Aryl formyl oxime formate photoinitiator and preparation method thereof

Abstract

The invention relates to an oxime aryl formyl formate photoinitiator suitable for LED (light-emitting diode) photopolymerization, the photoinitiator has a structure as shown in a general formula (I), and Ar1, Ar2 and R1 are defined in the specification and claims. The invention also relates to a preparation method of the photoinitiator and application of the photoinitiator in an LED photopolymerization system. # imgabs0 #

Description

Technical Field

[0001] The invention relates to an aromatic formyl formic acid oxime ester photoinitiator suitable for LED light curing, a preparation method thereof and application thereof in light curing using an LED light source. Background Art

[0002] High-pressure mercury lamps, as the light source commonly used in traditional photocuring technology, are gradually being replaced by greener light sources. Compared with traditional mercury lamp light sources, LED light sources have the advantages of long life, low energy consumption, strong stability and rapid response. Therefore, photocuring using LED light sources (also known as LED photocuring or LED photopolymerization) has received more and more attention in the field of photosensitive polymers. Photoinitiators (also known as LED photoinitiators) that match the wavelength of LED light sources are one of the important factors affecting the applicability of LED photocuring technology. So far, most of the LED photoinitiators that have been reported contain large conjugated structures (chromophores) in their structures. Although these large conjugated structures provide LED photoinitiators with good light absorption ability, they also bring color to the curing system because of the absorption of visible light. Darker colors will prevent light from passing through the curing system to reach the deep layers of the system, which undoubtedly limits the application of such LED photoinitiators in photocuring systems that require colorless and deep curing.

[0003] At present, the main way to solve the above problems is to develop LED photoinitiators with photobleaching properties. This type of photoinitiator can be cleaved at a specific wavelength, and the resulting fragments do not absorb in the visible light region, thereby obtaining a colorless cured product. However, one disadvantage of this type of photoinitiator is that it is difficult to completely cleave in the curing system, especially for systems that require deep curing, the color brought by the photoinitiator is difficult to completely disappear.

[0004] Another problem associated with this type of photoinitiator is that it migrates out of the curing system, causing adverse effects on human health. Therefore, the development of photoinitiators with low migration has become a new challenge in the field of photocurable materials in recent years. Summary of the invention

[0005] The object of the present invention is to provide a photoinitiator which can effectively generate active free radicals that initiate polymerization and / or crosslinking reactions at the emission wavelengths of commonly used LED light sources (e.g., 385 nm, 395 nm, and 405 nm), but at the same time has no absorption or very low absorption of visible light, and the photoinitiator preferably has low mobility.

[0006] The inventors of the present invention surprisingly found that the above-mentioned purpose is achieved by an α,β-unsaturated oxime ester compound having an α-dicarbonyl structure, which has a suitable weak absorption in the visible light region, and such a degree of absorption can lead to effective photolysis and generate active free radicals, but will not bring unacceptable color to the curing system, so that deep curing can be initiated. In addition, the oxime ester photoinitiator of the present invention has significantly lower mobility than commercially available oxime ester photoinitiators, that is, it has significantly improved migration stability.

[0007] In a first aspect, the present invention provides an aromatic formyl formate oxime ester compound having a structure shown in formula (I):

[0008]

[0009] in,

[0010] Ar1 and Ar2 are independently selected from C6-C 10 -aryl, or a C6-C 10 -Aryl: halogen, nitro, hydroxyl, thiol, amino, C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino is optionally substituted by at least one selected from halogen, nitro, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups;

[0011] R1 is selected from hydrogen, C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -cycloalkyl, the aforementioned C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10-cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group.

[0012] In a second aspect, the present invention provides a method for preparing the aromatic formyl formic acid oxime ester compound represented by the aforementioned formula (I), the method comprising subjecting the aromatic formyl formic acid represented by the formula (II) to an esterification reaction with the oxime represented by the formula (III):

[0013]

[0014] Wherein, Ar1 in formula (II) and R1 and Ar2 in formula (III) have the same meanings as Ar1, R1 and Ar2 in formula (I), respectively.

[0015] In a third aspect, the present invention provides a composition for LED light curing, the composition comprising:

[0016] - at least one aromatic oxime ester compound represented by the aforementioned formula (I) as a photoinitiator, and

[0017] - a photocurable component selected from at least one of monomers, oligomers and prepolymers having ethylenically unsaturated functions,

[0018] Wherein, the mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100.

[0019] In a fourth aspect, the present invention provides the use of the aromatic formyl formic acid oxime ester compound represented by the aforementioned formula (I) as a photoinitiator in an LED photocuring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The process of initiating polymerization using an aromatic formyl formic acid oxime ester compound as a photoinitiator according to the present invention is schematically shown;

[0021] Figure 2 The ultraviolet absorption spectra of cinnamaldehyde oxime benzoylformate (CAOXE), p-fluorobenzoylformate cinnamaldehyde oxime (F-CAOXE), p-chlorobenzoylformate cinnamaldehyde oxime (Cl-CAOXE) and p-methoxybenzoylformate cinnamaldehyde oxime (O-CAOXE) synthesized according to Examples 1 to 4 are shown in the range of 200nm to 450nm, wherein the small figure in the upper right corner is a partial screenshot of the ultraviolet absorption spectrum in the range of 380nm to 420nm;

[0022] Figure 3 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercially available photoinitiator OXE-01 under a 385 nm LED light source to initiate the polymerization of the monomer tripropylene glycol diacrylate;

[0023] Figure 4 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercially available photoinitiator OXE-01 under a 405 nm LED light source to initiate the polymerization of the monomer tripropylene glycol diacrylate;

[0024] Figure 5 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercial photoinitiator OXE-01 initiating the polymerization of the monomer trimethylolpropane triacrylate under a 405 nm LED light source are shown;

[0025] Figure 6 A comparison chart showing the deep polymerization of tripropylene glycol diacrylate initiated by the photoinitiator F-CAOXE synthesized according to Example 2 and the commercially available photoinitiator OXE-01;

[0026] Fig. 7A and 7B The UV absorption spectra of the photoinitiators CAOXE and F-CAOXE synthesized according to Examples 1 and 2 and the commercially available photoinitiator OXE-01 in the migration test are shown. DETAILED DESCRIPTION

[0027] Herein, "halogen" refers to fluorine, chlorine, bromine and iodine. In the present invention, halogen is preferably fluorine, chlorine, bromine or a combination thereof, particularly preferably fluorine or chlorine.

[0028] In this document, the prefix “C n -C m -" in each case means that the defined group contains n to m carbon atoms, where n and m are the numbers specifically mentioned. For example, "C1-C 16 -" indicates that the defined group has 1 to 16 carbon atoms. In the case where the defined group has a substituent, the number of carbon atoms "C n -C m The "-" does not include the carbon atoms contained in the substituent.

[0029] In this article, “C1-C 16 "-alkyl" refers to a straight or branched chain alkyl group having 1 to 16 carbon atoms, such as C1-C12 -alkyl, preferably C1-C8-alkyl, more preferably C1-C6-alkyl, and especially preferably C1-C4-alkyl. More specific examples include, but are not limited to, methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 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 and their isomers. “C1-C 16 "-alkyl" is preferably C1-C6-alkyl, more preferably C1-C4-alkyl, for example methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl.

