WO2020189556A1 - Polyimide film - Google Patents

Abstract

This polyimide film has an elastic modulus (E'_RT) of 3.0×10⁹ Pa or more at 30 °C and an elastic modulus (G_N ⁰) of less than 1.5×10⁷ Pa in a rubbery flat area thereof. Provided is a polyimide film having both high surface hardness and bending resistance. The elastic modulus (E'_RT) at 30 °C is preferably 3.5×10⁹ Pa or more, and more preferably 4.0×10⁹ Pa or more. It is preferable to contain an alicyclic structure in a tetracarboxylic acid residue that constitutes a polyimide included in the polyimide film.

Description

Polyimide film

The present invention relates to a polyimide film having both high surface hardness and bending resistance.

In recent years, various device applications have been demanding materials having heat resistance, light transmission, high elastic modulus, and flexibility.

For the above applications, for example, aromatic polyimide (for example, "Kapton" manufactured by DuPont) is known to be a light and flexible polyimide having high heat resistance. However, the aromatic polyimide has a brown color and cannot be used in applications that require high light transmission.

Therefore, the development of polyimide showing high light transmission is underway (Patent Document 1). Patent Document 1 has a description regarding heat resistance. However, in Patent Document 1, the surface hardness and bending resistance have not been sufficiently studied.

A rubber-like flat region in the dynamic viscoelasticity measurement of polyimide is described in Patent Document 2. Patent Document 2 shows that by introducing isocyanate as a cross-linking agent into polyimide, the downward curve becomes gentler as a thermal behavior in dynamic viscoelasticity measurement. However, Patent Document 2 does not describe the relationship between the elastic modulus ( _GN ⁰ ) in the rubber-like flat region and the surface hardness and bending resistance at all.

International Publication No. 2011/099518 Japanese Unexamined Patent Publication No. 2004-339363

An object of the present invention is to provide a polyimide film having both high surface hardness and bending resistance.

The present inventors have found that a polyimide film having an elastic modulus ( _E'RT ) at 30 ° C. or higher and an elastic modulus ( _GN ⁰ ) in a rubber-like flat region less than a predetermined value has high surface hardness and bending resistance. The present invention has been completed by finding that the characteristics are compatible with each other.

That is, the gist of the present invention is as follows.

[1] A polyimide film having an elastic modulus ( _E'RT ) at 30 ° C. of 3.0 × 10 ⁹ Pa or more and an elastic modulus ( _GN ⁰ ) of less than 1.5 × 10 ⁷ Pa in a rubber-like flat region. ..
[2] elastic modulus at 30 ℃ (E _'RT) is the 3.5 × ¹⁰ 9 Pa or more, a polyimide film according to [1].
[3] The polyimide film according to [1] or [2], which has an elastic modulus ( _E'RT ) at 30 ° C. of 4.0 × 10 ⁹ Pa or more.
[4] The polyimide film according to any one of [1] to [3], wherein the tetracarboxylic acid residue constituting the polyimide contained in the polyimide film contains an alicyclic structure.
[5] The polyimide film according to any one of [1] to [4], wherein the polyimide film has a film thickness of 1 μm or more and 300 μm or less.
[6] The polyimide film according to any one of [1] to [5], which is obtained by a casting method.
[7] A laminate having a hard coat layer on the surface of the polyimide film according to any one of [1] to [6].
[8] The laminate according to [7], wherein the hard coat layer has a film thickness of 50 μm or more and 200 μm or less.

According to the present invention, it is possible to provide a polyimide film having both high surface hardness and bending resistance.

FIG. 1 is a chart of dynamic viscoelasticity measurement for explaining the elastic modulus ( _GN ⁰ ) of the rubber-like flat region according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail. The following examples and methods are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents as long as the gist of the present invention is not deviated.

The polyimide of the present invention contains an imide ring in the main chain, and is composed of at least one selected from polyamic acid, polyamic acid ester, and polyimide.

In the present invention, the "elastic modulus" refers to the "storage elastic modulus".

The polyimide film of the present invention has an elastic modulus ( _E'RT ) at 30 ° C. of 3.0 × 10 ⁹ Pa or more, and an elastic modulus ( _GN ⁰ ) in a rubber-like flat region (hereinafter, simply “ _GN ⁰ ”). may be referred to as.) is equal to or less than 1.5 × ¹⁰ 7 Pa.

[mechanism]
The polyimide film of the present invention has a high surface hardness and bending resistance because the elastic modulus ( _E'RT ) at 30 ° C. is equal to or higher than a predetermined value and the elastic modulus ( _GN ⁰ ) in the rubber-like flat region is less than a predetermined value. The reasons for achieving the effect of achieving both sex are as follows.

As shown in FIG. 1, G _N ⁰ is generally represented by the following formula.
G _N ⁰ = ρRT / Me
= ΡRT / MvNv
Here, ρ, Me, Mv, Nv, R, and T are as follows.
ρ: Melt density Me: Molecular weight between entangled points Mv: Molecular weight of repeating unit Nv: Number of bonds between entangled points T: Temperature R: Gas constant It is also reported that the higher the flexibility of the polymer chain, the smaller the Nv. As a result, Me becomes large and _GN ⁰ becomes small.
Further, when _GN ⁰ is observed in multiple stages, it is set to the highest value among the elastic moduli observed in the rubber-like flat region.

G _N ⁰ is also considered as an indicator of the entanglement of molecules, G _N ⁰ and the entanglement of the molecule increases tend to go up. However, according to the study by the present inventor, it has been found that in this case, when an external stress is applied, it becomes difficult to disperse the force, the stress is locally applied, and the bending resistance deteriorates.
On the other hand, the more rigid the polyimide, the higher the flatness of the molecular chain and the tougher it is, so that it can withstand stress, and therefore, it is easy to obtain characteristics such as improved bending resistance.
In a general polymer, the elastic modulus and the like are improved by increasing the entanglement of molecules, but in a polyimide, if the structure is such that the molecules are entangled, the rigidity is lost and the performance may be deteriorated.
In the present invention, the elastic modulus ( _E'RT ) at 30 ° C. is set to be as high as a predetermined value or more, and the elastic modulus ( _GN ⁰ ) in the rubber-like flat region is designed to be low to suppress the entanglement of molecules and to make a flat surface. As a structure with high properties, by arranging molecular chains on the surface, both high surface hardness and bending resistance are achieved.

In order to achieve both the elastic modulus at 30 ° C. ( _E'RT ) and the elastic modulus in the rubber-like flat region ( _GN ⁰ ) in the present invention, as described later, an alicyclic is attached to the tetracarboxylic acid residue constituting the polyimide. The molecular structure of polyimide may be designed by introducing a structure.
Further, _E'RT and _GN ⁰ can also be controlled by the film forming conditions. For example, the temperature during film formation is raised above the Tg (glass transition temperature) of polyimide to make it amorphous, and then the cooling rate is slowed down to promote molecular chain orientation, achieving both high surface hardness and bending resistance. It is also possible.

[Elastic modulus of polyimide film]
The elastic modulus of the polyimide film of the present invention can be measured by viscoelasticity measurement. The elastic modulus ( _E'RT ) of the polyimide film of the present invention at 30 ° C. is 3.0 × 10 ⁹ Pa or more, preferably 3.5 × 10 ⁹ Pa or more, and more preferably 4.0 × 10 ⁹ Pa or more. ..
On the other hand, the elastic modulus ( _E'RT ) of the polyimide film of the present invention at 30 ° C. is preferably 8.0 × 10 ⁹ Pa or less, more preferably 7.5 × 10 ⁹ Pa or less, and further preferably 7.0 × 10 ^{It is 9} Pa or less.
When _E'RT is in the above range, it is possible to develop well-balanced physical properties in order to achieve both high surface hardness and bending resistance.

The elastic modulus ( _GN ⁰ ) of the polyimide film of the present invention in the rubber-like flat region is less than 1.5 × 10 ⁷ Pa, preferably 1.2 × 10 ⁷ Pa or less, more preferably 1.0 × 10 ⁷ It is Pa or less, more preferably 9.0 × 10 ⁶ Pa or less, particularly preferably 8.5 × 10 ⁶ Pa or less, and most preferably 8.0 × 10 ⁶ Pa or less. When _GN ⁰ is less than the above upper limit, a polyimide film capable of achieving both high surface hardness and bending resistance can be obtained.
On the other hand, the elastic modulus ( _GN ⁰ ) of the polyimide film of the present invention in the rubber-like flat region is not particularly limited as long as the rubber-like flat region is observed from the viewpoint of heat resistance, but for example, 1.0 × 10. ⁴ Pa or more can be mentioned.

The method of viscoelasticity measurement (dynamic viscoelasticity measurement) is as shown in the section of Examples described later. The rubber-like flat region is observed in a temperature range exceeding the glass transition temperature (Tg) of polyimide.

[Polyimide constituting polyimide film]
Hereinafter, preferred embodiments of the polyimide constituting the polyimide film of the present invention (hereinafter, may be referred to as “polyimide of the present invention”) will be described.

