WO2018062296A1 - Method for producing polyimide-based polymer varnish, method for producing polyimide-based polymer film, and transparent polyimide-based polymer film - Google Patents

Abstract

This method for producing a polyimide-based polymer varnish comprises: a step for obtaining a polyimide-based polymer precursor by polymerizing a starting material monomer of a polyimide-based polymer in a solvent; and a step for obtaining a solution of the polyimide-based polymer by imidizing the polyimide-based polymer precursor in a solvent containing a tertiary amine in a reduced pressure environment.

Description

Method for producing polyimide polymer varnish, method for producing polyimide polymer film, and transparent polyimide polymer film

The present invention relates to a method for producing a polyimide polymer varnish, a method for producing a polyimide polymer film, and a transparent polyimide polymer film.

Conventionally, a polyimide solution manufacturing method is known in which a polyimide raw material monomer is polymerized and imidized in a solvent in a nitrogen stream to obtain a polyimide solution. In such a reaction system, when the raw material monomer of polyimide is mixed in a solvent, the raw material monomer is polymerized to produce a polyamic acid, and further, the imidization of the polyamic acid proceeds by heating the polyimide. Is generated. At that time, it is known to add a tertiary amine compound as a catalyst for promoting imidization.

JP 2000-080272 A

However, when the catalyst-containing polyimide solution obtained by polymerization and imidization is cast into a film as it is, it is difficult to obtain a film with good folding resistance. It is also known that purification by an alcohol precipitation method or the like is performed before the film forming step. However, since the purification step is expensive, a process including the purification step tends to be disadvantageous in terms of cost.
In addition, it is also required to maintain high transparency of the polyimide polymer during mass production.

This invention is made | formed in view of the said subject, and it aims at providing the manufacturing method etc. of a polyimide-type polymer varnish etc. which can give high folding resistance to a film, without passing through a refinement | purification process.
Another object of the present invention is to provide a method for producing a polyimide polymer varnish suitable for mass production of a highly transparent polyimide polymer.

The method for producing a polyimide polymer varnish according to the present invention comprises a polymerization step of polymerizing a raw material monomer of a polyimide polymer in a solvent to obtain a polyimide polymer precursor, and a tertiary amine in a reduced pressure environment. In the solvent to contain, the imidization process which imidizes the said polyimide-type polymer precursor and obtains the solution of a polyimide-type polymer is included.

Here, the temperature of the imidization step may be 100 ° C. or more and 250 ° C. or less.

The tertiary amine may have a boiling point of 120 ° C. or higher and 350 ° C. or lower.

The polyimide polymer may contain 20% by mass or more of fluorine.

The pressure in the reduced pressure environment may be 350 mmHg or more and 730 mmHg or less, and the pressure in the reduced pressure environment may be 500 mmHg or more and 730 mmHg or less.

In addition, the oxygen concentration in the gas phase contacting the solvent in the imidization step may be 0.02% or less.

Further, the tertiary amine can be added in an amount of 0.05 to 0.7 parts by mass with respect to 100 parts by mass of the raw material monomer.

The above method may further comprise a step of adding an ultraviolet absorber to the obtained polyimide polymer solution. The method may further include a step of adding silica sol to the obtained polyimide polymer solution.

The method for producing a polyimide-based polymer film according to the present invention includes a step of performing the above-described method for producing a polyimide-based polymer varnish, and depositing and re-dissolving the polyimide-based polymer in the obtained polyimide-based polymer varnish. And a film forming step of casting the polyimide polymer varnish.

The film according to the present invention includes a polyimide polymer having a weight average molecular weight of 50,000 or more and 500,000 or less, and a third polymer having a weight average molecular weight of 0.01 mass% or more and 0.25 mass% or less based on the total mass of the film. And a secondary amine.
The tertiary amine may have a boiling point of 120 ° C. or higher and 350 ° C. or lower.

The production method of another polyimide polymer varnish according to the present invention is as follows:
(1) In a reaction vessel, a step of reacting monomer raw materials in solvent A to obtain a polyimide polymer solution;
(3) removing the solution from the reaction vessel;
(4) washing the reaction vessel with solvent C, and removing the washed solvent C from the reaction vessel, wherein the steps (1), (3), and (4) are the same reaction vessel. Repeat in this order. The polyimide polymer obtained in the step (1) is transparent and has a weight average molecular weight of 250,000 or more.

According to this invention, by having the washing step, the amount of the polymer produced in the previous step (1) remaining in the reaction vessel can be reduced in the second and subsequent steps (1). Therefore, the transparency fall of the polyimide-type polymer synthesize | combined in the process (1) after the 2nd time can be suppressed.

Here, the above method is
(5) After the step (4), the method may further comprise a step of washing the reaction vessel with a solvent D and taking out the solvent D after washing from the reaction vessel.
The steps (1), (3), (4) and (5) can be repeated in this order using the same reaction vessel.

According to this, the amount of the polymer remaining in the reaction vessel can be further reduced.

Moreover, the said method is between the said process (1) and the said process (3),
(2) The method may further comprise a step of diluting the solution obtained in the step (1) by adding the solvent B in the reaction vessel,
The steps (1) to (4) or the steps (1) to (5) can be repeated using the same reaction vessel.

According to this, since the concentration of the polyimide-based polymer in the reaction vessel before the solution is extracted is lowered, the remaining amount of the polymer in the reaction vessel after the extraction can be further reduced.

Also, the solvent B can be the solvent C taken out from the reaction vessel in the step (4).

According to this, since the polymer recovered in the solvent B becomes a part of the polyimide polymer in the varnish to be produced in the next batch, the yield is improved.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a polyimide varnish etc. which can give high folding resistance to a film even if it makes a polyimide-type polymer directly into a film without going through a refinement | purification process are provided.
Moreover, according to this invention, the manufacturing method of the polyimide-type polymer varnish suitable for mass production of a highly transparent polyimide-type resin is provided.

A method for producing a polyimide-based polymer varnish according to an embodiment of the present invention will be described. This method includes a polymerization step of polymerizing a raw material monomer of a polyimide polymer in a solvent to obtain a polyimide polymer precursor, and the polyimide polymer precursor in a solvent containing a tertiary amine under a reduced pressure environment. An imidization step of imidizing the body to obtain a polyimide polymer solution.

(Raw material monomer of polyimide polymer)
The raw material monomer includes a tetracarboxylic acid compound and a diamine.

(Tetracarboxylic acid compound)
Examples of the tetracarboxylic acid compound are an aromatic tetracarboxylic acid compound such as an aromatic tetracarboxylic dianhydride and an aliphatic tetracarboxylic acid compound such as an aliphatic tetracarboxylic dianhydride. A tetracarboxylic acid compound may be used independently and may use 2 or more types together. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as a tetracarboxylic acid chloride compound in addition to the tetracarboxylic acid dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride, and condensed polycyclic fragrance. Group tetracarboxylic dianhydride.
Non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2' , 3,3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxy) Phenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) ), 1, 2 Bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane Anhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride 4,4 ′-(p-phenylenedioxy) diphthalic dianhydride and 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride.
Examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalene tetracarboxylic dianhydride.
As the aromatic tetracarboxylic dianhydride, preferably 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3 ′ -Benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3-di Carboxyphenyl Ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3 , 4-Dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 ′-(p- And phenylenedioxy) diphthalic dianhydride and 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. 1, 2,3,4-cyclobutanetetracarboxylic dianhydride, cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl 3,3′-4,4′-tetracarboxylic dianhydride and their positional isomers . These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more.

From the viewpoint of transparency of the film and suppression of coloring, the tetracarboxylic acid compound is preferably the alicyclic tetracarboxylic dianhydride or the non-condensed polycyclic aromatic tetracarboxylic dianhydride. More preferred specific examples include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2-bis (3 , 4-dicarboxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA). These can be used alone or in combination of two or more.

(Tricarboxylic acid compound and dicarboxylic acid compound)
The raw material monomer can further contain a tricarboxylic acid compound and / or a dicarboxylic acid compound.
Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination.
Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic acid anhydride and benzoic acid are a single bond, —CH ₂ Examples thereof include compounds linked by —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, or a phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include dicarboxylic acid compounds of terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; And compounds in which two benzoic acids are linked by —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, or a phenylene group.

