CN116323762A

CN116323762A - Polyimide resin, polyimide varnish and polyimide film

Info

Publication number: CN116323762A
Application number: CN202180070349.0A
Authority: CN
Inventors: 安孙子洋平; 石井健太郎; 村谷孝博
Original assignee: Mitsubishi Gas Chemical Co Inc
Current assignee: Mitsubishi Gas Chemical Co Inc
Priority date: 2020-10-26
Filing date: 2021-10-15
Publication date: 2023-06-23
Also published as: KR20230095953A; WO2022091814A1; JPWO2022091814A1; TW202222913A

Abstract

A polyimide resin comprising a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A comprises a structural unit (A1) derived from a tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule, and the structural unit B comprises a structural unit (B1) derived from a compound represented by the following formula (B1).

Description

Polyimide resin, polyimide varnish and polyimide film

Technical Field

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

Background

Polyimide resins are being studied for various uses in the fields of electric and electronic parts and the like. For example, for the purpose of weight reduction and flexibility of a device, 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, and thus, research on a polyimide film suitable as the plastic substrate is underway.

Various optical properties are required for films used for image display devices. For example, when light emitted from a display element is emitted through a plastic substrate, transparency is required for the plastic substrate.

In order to satisfy the above-described required properties, development of polyimide resins of various compositions is underway. For example, patent document 1 discloses a polyimide film having a structure formed by a combination of a dianhydride having a norbornane skeleton and 2,2' -bis (trifluoromethyl) benzidine as a diamine component, in order to obtain a polyimide film excellent in transparency and high heat resistance.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 6431369

Disclosure of Invention

Problems to be solved by the invention

Polyimide films are required to replace glass substrates, and transparency is required.

Here, in the case of manufacturing an image display device, for example, since the heat treatment is performed in a state where an inorganic film is laminated on a polyimide film, exhaust gas generated from the polyimide film is accumulated between the polyimide film and the inorganic film, and thus coloring such as yellowing may occur in the polyimide film. Therefore, when the polyimide film is exposed to high temperature in a state where the inorganic film is laminated, heat resistance such as suppression of coloring is required.

In addition, when manufacturing an image display device, for example, a process temperature exceeding 400 ℃ can be reached, and therefore, heat resistance to a high temperature of 400 ℃ or more is required for a polyimide film as a substrate. When a polyimide film having a high glass transition temperature (Tg) and excellent heat resistance is exposed to high temperatures in a state in which inorganic films are laminated, defects such as cracks may occur in the inorganic films. Therefore, when the polyimide film is exposed to high temperature in a state in which the inorganic film is laminated, heat resistance is required for the inorganic film, and defects such as cracks are not generated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide: a polyimide film having excellent transparency and heat resistance when an inorganic film is laminated, a polyimide resin and a polyimide varnish, and a polyimide film having excellent transparency and heat resistance when an inorganic film is laminated can be obtained.

Solution for solving the problem

The present inventors have found that a polyimide resin comprising a structural unit derived from a tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule and a structural unit derived from a specific diamine can solve the above-mentioned problems, and have completed the present invention.

That is, the present invention relates to the following <1> to <11>.

<1> a polyimide resin comprising a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine,

the structural unit A comprises a structural unit (A1) derived from a tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule,

the structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (B1).

<2> the polyimide resin according to <1>, wherein the structural unit (A1) comprises at least one selected from the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11), a structural unit (a 12) derived from a compound represented by the following formula (a 12), a structural unit (a 13) derived from a compound represented by the following formula (a 13), and a structural unit (a 14) derived from a compound represented by the following formula (a 14).

<3> the polyimide resin according to <1> or <2>, wherein the structural unit A further comprises a structural unit (A2), and the structural unit (A2) comprises at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by the following formula (a 21) and a structural unit (A22) derived from a compound represented by the following formula (a 22).

<4> the polyimide resin according to any one of <1> to <3>, wherein the structural unit B further comprises a structural unit (B2), and the structural unit (B2) comprises at least one selected from the group consisting of a structural unit (B21) derived from a compound represented by the following formula (B21), a structural unit (B22) derived from a compound represented by the following formula (B22), and a structural unit (B23) derived from a compound represented by the following formula (B23).

<5> the polyimide resin according to <4>, wherein the structural unit (B2) comprises a structural unit (B21) derived from a compound represented by the following formula (B21).

<6> a polyimide varnish obtained by dissolving the polyimide resin according to any one of <1> to <5> in an organic solvent.

<7> a polyimide film comprising the polyimide resin according to any one of <1> to <5 >.

<8> the polyimide film according to <7>, which is based on JIS K7136: the total light transmittance measured at 2000 was 80% or more.

<9> the polyimide film according to <7> or <8>, which is used as a transparent substrate constituting a display device.

<10> a method for producing a polyimide film, comprising the step of coating or molding the polyimide varnish according to <6> into a film shape and then removing the organic solvent.

<11> an image display device comprising the polyimide film according to any one of <7> to <9> as a transparent substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there may be provided: a polyimide film having excellent transparency and heat resistance when an inorganic film is laminated, a polyimide resin and a polyimide varnish, and a polyimide film having excellent transparency and heat resistance when an inorganic film is laminated can be obtained.

Detailed Description

A mode for carrying out the present invention (hereinafter, simply referred to as "this embodiment") will be described in detail. The present embodiment is an example for explaining the present invention, and does not limit the content of the present invention. The present invention can be implemented by appropriately modifying the scope of the gist thereof. In this embodiment, any preferable regulation may be adopted, and it can be said that preferable combinations are more preferable. In the present embodiment, the expression "XX to YY" means "XX or more and YY or less".

