JP7230820B2 - Polyimide varnish composition, method for producing the same, and polyimide film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyimide varnish composition, a method for producing the same, and a polyimide film.

Generally, polyimide is obtained from aromatic tetracarboxylic acid anhydride and aromatic diamine, and has excellent heat resistance, chemical resistance, mechanical properties, and electrical properties due to molecular rigidity, resonance stabilization, and strong chemical bonding. , molding materials, composite materials, electrical and electronic parts, optical materials, displays, aerospace, and other fields.
In recent years, properties such as colorless transparency and solvent solubility as polyimide have been required. However, many conventional polyimides have problems such as high haze value and yellow index (YI: yellowness).

For example, in Patent Document 1, a polyimide containing a fluorinated polyimide layer made using a fluorinated diamine and a fluorinated acid anhydride and having a haze value of 4 or less, a YI of 3 or less, and a total light transmittance of 90% or more A film is disclosed.

JP 2016-27146 A

However, the polyimide film of Patent Document 1 is produced through a process of refining a fluorinated polyimide solution by reprecipitation. Therefore, it is desired to improve the colorless transparency of the polyimide film by a simpler method.
That is, the problem to be solved by the present invention is to provide a polyimide varnish composition capable of forming a film having excellent colorless transparency, a method for producing the same, and a polyimide film obtained from the polyimide varnish composition.

As a result of intensive studies by the inventors, the YI of a polyimide varnish composition containing a polyimide composed of specific structural units and a specific organic solvent is greatly reduced, and the polyimide film obtained from the varnish composition is It was found to be excellent in colorless transparency. Based on these findings, the inventors have completed the present invention. That is, the present invention relates to the following [1] to [3].
[1] A polyimide varnish composition containing polyimide and an organic solvent,
The polyimide has a structural unit A derived from a tetracarboxylic acid or a derivative thereof and a structural unit B derived from a diamine,
The structural unit A comprises a structural unit (A-1) derived from a compound represented by the following formula (a-1),
At least one organic solvent selected from lactone-based solvents is contained in an amount of 20% by mass or more with respect to the total amount of the polyimide varnish composition,
A polyimide varnish composition having a YI of 20 or less measured at 23° C. in a cell with an optical path length of 10 mm.

[2] A polyimide film obtained from the polyimide varnish composition.
[3] In the presence of at least one organic solvent selected from lactone solvents and in the absence of a catalyst and dehydrating agent, a diamine component and 4,4'-(hexafluoroisopropylidene)diphthalic acid or a derivative thereof A method for producing a polyimide varnish composition containing a polyimide and an organic solvent by reacting with a tetracarboxylic acid component, wherein the content of the lactone solvent is 20% by mass with respect to the total amount of the polyimide varnish composition A method for producing a polyimide varnish composition as described above, wherein YI of the polyimide varnish composition measured at 23° C. in a cell with an optical path length of 10 mm is 20 or less.

ADVANTAGE OF THE INVENTION According to this invention, the polyimide varnish composition which can form the film excellent in colorless transparency, its manufacturing method, and the polyimide film obtained from this polyimide varnish composition can be provided.

The polyimide varnish composition of the present invention contains polyimide and an organic solvent. The polyimide varnish composition of the present invention may be abbreviated as "varnish composition".
The polyimide varnish composition of the present invention is described below.

The polyimide contained in the varnish composition of the present invention has a structural unit A derived from a tetracarboxylic acid or a derivative thereof and a structural unit B derived from a diamine, and the structural unit A has the following formula (a-1 ) containing a structural unit (A-1) derived from a compound represented by

[Constituent unit A]
The structural unit A contained in the polyimide according to the present invention is a structural unit derived from tetracarboxylic acid or a derivative thereof. A tetracarboxylic acid or its derivative can be used individually or in combination of 2 or more types.
Derivatives of tetracarboxylic acids include anhydrides or alkyl esters of tetracarboxylic acids. As the alkyl ester of tetracarboxylic acid, the alkyl preferably has 1 to 3 carbon atoms, and examples thereof include dimethyl ester, diethyl ester and dipropyl ester of tetracarboxylic acid. As the tetracarboxylic acid or derivative thereof, tetracarboxylic dianhydride is preferred.

Structural unit A includes a structural unit (A-1) derived from the compound represented by formula (a-1) above. Including the structural unit (A-1) in the structural unit A improves the colorless transparency of the film.
The ratio of the structural unit (A-1) to the structural unit A is preferably 30 mol% or more, more preferably 35 mol% or more, still more preferably 40 mol% or more, still more preferably 45 mol% or more, still more preferably is 50 mol% or more, and preferably 100 mol% or less, more preferably 95 mol% or less, even more preferably 90 mol% or less, even more preferably 80 mol% or less, even more preferably 70 mol% or less, Even more preferably, it is 60 mol % or less.

Structural unit A may further contain a structural unit (A-2) derived from a compound represented by the following formula (a-2) from the viewpoint of heat resistance, mechanical properties (elastic modulus), and organic solvent resistance. preferable.

Examples of the compound represented by formula (a-2) include 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) represented by formula (a-2-1) below, 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a-2-2), 2 represented by the following formula (a-2-3) ,2′,3,3′-biphenyltetracarboxylic dianhydride (i-BPDA), among which 3,3′,4,4′-biphenyl represented by the following formula (a-2-1) Tetracarboxylic dianhydrides are preferred. The compounds represented by formula (a-2) can be used alone or in combination of two or more.
s-BPDA is preferable from the viewpoint of organic solvent resistance, and a-BPDA and i-BPDA are preferable from the viewpoint of heat resistance and solution processability.