The ratio of the tetracarboxylic acid compound to the total of the tetracarboxylic acid compound, tricarboxylic acid compound, and dicarboxylic acid compound is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol%. Or more, more preferably 90 mol% or more, and particularly preferably 98 mol% or more.

(Diamine)
Examples of diamines are aliphatic diamines, aromatic diamines or mixtures thereof. In the present embodiment, the “aromatic diamine” represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be included in a part of the structure. The aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferable. The “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be included in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornane diamine, 4,4′- Examples include cycloaliphatic diamines such as diaminodicyclohexylmethane, and these can be used alone or in combination of two or more.

Examples of aromatic diamines are p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, etc. Aromatic diamine having one aromatic ring, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′- Diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4 -Aminophenoxy) benzene, 4,4'-diaminodiphenylsulfur Bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2, 2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (TFMB) ), 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) ) Fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chloro) Eniru) fluorene, 9,9-bis (4-amino-3-fluorophenyl) fluorene, etc., an aromatic diamine having two or more aromatic rings. These can be used alone or in combination of two or more.

The diamine can also have a fluorine-based substituent. Examples of the fluorine-based substituent are a perfluoroalkyl group having 1 to 5 carbon atoms such as a trifluoromethyl group, and a fluoro group.

Among the diamines, from the viewpoint of high transparency and low colorability, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure. One or more selected from the group consisting of 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) benzidine (TFMB) and 4,4′-bis (4-aminophenoxy) biphenyl may be used. Further preferred.
The diamine is preferably a diamine having a biphenyl structure and a fluorine-based substituent, and an example thereof is 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (TFMB).

The molar ratio between the diamine in the raw material monomer and the carboxylic acid compound such as a tetracarboxylic acid compound can be suitably adjusted within a range of 0.9 mol to 1.1 mol of the tetracarboxylic acid with respect to 1.00 mol of the diamine. In order to develop high folding resistance, it is preferable that the obtained polyimide polymer has a high molecular weight, so that tetracarboxylic acid is 0.98 mol or more and 1.02 mol with respect to 1.00 mol of diamine. More preferably, they are 0.99 mol% or more and 1.01 mol% or less.
Further, from the viewpoint of suppressing the yellowness of the obtained polyimide-based polymer film, it is preferable that the proportion of amino groups in the resulting polymer terminal is low, and carboxylic acids such as tetracarboxylic acid compounds with respect to 1.00 mol of diamine The compound is preferably 1.00 mol or more.

Adjusting the number of fluorine in the molecule of diamine and carboxylic acid compound (for example, tetracarboxylic acid compound), the amount of fluorine in the resulting polyimide polymer is 1% by mass or more based on the mass of the polyimide polymer It can be 5 mass% or more, 10 mass% or more, or 20 mass% or more. Since the raw material cost tends to increase as the proportion of fluorine increases, the upper limit of the amount of fluorine is preferably 40% by mass or less. A fluorine-type substituent may exist in either diamine or a carboxylic acid compound, and may exist in both. By including a fluorine-based substituent, the YI value may be particularly reduced.

(Solvent A)
The solvent A used for the synthesis of the polyimide polymer (polymerization and imidization of raw material monomers) is a solvent capable of dissolving the polyimide polymer precursor produced by polymerization and the polyimide polymer produced by imidization. Is preferred. Examples of such solvents include lactone solvents, amide solvents, and sulfur-containing solvents. Specifically, γ-butyrolactone (boiling point 204 ° C.) (sometimes referred to as GBL), N, N-dimethylformamide (boiling point 153). C), N, N-dimethylacetamide (boiling point 165 ° C.) (sometimes referred to as DMAc), dimethyl sulfoxide (boiling point 189 ° C.) and the like. The solvent may be a mixture.

In the synthesis of polyimide, when the imidization reaction described later is performed at a high temperature, the solvent A is preferably a high boiling point solvent. The boiling point is preferably 160 ° C. or higher, and more preferably 180 ° C. or higher. Examples of such solvent A are GBL, DMAc, dimethyl sulfoxide.

(Tertiary amine)
The tertiary amine can function as an imidization catalyst for the polyimide polymer precursor in a solvent.
Examples of tertiary amines include tertiary amines represented by formula (a) (hereinafter also referred to as tertiary amine A) and tertiary amines represented by formula (b) (hereinafter also referred to as tertiary amine B). ), Tertiary amines represented by formula (c) (hereinafter also referred to as tertiary amine C), and tertiary amines represented by formula (d) (hereinafter also referred to as tertiary amine D).

　式（ａ）において、Ｒ_１Ａ、Ｒ_２Ａ、Ｒ_３Ａは、それぞれ異なっていてもよい炭素数１～１２の一価の炭化水素基であり、Ｒ_１Ａ、Ｒ_２Ａ及びＲ_３Ａの炭素数の合計は１０以上１８以下である。

In the formula (a), R _1A , R _2A and R _3A are each a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be different from each other, and the total number of carbon atoms of R _1A , R _2A and R _3A Is 10 or more and 18 or less.

Specific examples of tertiary amine A include tripropylamine, dibutylpropylamine, and ethyldibutylamine.

　式（ｂ）において、Ｒ_１Ｂは、炭素数２～１０の一価の炭化水素基であって、Ｒ_２Ｂは炭素数３～１２の二価の脂肪族炭化水素基であって、Ｒ_１Ｂ及びＲ_２Ｂの炭素数の合計は９～１６である。

In the formula (b), R _1B is a monovalent hydrocarbon group having 2 to 10 carbon atoms, R _2B is a divalent aliphatic hydrocarbon group having 3 to 12 carbon atoms, and R _1B and The total carbon number of R _2B is 9-16.

Specific examples of the tertiary amine B include N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine.

　式（ｃ）において、Ｒ_１Ｃは炭素数７～１５の三価の脂肪族炭化水素基である。

In the formula (c), R _1C is a trivalent aliphatic hydrocarbon group having 7 to 15 carbon atoms.

Specific examples of the tertiary amine C include azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2.2] nonane. Can be mentioned.

　式（ｄ）において、Ｒ_１Ｄは炭素数８～１５の三価の脂肪族炭化水素基である。

In the formula (d), R _1D is a trivalent aliphatic hydrocarbon group having 8 to 15 carbon atoms.

Specific examples of the tertiary amine D include 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4 , 6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, isoquinoline.

It is preferable that the tertiary amine used has a high boiling point because the amount of catalyst removed from the system tends to be suppressed when water is distilled off under reduced pressure. A tertiary amine having a boiling point of 120 ° C. or higher is preferable, a tertiary amine having a boiling point of 140 ° C. or higher is more preferable, a tertiary amine having a boiling point of 170 ° C. or higher is more preferable, and a tertiary amine having a boiling point of 200 ° C. or higher is still more preferable. preferable. Although the upper limit of the boiling point of the tertiary amine to be used is not particularly defined, it is usually 350 ° C. or lower. As the tertiary amine having a lower boiling point is used, it is necessary to increase the amount of the catalyst used in consideration of the distillate.

The tertiary amine is preferably a tertiary amine D, more preferably a tertiary amine D having 6 to 13 carbon atoms. More preferred is a tertiary amine D having 9 to 13 carbon atoms, and still more preferred is isoquinoline and its hydride.

(Production method of polyimide polymer varnish)
This method includes a polymerization step of polymerizing a raw material monomer of a polyimide polymer in a solvent to obtain a polyimide polymer precursor, and the polyimide polymer precursor in a solvent containing a tertiary amine under a reduced pressure environment. An imidization step of imidizing the body to obtain a polyimide polymer solution.

In the present embodiment, the polyimide polymer varnish is obtained by adding a polyimide polymer solution obtained by imidation of a polyimide polymer precursor, and adding a solvent or an additive to the polyimide polymer solution. Solution.

