High-purity 4-hydroxystyrene solution, method for producing the same, and method for producing 4-hydroxystyrene polymer

Abstract

The subject of the present invention is to provide a 4-hydroxystyrene solution with high purity and good storage stability suitable as a raw material for manufacturing 4-hydroxystyrene polymers on a commercial scale and a method for manufacturing the same. The solution of the present invention is that the method for manufacturing the 4-hydroxystyrene solution based on the present invention includes the following (i) to (iv) steps: (i) a deprotection step of contacting 4-acetoxystyrene with a base in a solvent to generate 4-hydroxystyrene; (ii) a neutralization step of adding an acid to the deprotected solution containing 4-hydroxystyrene to neutralize it; (iii) a step of washing the neutralized solution containing 4-hydroxystyrene with water; (iv) a solvent that can dissolve 4-hydroxystyrene is added to the solution containing 4-hydroxystyrene, distilled at below 40°C, and a solvent replacement step of distilling off components other than 4-hydroxystyrene and excess solvent.

Description

Technical Field

[0001] The present invention relates to a high-purity 4-hydroxystyrene solution having excellent storage stability and a method for producing the same, and also to a method for producing a 4-hydroxystyrene polymer, comprising polymerizing the 4-hydroxystyrene solution as a raw material. Background Art

[0002] Polymers having structural units derived from 4-hydroxystyrene (hereinafter referred to as "4-hydroxystyrene polymers") have been used in many products such as photoresists, printed wiring boards, adhesives, PS printing plates, metal surface treatment agents, sealants, etc. In particular, in the application to photoresists, with the progress of fine patterning, it is required to highly reduce impurities such as insoluble components and metals contained in polymers. In the future, in order to cope with the further demand for fine pattern rules in EUV lithography, electron beam lithography, etc., more stringent property management is required for resist polymers.

[0003] In order to produce a 4-hydroxystyrene-based polymer, there are known a method of using 4-hydroxystyrene as a starting material and a method of using a monomer obtained by replacing the hydroxyl group of 4-hydroxystyrene with a protecting group.

[0004] In the method for using the monomer obtained by replacing the hydroxyl group of 4-hydroxystyrene with a protecting group, for example, it is known that there is a method (patent document 1, patent document 2) in which 4-acetoxystyrene, etc. are used as raw materials for polymerization, and the protecting group is removed by the action of acid or alkali, etc. to show the hydroxyl group. This method can easily obtain high-purity acetoxystyrene, so it is possible to stably produce polymers commercially. However, after polymerization, it is necessary to perform deprotection reactions based on acid and alkali, subsequent neutralization reactions, etc., therefore, there is a disadvantage that the number of manufacturing processes increases and the manufacturing cost becomes larger accordingly. In addition, if the number of processes increases, there is a worry that the risk of impurities being mixed into also increases accordingly. In addition, in the case of the polymer of chemically enhanced resist purposes, due to the structural unit with an acid dissociable group dissociated under the action of an acid contained in the polymer, therefore, during the deprotection reaction of the acetoxystyrene unit, there is also a situation where a part of the acid dissociable group is separated.

[0005] On the other hand, although a method using 4-hydroxystyrene as a starting material has been studied (Patent Document 3), the purity of 4-hydroxystyrene is not described at all. In addition, the production of polymers is only on a laboratory scale. The reason is that 4-hydroxystyrene is an extremely unstable compound that polymerizes rapidly even at room temperature, so it is difficult to pre-produce and store in large quantities as a raw material for industrial production of polymers.

[0006] As a method for producing high-purity 4-hydroxystyrene, there is known a method of reacting 4-acetoxystyrene with an alcohol in the presence of a catalytic amount of an appropriate base (Patent Document 4).

[0007] In addition, as a method for stably storing unstable 4-hydroxystyrene, a method of adding 3 to 1000% by weight of an alcohol such as methanol to 4-hydroxystyrene is known (Patent Document 5), but the inhibition of polymerization is not sufficient and the presence of alcohol is required. In addition, a polymerization raw material composition in which methanol is added to a 4-hydroxystyrene composition obtained by dehydrogenation of 4-ethylphenol is disclosed (Patent Document 6), but since it contains a large amount of impurities such as catalyst residues and residual ethylphenol during dehydrogenation of 4-ethylphenol, it is not a method suitable for producing a resist resin for cutting-edge photolithography.

[0008] In addition, as a method for producing 4-hydroxystyrene with a high yield and stably storing it, a method of obtaining 4-hydroxystyrene crystals by deprotecting a protected monomer of 4-hydroxystyrene using a base catalyst in the presence of 1,3,5-trihydroxybenzene and then crystallizing it, and a method of storing 4-hydroxystyrene containing 0.01 mass % to 10 mass % of 1,3,5-trihydroxybenzene (Patent Document 7) are disclosed. However, since 1,3,5-trihydroxybenzene is mixed into the polymer as an impurity, it is not suitable for use in resists for cutting-edge lithography.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 02-047109

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 63-023902

[0013] Patent Document 3: Japanese Patent Application Publication No. 2005-157401

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 4-283529

[0015] Patent Document 5: Japanese Patent Publication No. 51-29137

[0016] Patent Document 6: Japanese Patent Application Laid-Open No. 10-251315

[0017] Patent Document 7: Japanese Patent Application Publication No. 2016-098181 Summary of the invention

[0018] Problems to be solved by the invention

[0019] The present invention provides a 4-hydroxystyrene solution having high purity and good storage stability, which is suitable as a raw material for producing a 4-hydroxystyrene polymer on a commercial scale, and a method for producing the same. In addition, a method for producing a 4-hydroxystyrene polymer suitable for a resist for cutting-edge photolithography is provided, which can be produced on a commercial scale by a simple process that does not require a deprotection process.

[0020] Means for solving problems

[0021] The inventors of the present application have repeatedly conducted intensive studies to achieve the above-mentioned purpose, and as a result, found that a 4-hydroxystyrene solution having a 4-hydroxystyrene concentration of 10 to 70% and a 4-hydroxystyrene polymer content of 0.5% or less relative to 4-hydroxystyrene can suppress the generation of polymers for a long time and can be stored stably. It was further found that when preparing the above-mentioned 4-hydroxystyrene solution, 4-acetoxystyrene is used as a starting material, 4-hydroxystyrene is generated by a deprotection reaction using an alkali catalyst, a solvent capable of dissolving 4-hydroxystyrene is added to the solution containing 4-hydroxystyrene after neutralization, and reduced pressure distillation is performed at or below 40° C., and components other than 4-hydroxystyrene and the solvent and excess solvent are distilled off, thereby performing solvent replacement without crystallizing 4-hydroxystyrene, thereby making it possible to produce a 4-hydroxystyrene solution with high purity and good storage stability on a commercial scale. The inventors have also found that by using the 4-hydroxystyrene solution for polymerization, a polymer having a structural unit derived from 4-hydroxystyrene and in which insoluble components and metal impurities are highly suppressed from being mixed can be produced on a commercial scale through a simple process that does not require a deprotection process, thereby completing the present invention.

[0022] That is, according to the present invention, the following inventions can be provided.

[0023] [1] A method for producing a 4-hydroxystyrene solution, comprising the following steps (i) to (iv):

[0024] (i) a deprotection step of contacting 4-acetoxystyrene with a base in a solvent to generate 4-hydroxystyrene;

[0025] (ii) a neutralization step of adding an acid to the solution containing 4-hydroxystyrene after deprotection to neutralize the solution;

[0026] (iii) washing the neutralized solution containing 4-hydroxystyrene with water;

[0027] (iv) A solvent replacement step of adding a solvent capable of dissolving 4-hydroxystyrene to a solution containing 4-hydroxystyrene, and performing distillation at 40° C. or lower to distill off components other than 4-hydroxystyrene and excess solvent.

[0028] [2] The method for producing a 4-hydroxystyrene solution according to [1], wherein the base used in the deprotection step is a base from which dissolved oxygen has been removed by bubbling with an inert gas before use, and the deprotection step is performed under a nitrogen atmosphere.

[0029] [3] The method for producing a 4-hydroxystyrene solution according to [1] or [2], wherein the acid used in the neutralization step is an acid from which dissolved oxygen has been removed by bubbling with an inert gas before use.

[0030] [4] The method for producing a 4-hydroxystyrene solution according to any one of [1] to [3], wherein the base used in the deprotection step is a base selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium tert-butoxide, trimethylamine, triethylamine, ethanolamine, diazabicycloundecene, diazabicyclononene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine, and tetramethylammonium hydroxide.

[0031] [5] The method for producing a 4-hydroxystyrene solution according to any one of [1] to [4], wherein the organic solvent used in the solvent replacement step is any organic solvent selected from the group consisting of alcohols, ketones, ethers, glycol ethers, glycol ether esters, and esters.

[0032] [6] The method for producing a 4-hydroxystyrene solution according to any one of [1] to [5], wherein the solvent replacement step is performed so that the final 4-hydroxystyrene concentration is 10 to 70% by mass.

[0033] [7] The method for producing a 4-hydroxystyrene solution according to any one of [1] to [6], further comprising a step of passing the 4-hydroxystyrene solution through a filter having a nominal pore size of 1 μm or less before and / or after the solvent replacement step.

[0034] [8] A 4-hydroxystyrene solution having a 4-hydroxystyrene concentration of 10 to 70% by mass, wherein in gel permeation chromatography analysis of the solution, when the total area of ​​the chromatogram of components other than the organic solvent is set to 100, the chromatogram area of ​​4-hydroxystyrene is 99.5% or more.

[0035] [9] The 4-hydroxystyrene solution according to [8], wherein in gel permeation chromatography analysis of the solution, the chromatogram area of ​​the 4-hydroxystyrene polymer is 0.5% or less relative to the chromatogram area of ​​4-hydroxystyrene.

[0036]

[10] The 4-hydroxystyrene solution according to [8] or [9], wherein the chromatogram area of ​​the 4-hydroxystyrene is 99.7% or more.

[0037]

[11] The 4-hydroxystyrene solution according to [8] or [9], wherein the chromatogram area of ​​the 4-hydroxystyrene is 99.9% or more.

[0038]

[12] The 4-hydroxystyrene solution according to any one of [8] to

[11] , wherein the organic solvent is any one organic solvent selected from the group consisting of alcohols, ketones, ethers, glycol ethers, glycol ether esters, and esters.

[0039]

[13] The 4-hydroxystyrene solution according to any one of [8] to

[12] , which does not contain a polymerization inhibitor.

[0040]

[14] A raw material for polymerization of a resist polymer, comprising the 4-hydroxystyrene solution according to any one of [8] to

[13] .

[0041]

[15] A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, wherein the 4-hydroxystyrene solution described in any one of [8] to

[13] is used as a polymerization raw material and polymerized alone or with other monomers copolymerizable therewith.

[0042]

[16] A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, wherein a 4-hydroxystyrene solution produced by the method described in any one of [1] to [7] is used as a polymerization raw material and polymerized alone or with other monomers copolymerizable therewith.

[0043]

[17] A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, comprising the following steps:

[0044] A step of producing a 4-hydroxystyrene solution by the method described in any one of [1] to [7]; and

[0045] A step of using the 4-hydroxystyrene solution produced in the above step as a polymerization raw material to polymerize the 4-hydroxystyrene alone or with other monomers copolymerizable with 4-hydroxystyrene.

