atmosphere to obtain dispersion A. 0.1 g of dibutyltin dilaurate and 0.01 g of p-hydroxyanisole were dissolved and dispersed in 50 g of glycidyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 40 °C for 2 h to obtain dispersion B. After the addition was complete, 0.1 g of dibutyltin dilaurate and 0.01 g of p-hydroxyanisole were dissolved and dispersed in 50 g of glycidyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 70 °C for 2.5 h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 446, a weight-average molecular weight of 923, and a distribution ratio of 2.07.

[0076] Mix 100g of prepolymer, 40g of isobornyl methacrylate, and 0.6g of 4-acryloyloxybenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0077] The final optical adhesive had a curing shrinkage rate of 1.45%, a bond strength of 0.41 MPa, a thermal conductivity of 0.24 W / (m·K), and a light transmittance of 98.3%.

[0078] Example 8:

[0079] 1 g of tetraisopropyl di(dioctylphosphite)titanate was dissolved in 1000 mL of toluene, and then 10 g of 50 nm titanium dioxide and 20 g of liquid styrene-butadiene rubber were added. The mixture was stirred at 60 °C for 2 h to obtain modified titanium dioxide. The modified titanium dioxide was washed successively with water and acetone, then dried and pulverized.

[0080] All raw materials were dried in a vacuum oven for 12 hours before use.

[0081] 5g of modified titanium dioxide was ultrasonically dispersed in 100g of dicyclohexylmethane diisocyanate and kept at 45℃ under N2 atmosphere to obtain dispersion A. 0.5g of dibutyltin dilaurate and 0.03g of tert-butylhydroquinone were dissolved and dispersed in 30g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion A under N2 atmosphere while reacting. The mixture was stirred and polymerized at 50℃ for 2h to obtain dispersion B. After the addition was complete, 0.5g of dibutyltin dilaurate and 0.03g of tert-butylhydroquinone were dissolved and dispersed in 30g of 2-ethylhexyl methacrylate and slowly added dropwise to dispersion B under N2 atmosphere while reacting. The mixture was stirred and polymerized at 60℃ for 2h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 947, a weight-average molecular weight of 1872, and a distribution ratio of 1.98.

[0082] Mix 100g of prepolymer, 30g of 1,6-hexanediol diacrylate, and 0.5g of hydroxycyclohexylbenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a doctor blade, and then cure the optical adhesive with UV light.

[0083] The final optical adhesive had a curing shrinkage rate of 1.21%, a bond strength of 0.49 MPa, a thermal conductivity of 0.37 W / (m·K), and a light transmittance of 98.1%.

[0084] Comparative Example 1:

[0085] All raw materials were dried in a vacuum oven for 12 hours before use.

[0086] 100g of isophorone diisocyanate was heated at 40℃ under a N2 atmosphere to obtain dispersion A. 0.2g of di(dodecyl sulfide)dibutyltin and 0.05g of tert-butylhydroquinone were dissolved and dispersed in 30g of 2-ethylhexyl methacrylate, and slowly added dropwise to dispersion A under a N2 atmosphere while reacting. The mixture was stirred and polymerized at 40℃ for 2h to obtain dispersion B. After the addition was complete, another 0.2g of di(dodecyl sulfide)dibutyltin and 0.05g of tert-butylhydroquinone were dissolved and dispersed in 30g of 2-ethylhexyl methacrylate, and slowly added dropwise to dispersion B under a N2 atmosphere while reacting. The mixture was stirred and polymerized at 60℃ for 2h to obtain the prepolymer. The prepolymer had a number-average molecular weight of 526, a weight-average molecular weight of 1078, and a distribution of 2.05.

[0087] Mix 100g of prepolymer, 30g of isobornyl methacrylate, and 1g of hydroxycyclohexylbenzophenone evenly to form an adhesive solution. Apply the adhesive to the substrate film with a scraper, and then cure the optical adhesive with ultraviolet light.

[0088] The final optical adhesive had a curing shrinkage rate of 3.1%, a bond strength of 0.35 MPa, a thermal conductivity of 0.16 W / (m·K), and a light transmittance of 98.3%.

