Aromatic acyl formate oxime ester photoinitiator, and preparation method therefor

Abstract

The present invention relates to an aromatic acyl formate oxime ester photoinitiator suitable for LED photopolymerization. The photoinitiator has a structure represented by general formula (I), wherein Ar1, Ar2 and R1 are as defined in the description and claims. The present invention also relates to a preparation method for the photoinitiator and a use thereof in an LED photopolymerization system.

Description

Arylformyl oxime photoinitiators and their preparation methods Technical Field

[0001] This invention relates to an arbutin oxime photoinitiator suitable for LED photocuring, its preparation method, and its application in photocuring using an LED light source. Background Technology

[0002] High-pressure mercury lamps, commonly used in traditional photopolymerization technology, are gradually being replaced by greener light sources. Compared to traditional mercury lamps, LED light sources offer advantages such as longer lifespan, lower energy consumption, greater stability, and faster response. Therefore, photopolymerization using LED light sources (also known as LED photopolymerization or LED photopolymerization) is receiving increasing attention in the field of photosensitive polymers. The photoinitiator (also known as LED photoinitiator) that matches the wavelength of the LED light source is one of the important factors affecting the applicability of LED photopolymerization technology. To date, most reported LED photoinitiators contain large conjugated structures (chromophores) in their structure. While these large conjugated structures provide good light absorption, they also impart color to the cured system due to the absorption of visible light. A deeper color hinders light from penetrating the cured system to its deeper layers, which undoubtedly limits the application of such LED photoinitiators in photopolymerization systems requiring colorless curing or deep curing.

[0003] Currently, the main approach to solving these problems is to develop LED photoinitiators with photobleaching properties. These photoinitiators can undergo degradation at specific wavelengths, and the resulting fragments do not absorb in the visible light region, thus yielding a colorless cured product. However, a drawback of these photoinitiators is that they are difficult to completely degrade in the curing system, especially for systems requiring deep curing, where the color imparted by the photoinitiator is difficult to completely disappear.

[0004] Another problem associated with these photoinitiators is their migration from the cured system, which can have adverse effects on human health. Therefore, developing photoinitiators with low migration has become a new challenge in the field of photocurable materials in recent years. Summary of the Invention

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

[0006] The inventors of this invention have surprisingly discovered that the aforementioned objective is achieved through an α,β-unsaturated oxime ester compound having an α-dicarbonyl structure. This compound exhibits appropriate weak absorption in the visible light region. Such absorption leads to effective photolysis and the generation of active free radicals without imparting unacceptable color to the cured system, thus enabling deep curing. Furthermore, compared to commercially available oxime ester photoinitiators, the oxime ester photoinitiator of this invention exhibits significantly reduced migration, i.e., significantly improved migration stability.

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

[0008] in,

[0009] Ar1 and Ar2 are independently selected from C6-C 10 -aryl group, or C6-C group substituted with at least one group selected from the group consisting of ... 10 -Aryl: Halogen, Nitro, Hydroxyl, Thiol, Amino, C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 -Substitution of aryl groups;

[0010] 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 -The cycloalkyl group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 Substitution of alkyl amino groups.

[0011] In a second aspect, the present invention provides a method for preparing the arbutin oxime ester compound represented by formula (I) above, the method comprising esterifying an arbutin acid represented by formula (II) with an oxime represented by formula (III):

[0012] In Equation (II), Ar1 and in Equation (III), R1 and Ar2 have the same meaning as Ar1, R1 and Ar2 in Equation (I), respectively.

[0013] In a third aspect, the present invention provides a composition for LED photocuring, the composition comprising:

[0014] - At least one of the arbutin oxime compounds represented by formula (I) above is used as a photoinitiator, and

[0015] - A photocurable component, selected from at least one of monomers, oligomers, and prepolymers having olefinic unsaturated functional groups.

[0016] The mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100.

[0017] In a fourth aspect, the present invention provides the use of the arbutin oxime compound represented by the aforementioned formula (I) as a photoinitiator in an LED photocuring system. Attached Figure Description

[0018] Figure 1 schematically illustrates the polymerization process initiated by the arbutin oxime compound according to the present invention as a photoinitiator;

[0019] Figure 2 shows the UV absorption spectra of cinnamaldehyde oxime benzoylcarbamate (CAOXE), cinnamaldehyde oxime p-fluorobenzoylcarbamate (F-CAOXE), cinnamaldehyde oxime p-chlorobenzoylcarbamate (Cl-CAOXE), and cinnamaldehyde oxime p-methoxybenzoylcarbamate (O-CAOXE) synthesized according to Examples 1 to 4 in the range of 200 nm to 450 nm. The small image in the upper right corner is a partial screenshot of the UV absorption spectrum in the range of 380 nm to 420 nm.

[0020] Figure 3 shows the photopolymerization kinetics of monomer tripropylene glycol diacrylate polymerization initiated by photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4, as well as the commercially available photoinitiator OXE-01, under a 385nm LED light source.

[0021] Figure 4 shows the photopolymerization kinetics of monomer tripropylene glycol diacrylate polymerization initiated by photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4, as well as the commercially available photoinitiator OXE-01, under a 405 nm LED light source.

[0022] Figure 5 shows the photopolymerization kinetics of the polymerization of monomer trimethylolpropane triacrylate initiated by the commercially available photoinitiator OXE-01 synthesized according to Examples 1 to 4, namely CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE, under a 405nm LED light source.

[0023] Figure 6 shows a comparison of the deep polymerization of the monomer tripropylene glycol diacrylate initiated by the photoinitiator F-CAOXE synthesized according to Example 2 and the commercially available photoinitiator OXE-01.

[0024] Figures 7A and 7B show the UV absorption spectra of the photoinitiators CAOXE and F-CAOXE synthesized according to Examples 1 and 2, as well as the commercially available photoinitiator OXE-01, in a migration test. Detailed Implementation

[0025] In this document, "halogen" refers to fluorine, chlorine, bromine, and iodine. In this invention, the halogen is preferably fluorine, chlorine, bromine, or a combination thereof, and particularly preferably fluorine or chlorine.

[0026] In this paper, the prefix "C" used in the definition of groups n -C m - "In each case, it indicates that the defined group contains n to m carbon atoms, where n and m are specifically mentioned numbers. For example, "C1-C 16 "-" indicates that the defined group has 1 to 16 carbon atoms. When the defined group has substituents, the number of carbon atoms "C" is... n -C m - "Excluding carbon atoms contained in substituents."

