Polyimide Resin, Polyimide Varnish and Polyimide Film

Abstract

A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A includes a structural unit (A1) derived from 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, and the structural unit B includes a structural unit (B1) derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether.

Description

Technical Field

[0001] The present invention relates to a polyimide resin, a polyimide varnish, and a polyimide film. Background Art

[0002] A polyimide resin is obtained from an aromatic tetracarboxylic dianhydride and an aromatic diamine. Generally, due to the rigidity of the molecule, resonance stabilization, and strong chemical bonds, it has excellent heat resistance, chemical resistance, mechanical properties, and electrical properties. Therefore, it is widely used in the fields of molding materials, composite materials, electrical / electronic components, optical materials, displays, aerospace, etc.

[0003] In particular, for glass materials that have been used for electrical / electronic components, optical materials, displays, etc., their flexibility has been utilized to study their application in flexible devices.

[0004] For example, in Patent Document 1, a composition for forming a flexible device substrate is disclosed. For the purpose of improving heat resistance, retardation, flexibility, and transparency, it contains a polyimide and an organic solvent. The polyimide is a reaction product of a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a diamine component containing a fluorinated aromatic diamine.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: International Publication No. 2018 / 097143 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In recent years, in particular, the application of polyimide resins in displays and the front panels for protecting them has been promoted. From the aspect of replacing the glass materials used in the past, polyimide resins with high mechanical strength are required. However, the flexibility of high-strength polyimide resins is insufficient.

[0010] Recently, since polyimide films are also used as displays and protective plates for smartphones with a folding structure, both high strength and higher flexibility are required, and properties such as the property of restoring the shape after deformation and the film elongation rate are also needed.

[0011] Therefore, a polyimide resin having these properties is desired.

[0012] That is, the problem to be solved by the present invention is to provide a polyimide resin capable of forming a film with high strength, excellent deformation recovery property, and elongation rate, and a polyimide film with high strength, excellent deformation recovery property, and elongation rate.

[0013] Solutions for solving the problems

[0014] The inventors conducted in-depth research and found that a polyimide resin containing a combination of specific structural units can solve the above problems, thus achieving the present invention.

[0015] That is, the present invention relates to the following [1] to

[12] .

[0016] [1] A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A includes a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, and the structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1).

[0017]

[0018] [2] The polyimide resin according to the above [1], wherein the structural unit (A2) is a structural unit derived from an alicyclic tetracarboxylic dianhydride.

[0019] [3] The polyimide resin according to the above [1] or [2], wherein the structural unit (A2) includes at least one selected from a structural unit (A2-1) derived from a compound represented by the following formula (a2-1) and a structural unit (A2-2) derived from a compound represented by the following formula (a2-2).

[0020]

[0021] [4] The polyimide resin according to the above [3], wherein the structural unit (A2) includes the structural unit (A2-1).

[0022] [5] The polyimide resin according to the above [3], wherein the structural unit (A2) includes the structural unit (A2-2).

[0023] [6] The polyimide resin according to any one of the above [1] to [5], wherein the ratio of the total of the structural unit (A1) and the structural unit (A2) to the structural unit A is 50 mol% or more.

[0024] [7] The polyimide resin according to any one of the above [1] to [6], wherein the molar ratio [(A1) / (A2)] of the structural unit (A1) to the structural unit (A2) in the structural unit A is 20 / 80 to 99 / 1.

[0025] [8] The polyimide resin according to [4] above, wherein the molar ratio [(A1) / (A2-1)] of the structural unit (A1) to the structural unit (A2-1) in the structural unit A is 50 / 50 to 95 / 5.

[0026] [9] The polyimide resin according to [5], wherein the molar ratio [(A1) / (A2-2)] of the structural unit (A1) to the structural unit (A2-2) in the structural unit A is 20 / 80 to 50 / 50.

[0027]

[10] The polyimide resin according to any one of [1] to [9] above, wherein the proportion of the structural unit (B1) relative to the structural unit B is 60 mol% or more.

[0028]

[11] A polyimide varnish, which is obtained by dissolving the polyimide resin according to any one of [1] to

[10] above in an organic solvent.

[0029]

[12] A polyimide film, which contains the polyimide resin according to any one of [1] to

[10] above.

