Preparation method of cation curing epoxy glue for camera module

Abstract

The invention relates to the technical field of preparation of special epoxy resin glue, in particular to a preparation method of cation curing epoxy glue for a camera module. The invention relates to a cationic curing epoxy adhesive for a camera module. The cationic curing epoxy adhesive is prepared from 10-15 parts of toughening resin, 20-30 parts of matrix epoxy resin, 30-60 parts of filler, 5-10 parts of a diluent, 1-2 parts of an auxiliary agent and 1-3 parts of a cationic initiator. The toughening resin is epoxy group terminated flexible epoxy resin and / or a polyurethane prepolymer containing an epoxy group. The cation curing epoxy glue can be rapidly cured and is small in curing shrinkage, and the assembly capacity and the yield of the camera module are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of special epoxy resin adhesive preparation technology, and in particular to a method for preparing cationic curing epoxy adhesive for camera modules. Background Technology

[0002] Current camera module assembly primarily relies on assembly line production, with adhesives mainly consisting of UV-cured acrylic adhesives and high-temperature curing epoxy adhesives. While UV-cured acrylic adhesives offer rapid UV curing, their limitations in curing depth and excessive shrinkage negatively impact camera module yield. High-temperature curing epoxy adhesives address the yield issues related to curing depth and shrinkage, but their high-temperature curing method leads to low assembly efficiency and significant production capacity decline. Furthermore, the materials used in existing camera modules exhibit limited high-temperature resistance, necessitating strict requirements for the curing conditions of high-temperature curing epoxy adhesives, resulting in high costs for suitable medium-to-high-temperature curing epoxy adhesives. Excessive curing temperatures can damage camera modules, affecting product quality. Therefore, the inventors have provided a method for preparing cationic curing epoxy adhesives for camera modules. Summary of the Invention

[0003] To address the issues of reduced yield and damage to camera modules caused by excessively high curing temperatures in existing camera module adhesives due to issues with curing depth and shrinkage, which affect product quality, this invention provides a cationic curable epoxy adhesive for camera modules and its preparation method.

[0004] The present invention provides a method for preparing cationic curable epoxy adhesive for camera modules, which is achieved through the following technical solution:

[0005] A cationic curable epoxy adhesive for camera modules comprises 10-15 parts toughening resin, 20-30 parts matrix epoxy resin, 30-60 parts filler, 5-10 parts diluent, 1-2 parts additives, and 1-3 parts cationic initiator; wherein the toughening resin is an epoxy-terminated flexible epoxy resin and / or an epoxy-containing polyurethane prepolymer.

[0006] The cationic curing epoxy adhesive of this invention can cure quickly and has low curing shrinkage, making it suitable for camera module assembly production and greatly improving camera module assembly capacity and yield.

[0007] Preferably, the epoxy-based polyurethane prepolymer includes at least one of the following: a main-chain epoxy-terminated polyurethane prepolymer, a side-chain epoxy-terminated polyurethane prepolymer, a side-chain allyl-terminated and main-chain epoxy-terminated polyurethane prepolymer, and a side-chain epoxy-terminated and main-chain allyl-terminated polyurethane prepolymer.

[0008] In this invention, epoxy-based polyurethane prepolymers are used to toughen and modify the epoxy adhesive, giving it good adhesion, flexibility, and resistance to thermal shock, while also improving its water resistance and chemical corrosion resistance.

[0009] Preferably, the epoxy-containing polyurethane prepolymer is prepared from diisocyanate, polyol, chain extender, catalyst, and end-capping agent.

[0010] Preferably, the total molar amount of -NCO in the diisocyanate is 1.2-1.6 times the total molar amount of active hydrogen functional groups in the polyol and chain extender; and the total molar amount of active hydrogen functional groups in the polyol, chain extender, and capping agent is 1.0-1.02 times the total molar amount of -NCO in the diisocyanate.

[0011] Preferably, the diisocyanate is any one or a combination of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate.

[0012] Preferably, the polyol is composed of at least one of terminal hydroxyl polybutadiene and terminal hydroxyl epoxidized polybutadiene combined with at least one of polyether diol and polycarbonate diol.

[0013] Preferably, the catalyst is an organotin or organobismuth.

[0014] Preferably, the chain extender is a small molecule diol with a molecular weight ≤174.3.

[0015] Preferably, the capping agent is at least one selected from bisphenol A type epoxy resin, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid.

[0016] More preferably, the diisocyanate is isophorone diisocyanate or isophorone diisocyanate combined with any one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate; the polyol is composed of hydroxyl-terminated polybutadiene combined with at least one of polyether diol and polycarbonate diol; and the end-capping agent is bisphenol A type epoxy resin combined with at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid.

[0017] Alternatively, more preferably, the diisocyanate is isophorone diisocyanate or isophorone diisocyanate combined with any one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate; the polyol is composed of hydroxyl-terminated epoxidized polybutadiene combined with at least one of polyether diol and polycarbonate diol; and the end-capping agent is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate combined with at least one of bisphenol A epoxy resin, dimethylolpropionic acid, and dimethylolbutyric acid.

[0018] Preferably, the polyol is composed of hydroxyl-terminated polybutadiene, polyether glycol, and polycarbonate glycol in a molar ratio of (0.5-2):(1-4):(1-4);

[0019] Alternatively, preferably, the polyol is composed of hydroxyl-terminated epoxidized polybutadiene, polyether diol, and polycarbonate diol in a molar ratio of (0.5-2):(1-4):(1-4).

