JP7180617B2 - Polyimide resin composition and polyimide film - Google Patents

Description

The present invention relates to a polyimide resin composition and a polyimide film.

Polyimide resins have excellent mechanical properties and heat resistance, and are therefore being investigated for various uses in fields such as electric and electronic parts. For example, it is desired to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with plastic substrates for the purpose of reducing the weight and increasing the flexibility of devices. Research is ongoing. Polyimide films for such applications are required to be colorless and transparent.

In addition, films with poor resistance to organic solvents such as polar solvents (organic solvent resistance) may change their morphology due to elution or swelling of the surface when exposed to organic solvents such as polar solvents. In many cases, polyimide films are required to be resistant to organic solvents. In order to meet such demands, a polyimide film produced by adding a cross-linking agent to a polyimide resin has been proposed.
Patent Document 1 discloses a polyimide resin composition containing a polyimide resin having a carboxyl group and a cross-linking agent having at least two oxazolyl groups, and the polyimide resin composition provides a film having good transparency and high hardness. It is described that the formation of
Further, Patent Document 2 discloses a transparent flexible film containing a polyimide copolymer having a carboxyl group and a polyfunctional epoxide.

JP 2016-222797 A Japanese Patent No. 6174580

In an image display device, when the light emitted from the display element is emitted through a plastic substrate, the plastic substrate is required to be colorless and transparent. For example, liquid crystal displays, touch panels, etc.) are required to have high optical isotropy in addition to being colorless and transparent. However, Patent Document 1 does not describe anything about optical isotropy.
Further, in Patent Document 2, the epoxy group of the polyfunctional epoxide added as a cross-linking agent undergoes reaction with the carboxyl group even at a relatively low temperature (approximately 30° C. or higher). Therefore, when stored at room temperature, a composition containing a polyimide resin having a carboxyl group and a polyfunctional epoxide undergoes gelation due to cross-linking, resulting in poor storage stability. Further, the thermal decomposition temperature of epoxy resin is generally 250 to 350° C., and it is considered that the heat resistance is insufficient for applications requiring high-temperature processes.
The present invention has been made in view of the above circumstances, and an object of the present invention is to enable formation of a film excellent in mechanical properties, resistance to organic solvents, colorless transparency, and optical isotropy. Another object of the present invention is to provide a polyimide resin composition having excellent storage stability, and to provide a polyimide film obtained by cross-linking the polyimide resin in the polyimide resin composition with a cross-linking agent.

The present inventors have found that a polyimide resin composition containing a polyimide resin containing a combination of specific structural units and a specific cross-linking agent can solve the above problems, and have completed the invention.

（式（ｂ－１）中、Ｒはそれぞれ独立して、水素原子、フッ素原子、又はメチル基であり；式（ｂ－２）中、Ｘは単結合、置換若しくは無置換のアルキレン基、カルボニル基、エーテル基、下記式（ｂ－２－ｉ）で表される基、又は下記式（ｂ－２－ｉｉ）で表される基であり、ｐは０～２の整数であり、ｍ１は０～４の整数であり、ｍ２は０～４の整数である。ただし、ｐが０の場合、ｍ１は１～４の整数である。）

（式（ｂ－２－ｉ）中、ｍ３は０～５の整数であり；式（ｂ－２－ｉｉ）中、ｍ４は０～５の整数である。なお、ｍ１＋ｍ２＋ｍ３＋ｍ４は１以上であり、ｐが２の場合、２つのＸ及び２つのｍ２～ｍ４のそれぞれは独立して選択される。）That is, the present invention relates to the following [1] to [9].
[1]
A polyimide resin composition comprising a polyimide resin and a cross-linking agent having at least two oxazolyl groups,
The polyimide resin has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine,
A constitution in which the structural unit A is derived from a structural unit (A-1-1) derived from a compound represented by the following formula (a-1-1) and a compound represented by the following formula (a-1-2) including a structural unit (A-1) that is at least one selected from the group consisting of units (A-1-2),
The structural unit B is a structural unit (B-1) derived from a compound represented by the following formula (b-1), and a structural unit (B-2) derived from a compound represented by the following formula (b-2) ) and a polyimide resin composition.

(In formula (b-1), each R is independently a hydrogen atom, a fluorine atom, or a methyl group; In formula (b-2), X is a single bond, a substituted or unsubstituted alkylene group, carbonyl group, an ether group, a group represented by the following formula (b-2-i), or a group represented by the following formula (b-2-ii), p is an integer of 0 to 2, and m1 is is an integer of 0 to 4, and m2 is an integer of 0 to 4. However, when p is 0, m1 is an integer of 1 to 4.)

(In formula (b-2-i), m3 is an integer of 0 to 5; In formula (b-2-ii), m4 is an integer of 0 to 5. Note that m1 + m2 + m3 + m4 is 1 or more, When p is 2, each of the two Xs and the two m2-m4 are independently selected.)

［３］
前記架橋剤が、前記少なくとも２つのオキサゾリル基が結合したベンゼン環を含む、上記［１］又は［２］に記載のポリイミド樹脂組成物。
［４］
前記架橋剤中のオキサゾリル基と前記ポリイミド樹脂中のカルボキシル基とのモル比（オキサゾリル基／カルボキシル基）が１／４～１／０．５の範囲となるような比率で、前記ポリイミド樹脂と前記架橋剤とを含む、上記［１］～［３］のいずれかに記載のポリイミド樹脂組成物。
［５］
構成単位Ｂ中における構成単位（Ｂ－１）の比率が４０～９９モル％であり、
構成単位Ｂ中における構成単位（Ｂ－２）の比率が１～６０モル％である、上記［１］～［４］のいずれかに記載のポリイミド樹脂組成物。
［６］
構成単位Ａ中における構成単位（Ａ－１）の比率が５０モル％以上である、上記［１］～［５］のいずれかに記載のポリイミド樹脂組成物。
［７］
構成単位（Ａ－１）が構成単位（Ａ－１－１）である、上記［１］～［６］のいずれかに記載のポリイミド樹脂組成物。
［８］
構成単位（Ａ－１）が構成単位（Ａ－１－２）である、上記［１］～［６］のいずれかに記載のポリイミド樹脂組成物。
［９］
上記［１］～［８］のいずれかに記載のポリイミド樹脂組成物中の前記ポリイミド樹脂が前記架橋剤により架橋されてなるポリイミドフィルム。[2]
The polyimide resin composition according to [1] above, wherein the structural unit (B-2) is a structural unit (B-21) derived from a compound represented by the following formula (b-21).

