Raw material composition for optical adhesive, optical adhesive, and method for preparing and using the same

Abstract

The application provides a raw material composition of optical glue, the optical glue and a preparation method and application thereof.The raw material composition of the optical glue comprises the following components in parts by weight: 10-25 parts of bisphenol AF epoxy resin; 65-85 parts of fluorine-containing acrylic ester prepolymer; 1-5 parts of silane coupling agent; 0.1-2 parts of cationic photo initiator; and 0.1-2 parts of cationic thermal initiator; wherein the fluorine-containing acrylic ester prepolymer is obtained by reacting fluorine-containing acrylic ester monomers and epoxy acrylic ester compounds under the condition of ultraviolet light irradiation.The optical glue has low refractive index and high light transmittance, is suitable for optical communication, electronic device packaging and the like, meets the requirements of material bonding and high-temperature and high-humidity environment, has interface enhancement, multifunctionality, and low dielectricity, high hydrophobicity and high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a raw material composition for an optical adhesive, the optical adhesive itself, its preparation method, and its applications. Background Technology

[0002] Most existing low-refractive-index adhesives are prepared using fluorinated acrylic resins or silicone as raw materials. Due to the presence of ester bonds and carboxylic acid groups in the molecular chain of acrylic resins, the cured adhesives have poor resistance to humid heat aging and weak adhesion. Although silicone-based low-refractive-index adhesives have excellent resistance to humid heat aging, they suffer from drawbacks such as poor colloid strength, poor adhesion, and low glass transition temperature. Summary of the Invention

[0003] To overcome the shortcomings of existing adhesives, such as poor resistance to damp heat aging, poor bonding effect, and low glass transition temperature, this invention provides a raw material composition for an optical adhesive, the optical adhesive itself, its preparation method, and its applications. This optical adhesive has a low refractive index and high light transmittance, making it suitable for fields such as optical communication and electronic device packaging. It meets the requirements for material bonding and high-temperature and high-humidity environments, possesses interface enhancement properties, multifunctionality, and also features low dielectric constant, high hydrophobicity, and high-temperature resistance.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] This invention provides a raw material composition for an optical adhesive, comprising, by weight, the following components:

[0006] 10-25 parts of bisphenol AF epoxy resin;

[0007] 65-85 parts of fluorinated acrylate prepolymer;

[0008] 1-5 parts of silane coupling agent;

[0009] 0.1–2 parts of cationic photoinitiator;

[0010] 0.1–2 parts of cationic thermal initiator;

[0011] The fluorinated acrylate prepolymer is obtained by reacting fluorinated acrylate monomers and epoxy acrylate compounds under ultraviolet light.

[0012] In this invention, the bisphenol AF epoxy resin contains hexafluoropropylene (-C(CF3)2-) groups, giving it lower surface energy and hydrophobicity, relatively weaker polarity, and significantly enhanced heat resistance, hydrophobicity, chemical stability, and dielectric properties. This greatly reduces the resin's refractive index while retaining the heat resistance, wear resistance, and corrosion resistance of epoxy resins, meeting the requirement of a refractive index below 1.435 in the optical communication field. In contrast, conventional epoxy resins generally have higher refractive indices, including aromatic epoxy resins and alicyclic epoxy resins. Aromatic epoxy resins, due to the presence of benzene rings, generally have higher refractive indices, making them difficult to meet the requirements for optical communication applications; alicyclic epoxy resins have relatively lower refractive indices, but are still generally above 1.460.

[0013] In this invention, the fluorinated acrylate prepolymer refers to the fluorinated acrylate monomer that has undergone partial polymerization in advance. It has low polarity and high hydrophobicity, and its molecular chain has good flexibility. Its polarity is similar to that of bisphenol AF epoxy resin, and its compatibility is good, which is beneficial to increasing the adhesive performance of the adhesive. In the optical adhesive system of this application, if the fluorinated acrylate monomer is used directly, its polymerization process requires additional time, and its polymerization reaction is uncontrollable. Therefore, the optical adhesive prepared directly from this monomer cannot achieve the performance of the optical adhesive of this application.

