Polyimide resin, polyimide varnish and polyimide film

Abstract

A polyimide resin that has structural units A derived from tetracarboxylic acid dianhydride and structural units B derived from diamine, said structural units A containing structural units (A1) derived from 9,9-bis(3,4-dicarboxyphenyl)fluorene acid dianhydride and structural units (A2) derived from aliphatic tetracarboxylic acid dianhydride, and said structural units B containing structural units (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 technology]

[0002] Polyimide resins are obtained from aromatic tetracarboxylic acid anhydrides and aromatic diamines, and generally have excellent heat resistance, chemical resistance, mechanical properties, and electrical characteristics due to their molecular rigidity, resonance stabilization, and strong chemical bonds. Therefore, they are widely used in fields such as molding materials, composite materials, electrical and electronic components, optical materials, displays, and aerospace. In particular, glass materials have traditionally been used for electrical and electronic components, optical materials, displays, etc., but taking advantage of their flexibility, applications to flexible devices are also being considered.

[0003] For example, Patent Document 1 discloses a composition for forming a flexible device substrate, which contains a polyimide, which is a reaction product of a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a diamine component containing a fluorine-containing aromatic diamine, and an organic solvent, for the purpose of improving heat resistance, retardation, flexibility, and transparency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 097143 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, polyimide resins have been increasingly used for displays and their protective front panels, and polyimide resins with high mechanical strength are needed to replace the glass materials that have traditionally been used.However, high-strength polyimide resins have not been flexible enough. Recently, polyimide films have also been used for displays and protective plates in smartphones with foldable structures, so they are required to be highly flexible as well as strong, and they also need to have properties such as the ability to recover their shape after deformation and the ability to stretch. Therefore, a polyimide resin having these properties has been desired. In other words, the problem to be solved by the present invention is to provide a polyimide resin capable of forming a film that has high strength yet is excellent in deformation recovery and elongation, and a polyimide film that has high strength yet is excellent in deformation recovery and elongation. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have found that a polyimide resin containing a specific combination of structural units can solve the above problems, and have arrived at the present invention.

[0007] That is, the present invention relates to the following [1] to

[12] . [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): [ka] [2] The polyimide resin according to [1] above, wherein the structural unit (A2) is a structural unit derived from an alicyclic tetracarboxylic dianhydride. [3] The polyimide resin according to [1] or [2] above, wherein the structural unit (A2) comprises 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): [ka] [4] The polyimide resin according to [3] above, wherein the structural unit (A2) includes the structural unit (A2-1). [5] The polyimide resin according to [3] above, wherein the structural unit (A2) includes the structural unit (A2-2). [6] The polyimide resin according to any one of [1] to [5] above, wherein the total ratio of the structural unit (A1) and the structural unit (A2) to the structural unit A is 50 mol % or more. [7] The polyimide resin according to any one of [1] to [6] above, wherein the molar ratio of the structural unit (A1) to the structural unit (A2) in the structural unit A [(A1) / (A2)] is 20 / 80 to 99 / 1. [8] The polyimide resin according to [4] above, wherein the molar ratio of the structural unit (A1) to the structural unit (A2-1) in the structural unit A [(A1) / (A2-1)] is 50 / 50 to 95 / 5. [9] The polyimide resin according to [5] above, wherein the molar ratio of the structural unit (A1) to the structural unit (A2-2) in the structural unit A [(A1) / (A2-2)] is 20 / 80 to 50 / 50.

[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.

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

[10] in an organic solvent.

[12] A polyimide film comprising the polyimide resin according to any one of [1] to

[10] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyimide resin capable of forming a film having high strength yet excellent deformation recovery and elongation, a polyimide varnish containing the polyimide resin, and a polyimide film having high strength yet excellent deformation recovery and elongation. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a conceptual diagram showing a method for measuring the deformation recovery of a polyimide film. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Polyimide resin] 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, 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): [ka] The polyimide resin of the present invention will be described below.

[0011] [Structural unit A] The structural unit A contained in the polyimide of the present invention is a structural unit derived from a tetracarboxylic dianhydride contained in the polyimide resin. The structural unit A includes a structural unit (A1) derived from a compound represented by the above formula (a1) and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride.

[0012] The compound represented by the formula (a1) is 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). When the structural unit A contains the structural unit (A1), the mechanical strength of the resulting polyimide resin is improved.