The ratio of the structural unit (A-2) to the structural unit A is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably from the viewpoint of heat resistance, mechanical properties (elastic modulus), and organic solvent resistance. is 20 mol % or more, more preferably 30 mol % or more, and even more preferably 40 mol % or more. From the viewpoint of improving the colorless transparency of the film, the proportion of (A-2) is preferably 70 mol% or less, more preferably 65 mol% or less, even more preferably 60 mol% or less, and even more preferably 55 mol%. Below, it is more preferably 50 mol % or less.
When the structural unit A contains the structural unit (A-2), the molar ratio [(A-1)/(A-2)] between the structural unit (A-1) and the structural unit (A-2) is , Colorless transparency, heat resistance, from the viewpoint of mechanical properties (elastic modulus), preferably 30/70 to 95/5, more preferably 35/65 to 90/10, more preferably 40/60 to 80/20, 45/55 to 70/30 is even more preferred, and 50/50 to 60/40 is even more preferred

In the structural unit A constituting the polyimide according to the present invention, the total proportion of the structural unit (A-1) and the structural unit (A-2) is preferably 70 to 100 mol%, more preferably 85 to 100 mol %, more preferably 99 to 100 mol %, still more preferably 100 mol %.
In the polyimide according to the present invention, in the structural unit A, as a structural unit other than the structural units (A-1) and (A-2), the formula (a-1) and may contain structural units derived from a tetracarboxylic dianhydride other than the compound represented by (a-2), but preferably does not.

[Constituent unit B]
The structural unit B contained in the polyimide according to the present invention is a structural unit derived from diamine. The diamines can be used alone or in combination of two or more.
The structural unit B preferably contains at least one selected from the group consisting of a structural unit derived from an aliphatic diamine and a structural unit derived from an aromatic diamine, more preferably a structural unit derived from an aliphatic diamine, and structural units derived from aromatic diamines.
By including a structural unit derived from an aliphatic diamine in the structural unit B, organic solvent resistance and colorless transparency are improved.
In the present invention, the term "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, and part of its structure includes an aliphatic group and an alicyclic Formula groups, aromatic groups, and other substituents (eg, halogen atoms, sulfonyl groups, carbonyl groups, oxygen atoms, etc.) may be included. "Aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and part of its structure contains an aliphatic group, an alicyclic group, an aromatic group, or other substituents. You can For example, meta-xylylenediamine is an aliphatic diamine because the amino group is directly attached to an aliphatic hydrocarbon group (methylene group).

As structural units derived from an aliphatic diamine, a structural unit (B-1) derived from a compound represented by the following formula (b-1), a structural unit (B-2) derived from the following formula (b-2) ), and a structural unit (B-3) derived from a compound represented by the following formula (b-3), preferably containing at least one selected from the group consisting of: derived from the following formula (b-2) It is more preferable to contain a structural unit (B-2) that When the structural unit B contains at least one selected from the group consisting of the structural units (B-1) and (B-2), the organic solvent resistance and colorless transparency are improved. By including the structural unit (B-3) in the structural unit B, mechanical properties (elastic modulus) and colorless transparency are improved.

The cis:trans ratios of the compounds represented by formulas (b-1) and (b-2) are preferably 0:100 to 100:0, respectively, from the viewpoint of organic solvent resistance and heat resistance, and 0: 100 to 80:20 is more preferred, 0.1:99.9 to 70:30 is even more preferred, 0.5:99.5 to 60:40 is even more preferred, and 1:99 to 20:80 is even more preferred. preferable.

The ratio of the total structural units derived from aliphatic diamines to the structural unit B is preferably 10 to 95 mol%, more preferably 15 to 90 mol%, from the viewpoint of organic solvent resistance and colorless transparency. 20 to 80 mol % is more preferred, 35 to 75 mol % is even more preferred, and 45 to 60 mol % is even more preferred.
The ratio of the total of the structural units (B-1), (B-2) and (B-3) in the structural units derived from the aliphatic diamine is 60 from the viewpoint of organic solvent resistance and colorless transparency. mol % or more is preferable, 80 mol % or more is more preferable, 90 mol % or more is still more preferable, and 100 mol % is even more preferable.

The structural unit derived from an aromatic diamine preferably contains a structural unit (B-4) derived from a compound represented by the following formula (b-4) from the viewpoint of heat resistance and mechanical properties.

The ratio of the structural unit (B-4) to the structural unit B is preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, and even more preferably, from the viewpoint of organic solvent resistance. is 65 mol% or less, more preferably 55 mol% or less, and from the viewpoint of heat resistance and mechanical properties, preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, and more More preferably 20 mol % or more, still more preferably 25 mol % or more, still more preferably 40 mol % or more.
The proportion of the structural unit (B-4) in the structural units derived from the aromatic diamine is preferably 60 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and 100 mol%. is even more preferred.
From the viewpoint of heat resistance, mechanical properties, and organic solvent resistance, the ratio of the total structural units derived from aromatic diamines to the structural unit B is preferably 5 to 90 mol%, more preferably 10 to 85 mol%. Preferably, 20 to 80 mol % is more preferred, 25 to 65 mol % is even more preferred, and 40 to 55 mol % is even more preferred.
The ratio of the total of the structural units (B-1) to (B-4) to the structural unit B is preferably 70 to 100 mol%, more preferably 85 to 100 mol%, still more preferably 99 to 100 mol. %, more preferably 100 mol %.
The polyimide according to the present invention contains a structural unit derived from a diamine other than the compounds represented by the formulas (b-1) to (b-4) in the structural unit B within a range that does not impair the effects of the present invention. may be present, but preferably not.

[Method for producing polyimide]
A polyimide is obtained by reacting a tetracarboxylic acid component that provides the structural unit A with a diamine component that provides the structural unit B.
The tetracarboxylic acid component that provides the structural unit A includes tetracarboxylic acid and derivatives thereof. A tetracarboxylic acid component can be used individually or in combination of 2 or more types.
Derivatives of tetracarboxylic acids include anhydrides and alkyl esters of the tetracarboxylic acids.
As the alkyl ester of tetracarboxylic acid, the alkyl preferably has 1 to 3 carbon atoms, and examples thereof include dimethyl ester, diethyl ester and dipropyl ester of tetracarboxylic acid.
The tetracarboxylic acid component essentially contains 4,4'-(hexafluoroisopropylidene)diphthalic acid or a derivative thereof, preferably 4,4'-(hexafluoroisopropylidene)diphthalic anhydride [the above formula ( a-1)].
Furthermore, the tetracarboxylic acid component preferably contains biphenyltetracarboxylic acid and derivatives thereof, and more preferably contains biphenyltetracarboxylic dianhydride [the above formula (a-2)]. ,4′-biphenyltetracarboxylic dianhydride [the above formula (a-2-1)] is more preferable.

