High-transmittance uv-curing adhesive for LED light source plate and preparation method and application thereof

Abstract

This invention relates to a high-transmittance UV-curable adhesive for LED light source boards, its preparation method, and its application, belonging to the field of adhesive technology. The adhesive comprises, by weight, 40-70 parts of polyurethane acrylate oligomer, 20-50 parts of reactive diluent, 1-5 parts of photoinitiator, 0.5-3 parts of silane coupling agent, 0.1-1 parts of antioxidant, and 0.1-1 parts of UV absorber; wherein the polyurethane acrylate oligomer is an aliphatic polyurethane acrylate with a number average molecular weight of 1000-5000 and a functionality of 2-4; the reactive diluent is composed of IBOA and HEA in a mass ratio of (2-4):1. After curing, the adhesive of this invention exhibits a light transmittance ≥95% at a thickness of 1 mm, a curing shrinkage rate ≤2%, a yellowing index ΔE ≤2 after aging at 85℃ / 85%RH for 1000 h, an adhesion retention rate ≥90%, a deep curing depth ≥2.8 mm, and a shear strength ≥15 MPa against PC, glass, and other substrates. This invention solves the problems of low light transmittance, high shrinkage, and poor aging resistance of existing UV adhesives, and is especially suitable for LED chip fixing and lens bonding.

Description

Technical Field

[0001] This invention relates to the field of adhesives for LED light source boards, and more particularly to a high-transmittance UV-curable adhesive for LED light source boards, its preparation method, and its application. Background Technology

[0002] LED light source boards are widely used in lighting, display and other fields. Adhesives are required for fixing LED chips, bonding lenses to the light source board, and coating and protecting the surface of the light source board. Ultraviolet (UV) curing adhesives are favored due to their advantages such as fast curing speed, solvent-free, and environmentally friendly properties.

[0003] However, existing UV-curable adhesives have the following problems in LED light source board applications: when the adhesive layer thickness is large (>0.5mm), the light transmittance is less than 90%, affecting the LED light output efficiency; the curing shrinkage rate of conventional UV adhesives is more than 5%, which leads to internal stress after curing, causing chip displacement or lens deformation; after long-term use in high temperature and high humidity environments (85℃ / 85%RH), the adhesive layer yellows severely, and the adhesion decreases; when the adhesive layer thickness exceeds 1mm, it is difficult to cure completely, limiting its application in thick-walled lens bonding.

[0004] In addition, LED light source boards have the following unique characteristics: the junction temperature of LED chips can reach 80-100℃ under prolonged illumination, placing higher demands on the heat aging resistance of adhesives; some LED chips emit a small amount of ultraviolet light or high-energy blue light, which can easily cause the adhesive to yellow under long-term exposure; and excessive curing shrinkage can cause micron-level displacement or tilting of the chip, directly affecting the collimation of the optical path and the uniformity of light emission. Therefore, the fixing adhesive used for LED light source boards needs to maintain high light transmittance while also possessing excellent heat aging resistance, resistance to ultraviolet yellowing, and ultra-low shrinkage characteristics. The requirements for material performance are significantly higher than those in the general optical adhesive field.

[0005] Therefore, there is an urgent need to develop a UV-curable adhesive with high light transmittance, low shrinkage, aging resistance, and excellent deep curing performance to meet the special application requirements of LED light source boards. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-transmittance UV-curable adhesive for LED light source boards, which has high light transmittance, low shrinkage, aging resistance and excellent deep curing performance, as well as its preparation method and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a high-transmittance UV-curable adhesive for LED light source boards, comprising the following components in parts by weight: 40-70 parts of polyurethane acrylate oligomer, 20-50 parts of reactive diluent, 1-5 parts of photoinitiator, 0.5-3 parts of silane coupling agent, 0.1-1 parts of antioxidant, and 0.1-1 parts of ultraviolet light absorber; The polyurethane acrylate oligomer is an aliphatic polyurethane acrylate with a number average molecular weight of 1000-5000 and a functionality of 2-4; the reactive diluent is composed of isobornyl acrylate (IBOA) and hydroxyethyl acrylate (HEA) in a mass ratio of (2-4):1.

[0008] In a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, the photoinitiator is selected from one or more of 2-hydroxy-2-methyl-1-phenylpropanone (1173), 1-hydroxycyclohexylphenyl ketone (184), and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0009] As a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH-570) or γ-glycidoxypropyltrimethoxysilane (KH-560).

[0010] In a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, the antioxidant is a hindered phenolic antioxidant, such as 1010 or 1076, and / or a phosphite antioxidant, such as 168.

[0011] In a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, the ultraviolet absorber is a benzotriazole, such as UV-329, or a triazine, such as UV-1164.