[0020] Preferably, the toughening resin is an epoxy group-terminated flexible epoxy resin, which is prepared by a carboxyl-terminated compound, an epoxy resin with ≥2 epoxy functional groups, and a catalyst.

[0021] Preferably, the carboxyl-terminated compound is at least one of octadecadienoic acid dimer, C14-C18 dicarboxylic acid, 2-mercaptophenylacetic acid, ricinoleic acid, carboxyl-terminated polybutadiene, and carboxyl-terminated nitrile rubber.

[0022] Preferably, the epoxy resin with ≥2 epoxy functional groups is at least one of polybutadiene epoxy resin, bisphenol A (2,3-dihydroxypropyl) glycidyl ether, 1,3-bis(2',4'-bis(glycidyl ether)phenyl)adamantane, dicyclopentadiene dioxide, and diglycidyl 4,5-epoxytetrahydrophthalic acid.

[0023] Preferably, the catalyst is at least one selected from triphenylphosphine, 2-methylimidazole, 2-ethyl-4-methylimidazole, phosphine bromide complex, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

[0024] Preferably, the reaction conditions for the epoxy-terminated flexible epoxy resin are: under an inert atmosphere, the temperature is raised to 140-160℃ and reacted for 3-5 hours; the molar amount of epoxy functional groups in the epoxy resin with ≥2 epoxy functional groups is greater than the molar amount of carboxyl oxygen functional groups in the terminal carboxyl compound.

[0025] In this invention, epoxy-terminated flexible epoxy resin is used to toughen and modify the epoxy adhesive product, giving it good adhesion, flexibility, and resistance to thermal shock.

[0026] Preferably, the matrix epoxy resin is at least one selected from bisphenol F glycidyl 2,3-dihydroxypropyl ether, dicyclopentadiene dioxide, 2-biphenyl glycidyl ether, 4,4'-biphenyl bisphenol diglycidyl ether, and 2,2'-(naphthalene-1,6-dimethylbis(oxy))bis(methylene)diepoxyethylene.

[0027] Preferably, the filler has a median particle size D. 50 It is at least one of the following: spherical silica powder, spherical alumina, spherical silica, spherical aluminum nitride, and spherical hollow glass microspheres with a diameter of 1μm to 10μm.

[0028] Preferably, the diluent is at least one selected from oxabutane, oxabutane derivatives, ethylene oxide diluents, and vinyl ethers.

[0029] Preferably, the cationic initiator is at least one selected from iodonium salt, thionium salt, and ferrocene salt.

[0030] Preferably, the additives include antisettling agents, epoxy silane coupling agents, and leveling agents.

[0031] Preferably, the anti-settling agent is at least one of BYK-W9010 and BYK-985.

[0032] Preferably, the silane coupling agent is at least one selected from 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-aminopropyltriethoxysilane.

[0033] Preferably, the leveling agent is at least one of BYK-732 and BYK-322.

[0034] A method for preparing cationic curable epoxy adhesive for camera modules includes the following steps:

[0035] S1. Preparation of toughening resin;

[0036] S2. Accurately measure 10-15 parts of toughening resin, 20-30 parts of base epoxy resin, 30-60 parts of filler, 5-10 parts of diluent, and 1-2 parts of additives and mix them evenly at 15-25℃. Then adjust the temperature to 5-20℃ and add 1-3 parts of cationic initiator and mix evenly. Use a scraper fineness meter to scrape the particle size to confirm that it is controlled below 10μm. Centrifuge and degas to obtain cationic cured epoxy adhesive.

[0037] The curing conditions for the cationic curable epoxy adhesive are as follows: the wavelength of the ultraviolet light source is 200-450nm, specifically 365nm or 395nm, and the ultraviolet light energy is 1500-2000mJ / cm². 2The UV curing time is 10-20 seconds.

[0038] This invention provides a simple method for preparing cationic curing epoxy adhesive, which is easy to implement for industrial production. Furthermore, the application method of the cationic curing epoxy adhesive is simple, which can improve the assembly capacity and yield rate of camera modules.

[0039] In summary, the present invention has the following advantages:

[0040] 1. The cationic curing epoxy adhesive in this invention can cure quickly and has low curing shrinkage. Its excellent bonding strength can ensure the assembly quality of camera modules and greatly improve the assembly capacity and yield of camera modules.

[0041] 2. The method for preparing cationic curing epoxy adhesive provided by this invention is simple and suitable for large-scale production.

[0042] 3. In this invention, epoxy-based polyurethane prepolymers are used to toughen and modify the epoxy adhesive, giving it better bonding stability, flexibility, and resistance to thermal shock. At the same time, it can also improve the epoxy adhesive's water resistance and chemical corrosion resistance, making it better suited for camera module assembly. Attached Figure Description

[0043] Figure 1 The graphs show the strength retention rates of the epoxy resins in Examples 1-10 and Comparative Examples 1-2 after double 85.

[0044] Figure 2 The graphs show the thermal shock strength retention rates of the epoxy resins in Examples 1-10 and Comparative Examples 1-2. Detailed Implementation

[0045] To further understand the inventiveness and technical advancements of this invention, the preferred embodiments of this invention will be discussed in detail below with reference to examples and comparative examples.

[0046] Example: A cationic curable epoxy adhesive for camera modules consists of 10-15 parts toughening resin, 20-30 parts matrix epoxy resin, 30-60 parts filler, 5-10 parts diluent, 1-2 parts additives, and 1-3 parts cationic initiator.