The amount of 4,4′-(hexafluoroisopropylidene)diphthalic acid or a derivative thereof used is preferably 30 to 100 mol %, more preferably 35 to 100 mol %, based on the total tetracarboxylic acid component, from the viewpoint of colorless transparency. 95 mol %, more preferably 40 to 90 mol %, still more preferably 45 to 80 mol %, still more preferably 50 to 70 mol %, still more preferably 50 to 60 mol %.
From the viewpoint of heat resistance, mechanical properties (modulus of elasticity), and resistance to organic solvents, the amount of biphenyltetracarboxylic acid and its derivatives used is preferably 70 mol % or less, more preferably 5 mol % or less, based on the total tetracarboxylic acid component. ~65 mol%, more preferably 10 to 60 mol%, still more preferably 20 to 55 mol%, still more preferably 30 to 50 mol%, still more preferably 40 to 50 mol%.

Furthermore, it contains tetracarboxylic acid components other than 4,4′-(hexafluoroisopropylidene)diphthalic acid and its derivatives, and biphenyltetracarboxylic acid and its derivatives (hereinafter also referred to as “other tetracarboxylic acid components”). may
Other tetracarboxylic acid components include tetracarboxylic acids containing aromatic rings or derivatives thereof, and tetracarboxylic acids containing alicyclic hydrocarbon structures or derivatives thereof. Other tetracarboxylic acid components can be used alone or in combination of two or more.
Tetracarboxylic acids containing aromatic rings or derivatives thereof include pyromellitic acid, 3,3′,4,4′-diphenylsulfonetetracarboxylic acid, 3,3′,4,4′-benzophenonetetracarboxylic acid, 4, 4'-oxydiphthalic acid, 2,2',3,3'-benzophenonetetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)propane, 2,2-bis(2,3-dicarboxyphenyl ) propane, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane, 1,1-bis(2,3-dicarboxyphenyl)ethane, 1,2-bis(2,3-dicarboxyphenyl) ethane, 1,1-bis(3,4-dicarboxyphenyl)ethane, 1,2-bis(3,4-dicarboxyphenyl)ethane, bis(2,3-dicarboxyphenyl)methane, bis(3, 4-dicarboxyphenyl)methane, 4,4'-(p-phenylenedioxy)diphthalic acid, 4,4'-(m-phenylenedioxy)diphthalic acid, 2,3,6,7-naphthalenetetracarboxylic acid , 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,5,6-toluenetetracarboxylic acid, and derivatives thereof.

Tetracarboxylic acids containing an alicyclic hydrocarbon structure or derivatives thereof include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,4,5-cyclopentanetetracarboxylic acid, 1,2,4, 5-cyclohexanetetracarboxylic acid, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid, dicyclohexyltetracarboxylic acid, and cyclopentanonebisspironorbornanetetracarboxylic acid or these and their derivatives.
Examples of tetracarboxylic acids or derivatives thereof that contain neither an alicyclic hydrocarbon structure nor an aromatic ring include 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, etc. or Derivatives of these are included.

The amount of the other tetracarboxylic acid component used is preferably 30 mol% or less, more preferably 15 mol% or less, still more preferably 1 mol% or less, and even more preferably 0 mol%, based on the total tetracarboxylic acid component. is.

The diamine component that provides the structural unit B is not particularly limited, but from the viewpoint of colorless transparency, heat resistance, and mechanical properties, it preferably contains at least one selected from the group consisting of aliphatic diamines and aromatic diamines. , an aliphatic diamine, and an aromatic diamine. The diamine component that provides the structural unit B is not limited to diamine, and may be a derivative thereof (diisocyanate, etc.) as long as the same structural unit is formed, but diamine is preferred.
The aliphatic diamine preferably has 2 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and more preferably 6 to 8 carbon atoms.

Examples of the aliphatic diamine include hexamethylenediamine, polyethylene glycol bis(3-aminopropyl) ether, polypropylene glycol bis(3-aminopropyl) ether, 1,3-bis(aminomethyl)cyclohexane [the above formula (b -2)], 1,4-bis(aminomethyl)cyclohexane [the above formula (b-1)], meta-xylylenediamine [the above formula (b-3)], para-xylylenediamine, 1,4-bis( 2-amino-isopropyl)benzene, 1,3-bis(2-amino-isopropyl)benzene, isophoronediamine, norbornanediamine, siloxanediamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4, 4'-diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodicyclohexylmethane, 2,3-bis (Aminomethyl)-bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl)-bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)-bicyclo[2.2 .1]heptane, 2,2-bis(4,4′-diaminocyclohexyl)propane, 2,2-bis(4,4′-diaminomethylcyclohexyl)propane and the like. These can be used individually or in combination of 2 or more types.
Aliphatic diamines include, among others, 1,3-bis(aminomethyl)cyclohexane [the above formula (b-2)], 1,4-bis(aminomethyl)cyclohexane [the above formula (b-1)], metaxyl It preferably contains at least one selected from the group consisting of diamine [the above formula (b-3)], paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(amino It is more preferable to contain at least one selected from the group consisting of methyl)cyclohexane and metaxylylenediamine, consisting of 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane More preferably, it contains at least one selected from the group, and even more preferably contains 1,3-bis(aminomethyl)cyclohexane.

The total amount of aliphatic diamine used is preferably 10 to 95 mol%, more preferably 15 to 90 mol%, more preferably 20 to 80 mol%, based on the total diamine component, from the viewpoint of organic solvent resistance and colorless transparency. is more preferred, 35 to 75 mol % is even more preferred, and 45 to 60 mol % is even more preferred.
The total amount of the aliphatic diamines represented by formulas (b-1), (b-2) and (b-3) is, from the viewpoint of organic solvent resistance and colorless transparency, the aliphatic 60 mol % or more is preferable, 80 mol % or more is more preferable, 90 mol % or more is still more preferable, and 100 mol % is even more preferable with respect to the total amount of diamine.
The amount of the aliphatic diamines other than the aliphatic diamines represented by formulas (b-1), (b-2) and (b-3) is preferably 10 mol% or less, more than It is preferably 5 mol % or less, more preferably 1 mol % or less, and even more preferably 0 mol %.