[3]
The polyimide resin composition according to the above [1] or [2], wherein the cross-linking agent contains a benzene ring to which the at least two oxazolyl groups are bonded.
[4]
The polyimide resin and the polyimide resin and the The polyimide resin composition according to any one of [1] to [3] above, comprising a cross-linking agent.
[5]
The ratio of the structural unit (B-1) in the structural unit B is 40 to 99 mol%,
The polyimide resin composition according to any one of [1] to [4] above, wherein the proportion of the structural unit (B-2) in the structural unit B is 1 to 60 mol%.
[6]
The polyimide resin composition according to any one of [1] to [5] above, wherein the proportion of the structural unit (A-1) in the structural unit A is 50 mol% or more.
[7]
The polyimide resin composition according to any one of [1] to [6] above, wherein the structural unit (A-1) is the structural unit (A-1-1).
[8]
The polyimide resin composition according to any one of [1] to [6] above, wherein the structural unit (A-1) is the structural unit (A-1-2).
[9]
A polyimide film obtained by cross-linking the polyimide resin in the polyimide resin composition according to any one of [1] to [8] above with the cross-linking agent.

The polyimide resin composition of the present invention has excellent storage stability and can form a film having excellent mechanical properties, organic solvent resistance, colorless transparency, and optical isotropy.

[Polyimide resin composition]
The polyimide resin composition of the present invention contains a polyimide resin and a cross-linking agent. The polyimide resin and the cross-linking agent in the present invention are described below.

（式（ｂ－１）中、Ｒはそれぞれ独立して、水素原子、フッ素原子又はメチル基であり；式（ｂ－２）中、Ｘは単結合、置換若しくは無置換のアルキレン基、カルボニル基、エーテル基、下記式（ｂ－２－ｉ）で表される基、又は下記式（ｂ－２－ｉｉ）で表される基であり、ｐは０～２の整数であり、ｍ１は０～４の整数であり、ｍ２は０～４の整数である。ただし、ｐが０の場合、ｍ１は１～４の整数である。）

（式（ｂ－２－ｉ）中、ｍ３は０～５の整数であり；式（ｂ－２－ｉｉ）中、ｍ４は０～５の整数である。なお、ｍ１＋ｍ２＋ｍ３＋ｍ４は１以上であり、ｐが２の場合、２つのＸ及び２つのｍ２～ｍ４のそれぞれは独立して選択される。）<Polyimide resin>
In the present invention, the polyimide resin has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, and the structural unit A is a compound represented by the following formula (a-1-1). A structure which is at least one selected from the group consisting of a structural unit derived from (A-1-1) and a structural unit (A-1-2) derived from a compound represented by the following formula (a-1-2) A structural unit (B-1) containing a unit (A-1), wherein the structural unit B is derived from a compound represented by the following formula (b-1), and a compound represented by the following formula (b-2) and the derived structural unit (B-2).

(In formula (b-1), each R is independently a hydrogen atom, a fluorine atom or a methyl group; In formula (b-2), X is a single bond, a substituted or unsubstituted alkylene group, a carbonyl group , an ether group, a group represented by the following formula (b-2-i), or a group represented by the following formula (b-2-ii), p is an integer of 0 to 2, m1 is 0 is an integer from 1 to 4, and m2 is an integer from 0 to 4. However, when p is 0, m1 is an integer from 1 to 4.)

(In formula (b-2-i), m3 is an integer of 0 to 5; In formula (b-2-ii), m4 is an integer of 0 to 5. Note that m1 + m2 + m3 + m4 is 1 or more, When p is 2, each of the two Xs and the two m2-m4 are independently selected.)

(Constituent unit A)
Structural unit A is a structural unit derived from a tetracarboxylic dianhydride in the polyimide resin, a structural unit derived from a compound represented by the following formula (a-1-1) (A-1-1) and a structural unit (A-1) which is at least one selected from the group consisting of a structural unit (A-1-2) derived from a compound represented by the following formula (a-1-2).

The compound represented by formula (a-1-1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride.
The compound represented by formula (a-1-2) is norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″- It is a tetracarboxylic dianhydride.
Including the structural unit (A-1) in the structural unit A contributes to improving the colorless transparency of the film. Further, when the structural unit (A-1-1) is included as the structural unit (A-1), it can contribute to improving the optical isotropy of the film.

The structural unit (A-1) may be only the structural unit (A-1-1) or only the structural unit (A-1-2). Further, the structural unit (A-1) may be a combination of the structural unit (A-1-1) and the structural unit (A-1-2).

The ratio of the structural unit (A-1) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, particularly preferably 99 mol. % or more. The upper limit of the proportion of the structural unit (A-1) is not particularly limited, ie, 100 mol %. Structural unit A may consist only of structural unit (A-1).

The structural unit A may contain structural units other than the structural unit (A-1). The tetracarboxylic dianhydride that provides such a structural unit is not particularly limited, but pyromellitic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,3, 3',4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl ) propane dianhydride, 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 3,4′-oxydiphthalic anhydride, 3,3′- oxydiphthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 4,4-(p-phenylenedi Aromatic tetracarboxylic dianhydrides such as oxy)diphthalic dianhydride and 4,4-(m-phenylenedioxy)diphthalic anhydride; 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride; alicyclic tetracarboxylic dianhydrides such as anhydrides (excluding compounds represented by formula (a-1-1) and compounds represented by formula (a-1-2)); and 1, Aliphatic tetracarboxylic dianhydrides such as 2,3,4-butanetetracarboxylic dianhydride can be mentioned.
In this specification, aromatic tetracarboxylic dianhydride means tetracarboxylic dianhydride containing one or more aromatic rings, and alicyclic tetracarboxylic dianhydride has one alicyclic ring. The term "aliphatic tetracarboxylic dianhydride" means a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.
Structural units other than the structural unit (A-1) optionally contained in the structural unit A may be of one type or two or more types.

A preferred embodiment of the structural unit other than the structural unit (A-1) is a structural unit (A-2) derived from a compound represented by the following formula (a-2).

The compound represented by formula (a-2) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4, represented by formula (a-2s) below. 4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a-2a), 2,2′,3,3′-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a-2i) can be mentioned.

When the structural unit A contains the structural unit (A-1) and the structural unit (A-2), the ratio of the structural unit (A-1) in the structural unit A is preferably 50 to 95 mol%, and more It is preferably 70 to 95 mol%, more preferably 85 to 95 mol%, and the ratio of the structural unit (A-2) in the structural unit A is preferably 5 to 50 mol%, more preferably It is 5 to 30 mol %, more preferably 5 to 15 mol %.
Structural unit A may consist of only structural unit (A-1) and structural unit (A-2).

