阅读说明：本技术 聚酰亚胺、聚酰亚胺溶液组合物、聚酰亚胺膜和基板 (Polyimide, polyimide solution composition, polyimide film, 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,其是包含相对于全部重复单元多于50摩尔％的下述化学式(1)所表示的重复单元的聚酰亚胺,在以厚度为10μm的膜进行测定的情况下,100～250℃之间的线性热膨胀系数为25ppm/K以下,并且,400nm波长的光透射率为80％以上。<Image he="244" wi="700" file="DDA0002635390280000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The present invention provides a polyimide which contains more than 50 mol% of a repeating unit represented by the following chemical formula (1) relative to the total repeating units, has a coefficient of linear thermal expansion of 25ppm/K or less at 100 to 250 ℃ when measured on a film having a thickness of 10 [ mu ] m, and has a light transmission of 400nm wavelengthThe rate is more than 80%.)

1. A polyimide comprising more than 50 mol% of a repeating unit represented by the following chemical formula (1) relative to the total repeating units,

in the case of measurement with a film thickness of 10 μm,

a linear thermal expansion coefficient of 25ppm/K or less at 100 to 250 ℃, and,

a light transmittance at a wavelength of 400nm of 80% or more,

[ solution 1]

2. A polyimide solution composition characterized by comprising a solvent and a polyimide dissolved therein, wherein the polyimide comprises more than 50 mol% of a repeating unit represented by the following chemical formula (1) relative to the total repeating units and has an imidization ratio of more than 90%,

[ solution 2]

3. A polyimide obtained by removing a solvent from the polyimide solution composition according to claim 2.

4. A polyimide film obtained by removing a solvent from the polyimide solution composition according to claim 2.

5. The polyimide according to claim 3 or the polyimide film according to claim 4, wherein a linear thermal expansion coefficient between 100 ℃ and 250 ℃ is 25ppm/K or less, and a light transmittance at a wavelength of 400nm is 80% or more, when measured at a film thickness of 10 μm.

6. A laminate comprising a glass substrate and a film comprising the polyimide according to claim 1 or the polyimide film according to claim 4 or 5 formed thereon.

7. A substrate for a display, a touch panel, or a solar cell, which comprises the polyimide according to claim 1 or 3 or the polyimide film according to claim 4 or 5.

8. A method for producing a polyimide film/substrate laminate, comprising:

a step of applying the polyimide solution composition according to claim 2 to a substrate; and

and heating the polyimide solution composition on a substrate.

9. A method for producing a polyimide film, comprising:

a step of applying the polyimide solution composition according to claim 2 to a substrate;

heating the polyimide solution composition on a substrate; and

and a step of peeling the polyimide film formed on the substrate from the substrate.

10. A method for producing a polyimide film, comprising:

a step of applying the polyimide solution composition according to claim 2 to a substrate;

drying the polyimide solution composition to obtain a self-supporting film; and

and a step of peeling the self-supporting film from the substrate and heating the peeled film.

Technical Field

The present invention relates to a polyimide having high transparency and an extremely low coefficient of linear thermal expansion, and a polyimide solution composition from which a polyimide having high transparency and an extremely low coefficient of linear thermal expansion can be obtained. In addition, the present invention also relates to a polyimide film 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. However, in the examples of patent documents 1 and 2, although the polyimide obtained from CpODA and a diamine component containing 50 mol% or more of TFMB has high transparency, the linear thermal expansion coefficient tends to be relatively large. When the polyimide has a large coefficient of linear thermal expansion and a large difference from the coefficient of linear thermal expansion of a conductor such as a metal, warpage may occur when a circuit board is formed, and it may be difficult to form a fine circuit for display applications in particular.

On the other hand, patent document 3 discloses a polyimide precursor produced by thermal imidization of a tetracarboxylic acid component and a diamine component containing a specific aromatic diamine, the imidization rate being 30% to 90%. More specifically, in the examples of patent document 3, the following polyimide precursors were produced: CpODA was used as the tetracarboxylic acid component, TFMB and other aromatic diamines (e.g., TFMB:4, 4' -diaminobenzanilide ═ 5:5 (molar ratio)) were used as the diamine component, and the imidization rate was 33 to 60%. Patent document 3 describes the following regarding the imidization rate: a polyimide having a low linear thermal expansion coefficient can be obtained by imidizing a polyimide precursor having an imidization rate of 30% or more to produce a polyimide, as compared with a case where a polyimide precursor having an imidization rate of 0% is imidized; on the other hand, if the imidization ratio is more than 90%, the solubility of the polyimide precursor (or polyimide) is lowered, and the polyimide precursor (or polyimide) precipitates, and a polyimide having excellent characteristics cannot be obtained.

