Photoradical polymerization initiator

Abstract

To provide a photo-radical polymerization initiator which does not generate acids inducing corrosion during radical polymerization, consists only of carbon atom, hydrogen atoms and oxygen atoms, is environmentally friendly, and has high radical polymerization initiation ability to light in the range from 350nm to 420nm.SOLUTION: The photoradical polymerizable composition contains a radical polymerizable compound and a photoradical polymerization initiator, wherein the polymerization initiator comprises a (substituted silyloxy) - 9,10 - anthraquinone compound represented by general formula (1) or (2). (R1 and R2 represent an alkyl group having a C number of 1 to 3.). ) SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a photoradical polymerization initiator and a photoradical polymerizable composition containing the photoradical polymerization initiator, and in particular to a photoradical polymerization initiator consisting of a bis(substituted silyloxy)-9,10-anthraquinone compound and a photoradical polymerizable composition containing the photoradical polymerization initiator. [Background technology]

[0002] Photoradical polymerizable compositions can be polymerized and cured by irradiation with energy rays such as ultraviolet rays and electron beams. This energy ray curing technique is used in a variety of applications, such as paints, coating materials, inks for screen printing and offset printing, inkjet inks, dry film resists used in electronic substrates, hologram materials, sealants, overcoat materials, resins for stereolithography, and adhesives.

[0003] This photoradical polymerizable composition is mainly composed of a polymerizable compound, a polymerization initiator that initiates polymerization of the polymerizable compound upon energy irradiation, and a polymerization sensitizer that is added as needed. Polymerization methods include radical polymerization, cationic polymerization, and anionic polymerization, of which radical polymerization has long been the most widely used. Radical polymerization typically involves using a photoradical polymerization initiator and a photoradical polymerization sensitizer together with a radical polymerizable compound, and irradiating the compound with energy rays, mainly ultraviolet rays, to generate radicals from the photoradical polymerization initiator, thereby initiating polymerization of the radical polymerizable compound.

[0004] Photoradical polymerization initiators are compounds that generate free radicals when exposed to energy rays such as ultraviolet light. Based on the mechanism of radical formation, photoradical polymerization initiators are generally classified into two classes: type I and type II. Type I photoradical polymerization initiators undergo homolytic bond cleavage within the initiator molecule upon irradiation and excitation with energy rays, generating free radicals. This is also known as intramolecular cleavage. On the other hand, type II photoradical polymerization initiators cannot generate radicals by themselves, but generate radical species through a bimolecular reaction. That is, type II initiators also become excited by energy rays, and this excited state interacts with a second molecule (a hydrogen donor) to abstract hydrogen from the second molecule, generating free radicals. Thus, type II photoradical polymerization initiators are also known as hydrogen abstraction initiators. In the former type I photoradical polymerization initiator, the structure of the excited initiator molecule undergoes significant changes due to bond cleavage, while the latter type II photoradical polymerization initiators only add hydrogen atoms and do not undergo any significant structural changes. Furthermore, when a radically polymerizable compound is polymerized using a photoradical polymerization initiator, a radical initiating species is attached to the polymer end. In the case of the former type I photoradical polymerization initiator, the radical initiating species generated by decomposition of the compound is attached to the polymer end, while in the latter type II photoradical polymerization initiator, the initiating species generated from a hydrogen donor such as a monomer or solvent is attached to the polymer end. Therefore, by analyzing the end of the polymer, it is possible to determine whether the mechanism of action of the photopolymerization initiator is type I or type II. For example, the polymerization mechanism can be analyzed by radically polymerizing fully deuterated methyl methacrylate in the presence of the radical polymerization initiator and analyzing the initiator fragments at the end of the radically polymerized polymer chain (Non-Patent Document 3).

[0005] Known Type I (intramolecular cleavage type) photoradical polymerization initiators include benzyl methyl ketal-based polymerization initiators, α-hydroxyalkylphenone-based polymerization initiators, oxime ester-based polymerization initiators, α-aminoacetophenone-based polymerization initiators, and acylphosphine oxide-based polymerization initiators (Patent Document 1).

[0006] On the other hand, known Type II (hydrogen abstraction) photoradical polymerization initiators include benzophenone-based polymerization initiators, thioxanthone-based polymerization initiators, and anthraquinone-based polymerization initiators, and are used in the coexistence of a tertiary amine or the like as a second molecule (hydrogen donor) (Patent Document 2). The compound of the present invention is also an anthraquinone compound.

[0007] In type I photoradical polymerization initiators, homolytic cleavage of the initiator occurs rapidly after photoexcitation, and free radicals derived from the initiator primarily initiate the polymerization reaction. Radicals, which serve as initiating species, have high reaction selectivity. For type I photoradical polymerization initiators, compounds with various functional groups that support the activation of type I photoradical polymerization initiators can be used as photoradical polymerization sensitizers. On the other hand, in type II photoradical polymerization initiators, excited species are known to undergo photoredox reactions with surrounding second molecules. When the second molecule is only a tertiary amine used as a co-initiator, electron transfer via an exciplex efficiently generates highly active carbon-centered radicals, which act as the main initiating species and promote polymerization. However, when a substance involved in the photoreaction with the excited species coexists as the second molecule, side reactions that do not contribute to polymerization can occur. For example, when hydrogen abstraction from an excited species generates a carbon-centered radical with a heteroatom with few substituents, it is known that this radical polymerization is rapidly converted to ketones, imines, or other radical polymerization-inactive products (Non-Patent Document 1). Furthermore, it is known that photochemical reactions other than hydrogen abstraction from excited aromatic ketones can occur between benzophenone-based polymerization initiators and alkenes, such as the Patano-Buechie reaction, which forms cyclic compounds that are inactive in radical polymerization (Non-Patent Document 2). Furthermore, acid components that are reactive with amines used as co-initiators may cause a decrease in the polymerization rate. Therefore, photopolymerization sensitizers that can be used in combination with type I photoradical polymerization initiators are not necessarily easily applicable to photopolymerization systems that use type II photoradical polymerization initiators.

[0008] On the other hand, when selecting a photoradical polymerization initiator, it is important to consider not only the activation of the polymerization reaction but also safety to living organisms.

[0009] In recent years, LEDs (light-emitting diodes) have come to be used as the irradiation source in polymerization reactions that use ultraviolet light as an energy beam. Unlike high-pressure mercury lamps, LEDs have the advantage of generating less heat and having a long lifespan, which has led to an acceleration in the development of UV curing technology using LEDs. Typical LEDs include ultraviolet LEDs and blue LEDs. In particular, ultraviolet LEDs have been developed as a UV curing irradiation source for inkjet or semiconductor-related resists. LEDs with central wavelengths of 405nm, 395nm, 385nm, 375nm, and 365nm have been developed. As photoradical polymerization initiators suitable for these wavelengths, among the photoradical polymerization initiators listed above, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (trade name OMNIRAD907), 2-benzylmethyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (trade name OMNIRAD369), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (trade name OMNIRADDTPO), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (trade name OMNIRAD819), and the like, all of which are Type I, are known to be highly sensitive (Patent Document 3).

[0010] However, these photopolymerization initiators contain nitrogen, sulfur, or phosphorus atoms as constituent elements in their molecular structure, which makes them highly bioactive and raises safety concerns. Some of these substances have been designated as SVHCs (Substances of Very High Concern) under the REACH Regulation. Furthermore, photopolymerization initiators containing nitrogen or sulfur atoms can cause odor problems during processing or in the cured product. In other words, in order to increase activity with energy rays containing light in the wavelength range of 350 to 420 nm, the inclusion of nitrogen, sulfur, or phosphorus atoms is currently necessary. Therefore, there is a need for environmentally friendly photopolymerization initiators that are highly active with energy rays containing light in the wavelength range of 350 to 420 nm and are composed solely of safe atoms. These initiators are expected to be replaced by less hazardous substances in the future.

[0011] Furthermore, Type II photoradical polymerization initiators generally use amine compounds as co-initiators because the efficiency of generating initiating radicals is lower than that of Type I photoradical polymerization initiators, which raises concerns about odor and safety.

[0012] Meanwhile, the present applicant has already proposed a photoradical polymerization initiator composed solely of carbon, hydrogen, oxygen, and silicon as a highly safe radical polymerization initiator composed only of atoms. For example, Patent Document 4 proposes a photopolymerizable composition containing a 10,10'-bis(silyloxy)-9,9'-bianthracene compound. Patent Document 5 proposes a photopolymerizable composition containing a 9-silyloxyanthracene compound. Furthermore, Patent Document 6 proposes a photopolymerizable composition containing a 4-silyloxy-1-hydroxy-2-naphthoic acid compound. However, all of these are primarily used in cationic polymerization compositions as sensitizers for photosensitizing polymerization initiators such as onium salts, rather than as polymerization initiators. Furthermore, Patent Document 7 proposes a (substituted silyloxy)-1,4-naphthoquinone compound as a photoradical polymerization initiator. This compound has a naphthoquinone skeleton. Furthermore, Patent Document 8 proposes a (substituted silyloxy)-9,10-anthraquinone compound as an environmentally friendly photoradical polymerization initiator that consists only of carbon, hydrogen, oxygen, and silicon atoms and is active against energy rays including light having a wavelength in the range of 300 to 400 nm. Among these, 1,4-bis(substituted silyloxy)-9,10-anthraquinone compounds and 1,5-bis(substituted silyloxy)-9,10-anthraquinone compounds are also disclosed, but they are not differentiated from 1-(substituted silyloxy)-9,10-anthraquinone compounds and are disclosed as radical polymerization initiators having the same action and effect. In the examples evaluating their activity as initiators, the evaluation results show anthraquinone compounds substituted with a silyloxy group only at the 1-position, anthraquinone compounds substituted with a silyloxy group only at the 2-position, and anthraquinone compounds disubstituted with silyloxy groups at the 1,2-, 1,5-, and 1,4-positions, and the anthraquinone compound substituted with a silyloxy group only at the 1-position was found to be the best in terms of tack-free time both when irradiated with light at 365 nm and when irradiated with light at 395 nm. This document makes no mention of the relationship between the substitution position of alkylsilyloxy groups and activity, nor does it make any mention of the effect of the number of alkylsilyloxy groups substituted on activity.

