Sulfur-containing photoinitiator, its preparation method and application

Abstract

The present application relates to a kind of sulfur-containing photoinitiator and its preparation method and application, the sulfur-containing photoinitiator compared with traditional free radical type II photoinitiator BP, it has more optimal photo-curing activity under ultraviolet light irradiation, the energy required for photo-curing is lower, and the migration rate in coating after photo-curing is low, and good use safety.

Description

Technical Field

[0001] The invention belongs to the field of photoinitiators and relates to a sulfur-containing photoinitiator and a preparation method and application thereof. Background Art

[0002] Photoinitiators are a type of compound that can absorb energy of a certain wavelength in the ultraviolet or visible light region to generate free radicals, cations, etc., thereby initiating monomer polymerization, cross-linking and curing.

[0003] With the development of the light-curing technology industry, the requirements for photoinitiators are getting higher and higher, and the research is becoming more and more in-depth. Benzophenone, as a commonly used free radical type II photoinitiator, belongs to a small molecule photoinitiator. During use, it has problems such as high migration rate, which limits its application range.

[0004] Therefore, it is still of great significance to develop a photoinitiator with high activity and low mobility in the cured coating and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a sulfur-containing photoinitiator and its preparation method and application. Compared with the traditional free radical type II photoinitiator BP, the sulfur-containing photoinitiator has better photocuring activity under ultraviolet light irradiation, lower energy required for photocuring, low migration rate in the coating after photocuring, and good safety in use.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a sulfur-containing photoinitiator, the chemical structure of the sulfur-containing photoinitiator is shown as a compound of formula a;

[0008]

[0009] wherein n is selected from 2;

[0010] R1 is selected from any one of the following chemical structural formulas;

[0011]

[0012] R2 and R3 are each independently selected from a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group or a butyl group.

[0013] Compared with the free radical II type photoinitiator BP, the sulfur-containing photoinitiator of the present invention has better photoinitiating activity and lower mobility in the coating.

[0014] Preferably, R2 and R3 are selected from methyl.

[0015] Preferably, the chemical structural formula of the sulfur-containing photoinitiator is as follows:

[0016]

[0017] Preferably, the compound of formula I is a white solid with a melting point of 109°C to 112°C.

[0018] Preferably, the compound of formula II is a light yellow solid with a melting point of 98°C to 102°C.

[0019] Preferably, the compound of formula III is a milky white colloid.

[0020] In a second aspect, the present invention provides a method for preparing the sulfur-containing photoinitiator according to the first aspect, the method comprising: mixing a compound of formula b, a compound of formula c, a catalyst, and an organic solvent, and heating the mixture to carry out an esterification reaction to obtain a compound of formula a;

[0021]

[0022] wherein n is selected from 2, and X is selected from Cl or Br;

[0023] R1 is selected from any one of the following chemical structural formulas;

[0024]

[0025] R2 and R3 are each independently selected from a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group or a butyl group.

[0026] The sulfur-containing photoinitiator of the present invention uses the above-mentioned compound of formula b and compound of formula c as raw materials, and can obtain the target photoinitiator through a one-step esterification reaction. The post-processing is simple and the yield of the target product is high. Taking the compound of formula I, the compound of formula II and the compound of formula III as examples, the yield of the target product is above 65%. The product is also high in purity and light in color. The obtained target product is used as a photoinitiator, has high photoinitiating activity, low volatility, low odor, and low migration rate in the coating.

[0027] The reaction equation for the preparation method of the sulfur-containing photoinitiator of the present invention is as follows:

[0028]

[0029] Preferably, the catalyst is selected from alkaline catalysts, preferably sodium hydroxide and / or potassium hydroxide.

[0030] Preferably, the organic solvent is selected from N,N-dimethylformamide.

[0031] Preferably, the molar ratio of the compound of formula b, the compound of formula c and the catalyst is 1:(0.9-1.05):(1-2), for example 1:1:1.2.

[0032] Preferably, the temperature for the esterification reaction is selected from 60°C to 80°C, such as 65°C, 70°C or 75°C.

