JP2018080344A - Polyimide precursor composition, method for producing polyimide, polyimide, polyimide film, and substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide precursor composition capable of giving a polyimide having excellent transparency, a small linear thermal expansion coefficient, higher heat resistance, and excellent mechanical characteristics, and to provide a method for producing a polyimide.SOLUTION: There are provided: a polyimide precursor composition which contains a polyimide precursor and an imidazole compound and in which the content of the imidazole compound is less than 4 moles per mole of a repeating unit of the polyimide precursor; and a polyimide film. The polyimide precursor composition contains the polyimide precursor which has a group having a tetravalent aromatic ring, preferably a group derived from 1,1-bis(3,4-dicarboxylic acid)-2,2,2-trifluoro-ethane.SELECTED DRAWING: None

Description

  The present invention is a solution composition (polyimide precursor composition) containing a polyimide precursor that is excellent in transparency, has a low coefficient of linear thermal expansion, has higher heat resistance, and has excellent mechanical properties. And a method for producing polyimide. The present invention also relates to a polyimide, a polyimide film, and a substrate that are excellent in transparency, have a low linear thermal expansion coefficient, high heat resistance, and excellent mechanical properties.

  In recent years, with the arrival of an advanced information society, development of optical materials such as a liquid crystal alignment film and a protective film for a color filter in the display device field, such as an optical fiber and an optical waveguide in the optical communication field, is progressing. In particular, in the field of display devices, a plastic substrate that is lightweight and excellent in flexibility as a substitute for a glass substrate has been studied, and a display that can be bent and rolled has been actively developed. For this reason, there is a demand for higher performance optical materials that can be used for such applications.

  Aromatic polyimide is essentially yellowish brown due to intramolecular conjugation and the formation of charge transfer complexes. For this reason, as a means to suppress coloration, for example, introduction of fluorine atoms into the molecule, imparting flexibility to the main chain, introduction of bulky groups as side chains, etc. inhibits intramolecular conjugation and charge transfer complex formation. Thus, a method for expressing transparency has been proposed.

  For example, Patent Document 1 discloses a highly transparent aromatic polyimide containing a fluorine atom.

  However, a polyimide having higher heat resistance is required depending on the application. Further, it is desired to further improve transparency, particularly in the field of display devices and the like. In some applications, it is also desired to reduce the linear thermal expansion coefficient. If the linear thermal expansion coefficient of polyimide is large and the difference in linear thermal expansion coefficient with a conductor such as metal is large, problems such as increased warping may occur when forming a circuit board, especially for display applications. A fine circuit formation process may not be easy.

  On the other hand, Patent Document 2 discloses a polyimide formed by heating a coating liquid obtained by blending a polyimide precursor (polyamic acid) with an imidazoline compound and / or an imidazole compound. More specifically, in Example 1, 2,4-dimethyl is added to a polyamic acid solution obtained from 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-diaminobiphenyl ether. A solution to which imidazoline has been added is applied onto a substrate and heated at 200 ° C. for 1 hour to obtain an aromatic polyimide film having a thickness of 1000 mm (0.1 μm). In Example 2, a solution obtained by adding 2-ethylimidazoline and 1,2-dimethylimidazole to a solution of polyamic acid obtained from pyromellitic dianhydride and 4,4′-diaminobiphenyl ether was applied onto a substrate. An aromatic polyimide film having a thickness of 800 mm (0.08 μm) is obtained by heating at 150 ° C. for 1 hour. In Patent Document 2, the addition of an imidazoline-based compound and / or an imidazole-based compound avoids the remarkable brown coloration, and it has become possible to obtain a liquid crystal display element with high light transmittance and excellent transparency. It is described. However, the light transmittance at a wavelength of 400 nm of the liquid crystal display element using the polyimide film (liquid crystal alignment film) of Example 1 is 82% (polyimide film thickness: 0.1 μm), and the polyimide film of Example 2 (liquid crystal alignment film). The light transmittance at a wavelength of 400 nm of the liquid crystal display element using the above is 83% (polyimide film thickness: 0.08 μm), and this polyimide does not have sufficient transparency.

  In addition, as a method for producing an aromatic polyimide having low transparency, Patent Document 3 discloses a polyimide precursor resin and a curing accelerator for a polyimide precursor resin such as imidazole and N-methylimidazole dissolved in an organic polar solvent. A method for forming a polyimide resin layer is disclosed in which a polyimide precursor resin-containing solution is applied onto a substrate, followed by drying and imidization to complete the formation of a polyimide resin layer within a range of 280 to 380 ° C., It is described that the thermal expansion coefficient can be controlled to be low by using these curing accelerators. Patent Document 3 also describes that a curing accelerator having a boiling point exceeding 120 ° C. is preferably used, and that a boiling point not exceeding the upper limit temperature of heat treatment is preferably selected. In addition, it is described that a curing accelerator having a boiling point of, for example, 400 ° C. or higher has a higher ratio of remaining in the polyimide resin layer after imidization and tends to affect the function of the polyimide resin layer.

JP 2011-074384 A JP-A 61-267030 JP 2008-115378 A

  The present invention has been made in view of the above circumstances, and is a polyimide precursor that provides a polyimide having excellent transparency, a low linear thermal expansion coefficient, higher heat resistance, and excellent mechanical properties. It aims at providing the body composition (solution composition containing a polyimide precursor), and the manufacturing method of a polyimide.

The present invention relates to the following items.
1. A polyimide precursor containing a repeating unit represented by the following chemical formula (1);
Including imidazole compounds,
Content of an imidazole type compound is less than 4 mol with respect to 1 mol of repeating units of a polyimide precursor, The polyimide precursor composition characterized by the above-mentioned.

（式中、Ｘ_１は芳香族環を有する４価の基であり、Ｙ_１は芳香族環を有する２価の基であり、ただし、Ｘ_１とＹ_１の少なくとも一方はフッ素原子を含有し、Ｒ_１、Ｒ_２はそれぞれ独立に水素、炭素数１〜６のアルキル基、または炭素数３〜９のアルキルシリル基である）

２． 前記化学式（１）中のＸ_１が下記化学式（１−Ｘ）で表される基であり、前記化学式（１）中のＹ_１が下記化学式（１−Ｙ）で表される基であることを特徴とする前記項１に記載のポリイミド前駆体組成物。

(In the formula, X ₁ is a tetravalent group having an aromatic ring, Y ₁ is a divalent group having an aromatic ring, provided that at least _one of X ₁ and Y ₁ contains a fluorine atom. , R ₁ and R ₂ are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms)

2. X ₁ in the chemical formula (1) is a group represented by the following chemical formula (1-X), and Y ₁ in the chemical formula (1) is a group represented by the following chemical formula (1-Y). Item 2. The polyimide precursor composition according to Item 1 above.