[ polyimide resin ]

The polyimide resin of the present invention is a polyimide resin comprising a structural unit a derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, the structural unit a comprising a structural unit (A1) derived from a tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule, and the structural unit B comprising a structural unit (B1) derived from a compound represented by the following formula (B1).

The reason why the polyimide film of the present invention can provide excellent transparency and heat resistance when an inorganic film is laminated is not clear, but it is considered that the polyimide film has a norbornane skeleton and a structural unit (B1) having a bent structure but a trifluoromethyl group having a large steric hindrance, and can be expected to suppress molecular movement, so that the polyimide film can maintain excellent transparency and can improve heat resistance, and therefore the transparency and heat resistance when an inorganic film is laminated (suppression of coloring and suppression of cracking of an inorganic film) are excellent.

< structural Unit A >

The structural unit a is a structural unit derived from tetracarboxylic dianhydride which is contained in the polyimide resin.

The structural unit a contains a structural unit (A1) derived from a tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule.

From the viewpoints of heat resistance, transparency, and optical isotropy, the structural unit (A1) preferably contains at least one selected from the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11), a structural unit (a 12) derived from a compound represented by the following formula (a 12), a structural unit (a 13) derived from a compound represented by the following formula (a 13), and a structural unit (a 14) derived from a compound represented by the following formula (a 14), and from the viewpoints of the molecular skeleton becoming more rigid and the heat resistance being further improved, more preferably contains at least one selected from the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11), a structural unit (a 12) derived from a compound represented by the following formula (a 12), and a structural unit (a 14) derived from a compound represented by the following formula (a 14), further preferably contains at least one selected from the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11) and a structural unit (a 14) derived from a compound represented by the following formula (a 14), and further preferably contains at least one structural unit (a 11) derived from the following formula (a 11) is further represented by the following formula (a).

By making the structural unit a contain the structural unit (A1) derived from tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule, the heat resistance, transparency, and optical isotropy of the resulting polyimide film can be improved.

The structural unit a may contain a structural unit (A2) in addition to the structural unit (A1). The structural unit (A2) may be at least one selected from the group consisting of a structural unit (a 21) derived from a compound represented by the following formula (a 21) and a structural unit (a 22) derived from a compound represented by the following formula (a 22).

The compound represented by the formula (a 21) is diphenyl tetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4' -diphenyl tetracarboxylic dianhydride (s-BPDA) represented by the following formula (a 211 s), 2, 3',4' -diphenyl tetracarboxylic dianhydride (a-BPDA) represented by the following formula (a 211 a), and 2,2', 3' -diphenyl tetracarboxylic dianhydride (i-BBDA) represented by the following formula (a 211 i). Among them, 3',4' -biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a 211 s) is preferable.

The ratio of the structural unit (A1) in the structural unit a is preferably 40 mol% or more, more preferably 50 mol% or more, further preferably 60 mol% or more, further preferably 80 mol% or more, further preferably 85 mol% or more, further preferably 90 mol% or more, further preferably 95 mol% or more, further preferably 99 mol% or more, from the viewpoints of heat resistance, transparency, and optical isotropy. The upper limit of the ratio is not particularly limited, but is 100 mol% or less.

In the case where the structural unit a further includes the structural unit (A2), the ratio of the structural unit (A2) in the structural unit a is preferably 60 mol% or less, more preferably 50 mol% or less, further preferably 40 mol% or less, further preferably 20 mol% or less, further preferably 15 mol% or less, further preferably 10 mol% or less, further preferably 5 mol% or less, further preferably 1 mol% or less, from the viewpoints of heat resistance, transparency, and optical isotropy. The lower limit of the ratio is not particularly limited, but is 0.01 mol% or more.

The structural unit a may contain structural units other than the structural unit (A1) and the structural unit (A2). The tetracarboxylic dianhydride providing such a structural unit is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as 4,4 '-oxydiphthalic anhydride, pyromellitic dianhydride and 4,4' - (hexafluoroisopropyl) diphthalic anhydride (excluding the compounds represented by formula (a 21) or (a 22)); alicyclic tetracarboxylic dianhydrides such as 1,2,4, 5-cyclohexane tetracarboxylic dianhydride and 1,2,3, 4-cyclobutane tetracarboxylic dianhydride (excluding the compounds represented by any of the formulae (a 11) to (a 14)); aliphatic tetracarboxylic dianhydrides such as 1,2,3, 4-butanetetracarboxylic dianhydride.

In the present specification, the aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, the alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more alicyclic rings and not containing an aromatic ring, and the aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride not containing an aromatic ring or an alicyclic ring.

Any of the structural units a may be 1 or 2 or more.

< structural Unit B >

The structural unit B is a structural unit derived from diamine that is occupied in the polyimide resin.

The compound represented by the formula (b 1) is 2, 2-bis (4-aminophenyl) hexafluoropropane. By including the structural unit (B1) in the structural unit B, toughness can be improved while maintaining heat resistance.

The ratio of the structural unit (B1) in the structural unit B is preferably 20 mol% or more, more preferably 40 mol% or more, further preferably 50 mol% or more, further preferably 55 mol% or more, further preferably 60 mol% or more, further preferably 80 mol% or more, further preferably 99 mol% or more, from the viewpoint of improving heat resistance when the inorganic film is laminated. The upper limit of the ratio is not particularly limited, but is 100 mol% or less.

