Polyimide resins, polyimide varnishes, and polyimide films

Abstract

A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, wherein structural unit A comprises a structural unit (A1) derived from 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride and a structural unit (A2) derived from aliphatic tetracarboxylic dianhydride, and structural unit B comprises a structural unit (B1) derived from 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane.

Description

Technical Field

[0001] This invention relates to polyimide resins, polyimide varnishes, and polyimide films. Background Technology

[0002] Polyimide resins are derived from aromatic tetracarboxylic anhydrides and aromatic diamines. Typically, due to the rigidity of the molecules, resonance stabilization, and strong chemical bonds, they possess excellent heat resistance, chemical resistance, mechanical properties, and electrical properties. Therefore, they are widely used in molding materials, composite materials, electrical / electronic components, optical materials, displays, aerospace, and other fields.

[0003] In particular, the application of glass, which has traditionally been used in electrical / electronic components, optical materials, displays, and other applications, has been explored in flexible devices, taking advantage of its flexibility.

[0004] For example, in order to improve heat resistance, delay, flexibility and transparency, Patent Document 1 discloses a composition for forming a flexible device substrate, which includes a polyimide and an organic solvent. The polyimide is a reactant of a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a diamine component containing a fluorinated aromatic diamine.

[0005] Existing technical documents

[0006] Patent documents

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

[0008] The problem the invention aims to solve

[0009] In recent years, especially with the application of polyimide resin in displays and their front panels, there has been a demand for polyimide resins with good mechanical strength, i.e., high strength and high elastic modulus, to replace the previously used glass materials. However, previous high-strength polyimide resins have problems such as insufficient flexibility and poor colorless transparency.

[0010] Recently, as polyimide films have also been used as displays and protective panels for smartphones with foldable structures, high strength, greater flexibility, and the property of restoring the shape of the polyimide film after deformation are required.

[0011] Therefore, polyimide resins that possess these properties are desirable.

[0012] That is, the problem to be solved by the present invention is to provide a polyimide resin that has both mechanical properties and colorless transparency, and is capable of forming a film with high strength and excellent deformation recovery, as well as a polyimide film that has both mechanical properties and colorless transparency, and has high strength and excellent deformation recovery.

[0013] Solution for solving the problem

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

[0015] That is, the present invention relates to the following [1] to [8].

[0016] [1] A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine.

[0017] Structural unit A comprises a structural unit (A1) derived from the compound shown in formula (a1) below and a structural unit (A2) derived from the aliphatic tetracarboxylic dianhydride, and structural unit B comprises a structural unit (B1) derived from the compound shown in formula (b1) below.

[0018]

[0019] [2] According to the polyimide resin described in [1] above, wherein the aforementioned structural unit (A2) is a structural unit derived from alicyclic tetracarboxylic dianhydride.

[0020] [3] According to the polyimide resin described in [1] or [2] above, wherein the aforementioned structural unit (A2) is selected from at least one of the following groups: structural unit (A2-1) derived from the compound shown in formula (a2-1), structural unit (A2-2) derived from the compound shown in formula (a2-2), and structural unit (A2-3) derived from the compound shown in formula (a2-3).

[0021]

[0022] [4] The polyimide resin according to any one of [1] to [3] above, wherein the proportion of the aforementioned structural unit (B1) to the aforementioned structural unit B is 30 mol% or more.

[0023] [5] The polyimide resin according to any one of [1] to [4] above, wherein the ratio of the aforementioned structural unit (A1) to the aforementioned structural unit A is 50 to 90 mol%.

[0024] [6] The polyimide resin according to any one of [1] to [5] above, wherein the aforementioned structural unit (A2) is a structural unit (A2-2) derived from the compound shown in the following formula (a2-2).

[0025]

[0026] [7] A polyimide varnish, which is made by dissolving the polyimide resin described in any one of [1] to [6] above in an organic solvent.

[0027] [8] A polyimide film comprising any one of the polyimide resins described in any one of [1] to [6].