[0013] Furthermore, most of the silyl groups are silyloxy groups substituted with methyl or ethyl groups, and the only silyloxy group other than the methyl or ethyl substituted silyloxy groups shown in the examples is 2-(triisopropylsilyloxy)-9,10-anthraquinone, in which a triisopropylsilyl group is substituted at the 2-position of anthraquinone, and its activity is evaluated as extremely low compared to other compounds. In this patent document, there is no difference in activity between mono(substituted silyloxy)-9,10-anthraquinone compounds in which one trialkylsilyl group is substituted on the anthraquinone ring and bis(substituted silyloxy)-9,10-anthraquinone compounds in which two trialkylsilyl groups are substituted, and in fact, mono(substituted silyloxy)-9,10-anthraquinone compounds are preferred. Furthermore, with regard to the silyl groups, most of them are silyloxy groups substituted with methyl or ethyl groups, and with regard to the triisopropylsilyl group, only 2-(triisopropylsilyloxy)-9,10-anthraquinone is substituted only at the 2-position, and no mention is made of differences in activity due to differences in alkyl groups, and the activity of the triisopropylsilyl group is rated low. Since this photoradical polymerization initiator is based on an anthraquinone skeleton, if we assume it is a Type II hydrogen abstraction initiator, the alkyl group of the silyloxy group only affects the electron-donating properties of the group, and it is thought that the alkyl group, whether methyl or isopropyl, has little effect on hydrogen abstraction.

[0014] On the other hand, Patent Document 9 discloses α-disilyloxyaryl ketone as a polymerization initiator having a silyl group. The group possessed by this compound is a disilyloxy group, which differs from the alkylsilyloxy group of the present invention and differs in the mechanism for generating the polymerization initiating species and initiating species. Patent Document 10 also discloses disilyloxyaryl ketone compounds as compounds that generate silyl radicals. However, unlike the alkylsilyloxy group of the present invention, the mechanism for generating the polymerization initiating species and initiating species is also different. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 63-150303 [Patent Document 2] Japanese Patent Application Publication No. 7-33809 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-016910 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-197497 [Patent Document 5] Japanese Patent Application Publication No. 2017-137425 [Patent Document 6] Japanese Patent Application Laid-Open No. 2017-8007 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-113393 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-113392 [Patent Document 9] Special Publication No. 2022-520705 [Patent Document 10] Japanese Patent Application Laid-Open No. 2010-229169 [Non-patent literature]

[0016] [Non-Patent Document 1] , Ichiro Moriya, Toru Sato, Organic Synthetic Chemistry, Vol. 27, No. 12, 1969, P1165-1177 [Non-patent document 2] Maurizio D'Auria, Photochemical & Photobiological Sci., 2019, Volume 18, P2297 [Non-patent document 3] Koichi HATADA, Tatsuki KITAYAMA, Eiji MASUDA, Polymer Journal, Vol. 18, No. 5, pp. 395-402 (1986) Summary of the Invention [Problem to be solved by the invention]

[0017] An object of the present invention is to provide a new photoradical polymerization initiator that is sensitive to energy rays including long-wavelength light, has high radical polymerization initiation ability, and is environmentally friendly and highly practical, consisting only of highly safe atoms. [Means for solving the problem]

[0018] As a result of extensive investigations into anthraquinone compounds substituted with (substituted) silyloxy groups, the inventors have found that the mechanism of generating radical species after excitation by light clearly differs depending on the substitution position of the (substituted) silyloxy group, and that compounds substituted with a silyloxy group at the alpha position are Type I intramolecular cleavage-type photoradical polymerization initiators, unlike general anthraquinone-based photoradical polymerization initiators. They have also found that compounds substituted with not one but two silyloxy groups, specifically two silyloxy groups at the 1,4-position or the 1,5-position and the alpha position of the anthraquinone ring, are the most active, and further found that compounds in which the alkyl group of the (substituted) silyloxy group is a secondary alkyl group exhibit specifically high activity, thereby completing the present invention.

[0019] That is, the present invention is summarized as follows: First, the first invention is a photoradical polymerizable composition containing a radical polymerizable compound and a photoradical polymerization initiator, characterized in that the photoradical polymerization initiator is a bis(substituted silyloxy)-9,10-anthraquinone compound represented by the following general formula (1) or (2):

[0020] [ka]

[0021] In general formula (1), R 1 and R 2 represents an alkyl group having 1 to 3 carbon atoms.

[0022] [ka]

[0023] In general formula (2), R 1 and R 2 represents an alkyl group having 1 to 3 carbon atoms.

[0024] A second invention resides in a method for photopolymerizing a photoradical polymerizable composition, characterized by irradiating the photoradical polymerizable composition according to the first invention with energy rays containing light having a wavelength in the range of 350 nm to 420 nm. [Effects of the Invention]

[0025] The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention acts as a photoradical polymerization initiator in a photoradical polymerization reaction induced by irradiation with energy rays including light having a wavelength in the range of 350 nm to 420 nm, and has the ability to polymerize radically polymerizable compounds at an extremely high rate. Furthermore, the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention is an environmentally friendly compound consisting only of carbon, hydrogen, oxygen, and silicon atoms, and is useful as a highly safe photoradical polymerization initiator.

[0026] The objects, features and advantages of the present invention will become more apparent from the following detailed description. [Brief explanation of the drawings]

[0027] [Figure 1] Absorption curve in the UV and visible light range for a 9,10-anthraquinone compound substituted with one or two triisopropylsilyloxy groups when dissolved in acetonitrile at a concentration of 10 ppm. The vertical axis is absorption intensity (Absorbance), and the horizontal axis is wavelength (Wavelength) in nm. [Figure 2] FIG. 1 is a comparison diagram of the results of measuring the amount of heat generated by Photo-DSC when a photoradical polymerizable composition containing a 9,10-anthraquinone compound substituted with one or two triisopropylsilyloxy groups is irradiated with 405 nm UV light for 5 seconds. [Figure 3] FIG. 1 shows the results of measuring the monomer conversion rate by real-time FT-IR when a photoradical polymerizable composition containing a 9,10-anthraquinone compound substituted with one or two triisopropylsilyloxy groups was irradiated with 405 nm UV light for 25 seconds. [Figure 4] FIG. 1 shows the results of measuring the monomer conversion rate by real-time FT-IR when a photoradical polymerizable composition containing a 9,10-anthraquinone compound substituted with one or two triisopropylsilyloxy groups was irradiated with 365 nm UV light for 25 seconds. [Figure 5] 1H-NMR chart of polymethyl methacrylate obtained by polymerizing methyl methacrylate and deuterated methyl methacrylate using 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone as a photoradical polymerization initiator. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will now be described in detail.

[0029] (Photoradical polymerization initiator) First, the present invention provides a photoradical polymerizable composition containing a radical polymerizable compound and a photoradical polymerization initiator, characterized in that the photoradical polymerization initiator contains a bis(substituted silyloxy)-9,10-anthraquinone compound.

[0030] (Bis(substituted silyloxy)-9,10-anthraquinone compounds) The photoradical polymerization initiator in the photoradical polymerizable composition of the present invention is a bis(substituted silyloxy)-9,10-anthraquinone compound represented by the following general formula (1) or (2).

[0031] [ka]

[0032] In general formula (1), R 1 and R2 represents an alkyl group having 1 to 3 carbon atoms.

[0033] [ka]

[0034] In general formula (2), R 1 and R 2 represents an alkyl group having 1 to 3 carbon atoms.

[0035] R in general formula (1) or general formula (2) 1 or R 2 Examples of the alkyl group having 1 to 3 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, and a propyl group.

[0036] The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention represented by general formula (1) or (2) is a compound consisting only of carbon atoms, hydrogen atoms, oxygen atoms, and silicon atoms, and is characterized in that the alkyl group of the silyloxy group is a secondary alkyl group.

[0037] Specific examples of the bis(substituted silyloxy)-9,10-anthraquinone compound represented by general formula (1) include 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone, 1,4-bis[tri(2-butyl)silyloxy]-9,10-anthraquinone, 1,4-bis[tri(3-pentyl)silyloxy]-9,10-anthraquinone, 1,4-bis[tri(2-methyl-3-pentyl)silyloxy]-9,10-anthraquinone, 1,4-bis[tri(2,4-dimethyl-3-pentyl)silyloxy]-9,10-anthraquinone, 1,4-bis[di(2-propyl)-2-butyl-silyloxy]-9,10-anthraquinone, and 1,4-bis[di(2-butyl)-2-propyl-silyloxy]-9,10-anthraquinone.