[0047] The matrix epoxy resin is at least one of bisphenol F glycidyl 2,3-dihydroxypropyl ether, dicyclopentadiene dioxide, 2-biphenyl glycidyl ether, 4,4'-biphenyl bisphenol diglycidyl ether, and 2,2'-(naphthalene-1,6-dimethylbis(oxy))bis(methylene)diepoxyethylene.

[0048] The filler has a median particle size D. 50The filler is at least one of the following: spherical silica micropowder with a particle size of 1μm to 10μm, spherical alumina, spherical silica, spherical aluminum nitride, and spherical hollow glass microspheres. The filler is preferably spherical silica micropowder (Jiangsu Lianrui New Material Co., Ltd.), with a median particle size D. 50 Customizable.

[0049] The diluent is at least one of oxabutane, oxabutane derivatives, ethylene oxide diluents, and vinyl ethers. The preferred diluent is 2-ethyl-3-hydroxymethyloxabutane or oxabutane OXT121.

[0050] The cationic initiator is at least one of iodonium salt, thionium salt, and ferrocene salt, specifically iodonium salt Irgacue 250 or iodonium salt Omnicat 320.

[0051] Additives include antisettling agents, epoxy silane coupling agents, and leveling agents.

[0052] The anti-settling agent is at least one of BYK-W9010 and BYK-985.

[0053] The silane coupling agent is at least one of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-aminopropyltriethoxysilane.

[0054] The leveling agent is at least one of BYK-732 and BYK-322.

[0055] The toughening resin is an epoxy-terminated flexible epoxy resin and / or an epoxy-containing polyurethane prepolymer.

[0056] The epoxy-based polyurethane prepolymers include at least one of the following: polyurethane prepolymers with main-chain epoxy end-capping, polyurethane prepolymers with side-chain epoxy end-capping, polyurethane prepolymers with side-chain allyl end-capping and main-chain epoxy end-capping, and polyurethane prepolymers with side-chain epoxy end-capping and main-chain allyl end-capping.

[0057] The epoxy-containing polyurethane prepolymer is prepared from diisocyanate, polyol, chain extender, catalyst, and end-capping agent. The total molar amount of -NCO in the diisocyanate is 1.2-1.6 times the total molar amount of active hydrogen functional groups in the polyol and chain extender, and the total molar amount of active hydrogen functional groups in the polyol, chain extender, and end-capping agent is 1.0-1.02 times the total molar amount of -NCO in the diisocyanate.

[0058] The diisocyanate is any one or a combination of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate. Preferably, the diisocyanate is isophorone diisocyanate or isophorone diisocyanate combined with any one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate.

[0059] The polyol is composed of at least one of terminal hydroxyl polybutadiene and terminal hydroxyl epoxidized polybutadiene combined with at least one of polyether diol and polycarbonate diol.

[0060] The catalyst is an organotin or organobismuth. The chain extender is a small molecule diol with a molecular weight ≤174.3.

[0061] The capping agent is at least one of bisphenol A type epoxy resin, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid.

[0062] Preferably, the polyol is composed of hydroxyl-terminated polybutadiene combined with at least one of polyether glycol and polycarbonate glycol. The end-capping agent is bisphenol A type epoxy resin combined with at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid. Specifically, the polyol is composed of hydroxyl-terminated polybutadiene, polyether glycol, and polycarbonate glycol in a molar ratio of (0.5-2):(1-4):(1-4).

[0063] Alternatively, preferably, the polyol is composed of hydroxyl-terminated epoxidized polybutadiene combined with at least one of polyether glycol and polycarbonate glycol. The capping agent is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate combined with at least one of bisphenol A epoxy resin, dimethylolpropionic acid, and dimethylolbutyric acid. Specifically, the polyol is composed of hydroxyl-terminated epoxidized polybutadiene, polyether glycol, and polycarbonate glycol in a molar ratio of (0.5-2):(1-4):(1-4).

[0064] In practical applications, toughening resins are mainly a mixture of epoxy-terminated flexible epoxy resins and epoxy-containing polyurethane prepolymers, because the production cost of epoxy-containing polyurethane prepolymers is higher.

[0065] Epoxy-terminated flexible epoxy resins are prepared from carboxyl-terminated compounds, epoxy resins with ≥2 epoxy functional groups, and catalysts. The carboxyl-terminated compounds are at least one of the following: octadecadienoic acid dimer, C14-C18 dicarboxylic acid, 2-mercaptophenylacetic acid, ricinoleic acid, carboxyl-terminated polybutadiene, and carboxyl-terminated nitrile rubber.

[0066] The epoxy resin with ≥2 epoxy functional groups is at least one of polybutadiene epoxy resin, bisphenol A (2,3-dihydroxypropyl) glycidyl ether, 1,3-bis(2',4'-bis(glycidyl ether)phenyl)adamantane, dicyclopentadiene dioxide, and diglycidyl 4,5-epoxytetrahydrophthalic acid diglycidyl ester.

[0067] The catalyst is at least one of triphenylphosphine, 2-methylimidazole, 2-ethyl-4-methylimidazole, phosphine bromide complex, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

[0068] The reaction conditions for epoxy-terminated flexible epoxy resin are as follows: under an inert atmosphere, the temperature is raised to 140-160℃ and reacted for 3-5 hours; the molar amount of epoxy functional groups in the epoxy resin with ≥2 epoxy functional groups is greater than the molar amount of carboxyl oxygen functional groups in the terminal carboxyl compound.

