An optical adhesive, its preparation method and application

Abstract

This invention provides an optical adhesive, its preparation method, and its application. The optical adhesive is prepared from raw materials comprising the following components: acrylate monomers, α-methacrylic acid, and vinyltrimethoxysilane; wherein the acrylate monomers include high refractive index acrylate monomers, flexible acrylate monomers, and hydroxyethyl methacrylate. By selecting suitable high refractive index and low shrinkage acrylate monomers and matching them with methacrylic acid and vinyltrimethoxysilane, this invention obtains an optical adhesive with a refractive index highly matched to K9 glass. It can cure rapidly at room temperature, enabling the bonding of optical components such as K9 glass.

Description

Technical Field

[0001] This invention relates to the field of optical materials technology, and more specifically, to an optical adhesive, its preparation method, and its application. Background Technology

[0002] Currently, optoelectronic devices are the core carrier of optoelectronic technology and a crucial foundation for the development of next-generation information technology. In recent years, with the rapid development of industries such as 5G, optical communication, optical display, and biometrics, the market demand for optoelectronic devices has continued to grow, and products are being updated and iterated rapidly, constantly evolving towards precision, intelligence, and efficiency. Displays, sensors, detectors, and optoelectronic devices are indispensable elements of intelligent systems, and high-performance optical materials can effectively achieve the high performance, lightweight, miniaturization, and integration of these optical components.

[0003] Optical adhesives, particularly those used in optical materials, are specialized bonding agents for optical components such as K9 glass. Optical component bonding is the process by which the surfaces of optical components are tightly bound together by chemical bonds, hydrogen bonds, or intermolecular attraction under the action of an adhesive. Adhesives for connecting optical structures are crucial for manufacturing LD modules, APD modules, optical couplers, and optical multiplexers. K9 glass, with its excellent optical transparency, low dispersion, high thermal stability, and superior mechanical strength, is an ideal choice for manufacturing lens windows and other optical components. In practical applications, K9 glass has a refractive index of approximately 1.51 to 1.53 in the visible light range (approximately 400 to 700 nanometers wavelength). To maintain the performance of the bonded optical components, the adhesive needs to have a refractive index matching the optical components, as well as excellent mechanical properties, heat resistance, light transmittance, and low volume shrinkage. Furthermore, the smooth and non-porous surface of K9 glass makes it difficult for ordinary adhesives to generate mechanical locking forces, resulting in low bond strength. Simultaneously, the low surface energy of K9 glass also leads to poor wetting properties of the adhesive.

[0004] In addition, optical adhesives need to have a rapid curing rate, especially the ability to complete the curing process in seconds to minutes. However, oxygen in the air usually inhibits the curing process, resulting in incomplete surface curing and thus affecting the quality and performance of the product.

[0005] Acrylic adhesives are widely used in optical adhesives due to their low viscosity, good flowability, wetting properties, formulation flexibility, rapid curing, and ease of use. However, currently developed acrylic adhesives have relatively limited basic properties. Therefore, there is an urgent need to develop an optical adhesive that combines high light transmittance, refractive index, weather resistance, low shrinkage, rapid curing, colorless and transparent properties, low viscosity, and high bond strength. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides an optical adhesive and its preparation method. By selecting suitable acrylate monomers with high refractive index and low shrinkage, and mixing them with methacrylic acid and a coupling agent, this invention obtains an optical adhesive with a refractive index highly matched to that of K9 glass. This adhesive can cure rapidly at room temperature, enabling the bonding of optical components such as K9 glass.

[0007] Firstly, one of the objectives of this invention is to provide an optical adhesive.

[0008] Specifically, the optical adhesive is made from raw materials including the following components: acrylate monomers, α-methacrylic acid, and vinyltrimethoxysilane; wherein the acrylate monomers include acrylate monomers with high refractive index, flexible acrylate monomers, and hydroxyethyl methacrylate.

[0009] It is worth mentioning that this invention, by selecting a variety of acrylate monomers, especially a variety of functional acrylate monomers working synergistically, yields an acrylic optical adhesive for bonding optical components with excellent adhesive strength, high refractive index, low shrinkage, and weather resistance (heat resistance, cold resistance, and moisture resistance).

