Method for producing tertiary ester-containing aromatic vinyl monomer

Abstract

The present invention relates to a method for producing a tertiary ester-containing aromatic vinyl monomer. The present invention addresses the problem of providing a method for producing a vinyl aromatic monomer containing a tertiary ester, which is particularly suitable for a resist composition for EB lithography and a resist composition for EUV lithography having a wavelength of 13.5 nm, and which is a novel method for producing a vinyl aromatic monomer having a higher efficiency and higher quality than known formulations. This problem is solved by a method for producing a tertiary ester-containing aromatic vinyl monomer using a metal alkoxide as a reaction accelerator.

Description

Technical Field

[0001] The present invention relates to a method for producing tertiary ester-containing aromatic vinyl monomers. Background Art

[0002] In recent years, with the high integration of integrated circuits, the formation of finer patterns is sought. Chemically amplified resists, which mainly use acids as catalysts, are used for processing patterns below 0.2μm. In addition, high-energy rays such as ultraviolet rays, far ultraviolet rays, and electron beams (EB) are used as exposure sources at this time. In particular, electron beam lithography, which is an ultra-fine processing technology, is also indispensable for the processing method of blank photomasks when manufacturing photomasks for semiconductor manufacturing.

[0003] A large number of polymers having an aromatic skeleton with an acidic side chain, such as polyhydroxystyrene, are effectively used as materials for KrF lithography resist compositions using KrF excimer lasers, but they exhibit large absorption for light with a wavelength of around 200 nm and cannot be used as materials for ArF lithography resist compositions using ArF excimer lasers. However, they are important materials for obtaining high etching resistance in EB lithography resist compositions and extreme ultraviolet (EUV) lithography resist compositions, which are powerful technologies for forming patterns smaller than the processing limit of ArF excimer lasers.

[0004] As for the base polymer of positive EB photolithography resist composition and EUV photolithography resist composition, the acid generated from the photoacid generator due to irradiation of high-energy rays is mainly used as a catalyst to deprotect the acid-decomposable protective group (acid-labile group) of the acidic functional group of the phenol side chain possessed by the shielding base polymer, and the material that can be dissolved in the alkaline developer. The aforementioned acid-decomposable protective group mainly uses tertiary alkyl, tert-butoxycarbonyl, acetal group, etc. Here, if a protective group with a small activation energy required for deprotection is used, such as an acetal group, although it has the advantage of obtaining a highly sensitive resist film, if the diffusion of the generated acid is not fully suppressed, the unexposed part in the resist film will also cause a deprotection reaction, and there will be problems such as deterioration of line edge roughness (LER) and reduction of dimensional uniformity (CDU) of the pattern.

[0005] ArF photoresist compositions containing polymers such as methacrylic acid in which the carboxyl groups are substituted with acid-labile groups are criticized for causing swelling in alkaline developers. On the other hand, KrF photoresist compositions containing polymers such as hydroxystyrene in which the phenolic groups are substituted with acid-labile groups have less swelling. However, hydroxystyrene has a large acid diffusion, so there is a concern that the resolution is reduced. In addition, structural units in which the carboxyl groups of styrene carboxylic acids are substituted with acid-labile groups have also been proposed (Patent Documents 1 to 3).

[0006] There have been reports of methods for producing tertiary ester-containing vinyl aromatic monomers by converting the carboxyl groups of styrene carboxylic acid, vinyl naphthalene carboxylic acid, etc. into tertiary esters (Patent Documents 1 to 3). Specifically, there have been proposed methods for producing tertiary ester-containing styrene monomers by using a corresponding tertiary alcohol to derive an acid chloride corresponding to styrene carboxylic acid, etc., and carrying out an esterification reaction in the presence of an organic base such as triethylamine, and methods for producing tertiary ester-containing styrene monomers by reacting an acid chloride of styrene carboxylic acid with a tertiary alkoxide produced by the action of an organic metal reagent and a ketone compound. However, there are many issues such as reaction conversion rate, anionic polymerization, and competition during the reaction.