[0069] A method for preparing cationic curable epoxy adhesive for camera modules includes the following steps:

[0070] S1. Preparation of toughening resin;

[0071] S2. Accurately measure 10-15 parts of toughening resin, 20-30 parts of base epoxy resin, 30-60 parts of filler, 5-10 parts of diluent, and 1-2 parts of additives and mix them evenly at 15-25℃. Then adjust the temperature to 5-20℃ and add 1-3 parts of cationic initiator and mix evenly. Use a scraper fineness meter to scrape the particle size to confirm that it is controlled below 10μm. Centrifuge and degas to obtain cationic cured epoxy adhesive.

[0072] The curing conditions for the cationic curable epoxy adhesive are as follows: the wavelength of the ultraviolet light source is 200-450nm, specifically 365nm or 395nm, and the ultraviolet light energy is 1500-2000mJ / cm². 2 The UV curing time is 10-20 seconds.

[0073] Example 1: A cationic curable epoxy adhesive for camera modules consists of 15 parts flexible epoxy resin, 10 parts dicyclopentadiene diester (CAS: 81-21-0), 10 parts 3-(1-naphthoxy)-1,2-epoxypropane (CAS: 461-42-9), and 45 parts of a median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane (CAS:53778-62-4), 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320.

[0074] A method for preparing a cationic curable epoxy adhesive for a camera module includes the following steps:

[0075] S1. Weigh 15 parts of octadecadienoic acid dimer (CAS: 61788-89-4), 85 parts of TDE-85 (4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester, CAS: 25293-64-5), and 0.1 parts of triphenylphosphine (CAS: 603-35-0) and add them to a four-necked flask. After purging with nitrogen, heat the flask to 140℃ under nitrogen protection and react for 4.0 h. Cool the flask to room temperature to obtain a flexible epoxy resin.

[0076] S2. Weigh 15 parts of the flexible epoxy resin prepared in S1, 10 parts of dicyclopentadiene diester (dicyclopentadiene diester, CAS: 81-21-0), 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane (CAS: 461-42-9), and 45 parts of the median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane (CAS:53778-62-4), 0.3 parts of anti-settling agent BYK-W9010, and 0.5 parts of silane coupling agent A-187 are added to a three-roll mill and mixed evenly. The working temperature of the three-roll mill is controlled at 20±1℃ with cooling water. Then, 1 part of cationic photoinitiator - iodonium salt Omnicat 320 (IGM photoinitiator Omnicat 320) is added. After mixing evenly with the three-roll mill, the particle size is confirmed to be below 10μm using a scraper fineness gauge. After centrifugation and degassing, cationic curing epoxy adhesive for camera modules is obtained.

[0077] Curing conditions for cationic curing epoxy adhesive: The cationic curing epoxy adhesive is applied to the dispensing tank of the camera module; the ultraviolet light source wavelength is 365nm; and the ultraviolet light energy is 1500mJ / cm². 2 Curing time is 15 seconds.

[0078] After centrifugation to remove bubbles, the adhesive is applied to the camera module dispensing tank, and then illuminated with a 365nm wavelength light source at an energy of 1500mJ / cm². 2 The cationic curing epoxy adhesive can be cured by irradiation for 15 seconds.

[0079] The difference between Example 2 and Example 1 is that the cationic curable epoxy adhesive consists of 12 parts of epoxy-terminated flexible epoxy resin, 10 parts of bisphenol F epoxy resin BPF-170 (CAS: 61788-97-4, Nanya), 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, 10 parts of alicyclic epoxy resin 2021p (CAS: 2386-87-0), and 50 parts of a medium particle size D. 50It is made of 5 μm spherical silica powder, 5 parts of oxetane OXT121, 0.5 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1.5 parts of yellowing-resistant cationic photoinitiator - iodine salt Irgacue 250.

[0080] The preparation method of cationic curable epoxy adhesive is as follows:

[0081] S1. Weigh 20 parts of modified epoxy resin liquid carboxyl-terminated butadiene-acrylonitrile rubber CTBN 13X1300, 80 parts of epoxy resin 128 (Nanya 128, CAS: 61788-97-4), and 0.1 parts of triphenylphosphine (CAS: 603-35-0) and add them to a four-necked flask. After nitrogen purging, heat the flask to 140℃ under nitrogen protection and react for 4.0 h. Cool the flask to room temperature to obtain flexible epoxy resin.

[0082] S2. Weigh 12 parts of S1 flexible epoxy resin, 10 parts of bisphenol F epoxy resin BPF-170 (CAS No. 61788-97-4, Nanya), 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, 10 parts of alicyclic epoxy resin 2021p (CAS: 2386-87-0), and 50 parts of median particle size D. 50 Spherical silica powder with a particle size of 5 μm, 5 parts of oxetane OXT121, 0.5 parts of anti-settling agent BYK-W9010, and 0.5 parts of silane coupling agent A-187 are added to a three-roll mill and mixed evenly. The working temperature of the three-roll mill is controlled at 20±1℃ using cooling water. Then, 1.5 parts of yellowing-resistant cationic photoinitiator - iodine salt Irgacue 250 (BASF IGM photoinitiator IRGACURE 250) are added. After mixing evenly with the three-roll mill, the particle size is confirmed to be below 10 μm using a scraper fineness gauge. After centrifugation and degassing, cationic curing epoxy adhesive for camera modules is obtained.