[0012] As a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards according to the present invention, the high-transmittance UV-curable adhesive satisfies at least one of the following properties: (a) When the cured thickness is 1 mm, the transmittance in the wavelength range of 400-800 nm is ≥95%, as measured according to GB / T 2410-2008; (b) The cured volume shrinkage rate is ≤2%, as determined by ASTM D2566.

[0013] As a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, after undergoing an aging test (85°C, 85% relative humidity, 1000h) according to GB / T 2423.3-2016, it meets at least one of the following properties: (a) According to ASTM E313, the yellowing index ΔE ≤ 2; (b) The shear strength retention rate of the polycarbonate substrate is ≥90%, as determined by GB / T 7124-2008.

[0014] As a preferred embodiment of the high-transmittance UV-curable adhesive for LED light source boards described in this invention, it does not contain non-curing polyoxyalkylene polyols (i.e., polyether polyol plasticizers that do not participate in the crosslinking network).

[0015] Secondly, the present invention provides a method for preparing the above-mentioned high-transmittance UV-curable adhesive for LED light source boards, which includes the following steps: 1) Weigh each component according to its weight parts; 2) Stir and mix the polyurethane acrylate oligomer and reactive diluent until homogeneous; 3) Add photoinitiator, silane coupling agent, antioxidant and ultraviolet light absorber, and continue stirring until completely dissolved; 4) Filter and degas under light-protected conditions to obtain the final product.

[0016] Preferably, the mixing temperature in step 2) is 40-60°C.

[0017] Preferably, the stirring time in step 3) is 30-60 minutes.

[0018] Thirdly, the present invention provides an LED light source board, including a substrate, an LED chip, and an adhesive layer for fixing the LED chip onto the substrate, wherein the adhesive layer is formed by curing the aforementioned UV-curable adhesive with ultraviolet light.

[0019] Fourthly, the present invention provides the application of the above-mentioned high-transmittance UV-curable adhesive for LED light source boards in LED chip fixing, lens bonding, or surface coating protection of light source boards.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The high-transmittance UV-curable adhesive provided by this invention comprises, by weight, the following components: 40-70 parts of polyurethane acrylate oligomer, 20-50 parts of reactive diluent, 1-5 parts of photoinitiator, 0.5-3 parts of silane coupling agent, 0.1-1 parts of antioxidant, and 0.1-1 parts of UV absorber; wherein the polyurethane acrylate oligomer is an aliphatic polyurethane acrylate with a number average molecular weight of 1000-5000 and a functionality of 2-4; the reactive diluent is composed of isobornyl acrylate and hydroxyethyl acrylate in a mass ratio of (2-4):1.

[0021] This invention uses aliphatic polyurethane acrylate compounded with a specific reactive diluent, combined with the synergistic effect of antioxidants and ultraviolet absorbers. After curing, the transmittance of the adhesive layer (1mm thick) in the visible light region is ≥95%, effectively improving the light extraction efficiency of LEDs. By using a reactive diluent composed of IBOA and HEA in a ratio of (2-4):1, the curing volume shrinkage rate is ≤2%, far lower than the 5% or more of conventional UV adhesives, preventing LED chip displacement. Under the synergistic compounding of antioxidants and ultraviolet absorbers, after aging at 85℃ / 85%RH for 1000h, the yellowing index ΔE of the adhesive layer is ≤2, the adhesion retention rate is ≥90%, and the transmittance retention rate is ≥93%, meeting the requirements for long-term LED operation. Using the long-wavelength photoinitiator TPO, the deep curing depth of this invention is ≥2.8mm, meeting the packaging requirements of thick-walled lenses and large-size LED chips. The combination of silane coupling agent and polyurethane acrylate enables this invention to achieve a shear strength ≥15MPa on various substrates such as PC, glass, and aluminum / copper, ensuring high bonding reliability.

[0022] In summary, the present invention is significantly superior to the prior art in terms of light transmittance, shrinkage, anti-aging, deep curing and adhesion, and in particular solves the problems of yellowing and chip displacement of UV adhesives used in LED light source boards during long-term use. Detailed Implementation

[0023] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. The embodiments described below are some, but not all, embodiments of this invention. The embodiments of this invention are used to illustrate the invention, not to limit it. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Unless otherwise specified, experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. The raw materials and reagents used are commercially available conventional products or products that conform to relevant national / industry standards and are all commercially available.

[0024] Some of the raw materials and their sources are shown in Table 1 below.

[0025] Table 1

[0026] Example 1 This embodiment provides a high-transmittance UV-curable adhesive, which, by weight, comprises the following components: 50 parts of polyurethane acrylate oligomer (aliphatic polyurethane acrylate, functionality 2, number average molecular weight 2000, model: CN9010, Sartoma), 30 parts of reactive diluent A (IBOA), 10 parts of reactive diluent B (HEA), 2 parts of photoinitiator (TPO), 1.5 parts of silane coupling agent (KH-570), 0.5 parts of antioxidant (antioxidant 1010), and 0.5 parts of ultraviolet light absorber (UV-329).