[0014] In this invention, the optical adhesive, also known as an "adhesive," is prepared by using bisphenol AF epoxy resin and fluorinated acrylate prepolymer as the matrix to form a hybrid curing system, and combining it with a silane coupling agent, a cationic photoinitiator, and a cationic thermal initiator to obtain a photocurable adhesive with high interfacial bonding strength, simultaneously achieving deep curing and low-energy surface modification. The synergistic effect of these raw materials reduces the refractive index of the entire adhesive system and improves the resistance to humid heat aging after curing.

[0015] In some embodiments, the silane coupling agent is selected from at least one of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0016] In some embodiments, the cationic photoinitiator is selected from at least one of aromatic thioonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic phosphonium salts, aromatic selenium salts, and iron aromatic salts.

[0017] In a specific embodiment, the cationic photoinitiator is selected from at least one of diaryliodonium pentafluorophenylboronate, diaryliodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, triarylthionium hexafluoroantimonate, triarylthionium hexafluorophosphate, and ferrocene hexafluorophosphate.

[0018] In some embodiments, the cationic thermal initiator is selected from at least one of arylthionium salts, aryliodonium salts, aromatic ion complexes, quaternary ammonium salts, aluminum chelates, and boron trifluoride-amine complexes.

[0019] In a specific embodiment, the cationic thermal initiator is selected from arylsulfonium hexafluoroantimonate.

[0020] In some embodiments, the bisphenol AF epoxy resin may be commercially available or homemade, such as Bisphenol AF epoxy resin from Huizhou Sanhua.

[0021] In some embodiments, the bisphenol AF epoxy resin has an epoxy value of 0.35 to 0.5 Eq / 100g and a viscosity of ≤5000 cps at 50°C.

[0022] In some embodiments, the preparation method of the bisphenol AF epoxy resin includes the following steps:

[0023] s1. The first mixture is mixed with the first alkaline substance to carry out the first reaction, and a mixed solution is obtained; the first mixture includes 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; the temperature of the first reaction is 80-110℃;

[0024] s2. The mixture, organic solvent and second alkaline substance are mixed to carry out a second reaction, the temperature of the second reaction is below 65°C; then, the bisphenol AF epoxy resin is obtained by purification.

[0025] In a specific embodiment, the molar ratio of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, epichlorohydrin, the first alkaline substance, and the second alkaline substance is 1:(2-12):(1-4).

[0026] In a specific embodiment, the first alkaline substance and the second alkaline substance include a sodium hydroxide solution with a concentration of 20%-40%, where % refers to the mass percentage of sodium hydroxide in the solution.

[0027] In a specific embodiment, in step s1, the mixing temperature of the 2,2-bis(4-hydroxyphenyl)hexafluoropropane and the epichlorohydrin is 40-60°C.

[0028] In a specific implementation, in step s1, the time for the first reaction is 1-5 hours.

[0029] In a specific implementation, in step s1, after the first reaction, unreacted epichlorohydrin is recovered by reducing pressure.

[0030] In a specific implementation, in step s2, the organic solvent is one or more of toluene, xylene, chlorobenzene, o-dichlorobenzene, and heptane.

[0031] In a specific embodiment, in step s2, the mass ratio of the organic solvent to the 2,2-bis(4-hydroxyphenyl)hexafluoropropane is (1-10):1.

[0032] In a specific implementation, in step s2, the second reaction takes 1-5 hours.

[0033] In a specific implementation, step s2 includes the following purification process in sequence: cooling, washing, separating the aqueous phase, and distilling the organic solvent.

[0034] In this invention, the preparation process of the bisphenol AF epoxy resin includes: a polycondensation reaction of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin to obtain the bisphenol AF epoxy resin. The reaction process involves etherification, ring closure, and then condensation. The addition of an alkaline substance (such as NaOH) serves two purposes: firstly, as a catalyst for the reaction of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; and secondly, to remove HCl from the intermediate reaction product and achieve ring closure. The etherification and ring closure reaction processes are as follows:

[0035]

[0036] In a preferred embodiment, the preparation method of the bisphenol AF epoxy resin includes the following steps:

[0037] s1. Add 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin to a reaction vessel, heat to 40-60℃ to completely dissolve the reaction mixture, slowly add NaOH solution dropwise, maintain the reaction temperature at 80-110℃, and react for 1-5 hours; then reduce the pressure to recover the unreacted epichlorohydrin and obtain a mixture.