[0027] In this article, "C1-C 16 "-alkyl" refers to a straight-chain or branched alkyl group having 1 to 16 carbon atoms, such as C1-C1 alkyl. 12-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, etc. "C1-C 16 "-alkyl" is preferably C1-C6-alkyl, more preferably C1-C4-alkyl, such as methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl.

[0028] In this article, "C6-C 10 "-aryl" refers to monocyclic or bicyclic aromatic hydrocarbon groups containing 6-10 carbon atoms, such as phenyl, tolyl, ethylphenyl, propanylphenyl, butylphenyl, xylyl, methylethylphenyl, diethylphenyl, methylpropylphenyl, naphthyl and their isomers, etc. "C6-C" 10 The aryl group is preferably phenyl or naphthyl, and more preferably phenyl.

[0029] In this article, "C3-C 10 "-Cycloalkyl" refers to a saturated alicyclic group having 3-10 carbon atoms, preferably having a monocyclic structure, such as C3-C6-cycloalkyl, and more specifically cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl and their isomers.

[0030] In this article, "C3-C 10 -cycloalkyl-C1-C 16 "-alkyl" indicates that it is formed by C3-C 10 -Cycloalkyl-substituted C1-C 16 -alkyl, wherein the alkyl group is attached to the rest of the compound via an alkyl structure. Here, "C3-C" 10 -cycloalkyl" and "C1-C 16 "-alkyl" has the meaning, preferred meaning, and specific examples 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 their isomers.

[0031] In this article, "C1-C 16 -alkyl-C3-C 10 "-cycloalkyl" indicates that it is C1-C 16 -alkyl-substituted -C3-C 10 -Cycloalkyl, wherein the cycloalkyl group is linked to the rest of the compound via a cycloalkyl structure. Here, "C1-C..." 16 -alkyl" and "C3-C" 10 "-cycloalkyl" has the meaning, preferred meaning, and specific examples 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 their isomers.

[0032] In this article, "C1-C 16 -alkoxy group and C1-C 16 "-alkylthio" refers to the group at C1-C2. 16 -A group in which a hydrogen atom on any carbon atom of an alkane chain is replaced by an oxygen (-O-) or sulfur (-S-) atom, thereby connecting the alkane to the rest of the compound through that oxygen or sulfur atom. These two groups can also be represented as "C1-C". 16 -alkyl-O-" and "C1-C" 16 -alkyl-S-". Here "C1-C" 16 "alkyl" has the meaning, preferred meaning, and specific examples described above. "C1-C 16 "-alkoxy" is preferably a C1-C6 alkoxy, such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, 2-butoxy, tert-butoxy, pentoxy, isopentoxy, hexoxy, and their isomers. "C1-C 16 "-alkylthio" is preferably C1-C6-alkylthio, which can be methylthio, ethylthio, propylthio, isopropylthio, n-butylthio, 2-butylthio, tert-butylthio, pentylthio, isopentylthio, hexylthio and their isomers, etc.

[0033] In this article, "single (C1-C 16 "-alkyl)amino" refers to a substance with a C1-C1 group. 16 -Alkyl-substituted amino groups. "Di(C1-C 16 "-alkyl)amino" refers to a compound containing two C1-C2 groups. 16 -Alkyl-substituted amino group, wherein two C1-C 16 -The alkyl substituents can be the same or different. Here, "C1-C" 16 "-alkyl" has the meaning, preferred meaning and specific examples described above.

[0034] In the following description of the invention, unless otherwise expressly stated, all numerical values ​​are to be regarded as being modified by the word "approximately". The inventors have reported the numerical values ​​in the embodiments as accurately as possible, although these values ​​inevitably include a certain degree of error.

[0035] In a first aspect, the present invention provides an arbutin oxime compound having the structure shown in formula (I):

[0036] in,

[0037] Ar1 and Ar2 are independently selected from C6-C 10 -aryl group, or C6-C group substituted with at least one group selected from the group consisting of ... 10 -Aryl: Halogen, Nitro, Hydroxyl, Thiol, Amino, C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 -Substitution of aryl groups;

[0038] 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-C16 -alkyl, C3-C 10 -Cycloalkyl, C3-C 10 -cycloalkyl-C1-C 16 -alkyl and C1-C 16 -alkyl-C3-C 10 -The cycloalkyl group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 Substitution of alkyl amino groups.

[0039] In formula (1), Ar1 and Ar2 are independent of each other, for example, phenyl or naphthyl groups that are unsubstituted or substituted with at least one group selected from the group consisting of: halogen, nitro, hydroxyl, mercapto, C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -Alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -The alkylthio group is optionally selected from at least one group chosen from halogen, hydroxyl, mercapto, amino, and C6-C. 10 -Aromatic group substitution.

[0040] Ar1 and Ar2, independently of each other, particularly unsubstituted or substituted phenyl or naphthyl groups 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 groups are optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, and C6-C 10 -Aromatic group substitution.

[0041] Ar1 and Ar2, independently of each other, are preferably phenyl or phenyl substituted with 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 with at least one group selected from halogen, hydroxyl, and mercapto.

[0042] In some embodiments, Ar1 and Ar2, independently of each other, are phenyl or phenyl substituted with a group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0043] Preferably, Ar1 is a phenyl or a phenyl substituted at the para position with 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 a phenyl.

[0044] For example, Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl, or p-ethoxyphenyl, and / or Ar2 is phenyl.

[0045] In equation (1), R1 is selected, for example, 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, optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C6. 12 -alkoxy group, C1-C 12 -alkylthio group, mono(C1-C) 12 -alkyl)amino and di(C1-C 12 Substitution of alkyl amino groups.

[0046] In particular, R1 is selected from hydrogen, C1-C8-alkyl, or C1-C8-alkyl substituted with at least one group selected from the group consisting of halogen, hydroxyl, mercapto, C1-C6-alkoxy, and C1-C6-alkylthio.

[0047] In some embodiments, R1 is hydrogen or a C1-C6-alkyl group. Preferably, R1 is hydrogen or a C1-C4-alkyl group, such as methyl or ethyl, and more preferably hydrogen.

[0048] In an exemplary embodiment of the first aspect of the invention, the arbutin oxime compound has the structure shown in formula (I):

[0049] in,

[0050] Ar1 and Ar2, independently of each other, are phenyl or phenyl substituted with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy, and C1-C6-alkylthio.

[0051] R1 is hydrogen or C1-C6-alkyl.

[0052] Specifically, in the aforementioned formula (I), Ar1 and Ar2 are, independently of each other, phenyl or phenyl substituted at the para position with 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.