[0007] In order to meet the future demand for miniaturization of resist patterns, it is also important to improve the method for producing tertiary ester-containing vinyl aromatic monomers, and the development of an efficient and high-quality method for producing tertiary ester-containing vinyl aromatic monomers is desired.

[0008] Prior art literature

[0009] Patent Literature

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2006-335715

[0011] [Patent Document 2] Japanese Patent No. 7055070

[0012] [Patent Document 3] Japanese Patent No. 6694451 Summary of the invention

[0013] [Problems to be solved by the invention]

[0014] In the chemically amplified resist composition using an acid as a catalyst, attention is paid to tertiary ester-containing vinyl aromatic monomers in the formation of fine patterns. It is desired to develop a method for producing tertiary ester-containing vinyl aromatic monomers with higher efficiency and higher quality than the known formulations.

[0015] The present invention is made in view of the above situation, and its purpose is to provide a method for producing a tertiary ester-containing vinyl aromatic monomer that is particularly suitable for EB lithography resist compositions and EUV lithography resist compositions with a wavelength of 13.5 nm, which is a novel production method with higher efficiency and higher quality than the known formula.

[0016] [Methods to solve the problem]

[0017] The inventors of the present application have conducted in-depth studies to achieve the aforementioned objectives and have found that, when producing tertiary ester-containing aromatic vinyl monomers, the use of metal alkoxides as reaction promoters is extremely effective in obtaining tertiary ester-containing aromatic vinyl monomers with higher yields and higher quality than the known production methods, thereby completing the present invention.

[0018] That is, the present invention provides the following method for producing a tertiary ester-containing aromatic vinyl monomer.

[0019] 1. A method for producing a tertiary ester-containing aromatic vinyl monomer, using a metal alkoxide as a reaction accelerator.

[0020] 2. The method for producing a tertiary ester-containing aromatic vinyl monomer according to 1., wherein a metal alkoxide is used as a reaction accelerator and a tertiary alcohol compound and an N-acyl imidazole compound are reacted.

[0021] 3. A method for producing a tertiary ester-containing aromatic vinyl monomer as described in 2., wherein the aforementioned N-acyl imidazole compound is represented by the following formula (A1), the aforementioned tertiary alcohol compound is represented by the following formula (A2), and the aforementioned tertiary ester-containing aromatic vinyl monomer is represented by the following formula (A3).

[0022] [Chemistry 1]

[0023]

[0024] In the formula, n1 is 0 or 1. n2 is 1 or 2. n3 is an integer from 0 to 6. However, when n1 is 0, 1≤n2+n3≤5, and when n1 is 1, 1≤n2+n3≤7.

[0025] R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0026] R 1 It is a halogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom, or a hydrocarbon oxy group having 1 to 20 carbon atoms which may contain a hetero atom.

[0027] R L1 , R L2 and R L3 are each independently a hydrocarbon group having 1 to 30 carbon atoms, R L1 , R L2 and R L3 Any two of them may be bonded to each other and form a ring together with the carbon atoms to which they are bonded. In addition, the -CH2- contained in the aforementioned hydrocarbon group and cyclic group may be substituted with -O- or -S-.

[0028] 4. The method for producing a tertiary ester-containing aromatic vinyl monomer according to any one of 1. to 3., wherein the metal alkoxide is an alkali metal alkoxide or an alkaline earth metal alkoxide.

[0029] 5. The method for producing a tertiary ester-containing aromatic vinyl monomer according to 4., wherein the metal alkoxide is an alkali metal alkoxide.

[0030] 6. The method for producing a tertiary ester-containing aromatic vinyl monomer according to 5., wherein the cation of the alkali metal alkoxide is a sodium cation or a potassium cation.

[0031] 7. The method for producing a tertiary ester-containing aromatic vinyl monomer according to 5. or 6., wherein the anion of the alkali metal alkoxide is an alkoxide anion bonded to a tertiary carbon atom.