[0038] s2. Cool the mixture in step s1 to below 65°C, add organic solvent, and slowly add NaOH solution dropwise. React for 1-5 hours. Cool, wash with hot water until the organic solvent solution is clear, separate the aqueous layer, and distill the organic phase to remove the organic solvent to obtain bisphenol AF epoxy resin.

[0039] The molar ratio of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, epichlorohydrin and NaOH is 1:(2-12):(1-4), and the mass fraction of the NaOH solution is 20%-40%.

[0040] The organic solvent is one or more of toluene, xylene, chlorobenzene, o-dichlorobenzene, and heptane, and the mass ratio of the organic solvent to 2,2-bis(4-hydroxyphenyl)hexafluoropropane is (1-10):1.

[0041] In some embodiments, the method for preparing the fluorinated acrylate prepolymer includes the following steps:

[0042] ss1. Under an inert atmosphere, the raw materials are stirred and mixed to obtain a second mixture; the raw materials include the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator;

[0043] ss2. The second mixture is subjected to ultraviolet (UV) light treatment to obtain the fluorinated acrylate prepolymer; the wavelength of the ultraviolet light is 200-450nm, and the light treatment time is 30-90s.

[0044] In this invention, the preparation process of the fluorinated acrylate prepolymer does not require the use of solvents, is simple, environmentally friendly and non-toxic, and highly efficient and energy-saving. Furthermore, the prepared fluorinated acrylate prepolymer has high crosslinking density and low shrinkage.

[0045] In a specific embodiment, in step ss1, the mass ratio of the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator is (35-60):(10-30):(0.5-2); preferably, the mass ratio of the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator is (40-55):(10-25):(0.5-1.5).

[0046] In a specific implementation, in step ss1, the fluorinated acrylate monomer is selected from at least one of perfluorobutyl ethyl methacrylate (CAS1799-84-4), 2-(perfluorobutyl)ethyl acrylate (CAS 52591-27-2), perfluorooctyl ethyl methacrylate (CAS1996-88-9), perfluorooctyl ethyl acrylate (CAS 27905-45-9), perfluorohexyl ethyl acrylate (CAS17527-29-6), and perfluorohexyl ethyl methacrylate (CAS2144-53-8).

[0047] In a specific embodiment, in step ss1, the epoxy acrylate compound is selected from at least one of 3,4-epoxycyclohexyl methyl methacrylate (CAS 82428-30-6), 3,4-epoxycyclohexyl methacrylate (CAS 64630-63-3), and glycidyl methacrylate (CAS106-91-2).

[0048] In a specific implementation, in step ss1, the photoinitiator is a free radical photoinitiator, which is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, and benzoyladium dimethyl ether.

[0049] In a specific implementation, in step ss1, the inert atmosphere includes a nitrogen atmosphere.

[0050] In a specific implementation, in step ss1, the stirring and mixing speed is 40-100 rpm, for example, 60 rpm.

[0051] In a specific implementation, in step ss2, the energy density of the ultraviolet light is 5000–8000 mJ / cm². 2 .

[0052] In one embodiment, the raw material composition of the optical adhesive, by weight, comprises the following components: 10 parts of bisphenol AF epoxy resin; 84.5 parts of fluorinated acrylate prepolymer; 4 parts of silane coupling agent; 1 part of cationic photoinitiator; and 0.5 parts of cationic thermal initiator; wherein the bisphenol AF epoxy resin is obtained by polycondensation of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; and the fluorinated acrylate prepolymer is obtained by reacting perfluorobutyl ethyl methacrylate and 3,4-epoxycyclohexyl methyl methacrylate under ultraviolet light.

