Nonlinear optical crystal and crystal combined adhesive and preparation method thereof

Abstract

The invention relates to a nonlinear optical crystal and crystal combined adhesive and a preparation method thereof. The nonlinear optical crystal and crystal combined adhesive comprises the following components in parts by weight: 40-70 parts of hydrogenated bisphenol A type acrylate monomer; 20 to 40 parts of a polyfunctional thiol compound; the core of the core-shell structure nanoparticles is ZrO2, the shell of the core-shell structure nanoparticles is SiO2, the particle size of the core is 20-50nm, and the thickness of a shell layer is 3-8nm; and 0.1 to 0.5 part of a coupling agent containing a phosphate group. Through accurate regulation and control of the ZrO2atSiO2 core-shell nanoparticles, the refractive index of the adhesive can be adjusted in a range of 1.65-2.10, and is highly matched with the refractive index 1.7-2.2 of nonlinear optical crystals such as KTP, BBO and LBO, so that the Fresnel loss of a bonding interface is reduced to be less than or equal to 0.5 dB / cm, the laser frequency conversion efficiency is remarkably improved, agglomeration is effectively inhibited by the core-shell structure of the nanoparticles, and the laser frequency conversion efficiency is improved. The light transmittance of a cured adhesive layer under common laser wavelengths such as 1064 nm, 532 nm and 355 nm is larger than or equal to 99.5%, the adhesive layer is suitable for a high-power laser system, by adding the quantum dot material, the refractive index matching of the specific wavelength can be further optimized, and the application scene is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal admixtures, and specifically to a nonlinear optical crystal and crystal combination adhesive and a preparation method thereof. Background Art

[0002] A nonlinear optical crystal is a crystal that exhibits a nonlinear optical effect of second order or higher for a strong laser electric field. A nonlinear optical crystal is a functional material, and among them, a frequency doubling (or "frequency conversion") crystal can be used to convert the laser wavelength, thereby expanding the tunable range of the laser, and has important application value in the field of laser technology.

[0003] Currently, optical adhesives are mostly used for nonlinear optical crystals and crystal combination adhesives. Optical adhesives have the characteristics of being colorless and transparent, having a light transmittance of more than 90%, good bonding strength, being curable at room temperature or medium temperature, and having a small curing shrinkage.

[0004] For example, the optical adhesive and its preparation method and application proposed in Chinese Patent 202411995730.X achieve the requirement of reducing the water vapor transmittance of the optical adhesive by adjusting the ratio of soft and hard monomers and the ratio of hydrophilic groups hydroxyl in the formula of the optical adhesive, which can effectively prevent the intrusion and erosion of water vapor and ensure the stability and performance of the optical adhesive system.

[0005] However, traditional optical adhesives such as epoxy resins and UV adhesives have a refractive index of 1.4 - 1.6, which is seriously mismatched with that of nonlinear crystals (1.7 - 2.2), resulting in an interfacial Fresnel loss > 15%. The high-temperature curing process > 120°C is likely to cause the destruction of the domain structure of ferroelectric crystals such as LiNbO3. Existing silicon-based adhesives have an absorption peak at 532 nm, which affects the frequency doubling efficiency. Therefore, a nonlinear optical crystal and crystal combination adhesive and a preparation method thereof are proposed to solve the above problems. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a nonlinear optical crystal and crystal combination adhesive and a preparation method thereof, which have the advantages of high refractive index matching, low light scattering loss, low curing shrinkage rate, and wide compatibility, and solve the problems that traditional optical adhesives such as epoxy resins and UV adhesives have a refractive index of 1.4 - 1.6, which is seriously mismatched with that of nonlinear crystals (1.7 - 2.2), resulting in an interfacial Fresnel loss > 15%. The high-temperature curing process > 120°C is likely to cause the destruction of the domain structure of ferroelectric crystals such as LiNbO3. Existing silicon-based adhesives have an absorption peak at 532 nm, which affects the frequency doubling efficiency.

