Charge transfer compound-based photoinitiator, adhesive composition and preparation method thereof

Abstract

The invention discloses a charge transfer compound-based photoinitiator. The charge transfer compound-based photoinitiator is formed by an electron donor and an electron withdrawing body through charge transfer. Wherein the molecular number ratio of the electron donor (electron donor) to the electron acceptor (electron acceptor) is (1-5): 1. The invention also discloses an adhesive composition containing the charge transfer compound-based photoinitiator and a preparation method of the charge transfer compound-based photoinitiator. The adhesive composition prepared by adopting the charge transfer compound-based photoinitiator has a window period for delaying curing, and can be used for bonding low ultraviolet light transmission base materials.

Description

Technical Field

[0001] This invention belongs to the field of photocuring technology, and particularly relates to a charge transfer composite-based photoinitiator, an adhesive composition, and a method for preparing the same. Background Technology

[0002] UV adhesives are a type of adhesive system that cures upon exposure to ultraviolet light. Their curing mechanism involves photoinitiators in their components generating active species that can polymerize monomers under light irradiation. Due to their advantages such as safety, environmental friendliness, rapid curing, excellent compatibility, and high bond strength, they have been widely used in industry in recent years. However, when the substrate to be bonded is opaque to ultraviolet light (either opaque or containing substances that absorb ultraviolet light), the photoinitiator cannot be activated, and final curing cannot be achieved.

[0003] If the active species are released slowly rather than immediately after light exposure, a certain delay window can be provided to enable the bonding of such substrates. In recent years, based on specific formulation designs and resin structural designs, some adhesives with UV-delayed curing have been prepared. For example, CN118307767A achieves a certain delay time through structural design of epoxy compounds. Zhu et al. also developed an adhesive for delayed curing by utilizing the relatively slow curing speed of multifunctional glycidyl ethers (RSC Adv. 2017, 7, 4046-4053). Harikrishna, by adding amine compounds to cationic curing compositions, was able to consume the generated hydrogen ions in the early stages of the reaction, thus delaying the gelation time (Journal of Photochemistry and Photobiology A: Chemistry 2015, 303, 17). However, these strategies are mostly effective in certain formulation ranges. When the formulation contains highly reactive resins (such as alicyclic epoxy resins), the system will still cure rapidly. Therefore, these solutions are difficult to be universal and are difficult to apply widely in industry.

[0004] In summary, there is an urgent need in this field for a delayed curing platform that can achieve a delay effect and allow for manual adjustment of the delay window according to actual process requirements. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a charge transfer complex-based photoinitiator, an adhesive composition, and a method for preparing the same.

[0006] In a first aspect, the present invention provides a charge-transfer complex-based photoinitiator with the following structural formula: or ,in, R1+ Selected from iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, or chloride ions; R2 is selected from hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, or polymer chain groups; X - Selected from BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I - Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate, or substituted methanesulfonate. R3 is independently selected from compounds with electron-donating ability, preferably from tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, or coumarin and its derivatives. n is an integer selected from 1 to 5; R4 is selected independently from: , or .

[0007] In a second aspect, the present invention provides a method for preparing the charge-transfer complex-based photoinitiator described in the first aspect, comprising: mixing an electron acceptor and an electron donor to obtain the charge-transfer complex-based photoinitiator; wherein the molar ratio of the electron acceptor to the electron donor is 1:1-5; preferably, the reaction temperature of the electron acceptor and the electron donor is -20 to 100°C; The electron acceptor is composed of R1 + R2 and X - Composition, wherein, R1 + Selected from iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, or chloride ions; The R2 is selected from hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, or polymer chain groups; The X - Selected from BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I- Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate, or substituted methanesulfonate. The electron donor is a compound with electron-donating ability, preferably selected from tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, or coumarin and its derivatives.

[0008] In a third aspect, the present invention provides an adhesive composition comprising, by parts by weight: 0.01-1 parts of charge-transfer complex-based photoinitiator; 1-10 parts epoxy resin; 0.01 - 1 part silane coupling agent; 0.01 - 1 part photosensitizer; The charge-transfer complex-based photoinitiator is R1 as described in the first aspect. + R1 is a charge-transfer complex-based photoinitiator of iodine ions or prepared by the method described in the second aspect. + It is a charge-transfer complex-based photoinitiator for iodonium ions.

[0009] In a fourth aspect, the present invention provides an adhesive composition comprising, by parts by weight: 0.01-1 parts of charge-transfer complex-based photoinitiator; 1-10 parts epoxy resin; 0.01 - 1 part silane coupling agent; The charge-transfer complex-based photoinitiator is R1 as described in the first aspect. + The R1 is a charge-transfer complex based photoinitiator of thionium, ferrocene, quaternary ammonium, diazo, phosphonium, bromium, and chloride ions, or prepared by the method described in the second aspect. + It is a charge-transfer complex-based photoinitiator for thionium, ferromagnesite, quaternary ammonium, diazo, phosphonium, bromium, and chloride ions.

[0010] In a fifth aspect, the present invention provides the use of the adhesive composition described in the third or fourth aspect for bonding substrates.

[0011] This invention provides an adhesive composition containing a charge-transfer composite-based photoinitiator that has a delayed-curing function and can be used to bond substrates with low ultraviolet (UV) transmittance. Furthermore, the delayed-curing window can be artificially controlled by adjusting the type and number of electron donors. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other implementation schemes can be obtained based on these drawings without creative effort.