<Imidization rate of polyimide>
The imidization ratio of the polyimide of the present invention is not particularly limited, but is preferably 70% or more, more preferably 80% or more, still more preferably 85% or more. The upper limit of the imidization rate is 100% or less. When the imidization ratio is in this range, dehydration due to imide ring closure during molding is reduced, and a molded product with few voids tends to be obtained, which is preferable.
The imidization ratio indicates the ratio of imide bonds in the main chain of polyimide, and can be determined by a conventionally known method, for example, an NMR method, an IR method, a titration method, or the like.

<Polyimide structure>
The structure of the polyimide of the present invention is not particularly limited, but has a unit derived from a tetracarboxylic dianhydride (tetracarboxylic acid residue) and a unit derived from a diamine compound and / or a diisocyanate compound (diamine residue).

The tetracarboxylic acid residue and diamine residue contained in the polyimide of the present invention have the elastic modulus ( _E'RT ) at 30 ° C. and the elastic modulus ( _GN ⁰ ) in the rubber-like flat region of the obtained polyimide film. The type is selected and the content ratio is set so as to satisfy the conditions of.

<Unit derived from tetracarboxylic dianhydride (tetracarboxylic acid residue)>
The tetracarboxylic dianhydride containing the tetracarboxylic acid residue contained in the polyimide of the present invention is not particularly limited. The tetracarboxylic dianhydride includes an aliphatic tetracarboxylic dianhydride (the aliphatic tetracarboxylic dianhydride includes an alicyclic tetracarboxylic dianhydride and a chain aliphatic tetracarboxylic dianhydride). ), Aromatic tetracarboxylic dianhydride and the like. One of these tetracarboxylic dianhydrides may be used alone, or two or more thereof may be used in any ratio and combination.

(Alicyclic tetracarboxylic dianhydride)
Examples of the alicyclic tetracarboxylic dianhydride include 3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1 , 2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4 -Cyclobutanetetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, tricyclo [6.4.0.0 ^{2, 7} ] Dodecane-1,8: 2,7-tetracarboxylic dianhydride, Bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 4- Examples thereof include (2,5-dioxo tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride.
Among them, those having an alicyclic structure of 5 or more members are preferable, and those having an alicyclic structure of 6 or more members are more preferable because the production stability tends to be improved.

(Chain aliphatic tetracarboxylic dianhydride)
Examples of the chain aliphatic tetracarboxylic dianhydride include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, meso-butane-1,2,3,4-tetracarboxylic dianhydride and the like. Can be mentioned.

(Aromatic tetracarboxylic dianhydride)
Examples of the aromatic tetracarboxylic acid dianhydride include tetracarboxylic acid dianhydride having one aromatic ring in one molecule, tetracarboxylic acid dianhydride having two or more independent aromatic rings in one molecule, and 1 Examples thereof include tetracarboxylic acid dianhydride having a condensed aromatic ring in the molecule.

Among these, tetracarboxylic dianhydride having one aromatic ring in one molecule or tetracarboxylic dianhydride having one aromatic ring in one molecule tends to be easy to control the viscosity at the time of production, improve solvent solubility, and improve coating flexibility. A tetracarboxylic dianhydride having two or more independent aromatic rings in one molecule is preferable, and a tetracarboxylic dianhydride having two or more independent aromatic rings in one molecule is particularly preferable.

Examples of the tetracarboxylic dianhydride having one aromatic ring in one molecule include pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride and the like.

Examples of the tetracarboxylic dianhydride having two or more independent aromatic rings in one molecule include 1,1-bis (2,3-dicarboxyphenyl) ethanedianhydride and bis (2,3-di). Carboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4) -Dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, 3,3', 4 , 4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic acid dianhydride, 4,4- (p-phenylenedi) Examples thereof include oxy) diphthalic acid dianhydride, 4,4- (m-phenylenedioxy) diphthalic acid dianhydride, 2,2', 6,6'-biphenyltetracarboxylic dianhydride and the like.

Examples of the tetracarboxylic dianhydride having a condensed aromatic ring in one molecule include 1,2,5,6-naphthalenedicarboxylic dianhydride, 1,4,5,8-naphthalenedicarboxylic dianhydride, 2, 3,6,7-naphthalenedicarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7 , 8-Phenyltetracarboxylic dianhydride and the like.

(Other tetracarboxylic dianhydrides)
As the tetracarboxylic dianhydride, a silicone-based tetracarboxylic dianhydride or a tetracarboxylic dianhydride containing a fluorine atom can also be used in addition to the above. Examples of the tetracarboxylic dianhydride containing a fluorine atom include 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanedianhydride (also known as). : 4,4'-(hexafluoroisopropyridene) -diphthalic dianhydride), 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane Dichloride, 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluorotrimethylethylene) diphthalic acid dianhydride , 4,4'-(octafluorotetramethylene) diphthalic acid dianhydride, 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride, 4, 4'-(hexafluorotrimethylethylene) diphthalic acid dianhydride, 4,4'-(octafluorotetramethylene) diphthalic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1 , 1,3,3,3-hexafluoropropanedianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanedianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,1,3,3,3-hexafluoropropanedianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1 , 1,1,3,3,3-hexafluoropropanedianhydride and the like.

The tetracarboxylic dianhydride containing the tetracarboxylic acid residue contained in the polyimide of the present invention may contain only one type or two or more types. Tetracarboxylic acid residues derived from aliphatic tetracarboxylic dianhydrides and / or tetracarboxylic acid residues derived from tetracarboxylic dianhydrides containing fluorine atoms in order to improve high surface hardness and bending resistance. It is preferable to contain a tetracarboxylic acid residue derived from an alicyclic tetracarboxylic dianhydride and / or a tetracarboxylic acid residue derived from a tetracarboxylic dianhydride containing a fluorine atom. .. Further, the above structure tends to improve the solvent solubility of the polyimide.

The ratio of the tetracarboxylic acid residue derived from the aliphatic tetracarboxylic acid dianhydride to the total tetracarboxylic acid residue contained in the polyimide of the present invention is not particularly limited, but is preferably 10 mol% or more, preferably 25 mol% or more. More preferably, 40 mol% or more is further preferable. Further, there is no upper limit of this ratio, and it may be 100 mol%. When the ratio of the tetracarboxylic acid residue derived from the tetracarboxylic dianhydride is equal to or higher than the above lower limit, the high surface hardness and bending resistance tend to be improved, and the solubility in a solvent tends to be high.

<Unit derived from diamine compound>
Examples of the diamine compound for inducing the diamine residue contained in the polyimide of the present invention include aromatic diamine compounds and aliphatic diamine compounds (aliphatic diamine compounds include alicyclic diamine compounds and chain aliphatic diamine compounds). Can be mentioned. One of these diamine compounds may be used alone, or two or more of these diamine compounds may be used in any ratio and combination.

(Aromatic diamine compound)
Examples of the aromatic diamine compound include a diamine compound having one aromatic ring in one molecule, a diamine compound having a condensed aromatic ring in one molecule, and a diamine compound having two or more independent aromatic rings in one molecule. Can be mentioned.

Examples of the diamine compound having one aromatic ring in one molecule include 1,4-phenylenediamine, 1,2-phenylenediamine, 1,3-phenylenediamine, 4-fluoro-1,2-phenylenediamine, and the like. 4-Fluoro-1,3-phenylenediamine, 3-trifluoromethyl-1,5-phenylenediamine, 4-trifluoromethyl-1,5-phenylenediamine, 4-trifluoromethyl-1,2-phenylenediamine, Examples thereof include 2-trifluoromethyl-1,4-phenylenediamine.

Examples of the diamine compound having a condensed aromatic ring in one molecule include 4,4'-(9-fluorenylidene) dianiline, 2,7-diaminofluorene, 1,5-diaminonaphthalene, and 3,7-diamino-2,8-. Examples thereof include dimethyldibenzothiophene 5,5-dioxide.

Diamine compounds having two or more independent aromatic rings in one molecule include 4,4'-(biphenyl-2,5-diylbisoxy) bisaniline and 4,4'-diamino as having a biphenyl structure. -3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl (also known as 3,3'-dimethylbenzidine), 4,4'-bis (4-aminophenoxy) biphenyl, 4 , 4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diamino-2,2'-dichlorobiphenyl, 4,4'-diamino -3,3'-dichlorobiphenyl, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 4,4'-diamino-2-methyl-2'-trifluoromethylbiphenyl and the like. Be done. Further, assuming that the aromatic rings are linked to each other by a linker, 4,4-diaminozensanilide, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 1,4-bis (4-aminophenoxy) benzene are used. , 1,3-bis (4-aminophenoxy) benzene, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, bis (4-) (3-Aminophenoxy) phenyl) sulfone, 1,3-bis (4-aminophenoxy) neopentane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, N- (4-aminophenoxy) -4-aminobenzamine, bis (3-aminophenyl) sulfone, norbornandiamine, bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3-aminophenoxy) ) Phen) Sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, N- [4- (4-aminophenoxy) phenyl] -4-aminobenzamide, 4,4-diaminobenzanilide, Examples include bis (3-aminophenyl) sulfone. Further, as those having a fluorine atom, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane and 2,2-bis [4- {4-amino-2- (trifluoromethyl) phenoxy) } Phenyl] Hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-Aminophenyl) Hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2-bis {4- (4-aminophenoxy) -3,5-dibromophenyl} hexafluoropropane And so on.

