Preparation method of amino ketone photoinitiator

Abstract

The invention discloses a preparation method of an amido ketone photoinitiator, in the preparation method of an alpha-amido ketone compound, naphthalene is used as a raw material, the cost of the raw material is reduced, the yield of the preparation method is high and can reach 80% or above, and the purity of the alpha-amido ketone compound can reach 95% or above. According to the preparation method of the amido ketone photoinitiator, cheap and easily available industrial-grade raw materials are used as a starting point breakthrough, naphthalene is used as a key group, and alpha-amido aromatic ketone is prepared through easy-to-operate technological processes such as Friedel-Crafts reaction, halogenation, substitution and rearrangement, so that the photoinitiation efficiency is improved; the prepared compound is an environment-friendly, non-toxic and efficient photoinitiator, the problems that volatile toxic small-molecule organic compounds escape in the photocuring process, or irritant and unpleasant smells are generated, or physiological toxicity is caused by compound migration, and the like are solved; the method has a good promotion effect on popularization and application in the field of ultraviolet radiation photocuring.

Description

Technical Field

[0001] The present invention relates to the technical field of photoinitiators, and specifically to a preparation method of an amino ketone photoinitiator. Background Art

[0002] A photoinitiator, also known as a photosensitizer or a photocuring agent, is a type of compound that can absorb energy of a certain wavelength in the ultraviolet region (250 - 420 nm) or the visible light region (400 - 800 nm), generate free radicals, cations, etc., thereby initiating the polymerization and crosslinking curing of monomers. In a photocuring system, including UV adhesives, UV coatings, UV inks, etc., after receiving or absorbing external energy, it undergoes a chemical change itself and decomposes into free radicals or cations, thereby initiating a polymerization reaction. α-Amino ketone compounds are a type of highly active free radical photoinitiators used in vinyl unsaturated compound systems. However, in polymerization applications, there are drawbacks such as carcinogenicity caused by cleavage or residues, reproductive toxicity compound benzene / aromatic hydrocarbon pollution caused by compound migration, VOCs release, unpleasant odors remaining after packaging the finished product, and limited use range and dosage due to poor solubility.

[0003] Referring to an α-amino ketone compound, a preparation method thereof, and an application thereof in the field of radiation curing with the Chinese patent publication number CN116003273B, starting from using inexpensive and readily available industrial raw materials as a breakthrough point, using biphenyl as a key group, and preparing α-amino aromatic ketone through easy-to-operate process flows such as Friedel-Crafts reaction, halogenation, substitution, rearrangement, etc., reduces the overall cost and improves the photoinitiating efficiency; at the same time, this compound is an environmentally friendly, non-toxic, and highly efficient photoinitiator, avoiding problems such as the escape of volatile toxic small molecule organic compounds during the photocuring process, the generation of irritating and unpleasant odors, or physiological toxicity caused by compound migration, and has a good promoting effect on the popularization and application in the field of ultraviolet radiation photocuring.

[0004] Referring to a kind of α-amino ketone difunctionalized compound, its preparation method and its photopolymerization initiator with reference to Chinese patent publication number CN115010614B, by using derivatives such as diphenylmethane or diphenyl ether as key groups, aromatic ketones substituted with or without heteroatoms (elements such as oxygen, nitrogen, phosphorus, silicon, etc.) may be used. The compound does not contain any sulfur element and is an environmentally friendly, non-toxic and efficient photoinitiator, which avoids the problems of volatile toxic small molecule organic compounds escaping from the reaction, or generating irritating odors, or physiological toxicity caused by compound migration. Compared with existing products, the present invention uses cheap and easily available industrial-grade raw materials as a starting point for breakthrough, and applies the compound to the photoinitiator use in radiation curing, and strives to solve the toxicity of the photoinitiator itself and the VOCs pollution problem while striving for its economic competitiveness to reduce the overall cost and improve the efficiency of photoinitiation. The present invention applies α-amino ketone bifunctional compounds to photoinitiators in radiation curing, which can solve the toxicity and VOCs pollution problems of the photoinitiator itself while striving for its economic competitiveness, so as to reduce the overall cost and improve the photoinitiator efficiency.

