阅读说明：本技术 聚酰亚胺前体、聚酰亚胺、聚酰亚胺膜、清漆和基板 (Polyimide precursor, polyimide film, varnish, and substrate ) 是由 冈卓也 小滨幸德 中川美晴 久野信治 于 2018-12-27 设计创作，主要内容包括：本发明提供一种聚酰亚胺,其包含下述通式(5)所表示的重复单元,此处,通式(5)的A<Sub>2</Sub>包含式(A-1)所表示的4价基团,并且,通式(5)的B<Sub>2</Sub>包含式(B-1)所表示的2价基团,此外,A<Sub>2</Sub>和/或B<Sub>2</Sub>以特定的比例包含具有特定结构的4价或2价基团。该聚酰亚胺具有高透明性和低线性热膨胀系数,厚度方向相位差(延迟)也小。(式中,A<Sub>2</Sub>为具有芳香族环或脂环结构的4价基团,B<Sub>2</Sub>为具有芳香族环或脂环结构的2价基团。其中,各重复单元中包含的A<Sub>2</Sub>和B<Sub>2</Sub>可以相同也可以不同。)<Image he="984" wi="700" file="DDA0002635458550000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The present invention provides a polyimide comprising a repeating unit represented by the following general formula (5), wherein A of the general formula (5) 2 Containing a 4-valent group represented by the formula (A-1), and B of the general formula (5) 2 Containing a 2-valent group represented by the formula (B-1), and further, A 2 And/or B 2 In a specific proportionContaining a 4-or 2-valent group having a specific structure. The polyimide has high transparency, a low linear thermal expansion coefficient, and a small retardation in the thickness direction. (in the formula, A) 2 Is a 4-valent group having an aromatic or alicyclic structure, B 2 Is a 2-valent group having an aromatic or alicyclic structure. Wherein A is contained in each repeating unit 2 And B 2 May be the same or different. ))

1. A polyimide precursor comprising a repeating unit represented by the following general formula (1),

a of the following general formula (1)₁Contains a 4-valent group represented by the following formula (A-1), and B of the following general formula (1)₁Comprising a 2-valent group represented by the following formula (B-1),

further, A in the following general formula (1)₁And/or B₁Contains a 4-or 2-valent group having a structure represented by the following formula (2), or A of the following general formula (1)₁Comprises a 4-valent group represented by the following formula (3) and/or a 4-valent group represented by the following formula (4),

a of the formula (1)₁The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (1)₁The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more,

wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less relative to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and wherein,

the proportion of the 2-valent group having a structure represented by formula (2) is 80 mol% or less relative to the total of the 2-valent group represented by formula (B-1) and the 2-valent group having a structure represented by formula (2),

[ solution 1]

In the formula, A₁Is a 4-valent group having an aromatic or alicyclic structure, B₁Is a 2-valent group having an aromatic or alicyclic structure, R₁、R₂Each independently hydrogen, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms, wherein A is contained in each repeating unit₁And B₁Which may be the same or different from each other,

[ solution 2]

[ solution 3]

[ solution 4]

[ solution 5]

[ solution 6]

2. A polyimide comprising a repeating unit represented by the following general formula (5),

a of the following general formula (5)₂Contains a 4-valent group represented by the following formula (A-1), and B of the following general formula (5)₂Comprising a 2-valent group represented by the following formula (B-1),

further, A of the following general formula (5)₂And/or B₂Contains a 4-or 2-valent group having a structure represented by the following formula (2), or A of the following general formula (5)₂Comprises a 4-valent group represented by the following formula (3) and/or a 4-valent group represented by the following formula (4),

a of the general formula (5)₂The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (5)₂The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more,

wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less relative to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and wherein,

the proportion of the 2-valent group having a structure represented by formula (2) is 80 mol% or less relative to the total of the 2-valent group represented by formula (B-1) and the 2-valent group having a structure represented by formula (2),

[ solution 7]

In the formula, A₂Is a 4-valent group having an aromatic or alicyclic structure, B₂Is a 2-valent group having an aromatic or alicyclic structure, wherein A contained in each repeating unit₂And B₂Which may be the same or different from each other,

[ solution 8]

[ solution 9]

[ solution 10]

[ solution 11]

[ solution 12]

3. A polyimide obtained from the polyimide precursor of claim 1.

4. A varnish comprising the polyimide precursor of claim 1 or the polyimide of claim 2.

5. A polyimide film obtained by using a varnish containing the polyimide precursor according to claim 1 or the polyimide according to claim 2.

6. A laminate comprising a film comprising the polyimide according to claim 2 or 3 or the polyimide film according to claim 5 formed on a glass substrate.

7. A substrate for a display, a touch panel, or a solar cell, which comprises the polyimide according to claim 2 or 3 or the polyimide film according to claim 5.

Technical Field

The present invention relates to a polyimide having high transparency, a low linear thermal expansion coefficient and a small phase difference (retardation) in the thickness direction, and a precursor thereof. In addition, the present invention relates to a polyimide film, a varnish containing a polyimide precursor or polyimide, and a substrate.

Background

In recent years, with the advent of a highly information-oriented society, development of optical materials such as liquid crystal alignment films and color filter protective films in the field of display devices such as optical fibers and optical waveguides in the field of optical communications has been advanced. In particular, in the field of display devices, research into lightweight and highly flexible plastic substrates as substitutes for glass substrates has been carried out, and displays that can be bent or rolled up have been actively developed. Therefore, higher performance optical materials capable of being used for such applications are required.

Aromatic polyimides are inherently tan colored due to intramolecular conjugation and the formation of charge transfer complexes. Therefore, as a means for suppressing coloring, for example, a method of inhibiting intramolecular conjugation or formation of a charge transfer complex by introducing a fluorine atom into a molecule, imparting flexibility to a main chain, introducing a bulky group as a side chain, or the like, thereby expressing transparency has been proposed.

Further, there has been proposed a method of expressing transparency by using a semi-alicyclic or full-alicyclic polyimide which does not form a charge transfer complex in principle. In particular, various semi-alicyclic polyimides having high transparency have been proposed, which use an aromatic tetracarboxylic dianhydride as the tetracarboxylic acid component and an alicyclic diamine as the diamine component; and a semi-alicyclic polyimide having high transparency, wherein an alicyclic tetracarboxylic dianhydride is used as the tetracarboxylic acid component and an aromatic diamine is used as the diamine component.

For example, patent document 1 discloses a polyimide using norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ″ -norbornane-5, 5 ″,6,6 ″ -tetracarboxylic dianhydride (abbreviated as CpODA) as a tetracarboxylic acid component, and 2,2 ' -bis (trifluoromethyl) benzidine (abbreviated as TFMB) or TFMB and another aromatic diamine (for example, TFMB:4,4 ' -diaminobenzanilide: 9, 9-bis (4-aminophenyl) fluorene ═ 5:4:1 (molar ratio)) as a diamine component. Patent document 2 discloses a polyimide using CpODA having a specific ratio of steric isomers as a tetracarboxylic acid component and TFMB and other aromatic diamines (for example, TFMB:4, 4' -diaminobenzanilide ═ 5:5 (molar ratio)) as a diamine component.