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, benzidine, o-tolidine, m-tolidine and bis(trifluoromethyl)benzidine. [Formula (b-4) above], octafluorobenzidine, 3,3′-dihydroxy-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dichloro -4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,6-diaminonaphthalene, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 2,2-bis(4-(4-amino phenoxy)phenyl)propane, 2,2-bis[4-(2-methyl-4-aminophenoxy)phenyl]propane, 2,2-bis[4-(2,6-dimethyl-4-aminophenoxy)phenyl] Propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis[4-(2-methyl-4-aminophenoxy)phenyl]hexafluoropropane, 2,2- Bis[4-(2,6-dimethyl-4-aminophenoxy)phenyl]hexafluoropropane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(2-methyl-4-amino phenoxy)biphenyl, 4,4'-bis(2,6-dimethyl-4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl] Sulfone, bis[4-(2-methyl-4-aminophenoxy)phenyl]sulfone, bis[4-(2,6-dimethyl-4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy) phenyl] ether, bis[4-(2-methyl-4-aminophenoxy)phenyl]ether, bis[4-(2,6-dimethyl-4-aminophenoxy)phenyl]ether, 1,4-bis(4- aminophenoxy)benzene, 1,4-bis(2-methyl-4-aminophenoxy)benzene, 1,4-bis(2,6-dimethyl-4-aminophenoxy)benzene , 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(2-methyl-4-aminophenoxy)benzene, 1,3-bis(2,6-dimethyl-4-aminophenoxy)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene,

2,2-bis(4-aminophenyl)propane, 2,2-bis(2-methyl-4-aminophenyl)propane, 2,2-bis(3-methyl-4-aminophenyl)propane, 2,2 -bis(3-ethyl-4-aminophenyl)propane, 2,2-bis(3,5-dimethyl-4-aminophenyl)propane, 2,2-bis(2,6-dimethyl-4-aminophenyl) Propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis(2-methyl-4-aminophenyl)hexafluoropropane, 2,2-bis(2,6-dimethyl-4- aminophenyl)hexafluoropropane, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, α,α'-bis(2-methyl-4-aminophenyl)-1,4-diisopropylbenzene , α,α'-bis(2,6-dimethyl-4-aminophenyl)-1,4-diisopropylbenzene, α,α'-bis(3-aminophenyl)-1,4-diisopropylbenzene, α,α '-Bis(4-aminophenyl)-1,3-diisopropylbenzene, α,α'-bis(2-methyl-4-aminophenyl)-1,3-diisopropylbenzene, α,α'-bis(2, 6-dimethyl-4-aminophenyl)-1,3-diisopropylbenzene, α,α'-bis(3-aminophenyl)-1,3-diisopropylbenzene, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(2-methyl-4-aminophenyl)fluorene, 9,9-bis(2,6-dimethyl-4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl) ) fluorene, 9,9-bis(3-methyl-4-aminophenyl)fluorene, 5-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indane, 1,1-bis(4 -aminophenyl)cyclopentane, 1,1-bis(2-methyl-4-aminophenyl)cyclopentane, 1,1-bis(2,6-dimethyl-4-aminophenyl)cyclopentane, 1,1-bis (4-aminophenyl)cyclohexane, 1,1-bis(2-methyl-4-aminophenyl)cyclohexane, 1,1-bis(2,6-dimethyl-4-aminophenyl)cyclohexane, 1,1-bis( 4-aminophenyl)4-methyl-cyclohexane, 1,1-bis(4-aminophenyl)norbornane, 1,1-bi Su(2-methyl-4-aminophenyl)norbornane, 1,1-bis(2,6-dimethyl-4-aminophenyl)norbornane, 1,1-bis(4-aminophenyl)adamantane, 1,1-bis (2-methyl-4-aminophenyl)adamantane, 1,1-bis(2,6-dimethyl-4-aminophenyl)adamantane and the like. These can be used individually or in combination of 2 or more types.
Among these, 2,2'-bis(trifluoromethyl)benzidine [the above formula (b-4)] is preferable from the viewpoint of heat resistance and mechanical properties.
From the viewpoint of organic solvent resistance, heat resistance, and mechanical properties, the amount of the aromatic diamine used is preferably 5 to 90 mol%, more preferably 10 to 85 mol%, still more preferably 20%, based on the total diamine component. ~80 mol%, more preferably 25 to 65 mol%, even more preferably 40 to 55 mol%.
The amount of aromatic diamines other than 2,2'-bis(trifluoromethyl)benzidine used is preferably 20 mol% or less, more preferably 10 mol% or less, still more preferably 1 mol%, based on the total diamine component. Below, it is more preferably 0 mol %.

When producing the polyimide according to the present invention, the ratio of the amount of the tetracarboxylic acid component and the diamine component charged is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

When producing the polyimide according to the present invention, a terminal blocker may be used in addition to the tetracarboxylic acid component and the diamine component. Monoamines or dicarboxylic acids are preferable as the terminal blocking agent. The amount of the terminal blocker to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Monoamine terminal blockers include, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3- Ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline and the like are recommended. Among these, benzylamine and aniline are preferably used. Dicarboxylic acids are preferable as the dicarboxylic acid end blocking agent, and a part of them may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclopentane-1,2 -dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid and the like are recommended. Among these, phthalic acid and phthalic anhydride can be preferably used.

The method for reacting the tetracarboxylic acid component and the diamine component described above is not particularly limited, and a known method can be used.
As a specific reaction method, (1) a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, stirred at room temperature to 80° C. for 0.5 to 30 hours, and then heated to imidize. (2) After charging the diamine component and the reaction solvent into a reactor and dissolving them, charging the tetracarboxylic acid component, stirring at room temperature to 80° C. for 0.5 to 30 hours as necessary, and then and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor and the imidization reaction is carried out by immediately raising the temperature.

The reaction solvent used in the production of polyimide does not interfere with the imidization reaction, as long as it can dissolve the resulting polyimide, but from the viewpoint of reducing the YI of the polyimide varnish composition of the present invention, preferably a lactone At least one organic solvent selected from solvents is selected. The above reaction solvents may be used alone or in combination of two or more.