[0053] In one embodiment, the raw material composition of the optical adhesive, by weight, comprises the following components: 15 parts of bisphenol AF epoxy resin; 78.5 parts of fluorinated acrylate prepolymer; 4 parts of silane coupling agent; 1 part of cationic photoinitiator; and 0.5 parts of cationic thermal initiator; wherein the bisphenol AF epoxy resin is obtained by polycondensation of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; and the fluorinated acrylate prepolymer is obtained by reacting perfluorooctyl ethyl methacrylate and glycidyl methacrylate under ultraviolet light.

[0054] In one embodiment, the raw material composition of the optical adhesive, by weight, comprises the following components: 20 parts of bisphenol AF epoxy resin; 73 parts of fluorinated acrylate prepolymer; 4 parts of silane coupling agent; 1 part of cationic photoinitiator; and 0.5 parts of cationic thermal initiator; wherein the bisphenol AF epoxy resin is obtained by polycondensation of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; and the fluorinated acrylate prepolymer is obtained by reacting perfluorobutyl ethyl methacrylate and 3,4-epoxycyclohexyl methyl methacrylate under ultraviolet light.

[0055] In one embodiment, the raw material composition of the optical adhesive, by weight, comprises the following components: 25 parts of bisphenol AF epoxy resin; 68 parts of fluorinated acrylate prepolymer; 4 parts of silane coupling agent; 1 part of cationic photoinitiator; and 0.5 parts of cationic thermal initiator; wherein the bisphenol AF epoxy resin is obtained by polycondensation of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; and the fluorinated acrylate prepolymer is obtained by reacting perfluorooctyl ethyl methacrylate and glycidyl methacrylate under ultraviolet light.

[0056] The present invention also provides a method for preparing an optical adhesive, which includes the following steps:

[0057] The raw material composition of the optical adhesive as described above is homogenized to obtain the optical adhesive; the stirring speed of the homogenization is 1000-3000 rpm and the stirring time is 1-10 min.

[0058] In some embodiments, the preparation method of the optical adhesive includes the following steps: placing the above-mentioned bisphenol AF epoxy resin, the above-mentioned fluorinated acrylate prepolymer, silane coupling agent, cationic photoinitiator, and cationic thermal initiator into a light-proof mixer and stirring at a stirring speed of 1000-3000 rpm for 1-10 minutes to homogenize the mixture and obtain the optical adhesive.

[0059] The present invention also provides an optical adhesive, which is prepared by the optical adhesive preparation method described above.

[0060] The present invention also provides an application of the optical adhesive described above in chip bonding and optical communication.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. The optical adhesive of the present invention has the advantages of good adhesion and high glass transition temperature after curing. Among them, bisphenol AF epoxy resin is beneficial to improve the adhesive strength and resistance to humid heat aging of the optical adhesive, but its viscosity is high and not convenient for construction. The fluorinated acrylate prepolymer is in a liquid state, which can act as a diluent to adjust the overall viscosity of the system and facilitate construction. On the other hand, it can significantly reduce the refractive index of the optical adhesive, meet the requirements of optical communication, reduce light loss, and further improve the resistance to humid heat aging of the cured optical adhesive.

[0063] 2. The optical adhesive of this invention belongs to a synergistic curing system, utilizing a hybrid light and heat curing system to achieve simultaneous cross-linking. The prepared optical adhesive has a low refractive index, high light transmittance, high glass transition temperature, low viscosity, and excellent resistance to damp heat aging. Specifically, this optical adhesive has a refractive index below 1.435, a light transmittance greater than 80%, a glass transition temperature above 110°C, an adhesive strength greater than 15 MPa, and an adhesive strength attenuation of less than 20%, preferably less than 15%, after 2000 hours of high temperature and high humidity. Detailed Implementation

[0064] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0065] Preliminary Example 1

[0066] This preliminary embodiment discloses a method for preparing bisphenol AF epoxy resin in the raw material composition of optical adhesive, which includes the following steps:

[0067] s0. Weigh each material according to the molar ratio of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, epichlorohydrin and NaOH of 1:8:2.2; prepare NaOH into a 25% aqueous solution; weigh toluene according to the mass ratio of toluene to 2,2-bis(4-hydroxyphenyl)hexafluoropropane of 5:1.