Patent document 3 discloses a polyimide resin containing a structural unit a derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine compound, wherein the structural unit a contains at least one of a structural unit (a-1) derived from CpODA, a structural unit (a-2) derived from pyromellitic dianhydride, and a structural unit (a-3) derived from 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, the structural unit B contains a structural unit (B-1) derived from 9, 9-bis (4-aminophenyl) fluorene, and the proportion of the structural unit (B-1) in the structural unit B is 60 mol% or more. More specifically, in example 4 of patent document 3, a polyimide resin was produced from CpODA (A-1) and 9, 9-bis (4-aminophenyl) fluorene (B-1). In example 5 of patent document 3, a polyimide resin was produced from CpODA (a-1), 1,2,4, 5-cyclohexanetetracarboxylic dianhydride (a-3), and 9, 9-bis (4-aminophenyl) fluorene (B-1) (a-1: 1 (a-3) ═ 1:1 (molar ratio)). In example 6 of patent document 3, a polyimide resin ((B-1): (B-2) ═ 4:1 (molar ratio)) was produced from CpODA (a-1), 9-bis (4-aminophenyl) fluorene (B-1) and 2, 2' -dimethylbenzidine (B-2).

In addition, in example 1 and comparative example 1 of patent document 4, polyimides obtained from CpODA, 4 '-diamino-2, 2' -dimethylbiphenyl and 9, 9-bis (4-aminophenyl) fluorene (molar ratio: 1/1) and polyimides obtained from CpODA and 9, 9-bis (4-aminophenyl) fluorene are described.

Disclosure of Invention

Problems to be solved by the invention

Depending on the application, for example, in the application to a display, polyimide and a polyimide film having high transparency and a low linear thermal expansion coefficient and having a small retardation (retardation) in the thickness direction are required. When light passes through a film having a large retardation in the thickness direction, problems such as failure to accurately display the color of the transmitted light, color blur, and a narrow viewing angle may occur. Therefore, in particular, in the display application, it is desired to reduce the thickness direction phase difference.

The purpose of the present invention is to provide a polyimide having high transparency, a low linear thermal expansion coefficient and a small phase difference (retardation) in the thickness direction, and a precursor thereof.

Means for solving the problems

The present invention relates to the following.

1. A polyimide precursor comprising a repeating unit represented by the following general formula (1),

a of the following general formula (1)₁Contains a 4-valent group represented by the following formula (A-1), and B of the following general formula (1)₁Comprises the followingA 2-valent group represented by the formula (B-1),

further, A in the following general formula (1)₁And/or B₁Contains a 4-or 2-valent group having a structure represented by the following formula (2), or A of the following general formula (1)₁Comprises a 4-valent group represented by the following formula (3) and/or a 4-valent group represented by the following formula (4),

a of the formula (1)₁The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (1)₁The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more,

wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less relative to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and wherein,

the proportion of the 2-valent group having a structure represented by formula (2) is 80 mol% or less relative to the total of the 2-valent group represented by formula (B-1) and the 2-valent group having a structure represented by formula (2).

[ solution 1]

(in the formula, A)₁Is a 4-valent group having an aromatic or alicyclic structure, B₁Is a 2-valent group having an aromatic or alicyclic structure, R₁、R₂Each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. Wherein A is contained in each repeating unit₁And B₁May be the same or different. )

[ solution 2]

[ solution 3]

[ solution 4]

[ solution 5]

[ solution 6]

2. A polyimide comprising a repeating unit represented by the following general formula (5),

a of the following general formula (5)₂Contains a 4-valent group represented by the following formula (A-1), and B of the following general formula (5)₂Comprising a 2-valent group represented by the following formula (B-1),

further, A of the following general formula (5)₂And/or B₂Contains a 4-or 2-valent group having a structure represented by the following formula (2), or A of the following general formula (5)₂Comprises a 4-valent group represented by the following formula (3) and/or a 4-valent group represented by the following formula (4),

a of the general formula (5)₂The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (5)₂The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more,

wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less relative to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and wherein,

the proportion of the 2-valent group having a structure represented by formula (2) is 80 mol% or less relative to the total of the 2-valent group represented by formula (B-1) and the 2-valent group having a structure represented by formula (2).

[ solution 7]

(in the formula, A)₂Is a 4-valent group having an aromatic or alicyclic structure, B₂Is a 2-valent group having an aromatic or alicyclic structure. Wherein A is contained in each repeating unit₂And B₂May be the same or different. )

[ solution 8]

[ solution 9]

[ solution 10]

[ solution 11]

[ solution 12]

3. A polyimide obtained from the polyimide precursor described in the above item 1.

4. A varnish comprising the polyimide precursor described in the above item 1 or the polyimide described in the above item 2.

5. A polyimide film obtained by using a varnish containing the polyimide precursor described in the above item 1 or the polyimide described in the above item 2.

6. A laminate comprising a glass substrate and a film comprising the polyimide according to the above item 2 or 3 or the polyimide film according to the above item 5 formed thereon.

7. A substrate for a display, a touch panel, or a solar cell, which comprises the polyimide according to the above item 2 or 3 or the polyimide film according to the above item 5.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a polyimide having high transparency, a low linear thermal expansion coefficient and a small phase difference (retardation) in the thickness direction and a precursor thereof can be provided.

The polyimide obtained from the polyimide precursor of the present invention and the polyimide of the present invention have high transparency, a low coefficient of linear thermal expansion, and a small phase difference (retardation) in the thickness direction, and therefore can be suitably used for forming a substrate for display applications and the like. The polyimide obtained from the polyimide precursor of the present invention and the polyimide of the present invention can also be suitably used for forming a substrate for a touch panel or a solar cell.

Detailed Description

The polyimide precursor of the present invention is a polyimide precursor containing a repeating unit represented by the above general formula (1). The total content of the repeating units represented by the above general formula (1) is preferably 90 mol% or more, more preferably 95 mol% or more, and particularly preferably 100 mol% based on the total repeating units. A in the general formula (1)₁The group having a 4-valent valence having an aromatic ring or an alicyclic structure is preferably a group having a 4-valent valence having an alicyclic structure. B in the general formula (1)₁The 2-valent group having an aromatic ring or an alicyclic structure is preferably a 2-valent group having an aromatic ring.