Examples of the lactone-based solvent include γ-butyrolactone, γ-valerolactone, etc. Among them, γ-butyrolactone is preferred.

Although a reaction solvent other than a lactone solvent may be used, from the viewpoint of reducing the YI of the polyimide varnish composition, N,N-dimethylisobutyramide, N,N-dimethylformamide, N,N-dimethylacetamide, N - Methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, amide solvents such as tetramethylurea, picoline, amine solvents such as pyridine, and hexamethylphosphoric amide, hexamethylphosphine tri It is preferable not to contain a phosphorus-containing amide solvent such as amide.
When an amide-based solvent, an amine-based solvent, a phosphorus-based amide-based solvent, or the like is contained in the reaction system as a reaction solvent, the YI of the resulting varnish composition increases due to the temperature rise in the imidization reaction, and the polyimide film. It is unavoidable that the colorless transparency is lowered.

Examples of reaction solvents other than lactone solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, phenolic solvents such as 3,4-xylenol and 3,5-xylenol; sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide and sulfolane; ketone solvents such as acetone, cyclohexanone and methylcyclohexanone; -methylethyl), 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl ] ether solvents such as ether, tetrahydrofuran and 1,4-dioxane, and carbonate solvents such as diethyl carbonate, methyl ethyl carbonate, ethylene carbonate and propylene carbonate. Among these, phenolic solvents are preferred.
The total content of the lactone-based solvent is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, and still more preferably 100% by mass.

In the imidization reaction, it is preferable to carry out the reaction while removing water produced during production using a Dean-Stark apparatus or the like. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

In the reaction between the diamine component and the tetracarboxylic acid component, a polyimide solution containing at least the polyimide and the reaction solvent can be obtained after completion of the imidization reaction.
In the reaction between the diamine component and the tetracarboxylic acid component, a catalyst, a dehydrating agent, and the like can be used as appropriate within a range that does not impair the effects of the present invention. is preferred. Among them, pyridine derivatives such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine and 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, N,N-dimethylaniline, It is preferable to carry out the imidization reaction without using a tertiary amine such as N,N-diethylaniline or triethylenediamine. In the present invention, by reacting a diamine component and a tetracarboxylic acid component under conditions in which a catalyst and a dehydrating agent are not present, imidization is performed in a shorter reaction time than when a tertiary amine such as triethylamine is used as an imidization catalyst. It was found that the reaction was completed and the YI of the resulting polyimide varnish composition was significantly reduced.

The temperature of the imidization reaction is preferably 120 to 350°C, more preferably 160 to 250°C, still more preferably 170 to 190°C, from the viewpoints of improving the reaction rate and suppressing gelation and the like. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, still more preferably 2 to 6 hours after the start of distillation of the produced water.

[Polyimide]
The weight average molecular weight of the polyimide according to the present invention is preferably 500 to 1,000,000, more preferably 5,000 to 100,000, from the viewpoint of mechanical strength of the resulting polyimide film. The weight average molecular weight of polyimide can be measured by gel filtration chromatography or the like.
As an example of measuring the weight average molecular weight, there is a method of measuring the absolute molecular weight with a light scattering detector using N,N-dimethylformamide as a developing solvent.

[Polyimide varnish composition and method for producing the same]
The polyimide varnish composition of the present invention contains the polyimide of the present invention and an organic solvent. In the varnish composition of the invention, the polyimide is dissolved in the organic solvent. The polyimide varnish composition of the present invention may be the polyimide solution itself obtained by the reaction of the diamine component and the tetracarboxylic acid component described above. Alternatively, the polyimide solution may be mixed with at least one organic solvent selected from diluent solvents described below.
The organic solvent contained in the varnish composition preferably contains at least the organic solvent used as the reaction solvent. The content of the organic solvent used as the reaction solvent is preferably 20% by mass or more, more preferably 22% by mass, based on the total amount of the polyimide varnish composition, from the viewpoint of the solubility of polyimide and ease of processing into a polyimide film. Above, more preferably 24% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less. The content of the lactone solvent contained in the varnish composition is 20% by mass or more, preferably 22% by mass or more, more preferably 24% by mass or more, relative to the total amount of the polyimide varnish composition, preferably It is 50% by mass or less, more preferably 40% by mass or less.

The polyimide varnish composition of the present invention may further contain various additives as long as the effects of the present invention are not impaired. Examples of additives include antioxidants, light stabilizers, surfactants, flame retardants, plasticizers, inorganic fillers, and polymer compounds other than the polyimide.
As the polymer compound, polyimide other than the polyimide according to the present invention, polycarbonate, polystyrene, polyamide, polyamideimide, polyester such as polyethylene terephthalate, polyethersulfone, polycarboxylic acid, polyacetal, polyphenylene ether, polysulfone, polybutylene, polypropylene, poly Examples include acrylamide and polyvinyl chloride.

The solid content concentration of the polyimide varnish composition can be appropriately selected according to the workability and the like when forming the polyimide film described later, and the reaction solvent used in the production of the polyimide according to the present invention is volatilized and condensed. Alternatively, the solid content concentration and viscosity of the polyimide varnish composition of the present invention may be adjusted by adding an organic solvent as a diluent solvent.
By adjusting the solid content concentration and viscosity of the polyimide varnish composition as described above, the thickness of the polyimide film according to the present invention described later can be easily controlled, and the polyimide film can be easily produced. .

The diluting solvent is not particularly limited as long as it can dissolve the polyimide, but from the viewpoint of the solubility of the polyimide and the viewpoint of facilitating the removal of the solvent during processing into a polyimide film, it should contain an amide solvent. is preferred.
Specific examples of amide solvents include N,N-dimethylisobutyramide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazo lysinone, tetramethylurea and the like. Among these, N,N-dimethylacetamide is preferred.
The content of the dilution solvent relative to the total amount of the varnish composition is preferably 70% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less, and preferably 10% by mass or more and 20% by mass or more. , 25% by mass or more. The content of the amide-based solvent used as a diluent solvent contained in the varnish composition is also preferably within the same range as above.
In the present invention, even when an amide-based solvent is used as a diluent solvent, the YI of the varnish composition can be reduced, and a polyimide excellent in colorless transparency can be produced.