(Generation of polyimide polymer precursor by polymerization of raw material monomer)
The raw material monomer of the polyimide polymer is polymerized in the solvent A described above in the reaction vessel. The amount of the raw material monomer in the total liquid including the raw material monomer and the solvent A can be 10 to 60% by mass. When the amount of the monomer is large, the polymerization rate tends to increase, and the molecular weight can be increased. Further, the polymerization time can be shortened, and the coloring of the polyimide polymer tends to be suppressed. If the amount of the monomer is too large, the viscosity of the polymer or the solution containing the polymer tends to increase, which makes it difficult to stir or the polymer adheres to the reaction vessel or stirring blade, resulting in a low yield. Sometimes.

The order of mixing each component of the raw material monomer and the solvent A is not particularly limited, and all of them may be mixed simultaneously or separately, but after mixing at least a part of the diamine and the solvent It is preferable to add a carboxylic acid compound. The diamine and carboxylic acid compound may be added in portions, or may be added stepwise for each compound.

By sufficiently stirring the raw material monomer in the reaction mass, polymerization of the raw material monomer is promoted and a polyimide polymer precursor is formed. If necessary, the reaction mass may be heated to about 40 to 90 ° C. The imidization process described later can also proceed in parallel with the progress of the raw material monomer polymerization process. In this case, the reaction mass may be heated to a higher temperature in accordance with the imidization conditions described later.
The polymerization reaction time can be, for example, 24 hours or less, can be 1 hour or less, and can be 1 to 24 hours.

The reaction mass may contain a tertiary amine during the polymerization step of the polyimide polymer precursor. In this case, the tertiary amine may be added before mixing the diamine and the solvent, may be added after mixing, or may be added after mixing the diamine, the solvent, and the carboxylic acid compound. Further, after diluting with a part of the solvent to be used, it may be added to the reaction mass.

(Imidization of polyimide polymer precursor)
Subsequently, imidation of the polyimide polymer precursor is promoted by heating a reaction mass containing a tertiary amine in a reduced pressure environment, and water produced as a by-product is distilled off while forming a polyimide. It is preferable to imidize the polyimide polymer precursor in the solvent A in the reaction vessel in which the above polymerization is performed. The tertiary amine may be added during or before the polymerization step of polymerizing the raw material monomer to produce the polyimide polymer precursor as described above, but in the step of producing the polyimide polymer precursor. It may be added later.
The formation reaction of the polyimide polymer precursor and the imidization reaction may proceed simultaneously. In that case, the bond of an amide group may be cut | disconnected by the water produced | generated by imidation reaction, and the molecular weight of the polyimide-type polymer obtained may become low. A film obtained from a varnish containing such a polyimide-based polymer may have low folding resistance. In the imidization step, the pressure in the reaction solution is reduced and water in the reaction solution is quickly removed, so that the cleavage reaction of the amide group can be suppressed and the molecular weight of the resulting polyimide polymer can be increased. Therefore, in particular, when the formation reaction of the polyimide polymer precursor and the imidization reaction proceed simultaneously, by performing the imidization step under a reduced pressure environment, the varnish containing the polyimide polymer can be used without going through a purification step. Even if the film is produced directly, the film tends to have high folding resistance.

In the reaction mass, from the viewpoint of improving folding resistance, the amount of tertiary amine added to 100 parts by mass of the raw material monomer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more. More preferably, it is 0.2 parts by mass or more. On the other hand, for the purpose of suppressing coloration of the film, it is preferable that the addition amount of the catalyst is small. The amount of tertiary amine added is preferably 2 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0.7 parts by mass or less, still more preferably 0.5 parts by mass or less. Especially preferably, it is 0.3 mass part or less.

The temperature in the imidization step is preferably 100 ° C. or higher and 250 ° C. or lower, and more preferably 150 ° C. or higher and 210 ° C. or lower. The pressure in the imidization step is preferably 730 mmHg or less, more preferably 700 mmHg or less, and further preferably 675 mmHg or less.

The pressure in the imidization step can be, for example, 350 mmHg or more, and may be 500 mmHg or more. Depending on the vapor pressure of the solvent at the temperature of the imidization step, it may be preferable to perform the pressure at 400 mmHg or higher in order to increase the stability of the reaction. For the same reason, it may be more preferable to carry out at 600 mmHg.
If the pressure in the imidization step is set near the saturated vapor pressure of the solvent in the imidization step, YI tends to be suppressed. A pressure within 50 mmHg from the saturated vapor pressure is preferred.

The heating time can be, for example, 1 to 24 hours. The time is preferably 1 to 12 hours, more preferably 2 to 9 hours, still more preferably 2 to 8 hours, still more preferably 2 to 6 hours, and particularly preferably 2 to 5 hours. Stirring is preferred during heating.
As the reaction time becomes longer, the molecular weight increases, but the yellowishness of the resin tends to increase. On the other hand, when the reaction time is short, the molecular weight tends to be low, and the yellow color tends to be weak.

In the imidization step, when the oxygen concentration in the gas phase contacting the liquid phase containing the solvent A in the reaction vessel is low, coloring of the polyimide polymer tends to be suppressed, and a film obtained from a varnish containing the same The YI value tends to be low. In the production method, the imidization step by heating the reaction mass in a reduced pressure environment may be performed in a state where the oxygen concentration in the gas phase of the reaction vessel is low. For example, the pressure reduction is started before the heating in the reduced pressure environment. The oxygen concentration may be low from the time when the raw material monomer or the like is added. The oxygen concentration is preferably 0.02% or less, and more preferably 0.01% or less. If the oxygen concentration is high when heated to a high temperature, it causes coloring in particular. For example, when the temperature of the reaction solution is 130 ° C. or higher, the oxygen concentration is preferably 0.02% or lower. In the synthesis of the precursor and the imidization of the precursor, oxygen is not substantially generated. For example, by reducing the oxygen concentration in the gas phase by replacing the inside of the reaction vessel with nitrogen gas before starting the raw material, The oxygen concentration in the gas phase in the conversion step can be reduced. The oxygen concentration in the imidization step can be grasped, for example, by analyzing the oxygen concentration in the gas removed from the reaction vessel when the pressure inside the reaction vessel is reduced. If it is difficult to measure the oxygen concentration during decompression, the oxygen concentration may be measured by sampling the gas phase before and after decompression.

After heating, it is returned to atmospheric pressure and cooled to obtain a polyimide polymer solution.
This polyimide polymer solution may be used as it is as a polyimide polymer varnish.

(Dilution process)
Moreover, the polyimide polymer varnish can also be obtained by adjusting the concentration of the polyimide polymer by adding solvent B to the obtained polyimide polymer solution. The solid content concentration in a suitable polyimide-based polymer varnish is 10 to 25% by mass.
In addition, when producing a film from a polyimide-based polymer varnish, if a varnish containing 30% by mass or more of a polyimide-based polymer is used with respect to the total amount of solids in the varnish, one of the main components described later is a polyimide-based polymer. A polyimide polymer film which is a polymer can be easily obtained. The concentration of the polyimide polymer is preferably 10% by mass or more, more preferably 13% by mass or more based on the total mass of the varnish.

Dilution can be performed in the reaction vessel, and can also be performed on the solution recovered from the reaction vessel.

In the reaction vessel, when the solvent B is added to the polyimide polymer solvent after imidization and the concentration of the polyimide polymer in the reaction vessel is diluted, the polymer remaining in the reaction vessel in the next extraction step Thus, the yield of the polymer can be improved. Further, when the amount of the polymer remaining in the reaction vessel is reduced, coloring (for example, yellow) of the obtained polyimide-based polymer is improved in the subsequent polymerization and imidation repeating steps using this reaction vessel.

The solvent B for dilution can be the same as the solvent A described above. The solvent B and the solvent A may be the same type or different types. By appropriately selecting a solvent having high solubility in the polyimide resin as the solvent B for dilution, the recovery rate of the polyimide polymer from the reaction vessel is increased. Examples of such a solvent include N, N-dimethylacetamide, cyclopentanone (boiling point 131 ° C.) and the like.

The dilution in the reaction vessel can be performed a plurality of times using a plurality of different types of solvents B.