[0033] In the present invention, the above-mentioned catalyst, reaction solvent, raw material ratio and reaction temperature are used in the esterification reaction process, the reaction rate is fast, the required reaction time is 3 hours to 4 hours, and the reaction process has good selectivity and a high yield of the target product. After the esterification reaction is completed, the reaction product is easy to purify, making it easy to obtain the target sulfur-containing photoinitiator with a narrow melting range and high purity.

[0034] Preferably, after the esterification reaction is completed, the reaction solution of the esterification reaction is filtered, desalted, desolventized, and purified to obtain the compound of formula A. The filtration and desalting is used to remove solid salts generated during the reaction.

[0035] Preferably, the purification method comprises chromatography and / or recrystallization.

[0036] The purification method in the present invention can be determined according to the properties of the target product. Taking the compound of formula I as an example, the desolvated product can be subjected to petroleum ether / ethyl acetate column chromatography to obtain a white solid product; taking the compound of formula II as an example, the desolvated product is dissolved in ethyl acetate, washed with water, desolvated, and then the desolvated product is recrystallized in dichloromethane to obtain a light yellow solid photoinitiator; taking the compound of formula III as an example, the desolvated product is dissolved in ethyl acetate, washed with water, desolvated, and subjected to petroleum ether / ethyl acetate column chromatography to obtain a milky white colloid.

[0037] Preferably, taking n as an example, the compound of formula c' is prepared by the following method, which comprises the following steps:

[0038] (a) mixing a compound of formula d, a first catalyst, mercaptoethanol, and a first reaction solvent, heating to reflux for reaction, cooling after the reaction is complete, filtering to remove the generated salt, desolventizing, and recrystallizing to obtain a compound of formula e;

[0039]

[0040] (b) mixing the compound of formula e obtained in step (a), the second catalyst and the second reaction solvent, adding an acylating agent dropwise to carry out an acylation reaction, and after the reaction is completed, filtering to remove the generated salt, then washing with alkali, washing with water, drying, and desolventizing to obtain a compound of formula c'.

[0041] The reaction equation for the preparation method of the compound of formula c' is shown below:

[0042]

[0043] Preferably, in step (a), the first catalyst is selected from sodium hydroxide and / or potassium hydroxide.

[0044] Preferably, in step (a), the first reaction solvent is selected from N,N-dimethylformamide.

[0045] Preferably, in step (a), the molar ratio of the compound of formula d, the first catalyst and mercaptoethanol is 1:(1-1.5):(1-1.2), for example 1:1:1 or 1:1.2:1.1.

[0046] Preferably, the desolventizing in step (a) is carried out by distillation under reduced pressure.

[0047] Preferably, the solvent for the recrystallization in step (a) is selected from toluene.

[0048] Preferably, in step (b), the second catalyst is selected from triethylamine.

[0049] Preferably, in step (b), the second reaction solvent is selected from dichloromethane and / or dichloroethane.

[0050] Preferably, the acylating agent in step (b) is selected from chloroacetyl chloride.

[0051] Preferably, in step (b), the molar ratio of the compound of formula e, the second catalyst and the acylating agent is 1:(1-1.5):(1-1.5), for example, 1:1.2:1.2.

[0052] Preferably, the alkali solution used for alkali washing in step (b) is selected from saturated sodium bicarbonate solution.

[0053] Preferably, the detergent used for water washing in step (b) is selected from saturated NaCl solution.

[0054] In a third aspect, the present invention provides a photocurable composition comprising the sulfur-containing photoinitiator described in the first aspect.

[0055] Preferably, in the photocurable composition, the mass proportion of the sulfur-containing photoinitiator is 0.5% to 6%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or 5.5%, etc., preferably 3% to 5%.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The sulfur-containing photoinitiator of the present invention has lower energy required for photocuring and lower migration rate in the cured coating, thereby improving safety in use. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is the ultraviolet absorption spectrum of the sulfur-containing photoinitiator in Example 1 of the present invention;

[0059] Figure 2 is the ultraviolet absorption spectrum of the sulfur-containing photoinitiator in Examples 2 and 3 of the present invention;

[0060] Figure 3 It is the ultraviolet absorption spectrum of the photoinitiator in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] Example 1

[0063] This embodiment provides a sulfur-containing photoinitiator and a preparation method thereof. The sulfur-containing photoinitiator is prepared by the following method, which specifically includes the following steps:

[0064] (1) Add the compound of formula b', the compound of formula c', NaOH and N,N-dimethylformamide to a 100 mL three-necked flask, and heat the mixture to 70°C under electromagnetic stirring for 4 hours to carry out esterification reaction until the raw materials are substantially reacted; wherein the molar ratio of the compound of formula b', the compound of formula c' and NaOH is 1:1:1.2;

[0065]

[0066] (2) After the reaction solution in step (1) is cooled to room temperature, it is filtered to remove the solid salt produced during the reaction, and the solvent is removed by distillation under reduced pressure. The residue is subjected to column chromatography using petroleum ether / ethyl acetate (V / V=5 / 1) to obtain a white solid with a yield of 66% and a melting point of 109°C to 112°C.

[0067] The chemical structural formula of the white solid sulfur-containing photoinitiator obtained in this embodiment is as follows:

[0068]

[0069] The nuclear magnetic resonance test results of the above sulfur-containing photoinitiator are shown below;

[0070] 1H NMR (400MHz, CDCl3) δ / ppm: 7.86 (d, J = 9.2Hz, 2H), 7.67 (dd, J = 10.4, 7.0Hz, 4H), 7.49 (t, J = 7.4Hz, 1H), 7.39 (t, J = 7.6Hz, 2H), 7.32 (d, J = 8.4Hz, 2H), 6.55 (d, J = 9.2Hz, 2H), 4.70 (s, 2H), 4.31 (t, J = 7.2Hz, 2H), 3.19 (t, J = 7.1Hz, 2H), 2.95 (s, 2H).

[0071] 13 C NMR(101MHz, CDCl3)δ / ppm:195.76,168.34,166.23,153.68,141.86,137.62,134.80,132. 37,131.76,130.85,129.91,128.35,127.03,115.48,110.72,63.12,60.56,40.04,30.48.

[0072] The mass spectrometry test results are shown below;

[0073] HRMS (ESI, m / z): Calcd. for C 26 H 25 NO5S[M + ]:463.1453,found 486.1348[M+Na].

[0074] Example 2

[0075] This embodiment provides a sulfur-containing photoinitiator and a preparation method thereof. The sulfur-containing photoinitiator is prepared by the following method, which specifically includes the following steps:

[0076] (1) dissolving the compound of formula b', the compound of formula c', and sodium hydroxide in N,N-dimethylformamide, heating to 70°C for 4 hours to complete the esterification reaction; wherein the molar ratio of the compound of formula b', the compound of formula c', and NaOH is 1:1:1;

[0077]

[0078] (2) The reaction solution in step (1) was cooled to room temperature, and the solid salt generated during the reaction was filtered out. After removing the solvent, ethyl acetate was added to dissolve the product, and the product was washed with water. After the organic phase was dried, the solvent was concentrated to obtain a crude product, which was recrystallized from dichloromethane to obtain a light yellow solid; the yield was 78%, and the melting point was 98°C to 102°C.

[0079] The chemical structural formula of the light yellow solid sulfur-containing photoinitiator obtained in this example is as follows:

[0080]

[0081] The nuclear magnetic resonance test results of the above sulfur-containing photoinitiator are shown below;

[0082] 1 H NMR (400MHz, CDCl3) δ / ppm: 8.93 (dd, J=8.0, 1.7Hz, 1H), 8.56 (dd, J=7.6, 1.7Hz, 2H), 7.78-7.74 (m, 4H), 7.65- 7.64(m,2H),7.60-7.46(m,5H),7.42-7.40(m,2H),4.94(s,2H),4.47(t,J=7.0Hz,2H),3.32(t,J=7.0Hz,2H).

[0083] 13 C NMR(101MHz, CDCl3)δ / ppm:195.67,179.61,167.29,164.92,141.63,140.78,138.35,137.55,136.25,135.67,134.93,1 32.77,132.40,130.85,130.71,129.88,129.25,128.34,127.10,126.86,126.59,125.12,124.33,63.47,61.32,30.63.

[0084] The mass spectrometry test results are shown below;

[0085] HRMS (ESI, m / z): Calcd. for C 31 H 22 O6S2[M+]:554.0858,found 577.0755[M+Na].