[0032] [Effects of the Invention]

[0033] By using the production method of the present invention, a tertiary ester-containing aromatic vinyl monomer can be obtained with high yield and high quality. DETAILED DESCRIPTION

[0034] The method for producing a tertiary ester-containing aromatic vinyl monomer of the present invention is characterized by using a metal alkoxide as a reaction accelerator. Specifically, a tertiary alcohol compound and an N-acyl imidazole compound are reacted using a metal alkoxide as a reaction accelerator to produce the tertiary ester-containing aromatic vinyl monomer.

[0035] The aforementioned N-acyl imidazole compound is preferably represented by the following formula (A1) (hereinafter also referred to as compound (A1)), the aforementioned tertiary alcohol compound is preferably represented by the following formula (A2) (hereinafter also referred to as compound (A2)), and the obtained tertiary ester-containing aromatic vinyl monomer is preferably represented by the following formula (A3) (hereinafter also referred to as compound (A3)).

[0036] [Chemistry 2]

[0037]

[0038] In formula (A1) and (A3), n1 is 0 or 1. When n1 is 0, it represents a benzene ring, and when n1 is 1, it represents a naphthalene ring. In view of solvent solubility, a benzene ring in which n1 is 0 is more preferred. n2 is 1 or 2. n3 is an integer of 0 to 6. However, when n1 is 0, 1≤n2+n3≤5, and when n1 is 1, 1≤n2+n3≤7.

[0039] In formula (A1) and (A3), R A It is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. Among them, it is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

[0040] In formula (A1) and (A3), R 1 It is a halogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom, or a hydrocarbon oxy group having 1 to 20 carbon atoms which may contain a hetero atom.

[0041] R 1 Examples of the halogen atom represented by include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like, and a fluorine atom or an iodine atom is preferable.

[0042] R 1 The hydrocarbon radical and the hydrocarbon radical part of the hydrocarbon radical oxy group represented by may be saturated or unsaturated, and may be straight-chain, branched, or cyclic. Specific examples thereof include: alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; cyclic saturated hydrocarbon groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; cyclic unsaturated hydrocarbon groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; groups obtained by combining them, etc. Among them, aryl groups are preferred. Furthermore, part or all of the hydrogen atoms of the aforementioned hydrocarbon group may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and part of the -CH2- constituting the aforementioned hydrocarbon group may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonate bonds, carbonate bonds, lactone rings, sultone rings, carboxylic anhydrides, haloalkyl groups, and the like. When n3≥2, multiple R 1 They may also bond to each other and to the carbon atoms on the aromatic rings to which they are bonded to form a ring structure.

[0043] The compound having the N-acyl imidazole structure represented by formula (A1) is preferably obtained by mixing the corresponding aromatic carboxylic acid with N,N-carbonyldiimidazole. It is more preferably used directly in the subsequent reaction without purification after being produced in the reaction system.

[0044] The aromatic carboxylic acid as a precursor of the compound having an N-acylimidazole structure represented by formula (A1) is preferably styrene carboxylic acid which may have a substituent or a vinylnaphthalene carboxylic acid structure, and can be obtained by using a commercially available product or a known organic synthesis reaction.

[0045] In formula (A2) and (A3), R L1 , R L2 and R L3 are each independently a hydrocarbon group having 1 to 30 carbon atoms, R L1 , R L2 and R L3 Any two of them may be bonded to each other and form a ring together with the carbon atoms to which they are bonded. In addition, the -CH2- contained in the above-mentioned hydrocarbon group and cyclic group may be substituted with -O- or -S-.

[0046] In formula (A2) and (A3), -C(R L1 )(R L2 )(R L3) The specific examples of the structure (acid-labile group) represented by may be listed as follows, but are not limited thereto. In the following formula, * represents an atomic bond with an adjacent hydroxyl group.

[0047] [Chemistry 3]

[0048]

[0049] [Chemistry 4]

[0050]

[0051] [Chemistry 5]

[0052]

[0053] [Chemistry 6]

[0054]

[0055] [Chemistry 7]

[0056]

[0057] [Chemistry 8]

[0058]

[0059] [Chemistry 9]

[0060]

[0061] [Chemistry 10]

[0062]

[0063] [Chemistry 11]

[0064]

[0065] [Chemistry 12]

[0066]

[0067] [Chemistry 13]

[0068]

[0069] In the reaction of compound (A1) and compound (A2), the amount of compound (A2) used is not particularly limited. From the perspective of obtaining compound (A3) in good yield, the amount of compound (A1) is preferably 1.0 to 2.0 mol, more preferably 1.0 to 1.5 mol.

