Formylformic acid-based coumarin compound, preparation method therefor, use thereof, and photoinitiator composition and photocurable composition comprising same

Abstract

The present invention relates to a 3-formylformic acid-based coumarin compound of (I), a preparation method therefor, a use thereof, a photoinitiator composition and photocurable composition comprising same, a cured material obtained from the photocurable composition, and a method for preparing a photocurable material. The compound of the present invention can be used not only as an oil-soluble photoinitiator but also as an aqueous photoinitiator, has obvious advantages in photosensitivity, and is suitable for being used as a photoinitiator for UV-VIS LED light source curing, and the compound can not only initiate free radical polymerization but also sensitize an onium salt compound such as an iodonium salt or a sulfonium salt to initiate cationic polymerization of an epoxy monomer, an oxetane monomer, etc.

Description

Formylformate coumarin compound, preparation method and use thereof, and photoinitiator composition and photocurable composition containing same Technical Field

[0001] The present invention belongs to the field of photocuring technology and relates to a 3-formylformic acid coumarin compound. This compound can be used as both a water-based and oil-soluble photoinitiator and is particularly suitable for UV-VIS LED light source curing. The present invention also relates to the preparation and use of the 3-formylformic acid coumarin compound, a photoinitiator composition and a photocurable composition containing the 3-formylformic acid coumarin compound, a curable material obtainable from the photocurable composition, and a method for preparing the photocurable material. Background Art

[0002] Photoinitiators, also known as photosensitizers or photocuring agents, are compounds that absorb energy of a certain wavelength in the ultraviolet (250-400nm) or visible (400-600nm) region, generating free radicals and cations, thereby initiating polymerization and crosslinking of monomers. As a crucial component of photocuring systems, although present in low concentrations, photoinitiators are crucial and determine the curing rate. They must also meet the requirements of different curing conditions and applications. They determine whether the formulation can rapidly crosslink and cure upon exposure to light, transforming from a liquid to a solid state. With the widespread application of photocuring technology in traditional fields such as coatings, inks, microelectronics, and printing, as well as in emerging fields such as the preparation of laser recording and three-dimensional components, and with the continued development of UV-VIS LED curing technology, the development of photoinitiators suitable for UV-VIS LED light sources is needed to meet the widespread application needs of UV-VIS LED curing technology.

[0003] Traditional photocuring systems usually require the use of reactive diluents (monomers) to reduce the viscosity of the resin, and some monomers are easy to volatilize, producing toxicity and odor, which will cause certain pollution to the environment. Water is non-toxic and low-cost. Based on environmental protection requirements, research on water-based photocuring systems has attracted much attention. Water-based photocuring systems are relatively less irritating and have less odor, and their viscosity is easy to adjust. Currently, most photoinitiators on the market are oil-soluble, and oil-soluble photoinitiators have poor compatibility with water-soluble resins, which inevitably affects the final performance of the cured product. Water-based photoinitiators are low-pollution and environmentally friendly. Therefore, research on water-based photoinitiators has good application prospects.

[0004] Furthermore, cationic photocuring reactions initiated by cationic photoinitiators offer advantages such as resistance to oxygen inhibition, low shrinkage, excellent adhesion and chemical resistance, and a relatively thorough curing reaction. Consequently, cationic photocuring technology is widely used in electronics, metal decoration, adhesives, inks, and other fields. Onium salts, particularly sulfonium and iodonium salts, serve as important photoacid generators and are widely used in cationic photocuring. However, the short UV absorption slope of these substances limits their application under long-wavelength UV-visible LED light sources. Photosensitizers are often used to expand their application range, but photoinitiators capable of sensitizing sulfonium salts are relatively rare. Currently reported are mostly anthraquinones, which have polyphenyl ring structures and exhibit certain reproductive toxicity. The development of suitable photoinitiators is urgently needed. Summary of the Invention

[0005] One object of the present invention is to provide a 3-formylformic acid coumarin compound of formula (I), which can be used as a photoinitiator, such as a cleavage-type photoinitiator or a hydrogen abstraction-type photoinitiator, to initiate free radical photopolymerization reactions. It can also be used as a photoinitiator sensitizing onium salt photoinitiator to initiate cationic photopolymerization reactions. The absorption wavelength of the compound of the present invention is not only suitable for UV-VIS LED light source radiation curing, but also has excellent hydrophilicity and lipophilicity, and can be used as both a water-based photoinitiator and an oil-soluble photoinitiator.

[0006] Another object of the present invention is to provide a method for preparing the 3-formylformic acid coumarin compound of formula (I) of the present invention.

[0007] Another object of the present invention is to provide the use of the 3-formylformic acid coumarin compound of formula (I) of the present invention as a photoinitiator.

[0008] Another object of the present invention is to provide a photoinitiator composition comprising the 3-formylformic acid coumarin compound of formula (I) of the present invention.

[0009] Another object of the present invention is to provide a photocurable composition comprising the 3-formylformic acid coumarin compound of formula (I) of the present invention or the photoinitiator composition of the present invention.

[0010] Another object of the present invention is to provide a cured material obtainable from the photocurable composition of the present invention.

[0011] Another object of the present invention is to provide a method for preparing a photocurable material.

[0012] The technical solutions for achieving the above-mentioned purpose of the present invention can be summarized as follows:

[0013] 1. 3-Formylformic acid coumarin compound of formula (I):

[0014] in:

[0015] R1 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0016] R2 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0017] R3 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0018] R4 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group; and

[0019] R5 is H, a linear or branched C1-C 16Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0020] or

[0021] R1 and R2, R2 and R3, or R3 and R4 together with the carbon atoms to which they are bound form a 3-, 4-, 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members;

[0022] or

[0023] R1, R2 and R3, or R2, R3 and R4 together with the carbon atoms to which they are bound form a 6-, 7-, 8-, 9- or 10-membered partially unsaturated or aromatic bicarbocyclic or biheterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicarbocyclic or biheterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the biheterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

[0024] 2. A 3-formylformic acid coumarin compound of formula (I) according to item 1, wherein:

[0025] R1 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0026] R2 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0027] R3 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group; and

[0028] R4 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0029] R5 is H or a linear or branched C1-C 16 alkyl;

[0030] or

[0031] R1 and R2, R2 and R3, or R3 and R4 together with the carbon atoms to which they are bound form a 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members;

[0032] or

[0033] R1, R2 and R3, or R2, R3 and R4 together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated or aromatic bicarbocyclic or biheterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicarbocyclic or biheterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the biheterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

[0034] 3. A 3-formylformic acid coumarin compound of formula (I) according to item 1 or 2, wherein:

[0035] R1 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0036] R2 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0037] R3 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0038] R4 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group; and

[0039] R5 is H or a linear or branched C1-C 16 alkyl;

[0040] or

[0041] R1 and R2, R2 and R3, or R3 and R4 together with the carbon atoms to which they are bound form a 5-, 6- or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members;

[0042] or

[0043] R1, R2 and R3, or R2, R3 and R4 (preferably R1, R2 and R3) together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

[0044] 4. A 3-formylformic acid coumarin compound according to any one of formula (I) of items 1 to 3, wherein:

[0045] R1 is H, a straight or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl, or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0046] R2 is H, a straight or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl, mono- or di-C1-C4 alkylamino or C1-C 12 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0047] R3 is H, a straight or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0048] R4 is H, a straight or branched C1-C12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group; and

[0049] R5 is H or a linear or branched C1-C 12 alkyl;

[0050] or

[0051] R1 and R2, R2 and R3, or R3 and R4 together with the carbon atoms to which they are bound form a 5-, 6- or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members;

[0052] or

[0053] R1, R2 and R3, or R2, R3 and R4 together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

[0054] 5. A 3-formylformic acid coumarin compound of formula (I) according to any one of items 1 to 4, wherein:

[0055] R1 is H or a linear or branched C1-C 12 alkyl;

[0056] R2 is H, a straight or branched C1-C 12 Alkyl, di-C1-C4 alkylamino or C1-C 16 Alkoxy(thio) group;

[0057] R3 is H, a straight or branched C1-C 12 Alkyl or C1-C 16 Alkoxy(thio) group;

[0058] R4 is H, a straight or branched C1-C 12 Alkyl or C1-C 16 alkoxy(thio) groups; and

[0059] R5 is H;

[0060] or

[0061] R1, R2 and R3, or R2, R3 and R4 together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated bicyclic heterocycle fused to the benzene ring in the coumarin structure, wherein the bicyclic heterocycle is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C4 alkyl, the bicyclic heterocycle contains one N heteroatom as a ring member, preferably the N heteroatom is a shared atom of the bicyclic heterocycle; more preferably, the bicyclic heterocycle has the structure of formula (a):

[0062] in

[0063] * indicates the position of fusion with the benzene ring in the coumarin structure; and

[0064] The structure represented by formula (a) is unsubstituted or contains one or more C1-C4 alkyl groups as substituents.

[0065] 6. A 3-formylformic acid coumarin compound of formula (I) according to any one of items 1 to 5, wherein at least one of R1, R2, R3 and R4 is not H and R5 is H, or preferably 2 or 3 of R1, R2, R3 and R4 are H and R5 is H.

[0066] 7. The 3-formylformic acid coumarin compound of formula (I) according to any one of items 1 to 5, wherein the 3-formylformic acid coumarin compound of formula (I) is selected from the group consisting of:

[0067] 8. A method for preparing a 3-formylformic acid coumarin compound of formula (I) as described in any one of items 1 to 7, comprising the following steps:

[0068] (1) Knoevenagel condensation reaction: The compound of formula (II) is subjected to a Knoevenagel condensation reaction with a C1-C6 alkyl acetoacetate to obtain a compound of formula (III):

[0069] (2) Oxidation reaction: The compound of formula (III) is oxidized with an oxidant to obtain a compound of formula (I)

[0070] wherein R1, R2, R3, R4 and R5 in the above formulae are as defined in any one of items 1 to 7.

[0071] 9. The method according to item 8, wherein:

[0072] The Knoevenagel condensation reaction of step (1) is carried out in the presence of one or more catalysts selected from the group consisting of: amines such as primary amines, secondary amines, tertiary amines and their corresponding ammonium salts, preferably piperidine; inorganic bases such as alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, and alkali metal or alkaline earth metal bicarbonates; inorganic salts such as potassium fluoride, aluminum phosphate, diammonium hydrogen phosphate; combinations of Lewis acids and tertiary amines such as TiCl4 / piperidine or TiCl4 / triethylamine.

