A photoinitiator with space charge transfer property under low power illumination, and a preparation method and application thereof

Abstract

The application provides a photoinitiator with space charge transfer properties under low-power light irradiation, a preparation method and application thereof, and relates to the field of photoinitiators. The photoinitiator is composed of different electron donors and acceptors connected by a spirofluorene bridge. The excited state species formed by space charge transfer under low-power light excitation has the properties of long lifetime and strong excited state reduction ability. By regulating different electron donors and acceptors, charge transfer triplet and local triplet species are generated. Both kinds of excited state species can efficiently initiate polymerization of acrylate monomers under UV visible light irradiation in different systems. Moreover, the photopolymerization system can be well matched with photoresist after adding a film-forming resin, and a clear 10 μm line width photoresist pattern can be etched under 16 mW cm ‑2 A clear 10 μm line width photoresist pattern is etched under light irradiation.

Description

Technical Field

[0001] This application relates to the field of organic photoinitiator materials technology, and more specifically, to a photoinitiator with space charge transfer properties under low-power light irradiation, its preparation method, and its application. Background Technology

[0002] Free radical photopolymerization has wide applications in various fields such as 3D / 4D printing, microelectronic lithography, biomedicine, and the coatings industry. It is renowned for its environmental and energy-saving advantages. Based on the way active free radicals are generated, photopolymerization can be divided into Type I and Type II. In Type I systems, the excited photoinitiator undergoes chemical bond breaking upon exposure to light, generating active free radicals that initiate the polymerization reaction. In contrast, Type II photopolymerization typically involves hydrogen donors / photoinitiators and co-initiators, with the main mechanism being intermolecular electron transfer.

[0003] Type II photopolymerization, consisting of a photoinitiator and a co-initiator, has the advantages of being a universal system and being activatable by low-energy photons. The excited-state properties of the photoinitiator are crucial in determining the electron transfer efficiency with the co-initiator and subsequent monomer photopolymerization. The transition from the triplet excited state to the ground state is spin-forbidden, which typically leads to a longer excited-state lifetime (μs-ms) compared to the singlet excited state (ps-ns). Excited triplet states include charge-transfer triplet states (…). 3 CT) and local triplet state ( 3 LE), currently photoinitiation is mainly based on 3 LE-type polymers undergo electron transfer with co-initiators to further initiate polymerization; however, the long-lived... 3 Whether CT can undergo electron transfer to initiate polymerization requires further investigation, mainly due to the difficulty in constructing long-lived CT-state photoinitiators.

[0004] Application content

[0005] To overcome at least one of the problems existing in the prior art, the primary objective of this application is to provide a photoinitiator with space charge transfer properties under low-power illumination. This type of photoinitiator improves the excited state lifetime through space charge transfer, and at the same time, different long-lived excited state species can be obtained through different donor-acceptor regulation.

[0006] Another objective of this application is to provide the above-described preparation method.

[0007] Another object of this application is to provide the application of the above-mentioned photoinitiator with space charge transfer properties in photopolymerization.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this application is:

[0009] A photoinitiator with space charge transfer property under low power light, the photoinitiator is spirofluorene bridged, and has one of the following molecular structures:

[0010]

[0011] wherein R represents naphthalene, anthracene, perylene, pyrene, naphthalimide functional groups.

[0012] Preferably, the photoinitiator with space charge transfer property is selected from any of the following structures:

[0013]

[0014]

[0015]

[0016] More preferably, the photoinitiator with space charge transfer property has one of the following molecular structures:

[0017]

[0018] The application also provides a preparation method of the above-mentioned photoinitiator with space charge transfer property TSC-1, which comprises the following steps:

[0019] S1. Preparation of intermediate PXZ-Br:

[0020] PXZ, 2-bromine iodobenzene, cuprous iodide, 18-crown-6 ether and potassium carbonate are dissolved in a two-necked flask containing o-dichlorobenzene, then heated to 180 degrees Celsius under nitrogen atmosphere, and refluxed for 48 hours. After the reaction solution is cooled to room temperature, the solvent is rotary evaporated, extracted with dichloromethane and water for three times, dried over anhydrous sodium sulfate, and then the crude product is purified by silica gel column to obtain the intermediate PXZ-Br;

[0021] S2. Preparation of intermediate LW-Br:

[0022] The PXZ-Br is dissolved in tetrahydrofuran under argon atmosphere, and is placed in a 10 ml two-necked flask. The solution is cooled to -78°C, and then n-butyllithium is added dropwise through a syringe. The mixture is stirred at -78°C for 1 hour, and then 1-bromo-9H-fluoren-9-one is added within 15 minutes. After the reaction at -78°C for 2 hours, the mixture is stirred at room temperature for 3 hours. Water is added to quench the reaction, and then tetrahydrofuran is evaporated under reduced pressure. The obtained solid is dissolved in dichloromethane, and is washed with water. Then the organic layer is separated, dried over sodium sulfate, filtered and evaporated. The crude product is directly used for the next reaction without further purification. The crude product is dissolved in acetic acid and hydrochloric acid. After the reaction at 110°C for 4 hours, it is cooled to room temperature, and is extracted with dichloromethane and water for three times. After drying over anhydrous sodium sulfate, the crude product is purified by silica gel column to obtain the intermediate LW-Br.