[0086] Example 3

[0087] This embodiment provides a sulfur-containing photoinitiator and a preparation method thereof. The sulfur-containing photoinitiator is prepared by the following method, which specifically includes the following steps:

[0088] (1) Add the compound of formula b', the compound of formula c', sodium hydroxide and N,N-dimethylformamide into a 100 mL three-necked flask, stir evenly with electromagnetic stirring, and heat the reaction solution to 70°C for 3 hours to complete the esterification reaction; wherein the molar ratio of the compound of formula b', the compound of formula c' and NaOH is 1:1:1.5;

[0089]

[0090] (2) After the reaction solution in step (1) is cooled to room temperature, the solid salt generated during the reaction is filtered out, the solvent is evaporated, and ethyl acetate is added to dissolve the product, washed with water, separated, and the organic phase is dried over anhydrous sodium sulfate. After filtering out the desiccant, the solvent is evaporated to dryness to obtain an orange-yellow oil, which is then purified by petroleum ether / ethyl acetate (V / V=4 / 1) column chromatography to obtain a milky white colloid with a yield of 70%.

[0091] The chemical structural formula of the milky white colloid sulfur-containing photoinitiator obtained in this embodiment is as follows:

[0092]

[0093] The nuclear magnetic resonance test results of the above sulfur-containing photoinitiator are shown below;

[0094] 1 H NMR (400MHz, CDCl3) δ / ppm: 8.13 (d, J = 8.0Hz, 1H), 7.77-7.71 (m, 6H), 7.64 (t, J = 7.5Hz, 1H), 7.58-7.53 ( m,2H),7.52-7.44(m,3H),7.42-7.35(m,5H),4.59(s,2H),4.28(t,J=7.1Hz,2H),3.16(t,J=7.1Hz,2H).

[0095] 13 C NMR (101MHz, CDCl3) δ / ppm: 196.70, 195.62, 167.05, 165.20, 142.22, 141.84, 137.58, 136.93, 134.75, 133.27, 132. 97,132.42,130.82,130.56,129.88,129.75,129.50,128.56,128.37,128.07,127.88,126.93,63.21,61.18,30.21.

[0096] The mass spectrometry test results are shown below;

[0097] HRMS (ESI, m / z): Calcd. for C 31 H 24 O6S[M + ]:524.1294,found 547.1188[M+Na].

[0098] In the above Examples 1-2, the compound of formula c' can be prepared by the following method, which specifically comprises the following steps:

[0099] (a) dissolving a compound of formula d, NaOH, and mercaptoethanol in N,N-dimethylformamide, heating to reflux, and monitoring the completion of the reaction by thin-layer chromatography, followed by cooling to room temperature, filtering to remove the generated salt, and distilling the filtrate under reduced pressure to remove the solvent. The residue is recrystallized from toluene to obtain a compound of formula e; wherein the molar ratio of the compound of formula d, NaOH, and mercaptoethanol is 1:1:1;

[0100]

[0101] (b) adding the compound of formula e obtained in step (a), triethylamine, and dichloromethane to a 50 mL three-necked flask, and adding dropwise a mixture of chloroacetyl chloride and dichloromethane at room temperature under electromagnetic stirring, wherein the molar ratio of the compound of formula e, triethylamine, and chloroacetyl chloride is 1:1.2:1.2; monitoring the reaction progress by thin layer chromatography; after the reaction is completed, filtering to remove triethylamine salt; washing with saturated sodium bicarbonate solution, and then washing with saturated NaCl solution, collecting the lower organic phase and drying it with anhydrous sodium sulfate, and concentrating the solvent by rotary evaporation to obtain a brown oil, which is then subjected to column chromatography to obtain a colorless transparent oil, which solidifies after standing to obtain compound c'.

[0102] Comparative Example 1

[0103] This comparative example uses free radical type II photoinitiator BP as a control.

[0104] Comparative Example 2

[0105] This comparative example uses free radical type II photoinitiator ITX as a control.