[0038] Specific examples of the bis(substituted silyloxy)-9,10-anthraquinone compound represented by general formula (2) include 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone, 1,5-bis[tri(2-butyl)silyloxy]-9,10-anthraquinone, 1,5-bis[tri(3-pentyl)silyloxy]-9,10-anthraquinone, 1,5-bis[tri(2-methyl-3-pentyl)silyloxy]-9,10-anthraquinone, 1,5-bis[tri(2,5-dimethyl-3-pentyl)silyloxy]-9,10-anthraquinone, 1,5-bis[di(2-propyl)-2-butyl-silyloxy]-9,10-anthraquinone, and 1,5-bis[di(2-butyl)-2-propyl-silyloxy]-9,10-anthraquinone.

[0039] Among the compounds exemplified above, 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone and 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone are preferred due to their high activity and ease of synthesis, with 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone being particularly preferred.

[0040] (Manufacturing method) Next, a method for producing the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention represented by the above general formula (1) or (2) will be described. The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention can be produced by reacting a dihydroxy-9,10-anthraquinone compound represented by the following structural formula (3) or (4) with a silylating agent.

[0041] [ka]

[0042] [ka]

[0043] As the silylating agent, preferably use halogenated silane compound or bis(trialkylsilylacetamide).As halogenated silane compound, for example, tri(2-propyl)chlorosilane, tri(2-butyl)chlorosilane, tri(3-pentyl)chlorosilane, tri(2-methyl-3-pentyl)chlorosilane, tri(2,5-dimethyl-3-pentyl)chlorosilane, di(2-propyl)-2-butylchlorosilane, di(2-butyl)-2-propylchlorosilane, tri(2-propyl)bromosilane, tri(2-butyl)bromosilane, tri(3-pentyl)bromosilane, tri(2-methyl-3-pentyl)bromosilane, tri(2,5-dimethyl-3-pentyl)bromosilane, di(2-propyl)-2-butylbromosilane, di(2-butyl)-2-propylbromosilane etc. Examples of bistrialkylsilylacetamide include bistri(2-propyl)silylacetamide and bistri(2-butyl)silylacetamide.

[0044] The amount of the silylating agent used is usually 1.0 equivalent or more and 1.5 equivalents or less, and preferably 1.1 equivalents or more and 1.3 equivalents or less, relative to one molecule of hydroxyl group contained in the dihydroxy-9,10-anthraquinone compound represented by the above general formula (3) or (4). If the amount of the silylating agent used is less than 1.0 equivalent, the amount of unreacted dihydroxy-9,10-anthraquinone compound increases, while if added in an amount exceeding 1.5 equivalents, the solubility of the produced bis(substituted silyloxy)-9,10-anthraquinone compound in the solvent increases, resulting in a decrease in the isolation yield of the bis(substituted silyloxy)-9,10-anthraquinone compound, which is undesirable.

[0045] The reaction temperature is usually 0°C or higher and 150°C or lower, preferably 15°C or higher and 80°C or lower. If the reaction temperature is lower than 0°C, the reaction rate is too slow and the reaction takes a long time, while if the reaction temperature is higher than 150°C, side reactions occur and the purity of the product decreases. The reaction time varies depending on the reaction temperature, but is usually 0.5 to 20 hours. The reaction is usually carried out under atmospheric pressure, and it is preferable to fill the reaction vessel with an inert gas atmosphere such as argon or nitrogen.

[0046] When the silylating agent is a halogenated silane compound, the reaction is carried out in the presence of a basic compound. That is, when a dihydroxy-9,10-anthraquinone compound is reacted with a halogenated silane compound to produce a bis(substituted silyloxy)-9,10-anthraquinone compound represented by general formula (1) or (2), it is necessary to add a basic compound. When the silylating agent is a bistrialkylsilylacetamide, the bistrialkylsilylacetamide itself functions as a basic compound, so the reaction proceeds without the need for additional addition of a basic compound.

[0047] Examples of the basic compound to be used include primary amines, secondary amines, tertiary amines, and pyridines. Primary amines include methylamine, ethylamine, and propylamine. Secondary amines include dimethylamine, diethylamine, dibutylamine, and piperidine. Tertiary amines include trimethylamine, triethylamine, tripropylamine, and tributylamine. Pyridines include pyridine, α-picoline, β-picoline, γ-picoline, and lutidine.

[0048] The amount of the basic compound used is usually 1.0 equivalent or more and 1.5 equivalents or less, preferably 1.1 equivalents or more and 1.3 equivalents or less, relative to one molecule of hydroxyl group contained in the dihydroxy-9,10-anthraquinone compound. If the amount of the basic compound used is less than 1.0 equivalent, the amount of unreacted dihydroxy-9,10-anthraquinone compound increases, while if added in an amount exceeding 1.5 equivalents, the solubility of the produced bis(substituted silyloxy)-9,10-anthraquinone compound in the solvent increases, resulting in a decrease in the isolation yield of the bis(substituted silyloxy)-9,10-anthraquinone compound, which is undesirable.

[0049] Suitable solvents include aromatic solvents such as benzene, toluene, xylene, and chlorobenzene, halogenated carbon solvents such as methylene chloride, dichloroethane, and dichloroethylene, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, amide solvents such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide, and ether solvents such as tetrahydrofuran and 1,4-dioxane. Since the (substituted silyloxy)-9,10-anthraquinone compound of the present invention is susceptible to hydrolysis, water-immiscible solvents such as toluene and methylene chloride are preferred.

[0050] After the reaction is complete, the reaction mixture is added to a poor solvent such as hexane, concentrated, and the precipitated crystals are filtered and dried, and if necessary, recrystallized to obtain the target product in high purity.

[0051] The bis(substituted silyloxy)-9,10-anthraquinone compounds of the present invention have a secondary alkyl group in the silyloxy group. However, when the alkyl group in the silyloxy group is a short alkyl group such as methyl or ethyl, the compounds tend to lack storage stability after production and gradually decompose into the starting hydroxy-9,10-anthraquinone. Furthermore, when the alkyl group in the silyloxy group is too large, the synthesis yield significantly decreases. Furthermore, unlike typical anthraquinone-based photoradical polymerization initiators, the bis(substituted silyloxy)-9,10-anthraquinone compounds of the present invention are excited by light irradiation, and the excited species decompose to generate radical species. Therefore, the nature of the generated radical species significantly affects their activity and reactivity. As noted on page 1 of the "Radical Reactions" lecture in the Department of Applied Chemistry, Faculty of Science and Technology, Meijo University, the unpaired electron of the alkyl radical resides in the P orbital of carbon, and this radical is known to be stabilized by hyperconjugation. Therefore, the stability of the generated radicals is in the order of tertiary radical > secondary radical > primary radical > methyl radical, and it can be seen that the type of radical generated has an important effect on reactivity. Furthermore, it is known that the size of the generated alkyl radical is related to its mobility within the monomer. In this respect, too, it is presumed that the type of radical generated has an important effect on reactivity. The present invention was made based on the discovery that the generated radical species is the most reactive when it is a secondary radical.

[0052] (Photoradical polymerization initiator) The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention represented by the above general formula (1) or (2) has excellent radical polymerization initiation ability in photoradical polymerization.

[0053] The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention represented by the above general formula (1) or (2) has an anthraquinone structure, but the mechanism by which it exhibits radical polymerization initiation ability is not hydrogen abstraction but internal fission to generate initiating species radicals, making it a novel Type I photoradical polymerization initiator.

[0054] The bis(substituted silyloxy)-9,10-anthraquinone compound represented by the general formula (1) or (2) of the present invention can be used as a photoradical polymerization initiator to photopolymerize the polymerizable compound methyl methacrylate to synthesize polymethyl methacrylate. In this case, deuterated methyl methacrylate, in which all hydrogen atoms of methyl methacrylate are replaced with deuterium atoms, is used for polymerization to synthesize polymethyl methacrylate. The type of initiating species can be determined by analyzing the polymerization terminals. Specifically, in the case of a Type I photoradical polymerization initiator, the radical initiating species generated by decomposition of the compound is added to the polymer terminal, whereas in the case of a Type II photoradical polymerization initiator, the initiating species generated from a hydrogen donor such as a monomer or solvent is added to the terminal. Therefore, by analyzing the terminals of the polymer, it is possible to determine whether the mechanism of action of a photopolymerization initiator is Type I or Type II (Non-Patent Document 3).

[0055] Analysis using this technique revealed that, while common anthraquinone-based photoradical polymerization initiators are Type II, the bis(substituted silyloxy)-9,10-anthraquinone compounds of the present invention, in which a silyloxy group is substituted at the alpha position of anthraquinone, exhibit Type I internal cleavage photoradical polymerization. On the other hand, compounds in which a silyloxy group is substituted at the beta position of anthraquinone not only exhibit a slow polymerization rate but are also Type II hydrogen abstraction initiators. Specifically, when deuterated methyl methacrylate was polymerized using 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone or 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone, which are bis(substituted silyloxy)-9,10-anthraquinone compounds represented by the above general formula (1) or general formula (2) of the present invention, as a photoradical polymerization initiator, it was confirmed that an undeuterated isopropyl group was attached to the terminal of the polymer. In other words, 9,10-anthraquinone compounds substituted with a silyloxy group at the 2-position are initiators that generate radicals by abstracting hydrogen from other molecules, while 9,10-anthraquinone compounds substituted with silyloxy groups at the 1,4- or 1,5-positions are surprisingly intramolecular cleavage polymerization initiators that undergo photocleavage upon irradiation to generate two radicals.