[0068] s1. Add 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin to a three-necked flask in proportion, heat to 50°C to completely dissolve the reaction mixture; slowly add NaOH solution dropwise; here, the amount of NaOH solution added is three-tenths of the total mass of NaOH solution; maintain the reaction temperature at 90°C, reflux for 3 hours, and recover the unreacted epichlorohydrin under reduced pressure to obtain a mixed solution.

[0069] s2. Cool the mixture from step s1 to 60°C, add the organic solvent toluene, and slowly add the remaining NaOH solution dropwise. Reflux for 3 hours, cool, and wash with hot water until the organic solvent solution is clear. Separate the aqueous layer, and distill the organic phase to remove toluene, to obtain bisphenol AF epoxy resin.

[0070] The bisphenol AF epoxy resin prepared in this preliminary example has an epoxy value of 0.35 to 0.5 Eq / 100g and a viscosity of ≤5000 cps at 50°C.

[0071] Preliminary Example 2

[0072] This preliminary embodiment discloses a method for preparing a fluorinated acrylate prepolymer in the raw material composition of an optical adhesive, which includes the following steps:

[0073] ss1. Under a nitrogen atmosphere, fluorinated acrylate monomers, epoxy acrylate compounds and photoinitiators are stirred and mixed at a speed of 60 rpm to obtain a mixture;

[0074] ss2. The mixture is irradiated with ultraviolet light (UV) to obtain a fluorinated acrylate prepolymer; the wavelength of the UV light is 365 nm, the irradiation time is 60 s, and the energy density is 6000 mJ / cm². 2 .

[0075] Due to the different raw materials of fluorinated acrylate monomers and epoxy acrylate compounds, two types of fluorinated acrylate prepolymers were prepared, and their raw materials and formulations are shown in Table 1.

[0076] Table 1 Raw materials and proportions of fluorinated acrylate prepolymer

[0077]

[0078] Among them, photoinitiator 1173 refers to 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0079] Example 1

[0080] This embodiment discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0081] The raw material composition of the optical adhesive in this embodiment consists of the following components in parts by weight:

[0082] 10 parts of bisphenol AF epoxy resin prepared in Example 1

[0083] 84.5 parts of the first fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0084] 2 parts of silane coupling agent (A-187)

[0085] 2 parts of silane coupling agent (A-186)

[0086] 1 part of cationic photoinitiator (UVI6976)

[0087] 0.5 parts of cationic thermal initiator (SI-100L).

[0088] The method for preparing the optical adhesive in this embodiment is as follows:

[0089] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, first fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0090] Example 2

[0091] This embodiment discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0092] The raw material composition of the optical adhesive in this embodiment consists of the following components in parts by weight:

[0093] 15 parts of bisphenol AF epoxy resin prepared in Preliminary Example 1

[0094] 78.5 parts of the second fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0095] 2 parts of silane coupling agent (A-187)

[0096] 2 parts of silane coupling agent (A-186)

[0097] One part of cationic photoinitiator (UVI6976);

[0098] 0.5 parts of cationic thermal initiator (SI-100L).

[0099] The method for preparing the optical adhesive in this embodiment is as follows:

[0100] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, second fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0101] Example 3

[0102] This embodiment discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0103] The raw material composition of the optical adhesive in this embodiment consists of the following components in parts by weight:

[0104] 20 parts of bisphenol AF epoxy resin prepared in Example 1

[0105] 73 parts of the first fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0106] 2 parts of silane coupling agent (A-187)

[0107] 2 parts of silane coupling agent (A-186)

[0108] One part of cationic photoinitiator (UVI6976);

[0109] 0.5 parts of cationic thermal initiator (SI-100L).

[0110] The method for preparing the optical adhesive in this embodiment is as follows:

[0111] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, first fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0112] Example 4

[0113] This embodiment discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0114] The raw material composition of the optical adhesive in this embodiment consists of the following components in parts by weight:

[0115] 25 parts of bisphenol AF epoxy resin prepared in Preliminary Example 1

[0116] 68 parts of the second fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0117] 2 parts of silane coupling agent (A-187)

[0118] 2 parts of silane coupling agent (A-186)

[0119] One part of cationic photoinitiator (UVI6976);

[0120] 0.5 parts of cationic thermal initiator (SI-100L).