[0013] Figure 1 The modified electron donors used in the preparation of CTC-8 are shown. 1 H NMR spectrum. Detailed Implementation

[0014] The present invention will be described in detail below. It should be understood that the following description is merely illustrative and is not intended to limit the scope of the invention; the scope of protection of the invention is defined by the appended claims. Furthermore, those skilled in the art will understand that modifications can be made to the technical solutions of the present invention without departing from its spirit and intent. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter pertains. Before a detailed description of the invention, the following definitions are provided to better understand it.

[0016] In the context of this invention, many embodiments use the expressions "comprising," "including," or "basically / mainly composed of." The expressions "comprising," "including," or "basically / mainly composed of" should be understood as open-ended expressions, indicating that they include not only the elements, components, parts, and method steps specifically listed after the expression, but also other elements, components, parts, and method steps. Additionally, in this document, the expressions "comprising," "including," or "basically / mainly composed of" may also be understood as closed-ended expressions in certain circumstances, indicating that they only include the elements, components, parts, and method steps specifically listed after the expression, and do not include any other elements, components, parts, or method steps. In this case, the expression is equivalent to the expression "composed of."

[0017] It should be noted that, unless explicitly stated in the context, all numerical values ​​or ranges mentioned in this article are defined by the term "about". In this article, for a given numerical value, the term "about" means ±5% of that value, such as ±4%, ±3%, ±2%, or ±1%. For a range of numerical values, the term "about" means ±5% of the upper or lower limit of that range, such as ±4%, ±3%, ±2%, or ±1%.

[0018] In this paper, ordinal numbers such as "first," "second," and "third" are sometimes used to modify or limit elements, components, parts, method steps, solutions, solvents, temperatures, systems, etc. It should be noted that in this paper, these expressions are only used to distinguish the elements, components, parts, method steps, solutions, solvents, temperatures, systems, etc. that they modify or limit, and are not intended to limit their order or importance.

[0019] In view of the problems existing in the prior art, such as the inability of photoinitiators to be activated when the substrate to be bonded cannot transmit ultraviolet light, thus failing to achieve final curing, and the incompatibility of existing delayed-curing adhesives with highly reactive resins, the present invention aims to provide a charge transfer composite-based photoinitiator, an adhesive composition, and a method for preparing the same, to solve at least one of the above-mentioned problems.

[0020] In a first aspect, the present invention provides a charge-transfer composite-based photoinitiator with the following structural formula: , Among them, R1 + The cations are selected from cationic photoinitiators, including but not limited to iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, and chloride ions; R2 is a substituent linked to the cation, including but not limited to hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic rings, ester groups, hydroxyl groups, carboxyl groups, and polymer chain groups. X - To counteract anions, including but not limited to BF4 - PF6 - SbF6 - B(Ar)4 - , Br - I - Cl - and CN - Halogen and halide-like ions, p-toluenesulfonate (-OTs), substituted p-toluenesulfonate, trifluoromethanesulfonate (-OTf), substituted trifluoromethanesulfonate, methanesulfonate (-OMs) and substituted methanesulfonate. R3 is independently selected from any compound with electron-donating ability, including but not limited to tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, coumarin and its derivatives, etc. Where n is an integer selected from 1 to 5.

[0021] Furthermore, a modifying group is attached to R3, with the specific structural formula as follows: , OR4 is a modifying group attached to R3.

[0022] The R4 in OR4 is independently selected from: , or .

[0023] The function of the OR4 modifying group attached to R3 is to modify the electron donor R3 by introducing the modifying group, enabling it to participate in the curing reaction of the epoxy resin, thereby eliminating the adverse effects of the small molecule electron donor compound on the adhesive performance. It is worth noting that conventional electron donors, after releasing the photoinitiator, remain in the adhesive formulation as small molecules and do not participate in the reaction. When the adhesive is used at high temperatures, the small electron donor molecules migrate to the adhesive surface, thus affecting the adhesive performance. Therefore, by introducing the OR4 modifying group into the electron donor R3, the adhesive performance of the adhesive composition is further improved.

[0024] The cationic photoinitiator described in this invention is a type of catalyst that, under illumination, absorbs light energy to convert into an excited state, subsequently undergoes a series of decomposition reactions, and ultimately generates a superprotic acid, thereby initiating a chemical reaction. These superprotic acids possess high reactivity and can undergo cationic polymerization with monomers such as epoxides, vinyl ethers, lactones, acetals, and cyclic ethers to form a cross-linked network.

[0025] The counter anions described in this invention refer to single atoms or groups of atoms that pair with positively charged onon centers (S⁺, I⁺, etc.) to maintain electrical neutrality. After photolysis, they remain in the system and directly determine the strength of the released superacid and the polymerization kinetics.

[0026] A charge transfer complex (CTC) is a complex formed by partial charge transfer between an electron donor (also called an electron donor, abbreviated as D) and an electron acceptor (also called an electron withdrawer, abbreviated as A). It is worth noting that in a charge transfer complex, no physical chemical bond is formed between the electron donor and the electron withdrawer; the main force between them is the intermolecular force, a special and strong intermolecular force known as charge transfer interaction. This invention prepares a series of charge transfer complex (CTC)-based photoinitiators. In these CTC-based photoinitiators, the electron withdrawer (photoinitiator) is bound by the electron donor. Upon irradiation, the photolysis of the electron withdrawer (photoinitiator) is not instantaneous but rather occurs slowly, separating from the electron donor before photolysis. Finally, as protic acids gradually accumulate, they rapidly promote the cationic polymerization of epoxy resins. The delayed curing mechanism of the CTC-based photoinitiator is as follows: .