[0056] Furthermore, since this is an internal cleavage type photoradical polymerization initiator, the radical species generated by its decomposition is an alkyl radical, and this alkyl radical is generated from the alkyl group in the silyloxy group, it was found that the alkyl group of the (substituted) silyloxy group is significantly related to the polymerization initiation ability. It was also found that the alkyl group substituted on the silyloxy group is not just any alkyl group, but is limited to specific alkyl groups in terms of reactivity and stability, with secondary alkyl groups being most preferable.

[0057] (Photoradical polymerizable composition) A photoradical polymerizable composition can be prepared by mixing the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention represented by the above general formula (1) or (2) with a radical polymerizable compound. The photoradical polymerizable composition can be easily photopolymerized by irradiating it with energy rays containing light having a wavelength in the range of 350 nm to 420 nm.

[0058] (Radical polymerizable compound) The radically polymerizable compound used in the photoradical polymerizable composition of the present invention is not particularly limited as long as it is a compound having radical polymerizability, and examples thereof include styrene, p-hydroxystyrene, vinyl acetate, acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, acrylamide, acrylic acid esters, methacrylic acid esters, etc., and / or oligomers thereof.

[0059] Examples of acrylic acid esters include monofunctional acrylates having one acrylate group, and bifunctional or polyfunctional acrylates having multiple acrylate groups. Examples of monofunctional acrylates include methyl acrylate, n-butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, phenoxypolyethylene glycol acrylate, 2-acryloyloxyethyl succinate, isostearyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, stearyl acrylate, isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate, lauryl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, tridecyl acrylate, and the like. Examples of the acrylates include methyl acrylate, caprolactone acrylate, ethoxylated nonylphenyl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, benzyl acrylate, 3,3,5-trimethylcyclohexyl acrylate (TMCHA), and dicyclopentenyl acrylate (DCPA). Examples of bifunctional acrylates include ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, tricyclodecane dimethanol diacrylate, 1,10-decanediol diacrylate, 1,9-nonanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, ethoxylated (3) bisphenol A diacrylate, and alkoxylated neopentyl glycol diacrylate.

[0060] Examples of polyfunctional acrylates include ethoxylated isocyanuric acid triacrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, pentaerythritol triacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, etc. Furthermore, epoxy acrylate, urethane acrylate, polyester acrylate, polybutadiene acrylate, polyol acrylate, polyether acrylate, silicone resin acrylate, imide acrylate, etc. can also be used.

[0061] Similarly, examples of the methacrylate compound include monofunctional methacrylates, difunctional methacrylates, and polyfunctional methacrylates. Examples of the monofunctional methacrylates include methyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, phenoxyethylene glycol methacrylate, stearyl methacrylate, 2-methacryloyloxyethyl succinate, tetrahydrofurfuryl methacrylate, isodecyl methacrylate, lauryl methacrylate, 2-phenoxyethyl methacrylate, isobornyl methacrylate, and tridecyl methacrylate. Examples of bifunctional methacrylates include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethoxylated bisphenol A dimethacrylate, tricyclodecane dimethanol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, glycerin dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, diethylene glycol dimethacrylate, 1,3-butylene diol dimethacrylate, and ethoxylated bisphenol A dimethacrylate. Examples of polyfunctional methacrylates include trimethylolpropane trimethacrylate.

[0062] These radical polymerizable compounds may be used alone or in combination of two or more.

[0063] (polymerizable resin) The photoradical polymerizable composition of the present invention may further contain a polymerizable resin. Examples of the polymerizable resin include photopolymerizable prepolymers, binder polymers such as acrylic resins, styrene resins, and epoxy resins, and alkali-soluble resins.

[0064] The photopolymerizable prepolymer is not particularly limited, and examples thereof include polyester acrylate, polyester methacrylate, epoxy acrylate, epoxy methacrylate, polyurethane acrylate, polyurethane methacrylate, etc. These photopolymerizable prepolymers may be used alone or in combination of two or more. Among these photopolymerizable prepolymers, polyurethane acrylate and polyurethane methacrylate are preferred.

[0065] As the alkali-soluble resin, a compound having a hydroxyl group and / or a carboxyl group and an ethylenically unsaturated bond group can be preferably used. A compound having an ethylenically unsaturated bond group and a group that generates a hydroxyl group during the reaction, such as an epoxy compound, can also be used.

[0066] Examples of the compound having a hydroxyl group and an ethylenically unsaturated bond group include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 3-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid, glycerol mono(meth)acrylate, dihydroxyacrylate, glycerol (meth)acrylate, pentaerythritol mono(meth)acrylate, and dipentaerythritol mono(meth)acrylate. Further examples include 2-hydroxy 3-acryloyloxypropyl methacrylate, pentaerythritol di(meth)acrylate, dipentaerythritol di(meth)acrylate, pentaerythritol diacrylate, isocyanuric acid EO-modified diacrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, etc. Glycidyl (meth)acrylate, which generates a hydroxyl group upon reaction, can also be used, but is not limited to these.

[0067] Examples of compounds having a carboxyl group and an ethylenically unsaturated bond group include acrylic acid, methacrylic acid, 2-acryloyloxyethyl succinate, crotonic acid, isocrotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, α-hydroxyacrylic acid, α-chloroacrylic acid, and cinnamic acid. Other examples include maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid. Other examples include mono(2-acryloyloxyethyl) succinate, mono(2-methacryloyloxyethyl) succinate, mono(2-acryloyloxyethyl) phthalate, and mono(2-methacryloyloxyethyl) phthalate. Other examples include ω-carboxypolycaprolactone monoacrylate and ω-carboxypolycaprolactone monomethacrylate.

[0068] The alkali-soluble resin may be not only a monomer but also an oligomerized alkali-soluble resin. As the oligomerized alkali-soluble resin, those generally used in negative resists can be used, and any resin may be used as long as it is soluble in an alkaline aqueous solution, without any particular limitation. For example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, Examples of the copolymer include copolymers of one or more selected from the group consisting of (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinylacetic acid, and anhydrides thereof, and copolymers of one or more selected from the group consisting of methyl (meth)acrylate, benzyl (meth)acrylate, styrene, γ-methylstyrene, N-vinyl-2-pyrrolidone, glycidyl (meth)acrylate, and the like, and copolymers of one or more selected from the group consisting of (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinylacetic acid, and anhydrides thereof, and examples also include polymers in which an ethylenically unsaturated compound having a glycidyl group or a hydroxyl group is added to the above copolymers.Further, for example, carboxyl group-containing resins obtained by copolymerization of unsaturated carboxylic acids such as (meth)acrylic acid with unsaturated group-containing compounds such as styrene, α-methylstyrene, lower alkyl (meth)acrylates, and isobutylene; carboxyl group-containing urethane resins obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups; and diisocyanate compounds such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with polycarbonate polyols, polyether polyols, Examples of such urethane resins include carboxyl-terminated urethane resins obtained by reacting an acid anhydride with the end of a urethane resin obtained by the polyaddition reaction of a diol compound such as a bisphenol A-based polyol, a polyester-based polyol, a polyolefin-based polyol, an acrylic polyol, a bisphenol A-based alkylene oxide adduct diol, or a compound having a phenolic hydroxyl group and an alcoholic hydroxyl group; carboxyl-terminated urethane resins obtained by the polyaddition reaction of a diisocyanate with a (meth)acrylate or a partially acid anhydride-modified product thereof of a bifunctional epoxy resin such as a bisphenol A-based epoxy resin, a hydrogenated bisphenol A-based epoxy resin, a bisphenol F-based epoxy resin, a bisphenol S-based epoxy resin, a bixylenol-based epoxy resin, or a biphenol-based epoxy resin; and carboxyl-terminated carboxyl-containing urethane resins obtained by the polyaddition reaction of a carboxyl-containing dialcohol compound and a diol compound; and carboxyl-terminated carboxyl-containing urethane resins obtained by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate.Commercially available alkali-soluble resins include the Dianale NR series (manufactured by Mitsubishi Rayon Co., Ltd.), Viscoat R-264, KS Resist 106 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), Ebecryl 3800 (manufactured by Daicel-Allnex Corporation), Acrylicure RD-F8 (manufactured by Nippon Shokubai Co., Ltd.), and Folet ZAH-110 (manufactured by Soken Chemical & Engineering Co., Ltd.).

[0069] The amount of the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention to be blended is usually preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, per 100 parts by weight of the radical polymerizable compound, from the viewpoints of its effect as a radical polymerization initiator and economy.

[0070] (Other photoradical polymerization initiators) The radical polymerizable composition containing the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention may also contain a photoradical polymerization initiator other than the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention, depending on the application.

[0071] Photoradical polymerization initiators that can be used in combination with the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention include photoradical polymerization initiators that are composed only of biologically safe atoms, similar to the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention. Examples of such photoradical polymerization initiators include alkylphenone-based photoradical polymerization initiators and benzophenone-based radical polymerization initiators.