[0030] Effects of the invention

[0031] According to the present invention, a polyimide resin capable of forming a film having high strength, excellent deformation recovery property and elongation, a polyimide varnish containing the polyimide resin, and a polyimide film having high strength, excellent deformation recovery property and elongation can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram showing a method for measuring the deformation recovery property of a polyimide film. DETAILED DESCRIPTION OF THE INVENTION

[0033] [Polyimide Resin]

[0034] The polyimide resin of the present invention is a polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine,

[0035] The structural unit A contains a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, and the structural unit B contains a structural unit (B1) derived from a compound represented by the following formula (b1).

[0036]

[0037] Hereinafter, the polyimide resin of the present invention will be described.

[0038] (Structural unit A)

[0039] The structural unit A contained in the polyimide of the present invention is the structural unit derived from a tetracarboxylic dianhydride in the polyimide resin.

[0040] The structural unit A includes a structural unit (A1) derived from the compound represented by the foregoing formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride.

[0041] The compound represented by the foregoing formula (a1) is 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

[0042] By including the structural unit (A1) in the structural unit A, the mechanical strength of the obtained polyimide resin is improved.

[0043] The structural unit (A2) is a structural unit derived from an aliphatic tetracarboxylic dianhydride. The structural unit (A2) preferably includes a structural unit derived from an alicyclic tetracarboxylic dianhydride, and more preferably includes a structural unit derived from a tetracarboxylic dianhydride having an alicyclic ring with 4 to 15 carbon atoms. By including the structural unit derived from the tetracarboxylic dianhydride having an alicyclic ring, the elongation at break is improved, and the deformation recovery and transparency become good.

[0044] It should be noted that in this specification, an aliphatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride without an aromatic ring, and an alicyclic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more alicyclic rings in the aliphatic tetracarboxylic dianhydride.

[0045] Here, the "alicyclic ring" refers to a cyclic aliphatic hydrocarbon structure other than an aromatic ring in a structure where carbon atoms are cyclically bonded, and the number of carbon atoms in the alicyclic ring refers to the number of carbon atoms constituting the ring.

[0046] Specific examples of the alicyclic tetracarboxylic dianhydride include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2'-norbornane-5,5",6,6"-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyltetracarboxylic dianhydride, or their positional isomers, etc.

[0047] Specific examples of the aliphatic tetracarboxylic dianhydride other than the alicyclic tetracarboxylic dianhydride include 1,2,3,4-butane tetracarboxylic dianhydride, etc.

[0048] Among them, as the structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, it preferably contains at least one selected from the structural unit (A2-1) derived from the compound represented by the following formula (a2-1) and the structural unit (A2-2) derived from the compound represented by the following formula (a2-2), and more preferably at least one selected from the structural unit (A2-1) derived from the compound represented by the following formula (a2-1) and the structural unit (A2-2) derived from the compound represented by the following formula (a2-2).

[0049]

[0050] The compound represented by the foregoing formula (a2-1) is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0051] The compound represented by the foregoing formula (a2-2) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA).

[0052] Since the structural unit A contains the structural unit (A2), the elongation rate is improved, and the deformation recovery property and transparency are improved.

[0053] Thus, since the structural unit A of the structural unit derived from the tetracarboxylic dianhydride has the structural units (A1) and (A2), the reason why the polyimide resin and polyimide film of the present invention are excellent in deformation recovery property and elongation rate although they have high strength is not yet determined, but it is considered to be due to the rigidity of the fluorene group and the freedom degree of the aliphatic compound.

[0054] The ratio of the structural unit (A1) to the structural unit A is preferably 20 to 99 mol%, more preferably 30 to 97 mol%, further preferably 40 to 96 mol%, and still more preferably 50 to 95 mol%.

[0055] The ratio of the structural unit (A2) to the structural unit A is preferably 1 to 80 mol%, more preferably 3 to 70 mol%, further preferably 4 to 60 mol%, and still more preferably 5 to 50 mol%.

[0056] The total ratio of the structural unit (A1) and the structural unit (A2) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more. The upper limit value of the total ratio of the structural unit (A1) and the structural unit (A2) is not particularly limited and is 100 mol% or less. The structural unit A may also be composed only of the structural unit (A1) and the structural unit (A2).

[0057] From the viewpoint of improving mechanical properties and deformation recovery properties, the molar ratio [(A1) / (A2)] of structural unit (A1) to structural unit (A2) in structural unit A is preferably 20 / 80 to 99 / 1, more preferably 30 / 70 to 97 / 3, still more preferably 40 / 60 to 96 / 4, and even more preferably 50 / 50 to 95 / 5.

[0058] Among them, especially from the viewpoint of improving deformation recovery properties, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 80 / 20 to 97 / 3.