[0027] It is worth noting that the electron donor or electron donor described in this invention refers to a chemical entity capable of providing electrons or electron density to the reaction system. During the polymerization reaction initiated by the CTC-based photoinitiator, the electron donor slowly releases the electron-withdrawing body (photoinitiator) it combines with. The electron-withdrawing body (photoinitiator) decomposes under light irradiation, generating a superacid, thereby initiating the polymerization reaction.

[0028] In the CTC-based photoinitiator prepared by this invention, the molecular ratio of the electron acceptor (electron-withdrawing body) to the electron donor (electron-donating body) is 1:1-5, for example, 1:1, 1:2, 1:3, 1:4, or 1:5. It is worth noting that the molecular ratio of the electron donor to the electron-withdrawing body in the CTC-based photoinitiator of this invention can be any range prepared according to actual needs.

[0029] Furthermore, the acid-producing properties of the CTC-based photoinitiator prepared by this invention are closely related to the type and structure of the electron-withdrawing body, and also to the strength of the binding force between the electron donor and electron-withdrawing body in the CTC-based photoinitiator.

[0030] The results of the acid production performance study show that the CTC-based photoinitiators prepared in this invention all achieved the effect of delayed color change.

[0031] In a second aspect, the present invention provides a method for preparing a CTC-based photoinitiator, comprising: mixing an electron acceptor and an electron donor to obtain the charge-transfer complex-based photoinitiator; wherein the molar ratio of the electron acceptor to the electron donor is 1:1-5; preferably, the reaction temperature of the electron acceptor and the electron donor is -20 to -100°C; The electron acceptor is composed of R1 + R2 and X - Composition, wherein, R1 + The cations selected from cationic photoinitiators include, but are not limited to, iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, and chloride ions; R2 is a substituent linked to the cation, including but not limited to hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, and polymer chain groups. The X - To counteract anions, including but not limited to BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I - Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate and substituted methanesulfonate; The electron donor is selected from any compound with electron-donating ability, including but not limited to tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, and coumarin and its derivatives.

[0032] It is worth noting that any common solvent can be used in the preparation method of CTC-based photoinitiators, including but not limited to methanol, ethanol, acetone, chloroform, water, diethyl ether, toluene, benzene, 1,4-dioxane, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, dichloromethane, ethyl acetate, petroleum ether, n-hexane, isopropanol, and tert-butanol. The reaction atmosphere for preparing CTC-based photoinitiators can be selected from helium, nitrogen, oxygen, and air. The reaction temperature of the CTC-based photoinitiator can be selected from any value between -20 and 100°C, such as -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, preferably 0-50°C; the stirring speed of the CTC-based photoinitiator can be selected from any value between 10 and 2000 rpm, such as 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, and 1400 rpm. rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, preferably 50-1000 rpm.

[0033] In a preferred embodiment, the electron donor further comprises an OR4 modifying group, wherein the R4 in the OR4 is independently selected from: , or .

[0034] The electron donor containing the OR4 modified group is prepared by reacting a hydroxyl derivative of the electron donor with an ester derivative of an oxygen-containing cycloalkanes or an oxygen-containing unsaturated hydrocarbon under basic conditions. The basic conditions include any basic compound capable of providing an alkaline environment, preferably potassium carbonate, sodium carbonate, cesium carbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium ethoxide, sodium methoxide, n-butyllithium, lithium diisopropylamine, sodium hydride, sodium bicarbonate, and / or potassium phosphate. It is worth noting that any common solvent can be used in the preparation of the electron donor, including but not limited to methanol, ethanol, acetone, chloroform, water, diethyl ether, toluene, benzene, 1,4-dioxane, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, dichloromethane, ethyl acetate, petroleum ether, n-hexane, isopropanol, and tert-butanol. The reaction atmosphere for preparing the electron donor can be selected from helium, nitrogen, oxygen, and air. The reaction temperature for preparing the electron donor can be selected from any value between -20 and 100°C, such as -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, preferably 0-50°C. The stirring speed for preparing the electron donor can be selected from any value between 10 and 2000 rpm, such as 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, and 1500 rpm. rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, preferably 50 - 1000 rpm.

[0035] In a third aspect, the present invention provides an adhesive composition comprising, by parts by weight: 1-10 parts epoxy resin; 0.01 - 1 part of charge-transfer complex-based photoinitiator; 0.01 - 1 part silane coupling agent; 0.01 - 1 part photosensitizer; The charge-transfer complex-based photoinitiator is R1 as described in the first aspect. + R1 is a charge-transfer complex-based photoinitiator of iodine ions or prepared by the method described in the second aspect. +The photoinitiator is a charge-transfer complex based photoinitiator of iodine ions. The mass fraction of the charge-transfer complex based photoinitiator is 0.01-1 part, such as 0.01 part, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, or 1 part, preferably 0.1-0.5 parts.