[0005] A comprehensive analysis of the above reference patents reveals the following defects:

[0006] 1) The existing aminoketone photoinitiators have poor photosensitivity. For example, the α-aminoketone compound, preparation method thereof and application thereof in the field of photoradiation curing disclosed in patent CN116003273B uses biphenyl as a raw material for reaction preparation. Although the stability is good, the photosensitivity of the photoinitiator obtained is poor due to the relative inactivity of biphenyl, which affects the curing speed. It is not possible to greatly enhance the photosensitivity of the photoinitiator by using naphthalene, propionyl chloride and benzyl halide as raw materials, and it is impossible to achieve the purpose of both ensuring the stability of the photoinitiator and greatly improving the curing speed, which brings great inconvenience to the actual use of the photoinitiator.

[0007] 2) Existing aminoketone photoinitiators have poor compatibility. For example, the reference patent CN115010614B discloses a difunctionalized α-aminoketone compound, a preparation method thereof, and a photopolymerization initiator. The photoinitiator is prepared by using derivatives such as diphenylmethane or diphenyl ether as raw materials. The low-solubility photoinitiator can only be used in low-migration specific curing scenarios and cannot be used in transparent systems with high reaction efficiency. The poor solubility leads to uneven dispersion and low reaction efficiency, and the purpose of improving the reaction efficiency by greatly improving the solubility of the photoinitiator cannot be achieved, which is very unfavorable for the promotion and use of the photoinitiator. Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] In view of the deficiencies of the prior art, the present invention provides a preparation method of an amino ketone photoinitiator. The prepared compound has a photoinitiator with stronger light absorption ability and higher initiation activity, is easy to prepare, easy to store, and has low cost.

[0010] (II) Technical solution

[0011] To achieve the above objectives, the present invention is realized through the following technical solutions: In the first aspect, the present invention provides an amino ketone photoinitiator, and the amino ketone photoinitiator is an α-amino ketone compound. The specific structural formula of the α-amino ketone compound is as follows:

[0012]

[0013] Among them, X represents R1 or R2 are respectively selected from any one of straight-chain or branched-chain alkyl groups representing C1-C 10 and cycloalkyl groups representing C4-C 10 ; or R1 and R2 are connected to each other or form a five-membered or six-membered cyclic group through -O-, -S-, -N-.

[0014] Preferably, the structural formula of the α-amino ketone compound is any one of the following structures:

[0015]

[0016] In the above reaction formula, the definitions of each group are the same as the corresponding items in claim 1.

[0017] In the second aspect, the present invention also provides a preparation method of an α-amino ketone compound. The target product α-amino ketone compound is prepared from the corresponding raw materials naphthalene A, propionyl chloride B and raw material C under the action of appropriate reaction conditions Conditions. The specific reaction formula is as follows:

[0018]

[0019] Among them, the definitions of each group and substance are the same as the corresponding items in claim 1. Conditions refer to any one of organic bases, inorganic bases, catalysts, promoters, inhibitors, heat, microwave, ultrasonic waves, vacuum, pressure or solvent conditions, or the combined use of any two or more of the above factors. Among them, the catalyst or promoter refers to a Lewis acidic or basic compound, such as aluminum trichloride, zinc dichloride, magnesium dichloride, etc. Specifically, it includes the following steps:

[0020] S1. The raw material naphthalene A and the raw material propionyl chloride B are subjected to a Friedel-Crafts acylation reaction under the catalysis of a Lewis acid to obtain an intermediate compound II. The specific reaction formula is as follows;

[0021]

[0022] S2. Intermediate compound Ⅱ undergoes an α-H halogenation reaction of the carbonyl group with chlorine gas to obtain intermediate compound Ⅲ. The specific reaction formula is as follows;

[0023]

[0024] S3. Intermediate compound Ⅲ then undergoes an ammonolysis reaction with raw material X to generate intermediate compound Ⅳ. The specific reaction formula is as follows;

[0025]

[0026] where the raw material X is

[0027] S4. Intermediate compound Ⅳ then undergoes a Stevevs rearrangement reaction with raw material C under alkaline conditions to generate the target product α-amino ketone compound. The specific reaction formula is as follows:

[0028]

[0029] Preferably, in step S4, the quaternary ammonium salt compound is dissolved in a 20 wt%-40 wt% sodium hydroxide solution, and the rearrangement reaction is carried out at 50-100 °C for 5-6 h.

[0030] Preferably, in step S1, raw material naphthalene A is dissolved in dichloroethane, a Lewis acid is added at 0 °C, and raw material propionyl chloride B is added dropwise. After the addition is completed, the reaction is carried out at 0 °C for 4-6 h.