[0059] Especially from the viewpoint of improving strength, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 92 / 8 to 99 / 1.

[0060] From the viewpoint of further improving elongation, it is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and still more preferably 40 / 60 to 60 / 40.

[0061] From the viewpoint of improving mechanical properties and deformation recovery properties, the molar ratio [(A1) / (A2-1)] of structural unit (A1) to structural unit (A2-1) in structural unit A is preferably 40 / 60 to 99 / 1, more preferably 45 / 55 to 96 / 4, and still more preferably 50 / 50 to 95 / 5.

[0062] Among them, especially from the viewpoint of improving deformation recovery properties, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 80 / 20 to 97 / 3.

[0063] Especially from the viewpoint of improving strength, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 92 / 8 to 99 / 1.

[0064] From the viewpoint of further improving elongation, it is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and still more preferably 40 / 60 to 60 / 40.

[0065] From the viewpoint of improving mechanical properties and deformation recovery properties, the molar ratio [(A1) / (A2-2)] of structural unit (A1) to structural unit (A2-2) in structural unit A is preferably 20 / 80 to 99 / 1, more preferably 20 / 80 to 60 / 40, and still more preferably 20 / 80 to 50 / 50.

[0066] Among them, especially from the viewpoint of improving deformation recovery properties, it is preferably 20 / 80 to 60 / 40, more preferably 20 / 80 to 50 / 50, and still more preferably 20 / 80 to 40 / 60.

[0067] Particularly from the viewpoint of improving strength, it is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and further preferably 40 / 60 to 60 / 40.

[0068] From the viewpoint of further improving elongation, it is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and further preferably 40 / 60 to 60 / 40.

[0069] Within the range that does not impair the effects of the present invention, the polyimide resin of the present invention may also contain a structural unit derived from a tetracarboxylic dianhydride other than the structural unit (A1) and the structural unit (A2) in the structural unit A.

[0070] The tetracarboxylic dianhydride that provides a structural unit other than the structural unit (A1) and the structural unit (A2) is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 2,3,5,6-tetramethylpyromellitic dianhydride, and 1,4,5,8-naphthalenetetracarboxylic dianhydride. They can be used alone or in combination of two or more.

[0071] It should be noted that in this specification, the aromatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more aromatic rings.

[0072] [Structural unit B]

[0073] The structural unit B contained in the polyimide of the present invention is a structural unit derived from a diamine.

[0074] The structural unit B contains a structural unit (B1) derived from the compound represented by the following formula (b1).

[0075]

[0076] The compound represented by the aforementioned formula (b1) is 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA).

[0077] The structural unit B contains the structural unit (B1), whereby in addition to various physical properties such as the transparency of the obtained polyimide resin, the mechanical strength can be improved while maintaining the elongation and the deformation recovery property.

[0078] The proportion of the structural unit (B1) relative to the structural unit B is preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 50 mol% or more, still further preferably 60 mol% or more, still further preferably 70 mol% or more, and further preferably 90 mol% or more. In addition, the upper limit value of the proportion of the structural unit (B1) is not particularly limited and is 100 mol% or less. The structural unit B may also consist only of the structural unit (B1).

[0079] Within the scope not impairing the effects of the present invention, the polyimide resin of the present invention may, in the structural unit B, as a structural unit other than the aforementioned structural unit (B1), also contain a structural unit derived from a diamine other than the compound represented by the aforementioned general formula (b1).

[0080] The diamine other than the compound represented by the aforementioned general formula (b1) is not particularly limited, and examples thereof include aromatic diamines such as 1,4-phenylenediamine, p-xylenediamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; aliphatic diamines such as ethylenediamine and hexamethylenediamine; and modified silicone diamines. They may be used alone or in combination of two or more.

[0081] It should be noted that, in this specification, an aromatic diamine refers to a diamine containing one or more aromatic rings, an aliphatic diamine refers to a diamine not containing an aromatic ring, and an alicyclic diamine refers to an aliphatic diamine containing one or more alicyclic rings.

[0082] (Properties of polyimide resin, etc.)

[0083] From the viewpoint of the mechanical strength of the obtained polyimide film, the number average molecular weight of the polyimide resin of the present invention is preferably 5000 to 100000. It should be noted that the number average molecular weight of the polyimide resin can be measured by gel filtration chromatography or the like.

[0084] Within the scope not impairing the effects of the present invention, the polyimide resin of the present invention may also be mixed with various additives. Examples of the additives include antioxidants, light stabilizers, surfactants, flame retardants, plasticizers, and high molecular compounds other than the aforementioned polyimide resin.