Among them, a diamine compound having a biphenyl structure or a diamine compound in which aromatic rings are linked to each other by a linker is preferable because high surface hardness and bending resistance are improved and the elastic modulus tends to be high. A diamine compound having is more preferable.

(Aliphatic diamine compound)
Examples of the aliphatic diamine compound include an alicyclic diamine compound and a chain aliphatic diamine compound.

Examples of the alicyclic diamine compound include 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1,4-diaminocyclohexane, and 4,4'-methylenebis (cyclohexylamine). Examples thereof include 4,4'-methylenebis (2-methylcyclohexylamine).

Examples of the chain aliphatic diamine compound include 1,2-ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-hexamethylenediamine, and 1,5-. Examples thereof include diaminopentane, 1,10-diaminodecane, 1,2-diamino-2-methylpropane, 2,3-dimethyl-2,3-butanediamine, 2-methyl-1,5-diaminopentane and the like.

Among these, alicyclic diamine compounds are preferable because they tend to have high surface hardness, bending resistance, and heat resistance, and are particularly 1,4-diaminocyclohexane or 1,3-bis (1,4-diaminocyclohexane). Aminomethyl) cyclohexane is preferred.

<Unit derived from diisocyanate compound>
Examples of the diisocyanate compound for inducing the diamine residue contained in the polyimide of the present invention include aromatic diisocyanate compounds and aliphatic diisocyanate compounds. One of these diisocyanate compounds may be used alone, or two or more of these diisocyanate compounds may be used in any ratio and combination.

Examples of the aromatic diisocyanate compound include 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 2,2-bis (4-isocyanatophenyl) hexafluoropropane, and 4,4'-diisocyanato-3,3. '-Dimethyldiphenylmethane, 1,5-diisocyanatonaphthalene, 4,4'-methylenediphenyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylenediisocyanate, 1,3-bis (isocyanatomethyl) ) Benzene, toluene diisocyanate and the like.

Examples of the aliphatic diisocyanate compound include 1,3-bis (isocyanatomethyl) cyclohexane, hexamethylene diisocyanate, and isophorone diisocyanate.

The diamine compound and / or diisocyanate compound that induces the diamine residue contained in the polyimide of the present invention may be only one kind or may contain two or more kinds. High surface hardness and bending resistance are improved, and the elasticity at 30 ° C. tends to be high. Therefore, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2 , 2'-Dimethylbiphenyl (also known as 3,3'-dimethylbenzidine), 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diamino-2,2'-dimethitoxybiphenyl, 4 , 4'-bis (4-aminophenoxy) biphenyl, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 4,4'-diamino-2-methyl-2'-trifluoromethyl Biphenyl-based diamine compounds such as biphenyl and / or bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3-aminophenoxy) phenyl) sulfone, 4,4'-diaminodiphenyl sulfone, 3 , 3'-diaminodiphenyl sulfone, N- [4- (4-aminophenoxy) phenyl] -4-aminobenzamide, 4,4-diaminobenzanilide, bis (3-aminophenyl) sulfone and other sulfone-based diamine compounds It preferably contains an induced diamine residue. Above all, it is more preferable to contain a diamine residue derived from the above-mentioned biphenyl-based diamine compound.

<Structure represented by general formula (1)>
The polyimide of the present invention may have a structure represented by the following general formula (1). When the polyimide of the present invention has the structure, both high surface hardness and bending resistance can be more effectively achieved, and the solubility tends to be further improved.

In the general formula (1), R represents at least one selected from the group consisting of a divalent aromatic ring group, a heterocyclic group, an alicyclic group and a chain aliphatic group which may have a substituent. .. * Indicates a bond.

In the general formula (1), R represents at least one selected from the group consisting of a divalent aromatic ring group, a heterocyclic group, an alicyclic group and a chain aliphatic group which may have a substituent. ..
The aromatic ring and the heterocycle are not particularly limited, and may be a fused ring. The alicyclic is not particularly limited, but is preferably a 3- to 10-membered ring. The chain aliphatic group is also not particularly limited, but is preferably a linear group having 1 to 20 carbon atoms.
Further, since the molecular weight can be easily controlled and the production stability is good, at least one selected from the group consisting of an aromatic ring group and a chain aliphatic group is preferable. Among these, as the aromatic ring group, a group composed of a benzene ring, a naphthalene ring, a biphenyl ring, a biphenyl ether, a benzophenone, a phenyl sulfide, a biphenyl sulfoxide, and a biphenyl sulfone is preferable, and a group having a monocyclic ring or two aromatic rings is preferable. Is preferable. On the other hand, the chain aliphatic group preferably has 1 or more and 10 or less carbon atoms. When R is these groups, the effect of the present invention tends to be particularly easily obtained.
These aromatic ring groups, heterocyclic groups, alicyclic groups and chain aliphatic groups may have substituents. Examples of the substituent which may be possessed include an alkyl group, an alkoxy group, an alkyl halide group, a hydroxyl group, a carboxy group and the like.

These aromatic ring groups, heterocyclic groups, alicyclic groups and chain aliphatic groups may be used alone or in combination.

Specific examples of the structure represented by the general formula (1) include structures derived from the respective compounds mentioned in the reaction between the dicarboxylic acid compound and the diamine compound described later and the reaction between the tetracarboxylic dianhydride and the dihydrazide compound. Be done.

The polyimide of the present invention may have only one type of the structure represented by the general formula (1), or may have a plurality of types.
The structure represented by the general formula (1) is preferably derived from the reaction between the dicarboxylic acid compound and the diamine compound and / or the reaction between the tetracarboxylic dianhydride and the dihydrazide compound. The structure represented by the general formula (1) preferably has a structure derived from at least the reaction of the tetracarboxylic dianhydride and the dihydrazide compound.

Examples of the dicarboxylic acid compound that induces the structure represented by the general formula (1) include compounds such as aromatic dicarboxylic acid, heterocyclic dicarboxylic acid, alicyclic dicarboxylic acid, and chain aliphatic dicarboxylic acid. The dicarboxylic acid compound can also be used as an acid halide in which a carboxyl group is halogenated, for example, an acid chloride in which a carboxyl group is chlorinated in order to improve the reactivity. In the present invention, it is said that the structure is derived from the reaction between the dicarboxylic acid compound and the diamine compound even when a halide such as dicarboxylic acid chloride is used as the dicarboxylic acid compound.

The amount introduced into the polyimide having the structure represented by the general formula (1) is not particularly limited, but the concentration of the amide bond with respect to the imide ring of the main chain is preferably 1 mol% or more, more preferably 5 mol% or more, and 8 mol% or more. Is even more preferable. The amount introduced into the polyimide having the structure represented by the general formula (1) is preferably 900 mol% or less, more preferably 700 mol% or less, further preferably 500 mol% or less, and particularly preferably 400 mol% or less. It is preferable that the amount of the structure represented by the general formula (1) introduced in the polyimide is within this range because the solvent solubility and the elastic modulus tend to be compatible with each other.

The ratio of the structure represented by the general formula (1) derived from the reaction between the dicarboxylic acid compound and the diamine compound and the structure derived from the reaction between the dihydrazide compound and the tetracarboxylic dianhydride is not particularly limited. The ratio of the dihydrazide compound to the structure represented by the general formula (1), which is derived from the reaction of the dihydrazide compound and the tetracarboxylic acid dianhydride, is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 25 mol% or more. , 50 mol% or more is particularly preferable. There is no upper limit to the ratio of the dihydrazide compound derived from the reaction of the tetracarboxylic dianhydride, which may be 100 mol%. When the ratio of the dihydrazide compound derived from the reaction of the tetracarboxylic dianhydride is not more than the above lower limit value, solvent solubility and elastic modulus tend to be compatible, which is preferable.

The ratio of tetracarboxylic acid residue, diamine residue, dicarboxylic acid residue, and dihydrazide residue contained in the polyimide of the present invention can be determined by analyzing the composition of the raw material monomer by NMR, solid NMR, IR, or the like. Can be done. This ratio can also be determined by gas chromatography (GC), ¹ H-NMR, ¹³ C-NMR, two-dimensional NMR, mass spectrometry, etc. after dissolution in alkali.

<< Structure derived from the reaction between the dicarboxylic acid compound and the diamine compound >>
(Diamine compound)
Examples of the diamine compound include an aromatic diamine compound and an aliphatic diamine compound (the aliphatic diamine compound includes an alicyclic diamine compound and a chain aliphatic diamine compound). One of these diamine compounds may be used alone, or two or more of these diamine compounds may be used in any ratio and combination.

Examples of the diamine compound to be reacted with the dicarboxylic acid compound include the compounds described above in the description of the diamine residue, and the preferable range is also the same.

(Dicarboxylic acid compound)
Examples of the dicarboxylic acid compound include an aromatic dicarboxylic acid compound (including a heteroaromatic dicarboxylic acid compound), an alicyclic dicarboxylic acid compound, and a chain aliphatic dicarboxylic acid compound. One of these dicarboxylic acid compounds may be used alone, or two or more of them may be used in any ratio and combination.