[0053] According to the foregoing exemplary embodiments, the arbutin oxime compound more preferably has the structure shown in formula (I):

[0054] in,

[0055] Ar1 and Ar2, independently of each other, are phenyl or phenyl substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0056] R1 is hydrogen or C1-C4-alkyl.

[0057] According to the foregoing exemplary embodiments, the arbutin oxime compound more preferably has the structure shown in formula (I):

[0058] in,

[0059] Ar1 is a phenyl group or a phenyl group substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0060] Ar2 is a phenyl group, and

[0061] R1 is hydrogen or C1-C4-alkyl.

[0062] According to the foregoing exemplary embodiments, the arbutin oxime ester compound is particularly preferably having the structure shown in formula (I):

[0063] Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl, or p-ethoxyphenyl, Ar2 is phenyl, and R1 is hydrogen.

[0064] Compound (I) has (Z) 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 mixtures of isomers can also be used as photoinitiators.

[0065] In this document, the structure shown in Formula (I) is merely a description of the connection between the atoms and functional groups constituting the compound, and is not intended to indicate double bond isomers or any other isomers that may exist. Unless otherwise specified, the arethaneylformate oxime compounds shown in Formula (I) herein encompass any of the aforementioned double bond configurations and mixtures of isomers of two configurations.

[0066] In a second aspect, the present invention provides a method for preparing the arbutin oxime ester compound represented by formula (I) above, the method comprising esterifying an arbutin acid represented by formula (II) with an oxime represented by formula (III):

[0067]

[0068] In Equation (II), Ar1 and in Equation (III), Ar2 and R1 have the same meaning as Ar1, Ar2 and R1 in Equation (I), respectively.

[0069] The esterification reaction between the arcarboxylic acid of formula (II) and the oxime of formula (III) can be carried out in a manner known in the art. Through this esterification reaction, the carboxyl group in formula (II) condenses with the hydroxyl group in formula (III) to form an ester group, thereby obtaining the compound of formula (I). In this esterification reaction, there is no particular limitation on the relative amounts of the arcarboxylic acid of formula (II) and the oxime of formula (III), for example, they can be used in a molar ratio of 1:1.5 to 1.5:1, preferably 1:1.2 to 1.2:1, for example, 1:1.

[0070] The esterification reaction between the arethanecarboxylic acid represented by formula (II) and the oxime represented by formula (III) is generally carried out in the presence of a base. The base is, for example, an organic base, particularly a nitrogen-containing organic base. As a non-limiting example of such a base, at least one selected from the group consisting of: pyridine, alkyl-substituted pyridines such as 2-methylpyridine, 3-methylpyridine and 4-dimethylaminopyridine, dialkylamines such as diethylamine, and trialkylamines such as triethylamine.

[0071] Preferably, the base is selected from at least one of the following groups: pyridine, 2-methylpyridine, 3-methylpyridine, 4-dimethylaminopyridine, diethylamine and triethylamine, more preferably from at least one of the following groups: pyridine, 2-methylpyridine, 3-methylpyridine and 4-dimethylaminopyridine.

[0072] Bases are typically used in catalytic amounts. Although bases can also be used in equimolar amounts, in excess amounts, or in solvent amounts, catalytic amounts are preferred. The catalytic amount can be determined based on common sense in the art or through routine preliminary experiments, referring to the examples given herein. For example, the base is used with the arylformic acid of formula (II) 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.

[0073] The esterification reaction between the arylformic acid shown in formula (II) and the oxime shown in formula (III) can be carried out under conditions of water removal. This can be done, for example, by distillation / condensation.

[0074] Preferably, the esterification reaction can be carried out under a dehydrating agent. The choice of dehydrating agent is not particularly limited, but organic dehydrating agents are preferred. As non-limiting examples of dehydrating agents, 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.

[0075] The dehydrating agent can be used in conventional amounts, such as in equimolar amounts with the reactants, and preferably in appropriate excess amounts. For example, the dehydrating agent is used with the arylformic acid shown in formula (II) in the following molar ratio: 1.5:1 to 1:1, preferably 1.2:1 to 1:1, more preferably 1.2:1.

[0076] The esterification reaction between the arylformic acid represented by formula (II) and the oxime represented by formula (III) is generally carried out in a solvent, preferably an organic solvent. There are no particular limitations on the choice of solvent, for example, at least one of tetrahydrofuran, benzene, toluene, ethyl acetate, N,N-dimethylformamide, dichloromethane and acetone can be used.

[0077] The esterification reaction can be carried out over a very wide temperature range. Advantageously, according to the invention, the esterification reaction is carried out at a temperature of -10°C to 150°C, preferably 0°C to 100°C, and most preferably at room temperature.

[0078] After the esterification reaction is complete, a mixture of products containing compound (I) is obtained. This mixture of products can be post-processed by any separation and purification method known in the art, such as filtration, drying, distillation, recrystallization, chromatography, etc.

[0079] The reactants of the aforementioned esterification reaction, namely, the arylformic acid represented by formula (II) and the oxime represented by formula (III), can be synthesized or obtained commercially by methods known in the art, without any particular limitation.

[0080] In some embodiments of the method of the present invention, the arylformic acid represented by formula (II) is prepared, for example, by Friedel-Crafts acylation, comprising: reacting the aromatic hydrocarbon Ar1-H corresponding to the Ar1 group in formula (II) with a chloroformyl ester in the presence of a Lewis acid (such as aluminum chloride) to obtain the arylformyl ester, followed by hydrolysis to obtain the corresponding arylformic acid. The chloroformyl ester is used as an acylation agent and may be, for example, methyl chloroformate (i.e., monomethyl oxaloyl chloride) or ethyl chloroformate (i.e., monoethyl oxaloyl chloride). There is no particular limitation on the relative amounts of the aromatic hydrocarbon Ar1-H and the chloroformyl ester; for example, they may be used in a molar ratio of 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, such as in equimolar amounts or in appropriate excess amounts compared to the reactants. More specifically, the Lewis acid is used with methyl chloroformate in a molar ratio of 2.5:1 to 1:1, preferably 2:1 to 1.3:1, and more preferably 1.5:1.

[0081] The Friedel-Crafts acylation reaction can be carried out in solvents known in the art without particular limitation. Following the Friedel-Crafts acylation reaction, the arcarbamate is hydrolyzed to obtain the arcarbamate of formula (II). This hydrolysis can be carried out in a manner known in the art, for example, hydrolysis in the presence of a base to give the corresponding salt, followed by acidification to obtain the arcarbamate.