[0010] Furthermore, in the raw material components for preparing the optical adhesive, based on a total weight of 100 parts by weight of acrylate monomers, α-methacrylic acid, and vinyltrimethoxysilane, the weight parts of each type of acrylate monomer, α-methacrylic acid, and vinyltrimethoxysilane are as follows:

[0011] 40-60 parts by weight of high refractive index acrylate monomer; preferably 45-55 parts by weight;

[0012] 35-50 parts by weight of flexible acrylate monomer; preferably 40-45 parts by weight;

[0013] 3-7 parts by weight of α-methacrylic acid; preferably 5-6 parts by weight;

[0014] 5-18 parts by weight of hydroxyethyl methacrylate; preferably 6-10 parts by weight.

[0015] Vinyltrimethoxysilane 3 to 7 parts by weight; preferably 5 to 6 parts by weight.

[0016] Preferably, the high refractive index acrylate monomer is selected from 2-phenoxyethyl acrylate, isobornyl methacrylate, and dicyclopentenyl methacrylate monomers; more preferably, it is a combination of 2-phenoxyethyl acrylate, isobornyl methacrylate, and dicyclopentenyl methacrylate monomers. The 2-phenoxyethyl acrylate, dicyclopentenyl methacrylate, and isobornyl methacrylate used in this invention have refractive indices of 1.518, 1.497, and 1.471, respectively, and are used to adjust the refractive index of the acrylate system. Furthermore, the presence of benzene ring structures and / or cyclic structures in the above monomers also helps to improve optical transparency, weather resistance, and low curing shrinkage.

[0017] Preferably, the flexible acrylate monomer is selected from 1,6-hexanediol dimethacrylate and triethylene glycol dimethacrylate monomers; more preferably, it is a combination of 1,6-hexanediol dimethacrylate and triethylene glycol dimethacrylate. The 1,6-hexanediol dimethacrylate and triethylene glycol dimethacrylate used in this invention can adjust the adhesiveness of the acrylate system and act as crosslinking agents to improve the cohesive strength of the optical adhesive after curing.

[0018] Furthermore, the raw materials for preparing the optical adhesive of the present invention also include a photoinitiator. Based on 100 parts by weight of the total weight of acrylate monomer, α-methacrylic acid and vinyltrimethoxysilane, the weight of the photoinitiator is 0.1 to 1 part by weight; preferably 0.4 to 0.6 parts by weight.

[0019] Preferably, the photoinitiator is a combination of 2-isopropylthioxanthone and 1-hydroxycyclohexylphenyl ketone and / or 2-hydroxy-2-methyl-1-phenyl-1-propanone. More preferably, it is a combination of 2-isopropylthioxanthone and 1-hydroxycyclohexylphenyl ketone. Currently, the most widely used ultraviolet light sources in industrial applications are mostly at 365 nm, while the absorption peaks of 2-hydroxy-2-methyl-1-phenyl-1-propanone or 1-hydroxycyclohexylphenyl ketone are located at 280 nm. Ultraviolet light in this band is extremely harmful to the human body and should not be used for a long time. Moreover, if used alone under 365 nm ultraviolet light, its initiation efficiency is low, resulting in incomplete curing. The absorption peak wavelength of 2-isopropylthioxanthrone is located at 365nm, but 2-isopropylthioxanthrone will cause the optical adhesive system to turn yellow. In this invention, it is compounded with 1-hydroxycyclohexylphenyl ketone and / or 2-hydroxy-2-methyl-1-phenyl-1-propanone to obtain an optical adhesive that not only has high bonding strength but is also colorless and transparent.

[0020] Secondly, another objective of the present invention is to provide a method for preparing an optical adhesive, which is one of the objectives of the present invention.

[0021] Specifically, the method includes the following steps:

[0022] Step 1: Mix high refractive index acrylate monomers, flexible acrylate monomers, α-methacrylic acid, hydroxyethyl methacrylate, and vinyltrimethoxysilane to obtain monomer prepolymers;

[0023] Step 2: Mix the above monomer prepolymer and photoinitiator to obtain optical adhesive.