[0085] Examples of the high molecular compounds include polyimide, polycarbonate, polystyrene, polyamide, polyamideimide, polyester such as polyethylene terephthalate, polyethersulfone, polycarboxylic acid, polyacetal, polyphenylene ether, polysulfone, polybutene, polypropylene, polyacrylamide, and polyvinyl chloride other than the polyimide resin of the present invention.

[0086] (Method for manufacturing polyimide resin)

[0087] The polyimide resin of the present invention can be manufactured by reacting a tetracarboxylic acid component containing a compound providing the above structural unit (A1) and a compound providing structural unit (A2) with a diamine component containing a compound providing structural unit (B1).

[0088] Examples of the compound providing structural unit (A1) include, but are not limited to, the compound represented by formula (a1), and derivatives thereof may also be used within the range of providing the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydrides represented by formula (a1) and alkyl esters of such tetracarboxylic acids. As the compound providing structural unit (A1), the compound represented by formula (a1) (i.e., dianhydride) is preferred.

[0089] Similarly, examples of the compound providing structural unit (A2) include aliphatic tetracarboxylic dianhydrides, preferably alicyclic tetracarboxylic dianhydrides, and more preferably the compounds represented by formula (a2-1) or formula (a2-2), but are not limited thereto, and derivatives thereof may also be used within the range of providing the same structural unit. Examples of derivatives of the compounds represented by formula (a2-1) or formula (a2-2) include tetracarboxylic acids corresponding to the tetracarboxylic dianhydrides represented by formula (a2-1) or formula (a2-2) and alkyl esters of such tetracarboxylic acids. As the compound providing structural unit (A2), the compounds represented by formula (a2-1) or formula (a2-2) (i.e., dianhydrides) are preferred.

[0090] For the tetracarboxylic acid component, it is preferred to contain 20 to 99 mol%, more preferably 30 to 97 mol%, further preferably 40 to 96 mol%, and still more preferably 50 to 95 mol% of the compound providing structural unit (A1).

[0091] For the tetracarboxylic acid component, it is preferred to contain 1 to 80 mol%, more preferably 3 to 70 mol%, further preferably 4 to 60 mol%, and still more preferably 5 to 50 mol% of the compound providing structural unit (A2).

[0092] In the total tetracarboxylic acid component, the total content ratio of the compound providing structural unit (A1) and the compound providing structural unit (A2) is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more. The upper limit value of the total content ratio of the compound providing structural unit (A1) and the compound providing structural unit (A2) is not particularly limited and is 100 mol% or less. The tetracarboxylic acid component may also be composed only of the compound providing structural unit (A1) and the compound providing structural unit (A2).

[0093] From the viewpoint of improving mechanical properties and deformation recovery properties, the molar ratio [(A1) / (A2)] of the compound providing the structural unit (A1) and the compound providing the structural unit (A2) in the tetracarboxylic acid component is preferably 20 / 80 to 99 / 1, more preferably 30 / 70 to 97 / 3, still more preferably 40 / 60 to 96 / 4, and even more preferably 50 / 50 to 95 / 5.

[0094] Among them, especially from the viewpoint of improving deformation recovery properties, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 80 / 20 to 97 / 3.

[0095] Especially from the viewpoint of improving strength, it is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and still more preferably 92 / 8 to 99 / 1.

[0096] From the viewpoint of further improving elongation, it is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and still more preferably 40 / 60 to 60 / 40.

[0097] The tetracarboxylic acid component may contain compounds other than the compound providing the structural unit (A1) and the compound providing the structural unit (A2). Examples of such compounds include the above-mentioned aromatic tetracarboxylic dianhydrides and their derivatives (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.).

[0098] The compounds optionally contained in the tetracarboxylic acid component (that is, compounds other than the compounds providing the structural unit (A1) and the structural unit (A2)) may be one kind or two or more kinds.

[0099] Examples of the compound providing the structural unit (B1) include, but are not limited to, the compound represented by the formula (b1), and derivatives thereof may also be used within the range of providing the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by the formula (b1). As the compound providing the structural unit (B1), the compound represented by the formula (b1) (that is, diamine) is preferred.

[0100] For the diamine component, it is preferably to contain 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol%, even more preferably 60 mol% or more, even more preferably 70 mol% or more, and even more preferably 90 mol% or more of the compound providing the structural unit (B1). In addition, the upper limit value of the proportion of the compound providing the structural unit (B1) is not particularly limited and is 100 mol% or less. The diamine component may also consist only of the compound providing the structural unit (B1).