[0082] In some embodiments of the method of the present invention, the oxime represented by formula (III) is prepared, for example, by oximation of a ketone or aldehyde represented by formula (IV) with an oximating agent selected from hydroxylamine hydrochloride, hydroxylamine, or mixtures thereof:

[0083] R1 and Ar2 have the same meaning as in equation (III).

[0084] Oximation reactions are typically carried out in organic solvents, preferably in polar organic solvents. Suitable solvents include, for example, tetrahydrofuran or aqueous tetrahydrofuran. To promote complete oximation, salts or bases such as sodium acetate, potassium acetate, pyridine, piperidine, or triethylamine can be added. Oximation reactions can be carried out at room temperature or under heating. There are no particular limitations on the relative amounts of the aldehyde or ketone to the oximating agent; for example, they can be used in a molar ratio of 1:2.5 to 1:1.1, preferably 1:2 to 1:1.3, such as 1:1.5. If the salt or base is used, it can be used in a molar ratio of 3:1 to 1:0.5, preferably 2:1 to 1:1, such as 2:1.5.

[0085] The aldehydes or ketones represented by formula (IV) are commercially available or prepared according to known conventional methods.

[0086] The arbamate oxime compound of formula (I) according to the present invention has suitable 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, thereby enabling effective photolysis to generate active free radicals that initiate polymerization and / or crosslinking, but without giving the cured system color. Therefore, it can be used as a photoinitiator in photocurable systems that require colorless curing and photocurable systems that require deep curing.

[0087] Unrestricted by any theory, the inventors of this invention hypothesize that the arbutin oxime ester compound represented by formula (I) undergoes photolysis under LED light irradiation as shown in Figure 1. Specifically, as shown in Figure 1, under LED light irradiation, the compound first undergoes nitric oxide bond cleavage at the oxime ester structure, generating one molecule of arbutinoxy radical and one molecule of imine radical. Subsequently, the benzoyloxy radical cleaves, removing one molecule of carbon dioxide, to generate one molecule of benzoyl radical. This radical, as the dominant active radical, initiates polymerization and / or crosslinking reactions in the curing system.

[0088] Therefore, in a third aspect, the present invention provides a composition for LED photocuring, the composition comprising:

[0089] - At least one of the arbutin oxime compounds represented by formula (I) above is used as a photoinitiator, and

[0090] - A photocurable component, selected from at least one of monomers, oligomers, and prepolymers having olefinic unsaturated functional groups.

[0091] The mass ratio of the photoinitiator to the photocurable component is in the range of 0.2:100 to 6:100.

[0092] In some embodiments, the photoinitiator and the photocuring component are present in the composition for LED photocuring at a mass ratio ranging from 0.5:100 to 5:100, particularly from 1:100 to 3:100.

[0093] The present invention does not impose any particular limitation on monomers with olefinic unsaturated functions that are suitable for use as photocuring components, such as monofunctional or polyfunctional olefinic unsaturated compounds.

[0094] Examples of suitable monofunctional alkenyl unsaturated compounds include, but are not limited to: (meth)acrylic acid and its salts; (meth)acrylates, such as alkyl esters like methyl, ethyl, 2-chloroethyl, N,N-dimethylaminoethyl, n-butyl, isobutyl, pentyl, and hexyl esters; hydroxyalkyl esters like 2-hydroxyethyl, 2-hydroxypropyl, and 4-hydroxybutyl esters; and epoxyalkyl esters like glycidyl, 2,3-epoxybutyl, 3,4-epoxybutyl, 2,3-epoxycyclohexyl, and 10,11-epoxyundecyl esters. (Methacrylamide), N-substituted (meth)acrylamides, such as N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-hexylacrylamide, N-hexylmethacrylamide, N-cyclohexylacrylamide, N-cyclohexylmethacrylamide, N-hydroxyethylacrylamide, N-phenylacrylamide, N-phenylmethacrylamide, N-benzylacrylamide, N-benzylmethacrylamide, N-nitrophenylacrylamide, N-nitro... N-(4-hydroxyphenyl)acrylamide, N-ethyl-N-phenylacrylamide, N-ethyl-N-phenylmethylacrylamide, N-(4-hydroxyphenyl)acrylamide and N-(4-hydroxyphenyl)methylacrylamide; (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 styrene, such as methylstyrene, chloromethylstyrene and ortho-, meta- and para-hydroxystyrene. Alkenes, divinylbenzene; vinyl ethers and halogenated vinyls, 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, and triallyl phosphate.

[0095] Examples of suitable polyfunctional olefinic unsaturated compounds include, but are not limited to: di(meth)acrylates, such as 1,6-hexanediol diacrylate (HDDA), ethylene glycol diacrylate, propylene glycol diacrylate, glyceryl diacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, glyceryl dimethacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate, hexamethylene glycol diacrylate, bisphenol A diacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, dipentaerythritol diacrylate, etc. Dimethacrylates, tetramethylene glycol dimethacrylates, triethylene glycol dimethacrylates; 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.

[0096] The present invention does not impose any particular limitation on prepolymers or oligomers with olefinic unsaturated functions suitable for use as photocuring 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.

[0097] The composition for LED photocuring of the present invention may optionally contain an organic solvent. The choice of organic solvent is conventional. Examples of organic solvents include aromatic hydrocarbons such as benzene and toluene, halogenated alkanes such as chloroform, dichloromethane, and chloroethane, ketones such as acetone, butanone, and pentanone, alcohols such as methanol, ethanol, propanol, isopropanol, and ethylene glycol, as well as ethylene glycol ethers, ethylene glycol ether acetates, propylene glycol ethers, and propylene glycol ether acetates.

[0098] The composition for LED curing of the present invention may optionally contain other additives, such as leveling agents, antioxidants, antisettling agents, colorants, microbial agents, such as antibacterial agents, and thermal insulation material additives.

[0099] It should be understood that the composition for LED curing of the present invention may be a mixture of the components; the composition for LED 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 only formulated together to form a curing system when applied.

[0100] In a fourth aspect, the present invention provides the use of the arbutin oxime compound represented by the aforementioned formula (I) as a photoinitiator in an LED photocuring system.

[0101] In particular, the present invention provides the use of the arbamoylformate oxime compound represented by the aforementioned formula (I) in LED curing systems requiring colorless curing and LED curing systems requiring deep curing.