[0083] Curing conditions for cationic curing epoxy adhesive: The cationic curing epoxy adhesive is applied to the dispensing tank of the camera module; the ultraviolet light source wavelength is 365nm; and the ultraviolet light energy is 1500mJ / cm². 2 Curing is achieved by irradiation for 12 seconds.

[0084] The difference between Example 3 and Example 1 is that the cationic curing epoxy adhesive consists of 10 parts of epoxy-terminated flexible epoxy resin, 8 parts of epoxy soybean oil (CAS: 8013-07-8), 15 parts of 3-(1-naphthoxy)-1,2-epoxypropane, 10 parts of alicyclic epoxy resin 2021p, and 60 parts of a medium particle size D. 50It is made from spherical silica powder with a diameter of 5 μm, 8 parts of oxetane OXT121, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1.5 parts of iodine salt Irgacue 250.

[0085] The preparation method of cationic curable epoxy adhesive is as follows:

[0086] S1. Weigh 20 parts of modified epoxy resin liquid carboxyl-terminated butadiene-acrylonitrile rubber CTBN 13X1300, 80 parts of epoxy resin 128, and 0.05 parts of 2-methylimidazole into a four-necked flask. After nitrogen purging, heat to 140℃ under nitrogen protection and react for 4.0 h. Cool to room temperature to obtain flexible epoxy resin.

[0087] S2. Weigh 10 parts of S1 flexible epoxy resin, 8 parts of epoxidized soybean oil (CAS: 8013-07-8), 15 parts of 3-(1-naphthoxy)-1,2-epoxypropane, 10 parts of alicyclic epoxy resin 2021p, and 60 parts of median particle size D. 50 =5μm spherical silica powder, 8 parts of oxetane OXT121, 0.3 parts of anti-settling agent BYK-W9010, and 0.5 parts of silane coupling agent A-187 are added to a three-roll mill and mixed evenly. The working temperature of the three-roll mill is controlled at 20±1℃ with cooling water. Then, 1.5 parts of yellowing-resistant cationic photoinitiator - iodine salt Irgacue 250 are added. After mixing evenly with the three-roll mill, the particle size is confirmed to be below 10μm using a scraper fineness gauge. After centrifugation and degassing, cationic curing epoxy adhesive for camera modules is obtained.

[0088] Curing conditions for cationic curing epoxy adhesive: The cationic curing epoxy adhesive is applied to the dispensing tank of the camera module; the ultraviolet light source wavelength is 365nm; and the ultraviolet light energy is 1500mJ / cm². 2 Curing is achieved by irradiation for 12 seconds.

[0089] The difference between Example 4 and Example 1 is that: a cationic curable epoxy adhesive for a camera module consists of 15 parts of epoxy-containing polyurethane prepolymer A, 10 parts of dicyclopentadiene diester, 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 45 parts of median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320.

[0090] The epoxy-containing polyurethane prepolymer A was prepared from 266.8 g of isophorone diisocyanate (Wanhua IPDI), 175.2 g of polytetrahydrofuran glycol PTMEG-850 (Mitsubishi Chemical Corporation, Japan), 200.0 g of polycarbonate diol CD210HL (Dairu Corporation, Japan), 240.0 g of hydroxyl-terminated polybutanediol R-20LM (Cray Valley), 36.0 g of 1,4-butanediol (Aladdin), 90.8 g of bisphenol A type epoxy resin (Phoenix E44), and 0.24 g of dibutyltin dilaurate T12.

[0091] The preparation methods of cationic curable epoxy adhesives differ as follows: S1. Preparation of polyurethane prepolymers containing epoxy groups: Weigh 175.2g of polytetrahydrofuran diol PTMEG-850 (Mitsubishi Chemical Corporation, Japan) and 200.0g of polycarbonate diol CD210HL (Dairu Corporation, Japan) and place them in a reaction vessel. Vacuum heat to 120°C for dehydration for 2 hours to obtain a mixed polyol. After purging nitrogen into the reaction vessel to restore atmospheric pressure, cool to 75°C and add 266.8g of isophorone diisocyanate and 240.0g of hydroxyl-terminated polybutanediol R-20LM (Cray). Valley Corporation) and 0.24 g of dibutyltin dilaurate T12 were stirred at 400 rpm for 30 min, followed by the addition of 36.0 g of 1,4-butanediol. The reaction was maintained at 75 °C for 3 hours. Then, 90.8 g of bisphenol A type epoxy resin E44 was added for end-capping. After 2 hours of end-capping, the NCO content of the system was found to be 0. The mixture was cooled to room temperature and discharged to obtain polyurethane prepolymer A containing epoxy groups.

[0092] The difference between Example 5 and Example 1 is that 15 parts of epoxy-containing polyurethane prepolymer A are replaced with 15 parts of epoxy-containing polyurethane prepolymer B.

[0093] The epoxy-containing polyurethane prepolymer B was prepared from 266.8 g of isophorone diisocyanate (Wanhua IPDI), 175.2 g of polytetrahydrofuran glycol PTMEG-850 (Mitsubishi Chemical Corporation, Japan), 200.0 g of polycarbonate diol CD210HL (Dairu Corporation, Japan), 270.0 g of hydroxyl-terminated epoxidized polybutylene glycol Poly bd 600E (CrayValley, hydroxyl value 1.86 mmol / g, epoxy value 2.2 mmol / g), 41.4 g of 1,4-butanediol (Aladdin), 32.6 g of hydroxyethyl methacrylate (CAS No.: 868-77-9, Aladdin), and 0.28 g of dibutyltin dilaurate T12.