[0073] 10. The method according to item 8 or 9, wherein in the Knoevenagel condensation reaction of step (1), the molar ratio of the compound of formula (II) to the C1-C6 alkyl acetoacetate is 1:0.1-1:10, preferably 1:0.3-1:5, more preferably 1:0.9-1:3.

[0074] 11. The method according to any one of items 8 to 10, wherein in the oxidation reaction of step (2), the molar ratio of the compound of formula (III) to the oxidizing agent is 1:1-1:5, preferably 1:1-1:3.

[0075] 12. The method according to any one of items 8 to 11, wherein the oxidizing agent in step (2) is selected from selenium dioxide and acidic peroxides, such as acidic hydrogen peroxide and acidic alkali metal peroxides.

[0076] 13. Use of the 3-formylformic acid coumarin compound of formula (I) as described in any one of items 1 to 7 as a photoinitiator.

[0077] 14. The use according to item 13, wherein the 3-formylformic acid coumarin compound of formula (I) is used as a cleavage-type photoinitiator in a UV-VIS LED light source curing system, particularly as a cleavage-type photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0078] 15. The use according to item 13, wherein the 3-formylformic acid coumarin compound of formula (I) is used as a hydrogen abstraction photoinitiator in a UV-VIS LED light source curing system, particularly as a hydrogen abstraction photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0079] 16. The use according to item 15, wherein the 3-formylformic acid coumarin compound of formula (I) is used together with a compound selected from a tertiary amine compound, an α-amino acid compound or a thiol compound.

[0080] 17. Use of the 3-formylformic acid coumarin compound of formula (I) as described in any one of items 1 to 7 as a photoinitiator sensitized onium salt, especially use as a photoinitiator sensitized onium salt in a UV-VIS LED light source curing system, especially use as a photoinitiator sensitized onium salt in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0081] 18. The use according to item 17, wherein the onium salt is selected from iodonium salts and sulfonium salts, preferably selected from diaryliodonium salts and triarylsulfonium salts.

[0082] 19. The use according to item 17 or 18, wherein an onium salt sensitized with a 3-formylformic acid coumarin compound of formula (I) is used to initiate free radical photopolymerization, or to initiate cationic photopolymerization, or to initiate free radical-cationic hybrid photopolymerization.

[0083] 20. A photoinitiator composition comprising the 3-formylformic acid coumarin compound of formula (I) according to any one of items 1 to 7.

[0084] 21. The photoinitiator composition according to item 20, wherein the composition comprises the 3-formylformic acid coumarin compound of formula (I) and a compound selected from a tertiary amine compound, an α-amino acid compound or a thiol compound.

[0085] 22. The photoinitiator composition according to item 20, wherein the photoinitiator composition comprises the 3-formylformic acid coumarin compound of formula (I) and an onium salt, preferably the onium salt is selected from iodonium salts and sulfonium salts, more preferably selected from diaryliodonium salts and triarylsulfonium salts.

[0086] 23. A photocurable composition comprising at least one 3-formylformic acid coumarin compound of formula (I) as described in any one of items 1 to 7 or a photoinitiator composition as described in any one of items 20 to 22.

[0087] 24. A cured material obtainable from the photocurable composition according to item 23.

[0088] 25. A method for preparing a photocurable material, comprising irradiating the photocurable composition of item 23 with a light source having a radiation wavelength of 300-550 nm, especially 365-475 nm, such as a UV-VIS LED light source.

[0089] The 3-formylformic acid coumarin compound of formula (I) of the present invention not only comprises the coumarin-based structural portion, but also comprises the 3-formylformic acid structural portion. This compound has good photosensitivity absorption within the range of 300-550nm, especially within the range of 365-475nm. After absorbing light energy, it can rapidly undergo cracking to generate active free radicals, continuously initiate polymerization, and rapidly (as in a few seconds) initiate polymerizable monomers to polymerize, and in a short time (as in 10 minutes, particularly 3 minutes), polyreaction is completed. The 3-formylformic acid coumarin compound of formula (I) of the present invention also has excellent sensitization properties. After absorbing light energy, it can transfer energy to other co-initiators such as hydrogen donors, onium salt compounds, etc., to initiate free radical polymerization or cationic polymerization. The 3-formylformic acid coumarin compound of formula (I) of the present invention can be used as both an oil-soluble and water-based photoinitiator, and can initiate deep curing of monomers (such as oil-soluble acrylate monomers or water-based acrylate monomers) at relatively low concentrations (e.g., 0.01% by mass). Therefore, it has significant advantages in photosensitivity and is suitable for use as a photoinitiator for UV-VIS LED light source curing. The compound of formula (I) of the present invention is safe and non-toxic, and compared to traditional photoinitiators, it poses less harm to humans and the environment, and can also be used in areas such as food packaging. Description of the drawings:

[0090] FIG1 is a UV-visible absorption spectrum of the 3-formylformic acid coumarin compound of Example 1-3 in acetonitrile;

[0091] FIG2 is a graph showing the relationship between monomer conversion and exposure time when the 3-formylformic acid coumarin compound of the present invention is used as a photoinitiator to initiate free radical photopolymerization of acrylate monomers; wherein (a) the compound of Example 3 is used as a photoinitiator (1% w / w) to initiate TPGDA polymerization under different light sources; (b) the compounds of Examples 1-3 are used as photoinitiators / EDB (1% / 1.16% w / w) at 415 nm and 50 mW / cm 2 (c) the compound of Example 1-3 as a photoinitiator / GR54 (2% / 4% w / w) at 415nm, 100mW / cm 2 PEG(400)DA polymerization was initiated under LED light source;

[0092] FIG3 is a graph showing the relationship between the monomer conversion rate and exposure time for the ring-opening polymerization of epoxy monomer 6110 initiated by iodonium salt and sulfonium salt sensitized by the 3-formylformic acid coumarin compound of the present invention; wherein (a) the compound of Example 1 or 3 / iodonium salt GR54 (0.2% / 4% w / w) or iodonium salt GR54 alone; (b) the compound of Examples 1-3 / sulfonium salt GR-SS061 (0.2% / 4% w / w) or sulfonium salt GR-SS061 alone; wherein the light source is a 415 nm LED, and the light intensity is 100 mW / cm 2 LED;

[0093] Figure 4 is a photograph of deep curing induced by 3-formylformic acid coumarin compounds in Examples 1 and 2; wherein (a) the length of deep curing of TPGDA induced by 0.01% of the compound in Example 1; (b) the length of deep curing of TPGDA induced by 0.01% of the compound in Example 2; (c) the length of deep curing of PEG (400) DA induced by 0.01% of the compound in Example 1; (d) the length of deep curing of PEG (400) DA induced by 0.01% of the compound in Example 2; wherein the light source is 415 nm, 100 mW / cm 2 . DETAILED DESCRIPTION

[0094] 3-Formylformic acid coumarin compound of formula (I):

[0095] in:

[0096] R1 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0097] R2 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0098] R3 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0099] R4 is H, a straight or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group; and

[0100] R5 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, C6-C 10 Aryl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy (thio) group;

[0101] or

[0102] R1 and R2, R2 and R3, or R3 and R4 together with the carbon atoms to which they are bound form a 3-, 4-, 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members;

[0103] or

[0104] R1, R2 and R3, or R2, R3 and R4 together with the carbon atoms to which they are bound form a 6-, 7-, 8-, 9- or 10-membered partially unsaturated or aromatic bicarbocyclic or biheterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicarbocyclic or biheterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the biheterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

[0105] In the present invention, the prefix "C n -C m " in each case means that the number of carbon atoms contained in the group is nm.

[0106] "Halogen" refers to fluorine, chlorine, bromine and iodine. In the present invention, preferably halogen is fluorine, chlorine, bromine or a combination thereof.

[0107] The term "C n -C m "Alkyl" refers to a straight-chain or branched saturated hydrocarbon group having nm, such as 1-16, 1-12, 1-8, 1-4 or 2, 4, 6, 8, 10, 12 or 14 carbon atoms, for example methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, n-hexyl, 1-methylpentyl , 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-dodecyl and n-hexadecyl and their isomers, etc.

[0108] The term "C6-C m The term "aryl" refers to a monocyclic or bicyclic aromatic hydrocarbon group containing 6 to m carbon atoms, such as 6 to 10 carbon atoms, for example, phenyl, tolyl, ethylphenyl, propylphenyl, butylphenyl, xylyl, methylethylphenyl, diethylphenyl, methylpropylphenyl, naphthyl and isomers thereof.

[0109] The term "C3-C m"Cycloalkyl" refers to a saturated alicyclic monocyclic group having 3-m, such as 3-10, 3-8, 3-7, 4-8, 4-7, 5-8, 5-7 or 4, 5, 6, 7, 8 or 9 ring carbon atoms, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl and isomers thereof.

[0110] The term "C3-C m Cycloalkyl-C n -C m "Alkyl" means C3-C m Cycloalkyl substituted C n -C m Alkyl, in which case the two m's may be the same or different, wherein C n -C m Alkyl and C3-C m The definition of cycloalkyl herein applies. m Cycloalkyl-C n -C m The alkyl group can be a C3-C6 cycloalkyl-C1-C4 alkyl group, for example, cyclopropylmethyl, cyclopropylethyl, cyclopropylpropyl, cyclopropylbutyl, cyclobutylmethyl, cyclobutylethyl, cyclobutylpropyl, cyclobutylbutyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylpropyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylpropyl, cyclohexylbutyl and isomers thereof, etc.

[0111] The term "C n -C m "Alkoxy (thio) group" includes "C n -C m Alkoxy" and "C n -C m "Alkylthio" refers to a C n -C m Alkyl corresponding open chain C n -C m Any carbon atom of an alkane is bonded with an oxygen atom or a sulfur atom as a linking group. n -C m Alkyl. C n -C m C in alkoxy (thio) group n -C m The definition herein applies to alkyl. Examples of C1-C6 alkoxy(thio) groups include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, 2-butoxy, tert-butoxy, pentyloxy, isopentyloxy, hexyloxy, and isomers thereof. C1-C8 alkylthio groups may include methylthio, ethylthio, propylthio, isopropylthio, n-butylthio, 2-butylthio, tert-butylthio, pentylthio, isopentylthio, hexylthio, and isomers thereof.

[0112] The term "mono- or di-C n -C m "Alkylamino" refers to a group consisting of one or two C n -C m An amino group substituted by an alkyl group, wherein C n -C m Alkyl is as defined herein.