[0023] S3. Preparation of the target product TSC-1:

[0024] The intermediate LW-Br, 4-boronate naphthalimide and potassium carbonate are dissolved in a mixture of N,N-dimethylformamide and water, and then Pd3(PPd3)4 is added under N2 atmosphere. The reaction mixture is heated to 90°C and refluxed with stirring. After cooling to room temperature, the product is extracted with dichloromethane and water, and is dried over anhydrous sodium sulfate. The crude product is purified by silica gel column to obtain the target product TSC-1.

[0025] Preferably, the crude product in step S1 is purified by silica gel column with polarity dichloromethane: petroleum ether = 3:7.

[0026] Preferably, the crude product in step S2 is purified by silica gel column with pure petroleum ether.

[0027] Preferably, the crude product in step S3 is purified by silica gel column with polarity dichloromethane: petroleum ether = 1:8.

[0028] Preferably, in step S2, the column chromatography is performed by using neutral alumina with petroleum ether as eluent.

[0029] The application also provides a preparation method of the photoinitiator TSC-2 with space charge transfer property, comprising the following steps:

[0030] S1. Preparation of the intermediate PXZ-Br:

[0031] PXZ, 2-bromoiodobenzene, cuprous iodide, 18-crown-6 ether and potassium carbonate are dissolved in a two-necked flask of o-dichlorobenzene, and then heated to 180°C to reflux under nitrogen atmosphere. After the reaction for 48 hours, the reaction solution is cooled to room temperature, and then the solvent is evaporated. The product is extracted with dichloromethane and water for three times, and is dried over anhydrous sodium sulfate. The crude product is purified by silica gel column to obtain the intermediate PXZ-Br.

[0032] S2. Preparation of intermediate LW-Br:

[0033] Under argon atmosphere, PXZ-Br was dissolved in tetrahydrofuran in a 10 ml two-necked flask, the solution was cooled to -78℃, then n-butyllithium was added dropwise by syringe, the obtained mixture was stirred at -78℃ for 1 hour, then compound 1-bromo-9H-fluoren-9-one was added within 15 minutes, the mixture was reacted at -78℃ for 2 hours, then stirred at room temperature for 3 hours, water was added to quench the reaction, then tetrahydrofuran was evaporated under reduced pressure, the obtained solid was dissolved in dichloromethane, and washed with water, then the organic layer was separated, dried with sodium sulfate, filtered and evaporated, directly used in the next reaction without further purification, the crude product was dissolved in acetic acid and hydrochloric acid, reacted at 110℃ for 4 hours, then cooled to room temperature, extracted with dichloromethane and water for three times, dried with anhydrous sodium sulfate, then the crude product was purified by silica gel column to obtain intermediate LW-Br;

[0034] S4. Preparation of target product TSC-2:

[0035] Intermediate LW-Br, 9-anthracene boronic acid and potassium carbonate were dissolved in a mixture of N,N-dimethylformamide / water, then Pd3(PPd3)4 was added under N2 atmosphere, the reaction mixture was heated to 140℃ and refluxed under stirring, then cooled to room temperature, the product was extracted with dichloromethane and water, and dried with anhydrous sodium sulfate, the crude product was purified by silica gel column to finally obtain target product TSC-2.

[0036] The application also provides a photopolymerization system consisting of the photoinitiator of claim 1 and a co-initiator, an acrylic resin monomer, and the molar ratio of the photoinitiator:co-initiator:acrylic resin is 0.01:10:100-0.001:1:1000.

[0037] Finally, the application also provides the application of the above photoinitiator in photoresist.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] The application provides a novel electron donor-acceptor regulated excitation state photoinitiator, a preparation method and application thereof. The photoinitiator is composed of different electron donors and acceptors connected by a spirofluorene bridge. The excitation state species formed by space charge transfer under light excitation has the properties of long lifetime and strong excitation state reducing capacity. By regulating different electron donors and acceptors, charge transfer triplet and local triplet state species are generated. Both excitation state species can efficiently initiate polymerization of acrylic ester monomers under UV visible light irradiation in different systems. Moreover, the photopolymerization system can be well matched with photoresist after adding a film-forming resin, and a clear 10 μm line width photoetching pattern can be etched out. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Molecular hydrogen spectrum of the photoinitiator TSC-1 prepared in Example 1 of the present application.