[0024] Preferably, in step two, the mixing method is as follows: first, the above monomer prepolymer is mixed at a speed of 400 rpm for 0.5 to 1 hour, and then a photoinitiator is added and the mixture is continued for 30 minutes.

[0025] Thirdly, a third objective of the present invention is to provide the application of the optical adhesive, which is one of the objectives of the present invention.

[0026] Specifically, the optical adhesive provided by this invention is used for bonding optical components.

[0027] More specifically, the method for bonding optical components using the aforementioned optical adhesive is as follows: the optical adhesive is applied to the optical component, and another optical component is covered on top. Air bubbles are continuously removed by moving the adhesive around, and then the adhesive is cured under ultraviolet light.

[0028] Preferably, the wavelength of the ultraviolet light is 320–400 nm, and the light intensity is 5–80 mW / cm². 2 Pre-curing time: 3-10 minutes.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. This invention, by selecting suitable acrylate monomers with high refractive index and low shrinkage, and compounding them with methacrylic acid and vinyltrimethoxysilane, yields an optical adhesive with excellent bonding strength, high refractive index, low shrinkage, and weather resistance (heat resistance, cold resistance, and moisture resistance). Furthermore, this optical adhesive can cure rapidly at room temperature. The optical adhesive provided by this invention can be used for bonding optical components such as K9 glass, exhibiting extremely high bonding strength and environmental stability, and possessing highly matched refractive index characteristics with K9 glass.

[0031] 2. This invention utilizes a variety of acrylate monomers to design the structure of acrylate resin molecules, specifically selecting a particular ratio of various functional acrylate monomers to achieve synergistic effects, resulting in an acrylic resin suitable for optical components. When applied to optical components such as K9 glass bonding, the resulting adhesive not only exhibits a matching high refractive index but also low curing shrinkage, excellent bonding performance, weather resistance (heat, cold, and moisture resistance), and a long working time. This invention addresses the urgent need in the field of optical component bonding for optical adhesives with high bonding strength, high refractive index, low curing shrinkage, and rapid curing.

[0032] 3. All the acrylate monomers used in this invention have methyl side chains, which can give the optical adhesive good chemical resistance and make it resistant to the erosion of many acids, alkalis and solvents.

[0033] 4. This invention provides an optical adhesive with a refractive index of about 1.51, low viscosity (viscosity of about 7 mPa·s at 25℃), and low curing shrinkage (9-10%), which can effectively bond optical components. It can prevent the bonded components from detaching and prevent cohesive failure at the bonding joint in humid, steamy, or chemical solvent environments. Attached Figure Description

[0034] Figure 1 The glass transition temperature test diagrams are of the optical adhesives prepared in Example 7 and Comparative Examples 1-5 of this invention after curing.

[0035] Figure 2 The water resistance test diagrams of the K9 glass bonded with optical adhesive prepared in Examples 5-7 of this invention (K9 glass specifications 100x10x10mm);

[0036] Figure 3 The solvent resistance test diagrams are for K9 glass bonded with optical adhesive prepared in Examples 1-3 and Example 7 of this invention (K9 glass size 100x10x10mm).

[0037] Figure 4 The humidity resistance test diagrams are for K9 glass bonded with optical adhesive prepared in Examples 4, 5, and 7 of this invention (K9 glass specifications: 100x10x10mm).

[0038] Figure 5 Tensile strength test diagrams of K9 glass bonded with optical adhesive prepared in Example 7 and Comparative Examples 8-12 of this invention (K9 glass specifications: 20x20x100mm);

[0039] Figure 6 The tensile strength test diagrams are of K9 glass (20x20x100mm) bonded with optical adhesive prepared in Example 7 and Comparative Examples 13-15 of this invention. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0041] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0042] Example

[0043] The following describes the preparation of the optical adhesive in the examples, and the specific steps are as follows:

[0044] Step 1: Mix different monomers and vinyltrimethoxysilane to obtain monomer prepolymers;

[0045] Step 2: Under nitrogen protection, the above monomer prepolymer is stirred at 400 rpm for 30 min, and then the photoinitiator is added and mixed for 30 min to obtain the optical adhesive.

[0046] The raw materials and their quantities used in different embodiments are detailed in Tables 1 to 3.