[0094] The preparation methods for cationic curable epoxy adhesives differ as follows: 175.2g of polytetrahydrofuran glycol PTMEG-850 (Mitsubishi Chemical Corporation, Japan) and 200.0g of polycarbonate glycol CD210HL (Dairu Corporation, Japan) are weighed and placed in a reaction vessel. The mixture is then heated under vacuum to 120°C for 2 hours to remove water, yielding a mixed polyol. Nitrogen gas is introduced into the reaction vessel to restore atmospheric pressure. After cooling to 70°C, 266.8g of isophorone diisocyanate and 270.0g of hydroxyl-terminated epoxidized polybutylene glycol (Polybd) are added. 600E and 0.28g of dibutyltin dilaurate T12 were stirred at 400rpm for 60min, followed by the addition of 36.0g of 1,4-butanediol. The reaction was maintained at 70℃ for 4 hours. The temperature was then adjusted to 60℃ and 32.6g of hydroxyethyl methacrylate was added for end-capping. After 80 minutes of end-capping, the NCO content of the system was found to be 0. The mixture was cooled to room temperature, and the epoxy-containing polyurethane prepolymer B was obtained.

[0095] The difference between Example 6 and Example 1 is that 15 parts of epoxy-containing polyurethane prepolymer A are replaced with 15 parts of epoxy-containing polyurethane prepolymer C.

[0096] The epoxy-containing polyurethane prepolymer C was prepared from 266.8 g of isophorone diisocyanate (Wanhua IPDI), 175.2 g of polytetrahydrofuran glycol PTMEG-850 (Mitsubishi Chemical Corporation, Japan), 200.0 g of polycarbonate diol CD210HL (Dairu Corporation, Japan), 270.0 g of hydroxyl-terminated epoxidized polybutylene glycol Poly bd 600E (CrayValley, hydroxyl value 1.86 mmol / g, epoxy value 2.2 mmol / g), 35.4 g of 1,4-butanediol (Aladdin), 6.7 g of dimethylolpropionic acid (CAS No.: 4767-03-7), 22.5 g of bisphenol A type epoxy resin E44, 32.6 g of hydroxyethyl methacrylate (CAS No.: 868-77-9, Aladdin), and 0.30 g of dibutyltin dilaurate T12.

[0097] The preparation methods for cationic curable epoxy adhesives differ as follows: 175.2g of polytetrahydrofuran glycol PTMEG-850 (Mitsubishi Chemical Corporation, Japan) and 200.0g of polycarbonate glycol CD210HL (Dairu Corporation, Japan) are weighed and placed in a reaction vessel. The mixture is then heated under vacuum to 120°C for 2 hours to remove water, yielding a mixed polyol. Nitrogen gas is introduced into the reaction vessel to restore atmospheric pressure. After cooling to 70°C, 266.8g of isophorone diisocyanate and 270.0g of hydroxyl-terminated epoxidized polybutylene glycol (Polybd) are added. 600E and 0.28g of dibutyltin dilaurate T12 were stirred at 400rpm for 60min. Then, 35.4g of 1,4-butanediol and 6.7g of dimethylolpropionic acid were added, and the reaction was maintained at 70℃ for 4 hours. The temperature was adjusted to 60℃, and 22.5g of bisphenol A type epoxy resin E44 and 32.6g of hydroxyethyl methacrylate were added for end-capping reaction. After 90 minutes of end-capping reaction, the NCO content of the system was 0 and the acid value of the system was 0.12mg KOH / g. The mixture was cooled to room temperature, and the epoxy-containing polyurethane prepolymer C was obtained.

[0098] The difference between Example 7 and Example 1 is that: the cationic curable epoxy adhesive for camera modules consists of 10 parts of epoxy-terminated flexible epoxy resin prepared in Example 1, 5 parts of epoxy-containing polyurethane prepolymer A prepared in Example 4, 10 parts of dicyclopentadiene diester, 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 45 parts of a median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320.

[0099] The difference between Example 8 and Example 1 is that: the cationic curable epoxy adhesive for camera modules consists of 10 parts of epoxy-terminated flexible epoxy resin prepared in Example 1, 5 parts of epoxy-containing polyurethane prepolymer B prepared in Example 5, 10 parts of dicyclopentadiene diester, 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 45 parts of a median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320.

[0100] The difference between Example 9 and Example 1 is that: the cationic curable epoxy adhesive for camera modules consists of 10 parts of epoxy-terminated flexible epoxy resin prepared in Example 1, 5 parts of epoxy-containing polyurethane prepolymer C prepared in Example 6, 10 parts of dicyclopentadiene diester, 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 45 parts of a median particle size D. 50 =5μm spherical silica powder, 6 parts of 2-ethyl-3-methyl-oxetane, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320.

[0101] The difference between Example 10 and Example 1 is that: the cationic curable epoxy adhesive for camera modules consists of 8 parts of epoxy-terminated flexible epoxy resin prepared in Example 1, 7 parts of epoxy-containing polyurethane prepolymer C prepared in Example 6, 10 parts of dicyclopentadiene diester, 10 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 35 parts of a median particle size D. 50 =5μm spherical silica powder, 10 parts median particle size D 50 The composition consists of spherical aluminum nitride with a median particle size of 5 μm, 6 parts of 2-ethyl-3-methyloxetane, 0.3 parts of anti-settling agent BYK-W9010, 0.5 parts of silane coupling agent A-187, and 1 part of iodonium salt Omnicat 320. The median particle size of the spherical aluminum nitride is D. 50 =5μm, Nangong Rongbang New Materials Technology Co., Ltd.