[0102] Specifically, the present invention includes, but is not limited to, the following technical solutions:

[0103] 1. An arbutin oxime ester compound having the structure shown in formula (I):

[0104] in,

[0105] Ar1 and Ar2 are independently selected from C6-C 10 -aryl group, or C6-C group substituted with at least one group selected from the group consisting of ... 10 -Aryl: Halogen, Nitro, Hydroxyl, Thiol, Amino, C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 -Substitution of aryl groups;

[0106] 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-The cycloalkyl group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 Substitution of alkyl amino groups.

[0107] 2. The arbutin oxime compound according to embodiment 1, wherein in formula (I), Ar1 and Ar2 are independently unsubstituted or substituted with at least one group selected from the group consisting of: halogen, nitro, hydroxyl, mercapto, C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -Alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -The alkylthio group is optionally selected from at least one group chosen from halogen, hydroxyl, mercapto, amino, and C6-C. 10 -Substitution of aryl groups;

[0108] Specifically, Ar1 and Ar2 are independently phenyl or naphthyl groups that are either unsubstituted or substituted with 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 groups are optionally selected with at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, and C6-C 10 -Substitution of aryl groups;

[0109] Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted with 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 with at least one group selected from halogen, hydroxyl and mercapto.

[0110] More preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

[0111] 3. The arylformyl oxime compound according to embodiment 1 or 2, wherein in formula (I), Ar1 is a phenyl or a phenyl group substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0112] 4. The arylformyl oxime compound according to any one of embodiments 1-3, wherein Ar2 in formula (I) is phenyl.

[0113] 5. The arylformyl oxime compound according to any one of embodiments 1-4, 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, optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C6. 12 -alkoxy group, C1-C 12 -alkylthio group, mono(C1-C) 12 -alkyl)amino and di(C1-C 12 Substitution of alkyl)amino groups;

[0114] In particular, R1 is selected from hydrogen, C1-C8-alkyl, or C1-C8-alkyl substituted with at least one group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C6-alkoxy, and C1-C6-alkylthio.

[0115] More specifically, R1 is hydrogen or C1-C6-alkyl.

[0116] 6. The arbutin oxime compound according to embodiment 5, wherein in formula (I), R1 is hydrogen or C1-C4-alkyl such as methyl or ethyl.

[0117] 7. The arylformyl oxime compound according to embodiment 6, wherein R1 in formula (I) is hydrogen.

[0118] 8. The arbutin oxime compound according to any one of the preceding embodiments 1-7, wherein in formula (I),

[0119] Ar1 and Ar2 are independently phenyl groups or phenyl groups substituted with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy, and C1-C6-alkylthio.

[0120] R1 is hydrogen or a C1-C6-alkyl group;

[0121] Preferably, Ar1 and Ar2 are phenyl or phenyl substituted at the para position with 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.

[0122] 9. The arbutin oxime compound according to embodiment 8 above, wherein in formula (I),

[0123] Ar1 and Ar2 are independently phenyl or phenyl groups substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0124] R1 is hydrogen or C1-C4-alkyl.

[0125] 10. The arbutin oxime compound according to embodiment 9 above, wherein in formula (I),

[0126] Ar1 is a phenyl group or a phenyl group substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio.

[0127] Ar2 is a phenyl group, and

[0128] R1 is hydrogen or C1-C4-alkyl.

[0129] 11. The arbutin oxime compound according to embodiment 10 above, wherein in formula (I), Ar1 is phenyl, p-fluorophenyl, p-chlorophenyl, p-methoxyphenyl or p-ethoxyphenyl, Ar2 is phenyl, and R1 is hydrogen.

[0130] 12. A method for preparing an arbutin oxime compound according to any one of embodiments 1-11, the method comprising esterifying an arbutinic acid of formula (II) with an oxime of formula (III):

[0131] In Equation (II), Ar1 and in Equation (III), R1 and Ar2 have the same meaning as Ar1, R1 and Ar2 in Equation (I), respectively.

[0132] 13. A composition for LED photocuring, the composition comprising:

[0133] - At least one arbutin oxime compound according to any one of embodiments 1-11 as a photoinitiator, and

[0134] - A photocurable component, selected from at least one of monomers, oligomers, and prepolymers having olefinic unsaturated functional groups.

[0135] 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.

[0136] 14. The composition according to embodiment 13, wherein the monomer is selected from at least one of the following: monofunctional alkenyl 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 styrene, vinyl ethers and halogenated vinyls, vinyl and allyl esters of carboxylic acids; and polyfunctional alkenyl unsaturated compounds, such as (meth)acrylic acid type monomers such as di(meth)acrylate, tri(meth)acrylate, tetra(meth)acrylate and penta(meth)acrylate.

[0137] 15. The composition according to embodiment 13, wherein the prepolymer or oligomer is selected from at least one of the following groups: epoxy (meth)acrylate resin, polyurethane (meth)acrylate resin, polyester (meth)acrylate resin, polyether (meth)acrylate resin, and acrylated poly (meth)acrylate resin.

[0138] 16. The use of the arylformyl oxime compound according to any one of embodiments 1-11 as a photoinitiator in LED curing systems, particularly in LED curing systems requiring colorless curing and LED curing systems requiring deep curing.

[0139] Example

[0140] The technical solution of the present invention will be further described in detail below by way of embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature or product specifications in the art.

[0141] Example 1: Synthesis of a photoinitiator CAOXE (cinnamaldehyde oxime benzoylformate) with the following structure

[0142] 1.1 Synthesis of Cinnamaldehyde Oxime

[0143] Cinnamaldehyde (1.32 g, 10 mmol), hydroxylamine hydrochloride (1.05 g, 15 mmol), and sodium acetate (1.64 g, 20 mmol) were added to a 100 mL single-necked flask, followed by 30 mL of tetrahydrofuran. The mixture was reacted at room temperature for 5 h. The tetrahydrofuran was removed by vacuum distillation. 30 mL of dichloromethane was added to the resulting product, and the mixture was washed three times with 30 mL of deionized water. The resulting organic phase was dried over anhydrous sodium sulfate, and the dichloromethane was removed by vacuum distillation to obtain cinnamaldehyde oxime.

[0144] 1.2 Synthesis of cinnamaldehyde oxime benzoylcarbamate

[0145] 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, along with 30 mL of dichloromethane as a solvent. Cinnamaldehyde oxime (1.47 g, 10 mmol) was dissolved in 10 mL of dichloromethane and slowly added dropwise to the same single-necked flask. The mixture was stirred at 25 °C until the addition was complete. The white precipitate was then removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was then dissolved in dichloromethane and purified by silica gel column chromatography, using a 1:15 mixture of ethyl acetate and petroleum ether as the eluent. The eluent was then distilled under reduced pressure to obtain the final product, CAOXE.

