WO2021033544A1

WO2021033544A1 - Polyimide resin composition, polyimide varnish, and polyimide film

Info

Publication number: WO2021033544A1
Application number: PCT/JP2020/029989
Authority: WO
Inventors: 洋平安孫子; 健太郎石井; 三田寺　淳
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2019-08-20
Filing date: 2020-08-05
Publication date: 2021-02-25
Also published as: KR20220051335A; TW202112905A; CN114245809A; JPWO2021033544A1

Abstract

A polyimide resin composition including a polyimide resin and a crosslinking agent having at least two oxazolyl groups, wherein the polyimide resin is a polyimide resin having constituent units A derived from a tetracarboxylic acid dianhydride, and constituent units B derived from a diamine, the constituent units A including constituent units (A-1) derived from CpODA, and the constituent units B including constituent units (B-1) derived from TFMB and constituent units (B-2) derived from a specific compound typified by 3,5-DABA.

Description

Polyimide resin composition, polyimide varnish and polyimide film

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

In general, polyimide resin has excellent heat resistance, so various uses are being studied in fields such as electrical and electronic parts. For example, it is desired to replace a glass substrate used in an image display device such as a liquid crystal display or an OLED display with a plastic substrate for the purpose of reducing the weight and flexibility of the device, and a polyimide film suitable as the plastic substrate. Research is underway. Colorless transparency is required for polyimide films for such applications.

When the varnish applied on the glass support or silicon wafer is heat-cured to form a polyimide film, residual stress is generated in the polyimide film. If the residual stress of the polyimide film is large, there is a problem that the glass support and the silicon wafer are warped. Therefore, the polyimide film is also required to reduce the residual stress.

By the way, in order for a polyimide film to be suitable as a substrate, not only colorless transparency and low residual stress, but also chemical resistance (for example, acid resistance, alkali resistance, solvent resistance) are important physical properties. For example, when a polyimide film is used as a substrate for forming an ITO (Indium Tin Oxide) film, the polyimide film is required to have resistance to the acid used for etching the ITO film. If the acid resistance of the polyimide film is insufficient, the film may turn yellow and the colorless transparency may be impaired.

Further, an alkaline aqueous solution such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is mainly used for cleaning a support (a support to which a polyimide varnish is applied) such as a glass plate used in manufacturing a polyimide film. .. Cleaning with an alkaline aqueous solution may be performed even when a polyimide film is formed on a support such as a glass plate. Therefore, the polyimide film is also required to have resistance to alkali.

Furthermore, in the process of forming electronic circuits such as various TFTs on the polyimide film, an organic solvent such as NMP may be used, and the polyimide film is also required to have resistance to the organic solvent.

On the other hand, after processing the polyimide resin composition into a polyimide film, it is necessary to clean the piping and equipment used for coating and the like. In order to sufficiently clean the apparatus, the polyimide resin composition is also required to be soluble in the cleaning liquid used (for example, "OK73 thinner" manufactured by Tokyo Ohka Kogyo Co., Ltd. and various organic solvents such as NMP), and is solvent resistant. Conflicting performances of property and detergency are required.

In Patent Document 1, 4,4'-oxydiphthalic dianhydride is used as a tetracarboxylic dian component as a polyimide resin that gives a film having a low residual stress, and α, ω-aminopropyl poly having a number average molecular weight of 1000 is used as a diamine component. A polyimide resin synthesized using dimethylsiloxane and 4,4'-diaminodiphenyl ether is disclosed.

Patent Document 2 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 stated that the formation of is possible.

However, Patent Document 1 does not describe any chemical resistance and detergency. Further, in Patent Document 2, resistance to a solvent (N, N-dimethylacetamide) has not been evaluated, and detergency and residual stress have not been examined at all.

Japanese Unexamined Patent Publication No. 2005-232383 Japanese Unexamined Patent Publication No. 2016-222777

As described above, the polyimide film is required to have colorless transparency, low residual stress, and chemical resistance, but it is not easy to improve these properties while maintaining excellent heat resistance.
The problem to be solved by the present invention includes a polyimide resin composition having excellent heat resistance, colorless transparency, chemical resistance and cleanability, and capable of forming a film having low residual stress, and the polyimide resin composition. The present invention is to provide a polyimide varnish and a polyimide film.

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-mentioned problems, and have completed the invention.

That is, the present invention relates to the following <1> to <11>.
<1> A polyimide resin composition containing a polyimide resin and a cross-linking agent having at least two oxazolyl groups.
The polyimide resin is a polyimide resin having a structural unit A derived from tetracarboxylic acid dianhydride and a structural unit B derived from diamine, and the structural unit A is derived from a compound represented by the following formula (a-1). The structural unit B is represented by the following formula (b-2) and the structural unit (B-1) derived from the compound represented by the following formula (b-1). A polyimide resin composition containing a structural unit (B-2) derived from a compound.

(In the formula (b-2), X is a single-bonded, substituted or unsubstituted alkylene group, a carbonyl group, an ether group, a group represented by the following formula (b-2-i), or the following formula (b-2). -Ii), p is an integer of 0 to 2, m1 is an integer of 0 to 4, m2 is an integer of 0 to 4. However, when p is 0, m1 Is an integer from 1 to 4.)

(In the formula (b-2-i), m3 is an integer of 0 to 5; in the 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 to m4 are independently selected.)
<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 <1> or <2> above, wherein the ratio of the structural unit (A-1) in the structural unit A is 40 mol% or more.
<4> The ratio of the constituent unit (B-1) in the constituent unit B is 35 to 95 mol%.
The polyimide resin composition according to any one of <1> to <3> above, wherein the ratio of the structural unit (B-2) in the structural unit B is 5 to 65 mol%.
<5> The above-mentioned <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). Polyimide resin composition.

<6> The polyimide resin composition according to any one of <1> to <5> above, wherein the structural unit A further contains a structural unit (A-3) derived from both terminal acid anhydride-modified silicones.
<7> The polyimide resin composition according to any one of <1> to <6> above, wherein the cross-linking agent is a compound containing an aromatic ring or an aromatic heterocycle having at least two oxazolyl groups bonded thereto.
<8> The polyimide resin composition according to any one of <1> to <7> above, wherein the cross-linking agent is a compound containing a benzene ring in which at least two oxazolyl groups are bonded.
<9> The polyimide resin composition according to any one of <1> to <8> above, wherein the cross-linking agent is 1,3-bis (4,5-dihydro-2-oxazolyl) benzene.
<10> A polyimide varnish in which the polyimide resin composition according to any one of <1> to <9> above is dissolved in an organic solvent.
<11> A polyimide film obtained by cross-linking the polyimide resin in the polyimide resin composition according to any one of <1> to <9> with the cross-linking agent.