[0072] (i) Alkylphenone-based photoradical polymerization initiators The alkylphenone-based photoradical polymerization initiator used in the present invention is not particularly limited as long as it has an alkylphenone structure and is excited by light irradiation, decomposed, and generates radical species. Various compounds are known as examples of alkylphenone-based photoradical polymerization initiators, but among them, at least one selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-1-{[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, and 2,2-dimethoxy-1,2-diphenylethan-1-one is preferred, and 1-hydroxycyclohexyl phenyl ketone is most preferred. Commercially available alkylphenone-based photoradical polymerization initiators include OMNIRAD184 (OMNIRAD is a registered trademark of IGM Group BV), OMNIRAD1173, OMNIRAD2959, OMNIRAD127, and OMNIRAD651. OMNIRADMBF (R), which has a structure similar to that of alkylphenone-based photoradical polymerization initiators, is also available. 2 and R 3 (Example where =O is used) OMNIRAD754 is also included.

[0073] The alkylphenone-based photoradical polymerization initiator used in the present invention is composed solely of carbon, hydrogen, and oxygen atoms. Its known features include minimal coloration upon curing and high adhesion of the cured coating to the substrate. However, alkylphenone-based photoradical polymerization initiators exhibit weak light absorption in the wavelength range of 350 to 420 nm, and exhibit low activity as photoradical polymerization initiators for energy rays containing light in this range. However, by combining an alkylphenone-based photoradical polymerization initiator with the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention, the activity as a photoradical polymerization initiator is improved, not only improving the polymerization rate of the alkylphenone-based photoradical polymerization initiator but also providing synergistic effects such as improved surface hardness. Furthermore, by combining a bis(substituted silyloxy)-9,10-anthraquinone compound with an alkylphenone-based photoradical polymerization initiator, ultraviolet absorption over a wider wavelength range is possible, potentially further improving the polymerization rate when irradiated with light from a high-pressure mercury lamp or the like, which has absorption over a wide wavelength range.

[0074] ((ii) Benzophenone-based photoradical polymerization initiators) The benzophenone-based photoradical polymerization initiator used in the present invention is not particularly limited as long as it has a benzophenone structure and is excited by light irradiation to cause a hydrogen abstraction reaction and generate radical species. Various compounds are known as examples of benzophenone-based photoradical polymerization initiators, but among them, at least one selected from the group consisting of benzophenone, benzoylbenzoic acid, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-methoxybenzophenone, 4-hydroxybenzophenone, 4,4'-dihydroxybenzophenone, acrylated benzophenone, 4-methylbenzophenone, 4,4'-dimethylbenzophenone, 4,4'-dimethoxybenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,4,6-trimethylbenzophenone, 3,3,4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 4,4'-diphenoxybenzophenone, and fluorenone is preferred. Alternatively, the benzophenone compound may be a linear polymer, a branched polymer, or a dendritic polymer containing the benzophenone compound in the main chain, terminal, or side chain. Among these compounds, methyl o-benzoylbenzoate, benzophenone, and 4-phenylbenzophenone are most preferred. Commercially available benzophenone-based photoradical polymerization initiators include OMNIRAD4PBZ (OMNIRAD is a registered trademark of IGM Group BV) and OMNIRAD OMBB.

[0075] Benzophenone-based photoradical polymerization initiators are known to be composed only of carbon atoms, hydrogen atoms, and oxygen atoms, and also to produce cured coating films with high adhesiveness.

[0076] Furthermore, like alkylphenone-based photoradical polymerization initiators, benzophenone-based photoradical polymerization initiators have weak light absorption in the wavelength range of 350 nm to 420 nm, and have low activity as photoradical polymerization initiators for energy rays including light in this range. However, by using a benzophenone-based photoradical polymerization initiator in combination with the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention, the activity as a radical polymerization initiator is further improved, and not only is the polymerization rate by the benzophenone-based photoradical polymerization initiator increased, but synergistic effects such as improved adhesion of the cured coating film can also be expected.

[0077] Furthermore, by using the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention in combination with a benzophenone-based photoradical polymerization initiator, ultraviolet light can be absorbed over a wider wavelength range, and a further improvement in the polymerization rate using a multi-wavelength irradiation source such as a high-pressure mercury lamp can be expected.

[0078] Depending on the application, benzophenone-based photoradical polymerization initiators having heteroatoms or halogen atoms can also be used. Examples of benzophenone-based photoradical polymerization initiators having heteroatoms or halogen atoms include 2,4-dichlorobenzophenone, 2,4'-dichlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 4,4'-morpholinobenzophenone.

[0079] On the other hand, depending on the application, it is possible to use a photoradical polymerization initiator containing an atom that poses environmental concerns, such as a nitrogen atom, a sulfur atom, or a phosphorus atom. For example, photoradical polymerization initiators that can be used in combination in the present invention include acylphosphine oxide-based photoradical polymerization initiators, oxime ester-based photoradical polymerization initiators, α-aminoacetophenone-based photoradical polymerization initiators, triazine-based photoradical polymerization initiators, thioxanthone-based photoradical polymerization initiators, biimidazole-based photoradical polymerization initiators, and acridine-based photoradical polymerization initiators. Among these, (iv) acylphosphine oxide-based photoradical polymerization initiators and (v) oxime ester-based photoradical polymerization initiators are preferred because they are expected to provide high sensitivity when used in combination. Furthermore, (vi) biimidazole-based photoradical polymerization initiators are particularly preferred because they not only increase the curing rate when used in combination, but also provide synergistic effects, such as increasing the curing rate without the need for the use of a reducing agent such as leuco crystal violet. Furthermore, the photoradical polymerization initiators listed above are compounds containing atoms that pose environmental concerns, such as nitrogen atoms, sulfur atoms, and phosphorus atoms. However, by using them in combination with the bis(substituted silyloxy)-9,10-anthraquinone compound, which is the photoradical polymerization initiator of the present invention, it is possible to reduce the amount of these compounds used, thereby reducing the burden on the environment.

[0080] (iv) Acylphosphine oxide-based photoradical polymerization initiators The acylphosphine oxide-based photoradical polymerization initiator used in the present invention is not particularly limited as long as it has a phenylbisacylphosphine oxide structure and is excited and decomposed by light irradiation to generate radical species. Various compounds are known as acylphosphine oxide-based photoradical polymerization initiators, and among them, at least one selected from the group consisting of benzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyl-diphenylphosphine oxide, 3,4-dimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-phenylethoxyphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and bis(2,6-dimethylbenzoyl)-ethylphosphine oxide is preferred. Commercially available acylphosphine oxide photoradical polymerization initiators include OMNIRADTPO, OMNIRADTPO-L, and OMNIRAD819.

[0081] (v) Oxime ester-based photoradical polymerization initiators The oxime ester-based photoradical polymerization initiator used in the present invention is not particularly limited as long as it has an oxime ester structure and is excited and decomposed by light irradiation to generate radical species. Various compounds are known as oxime ester-based photoradical polymerization initiators, but at least one selected from the group consisting of N-benzoyloxy-1-(4-phenylsulfanylphenyl)octan-1-one-2-imine, N-acetyloxy-1-(4-phenylsulfanylphenyl)-3-cyclohexylpropan-1-one-2-imine, N-acetoxy-1-[9-ethyl-6-{2-methyl-4-(3,3-dimethyl-2,4-dioxacyclopentanylmethyloxy)benzoyl}-9H-carbazol-3-yl]ethan-1-imine, and 1-[7-(2-methylbenzoyl)-9,9-dipropyl-9H-fluoren-2-yl]ethanone O-acetyloxime is preferred. Commercially available oxime ester-based photoradical polymerization initiators include Irgacure OXE01, Irgacure OXE02, and Irgacure OXE03.

[0082] Acylphosphine oxide-based photoradical polymerization initiators and oxime ester-based photoradical polymerization initiators absorb, excite, and cleave light in the 350 to 420 nm range, efficiently generating radical species. Meanwhile, the combined use of an acylphosphine oxide-based photoradical polymerization initiator and / or an oxime ester-based photoradical polymerization initiator with the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention can further improve the polymerization rate of radically polymerizable compounds and shorten the time until polymerization begins, i.e., the induction period. Acylphosphine oxide-based photoradical polymerization initiators undergo photodecomposition to convert into substances that have no or weak absorption in the 350 to 420 nm range of light, thereby promoting deep curing when used in combination. Oxime ester-based photoradical polymerization initiators undergo photodecarboxylation to generate methyl or phenyl radicals with low molecular weights, i.e., high mobility and high polymerization initiation activity. This can be expected to improve the curability and deep curing of systems with high viscosity or pigment-containing compositions.

[0083] (vi) Biimidazole-based photoradical polymerization initiators The biimidazole-based photoradical polymerization initiator used in the present invention is not particularly limited as long as it has a biimidazole structure and is excited and decomposed by light irradiation to generate radical species. Examples of biimidazole-based photoradical polymerization initiators include 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, and 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer.

[0084] Even when a polymerization initiator other than the above-mentioned photoradical polymerization initiator is used in combination with the bis(substituted silyloxy)-9,10-anthraquinone compound, which is the photoradical polymerization initiator of the present invention, effects such as improved activity upon irradiation with light in the wavelength range of 350 nm to 420 nm, reduced use of the compound, improved pattern formation ability, and improved storage stability of the radically polymerizable composition can be expected.