[0028] The effects of the invention

[0029] According to the present invention, there are provided: a polyimide resin capable of combining mechanical properties and colorless transparency, forming a film with high strength and excellent deformation recovery; a polyimide varnish containing the polyimide resin; and a polyimide film that combines mechanical properties and colorless transparency, high strength and excellent deformation recovery. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating a method for determining the deformation recovery of polyimide films. Detailed Implementation

[0031] [Polyimide resin]

[0032] The polyimide resin of the present invention is a polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine. The structural unit A comprises a structural unit (A1) derived from the compound shown in formula (a1) below and a structural unit (A2) derived from aliphatic tetracarboxylic dianhydride, and the structural unit B comprises a structural unit (B1) derived from the compound shown in formula (b1) below.

[0033]

[0034] The polyimide resin of the present invention will be described below.

[0035] [Structural Unit A]

[0036] The structural unit A contained in the polyimide of the present invention is a structural unit derived from tetracarboxylic acid dianhydride that occupies a position in the polyimide resin.

[0037] Structural unit A comprises structural units (A1) derived from the compound shown in the aforementioned formula (a1) and structural units (A2) derived from aliphatic tetracarboxylic dianhydrides.

[0038] The compound shown in formula (a1) above is 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride (BPAF).

[0039] The mechanical strength of the polyimide resin is improved by making structural unit A contain structural unit (A1).

[0040] The structural unit (A2) is derived from aliphatic tetracarboxylic dianhydride. Preferably, structural unit (A2) contains structural units derived from alicyclic tetracarboxylic dianhydride, and more preferably, structural units derived from alicyclic tetracarboxylic dianhydride having 4 to 25 carbon atoms. By including structural units derived from alicyclic tetracarboxylic dianhydride, mechanical strength, deformation recovery, and colorless transparency are improved.

[0041] It should be noted that, in this specification, aliphatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride that does not contain an aromatic ring, while alicyclic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride that contains one or more alicyclic rings.

[0042] Here, "alicyclic" refers to a cyclic hydrocarbon structure other than an aromatic ring in a structure in which carbon atoms are linked in a ring. The number of carbon atoms in an alicyclic ring refers to the number of carbon atoms that make up the ring.

[0043] Specific examples of alicyclic tetracarboxylic dianhydrides include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, norbornane-2-spirocyclic-α-cyclopentanone-α'-spirocyclic-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.

[0044] Specific examples of alicyclic tetracarboxylic dianhydrides other than alicyclic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydrides, etc.

[0045] The structural unit (A2) derived from aliphatic tetracarboxylic dianhydride preferably comprises at least one selected from the structural units (A2-1) derived from the compound shown in formula (a2-1), the structural unit (A2-2) derived from the compound shown in formula (a2-2), and the structural unit (A2-3) derived from the compound shown in formula (a2-3), and more preferably comprises the structural unit (A2-2) derived from the compound shown in formula (a2-2). Furthermore, the structural unit (A2) derived from aliphatic tetracarboxylic dianhydride preferably comprises at least one selected from the structural units (A2-1) derived from the compound shown in formula (a2-1), the structural unit (A2-2) derived from the compound shown in formula (a2-2), and the structural unit (A2-3) derived from the compound shown in formula (a2-3), and more preferably comprises the structural unit (A2-2) derived from the compound shown in formula (a2-2).

[0046]

[0047] The compound represented by the aforementioned formula (a2-1) is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0048] The compound represented by the aforementioned formula (a2-2) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA).

[0049] The compound represented by the aforementioned formula (a2-3) is norbornane-2-spirocyclic-α-cyclopentanone-α'-spirocyclic-2”-norbornane-5,5”,6,6”-tetracarboxylic acid dianhydride (CpODA).

[0050] By including structural unit (A2) in structural unit A, mechanical strength is maintained, and deformation recovery and colorless transparency are improved.

[0051] Since the structural unit A derived from tetracarboxylic dianhydride has structural units (A1) and (A2), the polyimide resin and polyimide film of the present invention combine mechanical properties and colorless transparency. Although the reason for their high strength and excellent deformation recovery is still uncertain, it is believed to be due to the rigidity of the fluorene group and the freedom of aliphatic compounds.

[0052] The ratio of structural unit (A1) to structural unit A is preferably 30-90 mol%, more preferably 40-90 mol%, further preferably 50-90 mol%, and even more preferably 50-80 mol%.

[0053] The ratio of structural unit (A2) to structural unit A is preferably 10-70 mol%, more preferably 10-60 mol%, further preferably 10-50 mol%, and even more preferably 20-50 mol%.