[0013] The structural unit (A2) is a structural unit derived from an aliphatic tetracarboxylic dianhydride, and preferably contains a structural unit derived from an alicyclic tetracarboxylic dianhydride, and more preferably contains a structural unit derived from a tetracarboxylic dianhydride having an alicyclic ring with 4 to 15 carbon atoms. By containing a structural unit derived from a tetracarboxylic dianhydride having an alicyclic ring, elongation is improved and deformation recovery and transparency are improved. In this specification, an aliphatic tetracarboxylic acid dianhydride refers to a tetracarboxylic acid dianhydride that does not contain an aromatic ring, and an alicyclic tetracarboxylic acid dianhydride refers to an aliphatic tetracarboxylic acid dianhydride that contains one or more alicyclic rings. Here, the term "alicyclic ring" refers to a cyclic aliphatic hydrocarbon structure excluding aromatic rings, among structures in which carbon atoms are bonded in a ring, and the number of carbon atoms in the alicyclic ring refers to the number of carbon atoms constituting the ring.

[0014] 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, and positional isomers thereof. Specific examples of aliphatic tetracarboxylic dianhydrides other than alicyclic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride.

[0015] Among these, the structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride preferably includes at least one selected from the structural unit (A2-1) derived from a compound represented by the following formula (a2-1) and the structural unit (A2-2) derived from a compound represented by the following formula (a2-2), and more preferably at least one selected from the structural unit (A2-1) derived from a compound represented by the following formula (a2-1) and the structural unit (A2-2) derived from a compound represented by the following formula (a2-2). [ka] The compound represented by the formula (a2-1) is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA). The compound represented by the formula (a2-2) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA). When the structural unit A contains the structural unit (A2), the elongation is improved, and the deformation recovery property and transparency are improved. Thus, the polyimide resin and polyimide film of the present invention have excellent deformation recovery and elongation while also having high strength due to the structural unit A, which is a structural unit derived from a tetracarboxylic dianhydride, containing the structural units (A1) and (A2). Although the reason for this is unclear, it is thought to be due to the rigidity of the fluorene group and the flexibility of the aliphatic compound.

[0016] The proportion of the structural unit (A1) relative to the structural unit A is preferably 20 to 99 mol %, more preferably 30 to 97 mol %, even more preferably 40 to 96 mol %, and even more preferably 50 to 95 mol %. The proportion of the structural unit (A2) relative to the structural unit A is preferably 1 to 80 mol %, more preferably 3 to 70 mol %, even more preferably 4 to 60 mol %, and even more preferably 5 to 50 mol %.

[0017] The total proportion 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 even more preferably 90 mol% or more. There are no particular upper limits for the total proportion of the structural unit (A1) and the structural unit (A2), and it is 100 mol% or less. The structural unit A may be composed only of the structural unit (A1) and the structural unit (A2).

[0018] From the viewpoint of improving mechanical properties and deformation recovery, the molar ratio of the structural unit (A1) to the structural unit (A2) in the structural unit A [(A1) / (A2)] is preferably 20 / 80 to 99 / 1, more preferably 30 / 70 to 97 / 3, even more preferably 40 / 60 to 96 / 4, and still more preferably 50 / 50 to 95 / 5. In particular, from the viewpoint of improving deformation recovery, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 80 / 20 to 97 / 3. Particularly from the viewpoint of improving strength, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 92 / 8 to 99 / 1. From the viewpoint of further improving elongation, the ratio is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and even more preferably 40 / 60 to 60 / 40.

[0019] The molar ratio of the structural unit (A1) to the structural unit (A2-1) in the structural unit A [(A1) / (A2-1)] is preferably 40 / 60 to 99 / 1, more preferably 45 / 55 to 96 / 4, and even more preferably 50 / 50 to 95 / 5, from the viewpoint of improving mechanical properties and deformation recovery. In particular, from the viewpoint of improving deformation recovery, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 80 / 20 to 97 / 3. Particularly from the viewpoint of improving strength, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 92 / 8 to 99 / 1. From the viewpoint of further improving elongation, the ratio is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and even more preferably 40 / 60 to 60 / 40.

[0020] The molar ratio of the structural unit (A1) to the structural unit (A2-2) in the structural unit A [(A1) / (A2-2)] is preferably 20 / 80 to 99 / 1, more preferably 20 / 80 to 60 / 40, and even more preferably 20 / 80 to 50 / 50, from the viewpoint of improving mechanical properties and deformation recovery. In particular, from the viewpoint of improving deformation recovery, the ratio is preferably 20 / 80 to 60 / 40, more preferably 20 / 80 to 50 / 50, and even more preferably 20 / 80 to 40 / 60. Particularly from the viewpoint of improving strength, the ratio is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and even more preferably 40 / 60 to 60 / 40. From the viewpoint of further improving elongation, the ratio is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and even more preferably 40 / 60 to 60 / 40.