According to the present invention, it is possible to form a film having excellent heat resistance, colorless transparency, chemical resistance and detergency, and further having low residual stress.

[Polyimide resin composition]
The polyimide resin composition of the present invention contains a polyimide resin and a cross-linking agent. Hereinafter, the polyimide resin and the cross-linking agent in the present invention will be described.

<Polyimide resin>
The polyimide resin of the present invention has a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, and the structural unit A is derived from a compound represented by the following formula (a-1). A structural unit (B-1) containing a structural unit (A-1) and whose 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). Includes a structural unit (B-2) derived from.

(In the formula (b-2-i), m3 is an integer of 0 to 5; in the 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 to m4 are independently selected.)

(Structural unit A)
The structural unit A is a structural unit derived from tetracarboxylic dianhydride in the polyimide resin, and includes a structural unit (A-1) derived from a compound represented by the following formula (a-1).

The compound represented by the formula (a-1) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2 "-norbornane-5,5", 6,6 "-tetracarboxylic dianhydride. By including the constituent unit (A-1) in the constituent unit A, the colorless transparency and heat resistance of the film are improved.

The ratio of the structural unit (A-1) in the structural unit A is preferably 40 mol% or more, more preferably 50 mol% or more, and further preferably 60 mol% or more. The upper limit of the ratio of the structural unit (A-1) is not particularly limited, that is, 100 mol%. The structural unit A may consist of only the structural unit (A-1).

The structural unit A may include a structural unit other than the structural unit (A-1).
The structural unit A preferably further contains a structural unit (A-2) derived from a compound represented by the following formula (a-2) in addition to the structural unit (A-1).

The compound represented by the formula (a-2) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof are 3,3', 4, represented by the following formula (a-2s). 4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3', 4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a-2a), Examples thereof include 2,2', 3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a-2i). 3,3', 4,4'-biphenyltetracarboxylic dianhydride is preferable because it can reduce the residual stress of the polyimide film of the present invention.

When the constituent unit A includes the constituent unit (A-1) and the constituent unit (A-2), the ratio of the constituent unit (A-1) in the constituent unit A is preferably 40 to 95 mol%, and more. It is preferably 50 to 90 mol%, more preferably 55 to 85 mol%, and the ratio of the constituent unit (A-2) in the constituent unit A is preferably 5 to 60 mol%, more preferably. It is 10 to 50 mol%, more preferably 15 to 45 mol%.
The total ratio of the structural units (A-1) and (A-2) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more. It is particularly preferably 99 mol% or more. The upper limit of the total ratio of the structural units (A-1) and (A-2) is not particularly limited, that is, 100 mol%. The structural unit A may consist only of the structural unit (A-1) and the structural unit (A-2).

When the structural unit A further includes the structural unit (A-2), the residual stress is further reduced.
Further, when the structural unit A further includes the structural unit (A-2), the light transmittance of the film at a wavelength of 308 nm becomes small. In recent years, a laser peeling process called laser lift-off (LLO) has attracted attention as a method for peeling the support and the resin film on a support on which a resin film is laminated. The smaller the light transmittance at a wavelength of 308 nm, the better the laser exfoliation property by the XeCl excimer laser at a wavelength of 308 nm.

The structural unit A preferably further contains a structural unit (A-3) derived from the biterminal acid anhydride-modified silicone in addition to the structural unit (A-1).
As the biterminal acid anhydride-modified silicone, a compound represented by the following formula (a-3) is preferable.

(In equation (a-3),
R ¹ to R ⁶ are independently monovalent hydrocarbon groups having 1 to 20 carbon atoms.
L ¹ and L ² are independently single-bonded or divalent hydrocarbon groups having 1 to 20 carbon atoms.
Z ¹ and Z ² are independently trivalent hydrocarbon groups having 1 to 20 carbon atoms.
n is 1 to 200. )

^{R 1} to R ⁶ in the formula (a-3) are independently monovalent hydrocarbon groups having 1 to 20 carbon atoms.
The monovalent hydrocarbon group having 1 to 20 carbon atoms includes an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. Examples thereof include a group and an alkenyl group having 2 to 20 carbon atoms.
The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, and the like. And hexyl groups. The cycloalkyl group having 3 to 20 carbon atoms is preferably a cycloalkyl group having 3 to 10 carbon atoms, and examples thereof include a cyclopentyl group and a cyclohexyl group. As the aryl group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms is preferable, and examples thereof include a phenyl group and a naphthyl group. The aralkyl group having 7 to 20 carbon atoms is preferably an aralkyl group having 7 to 10 carbon atoms, and examples thereof include a benzyl group and a phenethyl group. The alkenyl group having 2 to 20 carbon atoms is preferably an alkenyl group having 2 to 10 carbon atoms, and examples thereof include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, and a butenyl group.

R ¹ to R ⁶ are independent of each other, preferably an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. Selected from the group consisting of groups and alkenyl groups having 2 to 20 carbon atoms; more preferably alkyl groups having 1 to 10 carbon atoms, cycloalkyl groups having 3 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, etc. It is selected from the group consisting of an aralkyl group having 7 to 10 carbon atoms and an alkenyl group having 2 to 10 carbon atoms; more preferably, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and a carbon number of carbon atoms. Selected from the group consisting of 2-10 alkyl groups; particularly preferably methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group, phenyl group, naphthyl. It is selected from the group consisting of a group, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, and a butenyl group; most preferably it is selected from the group consisting of a methyl group, an ethyl group, a phenyl group, and a vinyl group.

^{L 1} and L ² in the formula (a-3) are independently single-bonded or divalent hydrocarbon groups having 1 to 20 carbon atoms.
Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, and an arylene group having 6 to 20 carbon atoms.
The alkylene group having 1 to 20 carbon atoms is preferably an alkylene group having 1 to 10 carbon atoms, and examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group.
The cycloalkylene group having 3 to 20 carbon atoms is preferably a cycloalkylene group having 3 to 10 carbon atoms, and examples thereof include a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, and a cycloheptylene group.
As the arylene group having 6 to 20 carbon atoms, an arylene group having 6 to 10 carbon atoms is preferable, and examples thereof include a phenylene group and a naphthylene group.

L ¹ and L ² are independent of each other, preferably from the group consisting of a single bond, an alkylene group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, and an arylene group having 6 to 20 carbon atoms. Selected; more preferably selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, and an arylene group having 6 to 10 carbon atoms; more preferably a single bond. Selected from the group consisting of bonds, alkylene groups with 1 to 10 carbons, and arylene groups with 6 to 10 carbons; particularly preferably single bonds, methylene groups, ethylene groups, propylene groups, butylene groups, pentylene groups, hexylenes. It is selected from the group consisting of groups, phenylene groups and naphthylene groups; most preferably it is selected from the group consisting of single bonds, methylene groups, ethylene groups, propylene groups, and phenylene groups.