[0054] The ratio of structural unit (A1) to structural unit (A2) in structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more. There is no particular upper limit to the ratio of structural unit (A1) to structural unit (A2), but it is 100 mol% or less. Structural unit A may also consist only of structural unit (A1) and structural unit (A2).

[0055] From the viewpoint of improving mechanical properties, colorless transparency and deformation recovery, the molar ratio [(A1) / (A2)] of structural unit A1 to structural unit A2 in structural unit A is preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 90 / 10, further preferably 40 / 60 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0056] In particular, from the viewpoint of improving deformation recovery at high temperatures, 40 / 60 to 80 / 20 is preferred, 40 / 60 to 70 / 30 is more preferred, and 40 / 60 to 60 / 40 is even more preferred.

[0057] The polyimide resin of the present invention may also include structural units derived from tetracarboxylic dianhydrides other than structural units (A1) and (A2) in structural unit A, without impairing the effects of the present invention.

[0058] There are no particular limitations on the tetracarboxylic dianhydrides that provide structural units other than structural units (A1) and (A2), and examples include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 2,3,5,6-toluenetetracarboxylic dianhydride, and 1,4,5,8-naphthalenetetracarboxylic dianhydride. They can be used alone or in combination of two or more.

[0059] It should be noted that, in this specification, aromatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more aromatic rings.

[0060] [Structural Unit B]

[0061] The structural unit B contained in the polyimide of the present invention is a structural unit derived from diamine.

[0062] Structural unit B contains structural units (B1) derived from the compound shown in formula (b1) below.

[0063]

[0064] The compound represented by the aforementioned formula (b1) is 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP).

[0065] By incorporating structural unit B into structural unit (B1), the mechanical strength can be improved while maintaining the colorless and transparent properties of the obtained polyimide resin.

[0066] The ratio of structural unit (B1) to structural unit B is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, and even more preferably 50 mol% or more.

[0067] In particular, from the viewpoint of improving the elongation of the obtained polyimide film, it is even more preferable to have 70 mol% or more, and even more preferably 90 mol% or more.

[0068] Furthermore, there is no specific upper limit to the proportion of structural unit (B1), which is 100 mol% or less. Structural unit B may also consist solely of structural unit (B1).

[0069] For the polyimide resin of the present invention, without impairing the effects of the present invention, structural unit B may also contain structural units derived from diamines other than those shown in the general formula (b1) above, as structural units other than the above-described structural unit (B1).

[0070] As diamines other than those shown in the general formula (b1) above, there are no particular limitations, and examples include 3,5-diaminobenzoic acid (3,5-DABA), bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS-M), 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 1,4-phenyldiamine, 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... Aromatic diamines such as (4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzoylaniline, 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 organosilicon diamines. They can be used alone or in combination of two or more.

[0071] From the viewpoint of high strength and improved deformation recovery at high temperatures, at least one of the following is preferably selected from the group consisting of 3,5-diaminobenzoic acid (3,5-DABA), bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS-M) and 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA).

[0072] It should be noted that, in this specification, aromatic diamines refer to diamines containing one or more aromatic rings, aliphatic diamines refer to diamines that do not contain aromatic rings, and alicyclic diamines refer to aliphatic diamines containing one or more alicyclic rings.

[0073] [Properties of polyimide resins, etc.]

[0074] 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 5,000 to 100,000. It should be noted that the number-average molecular weight of the polyimide resin can be determined by methods such as gel filtration chromatography.

[0075] The polyimide resin of the present invention may also be mixed with various additives without impairing the effects of the present invention. Examples of additives include antioxidants, light stabilizers, surfactants, flame retardants, plasticizers, and polymeric compounds other than the aforementioned polyimide resin.

[0076] Examples of polymer compounds include polyimides other than the polyimide resin of this invention, such as polycarbonate, polystyrene, polyamide, polyamide-imide, polyethylene terephthalate, polyester, polyethersulfone, polycarboxylic acid, polyacetal, polyphenylene ether, polysulfone, polybutene, polypropylene, polyacrylamide, and polyvinyl chloride.

[0077] [Manufacturing method of polyimide resin]

[0078] The polyimide resin of the present invention can be manufactured by reacting a tetracarboxylic acid component comprising a compound providing the aforementioned structural unit (A1) and a compound providing structural unit (A2) with a diamine component comprising a compound providing structural unit (B1).