The structural unit B may contain structural units other than the structural unit (B1).

The structural unit B preferably contains a structural unit (B2) in addition to the structural unit (B1). The structural unit (B2) preferably contains at least one selected from the group consisting of a structural unit (B21) derived from a compound represented by the following formula (B21), a structural unit (B22) derived from a compound represented by the following formula (B22), and a structural unit (B23) derived from a compound represented by the following formula (B23), and more preferably contains a structural unit (B21) derived from a compound represented by the following formula (B21) from the viewpoint of further improving the rigidity and heat resistance of the molecular skeleton. By including the structural unit (B2), particularly, heat resistance improves, and optical isotropy improves.

When the structural unit B further includes the structural unit (B2), the ratio of the structural unit (B2) in the structural unit B is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more, further preferably 70 mol% or less, more preferably 60 mol% or less, further preferably 50 mol% or less.

When the structural unit B further includes the structural unit (B2), the ratio of the total of the structural units (B1) and (B2) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, further preferably 95 mol% or more, further preferably 99 mol% or more. The upper limit of the ratio of the total of the structural units (B1) and (B2) in the structural unit B is not particularly limited, and is, for example, 100 mol% or less. The structural unit B may be composed of only the structural unit (B1) and the structural unit (B2).

In the case where the structural unit B further includes the structural unit (B2), the molar ratio [ (B1)/(B2) ] of the structural unit (B1) to the structural unit (B2) in the structural unit B is preferably 30/70 to 90/10, more preferably 40/60 to 80/20, still more preferably 50/50 to 70/30 from the viewpoint of improving transparency, optical isotropy, toughness and heat resistance.

The structural unit B may contain structural units other than the structural unit (B1) and the structural unit (B2). The diamine providing such a structural unit is not particularly limited, examples thereof include 1, 4-phenylenediamine, paraxylylenediamine, 1, 5-diaminonaphthalene, 2 '-dimethylbiphenyl-4, 4' -diamine, 4 '-diaminodiphenyl ether, 4' -diamino-2, 2 '-bistrifluoromethyl diphenyl ether 4,4' -diaminodiphenylmethane, 4 '-diaminobenzanilide, 1- (4-aminophenyl) -2, 3-dihydro-1, 3-trimethyl-1H-inden-5-amine, alpha, aromatic diamines such as α' -bis (4-aminophenyl) -1, 4-diisopropylbenzene, N '-bis (4-aminophenyl) terephthalamide, 4' -bis (4-aminophenoxy) biphenyl, 2-bis [ 4- (4-aminophenoxy) phenyl ] propane, and 2, 2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane (excluding compounds represented by any of formulas (b 1), (b 21) to (b 23)); alicyclic diamines such as 1, 3-bis (aminomethyl) cyclohexane and 1, 4-bis (aminomethyl) cyclohexane; aliphatic diamines such as ethylenediamine and hexamethylenediamine.

In the present specification, an aromatic diamine means a diamine containing one or more aromatic rings, an alicyclic diamine means a diamine containing one or more alicyclic rings and containing no aromatic rings, and an aliphatic diamine means a diamine containing no aromatic rings or alicyclic rings.

Any of the structural units B may be 1 or 2 or more.

< Property of polyimide resin >

The polyimide resin preferably has a weight average molecular weight of 5000 to 300000 from the viewpoint of mechanical strength of the obtained polyimide film. The weight average molecular weight of the polyimide resin can be determined, for example, from a standard polymethyl methacrylate (PMMA) conversion measured by gel filtration chromatography.

The polyimide resin may contain a structure other than a polyimide chain (a structure in which the structural unit a and the structural unit B are bonded through an imide). 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 a structural unit a and a structural unit B are bonded to each other with an imide) 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, still more preferably 90% by mass or more, particularly preferably 99% by mass or more, and further 100% by mass or less. The polyimide resin may be composed of only polyimide chains.

The polyimide resin composition containing the polyimide resin can form a polyimide film which maintains transparency and optical isotropy and is excellent in heat resistance, and the polyimide film has the following suitable physical properties.

When the polyimide resin is formed into a film having a thickness of 10 μm, the total light transmittance is preferably 80% or more, more preferably 85% or more, further preferably 88% or more, further preferably 88.5% or more, further preferably 89% or more.

When the polyimide resin is formed into a film having a thickness of 10. Mu.m, the Yellowness Index (YI) is preferably 5.0 or less, more preferably 3.0 or less, further preferably 2.5 or less, and still further preferably 2.0 or less.

When the polyimide resin is formed into a film having a thickness of 10. Mu.m, the absolute value of the thickness retardation (Rth) is preferably 200nm or less, more preferably 180nm or less, and still more preferably 160nm or less.

The film formed using the polyimide resin also has good heat resistance and the following suitable physical properties.

The glass transition temperature (Tg) is preferably 380℃or higher, more preferably 390℃or higher, and still more preferably 400℃or higher.

The 5% weight reduction temperature (Td 5%) is preferably 480℃or higher, more preferably 490℃or higher, and still more preferably 495℃or higher.

For heat resistance when an inorganic film is laminated, siO with a thickness of 300nm is formed on a polyimide film by sputtering ₂ When an ITO (indium tin oxide) film having a thickness of 1230nm is formed on the film to form a laminated film, it is preferable that the laminated film does not suffer from defects such as cracks and yellowing at "400 ℃ for 1 hour of annealing treatment", and it is more preferable that the laminated film does not suffer from defects such as cracks and yellowing at "420 ℃ for 1 hour of annealing treatment".