The solid content concentration of the polyimide varnish composition of the present invention is not particularly limited, but is preferably 5 to 60% by mass, more preferably 10 to 45% by mass, still more preferably 10 to 30% by mass, and 15 to 25% by mass. Even more preferred.
The viscosity of the polyimide varnish composition of the present invention at 25° C. is preferably 1 to 200 Pa·s, more preferably 5 to 150 Pa·s, still more preferably 10 to 100 Pa·s.
The yellow index (YI) of the polyimide varnish composition of the present invention can be preferably 20 or less, more preferably 15 or less, even more preferably 12 or less, still more preferably 10 or less. When the YI of the polyimide varnish composition is 20 or less, the YI of the polyimide film obtained from the polyimide varnish composition is reduced, and a polyimide film having excellent colorless transparency can be obtained. YI of the polyimide varnish composition of the present invention is a value measured in a cell having an optical path length of 10 mm at 23° C. Specifically, it can be measured by the method described in Examples. Although the solid content concentration when measuring the YI of the varnish composition is not particularly limited, it is preferable to use a varnish composition having a solid content concentration adjusted to 20% by mass, for example.

The total content of tertiary amines, pyridine derivatives, and impurities derived from them contained in the polyimide varnish composition of the present invention is preferably 30 mass ppm or less with respect to polyimide, and is 20 mass ppm or less. is more preferably 10 ppm by mass or less. If the total content of tertiary amines, pyridine derivatives, and impurities derived from them contained in the polyimide varnish composition is 30 ppm by mass or less, a polyimide varnish composition having a YI of 20 or less can be prepared, A polyimide film having excellent colorless transparency can be formed. Specifically, the total content of tertiary amines, pyridine derivatives, and impurities derived therefrom contained in the polyimide varnish composition can be measured by the method described in Examples. Tertiary amines and pyridine derivatives include those exemplified above.
In the reaction between the diamine component and the tetracarboxylic acid component, it is common practice to use a tertiary amine or pyridine derivative as an imidization catalyst, dehydrating agent, solvent, or the like. Then, tertiary amines, pyridine derivatives, or compounds derived from these exist as impurities in the polyimide solution, and as a result, the YI of the varnish composition is considered to deteriorate. In the present invention, from the viewpoint of reducing the YI of the varnish composition, by reacting a diamine component and a tetracarboxylic acid component without using a tertiary amine and a pyridine derivative, the tertiary The total content of amines, pyridine derivatives, and impurities derived from them can be 30 mass ppm or less.

[Polyimide film]
The polyimide film of the present invention is characterized by being obtained from the polyimide varnish composition of the present invention, and is excellent in colorless transparency. The polyimide film of the present invention preferably comprises the polyimide contained in the polyimide varnish composition of the present invention.
The method for producing the polyimide film of the present invention is not particularly limited, and known methods can be used. For example, a method of applying the polyimide varnish composition of the present invention onto a smooth support such as a glass plate, a metal plate, or plastic, or forming it into a film, and then removing the solvent component contained in the varnish composition. etc.

A release agent may be applied to the surface of the support, if necessary. As a method for removing the solvent component by heating after coating the polyimide varnish composition on the support, the following method is preferable. That is, after evaporating the solvent component at a temperature of 120° C. or less to form a self-supporting film, the self-supporting film is peeled off from the support, the ends of the self-supporting film are fixed, and the solvent component used is It is preferable to produce a polyimide film by drying at a temperature of 350° C. or less. Moreover, it is preferable to dry in a nitrogen atmosphere. The pressure of the drying atmosphere may be reduced pressure, normal pressure, or increased pressure.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the intended use and the like, and is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, still more preferably 10 to 90 μm. A thickness of 1 to 250 μm enables practical use as a self-supporting film.
In the present invention, a polyimide film having a total light transmittance of preferably 80% or more, more preferably 85% or more, and still more preferably 88% or more at a thickness of 80 μm can be obtained.
In the present invention, the yellow index (YI) at a thickness of 80 μm is preferably 3.5 or less, more preferably 3.3 or less, still more preferably 3.1 or less, and still more preferably 2.6 or less. can be done.
In the present invention, the haze at a thickness of 80 μm is preferably 1.0% or less, more preferably 0.8% or less, still more preferably 0.7% or less, and even more preferably 0.6% or less. can be done.
Specifically, the total light transmittance, YI, and haze of the polyimide film can be measured by the methods described in Examples.
In the present invention, when a polyimide film having a thickness of 80 μm has a total light transmittance of 80% or more, a YI of 3.5 or less, and a haze of 1.0% or less, the polyimide film is excellent in colorless transparency. It can be said. In other words, the polyimide film of the present invention preferably has a YI of 3.5 or less, a total light transmittance of 80% or more, and a haze of 1.0% or less at a thickness of 80 μm.
In the present invention, a polyimide film having a glass transition temperature of preferably 200° C. or higher, more preferably 220° C. or higher, still more preferably 235° C. or higher, and even more preferably 250° C. or higher can be used.

A polyimide film obtained from the polyimide varnish composition of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members.

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is by no means limited to these examples.
The physical properties of the varnish compositions and polyimide films obtained in the following Examples and Comparative Examples were measured by the methods described below.
(1) Total light transmittance, yellow index (YI), haze:
The total light transmittance, YI and haze of the polyimide film were measured using a simultaneous color/turbidity measuring instrument "COH400" manufactured by Nippon Denshoku Industries Co., Ltd.
The YI of the varnish composition was measured and calculated in the same manner as above at 23° C. with the varnish composition placed in a 10 mm square quartz glass cell.
Total light transmittance and YI were measured according to JIS K7361-1:1997, and haze was measured according to JIS K7136:2000.
(2) Solid content concentration:
The solid content concentration of the polyimide varnish composition was calculated by heating a sample at 300° C.×30 min in a small electric furnace MMF-1 manufactured by AS ONE Co., Ltd. and calculating the difference in weight of the sample before and after heating.
(3) Polyimide film thickness:
The polyimide film thickness was measured using a Mitutoyo micrometer.
(4) Viscosity of Polyimide Varnish Composition The viscosity of the polyimide varnish composition was measured at 25° C. using a viscometer TV-25 manufactured by Toki Sangyo Co., Ltd.
(5) Content of tertiary amines, pyridine derivatives, and impurities derived from them Tertiary amines in the polyimide varnish composition, pyridine derivatives, and the total content of impurities derived from them ) was measured by analyzing by the following method using gas chromatography (GC).
(GC analysis conditions)
Analysis was performed using a column DB-624 (length 30 m×inner diameter 0.25 mm, film thickness 1.4 μm) manufactured by Agilent Technology 7890A as a measuring apparatus.
In addition, below the detection limit means that the content of specific impurities in polyimide is 30 ppm by mass or less.