Patent document 4 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 4, a polyimide resin was produced from CpODA (A-1) and 9, 9-bis (4-aminophenyl) fluorene (B-1). In example 5 of patent document 4, 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 4, 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 the examples of patent document 4, after a polyimide resin solution is obtained, the polyimide resin solution is applied to a substrate, and the solvent is removed by drying, thereby obtaining a polyimide film.

In addition, in example 1 and comparative example 1 of patent document 5, 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. Also in example 1 and comparative example 1 of patent document 5, a polyimide film was obtained by obtaining a polyimide solution, applying the polyimide solution onto a substrate, and curing the coating film.

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a polyimide that achieves both high transparency and low linear thermal expansion at a high level, that is, a polyimide having high transparency and an extremely low linear thermal expansion coefficient; and a polyimide solution composition from which a polyimide having high transparency and an extremely low coefficient of linear thermal expansion can be obtained.

Means for solving the problems

The present invention relates to the following.

1. A polyimide comprising more than 50 mol% of a repeating unit represented by the following chemical formula (1) relative to the total repeating units,

in the case of measurement with a film thickness of 10 μm,

a linear thermal expansion coefficient of 25ppm/K or less at 100 to 250 ℃, and,

the light transmittance at 400nm is 80% or more.

[ solution 1]

2. A polyimide solution composition characterized by dissolving in a solvent a polyimide comprising more than 50 mol% of a repeating unit represented by the following chemical formula (1) relative to the total repeating units and having an imidization rate of more than 90%.

[ solution 2]

3. A polyimide obtained by removing a solvent from the polyimide solution composition described in the above item 2.

4. A polyimide film obtained by removing a solvent from the polyimide solution composition described in the above item 2.

5. The polyimide film according to the above item 3 or the polyimide film according to the above item 4, wherein a linear thermal expansion coefficient is 25ppm/K or less at 100 to 250 ℃ when measured at a film thickness of 10 μm, and a light transmittance at a wavelength of 400nm is 80% or more.

6. A laminate comprising a glass substrate and a film comprising the polyimide according to the above item 1 or the polyimide film according to the above item 4 or 5 formed thereon.

7. A substrate for a display, a touch panel, or a solar cell, comprising the polyimide according to the above item 1 or 3 or the polyimide film according to the above item 4 or 5.

8. A method for producing a polyimide film/substrate laminate, comprising:

a step of applying the polyimide solution composition described in the above item 2 to a substrate; and

and heating the polyimide solution composition on a substrate.

9. A method for producing a polyimide film, comprising:

a step of applying the polyimide solution composition described in the above item 2 to a substrate;

heating the polyimide solution composition on a substrate; and

and a step of peeling the polyimide film formed on the substrate from the substrate.

10. A method for producing a polyimide film, comprising:

a step of applying the polyimide solution composition described in the above item 2 to a substrate;

drying the polyimide solution composition to obtain a self-supporting film; and

and a step of peeling the self-supporting film from the substrate and heating the peeled film.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a polyimide that realizes both high transparency and low linear thermal expansion at a high level, that is, a polyimide having high transparency and an extremely low linear thermal expansion coefficient can be provided. Further, according to the present invention, a polyimide solution composition from which a polyimide having high transparency and an extremely low coefficient of linear thermal expansion can be obtained can be provided.

The polyimide of the present invention and the polyimide obtained from the polyimide solution composition of the present invention have high transparency and extremely low linear thermal expansion coefficient, and therefore, can be easily formed into a fine circuit, and can be suitably used for forming a substrate for display applications and the like. The polyimide of the present invention and the polyimide obtained from the polyimide solution composition of the present invention can also be suitably used for forming a substrate for a touch panel or a solar cell.

Detailed Description

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 repeating unit represented by the above chemical formula (1) is CpODA or the like, and the diamine component providing the repeating unit represented by the above chemical formula (1) is TFMB.