[0102] The difference between Comparative Example 1 and Example 1 is as follows: The epoxy adhesive preparation method is as follows: 40 parts of PUA resin, 20 parts of EA resin, 10 parts of tetrahydrofurfuryl acrylate (THFA) (CAS: 2399-48-6), 8 parts of isobornyl acrylate (IBOA) (CAS: 5888-33-5), 10 parts of dicyclopentadiene acrylate (DCPA) (CAS: 33791-58-1), and 3 parts of fumed silica (Degussa silica AEROSIL R972, CAS No. 68611-44-9) were weighed in a high-speed disperser and mixed evenly. Then, 4 parts of 184 photoinitiator (CAS: 947-19-3) were added and mixed evenly to obtain the UV adhesive. The UV adhesive was applied to the camera module dispensing tank, and then a light source with a wavelength of 365nm and a light energy of 1200mJ / cm² was used. 2 Curing is performed by irradiation for 15 seconds.

[0103] The difference between Comparative Example 2 and Example 1 is as follows: The epoxy resin preparation method is as follows: Weigh 25 parts of epoxy resin 128, 20 parts of 3-(1-naphthoxy)-1,2-epoxypropane, and 50 parts of median particle size D. 50=8μm spherical silica powder, 10 parts of low-chlorine diluent ED-509S, 1 part of anti-settling agent BYK-W9010, and 1 part of silane coupling agent A-187 are added to a three-roll mill. The operating temperature of the three-roll mill is controlled at 20±1℃ using cooling water. After mixing evenly, 8 parts of imidazole latent curing agent AJICURE PN-23 are added. After mixing evenly, the particle size is confirmed to be below 10μm using a scraper fineness gauge. Centrifugation and degassing yield the epoxy adhesive. The epoxy adhesive is applied to the dispensing tank of the camera module and then cured in a 120℃ oven for 30 minutes to complete the curing process.

[0104] Performance testing: 1. Tensile strength and elongation at break were tested according to GB / T 1040.1-2018 Plastics – Determination of tensile properties – Part 1: General rules. 2. Glass transition temperature and coefficient of thermal expansion were tested according to GB / T 36800.2-2018 Plastics – Thermomechanical analysis (TMA) – Part 2: Determination of linear coefficient of thermal expansion and glass transition temperature. 3. Adhesive strength: The adhesive strength of the vehicle camera samples assembled with EP adhesive prepared in the examples and comparative examples was tested using a DAGE 4000Plus push-pull force tester. 4. Thermal shock strength after 1000 cycles from -40°C to 120°C (hereinafter referred to as thermal shock strength): The vehicle camera samples assembled with EP adhesive prepared in the examples and comparative examples were placed at a temperature of -40°C for 30 minutes, then heated to 120°C within 1 minute and held for 30 minutes. This thermal cycle was repeated 1000 times, and then the adhesive thrust was tested using a DAGE 4000Plus push-pull force tester. 5. Water absorption rate: Tested according to GB / T 1037-2021 "Determination of water vapor transmission performance of plastic films and sheets - cup method for weight gain and loss". 6. 85% relative humidity strength: The vehicle camera samples assembled with EP adhesive prepared in the examples and comparative examples were placed at a temperature of 85°C and a relative humidity of 85% for 1000 hours, and then their respective adhesive strengths were tested.

[0105] Table 1: Test parameters of EP adhesive in Examples 1-3 and Comparative Examples 1-2

[0106]

[0107]

[0108] As can be seen from Examples 1-3 and Comparative Examples 1-2 and Table 1, the cationic curing epoxy adhesives of Examples 1-3 have advantages such as high flexibility, excellent weather resistance, excellent resistance to thermal shock, high adhesion, and low curing shrinkage, making them suitable for use in vehicle camera assembly.

[0109] Table 2: Test parameters of EP adhesive in Examples 1 and 4-6

[0110]

[0111] Based on Examples 1, 4-6, and Comparative Example 3, and in conjunction with Table 2, it can be seen that using polyurethane prepolymers containing epoxy groups as toughening components can further improve the flexibility, weather resistance, thermal shock resistance, and bond strength of cationic curing epoxy adhesives. However, it will lead to a decrease in the glass transition temperature (Tg) of the cured cationic curing epoxy adhesive. Even with a Tg ≥ 100℃, it still possesses certain heat resistance properties and can be used as an adhesive for assembling automotive cameras.

[0112] Table 3: Test parameters of EP adhesive in Examples 1 and 7-10

[0113]

[0114] As can be seen from Examples 1 and 4-10, and Tables 2-3, using a compound of epoxy-containing polyurethane prepolymer and epoxy-terminated flexible epoxy resin as a toughening agent can further improve the flexibility, weather resistance, thermal shock resistance, and bond strength of cationic curing epoxy adhesives. Furthermore, the glass transition temperature (Tg) of the cured cationic curing epoxy adhesive remains ≥140℃, maintaining good heat resistance. In addition, the production cost of epoxy-containing polyurethane prepolymers is relatively high. Using a compound of epoxy-containing polyurethane prepolymer and epoxy-terminated flexible epoxy resin as a toughening agent can improve the physicochemical properties of cationic curing epoxy adhesives while reducing their production cost, which is beneficial for industrial-grade manufacturing.