(Solution extraction process)
Subsequently, the polyimide polymer varnish is extracted from the reaction vessel. The extracted varnish can be used in a film forming process described later.

(Cleaning of reaction vessel with solvent C)
Subsequently, the solvent C is supplied into the reaction container after the extraction, the polymer remaining in the reaction container is dissolved in the solvent C, and then the solvent C in which the polymer is dissolved is recovered from the reaction container. The remaining polymer can be further removed.

By washing the reaction vessel, the amount of polymer remaining in the reaction vessel can be reduced, and the color (for example, yellow) of the resulting polyimide polymer can be improved in the subsequent polymerization and imidation repeating steps using this reaction vessel. Is done.

Solvent C can be exemplified by solvent A and solvent B. The solvent C may be the same type as the solvent A or different from the solvent A. The solvent C may be the same type as the solvent B or may be different from the solvent B. By employing an appropriate washing solvent, the amount of polymer remaining in the reaction vessel can be reduced. Examples of such a solvent include N, N-dimethylacetamide, cyclopentanone and the like.

The solvent C may be supplied to the reaction vessel and then recovered, then the solvent D may be supplied to the reaction vessel to dissolve the polymer, and then the solvent D may be recovered. You may perform the washing | cleaning by the solvent D in multiple times. The solvent D may be the same type as the solvent C or may be different from the solvent C.

(repetition)
After washing, using the washed reaction vessel again, the steps of polymerization, imidization, dilution, extraction, and washing can be repeated to efficiently produce a polyimide polymer varnish using one reaction vessel. it can.

(Reuse of solvent C and solvent D)
As the solvent B used in the above-described dilution step, it is preferable to use the solvent C used for washing the reaction vessel. As the solvent B, the solvent D used for washing can also be used. It is preferable to use at least the solvent C as the solvent B for dilution. By using a solvent C containing a polymer as the solvent B for dilution, the yield of the polymer can be increased.

Here, with respect to the theoretical amount (weight) of the polyimide-based polymer calculated from the charged amount of raw material monomer in one polymerization step, the yield in the polyimide varnish actually obtained in the subsequent extraction step It is the weight of resin solids. When the polyimide varnish contains the solvent C after washing the reaction vessel, the weight of the resin solids in the polyimide varnish is the resin solids contained in the solvent C and the resin solids in the polyimide varnish synthesized in the reaction vessel. Total amount.

In particular, in the production of a transparent polyimide polymer varnish having a weight average molecular weight of 250,000 or more, the obtained polymer tends to adhere to the reaction vessel, and the polymer remains in the reaction vessel after extraction of the solution, resulting in a high yield. When the polymer is reduced or the polymer remaining in the reaction vessel has an adverse effect on the synthesis of the polyimide in the next step, resulting in a high yellow color of the resulting polymer or an increase in foreign matter contained in the resulting polymer There is.

Such a problem can be solved by diluting the solution before extraction with the solvent B and / or washing the reaction vessel using the solvent C. Washing with the solvent D in addition to the solvent C, that is, washing with a plurality of times with two or more solvents, tends to make the reaction vessel easier to clean.

For example, if the polymerization is repeated in a situation where the reaction vessel is not washed or insufficiently washed, deposits derived from the polymer remain on the wall surface of the reaction vessel, and the YI value of the polyimide polymer is high. May be. In such a case, by washing with a plurality of solvents (solvent C and solvent D), washing of the reaction vessel is further strengthened, and an increase in the YI value is suppressed.

In addition, said "transparent" means the total light transmittance (Tt) when the polyimide-type polymer contained in a varnish produces and measures a polymer film with a film thickness of 80 micrometers according to JIS K7105: 1981. Is 85% or more. The total light transmittance is preferably 90% or more.

In addition, the said weight average molecular weight is a standard polystyrene conversion molecular weight measured by GPC.

Solvent A used for the synthesis of polyimide and solvent B and / or solvent C used for dilution and washing may be the same solvent, but if they are different from each other, the transparency of the polymer obtained by improving the cleaning degree of the reaction vessel is improved. Can be improved. Suitable solvents for solvents B and C include N, N-dimethylacetamide, cyclopentanone and the like as described above. These solvents are preferable because they have a boiling point lower than that of GBL but are advantageous for extraction from the reaction vessel because the viscosity of the polyimide polymer varnish is lowered. On the other hand, the solvent A used for the synthesis of polyimide is preferably a high boiling point solvent such as GBL when the imidization reaction is performed at a high temperature as described above.

Furthermore, an additive other than a solvent can be added to the polyimide polymer solution to prepare a polyimide polymer varnish. Examples of the additive include inorganic particles and ultraviolet absorbers.

(Inorganic particles)
Specific examples of the inorganic particles include silica fine particles.

The average primary particle diameter of the inorganic particles used in the present invention is usually 100 nm or less.
When the average primary particle diameter of the inorganic particles is 100 nm or less, the transparency of the film tends to be improved. The measurement of the primary particle diameter of the inorganic particles in the film can be a constant diameter by a transmission electron microscope (TEM). The average primary particle diameter can be obtained, for example, by measuring 10 primary particle diameters by TEM observation and calculating the average value thereof.

When the inorganic particles are silica fine particles, the silica fine particles may be a silica sol in which the silica particles are dispersed in an organic solvent or the like, or a silica fine particle powder produced by a vapor phase method may be used, but handling is easy. Therefore, a silica sol is preferable. The average primary particle diameter of the raw material silica particles can be determined, for example, by BET measurement.

The amount of inorganic particles added is set in accordance with the amount of the resin component in the polyimide-based polymer solution so that the concentration of the inorganic particles in the film after casting is, for example, from 0% by mass to 90% by mass. can do. Preferably they are 10 mass% or more and 60 mass% or less, More preferably, they are 20 mass% or more and 50 mass% or less. There exists a tendency which is easy to make transparency and mechanical strength of an optical film compatible as a compounding ratio exists in said range.

(UV absorber)
The ultraviolet absorber can be appropriately selected from those usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber can be determined from the compound that absorbs light having a wavelength of 400 nm or less, and the type and amount of the ultraviolet absorber can be determined according to the required characteristics of the light absorption capability according to the application. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds. The ultraviolet absorber is preferably a benzotriazole compound.

In this embodiment, the “system compound” refers to a derivative of the compound to which the “system compound” is attached. For example, a “benzophenone compound” refers to a compound having benzophenone as a host skeleton and a substituent bonded to benzophenone.

(Other additives)
Other additives may be added to the polyimide polymer solution as long as the transparency and flexibility are not impaired. Examples of other components include colorants such as antioxidants, mold release agents, stabilizers, and bluing agents, flame retardants, lubricants, thickeners, and leveling agents.

The total amount of additive components other than inorganic particles can be appropriately set so that the concentration in the film after casting is 0% or more and 20% by mass or less, preferably more than 0% and 10% by mass or less.

(Polyimide polymer obtained by polymerization and imidization)
In the present embodiment, the polyimide is a polymer containing a repeating structural unit containing an imide group, and the polyamide is a polymer containing a repeating structural unit containing an amide group. The polyimide polymer is a polyimide; a polymer containing a repeating structural unit containing both an imide group and an amide group; and a repeating structural unit containing an imide group and a repeating structural unit containing an amide group. A polymer is shown.

The polyimide polymer obtained by polymerization and imidation has a repeating structural unit represented by the following formula (10). Here, G is a tetravalent organic group, and A is a divalent organic group. The structure represented by two or more types of Formula (10) from which G and / or A differ may be included. In addition, the polyimide polymer according to the present embodiment has a structure represented by the formula (11), the formula (12), and the formula (13) as long as various physical properties of the obtained polyimide polymer film are not impaired. Any one or more may be included.