[0047] The following describes the bonding of K9 glass using the aforementioned optical adhesive. The specific steps are as follows:

[0048] Place a K9 glass pane horizontally and evenly coat it with the aforementioned optical adhesive. Cover the K9 glass pane with another K9 glass pane, continuously moving it to remove air bubbles to obtain a bonded optical element. Then place the bonded optical element under 365nm ultraviolet light with a light intensity of 5mw / cm². 2 Pre-curing for 2 minutes, then adjusting the light intensity to 80 mw / cm². 2 Then cure for another 8 minutes to obtain the cured optical element.

[0049] Comparative Example

[0050] The preparation method of the optical adhesive in the comparative example and the bonding steps to K9 glass are the same as those in the example. The raw materials used and the amount of raw materials are detailed in Tables 1 to 3.

[0051] The following describes the optical performance tests of the optical adhesives prepared in Examples 1-7 and Comparative Examples 1-7.

[0052] Table 1 shows the acrylate monomers, α-methacrylic acid, vinyltrimethoxysilane and their weight parts used in Examples 1-7 and Comparative Examples 1-7, as well as the optical performance test data of the prepared optical adhesives. In the examples and comparative examples, the combination of 1-hydroxycyclohexylphenyl ketone (0.3 parts by weight) and 2-isopropylthioxanthraquinone (0.3 parts by weight) was used as the photoinitiator.

[0053] The optical properties of the prepared optical adhesive were tested using the following methods:

[0054] Refractive index testing method: The Psi-Delta curve in the 380–1000 nm light range was measured using an SE-VM-L ellipsometer. The steps are as follows: First, the sample is placed on the sample stage, the optical path is adjusted, and the Psi-Delta curve is obtained by measurement. Second, a physical model is established based on the sample information. Third, the refractive index n value of the sample is obtained by fitting the model.

[0055] Viscosity testing method: The viscosity of OCA optical adhesive was tested using an Anton Paar MCR 102 rheometer. First, the sample was prepared, ensuring it was uniform and free of air bubbles. The test conditions were: temperature 25℃ and rotation speed 50 rpm / min.

[0056] Transmittance testing method: The transmittance of OCA materials in the range of 400–800 nm was tested using a UV-Vis spectrophotometer to evaluate its optical performance. First, the baseline (I0) needs to be measured, i.e., the intensity of diffuse reflected light within the integrating sphere without a sample. Then, the sample to be tested is placed in the sample port of the integrating sphere, ensuring the sample surface completely covers the port, and the spectrophotometer is started to measure the intensity of diffuse reflected light (I) at different wavelengths. Finally, by comparing the intensity of reflected light from the sample with the baseline intensity, the reflectance spectrum of the sample at different wavelengths is calculated.

[0057] Curing shrinkage rate test method: Performed according to the relevant provisions of international standard ISO 3521. First, measure the density of the resin before and after curing, then calculate the shrinkage rate based on the density. Shrinkage rate = (ρ... 后 -ρ 前 ) / ρ 后 X100%, where ρ 后 and ρ 前 These are the densities before and after curing, respectively. The density before and after curing can be determined using the hydrostatic bottle method, with water as a reference.

[0058] Table 1:

[0059]

[0060]

[0061] As shown in Table 1, the optical adhesives prepared in Examples 1 to 7 have good refractive index, light transmittance, low viscosity and curing shrinkage.

[0062] As can be seen from Comparative Examples 1-3, when only 2-phenoxyethyl acrylate is added, although the refractive index and transmittance of the optical adhesives in Comparative Examples 1-3 are improved and the curing shrinkage is reduced as the amount of 2-phenoxyethyl acrylate increases, they are still far less than the high refractive index and transmittance and low curing shrinkage of the optical adhesives in Examples 1-7. The relatively low refractive index and transmittance of the optical adhesives in Comparative Examples 1-3 cannot meet the requirements for the application of K9 glass. At the same time, the large curing shrinkage will not only cause changes in the size of the optical elements, making it difficult to maintain accurate geometry and size, but will also introduce interfacial stress between the optical elements, leading to interfacial peeling or decreased bonding strength, which also cannot meet the application requirements.