[0113] In one embodiment, R1 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group. Of course, each group in the definition of R1 may contain no substituents.

[0114] In one embodiment, R1 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0115] In one embodiment, R1 is H, a linear or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0116] In one embodiment, R1 is H or a linear or branched C1-C 12 alkyl.

[0117] In one embodiment, R2 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16Alkoxy (thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy (thio) group. Of course, each group in the definition of R2 may contain no substituents.

[0118] In one embodiment, R2 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0119] In one embodiment, R2 is H, a linear or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl, mono- or di-C1-C4 alkylamino or C1-C 12 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0120] In one embodiment, R2 is H, a linear or branched C1-C 12 Alkyl, mono- or di-C1-C4 alkylamino or C1-C 16 In one embodiment, R2 is H, a linear or branched C1-C 12 Alkyl, di-C1-C4 alkylamino or C1-C 16 Alkoxy(thio) group.

[0121] In one embodiment, R3 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups. Of course, each group in the definition of R3 may contain no substituents.

[0122] In one embodiment, R3 is H, a linear or branched C1-C 16 Alkyl, C3-C10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0123] In one embodiment, R3 is H, a linear or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0124] In one embodiment, R3 is H, a linear or branched C1-C 12 Alkyl or C1-C 16 Alkoxy(thio) group.

[0125] In one embodiment, R4 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups. Of course, each group in the definition of R4 may contain no substituents.

[0126] In one embodiment, R4 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C1-C 16 Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0127] In one embodiment, R4 is H, a linear or branched C1-C 12 Alkyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl-C1-C 12 Alkyl or C1-C 16Alkoxy(thio) group; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group.

[0128] In one embodiment, R4 is H, a linear or branched C1-C 12 Alkyl or C1-C 16 Alkoxy(thio) group.

[0129] In one embodiment, R5 is H, a linear or branched C1-C 16 Alkyl, C3-C 10 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 16 Alkyl or C6-C 10 Aryl; wherein each of the aforementioned groups except H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) groups. Of course, each group in the definition of R5 may contain no substituents.

[0130] In one embodiment, R5 is H or a linear or branched C1-C 16 In one embodiment, R5 is H or a linear or branched C1-C 12 In one embodiment, R5 is H.

[0131] In one embodiment, R1 and R2, R2 and R3, or R3 and R4, together with the carbon atoms to which they are bound, form a 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members.

[0132] In one embodiment, R1 and R2, R2 and R3, or R3 and R4, together with the carbon atoms to which they are bound, form a 5-, 6- or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members.

[0133] In one embodiment, R1 and R2, R2 and R3, or R3 and R4, together with the carbon atoms to which they are bound, form a 5-, 6-, or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio)yl, the heterocyclic ring containing 1 N heteroatom as a ring member.

[0134] According to the present invention, the partially unsaturated carbocyclic or heterocyclic ring mentioned in the definition of "R1 and R2, R2 and R3, or R3 and R4" no longer contains unsaturated carbon atoms as ring members except for the partial benzene ring structure fused thereto.

[0135] In one embodiment, R1, R2 and R3, or R2, R3 and R4 (preferably R1, R2 and R3) together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated or aromatic bicarbocyclic or biheterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicarbocyclic or biheterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the biheterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members.

[0136] In one embodiment, R1, R2 and R3, or R2, R3 and R4 (preferably R1, R2 and R3) together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, the bicyclic heterocyclic ring containing 1 or 2 heteroatoms selected from N, O and S as ring members.

[0137] In one embodiment, R1, R2 and R3, or R2, R3 and R4 (preferably R1, R2 and R3) together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered partially unsaturated bicyclic heterocycle fused to the benzene ring in the coumarin structure, wherein the bicyclic heterocycle is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C4 alkyl, the bicyclic heterocycle contains 1 N heteroatom as a ring member, preferably the N heteroatom is a shared atom of the bicyclic heterocycle; more preferably the bicyclic heterocycle has the structure of formula (a):

[0138] in

[0139] * indicates the position of fusion with the benzene ring in the coumarin structure; and

[0140] The structure represented by formula (a) is unsubstituted or contains one or more (eg, 1-8, or 1-6, or 2-6) C1-C4 alkyl groups (eg, methyl or ethyl) as substituents.

[0141] According to the present invention, the partially unsaturated bicarbocyclic or biheterocyclic ring mentioned in the definition of "R1, R2 and R3, or R2, R3 and R4" no longer contains unsaturated carbon atoms as ring members except for the partial benzene ring structure fused thereto.

[0142] In one embodiment, at least one of R1, R2, R3 and R4 is not H, and R5 is H.

[0143] In one embodiment, 1, 2 or 3 of R1-R4 are H, preferably 2 are H, or 3 are H, and R5 is H.

[0144] In one embodiment, R1 is H or a linear or branched C1-C 12 Alkyl, preferably H or a linear or branched C1-C6 alkyl;

[0145] R2 is H, a straight or branched C1-C 12 Alkyl, di-C1-C4 alkylamino or C1-C 16 Alkoxy (sulfur) group; preferably H, linear or branched C1-C6 alkyl, di-C1-C4 alkylamino or C1-C 14 Alkoxy(thio) group;

[0146] R3 is H, a straight or branched C1-C 12 Alkyl or C1-C 16 Alkoxy (sulfur) group, preferably H, linear or branched C1-C6 alkyl or C1-C 14 Alkoxy(thio) group;

[0147] R4 is H, a straight or branched C1-C 12 Alkyl or C1-C 16 Alkoxy (sulfur) group, preferably H, linear or branched C1-C6 alkyl or C1-C 14 alkoxy(thio) groups; and

[0148] R5 is H;

[0149] or

[0150] R1, R2 and R3 together with the carbon atoms to which they are bound form an 8-, 9- or 10-membered (preferably 8- or 10-membered) partially unsaturated bicyclic heterocycle fused to the benzene ring in the coumarin structure, wherein the bicyclic heterocycle is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C4 alkyl, the bicyclic heterocycle contains one N heteroatom as a ring member, preferably the N heteroatom is a shared atom of the bicyclic heterocycle; more preferably, the bicyclic heterocycle has the structure of formula (a):

[0151] in

[0152] * indicates the position of fusion with the benzene ring in the coumarin structure; and

[0153] The structure represented by formula (a) is unsubstituted or contains one or more C1-C4 alkyl groups as substituents; preferably, at least one of R1, R2, R3 and R4 is not H, for example, 1, 2 or 3 of R1-R4 are H, preferably 2 are H, or 3 are H.

[0154] In one embodiment, the heterocyclic or bicyclic heterocyclic rings of the present invention do not contain hydrogen atoms on the nitrogen atoms, if present.

[0155] In one embodiment, the 3-formylformate coumarin compound of formula (I) has the structure shown in formula (I-1):

[0156] wherein R4 and R5 are as defined above;

[0157] Rx and Ry are independently selected from C1-C6 alkyl and C1-C6 alkoxy(thio) groups, preferably C1-C6 alkyl, more preferably C1-C4 alkyl; and

[0158] a and b are independently 0-6, preferably 0, 1, 2, 3 or 4.

[0159] In the structure represented by formula (I-1), R1, R2 and R3 form a bicyclic heterocycle of formula (a).

[0160] In one embodiment, the 3-formylformic acid coumarin compound of formula (I) is selected from the following group:

[0161] Method for preparing 3-formylformic acid coumarin compound of formula (I)

[0162] One aspect of the present invention provides a method for preparing a 3-formylformic acid coumarin compound of formula (I) of the present invention, comprising the following steps:

[0163] (1) Knoevenagel condensation reaction: The compound of formula (II) is subjected to Knoevenagel condensation reaction with a C1-C6 alkyl acetoacetate to obtain a compound of formula (III):

[0164] (2) Oxidation reaction: The compound of formula (III) is oxidized with an oxidant to obtain a compound of formula (I)

[0165] wherein R1, R2, R3, R4 and R5 in the above formulae are as defined above.

[0166] According to the present invention, starting from the compound of formula (II), a Knoevenagel condensation reaction can be performed to obtain a 3-acetylcoumarin compound of formula (III), which is then subjected to an oxidation reaction to prepare a 3-formylformic acid coumarin compound of formula (I).

[0167] Step (1) Knoevenagel condensation reaction

[0168] The compound of formula (II) is subjected to Knoevenagel condensation reaction with C1-C6 alkyl acetoacetate to obtain a compound of formula (III):

[0169] wherein R1, R2, R3, R4 and R5 are as defined above.

[0170] According to the present invention, the compound of formula (II), as a benzene ring structure containing adjacent -C(=O)R5 and hydroxyl groups, can be synthesized into a coumarin ring via a Knoevenagel condensation reaction. Specifically, in this reaction, -C(=O)R5 preferably condenses with a C1-C6 alkyl acetoacetate in the presence of a catalyst, undergoing dehydration to form a carbon-carbon double bond. The hydroxyl group then undergoes an exchange reaction with the ester bond of the C1-C6 alkyl acetoacetate, removing the corresponding alcohol to form a new ester bond, thereby forming a coumarin ring and obtaining the compound of formula (III).

[0171] To accelerate the Knoevenagel condensation reaction, the above reaction is typically carried out in the presence of a catalyst suitable for the Knoevenagel condensation reaction. Catalysts typically used include amines such as primary, secondary, and tertiary amines and their corresponding ammonium salts, preferably piperidine; inorganic bases such as alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, and alkali metal or alkaline earth metal bicarbonates; inorganic salts such as potassium fluoride, aluminum phosphate, and diammonium hydrogen phosphate; and combinations of Lewis acids and tertiary amines such as TiCl₄ / piperidine or TiCl₄ / triethylamine. The amount of catalyst used, based on the compound of formula (II), can range from 1 to 20% by weight, or from 2 to 15% by weight, or from 3 to 15% by weight.

[0172] The Knoevenagel condensation reaction is typically carried out in a solvent, preferably an organic solvent, preferably a protic solvent. There are no particular restrictions on the type of solvent, as long as it can dissolve the compound of formula (II) and the C1-C6 alkyl acetoacetate and is chemically inert to the Knoevenagel condensation reaction, i.e., does not participate in the Knoevenagel condensation reaction. Examples of solvents include alcohols (such as ethanol), ethers (such as diethyl ether), ketones (such as acetone), aromatic hydrocarbons (such as toluene), dimethyl sulfoxide, or N,N-dimethylformamide. Alcohols such as ethanol are preferred.