[0106] The photoinitiators in Examples 1-3 and Comparative Example 1 were subjected to UV absorption tests. The test method included preparing 5×10 -5 mol / L) of photoinitiator and BP in acetonitrile solution, take appropriate amount of solution and acetonitrile (as blank control) in cuvette for UV-visible light absorption test; the test results are as follows Figures 1 to 3 The corresponding maximum molar absorption coefficient is shown in Table 1;

[0107] Table 1

[0108]

[0109] As can be seen from the above table, the maximum absorption wavelength in Example 1 is significantly red-shifted, the ultraviolet-visible maximum absorption wavelength in Example 2 is not significantly different from that in Comparative Example 1, but the ultraviolet absorption intensity at 300nm and 380nm is greater than that of BP, and the ultraviolet-visible maximum absorption wavelength in Example 3 is slightly blue-shifted compared with BP, but the ultraviolet absorption intensity at 300nm and 380nm is greater than that of BP; and the maximum molar extinction coefficient of the photoinitiator in the embodiments of the present invention is significantly greater than that of BP, which can improve the ultraviolet absorption ability to a certain extent, is more conducive to the generation of free radicals, and thus better initiates the polymerization of the system.

[0110] Application Examples

[0111] This application example uses the sulfur-containing photoinitiator prepared in Examples 1-3 and the photoinitiator in Comparative Examples 1-2 as raw materials to prepare a photocurable composition, tests its curing performance, and tests the migration of the sulfur-containing photoinitiator in the cured coating. Specifically, the following contents are included:

[0112] (I) Light curing energy test, the test method is as follows:

[0113] The photoinitiator, co-initiator, resin, and monomer were weighed in proportion and mixed evenly by ultrasonic stirring. The mixed coating was applied to a glass slide with a film applicator to a thickness of 10 μm. The mixed coating was irradiated once under a high-pressure mercury lamp or an LED (395 nm) light source to form a film. The energy required for curing was recorded using a UV energy meter. The test results are shown in Table 2 (high-pressure mercury lamp curing) and Table 3 (LED curing);

[0114] In the above test, the resin was selected from epoxy acrylic resin E51, and the monomers were pentaerythritol triacrylate (PETA) and ethoxylated trimethylolpropane triacrylate (EO3-TMPTA); the mass ratio of the above resin and monomers was as follows: epoxy acrylic resin E51:PETA:EO3TMPTA = 5:3:2;

[0115] Taking the total mass of the photoinitiator, co-initiator, resin and monomer as 100%, the co-initiator is ethyl p-dimethylaminobenzoate (EDB), accounting for 3% by mass; the sulfur-containing photoinitiator is used in two proportions, 3% and 5% respectively;

[0116] Table 2

[0117]

[0118]

[0119] In the table above, "-" indicates that the corresponding substance is not present in the formulation. At both 3% and 5% photoinitiator ratios, the photoinitiators in Examples 1-2 exhibited superior activity to that of the photoinitiator in Comparative Example 1. Furthermore, the photoinitiator in Example 1 was able to initiate photocuring in a system without a co-initiator, and exhibited superior initiation activity to that of Comparative Example 1. This is because the photoinitiator in Example 1 is more efficient in initiating resin polymerization by generating aminoalkyl radicals through intramolecular hydrogen abstraction than in the intermolecular hydrogen abstraction of the BP / EDB system.

[0120] Table 3

[0121] Photoinitiator Photoinitiator ratio Co-initiator (3%) Photocuring energy (mJ / cm2) Example 2 5％ EDB 43 Comparative Example 1 5％ EDB Unable to solidify Comparative Example 2 5％ EDB 28.2

[0122] As can be seen from the above table, the photoinitiator in Example 2 still has excellent photocuring activity under LED light source, and the energy required for photocuring is relatively small. The reason may be that it still has a large ultraviolet absorption intensity at 300nm and 380nm.

[0123] (II) Migration test in coating, the test method is as follows:

[0124] Weigh the photoinitiator, co-initiator, resin and monomer in proportion, mix them evenly with ultrasonic stirring, apply the mixed coating on a glass slide (10mm×30mm) with a film applicator with a thickness of 10μm, and place it under a high-pressure mercury lamp for 3-5 minutes to completely cure it;

[0125] A glass slide with a uniform film mass was immersed in a brown glass bottle containing 20 mL of acetonitrile for 4 days. An appropriate volume of the immersion solution was then sampled for UV absorption testing. The relative mobility of the photoinitiator and BP was calculated using the following equations: C = A / (ε·L); R = 100 × C1 / C2. The results are shown in Table 4.