[0021] The polyimide resin of the present invention may contain, within the structural unit A, a structural unit derived from a tetracarboxylic dianhydride other than the structural unit (A1) and the structural unit (A2), as long as the effects of the present invention are not impaired. The tetracarboxylic acid dianhydride that provides a structural unit other than the structural unit (A1) and the structural unit (A2) is not particularly limited, but examples include aromatic tetracarboxylic acid dianhydrides such as pyromellitic anhydride, 2,3,5,6-toluenetetracarboxylic acid dianhydride, and 1,4,5,8-naphthalenetetracarboxylic acid dianhydride. These can be used alone or in combination of two or more.

[0022] In this specification, the aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings.

[0023] [Structural unit B] The structural unit B contained in the polyimide of the present invention is a structural unit derived from a diamine. The structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1). [ka]

[0024] The compound represented by the formula (b1) is 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA). When the structural unit B includes the structural unit (B1), the resulting polyimide resin can have improved physical properties such as transparency, as well as improved mechanical strength while maintaining elongation and deformation recovery.

[0025] 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, even more preferably 50 mol% or more, still more preferably 60 mol% or more, even more preferably 70 mol% or more, and even more preferably 90 mol% or more. There is no particular upper limit for the proportion of the structural unit (B1), and it is 100 mol% or less. The structural unit B may consist solely of the structural unit (B1).

[0026] The polyimide resin of the present invention may contain, in the structural unit B, a structural unit derived from a diamine other than the compound represented by the general formula (b1) above, as a structural unit other than the structural unit (B1) above, as long as the effects of the present invention are not impaired. Diamines other than the compound represented by the general formula (b1) are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 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-trimethylsilyl Examples of suitable diamines include aromatic diamines such as methyl-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. These may be used alone or in combination of two or more.

[0027] In this specification, aromatic diamine means a diamine containing one or more aromatic rings, aliphatic diamine means a diamine containing no aromatic rings, and alicyclic diamine means an aliphatic diamine containing one or more alicyclic rings.

[0028] [Properties of polyimide resin] From the viewpoint of the mechanical strength of the resulting polyimide film, the number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 100,000. The number average molecular weight of the polyimide resin can be measured by gel filtration chromatography or the like.

[0029] The polyimide resin of the present invention may further contain various additives, such as antioxidants, light stabilizers, surfactants, flame retardants, plasticizers, and polymer compounds other than the polyimide resins, as long as the effects of the present invention are not impaired. Examples of the polymer compound include polyimides other than the polyimide resin of the present invention, polycarbonates, polystyrenes, polyamides, polyamideimides, polyesters such as polyethylene terephthalate, polyethersulfones, polycarboxylic acids, polyacetals, polyphenylene ethers, polysulfones, polybutylenes, polypropylenes, polyacrylamides, and polyvinyl chlorides.

[0030] [Method for producing polyimide resin] The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component containing a compound that provides the structural unit (A1) and a compound that provides the structural unit (A2) with a diamine component that contains a compound that provides the structural unit (B1).

[0031] Examples of compounds that provide the structural unit (A1) include compounds represented by formula (a1), but are not limited thereto and may also be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic acid dianhydrides represented by formula (a1) and alkyl esters of such tetracarboxylic acids. Compounds that provide the structural unit (A1) are preferably compounds represented by formula (a1) (i.e., dianhydrides). Similarly, compounds that provide the structural unit (A2) include aliphatic tetracarboxylic dianhydrides, preferably alicyclic tetracarboxylic dianhydrides, and more preferably compounds represented by formula (a2-1) or formula (a2-2). However, the present invention is not limited to these, and derivatives thereof may also be used as long as they provide the same structural unit. 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 the tetracarboxylic acids. Compounds that provide the structural unit (A2) are preferably compounds represented by formula (a2-1) or formula (a2-2) (i.e., dianhydrides).

[0032] The tetracarboxylic acid component preferably contains 20 to 99 mol %, more preferably 30 to 97 mol %, even more preferably 40 to 96 mol %, and even more preferably 50 to 95 mol % of the compound that provides the structural unit (A1). The tetracarboxylic acid component preferably contains 1 to 80 mol %, more preferably 3 to 70 mol %, even more preferably 4 to 60 mol %, and even more preferably 5 to 50 mol % of the compound that provides the structural unit (A2).