[0063] Furthermore, as shown in Comparative Examples 4-5, when only isobornyl methacrylate or dicyclopentenyl methacrylate is added, the refractive index of the optical adhesives in Comparative Examples 4-5 is far lower than that of the optical adhesives in Examples 1-7; at the same time, the shrinkage rate after curing still exceeds 10%. This is because although the aromatic groups of 2-phenoxyethyl acrylate can reduce the shrinkage during polymerization to some extent, its molecular structure contains flexible chain segments, resulting in a large volume change after polymerization. In contrast, dicyclopentenyl methacrylate and isobornyl methacrylate have rigid cyclic structures, which are relatively stable during polymerization, have smaller volume changes, and shrink less during curing.

[0064] Furthermore, as shown in Comparative Examples 6 and 7, when the total weight parts of 2-phenoxyethyl acrylate, isobornyl methacrylate, and dicyclopentenyl methacrylate are the same, the refractive index of the resulting optical adhesive remains low when the amount of 2-phenoxyethyl acrylate added is insufficient. Examples 1 to 7 perfectly resolve this contradiction. Although all three monomers—2-phenoxyethyl acrylate, isobornyl methacrylate, and dicyclopentenyl methacrylate—have high refractive indices, only by mixing them and optimizing the monomer ratio can a copolymer with a higher refractive index, higher transmittance, and lower curing shrinkage be obtained. When this optical adhesive is applied to optical components, it can maintain the performance and dimensional stability of the optical components and reduce internal stress and deformation.

[0065] The following describes the performance tests of the glass transition temperature of the optical adhesives prepared in Examples 7 and Comparative Examples 1-5.

[0066] Depend on Figure 1 It can be seen that the glass transition temperature of Comparative Examples 1 to 5 and Example 7 gradually increases, and the glass transition temperature of Example 1 can reach 114°C, indicating that the addition of 2-phenoxyethyl acrylate, dicyclopentenyl methacrylate and isobornyl methacrylate can effectively improve the heat resistance of optical adhesive.

[0067] The following is used to illustrate the weather resistance test of optical adhesives.

[0068] The water resistance test process is as follows: After the optical adhesive prepared in Examples 5 to 7 is applied to K9 glass and cured, it is immersed in water at 80°C for 100 hours and then subjected to tensile shear test.

[0069] Depend on Figure 2 It can be seen that the K9 glass bonded in Examples 5 to 7 experienced optical glass breakage at 10.9 MPa, 10.2 MPa, and 11.3 MPa, respectively, while the adhesive joint did not show any damage, indicating that the optical adhesive provided in Examples 5 to 7 has excellent water resistance.

[0070] The solvent resistance test process is as follows: After the optical adhesives prepared in Examples 1-3 and Example 7 are applied to K9 glass and cured, they are immersed in acetone at 30°C for 72 hours and then subjected to tensile shear test.

[0071] Depend on Figure 3 It can be seen that the K9 glass bonded in Examples 1-3 and Example 7 fractured at 11.6MPa, 10.4MPa, 11.7MPa and 11.5MPa respectively, while the adhesive joint was not damaged, indicating that the optical adhesive provided in Examples 1-3 and Example 7 has excellent solvent resistance.

[0072] The humidity resistance cycling performance test process is as follows: After the optical adhesive prepared in Examples 4, 5 and 7 is applied to K9 glass and cured, it is subjected to tensile shear test after being treated for 50 cycles at -40℃ to +80℃ and 95%RH / 6h.

[0073] Depend on Figure 4 It can be seen that the K9 glass bonded in Examples 4, 5, and 7 experienced optical glass fracture at 10.7 MPa, 10.4 MPa, and 10.1 MPa, respectively, while the adhesive joint was not damaged, indicating that the optical adhesives provided in Examples 4, 5, and 7 have excellent humidity resistance.

[0074] The following describes the bonding performance tests of the optical adhesives prepared in Examples 7 and Comparative Examples 8-12.

[0075] Table 2 shows the acrylate monomers, α-methacrylic acid, vinyltrimethoxysilane and their weight parts used in Examples 7 and Comparative Examples 8-10, as well as the data on the optical properties of the prepared optical adhesives and the bonding performance of optical components. In the comparative examples above, a combination of 1-hydroxycyclohexylphenyl ketone (0.3 parts by weight) and 2-isopropylthioxanthone (0.3 parts by weight) was used as the photoinitiator.