[0121] The method for preparing the optical adhesive in this embodiment is as follows:

[0122] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, second fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0123] Comparative Example 1

[0124] This comparative example discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0125] The raw material composition of the optical adhesive in this comparative example consists of the following components, in parts by weight:

[0126] 40 parts of bisphenol AF epoxy resin prepared in Preliminary Example 1

[0127] 55 parts of the first fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0128] 2 parts of silane coupling agent (A-187)

[0129] 2 parts of silane coupling agent (A-186)

[0130] One part of cationic photoinitiator (UVI6976);

[0131] 0.5 parts of cationic thermal initiator (SI-100L).

[0132] The preparation method of the optical adhesive in this comparative example is as follows:

[0133] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, first fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0134] Comparative Example 2

[0135] This comparative example discloses a raw material composition for an optical adhesive, the optical adhesive itself, and a method for preparing the same.

[0136] The raw material composition of the optical adhesive in this comparative example consists of the following components, in parts by weight:

[0137] Five parts of bisphenol AF epoxy resin prepared in Preliminary Example 1

[0138] 90 parts of the first fluorinated acrylate prepolymer obtained in Preliminary Example 2

[0139] 2 parts of silane coupling agent (A-187)

[0140] 2 parts of silane coupling agent (A-186)

[0141] One part of cationic photoinitiator (UVI6976);

[0142] 0.5 parts of cationic thermal initiator (SI-100L).

[0143] The preparation method of the optical adhesive in this comparative example is as follows:

[0144] According to the above-mentioned weight proportions, bisphenol AF epoxy resin, first fluorinated acrylate prepolymer, silane coupling agent (A-187), silane coupling agent (A-186), cationic photoinitiator (UVI6976), and cationic thermal initiator (SI-100L) are placed in a light-proof mixer and stirred at 2000 RPM for 2 minutes to homogenize the mixture and obtain a low-refractive-index transparent optical adhesive.

[0145] In the above examples and comparative examples, the silane coupling agent (A-187) refers to γ-glycidyl etheroxypropyltrimethoxysilane, the silane coupling agent (A-186) refers to β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, the cationic photoinitiator (UVI6976) refers to triarylsulfonium hexafluoroantimonate, and the cationic thermal initiator (SI-100L) refers to arylsulfonium hexafluoroantimonate purchased from Sanshin Chemical Co., Ltd. of Japan.

[0146] Table 2 shows the raw material information and raw material ratios of the optical adhesives used in the above embodiments and comparative examples.

[0147] Table 2

[0148]

[0149] Example 1

[0150] This embodiment discloses the performance parameters of different types of optical adhesives in Examples 1-4 and Comparative Examples 1-2. The test methods for each performance parameter are as follows:

[0151] 1. Viscosity: The viscosity of the adhesive at 25°C was tested using a Brookfield CP52 viscometer.

[0152] 2. Refractive index before curing: The refractive index of the wet adhesive at 25°C was measured using an Abbe refractometer.

[0153] 3. Bonding strength after curing: Apply adhesive with a thickness of 0.1mm to a glass slide, cover with a 1.5mm × 1.5mm glass slide to create a bonding sample. First, pass the sample through a 365nm LED ultraviolet lamp (curing energy 6000mJ / cm²). 2 Irradiate for 60 seconds, then place in an oven at 100℃ for 1 hour, and then test the shear strength.

[0154] 4. Resistance to damp heat aging: The bonded sample was placed in an environment of 85℃ and 85%RH for 2000 hours. After being removed and placed at room temperature for 2 hours, the bond strength was tested and compared with the sample that had not undergone damp heat aging.

[0155] 5. Glass transition temperature Tg: The glass transition temperature of the cured adhesive was tested using a dynamic mechanical analyzer (DMA).

[0156] 6. Transmittance: The transmittance of the cured adhesive in the wavelength range of 380nm-800nm ​​was tested using a spectrophotometer (sample thickness 0.45mm).

[0157] 7. Volume shrinkage rate: The shrinkage rate of the adhesive before and after UV curing and heat curing was tested using the density method.