[0033] The total content of the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2) is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more, of the total tetracarboxylic acid component. There are no particular limitations on the upper limit of the total content of the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2), and it is 100 mol% or less. The tetracarboxylic acid component may consist solely of the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2).

[0034] The molar ratio of the compound that provides the structural unit (A1) to the compound that provides the structural unit (A2) in the tetracarboxylic acid component [(A1) / (A2)] is preferably 20 / 80 to 99 / 1, more preferably 30 / 70 to 97 / 3, even more preferably 40 / 60 to 96 / 4, and still more preferably 50 / 50 to 95 / 5, from the viewpoint of improving mechanical properties and deformation recovery. In particular, from the viewpoint of improving deformation recovery, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 80 / 20 to 97 / 3. Particularly from the viewpoint of improving strength, the ratio is preferably 60 / 40 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 92 / 8 to 99 / 1. From the viewpoint of further improving elongation, the ratio is preferably 20 / 80 to 92 / 8, more preferably 30 / 70 to 80 / 20, and even more preferably 40 / 60 to 60 / 40.

[0035] The tetracarboxylic acid component may contain compounds other than the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2). Examples of such compounds include the above-mentioned aromatic tetracarboxylic acid dianhydrides and derivatives thereof (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.). The compound optionally contained in the tetracarboxylic acid component (that is, a compound other than the compound that provides the structural unit (A1) and the structural unit (A2)) may be one type, or two or more types.

[0036] Compounds that provide the structural unit (B1) include, but are not limited to, compounds represented by formula (b1), and may also be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by formula (b1). Compounds that provide the structural unit (B1) are preferably compounds represented by formula (b1) (i.e., diamines).

[0037] The diamine component preferably contains 30 mol% or more of the compound that provides the structural unit (B1), more preferably 40 mol% or more, even 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. There are no particular upper limits for the proportion of the compound that provides the structural unit (B1), and it is 100 mol% or less. The diamine component may consist solely of the compound that provides the structural unit (B1).

[0038] The diamine component may contain compounds other than the compound that provides the structural unit (B1), and examples of such compounds include the above-mentioned aromatic diamines, alicyclic diamines, aliphatic diamines, modified silicone diamines, and derivatives thereof (diisocyanates, etc.). The compound optionally contained in the diamine component (that is, a compound other than the compound that provides the structural unit (B1)) may be one type, or two or more types.

[0039] When producing the polyimide resin according to the present invention, the ratio of the amount of the tetracarboxylic acid component to the amount of the diamine component charged is preferably 0.9 to 1.1 moles of the diamine component per mole of the tetracarboxylic acid component.

[0040] When producing the polyimide resin of the present invention, a terminal blocking agent may be used in addition to the tetracarboxylic acid component and the diamine component. Monoamines or dicarboxylic acids are preferred as terminal blocking agents. The amount of terminal blocking agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per mol of the tetracarboxylic acid component. Preferred monoamine terminal blocking agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline. Of these, benzylamine and aniline are more preferred. Preferred dicarboxylic acid terminal blocking agents are dicarboxylic acids, some of which may be ring-closed. Preferred dicarboxylic acids include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. Of these, phthalic acid and phthalic anhydride are more preferred.

[0041] There are no particular limitations on the method for reacting the tetracarboxylic acid component and the diamine component, and any known method can be used. Specific reaction methods include: (1) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which a diamine component and a reaction solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours as needed, and then the temperature is raised to carry out the imidization reaction; and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

[0042] The reaction solvent used in the production of the polyimide resin may be any solvent that does not inhibit the imidization reaction and can dissolve the resulting polyimide resin, such as aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0043] 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, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, cyclohexanone, and methylcyclohexane; amine solvents such as picoline and pyridine; and ester solvents such as 2-methoxy-1-methylethyl acetate.

[0044] Specific examples of phenol-based solvents 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 ether solvents 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 carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above reaction solvents, amide-based solvents and lactone-based solvents are preferred. The above reaction solvents may be used alone or in combination of two or more.

[0045] The imidization reaction is preferably carried out while removing water generated during the production using a Dean-Stark apparatus, etc. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

[0046] In the imidization reaction, a known imidization catalyst can be used, such as a base catalyst or 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, tripropylamine, tributylamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more. Of the above, from the viewpoint of ease of handling, it is preferable to use a base catalyst, more preferable to use an organic base catalyst, and even more preferable to use triethylamine.