３． このポリイミド前駆体組成物から得られるポリイミドが、厚さ１０μｍのフィルムでの波長４００ｎｍの光透過率が７９％以上であることを特徴とする前記項１又は２に記載のポリイミド前駆体組成物。
４． 前記イミダゾール系化合物の含有量が、ポリイミド前駆体の繰り返し単位１モルに対して０．０５モル以上２モル以下であることを特徴とする前記項１〜３のいずれかに記載のポリイミド前駆体組成物。
５． 前記イミダゾール系化合物が、１，２−ジメチルイミダゾール、１−メチルイミダゾール、２−メチルイミダゾール、２−フェニルイミダゾール、イミダゾール、またはベンゾイミダゾールのいずれかであることを特徴とする前記項１〜４のいずれかに記載のポリイミド前駆体組成物。
６． 前記項１〜５のいずれかに記載のポリイミド前駆体組成物を、最高加熱温度３５０℃以上で加熱処理して、ポリイミド前駆体をイミド化することを特徴とするポリイミドの製造方法。
７． 前記項１〜５のいずれかに記載のポリイミド前駆体組成物を基材上に塗布する工程と、
基材上のポリイミド前駆体組成物を、最高加熱温度３５０℃以上で加熱処理して、ポリイミド前駆体をイミド化する工程と
を有することを特徴とする前記項６に記載のポリイミドの製造方法。
８． 前記項６又は７に記載の方法により製造されるポリイミド。
９． 厚さ１０μｍのフィルムでの波長４００ｎｍの光透過率が８０％以上であることを特徴とする前記項８に記載のポリイミド。
１０． 前記項６又は７に記載の方法により製造されるポリイミドフィルム。
１１． 前記項８又は９に記載のポリイミド、又は前記項１０に記載のポリイミドフィルムを含むことを特徴とするディスプレイ用、タッチパネル用、または太陽電池用の基板。

3. Item 3. The polyimide precursor composition according to item 1 or 2, wherein the polyimide obtained from the polyimide precursor composition has a light transmittance of 79% or more at a wavelength of 400 nm in a film having a thickness of 10 μm.
4). Content of the said imidazole compound is 0.05 mol or more and 2 mol or less with respect to 1 mol of repeating units of a polyimide precursor, The polyimide precursor composition in any one of said claim | item 1-3 characterized by the above-mentioned. object.
5. Any one of Items 1 to 4, wherein the imidazole compound is any one of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole, and benzimidazole. A polyimide precursor composition according to claim 1.
6). Item 6. The polyimide precursor composition according to any one of Items 1 to 5, wherein the polyimide precursor composition is heat-treated at a maximum heating temperature of 350 ° C or higher to imidize the polyimide precursor.
7). The process of apply | coating the polyimide precursor composition in any one of said claim | item 1-5 on a base material,
The method for producing polyimide according to Item 6, further comprising a step of heat-treating the polyimide precursor composition on the substrate at a maximum heating temperature of 350 ° C. or higher to imidize the polyimide precursor.
8). 8. A polyimide produced by the method according to item 6 or 7.
9. Item 9. The polyimide according to Item 8, wherein the light transmittance at a wavelength of 400 nm in a film having a thickness of 10 μm is 80% or more.
10. The polyimide film manufactured by the method of said claim | item 6 or 7.
11. Item 10. A substrate for display, touch panel, or solar cell comprising the polyimide according to item 8 or 9, or the polyimide film according to item 10.

  According to the present invention, a polyimide precursor composition (solution composition containing a polyimide precursor) that provides a polyimide having excellent transparency, a low linear thermal expansion coefficient, higher heat resistance, and excellent mechanical properties, And a method for producing polyimide can be provided.

  The polyimide obtained from the polyimide precursor composition of the present invention (polyimide of the present invention) has high heat resistance, high transparency, low coefficient of linear thermal expansion, and easy formation of a fine circuit. It can be suitably used for forming a substrate for use. Moreover, the polyimide of this invention can be used suitably also in order to form the board | substrate for touch panels and a solar cell.

  The polyimide precursor composition of the present invention includes a polyimide precursor containing at least one repeating unit represented by the chemical formula (1) and an imidazole compound, and the content of the imidazole compound is that of the polyimide precursor. The amount is less than 4 moles per mole of repeating units.

  A polyimide obtained from a polyimide precursor containing at least one repeating unit represented by the chemical formula (1), that is, an aromatic polyimide containing a fluorine atom has high transparency. In the case of such a highly transparent polyimide, the use of additives that can cause coloring is not preferred. However, by adding the imidazole compound to the polyimide precursor composition at a ratio of less than 4 mol, preferably 0.05 mol or more and 2 mol or less, with respect to 1 mol of the repeating unit of the polyimide precursor, high transparency is achieved. The heat resistance of the resulting polyimide is increased while keeping it. That is, according to the present invention, a polyimide having higher heat resistance can be obtained from a polyimide precursor having the same composition while maintaining high transparency. In addition, when an imidazole compound having a boiling point at 1 atm of less than 360 ° C., preferably 340 ° C. or less is used, the transparency of the resulting polyimide may be further improved.

  Furthermore, in order to obtain a highly transparent polyimide, it is generally considered that it is preferable to complete the imidization by heat-treating the polyimide precursor at a relatively low temperature. Even if the polyimide precursor is imidized by heat treatment at a temperature of 350 ° C. or higher, a highly transparent polyimide can be produced. As a result, the maximum heating temperature of the heat treatment for imidization can be set to 350 ° C. or higher, so that the mechanical properties of the resulting polyimide are improved. That is, according to the present invention, a polyimide having high transparency, low linear thermal expansion coefficient, high heat resistance, and excellent mechanical properties can be obtained.

  As above-mentioned, the polyimide precursor composition of this invention contains the polyimide precursor containing at least 1 sort (s) of the repeating unit represented by the said Chemical formula (1).