[0158] 8. Compatibility and stability: Store the adhesive in the dark for 30 days and observe whether it separates into layers.

[0159] 9. Modulus: The storage modulus of the adhesive at different temperatures was tested using a dynamic mechanical analyzer (DMA) at a heating rate of 10℃ / min, with a test range of 25~300℃.

[0160] 10. Coefficient of thermal expansion: The coefficient of thermal expansion of the adhesive was tested using a thermomechanical analyzer (TMA) at a heating rate of 10℃ / min, with a test range of 25~300℃.

[0161] Table 3 shows the performance parameters of the optical adhesives in Examples 1-4 and Comparative Examples 1-2 obtained using the above test methods.

[0162] Table 3

[0163]

[0164]

[0165] In the table above, the bond strength attenuation rate is calculated as: (bond strength after curing - bond strength after damp heat aging) / bond strength after curing.

[0166] As shown in the table above, the optical adhesives in Examples 1-4 have low viscosity and a refractive index before curing (below 1.435, meeting the refractive index requirements for optical adhesives in the optical communication field). Simultaneously, they exhibit excellent adhesive strength and resistance to damp heat aging, as well as a small adhesive strength attenuation rate. Furthermore, their UV-curing volume shrinkage rate and thermosetting volume shrinkage rate are both low, below 1.38% and below 0.35%, respectively, which can improve the dimensional accuracy and stability of the product. In contrast, the optical adhesive in Comparative Example 1 has a higher viscosity, which is unfavorable for application; it has poor compatibility and delamination; and its refractive index before curing exceeds 1.435, failing to meet the requirements of the optical communication field. The optical adhesive in Comparative Example 2 has insufficient adhesive strength, and its adhesive strength attenuation rate after damp heat aging reaches 33.05%, with high UV-curing and thermosetting volume shrinkage rates.

[0167] The optical adhesive prepared in the above embodiments has the characteristics of low refractive index, high light transmittance, high glass transition temperature, low viscosity, and excellent resistance to damp heat aging. Specifically, this optical adhesive has a refractive index below 1.435, a light transmittance greater than 80%, a glass transition temperature above 110°C, an adhesive strength greater than 15 MPa, and an adhesive strength attenuation of less than 20%, preferably less than 15%, after 2000 hours of high temperature and high humidity.

[0168] Existing optical adhesives typically use epoxy resin and fluorinated epoxy resin as raw materials. Fluorinated epoxy resin is linear and has poor compatibility with conventional epoxy resins, especially resulting in poor long-term stability after mixing, leading to delamination. In contrast, the mixture system formed by a specific ratio of bisphenol AF epoxy resin and fluorinated acrylate prepolymer in this application reduces the volume shrinkage rate of the optical adhesive and exhibits a lower refractive index.

[0169] The embodiments described above are merely preferred embodiments, and are described in detail, but the scope of protection of this invention is not limited thereto. Any improvements or variations made by those skilled in the art based on this invention should fall within the scope of protection of this invention.

Claims

1. A raw material composition for an optical adhesive, characterized in that, It comprises the following components in parts by weight: 10-25 parts of bisphenol AF epoxy resin; 65-85 parts of fluorinated acrylate prepolymer; 1-5 parts of silane coupling agent; 0.1-2 parts of cationic photoinitiator; 0.1-2 parts of cationic thermal initiator; The fluorinated acrylate prepolymer is obtained by reacting fluorinated acrylate monomers and epoxy acrylate compounds under ultraviolet light irradiation. The bisphenol AF epoxy resin is obtained by polycondensation reaction of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; the bisphenol AF epoxy resin contains hexafluoropropylene groups; the epoxy value of the bisphenol AF epoxy resin is 0.35~0.5 Eq / 100g, and the viscosity at 50℃ is ≤5000 cps.

2. The raw material composition of the optical adhesive as described in claim 1, characterized in that, The raw material composition of the optical adhesive satisfies at least one of the following conditions: i. The silane coupling agent is selected from at least one of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane; ii. The cationic photoinitiator is selected from at least one of aromatic thionium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic phosphonium salts, aromatic selenium salts, and iron aromatic salts; iii. The cationic thermal initiator is selected from at least one of aryl thioonium salts, aryl iodonium salts, aromatic ion complexes, quaternary ammonium salts, aluminum chelates, and boron trifluoride-amine complexes.