[0007] To achieve the above object, the present invention provides the following technical solution: A nonlinear optical crystal and crystal combination adhesive, comprising the following components in parts by weight: Hydrogenated bisphenol A acrylate monomer: 40 - 70 parts; Polyfunctional thiol compound: 20 - 40 parts; Core - shell structured nanoparticles: 10 - 20 parts, with a core of ZrO2 and a shell of SiO2, a core particle size of 20 - 50 nm, and a shell layer thickness of 3 - 8 nm; Coupling agent containing phosphate ester group: 0.1 - 0.5 parts; Photoinitiator: 1 - 3 parts.

[0008] Furthermore, the hydrogenated bisphenol A - type acrylate monomer is at least one of hydrogenated bisphenol A diacrylate and hydrogenated bisphenol A epoxy acrylate, and 1 - 5 parts of hyperbranched polyester acrylate with a molecular weight of 2000 - 5000 g / mol is doped in the hydrogenated bisphenol A - type acrylate monomer.

[0009] Furthermore, the polyfunctional thiol compound is at least one of pentaerythritol tetra(3 - mercaptopropionate), trimethylolpropane tri(3 - mercaptopropionate), and ethylene glycol bis(3 - mercaptopropionate).

[0010] Furthermore, in the core - shell structured nanoparticles, the refractive index of the ZrO2 core is 2.1 - 2.2, the refractive index of the SiO2 shell is 1.45 - 1.55, and the core - shell volume ratio is 1:(0.15 - 0.35). The shell layer of the core - shell structured nanoparticles has a gradient refractive index structure, and the refractive index from the core to the shell shows a step - by - step decrease from 1.8 to 1.6 to 1.45.

[0011] Furthermore, the coupling agent containing phosphate ester group is at least one of (2 - methacryloyloxyethyl) phosphate and (3 - acryloyloxypropyl) phosphate.

[0012] Furthermore, the photoinitiator is an α - hydroxy ketone - type, benzoyl formate - type, or phosphine oxide - type photoinitiator.

[0013] Furthermore, it also contains 0.01 - 0.1 parts of quantum dot material. The quantum dot material is a CdSe / ZnS core - shell structure with a particle size of 3 - 5 nm, and is used to match the 532 nm or 355 nm laser wavelength.

[0014] A preparation method of a nonlinear optical crystal and crystal combination adhesive is as follows: 1) Dispersing ZrO2 nanoparticles in ethanol, adding tetraethyl orthosilicate and ammonia water, and reacting at 50 - 70 °C for 2 - 4 hours to obtain core - shell structured ZrO2@SiO2 nanoparticles; 2) Mixing the hydrogenated bisphenol A - type acrylate monomer, polyfunctional thiol compound, core - shell structured ZrO2@SiO2 nanoparticles, coupling agent, and photoinitiator, and ultrasonically dispersing for 30 - 60 minutes; 3) Vacuum degassing treatment is carried out to obtain a uniform and transparent adhesive liquid.

[0015] Furthermore, in the step 1), the concentration of ammonia water is 25 - 28 wt%, and the mass ratio of tetraethyl orthosilicate to ZrO₂ is 1:(5 - 10).

[0016] Furthermore, the ultrasonic dispersion in the step 2) is carried out under the protection of inert gas, the ultrasonic power is 200 - 400 W, and the frequency is 40 kHz.

[0017] Compared with the prior art, the technical solution of the present application has the following beneficial effects: 1. Through the precise regulation of ZrO₂@SiO₂ core-shell nanoparticles in the present invention, the refractive index of the adhesive can be adjusted in the range of 1.65 - 2.10, which is highly matched with the refractive index of 1.7 - 2.2 of nonlinear optical crystals such as KTP, BBO, and LBO. The Fresnel loss at the bonding interface is reduced to ≤0.5 dB / cm, significantly improving the laser frequency conversion efficiency. The core-shell structure of the nanoparticles effectively inhibits agglomeration, and the light transmittance of the cured adhesive layer at common laser wavelengths such as 1064 nm, 532 nm, and 355 nm is ≥99.5%, which is suitable for high-power laser systems. By adding quantum dot materials, the refractive index matching at specific wavelengths can be further optimized, expanding the application scenarios.