X ₁ in the chemical formula (1) is preferably a tetravalent group having an aromatic ring having 6 to 40 carbon atoms, and Y ₁ is a divalent having an aromatic ring having 6 to 40 carbon atoms. Are preferred. The may be one in which one of X ₁ or Y ₁ contains a fluorine atom, or may be both of X ₁ and Y ₁ contains a fluorine atom.

  Examples of the tetracarboxylic acid component containing a fluorine atom that gives the repeating unit of the chemical formula (1) include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane and its tetracarboxylic acid dicarboxylic acid. Derivatives such as anhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, tetracarboxylic acid chlorides and the like can be mentioned. Examples of the tetracarboxylic acid component not containing a fluorine atom include 4- (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, Pyromellitic acid, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 4 , 4′-oxydiphthalic acid, bis (3,4-dicarboxyphenyl) sulfone dianhydride, m-terphenyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, p-terphenyl-3 , 4,3 ′, 4′-tetracarboxylic dianhydride, biscarboxyphenyldimethylsilane, bisdicarboxyphenoxydiphenyl sulfide, sulfonyldiphthalic acid, These tetracarboxylic acid dianhydrides, tetracarboxylic acid silyl ester, tetracarboxylic acid esters, derivatives of such tetracarboxylic acid chloride. A tetracarboxylic acid component may be used independently and can also be used in combination of multiple types.

  Examples of the diamine component containing a fluorine atom that gives the repeating unit of the chemical formula (1) include 2,2′-bis (trifluoromethyl) benzidine, 3,3′-bis (trifluoromethyl) benzidine, 2 , 2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2′-bis (3-amino-4-hydroxyphenyl) Hexafluoropropane is mentioned. Examples of the diamine component not containing a fluorine atom include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3′-diamino-biphenyl, o-tolidine, m-tolidine, and 4,4′-diaminobenz. Anilide, 3,4'-diaminobenzanilide, N, N'-bis (4-aminophenyl) terephthalamide, N, N'-p-phenylenebis (p-aminobenzamide), 4-aminophenoxy-4-diamino Benzoate, bis (4-aminophenyl) terephthalate, biphenyl-4,4′-dicarboxylic acid bis (4-aminophenyl) ester, p-phenylenebis (p-aminobenzoate), bis (4-aminophenyl)-[1 , 1′-biphenyl] -4,4′-dicarboxylate, [1,1′-biphenyl] -4,4′-diyl bis ( 4-aminobenzoate), 4,4′-oxydianiline, 3,4′-oxydianiline, 3,3′-oxydianiline, p-methylenebis (phenylenediamine), 1,3-bis (4-amino) Phenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, bis (4-aminophenyl) sulfone, 3,3′-bis ((aminophenoxy) phenyl) propane, bis (4- (4-aminophenoxy) diphenyl) sulfone, bis (4- (3-aminophenoxy) diphenyl) sulfone, octafluorobenzidine, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3 , 3′-dichloro-4,4′-diaminobiphenyl, 3,3′-difluoro-4,4′-diaminobiphenyl, 2,4-bis (4-aminoanilino) -6-amino-1,3,5- Triazine, 2,4-bis (4-aminoanilino) -6-methylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-ethylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-anilino-1,3,5-triazine may be mentioned. A diamine component may be used independently and can also be used in combination of multiple types.

  This polyimide precursor can contain other repeating units other than the repeating unit represented by the chemical formula (1). The tetracarboxylic acid component and diamine component that give other repeating units are not particularly limited, and any other known aromatic or aliphatic tetracarboxylic acids or known aromatic or aliphatic diamines can be used. . Other tetracarboxylic acid components may be used alone or in combination of two or more. Other diamine components may be used alone or in combination of two or more.

  The content of other repeating units other than the repeating unit represented by the chemical formula (1) is preferably 30 mol% or less or less than 30 mol%, more preferably 20 mol% or less, based on all repeating units. More preferably, it is 10 mol% or less.

In one embodiment, as the polyimide precursor, for example, X ₁ is a group represented by the chemical formula (1-X), and Y ₁ is a group represented by the chemical formula (1-Y). A polyimide precursor containing a repeating unit represented by the chemical formula (1) is preferred.

  In other words, in one embodiment, the polyimide precursor is 4,4 ′-(2,2-hexafluoroisopropylene) diphthalic acid or the like (tetracarboxylic acid containing diphthalic acid or the like is tetracarboxylic acid, A tetracarboxylic acid component including a tetracarboxylic acid dianhydride, a tetracarboxylic acid silyl ester, a tetracarboxylic acid ester, a tetracarboxylic acid derivative such as tetracarboxylic acid chloride), and 2,2′-bis (trifluoromethyl) It is a polyimide precursor obtained from a diamine component containing benzidine. As the tetracarboxylic acid component, one kind such as 4,4 '-(2,2-hexafluoroisopropylene) diphthalic acid may be used alone, or a plurality of kinds may be used in combination.

In the polyimide precursor, X ₁ is a group represented by the chemical formula (1-X) in 100 mol% of the repeating unit represented by the chemical formula (1), and Y ₁ is the chemical formula (1-Y). The ratio of the repeating unit represented by the chemical formula (1) which is a group represented by is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. In one embodiment, X ₁ is a group represented by the chemical formula (1-X) in 100 mol% of the repeating unit represented by the chemical formula (1) from the viewpoint of characteristics of the obtained polyimide. , Y ₁ is a group represented by the chemical formula (1-Y), and the proportion of the repeating unit represented by the chemical formula (1) is preferably 60 mol% or less, more preferably 70 mol% or less. It may be preferable. For example, other tetracarboxylic acids such as 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, etc. are added in 100 mol% of the tetracarboxylic acid component giving the repeating unit of the chemical formula (1), for example, It may be preferred to use at 40 mol% or less, preferably 30 mol% or less.

In addition, X ₁ is a group represented by the chemical formula (1-X), and Y ₁ is a group represented by the chemical formula (1-Y), and includes a repeating unit represented by the chemical formula (1). The polyimide precursor may include other repeating units represented by the other chemical formula (1), and may include other repeating units other than the repeating unit represented by the chemical formula (1). You can also. The content of other repeating units other than the repeating unit represented by the chemical formula (1) is preferably 30 mol% or less or less than 30 mol%, more preferably 20 mol% or less, based on all repeating units. More preferably, it is 10 mol% or less.