[0030] In this article, “C6-C 10 "-aryl" refers to a monocyclic or bicyclic aromatic hydrocarbon group containing 6 to 10 carbon atoms, such as phenyl, tolyl, ethylphenyl, propylphenyl, butylphenyl, xylyl, methylethylphenyl, diethylphenyl, methylpropylphenyl, naphthyl and isomers thereof. "C6-C 10 The "aryl" is preferably phenyl or naphthyl, more preferably phenyl.

[0031] In this article, “C3-C 10 "-Cycloalkyl" refers to a saturated alicyclic group having 3 to 10 carbon atoms, preferably having a monocyclic structure, such as C3-C6-cycloalkyl, more specifically cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl and isomers thereof, etc.

[0032] In this article, “C3-C 10 -cycloalkyl-C1-C 16 -alkyl" means C3-C 10 -cycloalkyl substituted C1-C 16 -alkyl, wherein the alkyl group is connected to the rest of the compound through the alkyl structure. 10 -cycloalkyl" and "C1-C 16 -alkyl" have the meanings, preferred meanings and specific examples as described above. "C3-C 10 -cycloalkyl-C1-C 16"-alkyl" is preferably C3-C6-cycloalkyl-C1-C4-alkyl, and more specific examples include, but are not limited to, cyclopropylmethyl, cyclopropylethyl, cyclopropylpropyl, cyclopropylbutyl, cyclobutylmethyl, cyclobutylethyl, cyclobutylpropyl, cyclobutylbutyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylpropyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylpropyl, cyclohexylbutyl and isomers thereof.

[0033] In this article, “C1-C 16 -alkyl-C3-C 10 -cycloalkyl" means a C1-C 16 -alkyl-substituted-C3-C 10 -cycloalkyl, wherein the cycloalkyl structure is connected to the rest of the compound. 16 -alkyl" and "C3-C 10 -cycloalkyl" have the meanings, preferred meanings and specific examples as described above. "C1-C 16 -alkyl-C3-C 10 "-cycloalkyl" is preferably C1-C4-alkyl-C3-C6-cycloalkyl, and more specific examples include, but are not limited to, methylcyclopropyl, ethylcyclopropyl, propylcyclopropyl, butylcyclopropyl, methylcyclobutyl, ethylcyclobutyl, propylcyclobutyl, butylcyclobutyl, methylcyclopentyl, ethylcyclopentyl, propylcyclopentyl, butylcyclopentyl, methylcyclohexyl, ethylcyclohexyl, propylcyclohexyl, butylcyclohexyl and isomers thereof.

[0034] In this article, “C1-C 16 -alkoxy" and "C1-C 16 -alkylthio" refers to C1-C 16 - A group in which the hydrogen on any carbon atom of an alkane chain is replaced by an oxygen (-O-) or sulfur (-S-) atom and is thus connected to the rest of the compound through the oxygen or sulfur atom. These two groups can also be represented by "C1-C 16 -alkyl-O-" and "C1-C 16 -alkyl-S-". Here "C1-C 16 "Alkyl" has the meaning, preferred meaning and specific examples as described above. "C1-C 16 "-alkoxy" is preferably C1-C6 alkoxy, such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, 2-butoxy, tert-butoxy, pentyloxy, isopentyloxy, hexyloxy and isomers thereof. "C1-C6 alkoxy" is preferably C1-C6 alkoxy, such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, 2-butoxy, tert-butoxy, pentyloxy, isopentyloxy, hexyloxy and isomers thereof. 16 "-alkylthio" is preferably C1-C6-alkylthio and can be methylthio, ethylthio, propylthio, isopropylthio, n-butylthio, 2-butylthio, tert-butylthio, pentylthio, isopentylthio, hexylthio and isomers thereof, etc.

[0035] In this article, "single (C1-C 16 -alkyl)amino" refers to a C1-C 16 -alkyl substituted amino group. 16 -alkyl)amino" refers to amino groups with two C1-C 16 -alkyl-substituted amino groups, wherein the two C1-C 16 -alkyl substituents may be the same or different. 16 "-alkyl" has the meanings, preferred meanings and specific examples as described above.

[0036] In the following description of the present invention, unless otherwise expressly stated, the numerical values ​​in the present application can be regarded as being modified by the word "about". The inventors have reported the numerical values ​​in the examples as accurately as possible, although these numerical values ​​inevitably include certain errors.

[0037] In a first aspect, the present invention provides an aromatic formyl formate oxime ester compound having a structure shown in formula (I):

[0038]

[0039] in,

[0040] Ar1 and Ar2 are independently selected from C6-C 10 -aryl, or a C6-C 10 -Aryl: halogen, nitro, hydroxyl, thiol, amino, C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino is optionally substituted by at least one selected from halogen, nitro, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups;

[0041] R1 is selected from hydrogen, C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16-alkyl-C3-C 10 -cycloalkyl, the aforementioned C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group.

[0042] In formula (1), Ar1 and Ar2 are, independently of each other, phenyl or naphthyl, which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, nitro, hydroxyl, mercapto, C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio is optionally substituted with at least one selected from halogen, hydroxy, mercapto, amino and C6-C 10 - Group substitution of aryl groups.

[0043] Ar1 and Ar2, independently of one another, are in particular phenyl or naphthyl which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, hydroxy, mercapto, C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio, the aforementioned C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio optionally being substituted by at least one group selected from the group consisting of halogen, nitro, hydroxy, mercapto, amino and C6-C 10 - Group substitution of aryl groups.

[0044] Ar1 and Ar2, independently of each other, are preferably phenyl or phenyl substituted by at least one, preferably one, group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, wherein the aforementioned C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio are optionally substituted by at least one group selected from halogen, hydroxyl and mercapto.

[0045] In some embodiments, Ar1 and Ar2, independently of each other, are phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

[0046] Preferably, Ar1 is phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio; and / or Ar2 is phenyl.

[0047] For example, Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl or p-ethoxyphenyl, and / or Ar2 is phenyl.

[0048] In formula (1), R1 is selected from hydrogen, C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl, the aforementioned C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 12 -alkoxy, C1-C 12 -alkylthio, mono(C1-C 12 -alkyl)amino and di(C1-C 12 -alkyl)amino group.

[0049] In particular, R1 is selected from hydrogen, C1-C8-alkyl or C1-C8-alkyl substituted by at least one group selected from the group consisting of halogen, hydroxy, mercapto, C1-C6-alkoxy and C1-C6-alkylthio.

[0050] In some embodiments, R1 is hydrogen or C1-C6-alkyl. Preferably, R1 is hydrogen or C1-C4-alkyl, such as methyl or ethyl, preferably hydrogen.

[0051] In an exemplary embodiment according to the first aspect of the present invention, the aromatic oxime formate compound has a structure represented by the following formula (I):

[0052]

[0053] in,

[0054] Ar1 and Ar2, independently of one another, are phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and

[0055] R1 is hydrogen or C1-C6-alkyl.

[0056] In particular, in the aforementioned formula (I), Ar1 and Ar2, independently of each other, are phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and R1 is hydrogen or C1-C6-alkyl.

[0057] According to the aforementioned exemplary embodiment, the aromatic oxime formate compound more preferably has a structure represented by the following formula (I):

[0058]

[0059] Ar1 and Ar2, independently of one another, are phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio, and

[0060] R1 is hydrogen or C1-C4-alkyl.

[0061] According to the aforementioned exemplary embodiment, the aromatic oxime formate compound more preferably has a structure represented by the following formula (I):

[0062]

[0063] in,

[0064] Ar1 is phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio,

[0065] Ar2 is phenyl, and

[0066] R1 is hydrogen or C1-C4-alkyl.