[0031] Preferably, in step S1, the Lewis acid is one of aluminum trichloride, iron trichloride, zinc chloride, or titanium tetrachloride, preferably aluminum trichloride and iron trichloride.

[0032] Preferably, in step S4, the base is selected from one or more of potassium carbonate, potassium hydroxide, and sodium hydroxide. The ratio of the base to the compound is 1:(3-10), and exemplary ratios are 1:4, 1:5, 1:6, 1:7, or 1:8, but are not limited thereto.

[0033] Preferably, the raw material C is benzyl chloride or benzyl bromide.

[0034] Preferably, after the rearrangement reaction in step S4 is completed, it further includes a step of purifying the obtained product. Specifically, the reaction is cooled to room temperature, ethyl acetate is added for extraction, the organic phase is washed twice with water, dried over anhydrous sodium sulfate, and concentrated to obtain the target product α-amino ketone compound. Preferably, after the reaction is completed and extraction is carried out, the ethyl acetate added to the product is recovered and reused after concentration.

[0035] Thirdly, the present invention also provides a photocurable composition, comprising at least one rare-earth unsaturated double bond compound and at least one amino ketone photoinitiator as described in claim 1 or 2. The photocurable composition undergoes polymerization under irradiation with a light source in the range of 200 - 405 nm, and in particular, a light source of 385 - 405 nm can be used.

[0036] (III) Beneficial effects

[0037] The present invention provides a preparation method of an amino ketone photoinitiator. Compared with the prior art, it has the following beneficial effects:

[0038] (1) In the preparation method of the amino ketone photoinitiator of the present invention, in the preparation method of the α-amino ketone compound, using naphthalene as the raw material reduces the cost of the raw material. In addition, the yield of the preparation method of the present invention is high, reaching more than 80%, and the purity can reach more than 95%. Compared with existing products, the present invention uses inexpensive and readily available industrial-grade raw materials as the starting breakthrough point, uses naphthalene as the key group, and prepares α-amino aromatic ketone through easy-to-operate process flows such as Friedel-Crafts reaction, halogenation, substitution, and rearrangement, improving the photoinitiation efficiency.

[0039] (2) The preparation method of the amino ketone photoinitiator prepares a compound that is an environmentally friendly, non-toxic, and highly efficient photoinitiator, avoiding problems such as the emission of volatile toxic small-molecule organic compounds during the photocuring process, or the generation of irritating and unpleasant odors, or physiological toxicity caused by compound migration, which has a good promoting effect on the popularization and application in the field of ultraviolet radiation photocuring.

[0040] (3) The preparation method of the amino ketone photoinitiator greatly enhances the photosensitivity efficiency of the photoinitiator by using naphthalene, propionyl chloride, and benzyl halide as raw materials, achieving the purpose of ensuring the stability of the photoinitiator and greatly improving the curing speed, thus greatly facilitating the actual use of the photoinitiator.

[0041] (4) The preparation method of the amino ketone photoinitiator can be applied in a transparent system with high reaction efficiency. Due to poor solubility, the reaction efficiency is low due to uneven dispersion. The purpose of improving the reaction efficiency by greatly enhancing the solubility of the photoinitiator is achieved. Existing amino ketone photoinitiators have poor compatibility, which is very beneficial for the popularization and use of photoinitiators. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flowchart of the preparation method of the amino ketone photoinitiator of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] The following will combine the drawings in the embodiments of the present invention to describe the technical solutions in the embodiments of the present invention

[0044] Describe clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, and

[0045] not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0046]

[0047] Figure 1 Please refer to , the embodiments of the present invention provide five technical solutions: a preparation method of an amino ketone photoinitiator, which specifically includes the following embodiments:

[0048] Example 1: Prepare a target product of an α-amino ketone compound with the following structural formula:

[0049]

[0050] Under nitrogen protection, add 128 grams of naphthalene to 384 grams of dichloroethane, lower the temperature to 0 °C, slowly add 147 grams of anhydrous aluminum trichloride, stir for 30 minutes, and then slowly dropwise add 93 grams of propionyl chloride at this temperature. After the dropwise addition is completed, keep the temperature for 3 hours, add ice water to quench, separate the organic layer, wash until neutral, dry, and concentrate and purify to obtain a Friedel-crafts acylation intermediate;

[0051] Add the above oily liquid to 500 grams of dichloroethane, add a catalyst, stir evenly, heat to 50 °C, and introduce 71 grams of chlorine gas to purify to obtain a chloro intermediate;