[0173] An example of the C1-C6 alkyl acetoacetate is ethyl acetoacetate.

[0174] The molar ratio of the compound of formula (II) to the C1-C6 alkyl acetoacetate is 1:0.1-1:10 (such as 1:0.2, 1:0.3, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:3, 1:4, 1:5 or 1:8), preferably 1:0.3-1:5, more preferably 1:0.9-1:3 or 1:1.1-1:3.

[0175] The temperature range of the Knoevenagel condensation reaction is usually 40-120° C., preferably 60-90° C. The reaction time is not particularly limited, and is usually 2-20 hours or 3-15 hours, preferably 3-10 hours or 3-6 hours.

[0176] After the Knoevenagel condensation reaction is completed, a crude product of compound of formula (III) is obtained. If you want to further improve the purity of compound of formula (III), this compound can also be further purified, and this can be carried out by means of recrystallization, for example. The selection of the recrystallization solvent is conventional and has no particular restrictions. According to the present invention, it is advantageous to adopt alcohol (such as ethanol) to recrystallize the crude product of compound of formula (III).

[0177] Step (2) oxidation reaction

[0178] The compound of formula (III) is oxidized with an oxidant to obtain a compound of formula (I)

[0179] wherein R1, R2, R3, R4 and R5 are as defined above.

[0180] The oxidizing agent may be selected from selenium dioxide and acidic peroxides, such as acidic hydrogen peroxide and acidic alkali metal peroxides.

[0181] The oxidation reaction is usually carried out in an organic solvent, preferably a polar organic solvent. Examples of the solvents that can be used include pyridine, piperidine, triethylamine, and the like.

[0182] The molar ratio of the compound of formula (III) to the oxidant can be 1:1-1:5 (such as 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.5, 1:3 or 1:4), preferably 1:1.5-1:3.

[0183] The temperature range of the oxidation reaction is usually 30-200° C., preferably 40-150° C. (e.g., 50° C., 60° C., 80° C., 100° C., 150° C. or 180° C.) The oxidation reaction time can be 0.1-10 hours, preferably 0.3-5 hours.

[0184] According to the present invention, the reaction process can be monitored during the oxidation reaction. In one embodiment, when impurities are generated during the oxidation reaction, the reaction is stopped. The monitoring can be performed by a spot plate. After the reaction is completed, the reactants can be treated with hydrochloric acid.

[0185] The 3-formylformic acid coumarin compound of formula (I) of the present invention has strong absorption in the wavelength range of 300-550 nm, particularly in the wavelength range of 365-475 nm. Therefore, it can be used as a photoinitiator in UV-VIS LED light source curing systems, especially for long-wavelength UV-VIS LED light source curing. Furthermore, the compound of formula (I) of the present invention is safe and non-toxic, and compared with traditional photoinitiators, it poses less harm to humans and the environment. It can also be used in fields such as food packaging.

[0186] Use of the compounds of the present invention as photoinitiators

[0187] One aspect of the present invention provides use of the 3-formylformic acid coumarin compound of formula (I) of the present invention as a photoinitiator, such as a cleavage-type photoinitiator or a hydrogen abstraction-type photoinitiator.

[0188] The 3-formylformic acid coumarin compound of formula (I) of the present invention can be used as a photoinitiator in a UV-VIS LED light source curing system, particularly as a photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0189] The 3-formylformic acid coumarin compound of formula (I) of the present invention can be used as a cleavage-type photoinitiator in a UV-VIS LED light source curing system, particularly as a cleavage-type photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0190] The 3-formylformic acid coumarin compound (I) of the present invention can also be used as a hydrogen abstraction type photoinitiator in a UV-VIS LED light source curing system, especially as a hydrogen abstraction type photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

[0191] According to the present invention, the 3-formylformic acid coumarin compound of formula (I) can be used together with a compound selected from a tertiary amine compound (such as ethyl 4-dimethylaminobenzoate, i.e., EDB), an α-amino acid compound, or a thiol compound. According to the present invention, these compounds act as hydrogen donors, and the 3-formylformic acid coumarin compound acts as a hydrogen abstraction photoinitiator together with the hydrogen donor, such as EDB, to initiate a free radical polymerization reaction.

[0192] One aspect of the present invention provides the use of a 3-formylformic acid coumarin compound of formula (I) as a photoinitiator-sensitizing onium salt, particularly in a UV-VIS LED light source curing system, and particularly in a light source curing system with a radiation wavelength of 300-550 nm, particularly 365-475 nm. In this aspect, the 3-formylformic acid coumarin compound of formula (I) may also be referred to as a photosensitizer.

[0193] The onium salt may be selected from iodonium salts and sulfonium salts.

[0194] The iodonium salt and sulfonium salt have the following general formulas (A) and (B) respectively:

[0195] in

[0196] R a 、R b 、R c 、R d 、R e Each independently is an unsubstituted C6-C 10 Aryl, or selected from halogen, nitro, carbonyl, C1-C 12 Alkyl, C1-C 12 C6-C substituted with alkoxy, phenylthio, phenyl and substituted phenyl 10 Aryl, preferably phenyl or naphthyl, or phenyl or naphthyl substituted by a substituent selected from halogen, nitro, C1-C6 alkyl and substituted phenyl, wherein the substituted phenyl comprises one or more substituents selected from halogen, nitro, C1-C6 alkyl and C1-C6 alkoxy; and

[0197] Y and Z are non-nucleophilic anions, such as trifluoromethanesulfonate, BF4 - 、ClO4 - PF6 - 、AsF6 - 、SbF6 - .

[0198] Preferably, the sulfonium salt is selected from one or more of the following groups: mixed sulfonium hexafluorophosphate (GR-SS058), 4-(phenylthio)phenyl diphenylsulfonium hexafluorophosphate, 4-(phenylthio)phenyl diphenylsulfonium hexafluoroantimonate (GRSS059), diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate (GRSS059B), and mixed sulfonium hexafluoroantimonate (GR-SS061).

[0199] Preferably, the iodonium salt is selected from one or more of the following groups: diphenyliodonium hexafluorophosphate (810), 4-isobutylphenyl-4'-tolyliodonium hexafluorophosphate (GR-IS051), bis(4-dodecylbenzene)iodonium hexafluoroantimonate (GR-IS052), bis(4-dodecylbenzene)iodonium hexafluorophosphate (GR-IS052B), (4-octyloxyphenyl)benzeneiodonium hexafluoroantimonate (GR-IS053), bis(4-tert-butylbenzene)iodonium hexafluorophosphate (GR-IS054), bis(4-tert-butylbenzene)iodonium hexafluoroantimonate (GR-IS225), 4,4'-dimethylphenyliodonium hexafluorophosphate, 4,4'-dimethylphenyliodonium hexafluoroantimonate.

[0200] In one embodiment, the iodonium salt is a diaryl iodonium salt, preferably a diphenyl iodonium salt. The sulfonium salt is a triaryl sulfonium salt, preferably a triphenyl sulfonium salt.

[0201] The onium salt sensitized by the 3-formylformic acid coumarin compound of formula (I) can be used to initiate free radical photopolymerization, or to initiate cationic photopolymerization, or to initiate free radical-cationic hybrid photopolymerization.

[0202] Photoinitiator composition

[0203] The present invention also relates to a photoinitiator composition comprising the 3-formylformic acid coumarin compound of formula (I) of the present invention.

[0204] In one embodiment, the composition comprises a 3-formylformic acid coumarin compound of the formula (I) and a compound selected from a tertiary amine compound, an α-amino acid compound or a thiol compound. As described above, these compounds serve as hydrogen donors. The weight ratio of the 3-formylformic acid coumarin compound of the formula (I) to the compound selected from a tertiary amine compound, an α-amino acid compound or a thiol compound can be 10:1-1:10 (e.g., 8:1, 5:1, 2:1, 1:1, 1:2, 1:5, 1:8), preferably 5:1-1:5, more preferably 2:1-1:2.

[0205] In one embodiment, the composition comprises the 3-formylformic acid coumarin compound of formula (I) and an onium salt. The onium salt may be selected from iodonium salts and sulfonium salts, in particular the iodonium salts and sulfonium salts described above.

[0206] The weight ratio of the 3-formylformic acid coumarin compound of formula (I) to the onium salt can be 10:1-1:100 (such as 8:1, 5:1, 2:1, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:80), preferably 5:1-1:80, more preferably 1:1-1:50 or 1:2-1:50.

[0207] The 3-formylformic acid coumarin compound of formula (I) of the present invention can be used as a photoinitiator in UV-VIS LED photocuring technology. The 3-formylformic acid coumarin compound of formula (I) of the present invention can also be used as a photoinitiator in the fields of coatings, inks, microelectronics, printing, etc. When the 3-formylformic acid coumarin compound of formula (I) of the present invention is used as a photoinitiator, the amount thereof is as described below for the photocurable composition.

[0208] Photocurable composition

[0209] The present invention furthermore relates to a photocurable composition comprising at least one 3-formylformic acid coumarin compound of the formula (I) according to the invention or a photoinitiator composition according to the invention.

[0210] In the photocurable composition, the amount of the 3-formylformic acid coumarin compound of formula (I) of the present invention or the photoinitiator composition of the present invention is generally 0.001 to 10 weight % (such as 0.005 weight %, 0.01 weight %, 0.05 weight %, 0.1 weight %, 0.2 weight %, 0.5 weight %, 1 weight %, 2 weight %, 5 weight % or 8 weight %), preferably 0.1 to 6 weight %, such as 0.2 to 5 weight %, based on the amount of active ingredients of the photocurable composition.

[0211] In the context of this disclosure, active ingredients refer to the ingredients in the photocurable composition other than the solvent.

[0212] In addition to the photoinitiator of the present invention, the photocurable composition further comprises a photopolymerizable component, such as a photocurable resin. The photocurable resin may be a free radical photocurable resin and / or a cationic photocurable resin.

[0213] In the present invention, the photocurable resin has photocurable reactive groups, such as unsaturated carbon-carbon double bonds and / or epoxy groups. For example, the photocurable resin can be an oligomer or prepolymer containing unsaturated carbon-carbon double bonds and / or epoxy groups. Upon exposure to light, the oligomer or prepolymer can undergo a polymerization reaction initiated by a photoinitiator, leading to crosslinking and curing. The photocurable resin is the main component of photocurable products (such as UV coatings, UV inks, and UV adhesives).