[0070] In the reaction of compound (A1) and compound (A2), a metal alkoxide is used as a reaction accelerator in order to obtain compound (A3) in high yield. The metal alkoxide is preferably an alkali metal alkoxide or an alkaline earth metal alkoxide.

[0071] Examples of the alkali metal alkoxide include lithium alkoxide, sodium alkoxide, potassium alkoxide, etc., and sodium alkoxide or potassium alkoxide is preferred in terms of availability and preparation. Examples of the alkaline earth metal alkoxide include magnesium alkoxide, calcium alkoxide, strontium alkoxide, etc., and magnesium alkoxide is preferred in terms of availability and preparation.

[0072] The aforementioned metal alkoxide is preferably an alkali metal alkoxide.

[0073] Examples of the anion of the metal alkoxide include an alkoxide anion bonded to a primary carbon atom, an alkoxide anion bonded to a secondary carbon atom, and an alkoxide anion bonded to a tertiary carbon atom, and an alkoxide anion bonded to a tertiary carbon atom is preferred.

[0074] The alkoxide anion bonded to the tertiary carbon atom may be exemplified by tert-butoxy anion, tert-pentyloxy anion, 1-adamantyloxy anion, etc., and tert-butoxy anion is preferred from the viewpoint of easy availability. In addition, an alkoxide anion obtained by deprotonation of the hydroxyl group in the compound (A2) may be prepared separately and used in the reaction.

[0075] The alkoxide anion obtained by deprotonation of the hydroxyl group in the compound (A2) can be prepared by reacting the compound (A2) with an alkali metal hydride such as sodium hydride or potassium hydride, or an organometallic reagent such as n-butyllithium or Grignard reagent, but the invention is not limited thereto.

[0076] The amount of the metal alkoxide used is preferably 0.01 to 0.4 mol, more preferably 0.01 to 0.2 mol, based on 1 mol of the compound (A1).

[0077] A solvent may also be used in the reaction between compound (A1) and compound (A2). The aforementioned solvent is not particularly limited as long as it is a solvent that does not react with compound (A1) and compound (A2). For example, it can be listed as: aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as hexane, heptane, octane, cyclohexane; ether solvents such as diethyl ether, diisopropyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane; polar aprotic solvents such as acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide. The aforementioned solvents may be used alone or in combination of two or more. The amount of the solvent used may be appropriately set, and is generally about 100 to 500 parts by mass relative to 100 parts by mass of compound (A1).

[0078] In the reaction between compound (A1) and compound (A2), a polymerization inhibitor may be added to inhibit polymerization in the reaction system. Examples of the polymerization inhibitor include hydroquinone monomethyl ether, hydroquinone, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxyl radical, 4-tert-butylcatechol, tert-butylhydroquinone, dibutylhydroxytoluene, phenothiazine, copper salts, etc., but are not limited thereto. The above-mentioned polymerization inhibitors may be used alone or in combination of two or more.

[0079] In the reaction of compound (A1) and compound (A2), the reaction temperature may be any temperature generally used in esterification reactions. From the perspective of shortening the reaction time, the reaction temperature is preferably 40°C to the boiling point of the solvent used. In order to suppress side reactions, polymerization reactions, etc., the reaction temperature is preferably 100°C or less, and more preferably 80°C or less. The reaction time varies depending on the reaction temperature, etc., so it may be appropriately determined, and is generally about 0.5 to 30 hours.

[0080] The compound (A3) obtained by the reaction of the compound (A1) and the compound (A2) is preferably purified. The purification of the compound (A3) can be carried out by appropriately combining known purification methods such as alkaline water washing, water washing, distillation, recrystallization, filtration, etc., taking into account the physical properties of the product and the type of solvent.