[0047] When the above catalyst is used, the temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 190° C., and even more preferably 180 to 190° C., from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water. When no catalyst is used, the temperature for the imidization reaction is preferably 200 to 350°C.

[0048] [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, but it is preferable to use the compounds described above as reaction solvents used in the production of polyimide resins, either alone or in combination of two or more. The polyimide varnish of the present invention preferably contains 5 to 60 mass %, more preferably 5 to 45 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.

[0049] [Polyimide film] The polyimide film of the present invention contains the above-mentioned polyimide resin, and preferably consists of the above-mentioned polyimide resin. That is, the polyimide resin has 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 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 formula (b1). By containing such a polyimide resin, the polyimide film of the present invention has high strength and also excellent elongation and deformation recovery.

[0050] The method for producing the polyimide film of the present invention is not particularly limited, and any known method can be used, such as a method in which 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 described above is applied to a smooth support such as a glass plate, a metal plate, or a plastic, or formed into a film, and then solvent components such as organic solvents contained in the solution are removed.

[0051] The polyimide resin-containing solution may be a polyimide resin solution obtained by polymerization. Alternatively, the polyimide resin solution may be a mixture of at least one compound selected from the compounds listed above as a solvent in which the polyimide resin dissolves. By adjusting the solids concentration and viscosity of the polyimide resin-containing solution as described above, the thickness of the polyimide film of the present invention can be easily controlled.

[0052] A release agent may be applied to the surface of the support as needed. The following method is preferred as a method for applying a solution containing the polyimide resin or the polyimide resin composition to the support and then heating to evaporate the solvent component. That is, it is preferred to evaporate the solvent at a temperature of 120°C or less to form a self-supporting film, peel the self-supporting film from the support, fix the edges of the self-supporting film, and dry at a temperature of the boiling point of the solvent component used and 350°C or less to produce a polyimide film. Drying under a nitrogen atmosphere is also preferred. The pressure of the drying atmosphere may be reduced, normal, or increased.

[0053] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and even more preferably 10 to 80 μm. A thickness of 1 to 250 μm enables practical use as a free-standing film.

[0054] The polyimide film containing the polyimide resin of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. [Example]

[0055] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0056] The physical properties of the polyimide films obtained in the following Examples and Comparative Examples were measured by the following methods. (1) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation. (2) Tensile modulus and tensile strength The measurement was performed in accordance with JIS K7127 using a tensile tester "Strograph VG1E" manufactured by Toyo Seiki Co., Ltd. (3) Tensile elongation at break (evaluation of elongation) The tensile elongation at break was measured by a tensile test (measurement of elongation) in accordance with JIS K 7127. Test pieces having a width of 10 mm and a thickness of 10 to 70 μm were used. (4) Deformation recovery As shown in Figure 1(a), polyimide film 1 cut to a size of 10 mm wide x 100 mm long was fixed with a jig at an R of 3 mm and left to stand for 24 hours or 100 hours under conditions of 65°C and 90% relative humidity, or 70°C and dry conditions. The jig was then removed and the film was left to stand for 170 hours at 23°C and 50% relative humidity. The deformation recovery was evaluated by measuring the angle θ of the film's return, as shown in Figure 1(b). Note that a smaller measured angle indicates better deformation recovery, and a smaller value is preferable.

[0057] [Example 1] A 300 mL five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark apparatus fitted with a condenser, a thermometer, and a glass end cap was charged with 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) as the diamine component, 56.7 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as GBL) as the organic solvent, and 0.309 g of triethylamine (manufactured by Kanto Chemical Co., Ltd., hereinafter referred to as TEA) as the imidization catalyst, and the mixture was stirred at 150 rpm under a nitrogen atmosphere at a system temperature of 70°C to obtain a solution. To this mixture were added 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) as tetracarboxylic acid components, 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 all at once.The mixture was then heated with a mantle heater, and the temperature in the reaction system was raised to 190°C over approximately 20 minutes.The distilled components were collected, and the temperature in the reaction system was maintained at 190°C and refluxed for 2 hours while adjusting the rotation speed according to the increase in viscosity, to obtain a polyimide solution. After that, when 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 achieve the specified solid content concentration, and the mixture was further stirred for approximately 3 hours to homogenize, thereby obtaining polyimide varnish (A) with a solid content concentration of 15.0 mass%.