^{Z 1} and Z ² in the formula (a-3) are independently trivalent hydrocarbon groups having 1 to 20 carbon atoms.
Z ¹ and Z ² are independent of each other, preferably a group represented by the following formula (a-3-i), a group represented by the following formula (a-3-ii), and the following formula (a-ii). It is selected from the group consisting of a group represented by 3-iii) and a group represented by the following formula (a-3-iv).

The group represented by the formula (a-3-i) is a succinic acid residue, the group phthalic acid residue represented by the formula (a-3-ii), and the formula (a-3-iii). The group represented is a 2,3-norbornanedicarboxylic acid residue, and the group represented by (a-3-iv) is a 5-norbornane-2,3-dicarboxylic acid residue. In the formulas (a-3-i) to (a-3-iv), "*" indicates the bonding position.

N in the formula (a-3) is 1 to 200. n is preferably 3 to 150, more preferably 5 to 120.

Commercially available products of biterminal acid anhydride-modified silicone include "X22-168AS", "X22-168A", "X22-168B", and "X22-168-P5-" manufactured by Shin-Etsu Chemical Co., Ltd. 8 ”,“ DMS-Z21 ”manufactured by Gerest, and the like.

When the constituent unit A includes the constituent unit (A-1) and the constituent unit (A-3), the ratio of the constituent unit (A-1) in the constituent unit A is preferably 50 to 99 mol%, and more. It is preferably 60 to 98 mol%, more preferably 70 to 97 mol%, and the ratio of the constituent unit (A-3) in the constituent unit A is preferably 1 to 50 mol%, more preferably 2 It is -40 mol%, more preferably 3-30 mol%.
The total ratio of the structural units (A-1) and (A-3) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more. It is particularly preferably 99 mol% or more. The upper limit of the total ratio of the structural units (A-1) and (A-3) is not particularly limited, that is, 100 mol%. The structural unit A may consist only of the structural unit (A-1) and the structural unit (A-3).

By further including the structural unit (A-3) in the structural unit A, it is possible to improve the colorless transparency while keeping the residual stress of the film low.

Further, it is preferable that the structural unit A further includes both the structural unit (A-2) and the structural unit (A-3) in addition to the structural unit (A-1).
When the constituent unit A includes the constituent unit (A-1), the constituent unit (A-2), and the constituent unit (A-3), the ratio of the constituent unit (A-1) in the constituent unit A is preferably It is 50 to 90 mol%, more preferably 60 to 85 mol%, further preferably 65 to 80 mol%, and the ratio of the constituent unit (A-2) in the constituent unit A is preferably 5 to 30 mol%. %, More preferably 5 to 25 mol%, still more preferably 5 to 20 mol%, and the ratio of the constituent unit (A-3) in the constituent unit A is preferably 1 to 25 mol%. Yes, more preferably 2 to 20 mol%, still more preferably 3 to 15 mol%.
The total ratio of the structural units (A-1) to (A-3) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more. It is particularly preferably 99 mol% or more. The upper limit of the total ratio of the structural units (A-1) to (A-3) is not particularly limited, that is, 100 mol%. The structural unit A may be composed of only the structural unit (A-1), the structural unit (A-2), and the structural unit (A-3).

The structural units other than the structural unit (A-1) arbitrarily included in the structural unit A are not limited to the structural units (A-2) and (A-3). The tetracarboxylic dianhydride giving such an arbitrary constituent unit is not particularly limited, but is pyromellitic dianhydride, 9,9'-bis (3,4-dicarboxyphenyl) fluorene dianhydride, and the like. And aromatic tetracarboxylic dianhydrides such as 4,4'-(hexafluoroisopropyridene) diphthalic dianhydride; 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5 -Alicyclic tetracarboxylic dianhydride such as cyclohexanetetracarboxylic dianhydride (excluding the compound represented by the formula (a-1)); and 1,2,3,4-butanetetracarboxylic acid. Examples thereof include aliphatic tetracarboxylic dianhydrides such as dianhydrides.
In the present specification, the aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and the alicyclic tetracarboxylic dianhydride has one alicyclic ring. The tetracarboxylic acid dianhydride containing the above and containing no aromatic ring is meant, and the aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.
The structural unit other than the structural unit (A-1) arbitrarily included in the structural unit A may be one type or two or more types.

(Structural unit B)
The structural unit B is a structural unit derived from diamine in the polyimide resin, and is a structural unit (B-1) derived from a compound represented by the following formula (b-1) and the following formula (b-2). Includes a structural unit (B-2) derived from the compound represented by.

(In the formula (b-2-i), m3 is an integer of 0 to 5; in the 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 to m4 are independently selected.)
In the formulas (b-2-i) and (b-2-ii), "*" indicates the bonding position.

The compound represented by the formula (b-1) is 2,2'-bis (trifluoromethyl) benzidine. When the structural unit B includes the structural unit (B-1), the colorless transparency of the film is improved and the residual stress is reduced.

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

Specific examples of the compound represented by the formula (b-21) include a compound represented by the following formula (b-211), that is, 3,5-diaminobenzoic acid.

The structural unit (B-2) is preferably a structural unit (B-21) derived from the compound represented by the formula (b-21), and is derived from the compound represented by the formula (b-211). It is more preferably a structural unit (B-211).

The heat resistance of the film is improved by including the structural unit (B-2) in the structural unit B.

The ratio of the structural unit (B-1) in the structural unit B is preferably 35 to 95 mol%, more preferably 40 to 90 mol%, and further preferably 45 to 85 mol%.
The ratio of the structural unit (B-2) in the structural unit B is preferably 5 to 65 mol%, more preferably 10 to 60 mol%, still more preferably 15 to 55 mol%.
The total ratio of the structural units (B-1) and (B-2) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more. It is particularly preferably 99 mol% or more. The upper limit of the total ratio of the structural units (B-1) and (B-2) is not particularly limited, that is, 100 mol%. The structural unit B may consist only of the structural unit (B-1) and the structural unit (B-2).