The polyimide polymer according to the present embodiment can be produced using a tetracarboxylic acid compound and a diamine compound, which will be described later, as main raw materials, and the repeating structural unit represented by the formula (10) is a polyimide polymer. The main structural unit is preferable from the viewpoint of the strength and transparency of the film. The repeating structural unit represented by the formula (10) is preferably 40 mol% or more, more preferably 50 mol% or more, further preferably 70 mol%, based on all repeating structural units of the polyimide polymer. More preferably, it is 90 mol% or more, and still more preferably 98 mol% or more. 100 mol% may be sufficient as the repeating structural unit represented by Formula (10).

G and G ¹ are tetravalent organic groups, preferably organic groups which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and are represented by the following formulas (20), (21), Groups represented by formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) and the number of tetravalent carbon atoms Six or less chain hydrocarbon groups are exemplified. In the formula * represents a bond, Z is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, —C (CF ₃ ) ₂ —, —Ar—, —SO ₂ —, —CO—, —O—Ar—O—, —Ar—O—Ar—, —Ar—CH ₂ —Ar—, —Ar— C (CH ₃ ) ₂ —Ar— or —Ar—SO ₂ —Ar— is represented. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. The groups represented by the formulas (20) to (27) are preferred because the yellowness of the resulting film can be easily suppressed.

G ² is a trivalent organic group, and is preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. The organic group of G ^2, the above expression (20), equation (21), equation (22), equation (23), equation (24), equation (25), equation (26), equation (27), wherein Examples include a group in which any one of the bonds of the group represented by (28) or formula (29) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms.

G ³ is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As the organic group of G ³ , the above formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula Examples of the bond of the group represented by (28) or formula (29) include a group in which two that are not adjacent to each other are replaced with hydrogen atoms, and a divalent chain hydrocarbon group having 6 or less carbon atoms.

A, A ¹ , A ² and A ³ are all divalent organic groups. Preferably, it is an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. The following formula (30), formula (31), formula (32), formula (33), formula (34) ), A group represented by formula (35), formula (36), formula (37) or formula (38); a group in which they are substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and carbon A chain hydrocarbon group having a number of 6 or less is exemplified.
In the formula * represents a ^bond, Z 1, ^{Z 2} and ^{Z 3} are each independently a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3 )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO ₂ -or -CO-. One example is when Z ¹ and Z ³ are —O— and Z ² is —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ — or —SO ₂ —. is there. Z ¹ and Z ² , and Z ² and Z ³ are each preferably in the meta position or the para position with respect to each ring.

The repeating structural units represented by formula (10) and formula (11) are usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by the formula (12) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (13) is usually derived from a diamine and a dicarboxylic acid compound.

The polyimide polymer according to the present embodiment may be a copolymer including a plurality of different types of repeating structural units. The weight average molecular weight of the polyimide polymer is usually 50,000 to 500,000. The weight average molecular weight of the polyimide polymer is preferably 80,000 to 500,000, more preferably 100,000 to 500,000, and further preferably 130,000 to 400,000. The weight average molecular weight is a standard polystyrene equivalent molecular weight measured by GPC. If the weight average molecular weight of the polyimide polymer is large, high flexibility tends to be obtained, but if the weight average molecular weight of the polyimide polymer is too large, the viscosity of the varnish tends to increase and the workability tends to decrease. is there.

When the polyimide polymer and the polyamide contain a fluorine-containing substituent, the elastic modulus of the obtained film is improved and the YI value of the film tends to be reduced. When the elastic modulus of the film is high, generation of scratches and wrinkles tends to be suppressed. From the viewpoint of transparency of the film, the polyimide polymer and the polyamide preferably have a fluorine-containing substituent. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group.

The fluorine atom content in the polyimide polymer can be 1% by mass or more, 5% by mass or more, 10% by mass or more, or 20% by mass or more based on the mass of the polyimide polymer. An upper limit can be 40 mass% or less.

(Film forming method)
An example of the manufacturing method of the polyimide-type polymer film using the obtained polyimide varnish is demonstrated. A polyimide polymer varnish is cast on the substrate to form a coating film, the solvent is removed from the coating film, and the dried coating film is peeled off from the substrate. Thereby, a polyimide polymer film is obtained.

Casting can be performed on a resin substrate, a stainless steel belt, or a glass substrate by a roll-to-roll or batch method. Examples of the resin substrate include PET, PEN, polyimide, polyamideimide and the like. The resin base material is preferably a resin excellent in heat resistance.
In the case of a polyimide polymer film, a PET substrate is preferable from the viewpoints of adhesion to the film and cost.

Even if the varnish obtained by the production method of the present invention is formed into a film without undergoing a purification step, a film having good physical properties can be obtained. For this reason, it is preferable to form a film without going through a purification step in which the polyimide polymer is once precipitated as a solid and then redissolved in a solvent. This is a cost-effective process.

In the method for producing a polyimide-based film of the present invention, a certain amount of organic solvent is volatilized by passing the coating film through a dryer that contacts a heated gas with the surface of the coating film, and the coating film is self-supporting. It may be obtained by peeling from the support as a film. The working temperature is adjusted depending on the substrate used, and when a resin substrate is used, it is generally carried out at or below the glass transition temperature thereof. Usually, the heating may be performed at an appropriate temperature of 50 ° C. to 300 ° C., and the heating temperature may be adjusted in multiple stages or a temperature gradient may be provided. It is also suitable to carry out under an inert atmosphere or under reduced pressure as appropriate.

If necessary, the peeled polyimide polymer film may be further heated at 80 to 300 ° C.

(Polyimide polymer film)
The polyimide polymer film thus obtained is formed by the solid content in the polyimide polymer varnish, and one of the main components is the polyimide polymer. The polyimide polymer is preferably 30% by mass or more based on the total amount of the polyimide polymer film. The polyimide polymer film may contain the silica fine particles, the ultraviolet absorber and / or the additive. The concentration of the polyimide polymer is preferably 10% by mass or more, more preferably 13% by mass or more based on the total mass of the polyimide polymer film.

The polyimide polymer film contains a tertiary amine. Preferred examples of the type of tertiary amine are as described in the above section (Tertiary amine). From the viewpoint of improving the folding resistance of the obtained polyimide polymer film, the content of the tertiary amine in the polyimide polymer film is preferably small. The content of the tertiary amine is preferably 0.25% by mass or less, more preferably 0.20% by mass or less, and still more preferably 0.15% by mass or less. By reducing the content, the coloring of the film also tends to be suppressed.

On the other hand, when a polyimide film laminate is prepared and applied to various applications, it is preferable that a tertiary amine is contained from the viewpoint that ultraviolet transmission can be suppressed. The content of the tertiary amine is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and further preferably 0.05% by mass or more.

The thickness of the polyimide polymer film can be 10 to 200 μm.

The polyimide-based polymer film obtained according to the present embodiment can show a folding number of 5000 times or more in a folding resistance test with R = 1 mm. By optimizing the production conditions of the polyimide-based polymer varnish, it is also possible to obtain a film showing the number of folding times of 6000 times or more, 8000 times or more, 10,000 times or more, 20000 times or more. The R = 1mm folding resistance test means that the center of a film cut into a strip of 10 mm × 100 mm is alternately turned in both the front and back directions at a curvature radius of 1.0 mm, a bending angle of 135 °, a load of 750 g, and a test speed of 175 cpm. It is the number of times of folding when the sheet is broken when folded.

The polyimide polymer film obtained according to the present embodiment can sufficiently suppress the yellowness YI based on JIS K 7373: 2006, and the yellowness YI is 2.5 or less, 2.4 or less, 2.3 or less. 2.2 or less. By optimizing the synthesis conditions such as the temperature during film formation, it can be made 2.1 or less, 2.0 or less, 1.9 or less, or 1.8 or less.

The polyimide polymer film obtained by this embodiment is transparent. Specifically, the polyimide polymer film can have a total light transmittance (Tt) measured in accordance with JIS K7105: 1981 of 85% or more, and preferably 90% or more.
More preferably, it is 91% or more, More preferably, it is 92% or more. The polyimide polymer film may have a haze of 1% or less, preferably 0.8% or less, measured according to JIS K 7105: 1981. More preferably, it is 0.5% or less, More preferably, it is 0.3% or less.