[0036] In a fourth aspect, the present invention provides an adhesive composition comprising, by parts by weight: 0.01-1 parts of charge-transfer complex-based photoinitiator; 1-10 parts epoxy resin; 0.01 - 1 part silane coupling agent; The charge-transfer complex-based photoinitiator is R1 as described in the first aspect. + The R1 is a charge-transfer complex based photoinitiator of thionium, ferrocene, quaternary ammonium, diazo, phosphonium, bromium, and chloride ions, or prepared by the method described in the second aspect. + The photoinitiator is a charge-transfer complex based photoinitiator comprising sulfonium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, and chloride ions. The charge-transfer complex based photoinitiator is present in a mass fraction of 0.01-1 part, such as 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1 part, preferably 0.1-0.5 parts.

[0037] It is worth noting that "by mass parts" in this invention refers to the number of parts of each component in the adhesive composition calculated based on mass. Specifically, in the adhesive composition described in the third or fourth aspect, the epoxy resin can be any type of epoxy resin. Preferably, the epoxy resin is selected from one or more of the group consisting of bisphenol A type glycidyl ether epoxy resin, bisphenol F type glycidyl ether epoxy resin, a mixture of bisphenol A and bisphenol F type glycidyl ether epoxy resins, rubber toughening type glycidyl ether epoxy resin, aliphatic epoxy resin, and / or alicyclic epoxy resin. The mass parts of the epoxy resin are 1-10 parts, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, preferably 2-8 parts.

[0038] The silane coupling agent can be any silane coupling agent. Preferably, the silane coupling agent is selected from one or more of the group consisting of 3-glycidoxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, (3-epoxypropylpropoxy)trimethoxysilane, (3-epoxypropylpropoxy)triethoxysilane, and / or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The silane coupling agent is present in parts by weight of 0.01 to 1, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, preferably 0.01 to 0.5.

[0039] Because the maximum absorption wavelength of iodonium salts is typically short, while the main emission lines of commonly used industrial ultraviolet light sources are usually in the long-wavelength range, direct irradiation results in low light utilization, leading to slow curing speeds or even failure to cure. To address the mismatch between the absorption of iodonium salts and practical light sources, a photosensitizer needs to be added when using iodonium salt-based photoinitiators to achieve efficient and practical photocuring. Specifically, in the adhesive composition described in the third aspect, the photosensitizer can be any photosensitizer; preferably, the photosensitizer is selected from one or more of the group consisting of 2-isopropylthioxanthone, camphorquinone, anthraquinones and their derivatives, methylene blue and / or porphyrins and their derivatives. The photosensitizer is present in parts by weight of 0.01 to 1, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, preferably 0.01 to 0.5.

[0040] It is worth noting that in practical use, when the viscosity of the adhesive composition described in the third or fourth aspect is high (e.g., above 30,000 mPa·s), an active diluent can be added to adjust the viscosity of the system and participate in the curing reaction. The active diluent can be any active diluent; preferably, it is selected from one or more of the group consisting of benzyl glycidyl ether (and its derivatives), alkyl glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl glycidyl ether, trifunctional glycidyl ether, and / or tetrafunctional glycidyl ether.

[0041] The results show that adhesive compositions prepared using the CTC-based photoinitiators of this invention (such as CTC-1, CTC-2, CTC-3, CTC-4, CTC-5, CTC-6, CTC-7, CTC-8, and CTC-9) all achieved delayed curing. Specifically, the electron-donating ability and the number of electron-donators in the CTC-based photoinitiator both affect the delay window of the adhesive composition. The stronger the electron-donating ability of the electron-donator in the CTC-based photoinitiator, the stronger the electron-donator-electron-withdrawer (DA) interaction, resulting in a longer delay window for the adhesive composition. A greater number of electron-donators in the CTC-based photoinitiator also leads to a longer delay window for the adhesive composition.

[0042] In a fifth aspect, the present invention provides an application of the adhesive composition described in the third or fourth aspect for bonding substrates, comprising: (1) The adhesive composition is irradiated with ultraviolet light and initiated, and the adhesive composition enters a delayed curing window; (2) During the window period, the adhesive composition is bonded to the substrate.

[0043] The adhesive composition of this invention is applicable to a variety of substrates (such as glass, crystalline materials, plastics, etc.). Because the adhesive composition of this invention has a delayed curing window, for substrates with low ultraviolet (UV) transmittance, the adhesive composition can be pre-applied to the substrate surface. After excitation with UV light, the adhesive composition can remain in a flowing state within a certain window, during which time it can bond to the low UV transmittance substrate. Therefore, the adhesive composition of this invention can also achieve good adhesion to low UV transmittance substrates. The low UV transmittance substrates described in this invention include opaque substrates, substrates containing UV absorbers, multilayer composite substrates, etc.

[0044] It should be noted that there is no particular limitation on the adhesive application thickness; it depends on the bonding requirements. The UV irradiation time can be determined for different adhesive application thicknesses. In a preferred embodiment, the adhesive composition of the present invention, with an application thickness of 0.2-1 mm, uses a wavelength of 200-500 nm and a curing energy of 200-100000 mJ / cm². 2After irradiation with ultraviolet (UV) light, the adhesive undergoes delayed curing, with a delayed curing window of 5 min to 30 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, and 30 min. The source of the UV light can be any light source capable of producing the aforementioned wavelength and curing energy, such as a mercury lamp, LED light source, or xenon lamp light source.