The physical property values in the present invention can be specifically measured by the methods described in examples.

< method for producing polyimide resin >

The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component comprising a compound providing the above-mentioned structural unit (A1) with a diamine component comprising a compound providing the above-mentioned structural unit (B1).

The compound providing the structural unit (A1) may be a compound represented by any one of the formulae (a 11) to (a 14), but is not limited thereto, and may be a derivative thereof within a range in which the same structural unit is provided. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by any one of the formulas (a 11) to (a 14), and an alkyl ester of the tetracarboxylic acid. Among them, tetracarboxylic dianhydride represented by the formula (a 11) is preferable.

The tetracarboxylic acid component may contain, in addition to the compound providing the structural unit (A1), a compound providing the structural unit (A2).

The compound providing the structural unit (A2) may be a compound represented by the formula (a 21), a compound represented by the formula (a 22), or the like, but is not limited thereto, and may be a derivative thereof within a range in which the same structural unit is provided.

The compound providing the structural unit (A1) for the tetracarboxylic acid component preferably contains 40 mol% or more, more preferably contains 50 mol% or more, further preferably contains 60 mol% or more, further preferably contains 80 mol% or more, further preferably contains 85 mol% or more, further preferably contains 90 mol% or more, further preferably contains 95 mol% or more, further preferably contains 99 mol% or more. The upper limit of the ratio is not particularly limited, but is 100 mol% or less.

The tetracarboxylic acid component may contain any compound other than the compound providing the structural unit (A1) and the compound providing the structural unit (A2).

Examples of such arbitrary compounds include the above-mentioned aromatic tetracarboxylic acid dianhydride, alicyclic tetracarboxylic acid dianhydride, aliphatic tetracarboxylic acid dianhydride, and derivatives thereof (tetracarboxylic acid, alkyl esters of tetracarboxylic acid, and the like).

The number of compounds contained in any of the tetracarboxylic acid components may be 1 or 2 or more.

The compound providing the structural unit (B1) may be a compound represented by the formula (B1), but is not limited thereto, and may be a derivative thereof within a range in which the same structural unit is provided. The derivative includes a diisocyanate corresponding to the compound represented by the formula (b 1). As the compound providing the structural unit (B1), a compound represented by the formula (B1) (i.e., diamine) is preferable.

The diamine component may contain, in addition to the compound providing the structural unit (B1), a compound providing the structural unit (B2). Examples of the compound providing the structural unit (B2) include a compound represented by the formula (B21), a compound represented by the formula (B22), a compound represented by the formula (B23), and the like, but the compound is not limited thereto, and may be a derivative thereof within a range in which the same structural unit is provided. Examples of the derivative include diisocyanates corresponding to the compound represented by the formula (b 21), the compound represented by the formula (b 22) and the compound represented by the formula (b 23). As the compound providing the structural unit (B2), a compound represented by the formula (B21), a compound represented by the formula (B22), a compound represented by the formula (B23) (i.e., diamine) are preferable.

The compound providing the structural unit (B1) for the diamine component preferably contains 20 mol% or more, more preferably contains 40 mol% or more, further preferably contains 50 mol% or more, further preferably contains 60 mol% or more, further preferably contains 80 mol% or more, and particularly preferably contains 99 mol% or more. The upper limit of the ratio is not particularly limited, but is 100 mol% or less.

In the case of the diamine component, when the compound providing the structural unit (B2) is included, the compound providing the structural unit (B2) preferably includes 10 mol% or more, more preferably includes 20 mol% or more, still more preferably includes 30 mol% or more, still more preferably includes 70 mol% or less, still more preferably includes 60 mol% or less, and still more preferably includes 50 mol% or less.

In the case of the diamine component, when the compound providing the structural unit (B2) is included, the total of the compound providing the structural unit (B1) and the compound providing the structural unit (B2) is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, further preferably 95 mol% or more, further preferably 99 mol% or more. The upper limit is not particularly limited, and the total of the compound providing the structural unit (B1) and the compound providing the structural unit (B2) is, for example, 100 mol% or less with respect to the diamine component. The tetracarboxylic acid component may be composed of only the compound providing the structural unit (B1) and the compound providing the structural unit (B2).

In the case where the diamine component contains the compound providing the structural unit (B2), the molar ratio [ (B1)/(B2) ] of the compound providing the structural unit (B1) to the compound providing the structural unit (B2) in the diamine component is preferably 30/70 to 90/10, more preferably 40/60 to 80/20, still more preferably 50/50 to 70/30 from the viewpoint of improving transparency, optical isotropy, toughness and heat resistance.

The diamine component may further contain any compound other than the compound providing the structural unit (B1) and the compound providing the structural unit (B2).

Examples of such arbitrary compounds include the above aromatic diamine, alicyclic diamine, aliphatic diamine, and their derivatives (diisocyanate, etc.).

The number of compounds contained in any of the diamine components may be 1 or 2 or more.

In the production of the polyimide resin of the present invention, the ratio of the amount of the tetracarboxylic acid component to the amount of the diamine component to be added used in the production of the polyimide resin is preferably 0.9 to 1.1 mol based on 1 mol of the diamine component.