The structural unit B may include a structural unit other than the structural units (B-1) and (B-2). The diamine that gives such a structural unit is not particularly limited, but is limited to 1,4-phenylenediamine, p-xylylene diamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine. , 4,4'-Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 1- (4-aminophenyl) -2,3-dihydro-1,3,3-trimethyl-1H-inden-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, Aromatic diamines such as 2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane and 9,9-bis (4-aminophenyl) fluorene (however, compounds represented by the formula (b-1)). And compounds represented by the formula (b-2)); alicyclic diamines such as 1,3-bis (aminomethyl) cyclohexane and 1,4-bis (aminomethyl) cyclohexane; and ethylenediamine and hexamethylenediamine. Etc. include aliphatic diamines.
In the present specification, the aromatic diamine means a diamine containing one or more aromatic rings, and the alicyclic diamine means a diamine containing one or more alicyclic rings and not containing an aromatic ring, and is a fat. The group diamine means a diamine that does not contain an aromatic ring or an alicyclic ring.
The structural units other than the structural units (B-1) and (B-2) arbitrarily included in the structural unit B may be one type or two or more types.

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 obtained polyimide film. The number average molecular weight of the polyimide resin can be obtained from, for example, a standard polymethylmethacrylate (PMMA) conversion value measured by gel filtration chromatography.

The polyimide resin may contain a structure other than the polyimide chain (a structure in which the structural unit A and the structural unit B are imide-bonded). Examples of the structure other than the polyimide chain that can be contained in the polyimide resin include a structure containing an amide bond.
The polyimide resin preferably contains a polyimide chain (a structure in which the structural unit A and the structural unit B are imide-bonded) as a main structure. Therefore, the ratio of the polyimide chain to the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 99% by mass or more. is there.

The polyimide resin composition of the present invention containing the above-mentioned polyimide resin can form a film having excellent heat resistance, colorless transparency, chemical resistance and cleanability, and further has low residual stress, and has suitable physical properties of the film. The values are as follows.

The glass transition temperature (Tg) is preferably 380 ° C. or higher, more preferably 400 ° C. or higher, and even more preferably 450 ° C. or higher.
The total light transmittance is preferably 88% or more, more preferably 89% or more, still more preferably 90% or more when the film has a thickness of 10 μm.
The yellow index (YI) is preferably 5.0 or less, more preferably 4.0 or less, and further preferably 3.0 or less when the film has a thickness of 10 μm.
The residual stress is preferably 25.0 MPa or less, more preferably 24.0 MPa or less, and further preferably 22.0 MPa or less.

Further, by using a polyimide resin in which the structural unit A further contains the structural unit (A-2), which is one aspect of the polyimide resin, a film having further excellent laser peelability can be formed, and the film can be formed. Suitable physical property values to have are as follows.
The light transmittance at a wavelength of 308 nm is preferably 0.8% or less, more preferably 0.6% or less, still more preferably 0.4% or less when the film has a thickness of 10 μm.

In addition, the film that can be formed using the polyimide resin has good mechanical properties and has the following suitable physical property values.
The tensile elastic modulus is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, and further preferably 4.0 GPa or more.
The tensile strength is preferably 80 MPa or more, more preferably 100 MPa or more, and further preferably 120 MPa or more.
The above-mentioned physical property values in the present invention can be specifically measured by the method described in Examples.

<Manufacturing method of polyimide resin>
In the present invention, the polyimide resin contains a tetracarboxylic acid component containing the compound giving the above-mentioned structural unit (A-1), the compound giving the above-mentioned structural unit (B-1), and the above-mentioned structural unit (B-2). It can be produced by reacting with a diamine component containing a compound that gives.

Examples of the compound giving the structural unit (A-1) include the compound represented by the formula (a-1), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. The derivative is a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by the formula (a-1) (that is, norbornan-2-spiro-α-cyclopentanone-α'-spiro-2 "-. Norbornan-5,5 ", 6,6" -tetracarboxylic acid), and an alkyl ester of the tetracarboxylic acid. Examples of the compound giving the structural unit (A-1) are represented by the formula (a-1). The compound (ie, dianhydride) to be used is preferred.

The tetracarboxylic acid component preferably contains 40 mol% or more, more preferably 50 mol% or more, and further preferably 60 mol% or more of the compound giving the constituent unit (A-1). The upper limit of the content of the compound giving the structural unit (A-1) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may consist only of the compound giving the structural unit (A-1).

The tetracarboxylic acid component may contain a compound other than the compound giving the structural unit (A-1).
The tetracarboxylic acid component preferably further contains a compound that gives the structural unit (A-2) in addition to the compound that gives the structural unit (A-1).
Examples of the compound giving the structural unit (A-2) include the compound represented by the formula (a-2), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by the formula (a-2) and an alkyl ester of the tetracarboxylic acid. As the compound giving the structural unit (A-2), the compound represented by the formula (a-2) (that is, dianhydride) is preferable.

When the tetracarboxylic acid component contains a compound giving a structural unit (A-1) and a compound giving a structural unit (A-2), the tetracarboxylic acid component preferably contains a compound giving a structural unit (A-1). It contains 40 to 95 mol%, more preferably 50 to 90 mol%, further preferably 55 to 85 mol%, and preferably contains 5 to 60 mol% of the compound giving the constituent unit (A-2), more preferably. Contains 10 to 50 mol%, more preferably 15 to 45 mol%.
The tetracarboxylic acid component contains, in total, a compound that gives the structural unit (A-1) and a compound that gives the structural unit (A-2), preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably. Contains 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound giving the structural unit (A-1) and the compound giving the structural unit (A-2) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may consist only of a compound that gives a constituent unit (A-1) and a compound that gives a constituent unit (A-2).

The tetracarboxylic acid component preferably further contains a compound that gives the structural unit (A-3) in addition to the compound that gives the structural unit (A-1).
Examples of the compound giving the structural unit (A-3) include, but are not limited to, biterminal acid anhydride-modified silicone (for example, the compound represented by the formula (a-3)), and the range giving the same structural unit is not limited thereto. And it may be a derivative thereof. Examples of the derivative include a tetracarboxylic acid corresponding to both terminal acid anhydride-modified silicones and an alkyl ester of the tetracarboxylic acid. As the compound that gives the structural unit (A-3), double-terminal acid anhydride-modified silicone (that is, dianhydride) is preferable.

When the tetracarboxylic acid component contains a compound giving a structural unit (A-1) and a compound giving a structural unit (A-3), the tetracarboxylic acid component preferably contains a compound giving a structural unit (A-1). It contains 50 to 99 mol%, more preferably 60 to 98 mol%, further preferably 70 to 97 mol%, and preferably contains 1 to 50 mol% of the compound giving the constituent unit (A-3), more preferably. Contains 2-40 mol%, more preferably 3-30 mol%.
The tetracarboxylic acid component contains, in total, a compound that gives the constituent unit (A-1) and a compound that gives the constituent unit (A-3), preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably. Contains 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound giving the structural unit (A-1) and the compound giving the structural unit (A-3) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may consist only of a compound giving a structural unit (A-1) and a compound giving a structural unit (A-3).