In the polyimide precursor of the present invention, A in the general formula (1)₁Contains a 4-valent group represented by the formula (A-1) and B in the formula (1)₁Containing a 2-valent group represented by the formula (B-1) above, and further, A of the formula (1) above₁And/or B₁Containing a 4-or 2-valent group having a structure represented by the above formula (2), or A of the above general formula (1)₁Comprises a 4-valent group represented by the formula (3) and/or a 4-valent group represented by the formula (4). It can also be: a. the₁And/or B₁Contains a 4-or 2-valent group having a structure represented by the above formula (2), and A₁Comprises a 4-valent group represented by the formula (3) and/or a 4-valent group represented by the formula (4).

Further, regarding their content, A of the formula (1)₁The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (1)₁The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more, preferably 160 mol% or more, and more preferably 180 mol% or more. Wherein, A of the general formula (1)₁Wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less with respect to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and B in the general formula (1)₁Wherein the proportion of the 2-valent group having a structure represented by formula (2) is 80 mol% or less relative to the total of the 2-valent group represented by formula (B-1) and the 2-valent group having a structure represented by formula (2). The sum of these 2 ratios is preferably 125 mol% or less.

The polyimide of the present invention is a polyimide comprising a repeating unit represented by the above general formula (5). The total content of the repeating units represented by the above general formula (5) is preferably 90 mol% or more based on the total repeating unitsMore preferably 95 mol% or more, and particularly preferably 100 mol%. A in the general formula (5)₂The group having a 4-valent valence having an aromatic ring or an alicyclic structure is preferably a group having a 4-valent valence having an alicyclic structure. B in the general formula (5)₂The 2-valent group having an aromatic ring or an alicyclic structure is preferably a 2-valent group having an aromatic ring.

In the polyimide of the present invention, A in the general formula (5)₂Contains a 4-valent group represented by the formula (A-1) and B in the formula (5)₂Containing a 2-valent group represented by the formula (B-1) above, and further, A of the formula (5) above₂And/or B₂Containing a 4-or 2-valent group having a structure represented by the above formula (2), or A of the above general formula (5)₂Comprises a 4-valent group represented by the formula (3) and/or a 4-valent group represented by the formula (4). It can also be: a. the₂And/or B₂Contains a 4-or 2-valent group having a structure represented by the above formula (2), and A₂Comprises a 4-valent group represented by the formula (3) and/or a 4-valent group represented by the formula (4).

Further, with respect to their content, A of the formula (5)₂The total content ratio of the 4-valent group represented by the formula (A-1), the 4-valent group having the structure represented by the formula (2), the 4-valent group represented by the formula (3), and the 4-valent group represented by the formula (4) in 100 mol% is the same as that of B in the general formula (5)₂The sum of the total content ratio of the 2-valent group represented by the formula (B-1) and the 2-valent group having the structure represented by the formula (2) in 100 mol% is 120 mol% or more, preferably 160 mol% or more, and more preferably 180 mol% or more. Wherein, A of the general formula (5)₂Wherein the ratio of the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4) is 80 mol% or less with respect to the total of the 4-valent group represented by formula (A-1), the 4-valent group having a structure represented by formula (2), the 4-valent group represented by formula (3), and the 4-valent group represented by formula (4), and B in the general formula (5)₂Wherein the ratio of the 2-valent group having a structure represented by the formula (2) to the total of the 2-valent group represented by the formula (B-1) and the 2-valent group having a structure represented by the formula (2)Examples are 80 mol% or less. The sum of these 2 ratios is preferably 125 mol% or less.

In the present specification, the following abbreviations are used as appropriate.

CpODA: norbornane-2-spiro-alpha-cyclopentanone-alpha '-spiro-2' -norbornane-5, 5 ', 6, 6' -tetracarboxylic dianhydride

CpODA et al: norbornane-2-spiro- α -cyclopentanone- α' -spiro-2 ″ -norbornane-5, 5 ″,6,6 ″ -tetracarboxylic acids and the like (tetracarboxylic acids and the like mean tetracarboxylic acid and tetracarboxylic acid dianhydride, tetracarboxylic acid silyl ester, tetracarboxylic acid chloride and other tetracarboxylic acid derivatives)

TFMB: 2, 2' -bis (trifluoromethyl) benzidine

The tetracarboxylic acid component providing the 4-valent group represented by the formula (A-1) is CpODA or the like, and the diamine component providing the 2-valent group represented by the formula (B-1) is TFMB. Polyimides derived from CpODA et al and TFMB (i.e., from A)₁Is a 4-valent group represented by the formula (A-1) above, B₁A polyimide obtained from a polyimide precursor comprising a repeating unit of the general formula (1) which is a 2-valent group represented by the formula (B-1), and a polyimide₂Is a 4-valent group represented by the formula (A-1) above, B₂Polyimide comprising the repeating unit of the general formula (5) which is a 2-valent group represented by the formula (B-1) has high transparency and a low linear thermal expansion coefficient, but tends to have a relatively large retardation (retardation) in the thickness direction. When a polyimide film is used for a display or the like, if the phase difference in the thickness direction is large as described above, problems such as failure to accurately display the color of transmitted light, color blur, and a narrow viewing angle may occur. On the other hand, the component A in the general formula (1) which is a structure derived from a tetracarboxylic acid component is added in the above-mentioned content (ratio)₁A of the formula (5)₂And/or B of the general formula (1) as a structure derived from a diamine component₁B of the general formula (5)₂In which a group having a structure represented by the above formula (2) is introduced, or in which A in the general formula (1) is a structure derived from a tetracarboxylic acid component₁A of the formula (5)₂Wherein the 4-valent group represented by the formula (3) and/or the 4-valent group represented by the formula (4) is introduced intoThe thickness direction phase difference (retardation) is reduced while maintaining high transparency and a low linear thermal expansion coefficient. As a result, a polyimide having high transparency, a low linear thermal expansion coefficient, and a small retardation (retardation) in the thickness direction can be obtained.

In the structure represented by the above formula (2), the adjacent aromatic rings may be further connected by a direct bond, an ether bond or the like, and may be, for example, a structure represented by the following formula (2').

[ solution 13]

(wherein R is a direct bond or an ether bond (-O-))

The aromatic ring included in the structure represented by the above formula (2) may be substituted with a substituent such as an alkyl group such as a methyl group, a fluoroalkyl group such as a trifluoromethyl group, or a halogen group, but it is generally preferable that the aromatic ring does not have a substituent. The substitution position is not particularly limited.

Examples of tetracarboxylic acid components which provide a 4-valent group having a structure represented by the above formula (2) include tetracarboxylic acids having a structure represented by the above formula (2), and examples thereof include 9, 9' -bis (3, 4-dicarboxyphenyl) fluorene dianhydride and other derivatives (tetracarboxylic acid derivatives other than tetracarboxylic acid dianhydrides such as tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides). The diamine component providing the 2-valent group having the structure represented by the formula (2) is a diamine having the structure represented by the formula (2), and examples thereof include 9, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, 9-bis (4-amino-3-fluorophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, and 4,4 '- (spiro [ fluorene-9, 9' -xanthene ] -3 ', 6' -diylbis (oxy)) diphenylamine.