3. The raw material composition of the optical adhesive as described in claim 1, characterized in that, The preparation method of the bisphenol AF epoxy resin includes the following steps: s1. The first mixture is mixed with the first alkaline substance to carry out the first reaction, and a mixed solution is obtained; the first mixture includes 2,2-bis(4-hydroxyphenyl)hexafluoropropane and epichlorohydrin; the temperature of the first reaction is 80-110℃; s2. The mixture, organic solvent and second alkaline substance are mixed to carry out a second reaction, the temperature of the second reaction is below 65°C; then, the bisphenol AF epoxy resin is obtained by purification.

4. The raw material composition of the optical adhesive as described in claim 3, characterized in that, The preparation method of the bisphenol AF epoxy resin satisfies at least one of the following conditions: i. The molar ratio of the 2,2-bis(4-hydroxyphenyl)hexafluoropropane, the epichlorohydrin, the first alkaline substance, and the second alkaline substance is 1:(2-12):(1-4). ii. The first alkaline substance and the second alkaline substance include a sodium hydroxide solution with a concentration of 20%-40%, where % refers to the mass percentage of sodium hydroxide in the solution; iii. In step s1, the mixing temperature of the 2,2-bis(4-hydroxyphenyl)hexafluoropropane and the epichlorohydrin is 40-60°C; iv. In step s1, the time for the first reaction is 1-5 h; v. In step s1, after the first reaction, unreacted epichlorohydrin is recovered by reducing pressure. vi. In step s2, the organic solvent is one or more of toluene, xylene, chlorobenzene, o-dichlorobenzene, and heptane; vii. In step s2, the mass ratio of the organic solvent to the 2,2-bis(4-hydroxyphenyl)hexafluoropropane is (1-10):1; viii. In step s2, the second reaction takes 1-5 hours; viiii, in step s2, the purification process includes, in sequence: cooling, washing, separation of aqueous phase, and distillation of organic solvent.

5. The raw material composition of the optical adhesive as described in claim 1, characterized in that, The preparation method of the fluorinated acrylate prepolymer includes the following steps: ss1. Under an inert atmosphere, the raw materials are stirred and mixed to obtain a second mixture; the raw materials include the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator; ss2. The second mixture is subjected to ultraviolet light irradiation to obtain the fluorinated acrylate prepolymer; the wavelength of the ultraviolet light is 200-450 nm, and the irradiation time is 30-90 s.

6. The raw material composition of the optical adhesive as described in claim 5, characterized in that, Step ss1 satisfies at least one of the following conditions: i. The mass ratio of the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator is (35-60):(10-30):(0.5-2). ii. The fluorinated acrylate monomer is selected from at least one of perfluorobutyl ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, perfluorooctyl ethyl methacrylate, perfluorooctyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate. iii. The epoxy acrylate compound is selected from at least one of 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexyl methacrylate, and glycidyl methacrylate.

7. The raw material composition of the optical adhesive as described in claim 6, characterized in that, The method for preparing the fluorinated acrylate prepolymer satisfies at least one of the following conditions: i. In step ss1, the photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, and benzoyladium dimethyl ether; ii. In step ss1, the mass ratio of the fluorinated acrylate monomer, the epoxy acrylate compound, and the photoinitiator is (40-55):(10-25):(0.5-1.5). iii. In step ss2, the energy density of the ultraviolet light is 5000~8000mJ / cm².

8. A method for preparing an optical adhesive, characterized in that, It includes the following steps: The raw material composition of the optical adhesive as described in any one of claims 1-7 is homogenized to obtain the optical adhesive; the stirring speed of the homogenization is 1000-3000 rpm and the stirring time is 1-10 min.

9. An optical adhesive, characterized in that, It is prepared using the optical adhesive preparation method as described in claim 8.

10. The application of the optical adhesive as described in claim 9 in chip bonding and optical communication.

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