In the polyimide precursor of the present invention, R ₁ and R _{2 in} the chemical formula (1) are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, or an alkyl group having 3 to 9 carbon atoms. One of the silyl groups. R ₁ and R ₂ can change the type of functional group and the introduction rate of the functional group by the production method described later.

When R ₁ and R ₂ are hydrogen, polyimide tends to be easily produced.

Further, R ₁ and R ₂ is 1 to 6 carbon atoms, preferably when an alkyl group having 1 to 3 carbon atoms, tend to excellent storage stability of the polyimide precursor. In this case, R ₁ and R ₂ are more preferably a methyl group or an ethyl group.

Furthermore, when R < ₁ > and R < ₂ > are C3-C9 alkylsilyl groups, there exists a tendency for the solubility of a polyimide precursor to be excellent. In this case, R ₁ and R ₂ are more preferably a trimethylsilyl group or a t-butyldimethylsilyl group.

The introduction rate of the functional group is not particularly limited, but when an alkyl group or an alkylsilyl group is introduced, each of R ₁ and R ₂ is 25% or more, preferably 50% or more, more preferably 75% or more. Alternatively, it can be an alkylsilyl group.

The polyimide precursor of the present invention has a chemical structure in which R ₁ and R ₂ take 1) polyamic acid (R ₁ and R ₂ are hydrogen), 2) polyamic acid ester (at least part of R ₁ and R ₂ is alkyl) Group), 3) and 4) polyamic acid silyl ester (at least a part of R ₁ and R ₂ is an alkylsilyl group). And the polyimide precursor of this invention can be easily manufactured with the following manufacturing methods for every classification. However, the manufacturing method of the polyimide precursor of this invention is not limited to the following manufacturing methods.

1) Polyamic acid The polyimide precursor of the present invention comprises a tetracarboxylic dianhydride as a tetracarboxylic acid component and a diamine component in a solvent in an approximately equimolar amount, preferably a molar ratio of the diamine component to the tetracarboxylic acid component [diamine. The number of moles of component / number of moles of tetracarboxylic acid component] is preferably 0.90 to 1.10, more preferably 0.95 to 1.05, for example, imidization at a relatively low temperature of 120 ° C. or less. It can obtain suitably as a polyimide precursor solution composition by reacting, suppressing.

  Although it does not limit, more specifically, diamine is melt | dissolved in an organic solvent, Tetracarboxylic dianhydride is added gradually, stirring to this solution, 0-120 degreeC, Preferably it is 5-80. A polyimide precursor is obtained by stirring for 1 to 72 hours in the range of ° C. When the reaction is carried out at 80 ° C. or higher, the molecular weight varies depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be produced stably. The order of addition of diamine and tetracarboxylic dianhydride in the above production method is preferable because the molecular weight of the polyimide precursor is likely to increase. Moreover, it is also possible to reverse the order of addition of the diamine and tetracarboxylic dianhydride in the above production method, and this is preferable because precipitates are reduced.

  Moreover, when the molar ratio of the tetracarboxylic acid component and the diamine component is an excess of the diamine component, if necessary, an amount of a carboxylic acid derivative substantially corresponding to the excess mole number of the diamine component is added, and the tetracarboxylic acid component and the diamine are added. The molar ratio of the components can be approximated to the equivalent. As the carboxylic acid derivative herein, a tetracarboxylic acid that does not substantially increase the viscosity of the polyimide precursor solution, that is, substantially does not participate in molecular chain extension, or a tricarboxylic acid that functions as a terminal terminator and its anhydride, Dicarboxylic acid and its anhydride are preferred.

2) Polyamic acid ester After reacting tetracarboxylic dianhydride with an arbitrary alcohol to obtain a diester dicarboxylic acid, it is reacted with a chlorinating reagent (thionyl chloride, oxalyl chloride, etc.) to obtain a diester dicarboxylic acid chloride. The polyimide precursor is obtained by stirring the diester dicarboxylic acid chloride and the diamine in the range of -20 to 120 ° C, preferably -5 to 80 ° C for 1 to 72 hours. When the reaction is carried out at 80 ° C. or higher, the molecular weight varies depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be produced stably. Alternatively, a polyimide precursor can be easily obtained by dehydrating and condensing diester dicarboxylic acid and diamine using a phosphorus condensing agent or a carbodiimide condensing agent.

  Since the polyimide precursor obtained by this method is stable, it can be purified by reprecipitation by adding a solvent such as water or alcohol.

3) Polyamide acid silyl ester (indirect method)
A diamine and a silylating agent are reacted in advance to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or the like. Then, the silylated diamine is dissolved in the dehydrated solvent, and tetracarboxylic dianhydride is gradually added while stirring, and the temperature is 0 to 120 ° C., preferably 5 to 80 ° C. A polyimide precursor is obtained by stirring for 72 hours. When the reaction is carried out at 80 ° C. or higher, the molecular weight varies depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be produced stably.

  As the silylating agent used here, it is preferable to use a silylating agent not containing chlorine because it is not necessary to purify the silylated diamine. Examples of the silylating agent not containing a chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and are low in cost.

  In addition, amine-based catalysts such as pyridine, piperidine and triethylamine can be used in the silylation reaction of diamine in order to accelerate the reaction. This catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

4) Polyamide acid silyl ester (direct method)
The polyimide precursor is obtained by mixing the polyamic acid solution obtained by the method 1) and the silylating agent and stirring for 1 to 72 hours in the range of 0 to 120 ° C, preferably 5 to 80 ° C. When the reaction is carried out at 80 ° C. or higher, the molecular weight varies depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be produced stably.

  As the silylating agent used here, it is preferable to use a silylating agent not containing chlorine because it is not necessary to purify the silylated polyamic acid or the obtained polyimide. Examples of the silylating agent not containing a chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and are low in cost.

  Any of the above production methods can be suitably carried out in an organic solvent, and as a result, a solution or solution composition containing a polyimide precursor can be easily obtained.

  Solvents used in preparing the polyimide precursor are, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide An aprotic solvent such as N, N-dimethylacetamide is preferred, but any type of solvent can be used without any problem as long as the raw material monomer component and the polyimide precursor to be produced are dissolved. The structure is not limited. As solvents, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α- Cyclic ester solvents such as methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, phenols such as m-cresol, p-cresol, 3-chlorophenol and 4-chlorophenol A system solvent, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like are preferably employed. Furthermore, other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran , Dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpenes, mineral spirit, petroleum A naphtha solvent can also be used. In addition, a solvent can also be used in combination of multiple types.