[0126] Wherein: C1 is the concentration of the photoinitiator in the example in the extract, mol / L; A is the absorbance at λmax; ε is the molar extinction coefficient, L·mol-1·cm-1; L is the optical path length, 1 cm; C2 is the concentration of BP in the extract; and R is the relative mobility.

[0127] In the above test method, the resin is selected from epoxy acrylic resin E51, and the monomers are pentaerythritol triacrylate (PETA) and ethoxylated trimethylolpropane triacrylate (EO3-TMPTA); the mass ratio of the above resin and monomer is as follows: epoxy acrylic resin E51:PETA:EO3TMPTA = 5:3:2;

[0128] The photoinitiator is the sulfur-containing photoinitiator in Examples 1-3 or the photoinitiator in Comparative Example 1; the co-initiator is ethyl p-dimethylaminobenzoate (EDB), and based on the total mass of the mixed coating being 100%, the mass proportion of the co-initiator is 3%, and the mass proportion of the photoinitiator is selected from 3%;

[0129] Table 4

[0130]

[0131] In the above table, the lower the concentration of the photoinitiator in the immersion solution, the less the migration of the photoinitiator, and the photoinitiator has the advantage of low migration. As can be seen from the above table, the photoinitiator of the present invention has the advantage of low migration. The reason may be that the photoinitiator of the present invention participates in both photoinitiation and photopolymerization during the resin polymerization process, so that most of the photoinitiator is anchored in the cured film system, thereby reducing the migration of the photoinitiator in the cured film.

[0132] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A sulfur-containing photoinitiator, characterized in that The chemical structural formula of the sulfur-containing photoinitiator is shown in Formula a: Where n is 2; R1 is selected from any one of the following chemical structural formulas; R2 and R3 are each independently selected from C1-C4 alkyl groups.

2. The sulfur-containing photoinitiator according to claim 1, characterized in that R2 and R3 are selected from methyl groups.

3. The sulfur-containing photoinitiator according to claim 2, characterized in that The chemical structural formula of the sulfur-containing photoinitiator is shown below:

4. A method for preparing a sulfur-containing photoinitiator, wherein the sulfur-containing photoinitiator is the sulfur-containing photoinitiator according to any one of claims 1 to 3, characterized in that: The method comprises: mixing a compound of formula b, a compound of formula c, a catalyst and an organic solvent, and heating the mixture to carry out an esterification reaction to obtain a compound of formula a; wherein n is 2, and X is selected from Cl or Br; R1 is selected from any one of the following chemical structural formulas; R2 and R3 are each independently selected from C1-C4 alkyl groups.

5. The preparation method according to claim 4, characterized in that The catalyst is selected from basic catalysts.

6. The preparation method according to claim 5, characterized in that The catalyst is sodium hydroxide or potassium hydroxide.

7. The preparation method according to claim 5, characterized in that The organic solvent is N,N-dimethylformamide.

8. The preparation method according to claim 4, characterized in that The molar ratio of the compound of formula b, the compound of formula c and the catalyst is 1:(0.9-1.05):(1-2).

9. The preparation method according to claim 4, characterized in that The temperature for the esterification reaction is selected from 60°C to 80°C.

10. The preparation method according to claim 4, characterized in that After the esterification reaction is completed, the reaction liquid of the esterification reaction is filtered, desalted, desolventized, and purified to obtain the compound of formula a.

11. The preparation method according to claim 10, characterized in that: The purification method includes chromatography or recrystallization.

12. A photocurable composition, characterized in that: The photocurable composition comprises the sulfur-containing photoinitiator according to any one of claims 1 to 3.

13. The photocurable composition according to claim 12, characterized in that In the photocurable composition, the mass proportion of the sulfur-containing photoinitiator is 0.5% to 6%.

14. The photocurable composition according to claim 13, wherein In the photocurable composition, the mass proportion of the sulfur-containing photoinitiator is 3% to 5%.

Images