[Example 1]
1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., hereinafter referred to as 1,3-BAC: trans ratio of 30) was added as a diamine component to an approximately 240 L SUS reactor equipped with a stainless steel three-stage paddle stirring blade. %), 12476 g of 2,2′-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd.), and 61.44 kg of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) as a reaction solvent, A solution was obtained by stirring under a nitrogen atmosphere at a system temperature of about 90°C. To this, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Daikin Industries, Ltd.) 17333 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi After adding 11466 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) and 15000 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a reaction solvent, the temperature in the reaction system was raised to 180° C. over about 80 minutes. A polyimide solution was obtained by collecting the components distilled off and stirring for 5.25 hours while maintaining the temperature in the reaction system at 180°C. Thereafter, the temperature inside the reaction system was cooled to 120° C. to stop the reaction, and a total of 113,800 g of N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added as a dilution solvent. The solution was stirred until it became uniform to obtain a polyimide varnish composition (A) having a solid concentration of 16.5% by mass. This polyimide varnish composition (A) had a YI value of 6.3, a content of specific impurities below the detection limit, and a viscosity of 55.0 Pa·s.

Subsequently, the polyimide varnish composition (A) is applied onto a glass substrate and held at 60° C. for 30 minutes and at 100° C. for 1 hour to volatilize the solvent to form a colorless transparent primary dry film having self-supporting properties. Further, the film was fixed on a stainless steel frame and dried at 280° C. under a nitrogen atmosphere for 2 hours to remove the solvent to obtain a film with a thickness of 73 μm. FT-IR analysis of the obtained film confirmed the disappearance of the starting material peak and the appearance of a peak derived from the imide skeleton. This polyimide film had a total light transmittance of 90.4%, a YI value of 2.6, and a haze of 0.2.

[Example 2]
1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-BAC: trans ratio of 30%) was added as a diamine component to an approximately 240 L SUS reactor equipped with a three-stage stainless steel paddle stirring blade. ) 5589 g, 2,2′-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd.) 12476 g, and 61.44 kg of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) as a reaction solvent were added, and the system temperature was about A solution was obtained by stirring at 90° C. under a nitrogen atmosphere. To this, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Daikin Industries, Ltd.) 17333 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi After adding 11466 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corp.) and 15000 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corp.) as a reaction solvent, the temperature in the reaction system was raised to 180° C. over about 80 minutes. A polyimide solution was obtained by collecting the components distilled off and stirring for 4 hours while maintaining the temperature in the reaction system at 180°C. Thereafter, the temperature inside the reaction system was cooled to 120° C. to terminate the reaction, and a total of 105,870 g of N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added. The solution was stirred until it became uniform to obtain a polyimide varnish composition (B) having a solid concentration of 19.8% by mass. This polyimide varnish composition (B) had a YI value of 9.5, a content of specific impurities below the detection limit, and a viscosity of 47.7 Pa·s.

Subsequently, the polyimide varnish composition (B) is applied onto a glass substrate and held at 60° C. for 30 minutes and at 100° C. for 1 hour to volatilize the solvent to form a colorless transparent primary dry film having self-supporting properties. Further, the film was fixed to a stainless steel frame and dried at 280° C. under a nitrogen atmosphere for 2 hours to remove the solvent to obtain a film having a thickness of 80 μm. FT-IR analysis of the obtained film confirmed the disappearance of the starting material peak and the appearance of a peak derived from the imide skeleton. This polyimide film had a total light transmittance of 90.3%, a YI value of 3.1, and a haze of 0.6.

[Comparative Example 1]
1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-BAC: trans ratio of 30%) was added as a diamine component to an approximately 240 L SUS reactor equipped with a three-stage stainless steel paddle stirring blade. ) 5589 g, 2,2′-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd.) 12476 g, and 61.44 kg of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) as a reaction solvent were added, and the system temperature was about A solution was obtained by stirring at 90° C. under a nitrogen atmosphere. To this, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Daikin Industries, Ltd.) 17333 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi Chemical Co., Ltd.) and 15000 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a reaction solvent were added, and then 394 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) was added as a catalyst. The temperature was increased to 180°C. A polyimide solution was obtained by collecting the components distilled off and stirring for 9.5 hours while maintaining the temperature in the reaction system at 180°C. Thereafter, the temperature in the reaction system was cooled to 120° C. to terminate the reaction, and a total of 113,800 g of N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added as a dilution solvent. The solution was stirred until it became uniform to obtain a polyimide varnish composition (C) having a solid concentration of 18.5% by mass. This polyimide varnish composition (C) had a YI value of 56.1, a specific impurity content of 330 mass ppm, and a viscosity of 50.2 Pa·s.

Subsequently, the polyimide varnish composition (C) is applied to a glass substrate, held at 60° C. for 30 minutes and 100° C. for 1 hour, and the solvent is volatilized to obtain a primary dry film having self-supporting properties, and further The film was fixed on a stainless steel frame and dried at 280° C. under a nitrogen atmosphere for 2 hours to remove the solvent and obtain a film with a thickness of 76 μm. FT-IR analysis of the obtained film confirmed the disappearance of the starting material peak and the appearance of a peak derived from the imide skeleton. This polyimide film had a total light transmittance of 89.7%, a YI value of 5.8, and a haze of 0.4.