[0045] The adhesive composition of the present invention has at least one of the following beneficial effects: In the CTC-based photoinitiator of this invention, the electron-withdrawing component is bound to the electron-donating component. Upon exposure to light, its photolysis is not instantaneous but rather occurs slowly, separating it from the electron-donating component. Therefore, the CTC-based photoinitiator of this invention provides a certain delayed curing window.

[0046] The adhesive composition prepared using the CTC-based photoinitiator described in this invention can be used to bond substrates with low ultraviolet (UV) transmittance. In use, the adhesive composition is pre-applied to the substrate surface. After excitation with UV light, the adhesive composition has a delayed curing window, meaning it does not cure immediately and can remain in a fluid state within this window. Therefore, substrates with low UV transmittance (e.g., opaque substrates, substrates containing UV absorbers, multilayer composite substrates, etc.) can be bonded during this period.

[0047] The delayed curing window can be artificially controlled by adjusting the type and number of electron donors. This is possible when the adhesive thickness is 0.2–1 mm, the wavelength is 200–500 nm, and the curing energy is 200–100,000 mJ / cm². 2 After exposure to ultraviolet (UV) light, the adhesive composition has a delayed curing window of 5 minutes to 30 minutes. Therefore, different operating windows can be provided according to specific process requirements, greatly improving the convenience and user-friendliness of construction.

[0048] Compared to traditional cationic photoinitiators, the charge in CTC-based photoinitiators is effectively dispersed, thus making them readily soluble in adhesive formulations and solving the problem of poor solubility found in some ionic initiators. The CTC-based photoinitiators of this invention are also suitable for highly reactive resin systems, such as epoxy resins.

[0049] By modifying the electron donor and introducing modifying groups, it can participate in the curing reaction of epoxy resin, thereby eliminating the adverse effects of small molecule electron donor compounds on the adhesive properties of the adhesive.

[0050] Regarding the sources of reagents and solvents used in the following specific examples and comparative examples: The raw materials, reagents and solvents used in the following examples and comparative examples were all commercially available.

[0051] Example 1 Synthesis of CTC-based photoinitiator Synthesis Example 1: Synthesis of CTC-1 The synthetic route for CTC-1 is shown below: .

[0052] The synthesis method of CTC-1 is as follows: 1 mmol of diphenyl[4-(phenylthio)phenyl]-sulfonium hexafluoroantimonate and 1 mmol of methoxy-substituted triphenylamine were dissolved in 2 mL of methanol at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain pale yellow crystals of CTC-1. Elemental analysis: Theoretical value: C 45 H 40 F6NO3S2Sb: %C (57.34), %H (4.28), actual value: %C (57.22), %H (4.14).

[0053] Synthesis Example 2: Synthesis of CTC-2 The synthetic route for CTC-2 is shown below: .

[0054] The synthesis method of CTC-2 is as follows: 1 mmol of diphenyl[4-(phenylthio)phenyl]-sulfonium hexafluoroantimonate and 1 mmol of triphenylamine were dissolved in 2 mL of methanol at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain pale yellow crystals of CTC-2. Elemental analysis: Theoretical value: C 42 H 34 F6S2Sb: %C (59.17), %H (4.02), actual value: %C (59.03), %H (3.98).

[0055] Synthesis Example 3: Synthesis of CTC-3 The synthetic route for CTC-3 is shown below: .

[0056] The synthesis method of CTC-3 is as follows: 1 mmol of diphenyl[4-(phenylthio)phenyl]-sulfonium hexafluoroantimonate and 1 mmol of pyrene were dissolved in 2 mL of dichloromethane at room temperature. The two solutions were then thoroughly mixed, and a suitable amount of petroleum ether was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with petroleum ether, and dried in a vacuum oven to obtain pale yellow crystals of CTC-3. Elemental analysis: Theoretical value: C 40 H 31 F6S2Sb: %C (59.20), %H (3.85), actual value: %C (59.29), %H (3.98).

[0057] Synthesis Example 4: Synthesis of CTC-4 The synthesis of CTC-4 is shown below: .

[0058] The synthesis of CTC-4 is as follows: 1 mmol of diphenyliodonium-hexafluorophosphate and 1 mmol of methoxy-substituted triphenylamine were dissolved in 2 mL of chloroform at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain pale yellow crystals of CTC-4. Elemental analysis: Theoretical value: C 33 H 31 F6INO3P: %C (52.05), %H (4.10), actual value: %C (52.01), %H (4.15).

[0059] Synthesis Example 5: Synthesis of CTC-5 The synthetic route for CTC-5 is shown below: .

[0060] The synthesis method of CTC-5 is as follows: 1 mmol of diphenyliodonium-hexafluorophosphate and 1 mmol of triphenylamine were dissolved in 2 mL of chloroform at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain pale yellow crystals of CTC-5. Elemental analysis: Theoretical value: C30 H 25 F6INP: %C (53.67), %H (3.76), actual value: %C (53.59), %H (3.69).

[0061] Synthesis Example 6: Synthesis of CTC-6 The synthetic route for CTC-6 is shown below: .