[0067] According to the aforementioned exemplary embodiment, the aromatic formyl formic acid oxime ester compound particularly preferably has a structure represented by the following formula (I):

[0068]

[0069] Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl or p-ethoxyphenyl, Ar2 is phenyl, and R1 is hydrogen.

[0070] The compound of formula (I) has (Z) isomers and (E) isomers due to the presence of C=N and C=C double bonds, respectively. These isomers can be separated by conventional methods, but isomer mixtures can also be used as photoinitiators.

[0071] Herein, the structure shown in formula (I) is merely a description of the connection mode between the atoms and functional groups constituting the compound, and is not intended to indicate double bond isomeric forms, and any other isomeric forms that exist. Unless otherwise specified, the aromatic formyl formic acid oxime ester compound shown in formula (I) herein encompasses any one of the aforementioned double bond configurations and an isomeric mixture of both configurations.

[0072] In a second aspect, the present invention provides a method for preparing the aromatic formyl formic acid oxime ester compound represented by the aforementioned formula (I), the method comprising subjecting the aromatic formyl formic acid represented by the formula (II) to an esterification reaction with the oxime represented by the formula (III):

[0073]

[0074] Wherein, Ar1 in formula (II) and Ar2 and R1 in formula (III) have the same meanings as Ar1, Ar2 and R1 in formula (I), respectively.

[0075] The esterification reaction between the aromatic formylformic acid shown in formula (II) and the oxime shown in formula (III) can be carried out in a manner known in the art. Through the esterification reaction, the carboxyl group in formula (II) and the hydroxyl group in formula (III) are condensed to form an ester group, thereby obtaining a compound of formula (I). In the esterification reaction, the relative amount of the aromatic formylformic acid shown in formula (II) and the oxime shown in formula (III) is not particularly limited, for example, the two are used in the following molar ratio: 1:1.5 to 1.5:1, preferably 1:1.2 to 1.2:1, for example 1:1.

[0076] The esterification reaction between the aromatic formyl formic acid shown in formula (II) and the oxime shown in formula (III) is usually carried out in the presence of a base. The base is, for example, an organic base, particularly a nitrogenous organic base. As the limiting examples of the base, at least one selected from the group consisting of pyridine, alkyl-substituted pyridines such as 2-picoline, 3-picoline and 4-dimethylaminopyridine, dialkylamines such as diethylamine, and trialkylamines such as triethylamine can be mentioned.

[0077] Preferably, the base is selected from at least one of the group consisting of pyridine, 2-methylpyridine, 3-methylpyridine, 4-dimethylaminopyridine, diethylamine and triethylamine, more preferably selected from at least one of the group consisting of pyridine, 2-methylpyridine, 3-methylpyridine and 4-dimethylaminopyridine.

[0078] The base is usually used in a catalytic amount. Although the base can also be used in an equimolar amount, in excess or in a solvent amount, it is preferably used in a catalytic amount. The catalytic amount can be determined with reference to the examples given below, based on common knowledge in the art or by routine preliminary experiments. For example, the base and the aromatic formyl formic acid shown in formula (II) are used in the following molar ratio: 0.01:1 to 0.5:1, preferably 0.05:1 to 0.2:1, more preferably 0.1:1.

[0079] The esterification reaction between the aromatic formylformic acid represented by formula (II) and the oxime represented by formula (III) can be carried out under the operation of removing water. This can be carried out, for example, by distillation / condensation.

[0080] Preferably, the esterification reaction can be carried out under a dehydrating agent. The selection of the dehydrating agent is not particularly limited, and an organic dehydrating agent is preferably used. As non-limiting examples of the dehydrating agent, at least one selected from the group consisting of dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide and 1,1'-carbonylbis-1H-imidazole can be mentioned.

[0081] The dehydrating agent can be used in a conventional amount, for example, in an equimolar amount to the reactant, preferably in an appropriate excess amount. For example, the dehydrating agent and the aromatic formylformic acid represented by formula (II) are used in the following molar ratio: 1.5:1 to 1:1, preferably 1.2:1 to 1:1, more preferably 1.2:1.

[0082] The esterification reaction between the aromatic formyl formic acid represented by formula (II) and the oxime represented by formula (III) is usually carried out in a solvent, preferably in an organic solvent. The choice of solvent is not particularly limited, for example, at least one of tetrahydrofuran, benzene, toluene, ethyl acetate, N,N-dimethylformamide, dichloromethane and acetone can be used.

[0083] The esterification reaction can be carried out in a very wide temperature range. According to the present invention, it is advantageous that the esterification reaction is carried out at a temperature of -10°C to 150°C, preferably 0°C to 100°C, preferably at room temperature.

[0084] After the esterification reaction is completed, a product mixture containing the compound of formula (I) is obtained. The product mixture can be post-treated by any separation and purification means known in the art, for example, filtration, drying, distillation, recrystallization, chromatography, etc.

[0085] The reactants of the aforementioned esterification reaction, ie, the aromatic carboxylic acid represented by formula (II) and the oxime represented by formula (III), can be synthesized by methods known in the art or obtained commercially without particular limitation.

[0086] In some embodiments of the method of the present invention, the aromatic formic acid shown in formula (II) is prepared, for example, by Friedel-Crafts acylation, comprising: subjecting the aromatic hydrocarbon Ar1-H corresponding to the group Ar1 in formula (II) to Friedel-Crafts acylation with chloroformyl formate in the presence of a Lewis acid (such as aluminum chloride) to obtain aromatic formate, followed by hydrolysis to obtain the corresponding aromatic formic acid. The chloroformyl formate is used as an acylating agent, for example, methyl chloroformyl formate (i.e., monomethyl oxalyl chloride) or ethyl chloroformyl formate (i.e., monoethyl oxalyl chloride). There is no particular limitation on the relative amounts of the aromatic hydrocarbon Ar1-H and the chloroformyl formate, for example, the two are used in the following molar ratio: 1:1.5 to 1.5:1, preferably 1:1.2 to 1.2:1, for example 1:1. The Lewis acid can be used in conventional amounts, for example, in an equimolar amount or an appropriate excess amount compared to the reactants. More specifically, the Lewis acid and methyl chloroformylformate are used in a molar ratio of 2.5:1 to 1:1, preferably 2:1 to 1.3:1, and more preferably 1.5:1.

[0087] The Friedel-Crafts acylation reaction can be carried out in a solvent known in the art without particular limitation. After the Friedel-Crafts acylation reaction, the arylformic acid of formula (II) is obtained by hydrolyzing the arylformic acid ester. The hydrolysis can be carried out in a manner known in the art, for example, by hydrolysis in the presence of a base to obtain the corresponding salt, and then acidifying to obtain the arylformic acid.

[0088] In some embodiments of the method of the present invention, the oxime represented by formula (III) is prepared, for example, by an oximation reaction of a ketone or aldehyde represented by the following formula (IV) with an oximation agent selected from hydroxylamine hydrochloride, hydroxylamine or a mixture thereof:

[0089]

[0090] wherein R1 and Ar2 have the same meanings as in formula (III).

