Polyimide resin composition, polyimide precursor composition, varnish, and polyimide film

Abstract

A polyimide resin composition containing: a polyimide having a repeating unit represented by formula (1); and at least one compound selected from the group consisting of compounds represented by general formulas (2-1), (2-2), (2-3) and (2-4). (In the formulas, X1 is at least one tetravalent group having an aromatic ring or an alicyclic structure having a norbornane skeleton, X is a single bond, -NHCO-, -CONH-, -COO- or -OCO, R1 and R2 are hydrogen, a C1-6 alkyl group, a phenyl group, or a C1-6 aminoalkyl group, and R3 is a C1-6 alkyl group.)

Description

[Technical Field]

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

[0002] Polyimide resins have excellent mechanical properties and heat resistance, and various applications in fields such as electrical and electronic components are being considered. For example, there is a desire to replace the glass substrates used in image display devices such as liquid crystal displays and OLED displays with polyimide film substrates. Therefore, polyimide resins that meet the performance requirements for optical materials are being developed. However, in recent years, the increasing sophistication of electronic devices has created a need for electronic components to simultaneously satisfy various performance requirements. Therefore, attempts have been made to add new properties to or enhance the inherent properties of polyimide resins used in displays by blending various additives.

[0003] For example, Patent Document 1 discloses a resin composition containing a polyimide precursor containing structural units derived from 2,2'-bis(trifluoromethyl)benzidine, a silicone surfactant, and an organic solvent, with the aim of reducing color unevenness and residual stress. Furthermore, Patent Document 2 discloses a substrate for flexible devices that contains polyimide with a 5% thermal decomposition temperature of 350°C or higher and a compound having a chemical structure of -Si(OH)3 with a functional group, with the aim of preventing film thickness variations and device malfunctions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 147958 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-225638 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, polyimide films are expected to replace glass substrates used in image display devices. When manufacturing image display devices, for example, in the TFT process, heat treatment is performed on polyimide with an inorganic film laminated thereon. Outgassing from the polyimide accumulates between the polyimide and the inorganic film, which can cause yellowing. Therefore, polyimide films are required to have no color change due to heat treatment on the laminated inorganic film. However, it is difficult to achieve both heat resistance and prevention of yellowing. Even if heat resistance is improved by incorporating additives, it has been difficult to prevent yellowing. Furthermore, to achieve colorless transparency in polyimides themselves, aliphatic diamines or fluorine-containing diamines are generally used to suppress the formation of intermolecular or intramolecular charge-transfer complexes. However, under harsh conditions, such as temperatures of 350°C or higher used in the TFT manufacturing process for display manufacturing, aliphatic diamines lack the rigidity of aromatic diamines and are therefore less likely to exhibit heat resistance. Furthermore, fluorine-containing diamines also suffer from the problem of yellowing at high temperatures. Therefore, there has been a demand for polyimide films that exhibit excellent heat resistance and minimal color change after heat treatment. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyimide resin composition and polyimide film which have excellent heat resistance and little change in hue after heat treatment, as well as a polyimide precursor composition and varnish which can provide a polyimide film which has excellent heat resistance and little change in hue after heat treatment. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by a polyimide resin composition containing a specific fluorinated diamine, a polyimide containing repeating units derived from a tetracarboxylic acid having a specific alicyclic structure or an aromatic ring, and a specific silane compound, and have thus completed the present invention.