[0018] 2. The present invention uses the synergistic effect of multi-functional thiol compounds and hyperbranched polyester acrylate to reduce the polymerization stress, avoid crystal cracking or interfacial delamination. The thermal expansion coefficient of the cured adhesive is 30 - 50 ppm / °C, which is close to that of common optical crystals, and there is no cracking or peeling phenomenon in the range of -40 - 120 °C. Description of the Drawings

[0019] Figure 1 It is a flowchart of the preparation method of the nonlinear optical crystal and crystal combination adhesive of the present invention. Detailed Embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Example 1

[0022] Please refer to Figure 1 , a nonlinear optical crystal and crystal combination adhesive in this embodiment includes the following components in parts by weight: Hydrogenated bisphenol A acrylate monomer: 40 parts; Multifunctional thiol compound: 20 parts; Core-shell structured nanoparticles: 10 parts, with a core of ZrO2 and a shell of SiO2, a core particle size of 20 nm, and a shell layer thickness of 3 nm; Coupling agent containing phosphate ester group: 0.1 part; Photoinitiator: 1 part.

[0023] In this example, the hydrogenated bisphenol A type acrylate monomer is hydrogenated bisphenol A diacrylate, and 1 part of hyperbranched polyester acrylate with a molecular weight of 2000 g / mol is doped in the hydrogenated bisphenol A type acrylate monomer. The multifunctional thiol compound is pentaerythritol tetra(3-mercaptopropionate).

[0024] In this example, in the core-shell structured nanoparticles, the refractive index of the ZrO2 core is 2.1, the refractive index of the SiO2 shell is 1.45, and the core-shell volume ratio is 1:0.15. The shell layer of the core-shell structured nanoparticles has a gradient refractive index structure, and the refractive index from the core to the shell shows a stepwise decrease from 1.8 to 1.6 to 1.45. The coupling agent containing phosphate ester group is (2-methacryloyloxyethyl) phosphate.

[0025] In this example, the photoinitiator is an α-hydroxy ketone type photoinitiator, and it also contains 0.01 part of quantum dot material. The quantum dot material is a CdSe / ZnS core-shell structure with a particle size of 3 nm, which is used to match the 532 nm laser wavelength.

[0026] A preparation method of a nonlinear optical crystal and crystal combination adhesive, the preparation method is as follows: 1) Dispersing ZrO2 nanoparticles in ethanol, adding tetraethyl orthosilicate and ammonia water, and reacting at 50 °C for 2 hours to obtain core-shell structured ZrO2@SiO2 nanoparticles. The concentration of ammonia water is 25 wt%, and the mass ratio of tetraethyl orthosilicate to ZrO2 is 1:10; 2) Mixing the hydrogenated bisphenol A type acrylate monomer, multifunctional thiol compound, core-shell structured ZrO2@SiO2 nanoparticles, coupling agent and photoinitiator, and performing ultrasonic dispersion for 30 minutes. The ultrasonic dispersion is carried out under the protection of inert gas, with an ultrasonic power of 200 W and a frequency of 40 kHz; 3) Performing vacuum degassing treatment to obtain a uniform and transparent adhesive liquid.

[0027] Example 2

[0028] Please refer to Figure 1 , a nonlinear optical crystal and crystal combination adhesive in this example, characterized in that it includes the following components in parts by weight: Hydrogenated bisphenol A type acrylate monomer: 70 parts; Multifunctional thiol compound: 40 parts; Core-shell structured nanoparticles: 20 parts, with a core of ZrO2 and a shell of SiO2, the core particle size being 50 nm and the shell thickness being 8 nm; Coupling agent containing phosphate ester groups: 0.5 part; Photoinitiator: 3 parts.