In the production of the polyimide resin of the present invention, a blocking agent may be used in addition to the tetracarboxylic acid component and the diamine component described above. As the blocking agent, monoamines or dicarboxylic acids are preferred. The amount of the blocking agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, based on 1 mol of the tetracarboxylic acid component. Examples of monoamine type blocking agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline, and benzylamine and aniline are preferable. The dicarboxylic acid-based capping agent is preferably a dicarboxylic acid, and a part of the dicarboxylic acid may be closed. Examples thereof include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2, 3-benzophenone dicarboxylic acid, 3, 4-benzophenone dicarboxylic acid, cyclohexane-1, 2-dicarboxylic acid, cyclopentane-1, 2-dicarboxylic acid, and 4-cyclohexene-1, 2-dicarboxylic acid, and phthalic acid and phthalic anhydride are preferable.

The method for reacting the tetracarboxylic acid component with the diamine component is not particularly limited, and a known method can be used.

Specific reaction methods include the following: (1) A method comprising adding a tetracarboxylic acid component, a diamine component and a reaction solvent into a reactor, stirring at 0-10 ℃ for 0.5-30 hours, and then heating to perform imidization; (2) Adding diamine component and reaction solvent into a reactor to dissolve the diamine component and the reaction solvent, adding tetracarboxylic acid component, stirring the mixture for 0.5 to 30 hours at a temperature of between 0 and 10 ℃ according to requirements, and heating the mixture to perform imidization; (3) A method of charging a tetracarboxylic acid component, a diamine component and a reaction solvent into a reactor, and immediately heating the mixture to perform imidization; etc.

The reaction solvent used for producing the polyimide resin may be any solvent that can dissolve the polyimide produced without inhibiting the imidization reaction. Examples thereof include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

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

Specific examples of the phenol-based solvent include phenol, o-cresol, m-cresol, p-cresol, 2, 3-xylenol, 2, 4-xylenol, 2, 5-xylenol, 2, 6-xylenol, 3, 4-xylenol, and 3, 5-xylenol.

Specific examples of the ether solvent include 1, 2-dimethoxyethane, bis (2-methoxyethyl) ether, 1, 2-bis (2-methoxyethoxy) ethane, bis [ 2- (2-methoxyethoxy) ethyl ] ether, tetrahydrofuran, and 1, 4-dioxane.

Specific examples of the carbonate-based solvent include diethyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, and the like.

Among the above reaction solvents, aprotic solvents are preferable, amide solvents and lactone solvents are more preferable, and lactone solvents are still more preferable. The reaction solvent may be used alone or in combination of 2 or more kinds.

In the imidization reaction, the reaction is preferably performed while removing water generated during the production, using a dean-stark trap device or the like. By performing such an operation, the polymerization degree and the imidization rate can be further increased.

In the imidization reaction, a known imidization catalyst may be used. Examples of the imidization catalyst include a base catalyst and an acid catalyst.

Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α -picoline, β -picoline, 2, 4-lutidine, 2, 6-lutidine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, N-dimethylaniline, and N, N-diethylaniline; 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, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, and the like. The imidization catalyst may be used alone or in combination of 2 or more.

Among the above, from the viewpoint of operability, a base catalyst is preferably used, an organic base catalyst is more preferably used, and triethylamine and triethylenediamine are more preferably used.

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

[ polyimide varnish ]

The polyimide varnish of the present invention is obtained by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention and an organic solvent, and the polyimide resin is dissolved in the organic solvent.

The organic solvent is not particularly limited as long as it dissolves the polyimide resin, and the above-mentioned compounds are preferably used alone or in a mixture of 2 or more as the reaction solvent used in the production of the polyimide resin.

The polyimide varnish of the present invention may be a polyimide solution in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or may be a polyimide varnish diluted by adding a solvent to the polyimide solution.

The polyimide resin of the present invention has solvent solubility, and thus can be used as a varnish of high concentration stable at room temperature. The polyimide varnish of the present invention preferably contains 5 to 40 mass% of the polyimide resin of the present invention, more preferably 5 to 20 mass%. The viscosity of the polyimide varnish is preferably 1 to 200pa·s, more preferably 1 to 100pa·s. The viscosity of the polyimide varnish is a value measured at 25℃using an E-type viscometer.

The polyimide varnish of the present invention may contain various additives such as an inorganic filler, an adhesion promoter, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, an antifoaming agent, a fluorescent whitening agent, a crosslinking agent, a polymerization initiator, and a photosensitizer, as far as the required properties of the polyimide film are not impaired.

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 contains the polyimide resin of the present invention. Therefore, the polyimide film of the present invention is excellent in heat resistance, transparency, toughness, optical isotropy, peelability and chemical resistance. The polyimide film of the present invention has preferable physical properties as < characteristics of polyimide resin > as described above.

The method for producing the polyimide film of the present invention is not particularly limited, and a known method can be used. For example, the following methods can be mentioned: the polyimide varnish of the present invention is applied to a smooth support such as a glass plate, a metal plate, or a plastic to form a film, and then an organic solvent such as a reaction solvent or a diluting solvent contained in the varnish is removed by heating; etc. The method for producing a polyimide film of the present invention preferably includes a step of coating or molding a polyimide varnish into a film shape and then removing the organic solvent.

The coating method includes known coating methods such as spin coating, slit coating, and blade coating, and spin coating and slit coating are preferable. Among them, slit coating is more preferable from the viewpoint of handling properties by controlling intermolecular orientation and improving chemical resistance.

As a method for removing the organic solvent contained in the varnish by heating, it is preferable to evaporate the organic solvent at a temperature of 150 ℃ or lower to make it non-tacky, and then dry it at a temperature of the boiling point of the organic solvent used or higher (not particularly limited, preferably 200 to 500 ℃). In addition, drying under an air atmosphere or a nitrogen atmosphere is preferable. The pressure of the drying atmosphere may be any of reduced pressure, normal pressure, and increased pressure.