  In the present invention, the logarithmic viscosity of the polyimide precursor is not particularly limited, but the logarithmic viscosity in an N, N-dimethylacetamide solution having a concentration of 0.5 g / dL at 30 ° C. is 0.2 dL / g or more, more preferably 0. .3 dL / g or more, particularly preferably 0.4 dL / g or more. When the logarithmic viscosity is 0.2 dL / g or more, the molecular weight of the polyimide precursor is high, and the mechanical strength and heat resistance of the resulting polyimide are excellent.

  The polyimide precursor composition of the present invention includes a polyimide precursor and an imidazole compound, and may be prepared by adding an imidazole compound to a polyimide precursor solution or solution composition obtained by the above production method. it can. Moreover, a solvent may be removed or added as needed, and desired components other than an imidazole compound may be added. In addition, a tetracarboxylic acid component (tetracarboxylic dianhydride or the like), a diamine component, and an imidazole compound are added to a solvent, and the tetracarboxylic acid component and the diamine component are reacted in the presence of the imidazole compound. The polyimide precursor composition (solution composition containing a polyimide precursor and an imidazole compound) can also be obtained.

  The imidazole compound used in the present invention is not particularly limited as long as it is a compound having an imidazole skeleton. By adding an imidazole compound, a polyimide having higher heat resistance can be obtained.

  In one embodiment, it is preferable to use a compound having a boiling point at 1 atm of less than 360 ° C., preferably 350 ° C. or less, more preferably 340 ° C. or less as the imidazole compound. By adding an imidazole compound having a boiling point at 1 atm of less than 360 ° C., preferably 350 ° C. or less, more preferably 340 ° C. or less, a more transparent polyimide may be obtained.

  In one embodiment, a compound having a boiling point at 1 atm of less than 340 ° C., preferably 330 ° C. or less, more preferably 300 ° C. or less, and particularly preferably 270 ° C. or less is used as the imidazole compound. By adding an imidazole compound having a boiling point of less than 340 ° C. at 1 atm, a polyimide having a smaller linear thermal expansion coefficient may be obtained.

  The imidazole compound used in the present invention is not particularly limited, and examples thereof include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole, and benzimidazole. 1,2-dimethylimidazole (boiling point at 1 atmosphere: 205 ° C.), 1-methylimidazole (boiling point at 1 atmosphere: 198 ° C.), 2-methylimidazole (boiling point at 1 atmosphere: 268 ° C.), imidazole (boiling point at 1 atmosphere) : 256 ° C), 2-phenylimidazole (boiling point at 1 atm: 340 ° C), and the like are preferable, and 1,2-dimethylimidazole and 1-methylimidazole are particularly preferable. An imidazole compound may be used individually by 1 type, and can also be used in combination of multiple types.

  In this invention, content of the imidazole type compound of a polyimide precursor composition is less than 4 mol with respect to 1 mol of repeating units of a polyimide precursor. When the content of the imidazole compound is 4 mol or more with respect to 1 mol of the repeating unit of the polyimide precursor, the storage stability of the polyimide precursor composition is deteriorated. The content of the imidazole compound is preferably 0.05 mol or more with respect to 1 mol of the repeating unit of the polyimide precursor, and is 2 mol or less with respect to 1 mol of the repeating unit of the polyimide precursor. preferable. Here, 1 mol of the repeating unit of the polyimide precursor corresponds to 1 mol of the tetracarboxylic acid component.

  The polyimide precursor composition of the present invention usually contains a solvent. The solvent used for the polyimide precursor composition of the present invention is not a problem as long as the polyimide precursor is dissolved, and the structure is not particularly limited. As solvents, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone , Cyclic ester solvents such as α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, m-cresol, p-cresol, 3-chlorophenol, 4-chlorophenol Phenol solvents such as acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like are preferably employed. Furthermore, other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran , Dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpenes, mineral spirit, petroleum A naphtha solvent can also be used. Moreover, these can also be used combining multiple types. In addition, the solvent used when preparing a polyimide precursor can be used for the solvent of a polyimide precursor composition as it is.

  In the present invention, the total amount of the tetracarboxylic acid component and the diamine component is 5% by mass or more, preferably 10% by mass or more, more preferably 15%, based on the total amount of the solvent, the tetracarboxylic acid component and the diamine component. A ratio of not less than mass% is preferred. In general, the total amount of the tetracarboxylic acid component and the diamine component is 60% by mass or less, preferably 50% by mass or less, based on the total amount of the solvent, the tetracarboxylic acid component, and the diamine component. Is preferred. This concentration is a concentration approximately approximate to the solid content concentration resulting from the polyimide precursor, but if this concentration is too low, it becomes difficult to control the film thickness of the polyimide film obtained, for example, when producing a polyimide film. Sometimes.

In the present invention, the viscosity (rotational viscosity) of the polyimide precursor composition is not particularly limited, but the rotational viscosity measured at a temperature of 25 ° C. and a shear rate of 20 sec ⁻¹ using an E-type rotational viscometer is 0.01 to 1000 Pa · sec is preferable, and 0.1 to 100 Pa · sec is more preferable. Moreover, thixotropy can also be provided as needed. When the viscosity is in the above range, it is easy to handle when coating or forming a film, and the repelling is suppressed and the leveling property is excellent, so that a good film can be obtained.

  The polyimide precursor composition of the present invention includes chemical imidizing agents (acid anhydrides such as acetic anhydride, amine compounds such as pyridine and isoquinoline), antioxidants, fillers (inorganic particles such as silica, etc.) as necessary. ), Dyes, pigments, coupling agents such as silane coupling agents, primers, flame retardants, antifoaming agents, leveling agents, rheology control agents (flow aids), release agents and the like.

  The polyimide of the present invention can be obtained by imidizing the polyimide precursor composition of the present invention as described above (that is, subjecting the polyimide precursor to a dehydration ring-closing reaction). The imidization method is not particularly limited, and a known thermal imidation or chemical imidization method can be suitably applied. The form of the polyimide obtained can mention suitably a film, the laminated body of a polyimide film and another base material, a coating film, powder, a bead, a molded object, a foam.

  In the present invention, it is preferable to imidize the polyimide precursor by heat-treating the polyimide precursor composition at a maximum heating temperature of 350 ° C. or higher. By setting the maximum heating temperature of the heat treatment for imidization to a temperature of 350 ° C. or higher, the mechanical properties of the obtained polyimide are improved. Although the upper limit of the maximum heating temperature of heat processing is not specifically limited, Usually, 500 degrees C or less is preferable.