[0091] The oximation reaction is usually carried out in an organic solvent, preferably in an organic polar solvent. The solvent that can be used is, for example, tetrahydrofuran or aqueous tetrahydrofuran. In order to promote the oximation reaction to be complete, a salt or base such as sodium acetate, potassium acetate, pyridine, piperidine, triethylamine, etc. can be added. The oximation reaction can be carried out at room temperature or under heating. There is no particular restriction on the relative amount of the aldehyde or ketone and the oximation agent, for example, the two are used in the following molar ratio: 1:2.5 to 1:1.1, preferably 1:2 to 1:1.3, for example 1:1.5. If the salt or base is used, it is used with the oximation agent in the following molar ratio: 3:1 to 1:0.5, preferably 2:1 to 1:1, for example 2:1.5.

[0092] The aldehyde or ketone represented by formula (IV) is commercially available or can be prepared according to a known conventional method.

[0093] The aromatic formyl formic acid oxime ester compound represented by formula (I) according to the present invention has appropriate weak absorption in the near-ultraviolet to visible light radiation range, for example, 350 to 440 nm, especially in the wavelength range of 365 to 420 nm, so that it can effectively photolyze to generate active free radicals that initiate polymerization and / or crosslinking, but will not bring color to the curing system. Therefore, it can be used as a photoinitiator in a photocuring system that requires colorlessness and a photocuring system that requires deep curing.

[0094] Without being bound by any theory, the inventors of the present invention speculate that the aromatic formyl formate oxime ester compound shown in formula (I) is irradiated with an LED light source to attach Figure 1 Specifically, Figure 1 As shown, under the irradiation of LED light source, the compound first undergoes nitrogen-oxygen bond cleavage at the oxime ester structure to generate one molecule of aromatic formyloxy free radical and one molecule of imine free radical, and then the benzoyl formyloxy free radical cleaves one molecule of carbon dioxide to generate one molecule of benzoyl free radical. This free radical acts as the leading active free radical to initiate polymerization reaction and / or cross-linking reaction in the curing system.

[0095] Therefore, in a third aspect, the present invention provides a composition for LED light curing, the composition comprising:

[0096] - at least one aromatic oxime ester compound represented by the aforementioned formula (I) as a photoinitiator, and

[0097] - a photocurable component selected from at least one of monomers, oligomers and prepolymers having ethylenically unsaturated functions,

[0098] Wherein, the mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100.

[0099] In some embodiments, the photoinitiator and the photocurable component are present in the composition for LED photocuring in a mass ratio ranging from 0.5:100 to 5:100, especially from 1:100 to 3:100.

[0100] The monomer having ethylenically unsaturated functions suitable for use as the photocurable component of the present invention is not particularly limited, and may be, for example, a monofunctional or polyfunctional ethylenically unsaturated compound.

[0101] Examples of suitable monofunctional ethylenically unsaturated compounds include, but are not limited to: (meth)acrylic acid and its salts; (meth)acrylates, for example, alkyl esters such as methyl, ethyl, 2-chloroethyl, N,N-dimethylaminoethyl, n-butyl, isobutyl, pentyl, hexyl esters, hydroxyalkyl esters such as 2-hydroxyethyl, 2-hydroxypropyl, 4-hydroxybutyl esters, epoxyalkyl esters such as glycidyl, 2,3-epoxybutyl, 3,4-epoxybutyl, 2,3-epoxycyclohexyl, 10,11-epoxyundecyl esters (meth)acrylamide, N-substituted (meth)acrylamide, for example N-methylol acrylamide, N-hydroxymethyl methacrylamide, N-ethyl acrylamide, N-ethyl methacrylamide, N-hexyl acrylamide, N-hexyl methacrylamide, N-cyclohexyl acrylamide, N-cyclohexyl methacrylamide, N-hydroxyethyl acrylamide, N-phenyl acrylamide, N-phenyl methacrylamide, N-benzyl acrylamide, N-benzyl methacrylamide, N-nitrophenyl a ... phenylmethacrylamide, N-ethyl-N-phenylacrylamide, N-ethyl-N-phenylmethacrylamide, N-(4-hydroxyphenyl)acrylamide and N-(4-hydroxyphenyl)methacrylamide; (meth)acrylonitrile; anhydrides and esters of unsaturated carboxylic acids other than (meth)acrylic acid, such as itaconic anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, 2-chloromaleic anhydride, maleic esters; styrene and substituted styrenes, such as methylstyrene, chloromethylstyrene and o-, m- and p-hydroxystyrene acetate vinyl ethers and vinyl halides, such as isobutyl vinyl ether, ethyl vinyl ether, 2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, octyl vinyl ether and phenyl vinyl ether, vinyl chloride and vinylidene chloride; vinyl and allyl esters of carboxylic acids, such as vinyl acetate, vinyl acrylate, vinyl chloroacetate, vinyl butyrate and vinyl benzoate, divinyl succinate, diallyl phthalate, triallyl phosphate.

[0102] Examples of suitable multifunctional ethylenically unsaturated compounds include, but are not limited to, di(meth)acrylates such as 1,6-hexanediol diacrylate (HDDA), ethylene glycol diacrylate, propylene glycol diacrylate, glycerol diacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, glycerol dimethacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate, hexamethylene glycol diacrylate, bisphenol A diacrylate, dipentaerythritol diacrylate, pentaerythritol dimethacrylate, dipentaerythritol di ... tri(meth)acrylates, such as glycerol triacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, glycerol trimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol triacrylate, sorbitol triacrylate; tetra(meth)acrylates, such as pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate; penta(meth)acrylates, such as dipentaerythritol pentaacrylate, dipentaerythritol tetramethacrylate.

[0103] The present invention also has no particular restrictions on prepolymers or oligomers with ethylenically unsaturated functions suitable for use as photocurable components, such as epoxy (meth) acrylic resins, polyurethane (meth) acrylic resins, polyester (meth) acrylic resins, polyether (meth) acrylic resins, and acrylated poly (meth) acrylic resins.

[0104] The composition for LED light curing 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, methylene chloride, ethyl chloride, ketones such as acetone, butanone, pentanone, alcohols such as methanol, ethanol, propanol, isopropanol, ethylene glycol, and glycol ethers, glycol ether acetates, propylene glycol ethers, propylene glycol ether acetates, etc. may be mentioned.

[0105] The composition for LED light curing of the present invention may optionally further comprise other additives, such as a leveling agent, an antioxidant, an anti-settling agent, a colorant, a microbicide, such as an antibacterial agent, and a heat preservation material additive.

[0106] It should be understood that the composition for LED light curing of the present invention may be a mixture of components; the composition for LED light curing of the present invention may also be in the form of a component package, that is, one or more components are stored separately from one or more other components and are not formulated together to form a curing system until application.

[0107] In a fourth aspect, the present invention provides the use of the aromatic formyl formic acid oxime ester compound represented by the aforementioned formula (I) as a photoinitiator in an LED photocuring system.

[0108] In particular, the present invention provides the use of the aromatic formyl formic acid oxime ester compound represented by the aforementioned formula (I) in a LED light curing system requiring colorlessness and a LED light curing system requiring deep curing.

[0109] Specifically, the present invention includes but is not limited to the following technical solutions:

[0110] 1. An aromatic formyl formic acid oxime ester compound having a structure shown in formula (I):

[0111]

[0112] in,

[0113] Ar1 and Ar2 are independently selected from C6-C 10 -aryl, or a C6-C 10 -Aryl: halogen, nitro, hydroxyl, thiol, amino, C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino is optionally substituted by at least one selected from halogen, nitro, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups;

[0114] R1 is selected from hydrogen, C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -cycloalkyl, the aforementioned C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C10 -cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group.