[0079] Examples of compounds providing the structural unit (A1) include those represented by formula (a1), but are not limited thereto; derivatives thereof may also be derived from the same structural unit. Examples of such derivatives include tetracarboxylic acids and alkyl esters of tetracarboxylic dianhydrides corresponding to those represented by formula (a1). The compound represented by formula (a1) (i.e., dianhydride) is preferred as the compound providing the structural unit (A1).

[0080] Similarly, as compounds providing the structural unit (A2), examples include aliphatic tetracarboxylic dianhydrides, preferably alicyclic tetracarboxylic dianhydrides, and more preferably compounds shown in formulas (a2-1), (a2-2), or (a2-3), but these are not limited to these, and derivatives thereof may also be provided within the range of providing the same structural unit. As derivatives of the compounds shown in formulas (a2-1), (a2-2), or (a2-3), examples include tetracarboxylic acids and alkyl esters of the tetracarboxylic acids corresponding to the tetracarboxylic dianhydrides shown in formulas (a2-1), (a2-2), or (a2-3). As compounds providing the structural unit (A2), compounds shown in formulas (a2-1), (a2-2), or (a2-3) (i.e., dianhydrides) are preferred.

[0081] For the tetracarboxylic acid component, it is preferred to contain 30 to 90 mol%, more preferably 40 to 90 mol%, further preferably 50 to 90 mol%, and even more preferably 50 to 80 mol% of a compound that provides the structural unit (A1).

[0082] For the tetracarboxylic acid component, it is preferred to contain 10 to 70 mol%, more preferably 10 to 60 mol%, further preferably 10 to 50 mol%, and even more preferably 20 to 50 mol% of a compound that provides the structural unit (A2).

[0083] In all tetracarboxylic acid components, the total content ratio of the compound providing structural unit (A1) to the compound providing structural unit (A2) is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more. There is no particular upper limit to the total content ratio of the compound providing structural unit (A1) to the compound providing structural unit (A2), but it is 100 mol% or less. The tetracarboxylic acid component may also consist solely of the compound providing structural unit (A1) and the compound providing structural unit (A2).

[0084] From the viewpoint of improving mechanical properties, colorless transparency, and deformation recovery, the molar ratio [(A1) / (A2)] of the compound providing structural unit (A1) to the compound providing structural unit (A2) in the tetracarboxylic acid component is preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 90 / 10, further preferably 40 / 60 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0085] In particular, from the viewpoint of improving deformation recovery at high temperatures, 40 / 60 to 80 / 20 is preferred, 40 / 60 to 70 / 30 is more preferred, and 40 / 60 to 60 / 40 is even more preferred.

[0086] For a tetracarboxylic acid component, it may include compounds other than those providing structural unit (A1) and those providing structural unit (A2). Examples of such compounds include the aforementioned aromatic tetracarboxylic acid dianhydrides and their derivatives (tetracarboxylic acid, alkyl esters of tetracarboxylic acid, etc.).

[0087] The tetracarboxylic acid component may contain one or more compounds (i.e., compounds other than those that provide structural units (A1) and (A2)).

[0088] Examples of compounds providing the structural unit (B1) include those shown in formula (b1), but are not limited thereto; derivatives thereof may also be provided within the range of compounds providing the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamine shown in formula (b1). The compound shown in formula (b1) (i.e., the diamine) is preferred as the compound providing the structural unit (B1).

[0089] The diamine component preferably comprises 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, and even more preferably 50 mol% or more of a compound that provides the structural unit (B1). Particularly from the viewpoint of improving the elongation of the obtained polyimide film, it is even more preferable to include 70 mol% or more, and even more preferably 90 mol% or more of a compound that provides the structural unit (B1). Furthermore, the upper limit 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 solely of the compound providing the structural unit (B1).

[0090] The diamine component may include compounds other than those that provide the structural unit (B1). Examples of such compounds include the aromatic diamines, alicyclic diamines and aliphatic diamines, modified organosilicon diamines and their derivatives (such as diisocyanates).

[0091] The diamine component may contain one or more compounds (i.e., compounds other than those that provide the structural unit (B1)).

[0092] When manufacturing the polyimide resin of the present invention, the ratio of the tetracarboxylic acid component to the diamine component is preferably 0.9 to 1.1 moles of diamine component relative to 1 mole of tetracarboxylic acid component.