  For example, the polyimide precursor composition of the present invention is cast and applied on a base material, and the polyimide precursor composition on the base material is heat-treated at a maximum heating temperature of 350 ° C. or higher to obtain a polyimide precursor. By imidizing, a polyimide can be suitably produced. The heating profile is not particularly limited and can be selected as appropriate. However, from the viewpoint of productivity, it is preferable that the heat treatment time is short.

  In addition, the polyimide precursor composition of the present invention is cast and applied on a substrate, and preferably dried in a temperature range of 180 ° C. or less to form a polyimide precursor composition film on the substrate. The polyimide precursor composition film is peeled off from the substrate, and the polyimide precursor is imidized by heat treatment at a maximum heating temperature of 350 ° C. or higher with the ends of the film fixed. Also, the polyimide can be preferably produced.

  A more specific example of the method for producing the polyimide (polyimide film / substrate laminate or polyimide film) of the present invention will be described later.

  The polyimide obtained from the polyimide precursor composition of the present invention (polyimide of the present invention) is not particularly limited, but the linear thermal expansion coefficient from 150 ° C. to 250 ° C. when formed into a film is preferably 40 ppm / K or less, More preferably, it can be 30 ppm / K or less, more preferably 25 ppm / K or less, and particularly preferably 20 ppm / K or less, and has a very low coefficient of linear thermal expansion. When the linear thermal expansion coefficient is large, the difference in the linear thermal expansion coefficient with a conductor such as metal is large, which may cause problems such as an increase in warpage when a circuit board is formed.

  The polyimide obtained from the polyimide precursor composition of the present invention (polyimide of the present invention) is not particularly limited, but preferably has a total light transmittance (average light transmittance of a wavelength of 380 nm to 780 nm) in a film having a thickness of 10 μm. Is 89% or more, more preferably 90% or more, and has excellent light transmittance. When used for a display application or the like, if the total light transmittance is low, it is necessary to strengthen the light source, which may cause a problem that energy is applied.

  In particular, when a polyimide film such as a display application is used in an application where light is transmitted, it is desirable that the polyimide film has higher transparency. The polyimide obtained from the polyimide precursor composition of the present invention (polyimide of the present invention) is not particularly limited, but the light transmittance at a wavelength of 400 nm in a 10 μm-thick film is preferably 79% or more, more preferably 80%. % Or more, more preferably more than 80%.

  In addition, although the film which consists of a polyimide (polyimide of this invention) obtained from the polyimide precursor composition of this invention also depends on a use, as thickness of a film, Preferably it is 0.1 micrometer-250 micrometers, More preferably, it is 1 micrometer-. It is 150 μm, more preferably 1 μm to 50 μm, and particularly preferably 1 μm to 30 μm. When the polyimide film is used for light transmission, if the polyimide film is too thick, the light transmittance may be lowered.

  The polyimide obtained from the polyimide precursor composition of the present invention (polyimide of the present invention) is not particularly limited, but the 1% weight loss temperature, which is an index of heat resistance of the polyimide film, is preferably 495 ° C. or more, more preferably It can be 498 ° C. or higher, more preferably 500 ° C. or higher. When a gas barrier film or the like is formed on a polyimide by forming a transistor on the polyimide or the like, if the heat resistance is low, swelling may occur between the polyimide and the barrier film due to outgas accompanying decomposition of the polyimide.

  The polyimide obtained from the polyimide precursor composition of the present invention, that is, the polyimide of the present invention has excellent properties such as high transparency, bending resistance and high heat resistance, and also has a very low linear thermal expansion coefficient. In a use of a transparent substrate for a display, a transparent substrate for a touch panel, or a substrate for a solar cell, it can be suitably used.

  Below, an example of the manufacturing method of a polyimide film / base material laminated body or a polyimide film using the polyimide precursor composition of this invention is described. However, it is not limited to the following method.

  For example, the polyimide precursor composition (varnish) of the present invention is cast on a substrate such as ceramic (glass, silicon, alumina, etc.), metal (copper, aluminum, stainless steel, etc.), heat resistant plastic film (polyimide film, etc.), etc. In a vacuum, in an inert gas such as nitrogen, or in the air, drying is performed in a temperature range of 20 to 180 ° C., preferably 20 to 150 ° C. using hot air or infrared rays. Next, the obtained polyimide precursor film is peeled off from the substrate or the polyimide precursor film from the substrate, and the end of the film is fixed, in vacuum, in an inert gas such as nitrogen, Alternatively, a polyimide film / substrate laminate or a polyimide film can be produced by heating imidization in air using hot air or infrared rays, for example, at 200 to 500 ° C., preferably at a maximum heating temperature of 350 ° C. or higher. it can. In order to prevent the resulting polyimide film from being oxidized and deteriorated, it is desirable to carry out the heating imidization in a vacuum or in an inert gas. The thickness of the polyimide film here (in the case of a polyimide film / substrate laminate) is preferably 1 to 250 μm, more preferably 1 to 150 μm, for transportability in the subsequent steps.

  Also, the imidization reaction of the polyimide precursor, instead of the heat imidation by the heat treatment as described above, contains a dehydration cyclization reagent such as acetic anhydride in the presence of a tertiary amine such as pyridine or triethylamine. It is also possible to carry out by chemical treatment such as immersion in a solution. In addition, these dehydrating cyclization reagents are previously charged and stirred in a polyimide precursor composition (varnish), and cast and dried on a base material to obtain a partially imidized polyimide precursor. A polyimide film / base material laminate or a polyimide film can be obtained by further heat treatment as described above.

  The polyimide film / base laminate or the polyimide film thus obtained can be used to form a flexible conductive substrate by forming a conductive layer on one side or both sides thereof.

  A flexible conductive substrate can be obtained, for example, by the following method. That is, as a first method, the polyimide film / substrate laminate is not peeled off from the substrate, and the surface of the polyimide film is sputtered, vapor-deposited, printed, etc. by a conductive substance (metal or metal oxide). A conductive layer of conductive layer / polyimide film / base material is produced. Then, if necessary, a transparent and flexible conductive substrate comprising the conductive layer / polyimide film laminate can be obtained by peeling the conductive layer / polyimide film laminate from the substrate.