Examples of the aromatic dicarboxylic acid compound include monocyclic isophthalic acid, terephthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, and the like; 4,4'-carbonyldibenzoic acid having two or more independent aromatic rings, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 2,2-bis (4-carboxyphenyl) hexafluoropropane, 4- (carboxymethyl) benzoic acid, 4,4'-oxybis benzoic acid , 4,4'-sulfonyldibenzoic acid, 1,2-bis (4-carboxyphenyl) ethane, 4,4'-stylbenzicarboxylic acid, etc .; 1,4-naphthalenedicarboxylic acid having a fused ring, 2,3- Naphthalenedicarboxylic acid, etc .; 2,2'-bisinconic acid having a heterocycle, 2,2'-binicotinic acid, 2,2'-biisonicotinic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, 2, 2'-bipyridine-6,6'-dicarboxylic acid, 2,5-furandicarboxylic acid and the like;

Examples of the alicyclic dicarboxylic acid compound include bicyclo [2.2.2] octane-1,4-dicarboxylic acid, 1,3-adamantandicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and 1,4. -Cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decahydro-1,4-naphthalenedicarboxylic acid and the like can be mentioned.

Examples of the chain aliphatic dicarboxylic acid compound include glutaric acid, adipic acid, azelaic acid, malonic acid, sebacic acid, succinic acid and the like.

As the dicarboxylic acid compound, a monocyclic aromatic dicarboxylic acid compound, a dicarboxylic acid compound having two or more independent aromatic rings, and a chain dicarboxylic acid compound tend to have both solvent solubility and elastic modulus easily. preferable.

As described above, the dicarboxylic acid compound may be used as an acid chloride in order to improve the reactivity, and the preferable compound in that case is the same as the above content.

<< Structure derived from the reaction of tetracarboxylic dianhydride and dihydrazide compound >>
(Tetracarboxylic dianhydride)
Examples of tetracarboxylic dianhydrides include aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides (aliphatic tetracarboxylic dianhydrides are alicyclic tetracarboxylic dianhydrides and chain aliphatics. Includes tetracarboxylic dianhydride). One of these tetracarboxylic dianhydrides may be used alone, or two or more thereof may be used in any ratio and combination.

Examples of the tetracarboxylic dianhydride compound to be reacted with the dihydrazide compound include the compounds described above in the description of the tetracarboxylic acid residue, and the preferable range is also the same.

(Dihydrazide compound)
The dihydrazide compound is not particularly limited, and examples thereof include aromatic dihydrazide compounds and aliphatic dihydrazide compounds (including alicyclic dihydrazide compounds and chain aliphatic dihydrazide compounds). One of these dihydrazide compounds may be used alone, or two or more thereof may be used in any ratio and combination.

Examples of the aromatic dihydrazide compound include monocyclic isophthalic acid dihydrazide, terephthalic acid dihydrazide, phthalic acid dihydrazide, 2,5-dimethylterephthalic acid dihydrazide, and the like; 4,4'-carbonyl having two or more independent aromatic rings. Dihydrazide benzoate, 2,2'-biphenyldicarboxylic acid dihydrazide, 4,4'-biphenyldicarboxylic acid dihydrazide, 2,2-bis (4-carboxyphenyl) hexafluoropropanedihydrazide, 4- (carboxymethyl) dihydrazide benzoate , 4,4'-oxybis benzoic acid dihydrazide, 4,4'-sulfonyl dibenzoic acid dihydrazide, 1,2-bis (4-carboxyphenyl) ethanedihydrazide, 4,4'-stylbenzicarboxylic acid dihydrazide, etc .; 1,4-Naphthalenedicarboxylic acid dihydrazide, 2,3-naphthalenedicarboxylic acid dihydrazide, etc .; 2,2'-bisinconic acid dihydrazide, 2,2'-binicotinic acid dihydrazide, 2,2'-biisonicotinic acid dihydrazide having a heterocycle , 2,2'-bipyridine-5,5'-dicarboxylic acid dihydrazide, 2,2'-bipyridine-6,6'-dicarboxylic acid dihydrazide, 2,5-furandicarboxylic acid dihydrazide and the like.

Examples of the alicyclic dihydrazide compound include bicyclo [2.2.2] octane-1,4-dicarboxylic acid dihydrazide, 1,3-adamantandicarboxylic acid dihydrazide, cis-4-cyclohexene-1,2-dicarboxylic acid dihydrazide, and 1, , 4-Cyclohexanedicarboxylic acid dihydrazide, 1,3-cyclohexanedicarboxylic acid dihydrazide, decahydro-1,4-naphthalenedicarboxylic acid dihydrazide and the like.

Examples of the chain aliphatic dihydrazide compound include adipic acid dihydrazide, azelaic acid dihydrazide, dodecanoic acid dihydrazide, malonic acid dihydrazide, sebacic acid dihydrazide, succinate dihydrazide, and oxalyl dihydrazide.

As the dihydrazide compound, a monocyclic aromatic dihydrazide compound and a dihydrazide compound having two or more independent aromatic rings tend to improve the elastic modulus, and are preferable.

<Suitable design to satisfy _E'RT and _GN ⁰ >
No particular limitation is imposed on the suitable combinations molecular design of such a tetracarboxylic acid residue and a diamine residue of the polyimide to meet E _'RT and G _N ⁰ of the polyimide film of the present invention, the tetracarboxylic acid residues It preferably contains an alicyclic structure. From the viewpoint of achieving both high surface hardness and bending resistance, and both rigidity and flexibility of the molecular skeleton, at least the above-mentioned aliphatic tetracarboxylic dianhydride can be used as the raw material tetracarboxylic dianhydride for polyimide. It is preferable to use an alicyclic tetracarboxylic dianhydride, and it is particularly preferable to use 3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride and the like.

The ratio of the alicyclic tetracarboxylic acid residue to the total tetracarboxylic acid residue contained in the polyimide of the present invention is usually 10 mol% or more, further 30 mol% or more, particularly 50 mol% or more, particularly 80 mol% or more. It is preferable from the viewpoint of surface hardness and bending resistance. There is no particular upper limit to this ratio, and it may be 100 mol%.

<Molecular weight of polyimide>
The molecular weight of the polyimide of the present invention is not particularly limited, but is preferably a polystyrene-equivalent number average molecular weight (Mn) of 500 or more, more preferably 1000 or more, and further preferably 1500 or more. On the other hand, this molecular weight is preferably 80,000 or less, more preferably 60,000 or less, still more preferably 40,000 or less. When the number average molecular weight (Mn) of the polyimide is in this range, the solubility, the solution viscosity, and the like are in a range that can be easily handled by ordinary equipment, which is preferable.
The polystyrene-equivalent number average molecular weight (Mn) of the polyimide of the present invention can be determined by gel permeation chromatography (GPC).

The mass average molecular weight (Mw) of the polyimide of the present invention is preferably 1000 or more, more preferably 2000 or more, still more preferably 5000 or more. On the other hand, the mass average molecular weight (Mw) of polyimide is preferably 300,000 or less, more preferably 200,000 or less, still more preferably 100,000 or less. When the mass average molecular weight (Mw) of the polyimide is in this range, the solubility, the solution viscosity, and the like are in the range that can be easily handled by ordinary equipment, which is preferable.
The mass average molecular weight (Mw) of the polyimide of the present invention can be measured by the same method as the number average molecular weight (Mn).

The molecular weight distribution (PDI: Mw / Mn) of the polyimide of the present invention is usually 1 or more, preferably 1,1 or more, and more preferably 1.2 or more. On the other hand, Mw / Mn is usually 20 or less, preferably 15 or less, and more preferably 10 or less. When Mw / Mn is in this range, the uniformity and smoothness of the obtained molded product tend to be excellent.

<Glass transition temperature of polyimide>
The glass transition temperature (Tg) of the polyimide of the present invention is not particularly limited, but is preferably 150 ° C. or higher, more preferably 180 ° C. or higher, still more preferably 200 ° C. or higher, still more preferably 250 ° C. or higher, particularly preferably. It is 260 ° C. or higher. On the other hand, the glass transition temperature (Tg) of polyimide is preferably 400 ° C. or lower, more preferably 380 ° C. or lower. When the glass transition temperature (Tg) of polyimide is in this range, the heat resistance of the obtained molded product is improved, and the residual solvent in low-load process molding such as suppression of molding temperature and molding under air is reduced. Tend to do.
The glass transition temperature (Tg) of polyimide corresponds to the peak temperature (Ttanδ) of α relaxation of tanδ.

<Polyimide manufacturing method>
The method for producing the polyimide of the present invention is not particularly limited, and the polyimide can be produced by a conventionally known method. For example, a method of producing a polyimide precursor from a tetracarboxylic acid dianhydride and a diamine compound and / or a diisocyanate compound and imidizing the polyimide precursor to obtain a polyimide; directly from the tetracarboxylic acid dianhydride and a diamine compound and / or a diisocyanate compound. There is a method for producing polyimide;

As a method for producing a polyimide containing the structure represented by the general formula (1), a polyimide precursor is produced from a tetracarboxylic acid dianhydride and / or a dicarboxylic acid compound, a diamine compound, a diisocyanate compound and / or a dihydrazide compound. There is a method of imidizing this to obtain a polyimide; a method of directly producing a polyimide from a tetracarboxylic acid dianhydride and / or a dicarboxylic acid compound and a diamine compound, a diisocyanate compound, and / or a dihydrazide compound.