The tetracarboxylic acid component preferably further contains, in addition to the compound giving the structural unit (A-1), both the compound giving the structural unit (A-2) and the compound giving the structural unit (A-3).
When the tetracarboxylic acid component contains a compound that gives a constituent unit (A-1), a compound that gives a constituent unit (A-2), and a compound that gives a constituent unit (A-3), the tetracarboxylic acid component is a constituent unit. A compound containing (A-1) preferably 50 to 90 mol%, more preferably 60 to 85 mol%, still more preferably 65 to 80 mol%, and giving a structural unit (A-2). Containing 5 to 30 mol%, more preferably 5 to 25 mol%, further preferably 5 to 20 mol%, and preferably 1 to 25 mol% of the compound giving the structural unit (A-3). , More preferably 2 to 20 mol%, still more preferably 3 to 15 mol%.
The tetracarboxylic acid component contains a compound that gives the structural unit (A-1), a compound that gives the structural unit (A-2), and a compound that gives the structural unit (A-3) in total, preferably 50 mol% or more. , More preferably 70 mol% or more, further preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound giving the structural unit (A-1), the compound giving the structural unit (A-2), and the compound giving the structural unit (A-3) is not particularly limited, that is, 100. Mol%. The tetracarboxylic acid component may consist only of a compound that gives a constituent unit (A-1), a compound that gives a constituent unit (A-2), and a compound that gives a constituent unit (A-3).

The compound other than the compound that gives the structural unit (A-1) arbitrarily contained in the tetracarboxylic acid component is not limited to the compound that gives the structural unit (A-2) and the compound that gives the structural unit (A-3). Such arbitrary compounds include the above-mentioned aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydride, and derivatives thereof (tetracarboxylic acid, tetra). Alkyl ester of carboxylic acid, etc.) can be mentioned.
The compound other than the compound that gives the structural unit (A-1) arbitrarily contained in the tetracarboxylic acid component may be one kind or two or more kinds.

Examples of the compound giving the structural unit (B-1) include, but are not limited to, the compound represented by the formula (b-1), and may be a derivative thereof as long as the same structural unit is given. Examples of the derivative include diisocyanates corresponding to the diamine represented by the formula (b-1). As the compound giving the structural unit (B-1), the compound represented by the formula (b-1) (that is, diamine) is preferable.
Similarly, the compound giving the structural unit (B-2) includes a compound represented by the formula (b-2), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. .. Examples of the derivative include diisocyanates corresponding to the diamine represented by the formula (b-2). As the compound giving the structural unit (B-2), the compound represented by the formula (b-2) (that is, diamine) is preferable.

The diamine component preferably contains a compound that gives the structural unit (B-1) in an amount of 35 to 95 mol%, more preferably 40 to 90 mol%, still more preferably 45 to 85 mol%.
The diamine component preferably contains a compound that gives the structural unit (B-2) in an amount of 5 to 65 mol%, more preferably 10 to 60 mol%, and even more preferably 15 to 55 mol%.
The diamine component contains, in total, a compound giving the structural unit (B-1) and a compound giving the structural unit (B-2) in an amount of 50 mol% or more, more preferably 70 mol% or more, and further preferably 90. It contains more than mol%, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound giving the structural unit (B-1) and the compound giving the structural unit (B-2) is not particularly limited, that is, 100 mol%. The diamine component may consist only of a compound giving a structural unit (B-1) and a compound giving a structural unit (B-2).

The diamine component may contain a compound that gives the constituent unit (B-1) and a compound other than the compound that gives the constituent unit (B-2), and the compound includes the above-mentioned aromatic diamine, alicyclic diamine, and fat. Examples thereof include group diamines and derivatives thereof (diisocyanate, etc.).
The compound other than the compound giving the structural unit (B-1) arbitrarily contained in the diamine component and the compound giving the structural unit (B-2) may be one kind or two or more kinds.

In the present invention, the charging amount 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 with respect to 1 mol of the tetracarboxylic acid component.

Further, in the present invention, in addition to the above-mentioned tetracarboxylic acid component and diamine component, an end-capping agent may be used for producing the polyimide resin. Monoamines or dicarboxylic acids are preferable as the terminal encapsulant. The amount of the terminal encapsulant to be introduced is preferably 0.0001 to 0.1 mol, particularly preferably 0.001 to 0.06 mol, based on 1 mol of the tetracarboxylic acid component. Examples of the monoamine terminal sealant include 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. Of these, benzylamine and aniline can be preferably used. As the dicarboxylic acid terminal encapsulant, dicarboxylic acids are preferable, and a part thereof 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. Of these, phthalic acid and phthalic anhydride can be preferably used.

The method for reacting the above-mentioned tetracarboxylic acid component with the diamine component is not particularly limited, and a known method can be used.
Specific reaction methods include (1) charging a tetracarboxylic dian component, a diamine component, and a reaction solvent into a reactor, stirring at room temperature to 80 ° C. for 0.5 to 30 hours, and then raising the temperature to imidize. Method of carrying out the reaction, (2) After charging the diamine component and the reaction solvent into the reactor and dissolving them, the tetracarboxylic acid component is charged, and if necessary, the mixture is stirred at room temperature to 80 ° C. for 0.5 to 30 hours, and then. Examples thereof include a method of carrying out an imidization reaction by raising the temperature to (3) a method of charging a tetracarboxylic dian component, a diamine component and a reaction solvent into a reactor and immediately raising the temperature to carry out the imidization reaction.

The reaction solvent used in the production of the polyimide resin may be one that does not inhibit the imidization reaction and can dissolve the produced polyimide. For example, an aprotic solvent, a phenol solvent, an ether solvent, a carbonate solvent and the like can be mentioned.

Specific examples of the aprotonic solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetra. Amide solvents such as methyl urea, lactone solvents such as γ-butyrolactone (GBL) and γ-valerolactone, phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphintriamide, dimethyl sulfone and dimethyl sulfoxide. , Sulfur-containing solvent such as sulfolane, ketone solvent such as acetone, cyclohexanone, methylcyclohexanone, amine solvent such as picolin and pyridine, ester solvent such as acetic acid (2-methoxy-1-methylethyl) and the like. ..

Specific examples of the phenolic solvent 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 can be mentioned.
Specific examples of the ether solvent include 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, and bis [2- (2-methoxyethoxy) ethyl]. Examples include ether, tetrahydrofuran, 1,4-dioxane and the like.
Specific examples of the carbonate solvent include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate and the like.
Among the above reaction solvents, an amide solvent or a lactone solvent is preferable. Moreover, the above-mentioned reaction solvent may be used alone or in mixture of 2 or more types.