[0041] Figure 2 Nuclear magnetic resonance carbon spectrum of the photoinitiator TSC-1 prepared in Example 1 of the present application.

[0042] Figure 3 HRMS spectrum of the photoinitiator TSC-1 prepared in Example 1 of the present application.

[0043] Figure 4 Nuclear magnetic resonance hydrogen spectrum of the photoinitiator TSC-2 prepared in Example 2 of the present application.

[0044] Figure 5 Nuclear magnetic resonance carbon spectrum of the photoinitiator TSC-2 prepared in Example 2 of the present application.

[0045] Figure 6 HRMS spectrum of the photoinitiator TSC-2 prepared in Example 2 of the present application.

[0046] Figure 7 UV-Vis absorption spectrum of TSC-1 prepared in Example 1 of the present application in 1 x 10 -5 mol / L tetrahydrofuran.

[0047] Figure 8 UV-Vis absorption spectrum of TSC-2 prepared in Example 2 of the present application in 1 x 10 -5 mol / L tetrahydrofuran.

[0048] Figure 9 Fluorescence emission spectrum of TSC-1 prepared in Example 1 of the present application in 1 x 10 -5 mol / L tetrahydrofuran.

[0049] Figure 10 Fluorescence emission spectrum of TSC-2 prepared in Example 2 of the present application in 1 x 10 -5 mol / L tetrahydrofuran.

[0050] Figure 11 Nanosecond transient absorption spectrum and transient species lifetime spectrum at 420 nm of the photoinitiator TSC-1 prepared in Example 1 of the present application.

[0051] Figure 12 Nanosecond transient absorption spectrum and transient species lifetime spectrum at 420 nm of the photoinitiator TSC-2 prepared in Example 2 of the present application.

[0052] Figure 13 The photopolymerization system of the photoinitiator TSC-2 prepared in Example 2 of the present application in DMA monomer was prepared into a photoetching pattern. DETAILED DESCRIPTION

[0053] The embodiments of the present application will be described in detail below with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions are not specified in the examples, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be obtained by commercial purchase.

[0054] It should be noted that:

[0055] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions, unless otherwise specified.

[0056] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or according to the sequence. Preferably, the reaction method in the present application is carried out sequentially.

[0057] Unless otherwise specified, the professional and scientific terms used in the present application have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied in the present application.

[0058] The present application provides a photoinitiator with space charge transfer properties under low power light, which is a bridged spirofluorene with one of the following molecular structures:

[0059]

[0060] In which R represents naphthalene, anthracene, perylene, pyrene, naphthalimide functional groups.

[0061] In some preferred embodiments, the photoinitiator with space charge transfer properties is selected from any one of the following structures:

[0062]

[0063]

[0064]

[0065] In some more preferred embodiments, the photoinitiator with space charge transfer properties has one of the following molecular structures:

[0066]

[0067] The present application also provides a method for preparing the photoinitiator TSC-1 having space charge transfer properties as described above, which comprises the following steps:

[0068] S1. Preparation of intermediate PXZ-Br:

[0069] PXZ, 2-bromoiodobenzene, cuprous iodide, 18-crown-6 ether and potassium carbonate were dissolved in a two-necked flask containing o-dichlorobenzene, which was then heated to 180 degrees Celsius under a nitrogen atmosphere to reflux, and the reaction was allowed to proceed for 48 hours. After the reaction was cooled to room temperature, the solvent was evaporated, and the crude product was extracted with dichloromethane and water three times. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate PXZ-Br.

[0070] S2. Preparation of intermediate LW-Br:

[0071] PXZ-Br was dissolved in tetrahydrofuran under an argon atmosphere, and the solution was placed in a 10-milliliter two-necked flask. After the solution was cooled to -78 degrees Celsius, n-butyllithium was added dropwise through a syringe. The resulting mixture was stirred at -78 degrees Celsius for 1 hour, and then 1-bromo-9H-fluoren-9-one was added over 15 minutes. After the mixture was reacted at -78 degrees Celsius for 2 hours, it was stirred at room temperature for 3 hours. Water was added to the mixture to quench the reaction, and then tetrahydrofuran was evaporated under reduced pressure. The resulting solid was dissolved in dichloromethane and washed with water. Then, the organic layer was separated, dried with sodium sulfate, filtered, and evaporated. The crude product was used directly in the next reaction without further purification. The crude product was dissolved in acetic acid and hydrochloric acid, and reacted at 110 degrees Celsius for 4 hours. After the mixture was cooled to room temperature, it was extracted with dichloromethane and water three times. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate LW-Br.

[0072] S3. Preparation of target product TSC-1:

[0073] The intermediate LW-Br, 4-boronate naphthalimide, and potassium carbonate were dissolved in a mixture of N,N-dimethylformamide and water, and then Pd3(PPd3)4 was added under a nitrogen atmosphere. The reaction mixture was heated to 90 degrees Celsius and refluxed with stirring. After the mixture was cooled to room temperature, the product was extracted with dichloromethane and water, and dried with anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography to obtain the target product TSC-1.