[0029] In this example, the hydrogenated bisphenol A acrylate monomer is hydrogenated bisphenol A epoxy acrylate. 5 parts of hyperbranched polyester acrylate with a molecular weight of 5000 g / mol is doped in the hydrogenated bisphenol A acrylate monomer, and the polyfunctional mercaptan compound is trimethylolpropane tris(3-mercaptopropionate).

[0030] In this example, in the core-shell structured nanoparticles, the refractive index of the ZrO2 core is 2.2, the refractive index of the SiO2 shell is 1.55, and the core-shell volume ratio is 1:0.35. The shell layer of the core-shell structured nanoparticles has a gradient refractive index structure, and the refractive index from the core to the shell decreases stepwise from 1.8 to 1.6 to 1.45. The coupling agent containing phosphate ester groups is (3-acryloyloxypropyl) phosphate.

[0031] In this example, the photoinitiator is a benzoylformate photoinitiator, and it also contains 0.1 part of quantum dot material. The quantum dot material is a CdSe / ZnS core-shell structure with a particle size of 5 nm, which is used to match the 355 nm laser wavelength.

[0032] A preparation method of a nonlinear optical crystal and crystal combination adhesive, the preparation method is as follows: 1) Disperse ZrO2 nanoparticles in ethanol, add tetraethyl orthosilicate and ammonia water, and react at 70 °C for 4 hours to obtain core-shell structured ZrO2@SiO2 nanoparticles. The concentration of ammonia water is 28 wt%, and the mass ratio of tetraethyl orthosilicate to ZrO2 is 1:10; 2) Mix the hydrogenated bisphenol A acrylate monomer, polyfunctional mercaptan compound, core-shell structured ZrO2@SiO2 nanoparticles, coupling agent and photoinitiator, and perform ultrasonic dispersion for 60 minutes. The ultrasonic dispersion is carried out under the protection of inert gas, the ultrasonic power is 400 W, and the frequency is 40 kHz; 3) Perform vacuum degassing treatment to obtain a uniform and transparent adhesive liquid.

[0033] Example 3

[0034] Please refer to Figure 1 , a nonlinear optical crystal and crystal combination adhesive in this example, includes the following components in parts by weight: Hydrogenated bisphenol A acrylate monomer: 50 parts; Polyfunctional mercaptan compound: 30 parts; Core-shell structured nanoparticles: 18 parts, with a core of ZrO2 and a shell of SiO2, the core particle size is 30 nm, and the shell thickness is 6 nm; Coupling agent containing phosphate ester group: 0.4 part; Photoinitiator: 2 parts.

[0035] In this example, the hydrogenated bisphenol A type acrylate monomer is hydrogenated bisphenol A diacrylate, and 3 parts of hyperbranched polyester acrylate with a molecular weight of 3650 g / mol are doped in the hydrogenated bisphenol A type acrylate monomer. The polyfunctional thiol compound is ethylene glycol bis(3-mercaptopropionate).

[0036] In this example, in the core-shell structured nanoparticles, the refractive index of the ZrO2 core is 2.15, the refractive index of the SiO2 shell is 1.48, and the core-shell volume ratio is 1:0.25. The shell layer of the core-shell structured nanoparticles has a gradient refractive index structure, and the refractive index from the core to the shell decreases stepwise from 1.8 to 1.6 to 1.45. The coupling agent containing phosphate ester group is (2-methacryloyloxyethyl) phosphate.

[0037] In this example, the photoinitiator is a phosphine oxide type photoinitiator, and it also contains 0.08 part of quantum dot material. The quantum dot material is a CdSe / ZnS core-shell structure with a particle size of 4 nm, which is used to match the 532 nm laser wavelength.