The polyimide according to embodiment 1 of the present invention contains more than 50 mol% of the repeating unit represented by the above chemical formula (1) relative to the total repeating units, and has a coefficient of linear thermal expansion of 25ppm/K or less at 100 to 250 ℃ and a light transmittance at a wavelength of 400nm of 80% or more when measured as a film having a thickness of 10 μm. Preferably, the linear thermal expansion coefficient between 100 and 250 ℃ is preferably 20ppm/K or less, more preferably 15ppm/K or less, when measured as a film having a thickness of 10 μm. Further, when the film is measured to have a thickness of 10 μm, the light transmittance at a wavelength of 400nm is preferably 83% or more.

A conventionally known polyimide obtained from a tetracarboxylic acid component mainly containing CpODA and the like and a diamine component mainly containing TFMB is produced as follows: the polyimide film can be produced by reacting a tetracarboxylic acid component and a diamine component in a solvent at a relatively low temperature while inhibiting imidization to obtain a solution containing a polyimide precursor such as a polyamic acid, applying the polyimide precursor solution to a substrate, heating to remove the solvent (drying), and imidizing. As described above, the polyimide thus obtained tends to have a relatively large coefficient of linear thermal expansion although it has high transparency. In contrast, in the present invention, a tetracarboxylic acid component mainly comprising CpODA or the like and a diamine component mainly comprising TFMB are reacted in a solvent under the condition of undergoing an imidization reaction to obtain a solution (or solution composition) containing a soluble polyimide having an imidization rate of more than 90%, preferably an imidization rate of 95% or more, and then the solvent is removed from the polyimide solution (or solution composition) to produce a polyimide. When a polyimide is produced by this method, the linear thermal expansion coefficient can be significantly reduced as compared with the conventional one while maintaining high transparency. As a result, both high transparency and low linear thermal expansion can be achieved at a high level, and a polyimide having high transparency and an extremely low linear thermal expansion coefficient can be obtained.

In the polyimide according to embodiment 1 of the present invention, the content of the repeating unit represented by the above chemical formula (1) derived from CpODA and the like and TFMB may be more than 50 mol%, for example, 80 mol% or more, further 90 mol% or more, further 100 mol% based on the total repeating units.

The polyimide solution composition according to embodiment 2 of the present invention is a solution composition in which a polyimide containing more than 50 mol% of the repeating unit represented by the above chemical formula (1) relative to the total repeating units and having an imidization rate of more than 90%, preferably an imidization rate of 95% or more, is dissolved in a solvent. By removing the solvent from this polyimide solution composition, a polyimide having high transparency and an extremely low coefficient of linear thermal expansion can be obtained, and for example, the following polyimide can be obtained: when measured in a film thickness of 10 μm, the linear thermal expansion coefficient is 25ppm/K or less, preferably 20ppm/K or less, more preferably 15ppm/K or less at 100 to 250 ℃, and the light transmittance at a wavelength of 400nm is 80% or more, preferably 83% or more.

Here, when the imidization ratio is low, for example, when the imidization ratio is about 30% to 80%, haze may be generated depending on the composition of the polyimide, and transparency of the obtained polyimide may be lowered. In particular, in the case of a polyimide containing a repeating unit of the above chemical formula (1) [ a polyimide obtained from CpODA and the like and TFMB ], the haze tends to be increased easily.

In the polyimide solution composition according to embodiment 2 of the present invention, the content of the repeating unit represented by the above chemical formula (1) derived from CpODA and the like and TFMB is also more than 50 mol%, for example, 80 mol% or more, further 90 mol% or more, further 100 mol% based on the total repeating units.

Here, the imidization ratio is a ratio of the repeating unit of the imide structure to the total of the repeating unit of the amic acid structure and the repeating unit of the imide structure, and the polyimide (polyimide solution composition) can be measured¹The H-NMR spectrum is calculated from the ratio of the integrated value of the peak of the aromatic proton (6.2 to 8.5ppm) to the integrated value of the peak of the amide proton (9.5 to 11.0 ppm).

The polyimide in embodiment 1 of the present invention and the polyimide solution composition in embodiment 2 of the present invention are polyimides including more than 50 mol% of the repeating unit represented by the above chemical formula (1) with respect to the total repeating units, and are obtained from a tetracarboxylic acid component including CpODA and the like and a diamine component including TFMB.

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 trans-endo-and/or cis-endo-forms in CpODA and 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.

CpODA and the like may be used singly or in combination of two or more.

The polyimide in embodiment 1 of the present invention and the polyimide in the polyimide solution composition in embodiment 2 of the present invention may contain one or more kinds of repeating units other than the repeating unit represented by the above chemical formula (1) in a range of 50 mol% or less with respect to the total repeating units.