[0062] The synthesis of CTC-6 is as follows: 1 mmol of diphenyliodonium-hexafluorophosphate and 1 mmol of tetrathionene were dissolved in 2 mL of chloroform at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain orange-yellow crystals of CTC-6. Elemental analysis: Theoretical value: C 18 H 14 F6IPS4: %C (34.29), %H (2.24), actual value: %C (34.19), %H (2.16).

[0063] Synthesis Example 7: Synthesis of CTC-7 The synthetic route for CTC-7 is shown below: .

[0064] The synthesis of CTC-7 is as follows: 1 mmol of diphenyliodonium-hexafluorophosphate and 2 mmol of tetrathionyl fulvalene were dissolved in 2 mL of chloroform at room temperature. The two solutions were then thoroughly mixed, and an appropriate amount of n-hexane was quickly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain yellow crystals of CTC-7. Elemental analysis: Theoretical value: C 24 H 18 F6IPS8: %C (34.53), %H (2.17), actual value: %C (34.33), %H (2.21).

[0065] Synthesis Example 8: Synthesis of CTC-8 The synthetic route for CTC-8 is shown below: .

[0066] The synthesis method of CTC-8 is as follows: 2 mmol of 1-hydroxypyrene was dissolved in 10 mL of methanol, and 2.0 mmol of potassium carbonate was added. After stirring at room temperature for half an hour, 2 mmol of oxerocyclo-2-yl-p-toluenesulfonate was added dropwise to the reaction solution. After the reaction was monitored by TLC until complete, the reaction was quenched with water, washed with dichloromethane, extracted, and the organic phases were combined. The organic phases were dried over anhydrous sodium sulfate and evaporated to dryness to give 493 mg of yellow solid (i.e., the modified electron donor), with a yield of 90%. The 1H NMR spectrum of the obtained modified electron donor is shown below. Figure 1 As shown, the specific analysis is as follows: 1 H NMR (CDCl3, 400 MHz): 7.63 (dt, 1H), 7.54 (m, 1H), 7.37 (m, 1H), 7.32-7.13 (m, 3H), 6.43 (m, 1H), 6.22 (q, 1H), 5.98 (m, 1H), 3.78 (dd, 1H), 3.68 (dd, 1H), 3.54 (dd, 1H), 3.35 (q, 1H).

[0067] 1 mmol of the modified electron-donating product and 1 mmol of diphenyl[4-(phenylthio)phenyl]-sulfonium hexafluoroantimonyate were dissolved in methanol at room temperature. The two methanol solutions were then thoroughly mixed, and a suitable amount of n-hexane was rapidly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain yellow crystals CTC-8. Elemental analysis: Theoretical value: C 43 H 33 F6O2S2Sb: %C (58.58), %H (3.77), actual value: %C (58.44), %H (3.69).

[0068] Synthesis Example 9: Synthesis of CTC-9 The synthetic route for CTC-9 is shown below: .

[0069] The synthesis of CTC-9 was performed as follows: 2 mmol of 1-hydroxypyrene was dissolved in 10 mL of methanol, and 2.0 mmol of potassium carbonate was added. After stirring at room temperature for half an hour, 2 mmol of 3-(ethoxy)propyl 4-methylbenzenesulfonate was added dropwise to the reaction solution. After the reaction was monitored by TLC until complete, the reaction was quenched with water, washed with dichloromethane, extracted, and the organic phases were combined. The organic phases were dried over anhydrous sodium sulfate and evaporated to dryness to give 544 mg of a yellow solid (i.e., the modified electron donor), with a yield of 90%.

[0070] 1 mmol of the modified electron-donating product and 1 mmol of diphenyl[4-(phenylthio)phenyl]-sulfonium hexafluoroantimonyate were dissolved in methanol at room temperature. The two methanol solutions were then thoroughly mixed, and a suitable amount of n-hexane was rapidly added until a precipitate formed. The mixture was then placed in a refrigerator at 5°C and allowed to stand overnight to obtain a large amount of precipitate. The precipitate was filtered, the filter cake was washed with n-hexane, and dried in a vacuum oven to obtain yellow crystals CTC-9. Elemental analysis: Theoretical value: C 45 H 37 F6O2S2Sb: %C (59.42), %H (4.10), actual value: %C (59.36), %H (4.15).

[0071] Example 2 Preparation of adhesive composition Test Example 1 uses the compound CTC-1 synthesized in Example 1 as an initiator to prepare an adhesive composition.

[0072] The preparation method is as follows: 0.2 parts of CTC-1, 2.5 parts of bisphenol F epoxy resin NPEF-170, 2.5 parts of 2021p epoxy resin, and 0.05 parts of silane coupling agent A-187 are thoroughly mixed in a high-speed mixer to obtain an adhesive composition.

[0073] Test Example 2 The preparation method is the same as in Test Example 1, except that 0.18 parts of CTC-2 were used as the photoinitiator.

[0074] Test Example 3 The preparation method is the same as in Test Example 1, except that 0.17 parts of CTC-3 were used as the photoinitiator.

[0075] Test Example 4 The preparation method is the same as in Test Example 1, except that 0.13 parts of CTC-4 were used as the photoinitiator and 0.1 parts of 2-isopropylthioxanthraquinone (ITX) were added as the photosensitizer.

[0076] Test Example 5 The preparation method is the same as in Test Example 1, except that 0.14 parts of CTC-5 were used as the photoinitiator and 0.1 parts of 2-isopropylthioxanthraquinone (ITX) were added as the photosensitizer.