[0214] Examples of the photocurable resin containing unsaturated carbon-carbon double bonds (radical photocurable resin) include epoxy (meth)acrylate resins, polyester (meth)acrylates, polyether (meth)acrylates, polyurethane (meth)acrylates, ethylenically unsaturated polyesters, amino (meth)acrylate resins, photoimageable alkali-soluble resins, and the like. Advantageously, epoxy (meth)acrylate resins, polyester (meth)acrylates, polyether (meth)acrylates, polyurethane (meth)acrylates, or combinations thereof are employed according to the present invention.

[0215] [Corrected on 24.01.2025 according to Rule 26] The epoxy (meth)acrylate resin is preferably bisphenol A epoxy (meth)acrylate, bisphenol A epoxy acrylate diluted with tripropylene glycol di(meth)acrylate or a combination thereof, such as bisphenol A epoxy acrylate WSR-U125 from Wuxi Resin Factory, bisphenol A epoxy acrylate 621A-80 diluted with 20% tripropylene glycol diacrylate from Changxing Chemical Company of Taiwan, China, modified bisphenol A epoxy acrylate 623-100 from Changxing Chemical Company of Taiwan, China, and modified bisphenol A epoxy acrylate 6231A-80 diluted with 20% tripropylene glycol diacrylate from Changxing Chemical Company of Taiwan, China.

[0216] The polyester (meth)acrylate is preferably a high-functionality hyperbranched polyester acrylate resin, particularly a hyperbranched polyester acrylate resin having a functionality of 5-30, such as a hyperbranched polyester acrylate prepolymer having a functionality of 6-20. Examples of such prepolymers include hyperbranched polyester acrylate prepolymer 932-100 (6 functionality) from Wuxi Knox Co., Ltd., and hyperbranched polyester acrylate prepolymers CN2300 (8 functionality), CN2301 (9 functionality), and CN2302 (16 functionality) from Sartomer Co., Ltd., USA.

[0217] The polyether (meth)acrylate can be polyethylene oxide (meth)acrylate, polypropylene oxide (meth)acrylate, polyethylene oxide-propylene oxide (meth)acrylate, or a combination thereof. One example is PEG (400) diacrylate.

[0218] [Corrected 24.01.2025 in accordance with Rule 26] The polyurethane (meth)acrylate is preferably an aliphatic polyurethane acrylate resin. Examples of the polyurethane (meth)acrylate include aliphatic polyurethane hexaacrylates 6145-100 and 6161-100 from Chang Hsing Chemical Co., Ltd. in Taiwan, China; aliphatic polyurethane diacrylate 611B-85 diluted with 15% 1,6-hexanediol diacrylate (HDDA); polyester polyol acrylate resin diluted with 20% ethoxylated trimethylolpropane triacrylate; and aliphatic polyurethane diacrylate 6141H-80; aliphatic polyurethane acrylate CN9013 (9-functionality) from Sartomer Co., Ltd. in the United States; aliphatic polyurethane acrylate CN966B85 (2-functionality) diluted with 15% 1,6-hexanediol diacrylate (HDDA) from Sartomer Co., Ltd. in the United States; and aliphatic polyurethane acrylate CN962 (2-functionality) from Sartomer Co., Ltd. in the United States.

[0219] The amount of the photocurable resin used in the photocurable composition is generally 10-90 wt%, preferably 55-80 wt%, based on the amount of active ingredients in the photocurable composition. In the context of this disclosure, active ingredients refer to ingredients in the photocurable composition excluding the solvent.

[0220] The photocurable composition may further include a multifunctional reactive diluent.

[0221] In the present invention, a multifunctional reactive diluent refers to a monomer containing two or more photopolymerizable groups. Multifunctional reactive diluents have low viscosity and strong dissolving power. Upon irradiation with a light source, these diluents can be polymerized by reactive free radicals to form a crosslinked network.

[0222] According to the present invention, the preferred multifunctional reactive diluent is a multifunctional (meth)acrylate reactive diluent. This refers to a monomer containing two or more (meth)acrylate polymerizable groups. Examples of multifunctional (meth)acrylate reactive diluents include trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate (PETTA), propoxylated trimethylolpropane triacrylate (PO-TMPTA) or ethoxylated trimethylolpropane triacrylate (EO-TMPTA), pentaerythritol triacrylate (PETA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPEPA), dipentaerythritol hexaacrylate (DPHA), glycol diacrylates such as tripropylene glycol diacrylate (TPGDA), 1,6-hexanediol diacrylate (HDDA), triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, glycerol diacrylate, and urethane dimethacrylate (UDMA).

[0223] The amount of the multifunctional reactive diluent used in the photocurable composition is generally 8 to 60% by weight, preferably 15 to 45% by weight, based on the amount of the active ingredients in the photocurable composition.

[0224] According to the present invention, the photocurable composition may further comprise a monofunctional reactive diluent.

[0225] In the present invention, as a monofunctional reactive diluent, it refers to a monomer containing a photopolymerizable group. It has a low viscosity and a strong dissolving power, and can act as a partial organic solvent. After being irradiated by a light source, the monofunctional reactive diluent can be initiated to undergo polymerization by active free radicals. Monofunctional reactive diluents mainly include (meth)acrylate compounds and vinyl compounds. As (meth)acrylate monofunctional reactive diluents, methyl methacrylate (MMA), n-butyl acrylate (BA), isooctyl acrylate (2-EHA), isodecyl acrylate (IDA), lauryl acrylate (LA), hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and some (meth)acrylates with cyclic structures can be mentioned. In addition, as vinyl monofunctional reactive diluents, styrene (St), vinyl acetate (VA), N-vinyl pyrrolidone (NVP), etc. can be mentioned.

[0226] The monofunctional reactive diluent is generally used in the photocurable composition in an amount of 5 to 50% by weight, preferably 8 to 40% by weight, based on the amount of the active ingredients in the photocurable composition.

[0227] In one embodiment of the present invention, the photocurable composition may be free of reactive diluents, such as free of multifunctional reactive diluents and monofunctional reactive diluents.

[0228] The photocurable composition of the present invention may also optionally contain an organic solvent. The selection of the organic solvent is conventional. As the organic solvent, aromatic hydrocarbons such as benzene and toluene, halogenated alkanes such as chloroform, dichloromethane, and ethyl chloride, ketones such as acetone, butanone, and pentanone, alcohols such as methanol, ethanol, propanol, isopropanol, and ethylene glycol, glycol ethers, glycol ether acetates, propylene glycol ethers, and propylene glycol ether acetates, etc. may be mentioned. In one embodiment, the photocurable composition may not contain an organic solvent.

[0229] In one embodiment of the present invention, the photocurable composition may be free of organic solvents.

[0230] The photocurable composition of the present invention may also optionally contain other additives, such as leveling agents, antioxidants, anti-settling agents, colorants, microbicides, such as antibacterial agents and thermal insulation additives. In a preferred embodiment of the present invention, the leveling agent is selected from the group consisting of A series of leveling agents, particularly preferably 360S, 372S, 384S, 392S, 400U, 415U, etc.

[0231] The preparation of the photocurable composition of the present invention is conventional, for example, each component of the photocurable composition of the present invention is uniformly mixed together.

[0232] In addition, the present invention also relates to a photocurable composition based on a cationic photopolymerization mechanism, comprising a 3-formylformic acid coumarin compound of formula (I) of the present invention. In addition to the 3-formylformic acid coumarin compound of the present invention, the photocurable composition of the present invention further comprises an onium salt co-initiator and a photocurable resin (cationic photocurable resin). The onium salt can be referred to in detail above.

[0233] In the present invention, an onium salt co-initiator can generate a conjugate acid under the sensitization of a 3-formylformic acid coumarin compound to initiate cationic photopolymerization of alkenyl ether compounds, oxirane compounds, and oxetane compounds. The alkenyl ether compounds, oxirane compounds, and oxetane compounds can be in the form of monomers or resins (including oligomers or prepolymers).

[0234] Photocurable resins (cationic photocurable resins) can include alkenyl ether compounds, oligomers or prepolymers containing ethylene oxide, propylene oxide, or oxetane functional groups. Upon exposure to light, these oligomers or prepolymers undergo a polymerization reaction initiated by a photoinitiator, leading to crosslinking and curing. Photocurable resins are the main component of photocurable products (such as UV coatings, UV inks, and UV adhesives).

[0235] In the present invention, the alkenyl ether compound may be a C1-C6 alkenyl ether compound, such as vinyl ether, 1-propenyl ether, 1-butenyl ether, 1-pentenyl ether, and the like, preferably a vinyl ether compound. The alkenyl ether compound may be, for example, an alkenyl ether derived from a monohydric alcohol having 1 to 12, preferably 1 to 6, carbon atoms, a dihydric alcohol having 2 to 12, preferably 2 to 8, carbon atoms, or a trihydric alcohol having 3 to 12, preferably 3 to 6, carbon atoms, or a higher alcohol, particularly a C1-C6 alkenyl ether. Examples of the alkenyl ether compound include polymers containing alkenyl ether functional groups, such as vinyl ether functional groups. Specific examples include triethylene glycol divinyl ether, isobutyl vinyl ether, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether (BVE), hydroxyethyl vinyl ether, diethylene glycol divinyl ether (DEGDVE), triethylene glycol divinyl ether (TEGDVE), octyl vinyl ether, divinyl-1,4-butanediol ether, 2-ethylhexyl vinyl ether, 1,4-cyclohexyl dimethanol divinyl ether, 4-hydroxybutyl vinyl ether (HBVE), triethylene glycol divinyl ether (DVE-3), glycerol carbonate vinyl ether, and dodecyl vinyl ether, or a combination of two or more thereof. Furthermore, compounds having both a vinyl ether and an alkyl (meth)acrylate structure may be mentioned; one or more of these compounds may be used simultaneously. The alkenyl compounds also include carbamates containing one or more, such as one to three, alkenyl ether structures. The carbamates containing an alkenyl ether structure can be obtained by reacting an alkenyl ether having a hydroxyl group with an isocyanate compound (e.g., a polyisocyanate compound). Examples thereof include bis(ethylene oxide) alkyl carbamate and trifunctional vinyl ether prepared from hexamethylene diisocyanate trimer and 4-hydroxyvinyl ether.