[0046]

[18] The method for producing a polymer according to any one of

[15] to

[17] , wherein the other copolymerizable monomer includes a monomer having an acid-dissociable group.

[0047]

[19] The method for producing a polymer according to

[18] , wherein the monomer having an acid-dissociable group is a group having a tertiary carbon atom bonded to an oxygen atom.

[0048]

[20] The method for producing a polymer according to any one of

[15] to

[19] , which is applied to polymerization using a polymerization container having a capacity of 30 L or more.

[0049] Effects of the Invention

[0050] According to the present invention, a 4-hydroxystyrene solution having high purity and good storage stability can be produced simply and on a commercial scale. In addition, a 4-hydroxystyrene polymer suitable for a resist for cutting-edge photolithography can be produced on a commercial scale by a simple process that does not require a deprotection process. DETAILED DESCRIPTION

[0051] The method for producing a 4-hydroxystyrene solution, a 4-hydroxystyrene solution, and a method for producing a 4-hydroxystyrene-based polymer according to the present invention will be described in detail below.

[0052] <Method for producing 4-hydroxystyrene solution>

[0053] (i) Deprotection Step

[0054] The deprotection step is a step of bringing 4-acetoxystyrene into contact with a base in a solvent to remove the acetyl group to generate 4-hydroxystyrene.

[0055] The base used in the deprotection reaction is not particularly limited. Specifically, examples include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; alkali metal alkoxides such as sodium methoxide, potassium methoxide, sodium ethoxide and potassium tert-butoxide; trimethylamine, triethylamine, ethanolamine, diazabicycloundecene, diazabicyclononene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine and tetramethylammonium hydroxide. Among them, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium tert-butoxide, trimethylamine, triethylamine, diazabicycloundecene, diazabicyclononene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine, tetramethylammonium hydroxide are preferred, and sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, diazabicycloundecene, diazabicyclononene, tetramethylammonium hydroxide are more preferred. The above bases may be used alone or in combination of two or more.

[0056] The amount of the base used is preferably 0.1 molar equivalent or more and 10.0 molar equivalent or less, and more preferably 0.5 molar equivalent or more and 3.0 molar equivalent or less relative to 4-acetoxystyrene. If the amount of the base used is within the above range, a sufficient reaction rate can be easily obtained.

[0057] The base is preferably supplied to the reaction system in a solution state, and the base solution is more preferably bubbled with an inert gas such as nitrogen in advance. Use of a degassed base solution has the effect of suppressing the formation of a hydroxystyrene polymer during the deprotection reaction.

[0058] The deprotection reaction is preferably carried out in an organic solvent, and the organic solvent is not particularly limited as long as it can dissolve 4-acetoxystyrene. Specifically, there can be exemplified alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, lauryl alcohol, cetyl alcohol, stearyl alcohol, benzyl alcohol, triphenylmethanol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol and the like; ketones such as methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone and the like; hydrocarbons such as pentane, hexane, heptane, octane, isooctane, decane, cyclopentane, cyclohexane, benzene, toluene and xylene and the like; ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetrahydrofuran, diethyl ether, diisopropyl ether and methyl tert-butyl ether and nitrile solvents such as acetonitrile and propionitrile and the like. These organic solvents can be used alone or in combination of two or more. Among them, alcohols are preferred, and methanol, ethanol, n-propanol, and isopropanol are particularly preferred. The solution obtained by dissolving 4-acetoxystyrene in the above organic solvent is preferably bubbled with an inert gas such as nitrogen in advance. Thus, there is an effect of suppressing the generation of a polymer of hydroxystyrene during the deprotection reaction.

[0059] The reaction temperature of the deprotection reaction is usually -20 to 50°C, preferably -10 to 20°C, more preferably -5 to 10°C from the viewpoint of suppressing the polymerization reaction.

[0060] The reaction time is not particularly limited as long as it is sufficient to completely convert 4-acetoxystyrene into 4-hydroxystyrene. The end of the reaction can be determined by using 1 The product was analyzed and confirmed by methods such as H-NMR, gas chromatography, and gel permeation chromatography.

[0061] The deprotection reaction of 4-acetoxystyrene is preferably carried out under an inert gas atmosphere such as nitrogen.

[0062] (ii) Neutralization process

[0063] The neutralization step is a step of adding an acid to the base catalyst remaining in the reaction solution after the deprotection reaction to neutralize. The type of acid used for neutralization is not particularly limited, and specifically, formic acid, hydrochloric acid, acetic acid, oxalic acid, sulfuric acid, trifluoroacetic acid, methanesulfonic acid, etc. can be cited. The acid used for neutralization is preferably diluted with a solvent as needed and bubbled with an inert gas such as nitrogen in advance. Thus, there is an effect of suppressing the generation of a polymer of 4-hydroxystyrene.

[0064] (iii) Washing process

[0065] The water washing step is a step of washing the neutralized solution containing 4-hydroxystyrene with water. For the solution containing 4-hydroxystyrene, it is preferred to extract it in an organic solvent that can dissolve 4-hydroxystyrene and can be separated from water, and then wash it with deionized water to remove impurities such as by-products and salts.

[0066] The solvent used for extracting 4-hydroxystyrene may be any solvent that can dissolve 4-hydroxystyrene and can be separated from water, and is preferably the same solvent as the solvent used in the solvent replacement step described later, or a solvent having a lower boiling point than the solvent used in the solvent replacement step described later. Thus, in the subsequent solvent replacement step, the extraction solvent can be easily distilled off, and the extraction solvent can be prevented from remaining in the final product.

[0067] Specifically, ethers such as diisopropyl ether, di-tert-butyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, and diethylene glycol dimethyl ether; ketones such as methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone; esters such as methyl acetate and ethyl acetate; hydrocarbons such as pentane, hexane, heptane, cyclohexane, and methylcyclohexane, etc. are mentioned. Ethers are preferred, and methyl tert-butyl ether is particularly preferred. These extraction solvents may be used alone or in combination of two or more.

[0068] The temperature during extraction is preferably in the range of -20°C or higher and lower than 50°C, but is more preferably -10°C or higher and 30°C or lower from the viewpoint of suppressing the polymerization reaction.

[0069] Regarding the water used for washing the obtained 4-hydroxystyrene extract, deionized water is preferably used to avoid the mixing of metal ions. There is no particular limitation on the amount of water used and the number of water washings, which can be appropriately determined in consideration of operability, extraction efficiency of metal ions, etc., and the amount of waste liquid.

[0070] The temperature during water washing is preferably 0°C or higher and 50°C or lower, more preferably 0°C or higher and 30°C or lower.

[0071] (iv) Solvent replacement step

[0072] The solvent replacement step is a step of replacing the 4-hydroxystyrene extract with a target solvent. That is, a replacement solvent capable of dissolving 4-hydroxystyrene is added to the 4-hydroxystyrene extract, and distillation is performed to remove reaction byproducts, components other than 4-hydroxystyrene such as the extraction solvent, and excess replacement solvent. Compared with the conventional crystallization method in which 4-hydroxystyrene is crystallized and then dissolved in a solvent, the formation of a 4-hydroxystyrene polymer can be suppressed by performing solvent replacement without crystallization to obtain a 4-hydroxystyrene solution.

[0073] The replacement solvent may be added to the 4-hydroxystyrene extract before or after the start of distillation, and is preferably added as appropriate during the distillation. When the concentration of the 4-hydroxystyrene extract is high, it is preferred to add the replacement solvent before distillation in order to suppress the polymerization of 4-hydroxystyrene.

[0074] From the viewpoint of suppressing the polymerization of 4-hydroxystyrene, the temperature during distillation is preferably 40°C or lower, more preferably 20 to 35°C, and even more preferably 20 to 30°C.

[0075] The distillation may be carried out under atmospheric pressure, but is preferably carried out under reduced pressure. The pressure of the reduced pressure distillation is not particularly limited, and can be appropriately adjusted in such a manner that components other than 4-hydroxystyrene, such as reaction by-products, the extraction solvent, and the excess replacement solvent can be distilled off. The pressure of the reduced pressure distillation is, for example, 1 to 100 kPa, preferably 1 to 30 kPa.

[0076] The type of solvent for replacement is any solvent that can dissolve 4-hydroxystyrene, and there is no particular restriction. When the obtained 4-hydroxystyrene solution is directly used as a polymerization raw material for manufacturing a polymer, it is more preferable if it can be used as a polymerization solvent. Specifically, alcohols such as methanol, ethanol, propanol, butanol, and octanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; ethers such as ethyl tert-butyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; glycol ether esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; esters such as ethyl acetate and ethyl lactate; N,N-dimethylformamide, acetonitrile, and the like. Preferred are alcohols, ketones, ethers, ether alcohols, ether esters, and esters; more preferred are methanol, ethanol, propanol, butanol, octanol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, ethyl acetate, and ethyl lactate; and particularly preferred are methanol, ethanol, 2-propanol, 2-butanol, n-octanol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.

[0077] The amount of the replacement solvent used is not particularly limited, and is determined in consideration of the cost and by adopting an amount that can sufficiently distill off impurities other than 4-hydroxystyrene.

[0078] (v) Filter-based filtering

[0079] The 4-hydroxystyrene solution is preferably filtered using a fine filter to remove insoluble components such as polymers slightly generated during the production process. Filtration using a filter may be performed before or after solvent replacement, or may be performed before or after solvent replacement.

[0080] As the form of the filter, a membrane filter, a hollow fiber membrane filter, a pleated membrane filter, and a filter filled with highly purified cellulose, diatomaceous earth and other filter materials can be used. The material of the membrane filter, the hollow fiber membrane filter, and the pleated membrane filter is preferably made of polyolefins such as polyethylene, ultra-high density polyethylene, and polypropylene, fluororesins such as PTFE, and nylon, etc., and is particularly preferably made of nylon. In addition, these filters can include ion exchange groups, cationic charge regulators that produce Zeta potential in the filter, etc. The ion exchange groups are preferably weakly acidic or weakly basic groups. In the case of weakly acidic or weakly basic ion exchange groups, the polymerization of 4-hydroxystyrene can be suppressed.

[0081] The nominal pore size of the filter is preferably 1 μm or less, more preferably 0.2 μm or less, and even more preferably 0.05 μm or less. The lower limit of the nominal pore size of the filter is not particularly limited, but is usually 0.01 μm.

[0082] (vi) Storage of 4-hydroxystyrene solution

[0083] In order to suppress polymerization during storage, the temperature of the produced 4-hydroxystyrene solution during storage is preferably -15°C to 40°C, more preferably -15°C to 20°C, and further preferably -15°C to 5°C.

[0084] <4-Hydroxystyrene solution>

[0085] The 4-hydroxystyrene solution of the present invention is obtained by dissolving 4-hydroxystyrene in a solvent at a specific concentration. By adjusting the concentration of 4-hydroxystyrene, the storage stability of 4-hydroxystyrene can be improved. The method for preparing the 4-hydroxystyrene solution is not particularly limited, and a solution obtained by a manufacturing method including the above-mentioned steps (i) to (iv) can be used. In addition, it can also be a 4-hydroxystyrene solution obtained by a method in which high-purity 4-hydroxystyrene crystals are obtained by a crystallization method known in the past and then dissolved in a solvent instead of the solvent replacement step (iv). In particular, in order to improve the purity of 4-hydroxystyrene, a 4-hydroxystyrene solution obtained by a manufacturing method including the above-mentioned steps (i) to (iv) is preferred.