[0052] Then put the above chloro intermediate into a flask, add a catalyst, 600 grams of dichloroethane, stir and cool to 5-10 °C, then introduce dimethylamine gas, and then raise the temperature to 35 °C and react for 8 hours. The organic phase is desolvated and recrystallized with methanol to obtain an ammonia-substituted intermediate;

[0053] Finally, put the above ammonia-substituted intermediate into a reaction flask, add 400 grams of toluene, slowly dropwise add 126 g of benzyl chloride, raise the temperature to 90 °C and react for 10 hours, then add liquid alkali and reflux for 2 hours. After cooling, separate the organic phase, extract and dry to obtain a crude product, and recrystallize with ethanol to obtain 261 grams of the target product, with a total yield of 82.3%.

[0054] Example 2: Prepare a target product of an α-amino ketone compound with the following structural formula:

[0055]

[0056] ​Under nitrogen protection, 128 g of naphthalene was added to 384 g of dichloroethane. The temperature was lowered to 0 °C, and 147 g of anhydrous aluminum trichloride was slowly added. After stirring for 30 min, 93 g of propionyl chloride was slowly added dropwise at this temperature. After the addition was completed, the mixture was kept warm for 3 h, quenched with ice water, the organic layer was separated, washed to neutral, dried, concentrated and purified to obtain the Friedel - crafts acylation intermediate;

[0057] The above oily liquid was added to 400 g of dichloroethane, a catalyst was added, stirred evenly, heated to 50 °C, and 71 g of chlorine gas was introduced, and then purified to obtain the chloro - intermediate;

[0058] Then the above chloro - intermediate was put into a flask, a catalyst, 600 g of dichloroethane were added, stirred evenly, 73 g of diethylamine was added, and the temperature was raised to 50 °C and reacted for 8 h. The organic phase was desolvated and recrystallized with methanol to obtain the amino - substitution intermediate;

[0059] Finally, the above amino - intermediate was put into a reaction flask, 400 g of toluene was added, 126 g of benzyl chloride was slowly added dropwise, the temperature was raised to 90 °C and reacted for 10 h, then liquid alkali was added and refluxed for 2 h. After cooling, the organic phase was separated, extracted and dried to obtain the crude product. After recrystallization with ethanol, 293 g of the target product was obtained, and the total yield was 85%.

[0060] Example 3: Preparation of the target product of α - amino ketone compounds with the following structural formula:

[0061]

[0062] Under nitrogen protection, 128 g of naphthalene was added to 384 g of dichloromethane. The temperature was lowered to 0 °C, and 147 g of anhydrous aluminum trichloride was slowly added. After stirring for 30 min, 93 g of propionyl chloride was slowly added dropwise at this temperature. After the addition was completed, the mixture was kept warm for 3 h, quenched with ice water, the organic layer was separated, washed to neutral, dried, concentrated and purified to obtain the Friedel - crafts acylation intermediate;

[0063] The above oily liquid was added to 400 g of dichloroethane, a catalyst was added, stirred evenly, heated to 50 °C, and 71 g of chlorine gas was introduced, and then purified to obtain the chloro - intermediate;

[0064] Then the above chloro - intermediate was put into a flask, a catalyst, 600 g of dichloroethane were added, stirred evenly, 87 g of morpholine was added, and the temperature was raised to 50 °C and reacted for 8 h. The organic phase was desolvated and recrystallized with methanol to obtain the amino - substitution intermediate;

[0065] Finally, the above-mentioned amino intermediate was put into a reaction flask, 400 g of toluene was added, 171 g of benzyl bromide was slowly added dropwise, the temperature was raised to 90 °C, and the reaction was carried out for 10 hours. Then liquid alkali was added and refluxed for 2 hours. After cooling, the organic phase was separated, and after extraction and drying, a crude product was obtained. After recrystallization with ethanol, 298 g of the target product was obtained, and the total yield was 83%.