  As a second method, the polyimide film is peeled off from the substrate of the polyimide film / substrate laminate to obtain a polyimide film, and a conductive substance (metal or metal oxide, conductive organic substance, A conductive layer of conductive carbon, etc.) is formed in the same manner as in the first method, and is a transparent and flexible conductive layer comprising a conductive layer / polyimide film laminate and a conductive layer / polyimide film laminate / conductive layer. A substrate can be obtained.

  In the first and second methods, if necessary, before forming a conductive layer on the surface of the polyimide film, a gas barrier layer such as water vapor or oxygen, light adjustment, etc. by sputtering, vapor deposition or gel-sol method. An inorganic layer such as a layer may be formed.

  The conductive layer is preferably formed with a circuit by a photolithography method, various printing methods, an inkjet method, or the like.

  The substrate of the present invention thus obtained has a circuit of a conductive layer on the surface of a polyimide film composed of the polyimide of the present invention through a gas barrier layer or an inorganic layer as necessary. This substrate is flexible, has excellent transparency, bendability, and heat resistance, and further has a very low linear thermal expansion coefficient and excellent solvent resistance, so that a fine circuit can be easily formed. Therefore, this board | substrate can be used suitably as a board | substrate for displays, a touch panel, or a solar cell.

  That is, a transistor (inorganic transistor, organic transistor) is further formed on this substrate by vapor deposition, various printing methods, an ink jet method or the like to manufacture a flexible thin film transistor, and a liquid crystal element, an EL element, a photoelectric transistor for a display device are manufactured. It is suitably used as an element.

  Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples. In addition, this invention is not limited to a following example.

  In each of the following examples, the evaluation was performed by the following method.

<Evaluation of polyimide precursor varnish>
[Storage stability]
If the varnish is stored at 23 ° C. and is in a uniform state with fluidity after 3 days,
If it becomes cloudy or gelled after 3 days, it is marked as x.

<Evaluation of polyimide film>
[400 nm light transmittance, total light transmittance]
Using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO), the light transmittance at 400 nm and the total light transmittance (average transmittance at 380 nm to 780 nm) of a polyimide film having a thickness of about 10 μm were measured. The light transmittance at 400 nm and the total light transmittance were calculated using the Lambert-Beer formula with the total light transmittance being 10% and the light transmittance at 400 nm having a thickness of 10 μm and the total light transmittance were calculated. The calculation formula is shown below.

Log ₁₀ ((T ₁ +10) / 100) = 10 / L × (Log ₁₀ ((T ₁ ′ +10) / 100))
Log ₁₀ ((T ₂ +10) / 100) = 10 / L × (Log ₁₀ ((T ₂ ′ +10) / 100))
T ₁ : Light transmittance (%) at 400 nm of a 10 μm-thick polyimide film with a reflectance of 10%
T ₁ ′: measured light transmittance at 400 nm (%)
T ₂ : Total light transmittance (%) of a 10 μm-thick polyimide film with a reflectance of 10%
T ₂ ': Measured total light transmittance (%)
L: Film thickness of the measured polyimide film (μm)

[Elastic modulus, elongation at break]
A polyimide film with a film thickness of about 10μm is punched into a IEC450 standard dumbbell shape as a test piece, and the initial elastic modulus and elongation at break are measured with a length of 30mm between chucks and a tensile speed of 2mm / min using TENILON manufactured by ORIENTEC. did.

[Linear thermal expansion coefficient (CTE)]
A polyimide film having a thickness of about 10 μm is cut into a strip having a width of 4 mm to form a test piece, and TMA / SS6100 (manufactured by SII Nano Technology Co., Ltd.) is used. The temperature was raised to 500 ° C. in minutes. The linear thermal expansion coefficient from 150 ° C. to 250 ° C. was determined from the obtained TMA curve.

[1% weight loss temperature]
A polyimide film having a film thickness of about 10 μm was used as a test piece, and the temperature was raised from 25 ° C. to 600 ° C. at a temperature rising rate of 10 ° C./min in a nitrogen stream using a calorimeter measuring device (Q5000IR) manufactured by TA Instruments. From the obtained weight curve, a 1% weight loss temperature was determined.

  Abbreviations, purity, etc. of raw materials used in the following examples are as follows.

[Diamine component]
TFMB: 2,2′-bis (trifluoromethyl) benzidine [Purity: 99.83% (GC analysis)]
[Tetracarboxylic acid component]
s-BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride [purity 99.9% (H-NMR analysis)]
6FDA: 4,4 ′-(2,2-hexafluoroisopropylene) diphthalic dianhydride [purity 99.77% (H-NMR analysis)]

[solvent]
NMP: N-methyl-2-pyrrolidone

  Table 1-1 shows tetracarboxylic acid components used in Examples and Comparative Examples, Table 1-2 shows Examples and Comparative Examples, and Diamine Components Used in Comparative Examples, Table 1-3 Examples and Comparative Examples Imidazole and Imidazoline The structural formula of the compound is described.

[Synthesis Example 1]
In a reaction vessel substituted with nitrogen gas, 32.02 g (0.100 mmol) of TFMB was charged, N-methyl-2-pyrrolidone was charged, and the total monomer mass (total of diamine component and carboxylic acid component) was 20% by mass. A certain amount of 287.79 g was added and stirred at room temperature for 1 hour. To this solution, 8.83 g (0.030 mol) of s-BPDA and 31.10 (0.070 mol) of 6FDA were gradually added. The mixture was stirred at room temperature for 12 hours to obtain a uniform and viscous polyimide precursor solution.