[0086] The concentration of 4-hydroxystyrene in the 4-hydroxystyrene solution is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and further preferably 20% by mass or more and 50% by mass or less. If the concentration of 4-hydroxystyrene in the 4-hydroxystyrene solution is 10% by mass or more, when used as a polymerization raw material, the polymerization efficiency can be prevented from being reduced. In addition, if it is 70% by mass or less, the precipitation of 4-hydroxystyrene can be prevented, so it is preferred. In addition, in the case of paying special attention to the stability of long-term storage, it is particularly preferably 50% by mass or less.

[0087] In addition, in a 4-hydroxystyrene solution having a 4-hydroxystyrene concentration of 10 to 70% by mass, when the total area of ​​the chromatogram of components other than the organic solvent is set to 100 in gel permeation chromatography analysis of the solution, the chromatogram area of ​​4-hydroxystyrene is preferably 99.5% or more, more preferably 99.7% or more, and even more preferably 99.9% or more.

[0088] The 4-hydroxystyrene polymer content in the 4-hydroxystyrene solution having a 4-hydroxystyrene concentration of 10 to 70% by mass is preferably 0.5% or less, more preferably 0.3% or less, and even more preferably 0.1% or less relative to 4-hydroxystyrene. If the 4-hydroxystyrene polymer content is less than the above values, it can be said that the progress of the polymerization reaction during storage can be sufficiently suppressed.

[0089] The 4-hydroxystyrene solution preferably does not contain a polymerization inhibitor. When the 4-hydroxystyrene solution is used to produce a polymer for a resist used in cutting-edge photolithography, the risk of impurities from the polymerization inhibitor being mixed into the polymer for the resist can be avoided. In addition, even if a polymerization inhibitor is not added, the progress of the polymerization reaction during storage can be suppressed.

[0090] The solvent used in the 4-hydroxystyrene solution is a solvent that can dissolve 4-hydroxystyrene, and there is no particular limitation. When the obtained 4-hydroxystyrene solution is directly used as a polymerization raw material for manufacturing a polymer, it is more preferable if it can be used as a polymerization solvent. Specifically, alcohols such as methanol, ethanol, propanol, butanol, and octanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; ethers such as ethyl tert-butyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; glycol ether esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; esters such as ethyl acetate and ethyl lactate; N,N-dimethylformamide, acetonitrile, and the like. Preferred are alcohols, ketones, ethers, ether alcohols, ether esters, and esters; more preferred are methanol, ethanol, propanol, butanol, octanol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, ethyl acetate, and ethyl lactate; and particularly preferred are methanol, ethanol, 2-propanol, 2-butanol, n-octanol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.

[0091] <Method for producing a polymer having a structural unit derived from 4-hydroxystyrene>

[0092] The method for producing a polymer having a structural unit derived from 4-hydroxystyrene of the present invention comprises the following steps: 4-hydroxystyrene is used as a polymerization raw material and polymerized alone or with other monomers copolymerizable therewith. As the polymerization raw material, the 4-hydroxystyrene solution obtained by the production method described in the above-mentioned <Production method of 4-hydroxystyrene solution> and the 4-hydroxystyrene solution described in the above-mentioned <4-hydroxystyrene solution> can be directly used as the polymerization raw material. When the 4-hydroxystyrene solution is directly provided to the polymerization step, an organic solvent in which 4-hydroxystyrene is dissolved can be directly used as the polymerization solvent.

[0093] (Other copolymerizable monomers)

[0094] The other copolymerizable monomer is not particularly limited as long as it can be polymerized with 4-hydroxystyrene, and in the case of resist applications, known monomers used in the production of resist polymers can be used.

[0095] The polymer for resist is a polymer whose solubility in a developer is changed by the action of an acid, and contains at least one or more repeating units (A) having a structure in which an alkali soluble group is protected by an acid dissociative dissolution inhibiting group. The so-called acid dissociative dissolution inhibiting group refers to a group that inhibits the dissolution of the copolymer in an alkaline developer and dissociates by the action of an acid so that the copolymer is dissolved in the alkaline developer. In addition, in order to improve the substrate adhesion of the polymer, a repeating unit (B) having a lactone ring structure, a repeating unit (C) having a hydroxyl group, etc. are sometimes included. In addition, as required, other repeating units such as a repeating unit (D) having a structure that inhibits dissolution in an alkaline developer and is stable for the action of an acid (hereinafter, sometimes referred to as an "acid stability dissolution inhibiting structure") may be included.

[0096] (Repeating unit (A))

[0097] The repeating unit (A) is a repeating unit having a structure in which an alkali-soluble group such as a carboxyl group, a phenolic hydroxyl group, or a sulfonic acid group is protected by an acid-dissociable dissolution-inhibiting group that dissociates under the action of an acid. Preferably, the repeating unit is a repeating unit in which an OH group such as a carboxyl group, a phenolic hydroxyl group, or a sulfonic acid group in a repeating unit derived from (meth)acrylic acid or hydroxystyrene is protected by an acid-dissociable dissolution-inhibiting group.

[0098] Examples of the acid-dissociative dissolution inhibiting group include a structure represented by the formula (a1) or (a2).

[0099] [Chemical formula 1]

[0100]

[0101] In formula (a1), * represents a bonding site in formula (a1), R 20 and R 21 Each independently represents a hydrocarbon group having 1 to 4 carbon atoms, and specific examples thereof include alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl. 22 represents a hydrocarbon group having 1 to 12 carbon atoms, and specifically, examples thereof include a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, cyclopentyl, cyclohexyl, norbornyl, tricyclo[5.2.1.02,6]decyl, adamantyl, tetracyclo[4.4.0.12,5.17,10]dodecyl, and an aryl group having 6 to 12 carbon atoms such as phenyl and naphthyl. It should be noted that R 22 Can be used with R 20 or R 21 Specifically, they are alicyclic rings having 5 to 12 carbon atoms, such as cyclopentane ring, cyclohexane ring, norbornane ring, tricyclo[5.2.1.02,6]decane ring, adamantane ring, tetracyclo[4.4.0.12,5.17,10]dodecane ring, etc. 22 Medium or R 22 With R 20 or R 21 When a saturated alicyclic ring is bonded, specifically a cyclopentane ring, a cyclohexane ring, a norbornane ring, a tricyclo[5.2.1.02,6]decane ring, an adamantane ring, a tetracyclo[4.4.0.12,5.17,10]dodecane ring, or the like, the difference in solubility in an alkaline developer before and after photolithography is large, and this is preferred for drawing fine patterns.

[0102] [Chemical formula 2]

[0103]

[0104] In formula (a2), * represents the bonding site of formula (a2), R 23 and R 24 Each independently represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and specific examples thereof include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and an alkyl group having 1 to 4 carbon atoms. 25 represents a hydrocarbon group having 1 to 12 carbon atoms, and specifically, examples thereof include a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, norbornyl, tricyclo[5.2.1.02,6]decyl, adamantyl, and tetracyclo[4.4.0.12,5.17,10]dodecyl. 23 Can be used with R24 or R 25 bonded to form a ring, respectively, as R 23 With R 24 Specific examples of the ring formed by bonding include cyclopentane ring, cyclohexane ring, norbornane ring, tricyclo[5.2.1.02,6]decane ring, adamantane ring, tetracyclo[4.4.0.12,5.17,10]dodecane ring, and the like. 23 With R 25 Specific examples of the ring formed by bonding include a hydrogenated furan ring and a hydrogenated pyran ring.

[0105] Specific examples of the repeating unit (A) are given below, but the present invention is not limited thereto. One or more repeating units (A) may be selected and used.

[0106] [Chemical formula 3]

[0107]

[0108] (In the formula, Rx represents H, CH 3 or CF 3 . )

[0109] [Chemical formula 4]

[0110]

[0111]

[0112] (In the formula, Rx represents H, CH 3 or CF 3 . )

[0113] (Repeating unit (B))

[0114] The repeating unit (B) is a repeating unit having a lactone structure or a sultone structure, and functions to improve adhesion to a substrate or a base film, or to control solubility in a photolithography solvent or an alkaline developer. A preferred example is a structure represented by formula (B1).

[0115] [Chemical formula 5]

[0116]

[0117] In formula (B1), R 30 represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, and specifically includes an alkyl group having 1 to 4 carbon atoms such as a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, and a trifluoromethyl group, and preferably a hydrogen atom, a methyl group, and a trifluoromethyl group. 31represents a single bond or a divalent linking group. The divalent linking group represents an alkylene group having 1 to 4 carbon atoms or a group obtained by substituting the alkylene group with an oxygen atom, a carbonyl group or a carbonyloxy group. 32 It represents a lactone structure-containing group represented by formula (b).

[0118] [Chemical formula 6]

[0119]

[0120] In formula (b), R 301 ~R 308 Any one of the above is represented as R 32 The bonding site is a single bond, and the remaining R 301 ~R 308 represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group, or R 301 ~R 308 Any one of the above indicates that R 32 The bonding site with other R 301 ~R 308 Any one or two of them are bonded to form an alicyclic group having 5 to 15 carbon atoms, a hydrocarbon group having 3 to 14 carbon atoms which may contain an oxygen atom or a sulfur atom, and the remaining R 301 ~R 308 Any one or two of them represent single bonds for forming the alicyclic ring having 5 to 15 carbon atoms, and the other R 301 ~R 308 represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group. m represents an integer of 0 or 1.

[0121] Specific examples of the above-mentioned alicyclic ring include cyclopentane ring, cyclohexane ring, norbornane ring, 7-oxa-norbornane ring, 7-thia-norbornane ring, tetracyclo[4.4.0.12,5.17,10]dodecane ring, etc., and preferably, norbornane ring and 7-oxa-norbornane ring are used. Specific examples of hydrocarbon groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, etc., and specific examples of alkoxy groups having 1 to 4 carbon atoms include methoxy and ethoxy.

[0122] In formula (b), R 301 ~R 308 Any one of the above indicates that R 32 The single bond of the bonding site, the remaining R 301 ~R 308 Particularly preferred examples of the lactone structure representing a hydrogen atom, or a hydrocarbon group or alkoxy group having 1 to 4 carbon atoms include a γ-butyrolactone structure and a δ-valerolactone structure. 301 ~R308 Any one of the above indicates that R 32 The bonding site with other R 301 ~R 308 Any one or two of them are bonded to form an alicyclic group having 5 to 15 carbon atoms, a hydrocarbon group having 3 to 14 carbon atoms which may contain an oxygen atom or a sulfur atom, and the remaining R 301 ~R 308 Particularly preferred examples of the lactone structure representing a hydrogen atom, or a hydrocarbon group or alkoxy group having 1 to 4 carbon atoms include a 1,3-cyclohexane carbolactone structure, a 2,6-norbornane carbolactone structure, a 7-oxa-2,6-norbornane carbolactone structure, and a 4-oxa-tricyclo[5.2.1.02,6]decan-3-one structure.