[0076] The adhesive strength test methods for the above embodiments and comparative examples are as follows: The adhesion between OCA optical adhesive and K9 glass was tested using the lap shear method. The cured bonding element was fixed on a uniaxial tensile testing machine, and the end of the K9 glass was tightly stretched and loaded at a speed of 5 mm / min until separation occurred. The adhesive strength was determined by dividing the maximum load force by the initial contact area.

[0077] Table 2:

[0078]

[0079] As shown in Table 2, when no 1,6-hexanediol dimethacrylate or only triethylene glycol dimethacrylate is added, the optical adhesives prepared in Comparative Examples 8-10 still have good refractive index, transmittance and low curing shrinkage. When no α-methacrylic acid and hydroxyethyl methacrylate or vinyltrimethoxysilane are added, the optical adhesives prepared in Comparative Examples 11-12 still have good refractive index and transmittance.

[0080] Furthermore, by Figure 5 It is evident that when 1,6-hexanediol dimethacrylate or triethylene glycol dimethacrylate is added without or only added, the adhesive strength of Comparative Examples 8-10 can only reach a maximum of 8 MPa, while the adhesive strength of Example 7 is 12.6 MPa. Therefore, the combined use of 1,6-hexanediol dimethacrylate and triethylene glycol dimethacrylate, two flexible crosslinking agents, can improve the adhesive strength of the optical adhesive while maintaining a high cohesive strength. On the one hand, the molecular structure of 1,6-hexanediol dimethacrylate contains a relatively long chain segment (1,6-hexanediol portion), resulting in a lower crosslinking density and a certain degree of flexibility in the polymer, which helps to absorb and buffer stress. On the other hand, the molecular structure of triethylene glycol dimethacrylate contains a relatively short chain segment (ethylene glycol portion), resulting in a higher crosslinking density and greater hardness in the polymer, providing higher mechanical strength and rigidity. Furthermore, the presence of 1,6-hexanediol dimethacrylate can regulate the high crosslinking density of triethylene glycol dimethacrylate, allowing the adhesive layer to form a network structure that is both strong and flexible during the curing process.

[0081] Furthermore, by Figure 5It is known that when α-methacrylic acid and hydroxyethyl methacrylate, or vinyltrimethoxysilane, are not added, the adhesive strength of Comparative Examples 11-12 can only reach a maximum of 8.2 MPa, while the adhesive strength of Example 7 is 12.6 MPa. Vinyltrimethoxysilane, as a coupling agent, hydrolyzes in the presence of α-methacrylic acid to generate silanol (-SiOH) and methanol (CH3OH). The generated silanol (Si-OH) groups undergo a condensation reaction with the hydroxyl groups (Si-OH) in the glass on the glass surface, forming a silicon-oxygen bridge (Si-O-Si), thereby firmly bonding vinyltrimethoxysilane to the glass surface. Meanwhile, the hydroxyl groups (-OH) in hydroxyethyl methacrylate can undergo hydrogen bonding with the silanol groups (Si-OH) on the glass surface, thereby enhancing the adsorption capacity of hydroxyethyl methacrylate on the glass surface. Simultaneously, the ethoxy chain segment (-CH2CH2O-) in its molecule has a certain degree of flexibility, which helps to form an adhesive layer with moderate flexibility. The synergistic effect of these three factors plays a positive role in improving the adhesive strength.

[0082] The following describes the color, curing rate, room temperature storage time, and weather resistance test of the optical adhesives prepared in Examples 7 and Comparative Examples 13-15.

[0083] Table 3 shows the photoinitiators and their weight parts used in Examples 7 and Comparative Examples 13-15, as well as the color, curing rate, room temperature storage time, and weather resistance test data of the prepared optical adhesives. The acrylate monomers, α-methacrylic acid, vinyltrimethoxysilane, and their weight parts used in the comparative examples are the same as those in Example 7.

[0084] Table 3:

[0085]

[0086] As shown in Table 3, the optical adhesive prepared in Example 7 has good color, curing rate, room temperature storage time, and weather resistance.