[0074] In some preferred embodiments, the crude product in step S1 is purified by silica gel column chromatography with dichloromethane: petroleum ether = 3:7 as the polarity.

[0075] In some preferred embodiments, the crude product in step S2 is purified by silica gel column chromatography with pure petroleum ether.

[0076] In some preferred embodiments, the crude product in step S3 is purified by silica gel column chromatography with a polarity of dichloromethane:petroleum ether = 1:8.

[0077] In some preferred embodiments, in step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.

[0078] This application also provides a method for preparing the photoinitiator TSC-2 with space charge transfer properties, comprising the following steps:

[0079] S1. Preparation of intermediate PXZ-Br:

[0080] PXZ, 2-bromoiodobenzene, cuprous iodide, 18-crown-6 ether, and potassium carbonate were dissolved in a two-necked flask containing o-dichlorobenzene. The mixture was then refluxed at 180°C under a nitrogen atmosphere for 48 hours. After the reaction was cooled to room temperature, the solvent was rotary evaporated and extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate PXZ-Br.

[0081] S2. Preparation of intermediate LW-Br:

[0082] Under argon atmosphere, PXZ-Br was dissolved in tetrahydrofuran and placed in a 1 mL double-necked flask. After the solution was cooled to -78°C, n-butyllithium was added dropwise using a syringe. The resulting mixture was stirred at -78°C for 1 hour, and then 1-bromo-9H-fluorene-9-one was added over 15 minutes. After reacting at -78°C for 2 hours, the mixture was stirred at room temperature for 3 hours. Water was added to the mixture to quench the reaction, and then tetrahydrofuran was evaporated under reduced pressure. The resulting solid was dissolved in dichloromethane and washed with water. The organic layer was then separated, dried with sodium sulfate, filtered, and evaporated. It was used directly for the next reaction without further purification. The crude product was dissolved in acetic acid and hydrochloric acid and reacted at 110°C for 4 hours. After cooling to room temperature, it was repeatedly extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate LW-Br.

[0083] S4. Preparation of the target product TSC-2:

[0084] The intermediate LW-Br, 9-anthraboric acid and potassium carbonate were dissolved in a mixture of N,N-dimethylformamide / water. Then, Pd3(PPd3)4 was added under N2 atmosphere. The reaction mixture was heated to 140°C and refluxed with stirring. After cooling to room temperature, the product was extracted with dichloromethane and water and dried with anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography to finally obtain the target product TSC-2.

[0085] This application also provides a photopolymerization system, which is composed of the photoinitiator and co-initiator described in claim 1 and acrylic resin monomer, wherein the molar ratio of photoinitiator:co-initiator:acrylic resin is 0.01:10:100 to 0.001:1:1000.

[0086] Finally, this application also provides the application of the above-mentioned photoinitiator in photoresist.

[0087] Next, the preparation method of the photoinitiator with space charge transfer properties of this application will be described in detail with specific embodiments.

[0088] Example 1

[0089] Preparation of a photoinitiator TSC-1 with space charge transfer properties under low-power illumination

[0090] The chemical reaction equations involved in this embodiment are as follows:

[0091]

[0092] The specific implementation process of step a, i.e. step S1, is as follows:

[0093] PXZ (1.83 g, 10.0 mmol), 2-bromoiodobenzene (4.23 g, 15.0 mmol), cuprous iodide (0.7 g, 3.7 mmol), 18-crown-6 ether (0.1 g, 0.38 mmol), and potassium carbonate (5.0 g, 3.65 mmol) were dissolved in a two-necked flask containing 80 mL of o-dichlorobenzene. The mixture was then refluxed at 180 °C under a nitrogen atmosphere for 48 h. After cooling to room temperature, the solvent was rotary evaporated. The product was extracted three times with dichloromethane and water, dried over anhydrous sodium sulfate, and purified by silica gel column chromatography with a polarity of dichloromethane:petroleum ether = 3:7 to give 2.36 g of the product. The yield was 70%.