[0123] Specific examples of the repeating unit (B) are given below, but the present invention is not limited thereto. One or more repeating units (B) may be selected and used.

[0124] [Chemical formula 7]

[0125]

[0126]

[0127] (In the formula, Rx represents H, CH 3 or CF 3 . )

[0128] (Repeating unit (C))

[0129] The repeating unit (C) is a repeating unit having a hydroxyl group or a carboxyl group in a side chain, and functions to improve the adhesion between the polymer and the substrate or base film, to control the solubility in a photolithography solvent or an alkaline developer, or to react with a curing agent to form a crosslinked structure.

[0130] As the structure of the repeating unit (C), structures represented by formulae (C1) to (C3) are particularly preferred.

[0131] [Chemical formula 8]

[0132]

[0133] In formula (C1), R 10 R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Specifically, examples thereof include a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a trifluoromethyl group and an alkyl group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Preferably, the alkyl group is a hydrogen atom, a methyl group or a trifluoromethyl group. 11 is a substituted or unsubstituted aromatic hydrocarbon group. 12represents a single bond, or a divalent hydrocarbon group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, or a carbonyl group. Specifically, examples thereof include a single bond, a methylene group, a 1,1-ethylene group, a 2,2-propylene group, a 1,1,1,3,3,3-hexafluoro-2,2-propylene group, a 1,1,1-trifluoro-2-trifluoromethyl-2,3-propylene group and an alkylene group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, preferably a single bond, a 1,1,1,3,3,3-hexafluoro-2,2-propylene group, a 1,1,1-trifluoro-2-trifluoromethyl-2,3-propylene group, and particularly preferably a single bond. i represents an integer of 1 or 2.

[0134] [Chemical formula 9]

[0135]

[0136] In formula (C2), R 13 R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Specifically, examples thereof include a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a trifluoromethyl group and an alkyl group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Preferably, the alkyl group is a hydrogen atom, a methyl group or a trifluoromethyl group. 14 R represents a divalent to tetravalent hydrocarbon group having 2 to 14 carbon atoms which may contain fluorine atoms, oxygen atoms or sulfur atoms, and specifically includes a linear or branched saturated hydrocarbon group having 2 to 4 carbon atoms such as ethylene and isopropylene; and a saturated alicyclic hydrocarbon group having 5 to 14 carbon atoms which may contain an oxygen atom or a sulfur atom, such as a cyclohexane ring, a norbornane ring, a 7-oxa-norbornane ring, a 7-thia-norbornane ring, an adamantane ring, a tetracyclo[4.4.0.12,5.17,10]dodecane ring, and preferably a cyclohexane ring, a norbornane ring, and an adamantane ring. 15 represents a single bond or a divalent hydrocarbon group having 1 to 4 carbon atoms which may be substituted with a fluorine atom. Specifically, examples thereof include a single bond, a methylene group, a 1,1-ethylene group, a 2,2-propylene group, a 1,1,1,3,3,3-hexafluoro-2,2-propylene group, a 1,1,1-trifluoro-2-trifluoromethyl-2,3-propylene group and other alkylene groups having 1 to 4 carbon atoms which may be substituted with a fluorine atom. Preferably, a single bond, a 1,1,1,3,3,3-hexafluoro-2,2-propylene group, a 1,1,1-trifluoro-2-trifluoromethyl-2,3-propylene group are preferred. R is particularly preferred. 14 is adamantyl, and R 15 is a combination of single bonds. j represents an integer of 1 to 3.

[0137] [Chemical formula 10]

[0138]

[0139] In formula (C3), R 16R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and specifically includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a trifluoromethyl group and an alkyl group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, preferably a hydrogen atom, a methyl group or a trifluoromethyl group. 17 represents a divalent alicyclic hydrocarbon group having 6 to 12 carbon atoms which may contain an oxygen atom or a sulfur atom, and specifically includes an alicyclic hydrocarbon group which may contain an oxygen atom or a sulfur atom such as a norbornane ring, a 7-oxa-norbornane ring, a 7-thia-norbornane ring, a tetracyclo[4.4.0.12,5.17,10]dodecane ring, etc., and is preferably a norbornane ring or a tetracyclo[4.4.0.12,5.17,10]dodecane ring. k represents an integer of 0 or 1.

[0140] Specific examples of the repeating unit (C) are given below, but the present invention is not limited thereto. One or more repeating units (C) may be selected and used.

[0141] [Chemical formula 11]

[0142]

[0143]

[0144] (In the formula, Rx represents H, CH 3 or CF 3 . )

[0145] (Repeating unit (D))

[0146] The repeating unit (D) is a repeating unit having a structure in which an alkali-soluble group such as a carboxyl group or a phenolic hydroxyl group is protected by an acid-stable dissolution-inhibiting group that does not dissociate even under the action of an acid. Preferably, the repeating unit is a repeating unit in which a carboxyl group or a phenolic hydroxyl group in a repeating unit derived from (meth)acrylic acid or hydroxystyrene is protected by an acid-stable dissolution-inhibiting group. This repeating unit has the function of controlling the solubility in a photolithography solvent or an alkaline developer, the refractive index of the film, the light transmittance and other optical properties.

[0147] Examples of the acid-stable dissolution inhibiting group include a structure in which a hydrogen atom of a carboxyl group or a phenolic hydroxyl group is substituted and the carbon atom bonded to the oxygen atom is a primary or secondary carbon atom and an aliphatic hydrocarbon group or an aromatic hydrocarbon group having 1 to 12 carbon atoms, or a methyl group and a 1-adamantyl group are bonded. Specifically, examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a cyclopentyl group, a cyclohexyl group, a 2-norbornyl group, a 2-isobornyl group, an 8-tricyclo[5.2.1.02,6]decyl group, a 1-adamantyl group, a 2-adamantyl group, a 4-tetracyclo[4.4.0.12,5.17,10]dodecyl group, a phenyl group, a benzyl group, a naphthyl group, an anthracenyl group, and the like.

[0148] Specific examples of the repeating unit (D) are given below, but the present invention is not limited thereto. One or more repeating units (D) may be selected and used.

[0149] [Chemical formula 12]

[0150]

[0151] (In the formula, Rx represents H, CH 3 or CF 3 . )

[0152] In addition, examples of repeating units having the same effects as those of the repeating unit (D) include repeating units represented by the formula (D').

[0153] [Chemical formula 13]

[0154]

[0155] In formula (D'), R 60 R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and specifically includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a trifluoromethyl group and an alkyl group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, preferably a hydrogen atom, a methyl group or a trifluoromethyl group. 61 is a hydrogen atom, or 62 Specific examples of the bonded single bond or alkylene group having 1 to 4 carbon atoms include a hydrogen atom, a single bond, a methylene group, an ethylene group, an isopropylene group, and the like. 62 It is an aromatic hydrocarbon group having 6 to 14 carbon atoms, and specific examples thereof include a benzene ring, a naphthalene ring, and an anthracene ring.

[0156] Specific examples of the repeating unit (D') are given below.

[0157] [Chemical formula 14]

[0158]

[0159] For the polymerization, a conventionally known polymerization method such as radical polymerization, cationic polymerization, anionic polymerization, etc. can be applied.

[0160] In the case of free radical polymerization, the raw material monomer, free radical polymerization initiator, chain transfer agent used as needed, etc. can be dissolved in a solvent, preferably in an inert gas atmosphere such as nitrogen, and heated and stirred. For example, it can be implemented by the following methods, etc.: the so-called one-time polymerization method, that is, all raw materials such as monomers, polymerization initiators, and chain transfer agents are dissolved in a solvent and heated to the polymerization temperature; the so-called dropwise polymerization method, that is, a solution obtained by dissolving monomers, polymerization initiators, etc. in a solvent is added dropwise to a solvent heated to the polymerization temperature. Among them, the dropwise polymerization method has high reproducibility for each manufacturing batch, so it is preferred, and it is particularly preferred to be the so-called independent dropwise method, that is, the monomer and the polymerization initiator as a free radical generation source are added dropwise. It should be noted that the monomer, polymerization initiator, chain transfer agent, etc. can be supplied to the polymerization system in advance. In the dropwise method, the composition and supply rate of each supply liquid can be changed according to the concentration and composition of the monomers in the polymerization system, the free radical concentration, etc., thereby controlling the molecular weight distribution and composition distribution of the copolymer.

[0161] The initiator of free radical polymerization can use the initiator known in the past. For example, free radical polymerization initiators such as azo compounds and peroxides are preferred. As specific examples of polymerization initiators of azo compounds, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 1,1'-azobis(cyclohexane-1-carbonitrile), 4,4'-azobis(4-cyanovaleric acid) and the like can be cited. As specific examples of polymerization initiators of peroxides, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, peroxide bis(3,5,5-trimethylhexanoyl), peroxysuccinic acid, peroxy-2-ethylhexanoic acid tert-butyl ester, peroxy-pivalic acid tert-butyl ester, peroxy-2-ethylhexanoic acid 1,1,3,3-tetramethylbutyl ester and the like can be cited. They can be used alone or in combination.

[0162] The amount of the polymerization initiator used can be selected according to the target molecular weight, the types of monomers, polymerization initiators, chain transfer agents, solvents, etc., the repeating unit composition, the polymerization temperature, the dropping speed, and the like.

[0163] As for the chain transfer agent, substances known as chain transfer agents can be used as needed. Among them, thiol compounds are preferred and can be widely selected from known thiol compounds. The amount of the chain transfer agent used can be selected according to the target molecular weight, the types of monomers, polymerization initiators, chain transfer agents and solvents, the repeating unit composition, the polymerization temperature, the dropping speed, etc.

[0164] The solvent used in the polymerization reaction is not particularly limited as long as it is a solvent that can stably dissolve the monomer, polymerization initiator, chain transfer agent, and polymerization reaction product. Specifically, the solvents exemplified as the solvents of the aforementioned 4-hydroxystyrene solution can be used. They can be used alone or in combination of two or more.

[0165] There is no particular restriction on the amount of the polymerization solvent used, but if the amount of the solvent used is too little, sometimes the monomers precipitate or the viscosity becomes too high, and the polymerization system cannot be kept uniform. If the amount of the solvent used is too much, sometimes the conversion rate of the monomers is insufficient, or the molecular weight of the copolymer cannot be increased to the desired value. Usually, it is 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight, relative to 1 part by weight of the monomer.

[0166] The amount of the polymerization solvent initially loaded into the reaction tank (hereinafter sometimes referred to as the initial loading solvent) may be at least the minimum amount that can be stirred, but if it is more than necessary, the amount of monomer solution that can be supplied will be reduced, and the production efficiency will be reduced, so it is not preferred. Usually, relative to the final input amount (i.e., the total amount of the initial loading solvent and the added monomer solution and initiator solution), it is selected from a range of, for example, 1 / 30 or more, preferably 1 / 20 to 1 / 2, and particularly preferably 1 / 10 to 1 / 3 in terms of volume ratio. It should be noted that a part of the monomer and / or polymerization initiator may also be mixed in advance in the initial loading solvent.