Claims

1. A method for preparing an optical adhesive with low curing shrinkage and high thermal conductivity, characterized in that, The preparation method includes the following steps: Step (1) Nanoparticle modification A titanate coupling agent is dissolved in toluene, and then nanoparticles and low molecular weight olefins are added. The mixture is stirred at 50-60℃ for 2-3 hours for modification. The product is washed with water and acetone sequentially, then dried and pulverized to obtain modified nanoparticles. The titanate coupling agent is tetraisopropyl di(dioctylphosphite) titanate. The nanoparticles are zirconium dioxide or aluminum nitride with a size of 20-100 nm and an addition amount of 0.2-2 parts by weight. The low molecular weight olefin is liquid styrene-butadiene rubber or 1,4-cyclohexadiene with a molecular weight of less than 1000. Step (2) Raw material dehydration The modified nanoparticles, monomer A, catalyst, polymerization inhibitor, monomer B, reactive diluent, and photoinitiator are dehydrated and dried. Monomer A is one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or lysine diisocyanate. The catalyst is an organotin catalyst. The polymerization inhibitor is one of p-hydroxyanisole, tert-butylhydroquinone, or di-tert-butylhydroquinone. Monomer B is 2-ethylhexyl methacrylate or glycidyl methacrylate. Step (3) Preparation of prepolymer 3-1 0.05-5 parts by weight of the modified nanoparticles obtained in step (1) were ultrasonically dispersed in 100 parts by weight of monomer A, and kept at 35-45℃ under N2 atmosphere to obtain dispersion A; 3-2 Dissolve and disperse the catalyst and polymerization inhibitor in 10-50 parts by weight of monomer B, and slowly drop it into dispersion A under N2 atmosphere. Stir and polymerize at 40-50℃ for 1.5-2.5h to obtain dispersion B; 3-3 Dissolve and disperse the catalyst and polymerization inhibitor in 10-50 parts by weight of monomer B, and slowly drop them into dispersion B under N2 atmosphere, and stir and polymerize at 60-70℃ for 1.5-2.5h. Step (4) Preparation of optical adhesive Mix 100 parts by weight of the prepolymer synthesized in step (3), 20-40 parts by weight of the reactive diluent, and 0.3-2 parts by weight of the photoinitiator evenly to form a glue solution, thereby obtaining an optical glue with low curing shrinkage and high thermal conductivity.

2. The preparation method according to claim 1, characterized in that, The monomer A is isophorone diisocyanate or dicyclohexylmethane diisocyanate.

3. The preparation method according to claim 1, characterized in that, The catalyst is one of dibutyltin dilaurate, di(dodecyl sulfide)dibutyltin, dibutyltin diacetate, and stannous octoate. The amount of catalyst added in steps 3-2 and 3-3 is 0.1-0.5 parts by weight.

4. The preparation method according to claim 1, characterized in that, The polymerization inhibitor is p-hydroxyanisole, and the amount of polymerization inhibitor added in steps 3-2 and 3-3 is 0.02-0.1 parts by weight.

5. The preparation method according to claim 1, characterized in that, The amount of monomer B added in steps 3-2 and 3-3 is 15-30 parts by weight, respectively.

6. The preparation method according to claim 1, characterized in that, The reactive diluent is one of isoborneol methacrylate, ethylene glycol diacrylate, 2-hydroxydimethylacetylbenzene, or 1,6-hexanediol diacrylate; the photoinitiator is one of 4-acryloyloxybenzophenone, trimethylbenzoyl-diphenylphosphine oxide, dimethoxydiphenylethynyl ketone, trimethylbenzoyldiphenyloxyphosphate, or hydroxycyclohexylbenzophenone, and the amount of photoinitiator added is 0.3-1 parts by weight.

7. An optical adhesive with low curing shrinkage and high thermal conductivity, prepared by the method described in any one of claims 1-6.

8. An optical adhesive film, prepared by UV curing of an optical adhesive coating substrate as described in claim 7.