[0081] [Example]

[0082] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The apparatus used is as follows.

[0083] IR: NICOLET 6700, manufactured by Thermo Fisher Scientific

[0084] · 1 H-NMR: ECA-500 manufactured by JEOL Ltd.

[0085] [1]Synthesis of monomers

[0086] [Example 1] Synthesis of Monomer A3-1-1

[0087] [Chemistry 14]

[0088]

[0089] Under nitrogen atmosphere, in a reaction vessel, N,N-carbonyldiimidazole (102.2 g) was suspended in toluene (270 g), and 4-phenylformic acid (88.9 g) was added thereto. After confirming that the reaction system became transparent with bubbling, the temperature in the reaction vessel was raised to 50°C and matured for 2 hours. After maturation, potassium tert-butoxide (3.37 g) was added. After addition, 2-methyl-3-butene-2-ol (62.0 g) was added dropwise. After the addition, the temperature in the reaction vessel was raised to 80°C and matured for 24 hours. Thereafter, the reaction solution was cooled, and a 1% by mass sodium hydroxide aqueous solution (150 g) was added to stop the reaction. Thereafter, a conventional aqueous work-up was performed, and after the solvent was distilled off, distillation purification was performed to obtain 122.0 g of monomer A3-1 (yield 94%) as a colorless oil.

[0090] IR spectrum data of monomer A3-1 and 1 The results of H-NMR are shown below.

[0091] IR(D-ATR): ν=3089,2981,2936,1714,1644,1630,1608,1567,1507,1470,1403,1379,136 5,1312,1285,1236,1201,1178,1166,1136,1105,1016,989,917,861,783,713,683,433cm -1 .

[0092] 1 H-NMR(600MHz in DMSO-d6): δ=7.87(2H,d),7.58(2H,d),6.80(1H,dd),6.17(1H,dd),5.96(1H,d),5.40(1H,d),5.25(1H,d),5.10(1H,d),1.59(6H,s)ppm.

[0093] [Examples 2 to 10]

[0094] Using the corresponding raw materials, monomers having the structures shown in Tables 1 and 2 below were synthesized according to the recipe of Example 1. In addition, each N-acyl imidazole intermediate shown in A1 in the following table is synthesized from the corresponding aromatic carboxylic acid and N,N-carbonyl diimidazole, and is directly used in the subsequent steps after being synthesized in the reaction system. The structures of the raw materials (A1 and A2) used and the obtained monomer (A3) are shown in Tables 1 and 2 below.

[0095] [Table 1]

[0096]

[0097]

[0098] [Table 2]

[0099]

[0100]

[0101] [Comparative Example 1] Synthesis of Monomer A3-1-2

[0102] [Chemistry 15]

[0103]

[0104] Under nitrogen atmosphere, a solution of 2-methyl-3-butene-2-ol (51.7 g) dissolved in THF (100 mL) was added dropwise to methylmagnesium chloride (3.0 mol / L THF solution, 200 mL) under ice bath, and stirred for 1 hour. Subsequently, a solution of acyl chloride prepared from p-phenylene formic acid (106.7 g) dissolved in THF (100 mL) was added dropwise under ice bath, and stirred at room temperature for 3 hours. Subsequently, the reaction solution was cooled, and saturated sodium bicarbonate water (250 g) was added to stop the reaction. Insoluble components were precipitated in the reaction solution, so they were filtered, and toluene (400 mL) was added to the filtrate to extract the target substance, and the usual aqueous work-up was performed. After the solvent was distilled off, it was purified by silica gel column chromatography, thereby obtaining 38.9 g of monomer A1 (yield 30%) as a colorless oil.