As the tetracarboxylic acid component providing another repeating unit, any of aromatic or aliphatic tetracarboxylic acids other than CpODA and the like can be used. Examples thereof include 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, 4- (2, 5-dioxotetrahydrofuran-3-yl) -1,2,3, 4-tetrahydronaphthalene-1, 2-dicarboxylic acid, pyromellitic acid, 3,3 ', 4,4 ' -benzophenonetetracarboxylic 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, dicarboxyphenyldimethylsilane, bis-dicarboxyphenoxydiphenyl sulfide, sulfonyl bisphthalic acid, 1,2,3, 4-cyclobutanetetracarboxylic acid, isopropylidenedioxybisphthalic acid, cyclohexane-1, 2,4, 5-tetracarboxylic 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 ' -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 dianhydride, etc.), and the like. Among these, derivatives such as 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, 2,3,3 ', 4 ' -biphenyltetracarboxylic acid, 4 ' -oxydiphthalic acid, cyclohexane-1, 2,4, 5-tetracarboxylic 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.

In addition, in the case where the diamine component to be combined is not a diamine component providing the repeating unit represented by the above chemical formula (1), the tetracarboxylic acid component providing the other repeating unit may be a tetracarboxylic acid component providing the repeating unit represented by the above chemical formula (1), that is, CpODA or the like.

As the diamine component that provides another repeating unit, any of other aromatic or aliphatic diamines other than TFMB may be used. Examples thereof include 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 ' -dicarboxylate, a, [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-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, 9-bis (4-aminophenyl) fluorene, 4 '- (spiro [ fluorene-9, 9' -xanthene ] -3 ', 6' -diylbis (oxy)) diphenylamine, 4 '-bis (4-aminophenoxy) biphenyl, 4' -bis (3-aminophenoxy) biphenyl, 1, 4-diaminocyclohexane, 1, 4-diamino-2-methylcyclohexane, and mixtures thereof, 1, 4-diamino-2-ethylcyclohexane, 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, 9-bis (4-aminophenyl) fluorene, 4 '- (spiro [ fluorene-9, 9' -xanthene ] -3 ', 6' -diylbis (oxy)) diphenylamine and the like are more preferable. These diamine components may be used alone, or two or more thereof may be used in combination.

In addition, 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 chemical formula (1), the diamine component that provides the other repeating unit may be a diamine component that provides the repeating unit represented by the above chemical formula (1), that is, TFMB.

The polyimide according to embodiment 1 of the present invention and the polyimide solution composition according to embodiment 2 of the present invention (hereinafter, also simply referred to as the polyimide according to the present invention and the polyimide solution composition according to the present invention) can be produced, for example, as follows. However, the polyimide of the present invention and the method for producing the polyimide solution composition of the present invention are not limited to the following production methods.

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 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 of the present invention contains at least a polyimide and a solvent, and the polyimide is preferably contained in a proportion of 5 mass% or more, preferably 10 mass% or more, more preferably 15 mass% or more, and particularly preferably 20 mass% or more, relative to 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 of the present invention is not limited to a film, a laminate of a polyimide film and another substrate, and a coating film, a powder, beads, a molded article, a foam, and the like can be appropriately exemplified.

The polyimide of the present invention thus obtained preferably has a linear thermal expansion coefficient of 25ppm/K or less, more preferably 20ppm/K or less, and particularly preferably 15ppm/K or less at 100 to 250 ℃ when measured as a film having a thickness of 10 μm. 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 linear thermal expansion coefficient in the present invention is a value measured on a polyimide film having a film thickness of 10 μm under conditions of a film width of 4mm, a chuck pitch of 15mm, a tensile load of 2g, and a temperature rise rate of 20 ℃/min, and tends to decrease when the film thickness is increased.

The polyimide of the present invention preferably has a light transmittance of 80% or more, more preferably 83% or more, at a wavelength of 400nm, when measured as a film having a thickness of 10 μm. 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 transmittance of light having a wavelength of 400nm tends to decrease when the film thickness increases.

The polyimide of the present invention preferably has a haze of 2% or less, more preferably 1.5% or less, and particularly preferably 1% or less, when measured as a film having a thickness of 10 μm. 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 haze tends to increase when the film thickness increases.

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 to transmit light, the light transmittance may decrease when 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 is 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 an extremely 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.