[0115] 2. The aromatic carboxylic acid oxime ester compound according to embodiment 1, wherein in formula (I), Ar1 and Ar2 are independently phenyl or naphthyl which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, nitro, hydroxyl, mercapto, C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio is optionally substituted with at least one selected from halogen, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups;

[0116] In particular, Ar1 and Ar2 are independently phenyl or naphthyl which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio, wherein the aforementioned C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio are optionally substituted by at least one group selected from the group consisting of halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 - radical substitution of aryl groups;

[0117] Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted by at least one, preferably one, group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, wherein the aforementioned C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio are optionally substituted by at least one group selected from halogen, hydroxyl and mercapto;

[0118] More preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

[0119] 3. An aromatic oxime ester compound according to embodiment 1 or 2, wherein in formula (I), Ar1 is phenyl or phenyl substituted at the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

[0120] 4. The aromatic carboxylic acid oxime ester compound according to any one of embodiments 1 to 3, wherein in formula (I), Ar2 is phenyl.

[0121] 5. The aromatic carboxylic acid oxime ester compound according to any one of embodiments 1 to 4, wherein in formula (I), R1 is selected from hydrogen, C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl, the aforementioned C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 12 -alkoxy, C1-C 12 -alkylthio, mono(C1-C 12 -alkyl)amino and di(C1-C 12 -alkyl)amino group substitution;

[0122] In particular, R1 is selected from hydrogen, C1-C8-alkyl or C1-C8-alkyl substituted by at least one group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkoxy and C1-C6-alkylthio;

[0123] More particularly, R1 is hydrogen or C1-C6-alkyl.

[0124] 6. The aromatic carboxylic acid oxime ester compound according to embodiment 5, wherein in formula (I), R1 is hydrogen or C1-C4-alkyl such as methyl or ethyl.

[0125] 7. The aromatic carboxylic acid oxime ester compound according to embodiment 6, wherein in formula (I), R1 is hydrogen.

[0126] 8. The aromatic carboxylic acid oxime ester compound according to any one of the preceding embodiments 1 to 7, wherein in formula (I),

[0127] Ar1 and Ar2 are independently phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and

[0128] R1 is hydrogen or C1-C6-alkyl;

[0129] Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and R1 is hydrogen or C1-C6-alkyl.

[0130] 9. The aromatic carboxylic acid oxime ester compound according to embodiment 8, wherein in formula (I),

[0131] Ar1 and Ar2 are independently phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio, and

[0132] R1 is hydrogen or C1-C4-alkyl.

[0133] 10. The aromatic formyl formic acid oxime ester compound according to embodiment 9, wherein in formula (I),

[0134] Ar1 is phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio,

[0135] Ar2 is phenyl, and

[0136] R1 is hydrogen or C1-C4-alkyl.

[0137] 11. The arylformic acid oxime ester compound according to the aforementioned embodiment 10, wherein in formula (I), Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl or p-ethoxyphenyl, Ar2 is phenyl, and R1 is hydrogen.

[0138] 12. A method for preparing an aromatic formylformic acid oxime ester compound according to any one of embodiments 1 to 11, the method comprising subjecting an aromatic formylformic acid represented by formula (II) to an esterification reaction with an oxime represented by formula (III):

[0139]

[0140] Wherein, Ar1 in formula (II) and R1 and Ar2 in formula (III) have the same meanings as Ar1, R1 and Ar2 in formula (I), respectively.

[0141] 13. A composition for LED light curing, comprising:

[0142] at least one arylformylformic acid oxime ester compound according to any one of embodiments 1 to 11 as a photoinitiator, and

[0143] - a photocurable component selected from at least one of monomers, oligomers and prepolymers having ethylenically unsaturated functions,

[0144] The mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100, preferably in the range of 0.5:100 to 5:100, and especially in the range of 1:100 to 3:100.

[0145] 14. A composition according to embodiment 13, wherein the monomer is selected from at least one of the following groups: monofunctional ethylenically unsaturated compounds, such as (meth)acrylic acid and its salts, (meth)acrylates, (meth)acrylamide, N-substituted (meth)acrylamide, (meth)acrylonitrile, anhydrides and esters of unsaturated carboxylic acids other than (meth)acrylic acid, styrene and substituted styrenes, vinyl ethers and halogenated vinyls, vinyl and allyl esters of carboxylic acids; and polyfunctional ethylenically unsaturated compounds, such as (meth)acrylic acid type monomers such as di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates and penta(meth)acrylates.

[0146] 15. The composition according to embodiment 13, wherein the prepolymer or oligomer is selected from at least one of the following groups: epoxy (meth) acrylic resin, polyurethane (meth) acrylic resin, polyester (meth) acrylic resin, polyether (meth) acrylic resin and acrylated poly (meth) acrylic resin.

[0147] 16. Use of the aromatic formylformic acid oxime ester compound according to any one of embodiments 1 to 11 as a photoinitiator in an LED photocuring system, especially in a colorless LED photocuring system and a deep-layer curing LED photocuring system.

[0148] Example

[0149] The technical scheme of the present invention will be further described in detail below by way of example. It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the examples, the techniques or conditions or product specifications described in the literature in the art are followed.

[0150] Example 1: Synthesis of a photoinitiator CAOXE (benzoylformic acid cinnamaldehyde oxime ester) having the following structure:

[0151]

[0152] 1.1 Synthesis of cinnamaldehyde oxime

[0153] Cinnamaldehyde (1.32g, 10mmol), hydroxylamine hydrochloride (1.05g, 15mmol) and sodium acetate (1.64g, 20mmol) were added to a 100mL single-necked flask, and 30mL tetrahydrofuran was added. The reaction was carried out at room temperature for 5h. The tetrahydrofuran was removed by distillation under reduced pressure, and 30mL dichloromethane was added to the obtained product, and the product was washed three times with 30mL deionized water each time. The obtained organic phase was dried over anhydrous sodium sulfate, and dichloromethane was removed by distillation under reduced pressure to obtain cinnamaldehyde oxime.

[0154] 1.2 Synthesis of benzoylformic acid cinnamaldehyde oxime

[0155] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), benzoylformic acid (1.50 g, 10 mmol) and 4-dimethylaminopyridine (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added as a solvent. Cinnamaldehyde oxime (1.47 g, 10 mmol) was dissolved in 10 mL of dichloromethane, slowly added dropwise to the single-necked flask, stirred at 25 ° C until the addition was completed, and then filtered to remove the white precipitate, and the solvent was removed by reduced pressure distillation to obtain a crude product. Then, the crude product was dissolved in dichloromethane and purified by silica gel column chromatography, and the eluent was a 1:15 mixture of ethyl acetate and petroleum ether. The effluent was distilled under reduced pressure to obtain the final product CAOXE.

[0156] The proton spectrum data of CAOXE are: 1 H NMR (400 MHz, CHLOROFORM-d) δ 8.31 (d, J = 9.8 Hz, 1H), 8.15–8.03 (m, 2H), 7.76–7.66 (m, 1H), 7.62–7.55 (m, 2H), 7.53–7.49 (m, 2H), 7.42 (dd, J = 5.1, 2.1 Hz, 3H), 7.11 (d, J = 16.0 Hz, 1H), 6.98 (dd, J = 16.0, 9.8 Hz, 1H).