[Comparative Example 2]
1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-BAC: trans ratio of 30%) was added as a diamine component to an approximately 240 L SUS reactor equipped with a three-stage stainless steel paddle stirring blade. ) 5589 g, 2,2′-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd.) 12476 g, and 61.44 kg of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) as a reaction solvent were added, and the system temperature was about A solution was obtained by stirring at 90° C. under a nitrogen atmosphere. To this, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Daikin Industries, Ltd.) 17333 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi Chemical Co., Ltd.) and 15000 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a reaction solvent were added, and then 236 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) was added as a catalyst. The temperature was increased to 180°C. A polyimide solution was obtained by collecting the components distilled off and stirring for 8 hours while maintaining the temperature in the reaction system at 180°C. Thereafter, the temperature inside the reaction system was cooled to 120° C. to terminate the reaction, and a total of 113,240 g of N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added as a dilution solvent. The solution was stirred until it became uniform to obtain a polyimide varnish composition (D) having a solid concentration of 18.7% by mass. This polyimide varnish composition (D) had a YI value of 36.1, a specific impurity content of 300 ppm by mass, and a viscosity of 49.5 Pa·s.

Subsequently, the polyimide varnish composition (D) is applied on a glass substrate, held at 60 ° C. for 30 minutes and 100 ° C. for 1 hour, and the solvent is volatilized to obtain a primary dry film having self-supporting properties. The film was fixed on a stainless steel frame and dried at 280° C. for 2 hours in a nitrogen atmosphere to remove the solvent and obtain a film with a thickness of 80 μm. FT-IR analysis of the obtained film confirmed the disappearance of the starting material peak and the appearance of a peak derived from the imide skeleton. This polyimide film had a total light transmittance of 89.6%, a YI value of 5.6, and a haze of 0.5.

Abbreviations in the table are as follows.
6FDA: 4,4'-(hexafluoroisopropylidene) diphthalic anhydride [compound represented by formula (a-1)]
s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride [compound represented by formula (a-2-1)]
1,3-BAC: trans ratio 30%: 1,3-bis(aminomethyl)cyclohexane [cis: trans = 70:30 (molar ratio) compound represented by formula (b-2)]
TFMB: 2,2'-bis(trifluoromethyl)benzidine [compound represented by formula (b-4)]
GBL: γ-butyrolactone DMAc: N,N-dimethylacetamide TEA: triethylamine

From Table 1, the YI of the polyimide varnish compositions of Examples 1 and 2 is low, the YI and haze of the polyimide film are low, and the total light transmittance is high, so that a polyimide film having excellent colorless transparency can be formed. I understand. On the other hand, the polyimide varnish compositions and polyimide films of Comparative Examples 1 and 2 had high YI, and the colorless and transparent polyimide films could not be improved.

Claims (14)

A polyimide varnish composition containing a polyimide and an organic solvent,
The polyimide has a structural unit A derived from a tetracarboxylic acid or a derivative thereof and a structural unit B derived from a diamine,
The structural unit A comprises a structural unit (A-1) derived from a compound represented by the following formula (a-1),
The structural unit B comprises a structural unit derived from an aliphatic diamine and a structural unit derived from an aromatic diamine,
A structural unit derived from the aliphatic diamine is derived from a structural unit (B-1) derived from a compound represented by the following formula (b-1), and a compound represented by the following formula (b-2) Containing at least one selected from the group consisting of structural units (B-2),
The ratio of the total structural units derived from the aliphatic diamine to the structural unit B is 10 to 95 mol%,
At least one organic solvent selected from lactone-based solvents is contained in an amount of 20% by mass or more with respect to the total amount of the polyimide varnish composition,
A polyimide varnish composition having a YI of 20 or less measured at 23° C. in a cell with an optical path length of 10 mm.

The polyimide varnish composition according to claim 1, wherein the total content of tertiary amines, pyridine derivatives, and impurities derived therefrom is 30 ppm by mass or less relative to the polyimide. The polyimide varnish composition according to claim 1 or 2 , wherein the structural unit derived from the aliphatic diamine further comprises a structural unit (B-3 ) derived from a compound represented by the following formula (b-3).

The structural unit derived from the aromatic diamine further comprises a structural unit (B-4) derived from a compound represented by the following formula (b-4), polyimide varnish according to any one of claims 1 to 3 Composition.

The polyimide varnish composition according to any one of claims 1 to 4 , wherein the structural unit A further contains a structural unit (A-2) derived from a compound represented by the following formula (a-2).

The polyimide varnish composition according to any one of claims 1 to 5 , wherein the ratio of said structural unit (A-1) to said structural unit A is 30 mol% or more. The polyimide varnish composition according to any one of claims 1 to 6 , wherein the ratio of the structural unit derived from the aromatic diamine to the structural unit B is 5 to 90 mol%. The polyimide varnish composition according to any one of claims 1 to 7 , wherein the content of the amide solvent is 70% by mass or less relative to the total amount of the polyimide varnish composition. A polyimide film obtained from the polyimide varnish composition according to any one of claims 1 to 8 . 10. The polyimide film according to claim 9 , which has a YI of 3.5 or less, a total light transmittance of 80% or more, and a haze of 1.0% or less at a thickness of 80 μm. A method for producing a polyimide varnish composition according to any one of claims 1 to 8, in the presence of at least one organic solvent selected from lactone solvents and in the absence of a catalyst and a dehydrating agent, A method for producing a polyimide varnish composition containing a polyimide and an organic solvent by reacting a diamine component with a tetracarboxylic acid component containing 4,4'-(hexafluoroisopropylidene)diphthalic acid or a derivative thereof. The polyimide varnish composition has a lactone solvent content of 20% by mass or more, and the polyimide varnish composition has a YI of 20 or less measured in a cell with an optical path length of 10 mm at 23 ° C. A method for producing a varnish composition. A tetracarboxylic acid containing a diamine component and 4,4'-(hexafluoroisopropylidene)diphthalic acid or a derivative thereof in the presence of at least one organic solvent selected from lactone solvents and in the absence of a catalyst and a dehydrating agent. The method for producing a polyimide varnish composition according to claim 11 , wherein the polyimide solution is obtained by reacting with an acid component, and the polyimide varnish composition is obtained by mixing the obtained polyimide solution and a diluent solvent. The method for producing a polyimide varnish composition according to claim 12 , wherein the diluent solvent comprises an amide solvent. The method for producing a polyimide varnish composition according to any one of claims 11 to 13 , wherein the reaction temperature is 170 to 190°C.