The dihydrazide compound can be reacted in the same manner as the diamine compound, and the dicarboxylic acid compound can be reacted in the same manner as the tetracarboxylic dianhydride. The dicarboxylic acid compound can also be used as a chain extender after producing polyimide from a tetracarboxylic dianhydride and a diamine compound, a diisocyanate compound and / or a dihydrazide compound.

Hereinafter, "tetracarboxylic acid dianhydride and / or dicarboxylic acid compound" is referred to as "tetracarboxylic acid dianhydride, etc.", and "one or more of diamine compounds, diisocyanate compounds and dihydrazide compounds" is referred to as "diamine compound, diisocyanate compound and dihydrazide compound". A method for producing the polyimide of the present invention by reacting a tetracarboxylic acid dianhydride or the like with a diamine compound or the like will be described with reference to "diamine compound or the like".

<< Method of producing polyimide via polyimide precursor >>
(Structure of polyimide precursor)
When the polyimide is produced via the polyimide precursor, the polyimide precursor can be obtained, for example, by reacting a tetracarboxylic dianhydride or the like with a diamine compound or the like in a solvent.
In this case, the order of addition and the method of addition of the tetracarboxylic dianhydride and the like and the diamine compound and the like are not particularly limited. For example, a polyimide precursor can be obtained by sequentially adding a diamine compound or the like and a tetracarboxylic dianhydride or the like to a solvent and stirring the mixture at an appropriate temperature.

The amount of the tetracarboxylic dianhydride or the like is usually 0.7 mol or more, preferably 0.8 mol or more, and usually 1.3 mol or less, preferably 1.2 mol, based on 1 mol of the diamine compound or the like. It is as follows. By setting the amount of tetracarboxylic dianhydride or the like in such a range, the yield of the obtained polyimide precursor tends to be improved.

The concentration of tetracarboxylic dianhydride, etc., diamine compound, etc. in the reaction solution can be appropriately set according to the reaction conditions and the viscosity of the obtained polyimide precursor.

The total concentration of the tetracarboxylic dianhydride and the like and the diamine compound and the like is not particularly limited, but is usually 1% by mass or more, preferably 5% by mass or more, and usually 70% by mass or less, based on the total amount of the reaction solution. It is preferably 50% by mass or less. If the concentrations of the tetracarboxylic dianhydride and the like and the diamine compound in the reaction solution are not too low, the molecular weight tends to be extended. When the concentrations of the tetracarboxylic dianhydride and the like and the diamine compound in the reaction solution are not too high, the viscosity of the reaction solution does not become too high and stirring tends to be easy.

The temperature at which the tetracarboxylic dianhydride and the like and the diamine compound and the like are reacted in the solvent is not particularly limited as long as the reaction proceeds, but is usually 0 ° C. or higher, preferably 20 ° C. or higher, and is usually used. It is 120 ° C. or lower, preferably 100 ° C. or lower.
The reaction time is usually 1 hour or more, preferably 2 hours or more, usually 100 hours or less, preferably 42 hours or less.
By carrying out under such conditions, a polyimide precursor tends to be obtained at low cost and in good yield.
The pressure during the reaction may be normal pressure, pressurization or depressurization.
The reaction atmosphere may be under air or under an inert atmosphere.

The solvent used when reacting the tetracarboxylic dianhydride or the like with the diamine compound or the like is not particularly limited. Examples of the reaction solvent include hydrocarbon solvents such as hexane, cyclohexane, heptane, benzene, toluene, xylene, mecitylene, and anisole; carbon tetrachloride, methylene chloride, chloroform, 1,2-dichloroethane, chlorobenzene, dichlorobenzene, and fluoro. Halogened hydrocarbon solvent such as benzene; Ether solvent such as diethyl ether, tetrahydrofuran, 1,4-dioxane, methoxybenzene; Ketone solvent such as acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone; ethylene glycol monomethyl ether, ethylene glycol Glycol-based solvents such as monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and propylene glycol monomethyl ether acetate; amide-based solvents such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone; dimethyl Sulphonic solvents such as sulfoxide; heterocyclic solvents such as pyridine, picolin, lutidine, quinoline, isoquinoline; phenolic solvents such as phenol and cresol; lactone solvents such as γ-butyrolactone, γ-valerolactone and δ-valerolactone ; Etc. can be mentioned. One of these solvents may be used alone, or two or more of these solvents may be used in any ratio and combination.

In the present invention, it is particularly preferable to use dimethylacetamide (DMAc) among these production solvents.

The obtained polyimide precursor may be used as it is for the next imidization, or may be added to a poor solvent to precipitate it in a solid state before use.

The poor solvent to be used is not particularly limited and may be appropriately selected depending on the type of polyimide precursor. Examples of the poor solvent include ether solvents such as diethyl ether and diisopropyl ether; ketone solvents such as acetone, methyl ethyl ketone, isobutyl ketone and methyl isobutyl ketone; alcohol solvents such as methanol, ethanol and isopropyl alcohol; and the like. Above all, an alcohol solvent is preferable because a precipitate can be efficiently obtained, a boiling point is low, and drying tends to be easy. One of these solvents may be used alone, or two or more of these solvents may be used in any ratio and combination.

(Immidization of polyimide precursor)
A polyimide can be obtained by dehydrating and cyclizing the polyimide precursor obtained by the above method or the like in the presence of a solvent. Imidization can be performed using any of the conventionally known methods. Examples of the imidization method include thermal imidization for thermal cyclization, chemical imidization for chemical cyclization, and the like. These imidization reactions may be carried out individually or in combination of two or more.

<Heating imidization>
Examples of the solvent for heat imidizing the polyimide precursor include the same solvent used in the reaction for obtaining the polyimide precursor. The solvent used for producing the polyimide precursor and the solvent used for producing the polyimide may be the same or different.
The water produced by imidization inhibits the ring closure reaction and may be discharged out of the system.
The concentration of the polyimide precursor at the time of the imidization reaction is not particularly limited, but is usually 1% by mass or more, preferably 5% by mass or more, and usually 70% by mass or less, preferably 40% by mass or less. By adjusting the concentration of the polyimide precursor in this range, it is possible to produce the polyimide precursor with a solution viscosity that is easy to produce and has high production efficiency.

The reaction temperature for imidization is not particularly limited, but is usually 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and usually 300 ° C. or lower, preferably 280 ° C. or lower, further preferably 250 ° C. or lower. .. It is preferable to carry out the reaction in this temperature range because the imidization reaction proceeds efficiently and reactions other than the imidization reaction tend to be suppressed.
The pressure during the reaction may be normal pressure, pressurization, or depressurization.
The reaction atmosphere may be under air or under an inert atmosphere.

As an imidization accelerator that promotes imidization, a compound having a function of enhancing nucleophile and electrophile can be added. Examples of the imidization accelerator include trimethylamine, triethylamine, tripropylamine, tributylamine, triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, triethylenediamine, N-methylpyrrolidin, N-. Tertiary amine compounds such as ethylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, imidazole, pyridine, quinoline, isoquinoline; acetic acid, 4-hydroxyphenylacetic acid, 3-hydroxybenzoic acid, N-acetylglycine, N-benzoylglycine Carboxylic acid compounds such as 3,5-dihydroxyacetophenone, methyl 3,5-dihydroxybenzoate, pyrogallol, methyl gallate, ethyl gallate, polyvalent phenol compounds such as naphthalene-1,6-diol; 2-hydroxypyridine, 3 -Hydroxypyridine, 4-hydroxypyridine, 4-pyridinemethanol, N, N-dimethylaminopyridine, nicotine aldehyde, isonicotin aldehyde, picolin aldehyde, picolin aldehyde oxime, nicotine aldehyde oxime, isonicotin aldehyde oxime, ethyl picolinate, nicotine Ethyl Acid, Ethyl Isonicotinate, Nicotinamide, Isonicotinamide, 2-Hydroxynicotinic Acid, 2,2'-Dipyridyl, 4,4'-Dipyridyl, 3-Methylpyridazine, Kinolin, Isoquinolin, Phenantroline, 1,10- Heterocyclic compounds such as phenanthroline, imidazole, benzimidazole, 1,2,4-triazole; and the like.

Of these, at least one selected from the group consisting of tertiary amine compounds, carboxylic acid compounds and heterocyclic compounds is preferable, and at least one selected from the group consisting of triethylamine, imidazole and pyridine controls the reaction rate. It is more preferable because it tends to be easy. One of these compounds may be used alone, or two or more thereof may be used in any ratio and combination.

The amount of the imidization accelerator used is usually 0.01 mol% or more, preferably 0.1 mol% or more, and further preferably 1 mol% or more, based on the carboxyl group of the polyimide precursor. The amount of the imidization accelerator used is preferably 50 mol% or less, more preferably 10 mol% or less, based on the carboxyl group of the polyimide precursor. When the amount of the imidization accelerator used is within the above range, the imidization reaction tends to proceed efficiently.
The timing of adding the imidization accelerator can be appropriately adjusted, and may be before the start of heating or during heating. Further, it may be added in a plurality of times.

<Chemical imidization>
A polyimide can be obtained by chemically imidizing a polyimide precursor with a dehydration condensing agent in the presence of a solvent.

Examples of the solvent used for chemical imidization include the same solvents as those used for the reaction for obtaining the polyimide precursor described above.