[0093] When manufacturing the polyimide resin of the present invention, in addition to the aforementioned tetracarboxylic acid component and diamine component, a capping agent may also be used. Monoamines or dicarboxylic acids are preferred as capping agents. The amount of the capping agent added is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, relative to 1 mol of the tetracarboxylic acid component. 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, and 4-methylaniline. Among these, benzylamine and aniline are more preferred. As a dicarboxylic acid capping agent, a dicarboxylic acid is preferred, and a portion of it may also be ring-closed. 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, and 4-cyclohexene-1,2-dicarboxylic acid. Among these, phthalic acid and phthalic anhydride are more preferred.

[0094] There are no particular restrictions on the method for reacting the aforementioned tetracarboxylic acid component with the diamine component; known methods may be used.

[0095] Specific reaction methods can be exemplified as follows: Method (1), a tetracarboxylic acid component, a diamine component, and a reaction solvent are added to a reactor and stirred at 10-110°C for 0.5-30 hours, and then the temperature is increased to carry out an imidization reaction; Method (2), a diamine component and a reaction solvent are added to a reactor to dissolve them, and then a tetracarboxylic acid component is added. The mixture is stirred at 10-110°C for 0.5-30 hours as needed, and then the temperature is increased to carry out an imidization reaction; Method (3), a tetracarboxylic acid component, a diamine component, and a reaction solvent are added to a reactor and the temperature is immediately increased to carry out an imidization reaction; etc.

[0096] The reaction solvent used in the manufacture of polyimide resin can be any solvent that does not hinder the imidization reaction and can dissolve the resulting polyimide resin. Examples of solvents include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0097] 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-dimethylimidazolium ketone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphoramide and hexamethylphosphonic triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, cyclohexanone, and methylcyclohexanone; amine solvents such as methylpyridine and pyridine; and ester solvents such as (2-methoxy-1-methylethyl)acetate.

[0098] 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, and 3,5-xylenol.

[0099] Specific examples of ether-based 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.

[0100] In addition, specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.

[0101] Among the above-mentioned reaction solvents, amide-based solvents or lactone-based solvents are preferred. Furthermore, the above-mentioned reaction solvents can be used alone or in combination of two or more.

[0102] In the imidization reaction, it is preferable to use a Dean-Stark water separator or similar device to remove water generated during manufacturing while carrying out the reaction. By performing this operation, the degree of polymerization and the imidization rate can be further increased.

[0103] In the above imidization reaction, known imidization catalysts can be used. Examples of imidization catalysts include base catalysts and acid catalysts.

[0104] Examples of base catalysts include 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, and N,N-diethylaniline, as well as inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0105] In addition, examples of acid catalysts include crotonic acid, acrylic acid, trans-3-hexenediaic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. These imidization catalysts can be used alone or in combination of two or more.

[0106] From an operational point of view, the use of a base catalyst is preferred, the use of an organic base catalyst is more preferred, and the use of triethylamine is even more preferred.

[0107] When using the catalyst described above, from the viewpoints of reaction rate and gelation inhibition, the temperature of the imidization reaction is preferably 120–250°C, more preferably 160–190°C, and even more preferably 180–190°C. Furthermore, the reaction time is preferably 0.5–10 hours after the distillation of water begins.

[0108] It should be noted that the preferred temperature for the imidization reaction without a catalyst is 200–350°C.

[0109] [Polyimide varnish]

[0110] 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 comprises the polyimide resin of the present invention and an organic solvent, wherein the polyimide resin is dissolved in the organic solvent.

[0111] There are no particular limitations on the organic solvent as long as it can dissolve the polyimide resin. It is preferred to use the above-mentioned compounds alone or in combination of two or more as the reaction solvent in the manufacture of polyimide resin.

[0112] 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.

[0113] [Polyimide film]

[0114] The polyimide film of the present invention comprises the aforementioned polyimide resin. Furthermore, the polyimide film of the present invention is preferably composed of the aforementioned polyimide resin.

[0115] That is, it comprises a polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine. Structural unit A comprises a structural unit (A1) derived from the compound shown in formula (a1) and a structural unit (A2) derived from aliphatic tetracarboxylic dianhydride, and structural unit B comprises a structural unit (B1) derived from the compound shown in formula (b1).

[0116] By incorporating such a polyimide resin, the polyimide film of the present invention possesses both mechanical properties and colorless transparency, exhibiting high strength and excellent deformation recovery.