[0105] [Comparative Example 2] Synthesis of Monomer A3-1-3

[0106] [Chemistry 16]

[0107]

[0108] Under nitrogen atmosphere, p-phenylene formic acid (106.7 g) was suspended in toluene (500 mL), and oxalyl chloride (109.7 g) was added dropwise. After the addition, the temperature in the reaction vessel was raised to 50°C and matured for 6 hours. Thereafter, the reaction solution was cooled to room temperature, and the solvent was concentrated to obtain an acid chloride. 2-methyl-3-butene-2-ol (51.7 g), 4-dimethylaminopyridine (7.3 g), and acetonitrile (450 mL) were added thereto, and the mixture was cooled with an ice bath. While maintaining the temperature in the reaction vessel below 20°C, a solution consisting of triethylamine (85.0 g) and acetonitrile (50 mL) was added dropwise. After the addition, the temperature in the reaction vessel was raised to 60°C and matured for 18 hours. Thereafter, the reaction solution was cooled, and saturated sodium bicarbonate water (250 g) was added to stop the reaction. The product was extracted with toluene (400 mL) and subjected to a conventional aqueous work-up. After the solvent was distilled off, the product was purified by silica gel column chromatography to obtain 22.1 g of monomer A1 as a colorless oil (yield 17%).

[0109] [Comparative Example 3] Synthesis of Monomer A3-1-4

[0110] [Chemistry 17]

[0111]

[0112] Under nitrogen atmosphere, p-phenylene formic acid (88.9 g), pyridine (189.8 g), and 2-methyl-3-butene-2-ol (62.0 g) were dissolved in N,N-dimethylacetamide (216 g). The temperature in the reaction vessel was raised to 50°C, and a solution consisting of p-toluenesulfonyl chloride (137.3 g) and N,N-dimethylacetamide (120 g) was added dropwise. The temperature in the reaction vessel was raised to 70°C and matured for 18 hours. Thereafter, the reaction solution was cooled, and a 5% by mass sodium hydroxide aqueous solution (360 g) was added to stop the reaction. Extraction was performed with toluene (600 mL), and a conventional aqueous work-up was performed. After the solvent was distilled off, purification was performed by distillation, thereby obtaining 62.3 g of monomer A1 (yield 48%) as a colorless oil.

[0113] As described above, by using the method for producing a tertiary ester-containing aromatic vinyl monomer of the present invention, a monomer with higher yield and higher quality can be obtained compared to the conventional production method.

Claims

1. A method for producing a tertiary ester-containing aromatic vinyl monomer, using a metal alkoxide as a reaction accelerator. 2 . The method for producing a tertiary ester-containing aromatic vinyl monomer according to claim 1 , wherein a metal alkoxide is used as a reaction accelerator to react the tertiary alcohol compound with the N-acyl imidazole compound.

3. The method for producing a tertiary ester-containing aromatic vinyl monomer according to claim 2, wherein: The N-acyl imidazole compound is represented by the following formula (A1), the tertiary alcohol compound is represented by the following formula (A2), and the tertiary ester-containing aromatic vinyl monomer is represented by the following formula (A3); Wherein, n1 is 0 or 1; n2 is 1 or 2; n3 is an integer from 0 to 6; however, when n1 is 0, 1≤n2+n3≤5, and when n1 is 1, 1≤n2+n3≤7; R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R 1 is a halogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom, or a hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom; R L1 , R L2 and R L3 are each independently a hydrocarbon group having 1 to 30 carbon atoms, R L1 , R L2 and R L3 Any two of them may be bonded to each other and form a ring together with the carbon atoms to which they are bonded; furthermore, the -CH2- contained in the hydrocarbon group and the ring group may be substituted with -O- or -S-.

4. The method for producing a tertiary ester-containing aromatic vinyl monomer according to any one of claims 1 to 3, wherein The metal alkoxide is an alkali metal alkoxide or an alkaline earth metal alkoxide.

5. The method for producing a tertiary ester-containing aromatic vinyl monomer according to claim 4, wherein: The metal alkoxide is an alkali metal alkoxide.

6. The method for producing a tertiary ester-containing aromatic vinyl monomer according to claim 5, wherein: The cation of the alkali metal alkoxide is a sodium cation or a potassium cation.

7. The method for producing a tertiary ester-containing aromatic vinyl monomer according to claim 5, wherein: The anion of the alkali metal alkoxide is an alkoxide anion bonded to a tertiary carbon atom.

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