[0236] According to the present invention, examples of the oxetane compounds include 3,3'-(oxybismethylene)bis(3-ethyl)oxetane, 3-ethyl-3-oxetane methanol, bis[(3-methyl-3-oxetanylmethoxy)methyl]ether, bis[(3-ethyl-3-oxetanylmethoxy)methyl]ether, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, Benzene, (3-methyl-3-oxetanyl)methyl acrylate, (3-ethyl-3-oxetanyl)methyl acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, 3-methyl-3-vinylhydroxymethyloxetane, 3-methyl-3-vinylhydroxypolyethoxylated methyloxetane, 1,4-bis(3- ethyl-3-oxetanylmethoxy)butane, 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, pentaerythritol tris(3-ethyl-3-oxetanylmethyl) ether, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, polyethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether methyl) ether, isobutoxymethyl (3-ethyl-3-oxetanyl methyl) ether, ethylene glycol bis (3-ethyl-3-oxetanyl methyl) ether, tricyclodecanediyl dimethylene (3-ethyl-3-oxetanyl methyl) ether, trimethylolpropane tris (3-ethyl-3-oxetanyl methyl) ether, pentaerythritol tetrakis (3-ethyl-3-oxetanyl methyl) ether, 3-oxiranyl 7-oxabicyclo [4.1.0] heptane, as well as 3-ethyl-3-oxetanemethanol (GR-OXT-01), 3-ethyl-3-chloromethyloxetane (GR-OXT-02), 3,3'-(oxybismethylene)bis(3-ethyl)oxetane GR-OXT-03, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane (GR-OXT-04), 3,3'-((((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(methylene))bis(3-ethyloxetane) (GR-OXT-05), 3-ethyl-3-(benzyloxymethyl)oxetane Polyfunctional oxetane compounds such as oxetane (GR-OXT-06), oxetane methacrylate (GR-OXT-09), and bis[(3-ethyloxetan-3-yl)methyl]benzene-1,4-dicarboxylate (GR-OXT-11), oligomers or copolymers thereof, and ethers of oxetane alcohol with hydroxyl-containing resins such as novolac resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, resorcinol calixarenes, or silsesquioxanes. Compounds having both oxetane and alkyl (meth)acrylate structures are also included.

[0237] The oxirane compound can be selected from, for example, glycidyl ether epoxy compounds, glycidyl ester epoxy compounds, glycidyl amine epoxy compounds, aliphatic epoxy compounds, alicyclic epoxy compounds, etc. The oxirane compound can be in the form of a monomer or a resin (such as an oligomer or a prepolymer). Compounds having both an oxirane group and a free radical polymerizable group (such as an acrylate group) can also be mentioned, such as epoxy (meth) acrylate resins. Glycidyl ether epoxy compounds (especially aliphatic glycidyl ether epoxy compounds, bisphenol A type glyceryl ether epoxy compounds) and aliphatic epoxy resins are preferred. In addition, compounds having both an oxirane group (such as an alicyclic oxirane group or a glycidyl ether group) and an alkyl (meth) acrylate structure are preferred.

[0238] As examples of these oxirane compounds, there may be mentioned 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (6110), bis(3,4-epoxycyclohexylmethyl) adipate (UVR-6128), trimethylolpropane glycidyl ether (TPEG), 1,2-epoxy-4-vinylcyclohexane, methyl 3,4-epoxycyclohexanecarboxylate, diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, bisphenol A diglycidyl ether (E-03 type), 3-oxiranyl 7-oxabicyclo[4,1,0]heptane, ethylene glycol diglycidyl ether, C 12 -C14 Multifunctional epoxy compounds such as alkyl glycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyether polyol glycidyl ether, glycidyl methacrylate, trimethylol triglycidyl ether, 1,4-butanediol diglycidyl ether, and oligomers or copolymers thereof, as well as EPIKOTE Resin 862, EPIKOTE Resin 827, EPIKOTE Resin 869, EPIKOTE Resin 320, EPIKOTE Resin 816, EPIKOTE Resin 232, and EPIKOTE Resin 144. These compounds can be used alone or in combination.

[0239] The present invention also relates to a photocurable composition comprising a 3-formylformic acid coumarin compound of formula (I) of the present invention, which is based on a free radical-cationic hybrid photopolymerization mechanism. In this type of photocurable composition, in addition to the 3-formylformic acid coumarin compound of the present invention, the photocurable composition further comprises an onium salt and a photocurable resin (a free radical photocurable resin and a cationic photocurable resin).

[0240] In the present invention, the onium salt is preferably selected from iodonium salts and sulfonium salts, more preferably selected from diaryliodonium salts and triarylsulfonium salts. Detailed description of the onium salt is given above.

[0241] The photocurable resin is a free radical photocurable resin and a cationic photocurable resin. Specific details of the free radical photocurable resin and the cationic photocurable resin are described in detail above.

[0242] The photocurable composition of the present invention may also optionally contain an organic solvent. The choice of organic solvent is conventional. As organic solvents, aromatic hydrocarbons such as benzene and toluene, halogenated alkanes such as chloroform, dichloromethane, and ethyl chloride, ketones such as acetone, butanone, and pentanone, alcohols such as methanol, ethanol, propanol, isopropanol, and ethylene glycol, and glycol ethers, glycol ether acetates, propylene glycol ethers, and propylene glycol ether acetates may be mentioned.

[0243] The photocurable composition of the present invention may also optionally contain other additives, such as leveling agents, antioxidants, anti-settling agents, colorants, microbicides, such as antibacterial agents and thermal insulation additives. In a preferred embodiment of the present invention, the leveling agent is selected from the group consisting of A series of leveling agents, particularly preferably 360S, 372S, 384S, 392S, 400U, 415U, etc.

[0244] The preparation of the photocurable composition of the present invention is conventional, for example, each component of the photocurable composition of the present invention is uniformly mixed together.

[0245] Photocurable materials and preparation methods

[0246] Another aspect of the present invention provides a cured material obtainable from the photocurable composition of the present invention. The cured material can be a photocurable coating, such as a coating containing a functional material, a coating for UV and / or visible light color filters; a sealant; a photolithographic material; a holographic recording material; a 3D printing material; a lithographic material; a material for preparing optical devices; and a material for improving mechanical properties, such as a carbon fiber composite material and / or inorganic and / or organic nanoparticles.

[0247] The present invention also relates to a method for preparing a photocurable material, which comprises irradiating the photocurable composition with a light source having a radiation wavelength of 300-550 nm, especially 365-475 nm, such as a UV-VIS LED light source.

[0248] Furthermore, the compounds of formula (I) disclosed in the present invention have a simple production process and high yield, making them very suitable for industrial production. These compounds exhibit excellent compatibility with UV-VIS LED light sources with a radiation wavelength of 300-550 nm, particularly 365-475 nm. They can be used as photoinitiators in a wide range of applications related to UV-VIS LED photocuring, such as coatings, inks, microelectronics, printing, 3D printing, and dental materials.

[0249] Furthermore, the limited availability of photoinitiators for deep-layer curing using UV-VIS LEDs, particularly long-wavelength UV-VIS LEDs, has limited their widespread application in the field of photocuring. The 3-formylformic acid coumarin compound of formula (I) of the present invention can be used for deep-layer curing using UV-VIS LEDs, thereby contributing to the widespread application of environmentally friendly UV-VIS LEDs in the UV photocuring industry.

[0250] Example

[0251] The scheme of the present invention will be explained below with reference to the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are followed.

[0252] Example 1: Preparation of Compound 1

[0253] The synthetic route of compound 1 is as follows:

[0254] Step (1): Synthesis of intermediate compound 1a

[0255] 4-Methyl-2-hydroxy-5-methylthiobenzaldehyde (0.05 mol, 9.10 g) was added to a 250 mL three-necked round-bottom flask containing 50 mL of ethanol and stirred thoroughly. Piperidine (0.015 mol, 1.28 g) and ethyl acetoacetate (0.07 mol, 9.11 g) were then added. The reaction mixture was then heated to reflux and stirred for 4 hours. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain a yellow solid, which was then recrystallized from ethanol to yield 11.41 g of the product in a 92% yield. This product was identified as compound 1a. 1H-NMR (400 MHz, CDCl3) δ 8.45 (s, 1H), 7.50 (s, 1H), 6.98 (s, 1H), 2.46 (s, 3H), 2.37 (s, 3H), 2.34 (s, 3H).

[0256] Synthesis of target product 1

[0257] The intermediate compound 1a (9.92 g, 0.04 mol), SeO2 (11.09 g, 0.1 mol) and 70 mL of pyridine were added to a 250 mL three-necked round-bottom flask. After stirring at 130°C for 2 h, the reaction progress was monitored by a plate. When impurities were detected during the reaction, the reaction was immediately stopped. The reaction solution was cooled to room temperature, insoluble matter was removed by filtration, and a large amount of ethyl acetate was added to the filtrate, and solid powder precipitated. The filter cake was filtered and acidified with aqueous hydrochloric acid to convert the pyridinium salt of coumarin 3-formylformic acid into the corresponding carboxylic acid. The product was stirred at room temperature for 2 h to obtain 5.89 g of a yellow solid product with a yield of 53%, which was identified as compound 1. The NMR data of compound 1 are shown in Table 1.

[0258] Example 2-14: Preparation of Compound 2-14

[0259] The method of Example 1 was repeated, and the reaction starting materials were appropriately changed to obtain compounds 2-14 and their NMR data in the following table.

[0260] Table 1

[0261] Characterization 1: UV-visible light absorption performance test:

[0262] Using the compounds of Examples 1-3 as examples, the UV-visible light absorption properties of the compounds of the present invention were tested. The molar extinction coefficients of the compounds of Examples 1-3 in acetonitrile (50 ppm) were measured and calculated by UV-Vis spectroscopy (Figure 1). Table 2 lists the maximum absorption wavelength (λmax) and the corresponding molar extinction coefficient, as well as the molar extinction coefficient at the emission wavelength of a common LED light source. As can be seen from Figure 1 and Table 2, the compounds of Examples 1-3 have good absorption in the near-UV-Vis range, matching the common UV-Vis LED light source in the 300nm-500nm range.

[0263] Table 2 Maximum absorption wavelength λ of the compounds of Examples 1-3 max And the corresponding molar extinction coefficient, as well as the molar extinction coefficient at the emission wavelength of common LED light sources.