[0117] There are no particular limitations on the method for manufacturing the polyimide film of the present invention, and known methods can be used. For example, methods include: 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, onto a smooth support such as a glass plate, metal plate, or plastic, or molding it into a film and then removing solvent components such as organic solvents contained in the solution.

[0118] The aforementioned solution containing polyimide resin can also be the polyimide resin solution itself obtained by polymerization. Furthermore, at least one compound selected from the aforementioned examples of compounds used as solvents to dissolve the polyimide resin can be mixed with the aforementioned polyimide resin solution. As described above, by adjusting the solid content concentration and viscosity of the solution containing polyimide resin, the thickness of the polyimide film of the present invention can be easily controlled.

[0119] A release agent can be applied to the surface of the aforementioned support as needed. As a method for evaporating the solvent component by applying a solution containing the aforementioned polyimide resin or the aforementioned polyimide resin composition to the aforementioned support and then heating it, the following method is preferred. Specifically, it is preferable to evaporate the solvent at a temperature below 120°C to form a self-supporting film, peel the self-supporting film from the support, fix the ends of the self-supporting film, and dry it at a temperature above the boiling point of the solvent component and below 350°C to manufacture the polyimide film. Furthermore, drying under a nitrogen atmosphere is preferred. The pressure of the drying atmosphere can be reduced pressure, atmospheric pressure, or pressurized pressure.

[0120] The thickness of the polyimide film of the present invention can be suitably selected according to the application, etc., 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 1-250 μm makes practical use as a self-supporting membrane possible.

[0121] Polyimide films containing the polyimide resin of the present invention are suitable for use as films for various components such as color filters, flexible displays, semiconductor components, and optical components.

[0122] Example

[0123] The present invention will now be described in detail with reference to embodiments. However, the present invention is not limited to these embodiments in any way.

[0124] The physical properties of the polyimide films obtained in the following examples and comparative examples were determined by the methods shown below.

[0125] (1) Thin film thickness

[0126] The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

[0127] (2) Tensile strength and tensile modulus

[0128] The test was conducted according to JIS K7127 using a tensile testing machine "Strograph VG1E" manufactured by Toyo Seiki Co., Ltd.

[0129] (3) Elongation at break

[0130] The tensile elongation at break was determined according to the tensile test (determination of elongation) based on JIS K7127. Test specimens with a width of 10 mm and a thickness of 10–70 μm were used.

[0131] (4) Total transmittance (evaluation of transparency)

[0132] The measurements were performed in accordance with ASTM E313-05 using a color / turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0133] (5) Yellow Index (YI) (Evaluation of colorlessness)

[0134] The measurements were performed according to ASTM E313-05 using a color / turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0135] (6) Deformation recovery

[0136] like Figure 1 As shown in (a), a polyimide film 1 cut into pieces 10 mm wide and 100 mm long was fixed with a clamp to a radius of 3 mm and left to stand for 24 hours or 100 hours at 65°C and 90% relative humidity, or at 70°C and in a dry environment. Afterwards, the clamp was removed at 23°C and 50% relative humidity, and the film was left to stand for 170 hours. The recovery of the film was then measured. Figure 1 (b) shows the angle θ, which is used to evaluate deformation recovery. It should be noted that the smaller the measured angle, the better the deformation recovery, and the smaller the value is preferred.

[0137] [Example 1]

[0138] In a 300 mL five-necked round-bottom flask equipped with a stainless steel crescent-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark water separator device with a condenser, a thermometer, and glass end caps, 27.66 g (0.053 mol) of 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (manufactured by Seika Co., Ltd., hereinafter referred to as HFBAPP) as the diamine component, 44.8 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as GBL) as the organic solvent, and 2.70 g of triethylamine (manufactured by Kanto Chemical Corporation, hereinafter referred to as TEA) as the imidization catalyst were added. The mixture was stirred at 70 °C under a nitrogen atmosphere at 150 rpm to obtain a solution. In this reaction, 12.23 g (0.027 mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride (manufactured by JFE Chemical Co., Ltd., hereinafter referred to as BPAF), 5.98 g (0.027 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd., hereinafter referred to as HPMDA), and 24.1 g of GBL were added simultaneously. The mixture was then heated in a covered heater, raising the temperature of the reaction system to 190°C over approximately 20 minutes. The components removed by distillation were collected, the rotation speed was adjusted according to the increase in viscosity, and the temperature of the reaction system was maintained at 190°C. The mixture was then refluxed for 2 hours to obtain a polyimide solution. Subsequently, after the temperature in the reaction system was cooled to 120°C, N,N-dimethylacetamide (manufactured by Mitsubishi Gas Chemical Co., Ltd., hereinafter referred to as DMAC) was added to achieve the specified solid component concentration. The mixture was then stirred for approximately 3 hours to homogenize the mixture, resulting in a polyimide varnish (A) with a solid component concentration of 20.0% by mass.