[0038] A preparation method of a nonlinear optical crystal and a crystal combination adhesive is as follows: 1) Dispersing ZrO2 nanoparticles in ethanol, adding tetraethyl orthosilicate and ammonia water, and reacting at 65 °C for 3 hours to obtain core-shell structured ZrO2@SiO2 nanoparticles. The concentration of ammonia water is 26 wt%, and the mass ratio of tetraethyl orthosilicate to ZrO2 is 1:8; 2) Mixing the hydrogenated bisphenol A type acrylate monomer, the polyfunctional thiol compound, the core-shell structured ZrO2@SiO2 nanoparticles, the coupling agent and the photoinitiator, and performing ultrasonic dispersion for 45 minutes. The ultrasonic dispersion is carried out under the protection of inert gas, the ultrasonic power is 350 W, and the frequency is 40 kHz; 3) Performing vacuum degassing treatment to obtain a uniform and transparent adhesive liquid.

[0039] Experimental example 1: Adhesive refractive index and light loss test Test method: Measuring the refractive index (@1064 nm, 532 nm, 355 nm) of the cured adhesive film by using a prism coupler (Metricon2010). Measuring the light loss (dB / cm) of the bonding interface by using an integrating sphere spectrometer (OceanOpticsHDX).

[0040] Sample preparation: Example 1: Prepare the adhesive according to the present invention, with the component ratios the same as in Example 1.

[0041] Comparative Example 1: Commercial optical epoxy resin (Norland NOA61).

[0042] Comparative Example 2: UV-curable acrylic adhesive (Loctite 352).

[0043]

[0044] Results: After testing, it is proved that the adhesive of the present invention significantly reduces the interfacial optical loss due to the refractive index regulation of the core-shell nanoparticles (ZrO2@SiO2) and is applicable to high-power laser transmission.

[0045] Experimental Example 2: Shear strength and thermal cycle test Test method: Bond the KTP crystal (10mm×10mm×2mm) and the BBO crystal with reference to the process of Claim 8. Use a universal material testing machine (Instron 5944) to test the shear strength (MPa). Conduct a thermal cycle of -40°C - 85°C (30 minutes per cycle) and observe whether the interface cracks or debonds.

[0046] Results:

[0047] After testing, it is proved that the adhesive of the present invention exhibits excellent mechanical and thermal stability due to the strong interfacial bonding force of the phosphate coupling agent and the low coefficient of thermal expansion (CTE≈40ppm / °C).

[0048] Experimental Example 3: Laser frequency doubling efficiency test Test method: Build a frequency doubling system for a Nd:YAG laser (1064nm) and compare the following two bonding components: Component A: KTP + BBO bonding (using the adhesive of Example 1). Component B: KTP + BBO bonding (using commercial optical epoxy resin). Measure the conversion efficiency (%) of the output 532nm green light.

[0049] Results:

[0050] After testing, it is proved that the adhesive of the present invention increases the frequency doubling efficiency by an average of 12%, mainly due to the low optical loss (0.4dB / cm vs. 3.2dB / cm) and the high refractive index matching.

[0051] In summary, through the precise regulation of ZrO2@SiO2 core-shell nanoparticles, the refractive index of the adhesive can be adjusted within the range of 1.65 - 2.10, which highly matches the refractive index of 1.7 - 2.2 of nonlinear optical crystals such as KTP, BBO, and LBO. This reduces the Fresnel loss at the bonding interface to ≤0.5 dB / cm, significantly improving the laser frequency conversion efficiency. The core-shell structure of the nanoparticles effectively inhibits agglomeration, and the cured adhesive layer has a transmittance ≥99.5% at common laser wavelengths such as 1064 nm, 532 nm, and 355 nm, making it suitable for high-power laser systems. By adding quantum dot materials, the refractive index matching at specific wavelengths can be further optimized, expanding the application scenarios. The synergistic effect of multi-functional thiol compounds and hyperbranched polyester acrylate reduces the polymerization stress, avoiding crystal cracking or interfacial delamination. The thermal expansion coefficient of the cured adhesive is 30 - 50 ppm / °C, which is close to that of common optical crystals, and there is no cracking or peeling phenomenon in the range of -40 - 120 °C, solving the problems of traditional optical adhesives such as epoxy resins and UV adhesives. Their refractive index is 1.4 - 1.6, which seriously mismatches with the 1.7 - 2.2 of nonlinear crystals, resulting in an interfacial Fresnel loss >15%. The high-temperature curing process >120 °C easily causes the destruction of the domain structure of ferroelectric crystals such as LiNbO3, and existing silicon-based adhesives have an absorption peak at 532 nm, affecting the second harmonic generation efficiency.