[0094] The specific implementation process of step b, i.e. step S2, is as follows:

[0095] PXZ-Br (1011 mg, 3.0 mmol) was dissolved in 60 mL of tetrahydrofuran under argon atmosphere in a 200 mL double-necked flask. After cooling the solution to -78 °C, 1.6 M n-butyllithium (2.0 mL, 3.20 mmol) was added dropwise using a syringe. The resulting mixture was stirred at -78 °C for 1 hour, followed by the addition of compound 1-bromo-9H-fluorene-9-one (771 mg, 3.0 mmol) over 15 minutes. After reacting at -78 °C for 2 hours, the mixture was stirred at room temperature for 3 hours. 10 mL of water was added to the mixture to quench the reaction, and the tetrahydrofuran was then evaporated under reduced pressure. The resulting solid was dissolved in 100 mL of dichloromethane and washed with water (3 × 50 mL). The organic layer was then separated, dried over sodium sulfate, filtered, and evaporated, and used directly for the next reaction without further purification. The crude product was dissolved in 30 mL of acetic acid and 8 mL of hydrochloric acid. After reacting at 110°C for 4 hours, the mixture was cooled to room temperature and extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography with pure petroleum ether to give 479 mg of product LW-Br. The yield was 32%. 1 H NMR(400MHz,Methylene Chloride-d2) 1 H NMR(400MHz,Methylene Chloride-d2)δ7.79(d,J=8.0Hz,1H),7.64(t,J=8.0Hz,2H),7.45(d,J=8.0Hz,2H),7.36–7.19(m,2H),7.1 8–7.11(m,2H),7.01–6.92(m,4H),6.71(d,J=8.0Hz,2H),6.58(t,J=8.0Hz,1H),6.46(s,1H),6.04(s,1H).

[0096] The specific implementation process of step c, i.e. step S3, is as follows:

[0097] LW-Br (73 mg, 0.14 mmol), 4-boronate naphthalimide (66 mg, 0.17 mmol), and potassium carbonate (96 mg, 0.7 mmol) were dissolved in a mixture of N,N-dimethylformamide / water (6 ml / 1 ml). Pd3(PPd3)4 (6 mg, 0.005 mmol) was then added under a nitrogen atmosphere. The reaction mixture was heated to 90 °C and refluxed with stirring for 12 hours. After cooling to room temperature, the product was extracted with dichloromethane and water and dried over anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography with a polarity of dichloromethane:petroleum ether = 1:8 to give product TSC-1 75.4 mg. The yield was 80%.

[0098] Example 2 Preparation of photoinitiator TSC-2 in formula (I)

[0099]

[0100] LW-Br (73 mg, 0.14 mmol), 9-anthraboronic acid (38 mg, 0.17 mmol), and potassium carbonate (96 mg, 0.7 mmol) were dissolved in a mixture of N,N-dimethylformamide / water (6 ml / 1 ml). Then, Pd3(PPd3)4 (6 mg, 0.005 mmol) was added under a nitrogen atmosphere. The reaction mixture was heated to 140 °C and refluxed with stirring for 12 hours. After cooling to room temperature, the product was extracted with dichloromethane and water and dried over anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography with a polarity of dichloromethane:petroleum ether = 1:7 to give product TSC-2 35.2 mg. The yield was 42%.

[0101] Compound structure determination: Bruker 400MHz superconducting nuclear magnetic resonance spectrometer, deuterated dichloromethane as solvent;

[0102] Mass spectrometry detection: TSC-1 and TSC-2 obtained in Examples 1-2 were dissolved in dichloromethane to prepare a solution with a concentration of 1 mg / mL, and mass spectrometry was performed using a liquid chromatography-mass spectrometry (LCMS-2020) instrument.

[0103] Ultraviolet absorption spectroscopy detection: Shimadzu UV-2700 UV-Vis spectrophotometer was used, with a scanning range of 300–500 nm;

[0104] Emission spectroscopy detection: A steady-state / transient fluorescence spectrometer (FLS980) was used with an excitation wavelength of 345 nm.

[0105] Under nitrogen protection, the test temperature was 298K.

[0106] The test results are as follows:

[0107] The molecular proton spectrum of the photoinitiator TSC-1 prepared in Example 1 is as follows: Figure 1 As shown, it can be seen that:

[0108] 1H NMR(400MHz,Methylene Chloride-d2)δ8.31–8.29(m,1H),8.05(t,J=8.0Hz,1H),7.97–7.93(m,1H),7.87–7.84(m,1H),7.77(d,J=8.0Hz,1H),7 .48–7.40(m,1H),7.37–7.31(m,1H),7.17–7.11(m,2H),7.08–6.91(m,2H),6.89(d,J=8.0Hz,1H),6.82(d,J=8.0Hz,1H) The peak energies of the above proton NMR spectrum correspond one-to-one with the target product, and the numbers are reasonable; indicating that the photoinitiator TSC-1 was prepared in Example 1, and that the compound has a simple structure and high purity.

[0109] The carbon NMR spectrum of the photoinitiator TSC-1 prepared in Example 1 is as follows: Figure 2 As shown, it can be seen that:

[0110] 13 C NMR(100MHz,Methylene Chloride-d2)δ164.2,163.9,163.7,163.2,144.0,143.3,132.2,130.6,130.4,130 .3,130.1,130.0,129.9,129.1,129.0,129.0,128.7,128.1,128.1,127.9,127.8,1 The molecular carbon spectrum peaks 27.7, 125.8, 125.6, 122.9, 121.9, 121.6, 120.5, 120.4, 119.9, 40.1, 30.1, 20.5, 20.5, 13.7, and 13.7 correspond one-to-one with the target product, and the numbers are reasonable; this indicates that the photoinitiator TSC-1 was prepared in Example 1, and that the compound has a simple structure and high purity.