[0167] When the monomer solution is added dropwise for a short time, the molecular weight distribution tends to become broad, and a large amount of solution is added dropwise at one time, which causes a decrease in the temperature of the polymerization solution, which is not preferred. On the contrary, when it is added dropwise for a long time, the copolymer undergoes a thermal history that is more than necessary, and the productivity decreases, which is not preferred. Therefore, it is usually selected from the range of 0.5 to 24 hours, preferably 1 to 12 hours, and particularly preferably 2 to 8 hours.

[0168] In addition, after the addition is completed, it is preferred to maintain the temperature for a certain period of time, or further increase the temperature, so as to perform aging and react the remaining unreacted monomers. If the aging time is too long, the production efficiency per unit time is reduced, and the copolymer undergoes a thermal history that is more than necessary, which is not preferred. Therefore, it is usually selected from the range of within 12 hours, preferably within 6 hours, and particularly preferably within 1 to 4 hours.

[0169] The polymerization temperature can be appropriately selected according to the boiling points of the solvent, monomer, chain transfer agent, etc., the half-life temperature of the polymerization initiator, etc. It is preferably selected in the range of 40 to 160°C, particularly preferably 60 to 120°C. The polymerization temperature greatly affects the molecular weight and copolymer composition of the copolymer, so it needs to be precisely controlled, but on the other hand, the polymerization reaction is generally an exothermic reaction, so it is difficult to control to a constant temperature. Therefore, it is preferred that at least one or more compounds having a boiling point close to the target polymerization temperature are contained as the polymerization solvent, and the polymerization temperature is set to be above the initial boiling point of the compound under the polymerization pressure. According to this method, the latent heat of vaporization of the polymerization solvent can be used to suppress the rise of the polymerization temperature.

[0170] The polymerization pressure can be appropriately set. However, when the initiator generates free radicals, nitrogen gas is generated in the case of an azo system and oxygen gas is generated in the case of a peroxide system. Therefore, in order to suppress the fluctuation of the polymerization pressure, it is preferred to make the polymerization system an open system and conduct it at near atmospheric pressure.

[0171] The polymer after the polymerization reaction contains low molecular weight impurities such as polymerization solvent, unreacted monomers, oligomers, polymerization initiators, chain transfer agents and their reaction byproducts, and they are preferably removed by a purification process. Specifically, it can be carried out in the following manner: after the polymerization reaction solution is diluted by adding a good solvent as needed, it is contacted with a poor solvent so that the copolymer is precipitated in solid form, and the impurities are extracted into the poor solvent phase (hereinafter referred to as reprecipitation), or, the impurities are extracted into the poor solvent phase in a liquid-liquid two-phase manner. In the case of reprecipitation, it can be further purified by the following process: after the precipitated solid is separated from the poor solvent by filtering, decantation and other methods, the solid is redissolved by a good solvent, and a poor solvent is further added to perform a reprecipitation process; or, the precipitated solid is washed by a poor solvent. In addition, in the case of liquid-liquid two-layer separation, after the poor solvent phase is separated by liquid separation, a poor solvent can be added to the obtained copolymer solution, and further purified by reprecipitation or liquid-liquid two-phase separation. These operations can be repeated to implement the same operation, or different operations can be combined.

[0172] As the poor solvent used in this purification process, compounds with hydroxyl groups such as water, methanol, ethanol, isopropanol, ethylene glycol, ethyl lactate, pentane, normal hexane, isohexane, normal heptane, cyclopentane, methylcyclohexane, straight-chain, branched or cyclic saturated hydrocarbons or aromatic hydrocarbons such as toluene and dimethylbenzene can be enumerated. These solvents can be used alone or mixed with more than two kinds. In addition, as good solvent, solvents exemplified in the above-mentioned polymerization solvent, the film forming solvent described later, etc. can be enumerated, and poor solvents can also be mixed in good solvents and used.

[0173] The type and amount of the poor solvent used in the purification process are not particularly limited as long as the copolymer can be separated from the low molecular weight compound. It can be appropriately selected according to the solubility of the copolymer in the poor solvent, the type and amount of the solvent used in the polymerization, the type and amount of impurities, etc. When the amount of the poor solvent is small, the separation of impurities such as the polymerization solvent and the unreacted monomer becomes insufficient. On the contrary, when the amount of the poor solvent is too much, the waste liquid increases, etc., which is not preferred from the perspective of workability and cost. Usually, it is 0.5 to 50 times by weight, preferably 1 to 20 times, and more preferably 2 to 10 times, relative to the total amount of the polymerization reaction solution diluted with a good solvent as needed.

[0174] The temperature of the purification process greatly affects the molecular weight, molecular weight distribution, removal rate of impurities such as residual monomers and initiator residues of the copolymer, and various characteristics in lithography, so it needs to be strictly controlled. When the temperature of the purification process is too low, the solubility of impurities in the reprecipitation solvent and the cleaning solvent becomes insufficient, and the impurities cannot be fully removed, so it is not efficient. On the contrary, when the temperature of the purification process is too high, the copolymer is dissolved into the reprecipitation solvent and the cleaning solvent, and the composition balance in the low molecular region of the copolymer is destroyed, or the yield is reduced, so it is not preferred. Therefore, the purification process is preferably implemented in a temperature range of 0 to 40°C (preferably in a range of 0 to 30°C).

[0175] A treatment for removing metal impurities contained in the polymer may be performed. As for the method, the solution obtained by dissolving the polymer in an organic solvent may be washed with pure water, or it may be brought into contact with an ion exchange resin, or it may be passed through a filter having an ion exchange capacity. In addition, these methods may be combined. The ion exchange resin and the filter having an ion exchange capacity may use known commercially available ion exchange resins and filters used for removing metals from resist polymers.

[0176] For the purified polymer, it can be dried and taken out as a powder, or before or after drying, it can be put into a good solvent and redissolved and taken out as a solution. In addition, it is also preferred to replace the solvent of the polymer solution with a solvent used in the resist composition, etc. by the method shown below, so as to prepare the polymer solution.

[0177] The replacement method is carried out by heating the polymer solution under reduced pressure, distilling off low-boiling substances such as the solvent used in purification, supplying a resist solvent thereto, and further distilling off the initial solvent together with the supplied solvent. The copolymer can be processed into a resist solution by removing low-boiling impurities such as the solvent used in purification.

[0178] The temperature of the heat source during reduced pressure heating is not particularly limited as long as it is a temperature at which the copolymer does not denature, and is generally preferably 100° C. or less, more preferably 70° C. or less, further preferably 60° C. or less, and particularly preferably 50° C. or less. In the solvent replacement process, since the low boiling point components and the final solvent are evaporated under reduced pressure, the copolymer solution in the process is cooled due to the heat of vaporization, and its temperature becomes lower than the temperature of the heat source. By limiting the temperature of the heat source, deterioration caused by overheating the copolymer can be prevented.

[0179] In addition, when the solvent is replaced, if the amount of the solvent supplied later is too small, the low boiling point compound cannot be sufficiently removed, and if it is too large, the replacement takes time and the copolymer undergoes a thermal history more than necessary, which is not preferred. The supply amount can usually be selected from the range of 1.05 to 10 times, preferably 1.1 to 5 times, and particularly preferably 1.2 to 3 times the amount required as the solvent of the final solution.

[0180] As the replacement solvent, there is no particular limitation as long as the copolymer is dissolved. For resist applications, known solvents used in resist compositions can be generally used. Specifically, solvents such as propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol n-butyl ether, dipropylene glycol n-propyl ether, dipropylene glycol n-butyl ether, ethyl lactate, methyl amyl ketone, γ-butyrolactone, cyclohexanone, and 4-methyl-2-pentanol can be cited.

[0181] In addition, in order to remove the microgel of the polymer which is not preferred due to the pattern defect of the resist, it is preferred to filter the copolymer solution (or the above-mentioned coating film forming solution) using a filter. The filtering accuracy of the filter is less than 0.2 μm, preferably less than 0.1 μm, and particularly preferably less than 0.05 μm. The material of the filter can include polyolefins such as polyethylene and polypropylene, resins containing polar groups such as polyamide, polyester, polyacrylonitrile, and fluorinated polyethylene. Fluorine-containing resins, particularly preferably polyamide. As examples of polyamide-based filters, Ultipleat P-nylon 66, Ultipor N66 made by Pall (Strain) of Japan, LifeASSURE PSN series, LifeASSURE EF series made by CUNO (Strain) can be cited (hereinafter referred to as trademarks). As polyolefin-based filters, Microgard PlusHC10, Optimizer D, etc. made by Nihon Entegris KK can be cited. These filters can be used alone or in combination of two or more.

[0182] The polymer obtained by the production method of the present invention preferably has a high level of reduced metal inclusion. Specifically, based on the mass of the polymer, the total metal content is preferably 50 ppb or less, more preferably 10 ppb or less, and further preferably 3 ppb or less, and it is particularly preferred that any metal is below the detection limit of the analytical device.

[0183] The metal content was determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0184] Typically, the above metal content is the sum of the contents of Na, K, Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sn, Co, Li, Ti, Ag, W, V, Ba, Pt, Au, As, Cd, Mo and Zr. In addition, the content of each of the above metals is preferably 1 ppb or less.

[0185] [Evaluation method for insoluble or poorly soluble components]

[0186] The insoluble or poorly soluble components contained in the polymer solution can be analyzed by the following procedure.

[0187] Step (i): The polymer solution is diluted with a good solvent to prepare a test solution having a polymer concentration of 10.0% by mass.

[0188] Step (ii): Place the test solution in a flask of a non-contact turbidity meter for rotary shaking culture (ODMonitor A&S manufactured by TAITEC installed on an oscillator NR-2). While rotating and shaking, add a poor solvent dropwise at a certain speed, and record the weight change of the test solution and the change in turbidity at a measuring wavelength of 950 nm.

[0189] Step (iii): Continue to add the poor solvent until the turbidity reaches 0.20 OD (optical density). At this time, record the amount of poor solvent added until the turbidity reaches 0.10 OD, 0.15 OD, and 0.20 OD.

[0190] When the amount of the poor solvent added to achieve each turbidity through the above-mentioned steps is small, it means that the amount of the insoluble or poorly soluble component is small.

[0191] The above-mentioned evaluation method of the insoluble or poorly soluble component can be applied to the above-mentioned 4-hydroxystyrene polymer solution and other polymer solutions.

[0192] Example

[0193] Hereinafter, the embodiments of the present invention will be described in detail with reference to the examples, but the present invention is not limited to these examples. It should be noted that, in the following examples, parts are based on mass unless otherwise specified.

[0194] The analysis in this example was performed as follows.

[0195] [Purity of 4-hydroxystyrene solution] and [Weight average molecular weight and molecular weight distribution of polymer]

[0196] The purity, polymer content, and weight average molecular weight and molecular weight distribution of the 4-hydroxystyrene solution synthesized below were measured by GPC (gel permeation chromatography) using polystyrene as a standard. The sample used for analysis was a sample prepared in a tetrahydrofuran solution having a polymer solid content concentration of 2% by mass. The sample injection volume into the device was 50 μL.