In the imidization reaction, it is preferable to carry out the reaction while removing water generated 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 above imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include a base catalyst and an acid catalyst.
Base catalysts include pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, Examples thereof include organic base catalysts such as N, N-dimethylaniline and N, N-diethylaniline, and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate and sodium hydrogencarbonate.
Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid and the like. Can be mentioned. The above-mentioned imidization catalyst may be used alone or in combination of two or more.
Of the above, from the viewpoint of handleability, it is preferable to use a base catalyst, more preferably an organic base catalyst, further preferably triethylamine, and particularly preferably 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 viewpoint of suppressing the reaction rate and gelation. 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 cross-linking agent 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 oxazoline groups (oxazoline rings) in the molecule.
The oxazolyl group has reactivity with the carboxyl group, and when the carboxyl group reacts with the oxazolyl group, an amide ester bond is formed as shown below. This reaction is particularly easy to proceed 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 with each other via a cross-linking agent to form a crosslinked polyimide resin. To. For this reason, the chemical resistance of the film is improved.

The cross-linking agent is not particularly limited as long as it is a polyfunctional oxazoline compound having two or more oxazoline groups in the molecule, and specific examples thereof include 1,3-bis (4,5-dihydro-2-oxazoline) benzene. 1,4-bis (4,5-dihydro-2-oxazoline) benzene, 2,2'-bis (2-oxazoline), K-2010E, K-2020E, K-2030E, 2, manufactured by Nippon Catalyst Co., Ltd. 6-bis (4-isopropyl-2-oxazoline-2-yl) pyridine, 2,6-bis (4-phenyl-2-oxazoline-2-yl) pyridine, 2,2'-isopropyridenebis (4-phenyl) -2-Oxazoline), 2,2'-isopropyridenebis (4-talshalbutyl-2-oxazoline) and the like.

The cross-linking agent is preferably a compound containing an aromatic ring or an aromatic heterocycle having at least two oxazolyl groups bonded thereto, more preferably a compound containing a benzene ring or a pyridine ring having at least two oxazolyl groups bonded thereto, and further. A compound containing a benzene ring in which at least two oxazolyl groups are bonded is preferable, and 1,3-bis (4,5-dihydro-2-oxazolyl) benzene is particularly preferable.
The cross-linking agent may be used alone or in combination of two or more.

In the polyimide resin composition of the present invention, the molar ratio (oxazolyl group / carboxyl group) of the oxazolyl group in the cross-linking agent to the carboxyl group in the polyimide resin is in the range of 1/8 to 1 / 0.5. Therefore, it is preferable to contain a polyimide resin and a cross-linking agent. The molar ratio is more preferably 1/6 to 1/1, still more preferably 1/4 to 1/2.
The above molar ratio means the molar ratio of the oxazolyl group contained in the cross-linking agent to the carboxyl group contained in the compound giving the structural unit (B-1) used for producing the polyimide resin, and the addition of the cross-linking agent. Calculated based on the amount and amount of compound added to give the building block (B-1).

[Polyimide varnish]
As a preferred embodiment of the polyimide resin composition of the present invention, a polyimide resin composition containing an organic solvent in addition to the above-mentioned polyimide resin and the above-mentioned cross-linking agent, and the polyimide resin is dissolved in the organic solvent ( Hereinafter, it is also referred to as "polyimide varnish").
The organic solvent may be any one that dissolves the polyimide resin, and is not particularly limited, but it is preferable to use the above-mentioned compounds alone or in combination of two or more as the reaction solvent used for producing the polyimide resin.
The polyimide varnish may be a solution in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, to which a cross-linking agent is added, or a solution in which a diluting solvent and a cross-linking agent are added. It may be.

The polyimide varnish preferably contains 5 to 40% by mass of the polyimide resin, more preferably 7 to 30% by mass, and even more preferably 8 to 20% by mass. The viscosity of the polyimide varnish is preferably 50 to 5000 Pa · s, more preferably 100 to 4000 Pa · s, and even more preferably 300 to 3500 Pa · s. The viscosity of the polyimide varnish is a value measured at 25 ° C. using an E-type viscometer.

In addition, the polyimide varnish of the present invention contains an inorganic filler, an adhesion accelerator, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, a defoaming agent, and an optical brightener as long as the required properties of the polyimide film are not impaired. Various additives such as a whitening agent, a cross-linking agent, a polymerization initiator, and a photosensitizer may be contained.
The method for producing the polyimide varnish of the present invention is not particularly limited, and a known method can be applied.

[Polyimide film]
The polyimide film of the present invention is obtained by cross-linking the above-mentioned polyimide resin contained in the polyimide resin composition of the present invention with the above-mentioned 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 heat resistance, colorless transparency and chemical resistance, and has low residual stress. Suitable physical property values of the polyimide film of the present invention are as described above.

In the method for producing a polyimide film of the present invention, a step of cross-linking at a temperature at which the cross-linking reaction between the polyimide resin and the cross-linking agent proceeds (preferably 80 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 150 ° C. or higher) is performed. If included, there are no particular restrictions. For example, a method of applying the above-mentioned polyimide varnish on a smooth support such as a glass plate, a metal plate, or plastic, or forming it into a film and then heating it can be mentioned. By this heat treatment, it is possible to remove organic solvents such as a reaction solvent and a diluting solvent contained in the polyimide varnish while advancing the cross-linking reaction between the polyimide resin in the polyimide varnish and the cross-linking agent. If necessary, a release agent may be applied to the surface of the support in advance.

The following method is preferable as the heat treatment. That is, it is preferable that the organic solvent is first evaporated at a temperature of 120 ° C. or lower and then dried at a temperature equal to or higher than the boiling point of the organic solvent to produce a polyimide film. Moreover, it is preferable to dry in a nitrogen atmosphere. The pressure in the dry atmosphere may be reduced pressure, normal pressure, or pressurized. A film having a smooth film surface and no defects can be obtained by drying at two stages of temperature. The drying temperature in the second stage is not particularly limited, but is preferably 200 to 450 ° C, more preferably 300 to 430 ° C, and particularly preferably 350 to 400 ° C. By drying in this temperature range, the transparency and yellowness of the film become good, and further good solvent resistance can be obtained.