Examples of the dehydration condensing agent include N, N-2 substituted carbodiimides such as N, N-dicyclohexylcarbodiimide and N, N-diphenylcarbodiimide; acid anhydrides such as acetic anhydride and trifluoroacetic anhydride; thionyl chloride, tosyl chloride and the like. Chloride; acetyl chloride, acetyl bromide, propionyl iodide, acetyl fluoride, propionyl chloride, propionyl bromide, propionyl iodide, propionyl fluoride, isobutyryl chloride, isobutyryl bromide, isobutyryl iodide, isobuchi Lilfluoride, n-butyryl chloride, n-butyryl bromide, n-butyryl iodide, n-butyryl fluoride, mono-, di-, tri-chloroacetyl chloride, mono-, di-, tri- Bromoacetyl chloride, mono-, di-, tri-iodoacetyl chloride, mono-, di-, tri-fluoroacetyl chloride, chloroacetic anhydride, phenylphosphonic dichloride, thionyl chloride, thionyl bromide, thionyliodide, thionylfluo Halogen compounds such as rides; phosphorus compounds such as phosphorus trichloride, triphenyl phosphite, and diethyl phosphate cyanide; and the like.

Among these, acid anhydrides and halogenated compounds are preferable, and acid anhydrides are particularly preferable because the imidization reaction tends to proceed efficiently. One of these compounds may be used alone, or two or more thereof may be used in any ratio and combination.

The amount of these dehydration condensing agents used is usually 0.1 mol or more, preferably 0.2 mol or more, and usually 1.6 mol or less, preferably 1.0 mol or less, with respect to 1 mol of the polyimide precursor. By setting the amount of the dehydration condensing agent used within this range, imidization can be performed efficiently.

The concentration of the polyimide precursor in the reaction solution during the imidization reaction is not particularly limited, but is usually 1% by mass or more, preferably 5% by mass or more, and usually 70% by mass or less, preferably 40% by mass or less. .. By setting the concentration of the polyimide precursor in the range, the production efficiency can be increased, and the solution viscosity tends to be easy to produce.

The imidization reaction temperature is not particularly limited, but is usually 0 ° C. or higher, preferably 10 ° C. or higher, and more preferably 20 ° C. or higher. Further, it is usually 150 ° C. or lower, preferably 130 ° C. or lower, and more preferably 100 ° C. or lower. It is preferable to carry out the reaction in this temperature range because the imidization reaction tends to proceed efficiently. Further, it is preferable because side reactions other than the imidization reaction are suppressed.
The pressure during the reaction may be normal pressure, pressurization or depressurization.
The reaction atmosphere may be under air or under an inert atmosphere.

As a catalyst for promoting imidization, an imidization accelerator such as the above-mentioned tertiary amine compound can be added in the same manner as for heat imidization.

<< Method of producing polyimide from tetracarboxylic dianhydride, etc. and diamine compound, etc. >>
Polyimide can be directly obtained from a tetracarboxylic dianhydride or the like and a diamine compound or the like by using a conventionally known method. This method involves the synthesis and imidization of the poimide precursor, and the imidization without stopping the reaction or isolating the precursor.

The order and method of adding the tetracarboxylic dianhydride and the like and the diamine compound and the like are not particularly limited. For example, the tetracarboxylic dianhydride and the like and the diamine compound and the like are added in order to the solvent, and the reaction up to imidization Polyimide can be obtained by stirring at a temperature at which

The amount of the diamine compound or the like is usually 0.7 mol or more, preferably 0.8 mol or more, usually 1.3 mol or less, preferably 1.2 mol or less, relative to 1 mol of the tetracarboxylic dianhydride or the like. By setting the amount of the diamine compound or the like in such a range, the yield of the obtained polyimide tends to be improved.

The concentrations of the tetracarboxylic dianhydride and the like and the diamine compound and the like in the reaction solution can be appropriately set according to each condition and the viscosity during the polymerization.
The total concentration of the tetracarboxylic dianhydride and the like and the diamine compound and the like in the reaction solution is not particularly set, but is usually 1% by mass or more, preferably 5% by mass or more, and usually 70% by mass or less, preferably 40. It is mass% or less. When the concentration in the reaction solution is in an appropriate range, the molecular weight tends to be extended and stirring tends to be easy.

Examples of the solvent used in this reaction include the same solvents used in the reaction for obtaining the polyimide precursor described above.

When the polyimide is obtained from a tetracarboxylic dianhydride or the like and a diamine compound or the like, heat imidization and / or chemical imidization can be adopted as in the case of obtaining a polyimide from a polyimide precursor. The reaction conditions for heat imidization and chemical imidization in this case are the same as described above.

The obtained polyimide may be used as it is, or may be added to a poor solvent to precipitate the polyimide into a solid state, and then redissolved in another solvent to be used as a polyimide composition.

The poor solvent at this time is not particularly limited and can be appropriately selected depending on the type of polyimide. Examples of the poor solvent include ether solvents such as diethyl ether and diisopropyl ether; ketone solvents such as acetone, methyl ethyl ketone, isobutyl ketone and methyl isobutyl ketone; alcohol solvents such as methanol, ethanol and isopropyl alcohol; and the like. .. Above all, an alcohol solvent such as isopropyl alcohol is preferable because a precipitate can be efficiently obtained, the boiling point is low, and drying tends to be easy. One of these solvents may be used alone, or two or more of these solvents may be used in any ratio and combination.

Examples of the solvent for redissolving polyimide include hydrocarbon solvents such as hexane, cyclohexane, heptane, benzene, toluene, xylene, mecitylene, and anisole; N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl. -Amid solvent such as pyrrolidone; Aproton solvent such as dimethyl sulfoxide; Glycol solvent such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate; chloroform, Examples thereof include halogen-based solvents such as methylene chloride and 1,2-dichloroethane. One of these solvents may be used alone, or two or more of these solvents may be used in any ratio and combination.

<< When using dicarboxylic acid chloride >>
When the polyimide of the present invention having the structure represented by the general formula (1) is produced by using dicarboxylic acid chloride as the dicarboxylic acid compound, the reaction with the diamine compound or the like can be carried out by a conventionally known method. For example, a dicarboxylic acid chloride or a tetracarboxylic acid dianhydride containing a dicarboxylic acid chloride may be added to a solution in which a diamine compound or the like is mixed with a solvent, or a tetracarboxylic acid dianhydride containing a dicarboxylic acid chloride or a dicarboxylic acid chloride in the solvent. A diamine compound or the like may be added to the mixed solution.

The temperature at which these compounds are added is not particularly limited, but is preferably −80 ° C. or higher, more preferably −50 ° C. or higher, still more preferably −30 ° C. or higher, preferably 100 ° C. or lower, and more preferably. It is 80 ° C. or lower, more preferably 50 ° C. or lower. When the temperature of addition is in this range, the reaction tends to be easily controlled, which is preferable.

The temperature at which the tetracarboxylic dianhydride containing the dicarboxylic acid chloride is reacted with the diamine compound or the like is not particularly limited, but is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, still more preferably 10 ° C. or higher, preferably 200 ° C. or higher. ° C. or lower, more preferably 150 ° C. or lower, still more preferably 120 ° C. or lower. It is preferable that the reaction temperature is in this range because the reaction tends to be easily controlled.

When reacting a tetracarboxylic dianhydride containing a dicarboxylic acid chloride with a diamine compound or the like, a catalyst may be added.
The catalyst to be added is not particularly limited as long as it is conventionally known. Examples of the catalyst include trimethylamine, triethylamine, tripropylamine, tributylamine, triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, triethylenediamine, N-methylpyrrolidine, N-ethylpyrrolidine, and the like. Examples thereof include tertiary amine compounds such as N-methylpyrrolidine, N-ethylpyrrolidine, imidazole, pyridine, quinoline, and isoquinolin. One of these may be used alone, or two or more thereof may be used in any ratio and combination.

[Manufacturing method of polyimide film]
The method for producing the polyimide film of the present invention is not particularly limited, and for example, it can be produced by applying a polyimide composition in which the polyimide of the present invention is dissolved in a solvent to a substrate by a casting method or the like.

The content of polyimide in the polyimide composition is not particularly limited, and can be appropriately adjusted according to the manufacturing process and the like. The content of polyimide in the polyimide composition is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 70% by mass or less, and more preferably 60% by mass or less. When the polyimide content is in this range, film formation and handling in ordinary equipment are easy, which is preferable.

The polyimide composition may contain other components in addition to the polyimide and the solvent.
Other components include, for example, surfactants, antioxidants, lubricants, colorants, stabilizers, UV absorbers, antistatic agents, flame retardants, plasticizers, mold release agents, leveling agents, defoamers, etc. Can be mentioned. In addition, if necessary, an inorganic filler or an organic filler such as powder, granular, plate, or fibrous may be blended as long as the object of the invention is not impaired.
These additive components may be added at any stage of any process for producing the polyimide precursor and / or the polyimide composition.

Among these components, it is preferable that the polyimide composition contains a surfactant because the solubility of the polyimide in a solvent tends to be improved.
Examples of the surfactant include a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant and the like. The surfactant may be used alone or in combination of two or more.