[0157] The carbon spectrum data of CAOXE is: 13 C NMR (101 MHz, chloroform-d) δ 185.50, 162.26, 159.37, 145.40, 135.27, 134.82, 132.38, 130.28, 130.05, 129.08, 129.04, 127.64, 119.13. Example 2: Synthesis of a photoinitiator F-CAOXE (p-fluorobenzoylformic acid cinnamaldehyde oxime ester) having the following structure:

[0158]

[0159] 2.1 Synthesis of p-fluorobenzoylformic acid

[0160] Monomethyl oxalyl chloride (1.22g, 10mmol) and aluminum chloride (1.99g, 15mmol) were added to a 100mL single-mouth flask, and 30mL of dichloromethane was added as a solvent. Fluorobenzene (0.96g, 10mmol) dissolved in 30mL of dichloromethane was slowly added dropwise to the aforementioned 100mL single-mouth flask using a dropping funnel, and stirred at 5°C until the addition was completed. After the addition was completed, the reaction was carried out for 5h, and then the solvent was removed by distillation under reduced pressure to obtain methyl parafluorobenzoylformate. 30mL of methanol and potassium hydroxide (1.12g, 20mmol) were added to the obtained methyl parafluorobenzoylformate, and the reaction was carried out for 3h. The reaction system was distilled under reduced pressure to remove the solvent, 30mL of deionized water was added, and the mixture was washed with 30mL of dichloromethane for three times. An appropriate amount of dilute hydrochloric acid was added to the obtained aqueous phase until the pH value was about 3, and then extracted with 30mL of dichloromethane for three times. The combined organic phases were dried over anhydrous sodium sulfate, and dichloromethane was removed by distillation under reduced pressure to obtain p-fluorobenzoylformic acid.

[0161] 1 H NMR (400 MHz, CHLOROFORM-d) δ 9.03 (s, 1H), 8.55–8.43 (m, 2H), 7.28–7.20 (m, 2H).

[0162] 13 C NMR (101 MHz, chloroform-d) δ 182.45, 168.70, 166.11, 160.77, 134.65, 134.55, 128.19, 116.56.

[0163] 2.2 Synthesis of 4-fluorobenzoylformic acid cinnamaldehyde oxime ester

[0164] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), p-fluorobenzoylformic acid (1.68 g, 10 mmol) and 4-dimethylaminopyridine (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added as a solvent. Cinnamaldehyde oxime (1.47 g, 10 mmol) prepared as described in Example 1 was dissolved in 10 mL of dichloromethane and slowly added dropwise to the single-necked flask, stirred at 25 ° C until the addition was completed, filtered to remove the white precipitate, and the solvent was removed by reduced pressure distillation to obtain a crude product. Then, the crude product was dissolved in dichloromethane and purified by silica gel column chromatography, and the eluent was a 1:16 mixture of ethyl acetate and petroleum ether. The effluent was distilled under reduced pressure to obtain the final product F-CAOXE.

[0165] The hydrogen spectrum data of F-CAOXE is: 1H NMR (400 MHz, CHLOROFORM-d) δ 8.32 (d, J = 9.8 Hz, 1H), 8.20–8.09 (m, 2H), 7.57–7.48 (m, 2H), 7.42 (dd, J = 5.1, 2.0 Hz, 3H), 7.27–7.19 (m, 2H), 7.11 (d, J = 16.1 Hz, 1H), 6.97 (dd, J = 16.0, 9.9 Hz, 1H).

[0166] The carbon spectrum data of F-CAOXE is: 13 C NMR (101 MHz, chloroform-d) δ 183.60, 168.31, 165.73, 159.47, 145.50, 134.80, 133.06, 132.96, 130.32, 129.05, 128.97, 127.65, 119.10, 116.60, 116.38.

[0167] Example 3: Synthesis of a photoinitiator having the following structure: Cl-CAOXE (p-chlorobenzoylformyl cinnamaldehyde oxime ester)

[0168]

[0169] 3.1 Synthesis of p-chlorobenzoylformic acid

[0170] Add methyl oxalyl chloride (1.22g, 10mmol) and aluminum chloride (1.99g, 15mmol) to a 100mL single-mouth flask, and add 30mL of dichloromethane as a solvent. Use a dropping funnel to slowly drop chlorobenzene (1.12g, 10mmol) dissolved in 30mL of dichloromethane into the aforementioned 100mL single-mouth flask, and stir at 5°C until the addition is completed. After the addition is completed, react for 5h, and then remove the solvent by vacuum distillation to obtain methyl p-chlorobenzoylformate. Add 30mL of methanol and potassium hydroxide (1.12g, 20mmol) to the obtained methyl p-chlorobenzoylformate and react for 3h. The reaction system is vacuum distilled to remove the solvent, 30mL of deionized water is added, and washed with 30mL of dichloromethane for three times. Add an appropriate amount of dilute hydrochloric acid to the obtained aqueous phase until the pH value is about 3, and then extract with 30mL of dichloromethane for three times. The combined organic phases were dried over anhydrous sodium sulfate, and dichloromethane was removed by distillation under reduced pressure to obtain p-chlorobenzoylformic acid.

[0171] 1 H NMR (400 MHz, CHLOROFORM-d) δ 8.44 (s, 1H), 8.38–8.32 (m, 2H), 7.57–7.50 (m, 2H).

[0172] 13C NMR (101 MHz, chloroform-d) δ 182.96, 160.89, 142.77, 132.79, 130.02, 129.47. 3.2 Synthesis of p-Chlorobenzoylformic acid cinnamaldehyde oxime

[0173] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), p-chlorobenzoylformic acid (1.84 g, 10 mmol) and 4-dimethylaminopyridine (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added as a solvent. Cinnamaldehyde oxime (1.47 g, 10 mmol) prepared as described in Example 1 was dissolved in 10 mL of dichloromethane and slowly added dropwise to the single-necked flask, stirred at 25 ° C until the addition was completed, filtered to remove the white precipitate, and the solvent was removed by vacuum distillation to obtain a crude product. The crude product was dissolved in dichloromethane and purified by silica gel column chromatography, and the eluent was a 1:16 mixture of ethyl acetate and petroleum ether. The effluent was vacuum distilled to obtain the final product Cl-CAOXE.

[0174] The hydrogen spectrum data of Cl-CAOXE is: 1 H NMR (400MHz, chloroform-d) δ8.31(d,J=9.9Hz,1H),8.10–7.97(m,2H),7.54(dd,J=9.1,2.4Hz,2H),7.52 –7.46(m,2H),7.41(dd,J=5.1,2.0Hz,3H),7.11(d,J=16.0Hz,1H),6.96(dd,J=16.0,9.9Hz,1H).

[0175] The carbon spectrum data of Cl-CAOXE is: 13 C NMR (101 MHz, chloroform-d) δ 184.01, 159.50, 145.57, 142.03, 134.78, 132.03, 131.42, 130.83, 130.34, 129.51, 129.05, 127.66, 119.05.