[0066] Example 4: Preparation of the target product of an α-amino ketone compound with the following structural formula:

[0067]

[0068] Under argon protection, 128 g of naphthalene was added to 384 g of dichloroethane, the temperature was lowered to 0 °C, 147 g of anhydrous aluminum trichloride was slowly added, and after stirring for 30 min, 93 g of propionyl chloride was slowly added dropwise at this temperature. After the addition was completed, the mixture was kept warm for 3 h, quenched with ice water, the organic layer was separated, washed to neutral, dried, and concentrated and purified to obtain a Friedel-crafts acylation intermediate;

[0069] The above oily liquid was added to 400 g of dichloroethane, a catalyst was added, stirred evenly, heated to 50 °C, and 71 g of chlorine gas was introduced, and then purified to obtain a chloro intermediate;

[0070] Then the above chloro intermediate was put into a flask, a catalyst, 600 g of dichloroethane were added, stirred evenly, 82 g of piperidine was added, and then the temperature was raised to 50 °C and the reaction was carried out for 8 h. The organic phase was desolvated and recrystallized with methanol to obtain an amino-substituted intermediate;

[0071] Finally, the above-mentioned amino intermediate was put into a reaction flask, 400 g of toluene was added, 171 g of benzyl bromide was slowly added dropwise, the temperature was raised to 90 °C, and the reaction was carried out for 10 hours. Then liquid alkali was added and refluxed for 2 hours. After cooling, the organic phase was separated, and after extraction and drying, a crude product was obtained. After recrystallization with ethanol, 291 g of the target product was obtained, and the total yield was 81.6%.

[0072] Example 5: Preparation of the target product of an α-amino ketone compound with the following structural formula:

[0073]

[0074] Under nitrogen protection, 128 g of naphthalene was added to 384 g of dichloroethane, the temperature was lowered to 0 °C, 147 g of anhydrous aluminum trichloride was slowly added, and after stirring for 30 min, 93 g of propionyl chloride was slowly added dropwise at this temperature. After the addition was completed, the mixture was kept warm for 3 h, quenched with ice water, the organic layer was separated, washed to neutral, dried, and concentrated and purified to obtain an intermediate;

[0075] The above oily liquid was added to 500 g of dichloroethane, a catalyst was added, stirred evenly, heated to 40 °C, and 71 g of chlorine gas was introduced, and then purified to obtain a chloro intermediate;

[0076] Then, the above-mentioned chloro intermediate was put into a flask, a catalyst, 600 g of dichloroethane were added. After stirring evenly, 114 g of 40% aqueous dimethylamine solution were added. Then the temperature was raised to 40 °C and the reaction was carried out for 8 h. The organic phase was desolvated and recrystallized with methanol to obtain the amino-substituted intermediate;

[0077] Finally, the above-mentioned amino intermediate was put into a reaction flask, 30% aqueous sodium hydroxide solution and 171 g of benzyl bromide were added. The temperature was raised to 90 °C and the reaction was carried out for 6 h. Then the temperature was cooled to room temperature. Ethyl acetate was added for extraction. The organic phase was washed with water, dried over anhydrous sodium sulfate, concentrated to obtain the crude product, and recrystallized with ethanol to obtain 280 g of the target product, with a total yield of 88.3%.

[0078] Comparison of solubility of different photoinitiators in the photocurable resin formulation:

[0079] The formulation is shown in Table 1, and all the data in the table represent parts by mass.

[0080]

[0081] Test method: Seal the 4 formulations in Table 1 and put them into an oven at 80 °C for baking for 2 hours, then cool to room temperature, and then transfer them to a refrigerator at 4 °C for 12 hours. Then transfer them to room temperature and place for

[0082] 1 hour. Observe whether the formulation is clear and transparent. The results are shown in Table 2.

[0083]

[0084] It can be seen from the test results in Table 2 that the solubility of the photoinitiator prepared by the present invention is less than that of 989 in the formulation.

[0085] Comparison of photocuring speed of different photoinitiators:

[0086] The curing formulation is shown in Table 3, and all the data in the table represent parts by mass.

[0087]

[0088]

[0089] According to the 2 formulations in Table 3, coat them on the PET substrate with a thickness of 10 μm, turn on a 1500 W mercury lamp, preheat for 5 minutes, place the two formulations on a belt conveyor with a linear speed of 50 m / min, cure once, and press the coating with fingers to see if there are fingerprint marks. The results are shown in Table 4

[0090] Table 4 Comparison results of photocuring speed of different photoinitiators

[0091] Number 1# 2# Whether there is a fingerprint mark There is a fingerprint mark There is no fingerprint mark

[0092] As can be seen from the test results in Table 4, the photocuring efficiency of the photoinitiator prepared by the present invention is lower than that of photoinitiator 989 in the formulation.