[Example 1]
1,9-dimethylimidazole (0.19 g, 2.0 mmol) and N-methyl-2-pyrrolidone (0.19 g) were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1,2-dimethylimidazole per 0.2 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

[Example 2]
A uniform solution was obtained by adding 0.38 g (4.0 mmol) of 1,2-dimethylimidazole and 0.38 g of N-methyl-2-pyrrolidone to the reaction vessel. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1,2-dimethylimidazole per 0.4 mole of the repeating unit of the polyimide precursor is 0.4 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 3
0.96 g (10.0 mmol) of 1,2-dimethylimidazole and 0.50 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1,2-dimethylimidazole per 1.0 mole of the repeating unit of the polyimide precursor is 1.0 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 4
1.92 g (20.0 mmol) of 1,2-dimethylimidazole and 0.50 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1,2-dimethylimidazole relative to 1 mole of the repeating unit of the polyimide precursor is 2.0 equivalents.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 5
A uniform solution was obtained by adding 0.16 g (2.0 mmol) of 1-methylimidazole and 0.16 g of N-methyl-2-pyrrolidone to the reaction vessel. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1-methylimidazole relative to 1 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 6
0.16 g (2.0 mmol) of 2-methylimidazole and 0.16 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol with respect to the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 2-methylimidazole relative to 1 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 7
0.14 g (2.0 mmol) of imidazole and 0.14 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of imidazole relative to 1 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 8
0.29 g (2.0 mmol) of 2-phenylimidazole and 0.29 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 2-phenylimidazole relative to 1 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

Example 9
A uniform solution was obtained by adding 0.24 g (2.0 mmol) of benzimidazole and 0.24 g of N-methyl-2-pyrrolidone to the reaction vessel. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of benzimidazole per 0.2 mol of the repeating unit of the polyimide precursor is 0.2 equivalent.

  A polyimide precursor solution filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is, and thermally imidized. A transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

[Comparative Example 1]
The varnish obtained in Synthesis Example 1 filtered through a PTFE membrane filter is applied to a glass substrate, and heated in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) from room temperature to 350 ° C. as it is to thermally imidize. A colorless and transparent polyimide film / glass laminate was obtained. Next, the obtained polyimide film / glass laminate was immersed in water and then peeled off and dried to obtain a polyimide film having a film thickness of about 10 μm.

  The results of measuring the properties of this polyimide film are shown in Table 2.

[Comparative Example 2]
0.10 g (1.0 mmol) of 2-ethyl-2-imidazoline and 0.90 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. When 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol with respect to the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, the varnish gelled. Even if it was stirred at room temperature for 3 hours, a uniform polyimide precursor solution could not be obtained. When calculated from the charged amount, the number of moles of 2-ethyl-2-imidazoline with respect to 1 mole of the repeating unit of the polyimide precursor is 0.1 equivalent.

[Comparative Example 3]
0.18 g (2.0 mmol) of 2-ethyl-2-imidazoline and 1.80 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. When 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol with respect to the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, the varnish gelled. Even if it was stirred at room temperature for 3 hours, a uniform polyimide precursor solution could not be obtained. When calculated from the charged amount, the number of moles of 2-ethyl-2-imidazoline with respect to 1 mole of the repeating unit of the polyimide precursor is 0.2 equivalent.

[Comparative Example 4]
1.85 g (40.0 mmol) of 1,2-dimethylimidazole and 0.50 g of N-methyl-2-pyrrolidone were added to the reaction vessel to obtain a uniform solution. 35.97 g of the varnish obtained in Synthesis Example 1 (10 mmol based on the molecular weight of the repeating unit of the polyimide precursor in the varnish) was added to the solution, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor. A solution was obtained. When calculated from the charged amount, the number of moles of 1,2-dimethylimidazole per 4.0 moles of the repeating unit of the polyimide precursor is 4.0 equivalents. When the obtained polyimide precursor solution was stored at 23 ° C., the polyimide precursor solution gelled by the third day.

  From the results shown in Table 2, it can be seen that the polyimide obtained from the polyimide precursor composition containing the imidazole compound has higher heat resistance (Examples 1 to 9 and Comparative Example 1). Moreover, it turns out that it is excellent also in storage stability as content of an imidazole type compound is less than 4 mol with respect to 1 mol of repeating units of a polyimide precursor (Examples 1-4 and Comparative Example 4).

  As described above, the polyimide obtained from the polyimide precursor composition of the present invention has excellent light transmittance, heat resistance and mechanical properties, and has a low linear thermal expansion coefficient. The film can be suitably used as a transparent substrate that is colorless and transparent and capable of forming fine circuits, such as for display applications.

  According to the present invention, a polyimide precursor composition (a solution composition containing a polyimide precursor) from which a polyimide having excellent transparency, low linear thermal expansion coefficient, higher heat resistance, and excellent mechanical properties can be obtained. ) And a method for producing polyimide. The polyimide obtained from this polyimide precursor composition is highly transparent and has a low coefficient of linear thermal expansion, so that it is easy to form a fine circuit. Therefore, substrates for displays, touch panels, solar cells, etc. It can be suitably used to form.

Claims (11)

A polyimide precursor containing a repeating unit represented by the following chemical formula (1);
Including imidazole compounds,
Content of an imidazole type compound is less than 4 mol with respect to 1 mol of repeating units of a polyimide precursor, The polyimide precursor composition characterized by the above-mentioned.

(In the formula, X ₁ is a tetravalent group having an aromatic ring, Y ₁ is a divalent group having an aromatic ring, provided that at least _one of X ₁ and Y ₁ contains a fluorine atom. , R ₁ and R ₂ are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms) X ₁ in the chemical formula (1) is a group represented by the following chemical formula (1-X), and Y ₁ in the chemical formula (1) is a group represented by the following chemical formula (1-Y). The polyimide precursor composition according to claim 1.

  3. The polyimide precursor composition according to claim 1, wherein the polyimide obtained from the polyimide precursor composition has a light transmittance at a wavelength of 400 nm of 79% or more in a film having a thickness of 10 μm.   Content of the said imidazole type compound is 0.05 mol or more and 2 mol or less with respect to 1 mol of repeating units of a polyimide precursor, The polyimide precursor composition in any one of Claims 1-3 characterized by the above-mentioned. object.   The imidazole compound is any one of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole, and benzimidazole. A polyimide precursor composition according to claim 1.   A polyimide precursor composition according to claim 1, wherein the polyimide precursor composition is heat-treated at a maximum heating temperature of 350 ° C. or higher to imidize the polyimide precursor. Applying the polyimide precursor composition according to any one of claims 1 to 5 on a substrate;
The method for producing polyimide according to claim 6, further comprising a step of heat-treating the polyimide precursor composition on the substrate at a maximum heating temperature of 350 ° C. or higher to imidize the polyimide precursor.   A polyimide produced by the method according to claim 6 or 7.   The polyimide according to claim 8, wherein a light transmittance at a wavelength of 400 nm in a film having a thickness of 10 μm is 80% or more.   The polyimide film manufactured by the method of Claim 6 or 7.   A substrate for display, a touch panel, or a solar cell, comprising the polyimide according to claim 6 or 7, or the polyimide film according to claim 10.