[0027] This embodiment provides a method for preparing a high-transmittance UV-curable adhesive, the specific steps of which are as follows: (1) Weigh each raw material according to the above weight parts, wherein the polyurethane acrylate oligomer is preheated to 50°C before use to reduce viscosity; (2) Add polyurethane acrylate oligomer, IBOA and HEA to the reactor and stir at 50°C and 200 rpm for 20 minutes until they are mixed evenly. (3) Add TPO, KH-570, antioxidant 1010 and UV-329, and continue to stir at 50℃ and 300rpm for 45 minutes until completely dissolved to form a transparent and homogeneous liquid; (4) Filter the mixture through a 1μm filter element, and then place it in a vacuum degassing machine. Degas for 15 minutes under a vacuum degree ≤ -0.09MPa (i.e., an absolute pressure of about 0.01MPa) to obtain the UV-curable adhesive.

[0028] The curing conditions in this embodiment are: using a 365nm UV-LED light source, a light intensity of 500mW / cm², and an irradiation time of 60 seconds.

[0029] Example 2 This embodiment provides a high-transmittance UV-curable adhesive, which, by weight, comprises the following components: 40 parts of polyurethane acrylate oligomer (aliphatic polyurethane acrylate, functionality 2, number average molecular weight 2000, model: CN9010, Sartoma), 13.4 parts of reactive diluent A (IBOA), 6.67 parts of reactive diluent B (HEA), 1 part of photoinitiator (2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO)), 0.5 parts of silane coupling agent (KH-570), 0.1 parts of antioxidant (antioxidant 1010), and 0.1 parts of ultraviolet light absorber (UV-329).

[0030] The preparation method in this embodiment is the same as that in Example 1.

[0031] The curing conditions in this embodiment are: using a 365nm UV-LED light source, a light intensity of 500mW / cm², and an irradiation time of 60 seconds.

[0032] Example 3 This embodiment provides a high-transmittance UV-curable adhesive, which, by weight, comprises the following components: 70 parts of polyurethane acrylate oligomer (aliphatic polyurethane acrylate, functionality 2, number average molecular weight 2000, model: CN9010, Sartoma), 40 parts of reactive diluent A (IBOA), 10 parts of reactive diluent B (HEA), 5 parts of photoinitiator (2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO)), 3 parts of silane coupling agent (KH-570), 1 part of antioxidant (antioxidant 1010), and 1 part of ultraviolet light absorber (UV-329).

[0033] The preparation method in this embodiment is the same as that in Example 1.

[0034] The curing conditions in this embodiment are: using a 365nm UV-LED light source, a light intensity of 500mW / cm², and an irradiation time of 60 seconds.

[0035] Comparative Example 1 (no antioxidants, no UV absorbers) The difference between the formulation of this comparative example and that of Example 1 is that antioxidant 1010 and ultraviolet absorber UV-329 are not added, while the remaining components, proportions, preparation methods and curing conditions are the same as those of Example 1.

[0036] Comparative Example 2 (Antioxidant alone, without UV absorber) The difference between the formulation of this comparative example and that of Example 1 is that 0.5 parts of antioxidant 1010 are added, but UV absorber UV-329 is not added. The remaining components, proportions, preparation methods and curing conditions are the same as those of Example 1.

[0037] Comparative Example 3 (UV absorber alone, no antioxidant) The difference between the formulation of this comparative example and that of Example 1 is that 0.5 parts of UV-329 are added, but antioxidant 1010 is not added. The remaining components, proportions, preparation methods and curing conditions are the same as those of Example 1.

[0038] It should be noted that, as a preferred embodiment of the present invention, the high-transmittance UV-curable adhesive does not contain non-curing polyoxyalkylene polyols. This embodiment does not add non-reactive plasticizers, and the resulting adhesive effectively avoids interfacial contamination and decreased adhesion caused by the migration of small molecule plasticizers, exhibiting good long-term stability. This application, through a specific ratio of IBOA and HEA compounding and molecular structure optimization of polyurethane acrylate oligomers, achieves an ultra-low curing shrinkage rate of ≤2% and a shear strength of ≥15MPa without relying on non-reactive plasticizers, making it more suitable for LED light source board packaging scenarios with stringent reliability requirements.

[0039] It should also be noted that the above-mentioned raw materials are all commercially available products commonly used in the field. Those skilled in the art can choose equivalent substitutes according to actual needs, and are not limited to specific brands or models.

[0040] Performance testing 1. Sample preparation and curing The adhesives prepared in Examples 1-3 and Comparative Examples 1-3 were made into samples according to the requirements of each test standard. They were placed in the dark for 24 hours under standard conditions (temperature 23±2℃, relative humidity 50±5%), and then cured according to the curing conditions (365nm UV-LED, 500mW / cm², 60 seconds) to obtain cured samples.