[0093] In summary, compared with the known commercially available amino ketone type photoinitiators, the α-amino ketone compounds disclosed in the present invention are environmentally friendly without sulfur, have good solubility, high photocuring efficiency, and have better solubility in the photocuring system and more excellent performance in application performance. They can greatly improve the performance of known photocured products or explore new uses in this field. In the preparation method of the α-amino ketone compounds of the present invention, using naphthalene as the raw material reduces the cost of the raw materials. In addition, the yield of the preparation method of the present invention is high, reaching more than 80%, and the purity can reach more than 95%. Compared with existing products, the present invention uses inexpensive and readily available industrial-grade raw materials as the starting breakthrough point, uses naphthalene as the key group, and prepares α-amino aromatic ketones through easy-to-operate process flows such as Friedel-Crafts reaction, halogenation, substitution, and rearrangement, improving the photoinitiating efficiency. The prepared compound is an environmentally friendly, non-toxic, and highly efficient photoinitiator, avoiding problems such as the emission of volatile toxic small molecule organic compounds during photocuring, the generation of irritating and unpleasant odors, or the physiological toxicity caused by compound migration. It has a good promoting effect on the popularization and application in the field of ultraviolet radiation photocuring.

[0094] Meanwhile, the content not detailedly described in this specification belongs to the prior art well-known to those skilled in the art.

[0095] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0096] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An amino ketone photoinitiator, characterized in that, The amino ketone photoinitiator is an α-amino ketone compound, and the specific structural formula of the α-amino ketone compound is as follows: Among them, X is represented as R1 or R2 is independently selected from a straight-chain or branched-chain alkyl group having C1-C 10 or a cycloalkyl group having C4-C 10 any one of them; or R1 and R2 are connected to each other or form a five-membered or six-membered cyclic group through -O-, -S-, -N-.

2. The amino ketone photoinitiator according to claim 1, wherein The structural formula of the α-amino ketone compound is any one of the structures shown below: In the above reaction formula, the definitions of each group are the same as those in the corresponding item of claim 1.

3. A method for preparing the α-amino ketone compound according to claim 1, characterized in that: Specifically, it includes the following steps: S1. The raw material naphthalene A and the raw material propionyl chloride B undergo a Friedel-Crafts acylation reaction under the catalysis of a Lewis acid to obtain an intermediate compound II. The specific reaction formula is as follows; S2. The intermediate compound II undergoes an α-H halogenation reaction of the carbonyl group with chlorine to obtain an intermediate compound III. The specific reaction formula is as follows; S3. The intermediate compound III reacts with the raw material X by ammonolysis to generate an intermediate compound IV. The specific reaction formula is as follows; where the raw material X is S4. The intermediate compound IV undergoes a Stevens rearrangement reaction with the raw material C under alkaline conditions to generate the target product α-amino ketone compound. The specific reaction formula is as follows:

4. The preparation method of an α-amino ketone compound according to claim 3, wherein: In step S4, the quaternary ammonium salt compound is dissolved in a 20wt%-40wt% sodium hydroxide solution, and the rearrangement reaction is carried out at 50-100 °C for 5-6 h.

5. The preparation method of an α-amino ketone compound according to claim 3, wherein: In step S1, the raw material naphthalene A is dissolved in dichloroethane, a Lewis acid is added at 0 °C, and the raw material propionyl chloride B is added dropwise. After the addition is completed, the reaction is carried out at 0 °C for 4-6 h.

6. The preparation method of an α-amino ketone compound according to claim 3, characterized in that: In step S1, the Lewis acid is one of aluminum trichloride, iron trichloride, zinc chloride or titanium tetrachloride.

7. The preparation method of an α-amino ketone compound according to claim 3, characterized in that: In step S4, the base is selected from one or more of potassium carbonate, potassium hydroxide, and sodium hydroxide, and the ratio of the base to the compound is 1:(3-10).

8. The preparation method of an α-amino ketone compound according to claim 3, wherein: The raw material C is benzyl chloride or benzyl bromide.

9. The preparation method of an α-amino ketone compound according to claim 4, characterized in that: After the rearrangement reaction in step S4 is completed, it also includes a step of purifying the obtained product. Specifically, the reaction is cooled to room temperature, ethyl acetate is added for extraction, the organic phase is washed twice with water, dried with anhydrous sodium sulfate, and concentrated to obtain the target product α-amino ketone compound.

10. A photocurable composition, characterized in that: It includes at least one rare earth unsaturated double bond compound and at least one amino ketone photoinitiator as described in claim 1 or 2. The photocurable composition undergoes polymerization under irradiation with a light source in the range of 200-405 nm.

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