The tetracarboxylic acid component which provides the 4-valent group represented by the formula (3) is 1,2,4, 5-cyclohexanetetracarboxylic acid or the like.

The tetracarboxylic acid component providing the 4-valent group represented by the formula (4) is 2,3,3 ', 4' -biphenyltetracarboxylic acid or the like.

In other words, with respect to the polyimide precursor of the present invention and the polyimide of the present invention,

obtained from a tetracarboxylic acid component comprising (a-1) CpODA or the like and (a-2) a tetracarboxylic acid having a structure represented by the above formula (2), 1,2,4, 5-cyclohexanetetracarboxylic acid or the like, 2,3,3 ', 4' -biphenyltetracarboxylic acid or the like, and (b) a diamine component comprising TFMB, or a diamine component comprising TFMB and a diamine having a structure represented by the above formula (2), or,

obtained from (a) a tetracarboxylic acid component containing CpODA or the like and (b) a diamine component containing TFMB and a diamine having a structure represented by the above formula (2).

As the tetracarboxylic acid component CpODA or the like used herein, among the 6 kinds of steric isomers, there may be cases where it is preferable to include (trans-endo) tetracarboxylic acids and/or (cis-endo-norbornane-2-spiro- α -cyclopentanone- α' -spiro-2 ″ -norbornane-5, 5 ″,6,6 ″ -tetracarboxylic acids and the like (trans-endo-isomers). In one embodiment, the total proportion of the trans-endo and/or cis-endo in CpODA or the like is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

The tetracarboxylic acid component 1,2,4, 5-cyclohexanetetracarboxylic acid used herein may preferably contain 1R,2S,4S, 5R-cyclohexanetetracarboxylic acid among the 6 kinds of steric isomers. In one embodiment, the proportion of 1R,2S,4S, 5R-cyclohexanetetracarboxylic acids in 1,2,4, 5-cyclohexanetetracarboxylic acids or the like is preferably 50 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and particularly preferably 95 mol% or more.

CpODA and the like may be used singly or in combination of two or more. Further, one kind of tetracarboxylic acid having a structure represented by the above formula (2), 1,2,4, 5-cyclohexane tetracarboxylic acid, and 2,3,3 ', 4' -biphenyl tetracarboxylic acid may be used alone, or two or more kinds may be used in combination. One kind of diamine having the structure represented by the above formula (2) may be used alone, or two or more kinds may be used in combination.

As the other tetracarboxylic acid component which provides the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5), any of other aromatic or alicyclic tetracarboxylic acids can be used. Examples of the solvent include, but are not particularly limited to, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, 4- (2, 5-dioxotetrahydrofuran-3-yl) -1,2,3, 4-tetrahydronaphthalene-1, 2-dicarboxylic acid, pyromellitic acid, 3 ', 4,4 ' -benzophenonetetracarboxylic acid, 3 ', 4,4 ' -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, dicarboxyphenyldimethylsilane, bis-dicarboxyphenoxydiphenyl sulfide, sulfonyl bisphthalic acid, 1,2,3, 4-cyclobutanetetracarboxylic acid, isopropylidenedioxybisphthalic acid, [1,1 '-bicyclohexyl ] -3, 3', 4,4 '-tetracarboxylic acid, [1, 1' -bicyclohexyl ] -2,3,3 ', 4' -tetracarboxylic acid, [1,1 '-bicyclohexyl ] -2, 2', 3,3 '-tetracarboxylic acid, 4, 4' -methylenebis (cyclohexane-1, 2-dicarboxylic acid), 4,4 '- (propane-2, 2-diyl) bis (cyclohexane-1, 2-dicarboxylic acid), 4, 4' -oxybis (cyclohexane-1, 2-dicarboxylic acid), 4,4 '-thiobis (cyclohexane-1, 2-dicarboxylic acid), 4, 4' -sulfonylbis (cyclohexane-1, 2-dicarboxylic acid), 4 '- (dimethylsilanediyl) bis (cyclohexane-1, 2-dicarboxylic acid), 4' - (tetrafluoropropane-2, 2-diyl) bis (cyclohexane-1, 2-dicarboxylic acid), octahydropentalene-1, 3,4, 6-tetracarboxylic acid, bicyclo [2.2.1] heptane-2, 3,5, 6-tetracarboxylic acid, 6- (carboxymethyl) bicyclo [2.2.1] heptane-2, 3, 5-tricarboxylic acid, bicyclo [2.2.2] octane-2, 3,5, 6-tetracarboxylic acid, bicyclo [2.2.2] oct-5-ene-2, 3,7, 8-tetracarboxylic acid, tricyclo [4.2.2.02,5] decane-3, 4,7, 8-tetracarboxylic acid, tricyclo [4.2.2.02,5] dec-7-ene-3, 4,9, 10-tetracarboxylic acid, 9-oxatricyclo [4.2.1.02,5] nonane-3, 4,7, 8-tetracarboxylic acid, (4arH,8acH) -decahydro-1 t,4t:5c,8 c-dimethylnaphthalene-2 c,3c,6c,7 c-tetracarboxylic acid, (4arH,8acH) -decahydro-1 t,4t:5c,8 c-dimethylnaphthalene-2 t,3t,6c,7 c-tetracarboxylic acid, and derivatives of these tetracarboxylic acids (tetracarboxylic dianhydrides and the like). Among these, derivatives such as 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, 4' -oxydiphthalic acid, 1,2,3, 4-cyclobutanetetracarboxylic acid, (4arH,8acH) -decahydro-1 t,4t:5c,8 c-dimethylnaphthalene-2 c,3c,6c,7 c-tetracarboxylic acid, (4arH,8acH) -decahydro-1 t,4t:5c,8 c-dimethylnaphthalene-2 t,3t,6c,7 c-tetracarboxylic acid and acid dianhydrides thereof are more preferable. These tetracarboxylic acid components may be used alone, or two or more kinds thereof may be used in combination.