The method for peeling the polyimide film formed on the support from the support is not particularly limited, and a mechanical peeling method, a laser peeling method, or the like can be used.

The polyimide film of the present invention can also be produced using a polyamic acid varnish in which a polyamic acid is dissolved in an organic solvent.

The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin of the present invention, and is a product of an addition reaction of a tetracarboxylic acid component including the compound providing the structural unit (A1) and a diamine component including the compound providing the structural unit (B1). The polyimide resin of the present invention can be obtained as a final product by imidizing (dehydrating and ring-closing) the 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 production of the polyimide film of the present invention, the polyamic acid varnish may be a polyamic acid solution itself obtained by an addition reaction of a tetracarboxylic acid component and a diamine component in a reaction solvent, or may be a polyamic acid solution obtained by further adding a solvent to the polyamic acid solution and diluting the solution.

The method for producing a polyimide film using the polyamic acid varnish is not particularly limited, and a known method can be used. For example, a polyimide film can be produced by applying a polyamic acid varnish to a smooth support such as a glass plate, a metal plate, or a plastic, or by molding the varnish into a film, heating the varnish to remove an organic solvent such as a reaction solvent or a dilution solvent contained in the varnish to obtain a polyamic acid film, and heating the polyamic acid in the polyamic acid film to imidize the polyamic acid film.

The heating temperature for drying the polyamic acid varnish to obtain a polyamic acid film is preferably 50 to 120 ℃. The heating temperature at the time of imidization of the polyamic acid by heating is preferably 200 to 450 ℃.

The imidization method is not limited to thermal imidization, and chemical imidization may be applied.

The thickness of the polyimide film of the present invention may be appropriately selected depending on the application, etc., and is preferably in the range of 1 to 250. Mu.m, more preferably 5 to 100. Mu.m, still more preferably 8 to 80. Mu.m, still more preferably 10 to 80. Mu.m. The use of a thickness of 1 to 250 μm can be practically used as a self-standing film.

The thickness of the polyimide film can be easily controlled by adjusting the solid concentration and viscosity of the polyimide varnish.

In the polyimide film of the present invention, from the viewpoint of further improving transparency, it is based on JIS K7136: the total light transmittance measured at 2000 is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, still more preferably 88.5% or more, still more preferably 89% or more.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor components, optical members, solar cells, and image display devices, and is particularly suitably used as a transparent substrate constituting these devices. The polyimide film of the present invention is particularly suitable for use as a transparent substrate constituting an image display device such as a liquid crystal display, an OLED display, or a touch panel.

[ image display device ]

The image display device of the present invention comprises the polyimide film of the present invention as a transparent substrate.

The image display device of the present invention includes, for example, a transparent substrate made of the polyimide film of the present invention and a display portion provided on the transparent substrate.

The display portion is not particularly limited, and examples thereof include a TFT element, an organic EL element, a color filter, an LED, a transistor, an electron-emitting element, electronic ink, an electrophoretic element, a GLV (grating light valve), a display element using MEMS (micro electro mechanical system), a DMD (digital micromirror device), a DMS (digital micro shutter), an IMOD (interferometric modulation) element, an electrowetting element, a piezoceramic display, a display element using carbon nanotubes, and the like.

Examples of the image display device of the present invention include a liquid crystal display, an OLED display, and a touch panel.

The image display device of the present invention can be manufactured based on known information, in addition to using the polyimide film of the present invention as a transparent substrate.

The image display device of the present invention uses the polyimide film of the present invention, which has excellent heat resistance when an inorganic film is laminated, as a transparent substrate, and therefore, it is difficult to cause cracking of the inorganic film, coloring of the transparent substrate, and the like, and has excellent reliability.

Examples

The present invention will be specifically described below with reference to examples. However, the present invention is not limited by these examples.

< film Properties and evaluation >

The physical properties of the films obtained in examples and comparative examples were measured by the methods shown below.

(1) Film thickness

The film thickness was measured by a micrometer made of Mitutoyo Corporation.

(2) Glass transition temperature (Tg)

The sample was heated to a temperature sufficient to eliminate residual stress under conditions of a sample size of 3mm X20 mm, a load of 0.1N and a heating rate of 10 ℃/min in a tensile mode using a thermo-mechanical analysis apparatus "TMA/SS6100" manufactured by Hitachi High-Tech Science Corporation, the residual stress was removed, and then cooled to room temperature. Then, the elongation of the test piece was measured under the same conditions as in the treatment for removing the residual stress, and the inflection point of the elongation was extrapolated to determine the glass transition temperature.

(3) Total light transmittance and Yellowness Index (YI)

Total light transmittance was based on JIS K7136:2000, YI was measured by using a color/turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku industries Co., ltd.) based on ASTM E313-05 (D light source, 65 °).

(4) 5% weight reduction temperature (Td 5%)

A differential thermogravimetry simultaneous measurement device "NEXTA STA200RV" manufactured by Hitachi High-Tech Science Corporation was used. The temperature of the sample was raised to 40 to 150 ℃ at a heating rate of 10 ℃/min, the sample was kept at 150 ℃ for 30 minutes, and the temperature was raised to 510 ℃ after removing the water. The temperature at which the weight was reduced by 5% was set to a 5% weight reduction temperature, as compared with the weight after being held at 150℃for 30 minutes. The larger the value of the weight reduction temperature, the more excellent the heat resistance.