[0111] Figure 3 This is the HRMS spectrum (i.e., mass spectrum) of the photoinitiator TSC-1 prepared in Example 1. Calculations show that the theoretical value of C for the photoinitiator TSC-1, which possesses space charge transfer properties, is...47 H 32 N₂O₃[(M+H)] + The actual m / z value, determined by mass spectrometry, is 673.2488, consistent with the relative molecular mass of the synthesized photoinitiator TSC-1. This further confirms that the compound prepared in Example 1 is indeed the photoinitiator TSC-1 with space charge transfer properties, and that the compound has a simple structure and high purity. Combining the above NMR and mass spectrometry results, it is clear that the product obtained in Example 1 is the photoinitiator TSC-1.

[0112] like Figure 4 The image shows the 1H NMR spectrum of TSC-2, a photoinitiator with space charge transfer properties prepared in Example 2. It can be seen that:

[0113] 1 H NMR(400MHz,Methylene Chloride-d2)δ8.00(dd,J=8.0Hz,1H),7.89(dt,J=8.0Hz,1H),7.73–7.67(m,2H),7.46(t ,J=8.0Hz,1H),7.37–7.33(m,1H),7.31–7.26(m,1H),7.18–7.09(m,2H),6.95–6.91(m,1H) The 1H NMR peak energies are 6.85–6.76 (m, 3H), 6.75–6.72 (m, 1H), 6.71–6.63 (m, 3H), 6.61–6.54 (m, 3H), 6.47 (s, 2H), 6.32 (s, 1H), 6.12 (d, J = 8.0 Hz, 1H), 5.90 (d, J = 8.0 Hz, 1H), 5.60 (s, 1H), and 5.24–5.22 (m, 1H). The above 1H NMR peak energies correspond one-to-one with the target product, and the number is reasonable; this indicates that the photoinitiator TSC-2 was successfully prepared in Example 2, and that the compound has a simple structure and high purity.

[0114] The carbon NMR spectrum of the photoinitiator TSC-2 prepared in Example 2 is as follows: Figure 5 As shown, it can be seen that:

[0115] 13 C NMR(100MHz,Methylene Chloride-d2)δ 13C10 NMR (100MHz, MethyleneChloride-d2) δ 140.4, 139.7, 137.6, 133.2, 131.9, 130.7, 130.3, 129.8, 129.8, 128.9, 128.4, 128.2, 128.1, 127.7, 127.5, 126.7, 126.3, 126.0, 124.6, 124.5, 124.4, 124.1, 120.2, 119.6. The molecular carbon spectrum peak energies correspond one-to-one with the target product, and the number is reasonable; this indicates that the photoinitiator TSC-2 was successfully prepared in Example 2, and that the compound has a simple structure and high purity.

[0116] Figure 6 The image shows the HRMS (mass spectrum) of the photoinitiator TSC-2 prepared in Example 2. Calculations show that the theoretical value of the photoinitiator TSC-2 with space charge transfer properties is: C 45 H 28 NO + The molecular weight [(M+H)+] is 598.2166, while the actual m / z value obtained by mass spectrometry is 598.2169, consistent with the relative molecular mass of the synthesized photoinitiator TSC-2. This further confirms that the compound prepared in Example 2 is the photoinitiator TSC-2 with space charge transfer properties, and that the compound has a simple structure and high purity. Combining the above NMR and mass spectrometry results, it can be concluded that the product obtained in Example 2 is the photoinitiator TSC-2.

[0117] Using a Shimadzu UV-2700 UV-Vis spectrophotometer, TSC-1 and TSC-2 prepared in Examples 1 and 2 were dissolved in dichloromethane solution to prepare a 1×10-3 mol / L stock solution, which was then diluted to 1×10-5 mol / L for testing.

[0118] Fluorescence emission spectroscopy was used: an FLS980 fluorescence spectrometer. The TSC-1 and TSC-2 prepared in the examples were dissolved in dichloromethane solution to prepare a 1×10⁻⁶ solution. -3 The stock solution, initially at mol / L, was diluted to 1×10⁻⁶ for testing. -5 mol / L.

[0119] Figure 7 Including the TSC-1 prepared in Example 1 at 1×10 -5 UV-Vis absorption spectrum of tetrahydrofuran in mol / L. Figure 7 It can be seen that TSC-1 has a high molar extinction coefficient (ε=2.39×10). 4 M -1 cm -1 The absorption occurs in the ultraviolet band.