As the other diamine component that provides the repeating unit of the above general formula (1) or the repeating unit represented by the above general formula (5), any of other aromatic or alicyclic diamines can be used. Examples of the monomer include, but are not particularly limited to, p-phenylenediamine, m-phenylenediamine, benzidine, 3 '-diaminobiphenyl, 3' -bis (trifluoromethyl) benzidine, m-tolidine, 4 '-diaminobenzanilide, 3, 4' -diaminobenzanilide, N '-bis (4-aminophenyl) terephthalamide, N' -p-phenylenebis (p-aminobenzamide), 4-aminophenoxy-4-diaminobenzoate, bis (4-aminophenyl) terephthalate, bis (4-aminophenyl) biphenyl-4, 4 '-dicarboxylic acid bis (4-aminophenyl) ester, p-phenylenebis (p-aminobenzoate), bis (4-aminophenyl) - [1, 1' -biphenyl ] -4,4 ' -dicarboxylic acid ester, [1,1 ' -biphenyl ] -4,4 ' -diylbis (4-aminobenzoate), 4 ' -oxydianiline, 3 ' -oxydianiline, bis (4-aminophenyl) sulfide, p-methylenebis (phenylenediamine), 1, 3-bis (4-aminophenoxy) benzene, 1, 3-bis (3-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, 2-bis (4-aminophenyl) hexafluoropropane, bis (4-aminophenyl) sulfone, 3-bis ((aminophenoxy) phenyl) propane, 2, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, bis (4- (4-aminophenoxy) diphenyl) sulfone, bis (4- (3-aminophenoxy) diphenyl) sulfone, octafluorobenzidine, 3 '-dimethoxy-4, 4' -diaminobiphenyl, 3 '-dichloro-4, 4' -diaminobiphenyl, 3 '-difluoro-4, 4' -diaminobiphenyl, 4 '-bis (4-aminophenoxy) biphenyl, 4' -bis (3-aminophenoxy) biphenyl, 1, 4-diaminocyclohexane, 1, 4-diamino-2-methylcyclohexane, 1, 4-diamino-2-ethylcyclohexane, bis (4-aminophenoxy) diphenyl sulfone, bis (4- (3-aminophenoxy) diphenyl) sulfone, bis (4-amino-4-diaminobiphenyl, 1, 4-diamino-2-n-propylcyclohexane, 1, 4-diamino-2-isopropylcyclohexane, 1, 4-diamino-2-n-butylcyclohexane, 1, 4-diamino-2-isobutylcyclohexane, 1, 4-diamino-2-sec-butylcyclohexane, 1, 4-diamino-2-tert-butylcyclohexane, 1, 2-diaminocyclohexane, 1, 4-diaminocyclohexane, and the like, or derivatives thereof. Among these, p-phenylenediamine, m-toluidine, 4 '-oxydianiline, 1, 4-bis (4-aminophenoxy) benzene, 4' -bis (4-aminophenoxy) biphenyl, and the like are more preferable. These diamine components may be used alone, or two or more thereof may be used in combination.

The polyimide precursor of the present invention and the polyimide of the present invention may contain one or more kinds of other repeating units other than the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5). The tetracarboxylic acid component and the diamine component which provide the other repeating units are not particularly limited, and any other known tetracarboxylic acids and any known diamines may be used. In addition, in the case where the diamine component to be combined is not a diamine component which provides the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5), the tetracarboxylic acid component which provides another repeating unit may be a tetracarboxylic acid exemplified as a tetracarboxylic acid component which provides the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5) (including CpODA and the like, tetracarboxylic acids having a structure represented by the above general formula (2) and the like, 1,2,4, 5-cyclohexane tetracarboxylic acids and the like, 2,3,3 ', 4' -biphenyl tetracarboxylic acids and the like). In the case where the tetracarboxylic acid component to be combined is not a tetracarboxylic acid component that provides the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5), the diamine component that provides another repeating unit may be a diamine (including TFMB, a diamine having a structure represented by the above general formula (2)) exemplified as a diamine component that provides the repeating unit represented by the above general formula (1) or the repeating unit represented by the above general formula (5).

In the polyimide precursor of the present invention, R in the above general formula (1)₁、R₂Each independently is any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms (particularly preferably a methyl group or an ethyl group), or an alkylsilyl group having 3 to 9 carbon atoms (particularly preferably a trimethylsilyl group or a tert-butyldimethylsilyl group). For R₁、R₂It can be changed by the manufacturing method described laterThe kind of the functional group and the introduction rate of the functional group.

The introduction rate of the functional group is not particularly limited, and when an alkyl group or an alkylsilyl group is introduced, R may be allowed to be introduced₁、R₂25% or more, preferably 50% or more, more preferably 75% or more of each is an alkyl group or an alkylsilyl group. By reacting R₁、R₂25% or more of each of them is an alkyl group or an alkylsilyl group, and the polyimide precursor has excellent storage stability.

According to R₁And R₂The polyimide precursors of the present invention can be classified into the following chemical structures, each independently taken: 1) polyamic acid (R)₁And R₂Hydrogen), 2) polyamic acid ester (R)₁、R₂At least a part of (1) is an alkyl group), 3)4) polyamic acid silyl ester (R)₁、R₂At least a portion of (a) is an alkylsilyl group). The polyimide precursor of the present invention can be easily produced by the following production method according to this classification. However, the method for producing the polyimide precursor of the present invention is not limited to the following production method.

1) Polyamic acid

The polyimide precursor of the present invention can be suitably obtained as a polyimide precursor solution composition by reacting a tetracarboxylic dianhydride and a diamine component as tetracarboxylic acid components in a solvent in a substantially equimolar amount, preferably in a ratio of the molar ratio of the diamine component to the tetracarboxylic acid component [ the number of moles of the diamine component/the number of moles of the tetracarboxylic acid component ] of preferably 0.90 to 1.10, more preferably 0.95 to 1.05, while suppressing imidization at a relatively low temperature of, for example, 120 ℃.

The method for synthesizing the polyimide precursor of the present invention is not limited, and more specifically, the polyimide precursor is obtained by dissolving diamine in an organic solvent, slowly adding tetracarboxylic dianhydride to the solution while stirring, and stirring at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours. The order of addition of the diamine and the tetracarboxylic dianhydride in the above production method is preferable because the molecular weight of the polyimide precursor is easily increased. In addition, the order of addition of the diamine and the tetracarboxylic dianhydride in the above production method may be reversed, and precipitates may be reduced, which is preferable.

In the case where the molar ratio of the tetracarboxylic acid component to the diamine component is in excess of the diamine component, the molar ratio of the tetracarboxylic acid component to the diamine component may be brought close to approximately the same amount by adding the carboxylic acid derivative in an amount approximately corresponding to the excess molar number of the diamine component, if necessary. As the carboxylic acid derivative herein, tetracarboxylic acid which does not substantially increase the viscosity of the polyimide precursor solution, that is, does not substantially participate in molecular chain extension is preferable; or tricarboxylic acids and anhydrides thereof, dicarboxylic acids and anhydrides thereof, and the like which function as a capping agent.