[0101] The diamine component may contain compounds other than the compound providing the structural unit (B1). Examples of such compounds include the aforementioned aromatic diamines, alicyclic diamines, aliphatic diamines, modified silicone diamines, and their derivatives (diisocyanates, etc.).

[0102] The compound optionally contained in the diamine component (i.e., the compound other than the compound providing the structural unit (B1)) may be one kind or two or more kinds.

[0103] When producing the polyimide resin of the present invention, the input ratio of the tetracarboxylic acid component to the diamine component is preferably 0.9 to 1.1 moles of the diamine component relative to 1 mole of the tetracarboxylic acid component.

[0104] When producing the polyimide resin of the present invention, in addition to the aforementioned tetracarboxylic acid component and the aforementioned diamine component, a capping agent may also be used. As the capping agent, monoamines or dicarboxylic acids are preferred. As the input amount of the introduced capping agent, relative to 1 mole of the tetracarboxylic acid component, it is preferably 0.0001 to 0.1 mole, more preferably 0.001 to 0.06 mole. Examples of preferred monoamine capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. Among these, benzylamine and aniline are more preferred. As the dicarboxylic acid capping agent, dicarboxylic acids are preferred, and a part of them can form a closed loop. Examples of preferred dicarboxylic acids 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, 4-cyclohexene-1,2-dicarboxylic acid, etc. Among these, phthalic acid and phthalic anhydride are more preferred.

[0105] There is no particular limitation on the method for reacting the aforementioned tetracarboxylic acid component with the diamine component, and a known method can be used.

[0106] As specific reaction methods, the following methods can be cited: Method (1), charging the tetracarboxylic acid component, the diamine component, and a reaction solvent into a reactor, stirring at 10 to 110 °C for 0.5 to 30 hours, and then raising the temperature to carry out an imidization reaction; Method (2), dissolving the diamine component and a reaction solvent in a reactor and then charging the tetracarboxylic acid component, stirring at 10 to 110 °C for 0.5 to 30 hours as needed, and then raising the temperature to carry out an imidization reaction; Method (3), charging the tetracarboxylic acid component, the diamine component, and a reaction solvent into a reactor and immediately raising the temperature to carry out an imidization reaction; etc.

[0107] In the production of polyimide resin, the reaction solvent used only needs to not hinder the imidization reaction and be able to dissolve the resulting polyimide resin. For example, aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, etc. can be cited.

[0108] Specific examples of aprotic solvents include amide solvents such as N,N-dimethylisobutylamide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, tetramethylurea, etc.; lactone solvents such as γ-butyrolactone, γ-valerolactone, etc.; phosphorus-containing amide solvents such as hexamethylphosphoramide, hexamethylphosphortriamide, etc.; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, sulfolane, etc.; ketone solvents such as acetone, cyclohexanone, methylcyclohexane, etc.; amine solvents such as methylpyridine, pyridine, etc.; ester solvents such as (2-methoxy-1-methylethyl) acetate, etc.

[0109] Specific examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, etc.

[0110] Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl] ether, tetrahydrofuran, 1,4-dioxane, etc.

[0111] In addition, specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, etc.

[0112] Among the above reaction solvents, amide solvents or lactone solvents are preferred. In addition, the above reaction solvents can be used alone or in combination of two or more.

[0113] In the imidization reaction, it is preferred to use a Dean-Stark trap or the like to remove the water generated during production while carrying out the reaction. By carrying out such an operation, the degree of polymerization and the imidization rate can be further increased.

[0114] In the above imidization reaction, a known imidization catalyst can be used. As the imidization catalyst, a base catalyst or an acid catalyst can be cited.

[0115] As the base catalyst, organic base catalysts such as pyridine, quinoline, isoquinoline, α-methylpyridine, β-methylpyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine, trimethylamine, triethylamine, tripropylamine, tributylamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline, etc., and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, etc. can be cited.

[0116] In addition, as the acid catalyst, crotonic acid, acrylic acid, trans-3-hexenedioic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, etc. can be cited. The above-mentioned imidization catalysts can be used alone or in combination of two or more.

[0117] Among the above, from the viewpoint of operability, a base catalyst is preferably used, an organic base catalyst is more preferably used, and triethylamine is further preferably used.

[0118] When using the above catalyst, from the viewpoints of reaction rate and gelation inhibition, etc., the temperature of the imidization reaction is preferably 120 to 250 °C, more preferably 160 to 190 °C, and further preferably 180 to 190 °C. In addition, after the distillation of the generated water starts, the reaction time is preferably 0.5 to 10 hours.