[0264] Characterization 2: Photoinitiation performance test:

[0265] Ingredients used:

[0266] TPGDA: tripropylene glycol diacrylate (acrylate monomer), purchased from Shanghai Yinchang New Materials Co., Ltd.;

[0267] PEG(400)DA: polyethylene oxide diacrylate (acrylate resin), purchased from Shanghai Yinchang New Materials Co., Ltd.;

[0268] 6110: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (epoxy monomer), purchased from Hubei Gurun Technology Co., Ltd.;

[0269] EDB: ethyl N,N-dimethylaminobenzoate, purchased from Beijing Yinuokai Technology Co., Ltd.;

[0270] GR-IS054: bis(4-tert-butylphenyl)iodonium hexafluorophosphate (iodonium salt, abbreviated as GR54), purchased from Hubei Gurun Technology Co., Ltd.;

[0271] GR-SS061: mixed sulfonium hexafluoroantimonate, composed of diphenyl-(4-phenylsulfonium)phenylsulfonium hexafluoroantimonate and bis(4-(diphenylsulfonium)phenyl)sulfide-bishexafluoroantimonate, purchased from Hubei Gurun Technology Co., Ltd.

[0272] Test method:

[0273] The photoinitiating properties of the above-mentioned compounds as oily photoinitiators for initiating free radical polymerization of acrylate monomer (TPGDA) and cationic polymerization of epoxy monomer (6110), as well as as water-based photoinitiators for initiating polymerization of acrylate resin (PEG (400) DA) were tested using Fourier transform infrared (FTIR) and FTIR-real-time infrared (FTIR-RT) methods. The characteristic peaks of acrylate and epoxy monomers were located at 1630 cm -1 (carbon-carbon double bond) and 916 cm -1 The carbon-carbon double bond conversion rates of TPGDA and PEG(400)DA after 300 seconds of exposure are shown in Tables 3 and 4, respectively. The photoinitiator performance of the photoinitiator under different test conditions was evaluated based on the time-dependent trends in conversion rates under different test conditions.

[0274] Preparation of photocurable composition:

[0275] (1) A free radical polymerizable photocurable composition 1 containing the compound of Example 3 as an oily photoinitiator was prepared according to the following composition:

[0276] 100 parts by mass of TPGDA acrylate monomer

[0277] 1 part by mass of the compound of Example 3 (photoinitiator)

[0278] (2) Free radical polymerizable photocurable compositions 2-15 containing the compounds of Examples 1-14 as oily photoinitiators were prepared according to the following compositions:

[0279] 100 parts by mass of TPGDA acrylate monomer

[0280] EDB 1.16 parts by mass

[0281] 1 part by mass of the compound of Example 1-14 (photoinitiator)

[0282] (3) Free radical polymerizable photocurable compositions 16-29 containing the compounds of Examples 1-14 as aqueous photoinitiators were prepared according to the following compositions:

[0283] 100 parts by mass of PEG (400) DA acrylate monomer

[0284] GR54 4 parts by mass

[0285] 2 parts by mass of the compound of Example 1-14 (photoinitiator)

[0286] (4) Cationic polymerizable photocurable compositions 30-32 containing the compounds of Examples 1-3 as photoinitiators to sensitize iodonium salts were prepared according to the following compositions:

[0287] 100 parts by mass of 6110 epoxy monomer

[0288] GR54 4 parts by mass

[0289] 0.2 parts by mass of the compound of Example 1-14 (photoinitiator)

[0290] (5) Cationic polymerizable photocurable compositions 33-35 containing the compounds of Examples 1-3 as photoinitiators to sensitize sulfonium salts were prepared according to the following compositions:

[0291] 100 parts by mass of 6110 epoxy monomer

[0292] GR-SS061 4 parts by mass

[0293] 0.2 parts by mass of the compound of Example 1-14 (photoinitiator)

[0294] (6) A cationically polymerizable photocurable comparative composition 1 not containing the compound of the present invention was prepared according to the following composition:

[0295] 100 parts by mass of 6110 epoxy monomer

[0296] GR54 4 parts by mass

[0297] (7) A cationically polymerizable photocurable comparative composition 2 not containing the compound of the present invention was prepared according to the following composition:

[0298] 100 parts by mass of 6110 epoxy monomer

[0299] GR-SS061 4 parts by mass

[0300] Testing of photoinitiation performance

[0301] After the above compositions are stirred and mixed evenly under yellow light, the photocurable composition is injected into a pre-treated KBr double salt sheet mold that meets the following conditions using a syringe:

[0302] KBr double salt plate size: 15mm×15mm

[0303] KBr double salt sheet thickness: 3mm

[0304] KBr double salt plate gap: 0.5mm

[0305] By observing the syringe scale, the amount of photocurable composition injected into the KBr double salt tablet mold was adjusted to 0.2 ml. After the injection was completed, the KBr double salt tablet mold was placed in a small black box in a Fourier transform infrared spectrometer used for real-time infrared testing. The structure of the small black box was such that the infrared test light above was vertically aligned to penetrate the KBr double salt tablet mold, and a 45° LED point light source above the KBr double salt tablet mold was aligned with the KBr double salt tablet mold, and the LED point light source was 1 cm above the KBr double salt tablet mold.

[0306] Simultaneously, infrared spectrum detection and LED light source are started, so that the photocurable composition in the KBr double salt plate mold is exposed while detecting the change in characteristic peak area.

[0307] Under the irradiation of LED point light source, the photopolymerizable compound undergoes polymerization reaction in the presence of initiator, so that the carbon-carbon double bond (1630cm -1 ) or epoxy functional group (916cm -1 ) The characteristic peak area decreases continuously until it almost disappears. Based on the data of the change of characteristic peak area with exposure time, the conversion rate of monomer over time is calculated.

[0308] Based on the data of the change of the characteristic peak area of ​​the carbon-carbon double bond or epoxy functional group with the exposure time, the formula for the conversion rate of the monomer over time is calculated:

[0309] The photocurable compositions 2-15 were prepared by compounding the compounds of Examples 1-14 with EDB under 365 nm, 385 nm, 400 nm, 415 nm, 425 nm, 450 nm, and 475 nm LED light sources (light intensity: 100 mW / cm 2 ) was used to initiate polymerization of the oil-soluble acrylic ester monomer TPGDA. The final double bond conversion rate (%) of TPGDA after 300 seconds of exposure is shown in Table 3.

[0310] Table 3

[0311] The compounds of Examples 1-14 were compounded with iodonium salt GR54 (photocurable compositions 16-29) and tested for their photocurability under 365nm, 385nm, 400nm, 415nm, 425nm, 450nm, and 475nm LED light sources (light intensity: 100mW / cm 2) was used to initiate polymerization of waterborne acrylate resin (PEG(400)DA) under exposure conditions of 500 nm. The final double bond conversion rate (%) of PEG(400)DA after 300 seconds of exposure is shown in Table 4.

[0312] Table 4

[0313] In addition, the kinetic curve of the double bond conversion rate of the monomer TPGDA under 415nm, 450nm, and 475nm light sources was tested for the photocurable composition 1 using the compound of Example 3 (Figure 2a). The data showed that the monomer showed high conversion rate and conversion rate under these three light sources. The conversion rate at 30s was: 415nm: 72.6%; 450nm: 70.6%; 475nm: 69.0%, so 415nm was the best (Figure 2a). At 415nm, 50mW / cm 2 Under light source, the conversion rate of photocurable compositions 2, 3 and 4 containing the compounds of Examples 1-3, amine (EDB) and monomer TPGDA was tested as a function of exposure time ( Figure 2 b ). The conversion rates at 30 s were: Example 1 compound + EDB: 77.7%; Example 2 compound + EDB: 72.5%; Example 3 compound + EDB: 76.8%.

[0314] At 415nm LED, 100mW / cm 2 Under LED light, the conversion rate of photocurable compositions 16, 17, and 18, comprising the compounds of Examples 1-3, the iodonium salt GR54, and PEG(400)DA, was plotted as a function of exposure time (Figure 2c). The conversion rates at 30 seconds were: Example 1 compound + GR54: 64.7%; Example 2 compound + GR54: 70.8%; and Example 3 compound + GR54: 74.5%. These results demonstrate that the compounds of Examples 1-3 can rapidly initiate photopolymerization of the acrylate resin (PEG(400)DA), achieving a final double bond conversion rate of 80%.

[0315] At 415nm LED, 100mW / cm 2Under a 415 nm LED light source, photocurable compositions 30 and 32 containing the compounds of Examples 1 or 3, iodonium salt GR54, and epoxy monomer (6110) were tested, as well as a comparative photocurable composition 1 containing only iodonium salt GR54 and epoxy monomer (6110). The conversion rate curve as a function of exposure time is shown in Figure 3a. The conversion rate at 100 s is as follows: Example 1 compound + GR54: 38.0%; Example 3 compound + GR54: 37.5%; GR54 alone: ​​13.1%. The data show that the two-component system of the compound of the present invention / GR54 (0.2% / 4% w / w) can induce ring-opening polymerization of epoxy monomer 6110 with good efficiency under a 415 nm LED light source (Figure 3a). Under the same conditions, the polymerization rate of epoxy monomer 6110 is lower when GR54 is used alone. This result shows that the compound of the present invention can effectively sensitize the iodonium salt to achieve efficient cationic photocuring.

[0316] At 415nm LED, 100mW / cm 2 Under a 415 nm LED light source, photocurable compositions 33, 34, and 35 containing the compounds of Examples 1-3, the sulfonium salt GR-SS061, and the epoxy monomer (6110) were tested, along with a comparative photocurable composition 2 containing only the sulfonium salt GR-SS061 and the epoxy monomer (6110). The conversion rate versus exposure time curves are shown in Figure 3b. The conversion rates at 100 s are: Example 1 compound + GR-SS061: 63.6%; Example 2 compound + GR-SS061: 60.4%; Example 3 compound + GR-SS061: 44.2%; and GR-SS061 alone: ​​0%. The data demonstrate that a two-component system of the compound of the present invention / GR-SS061 (0.2% / 4% w / w) can efficiently initiate ring-opening polymerization of the epoxy monomer 6110 under a 415 nm LED light source (Figure 3b). Under the same conditions, the polymerization rate of epoxy monomer 6110 is very low when GR-SS061 is used alone. This result shows that the compound of the present invention can effectively sensitize sulfonium salts to achieve efficient cationic photocuring.