[0197] Measuring device: HLC-8220GPC manufactured by TOSOH

[0198] Detector: Differential Refractive Index (RI) detector

[0199] Column: Shodex GPC KF804 × 3 (Showa Denko)

[0200] Eluent: Tetrahydrofuran

[0201] Flow rate: 1.0mL / min

[0202] Temperature: 40℃

[0203] Calibration curve: Prepared using polystyrene standard samples (manufactured by TOSOH)

[0204] [Water content of 4-hydroxystyrene solution]

[0205] The water content of the 4-hydroxystyrene solution synthesized below was measured using the following apparatus.

[0206] Measuring device: Karl Fischer micro-water content measuring device AQ-7 (manufactured by Hiranuma Sangyo Co., Ltd.)

[0207] [Quantification of low molecular weight components in polymers]

[0208] The quantitative determination of low molecular weight components contained in the polymer synthesized below was performed by LC (liquid chromatography) analysis.

[0209] Measuring device: HLC-8320GPC manufactured by TOSOH

[0210] Detector: Differential Refractive Index (RI) detector

[0211] Column: TOSOH TSKgel superHZ1000×4

[0212] Eluent: Tetrahydrofuran

[0213] Flow rate: 0.35mL / min

[0214] Temperature: 40℃

[0215] [Monomer composition ratio of polymer]

[0216] The monomer composition ratio of the polymer synthesized below is 13 C-NMR analysis.

[0217] Device: Bruker AV400

[0218] Deuterated solvent: acetone-d6

[0219] Relaxation reagent: Chromium(III) acetylacetonate

[0220] Measuring temperature: 40℃

[0221] [Metal Analysis of Polymer Solutions]

[0222] The metal content of the polymer synthesized below was analyzed using a high-frequency inductively coupled plasma mass spectrometer (ICP-MS). The metals determined were 26 elements in total, including Na, K, Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sn, Co, Li, Ti, Ag, W, V, Ba, Pt, Au, As, Cd, Mo, and Zr. The analysis value is the mass standard of the solid content of the polymer.

[0223] Apparatus: ICP mass spectrometer (manufactured by Agilent Technologies Inc., trade name: Agilent7500cs)

[0224] Sample preparation: Dilute the polymer solution with N-methyl-2-pyrrolidone

[0225] The abbreviations of the compounds used in the following experiments are as follows.

[0226] PACS: Para-acetoxystyrene

[0227] 4-HS: 4-Hydroxystyrene

[0228] MCpMA: 1-Methyl-1-cyclopentyl methacrylate

[0229] ECpMA: 1-Ethyl-1-cyclopentyl methacrylate

[0230] TBMA: tert-butyl methacrylate

[0231] GBLMA: γ-butyrolactone-α-methacrylate

[0232] NLM: 3,5-Norbornane lactone-2-yl methacrylate

[0233] MEK: Methyl Ethyl Ketone

[0234] MTBE: Methyl tert-butyl ether

[0235] PGMEA: Propylene glycol monomethyl ether acetate

[0236] PGME: Propylene glycol monomethyl ether

[0237] MeOH: Methanol

[0238] IPA: 2-propanol

[0239] SBA: 2-Butanol

[0240] EtOAc: ethyl acetate

[0241] THF: Tetrahydrofuran

[0242] <Method for producing 4-hydroxystyrene solution>

[0243] [Example 1]

[0244] In a 100L glass-lined reaction vessel equipped with a thermometer, a condenser and a stirring device, 7.9kg of PACS and 23.4kg of methanol were added and sealed with nitrogen. The contents were stirred while cooling to a liquid temperature of -5°C. Thereafter, the operation of reducing the pressure in the reaction vessel and restoring the pressure with nitrogen was repeated 3 times. In a container different from the reaction vessel, a 3M aqueous sodium hydroxide solution of equimolar amount relative to PACS was prepared, and the aqueous solution was bubbled with nitrogen for 1 hour. The nitrogen-bubbled sodium hydroxide solution was added dropwise to the reaction vessel over 100 minutes. After the addition, stirring was continued for further 30 minutes to implement the reaction of deprotecting PACS and converting it into 4-HS.

[0245] Next, 0.97 molar equivalent of 6M hydrochloric acid to the PACS used was added dropwise to the reaction vessel over 60 minutes, and the reaction solution was further stirred for 30 minutes to neutralize the reaction mixture. It should be noted that 6M hydrochloric acid was added dropwise after nitrogen was bubbled for 1 hour.

[0246] Next, the temperature of the neutralized reaction solution is raised to about 10-20°C, and 3 times the mass of MTBE of PACS is added thereto, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Next, 3 times the mass of ion exchange water of PACS is added, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Next, 2 times the mass of MTBE and 3 times the mass of ion exchange water of PACS are added, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Finally, the operation of adding 3 times the mass of ion exchange water of PACS, stirring for 15 minutes, allowing to stand for 15 minutes, and discharging the water layer is repeated twice.

[0247] The washed organic layer was transferred to another 100L reaction vessel, and 13 times the mass of MEK of the initial PACS was added. Under reduced pressure distillation was performed at 5kPa below 25°C to remove organic impurities other than 4-HS such as tert-butyl methyl ether and reaction by-products, and excess MEK, and finally processed into a solution with a 4-HS concentration of 25 mass%. Thereafter, the solution was passed through a polytetrafluoroethylene (PTFE) hollow fiber membrane filter with a pore size of 50nm to obtain 21kg of a 25 mass% 4-HS / MEK solution (yield 92%).

[0248] Part of the obtained 4-HS solution was dispensed into a plurality of containers, and a storage test was performed at each temperature of -15°C, -5°C, and 40°C. In the storage test, 4-HS and polymer in the 4-HS solution immediately after production, 20 days, 40 days, 90 days, and 180 days were analyzed by gel permeation chromatography (GPC), and the results are shown in Table 1.

[0249] [Table 1]

[0250]

[0251] The 25 mass % 4-HS / MEK solution obtained in Example 1 was stably stored at -15°C for 6 months without undergoing polymerization. In an accelerated test at 40°C, the generation of polymers was suppressed to 0.5% or less until 20 days.

[0252] [Example 2]

[0253] In a four-necked flask equipped with a thermometer, a condenser and a stirring device, 53.52g of PACS and 160.5g of methanol were put into it and sealed with nitrogen. The contents were stirred while cooling to make the liquid temperature -5 ° C. Thereafter, the operation of reducing the pressure in the reaction vessel and restoring the pressure with nitrogen was repeated 3 times. In a container different from the reaction vessel, a 3M aqueous sodium hydroxide solution was prepared in an equimolar amount relative to PACS, and the aqueous solution was bubbled with nitrogen for 15 minutes. The sodium hydroxide solution bubbled with nitrogen was added dropwise to the reaction vessel over 70 minutes. After the addition, stirring was continued for 30 minutes to implement the reaction of deprotecting PACS and converting it into 4-HS.

[0254] Next, 0.97 molar equivalent of 6N hydrochloric acid to the PACS used was added dropwise to the reaction vessel over 45 minutes, and the reaction solution was further stirred for 30 minutes to neutralize the reaction mixture. It should be noted that 6N hydrochloric acid was added dropwise after nitrogen was bubbled for 1 hour.

[0255] Next, the temperature of the neutralized reaction solution is raised to about 10-20°C, and 3 times the mass of MTBE of PACS is added thereto, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Next, 3 times the mass of ion exchange water of PACS is added, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Next, 2 times the mass of MTBE and 3 times the mass of ion exchange water of PACS are added, stirred for 15 minutes, allowed to stand for 15 minutes, and the water layer is discharged. Finally, the operation of adding 3 times the mass of ion exchange water of PACS, stirring for 15 minutes, allowing to stand for 15 minutes, and discharging the water layer is repeated twice.

[0256] The washed organic layer was transferred to another reaction vessel, and 13 times the mass of MEK of the initial PACS was added. The organic impurities other than 4-HS such as MTBE and reaction by-products and excess MEK were distilled off at a reduced pressure below 25°C, and finally processed into a solution with a 4-HS concentration of 50 mass%. Thereafter, the 4-HS solution was passed through a polytetrafluoroethylene (PTFE) membrane filter with a pore size of 50 nm.

[0257] A portion of the obtained 4-HS solution was dispensed into containers and subjected to a storage test at -15°C. In the storage test, 4-hydroxystyrene and polymers in the 4-HS solution immediately after production and 30 days later were analyzed by GPC. The results are shown in Table 2.

[0258] [Table 2]

[0259]

[0260] [Example 3]

[0261] The experiment was conducted in the same manner as in Example 2 except that propylene glycol methyl ether acetate (hereinafter referred to as PGMEA) was used as the replacement solvent instead of MEK, thereby finally obtaining a 25 mass % 4-HS / PGMEA solution.

[0262] A portion of the obtained 4-HS solution was dispensed into containers and subjected to a storage test at -15° C. 4-HS and polymers in the 4-HS solution immediately after production and 30 days later were analyzed by GPC. Table 3 shows the results.

[0263] [Table 3]

[0264]

[0265] [Comparative Example 1]

[0266] The deprotection reaction of PACS, neutralization and water washing were carried out in the same manner as in Example 2 to obtain a MTBE solution of 4-HS. The solution was transferred into a 1 L glass container and the solvent was distilled off by vacuum distillation at 20° C. or less. The obtained polymer was further dried under reduced pressure at 40° C. for 4 hours to obtain 32 g of 4-HS crystals. Next, the obtained 4-HS crystals were dissolved in MEK to prepare a 25 mass % 4-HS / MEK solution.

[0267] A portion of the obtained 4-HS solution was dispensed into containers and subjected to a storage test at -15° C. 4-HS and polymers in the 4-HS solution were analyzed by GPC immediately after production, 4 days later, and 7 days later. Table 4 shows the results.

[0268] [Table 4]

[0269]

[0270] In Comparative Example 1, the MTBE solvent was removed by vacuum distillation and vacuum drying without performing the solvent replacement step, and the obtained 4-HS crystals were dissolved in MEK to obtain a solution. The generation of 4-HS polymers could not be suppressed, and the storage stability was also insufficient.

[0271] <Storage stability test of 4-hydroxystyrene solution>

[0272] [Example 4]

[0273] The deprotection reaction of PACS, neutralization of the reaction solution and water washing were carried out in the same manner as in Example 1 to obtain an MTBE solution of 4-HS.

[0274] The MTBE solution was concentrated by an evaporator until the 4-HS concentration reached 70% by mass, and then added dropwise to n-hexane at 0° C., and then stirred while cooling the bottom of the container in an ice bath to crystallize 4-HS. The recovered 4-HS crystals were further washed with n-hexane and dried under reduced pressure at room temperature.

[0275] A portion of the obtained 4-HS crystals was dissolved in MEK to prepare a 4-HS concentration of 25 mass %. The 4-HS crystals were divided into a plurality of containers and subjected to a storage stability test. The results are shown in Table 5.

[0276] [Example 5] to [Example 13]

[0277] 4-HS crystals were synthesized by the same procedure as in Example 4, 4-HS solutions were prepared with the solvents and concentrations shown in Table 5, and the storage temperature was adjusted to -5°C, 15°C, or 40°C to perform a storage stability test. The results are shown in Table 5.