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

[17] . [1] A polyimide resin composition comprising a polyimide having a repeating unit represented by the following general formula (1) and at least one silane compound selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4): [ka] (In formula (1), X 1 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, -COO-, and -OCO-. 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. 3 is an alkyl group having 1 to 6 carbon atoms. [2] The polyimide resin composition according to [1] above, wherein the repeating unit represented by the general formula (1) is a repeating unit represented by the following general formula (1-2): [ka] (In formula (1-2), X 1 is a tetravalent group having an alicyclic structure or an aromatic ring having at least one norbornane skeleton, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, -COO-, and -OCO-. [3] The polyimide resin composition according to [1] or [2] above, wherein X in the formula (1) is a single bond. [4] X in the formula (1) 1is at least one selected from the group consisting of the following formula (3), the following formula (4), the following formula (5), the following formula (6), and the following formula (7): [ka] (In formula (5), W is at least one selected from the group consisting of a single bond and an organic group having 1 to 16 carbon atoms. In formula (6), Z is at least one selected from the group consisting of a single bond and an organic group having 1 to 8 carbon atoms. In formula (7), R each independently represents a methyl group or a trifluoromethyl group, m is 1 or 2, and n is an integer of 0 to 4.) [5] X in the formula (1) 1 is at least one selected from the group consisting of the following formula (8), the following formula (9), and the following formula (10): [ka] [6] The polyimide resin composition according to any one of [1] to [5] above, wherein the repeating units represented by the formula (1) account for 10 mol % or more of all repeating units of the polyimide. [7] The polyimide resin composition according to any one of [1] to [6] above, wherein the total content of the silane compounds is 10 ppm or more and 50,000 ppm or less based on the polyimide. [8] A varnish containing the polyimide resin composition according to any one of the above [1] to [7] and an organic solvent. [9] A polyimide film obtained by applying the varnish according to [8] above onto a support and heating it.

[10] The polyimide film according to [9] above, wherein the polyimide film has a glass transition temperature of 350°C or higher.

[11] A method for producing a polyimide film, comprising applying the varnish according to [8] above onto a support and heating the applied varnish.

[12] A polyimide precursor composition comprising a polyimide precursor having a repeating unit represented by the following general formula (11) and at least one silane compound selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4): [ka] (In formula (11), X 2 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-. 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. 3 is an alkyl group having 1 to 6 carbon atoms.

[13] The polyimide precursor composition according to

[12] , wherein the total content of the silane compounds is 10 ppm or more and 50,000 ppm or less based on the polyimide precursor.

[14] A varnish containing the polyimide precursor composition according to

[12] or

[13] above and an organic solvent.

[15] A polyimide film obtained by applying the varnish according to

[14] above onto a support and heating it.

[16] The polyimide film according to

[15] above, wherein the polyimide film has a glass transition temperature of 350°C or higher.

[17] A method for producing a polyimide film, comprising applying the varnish according to

[14] above onto a support and heating the applied varnish. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyimide resin composition and a polyimide film which have excellent heat resistance and little change in hue after heat treatment, as well as a polyimide precursor composition and a varnish which can give a polyimide film which have excellent heat resistance and little change in hue after heat treatment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Polyimide resin composition] The polyimide resin composition of the present invention contains a polyimide having a repeating unit represented by the following general formula (1) and at least one selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4). [ka] (In formula (1), X 1 is a tetravalent group having an alicyclic structure or aromatic ring having at least one norbornane skeleton, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-. In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. In formula (2-1), formula (2-2), formula (2-3) and formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms.

[0010] The reason why the use of the polyimide resin composition of the present invention enables the production of a polyimide film having excellent heat resistance and little change in color after heat treatment is not clear, but is thought to be as follows. The polyimide resin composition of the present invention is believed to be able to suppress side reactions or decomposition degradation of the terminals, particularly at high temperatures, by coordinating the silane compound to the polyimide terminals or by reacting the polyimide terminals with the silane compound, and further to suppress elimination of fluorine derived from the fluorine-containing diamine, thereby enabling the production of a polyimide film that is excellent in heat resistance and exhibits little change in hue after heat treatment.

[0011] <Polyimide> The polyimide contained in the polyimide resin composition of the present invention has a repeating unit represented by the following general formula (1). [ka] (In formula (1), X 1 is a tetravalent group having an alicyclic structure or an aromatic ring having at least one norbornane skeleton, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-.

[0012] In terms of heat resistance, X in the formula (1) is preferably a single bond. That is, the polyimide contained in the polyimide resin composition of the present invention preferably has a repeating unit represented by the following general formula (1-1). [ka] (In formula (1-1), X 1 is a tetravalent group having an alicyclic structure or aromatic ring having at least one norbornane skeleton.