Further, the polyimide film of the present invention can also be produced by using a polyamic acid varnish in which a polyamic acid and a cross-linking agent are dissolved in an organic solvent.
The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin in the present invention, and contains a tetracarboxylic acid component containing a compound giving the above-mentioned structural unit (A-1) and the above-mentioned structural unit (B-). It is a product of a polyaddition reaction with a diamine component containing a compound giving 1) and a compound giving the above-mentioned structural unit (B-2). A polyimide resin can be obtained by imidizing (dehydrating and ring-closing) this polyamic acid.
As the organic solvent contained in the polyamic acid varnish, the organic solvent contained in the polyimide varnish of the present invention can be used.
In the present invention, the polyamic acid varnish includes a tetracarboxylic acid component containing the compound giving the above-mentioned structural unit (A-1), a compound giving the above-mentioned structural unit (B-1), and the above-mentioned structural unit (B-2). It may be a polyamic acid solution itself obtained by subjecting a diamine component containing a compound to give a compound to a polyaddition reaction in a reaction solvent, or a diamine solvent is further added to the polyamic acid solution. Good.

In the method for producing a polyimide film using a polyamic acid varnish, the 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, still more preferably 150 ° C. or higher) There is no particular limitation as long as the step of cross-linking is included, and a known method can be used. For example, a polyamic acid varnish is applied onto a smooth support such as a glass plate, a metal plate, or a plastic, or formed into a film, and organic solvents such as a reaction solvent and a diluting solvent contained in the varnish are removed by heating. Then, a polyamic acid film is obtained, the polyamic acid in the polyamic acid film is imidized by heating, and the polyimide resin is further reacted with a cross-linking agent to cross-link the polyimide film, whereby the polyimide film can be produced.
The heating temperature for drying the polyamic acid varnish to obtain a polyamic acid film is preferably 50 to 120 ° C. The heating temperature for imidizing the polyamic acid by heating is preferably 200 to 400 ° C.
The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the intended use and the like, but is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and further preferably 10 to 80 μm. When the thickness is 1 to 250 μm, it can be practically used 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 a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly preferably used as a substrate for an image display device such as a liquid crystal display or an OLED display.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to these examples.
The solid content concentration of the varnish obtained in Examples and Comparative Examples and the physical characteristics of the film were measured by the methods shown below.

(1) Solid content concentration The solid content concentration of the varnish was measured by heating the sample at 320 ° C. × 120 min in a small electric furnace “MMF-1” manufactured by AS ONE Corporation and calculating from the mass difference of the sample before and after heating.

(2) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Co., Ltd.

(3) Total light transmittance, yellow index (YI)
The total light transmittance and YI were measured in accordance with JIS K7105: 1997 using a color / turbidity simultaneous measuring device "COH7700" manufactured by Nippon Denshoku Kogyo Co., Ltd.

(4) Glass transition temperature (Tg)
Using the thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Co., Ltd., residual stress is removed under the conditions of sample size 2 mm x 20 mm, load 0.1 N, and heating rate 10 ° C / min in tensile mode. The temperature was raised to a sufficient temperature to remove residual stress, and then cooled to room temperature. Then, the elongation of the test piece was measured under the same conditions as the treatment for removing the residual stress, and the place where the inflection point of the elongation was observed was determined as the glass transition temperature.

(5) Residual stress Polyamide varnish on a 4-inch silicon wafer with a thickness of 525 μm ± 25 μm for which the “warp amount” has been measured in advance using the residual stress measuring device “FLX-2320” manufactured by KLA Tencor. Alternatively, a polyamic acid varnish was applied using a spin coater and prebaked. Then, using a hot air dryer, heat curing treatment was performed at 350 to 400 ° C. for 30 minutes in a nitrogen atmosphere to prepare a silicon wafer with a polyimide film having a film thickness of 8 to 15 μm after curing. The amount of warpage of this wafer was measured using the above-mentioned residual stress measuring device, and the residual stress generated between the silicon wafer and the polyimide film was evaluated.

(6) Tensile Elastic Modulus and Tensile Strength The tensile elastic modulus and tensile strength were measured using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K7127. The distance between the chucks was 50 mm, the test piece size was 10 mm × 50 mm, and the test speed was 20 mm / min.

(7) Solvent resistance 1 (PGMEA)
A solvent was dropped on the polyimide film formed on the glass plate at room temperature, and it was confirmed whether the film surface was changed. As the solvent, propylene glycol monomethyl ether acetate (PGMEA) was used.
The evaluation criteria for solvent resistance were as follows.
◯: There was no change on the film surface.
Δ: Slight cracks were formed on the film surface.
X: The film surface was cracked or the film surface was melted.

(8) Solvent resistance 2 (NMP)
The polyimide film formed on the glass plate was peeled off and immersed in N-methyl-2-pyrrolidone (NMP) at room temperature for 60 minutes. The evaluation criteria are as follows.
〇: The film maintained its shape without melting.
X: The film melted and the shape could not be maintained.

(9) Detergency N-methyl-2-pyrrolidone and polyimide varnish were mixed, and it was confirmed whether or not they were mixed uniformly at room temperature. The evaluation criteria for detergency were as follows.
〇: Polyimide varnish and NMP mixed solution were uniformly mixed.
X: The polyimide varnish and the NMP mixed solution were not uniformly mixed, and a precipitate was formed.

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, and their abbreviations are as follows.

<Tetracarboxylic acid component>
CpODA: Norbornane-2-spiro-α-cyclopentanone-α'-spiro-2 "-norbornane-5,5", 6,6 "-tetracarboxylic dianhydride (manufactured by JX Energy Co., Ltd .; formula (a) -1) Compound)
s-BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation; compound represented by formula (a-2))

<Diamine>
TFMB: 2,2'-bis (trifluoromethyl) benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd .; compound represented by formula (b-1))
3,5-DABA: 3,5-diaminobenzoic acid (manufactured by Nippon Pure Chemical Industries, Ltd .; compound represented by formula (b-2))

<Crosslinking agent>
1,3-PBO: 1,3-bis (4,5-dihydro-2-oxazolyl) benzene (manufactured by Mikuni Pharmaceutical Co., Ltd.)

<Others>
GBL: γ-Butyrolactone (manufactured by Mitsubishi Chemical Corporation)
TEA: Triethylamine (manufactured by Kanto Chemical Co., Inc.)

Example 1
25.619 g (0.080 mol) of TFMB in a 1 L 5-necked round-bottom flask equipped with a stainless steel half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. , 3.043 g (0.020 mol) of 3,5-DABA and 161.040 g of GBL were added, and the mixture was stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 150 rpm to obtain a solution.
After adding 38.438 g (0.100 mol) of CpODA and 20.130 g of GBL in a batch to this solution, 0.506 g of TEA and triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 0 as an imidization catalyst. .056 g was added and heated with a mantle heater, and the temperature inside the reaction system was raised to 190 ° C. over about 20 minutes. The components to be distilled off were collected, and the temperature inside the reaction system was maintained at 190 ° C. and refluxed for 2 hours while adjusting the rotation speed according to the increase in viscosity.
Then, GBL was added so that the solid content concentration became 10% by mass, the temperature in the reaction system was cooled to 120 ° C., and then the mixture was further stirred for about 1 hour to homogenize. Subsequently, 0.167 g (0.25 mol% with respect to 1 mol% of 3,5-DABA) of 1,3-PBO was added to 100 g of the obtained varnish and stirred for 30 minutes to homogenize to obtain a polyimide varnish. ..
Subsequently, the obtained polyimide varnish was applied to a silicon wafer on a glass plate by spin coating, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 400 ° C. for 30 minutes in a nitrogen atmosphere. The solvent was evaporated to obtain a film having a thickness of 10 μm.