The polyimide-based polymer film obtained according to this embodiment may be particularly reduced in color by containing a fluorine-containing substituent. The content of fluorine atoms in the polyimide polymer can be 1% by mass or more, 5% by mass or more, 10% by mass or more, and 20% by mass or more based on the mass of the polyimide polymer. An upper limit can be 40 mass% or less.

(Use)
Since such an optical film has high folding resistance and good optical properties (yellowness, Tt, Haze), it can be suitably used as an optical member such as a front plate of a flexible device.

Examples of flexible devices include image display devices (flexible displays, electronic paper, etc.), solar cells, and the like. Examples of the flexible display include, in order from the surface side, a configuration of a front plate / polarizing plate protective film / polarizing plate / polarizing plate protective film / touch sensor film / organic EL element layer / TFT substrate. In addition, a hard coat layer, an adhesive layer, an adhesive layer, a retardation layer, and the like may be included. Such a flexible display can be used as an image display unit of a tablet PC, a smartphone, a portable game machine, or the like.

In addition, a laminate in which various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjusting layer, a refractive index adjusting layer, and the like are added to the surface of the optical film can be used.

(Evaluation of folding resistance)
The folding resistance of the polyimide polymer films obtained in Examples and Comparative Examples was evaluated according to the following criteria. The film was cut into a 10 mm × 100 mm strip using a dumbbell cutter. Set the cut film on MIT-DA MIT Folding Fatigue Testing Machine manufactured by Toyo Seiki Co., Ltd., both in the front and back direction under the conditions of test speed 175 cpm, bending angle 135 °, load 750 g, bending clamp R = 1.0 mm. The number of folds until bending and breaking were measured.

(Measurement of total light transmittance Tt)
The total light transmittance of each of the polyimide polymer films obtained in Examples and Comparative Examples was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K7105: 1981.

(Measurement of Haze)
The total light transmittance of each of the polyimide polymer films obtained in Examples and Comparative Examples was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K7105: 1981.

(Measurement of yellowness (YI value))
The yellowness (Yellow Index: YI value) of each of the polyimide-based polymer films obtained in Examples and Comparative Examples was measured with an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO Corporation. After performing background measurement in the absence of a sample, a polyimide film was set on a sample holder, transmittance was measured for light of 300 to 800 nm, and tristimulus values (X, Y, Z) were obtained. The YI value was calculated based on the following formula.
YI = 100 × (1.2769X−1.0592Z) / Y

(Evaluation of weight average molecular weight)
Gel permeation chromatography (GPC) measurement (1) Pretreatment method A sample was dissolved in γ-butyrolactone (GBL) to make a 20% solution, diluted 100 times with DMF eluent, and filtered through a 0.45 μm membrane filter. This was used as a measurement solution.
(2) Measurement condition column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0 mm ID × 150 mm × 3)
Eluent: DMF (10 mM lithium bromide added)
Flow rate: 0.6 mL / min.
Detector: RI detector Column temperature: 40 ° C
Injection volume: 20 μL
Molecular weight standard: Standard polystyrene

(Evaluation of residual catalyst concentration in film)
GC measurement was performed under the following conditions to determine the tertiary amine.
Solution preparation: 100 mg film is weighed into a screw tube and 5 ml DMSO is added to dissolve.
Apparatus: Agilent 6890 type, column: BPX-5 (0.25 mm × 30 m, film thickness: 0.25 μm), column temperature: 50 ° C. (5 min) → 20 ° C./min→350° C. (5 min), inlet Temperature: 280 ° C., flow rate: He 1.0 mL / min, detector: FID, detector temperature: 350 ° C., sample injection volume: 1.0 μL, split ratio: 50: 1, syringe cleaning solvent: DMSO, syringe cleaning Solvent: A: 3 times, B: 3 times

Example 1
(Manufacture of polyimide varnish)
Under a nitrogen atmosphere, 1.25 g of isoquinoline was charged into a reaction vessel connected to a vacuum pump equipped with a solvent trap and a filter. Next, 375.00 g of γ-butyrolactone (GBL) and 104.12 g of 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (TFMB) were added to the reaction vessel and stirred to completely dissolve. I let you. Further, 145.88 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added, and the temperature was raised in an oil bath while stirring. The molar ratio of TFMB and 6FDA added was 1.00: 0.99 for 6FDA: TFMB, and the monomer concentration in the liquid was 40 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.5. When the internal temperature reached 80 ° C., the pressure was reduced to 650 mmHg, and then the internal temperature was raised to 180 ° C. After reaching 180 ° C., the mixture was further heated and stirred for 4 hours, then returned to atmospheric pressure and cooled to 155 ° C. to obtain a polyimide solution. GBL was added at 155 ° C. to obtain a uniform solution having a polyimide solid content of 24 wt%, and then the polyimide varnish was taken out from the reaction vessel.

(Manufacture of polyimide film)
To 200.00 g of the obtained polyimide varnish, 38.31 g of GBL and 11.82 g of N, N-dimethylacetamide (DMAc) were added for further dilution. After casting it on a PET (polyethylene terephthalate) film to form a coating film, it was heated at 50 ° C. for 30 minutes and 140 ° C. for 10 minutes to obtain a polyimide film. The film having a film thickness of 80 μm, a Tt of 92.6%, a Haze of 0.1% and a yellowness of 2.2 was obtained by peeling from the PET and further heating at 200 ° C. for 40 minutes.

(Example 2)
A film having a Tt of 92.7%, a haze of 0.1% and a yellowness of 2.0 was obtained in the same manner as in Example 1 except that the heating and stirring time of the liquid after reaching 180 ° C. was 3 hours.

(Example 3)
A film having a Tt of 92.4%, a haze of 0.1%, and a yellowness of 1.8 was obtained except that the amount of isoquinoline was changed to 0.75 g. The mass part of the tertiary amine is 0.3 with respect to 100 parts by mass of the raw material monomer.

(Comparative Example 1)
The same procedure as in Example 1 was conducted except that the amount of isoquinoline was 2.00 g, no pressure reduction was performed during the process, and the mixture was heated and stirred for 5 hours after the internal temperature reached 180 ° C., Tt 92.5%, Haze 0. A film with 1% yellowness of 2.4 was obtained. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.8.

(Comparative Example 2)
The amount of isoquinoline was 2.50 g, the amount of γ-butyrolactone (GBL) was 464.29 g, the amount of TFMB was 103.50 g, the amount of 6FDA was 146.50 g, and the molar ratio of TFMB to 6FDA was 6FDA: Example 1 except that the TFMB was 1.00: 0.98, the monomer concentration in the liquid was 35 wt%, no pressure reduction was performed during the process, and the stirring was performed for 5 hours after the internal temperature reached 180 ° C. In the same manner, a film having a Tt of 92.5%, a haze of 0.1%, and a yellowness of 3.0 was obtained. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 1.0.

(Comparative Example 3)
In place of isoquinoline, 3.00 g of triethylamine was added, the amount of TFMB was 104.73 g, 6FDA was 145.27 g, the molar ratio of TFMB to 6FDA was 1.00: 1.00, and the monomer concentration in the liquid Was kept at 40 wt%, and was not subjected to any pressure reduction during the process, and was the same as Example 1 except that the stirring was carried out for 5 hours after the internal temperature reached 180 ° C. to obtain a film having a yellowness of 2.1. . The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 1.2.

Table 1 shows the conditions and results.

In Examples 1 to 3 in which the pressure was reduced during heating while adding a tertiary amine, high folding resistance could be achieved. On the other hand, in Comparative Examples 1 to 3 in which the pressure was not reduced during the heating, folding resistance could not be improved even when the amount of the catalyst was increased as compared with the Examples. If the catalyst amount in the comparative example is set to the same level as in the examples, the folding resistance is expected to be further deteriorated.