[0013] The repeating unit represented by the general formula (1) contained in the polyimide preferably includes a repeating unit represented by the following general formula (1-2), and more preferably is a repeating unit represented by the following general formula (1-2). [ka] (In formula (1-2), X 1 is a tetravalent group having an alicyclic structure or an aromatic ring having at least one norbornane skeleton, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-.

[0014] Examples of the repeating unit represented by formula (1-2) contained in the polyimide include repeating units represented by the following formulas (1-2-1) to (1-2-5), and from the viewpoint of heat resistance, the repeating unit represented by formula (1-2-1) is preferred. That is, in the formula (1-2), X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO- and -OCO-, and from the viewpoint of heat resistance, X is preferably a single bond. [ka] (In formulas (1-2-1) to (1-2-5), X 1 is a tetravalent group having an alicyclic structure or aromatic ring having at least one norbornane skeleton.

[0015] In the formula (1), X 1 is a tetravalent group having an alicyclic structure having at least one norbornane skeleton or an aromatic ring. 1 is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride that is the raw material for the structural unit A derived from a tetracarboxylic acid dianhydride, which will be described later. Similarly, in any of the formulas (1-1), (1-2), (1-2-1), (1-2-2), (1-2-3), (1-2-4), and (1-2-5), X 1 is a tetravalent group having an alicyclic structure having at least one norbornane skeleton or an aromatic ring. 1is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride that is the raw material for the structural unit A derived from a tetracarboxylic acid dianhydride, which will be described later.

[0016] X in the formula (1) 1 is preferably at least one selected from the group consisting of the following formula (3), the following formula (4), the following formula (5), the following formula (6) and the following formula (7). [ka] (In formula (5), W is at least one selected from the group consisting of a single bond and an organic group having 1 to 16 carbon atoms. In formula (6), Z is at least one selected from the group consisting of a single bond and an organic group having 1 to 13 carbon atoms. In formula (7), each R is independently a methyl group or a trifluoromethyl group, m is 1 or 2, and n is an integer of 0 to 4.

[0017] The organic group having 1 to 16 carbon atoms for W includes an alkenyl group, a phenylene group, -NHCO-, -CONH-, -COO- and -OCO-, each of which may have a substituent. The organic group having 1 to 13 carbon atoms in Z includes an alkenyl group, a phenylene group, -NHCO-, -CONH-, -COO- and -OCO-, each of which may have a substituent.

[0018] Among these, X in the formula (1) 1 is more preferably at least one selected from the group consisting of the following formula (8), the following formula (9) and the following formula (10). [ka]

[0019] The glass transition temperature of the polyimide contained in the polyimide resin composition of the present invention is preferably 350° C. or higher, more preferably 380° C. or higher, and even more preferably 400° C. or higher. When the glass transition temperature of the polyimide is within the above range, the polyimide film obtained using the polyimide resin composition has excellent heat resistance and undergoes little change in color after heat treatment.

[0020] <Each structural unit of polyimide> The polyimide contains a repeating unit represented by the general formula (1), and the structural units that constitute the polyimide will be described below. The polyimide has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine.

[0021] (Structural unit A) The structural unit A is a structural unit derived from a tetracarboxylic dianhydride, and is at least one selected from the group consisting of structural unit (A1) derived from an alicyclic tetracarboxylic dianhydride having at least one norbornane skeleton and structural unit (A2) derived from an aromatic tetracarboxylic dianhydride. From the viewpoint of reducing hue change, structural unit (A1) is preferred. From the viewpoint of heat resistance, structural unit (A2) is preferred. It is more preferred that the structural unit A contains both the structural unit (A1) derived from an alicyclic tetracarboxylic dianhydride having at least one norbornane skeleton and the structural unit (A2) derived from an aromatic tetracarboxylic dianhydride.

[0022] Examples of tetracarboxylic dianhydrides that provide the structural unit (A1) derived from a tetracarboxylic dianhydride having at least one norbornane skeleton include compounds represented by the following formula (a1), compounds represented by the following formula (a2), and compounds represented by the following formula (a3). [ka]

[0023] The compound represented by formula (a1) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (CpODA). The compound represented by formula (a2) is 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic dianhydride (BNBDA). The compound represented by formula (a3) ​​is decahydro-1H,3H-4,10:5,9-dimethanonaphtho[2,3-c:6,7-c']difuran-1,3,6,8-tetraone (DNDA).