(5) Thickness retardation (Rth) (evaluation of optical isotropy)

The thickness retardation (Rth) was measured by using an ellipsometer "M-220" manufactured by Japanese spectroscopic Co. The thickness phase difference value at a measurement wavelength of 590nm was measured. Note that Rth is expressed by the following formula, where nx is the largest refractive index in the plane of the polyimide film, ny is the smallest refractive index in the thickness direction is nz, and d is the thickness of the film.

Rth＝[{(nx+ny)/2}-nz]×d

(6) Evaluation of Heat resistance of laminated film

In a process for manufacturing a simulated image display device, a laminate film was manufactured, and the heat resistance of the laminate film was evaluated. The laminated film was produced as follows.

SiO was formed to a thickness of 300nm on the polyimide film by sputtering without peeling the polyimide films obtained in examples and comparative examples from the glass plate ₂ A film was formed thereon an ITO (indium tin oxide) film having a thickness of 1230nm, to obtain a laminated film.

Subsequently, the obtained laminated film was annealed (heated) at 360℃for 1 hour or at 400℃for 1 hour.

The laminated film before and after annealing was visually inspected for defects (cracks, yellowing, etc.), and the heat resistance of the polyimide film (laminated film) on which the inorganic film was laminated was evaluated on the basis of the following criteria.

And (2) the following steps: the laminated film before and after annealing does not generate defects such as cracks, yellowing and the like

X (crack or yellowing): cracking, yellowing, and other defects of the laminated film before and after annealing

If there is no problem, the polyimide film has excellent heat resistance when an inorganic film is laminated.

Abbreviation of < component, etc. >)

The tetracarboxylic acid component and the diamine component used in examples and comparative examples, and abbreviations thereof are as follows.

(tetracarboxylic acid component)

CpODA: norbornane-2-spiro-alpha-cyclopentanone-alpha '-spiro-2' -norbornane-5, 5', 6' -tetracarboxylic dianhydride (manufactured by ENEOS Co., ltd.; a compound represented by formula (a 11))

BNBDA:5,5' -bis-2-norbornane-5, 5', 6' -tetracarboxylic acid-5, 5', 6' -dianhydride (manufactured by ENEOS Co., ltd.; compound represented by formula (a 12))

BPDA:3,3', 4' -Biphenyltetracarboxylic dianhydride (Mitsubishi chemical Co., ltd., compound (s-BPDA) represented by formula (a 211 s)

BPAF:9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride (a compound represented by formula (a 22) manufactured by JFE chemical Co., ltd.)

(diamine component)

HFDA:2, 2-bis (4-aminophenyl) hexafluoropropane (Compound represented by formula (b 1) and manufactured by Tokyo chemical industry Co., ltd.)

BAFL:9, 9-bis (4-aminophenyl) fluorene (a compound represented by formula (b 21) and manufactured by JFE chemical Co., ltd.)

TFMB:2,2' -bis (trifluoromethyl) benzidine (Seika Corporation; compound represented by formula (b 22))

6FODA:2,2 '-bis (trifluoromethyl) -4,4' -diaminodiphenyl ether (ChinaTech (Tianjin) Chemical Co., ltd.)

< production of polyimide resin, varnish and polyimide film >

Example 1

Into a 500mL five-necked round-bottomed flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet pipe, a dean-Stark trap equipped with a condenser, a thermometer, and a glass end cap were charged HFDA33.427g (0.100 mol) and 86.238g of gamma-butyrolactone (Mitsubishi chemical Co., ltd.) and stirred at a temperature of 70℃in the system under a nitrogen atmosphere at a rotation speed of 200rpm, to obtain a solution.

To this solution, 38.438g (0.100 mol) of CpODA and 21.560g of gamma-butyrolactone (Mitsubishi chemical Co., ltd.) were added simultaneously, and then 0.506g of triethylamine (Kanto chemical Co., ltd.) and 0.056g of triethylenediamine (Tokyo chemical Co., ltd.) were added as imidization catalysts, and the mixture was heated in a covered heater to raise the temperature in the reaction system to 190℃for about 20 minutes. The distilled components were collected, and the rotational speed was adjusted according to the increase in viscosity while maintaining the temperature in the reaction system at 190℃and refluxing for 5 hours.

Then, gamma-butyrolactone (Mitsubishi chemical corporation) was added so that the solid content became 15% by mass, the temperature in the reaction system was cooled to 100℃and then stirred for about 1 hour to homogenize the mixture, thereby obtaining a polyimide varnish.

Next, the obtained polyimide varnish was spin-coated on a glass plate, kept at 80 ℃ for 20 minutes by a hot plate, and then heated at 400 ℃ for 30 minutes (heating rate 5 ℃/min) in a hot air dryer under a nitrogen atmosphere, and the solvent was evaporated to obtain a thin film.

Example 2

A polyimide varnish having a solid content of 15 mass% was obtained in the same manner as in example 1, except that the amount of HFDA was changed from 33.427g (0.100 mol) to 20.056g (0.060 mol) and bafl13.938g (0.040 mol) was used.

Using the obtained polyimide varnish, a film was obtained in the same manner as in example 1.

Example 3

A polyimide varnish having a solid content of 15 mass% was obtained in the same manner as in example 1, except that the amount of CpODA was changed from 38.438g (0.100 mol) to 23.063g (0.060 mol), BPDA 11.769g (0.040 mol) was used, and the amount of HFDA was changed from 33.427g (0.100 mol) to 20.056g (0.060 mol) and BAFL13.938g (0.040 mol) was used.