（式（ｂ－１）中、Ｒはそれぞれ独立して、水素原子、フッ素原子、又はメチル基であり；式（ｂ－２）中、Ｘは単結合、置換若しくは無置換のアルキレン基、カルボニル基、エーテル基、下記式（ｂ－２－ｉ）で表される基、又は下記式（ｂ－２－ｉｉ）で表される基であり、ｐは０～２の整数であり、ｍ１は０～４の整数であり、ｍ２は０～４の整数である。ただし、ｐが０の場合、ｍ１は１～４の整数である。）

（式（ｂ－２－ｉ）中、ｍ３は０～５の整数であり；式（ｂ－２－ｉｉ）中、ｍ４は０～５の整数である。なお、ｍ１＋ｍ２＋ｍ３＋ｍ４は１以上であり、ｐが２の場合、２つのＸ及び２つのｍ２～ｍ４のそれぞれは独立して選択される。）(Constituent unit B)
Structural unit B is a structural unit derived from a diamine occupying the polyimide resin, a structural unit (B-1) derived from a compound represented by the following formula (b-1), and the following formula (b-2) and a structural unit (B-2) derived from the compound represented by

(In formula (b-1), each R is independently a hydrogen atom, a fluorine atom, or a methyl group; In formula (b-2), X is a single bond, a substituted or unsubstituted alkylene group, carbonyl group, an ether group, a group represented by the following formula (b-2-i), or a group represented by the following formula (b-2-ii), p is an integer of 0 to 2, and m1 is is an integer of 0 to 4, and m2 is an integer of 0 to 4. However, when p is 0, m1 is an integer of 1 to 4.)

(In formula (b-2-i), m3 is an integer of 0 to 5; In formula (b-2-ii), m4 is an integer of 0 to 5. Note that m1 + m2 + m3 + m4 is 1 or more, When p is 2, each of the two Xs and the two m2-m4 are independently selected.)

In formula (b-1), each R is independently a hydrogen atom, a fluorine atom, or a methyl group, preferably a hydrogen atom. Compounds represented by formula (b-1) include 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, and 9,9-bis (3-methyl-4-aminophenyl)fluorene and the like are mentioned, and 9,9-bis(4-aminophenyl)fluorene is preferred.
Including the structural unit (B-1) in the structural unit B improves the optical isotropy of the film.

Specific examples of the compound represented by formula (b-2) include compounds represented by the following formulas (b-21) to (b-27).

Among the above compounds, the compound represented by the formula (b-21) is preferable, and the compound represented by the following formula (b-211), that is, 3,5-diaminobenzoic acid is more preferable.

The structural unit (B-2) is a structural unit that provides a carboxyl group to the polyimide resin. By having a carboxyl group in the polyimide resin, cross-linking between the polyimide resins via a cross-linking agent, which will be described later, becomes possible. Therefore, by including the structural unit (B-2) in the structural unit B, the organic solvent resistance of the film is improved.

The ratio of the structural unit (B-1) in the structural unit B is preferably 40 to 99 mol%, more preferably 45 to 95 mol%, still more preferably 75 to 95 mol%, particularly preferably is 80 to 90 mol %.
The ratio of the structural unit (B-2) in the structural unit B is preferably 1 to 60 mol%, more preferably 5 to 55 mol%, even more preferably 5 to 25 mol%, particularly preferably is 10 to 20 mol %.
The total ratio of the structural unit (B-1) and the structural unit (B-2) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol. % or more, particularly preferably 99 mol % or more. The upper limit of the total ratio of the structural unit (B-1) and the structural unit (B-2) is not particularly limited, ie, 100 mol %. The structural unit B may consist of only the structural unit (B-1) and the structural unit (B-2).

The structural unit B may contain structural units other than the structural units (B-1) and (B-2). Diamines that give such structural units are not particularly limited, but 1,4-phenylenediamine, p-xylylenediamine, 2,2′-dimethylbiphenyl-4,4′-diamine, 2,2′-bis (Trifluoromethyl)benzidine, 4,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl ) hexafluoropropane, bis(4-aminophenyl)sulfone, 4,4′-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene- 5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy ) biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 5,5′-(1,1 ,1,3,3,3-hexafluoro-2-hydroxyisopropyl)-2,2′-dimethylbiphenyl-4,4′-diamine and 9,9-bis(4-(4-aminophenoxy)phenyl)fluorene aromatic diamines such as (excluding compounds represented by formula (b-1) and compounds represented by formula (b-2)); 1,3-bis(aminomethyl)cyclohexane and 1,4- Alicyclic diamines such as bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.
In the present specification, the term "aromatic diamine" means a diamine containing one or more aromatic rings, and the term "alicyclic diamine" means a diamine containing one or more alicyclic rings and no aromatic ring. A group diamine means a diamine containing neither aromatic nor alicyclic rings.
Structural units other than the structural units (B-1) and (B-2) optionally contained in the structural unit B may be of one type or two or more types.

In the present invention, the number average molecular weight of the polyimide resin is preferably 5,000 to 100,000 from the viewpoint of the mechanical strength of the resulting polyimide film. Incidentally, the number average molecular weight of the polyimide resin can be obtained from, for example, a standard polymethyl methacrylate (PMMA) conversion value by gel filtration chromatography measurement.

<Method for producing polyimide resin>
In the present invention, the polyimide resin includes a tetracarboxylic acid component containing a compound that provides the above-described structural unit (A-1), a compound that provides the above-described structural unit (B-1), and the above-described structural unit (B-2 ) can be produced by reacting a diamine component containing a compound that provides

As the compound that provides the structural unit (A-1), at least one compound selected from the group consisting of compounds that provide the structural unit (A-1-1) and compounds that provide the structural unit (A-1-2) is used.
Compounds that provide the structural unit (A-1-1) include, but are not limited to, compounds represented by formula (a-1-1), and derivatives thereof within the range that provide the same structural unit good. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by formula (a-1-1) (that is, 1,2,4,5-cyclohexanetetracarboxylic acid), and the tetracarboxylic acid Alkyl esters of acids are mentioned. As the compound that provides the structural unit (A-1-1), a compound represented by formula (a-1-1) (ie, a dianhydride) is preferred.
Compounds that provide the structural unit (A-1-2) include, but are not limited to, compounds represented by formula (a-1-2), and derivatives thereof within the range that provide the same structural unit good. Examples of the derivative include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a-1-2), and alkyl esters of the tetracarboxylic acids. As the compound that provides the structural unit (A-1-2), a compound represented by formula (a-1-2) (ie, a dianhydride) is preferred.