[0058] Next, polyimide varnish (A) was applied to a PET substrate and held at 60°C for 20 minutes, 80°C for 20 minutes, and 100°C for 30 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed to a stainless steel frame and dried at 220°C in an air atmosphere for 20 minutes to remove the solvent, yielding a polyimide film. The measurement and evaluation results of physical properties are shown in Table 1.

[0059] [Example 2] A polyimide varnish (B) having a solids concentration of 15.0 mass% was obtained in the same manner as in Example 1, except that 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). A polyimide film was obtained using the obtained polyimide varnish (B) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0060] [Example 3] A polyimide varnish (C) having a solids concentration of 15.0 mass% was obtained in the same manner as in Example 1, except that 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). A polyimide film was obtained using the obtained polyimide varnish (C) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0061] [Example 4] A polyimide varnish (D) having a solids concentration of 15.0 mass% was obtained in the same manner as in Example 1, except that 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). A film was obtained using the obtained polyimide varnish (D) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0062] [Example 5] A polyimide varnish (E) with a solids concentration of 15.0 mass% was obtained in the same manner as in Example 1, except that 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. A film was obtained using the obtained polyimide varnish (E) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0063] [Example 6] A polyimide varnish (F) having a solids concentration of 20.0 mass% was obtained in the same manner as in Example 1, except that the amount of 6FODA was changed to 32.52 g (0.097 mol), the amount of BPAF was changed to 13.30 g (0.029 mol), CBDA was not used, and 15.17 g (0.068 mol) of HPMDA was added. A film was obtained using the obtained polyimide varnish (F) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0064] [Example 7] The amount of 6FODA was changed to 11.75 g (0.035 mol), and 9,9-bis[4-(aminophenoxy)phenyl]fluorene (manufactured by JFE Chemical Corporation, hereinafter referred to as BPF-AN) (0.035 mol) was added. The amount of BPAF was changed to 22.43 g (0.049 mol), and the amount of CBDA was changed to 4.11 g (0.021 mol). Except for this, a polyimide varnish (G) with a solids concentration of 18.5 mass% was obtained in the same manner as in Example 1. Using the obtained polyimide varnish (G), a polyimide film was obtained in the same manner as in Example 1. The measurement results and evaluation results of physical properties are shown in Table 1.

[0065] [Comparative Example 1] A polyimide varnish (H) having a solids concentration of 15.0 mass% was obtained in the same manner as in Example 1, except that the amount of 6FODA was changed to 19.93 g (0.059 mol), the amount of BPAF was changed to 27.18 g (0.059 mol), and CBDA was not used. A film was obtained using the obtained polyimide varnish (H) in the same manner as in Example 1. The measurement results and evaluation results of the physical properties are shown in Table 1.

[0066] Comparative Example 2 A polyimide varnish (I) having a solids concentration of 20 mass% was prepared in the same manner as in Example 5, except that the amount of 6FODA was changed to 38.45 g (0.11 mol), the amount of HPMDA was changed to 25.63 g (0.11 mol), and BPAF was not used. A film was prepared in the same manner as in Example 1 using the obtained polyimide varnish (I).

[0067] Comparative Example 3 A polyimide varnish (J) with a solids concentration of 15.0% by mass was obtained in the same manner as in Example 5, except that 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. A film was obtained using the obtained polyimide varnish (J) in the same manner as in Example 1. The measurement results and evaluation results of physical properties are shown in Table 1.

[0068] [Table 1]

[0069] It can be seen from Table 1 that the polyimide films of Examples 1 to 7 have high strength and 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 comprises 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, the structural unit B comprises a structural unit (B1) derived from a compound represented by the following formula (b1), and the structural unit (A2) comprises 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): 【Chemistry 1】 【change】

2. 2. The polyimide resin according to claim 1, wherein the structural unit (A2) comprises the structural unit (A2-1).

3. 2. The polyimide resin according to claim 1, wherein the structural unit (A2) comprises the structural unit (A2-2).

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

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

6. 3. The polyimide resin according to claim 2, wherein the molar ratio of the structural unit (A1) to the structural unit (A2-1) in the structural unit A, [(A1) / (A2-1)], is 50 / 50 to 95 / 5.

7. 4. The polyimide resin according to claim 3, wherein the molar ratio of the structural unit (A1) to the structural unit (A2-2) in the structural unit A, [(A1) / (A2-2)], is 20 / 80 to 50 / 50.

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

9. A polyimide varnish obtained by dissolving the polyimide resin according to any one of claims 1 to 8 in an organic solvent.

10. A polyimide film comprising the polyimide resin according to any one of claims 1 to 8.

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