Example 4

A polyimide varnish having a solid content concentration of 15 mass% was obtained in the same manner as in example 2, except that cpoda38.438g (0.100 mol) was changed to bnbda33.034g (0.100 mol) and the solvent used for the reaction and dilution was changed from GBL to NMP.

Comparative example 1

A polyimide varnish having a solid content concentration of 15 mass% was obtained in the same manner as in example 1, except that hfd a33.427g (0.100 mol) was changed to tfmb32.024g (0.100 mol) and the solvent used for the reaction and dilution was changed from GBL to NMP.

Comparative example 2

A polyimide varnish having a solid content concentration of 15 mass% was obtained in the same manner as in example 1, except that the amount of hfd a33.427g (0.100 mol) was changed to 6fod a33.624g (0.100 mol).

Comparative example 3

A polyimide varnish having a solid content of 15 mass% was obtained in the same manner as in example 2, except that the amount of CpODA was changed from 38.438g (0.100 mol) to 23.063g (0.060 mol), bpda11.769g (0.040 mol) was used, and hfda20.056g (0.060 mol) was changed to tfmb19.214g (0.060 mol).

Comparative example 4

A polyimide varnish having a solid content of 15 mass% was obtained in the same manner as in example 2, except that the amount of CpODA was changed from 38.438g (0.100 mol) to 34.594g (0.090 mol), bpa 4.584g (0.010 mol) was used, HFDA was not used, the amount of BAFL was changed from 13.938g (0.040 mol) to 15.680g (0.045 mol), and tfmb17.613g (0.055 mol) was used.

Comparative example 5

A300 mL five-necked round bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet pipe, a dean-Stark trap equipped with a condenser, a thermometer, and a glass end cap was charged with HFDA33.427g (0.100 mol) and NMP201.117g, and the mixture was stirred at a temperature of 25℃in the system under a nitrogen atmosphere at a rotation speed of 200rpm to obtain a solution.

To this solution, 29.428 g (0.100 mol) of BPDAand 50.279g of NMP were simultaneously charged and stirred for 3 hours to obtain a polyamic acid varnish having a solid content of 20.0% by mass.

Next, the obtained polyamic acid varnish was applied to a glass plate by spin coating, kept at 80 ℃ for 20 minutes by a hot plate, and then heated at 400 ℃ for 60 minutes (a heating rate of 5 ℃/min) in a hot air dryer under a nitrogen atmosphere, and the solvent was evaporated to obtain a film.

The polyimide films obtained in examples and comparative examples were subjected to the above-mentioned physical property measurement and evaluation. The results obtained are shown in Table 1.

TABLE 1

As shown in table 1, the polyimide film of examples was excellent in transparency and heat resistance when an inorganic film was laminated. Furthermore, the polyimide film of the examples was excellent in optical isotropy. The optical isotropy of comparative examples 1 and 2 and the heat resistance of the laminated film were poor. The Tg of comparative example 3 and comparative example 4 were good, but the optical isotropy and the heat resistance of the laminated film were poor. The optical isotropy of comparative example 5 was good, but Tg, colorless transparency, and heat resistance of the laminate film were poor.

Therefore, a polyimide film produced using an acid dianhydride having 2 norbornane skeletons in the molecule as a tetracarboxylic acid component and using HFDA as a diamine component is suitable as a transparent substrate for a display device such as a liquid crystal display, an OLED display, or a touch panel, which has excellent transparency, optical isotropy, and heat resistance of a laminate film.

Claims

1. A polyimide resin comprising a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine,

the structural unit A comprises a structural unit (A1) derived from tetracarboxylic dianhydride having 2 norbornane skeletons in the molecule,

the structural unit B comprises a structural unit (B1) derived from a compound represented by the following formula (B1),

2. the polyimide resin according to claim 1, wherein the structural unit (A1) comprises at least one selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a 11), a structural unit (A12) derived from a compound represented by the following formula (a 12), a structural unit (A13) derived from a compound represented by the following formula (a 13), and a structural unit (A14) derived from a compound represented by the following formula (a 14),

3. the polyimide resin according to claim 1 or 2, wherein the structural unit A further comprises a structural unit (A2), the structural unit (A2) comprising at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by the following formula (a 21) and a structural unit (A22) derived from a compound represented by the following formula (a 22),

4. the polyimide resin according to any one of claims 1 to 3, wherein the structural unit B further comprises a structural unit (B2), the structural unit (B2) comprising at least one selected from the group consisting of a structural unit (B21) derived from a compound represented by the following formula (B21), a structural unit (B22) derived from a compound represented by the following formula (B22), and a structural unit (B23) derived from a compound represented by the following formula (B23),

5. The polyimide resin according to claim 4, wherein the structural unit (B2) comprises a structural unit (B21) derived from a compound represented by the following formula (B21),

6. a polyimide varnish prepared by dissolving the polyimide resin according to any one of claims 1 to 5 in an organic solvent.

7. A polyimide film comprising the polyimide resin according to any one of claims 1 to 5.

8. The polyimide film according to claim 7, which is based on JIS K7136: the total light transmittance measured at 2000 was 80% or more.

9. The polyimide film according to claim 7 or 8, which is used as a transparent substrate constituting a display device.

10. A process for producing a polyimide film, which comprises the step of coating or molding the polyimide varnish according to claim 6 into a film and then removing the organic solvent.

11. An image display device comprising the polyimide film according to any one of claims 7 to 9 as a transparent substrate.