[0115] In summary, the cationic curing epoxy adhesive of this invention can cure quickly and has low curing shrinkage, which greatly improves the assembly capacity and yield of camera modules.

[0116] It should be noted that this specific embodiment is merely an explanation of the technical solution of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preparing cationic curable epoxy adhesive for camera modules, characterized in that: The cationic curable epoxy adhesive comprises 10-15 parts toughening resin, 20-30 parts matrix epoxy resin, 30-60 parts filler, 5-10 parts diluent, 1-2 parts additives, and 1-3 parts cationic initiator; the toughening resin is an epoxy-terminated flexible epoxy resin and / or an epoxy-containing polyurethane prepolymer.

2. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 1, characterized in that: The epoxy-containing polyurethane prepolymer includes at least one of the following: a polyurethane prepolymer with epoxy-terminated main chain, a polyurethane prepolymer with epoxy-terminated side chain, a polyurethane prepolymer with allyl-terminated side chain and epoxy-terminated main chain, and a polyurethane prepolymer with epoxy-terminated side chain and allyl-terminated main chain.

3. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 2, characterized in that: The epoxy-containing polyurethane prepolymer is prepared from diisocyanate, polyol, chain extender, catalyst, and end-capping agent. The total molar amount of -NCO in the diisocyanate is 1.2-1.6 times the total molar amount of active hydrogen functional groups in the polyol and chain extender; the total molar amount of active hydrogen functional groups in the polyol, chain extender, and end capping agent is 1.0-1.02 times the total molar amount of -NCO in the diisocyanate. The diisocyanate is any one or a combination of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate. The polyol is composed of at least one of terminal hydroxyl polybutadiene and terminal hydroxyl epoxidized polybutadiene combined with at least one of polyether diol and polycarbonate diol. The catalyst is an organotin or an organobismuth; The chain extender is a small molecule diol with a molecular weight ≤174.3; The capping agent is at least one of bisphenol A epoxy resin, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid.

4. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 3, characterized in that: The diisocyanate is composed of isophorone diisocyanate or isophorone diisocyanate combined with any one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate; the polyol is composed of hydroxyl-terminated polybutadiene combined with at least one of polyether diol and polycarbonate diol; the end-capping agent is bisphenol A type epoxy resin combined with at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, dimethylolpropionic acid, and dimethylolbutyric acid.

5. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 3, characterized in that: The diisocyanate is composed of isophorone diisocyanate or isophorone diisocyanate combined with any one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate; the polyol is composed of hydroxyl-terminated epoxidized polybutadiene combined with at least one of polyether diol and polycarbonate diol; the end-capping agent is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate combined with at least one of bisphenol A epoxy resin, dimethylolpropionic acid, and dimethylolbutyric acid.

6. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 3, characterized in that: The polyol is composed of hydroxyl-terminated polybutadiene, polyether glycol, and polycarbonate glycol in a molar ratio of (0.5-2):(1-4):(1-4); or the polyol is composed of hydroxyl-terminated epoxidized polybutadiene, polyether glycol, and polycarbonate glycol in a molar ratio of (0.5-2):(1-4):(1-4).

7. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 1, characterized in that: The toughening resin is an epoxy group-terminated flexible epoxy resin, which is prepared by a carboxyl-terminated compound, an epoxy resin with ≥2 epoxy functional groups, and a catalyst. The reaction conditions for the epoxy group-terminated flexible epoxy resin are: under an inert atmosphere, the temperature is raised to 140-160℃ and reacted for 3-5 hours. The molar amount of epoxy functional groups in the epoxy resin with ≥2 epoxy functional groups is greater than the molar amount of carboxyl oxygen functional groups in the carboxyl-terminated compound.

8. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 1, characterized in that: The matrix epoxy resin is at least one of bisphenol F glycidyl 2,3-dihydroxypropyl ether, dicyclopentadiene dioxide, 2-biphenyl glycidyl ether, 4,4'-biphenyl bisphenol diglycidyl ether, and 2,2'-(naphthalene-1,6-dimethylbis(oxy))bis(methylene)diepoxyethylene.

9. The method for preparing a cationic curable epoxy adhesive for a camera module according to claim 1, characterized in that: The filler has a median particle size D. 50 The diluent is at least one of the following: spherical silica powder (1 μm to 10 μm), spherical alumina, spherical silica, spherical aluminum nitride, and spherical hollow glass microspheres; the diluent is at least one of the following: oxabutane, oxabutane derivatives, ethylene oxide diluents, and vinyl ethers; the cationic initiator is at least one of the following: iodonium salt, thiodonium salt, and ferrocene salt; the additives include anti-settling agents, silane coupling agents, and leveling agents.

10. A method for preparing a cationic curable epoxy adhesive for a camera module according to claim 1, characterized in that: Includes the following steps: S1. Preparation of toughening resin; S2. Accurately measure 10-15 parts of toughening resin, 20-30 parts of base epoxy resin, 30-60 parts of filler, 5-10 parts of diluent, and 1-2 parts of additives and mix them evenly at 15-25℃. Then adjust the temperature to 5-20℃ and add 1-3 parts of cationic initiator and mix evenly. Use a scraper fineness meter to scrape the particle size to confirm that it is controlled below 10μm. Centrifuge and degas to obtain cationic cured epoxy adhesive. The curing conditions for the cationic curable epoxy adhesive are as follows: the wavelength of the ultraviolet light source is 200-450nm, and the ultraviolet light energy is 1500-2000mJ / cm². 2 The UV curing time is 10-20 seconds.

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