As the compound that provides the structural unit (A-1), only the compound that provides the structural unit (A-1-1) may be used, or only the compound that provides the structural unit (A-1-2) may be used.
Further, as the compound that provides the structural unit (A-1), a combination of a compound that provides the structural unit (A-1-1) and a compound that provides the structural unit (A-1-2) may be used.

The tetracarboxylic acid component preferably contains 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, particularly preferably 99 mol%, of the compound that provides the structural unit (A-1). Including above. The upper limit of the content of the compound that provides the structural unit (A-1) is not particularly limited, ie, 100 mol %. The tetracarboxylic acid component may consist only of the compound that provides the structural unit (A-1).

The tetracarboxylic acid component may contain a compound other than the compound that provides the structural unit (A-1). Examples of the compound include the above-described aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydrides, and their derivatives (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.).
The number of compounds other than the compound that gives the structural unit (A-1) optionally contained in the tetracarboxylic acid component may be one, or two or more.

A preferred embodiment of the compound other than the compound that provides the structural unit (A-1) is a compound that provides the structural unit (A-2).
The compound that provides the structural unit (A-2) includes, but is not limited to, the compound represented by formula (a-2), and may be a derivative thereof as long as it provides the same structural unit. Examples of the derivative include tetracarboxylic acids corresponding to the tetracarboxylic dianhydrides represented by formula (a-2), and alkyl esters of the tetracarboxylic acids. As the compound that provides the structural unit (A-2), a compound represented by formula (a-2) (ie, a dianhydride) is preferred.
When the tetracarboxylic acid component contains a compound that provides the structural unit (A-1) and a compound that provides the structural unit (A-2), the tetracarboxylic acid component contains the compound that provides the structural unit (A-1), preferably 50 ~95 mol%, more preferably 70 to 95 mol%, more preferably 85 to 95 mol%, a compound that gives the structural unit (A-2), preferably 5 to 50 mol%, more preferably It contains 5 to 30 mol %, more preferably 5 to 15 mol %.
The tetracarboxylic acid component may consist of only a compound that provides the structural unit (A-1) and a compound that provides the structural unit (A-2).

The compound that provides the structural unit (B-1) includes, but is not limited to, the compound represented by formula (b-1), and may be a derivative thereof as long as it provides the same structural unit. Such derivatives include diisocyanates corresponding to diamines represented by formula (b-1). As the compound that provides the structural unit (B-1), a compound represented by formula (b-1) (ie, diamine) is preferred.
The compound that provides the structural unit (B-2) includes, but is not limited to, the compound represented by formula (b-2), and may be a derivative thereof as long as it provides the same structural unit. Such derivatives include diisocyanates corresponding to diamines represented by formula (b-2). As the compound that provides the structural unit (B-2), a compound represented by formula (b-2) (ie, diamine) is preferred.

The diamine component preferably contains 40 to 99 mol%, more preferably 45 to 95 mol%, still more preferably 75 to 95 mol%, particularly preferably 80 to 95 mol% of a compound that provides the structural unit (B-1). Contains 90 mol %.
The diamine component preferably contains 1 to 60 mol%, more preferably 5 to 55 mol%, still more preferably 5 to 25 mol%, and particularly preferably 10 to 10 mol% of a compound that provides the structural unit (B-2). Contains 20 mol %.
The diamine component preferably contains 50 mol% or more, more preferably 70 mol% or more, still more preferably 90% in total of the compound that gives the structural unit (B-1) and the compound that gives the structural unit (B-2). It contains 99 mol % or more, particularly preferably 99 mol % or more. The upper limit of the total content of the compound that provides the structural unit (B-1) and the compound that provides the structural unit (B-2) is not particularly limited, ie, it is 100 mol %. The diamine component may consist only of a compound that provides the structural unit (B-1) and a compound that provides the structural unit (B-2).

The diamine component may contain a compound other than the compound that provides the structural unit (B-1) and the compound that provides the structural unit (B-2). Examples of such compounds include the aromatic diamines, alicyclic diamines, and aliphatic group diamines, as well as their derivatives such as diisocyanates.
The compounds other than the compound giving the structural unit (B-1) and the compound giving the structural unit (B-2) optionally contained in the diamine component may be one kind or two or more kinds.

In the present invention, the charging ratio of the tetracarboxylic acid component and the diamine component used in the production of the polyimide resin is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

In addition, in the present invention, a terminal blocker may be used in addition to the tetracarboxylic acid component and the diamine component described above for the production of the polyimide resin. 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, particularly 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, 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 temperature is immediately raised to carry out the imidization reaction.

The reaction solvent used for the production of the polyimide resin may be any solvent as long as it can dissolve the resulting polyimide resin without inhibiting the imidization reaction. Examples include aprotic solvents, phenolic solvents, ether solvents, carbonate solvents and the like.

Specific examples of aprotic solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, tetramethylurea and the like. , lactone solvents such as γ-butyrolactone and γ-valerolactone, phosphorus-containing amide solvents such as hexamethylphosphoricamide and hexamethylphosphinetriamide, sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane. ketone solvents such as acetone, cyclohexanone and methylcyclohexanone; amine solvents such as picoline and pyridine; and ester solvents such as acetic acid (2-methoxy-1-methylethyl).

Specific examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4 -xylenol, 3,5-xylenol, and the like.
Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl] ether, tetrahydrofuran, 1,4-dioxane and the like.
Specific examples of carbonate-based solvents include diethyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, and the like.
Among the above reaction solvents, amide solvents or lactone solvents are preferred. Moreover, the above reaction solvents may be used alone or in combination of two or more.

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

A known imidization catalyst can be used in the above imidization reaction. Examples of imidization catalysts include base catalysts and acid catalysts.
Base catalysts include pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N -dimethylaniline, N,N-diethylaniline and other organic base catalysts, and potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, sodium hydrogencarbonate and other inorganic base catalysts.
Acid catalysts include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, and the like. is mentioned. You may use said imidization catalyst individually or in combination of 2 or more types.
Among the above, from the viewpoint of handleability, it is preferable to use a base catalyst, more preferably to use an organic base catalyst, more preferably to use triethylamine, and particularly preferably to use a combination of triethylamine and triethylenediamine.

The temperature of the imidization reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoints of reaction rate and inhibition of gelation. Moreover, the reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

<Crosslinking agent>
In the present invention, the crosslinker has at least two oxazolyl groups. That is, the cross-linking agent in the present invention is a polyfunctional oxazoline compound having two or more oxazolyl groups (oxazoline rings) in the molecule.
An oxazolyl group is reactive with a carboxyl group, and when a carboxyl group and an oxazolyl group react, an amide ester bond is formed as shown below. This reaction proceeds particularly easily when heated to 80° C. or higher.