[0278] [Table 5]

[0279]

[0280] <Method for producing 4-hydroxystyrene polymer>

[0281] [Example 14] Preparation of 4-HS / MCpMA Copolymer

[0282] 80.0 g of the 25 mass% 4-HS / MEK solution obtained in Example 1 (in GPC analysis, the chromatogram area of ​​4-HS is 99.9% when the total chromatogram area of ​​components other than MEK is set to 100) , 45.6 g of MCpMA, 8.4 g of dimethyl 2,2-azobisisobutyrate and 13.0 g of MEK were added to a container and mixed to prepare a monomer solution.

[0283] MEK52.7 g was added to a 500 mL glass four-necked flask reaction container equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled at 79.0 to 80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0284] The polymer solution was mixed with 460 g of n-hexane, stirred to precipitate the polymer, and separated by decantation after standing. The following operation was repeated 4 times: the polymer was redissolved in a mixed solution containing 40 g of acetone and 30 g of 2-propanol, 460 g of n-hexane was added thereto, stirred to precipitate the polymer, and separated by decantation. The recovered polymer was dissolved in 140 g of ethyl acetate. A portion of the polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder for NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:MCpMA=41.0:59.0.

[0285] The remaining polymer solution was washed with a 1% by mass oxalic acid aqueous solution using a separatory funnel, and then washed 5 times with pure water. For the washed polymer solution, ethyl acetate was distilled off under a heat source temperature of 45°C and reduced pressure, while PGMEA was added and distilled, and a PGMEA solution of 4-HS / MCpMA copolymer with a polymer concentration of 15% by mass was finally obtained. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw=5800, Mw / Mn=1.40, and residual low molecular weight components with Mw less than 200=0.01% (LC area %).

[0286] [Example 15] Preparation of 4-HS / MCpMA Copolymer

[0287] The same operation as in Example 14 was carried out except that the capacity of the reaction container used in the polymerization reaction was changed to 2 L and the amounts of the monomers, solvents, reagents, etc. used were changed to 4 times those of Example 14.

[0288] The analysis results of the obtained polymer were as follows: 4-HS:MCpMA=40.3:59.7, Mw=5810, Mw / Mn=1.39, and residual low molecular weight components with Mw less than 200=0.00% (LC area %).

[0289] [Example 16] Preparation of 4-HS / MCpMA Copolymer

[0290] The same operation as in Example 14 was carried out except that the capacity of the reaction vessel used in the polymerization reaction was changed to 10 L and the amounts of the monomers, solvents, reagents, etc. used were changed to 25 times those of Example 14.

[0291] The analysis results of the obtained polymer were as follows: 4-HS:MCpMA=40.5 / 59.5, Mw=5,800, Mw / Mn=1.40, and residual low molecular weight components having a Mw of less than 200=0.00% (LC area %).

[0292] The results of Example 15 and Example 16 show that, according to the present method, even if the production scale is changed to a larger scale, it is possible to produce a polymer with good reproducibility of properties.

[0293] [Example 17] Preparation of 4-HS / ECpMA Copolymer

[0294] 400.0 g of a 25.9 mass % 4-HS / MEK solution (in GPC analysis, the chromatogram area of ​​4-HS is 100.0% when the total chromatogram area of ​​components other than MEK is 100) prepared by the same procedure as in Example 1, 280.6 g of ECpMA, 29.6 g of dimethyl 2,2-azobisisobutyrate and 86.0 g of MEK were added to a container and mixed to prepare a monomer solution.

[0295] 302 g of MEK was added to a 2L glass four-necked flask reaction vessel equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled at 79.0 to 80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0296] 1000 g of the polymer solution was mixed in a mixed solution of 2300 g of n-hexane and 100 g of methanol, stirred to precipitate the polymer, and separated the polymer by decantation after standing. The following operation was repeated 4 times: the polymer was redissolved in a mixed solution of 200 g of acetone and 100 g of methanol, 2000 g of n-hexane was added thereto, stirred to precipitate the polymer, and separated the polymer by decantation. The recovered polymer was dissolved in 400 g of acetone. A portion of the polymer solution was sampled, dried under reduced pressure at 40°C, and a polymer powder was obtained for NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:ECpMA=39.5:60.5.

[0297] For the remaining polymer solution, acetone was distilled off under the condition of a heat source temperature of 45°C and reduced pressure, while PGMEA was added and distilled, and the solvent was replaced with PGMEA, and finally a PGMEA solution of 4-HS / ECpMA copolymer with a polymer concentration of 20% by mass was obtained. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw=7430, Mw / Mn=1.46, and the residual low molecular weight component with Mw less than 200=0.01% (LC area %).

[0298] [Example 18] Preparation of 4-HS / ECpMA Copolymer

[0299] As the reaction tank used in the polymerization reaction, a 100-liter glass-lined reaction tank equipped with a stirrer, a heat medium circulation jacket, a pressure reducing pipeline, a nitrogen pipeline, and a condenser was used. The amounts of monomers, solvents, and reagents used were changed to 55 times those in Example 17. Except for this, polymerization, purification, and solvent replacement were carried out in the same manner as in Example 17.

[0300] The analysis results of the obtained polymer were as follows: 4-HS:ECpMA=39.8:60.2, Mw=7450, Mw / Mn=1.46, and residual low molecular weight components with Mw less than 200=0.01% (LC area %).

[0301] In addition, regarding the metal content of the PGMEA solution of the 4-HS / ECpMA copolymer having a polymer concentration of 20% by mass obtained in Example 18, the results of ICP mass spectrometry showed that Na was 8 ppb based on the polymer weight, and all other elements were less than 1.0 ppb.

[0302] The results of Example 17 and Example 18 show that the present method can produce polymers with good reproducibility of polymer properties even in commercial-scale production, and can produce polymers with extremely low amounts of low molecular weight impurities and metal impurities.

[0303] [Comparative Example 2] Preparation of 4-HS / MCpMA Copolymer

[0304] The same operation as in Example 15 was carried out except that a 25 mass % 4-HS / MEK solution was used (in the GPC analysis, the chromatogram area of ​​4-HS was 97.3% when the total chromatogram area of ​​components other than MEK was 100).

[0305] The analysis results of the obtained polymer were: 4-HS:MCpMA=40.4:59.6, Mw=5860, Mw / Mn=1.40, residual low molecular weight components with Mw less than 200 = 0.00% (LC area %). The above physical properties were roughly the same as those of the polymer obtained in Example 15.

[0306] [Evaluation of insoluble or poorly soluble components]

[0307] In order to compare the insoluble or poorly soluble components contained in the PGMEA solutions of the 4-HS / MCpMA copolymers obtained in Example 15 and Comparative Example 2, test solutions were prepared and the changes in turbidity of the test solutions when a poor solvent was added thereto were measured in real time. The detailed test method is shown below.

[0308] Regarding the preparation of the test solution, the polymer solutions obtained in Example 15 and Comparative Example 2 were further diluted with PGMEA to adjust the polymer concentration to 10.0% by mass, thereby preparing a test solution.

[0309] The turbidity was measured using a non-contact turbidity meter for rotary shaking culture (OD-Monitor A&S manufactured by TAITEC was installed on an oscillator NR-2 for use). 100.0 g of the test solution was added to a glass conical flask, and the opening of the conical flask was sealed with a stopper equipped with a tube for dropping a poor solvent to prevent evaporation of the solvent. The zero-point calibration of the turbidity meter was performed while the conical flask containing the test solution was rotated and shaken. While rotating and shaking the conical flask, n-hexane as a poor solvent was dropped at a rate of 0.3 g / min, and the weight change of the test solution and the change in turbidity were measured. The measured value OD (optical density; OD = common logarithm of the transmittance of transmitted light) of the turbidity meter used this time is the amount of light transmitted through infrared light (950 nm) converted to the OD of Escherichia coli. 600 The value represented by n-hexane was added continuously until the turbidity reached 0.50 OD. It should be noted that in the test solution with a turbidity of 0.50 OD, a small amount of turbidity was visually confirmed in the solution, but no precipitation of the polymer was observed. The measurement was performed 3 times each, and the average values ​​of the 3 times of n-hexane addition amount until the turbidity reached 0.10 OD, 0.15 OD, 0.20 OD, 0.30 OD, and 0.50 OD are summarized in Table 1.

[0310] [Table 6]

[0311]

[0312] *Average value of 3 measurements

[0313] According to the experimental results, when the turbidity is 0.30 OD or more, no difference is confirmed between the two, but at the level between 0.10 OD and 0.20 OD, that is, the difference is confirmed in the amount of n-hexane added required to produce very slight turbidity, which is the result of the larger amount of n-hexane added in Example 15. Although the copolymer of Example 15 is substantially the same as the copolymer of Comparative Example 2 in terms of physical properties such as monomer composition ratio, Mw, Mw / Mn, and the amount of residual low molecular weight components, it can be evaluated as a copolymer with a smaller amount of insoluble or poorly soluble components that may be an important factor for development defects.

[0314] [Example 19] Preparation of 4-HS / MCpMA / GBLMA Copolymer

[0315] 48.3 g of the 25 mass% 4-HS / MEK solution obtained in Example 1 (in GPC analysis, the chromatogram area of ​​4-HS is 99.9% when the total chromatogram area of ​​components other than MEK is set to 100) , 55.5 g of MCpMA, 28.6 g of GBLMA, 6.9 g of dimethyl 2,2-azobisisobutyrate and 61.2 g of MEK were added to a container and mixed to prepare a monomer solution.

[0316] 74.8 g of MEK was added to a 500 mL glass four-necked flask reaction container equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled at 79.0 to 80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0317] 275 g of the polymer solution was mixed with 620 g of n-hexane and 67 g of methanol, stirred to precipitate the polymer, and separated by decantation after standing. The following operation was repeated twice: the polymer was redissolved in a mixed solution containing 67 g of MEK and 67 g of methanol, 540 g of n-hexane was added thereto, stirred to precipitate the polymer, and separated by decantation.

[0318] The recovered polymer was dissolved in 270 g of ethyl acetate. A portion of the polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder, which was subjected to NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:MCpMA:GBLMA=18.8:51.8:29.4.

[0319] The remaining polymer solution was washed with a 1% by mass oxalic acid aqueous solution using a separatory funnel, and then washed 5 times with pure water. For the washed polymer solution, ethyl acetate was distilled off at 45°C under reduced pressure, while PGMEA was added and distilled, and finally a PGMEA solution of 4-HS / MCpMA / GBLMA copolymer with a polymer concentration of 20% by mass was obtained. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw = 9720, Mw / Mn = 1.59, and residual low molecular weight components with Mw less than 200 = 0.01% (LC area %).

[0320] [Example 20] Preparation of 4-HS / MCpMA / NLM copolymer

[0321] 52.8 g of the 25 mass% 4-HS / MEK solution obtained in Example 1 (in GPC analysis, the chromatogram area of ​​4-HS is 99.9% when the total chromatogram area of ​​components other than MEK is set to 100) , 66.7 g of MCpMA, 24.5 g of NLM, 18.4 g of dimethyl 2,2-azobisisobutyrate and 61.7 g of MEK were added to a container and mixed to prepare a monomer solution.

[0322] 75.4 g of MEK was added to a 500 mL glass four-necked flask reaction container equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled at 79.0 to 80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0323] The polymer solution was mixed with 690 g of n-hexane, stirred to precipitate the polymer, and after standing, the polymer was separated by decantation. The following operation was repeated 4 times: the polymer was redissolved in a mixed solvent of 120 g of MEK and 45 g of methanol, 690 g of n-hexane was added thereto, stirred to precipitate the polymer, and the polymer was separated by decantation.