2) Polyamide acid ester

Tetracarboxylic dianhydride is reacted with an arbitrary alcohol to obtain a dicarboxylic acid diester, and then reacted with a chlorinating agent (thionyl chloride, oxalyl chloride, or the like) to obtain a diester dicarboxylic acid chloride. The diester dicarboxylic acid chloride and the diamine are stirred at-20 to 120 ℃, preferably-5 to 80 ℃ for 1 to 72 hours, thereby obtaining a polyimide precursor. Further, a polyimide precursor can also be obtained simply by dehydrating and condensing a dicarboxylic acid diester and a diamine using a phosphorus-based condensing agent, a carbodiimide condensing agent, or the like.

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

3) Polyamic acid silyl ester (Indirect method)

The diamine is reacted with a silylating agent in advance to obtain a silylated diamine. The silylated diamine is purified by distillation or the like as necessary. Then, the silylated diamine is dissolved in the dehydrated solvent, the tetracarboxylic dianhydride is slowly added while stirring, and the mixture is stirred at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours to obtain a polyimide precursor.

When a chlorine-free silylating agent is used as the silylating agent used here, it is not necessary to purify the silylated diamine, which is preferable. Examples of the silylating agent containing no chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable for reasons of no fluorine atom and low cost.

In addition, in the silylation reaction of the diamine, an amine-based catalyst such as pyridine, piperidine, triethylamine or the like may be used in order to accelerate the reaction. The catalyst can be used as a polymerization catalyst for the polyimide precursor.

4) Polyamic acid silyl ester (direct Process)

Mixing the polyamic acid solution obtained in the method 1) with a silylating agent, and stirring the mixture at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours to obtain a polyimide precursor.

When a chlorine-free silylating agent is used as the silylating agent used here, it is not necessary to purify the silylated polyamic acid or the resulting polyimide, which is preferable. Examples of the silylating agent containing no chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable for reasons of no fluorine atom and low cost.

Since the above-described production methods can be carried out in an organic solvent as appropriate, the varnish of the polyimide precursor of the present invention can be easily obtained as a result.

The solvent used for the preparation of the polyimide precursor is preferably an aprotic solvent such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, or dimethylsulfoxide, and particularly preferably N, N-dimethylacetamide or N-methyl-2-pyrrolidone, and any solvent can be used without any problem as long as it can dissolve the raw material monomer component and the polyimide precursor to be produced, and the structure thereof is not particularly limited. As the solvent, an amide solvent such as N, N-dimethylformamide, N-dimethylacetamide, or N-methylpyrrolidone, a cyclic ester solvent such as γ -butyrolactone, γ -valerolactone, γ -caprolactone, or α -methyl- γ -butyrolactone, a carbonate solvent such as ethylene carbonate or propylene carbonate, a glycol solvent such as triethylene glycol, a phenol solvent such as m-cresol, p-cresol, 3-chlorophenol, or 4-chlorophenol, acetophenone, 1, 3-dimethyl-2-imidazolidinone, sulfolane, or dimethyl sulfoxide is preferably used. In addition, other common organic solvents, that is, 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, turpentine, mineral spirits, naphtha solvents, and the like can also be used. Two or more solvents may be used in combination.

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 0.5g/dL at 30 ℃ is preferably 0.2dL/g or more, more preferably 0.8dL/g or more, and particularly preferably 0.9dL/g or more. When the logarithmic viscosity is 0.2dL/g or more, the molecular weight of the polyimide precursor is high, and the obtained polyimide is excellent in mechanical strength and heat resistance.

In the present invention, the varnish of the polyimide precursor (polyimide precursor solution composition) contains at least the polyimide precursor of the present invention and a solvent, and the total amount of the tetracarboxylic acid component and the diamine component is preferably 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more, based on the total amount of the solvent, the tetracarboxylic acid component and the diamine component. It is usually preferably 60% by mass or less, and preferably 50% by mass or less. This concentration is a concentration approximately similar to the solid content concentration of the polyimide precursor, and when this concentration is too low, it is sometimes difficult to control the film thickness of the polyimide film obtained, for example, in the production of the polyimide film.

The solvent used in the varnish of the polyimide precursor of the present invention is not particularly limited as long as it can dissolve the polyimide precursor, and the structure thereof is not particularly limited. The solvent for the varnish of the polyimide precursor may be the same solvent as that used for the preparation of the polyimide precursor, and the solvent used for the preparation of the polyimide precursor may be used as it is as a solvent for the varnish of the polyimide precursor. Further, the solvent may be removed from the polyimide precursor solution prepared as described above or a solvent may be added thereto, as necessary.

In the present invention, the viscosity (rotational viscosity) of the varnish of the polyimide precursor is not particularly limited, and an E-type rotational viscometer is used at a temperature of 25 ℃ and a shear rate of 20sec^-1The rotational viscosity measured under the conditions (1) is preferably 0.01 to 1000 Pa.sec, more preferably 0.1 to 100 Pa.sec. Further, thixotropy may be imparted as necessary. At a viscosity within the above range, handling is easy when coating or film formation is performed, and a good coating film can be obtained because shrinkage is suppressed and leveling property is excellent.

The varnish of the polyimide precursor of the present invention may contain, as necessary, a chemical imidizing agent (an acid anhydride such as acetic anhydride, and an amine compound such as pyridine or isoquinoline), an antioxidant, a filler (inorganic particles such as silica), a coupling agent such as a dye, a pigment or a silane coupling agent, a primer, a flame retardant material, an antifoaming agent, a leveling agent, a rheology control agent (flow aid) or a release agent.

The polyimide of the present invention can be suitably produced by subjecting the polyimide precursor of the present invention as described above to a dehydration ring-closure reaction (imidization reaction). The method of imidization is not particularly limited, and a known thermal imidization or chemical imidization method can be suitably applied.

The form of the polyimide obtained may be suitably exemplified by films, laminates of polyimide films and other substrates, coating films, powders, beads, molded bodies, foams, varnishes and the like.

Hereinafter, an example of a polyimide film/substrate laminate or a method for producing a polyimide film using the polyimide precursor of the present invention will be described. However, the method is not limited to the following method.

The varnish of the polyimide precursor of the present invention is cast and coated on a substrate, and dried in vacuum, in an inert gas such as nitrogen or in air, using hot air or infrared rays at a temperature in the range of 20 to 180 ℃, preferably 20 to 150 ℃. Then, the polyimide film/substrate laminate or the polyimide film can be produced by heating and imidizing the polyimide film obtained on a substrate or by peeling the polyimide film from the substrate and fixing the ends of the film in vacuum, in an inert gas such as nitrogen, or in air, using hot air or infrared rays at a temperature of about 200 to 500 ℃, more preferably about 250 to 450 ℃. In order to prevent the polyimide film obtained from oxidative deterioration, thermal imidization is preferably performed in a vacuum or in an inert gas. The imidization may be carried out in air as long as the temperature for heating is not too high.