[0085] Examples of the α-aminoacetophenone-based photoradical polymerization initiator include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (trade name OMNIRAD907), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (trade name OMNIRAD369), and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholino-4-yl-phenyl)butan-1-one (trade name OMNIRAD379).

[0086] Examples of the triazine-based photoradical polymerization initiator include 2-(3,4-methylenedioxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine and 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine.

[0087] Examples of the thioxanthone-based polymerization initiator include 2,4-diethylthioxanthone and 2-isopropylthioxanthone.

[0088] Examples of the acridine-based photoradical polymerization initiator include acridine, 1,7-bis(9,9'-acridinyl)heptane, 9-phenylacridine, 1,6-bis(9-acridinyl)hexane, 1,7-bis(9-acridinyl)heptane, 1,8-bis(9-acridinyl)octane, 1,9-bis(9-acridinyl)nonane, 1,10-bis(9-acridinyl)decane, 1,11-bis(9-acridinyl)undecane, and 1,12-bis(9-acridinyl)dodecane.

[0089] As described above, the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention alone has excellent activity as a photoradical polymerization initiator. However, by using other photoradical polymerization initiators in combination, the radically polymerizable compound can be polymerized at an even higher rate due to the synergistic effect of the photoradical polymerization initiators, and the compound can be applied to high-viscosity systems and systems containing pigments, and various physical properties such as surface properties and deep curing can be improved.

[0090] The ratio of the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention to the other photoradical polymerization initiator is not particularly limited, but the blending ratio of the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention to the other photoradical polymerization initiator is preferably within a range of 99:1 to 1:99 by weight. Furthermore, because this effect is exhibited even with a small amount of the bis(substituted silyloxy)-9,10-anthraquinone compound added, the blending ratio may be within a range of 50:50 to 1:99 by weight, or even within a range of 10:90 to 1:99, including economical benefits. Furthermore, in the case of photoradical polymerization initiators containing nitrogen, sulfur, or phosphorus atoms, it is preferable to use the bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention in combination with the other photoradical polymerization initiator in order to reduce the amount of the other photoradical polymerization initiator added. In this case, the blending ratio may be within a range of 50:50 to 99:1 by weight.

[0091] Furthermore, the photoradical polymerizable composition of the present invention may contain various resin additives such as pigments and / or dyes, diluents, dispersants, organic or inorganic fillers, leveling agents, surfactants, antifoaming agents, thickeners, flame retardants, surface modifiers, penetration enhancers, moisturizing agents, fixing agents, antifungal agents, preservatives, antioxidants, polymerization inhibitors, UV absorbers, light stabilizers, chelating agents, pH adjusters, stabilizers, lubricants, plasticizers, etc., in addition to the above, within the range that does not impair the effects of the present invention. Depending on the application, the composition may also contain a solvent.

[0092] [Pigment] Examples of pigments that can be used in the present invention include the following (all shown by color index numbers): CI Pigment Yellow 12, 13, 14, 17, 20, 24, 55, 83, 86, 93, 109, 110, 117, 125, 137, 139, 147, 148, 153, 154, 166, 168, CI Pigment Orange 36, 43, 51, 55, 59, 61, CI Pigment Red 9, 97, 122, 123, 149, 168, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 240, CI Pigment Violet 19, 23, 29, 30, 37, 40, 50, CI Pigment Examples include Blue 15, 15:1, 15:4, 15:6, 22, 60, 64, CI Pigment Green 7, 36, CI Pigment Brown 23, 25, 26, etc.

[0093] Examples of black pigments include carbon black and titanium black. Specific examples of carbon black include Special Black 4, Special Black 100, Special Black 250, Special Black 350, and Special Black 550 manufactured by Degussa; Raven 1040, Raven 1060, Raven 1080, and Raven 1255 manufactured by Colombian Carbon; and MA7, MA8, MA11, MA100, MA220, and MA230 manufactured by Mitsubishi Chemical Corporation.

[0094] [solvent] The viscosity of the photopolymerizable composition of the present invention may be adjusted using a solvent to impart coating suitability. Examples of solvents include methanol, ethanol, toluene, cyclohexane, isophorone, cellosolve acetate, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, xylene, ethylbenzene, methyl cellosolve, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, diethylene glycol diethyl ether acetate, isoamyl acetate, ethyl lactate, methyl ethyl ketone, acetone, and cyclohexanone. These solvents may be used alone or in combination of two or more.

[0095] (Photopolymerization method) A polymer can be obtained by irradiating the photoradical polymerizable composition of the present invention with light to polymerize it. When irradiating the photoradical polymerizable composition with light to polymerize and harden it, the photoradical polymerizable composition can be formed into a film and then photopolymerized, or it can be formed into a block and then photopolymerized. When forming it into a film and then photopolymerizing it, the liquid photoradical polymerizable composition is applied to a substrate such as a polyester film using a bar coater or the like to a film thickness of 5 μm to 300 μm. A method of spraying the composition onto the substrate as droplets using an inkjet machine can also be used.

[0096] The substrates typically used include, but are not limited to, films, paper, aluminum foil, metal, wood, and plastic substrates. Materials used for film substrates include polyvinyl chloride (PVC), polyethylene terephthalate (PET), polycarbonate (PC), polystyrene (PS), polyurethane (PU), polyethylene (PE), and polypropylene (PP). Examples include films or sheets of ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid copolymer, nylon, polylactic acid, and polycarbonate, as well as cellophane, aluminum foil, and composites thereof. Laminates of various films onto fine paper, coated paper, art paper, construction paper, thin paper, cardboard, and various synthetic papers are also useful. Plastic films such as PE and PP are particularly preferred.

[0097] The method for applying the photoradically polymerizable composition of the present invention to a substrate film is not particularly limited, and for example, a bar coater, roll coater, gravure coater, flexo coater, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, curtain coater, cast coater, spray coater, die coater, spin coater, offset printing machine, screen printing machine, etc. can be appropriately used. A method in which the composition is sprayed onto the substrate as droplets using an inkjet machine can also be used. The photoradically polymerizable composition of the present invention can be cured at a sufficient speed, so that it can be cured simultaneously with application, and a cured film can be formed without complex equipment or processes. In addition, heat treatment, etc. can be performed after curing.

[0098] The coating film made of the photoradical polymerizable composition thus prepared is irradiated with energy rays at 1 to 1000 mW / cm 2A photopolymerization product can be obtained by irradiating the photopolymer with light at an intensity of about 1000 nm. Examples of light sources that can be used include high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, gallium-doped lamps, black lights, ultraviolet LEDs with a central wavelength of 365 nm, 375 nm, 385 nm, 395 nm, or 405 nm, blue LEDs, white LEDs, and Heraeus D-bulbs and V-bulbs. Natural light such as sunlight can also be used. Since the photoradical polymerization initiator of the present invention has ultraviolet absorption in the range of 350 nm to 420 nm and is capable of generating radical species by light in this wavelength range, an irradiation source that irradiates light in the wavelength range of 350 nm to 420 nm is particularly preferred. In this sense, ultraviolet LEDs and semiconductor lasers with a central wavelength of 365 nm, 375 nm, 385 nm, 395 nm, or 405 nm are preferred.

[0099] (FT-IR) In this example, the photocurability was evaluated by FT-IR measurement as follows: Using an FT-IR manufactured by Thermofisher Scientific Inc. equipped with a LIGHTNINGCURE manufactured by Hamamatsu Photonics K.K. as a UV irradiator, the 810 cm -1 Based on the absorption intensity of the peak vibration of the (meth)acrylic acid ester C=C bond in the vicinity of the curing rate, the curing rate was calculated by setting the absorption intensity before light irradiation as 0% curing rate and the curing rate when the absorption intensity became 0 as 100% curing rate.

[0100] FT-IR device: Thermofisher Scientific FT-IR Nicolet iS50 Irradiation intensity: 50mW / cm 2 Irradiation time: 25 seconds Sample thickness: 2 μm Measurement atmosphere: Nitrogen atmosphere UV irradiator: Hamamatsu Photonics LIGHTNINGCURE LC-8 (high-pressure mercury-xenon lamp) 405 nm bandpass filter.

[0101] The number average molecular weight (Mn) and weight average molecular weight (Mw) were measured by gel permeation chromatography (GPC) and converted into standard polystyrene. GPC: Measurement was performed using the following equipment configuration and conditions. JASCO Corporation, 2000 series Intelligent PDA Detector PDA-2010Plus(JASCO) Intelligent RI Detector RI-2031Plus(JASCO) Intelligent HPLC Pump PU-2080 Plus(JASCO) Intelligent Sampler AS-2057 Plus(JASCO) Intelligent Column Oven CO-8011 GPC column GMH XL -L (TSKgel) 3 in series Flow rate: 1ml / min Oven temperature: 40°C Carrier: tetrahydrofuran (THF)

[0102] Photo-curable (Photo-DSC) In this example, the photocurability was also evaluated by measuring the total heat generated by Photo-DSC. Specifically, the total heat generated per 1.00 mg of sample for 5 seconds from the start of light irradiation was determined. The Photo-DSC measurement conditions were as follows: Photo-DSC device: HITACHI differential thermal analysis device X-DSC700 UV irradiator: Hayashi Repic LA-410UV 405nm bandpass filter Irradiation intensity: 50mW / cm 2 Irradiation time: 5 seconds Measurement atmosphere: Nitrogen gas flow 100 ml / min Sample amount: 1 mg Sample thickness: about 300 μm [Example]

[0103] The present invention will be described in detail below with reference to examples, which are presented for illustrative purposes. That is, the following examples are not intended to be exhaustive or to limit the present invention to the exact form described. Therefore, the present invention is not limited to the following described examples unless it exceeds the spirit of the present invention. Furthermore, unless otherwise specified, all parts and percentages are by weight.