[0176] Example 4: Synthesis of a photoinitiator having the following structure: O-CAOXE (p-methoxybenzoylformic acid cinnamaldehyde oxime ester)

[0177]

[0178] 4.1 Synthesis of p-Anisylformic acid

[0179] Monomethyl oxalyl chloride (1.22g, 10mmol) and aluminum chloride (1.99g, 15mmol) were added to a 100mL single-mouth flask, and 30mL of dichloromethane was added as a solvent. Anisole (1.08g, 10mmol) dissolved in 30mL of dichloromethane was slowly added dropwise to the 100mL single-mouth flask using a dropping funnel, and stirred at 5°C until the addition was completed. After the addition was completed, the reaction was continued for 5h, and then the solvent was removed by distillation under reduced pressure to obtain methyl p-methoxybenzoylformate. 30mL of methanol and potassium hydroxide (1.12g, 20mmol) were added to the obtained methyl p-methoxybenzoylformate, and the reaction was continued for 3h. The reaction system was distilled under reduced pressure to remove the solvent, 30mL of deionized water was added, and the mixture was washed with 30mL of dichloromethane for three times. An appropriate amount of dilute hydrochloric acid was added to the obtained aqueous phase until the pH value was about 3, and then extracted with 30mL of dichloromethane for three times. The combined organic phases were dried over anhydrous sodium sulfate, and dichloromethane was removed by distillation under reduced pressure to obtain p-methoxybenzoylformic acid.

[0180] 1 H NMR (400 MHz, CHLOROFORM-d) δ 9.20 (s, 1H), 8.59–8.36 (m, 2H), 7.10–6.92 (m, 2H), 3.94 (s, 3H).

[0181] 13 C NMR (101 MHz, chloroform-d) δ 182.73, 165.72, 162.96, 134.06, 124.75, 114.41, 55.74.

[0182] 4.2 Synthesis of p-Anisylbenzoylformic acid cinnamaldehyde oxime

[0183] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), p-methoxybenzoylformic acid (1.80 g, 10 mmol) and 4-dimethylaminopyridine (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added as a solvent. Cinnamaldehyde oxime (1.47 g, 10 mmol) prepared as described in Example 1 was dissolved in 10 mL of dichloromethane, slowly added dropwise to the single-necked flask, stirred at 25 ° C until the addition was completed, filtered to remove the white precipitate, and the solvent was removed by reduced pressure distillation to obtain a crude product. Then, the crude product was dissolved in dichloromethane and purified by silica gel column chromatography, and the eluent was a 1:12 mixture of ethyl acetate and petroleum ether. The effluent was distilled under reduced pressure to obtain the final product O-CAOXE.

[0184] The hydrogen spectrum data of O-CAOXE is: 1H NMR (400 MHz, CHLOROFORM-d) δ 8.31 (d, J = 9.7 Hz, 1H), 8.11–8.03 (m, 2H), 7.54–7.47 (m, 2H), 7.45–7.37 (m, 3H), 7.10 (d, J = 16.1 Hz, 1H), 7.04–6.94 (m, 3H), 3.93 (s, 3H).

[0185] The carbon spectrum data of O-CAOXE is: 13 C NMR (101 MHz, chloroform-d) δ 183.71, 165.31, 159.26, 145.16, 134.88, 132.67, 130.22, 129.03, 127.61, 125.48, 119.32, 114.43, 55.72.

[0186] Example 5: Light absorption characterization

[0187] Prepare 50 mL of anhydrous acetonitrile solution of the photoinitiators synthesized in Examples 1 to 4 (i.e., CAOXE, F-CAOXE, Cl-CAOXE, and O-CAOXE) at a concentration of 1×10 -4 mol / L. The absorption curves of the four solutions in the wavelength range of 200 to 500 nm, namely, the UV-visible absorption spectra, were tested using an ultraviolet spectrophotometer (Shimadzu Corporation, Japan, model UV-3600).

[0188] The UV-visible absorption spectra of the four photoinitiators CAOXE, Cl-CAOXE, F-CAOXE and O-CAOXE are shown in Figure 2. Figure 2 As shown. Figure 2 From the partial screenshot within the wavelength range of 380nm to 420nm, it can be seen that these four photoinitiators have certain weak absorption at around 400nm. This weak absorption ability not only enables the initiator to initiate at the LED emission wavelength, but also facilitates its application in curing systems that require colorless and deep polymerization.

[0189] Example 6: Photopolymerization Test

[0190] The photoinitiators synthesized in Examples 1 to 4 were applied to an acrylate polymerization system to test the performance of these photoinitiators in LED photopolymerization.

[0191] 6.1 Preparation of photosensitive solution

[0192] Prepare a photosensitive solution using acrylate monomers and photoinitiators as follows:

[0193] The photoinitiator and tripropylene glycol diacrylate were mixed at a mass ratio of 1:100 and stirred evenly to prepare a photosensitive solution (A).

[0194] The photoinitiator and trimethylolpropane triacrylate were mixed at a mass ratio of 1:100 and stirred evenly to prepare a photosensitive solution (B).

[0195] 6.2 Performance test of photopolymerization initiation

[0196] The prepared photosensitive liquid (A) or (B) was evenly applied on the potassium bromide salt sheet, and the coating thickness was about 30 μm. Then the potassium bromide salt sheet was covered on the coating. A real-time infrared spectrometer (Thermo Fisher Scientific, USA, model Nicolet 5700) was used to detect the photosensitive liquid under the LED light source (Shenzhen Lanpulic Technology Co., Ltd., model UVEC-4II, light intensity 80 mW / cm 2 ) under irradiation.

[0197] The photopolymerization test results are as follows Figure 3 , Figure 4 and Figure 5 shown.

[0198] Figure 3 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercially available photoinitiator OXE-01 (a photoinitiator purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.) under a 385 nm LED light source to initiate the polymerization of the monomer tripropylene glycol diacrylate;

[0199] Figure 4 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercially available photoinitiator OXE-01 under a 405 nm LED light source to initiate the polymerization of the monomer tripropylene glycol diacrylate;

[0200] Figure 5 The photopolymerization kinetics of the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4 and the commercially available photoinitiator OXE-01 under a 405 nm LED light source to initiate the polymerization of the monomer trimethylolpropane triacrylate are shown;

[0201] Depend on Figures 3 to 5 It can be seen that the photoinitiator of the present invention can effectively initiate polymerization of acrylate monomers under the irradiation of 385nm and 405nm LED light sources, which shows that the photoinitiator of the present invention has good initiation performance and applicability under the LED photopolymerization system.

[0202] Example 7: Deep photopolymerization test

[0203] The F-CAOXE synthesized in Example 2 and the commercially available photoinitiator OXE-01 were respectively applied to an acrylate polymerization system to test the performance of these photoinitiators in initiating deep polymerization under the irradiation of an LED light source.

[0204] The two aforementioned photoinitiators were mixed with tripropylene glycol diacrylate monomer at a mass ratio of 1:100 respectively, and stirred evenly to prepare a photosensitive solution.

[0205] The photosensitive liquid was injected into a glass tube with a depth of 7.5 cm and a diameter of 0.7 cm. A 405 nm LED light source was used to illuminate the bottom of the tube, and the distance from the light source to the bottom of the glass tube was 4 cm. After irradiation for 60 seconds and 100 seconds, the depth of the polymerized polytripropylene glycol diacrylate in the test tube was measured. The test results are shown in the attached figure. Figure 6 shown.

[0206] Under the aforementioned conditions, the polymerization depths of the photosensitive composition using the photoinitiator F-CAXOE of the present invention after irradiation for 60s and 100s were 3.2cm and 6.35cm, respectively. Under the same conditions, the polymerization depths of the photosensitive composition using the commercially available photoinitiator OXE-01 were only 0.5cm and 3cm. This indicates that the photoinitiator of the present invention has a significantly improved ability to initiate deep polymerization under the LED photopolymerization system.

[0207] Example 8: Mobility Characterization

[0208] The CAOXE and F-CAOXE synthesized in Examples 1 and 2 and the commercially available photoinitiator OXE-01 were respectively applied to an acrylate polymerization system to test the mobility of these photoinitiators in the curing system.