(Example A1)
(Manufacture of polyimide varnish)
Under a nitrogen atmosphere, 1.25 g of isoquinoline was charged into a reaction vessel connected to a vacuum pump equipped with a solvent trap and a filter. Next, 305.58 g of γ-butyrolactone (GBL) and 104.43 g of 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl (TFMB) were added to the reaction vessel and stirred to completely dissolve. I let you. Further, 145.59 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added, and the temperature was raised in an oil bath while stirring. The molar ratio of TFMB and 6FDA added was 1.00: 0.995 for 6FDA: TFMB, and the monomer concentration was 45 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.5. When the internal temperature reached 120 ° C., the pressure was reduced to 610 mmHg, and then the internal temperature was raised to 200 ° C. After reaching 200 ° C., the mixture was further heated and stirred for 5.5 hours, then returned to atmospheric pressure and cooled to 170 ° C. to obtain a polyimide solution. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was 0.2%. GBL (solvent B) is added at 170 ° C. to obtain a homogeneous solution having a polyimide solid content of 40 wt%, and N, N-dimethylacetamide (solvent B) is added at 155 ° C. to obtain a polyimide solid content of 20 wt%. %, And the polyimide varnish was taken out from the reaction vessel.

(Manufacture of polyimide film)
To 200.00 g of the obtained polyimide varnish, 50 g of N, N-dimethylacetamide (DMAc) was added for further dilution. After casting it on a PET (polyethylene terephthalate) film to form a coating film, it was heated at 50 ° C. for 30 minutes and 140 ° C. for 10 minutes to obtain a polyimide film. The film having a film thickness of 80 μm, a Tt of 92.0%, a Haze of 0.1%, and a yellowness of 3.9 was obtained by peeling from the PET and further heating at 200 ° C. for 40 minutes.

(Example A2)
The amount of γ-butyrolactone (GBL) was changed to 375.03 g, and when the internal temperature reached 120 ° C., the pressure was reduced to 610 mmHg, then the internal temperature was increased to 180 ° C., and after reaching 180 ° C., further 8. A polyimide solution was obtained in the same manner as in Example A1 except that heating and stirring were performed for 5 hours. In all the solutions in the reaction vessel, the monomer concentration was 40 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.5. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was 0.2%. N, N-dimethylacetamide (DMAc) (solvent B) was added at 155 ° C. to obtain a homogeneous solution having a polyimide solid content of 20 wt%, and the polyimide varnish was taken out from the reaction vessel.
Using the obtained polyimide varnish, a polyimide film was produced in the same manner as in Example A1, and a film having a film thickness of 80 μm, Tt 92.0%, Haze 0.1%, and a yellowness of 3.9 was obtained.

(Example A3)
The amount of isoquinoline was changed to 0.5 g and the amount of γ-butyrolactone (GBL) was changed to 375.03 g. When the internal temperature reached 120 ° C., the pressure was reduced to 400 mmHg and then the internal temperature was raised to 180 ° C. Then, after reaching 180 ° C., a polyimide solution was obtained in the same manner as in Example A1, except that the mixture was further heated and stirred for 8.5 hours. In all the solutions in the reaction vessel, the monomer concentration was 40 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.2. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was less than 0.01%. N, N-dimethylacetamide (DMAc) (solvent B) was added at 155 ° C. to obtain a homogeneous solution having a polyimide solid content of 20 wt%, and the polyimide varnish was taken out from the reaction vessel.
Using the obtained polyimide varnish, a polyimide film was produced in the same manner as in Example A1, and a film having a thickness of 80 μm, Tt 92.6%, Haze 0.1%, and a yellowness of 2.0 was obtained.

(Example A4)
The amount of isoquinoline was changed to 0.5 g, and when the internal temperature reached 120 ° C., the pressure was reduced to 400 mmHg, then the internal temperature was increased to 180 ° C. After reaching 180 ° C., the mixture was further stirred for 5.5 hours. A polyimide solution was obtained in the same manner as in Example A1, except that this was performed. In all the solutions in the reaction vessel, the monomer concentration was 45 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.2. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was less than 0.01%. GBL (solvent B) and N, N-dimethylacetamide (solvent B) were respectively added to the polyimide solution in the same manner as in Example A1 to obtain a uniform solution having a polyimide solid content of 20 wt%. The varnish was removed.
Using the obtained polyimide varnish, a polyimide film was produced in the same manner as in Example A1, and a film having a thickness of 80 μm, Tt 92.7%, Haze 0.1%, and a yellowness of 1.7 was obtained.

(Example A5)
A polyimide varnish was produced in the same manner as in Example A4. A polyimide film was prepared in the same manner as in Example A4 except that N, N-dimethylacetamide (DMAc) to which a UV absorber (trade name Sumisorb 340 manufactured by Sumitomo Chemical Co., Ltd.) was added was added to the polyimide varnish. Manufactured. The film obtained had a thickness of 80 μm, Tt 92.4%, Haze 0.2%, and yellowness 2.3. In addition, the unit phr in Table 2 means a part by mass with respect to 100 parts by mass of the polyimide polymer contained in the varnish.

(Example A6)
The amount of isoquinoline was changed to 0.5 g, and when the internal temperature reached 120 ° C., the pressure was reduced to 500 mmHg, then the internal temperature was increased to 180 ° C. After reaching 180 ° C., the mixture was further stirred for 5.5 hours. A polyimide solution was obtained in the same manner as in Example A1, except that this was performed. In all the solutions in the reaction vessel, the monomer concentration was 45 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.2. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was less than 0.01%. GBL (solvent B) and N, N-dimethylacetamide (solvent B) were respectively added to the polyimide solution in the same manner as in Example A1 to obtain a uniform solution having a polyimide solid content of 20 wt%. The varnish was removed.
Using the obtained polyimide varnish, a polyimide film was produced in the same manner as in Example A1, and a film having a film thickness of 80 μm, Tt 92.6%, Haze 0.2%, and a yellowness of 2.0 was obtained.

(Example A7)
The amount of isoquinoline was changed to 0.5 g, and when the internal temperature reached 120 ° C., the pressure was reduced to 400 mmHg, then the internal temperature was increased to 180 ° C. After reaching 180 ° C., the mixture was further stirred for 5.5 hours. A polyimide solution was obtained in the same manner as in Example A1 except that the procedure was performed. In all the solutions in the reaction vessel, the monomer concentration was 45 wt%. The mass part of the tertiary amine with respect to 100 parts by mass of the raw material monomer is 0.2. When the oxygen concentration in the reaction vessel was confirmed before and after decompression, it was less than 0.01%. GBL (solvent B) is added to the polyimide solution at 170 ° C. to obtain a uniform solution having a polyimide solid content of 40 wt%, and further, cyclopentanone (solvent B) is added at 130 ° C. to solidify the polyimide. A homogeneous solution having a content of 20 wt% was taken out, and the polyimide varnish was taken out from the reaction vessel.
A polyimide film was produced in the same manner as in Example A1, except that 500.00 g of cyclopentanone was added instead of DMAc and further diluted with respect to 200.00 g of the obtained polyimide varnish, and the film thickness was 80 μm, Tt 92.6%, A film having a haze of 0.1% and a yellowness of 1.9 was obtained.

(Example A8)
A polyimide varnish was produced in the same manner as in Example A7. A polyimide film was produced in the same manner as in Example A7, except that cyclopentanone added with an ultraviolet absorber (trade name Sumisorb 340 manufactured by Sumitomo Chemical Co., Ltd.) was added to the polyimide varnish. The resulting film had a thickness of 80 μm, Tt 92.5%, Haze 0.1%, and yellowness 2.4. In addition, the unit phr in Table 2 means a part by mass with respect to 100 parts by mass of the polyimide polymer contained in the varnish.

Table 2 shows the conditions and results.

In the following examples, the yield of polyimide is expressed by the formula “(total amount of resin solids contained in solvent C after washing + total amount of resin solids in manufactured polyimide varnish (unit: weight)) / preparation of raw material monomers. The theoretical amount (unit: weight) of the polyimide-based polymer calculated from the amount × 100 ”was calculated. The solvent C after washing | cleaning is the washing | cleaning liquid performed after manufacture of the 1st polyimide varnish in the following examples. The produced polyimide varnish is a polyimide varnish obtained by the second production of the polyimide varnish in the following examples. The theoretical amount of polyimide polymer calculated from the charged amount of raw material monomer is the theoretical amount of polyimide polymer calculated from the charged amount of raw material monomer in the second production of polyimide varnish in the following example. .