[0119] It should be noted that when no catalyst is used, the temperature of the imidization reaction is preferably 200 to 350 °C.

[0120] [Polyimide varnish]

[0121] The polyimide varnish of the present invention is formed 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.

[0122] The organic solvent is not particularly limited as long as it can dissolve the polyimide resin, and it is preferably used alone or in combination of two or more of the above compounds as the reaction solvent used in the production of the polyimide resin.

[0123] The polyimide varnish of the present invention preferably contains 5 to 60% by mass, more preferably 5 to 45% by mass of the polyimide resin of the present invention. The viscosity of the polyimide varnish is preferably 0.1 to 200 Pa·s, more preferably 0.5 to 150 Pa·s.

[0124] [Polyimide film]

[0125] The polyimide film of the present invention contains the aforementioned polyimide resin. In addition, the polyimide film of the present invention is preferably composed of the aforementioned polyimide resin.

[0126] That is, it contains a polyimide resin, and the polyimide resin has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine. The structural unit A contains a structural unit (A1) derived from the compound represented by the formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, and the structural unit B contains a structural unit (B1) derived from the compound represented by the formula (b1).

[0127] By containing such a polyimide resin, the polyimide film of the present invention has high strength, and also excellent elongation and deformation recovery properties.

[0128] There is no particular limitation on the method for producing the polyimide film of the present invention, and known methods can be used. For example, a method of coating a solution containing the polyimide resin of the present invention, or a solution containing the polyimide resin of the present invention and the various additives on a smooth support such as a glass plate, a metal plate, or a plastic, or forming it into a film shape and then removing a solvent component such as an organic solvent contained in the solution, etc. can be cited.

[0129] The aforementioned solution containing the polyimide resin can be the polyimide resin solution itself obtained by a polymerization method. In addition, at least one selected from the compounds exemplified above as a solvent for dissolving the polyimide resin can be mixed into the aforementioned polyimide resin solution. As described above, by adjusting the solid content concentration and viscosity of the solution containing the polyimide resin, the thickness of the polyimide film of the present invention can be easily controlled.

[0130] A release agent can be coated on the surface of the aforementioned support as needed. As a method of heating and evaporating the solvent component after coating a solution containing the aforementioned polyimide resin or the aforementioned polyimide resin composition on the aforementioned support, the following method is preferred. That is, preferably, the solvent is evaporated at a temperature of 120°C or lower to form a self-supporting film, and then the self-supporting film is peeled off from the support, the end of the self-supporting film is fixed, and drying is performed at a temperature above the boiling point of the solvent component used and 350°C or lower to produce a polyimide film. In addition, drying is preferably performed in a nitrogen atmosphere. The pressure of the drying atmosphere can be reduced pressure, normal pressure, or increased pressure, all of which are acceptable.

[0131] The thickness of the polyimide film of the present invention can be appropriately selected according to uses, etc., and is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and further preferably 10 to 80 μm. By having a thickness of 1 - 250 μm, practical use as a self-standing film becomes possible.

[0132] The polyimide film containing the polyimide resin of the present invention is suitable for use as a film for various components such as color filters, flexible displays, semiconductor components, and optical members.

[0133] Examples

[0134] The present invention will be specifically described below based on examples. However, the present invention is not limited by any of these examples.

[0135] The physical properties of the polyimide films obtained in the following examples and comparative examples were measured according to the methods shown below.

[0136] (1) Film thickness

[0137] The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

[0138] (2) Tensile modulus, tensile strength

[0139] The measurement was carried out based on JIS K7127 using a tensile testing machine "Strograph VG1E" manufactured by Toyo Seiki Seisaku-sho, Ltd.

[0140] (3) Elongation at break in tension (evaluation of elongation)

[0141] The elongation at break in tension was measured according to the tensile test (measurement of elongation) based on JIS K7127. Test pieces with a width of 10 mm and a thickness of 10 - 70 μm were used.

[0142] (4) Deformation recovery

[0143] As Figure 1 (a) shows, the polyimide film 1 cut into a width of 10 mm × a length of 100 mm was fixed with a fixture to R = 3 mm and left standing for 24 hours or 100 hours under the conditions of 65°C and a relative humidity of 90%, or 70°C and dry conditions. Then, after removing the fixture at 23°C and a relative humidity of 50% and leaving it standing for 170 hours, for the recovery of the film, the Figure 1 (b) shows the angle θ was measured to evaluate the deformation recovery. It should be noted that the smaller the measured angle, the better the deformation recovery, and a smaller value is preferred.