[0146] CAOXE's proton NMR data are as follows: 1 ¹H NMR (400MHz, 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).

[0147] The carbon spectral data for CAOXE are as follows: 13 C NMR (101MHz, 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.

[0148] Example 2: Synthesis of a photoinitiator F-CAOXE (cinnamaldehyde oxime ester of p-fluorobenzoylcarboxylate) with the following structure

[0149] 2.1 Synthesis of p-fluorobenzoylcarboxylic acid

[0150] Oxaloyl chloride monomethyl ester (1.22 g, 10 mmol) and aluminum trichloride (1.99 g, 15 mmol) were added to a 100 mL single-necked flask, along with 30 mL of dichloromethane as a solvent. Fluorobenzene (0.96 g, 10 mmol) dissolved in 30 mL of dichloromethane was slowly added dropwise to the 100 mL single-necked flask using a dropping funnel, and the mixture was stirred at 5 °C until the addition was complete. After the addition was complete, the reaction was allowed to proceed for 5 h, and then the solvent was removed by vacuum distillation to obtain methyl p-fluorobenzoylformate. 30 mL of methanol and potassium hydroxide (1.12 g, 20 mmol) were added to the obtained methyl p-fluorobenzoylformate, and the reaction was allowed to proceed for 3 h. The solvent was removed by vacuum distillation of the reaction system, and 30 mL of deionized water was added. The mixture was washed three times with 30 mL of dichloromethane. A suitable amount of dilute hydrochloric acid was added to the resulting aqueous phase to adjust the pH to approximately 3, and then the mixture was extracted three times with 30 mL of dichloromethane. The combined organic phases were dried with anhydrous sodium sulfate and dichloromethane was removed by vacuum distillation to obtain p-fluorobenzoylcarboxylic acid.

[0151] 1 ¹H NMR (400 MHz, chloroform-d) δ 9.03 (s, 1H), 8.55–8.43 (m, 2H), 7.28–7.20 (m, 2H).

[0152] 13 C NMR (101MHz, chloroform-d) δ 182.45, 168.70, 166.11, 160.77, 134.65, 134.55, 128.19, 116.56.

[0153] 2.2 Synthesis of p-fluorobenzoylcarboxylate cinnamaldehyde oxime ester

[0154] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), p-fluorobenzoylcarboxylic 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 same single-necked flask. The mixture was stirred at 25 °C until the addition was complete. The white precipitate was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was then dissolved in dichloromethane and purified by silica gel column chromatography, using a 1:16 mixture of ethyl acetate and petroleum ether as the eluent. The eluent was then distilled under reduced pressure to obtain the final product, F-CAOXE.

[0155] The proton NMR data for F-CAOXE are as follows: 1¹H NMR (400MHz, 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).

[0156] The carbon spectral data for F-CAOXE are as follows: 13 C NMR (101MHz, 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.

[0157] Example 3: Synthesis of a photoinitiator with the following structure: Cl-CAOXE (cinnamaldehyde oxime ester of p-chlorobenzoylformate)

[0158] 3.1 Synthesis of p-chlorobenzoylcarboxylic acid

[0159] Oxaloyl chloride monomethyl ester (1.22 g, 10 mmol) and aluminum trichloride (1.99 g, 15 mmol) were added to a 100 mL single-necked flask, along with 30 mL of dichloromethane as a solvent. Chlorobenzene (1.12 g, 10 mmol) dissolved in 30 mL of dichloromethane was slowly added dropwise to the 100 mL single-necked flask using a dropping funnel, and the mixture was stirred at 5 °C until the addition was complete. After the addition was complete, the reaction was allowed to proceed for 5 h, and then the solvent was removed by vacuum distillation to obtain methyl p-chlorobenzoylformate. 30 mL of methanol and potassium hydroxide (1.12 g, 20 mmol) were added to the obtained methyl p-chlorobenzoylformate, and the reaction was allowed to proceed for 3 h. The solvent was removed by vacuum distillation of the reaction system, and 30 mL of deionized water was added. The mixture was washed three times with 30 mL of dichloromethane. A suitable amount of dilute hydrochloric acid was added to the resulting aqueous phase to adjust the pH to approximately 3, and then the mixture was extracted three times with 30 mL of dichloromethane. The combined organic phases were dried with anhydrous sodium sulfate and dichloromethane was removed by vacuum distillation to obtain p-chlorobenzoylformic acid.

[0160] 1 ¹H NMR (400 MHz, chloroform-d) δ 8.44 (s, 1H), 8.38–8.32 (m, 2H), 7.57–7.50 (m, 2H).

[0161] 13C10 NMR (101 MHz, chloroform-d) δ 182.96, 160.89, 142.77, 132.79, 130.02, 129.47. 3.2 Synthesis of p-chlorobenzoylcarboxylate cinnamaldehyde oxime ester

[0162] 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. The mixture was stirred at 25 °C until the addition was complete. The white precipitate was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was dissolved in dichloromethane and purified by silica gel column chromatography, using a 1:16 mixture of ethyl acetate and petroleum ether as the eluent. The eluent was distilled under reduced pressure to obtain the final product Cl-CAOXE.

[0163] The proton NMR data for Cl-CAOXE are as follows: 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).

[0164] The carbon spectral data for Cl-CAOXE are as follows: 13 C NMR (101MHz, 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.

[0165] Example 4: Synthesis of a photoinitiator O-CAOXE (cinnamaldehyde oxime ester of p-methoxybenzoylcarbamate) with the following structure

[0166] 4.1 Synthesis of p-methoxybenzoylcarboxylic acid

[0167] Oxaloyl chloride monomethyl ester (1.22 g, 10 mmol) and aluminum trichloride (1.99 g, 15 mmol) were added to a 100 mL single-necked flask, along with 30 mL of dichloromethane as a solvent. Anisole (1.08 g, 10 mmol) dissolved in 30 mL of dichloromethane was slowly added dropwise to the 100 mL single-necked flask using a dropping funnel, and the mixture was stirred at 5 °C until the addition was complete. After the addition was complete, the reaction was allowed to proceed for 5 h, and then the solvent was removed by vacuum distillation to obtain methyl p-methoxybenzoylformate. 30 mL of methanol and potassium hydroxide (1.12 g, 20 mmol) were added to the obtained methyl p-methoxybenzoylformate, and the reaction was allowed to proceed for 3 h. The solvent was removed by vacuum distillation of the reaction system, and 30 mL of deionized water was added. The mixture was washed three times with 30 mL of dichloromethane. A suitable amount of dilute hydrochloric acid was added to the resulting aqueous phase to adjust the pH to approximately 3, and then the mixture was extracted three times with 30 mL of dichloromethane. The combined organic phases were dried with anhydrous sodium sulfate and dichloromethane was removed by vacuum distillation to obtain p-methoxybenzoylcarboxylic acid.