[0104] (Synthesis Example 1) Synthesis of 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone A 500 mL three-neck flask equipped with a thermometer and stirrer was charged with 25.0 g (104.1 mmol) of 1,4-dihydroxy-9,10-anthraquinone, 188 g of DMF, and 28.3 g (416.3 mmol) of imidazole to form a vermilion solution. Then, 90.3 g (468.3 mmol) of triisopropylchlorosilane was added dropwise at room temperature. The solution quickly turned ochre, and the mixture was stirred at room temperature for 17 hours. The reaction mixture was concentrated under reduced pressure, and 130 g of toluene was added. The resulting white insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure. The precipitate was suction filtered, washed with methanol, and dried to obtain 38.5 g (69.5 mmol) of a yellow-orange powder of 1,4-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone. The isolated yield based on the starting material, 1,4-dihydroxy-9,10-anthraquinone, was 66 mol%. (1) Melting point: 123°C (2) IR (KBr, cm -1 ):2960,2940,1670,1330,1270,1220,990,880,830,800,730,690,660. (3) 1 H-NMR (CDCl3, 400MHz): 1.14 (d, 36H), 1.39 (sept, 6H), 7.09 (s, 2H), 7.66-7.68 (m, 2H), 8.14-8.16 (m, 2H).

[0105] (Synthesis Example 2) Synthesis of 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone The silylation reaction was carried out under the same conditions as in Synthesis Example 1, except that the starting material, 1,4-dihydroxy-9,10-anthraquinone, was replaced with 1,5-dihydroxy-9,10-anthraquinone, to obtain 26.7 g (48.3 mmol) of a brown powder of 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone. The isolated yield based on the starting material, 1,5-dihydroxy-9,10-anthraquinone, was 64 mol %.

[0106] (Comparative Synthesis Example 1) Synthesis of 1,8-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone The silylation reaction was carried out under the same conditions as in Synthesis Example 1, except that the starting material, 1,4-dihydroxy-9,10-anthraquinone, was replaced with 1,8-dihydroxy-9,10-anthraquinone, to obtain 38.5 g (69.5 mmol) of a yellow powder of 1,8-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone. The isolated yield based on the starting material, 1,8-dihydroxy-9,10-anthraquinone, was 84 mol %.

[0107] (Comparative Synthesis Example 2) Synthesis of 2,6-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone The silylation reaction was carried out under the same conditions as in Synthesis Example 1, except that the starting material, 1,4-dihydroxy-9,10-anthraquinone, was replaced with 2,6-dihydroxy-9,10-anthraquinone, to obtain 2.1 g (3.6 mmol) of pale yellow powder, 2,6-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone. The isolated yield based on the starting material, 2,6-dihydroxy-9,10-anthraquinone, was 87 mol %.

[0108] (Comparative Synthesis Example 3) Synthesis of 1-tri(2-propyl)silyloxy-9,10-anthraquinone The silylation reaction was carried out under the same conditions as in Synthesis Example 1, except that the starting material, 1,4-dihydroxy-9,10-anthraquinone, was replaced with 1-hydroxy-9,10-anthraquinone, to obtain 31.8 g (83.6 mmol) of yellow powder 1-tri(2-propyl)silyloxy-9,10-anthraquinone. The isolated yield based on the starting material, 1-hydroxy-9,10-anthraquinone, was 85 mol %.

[0109] (Comparative Synthesis Example 4) Synthesis of 2-tri(2-propyl)silyloxy-9,10-anthraquinone The silylation reaction was carried out under the same conditions as in Synthesis Example 1, except that the starting material, 1,4-dihydroxy-9,10-anthraquinone, was replaced with 2-hydroxy-9,10-anthraquinone, to obtain 14.5 g (38.0 mmol) of green powder 2-tri(2-propyl)silyloxy-9,10-anthraquinone. The isolated yield based on the starting material, 2-hydroxy-9,10-anthraquinone, was 57 mol %.

[0110] 1,5-bis(triethylsilyloxy)-9,10-anthraquinone, 1-triethylsilyloxy-9,10-anthraquinone, 2-triethylsilyloxy-9,10-anthraquinone, 1,2-bis(triethylsilyloxy)-9,10-anthraquinone, 1,5-bis(trimethylsilyloxy)-9,10-anthraquinone, 1-trimethylsilyloxy-9,10-anthraquinone, 2-trimethylsilyloxy-9,10-anthraquinone, and 1,2-bis(trimethylsilyloxy)-9,10-anthraquinone were synthesized according to the method described in JP 2016-113392 A.

[0111] These synthesized silyloxy-9,10-anthraquinone compounds were stored at room temperature for eight years, and while almost no increase in impurities was observed in bis[tri(2-propyl)silyloxy]-9,10-anthraquinones, it was found that the raw material hydroxy-9,10-anthraquinone had increased as an impurity by approximately 20% to 50% in triethylsilyloxy-9,10-anthraquinones. Compounds substituted with trimethylsilyloxy groups were almost completely decomposed and converted into hydroxy-9,10-anthraquinone compounds.

[0112] [UV-Vis absorption spectrum] 1,4-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone (symbol 14TIPS-AQ in the figure), 1-tri(2-propyl)silyloxy-9,10-anthraquinone (symbol 1TIPS-AQ in the figure), 2-tri(2-propyl)silyloxy-9,10-anthraquinone (symbol 2TIPS-AQ in the figure), and 2,6-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone (symbol 261TIPS-AQ in the figure), all synthesized in the same manner as in the synthesis examples, were dissolved in acetonitrile to a concentration of 10 ppm, and the UV-Vis absorption spectrum was measured using a Shimadzu UV-2600 apparatus. The results are shown in Figure 1.

[0113] As is clear from Figure 1, compared to compounds with silyloxy groups at the beta positions of the anthraquinone ring, such as the 2-position (symbol 2TIPS-AQ in the figure, dashed line) and the 2,6-position (symbol 261TIPS-AQ in the figure, dashed line), compounds with silyloxy groups at the alpha positions, such as the 1-position (symbol 1TIPS-AQ in the figure, dotted line) and the 1,4-position (symbol 14TIPS-AQ in the figure, solid line), have a strong absorption at wavelengths above 350 nm, suggesting that they may also be active at wavelengths of 365 nm and 405 nm. In particular, 1,4-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone exhibits an even longer wavelength shift in absorption, with a strong absorption around 420 nm, making it suitable for use in LED lamps with irradiation wavelengths above 400 nm.

[0114] [Photoradical polymerization curing rate 1] (Evaluation Example 1) To 100 parts of trimethylolpropane triacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, 0.5 parts of 1,4-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone as a photoradical polymerization initiator was added and dissolved by stirring, to obtain a liquid photoradical polymerizable composition. The photoradical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2 Photo-DSC measurements were performed under the above conditions to determine the total calorific value. The total calorific value for 5 seconds after the start of light irradiation was 241 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 14TIPS-AQ in the table and figure)

[0115] (Evaluation Example 2) A liquid photo-radical polymerizable composition was obtained by adding 0.5 parts of 1,5-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone as a photo-radical polymerization initiator to 100 parts of trimethylolpropane triacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, and dissolving the mixture with stirring. The photo-radical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2 Photo-DSC measurements were performed under the conditions above to determine the total calorific value. The total calorific value for 5 seconds after the start of light irradiation was 253 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 15 in the table and figure is TIPS-AQ.)

[0116] (Evaluation Comparison Example 1) To 100 parts of trimethylolpropane triacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, 0.5 parts of 1-tri(2-propyl)silyloxy)-9,10-anthraquinone as a photoradical polymerization initiator was added and dissolved by stirring, to obtain a liquid photoradical polymerizable composition. The photoradical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2Photo-DSC measurements were performed under the above conditions to determine the total calorific value. The total calorific value for 5 seconds after the start of light irradiation was 141 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 1TIPS-AQ in the table and figure)

[0117] (Evaluation Comparison Example 2) To 100 parts of trimethylolpropane triacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, 0.5 parts of 2-tri(2-propyl)silyloxy)-9,10-anthraquinone as a photoradical polymerization initiator was added and dissolved by stirring, to obtain a liquid photoradical polymerizable composition. The photoradical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2 Photo-DSC measurements were performed under the conditions above to determine the total calorific value. The total calorific value for 5 seconds from the start of light irradiation was 50 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 2TIPS-AQ in the table and figure)

[0118] (Evaluation Comparison Example 3) A liquid photo-radical polymerizable composition was obtained by adding 0.5 parts of 1,8-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone as a photo-radical polymerization initiator to 100 parts of trimethylolpropane triacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound and dissolving the mixture with stirring. The photo-radical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2 Photo-DSC measurements were performed under the above conditions to determine the total calorific value. The total calorific value for 5 seconds after the start of light irradiation was 74 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 18TIPS-AQ in the table and figure)

[0119] (Evaluation Comparison Example 4) To 100 parts of trimethylolpropane triacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, 0.5 parts of 2,6-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone as a photoradical polymerization initiator was added and dissolved by stirring, to obtain a liquid photoradical polymerizable composition. The photoradical polymerizable composition was subjected to irradiation with a light source having a wavelength of 405 nm in a nitrogen gas flow at an illuminance of 50 mW / cm. 2 Photo-DSC measurements were performed under the above conditions to determine the total calorific value. The total calorific value for 5 seconds after the start of light irradiation was 32 mJ / mg. The results are shown in Table 1 and Figure 2. (The symbol 26TIPS-AQ in the table and figure)

[0120] [Table 1]

[0121] As is clear from Evaluation Examples 1 and 2, Evaluation Comparative Examples 1 to 4, Table 1, and Figure 2, the compounds substituted with silyloxy groups at two positions (1,4 or 1,5) had an overwhelmingly higher total heat generation in the first 5 seconds than those using other initiators, indicating that many initiating species radicals were generated immediately after irradiation and that the polymerization initiation effect was high. Samples with silyloxy groups at both positions (1,8), which are the same alpha positions, and samples with silyloxy groups at both positions (2,8), only generated extremely low total heat generation, indicating that having silyloxy groups at two positions alone does not provide a high polymerization initiation effect, and that these compounds were less active than compounds substituted at only one position.