[0077] Test Example 6 The preparation method is the same as in Test Example 1, except that 0.13 parts of CTC-6 were used as the photoinitiator and 0.1 parts of 2-isopropylthioxanthraquinone (ITX) were added as the photosensitizer.

[0078] Test Example 7 The preparation method is the same as in Test Example 1, except that 0.18 parts of CTC-7 were used as the photoinitiator and 0.1 parts of 2-isopropylthioxanthraquinone (ITX) were added as the photosensitizer.

[0079] Test Example 8 The preparation method is the same as in Test Example 1, except that 0.19 parts of CTC-8 were used as the photoinitiator.

[0080] Test Example 9 The preparation method is the same as in Test Example 1, except that 0.19 parts of CTC-9 were used as the photoinitiator.

[0081] Test Case 10 The preparation method is the same as in Test Example 1, except that 5 parts of 2021p epoxy resin were used, bisphenol F epoxy resin was not used, and 0.36 parts of CTC-7 and 0.1 parts of photosensitizer 2-isopropylthioxanthonone (ITX) were used.

[0082] Test Example 11 The preparation method is the same as that in Test Example 1, except that 2.5 parts of bisphenol A epoxy resin NPEL-128 and 2.5 parts of bisphenol F epoxy resin NPEF-170 were used, and 0.19 parts of CTC-8 were used.

[0083] Comparative Example 1 The preparation method is the same as in Test Example 1, except that instead of using a charge-transfer photoinitiator, 0.13 parts of diphenyl[4-(phenylthio)phenyl]-hexafluoroantimony sulfonate was used.

[0084] Comparative Example 2 The preparation method is the same as in Test Example 1, except that instead of using a charge-transfer photoinitiator, 0.13 parts of diphenyl[4-(phenylthio)phenyl]-hexafluoroantimony sulfonate were used, and 0.07 parts of methoxy-substituted triphenylamine were added to the formulation.

[0085] The acid-producing performance of the synthesized photoinitiator was evaluated as follows: Using Rhodamine B as a pH indicator, the results of irradiation with 365 nm UV light (300 mW / cm²) on the CTC-based photoinitiator prepared in Example 1 and the photoinitiators used in Comparative Examples 1 and 2 were recorded after illumination. 2 The color change time of the indicator (unit: min). The test results are shown in Table 1 (where the test concentration of the CTC-based photoinitiator prepared in the examples and the photoinitiators used in Comparative Examples 1 and 2 is 10). -5For iodonium salt initiators (i.e., photoinitiators containing iodonium ions), ITX was added as a photosensitizer during testing to improve the photoinitiation efficiency of the iodonium salt photoinitiator. The concentration of ITX was 10. -6 M.

[0086] Table 1. Acid-producing performance test results of the CTC-based photoinitiators prepared in the examples and the photoinitiators used in Comparative Examples 1 and 2. As shown in Table 1, the CTC-based photoinitiator synthesized in Example 1 exhibited a color change time of over 4 minutes after UV irradiation, demonstrating a significant delayed effect compared to the photoinitiators in Comparative Examples 1-2. This is primarily because the electron-withdrawing agent (photoinitiator) in the CTC-based photoinitiator is bound to the electron-donating agent. Upon irradiation, its photolysis is not instantaneous but rather occurs slowly, separating from the electron-donating agent, thus providing a certain delayed curing window. Furthermore, the delayed curing window can be artificially controlled by adjusting the type and number of electron-donating agents.

[0087] The adhesive compositions obtained in Example 2 and Comparative Examples 1 and 2 were evaluated as follows: 1. Delay window: A 0.5 mm thick adhesive layer was prepared using a coating machine and placed under 365 nm ultraviolet light (light intensity: 300 mW / cm²). 2 Irradiate for 10 seconds. Gently poke the adhesive layer with a toothpick every 1 minute. The time it takes for the adhesive layer to start to string is defined as the delay time.

[0088] 2. Time required to reach 0.1 MPa strength: Samples were prepared using the chip shearing method, with glass substrates bonded together, the bonding area being 3 mm × 3 mm. The cured adhesive was tested every 2 minutes using a Dage chip pusher, and the time required for the strength value to first exceed 0.1 MPa (unit: min) and the actual strength value measured at that time (unit: MPa) were recorded.

[0089] 3. Final strength: Record the shear strength (unit: MPa) after 24 h.

[0090] The performance test results of the adhesive compositions prepared in Test Examples 1-11 and Comparative Examples 1-2 are shown in Table 2.

[0091] Table 2. Performance test results of the adhesive compositions prepared in Test Examples 1-11 and Comparative Examples 1-2 Table 2 shows that, compared with Comparative Example 1, Test Examples 1-11 all exhibit a significant delay window, demonstrating that the adhesive composition containing the CTC-based photoinitiator has a marked delayed curing performance. Test Examples 1, 2, 4, and 5 show that the stronger the electron-donating ability of the electron donor, the stronger the electron-donator-electron-withdrawer (DA) interaction of the CTC-based photoinitiator, ultimately allowing for artificial control of the delay window. Test Examples 6 and 7 show that the delay window can also be controlled by increasing the number of electron donors. Comparative Example 2, which simply adds a traditional photoinitiator and electron donor to the formulation, shows almost no delayed curing ability, significantly inferior to the effect obtained by the combination of the two. This indicates that the DA interaction between the electron-withdrawer and electron-donator is the key factor determining the delay capability.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, substitutions, improvements, etc., made within the spirit and principles of the present invention shall be protected by the present invention.