Since the polyimide resin contained in the polyimide resin composition of the present invention has a carboxyl group, when the polyimide resin composition of the present invention is heated, the polyimide resins are crosslinked via a cross-linking agent to form a crosslinked polyimide resin. be. For these reasons, the organic solvent resistance of the film is improved. Moreover, since the reaction between an oxazolyl group and a carboxyl group hardly progresses at room temperature, the polyimide resin composition of the present invention has excellent storage stability.

The crosslinking agent is not particularly limited as long as it is a compound having two or more oxazolyl groups in the molecule, and specific examples include 1,3-bis(4,5-dihydro-2-oxazolyl)benzene, 1,4 -Bis(4,5-dihydro-2-oxazolyl)benzene, 2,2'-bis(2-oxazoline), K-2010E, K-2020E, K-2030E, 2,6-bis manufactured by Nippon Shokubai Co., Ltd. (4-isopropyl-2-oxazolin-2-yl)pyridine, 2,6-bis(4-phenyl-2-oxazolin-2-yl)pyridine, 2,2′-isopropylidenebis(4-phenyl-2- oxazoline), 2,2′-isopropylidenebis(4-tert-butyl-2-oxazoline) and the like.
The cross-linking agent is preferably a compound containing an aromatic ring or aromatic heterocycle to which at least two oxazolyl groups are bonded, more preferably a compound containing a benzene ring to which at least two oxazolyl groups are bonded, and still more preferably 1,3-bis(4,5-dihydro-2-oxazolyl)benzene.
A crosslinking agent may be used independently and may be used in combination of 2 or more types.

In the polyimide resin composition of the present invention, the molar ratio of oxazolyl groups in the cross-linking agent to carboxyl groups in the polyimide resin (oxazolyl group/carboxyl group) is in the range of 1/4 to 1/0.5. and preferably contains a polyimide resin and a cross-linking agent. The molar ratio is more preferably 1/4 to 1/1, more preferably 1/2 to 1/1.
The above molar ratio means the molar ratio between the oxazolyl group contained in the cross-linking agent and the carboxyl group contained in the compound giving the structural unit (B-2) used in the production of the polyimide resin, and the addition of the cross-linking agent. It is calculated based on the added amount of the compound that gives the amount and the structural unit (B-2).

As a preferred embodiment of the polyimide resin composition of the present invention, in addition to the above-described polyimide resin and the above-described crosslinking agent, the polyimide resin composition further contains an organic solvent, and the polyimide resin is dissolved in the organic solvent ( hereinafter also referred to as "polyimide varnish").
The organic solvent is not particularly limited as long as it dissolves the polyimide resin, but it is preferable to use the compounds described above as the reaction solvent used in the production of the polyimide resin singly or in combination of two or more.
The polyimide varnish may be obtained by adding a cross-linking agent to the solution itself in which the polyimide resin obtained by the polymerization method is dissolved in the reaction solvent, or adding a diluting solvent and a cross-linking agent to the solution. may be

The polyimide resin described above is solvent soluble, and furthermore, the cross-linking reaction with the cross-linking agent hardly progresses at room temperature. Therefore, a high-concentration polyimide varnish that is stable at room temperature can be obtained. The polyimide varnish preferably contains 5 to 40% by mass of polyimide resin, more preferably 10 to 30% by mass. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, more preferably 5 to 150 Pa·s. The viscosity of the polyimide varnish is a value measured at 25° C. using an E-type viscometer.

Further, the polyimide resin composition of the present invention, in the range that does not impair the required properties of the polyimide film, an inorganic filler, an adhesion promoter, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, an antifoaming agent, Various additives such as fluorescent whitening agents, cross-linking agents, polymerization initiators, and photosensitizers may also be included.
The method for producing the polyimide resin composition of the present invention is not particularly limited, and known methods can be applied.

The polyimide resin composition of the present invention can form a film excellent in mechanical properties, organic solvent resistance, colorless transparency, and optical isotropy. Preferred physical properties of the film that can be formed using the polyimide resin composition of the present invention are as follows.

The tensile strength is preferably 50 MPa or higher, more preferably 60 MPa or higher, and even more preferably 70 MPa or higher.
The tensile modulus is preferably 2.0 GPa or higher, more preferably 2.2 GPa or higher, and even more preferably 2.5 GPa or higher.
The total light transmittance of a film having a thickness of 10 μm is preferably 87% or more, more preferably 88% or more, and still more preferably 89% or more.
The yellow index (YI) is preferably 6.8 or less, more preferably 3.5 or less, and still more preferably 2.2 or less when a film having a thickness of 10 μm is formed.
The absolute value of the thickness retardation (Rth) is preferably 75 nm or less, more preferably 25 nm or less, still more preferably 10 nm or less when a film having a thickness of 10 μm is formed.
The tensile strength, tensile modulus, total light transmittance, yellow index (YI), and thickness retardation (Rth) in the present invention can be specifically measured by the methods described in Examples.

[Polyimide film]
The polyimide film of the present invention is obtained by cross-linking the above-described polyimide resin contained in the polyimide resin composition of the present invention with the above-described cross-linking agent. That is, the polyimide film of the present invention contains a crosslinked polyimide resin which is a crosslinked product between polyimide resins via a crosslinking agent. Therefore, the polyimide film of the present invention is excellent in mechanical properties, organic solvent resistance, colorless transparency, and optical isotropy. Preferred physical properties of the polyimide film of the present invention are as described above.
The method for producing a polyimide film of the present invention includes a step of crosslinking at a temperature at which the crosslinking reaction between the polyimide resin and the crosslinking agent proceeds (preferably 80° C. or higher, more preferably 100° C. or higher, and still more preferably 150° C. or higher). There are no particular restrictions on inclusion. For example, the polyimide varnish described above may be coated on a smooth support such as a glass plate, a metal plate or plastic, or formed into a film and then heated. By this heat treatment, an organic solvent such as a reaction solvent and a dilution solvent contained in the polyimide varnish can be removed while the crosslinking reaction between the polyimide resin in the polyimide varnish and the crosslinking agent proceeds. If necessary, the surface of the support may be coated with a release agent in advance.
Examples of the method for applying the polyimide varnish onto the support include known coating methods such as spin coating, slit coating and blade coating.
As the heat treatment, the following method is preferable. That is, after evaporating the organic solvent at a temperature of 60 to 150° C. to form a self-supporting film, the self-supporting film is peeled off from the support, the end of the self-supporting film is fixed, and the organic solvent used is It is preferable to produce a polyimide film by drying at a temperature higher than the boiling point of the solvent. 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 heating temperature for drying the self-supporting film to produce the polyimide film is not particularly limited, but is preferably 250 to 400°C.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, still more preferably 10 to 80 μm. A thickness of 1 to 250 μm enables practical use as a self-supporting film.
The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the polyimide varnish.