[0122] [Photoradical polymerization curing speed 2] (Evaluation Example 3) 8.3 parts of carbon black were dispersed in 91.7 parts of dipropylene glycol diacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, and 1 part of 1,4-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was added as a photoradical polymerization initiator and stirred to obtain a photoradical polymerizable composition slurry. A film was formed on an aluminum disk using a spin coater (Mikasa MS-B100) on a Thermofisher Scientific FT-IR Nicolet iS50 equipped with a Hamamatsu Photonics LIGHTNINGCURE LC-8 (high-pressure mercury-xenon lamp) 405 nm bandpass filter, to a thickness of 2 μm. The sample chamber was replaced with nitrogen, and the light intensity was 50 mW / cm. 2 The measurement was carried out with light irradiation for 25 seconds, starting 15 seconds after the start of the measurement, at an illuminance of 810 cm -1 Based on the absorption intensity of the peak vibration of the (meth)acrylic acid ester C=C bond in the vicinity of the curing rate, the curing rate was calculated by taking the absorption intensity before light irradiation as 0% and the curing rate when the absorption intensity reached 0 as 100%. The results are shown in Figure 3.

[0123] (Evaluation Example 4) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 3, except that 1 part of 1,5-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 3.

[0124] (Evaluation Comparison Example 5) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 3, except that 1 part of 1,8-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 3.

[0125] (Evaluation Comparison Example 6) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 3, except that 1 part of 2,6-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 3.

[0126] (Evaluation Comparison Example 7) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 3, except that 1 part of 1-tri(2-propyl)silyloxy-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 3.

[0127] (Evaluation Comparison Example 8) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 3, except that 1 part of 2-tri(2-propyl)silyloxy-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 3.

[0128] As is clear from Figure 3, compounds substituted with tri(2-propyl)silyloxy groups at both the 1,4 and 1,5 positions exhibited overwhelmingly rapid conversion and reached high conversion rates. Among compounds substituted with tri(2-propyl)silyloxy groups at both the 1,4 and 1,5 positions, the compound substituted at the 2,6 positions exhibited extremely slow polymerization, indicating a weak initiation effect. Furthermore, among compounds substituted with tri(2-propyl)silyloxy groups at both the alpha positions, the compound substituted at the 1,8 positions exhibited slow polymerization initiation and achieved low conversion rates. These results also suggest that when excited molecules generate radical species, a cleavage reaction occurs due to a strong interaction with the ketone group of anthraquinone, generating radical species. It is speculated that when reacting with the same ketone group, as in the case of compounds substituted at the 1,8 positions, only one of the tri(2-propyl)silyloxy groups undergoes cleavage.

[0129] [Photoradical polymerization curing rate 3] (Evaluation Example 5) 8.3 parts of carbon black were dispersed in 91.7 parts of dipropylene glycol diacrylate (Tokyo Chemical Industry Co., Ltd.) as a radical polymerizable compound, and 1 part of 1,4-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was added as a photoradical polymerization initiator and stirred to obtain a photoradical polymerizable composition slurry. The photoradical polymerizable composition was applied to a Thermofisher Scientific FT-IR Nicolet iS50 equipped with a Hamamatsu Photonics LIGHTNINGCURE LC-8 (high-pressure mercury-xenon lamp) 365 nm bandpass filter, and formed into a film on an aluminum disk using a spin coater (Mikasa MS-B100) to a film thickness of 2 μm. The atmosphere in the sample chamber was replaced with nitrogen, and the irradiation was performed at 130 mW / cm. 2 The measurement was carried out with light irradiation for 25 seconds, starting 15 seconds after the start of the measurement, at an illuminance of 810 cm -1 Based on the absorption intensity of the peak vibration of the (meth)acrylic acid ester C=C bond in the vicinity of the curing rate, the curing rate was calculated by taking the absorption intensity before light irradiation as 0% and the curing rate when the absorption intensity reached 0 as 100%. The results are shown in Figure 4.

[0130] (Evaluation Example 6) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 5, except that 1 part of 1,5-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 4.

[0131] (Evaluation Comparison Example 9) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 5, except that 1 part of 1,8-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 4.

[0132] (Evaluation Comparison Example 10) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 5, except that 1 part of 2,6-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 4.

[0133] (Evaluation Comparison Example 11) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 5, except that 1 part of 1-tri(2-propyl)silyloxy-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 4.

[0134] (Evaluation Comparison Example 12) A photoradical polymerizable composition was prepared in the same manner as in Evaluation Example 5, except that 1 part of 2-tri(2-propyl)silyloxy-9,10-anthraquinone was used as the photoradical polymerization initiator. Light irradiation was carried out under the same conditions, and the curing rate was calculated. The results are shown in Figure 4.

[0135] As is clear from Figure 4, not only with 405 nm light irradiation but also with 365 nm light irradiation, compounds substituted with tri(2-propyl)silyloxy groups at both the 1,4 and 1,5 positions showed a rapid increase in conversion and reached a high conversion rate. With 365 nm light irradiation, a significant decrease in the conversion rate was observed when 1-tri(2-propyl)silyloxy-9,10-anthraquinone was used as the initiator.

[0136] [Photoradical polymerization of deuterated methyl methacrylate] A liquid photo-radical polymerizable composition was obtained by adding 10 parts of 1,5-bis[tri(2-propyl)silyloxy)-9,10-anthraquinone as a photo-radical polymerization initiator to 100 parts of non-deuterated methyl methacrylate or deuterated methyl methacrylate in which all hydrogen atoms have been replaced with deuterium as a radical polymerizable compound, and dissolving the mixture with stirring. The photo-radical polymerizable composition was then heated in a nitrogen gas stream using a light source with a wavelength of 405 nm and an illuminance of 300 mW / cm.2 The polymer was polymerized by irradiating it with light at an intensity of 1000 for 10 minutes. 1 H-NMR was measured. In the chart, the upper part shows the polymerized non-deuterated methyl methacrylate. 1 H-NMR, the bottom is polymethyl methacrylate when deuterated methyl methacrylate is polymerized 1 This is an H-NMR chart. In the deuterated methyl methacrylate polymer at the bottom, a peak of a hydrogen atom is observed that is not present in the deuterated methyl methacrylate used as the raw material, and it is clear that this hydrogen atom is the hydrogen atom of an isopropyl group. This isopropyl group is the alkyl group of the silyloxy group of 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone, which was added as a photoradical polymerization initiator. The photoradical polymerization initiator was excited and cleaved by light, generating isopropyl radicals as the initiating species, which is why the isopropyl group was observed in the polymer. Therefore, it is clear that 1,5-bis[tri(2-propyl)silyloxy]-9,10-anthraquinone acted as a Type I internal cleavage initiator, rather than a Type II hydrogen abstraction initiator. [Industrial Applicability]

[0137] The bis(substituted silyloxy)-9,10-anthraquinone compound of the present invention acts as a photoradical polymerization initiator in a photoradical polymerization reaction induced by irradiation with energy rays, including light having a wavelength in the range of 350 to 420 nm, and has the ability to polymerize radically polymerizable compounds at an extremely high rate. Furthermore, the bis(substituted silyloxy)-9,10-anthraquinone compound is an environmentally friendly compound consisting only of carbon, hydrogen, oxygen, and silicon, and is therefore industrially very useful as a highly safe photoradical polymerization initiator.

Claims

1. A photoradical polymerizable composition containing a radical polymerizable compound and a photoradical polymerization initiator, wherein the photoradical polymerization initiator is a bis(substituted silyloxy)-9,10-anthraquinone compound represented by the following general formula (1) or (2): 【Chemistry 1】 (In general formula (1), R １ and R ２ represents an alkyl group having 1 to 3 carbon atoms.) 【Chemistry 2】 (In general formula (2), R １ and R ２ represents an alkyl group having 1 to 3 carbon atoms.)

2. A method for photopolymerizing a photoradical polymerizable composition, comprising irradiating the photoradical polymerizable composition according to claim 1 with energy rays containing light having a wavelength in the range of 350 nm to 420 nm.

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