Here, the substrate is not particularly limited, and for example, a substrate such as ceramic (glass, silicon, alumina), metal (copper, aluminum, stainless steel), heat-resistant plastic film (polyimide film), or the like can be used. In one embodiment, the substrate is preferably glass, and a polyimide film/glass substrate laminate in which a polyimide film is formed on a glass substrate is suitably used for manufacturing a substrate for a display, for example.

In addition, instead of the thermal imidization by the thermal treatment as described above, the imidization reaction of the polyimide precursor may be performed by a chemical treatment such as dipping the polyimide precursor in a solution containing a cyclodehydration reagent such as acetic anhydride in the presence of a tertiary amine such as pyridine or triethylamine. Further, a polyimide film/substrate laminate or a polyimide film can be obtained by adding these cyclodehydration agents to a varnish of a polyimide precursor in advance, stirring the mixture, casting the cast product on a substrate, and drying the cast product to prepare a partially imidized polyimide precursor, and then subjecting the precursor to the heat treatment as described above.

The polyimide of the present invention can also be suitably produced by the following method: a solution composition (varnish) containing the polyimide of the present invention is prepared by reacting a tetracarboxylic acid component and a diamine component in a solvent, and the solvent is removed from the prepared polyimide solution composition by heating or the like.

Examples of the method for producing the polyimide solution composition (varnish containing polyimide) of the present invention, and the method for producing a polyimide film/substrate laminate or a polyimide film using the polyimide solution composition are described below. However, the method is not limited to the following method.

The polyimide solution composition of the present invention can be suitably obtained by reacting a tetracarboxylic acid component such as tetracarboxylic dianhydride with a diamine component in a solvent in a ratio of approximately equimolar, preferably in a molar ratio of the diamine component to the tetracarboxylic acid component [ the number of moles of the diamine component/the number of moles of the tetracarboxylic acid component ], preferably 0.90 to 1.10, and more preferably 0.95 to 1.05.

More specifically, a diamine component is dissolved in a solvent, a tetracarboxylic acid component such as tetracarboxylic dianhydride is slowly added to the solution while stirring, and after stirring for 0.5 to 30 hours at room temperature to 80 ℃ as necessary, the temperature is raised to perform an imidization reaction, thereby obtaining a polyimide solution. After the tetracarboxylic acid component is added, the temperature may be immediately raised to perform the imidization reaction. In addition, the order of addition of the diamine component and the tetracarboxylic acid component may be reversed, or the diamine component and the tetracarboxylic acid component may be added to the solvent at the same time.

The method of imidization is not particularly limited, and a known thermal imidization or chemical imidization method can be suitably applied. For example, the imidization reaction can be carried out by stirring a solution containing a tetracarboxylic acid component such as tetracarboxylic dianhydride and a diamine component at a temperature in the range of 100 ℃ or higher, preferably 120 ℃ or higher, and more preferably 150 to 250 ℃ for 0.5 to 72 hours to react the tetracarboxylic acid component with the diamine component. In the case of chemical imidization, a chemical imidizing agent (an acid anhydride such as acetic anhydride, and an amine compound such as pyridine, isoquinoline, and triethylamine) is added to the reaction solution to perform a reaction. If necessary, an imidization catalyst or the like may be added to the reaction solution to carry out the reaction.

Further, the imidization reaction can be carried out while removing water produced during the reaction.

When the molar ratio of the tetracarboxylic acid component to the diamine component is in excess of the diamine component, the molar ratio of the tetracarboxylic acid component to the diamine component can be made nearly equal by adding the carboxylic acid derivative in an amount approximately corresponding to the excess molar number of the diamine component, if necessary. As the carboxylic acid derivative herein, tetracarboxylic acid which does not substantially increase the viscosity of the polyimide solution, that is, does not substantially participate in molecular chain extension is preferable; or tricarboxylic acids and anhydrides thereof, dicarboxylic acids and anhydrides thereof, and the like which function as a capping agent.

The solvent used for preparing the polyimide solution is preferably an aprotic solvent such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, or dimethylsulfoxide, and particularly preferably N, N-dimethylacetamide or N-methyl-2-pyrrolidone, and any solvent can be used without any problem as long as it can dissolve the raw material monomer component and the polyimide to be produced, and the structure thereof is not particularly limited. As the solvent, an amide solvent such as N, N-dimethylformamide, N-dimethylacetamide, or N-methylpyrrolidone, a cyclic ester solvent such as γ -butyrolactone, γ -valerolactone, γ -caprolactone, or α -methyl- γ -butyrolactone, a carbonate solvent such as ethylene carbonate or propylene carbonate, a glycol solvent such as triethylene glycol, a phenol solvent such as m-cresol, p-cresol, 3-chlorophenol, or 4-chlorophenol, acetophenone, 1, 3-dimethyl-2-imidazolidinone, sulfolane, or dimethyl sulfoxide is preferably used. In addition, other common organic solvents, that is, 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, turpentine, mineral spirits, naphtha solvents, and the like can also be used. Two or more solvents may be used in combination.

After the imidization reaction is carried out as described above, the obtained reaction solution may be used as it is or after being concentrated or diluted, and further, if necessary, additives described later and the like may be added to the reaction solution, and used as the polyimide solution composition of the present invention. Alternatively, the soluble polyimide may be separated from the obtained reaction solution, and the separated polyimide may be added to a solvent to obtain the polyimide solution composition (varnish) of the present invention. The polyimide can be isolated, for example, by dropping or mixing the obtained reaction solution containing soluble polyimide into a poor solvent such as water to precipitate (reprecipitate) the polyimide.

The polyimide solution composition (polyimide varnish) of the present invention contains at least the polyimide of the present invention and a solvent, and the polyimide is preferably contained in a proportion of 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, based on the total amount of the solvent and the polyimide. When the concentration is too low, it is sometimes difficult to control the film thickness of the polyimide film obtained, for example, in the production of the polyimide film. Usually, the polyimide is preferably 60% by mass or less, and preferably 50% by mass or less.

The solvent of the polyimide solution composition of the present invention is not particularly limited as long as it can dissolve the polyimide, and the structure thereof is not particularly limited. The solvent for the polyimide solution composition may be the same solvent as that used for the preparation of the polyimide solution, and the solvent used for the preparation of the polyimide solution may be used as it is as the solvent for the polyimide solution composition. Further, the solvent may be removed from the polyimide solution composition prepared as described above or a solvent may be added thereto, as necessary.

In the present invention, the logarithmic viscosity of the polyimide is not particularly limited, but the logarithmic viscosity in an N, N-dimethylacetamide solution having a concentration of 0.5g/dL at 30 ℃ is preferably 0.2dL/g or more, more preferably 0.4dL/g or more, and particularly preferably 0.5dL/g or more. When the logarithmic viscosity is 0.2dL/g or more, the obtained polyimide is excellent in mechanical strength and heat resistance.