[0144] [Example 1]

[0145] In a 300 mL five-necked round-bottom flask equipped with a stainless-steel semi-circular stirring blade, a nitrogen inlet tube, a Dean-Stark trap with a condenser, a thermometer, and a glass end cap, 20.22 g (0.060 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (manufactured by ChinaTech Chemical (Taijin) Co., Ltd., hereinafter referred to as 6FODA), which is a diamine component, 56.7 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as GBL), which is an organic solvent, and 0.309 g of triethylamine (manufactured by Kanto Chemical Co., Inc., hereinafter referred to as TEA), which is an imidization catalyst, were charged. Stirring was carried out at a system temperature of 70 °C, under a nitrogen atmosphere, and at a rotation speed of 150 rpm to obtain a solution. To this, 26.18 g (0.057 mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (manufactured by JFE Chemical Corporation, hereinafter referred to as BPAF), which is a tetracarboxylic acid component, 0.59 g (0.003 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter referred to as CBDA), and 30.5 g of GBL were added simultaneously, and then heated in a hood heater. The temperature inside the reaction system was raised to 190 °C in about 20 minutes. The components removed by distillation were trapped, the rotation speed was adjusted according to the increase in viscosity, and the temperature inside the reaction system was maintained at 190 °C and refluxed for 2 hours to obtain a polyimide solution. After that, after the temperature inside the reaction system was cooled to 120 °C, N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Company, Inc., hereinafter referred to as DMAC) was added to make it a specified solid component concentration, and further stirred for about 3 hours for homogenization to obtain a polyimide varnish (A) with a solid component concentration of 15.0 mass%.

[0146] Next, the polyimide varnish (A) was coated on a PET substrate and held at 60 °C for 20 minutes, at 80 °C for 20 minutes, and at 100 °C for 30 minutes to volatilize the solvent, thereby obtaining a self-supporting transparent primary dried film. Further, the film was fixed to a stainless-steel frame and dried at 220 °C in an air atmosphere for 20 minutes to remove the solvent, obtaining a polyimide film. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0147] [Example 2]

[0148] The amount of 6FODA was changed to 20.54 g (0.061 mol), the amount of BPAF was changed to 25.21 g (0.055 mol), and the amount of CBDA was changed to 1.20 g (0.006 mol). Except for this, by the same method as in Example 1, a polyimide varnish (B) with a solid component concentration of 15.0% by mass was obtained. Using the obtained polyimide varnish (B), a polyimide film was obtained by the same method as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0149] [Example 3]

[0150] The amount of 6FODA was changed to 21.88 g (0.065 mol), the amount of BPAF was changed to 20.88 g (0.046 mol), and the amount of CBDA was changed to 3.83 g (0.020 mol). Except for this, by the same method as in Example 1, a polyimide varnish (C) with a solid component concentration of 15.0% by mass was obtained. Using the obtained polyimide varnish (C), a polyimide film was obtained by the same method as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0151] [Example 4]

[0152] The amount of 6FODA was changed to 23.41 g (0.070 mol), the amount of BPAF was changed to 15.96 g (0.035 mol), and the amount of CBDA was changed to 6.83 g (0.035 mol). Except for this, by the same method as in Example 1, a polyimide varnish (D) with a solid component concentration of 15.0% by mass was obtained. Using the obtained polyimide varnish (D), a film was obtained by the same method as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0153] [Example 5]

[0154] The amount of 6FODA was changed to 22.93 g (0.068 mol), the amount of BPAF was changed to 15.63 g (0.034 mol), CBDA was not used, and 7.64 g (0.034 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Company, Inc., hereinafter referred to as HPMDA) was added. Except for this, by the same method as in Example 1, a polyimide varnish (E) with a solid component concentration of 15.0% by mass was obtained. Using the obtained polyimide varnish (E), a film was obtained by the same method as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0155] [Example 6]

[0156] Change the amount of 6FODA to 32.52 g (0.097 mol), change the amount of BPAF to 13.30 g (0.029 mol), do not use CBDA, add 15.17 g (0.068 mol) of HPMDA. Except for this, obtain polyimide varnish (F) with a solid component concentration of 20.0% by mass in the same manner as in Example 1. Using the obtained polyimide varnish (F), obtain a film in the same manner as in Example 1. Show the measurement results and evaluation results of the physical properties in Table 1.