Specific examples of the cationic surfactant used in the present invention include amine type and quaternary ammonium salt type.
Examples of the amine type include aliphatic amines such as polyoxyethylene alkylamines and alkylamine salts, and heterocyclic amine salts such as alkylimidazolines.
The quaternary ammonium salt type includes alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkylbenzyldimethylammonium salt, polydiallyldimethylammonium salt; chlorine salt type such as alkyltrimethylammonium chloride and dialkyldimethylammonium chloride; alkyldimethylethylammonium. Non-chlorine type such as ethyl sulfate; and the like.

Specific examples of the anionic surfactant used in the present invention include sulfate ester type, phosphoric acid ester type, carboxylic acid type, and sulfonic acid type.
Specific examples of the sulfate ester type include alkyl sulfate ester, ethoxy sulfate ester, polyoxyethylene styrene phenyl sulfate ester, polyoxyethylene alkyl ether sulfate ester, long-chain alcohol sulfate ester, other sulfate esters, and salts thereof. Can be mentioned.
Specific examples of the phosphoric acid ester type include polyoxyethylene alkyl ether phosphoric acid esters and salts thereof.
Specific examples of the carboxylic acid type include fatty acids, polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl ether sulfosuccinic acid, alkenyl succinic acid, polyacrylic acid, styrene-maleic acid copolymer ammonium, carboxymethyl cellulose, polyacrylic acid, and polycarboxylic acid. Acids and salts thereof may be mentioned.
Specific examples of the sulfonic acid type include sulfonic acid, sulfosuccinic acid, alkylbenzene sulfonic acid, alkane sulfonic acid, alpha olefin sulfonic acid, phenol sulfonic acid, sodium naphthalene sulfonic acid formalin condensate, and salts thereof.

Specific examples of the amphoteric surfactant used in the present invention include betaine type, amine oxide type, N-alkylamino acid type and imidazoline type.
Specific examples of the betaine type include alkyl betaine, amide betaine such as aliphatic amide betaine, and the like.
Specific examples of the amine oxide type include alkylamine oxides and the like.
Specific examples of the N-alkyl amino acid type include N-alkyl-β-aminopropionate.
Specific examples of the imidazoline type include 2-alkylimidazoline derivatives.

Specific examples of the nonionic surfactant used in the present invention include ether type, ester type, ether ester type, polyhydric alcohol type, amide type, and polymer type.
Specific examples of the ether type include polyoxyalkylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, and polyoxyethylene alkyl amine.
Examples of the ester type include sorbitan fatty acid ester, glycerin fatty acid ester, sucrose fatty acid ester, sucrose derivative, and fatty acid ester.
Examples of the ether ester type include polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene fatty acid ester, and polyoxyethylene hydrogenated castor oil ether.
Examples of the polyhydric alcohol type include alkyl glucosides and alkyl polyglucosides.
Specific examples of the amide type include alkylalkanolamides.
Specific examples of the polymer type include polyvinylpyrrolidone, a polyalkylene polyamine alkylene oxide adduct, and a polyalkylene polyimine alkylene oxide adduct.

Specific examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as Emargen 123P, Emargen 130K, Emargen 150, Emargen 430, Emargen 409PV, Emargen 705, Emargen 707, and Emargen 709 (manufactured by Kao); Sorbitane fatty acid esters such as (Daiichi Kogyo Seiyaku Co., Ltd.), New Coal 20, New Coal 60, and New Coal 80 (manufactured by Nippon Emulsifier); Examples thereof include sucrose fatty acid esters such as DK ester F-110 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and polyvinylpyrrolidone such as Pittscol K-30 and Pittscol K-40 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

Among the above, it is preferable to use a nonionic surfactant. By using a nonionic surfactant, the solubility of polyimide in a solvent tends to be improved.

The polyimide composition is preferable because it tends to contain a leveling agent as another component to improve the smoothness of the obtained polyimide film.
Examples of the leveling agent include silicone compounds and the like. The silicone-based compound is not particularly limited, and for example, polyether-modified siloxane, polyether-modified polydimethylsiloxane, polyether-modified hydroxyl group-containing polydimethylsiloxane, polyether-modified polymethylalkylsiloxane, polyester-modified polydimethylsiloxane, and polyester-modified hydroxyl group. Examples thereof include polydimethylsiloxane contained, polyester-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, highly polymerized silicone, amino-modified silicone, amino derivative silicone, phenyl-modified silicone, and polyether-modified silicone. One of these may be used alone, or two or more thereof may be used in any ratio and combination.

The film forming method of the polyimide film using the above-mentioned polyimide composition is sometimes not limited, but examples thereof include a method of applying the polyimide composition to a substrate or the like.

Examples of the coating method include die coating, spin coating, dip coating, screen printing, spraying, casting method (single leaf method and continuous method), method using a coater, coating method by spraying, dipping method calendar method and the like. These methods can be appropriately selected depending on the coated area, the shape of the surface to be coated, and the like.
Of these, since the uniformity of the coating film thickness is good and the surface smoothness tends to be good, it is preferable to adopt a casting method or a method using a coater, and the casting method is more preferable.

There is no particular limitation on the method of volatilizing the solvent contained in the film formed by coating or the like. Usually, the solvent is volatilized by heating the film formed by coating or the like. The heating method is not particularly limited, and examples thereof include hot air heating, vacuum heating, infrared heating, microwave heating, and heating by contact using a hot plate / hot roll or the like.

As the heating temperature when the solvent is volatilized, a suitable temperature can be used depending on the type of solvent. The heating temperature is usually above the boiling point of the solvent, preferably above the boiling point of the solvent + 50 ° C, more preferably above the boiling point of the solvent + 100 ° C, usually below the boiling point of the solvent + 200 ° C, preferably above the boiling point of the solvent + 180 ° C. Hereinafter, the boiling point of the solvent is more preferably + 150 ° C. or lower. When the heating temperature is in the above range, the solvent is preferably sufficiently volatilized.

The polyimide film of the present invention can be obtained, for example, by applying a polyimide composition containing the polyimide of the present invention and a casting solvent to a support as described above, heating the support, and peeling the film from the support.

The method of peeling the polyimide film from the support is not particularly limited, but a physical peeling method or a laser peeling method is preferable in that the polyimide film can be peeled off without impairing the performance of the film or the like.

Examples of the method of physically peeling include a method of obtaining a polyimide film by cutting off the peripheral edge of a laminate made of a polyimide film / support, a method of sucking the peripheral edge portion to obtain a polyimide film, and a method of fixing the peripheral edge and supporting a base material. A method of obtaining a polyimide film by moving the film can be mentioned.

[Thickness of polyimide film]
The thickness of the polyimide film of the present invention is usually 1 μm or more, preferably 2 μm or more, and usually 300 μm or less, preferably 200 μm or less. When the thickness is 1 μm or more, the polyimide film can obtain sufficient strength and can be obtained as a self-supporting film, and the handleability tends to be improved. Further, by setting the thickness to 300 μm or less, the uniformity of the film tends to be easily ensured.

[Mechanical properties of polyimide film]
The performance required for the polyimide film of the present invention depends on the application, but it is preferable to have the following mechanical properties.

The tensile strength of the polyimide film of the present invention is not particularly limited, but is usually 50 MPa or more, preferably 70 MPa or more, more preferably 100 MPa or more, still more preferably 150 MPa or more in measurement at 23 ° C. and 50% humidity. It is usually 400 MPa or less, preferably 300 MPa or less.

The tensile elastic modulus of the polyimide film of the present invention is not particularly limited, but is usually 1500 MPa or more, preferably 1800 MPa or more, more preferably 2000 MPa or more, and particularly preferably 3000 MPa or more in measurement at 23 ° C. and 50% humidity. , Usually 20 GPa or less, preferably 10 GPa or less.

The tensile elongation of the polyimide film of the present invention is not particularly limited, but is usually 10% GL or more, preferably 20% GL or more, more preferably 50 GL% or more in measurement at 23 ° C. and 50% humidity. It is usually 400% GL or less, preferably 300% GL or less.

The pencil hardness of the polyimide film of the present invention is not particularly limited, but is preferably 2B or more, more preferably B or more, still more preferably F or more, and particularly preferably H or more.
Examples of the method for measuring the pencil hardness as the surface hardness include JIS K 5600-5-4.

It is preferable that the polyimide film has mechanical properties in such a range, so that the polyimide film has more excellent durability.

[Laminate]
The polyimide film of the present invention can also be used as a laminate. For example, on the polyimide film of the present invention, a hard coat layer having a function of imparting scratch resistance, abrasion resistance, etc., a layer having a function of imparting optical compensation, etc., an adhesive layer, and the like can be provided. The same or different layers may be provided on both sides of the polyimide film of the present invention.

The polyimide film of the present invention has a high surface hardness, excellent bending resistance, high light transmittance, elastic modulus, flexibility, transparency, high solvent solubility, and high device applicability. It is useful as a cover film for. In this application, it can be used as a laminate having a hard coat layer on the polyimide film of the present invention.

The hard coat layer can be formed directly on the polyimide film or through an adhesive layer or the like.
The hard coat layer is not particularly limited and can be formed by using a commonly used hard coat agent. Examples of the hard coating agent include curable resins such as light and heat, inorganic materials, and curable resins containing inorganic materials. The forming method can be selected according to each material. Further, a defoaming agent, a leveling agent, a thickener, an antistatic agent, an antifogging agent and the like may be appropriately added to the hard coating agent, if necessary.