In the present invention, the viscosity (rotational viscosity) of the polyimide solution composition is not particularly limited, and an E-type rotational viscometer is used at a temperature of 25 ℃ and a shear rate of 20sec^-1The rotational viscosity measured under the conditions (1) is preferably 0.01 to 1000 Pa.sec, more preferably 0.1 to 100 Pa.sec. Further, thixotropy may be imparted as necessary. At a viscosity within the above range, handling is easy when coating or film formation is performed, and a good coating film can be obtained because shrinkage is suppressed and leveling property is excellent.

The polyimide solution composition of the present invention may contain, as required, a filler (inorganic particles such as silica), a coupling agent such as a dye, a pigment, or a silane coupling agent, a primer, a flame retardant, an antifoaming agent, a leveling agent, a rheology control agent (flow aid), a release agent, and the like.

The polyimide of the present invention can be suitably obtained by removing the solvent from the polyimide solution composition prepared as above. For example, a polyimide film/substrate laminate can be produced by casting and coating a polyimide solution composition on a substrate, heating the polyimide solution composition on the substrate, and removing the solvent. The temperature of the heat treatment is not particularly limited, but is usually 80 to 500 ℃, preferably 100 to 500 ℃, and more preferably 150 to 450 ℃. The heat treatment may be performed in vacuum, in an inert gas such as nitrogen, or in air, and is preferably performed in vacuum or in an inert gas. Then, the polyimide film formed on the substrate is peeled off from the substrate, whereby a polyimide film can be produced.

Here, the substrate is not particularly limited, and for example, a substrate such as ceramic (glass, silicon, alumina), metal (copper, aluminum, stainless steel), heat-resistant plastic film (polyimide film), or the like can be used. In one embodiment, the substrate is preferably glass, and a polyimide film/glass substrate laminate in which a polyimide film is formed on a glass substrate is suitably used for manufacturing a substrate for a display, for example.

Further, a polyimide film can also be suitably produced by casting and coating the polyimide solution composition on a substrate, drying the polyimide solution composition on the substrate to such an extent that the polyimide solution composition is self-supporting, peeling the obtained self-supporting film from the substrate, heating the film in a state where the end of the film is fixed, and removing the solvent. The drying conditions for producing the self-supporting film may be appropriately determined, and for example, the polyimide solution composition may be dried on the substrate at a temperature of about 50 to 300 ℃. The temperature of the heat treatment of the self-supporting film is not particularly limited, and is usually 80 to 500 ℃, preferably 100 to 500 ℃, and more preferably 150 to 480 ℃. In this method, the heat treatment may be performed in vacuum, in an inert gas such as nitrogen, or in air, and is preferably performed in vacuum or in an inert gas.

The form of the polyimide obtained from the polyimide solution composition is not limited to a film, a laminate of a polyimide film and other substrates, and a coating film, powder, beads, a molded article, a foam, and the like can be appropriately exemplified.

The polyimide of the present invention thus obtained has a linear thermal expansion coefficient of preferably 40ppm/K or less, more preferably 35ppm/K or less, more preferably 30ppm/K or less, and particularly preferably 25ppm/K or less, when measured as a film having a thickness of 10 μm at 100 to 250 ℃. When the linear thermal expansion coefficient is large, the difference between the linear thermal expansion coefficient and that of a conductor such as a metal is large, and there may be a case where a defect such as an increase in warpage occurs when a circuit board is formed.

The polyimide of the present invention has a light transmittance at a wavelength of 400nm, which is not particularly limited, when measured as a film having a thickness of 10 μm, and is preferably 80% or more, more preferably 83% or more, and particularly preferably 85% or more. When a polyimide film is used for display applications or the like, a strong light source is required when the light transmittance is low, and problems such as power consumption may occur.

The haze of the polyimide of the present invention measured as a film having a thickness of 10 μm is not particularly limited, but is preferably 2% or less, more preferably 1.5% or less, and particularly preferably 1% or less. When a polyimide film is used for display applications or the like, light may be scattered and an image may be blurred when the haze is high.

The thickness direction retardation (Rth) of the polyimide of the present invention when measured as a film having a thickness of 10 μm is not particularly limited, but is preferably 500nm or less, more preferably 350nm or less, and particularly preferably 400nm or less. When a polyimide film is used for display applications or the like, when the retardation in the thickness direction is large, problems such as failure to accurately display the color of transmitted light, color blurring, and a narrow viewing angle may occur.

The thickness of the film comprising the polyimide of the present invention varies depending on the application, and the thickness of the film is preferably 1 to 250 μm, more preferably 1 to 150 μm, further preferably 1 to 100 μm, and particularly preferably 1 to 80 μm. When a polyimide film is used for applications that transmit light, the light transmittance may decrease if the polyimide film is too thick.

The polyimide film/base material laminate or polyimide film obtained as described above can be provided with a flexible conductive substrate by forming a conductive layer on one or both surfaces thereof.

The flexible conductive substrate can be obtained, for example, by the following method. That is, as a first method, a conductive layer/polyimide film/substrate laminate is manufactured by forming a conductive layer of a conductive material (metal or metal oxide, conductive organic material, conductive carbon, or the like) on the surface of a polyimide film by sputtering, vapor deposition, printing, or the like without peeling the polyimide film from the substrate. Then, the conductive layer/polyimide film laminate is peeled off from the base material as necessary, whereby a transparent and flexible conductive substrate composed of the conductive layer/polyimide film laminate can be obtained.

As a second method, a transparent and flexible conductive substrate composed of a conductive layer/polyimide film laminate or a conductive layer/polyimide film/conductive layer laminate can be obtained by peeling a polyimide film from a substrate of a polyimide film/substrate laminate to obtain a polyimide film, and forming a conductive layer of a conductive substance (metal or metal oxide, conductive organic substance, conductive carbon, or the like) on the surface of the polyimide film in the same manner as in the first method.

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

The conductive layer can be formed into a circuit by a method such as photolithography, various printing methods, or an ink jet method.

The substrate of the present invention thus obtained is a circuit substrate having a conductive layer on the surface of a polyimide film made of the polyimide of the present invention, with a gas barrier layer or an inorganic layer interposed therebetween as necessary. The substrate is flexible, has high transparency, excellent bendability and heat resistance, and has a low linear thermal expansion coefficient, and thus a fine circuit can be easily formed. Therefore, the substrate is suitable for use as a substrate for a display, a touch panel, or a solar cell.

That is, a transistor (an inorganic transistor or an organic transistor) is further formed on the substrate by vapor deposition, various printing methods, an ink-jet method, or the like, thereby producing a flexible thin film transistor, which is suitable for use as a liquid crystal element, an EL element, or an electro-optical element for a display device.

In the first method, after the conductive layer and at least a part of other elements or structures necessary for the transistor and/or the device are formed on the surface of the polyimide film/substrate laminated body, the substrate may be peeled off.