[0120] Figure 8 Including the TSC-1 prepared in Example 1 at 1×10 -5 Fluorescence emission spectrum in tetrahydrofuran at mol / L. From Figure 8 It can be seen that TSC-1 has a broad emission spectrum and weak fluorescence emission, exhibiting space charge transfer properties.

[0121] Figure 9 Including the TSC-2 prepared in Example 2 at 1×10 -5 UV-Vis absorption spectrum of tetrahydrofuran in mol / L. Figure 9 It can be seen that TSC-2 has a high molar extinction coefficient (ε=1.62×10). 4 M -1 cm -1 The absorption occurs in the ultraviolet band.

[0122] Figure 10 Including the TSC-2 prepared in Example 2 at 1×10 -5 Fluorescence emission spectrum in tetrahydrofuran at mol / L. From Figure 8 It can be seen that TSC-1 has a broad emission spectrum and weak fluorescence emission, exhibiting space charge transfer properties.

[0123] Figure 11 The nanosecond transient absorption spectrum and transient species lifetime spectrum at 420 nm of the photocatalyst TSC-1 prepared for Example 1 of this patent application are shown. Figure 11 It is known that TSC-1 has the characteristics of a charge-transfer triplet state and a long excited state lifetime. Specifically, the long excited state lifetime of TSC-1 is 5.7 μs, which is a huge improvement compared to the hundreds of nanoseconds in the existing technology.

[0124] Figure 12 The nanosecond transient absorption spectrum and transient species lifetime spectrum at 420 nm of the photoinitiator TSC-2 prepared for Example 2 of this patent application are shown. Figure 12 It is known that TSC-2 has the characteristics of local triplet state and long excited state lifetime. Specifically, the long excited state lifetime of TSC-2 is 67.2 μs, which is an improvement compared to the hundreds of nanoseconds in the prior art.

[0125] Examples of optical aggregation applications

[0126] The above-mentioned photoinitiator, co-initiator, and acrylic resin monomer are combined to form a polymerization system.

[0127] In the above photopolymerization system, the molar ratio of photoinitiator:co-initiator:acrylic resin is 0.01:10:100 to 0.001:1:1000.

[0128] The aforementioned photopolymerization system is characterized by varying polymerization efficiencies for different photoinitiators in different types of acrylic resins. Specifically, under 60s of illumination, with the same exposure power and photopolymerization system ratio, the TSC-1 photoinitiator, possessing a charge-transfer triplet state, achieves 74% efficiency in IBOA monomers but only 38% efficiency in DMA monomers. The TSC-2 photoinitiator, possessing a localized triplet state, achieves 66% efficiency in IBOA monomers but 96% efficiency in DMA monomers. This indicates that different triplet excited states of the photoinitiator result in different photopolymerization efficiencies.

[0129] Photolithography applications

[0130] Traditional high-power ultraviolet (UV) light sources tend to generate high temperatures, potentially causing material deformation, yellowing, or thermal damage to the substrate. Low-power systems reduce heat accumulation, making them particularly suitable for temperature-sensitive applications such as thin films, electronic components, and biomaterials. Low-power light sources are also more human- and environmentally friendly, reducing the harmful effects of UV radiation and making them suitable for fields with high safety requirements, such as medical and food packaging. Therefore, developing low-power photoinitiators is a crucial innovative direction in the field of photocuring technology. Its core objective is to drive the development of photocuring systems towards greater efficiency, environmental friendliness, and safety, while overcoming the limitations of traditional high-energy-consuming light sources to meet the needs of modern precision manufacturing and emerging fields.

[0131] The photopolymerization system of the aforementioned photoinitiator TSC-2 in DMA monomer was formulated into a photoresist. After a photolithography process, including spin coating, pre-baking, exposure, and development, a clear photolithographic pattern was obtained, and the pattern was then applied at 16mW cm⁻¹. -2 The etching under illumination was characterized by scanning electron microscopy, revealing a clear pattern with lines of 10 μm, which demonstrates the practical application value of this type of photopolymerization system under low-power conditions.

[0132] In summary, this application selected a spirofluorene-based photoinitiator with space charge transfer properties as a bridge. By constructing different electron donor-acceptor design strategies to enable different types of excited triplet states, the photoinitiator's light absorption capacity, intersystem crossing ability, and excited state lifetime were improved. Furthermore, it was shown that different types of excited triplet states of photoinitiators have different effects on polymerization efficiency and different polymerization efficiencies in different monomers, providing guidance for the design and synthesis of photoinitiators. Finally, the successful preparation of photolithographic patterns demonstrated its application value.