[0052] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0053] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nonlinear optical crystal and a crystal combination adhesive, characterized in that, Comprising the following components in parts by weight: Hydrogenated bisphenol A acrylate monomer: 40 - 70 parts; Polyfunctional thiol compound: 20 - 40 parts; Core-shell structured nanoparticles: 10 - 20 parts, with a core of ZrO2 and a shell of SiO2, the core particle size being 20 - 50 nm and the shell layer thickness being 3 - 8 nm; Coupling agent containing phosphate ester group: 0.1 - 0.5 part; Photoinitiator: 1 - 3 parts.

2. A nonlinear optical crystal and crystal combination adhesive according to claim 1, wherein The hydrogenated bisphenol A acrylate monomer is at least one of hydrogenated bisphenol A diacrylate and hydrogenated bisphenol A epoxy acrylate, and 1 - 5 parts of hyperbranched polyester acrylate with a molecular weight of 2000 - 5000 g / mol is doped in the hydrogenated bisphenol A acrylate monomer.

3. A nonlinear optical crystal and crystal combination adhesive according to claim 1, characterized in that, The polyfunctional thiol compound is at least one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and ethylene glycol bis(3-mercaptopropionate).

4. A nonlinear optical crystal and crystal combination adhesive according to claim 1, characterized in that, In the core-shell structured nanoparticles, the refractive index of the ZrO2 core is 2.1 - 2.2, the refractive index of the SiO2 shell is 1.45 - 1.55, and the core-shell volume ratio is 1:(0.15 - 0.35). The shell layer of the core-shell structured nanoparticles has a gradient refractive index structure, and the refractive index decreases stepwise from 1.8 to 1.6 to 1.45 from the core to the shell.

5. A nonlinear optical crystal and crystal combination adhesive according to claim 1, characterized in that, The coupling agent containing phosphate ester group is at least one of (2-methacryloyloxyethyl) phosphate and (3-acryloyloxypropyl) phosphate.

6. A nonlinear optical crystal and crystal combination adhesive according to claim 1, characterized in that, The photoinitiator is an α-hydroxy ketone-based, benzoyl formate-based, or phosphine oxide-based photoinitiator.

7. A nonlinear optical crystal and crystal combination adhesive according to claim 1, characterized in that, It also contains 0.01 - 0.1 part of quantum dot material, and the quantum dot material is a CdSe / ZnS core-shell structure with a particle size of 3 - 5 nm, which is used to match the 532 nm or 355 nm laser wavelength.

8. A method for preparing a nonlinear optical crystal and a crystal combination adhesive according to any one of claims 1-7, characterized in that, The preparation method is specifically as follows: 1) Disperse ZrO2 nanoparticles in ethanol, add tetraethyl orthosilicate and ammonia water, and react at 50 - 70 °C for 2 - 4 hours to obtain core-shell structured ZrO2@SiO2 nanoparticles; 2) Mix the hydrogenated bisphenol A acrylate monomer, polyfunctional thiol compound, core-shell structured ZrO2@SiO2 nanoparticles, coupling agent, and photoinitiator, and perform ultrasonic dispersion for 30 - 60 minutes; 3) Perform vacuum degassing treatment to obtain a uniform and transparent adhesive liquid.

9. The preparation method of a nonlinear optical crystal and a crystal combination adhesive according to claim 8, characterized in that, In the step 1), the concentration of ammonia water is 25 - 28 wt%, and the mass ratio of tetraethyl orthosilicate to ZrO2 is 1:(5 - 10).

10. The preparation method of a nonlinear optical crystal and a crystal combination adhesive according to claim 8, wherein, The ultrasonic dispersion in the step 2) is carried out under the protection of an inert gas, with an ultrasonic power of 200 - 400 W and a frequency of 40 kHz.

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