[0209] The three photoinitiators were mixed with tripropylene glycol diacrylate monomer at a mass ratio of 10 mg:1000 mg, and stirred evenly to prepare a photosensitive solution. The photosensitive solution was injected into a 30 mm × 4 mm × 2 mm (length × width × thickness) silicone mold and illuminated with a 405 nm LED light source (Shenzhen Lanpulik Technology Co., Ltd., model UVEC-4II, light intensity 80 mW / cm 2 ) for 5 min to completely cure the photosensitive solution. The obtained cured film was soaked in 50 mL of anhydrous acetonitrile for 12 h to obtain a cured film soaking solution. The ultraviolet absorption of the three soaking solutions in the wavelength range of 200 to 500 nm was tested using an ultraviolet spectrophotometer (Shimadzu Corporation, Japan, model UV-3600).

[0210] In addition, the three photoinitiators mentioned above were prepared into 1×10 -4The ultraviolet absorption of the three photoinitiator solutions in the wavelength range of 200 to 500 nm was tested using an ultraviolet spectrophotometer (Shimadzu Corporation, Japan, model UV-3600).

[0211] Fig. 7A and 7B The UV absorption spectra of the photoinitiator solution and the cured film immersion solution are shown respectively.

[0212] The concentration of the photoinitiator in the immersion solution was calculated according to the Beer-Lambert law, and then the mass of the migrated photoinitiator was calculated. The results are shown in Table 1 below.

[0213] Table 1

[0214]

[0215] It can be clearly determined from the results in Table 1 that the photoinitiators CAOXE and F-CAOXE according to the present invention have significantly reduced mobility and significantly improved anti-migration stability compared to the commercially available photoinitiator OXE-01.

[0216] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. Various process schemes that are not substantially different from the concept of the present invention are within the protection scope of the present invention.

Claims

1. An aromatic formyl formic acid oxime ester compound having a structure shown in formula (I): in, Ar1 and Ar2 are independently selected from C6-C 10 -aryl, or a C6-C 10 -Aryl: halogen, nitro, hydroxyl, thiol, amino, C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino is optionally substituted by at least one selected from halogen, nitro, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups; R1 is selected from hydrogen, C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -cycloalkyl, the aforementioned C1-C 16 -alkyl, C3-C 10 -cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 16 -alkoxy, C1-C 16 -alkylthio, mono(C1-C 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group.

2. The aromatic formyl formate oxime compound according to claim 1, wherein in formula (I), Ar1 and Ar2 are independently phenyl or naphthyl which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, nitro, hydroxyl, thiol, C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy and C1-C 12 -alkylthio is optionally substituted with at least one selected from halogen, hydroxy, mercapto, amino and C6-C 10 - radical substitution of aryl groups; In particular, Ar1 and Ar2 are independently phenyl or naphthyl which is unsubstituted or substituted by at least one group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio, wherein the aforementioned C1-C8-alkyl, C1-C8-alkoxy and C1-C8-alkylthio are optionally substituted by at least one group selected from the group consisting of halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 - radical substitution of aryl groups; Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted by at least one, preferably one, group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, wherein the aforementioned C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio are optionally substituted by at least one group selected from halogen, hydroxyl and mercapto; More preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

3. The aromatic oxime ester compound according to claim 1 or 2, wherein in formula (I), Ar1 is phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

4. The aromatic carboxylic acid oxime ester compound according to any one of claims 1 to 3, wherein in formula (I), Ar2 is a phenyl group.

5. The aromatic formyl formate oxime ester compound according to any one of claims 1 to 4, wherein in formula (I), R1 is selected from hydrogen, C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl, the aforementioned C1-C 12 -alkyl, C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C 12 -alkyl and C1-C 12 -alkyl-C3-C6-cycloalkyl is optionally substituted with at least one selected from halogen, nitro, hydroxy, mercapto, amino, C1-C 12 -alkoxy, C1-C 12 -alkylthio, mono(C1-C 12 -alkyl)amino and di(C1-C 12 -alkyl)amino group substitution; In particular, R1 is selected from hydrogen, C1-C8-alkyl or C1-C8-alkyl substituted by at least one group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkoxy and C1-C6-alkylthio; More particularly, R1 is hydrogen or C1-C6-alkyl.

6. The aromatic carboxylic acid oxime ester compound according to claim 5, wherein in formula (I), R1 is hydrogen or C1-C4-alkyl such as methyl or ethyl.

7. The aromatic carboxylic acid oxime ester compound according to claim 6, wherein in formula (I), R1 is hydrogen.

8. The aromatic carboxylic acid oxime ester compound according to any one of claims 1 to 7, wherein in formula (I), Ar1 and Ar2 are independently phenyl or phenyl substituted by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and R1 is hydrogen or C1-C6-alkyl; Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy and C1-C6-alkylthio, and R1 is hydrogen or C1-C6-alkyl.

9. The aromatic carboxylic acid oxime ester compound according to claim 8, wherein in formula (I), Ar1 and Ar2 are independently phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio, and R1 is hydrogen or C1-C4-alkyl.

10. The aromatic carboxylic acid oxime ester compound according to claim 9, wherein in formula (I), Ar1 is phenyl or phenyl substituted in the para position by a group selected from the group consisting of halogen, hydroxy, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio, Ar2 is phenyl, and R1 is hydrogen or C1-C4-alkyl.

11. The aromatic carboxylic acid oxime ester compound according to claim 10, wherein in formula (I), Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl or p-ethoxyphenyl, Ar2 is phenyl, and R1 is hydrogen.

12. A method for preparing an aromatic formylformic acid oxime ester compound according to any one of claims 1 to 11, the method comprising subjecting an aromatic formylformic acid represented by formula (II) to an esterification reaction with an oxime represented by formula (III): in, Ar1 in formula (II) and R1 and Ar2 in formula (III) have the same meanings as Ar1, R1 and Ar2 in formula (I), respectively.

13. A composition for LED light curing, comprising: - at least one aromatic oxime formate compound according to any one of claims 1 to 11 as a photoinitiator, and - a photocurable component selected from at least one of monomers, oligomers and prepolymers having ethylenically unsaturated functions, in, The mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100, preferably in the range of 0.5:100 to 5:100, and especially in the range of 1:100 to 3:

100.

14. A composition according to claim 13, wherein the monomer is selected from at least one of the following groups: monofunctional ethylenically unsaturated compounds, such as (meth)acrylic acid and its salts, (meth)acrylates, (meth)acrylamide, N-substituted (meth)acrylamide, (meth)acrylonitrile, anhydrides and esters of unsaturated carboxylic acids other than (meth)acrylic acid, styrene and substituted styrenes, vinyl ethers and halogenated vinyls, vinyl and allyl esters of carboxylic acids; and polyfunctional ethylenically unsaturated compounds, such as (meth)acrylic acid type monomers such as di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates and penta(meth)acrylates.

15. The composition according to claim 13, wherein the prepolymer or oligomer is at least one selected from the group consisting of epoxy (meth) acrylate resins, polyurethane (meth) acrylate resins, polyester (meth) acrylate resins, polyether (meth) acrylate resins, and acrylated poly (meth) acrylate resins.

16. Use of the aromatic formyl formic acid oxime ester compound according to any one of claims 1 to 11 as a photoinitiator in an LED light curing system, especially in a colorless LED light curing system and a deep curing LED light curing system.

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