[0133] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0134] Although several embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A photoinitiator exhibiting space charge transfer properties under low-power illumination, characterized in that: It has one of the following molecular structures: 。 2. The method for preparing the photoinitiator TSC-1 with space charge transfer properties according to claim 1, characterized in that: Includes the following steps: S1. Preparation of intermediate PXZ-Br: PXZ, 2-bromoiodobenzene, cuprous iodide, 18-crown-6 ether, and potassium carbonate were dissolved in a two-necked flask containing o-dichlorobenzene. The mixture was then refluxed at 180°C under a nitrogen atmosphere for 48 hours. After the reaction was cooled to room temperature, the solvent was rotary evaporated and extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate PXZ-Br. S2. Preparation of intermediate LW-Br: Under argon atmosphere, PXZ-Br was dissolved in tetrahydrofuran and placed in a 1 mL double-necked flask. After the solution was cooled to -78°C, n-butyllithium was added dropwise using a syringe. The resulting mixture was stirred at -78°C for 1 hour, and then 1-bromo-9H-fluorene-9-one was added over 15 minutes. After reacting at -78°C for 2 hours, the mixture was stirred at room temperature for 3 hours. Water was added to the mixture to quench the reaction, and then tetrahydrofuran was evaporated under reduced pressure. The resulting solid was dissolved in dichloromethane and washed with water. The organic layer was then separated, dried with sodium sulfate, filtered, and evaporated. It was used directly for the next reaction without further purification. The crude product was dissolved in acetic acid and hydrochloric acid and reacted at 110°C for 4 hours. After cooling to room temperature, it was repeatedly extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate LW-Br. S3. Preparation of the target product TSC-1: Intermediate LW-Br, 4-boronate naphthalimide, and potassium carbonate were dissolved in a mixture of N,N-dimethylformamide / water. Pd3(PPd3)4 was then added under N2 atmosphere. The reaction mixture was heated to 90°C and refluxed with stirring. After cooling to room temperature, the product was extracted with dichloromethane and water and dried with anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography to finally obtain the target product TSC-1.

3. The method for preparing the photoinitiator TSC-1 with space charge transfer properties according to claim 2, characterized in that: The crude product described in step S1 was purified by silica gel column chromatography using dichloromethane and petroleum ether in a volume ratio of 3:7 as the eluent.

4. The method for preparing the photoinitiator TSC-1 with space charge transfer properties according to claim 2, characterized in that: The crude product described in step S2 is purified by silica gel column chromatography using pure petroleum ether as the eluent.

5. The method for preparing the photoinitiator TSC-1 with space charge transfer properties according to claim 2, characterized in that: The crude product described in step S3 was purified by silica gel column chromatography using dichloromethane and petroleum ether at a volume ratio of 1:8 as the eluent.

6. The method for preparing the photoinitiator TSC-2 with space charge transfer properties according to claim 1, characterized in that: Includes the following steps: S1. Preparation of intermediate PXZ-Br: PXZ, 2-bromoiodobenzene, cuprous iodide, 18-crown-6 ether, and potassium carbonate were dissolved in a two-necked flask containing o-dichlorobenzene. The mixture was then refluxed at 180°C under a nitrogen atmosphere for 48 hours. After the reaction was cooled to room temperature, the solvent was rotary evaporated and extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate PXZ-Br. S2. Preparation of intermediate LW-Br: Under argon atmosphere, PXZ-Br was dissolved in tetrahydrofuran and placed in a 1 mL double-necked flask. After the solution was cooled to -78°C, n-butyllithium was added dropwise using a syringe. The resulting mixture was stirred at -78°C for 1 hour, and then 1-bromo-9H-fluorene-9-one was added over 15 minutes. After reacting at -78°C for 2 hours, the mixture was stirred at room temperature for 3 hours. Water was added to the mixture to quench the reaction, and then tetrahydrofuran was evaporated under reduced pressure. The resulting solid was dissolved in dichloromethane and washed with water. The organic layer was then separated, dried with sodium sulfate, filtered, and evaporated. It was used directly for the next reaction without further purification. The crude product was dissolved in acetic acid and hydrochloric acid and reacted at 110°C for 4 hours. After cooling to room temperature, it was repeatedly extracted three times with dichloromethane and water. After drying with anhydrous sodium sulfate, the crude product was purified by silica gel column chromatography to obtain the intermediate LW-Br. S4. Preparation of the target product TSC-2: The intermediate LW-Br, 9-anthraboric acid and potassium carbonate were dissolved in a mixture of N,N-dimethylformamide / water. Then, Pd3(PPd3)4 was added under N2 atmosphere. The reaction mixture was heated to 140°C and refluxed with stirring. After cooling to room temperature, the product was extracted with dichloromethane and water and dried with anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography to finally obtain the target product TSC-2.

7. A photopolymerization system, characterized in that: It is composed of the photoinitiator and co-initiator as described in claim 1, and acrylic resin monomer, wherein the molar ratio of photoinitiator:co-initiator:acrylic resin is 0.01:10:100 ~ 0.001:1:1000.

8. The use of the photoinitiator of claim 1 in photoresist.

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