[0168] 1 ¹H NMR (400MHz, chloroform-d) δ 9.20 (s, 1H), 8.59–8.36 (m, 2H), 7.10–6.92 (m, 2H), 3.94 (s, 3H).

[0169] 13 C NMR (101MHz, chloroform-d) δ 182.73, 165.72, 162.96, 134.06, 124.75, 114.41, 55.74.

[0170] 4.2 Synthesis of p-methoxybenzoylcarboxylic acid cinnamaldehyde oxime ester

[0171] Dicyclohexylcarbodiimide (2.47 g, 12 mmol), p-methoxybenzoylcarboxylic 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 and slowly added dropwise to the single-necked flask. The mixture was stirred at 25 °C until the addition was complete. The white precipitate was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was then dissolved in dichloromethane and purified by silica gel column chromatography, using a 1:12 mixture of ethyl acetate and petroleum ether as the eluent. The eluent was then distilled under reduced pressure to obtain the final product O-CAOXE.

[0172] The proton NMR data for O-CAOXE are as follows: 1¹H NMR (400MHz, 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).

[0173] The carbon spectral data for O-CAOXE are as follows: 13 C NMR (101MHz, 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.

[0174] Example 5: Light Absorption Characterization

[0175] Prepare 50 mL of anhydrous acetonitrile solution of each of the photoinitiators synthesized in Examples 1 to 4 (i.e., CAOXE, F-CAOXE, Cl-CAOXE, and O-CAOXE), with a concentration of 1 × 10⁻⁶. -4 mol / L. The absorption curves of the four solutions in the wavelength range of 200 to 500 nm were measured using a UV spectrophotometer (Shimadzu Corporation, Japan, model UV-3600), i.e., the UV-Vis absorption spectra.

[0176] The UV-Vis absorption spectra of the four photoinitiators CAOXE, Cl-CAOXE, F-CAOXE, and O-CAOXE are shown in Figure 2. From the partial cropping in the wavelength range of 380 nm to 420 nm in Figure 2, it can be seen that all four photoinitiators exhibit weak absorption around 400 nm. This weak absorption not only endows the initiators with the ability to initiate photocatalysis at LED emission wavelengths but also facilitates their application in curing systems requiring colorless curing and those requiring deep polymerization.

[0177] Example 6: Photopolymerization Test

[0178] The photoinitiators synthesized in Examples 1 to 4 were applied to acrylate polymerization systems to test their performance in LED photopolymerization.

[0179] 6.1 Preparation of photosensitive solution

[0180] The photosensitive solution is prepared using acrylate monomers and a photoinitiator as described below:

[0181] The photoinitiator and tripropylene glycol diacrylate were mixed at a mass ratio of 1:100 and stirred until homogeneous to prepare the photosensitive liquid (A).

[0182] The photoinitiator and trimethylolpropane triacrylate were mixed at a mass ratio of 1:100 and stirred until homogeneous to prepare the photosensitive liquid (B).

[0183] 6.2 Performance testing of photopolymerization initiation

[0184] The prepared photosensitive solution (A) or (B) was evenly applied onto a potassium bromide salt plate, with a coating thickness of approximately 30 μm. Then, a potassium bromide salt plate was placed over the coating. The photosensitive solution was analyzed using a real-time infrared spectrometer (Thermo Fisher Scientific, Nicolet 5700) under an LED light source (Shenzhen Lanpulike Technology Co., Ltd., UVEC-4II, 80 mW / cm²). 2 Polymerization under irradiation.

[0185] The results of the photopolymerization test are shown in Figures 3, 4 and 5, respectively.

[0186] Figure 3 shows the photopolymerization kinetics of the monomer tripropylene glycol diacrylate polymerization initiated by the photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4, as well as the commercially available photoinitiator OXE-01 (purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.) under a 385nm LED light source.

[0187] Figure 4 shows the photopolymerization kinetics of monomer tripropylene glycol diacrylate polymerization initiated by photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4, as well as the commercially available photoinitiator OXE-01, under a 405 nm LED light source.

[0188] Figure 5 shows the photopolymerization kinetics of the polymerization of monomer trimethylolpropane triacrylate initiated by photoinitiators CAOXE, F-CAOXE, Cl-CAOXE and O-CAOXE synthesized according to Examples 1 to 4, as well as the commercially available photoinitiator OXE-01, under a 405 nm LED light source.

[0189] As can be seen from Figures 3 to 5, the photoinitiator of the present invention can effectively initiate the polymerization reaction of acrylate monomers under LED light source irradiation at 385 nm and 405 nm, which indicates that the photoinitiator of the present invention has good initiation performance and applicability in LED photopolymerization system.

[0190] Example 7: Deep Photopolymerization Test

[0191] The F-CAOXE synthesized in Example 2 and the commercially available photoinitiator OXE-01 were applied to an acrylate polymerization system to test the performance of these photoinitiators in initiating deep polymerization under LED light source irradiation.

[0192] The two photoinitiators mentioned above were mixed with tripropylene glycol diacrylate monomer at a mass ratio of 1:100 and stirred evenly to prepare a photosensitive liquid.

[0193] The photosensitive solution was injected into glass tubes 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 tubes, with the distance between the light source and the bottom of the glass tube being 4 cm. After irradiation for 60 s and 100 s, the depth of the polymerized poly(tripropylene glycol diacrylate) in the test tubes was measured. The test results are shown in Figure 6.

[0194] Under the aforementioned conditions, the polymerization depths of the photosensitive compositions using the photoinitiator F-CAXOE of the present invention were 3.2 cm and 6.35 cm after irradiation for 60 s and 100 s, respectively. Under the same conditions, the polymerization depths of the photosensitive compositions using the commercially available photoinitiator OXE-01 were only 0.5 cm and 3 cm. This indicates that the photoinitiator of the present invention has a significantly improved ability to initiate deep polymerization in LED photopolymerization systems.

[0195] Example 8: Migration Characterization

[0196] The CAOXE and F-CAOXE synthesized in Examples 1 and 2, as well as the commercially available photoinitiator OXE-01, were applied to acrylate polymerization systems to test the migration of these photoinitiators in the curing system.