[0087] In Comparative Example 13, the addition of the photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide severely affected the color, curing rate, and room temperature storage time of the optical adhesive. At the same time, it had poor weather resistance and could not meet the requirements for application with K9 glass.

[0088] As can be seen from Comparative Examples 14-15, when only 1-hydroxycyclohexylphenyl ketone is added or when both 1-hydroxycyclohexylphenyl ketone and 2-hydroxy-2-methyl-1-phenyl-1-propanone are added, the initiation efficiency is low, the optical adhesive cannot achieve rapid curing, resulting in incomplete curing, which cannot meet the application requirements, and the weather resistance is also poor.

[0089] Figure 6The tensile strength test graphs of the optical adhesives prepared in Example 7 and Comparative Examples 13-15 bonded to K9 glass are shown. As can be seen from the graphs, after curing under ultraviolet light for 10 minutes, the bonding strength of the optical adhesives in Comparative Examples 13-15 is lower, while the bonding strength of the optical adhesives in Example 7 is higher, indicating that the optical adhesives in Example 7 have the advantage of rapid curing.

[0090] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An optical adhesive, made from raw materials including acrylate monomers, vinyltrimethoxysilane, α-methacrylic acid and a photoinitiator; The acrylate monomers include high refractive index acrylate monomers, flexible acrylate monomers, and hydroxyethyl methacrylate; The high refractive index acrylate monomer is selected from 2-phenoxyethyl acrylate, isobornyl methacrylate and dicyclopentenyl methacrylate monomer; The flexible acrylate monomer is selected from 1,6-hexanediol dimethacrylate and triethylene glycol dimethacrylate monomer; The photoinitiator is a combination of 2-isopropylthioxanthone and 1-hydroxycyclohexylphenyl ketone; Based on a total weight of 100 parts by weight of the acrylate monomer, vinyltrimethoxysilane, and α-methacrylic acid, the following components are present in parts by weight: 40-50 parts by weight of high refractive index acrylate monomer; 35-45 parts by weight of flexible acrylate monomer; 3-7 parts by weight of α-methacrylic acid; 5-18 parts by weight of hydroxyethyl methacrylate; Vinyltrimethoxysilane 3-7 parts by weight; In the high refractive index acrylate monomer, the 2-phenoxyethyl acrylate is present in a weight ratio of at least 30 parts.

2. The optical adhesive according to claim 1, characterized in that, Based on a total weight of 100 parts by weight of the acrylate monomer, vinyltrimethoxysilane, and α-methacrylic acid, the following components are present in parts by weight: 45-50 parts by weight of high refractive index acrylate monomer; 35-40 parts by weight of flexible acrylate monomer; 5-6 parts by weight of α-methacrylic acid; 5-10 parts by weight of hydroxyethyl methacrylate; 5-6 parts by weight of vinyltrimethoxysilane.

3. The optical adhesive according to claim 1, characterized in that, Based on a total weight of 100 parts by weight of the acrylate monomer, vinyltrimethoxysilane, and α-methacrylic acid, the photoinitiator comprises 0.1-1 parts by weight.

4. The optical adhesive according to claim 3, characterized in that, The photoinitiator is present in an amount of 0.4-0.6 parts by weight.

5. The method for preparing the optical adhesive according to any one of claims 1-4, characterized in that, The method includes the following steps: Step 1: Mix high refractive index acrylate monomers, flexible acrylate monomers, α-methacrylic acid, hydroxyethyl methacrylate, and vinyltrimethoxysilane to obtain monomer prepolymers; Step 2: Mix the above monomer prepolymer and photoinitiator to obtain optical adhesive.

6. The application of the optical adhesive according to any one of claims 1-4, for bonding optical components.

7. The application of the optical adhesive according to claim 6, characterized in that, The bonding method is as follows: apply optical adhesive to the optical element and cover it with another optical element, remove air bubbles, and cure under ultraviolet light.

8. The application of the optical adhesive according to claim 7, characterized in that, The ultraviolet light has a wavelength of 320-400 nm and a light intensity of 5-80 mw / cm². 2 Pre-curing time: 3-10 minutes.

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