[0324] The recovered polymer was dissolved in 450 g of ethyl acetate. A portion of the polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder, which was subjected to NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:MCpMA:NLM=20.2:59.4:20.4.

[0325] The remaining polymer solution was washed with a 1% by mass oxalic acid aqueous solution using a separatory funnel, and then washed 5 times with pure water. For the washed polymer solution, ethyl acetate was distilled off at 45°C under reduced pressure, while PGMEA was added and distilled, and a PGMEA solution of 4-HS / MCpMA / NLM copolymer with a polymer concentration of 15% by mass was finally obtained. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw5240, Mw / Mn=1.39, and residual low molecular weight components with Mw less than 200=0.00% (LC area %).

[0326] [Example 21] Preparation of 4-HS / TBMA Copolymer

[0327] 200.0 g of the 25 mass% 4-HS / MEK solution obtained in Example 1 (in GPC analysis, the chromatogram area of ​​4-HS is 99.9% when the total chromatogram area of ​​components other than MEK is set to 100) , 81.8 g of TBMA, 16.8 g of dimethyl 2,2-azobisisobutyrate and 17.0 g of MEK were added to a container and mixed to prepare a monomer solution.

[0328] MEK105.1 g was added to a 1000 mL glass four-necked flask reaction container equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled at 79.0 to 80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0329] The polymer solution was mixed with 880 g of n-hexane and 20 g of methanol, stirred to precipitate the polymer, and separated by decantation after standing. The following operation was repeated 4 times: the polymer was redissolved in a mixed solution containing 176 g of acetone and 12 g of methanol, 800 g of n-hexane was added thereto, stirred to precipitate the polymer, and separated by decantation.

[0330] The recovered polymer was dissolved in 180 g of acetone. A portion of the polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder, which was subjected to NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:TBMA=42.4:57.6.

[0331] The washed polymer solution was distilled off acetone at 45°C under reduced pressure, and PGMEA was added and distilled to finally obtain a PGMEA solution of 4-HS / TBMA copolymer having a polymer concentration of 20% by mass. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw = 6,090, Mw / Mn = 1.44, and residual low molecular weight components with Mw less than 200 = 0.00% (LC area %).

[0332] [Example 22] Preparation of 4-HS / TBMA Copolymer

[0333] Into a glass container, 589 g of a 25% by mass 4-HS / MEK solution (in GPC analysis, the chromatogram area of ​​4-HS is 99.8% when the total chromatogram area of ​​components other than MEK is 100), 267 g of TBMA, 55 g of dimethyl 2,2′-azobis(2-methylpropionate), and 84 g of MEK were supplied and dissolved to prepare a dropping solution.

[0334] While supplying 325 g of MEK to another 2L glass container and stirring, the temperature was raised to 79°C. The aforementioned dropwise solution was added dropwise over 4 hours, and the reaction was continued for another 2 hours, followed by cooling to room temperature. A hexane mixed solution containing 2% by mass of methanol was added to the polymer solution to precipitate the polymer, which was stirred and then separated by decantation. The following operation was repeated 4 times: the polymer was redissolved in an acetone mixed solution containing 7% by mass of methanol, hexane was added thereto to precipitate the polymer, which was stirred and separated by decantation.

[0335] The polymer was redissolved in acetone, PGMEA was added and vacuum distillation was performed. Finally, 1580 g of PGMEA solution containing 20% ​​by mass of the polymer was obtained. 13 As a result of C-NMR analysis, the composition ratio of the obtained copolymer was 4-HS / TBMA=38.8 / 61.2.

[0336] [Example 23] Preparation of 4-HS / ECpMA copolymer

[0337] 83.6 g of the 25 mass% 4-HS / PGMEA solution obtained in Example 3 (in GPC analysis, the chromatogram area of ​​4-HS is 99.9% when the total chromatogram area of ​​components other than PGMEA is set to 100) , 46.2 g of ECpMA, 11.4 g of dimethyl 2,2-azobisisobutyrate and 15.4 g of PGMEA were added to a container and mixed to prepare a monomer solution.

[0338] 67.1 g of PGMEA was added to a 500 mL glass four-necked flask reaction vessel equipped with a stirrer, a condenser, and a thermometer. After setting a nitrogen atmosphere, the temperature was raised to 79° C., and the above-mentioned monomer solution was added dropwise at a constant rate over 4 hours, and then the reaction was further continued for 2 hours. The temperature during the polymerization reaction was controlled to 79.0-80.5° C., and after the polymerization was completed, it was cooled to room temperature.

[0339] 200 g of the polymer solution was mixed in a mixed solution of 460 g of n-hexane and 20 g of methanol, stirred to precipitate the polymer, and separated the polymer by decantation after standing. The following operation was repeated 4 times: the polymer was redissolved in a mixed solution of 40 g of acetone and 20 g of methanol, 400 g of n-hexane was added thereto, stirred to precipitate the polymer, and separated the polymer by decantation.

[0340] The recovered polymer was dissolved in 80 g of acetone. A portion of the polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder, which was subjected to NMR analysis. The monomer composition ratio (molar ratio) of the polymer obtained by NMR analysis was 4-HS:ECpMA=42.6:57.4.

[0341] For the remaining polymer solution, acetone was distilled off under the condition of heat source temperature of 45°C and reduced pressure, while PGMEA was added and distilled, and the solvent was replaced with PGMEA, and finally a PGMEA solution of 4-HS / ECpMA copolymer with a polymer concentration of 20% by mass was obtained. The obtained polymer solution was analyzed by GPC and LC, and the results showed that Mw=5810, Mw / Mn=1.47, and residual low molecular weight components with Mw less than 200=0.01% (LC area %).

[0342] Industrial Applicability

[0343] The high-purity and storage-stable 4-hydroxystyrene solution of the present invention can be used as a raw material for a polymer for resists for EUV lithography and electron beam lithography. In addition, by using the solution, a 4-hydroxystyrene polymer suitable for resists for EUV lithography and electron beam lithography can be produced on a commercial scale through a simple process that does not require a deprotection process.

Claims

1. A method for producing a 4-hydroxystyrene solution, comprising the following steps (i) to (iv): (i) a deprotection step of contacting 4-acetoxystyrene with a base in a solvent to generate 4-hydroxystyrene; (ii) a neutralization step of adding an acid to the solution containing 4-hydroxystyrene after deprotection to neutralize the solution; (iii) washing the neutralized solution containing 4-hydroxystyrene with water; (iv) a solvent replacement step of adding a solvent capable of dissolving 4-hydroxystyrene to a solution containing 4-hydroxystyrene, performing distillation at 40° C. or less, and distilling off components other than 4-hydroxystyrene and excess solvent, The 4-hydroxystyrene solution does not contain a polymerization inhibitor, In the water washing step (iii), 4-hydroxystyrene is extracted in an organic solvent that can dissolve 4-hydroxystyrene and can be separated from water, and the organic solvent used to extract 4-hydroxystyrene is one or more selected from the group consisting of ethers, ketones, esters, and hydrocarbons. The organic solvent used in the solvent replacement step (iv) is any organic solvent selected from the group consisting of alcohols, ketones, ethers, and esters.

2. The method for producing a 4-hydroxystyrene solution according to claim 1, in, The base used in the deprotection step is a base from which dissolved oxygen has been removed by bubbling with an inert gas before use, and the deprotection step is performed under a nitrogen atmosphere.

3. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The acid used in the neutralization step is an acid from which dissolved oxygen has been removed by bubbling with an inert gas before use.

4. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The base used in the deprotection step is a base selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium tert-butoxide, trimethylamine, triethylamine, ethanolamine, diazabicycloundecene, diazabicyclononene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine and tetramethylammonium hydroxide.

5. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The organic solvent used in the solvent replacement step is any one organic solvent selected from the group consisting of glycol ethers and glycol ether esters.

6. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The organic solvent used in the solvent replacement step is any organic solvent selected from the group consisting of methanol, ethanol, propanol, butanol, octanol, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, ethyl acetate, and ethyl lactate.

7. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The solvent replacement step is performed so that the final concentration of 4-hydroxystyrene is 10 to 70% by mass.

8. The method for producing a 4-hydroxystyrene solution according to claim 1 or 2, in, The method further includes passing the 4-hydroxystyrene solution through a filter having a nominal pore size of 1 micron or less before and / or after the solvent replacement step.

9. A 4-hydroxystyrene solution obtained by the production method according to any one of claims 1 to 8, wherein the 4-hydroxystyrene concentration is 10 to 70% by mass, the solution does not contain a polymerization inhibitor, and in a gel permeation chromatography analysis of the solution, when the total area of ​​the chromatogram of components other than the organic solvent is set to 100, the chromatogram area of ​​4-hydroxystyrene is 99.5% or more, and the chromatogram area of ​​4-hydroxystyrene polymer relative to the chromatogram area of ​​4-hydroxystyrene is 0.5% or less.

10. The 4-hydroxystyrene solution according to claim 9, in, In gel permeation chromatography analysis of the solution, the chromatogram area of ​​the 4-hydroxystyrene polymer relative to the chromatogram area of ​​4-hydroxystyrene is 0.3% or less.

11. The 4-hydroxystyrene solution according to claim 9 or 10, in, The chromatogram area of ​​the 4-hydroxystyrene is greater than 99.7%.

12. The 4-hydroxystyrene solution according to claim 9 or 10, in, The chromatogram area of ​​the 4-hydroxystyrene is greater than 99.9%.

13. The 4-hydroxystyrene solution according to claim 9 or 10, in, The organic solvent is any one organic solvent selected from the group consisting of alcohols, ketones, ethers, and esters.

14. The 4-hydroxystyrene solution according to claim 9 or 10, in, The organic solvent is any one organic solvent selected from the group consisting of glycol ethers and glycol ether esters. 15 . A raw material for polymerization of a resist polymer, comprising the 4-hydroxystyrene solution according to claim 9 .

16. A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, in, The 4-hydroxystyrene solution according to any one of claims 9 to 14 is used as a polymerization raw material to carry out polymerization alone or with other monomers copolymerizable therewith.

17. A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, in, The 4-hydroxystyrene solution produced by the method according to any one of claims 1 to 8 is used as a polymerization raw material to carry out polymerization alone or with other monomers copolymerizable therewith.

18. A method for producing a polymer having a structural unit derived from 4-hydroxystyrene, comprising the following steps: A step of producing a 4-hydroxystyrene solution by the method according to any one of claims 1 to 8; and A step of using the 4-hydroxystyrene solution produced in the above step as a polymerization raw material to polymerize the 4-hydroxystyrene alone or with other monomers copolymerizable with 4-hydroxystyrene.

19. The method for producing a polymer according to any one of claims 16 to 18, in, The other copolymerizable monomer includes a monomer having an acid-dissociable group.

20. The method for producing a polymer according to claim 19, in, The monomer having an acid-dissociable group is a group having a tertiary carbon atom bonded to an oxygen atom.

21. The method for producing a polymer according to any one of claims 16 to 18, which is applied to polymerization using a polymerization container having a capacity of 30 L or more.

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