The polyimide film of the present invention is suitably used as films for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays.

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is in no way limited by these examples.

The solid content concentrations of the polyimide resin solutions and polyimide varnishes obtained in Examples and Comparative Examples, and the physical properties of the polyimide films were measured by the following methods.
(1) Solid content concentration The solid content concentration of the polyimide resin solution and the polyimide varnish was measured by heating the sample at 320 ° C. × 120 min in a small electric furnace “MMF-1” manufactured by AS ONE Co., Ltd., and the mass of the sample before and after heating. Calculated from the difference.
(2) Film thickness The film thickness was measured using a Mitutoyo micrometer.
(3) Tensile Strength, Tensile Modulus Measurements were carried out according to JIS K7127 using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd.
(4) Total light transmittance, yellow index (YI)
The measurement was performed in accordance with JIS K7361-1 using a simultaneous color/turbidity measuring instrument "COH400" manufactured by Nippon Denshoku Industries Co., Ltd.
(5) Thickness retardation (Rth)
The thickness retardation (Rth) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. A thickness retardation value was measured at a measurement wavelength of 590 nm. Rth is represented by the following formula, where nx is the maximum refractive index in the plane of the polyimide film, ny is the minimum one, nz is the refractive index in the thickness direction, and d is the thickness of the film. It is a thing.
Rth=[{(nx+ny)/2}-nz]×d
(6) Organic Solvent Resistance The resulting film was immersed in an organic solvent at 60° C. for 3 hours to evaluate the organic solvent resistance. N-methyl-2-pyrrolidone (NMP) was used as the organic solvent.
The organic solvent resistance evaluation criteria were as follows.
B: The film surface dissolved in less than 3 hours after being immersed in an organic solvent.
A: Even after 3 hours of immersion in an organic solvent, the film surface did not dissolve and remained unchanged.

The tetracarboxylic acid component, diamine component, cross-linking agent and their abbreviations used in Examples and Comparative Examples are as follows.
<Tetracarboxylic acid component>
HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Company; compound represented by formula (a-1-1))
CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (manufactured by JX Energy Corporation; compound represented by formula (a-1-2))
s-BPDA: 3,3′,4,4′-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation; compound represented by formula (a-2s))
<Diamine component>
BAFL: 9,9-bis(4-aminophenyl)fluorene (manufactured by Taoka Chemical Co., Ltd.; compound represented by formula (b-1))
3,5-DABA: 3,5-diaminobenzoic acid (manufactured by Nihon Junryaku Co., Ltd.; compound represented by formula (b-211))
mTB: 2,2'-dimethylbiphenyl-4,4'-diamine (manufactured by Seika Co., Ltd.)
<Crosslinking agent>
1,3-PBO: 1,3-bis(4,5-dihydro-2-oxazolyl)benzene (manufactured by Mikuni Pharmaceutical Industry Co., Ltd.)
TG: triglycidyl isocyanurate (manufactured by Tokyo Chemical Industry Co., Ltd.)

<Example 1A>
27.876 g (0.080 mol) of BAFL was placed in a 1 L 5-neck round-bottom flask equipped with a stainless steel half-moon stirrer, a nitrogen inlet tube, a Dean Stark condenser, a thermometer, and a glass end cap. Then, 3.043 g (0.020 mol) of 3,5-DABA and 79.242 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added, and the temperature in the system was 70 ° C., under a nitrogen atmosphere, at a rotation speed of 200 rpm. Stir to obtain a solution.
To this solution, 22.417 g (0.100 mol) of HPMDA and 19.811 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added all at once, and triethylamine (manufactured by Kanto Chemical Co., Ltd.) was used as an imidization catalyst. ) was added and heated with a mantle heater to raise the temperature in the reaction system to 190° C. over about 20 minutes. The components to be distilled off were collected, and the temperature in the reaction system was kept at 190° C. and refluxed for 3 hours while adjusting the number of revolutions according to the increase in viscosity.
After that, 351.779 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) is added, the temperature inside the reaction system is cooled to 120° C., and the mixture is further stirred for about 3 hours for homogenization to obtain a solid concentration of 10.0 mass. % polyimide resin solution (1) was obtained.
Subsequently, 0.216 g (0.001 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (1), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid concentration of 10.2% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/2.
Subsequently, the resulting polyimide varnish is applied onto a glass plate, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 350 ° C. for 30 minutes in a nitrogen atmosphere to evaporate the solvent. A film of 18 μm was obtained. Table 1 shows the results.

<Example 1B>
A polyimide varnish was prepared and crosslinked in the same manner as in Example 1A, except that the amount of the crosslinking agent 1,3-PBO added to the polyimide resin solution (1) was changed to 0.432 g (0.002 mol). A polyimide varnish having a solid concentration of 10.4% by mass containing the agent and the polyimide resin was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 1A to obtain a film with a thickness of 17 μm. Table 1 shows the results.

<Comparative Example 1>
A polyimide varnish was prepared in the same manner as in Example 1A, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (1). That is, the polyimide resin solution (1) was directly used as the polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 1A to obtain a film with a thickness of 16 µm. Table 1 shows the results.

<Example 2A>
31.361 g (0.090 mol) of BAFL was placed in a 1 L 5-necked round-bottom flask equipped with a stainless steel half-moon stirrer, a nitrogen inlet tube, a Dean Stark condenser, a thermometer, and a glass end cap. Then, 1.522 g (0.010 mol) of 3,5-DABA and 105.961 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added, and the temperature in the system was 70 ° C., under a nitrogen atmosphere, at a rotation speed of 200 rpm. Stir to obtain a solution.
To this solution, 38.438 g (0.100 mol) of CpODA and 26.490 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added all at once, and triethylamine (manufactured by Kanto Chemical Co., Ltd.) was used as an imidization catalyst. ) and 0.056 g of triethylenediamine (manufactured by Tokyo Kasei Kogyo Co., Ltd.) were added, heated with a mantle heater, and the temperature in the reaction system was raised to 190° C. over about 20 minutes. The components to be distilled off were collected, and the temperature in the reaction system was kept at 190° C. and refluxed for 3 hours while adjusting the number of revolutions according to the increase in viscosity.
After that, 478.614 g of γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) was added, the temperature inside the reaction system was cooled to 120° C., and the mixture was further stirred for about 3 hours to homogenize the solid content to a solid concentration of 10.0 mass. % polyimide resin solution (2) was obtained.
Subsequently, 0.0796 g (0.00037 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (2), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid concentration of 10.07% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/2.
Subsequently, the resulting polyimide varnish is applied onto a glass plate, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 350 ° C. for 30 minutes in a nitrogen atmosphere to evaporate the solvent. A 27 μm film was obtained. Table 1 shows the results.