[0197] The aforementioned three photoinitiators were respectively 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 tested using a 405 nm LED light source (Shenzhen Lanpurike Technology Co., Ltd., model UVEC-4II, light intensity 80 mW / cm²). 2 Irradiate for 5 minutes to allow the photosensitive solution to fully cure. Immerse the resulting cured film in 50 mL of anhydrous acetonitrile for 12 hours to obtain the curing film immersion solution. Use a UV spectrophotometer (Shimadzu Corporation, Japan, model UV-3600) to test the UV absorption of the three immersion solutions in the wavelength range of 200 to 500 nm.

[0198] In addition, the aforementioned three photoinitiators were each formulated into 1×10 -4 Anhydrous acetonitrile solutions were used to test the ultraviolet absorption of three photoinitiator solutions in the wavelength range of 200 to 500 nm using an ultraviolet spectrophotometer (Shimadzu Corporation, Japan, model UV-3600).

[0199] Figures 7A and 7B show the ultraviolet absorption spectra of the photoinitiator solution and the curing film immersion solution, respectively.

[0200] The concentration of photoinitiator in the immersion solution was calculated based on Beer-Lambert's law, and then the mass of the migrated photoinitiator was calculated. The results are shown in Table 1 below.

[0201] Table 1

[0202] The results in Table 1 clearly demonstrate that the photoinitiators CAOXE and F-CAOXE according to the present invention have significantly reduced migration rates and significantly improved anti-migration stability compared to the commercially available photoinitiator OXE-01.

[0203] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Various process solutions that are not substantially different from the concept of the present invention are all within the scope of protection of the present invention.

Claims

1. An arbutin oxime ester compound having the structure shown in formula (I): in, Ar1 and Ar2 are independently selected from C6-C 10 -aryl group, or C6-C group substituted with at least one group selected from the group consisting of ... 10 -Aryl: Halogen, Nitro, Hydroxyl, Thiol, Amino, C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino, the aforementioned C1-C 16 -alkyl, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 -alkyl)amino group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino and C6-C 10 -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 -The cycloalkyl group is optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C 16 -alkoxy group, C1-C 16 -alkylthio group, mono(C1-C) 16 -alkyl)amino and di(C1-C 16 Substitution of alkyl)amino groups.

2. The arbutin oxime compound according to claim 1, wherein in formula (I), Ar1 and Ar2 are independently unsubstituted or substituted with at least one group selected from the group consisting of: halogen, nitro, hydroxyl, mercapto, C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -Alkylthio, the aforementioned C1-C 12 -alkyl, C1-C 12 -alkoxy groups and C1-C 12 -The alkylthio group is optionally selected from at least one group chosen from halogen, hydroxyl, mercapto, amino, and C6-C. 10 -Substitution of aryl groups; Specifically, Ar1 and Ar2 are independently phenyl or naphthyl groups that are either unsubstituted or substituted with 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 groups are optionally selected with at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, and C6-C 10 -Substitution of aryl groups; Preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted with 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 with at least one group selected from halogen, hydroxyl and mercapto. More preferably, Ar1 and Ar2 are independently phenyl or phenyl substituted with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy and C1-C4-alkylthio.

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

4. The arylformyl oxime compound according to any one of claims 1-3, wherein Ar2 in formula (I) is phenyl.

5. The arbutin oxime compound according to any one of claims 1-4, wherein in formula (I), R1 is selected from hydrogen, C1-C64 ... 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, optionally selected from at least one group selected from halogen, nitro, hydroxyl, mercapto, amino, C1-C6. 12 -alkoxy group, C1-C 12 -alkylthio group, mono(C1-C) 12 -alkyl)amino and di(C1-C 12 Substitution of alkyl)amino groups; In particular, R1 is selected from hydrogen, C1-C8-alkyl, or C1-C8-alkyl substituted with at least one group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C6-alkoxy, and C1-C6-alkylthio. More specifically, R1 is hydrogen or C1-C6-alkyl.

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

7. The arbutin oxime compound according to claim 6, wherein in formula (I), R1 is hydrogen.

8. The arbutin oxime compound according to any one of claims 1-7, wherein in formula (I), Ar1 and Ar2 are independently phenyl groups or phenyl groups substituted with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C6-alkyl, C1-C6-alkoxy, and C1-C6-alkylthio. R1 is hydrogen or a C1-C6-alkyl group; Preferably, Ar1 and Ar2 are phenyl or phenyl substituted at the para position with 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 arbutin oxime compound according to claim 8, wherein in formula (I), Ar1 and Ar2 are independently phenyl or phenyl groups substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio. R1 is hydrogen or C1-C4-alkyl.

10. The arbutin oxime compound according to claim 9, wherein in formula (I), Ar1 is a phenyl group or a phenyl group substituted at the para position with a group selected from the group consisting of: halogen, hydroxyl, mercapto, C1-C4-alkyl, C1-C4-alkoxy, and C1-C4-alkylthio. Ar2 is a phenyl group, and R1 is hydrogen or C1-C4-alkyl.

11. The arbutin oxime 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 arbutin oxime compound according to any one of claims 1-11, the method comprising esterifying an arbutinic acid of formula (II) with an oxime of formula (III): in, Ar1 in equation (II) and R1 and Ar2 in equation (III) have the same meaning as Ar1, R1 and Ar2 in equation (I).

13. A composition for LED photocuring, the composition comprising: - At least one arbutin oxime compound according to any one of claims 1-11 as a photoinitiator, and - A photocurable component, selected from at least one of monomers, oligomers, and prepolymers having olefinic unsaturated functional groups. 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. The composition of claim 13, wherein the monomer is selected from at least one of the following: monofunctional alkenyl 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 styrene, vinyl ethers and halogenated vinyls, vinyl and allyl esters of carboxylic acids; and polyfunctional alkenyl unsaturated compounds, such as (meth)acrylic acid type monomers such as di(meth)acrylate, tri(meth)acrylate, tetra(meth)acrylate and penta(meth)acrylate.

15. The composition of claim 13, wherein the prepolymer or oligomer is selected from at least one of the following: epoxy (meth)acrylate resin, polyurethane (meth)acrylate resin, polyester (meth)acrylate resin, polyether (meth)acrylate resin, and acrylated poly (meth)acrylate resin.

16. The use of the arylformyl oxime compound according to any one of claims 1-11 as a photoinitiator in LED curing systems, particularly in LED curing systems requiring colorless curing and LED curing systems requiring deep curing.

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