[0041] The obtained samples were numbered as Sample A (Example 1), Sample B (Example 2), Sample C (Example 3), Sample D (Comparative Example 1: No antioxidant + No UV absorber), Sample E (Comparative Example 2: Antioxidant only), and Sample F (Comparative Example 3: UV absorber only). The performance test items, methods, and standards are shown in Table 2 below.

[0042] Table 2

[0043] Note: PC stands for polycarbonate.

[0044] 2. Test Results 2.1 The light transmittance, curing shrinkage, shear strength, deep curing depth, aging resistance and strength retention after thermal shock were tested on the sample AF. The test results are shown in Table 3 below.

[0045] Table 3

[0046] 3. Test Result Analysis As shown in Table 3, Example 1 (Sample A) exhibits the best overall performance, fully meeting the requirements of transmittance ≥95%, shrinkage ≤2%, ΔE ≤2 after aging, and shear strength retention ≥90%. Examples 2 (Sample B) and 3 (Sample C) also demonstrate excellent overall performance, with transmittance, deep curing depth, and strength retention after aging all superior to the comparative example. Although some performance characteristics are slightly lower than the preferred values ​​of Example 1, they still meet the packaging requirements of LED light source boards, proving that the technical solution of this invention has a wide range of applications and good adjustability.

[0047] Comparative Example 1 (D) lacked antioxidants and UV absorbers, resulting in severe yellowing and extremely low strength retention after aging, failing to meet the long-term use requirements of LED light source boards. Comparative Examples 2 (E) and 3 (F) only added antioxidants or UV absorbers, respectively, and although their aging performance was slightly better than that of Comparative Example 1, it was still significantly inferior to the examples.

[0048] In summary, this invention, through the synergistic combination of antioxidants and UV absorbers, significantly improves aging resistance (ΔE≤2, shear strength retention rate≥90%) while maintaining high light transmittance and low shrinkage. It solves the problems of yellowing and adhesion failure in UV adhesives used in LED light source boards during long-term use, and has outstanding substantive features and significant progress.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-transmittance UV-curable adhesive for LED light source boards, characterized in that, By weight, it includes the following components: 40-70 parts polyurethane acrylate oligomer, 20-50 parts reactive diluent, 1-5 parts photoinitiator, 0.5-3 parts silane coupling agent, 0.1-1 part antioxidant, and 0.1-1 part ultraviolet light absorber. The polyurethane acrylate oligomer is an aliphatic polyurethane acrylate with a number average molecular weight of 1000-5000 and a functionality of 2-4; the reactive diluent is composed of isobornyl acrylate and hydroxyethyl acrylate in a mass ratio of (2-4):

1.

2. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, The photoinitiator is selected from one or more of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

3. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, The silane coupling agent is γ-methacryloxypropyltrimethoxysilane or γ-glycidoxypropyltrimethoxysilane.

4. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, The antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant; and / or, the ultraviolet absorber is a benzotriazole or triazine ultraviolet absorber.

5. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, The high-transmittance UV-curable adhesive meets at least one of the following properties: (a) When the cured thickness is 1 mm, the transmittance in the wavelength range of 400-800 nm is ≥95%, as measured according to GB / T 2410-2008; (b) The cured volume shrinkage rate is ≤2%, as determined by ASTM D2566.

6. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, After undergoing an aging test (85℃, 85% relative humidity, 1000h) according to GB / T 2423.3-2016, it must meet at least one of the following performance requirements: (a) The yellowing index ΔE is ≤2.0 as determined by ASTM E313; (b) The shear strength retention rate of the polycarbonate substrate is ≥90%, as determined by GB / T 7124-2008.

7. The high-transmittance UV-curable adhesive as described in claim 1, characterized in that, It does not contain non-curing polyoxyalkylene polyols.

8. A method for preparing a high-transmittance UV-curable adhesive for LED light source boards as described in any one of claims 1-7, characterized in that, Includes the following steps: 1) Weigh each component according to its weight parts; 2) Stir and mix the polyurethane acrylate oligomer and reactive diluent until homogeneous; 3) Add photoinitiator, silane coupling agent, antioxidant and ultraviolet light absorber, and continue stirring until completely dissolved; 4) Filter and degas under light-protected conditions to obtain the final product.

9. An LED light source board, characterized in that, It includes a substrate, an LED chip, and an adhesive layer for fixing the LED chip onto the substrate, wherein the adhesive layer is formed by curing the UV-curable adhesive according to any one of claims 1-7 with ultraviolet light.

10. The application of a UV-curable adhesive as described in any one of claims 1-7 in LED chip fixing, lens bonding, or surface coating protection of a light source board.

Images