[0157] [Example 7]

[0158] Change the amount of 6FODA to 11.75 g (0.035 mol), further add 9,9-bis[4-(aminophenoxy)phenyl]fluorene (manufactured by JFE Chemical Corporation, hereinafter referred to as BPF-AN) (0.035 mol), change the amount of BPAF to 22.43 g (0.049 mol), change the amount of CBDA to 4.11 g (0.021 mol). Except for this, obtain polyimide varnish (G) with a solid component concentration of 18.5% by mass in the same manner as in Example 1. Using the obtained polyimide varnish (G), obtain a polyimide film in the same manner as in Example 1. Show the measurement results and evaluation results of the physical properties in Table 1.

[0159] [Comparative Example 1]

[0160] Change the amount of 6FODA to 19.93 g (0.059 mol), change the amount of BPAF to 27.18 g (0.059 mol), do not use CBDA. Except for this, obtain polyimide varnish (H) with a solid component concentration of 15.0% by mass in the same manner as in Example 1. Using the obtained polyimide varnish (H), obtain a film in the same manner as in Example 1. Show the measurement results and evaluation results of the physical properties in Table 1.

[0161] [Comparative Example 2]

[0162] Change the amount of 6FODA to 38.45 g (0.11 mol), change the amount of HPMDA to 25.63 g (0.11 mol), do not use BPAF. Except for this, prepare polyimide varnish in the same manner as in Example 5 to obtain polyimide varnish (I) with a solid component concentration of 20% by mass. Using the obtained polyimide varnish (I), obtain a film in the same manner as in Example 1.

[0163] [Comparative Example 3]

[0164] The amount of 6FODA was changed to 19.44 g (0.058 mol), the amount of HPMDA was changed to 5.18 g (0.023 mol), and 21.46 g (0.035 mol) of 2,2’,3,3’,5,5’-hexamethyl[1,1’-biphenyl]-4,4’-diyl bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (manufactured by Honshu Chemical Industry Co., Ltd., hereinafter referred to as TMPBP-TME) was used instead of BPAF. Otherwise, a polyimide varnish (J) with a solid component concentration of 15.0 mass% was obtained by the same method as in Example 5. Using the obtained polyimide varnish (J), a film was obtained by the same method as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0165] [Table 1]

[0166] Table 1

[0167]

[0168] As can be seen from Table 1, the polyimide films of Examples 1 to 7 have high strength, but also excellent deformation recovery and elongation.

Claims

1. A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A includes a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride, and the structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1). The proportion of the structural unit (A1) relative to the structural unit A is 20 to 99 mol%, the proportion of the structural unit (A2) relative to the structural unit A is 1 to 80 mol%, and the proportion of the structural unit (B1) relative to the structural unit B is 30 mol% or more.

2. The polyimide resin according to claim 1, wherein The structural unit (A2) is a structural unit derived from an alicyclic tetracarboxylic dianhydride.

3. The polyimide resin according to claim 1 or 2, wherein The structural unit (A2) includes at least one selected from a structural unit (A2-1) derived from a compound represented by the following formula (a2-1) and a structural unit (A2-2) derived from a compound represented by the following formula (a2-2).

4. The polyimide resin according to claim 3, wherein, The structural unit (A2) includes the structural unit (A2-1).

5. The polyimide resin according to claim 3, wherein, The structural unit (A2) includes the structural unit (A2-2).

6. The polyimide resin according to claim 1 or 2, wherein The ratio of the total of the structural unit (A1) and the structural unit (A2) relative to the structural unit A is 50 mol% or more.

7. The polyimide resin according to claim 1 or 2, wherein The molar ratio [(A1) / (A2)] of the structural unit (A1) to the structural unit (A2) in the structural unit A is 20 / 80 to 99 / 1.

8. The polyimide resin according to claim 4, wherein, The molar ratio [(A1) / (A2-1)] of the structural unit (A1) to the structural unit (A2-1) in the structural unit A is 50 / 50 to 95 / 5.

9. The polyimide resin according to claim 5, wherein, The molar ratio [(A1) / (A2-2)] of the structural unit (A1) to the structural unit (A2-2) in the structural unit A is 20 / 80 to 50 / 50.

10. The polyimide resin according to claim 1 or 2, wherein, The proportion of the structural unit (B1) relative to the structural unit B is 60 mol% or more.

11. A polyimide varnish obtained by dissolving the polyimide resin according to any one of claims 1 to 10 in an organic solvent.

12. A polyimide film containing the polyimide resin according to any one of claims 1 to 10.

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