[0317] Characterization 3: Deep curing performance test

[0318] The compounds from Examples 1 and 2 were used as photoinitiators to initiate the curing of acrylates (TPGDA and PEG(400)DA) to demonstrate their deep-cure capability. The depth of cure of the acrylates after 5 minutes of exposure is shown in Figure 4. The trends in the depth of cure under different test conditions were used to evaluate the photoinitiator's photoinitiating performance under different conditions.

[0319] Specifically, the photoinitiating performance of the compound was tested according to the following steps.

[0320] (i) A photocurable composition (i) was prepared according to the following composition:

[0321] TPGDA 100 parts by mass

[0322] 0.01 parts by mass of the compound of Example 1

[0323] (ii) A photocurable composition (ii) was prepared according to the following composition:

[0324] TPGDA 100 parts by mass

[0325] 0.01 parts by mass of the compound of Example 2

[0326] (iii) A photocurable composition (iii) was prepared according to the following composition:

[0327] PEG(400)DA 100 parts by mass

[0328] 0.01 parts by mass of the photoinitiator of Example 1

[0329] (iv) A photocurable composition (iv) was prepared according to the following composition:

[0330] PEG(400)DA 100 parts by mass

[0331] 0.01 parts by mass of the compound of Example 2

[0332] After the above compositions were stirred and dissolved evenly under yellow light, the photocurable composition was injected into a glass tube with an inner diameter of 1 cm and a length of 10 cm using a syringe and wrapped with tin foil. The light intensity used was 100 mW / cm 2 A 415nm LED light source was used to irradiate the bottom of the test tube. After irradiation, the curing depth of the sample was measured, and the results are shown in Figure 4. The experimental results show that a photoinitiator with a mass concentration of 0.01% can induce polymerization of the two monomers to a depth of more than 9 cm within 5 minutes of exposure. Specifically, the curing depths of photocurable compositions (i)-(iv) were 9.0 cm, 9.5 cm, 9.0 cm, and 9.2 cm, respectively (see Figures 4(a), 4(b), 4(c), and 4(d)). This shows that the compounds of the present invention have very excellent photoinitiating properties.

Claims

1. 3-Formylformic acid coumarin compounds of formula (I): Wherein: R1 is H, a linear or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a C6-C 10 aryl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R2 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a C6-C 10 aryl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl groups, and C1-C6 alkoxy(thio) groups; R3 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a C6-C 10 aryl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; provided that each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) group; R4 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a C6-C 10 aryl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; provided that each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) group; and R5 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a C6-C 10 aryl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; provided that each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) group; or R1 and R2, R2 and R3, or R3 and R4 together with the carbon atom to which they are bonded form a 3-, 4-, 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) group, and the heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members; or R1, R2 and R3, or R2, R3 and R4 together with the carbon atom to which they are bonded form a 6-, 7-, 8-, 9- or 10-membered partially unsaturated or aromatic bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: halogen, C1-C6 alkyl, and C1-C6 alkoxy(thio) group, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members.

2. The 3-formylformic acid coumarin compound of formula (I) according to claim 1, wherein: R1 is H, linear or branched C1-C 16 alkyl, C3-C 10 cycloalkyl, C3-C 10 cycloalkyl-C1-C 16 alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group; R2 is H, linear or branched C1-C 16 alkyl, C3-C 10 cycloalkyl, C3-C 10 cycloalkyl-C1-C 16 alkyl, mono- or di-C1-C6 alkylamino or C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) group; R3 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; and R4 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; provided that each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R5 is H or a straight-chain or branched C1-C 16 alkyl group; or R1 and R2, R2 and R3, or R3 and R4 together with the carbon atom to which they are bonded form a 5-, 6- or 7-membered partially unsaturated or aromatic carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: C1-C6 alkyl and C1-C6 alkoxy(thio) group, and the heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members; or R1, R2 and R3, or R2, R3 and R4 together with the carbon atom to which they are bonded form an 8-, 9- or 10-membered partially unsaturated or aromatic bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: C1-C6 alkyl and C1-C6 alkoxy(thio) group, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members.

3. The 3-formylformic acid coumarin compound of formula (I) according to claim 1 or 2, wherein: R1 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R2 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group, a mono- or di-C1-C6 alkylamino group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R3 is H, a linear or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R4 is H, a straight-chain or branched C1-C 16 alkyl group, a C3-C 10 cycloalkyl group, a C3-C 10 cycloalkyl-C1-C 16 alkyl group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; and R5 is H or a straight-chain or branched C1-C 16 alkyl group; or R1 and R2, R2 and R3, or R3 and R4 together with the carbon atom to which they are bonded form a 5-, 6- or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: C1-C6 alkyl and C1-C6 alkoxy(thio) group, and the heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members; or R1, R2 and R3, or R2, R3 and R4 (preferably R1, R2 and R3) together with the carbon atom to which they are bonded form an 8-, 9- or 10-membered partially unsaturated bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of: C1-C6 alkyl and C1-C6 alkoxy(thio) group, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O, and S as ring members.

4. The 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-3, wherein: R1 is H, a straight-chain or branched C1-C 12 alkyl group, a C5-C7 cycloalkyl group, a C5-C7 cycloalkyl-C1-C 12 alkyl group, or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R2 is H, a straight-chain or branched C1-C 12 alkyl group, a C5-C7 cycloalkyl group, a C5-C7 cycloalkyl-C1-C 12 alkyl group, a mono- or di-C1-C4 alkylamino group or a C1-C 12 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R3 is H, a linear or branched C1-C 12 alkyl group, a C5-C7 cycloalkyl group, a C5-C7 cycloalkyl-C1-C 12 alkyl group or a C1-C 16 alkoxy(thio) group; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl groups and C1-C6 alkoxy(thio) groups; R4 is H, a linear or branched C1-C 12 alkyl, a C5-C7 cycloalkyl, a C5-C7 cycloalkyl-C1-C 12 alkyl or a C1-C 16 alkoxy(sulfur)yl; wherein each of the foregoing groups other than H is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(sulfur)yl; and R5 is H or a straight-chain or branched C1-C 12 alkyl group; or R1 and R2, R2 and R3, or R3 and R4 together with the carbon atom to which they are bonded form a 5-, 6- or 7-membered partially unsaturated carbocyclic or heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the carbocyclic or heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the heterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members; or R1, R2 and R3, or R2, R3 and R4 together with the carbon atom to which they are bonded form an 8-, 9- or 10-membered partially unsaturated bicyclic carbocyclic or bicyclic heterocyclic ring fused to the benzene ring in the coumarin structure, wherein the bicyclic carbocyclic or bicyclic heterocyclic ring is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C6 alkyl and C1-C6 alkoxy(thio) groups, and the bicyclic heterocyclic ring contains 1 or 2 heteroatoms selected from N, O and S as ring members.

5. The 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-4, wherein: R1 is H or a straight-chain or branched C1-C 12 alkyl group; R2 is H, a linear or branched C1-C 12 alkyl group, a di-C1-C4 alkylamino group or a C1-C 16 alkoxy(thio) group; R3 is H, a straight-chain or branched C1-C 12 alkyl group or a C1-C 16 alkoxy(thio) group; R4 is H, a straight-chain or branched C1-C 12 alkyl group or a C1-C 16 alkoxy(thio) group; and R5 is H; or R1, R2, and R3, or R2, R3, and R4 together with the carbon atom to which they are bonded form an 8-, 9-, or 10-membered partially unsaturated bicyclic heterocycle fused to the benzene ring in the coumarin structure, wherein the bicyclic heterocycle is unsubstituted or contains one or more substituents independently selected from the group consisting of C1-C4 alkyl, and the bicyclic heterocycle contains 1 N heteroatom as a ring member, preferably the N heteroatom is a shared atom of the bicyclic heterocycle; more preferably the bicyclic heterocycle has the structure of formula (a): wherein * represents the position fused to the benzene ring in the coumarin structure; and the structure shown in formula (a) is unsubstituted or contains one or more C1-C4 alkyl groups as substituents.

6. The 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-5, wherein at least one of R1, R2, R3 and R4 is not H and R5 is H, or preferably 2 or 3 of R1, R2, R3 and R4 are H and R5 is H.

7. A 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-5, wherein the 3-formylformic acid coumarin compound of formula (I) is selected from the group consisting of:

8. A method for preparing the 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-7, comprising the following steps: (1) Knoevenagel condensation reaction: The compound of formula (II) is subjected to a Knoevenagel condensation reaction with an acetoacetic acid C1-C6 alkyl ester to obtain a compound of formula (III): (2) Oxidation reaction: The compound of formula (III) is subjected to an oxidation reaction with an oxidizing agent to obtain the compound of formula (I). wherein in the above formulas, R1, R2, R3, R4 and R5 are as defined in any one of claims 1-7.

9. Use of the 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-7 as a photoinitiator.

10. The use according to claim 9, wherein the 3-formylformic acid coumarin compound of formula (I) is used as a cleavage-type photoinitiator or a hydrogen abstraction-type photoinitiator in a UV-VIS LED light source curing system, especially as a cleavage-type photoinitiator or a hydrogen abstraction-type photoinitiator in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm.

11. The use according to claim 9 or 10, wherein the 3-formylformic acid coumarin compound of formula (I) is used in combination with a compound selected from tertiary amine compounds, α-amino acid compounds or thiol compounds.

12. Use of the 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-7 as a photoinitiator-sensitized onium salt, especially as a photoinitiator-sensitized onium salt in a UV-VIS LED light source curing system, especially as a photoinitiator-sensitized onium salt in a light source curing system with a radiation wavelength of 300-550 nm, especially 365-475 nm, and preferably the onium salt is selected from iodonium salts and sulfonium salts, especially selected from diaryliodonium salts and triarylsulfonium salts 13. A photoinitiator composition comprising a 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-7, preferably the composition comprises the 3-formylformic acid coumarin compound of formula (I) and a compound selected from a tertiary amine compound, an α-amino acid compound or a thiol compound, or preferably the photoinitiator composition comprises the 3-formylformic acid coumarin compound of formula (I) and an onium salt, more preferably the onium salt is selected from iodonium salts and sulfonium salts, especially selected from diaryliodonium salts and triarylsulfonium salts.

14. A photocurable composition comprising at least one 3-formylformic acid coumarin compound of formula (I) according to any one of claims 1-7 or a photoinitiator composition according to claim 13.

15. A cured material obtainable from the photocurable composition according to claim 14.

16. A method for preparing a photocured material, which comprises irradiating the photocurable composition according to claim 14 with a light source having a radiation wavelength of 300-550 nm, especially 365-475 nm, such as a UV-VIS LED light source.

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