Claims

1. A charge-transfer complex-based photoinitiator, with the following structural formula: ， in, R1 + Selected from iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, or chloride ions; R2 is selected from hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, or polymer chain groups; X - Selected from BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I - Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate, or substituted methanesulfonate. R3 is independently selected from compounds with electron-donating ability, preferably from tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, or coumarin and its derivatives. n is an integer selected from 1 to 5.

2. A charge-transfer complex-based photoinitiator, with the following structural formula: ， in, R1 + Selected from iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, or chloride ions; R2 is selected from hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, or polymer chain groups; X - Selected from BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I - Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate, or substituted methanesulfonate. R3 is independently selected from compounds with electron-donating ability, preferably from tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, or coumarin and its derivatives. n is an integer selected from 1 to 5; R4 is selected independently from: , or .

3. A method for preparing the charge-transfer composite-based photoinitiator according to any one of claims 1 or 2, comprising: The charge-transfer complex-based photoinitiator is obtained by mixing an electron acceptor and an electron donor; wherein the molar ratio of the electron acceptor to the electron donor is 1:1-5; preferably, the reaction temperature of the electron acceptor and the electron donor is -20 to 100°C. The electron acceptor is composed of R1 + R2 and X - Composition, wherein, R1 + Selected from iodonium ions, thionium ions, ferrocene ions, quaternary ammonium ions, diazo ions, phosphonium ions, bromium ions, or chloride ions; The R2 is selected from hydrogen atoms, halogen atoms, alkyl groups, carbonyl groups, carboxyl groups, aromatic ring groups, ester groups, hydroxyl groups, carboxyl groups, or polymer chain groups; The X - Selected from BF4 - PF6 - SbF6 - B(Ar)4 - ,Br - I - Cl - CN - p-Toluenesulfonate, substituted p-toluenesulfonate, trifluoromethanesulfonate, substituted trifluoromethanesulfonate, methanesulfonate, or substituted methanesulfonate. The electron donor is a compound with electron-donating ability, preferably selected from tetrathiofulvalene and its derivatives, triphenylamine and its derivatives, anthracene, naphthalene, polycyclic aromatic hydrocarbons, pentanebenzene, terthiophene, aniline and its derivatives, polythiophene, benzodithiophene and its derivatives, carbazole and its derivatives, or coumarin and its derivatives.

4. The method of claim 3, wherein the electron donor comprises an OR4 modifying group, wherein the R4 in the OR4 is independently selected from: , or .

5. An adhesive composition, comprising, by weight parts: 0.01-1 parts of charge-transfer complex-based photoinitiator; 1-10 parts epoxy resin; 0.01 - 1 part silane coupling agent; 0.01 - 1 part photosensitizer; The charge-transfer complex-based photoinitiator is R1 as described in claim 1 or 2. + R1 is a charge-transfer complex-based photoinitiator of iodine ions or prepared by the method described in claim 3 or 4. + It is a charge-transfer complex-based photoinitiator for iodonium ions.

6. An adhesive composition, comprising, by weight parts: 0.01-1 parts of charge-transfer complex-based photoinitiator; 1-10 parts epoxy resin; 0.01 - 1 part silane coupling agent; The charge-transfer complex-based photoinitiator is R1 as described in claim 1 or 2. + The photoinitiator is a charge-transfer complex based on thionium, ferrocene, quaternary ammonium, diazo, phosphonium, bromium, and chloride ions, or R1 prepared by the method described in claim 3 or 4. + It is a charge-transfer complex-based photoinitiator for thionium, ferromagnesite, quaternary ammonium, diazo, phosphonium, bromium, and chloride ions.

7. The adhesive composition of claim 5 or 6, wherein, The epoxy resin is selected from one or more of the following groups: bisphenol A type glycidyl ether epoxy resin, bisphenol F type glycidyl ether epoxy resin, mixture of bisphenol A type and bisphenol F type glycidyl ether epoxy resin, rubber toughening type glycidyl ether epoxy resin, aliphatic epoxy resin and / or alicyclic epoxy resin. The silane coupling agent is selected from one or more of the group consisting of 3-glycidoxypropyltrimethoxysilane, γ-(2,3-glycidoxy)propyltrimethoxysilane, (3-glycidoxypropylpropoxy)trimethoxysilane, (3-glycidoxypropylpropoxy)triethoxysilane and / or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and / or The photosensitizer is selected from one or more of the group consisting of 2-isopropylthioxanthone, camphorquinone, anthraquinone and its derivatives, methylene blue and / or porphyrin and its derivatives.

8. An application of the adhesive composition of claim 6 or 7 for bonding substrates.

9. The application of claim 8, wherein the substrate is a low ultraviolet light transmittance substrate.

10. The application as described in claim 8 or 9, comprising: (1) The adhesive composition is irradiated with ultraviolet light and initiated, and the adhesive composition enters a delayed curing window; (2) During the window period, the adhesive composition is bonded to the substrate; Preferably, the adhesive composition has an application thickness of 0.2-1 mm, the ultraviolet light wavelength is 200-500 nm, and the curing energy is 200-100000 mJ / cm². 2 .

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