(Example B1)
A polyimide varnish was produced in the same manner as in Example A7, and the obtained polyimide varnish was extracted from the reaction vessel, and then cyclopentanone was injected as a solvent C into the reaction vessel, heated to 130 ° C. and heated for 3 hours. And washed. The cyclopentanone used for washing was extracted from the reaction vessel and recovered (solvent C after washing). Thereafter, GBL was poured into the reaction vessel as solvent D, heated to 200 ° C., heated for 8 hours and washed. It was synthesized again according to Example 10 in the washed reaction vessel to obtain a second polyimide varnish. The polyimide varnish was obtained using the solvent C after washing as the cyclopentanone of the solvent B for dilution added to the solution before taking out from the reaction vessel. The polyimide contained in the obtained second polyimide varnish had a polystyrene-equivalent weight average molecular weight of 320,000, and the yield of polyimide was 97.2%.
Next, using this second polyimide varnish, a polyimide film was produced in the same manner as in Example A7, and a film having a film thickness of 80 μm, Tt 92.5%, Haze 0.1%, and a yellowness of 2.1 was obtained. .

(Example B2)
The second time in the same manner as in Example B1, except that the washing time with cyclopentanone in solvent C after the polyimide varnish was extracted from the reaction vessel was changed to 28 hours and the washing liquid was collected (solvent C after washing). The polyimide varnish was obtained. The polyimide contained in the obtained second polyimide varnish had a polystyrene equivalent weight average molecular weight of 340,000, and the yield of polyimide was 96.6%.
Next, using this second polyimide varnish, a polyimide film was produced in the same manner as in Example A7, and a film having a film thickness of 80 μm, Tt 92.6%, Haze 0.1%, and a yellowness of 2.2 was obtained. .

(Example B3)
A polyimide varnish was produced in the same manner as in Example A4. After the obtained polyimide varnish was extracted from the reaction vessel, GBL was injected as a solvent C into the reaction vessel, heated to 200 ° C., heated for 8 hours and washed. did. GBL used for washing was extracted from the reaction vessel and collected. Thereafter, GBL was poured into the reaction vessel as solvent D, heated to 200 ° C., heated for 8 hours and washed. A second polyimide varnish was produced in the same manner as in Example A4 using the washed reaction vessel. At this time, the solvents C and D after the washing were not added to the second production (dilution) of the polyimide varnish. The polyimide contained in the obtained second polyimide varnish had a polystyrene equivalent weight average molecular weight of 360,000, and the yield of polyimide was 92.2%.
Next, using this polyimide varnish for the second time, a polyimide film was produced in the same manner as in Example A4, and a film having a film thickness of 80 μm, Tt 92.7%, Haze 0.1%, and a yellowness of 1.7 was obtained. .

(Example B4)
A polyimide varnish was produced in the same manner as in Example A7. After the obtained polyimide varnish was extracted from the reaction vessel, GBL was injected as a solvent C into the reaction vessel, heated to 200 ° C., heated for 8 hours and washed. did. GBL used for washing was extracted from the reaction vessel and collected. Thereafter, GBL was poured into the reaction vessel as solvent D, heated to 200 ° C., heated for 8 hours and washed. A second polyimide varnish was produced in the same manner as in Example A7 using the washed reaction vessel. At this time, the solvents C and D after the washing were not added to the second production (dilution) of the polyimide varnish. The polyimide contained in the obtained second polyimide varnish had a polystyrene equivalent weight average molecular weight of 310,000, and the yield of polyimide was 91.3%.
Next, using this second polyimide varnish, a polyimide film was produced in the same manner as in Example A7, and a film having a thickness of 80 μm, Tt 92.6%, Haze 0.1%, and a yellowness of 1.9 was obtained. .

(Reference Example B1)
A polyimide varnish was produced in the same manner as in Example A2, and the obtained polyimide varnish was extracted from the reaction vessel. Then, GBL was injected as a solvent C into the reaction vessel, heated to 200 ° C., heated for 8 hours and washed. did. GBL used for washing was extracted from the reaction vessel and collected. Thereafter, GBL was poured into the reaction vessel as solvent D, heated to 200 ° C., heated for 8 hours and washed. A second polyimide varnish was produced in the same manner as in Example A2 using the washed reaction vessel. At this time, the solvents C and D after the washing were not added to the second production (dilution) of the polyimide varnish. The polyimide contained in the obtained second polyimide varnish had a polystyrene equivalent weight average molecular weight of 220,000, and the yield of polyimide was 94.5%.
Next, using the second polyimide varnish, a polyimide film was produced in the same manner as in Example A2, and a film having a thickness of 80 μm, Tt 92.0%, Haze 0.1%, and a yellowness of 3.9 was obtained. .
The conditions and results are shown in Table 3.

Claims (17)

A polymerization step of polymerizing a raw material monomer of a polyimide polymer in a solvent to obtain a polyimide polymer precursor, and imidation of the polyimide polymer precursor in a solvent containing a tertiary amine under a reduced pressure environment A method for producing a polyimide polymer varnish, comprising an imidization step of obtaining a polyimide polymer solution. The manufacturing method according to claim 1, wherein the temperature in the imidization step is 100 ° C or higher and 250 ° C or lower. The production method according to claim 1 or 2, wherein the tertiary amine has a boiling point of 120 ° C or higher and 350 ° C or lower. The production method according to any one of claims 1 to 3, wherein the polyimide polymer contains 20 mass% or more of fluorine. The manufacturing method according to any one of claims 1 to 4, wherein the pressure in the reduced pressure environment is 350 mmHg or more and 730 mmHg or less. The manufacturing method according to claim 5, wherein the pressure in the reduced pressure environment is 500 mmHg or more and 730 mmHg or less. The production method according to any one of claims 1 to 6, wherein an oxygen concentration in a gas phase contacting with a liquid phase containing the solvent in the imidization step is 0.02% or less. The production method according to any one of claims 1 to 7, wherein 0.05 parts by weight or more and 0.7 parts by weight or less of the tertiary amine is added to 100 parts by weight of the raw material monomer. The production method according to any one of claims 1 to 8, further comprising a step of adding an ultraviolet absorber to the obtained polyimide polymer solution. 10. The production method according to claim 1, further comprising a step of adding silica sol to the obtained polyimide polymer solution. Carrying out the method for producing a polyimide-based polymer varnish according to any one of claims 1 to 10,
A film forming step of casting the polyimide polymer varnish without depositing and re-dissolving the polyimide polymer in the obtained polyimide polymer varnish, and a method for producing a polyimide polymer film . A film containing a polyimide polymer having a weight average molecular weight of 50,000 or more and 500,000 or less and a tertiary amine of 0.01% by mass or more and 0.25% by mass or less with respect to the total mass of the film. The film according to claim 12, wherein the boiling point of the tertiary amine is 120 ° C or higher and 350 ° C or lower. (1) In a reaction vessel, a step of reacting monomer raw materials in solvent A to obtain a polyimide polymer solution;
(3) removing the solution from the reaction vessel;
(4) washing the reaction vessel with solvent C, and removing the washed solvent C from the reaction vessel, wherein the steps (1), (3), and (4) are the same reaction vessel. Repeat in this order using
The method for producing a polyimide polymer varnish, wherein the polyimide polymer obtained in the step (1) is transparent and has a weight average molecular weight of 250,000 or more. (5) After the step (4), further comprising a step of washing the reaction vessel with a solvent D and taking out the solvent D after washing from the reaction vessel,
The manufacturing method of the polyimide-type polymer varnish of Claim 14 which repeats the said process (1), (3), (4) and (5) in this order using the same reaction container. Between the step (1) and the step (3),
(2) The method further comprises the step of diluting the solution obtained in the step (1) by adding the solvent B in the reaction vessel,
The method according to claim 14 or 15, wherein the steps (1) to (4) or the steps (1) to (5) are repeated using the same reaction vessel. The method according to claim 16, wherein the solvent B is the solvent C removed from the reaction vessel in the step (4).