The thickness of the hard coat layer is not particularly limited, but is preferably 50 μm or more, and more preferably 60 μm or more. The thickness of the hard coat layer is preferably 200 μm or less, and preferably 180 μm or less. When the thickness of the hard coat layer is within this range, it tends to be excellent in high surface hardness and bending resistance.

The pencil hardness of the surface of the hard coat layer in the laminate of the present invention is not particularly limited, but is preferably B or higher, more preferably F or higher, still more preferably H or higher, and particularly preferably 2H or higher.

Especially when the laminate is used for light transmission such as display applications, it is desirable that the polyimide film / hard coat layer laminate has high transparency. The YI (yellowness) of the laminate of the present invention is not particularly limited, but is preferably 5 or less, more preferably 4.5 or less, still more preferably 4 or less, and particularly preferably 3.5 or less.

The haze of the laminate of the present invention is not particularly limited, but is preferably 3% or less, more preferably 2% or less, still more preferably 1.5% or less, and particularly preferably less than 1%.

The present invention will be described in more detail below by way of examples. The following examples are shown for explaining the present invention in detail, and the present invention is not limited to the following examples unless contrary to the gist thereof.

[Film molding]
A solution prepared by dissolving polyimide in N, N-dimethylacetamide at a concentration of 20% by mass was applied to a soda glass substrate using a 500 μm applicator, and dried at 330 ° C. or 280 ° C. for 30 minutes. Then, it was peeled off from the glass substrate to obtain a polyimide film having a thickness of 50 μm.

[Elastic modulus at 30 ° C. ( _E'RT ) and elastic modulus of rubber-like flat region ( _GN ⁰ )]
Using a dynamic viscoelastic analyzer (SII6100 manufactured by Hitachi High-Tech Science Co., Ltd.), the sample size was measured in a temperature range of room temperature to 480 ° C. with a sample size width of 10 mm, a length of 20 mm, a frequency of 10 Hz, and a heating rate of 5 ° C./min. The value of the curve plotting the storage elastic modulus with respect to temperature at 30 ° C. was determined as the elastic modulus ( _E'RT ) at 30 ° C.
Further, the value of the elastic modulus (E') in the flat region of the elastic modulus (E') in the temperature range exceeding Tg was determined as the elastic modulus ( _GN ⁰ ) in the rubber-like flat region.

[Bending resistance]
Using a MIT tester, a polyimide film having a width of 15 mm and a length of 110 mm was bent at a bending radius of 0.38 mm and a speed of 175 times / min, and evaluated as the number of reciprocating bends until the test piece broke.

[surface hardness]
In accordance with JIS K 5600-5-4, the pencil hardness was measured with a pencil hardness tester (manufactured by Yasuda Seiki Co., Ltd.) under a load condition of 750 g, and the surface hardness was evaluated.

[Example 1]
16.7 g of 3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride in a four-necked flask equipped with a nitrogen gas introduction tube, a cooler, a Dean-Stark aggregator filled with toluene, and a stirrer. 2,2-Bis (3,4-dicarboxyphenyl) -1,1,1,1,3,3,3-hexafluoropropane dianhydride 24.2 g, 4,4'-diamino-2,2'-dimethyl 23.4 g of biphenyl, 193 g of N-methyl-2-pyrrolidone (NMP), and 38.5 g of toluene were added, and the mixture was heated under reflux in an oil bath at 180 ° C. for 20 hours. 100 g of the obtained reaction solution was diluted 7-fold with N, N-dimethylacetamide (DMAc), and this solution was added dropwise to 3 L of isopropanol with stirring at room temperature. The precipitated solid was collected by filtration to obtain a wet cake. This wet cake was placed in a 500 mL separable flask, 1 L of isopropanol was added, the mixture was stirred in an oil bath at 60 ° C., collected by filtration, and dried under reduced pressure at 150 ° C. to obtain Polyimide 1.
A film was formed from the obtained polyimide 1 at a drying temperature of 330 ° C. The obtained polyimide film was subjected to dynamic viscoelasticity analysis, bending resistance and surface hardness evaluation. The results are shown in Table 1.

[Example 2]
3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride 16.7 g, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa Fluoropropane dianhydride 24.2 g, 4,4'-diamino-2,2'-dimethylbiphenyl 23.4 g, 3,3', 4,4'-bicyclohexanetetracarboxylic dianhydride 33.4 g, Polyethylene 2 was obtained in the same manner as in Example 1 except that 35.2 g of 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl was used.
A film was formed using the obtained polyimide 2 at a drying temperature of 330 ° C. The obtained polyimide film was subjected to dynamic viscoelasticity analysis, bending resistance and surface hardness evaluation. The results are shown in Table 1.

[Example 3]
3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride 30.9 g, 2,2'in a four-necked flask equipped with a nitrogen gas introduction tube, a cooler, a Dean-Stark aggregator, and a stirrer. -Bis (trifluoromethyl) -4,4'-diaminobiphenyl 24.0 g, isophthalic acid dihydrazide 4.9 g, NMP 140 g, xylene 92.7 g were added, and the mixture was heated and stirred in an oil bath at 80 ° C. for 1 hour, and then at 200 ° C. The mixture was heated under reflux in an oil bath for 13 hours. Of the obtained reaction solution, 20 g was diluted 5-fold with DMAc, and this solution was added dropwise to 500 mL of isopropanol with stirring at room temperature. After collecting the precipitated powder by filtration, the wet cake was placed in 200 mL of isopropanol and stirred at room temperature for 30 minutes. The powder was collected by filtration and dried under reduced pressure at 80 ° C. for 30 minutes and at 150 ° C. for 30 minutes to obtain Polyimide 3.
A film of the obtained polyimide 3 was formed at a drying temperature of 280 ° C. The obtained polyimide film was subjected to dynamic viscoelasticity analysis, bending resistance and surface hardness evaluation. The results are shown in Table 1.

[Comparative Example 1]
3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride 16.7 g, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa 24.2 g of fluoropropanedianhydride, 4,4'-diamino-2,2'-dimethylbiphenyl 23.4 g, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3 , 3,3-Hexafluoropropane dianhydride 48.4 g, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl 35.2 g, the same polyimide as in Example 1. I got 4.
A film was formed using the obtained polyimide 4 at a drying temperature of 330 ° C. The obtained polyimide film was subjected to dynamic viscoelasticity analysis and bending resistance evaluation. The results are shown in Table 1.

[Comparative Example 2]
3,3', 4,4'-biscyclohexanetetracarboxylic dianhydride 16.7 g, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa Polyethylene 5 was obtained in the same manner as in Example 1 except that 24.2 g of fluoropropane dianhydride was changed to 23.5 g of benzene-1,2,4,5-tetracarboxylic dianhydride.
A film was formed using the obtained polyimide 5 at a drying temperature of 330 ° C. The obtained polyimide film was subjected to dynamic viscoelasticity analysis, bending resistance and surface hardness evaluation. The results are shown in Table 1.

From Table 1, the elastic modulus ( _E'RT ) at 30 ° C. is 3.0 × 10 ⁹ Pa or more, and the elastic modulus ( _GN ⁰ ) in the rubber-like flat region is less than 1.5 × 10 ⁷ Pa. It can be seen that the polyimide film can achieve both high surface hardness and bending resistance.

In contrast, the polyimide film of Comparative Example 1, even the elastic modulus of 30 ℃ (E _'RT) is 3.0 × ¹⁰ 9 Pa or more, the elastic modulus of a rubber-like plateau region ^{_(G N} 0) There inferior in bending resistance was 1.5 × ¹⁰ 7 Pa.
In Comparative Example 2, no clear _GN ⁰ could be observed, the bending resistance was inferior, the pencil hardness was low, and it was difficult to achieve both high surface hardness and bending resistance.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the invention.
This application is based on Japanese Patent Application 2019-051100 filed on March 19, 2019 and Japanese Patent Application 2019-153990 filed on August 26, 2019, which are incorporated by reference in their entirety. ..

Claims (8)

1. Polyimide film 30 elastic modulus at ℃ (E _'RT) is 3.0 × ¹⁰ 9 Pa or more, the elastic modulus in the rubber-like flat regions _(G ^{N 0)} is less than 1.5 × ¹⁰ 7 Pa.
2. The polyimide film according to claim 1, wherein the elastic modulus ( _E'RT ) at 30 ° C. is 3.5 × 10 ⁹ Pa or more.
3. Is the elastic modulus at 30 ℃ (E _'RT) is 4.0 × ¹⁰ 9 Pa or more, a polyimide film according to claim 1 or 2.
4. The polyimide film according to any one of claims 1 to 3, wherein the tetracarboxylic acid residue constituting the polyimide contained in the polyimide film contains an alicyclic structure.
5. The polyimide film according to any one of claims 1 to 4, wherein the polyimide film has a film thickness of 1 μm or more and 300 μm or less.
6. The polyimide film according to any one of claims 1 to 5, which is obtained by a casting method.
7. A laminate having a hard coat layer on the surface of the polyimide film according to any one of claims 1 to 6.
8. The laminate according to claim 7, wherein the hard coat layer has a film thickness of 50 μm or more and 200 μm or less.

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