<Example 2B>
A polyimide varnish was prepared and crosslinked in the same manner as in Example 2A, except that the amount of the crosslinking agent 1,3-PBO added to the polyimide resin solution (2) was changed to 0.1592 g (0.00074 mol). A polyimide varnish having a solid content concentration of 10.14% by mass containing the agent and the polyimide resin was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 2A to obtain a film with a thickness of 23 μm. Table 1 shows the results.

<Comparative Example 2>
A polyimide varnish was prepared in the same manner as in Example 2A, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (2). That is, the polyimide resin solution (2) was used as it was as a polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 2A to obtain a film with a thickness of 14 μm. Table 1 shows the results.

<Example 3A>
The amount of BAFL was changed from 31.361 g (0.090 mol) to 27.876 g (0.080 mol) and the amount of 3,5-DABA was changed from 1.522 g (0.010 mol) to 3.043 g (0.080 mol). 020 mol), a polyimide resin solution was prepared in the same manner as in Example 2A to obtain a polyimide resin solution (3) having a solid concentration of 10.0% by mass.
Subsequently, 0.159 g (0.0007 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (3), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid content concentration of 10.14% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/2.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 2A to obtain a film with a thickness of 24 μm. Table 1 shows the results.
<Example 3B>
A polyimide varnish was prepared and crosslinked in the same manner as in Example 3A, except that the amount of the crosslinking agent 1,3-PBO added to the polyimide resin solution (3) was changed to 0.319 g (0.0015 mol). A polyimide varnish having a solid concentration of 10.29% by mass containing the agent and the polyimide resin was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 3A to obtain a film with a thickness of 23 μm. Table 1 shows the results.

<Comparative Example 3>
A polyimide varnish was produced in the same manner as in Example 3A, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (3). That is, the polyimide resin solution (3) was directly used as the polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 3A to obtain a film with a thickness of 20 μm. Table 1 shows the results.

<Example 4A>
The amount of BAFL was changed from 31.361 g (0.090 mol) to 17.423 g (0.050 mol) and the amount of 3,5-DABA was changed from 1.522 g (0.010 mol) to 7.608 g (0 050 mol), a polyimide resin solution was prepared in the same manner as in Example 2A to obtain a polyimide resin solution (4) having a solid concentration of 10.0% by mass.
Subsequently, 0.445 g (0.0021 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (4), and after stirring for 1 hour at room temperature, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid content concentration of 10.40% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/2.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 2A to obtain a film with a thickness of 12 μm. Table 1 shows the results.
<Example 4B>
A polyimide varnish was prepared and crosslinked in the same manner as in Example 4A, except that the amount of the crosslinking agent 1,3-PBO added to the polyimide resin solution (4) was changed to 0.890 g (0.0041 mol). A polyimide varnish having a solid concentration of 10.79% by mass containing the agent and the polyimide resin was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 4A to obtain a film with a thickness of 15 μm. Table 1 shows the results.

<Comparative Example 4>
A polyimide varnish was produced in the same manner as in Example 4A, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (4). That is, the polyimide resin solution (4) was used as it was as a polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 4A to obtain a film with a thickness of 20 μm. Table 1 shows the results.

<Example 5>
Same procedure as in Example 1A except that the amount of HPMDA was changed from 22.417 g (0.100 mol) to 11.209 g (0.050 mol) and 19.219 g (0.050 mol) of CpODA was added. to prepare a polyimide resin solution (5) having a solid concentration of 10.0% by mass.
Subsequently, 0.372 g (0.0017 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (5), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid concentration of 10.33% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 1A to obtain a film with a thickness of 9 μm. Table 1 shows the results.

<Comparative Example 5>
A polyimide varnish was produced in the same manner as in Example 5, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (5). That is, the polyimide resin solution (5) was used as it was as a polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 5 to obtain a film with a thickness of 9 μm. Table 1 shows the results.

<Example 6>
Same as Example 1A except the amount of HPMDA was changed from 22.417 g (0.100 mol) to 20.175 g (0.090 mol) and 2.942 g (0.010 mol) of s-BPDA was added. A polyimide resin solution was prepared by the method of No. to obtain a polyimide resin solution (6) having a solid concentration of 10.0 mass %.
Subsequently, 0.424 g (0.0020 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (6), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid content concentration of 10.38% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 1A to obtain a film with a thickness of 20 μm. Table 1 shows the results.

<Comparative Example 6>
A polyimide varnish was produced in the same manner as in Example 6, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (6). That is, the polyimide resin solution (6) was directly used as the polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Example 6 to obtain a film with a thickness of 17 μm. Table 1 shows the results.

<Comparative Example 7A>
The cross-linking agent added to the polyimide resin solution (1) was changed from 0.216 g (0.001 mol) of 1,3-PBO to 0.500 g (0.0017 mol) of TG. A polyimide varnish was prepared in the same manner as in Example 1A to obtain a polyimide varnish containing a cross-linking agent and a polyimide resin and having a solid concentration of 10.45% by mass.
Subsequently, the resulting polyimide varnish is applied onto a glass plate, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 350 ° C. for 30 minutes in a nitrogen atmosphere to evaporate the solvent. A 20 μm film was obtained. The obtained film had dotted defects on the entire surface. Table 2 shows the results.

<Comparative Example 7B>
A polyimide varnish was prepared in the same manner as in Comparative Example 7A, except that the amount of the cross-linking agent TG added to the polyimide resin solution (1) was changed to 1.000 g (0.0034 mol). A polyimide varnish having a solid content concentration of 10.89% by mass was obtained.
Using the obtained polyimide varnish, a film was produced in the same manner as in Comparative Example 7A to obtain a film with a thickness of 22 μm. The obtained film had dotted defects on the entire surface. Table 2 shows the results.