Example 2
A polyimide varnish was prepared by the same method as in Example 1 except that the amount of TFMB was changed to 27.220 g (0.085 mol) and the amount of 3,5-DABA was changed to 2.282 g (0.015 mol). , A polyimide varnish having a solid content concentration of 10% by mass was obtained.
Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 1 except that the drying temperature in the second step was changed to the conditions shown in Table 1, and a film having a thickness of 9 μm was obtained.

Example 3
25.619 g (0.080 mol) of TFMB in a 1 L 5-necked round-bottom flask equipped with a stainless steel half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. , 3,5-DABA (3.043 g (0.020 mol)) and GBL (156.713 g) were added, and the mixture was stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 150 rpm to obtain a solution.
To this solution, 30.750 g (0.08 mol) of CpODA, 5.884 g (0.02 mol) of s-BPDA and 39.178 g of GBL were added in a batch, and then 0.506 g of TEA as an imidization catalyst was added. , 0.056 g of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and heated with a mantle heater to raise the temperature inside the reaction system to 190 ° C. over about 20 minutes. The components to be distilled off were collected, and the temperature inside the reaction system was maintained at 190 ° C. and refluxed for 2 hours while adjusting the rotation speed according to the increase in viscosity.
Then, GBL was added so that the solid content concentration became 10% by mass, the temperature in the reaction system was cooled to 120 ° C., and then the mixture was further stirred for about 1 hour to homogenize. Subsequently, 0.173 g (0.25 mol% with respect to 1 mol% of 3,5-DABA) of 1,3-PBO was added and stirred for 30 minutes to homogenize, and a polyimide varnish having a solid content concentration of 10% by mass was added. Obtained.
Subsequently, the obtained polyimide varnish was applied to a silicon wafer on a glass plate by spin coating, held on a hot plate at 80 ° C. for 30 minutes, and then heated in a hot air dryer at 350 ° C. for 20 minutes in a nitrogen atmosphere. The solvent was evaporated to obtain a film having a thickness of 10 μm.

Example 4
A polyimide varnish was prepared by the same method as in Example 3 except that the amount of TFMB was changed to 28.822 g (0.090 mol) and the amount of 3,5-DABA was changed to 1.522 g (0.010 mol). , A polyimide varnish having a solid content concentration of 10% by mass was obtained.
Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 3 to obtain a film having a thickness of 10 μm.

Example 5
A polyimide varnish was prepared by the same method as in Example 1 except that the amount of TFMB was changed to 17.933 g (0.070 mol) and the amount of 3,5-DABA was changed to 3.652 g (0.030 mol). , A polyimide varnish having a solid content concentration of 10% by mass was obtained.
Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 3 to obtain a film having a thickness of 9 μm.

Comparative Example 1
A polyimide varnish was prepared in the same manner as in Example 1 except that 1,3-PBO was not added, to obtain a polyimide varnish having a solid content concentration of 10% by mass. Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 1 to obtain a film having a thickness of 10 μm.

Comparative Example 2
A polyimide varnish was prepared in the same manner as in Example 2 except that 1,3-PBO was not added, to obtain a polyimide varnish having a solid content concentration of 10% by mass. Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 1 to obtain a film having a thickness of 10 μm.

Comparative Example 3
A polyimide varnish was prepared in the same manner as in Example 3 except that 1,3-PBO was not added, to obtain a polyimide varnish having a solid content concentration of 10% by mass. Using the obtained polyimide varnish, a film was prepared in the same manner as in Example 1 to obtain a film having a thickness of 10 μm.

The above evaluation was performed on the obtained film. The results are shown in Table 1.

As shown in Table 1, the polyimide films of Examples 1 to 5 were excellent in heat resistance and colorless transparency, low residual stress, excellent chemical resistance, and good detergency. On the other hand, the polyimide film of the comparative example was inferior in solvent resistance.

Claims

A polyimide resin composition containing a polyimide resin and a cross-linking agent having at least two oxazolyl groups.
The polyimide resin is a polyimide resin having a structural unit A derived from tetracarboxylic acid dianhydride and a structural unit B derived from diamine, and the structural unit A is derived from a compound represented by the following formula (a-1). The structural unit B is represented by the following formula (b-2) and the structural unit (B-1) derived from the compound represented by the following formula (b-1). A polyimide resin composition containing a structural unit (B-2) derived from a compound.

(In the formula (b-2), X is a single-bonded, substituted or unsubstituted alkylene group, a carbonyl group, an ether group, a group represented by the following formula (b-2-i), or the following formula (b-2). -Ii), p is an integer of 0 to 2, m1 is an integer of 0 to 4, m2 is an integer of 0 to 4. However, when p is 0, m1 Is an integer from 1 to 4.)

(In the formula (b-2-i), m3 is an integer of 0 to 5; in the 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 to 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).
The polyimide resin composition according to claim 1 or 2, wherein the ratio of the structural unit (A-1) in the structural unit A is 40 mol% or more.
The ratio of the structural unit (B-1) in the structural unit B is 35 to 95 mol%.
The polyimide resin composition according to any one of claims 1 to 3, wherein the ratio of the structural unit (B-2) in the structural unit B is 5 to 65 mol%.
The polyimide resin 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 resin composition according to any one of claims 1 to 5, wherein the structural unit A further contains a structural unit (A-3) derived from both terminal acid anhydride-modified silicones.
The polyimide resin composition according to any one of claims 1 to 6, wherein the cross-linking agent is a compound containing an aromatic ring or an aromatic heterocycle having at least two oxazolyl groups bonded thereto.
The polyimide resin composition according to any one of claims 1 to 7, wherein the cross-linking agent is a compound containing a benzene ring having at least two oxazolyl groups bonded thereto.
The polyimide resin composition according to any one of claims 1 to 8, wherein the cross-linking agent is 1,3-bis (4,5-dihydro-2-oxazolyl) benzene.
A polyimide varnish in which the polyimide resin composition according to any one of claims 1 to 9 is dissolved in an organic solvent.
A polyimide film obtained by cross-linking the polyimide resin in the polyimide resin composition according to any one of claims 1 to 9 with the cross-linking agent.