[0139] Next, polyimide varnish (A) was coated onto a PET substrate and held at 60°C for 20 minutes, 80°C for 20 minutes, and 100°C for 30 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting, transparent, one-time dried film. This film was then fixed to a stainless steel frame and dried at 220°C in air for 20 minutes to remove the solvent, yielding a polyimide film. The results of the physical property measurements and evaluations are shown in Table 1.

[0140] [Example 2]

[0141] The amount of HFBAPP was changed to 24.25 g (0.047 mol), and 1.78 g (0.012 mol) of 3,5-diaminobenzoic acid (manufactured by Nippon Junya Ryohin Co., Ltd., hereinafter 3,5-DABA) was added. The amounts of TEA, BPAF, HPMDA, and TEA were changed to 0.296 g, BPAF, and HPMDA to 13.40 g (0.029 mol). Otherwise, a polyimide varnish (B) with a solid content of 15.0% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (B), a polyimide film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0142] [Example 3]

[0143] The amount of HFBAPP was changed to 14.58 g (0.028 mol), and 12.16 g (0.028 mol) of bis[4-(3-aminophenoxy)phenyl]sulfone (manufactured by Seika Corporation, hereinafter referred to as BAPS-M) was added. The amount of TEA was changed to 0.296 g, the amount of BPAF was changed to 12.89 g (0.028 mol), and the amount of HPMDA was changed to 6.31 g (0.028 mol). Otherwise, a polyimide varnish (C) with a solid content concentration of 18.5% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (C), a film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0144] [Example 4]

[0145] The amount of HFBAPP was changed to 19.15 g (0.037 mol), and 12.42 g (0.037 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (manufactured by ChinaTech Chemical (Taijin) Co., Ltd., hereinafter referred to as 6FODA) was added. The amount of TEA was changed to 0.296 g, the amount of BPAF was changed to 16.93 g (0.037 mol), and the amount of HPMDA was changed to 8.28 g (0.037 mol). Otherwise, a polyimide varnish (D) with a solid content concentration of 18.5% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (D), a film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0146] [Example 5]

[0147] The amounts of HFBAPP were changed to 12.08 g (0.023 mol), 6FODA to 18.28 g (0.054 mol), BPAF to 17.80 g (0.039 mol), and HPMDA to 8.70 g (0.039 mol). Otherwise, a polyimide varnish (E) with a solids content of 18.5% by mass was obtained using the same method as in Example 4. A film was obtained using the obtained polyimide varnish (E) using the same method as in Example 1. The results of the physical property measurements and evaluations are shown in Table 1.

[0148] [Example 6]

[0149] The amounts of HFBAPP were changed to 18.19 g (0.035 mol), 6FODA to 11.79 g (0.035 mol), BPAF to 22.51 g (0.049 mol), and HPMDA to 4.72 g (0.021 mol). Otherwise, a polyimide varnish (F) with a solids content of 18.5% by mass was obtained using the same method as in Example 4. A film was obtained using the obtained polyimide varnish (F) using the same method as in Example 1. The results of the physical property measurements and evaluations are shown in Table 1.

[0150] [Example 7]

[0151] The amount of HFBAPP was changed to 33.49 g (0.065 mol), the amount of BPAF was changed to 14.81 g (0.032 mol), HPMDA was not used, and 12.42 g (0.032 mol) of norbornane-2-spirocyclic-α-cyclopentanone-α'-spirocyclic-2”-norbornane-5,5”,6,6”-tetracarboxylic acid dianhydride (manufactured by JXTG Energy Co., Ltd., hereinafter referred to as CpODA) was added. Otherwise, a polyimide varnish (G) with a solid content concentration of 20.0% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (G), a film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0152] [Comparative Example 1]

[0153] The amounts of HFBAPP were changed to 30.52 g (0.059 mol), TEA to 0.298 g, and BPAF to 26.98 g (0.059 mol). HPMDA was not used. Otherwise, a polyimide varnish (H) with a solid content of 18.5% by mass was obtained using the same method as in Example 1. A film was obtained using the obtained polyimide varnish (H) using the same method as in Example 1. The results of the physical property measurements and evaluations are shown in Table 1.