<Comparative Example 8A>
10.615 g (0.050 mol) of mTB was added to a 1 L 5-necked round-bottom flask equipped with a stainless steel half-moon stirrer, a nitrogen inlet tube, a Dean Stark condenser, a thermometer, and a glass end cap. Then, 7.608 g (0.050 mol) of 3,5-DABA and 48.767 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added, and the temperature in the system was 70 ° C., under a nitrogen atmosphere, at a rotation speed of 200 rpm. Stir to obtain a solution.
To this solution, 22.417 g (0.100 mol) of HPMDA and 12.192 g of N,N'-dimethylacetamide (Mitsubishi Gas Chemical Co., Ltd.) were added all at once, followed by triethylamine ( 0.506 g of Kanto Kagaku Co., Ltd.) was added and heated with a mantle heater to raise the temperature in the reaction system to 180° C. over about 20 minutes. The components to be distilled off were collected, and the temperature in the reaction system was maintained at 180° C. and refluxed for 5 hours while adjusting the number of revolutions according to the increase in viscosity.
After that, 280.466 g of N,N'-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Co., Ltd.) is added, and the temperature in the reaction system is cooled to 120 ° C., and then stirred for about 3 hours to homogenize the solid content. A polyimide resin solution (7) having a concentration of 10.0% by mass was obtained.
Subsequently, 1.425 g (0.0066 mol) of 1,3-PBO as a cross-linking agent is added to 100 g of the polyimide resin solution (7), and after stirring at room temperature for 1 hour, the cross-linking agent and the polyimide resin are added. A polyimide varnish having a solid content concentration of 11.26% by mass was obtained. The molar ratio of oxazolyl group/carboxyl group calculated based on the added amount of 1,3-PBO and the added amount of 3,5-DABA is 1/1.
Subsequently, the resulting polyimide varnish is applied onto a glass plate, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 350 ° C. for 30 minutes in a nitrogen atmosphere to evaporate the solvent. A 16 μm film was obtained. Table 3 shows the results.

<Comparative Example 8B>
A polyimide varnish was prepared in the same manner as in Comparative Example 8A, except that the cross-linking agent 1,3-PBO was not added to the polyimide resin solution (7). That is, the polyimide resin solution (7) was directly used as the polyimide varnish.
Using the obtained polyimide varnish, a film was produced in the same manner as in Comparative Example 8A to obtain a film with a thickness of 15 μm. Table 3 shows the results.

As shown in Table 1, the films of Examples were all excellent in mechanical properties, organic solvent resistance, colorless transparency, and optical isotropy.
In particular, it was confirmed that the addition of 1,3-PBO improves the organic solvent resistance (comparison between Examples 1A and 1B and Comparative Example 1, comparison between Examples 2A and 2B and Comparative Example 2). Comparison, comparison between Examples 3A and 3B and Comparative Example 3, comparison between Examples 4A and 4B and Comparative Example 4, comparison between Example 5 and Comparative Example 5, and comparison between Example 6 and Comparative Example 6 ).
Surprisingly, even if 1,3-PBO is added, optical isotropy can be maintained (comparison with Examples 1A and 1B and Comparative Example 1), or by adding 1,3-PBO Optical isotropy is improved (comparison between Examples 2A and 2B and Comparative Example 2, comparison between Examples 3A and 3B and Comparative Example 3, comparison between Examples 4A and 4B and Comparative Example 4, Example 5 and Comparative Example 5, and Example 6 and Comparative Example 6).

The films obtained in Comparative Examples 7A and 7B using TG as a crosslinker (not a crosslinker with at least two oxazolyl groups) were not uniform films. This is probably because the polyimide resin and the additive TG have poor compatibility and are separated.
Moreover, as shown in Table 2, the film of Comparative Example 7B was significantly inferior in colorless transparency.

In Comparative Examples 8A and 8B, mTB was used instead of BAFL (compound represented by formula (b-1)) as the diamine component. The resulting films of Comparative Examples 8A and 8B had poor optical isotropy. Also, the film of Comparative Example 8B was inferior in organic solvent resistance. As can be seen by comparing Comparative Example 8A with Comparative Example 8B, the addition of 1,3-PBO improved the organic solvent resistance, but the colorless transparency (total light transmittance, YI) was greatly deteriorated. . As a result, the film of Comparative Example 8A was significantly inferior in colorless transparency to the films of Examples.

Claims (8)

A polyimide resin composition comprising a polyimide resin and a cross-linking agent having at least two oxazolyl groups,
The polyimide resin has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine,
A constitution in which the structural unit A is derived from a structural unit (A-1-1) derived from a compound represented by the following formula (a-1-1) and a compound represented by the following formula (a-1-2) including a structural unit (A-1) that is at least one selected from the group consisting of units (A-1-2),
The structural unit B is a structural unit (B-1) derived from a compound represented by the following formula (b-1), and a structural unit (B-2) derived from a compound represented by the following formula (b-2) ) and
The ratio of the structural unit (B-1) in the structural unit B is 75 to 99 mol%,
A polyimide resin composition in which the ratio of the structural unit (B-2) in the structural unit B is 1 to 25 mol% .

(In formula (b-1), each R is independently a hydrogen atom, a fluorine atom, or a methyl group; In formula (b-2), X is a single bond, a substituted or unsubstituted alkylene group, carbonyl group, an ether group, a group represented by the following formula (b-2-i), or a group represented by the following formula (b-2-ii), p is an integer of 0 to 2, and m1 is is an integer of 0 to 4, and m2 is an integer of 0 to 4. However, when p is 0, m1 is an integer of 1 to 4.)

(In formula (b-2-i), m3 is an integer of 0 to 5; In formula (b-2-ii), m4 is an integer of 0 to 5. Note that m1 + m2 + m3 + m4 is 1 or more, When p is 2, each of the two Xs and the two m2-m4 are independently selected.) The polyimide resin composition according to claim 1, wherein the structural unit (B-2) is a structural unit (B-21) derived from a compound represented by the following formula (b-21).

3. The polyimide resin composition according to claim 1, wherein the cross-linking agent contains a benzene ring to which the at least two oxazolyl groups are bonded. The polyimide resin and the polyimide resin and the The polyimide resin composition according to any one of claims 1 to 3, comprising a cross-linking agent. 5. The polyimide resin composition according to any one of claims 1 to 4 , wherein the ratio of the structural unit (A-1) in the structural unit A is 50 mol% or more. 6. The polyimide resin composition according to any one of claims 1 to 5 , wherein the structural unit (A-1) is the structural unit (A-1-1). 6. The polyimide resin composition according to any one of claims 1 to 5 , wherein the structural unit (A-1) is the structural unit (A-1-2). A polyimide film obtained by cross-linking the polyimide resin in the polyimide resin composition according to any one of claims 1 to 7 with the cross-linking agent.