[0154] [Comparative Example 2]

[0155] The amount of HFBAPP was changed to 39.23 g (0.076 mol), the amount of 3,5-DABA was changed to 2.88 g (0.019 mol), BPAF was not used, and the amount of HPMDA was changed to 21.20 g (0.095 mol). Otherwise, a polyimide varnish with a solid content of 20% by mass (I) was prepared by the same method as in Example 2. Using the obtained polyimide varnish (I), a film was obtained by the same method as in Example 1.

[0156] [Comparative Example 3]

[0157] Without using HFBAPP, 29.81 g (0.093 mol) of 2,2'-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Kogyo Co., Ltd., hereinafter referred to as TFMB) was added. The amounts of TEA, BPAF, and HPMA were changed to 0.471 g, BPAF to 21.34 g (0.047 mol), and HPMA to 10.43 g (0.047 mol). Otherwise, a polyimide varnish (J) with a solid content concentration of 20.0% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (J), a film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0158] [Comparative Example 4]

[0159] The amount of HFBAPP was changed to 29.96 g (0.058 mol), and 8.22 g (0.058 mol) of 1,4-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., hereinafter referred to as 1,4-BACT) was added. BPAF was not used, and the amount of HPMDA was changed to 25.91 g (0.116 mol). Otherwise, a polyimide varnish (K) with a solid content concentration of 20.0% by mass was obtained by the same method as in Example 1. Using the obtained polyimide varnish (K), a film was obtained by the same method as in Example 1. The results of the physical property determination and evaluation are shown in Table 1.

[0160] [Comparative Example 5]

[0161] The amount of HFBAPP was changed to 24.64 g (0.048 mol), the amount of TEA was changed to 0.481 g, and 17.41 g (0.048 mol) of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (manufactured by Wakayama Seika Kogyo Co., Ltd., hereinafter referred to as DABPAF) was added. Without using BPAF, the amount of HPMDA was changed to 21.31 g (0.095 mol). Otherwise, a polyimide varnish (L) with a solid content concentration of 20.0% by mass was obtained using the same method as in Example 1. A film was obtained using the obtained polyimide varnish (L) using the same method as in Example 1. The results of the physical property measurements and evaluations are shown in Table 1.

[0162] [Table 1]

[0163] Table 1

[0164]

[0165] As shown in Table 1, the polyimide films of Examples 1 to 7 possess both mechanical properties and colorless transparency. Although they have high strength, they exhibit excellent deformation recovery under any conditions, including high humidity and dry conditions.

Claims

1. A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, Structural unit A comprises a structural unit (A1) derived from the compound shown in formula (a1) below and a structural unit (A2) derived from an aliphatic tetracarboxylic dianhydride; structural unit B comprises a structural unit (B1) derived from the compound shown in formula (b1) below. The proportion of the structural unit (B1) to the structural unit B is 20-90 mol%.

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

3. The polyimide resin according to claim 1 or 2, wherein, The structural unit (A2) is selected from at least one of the following groups: structural unit (A2-1) derived from the compound shown in formula (a2-1), structural unit (A2-2) derived from the compound shown in formula (a2-2), and structural unit (A2-3) derived from the compound shown in formula (a2-3).

4. The polyimide resin according to claim 1 or 2, wherein, The ratio of the structural unit (B1) to the structural unit B is 30 to 90 moles.

5. The polyimide resin according to claim 1 or 2, wherein, The ratio of the structural unit (A1) to the structural unit A is 50 to 90 moles.

6. The polyimide resin according to claim 1 or 2, wherein, The structural unit (A2) is derived from the structural unit (A2-2) of the compound shown in the following formula (a2-2).

7. A polyimide varnish, which is formed by dissolving the polyimide resin according to any one of claims 1 to 6 in an organic solvent.

8. A polyimide film comprising the polyimide resin according to any one of claims 1 to 6.

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