[0024] Of these, the compound represented by formula (a1) is preferred, and the structural unit A preferably contains a structural unit derived from the compound represented by formula (a1). By using a structural unit derived from the compound represented by formula (a1) as a structural unit of the polyimide, a polyimide film with little change in hue can be obtained.

[0025] Examples of tetracarboxylic dianhydrides that provide the structural unit (A2) derived from an aromatic tetracarboxylic dianhydride include biphenyltetracarboxylic dianhydride (BPDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenonetetracarboxylic dianhydride. Among these, from the viewpoint of achieving both heat resistance and reduced hue change, at least one selected from the group consisting of compounds represented by the following formula (a4) and compounds represented by the following formula (a5) is preferred, and the compound represented by the following formula (a4) is more preferred. That is, the structural unit A preferably contains at least one selected from the group consisting of a structural unit derived from a compound represented by the following formula (a4) and a structural unit derived from a compound represented by the following formula (a5), and more preferably contains a structural unit derived from a compound represented by the following formula (a4): [ka]

[0026] The compound represented by formula (a4) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a4s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a4a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a4i). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a4s) is preferred. [ka]

[0027] The compound represented by formula (a5) is 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). When the structural unit A contains the structural unit (A1) and the structural unit (A2), the molar ratio of the structural unit (A1) to the structural unit (A2) [(A1) / (A2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0028] When the structural unit A contains a structural unit derived from the compound represented by formula (a4), the silane compound contained in the polyimide resin composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-1), the compounds represented by general formula (2-3), and the compounds represented by general formula (2-4), more preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-3) and the compounds represented by general formula (2-4), and even more preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-3).

[0029] Furthermore, when the structural unit A contains a structural unit derived from the compound represented by formula (a5), the silane compound contained in the polyimide resin composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-2), the compounds represented by general formula (2-3), and the compounds represented by general formula (2-4), more preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-2) and the compounds represented by general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of the compounds represented by general formula (2-3).

[0030] The structural unit A may contain a structural unit other than the above structural units. The tetracarboxylic acid dianhydride that provides such a structural unit is not particularly limited, but examples include alicyclic tetracarboxylic acid dianhydrides and aliphatic tetracarboxylic acid dianhydrides that provide structural units other than the structural unit (A1). Examples of alicyclic tetracarboxylic dianhydrides that provide structural units other than the structural unit (A1) include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride. Examples of aliphatic tetracarboxylic dianhydrides that provide structural units derived from aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride. The structural unit optionally contained in the structural unit A may be one type, or two or more types. In this specification, aromatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.

[0031] (Structural unit B) The structural unit B is a structural unit derived from a diamine, and includes a structural unit (B1) derived from a compound represented by formula (b1). By including the structural unit (B1) in the structural unit B, excellent heat resistance is achieved, and particularly when combined with a silane compound, the effect of reducing yellowness is excellent. [ka] (In formula (b1), X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, COO—, and —OCO—.)

[0032] The structural unit (B1) preferably includes a structural unit (B11) derived from a compound represented by the following formula (b11). [ka]

[0033] Furthermore, the structural unit (B1) preferably includes a structural unit (B12) derived from a compound represented by the following formula (b12). [ka] (In formula (b12), X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, COO—, and —OCO—.)

[0034] The structural unit (B12) comprises at least one selected from the group consisting of a structural unit (B121) derived from a compound represented by the following formula (b121), a structural unit (B122) derived from a compound represented by the following formula (b122), and a structural unit (B123) derived from a compound represented by the following formula (b123). Of these, from the viewpoint of heat resistance, the structural unit (B121) derived from a compound represented by the following formula (b121) is preferred, and the structural unit (B121) derived from a compound represented by the following formula (b121) is more preferred. [ka]

[0035] The compound represented by formula (b121) is 2,2'-bis(trifluoromethyl)benzidine (TFMB). By including the structural unit (B1) in the structural unit B, a polyimide film that is excellent in heat resistance and exhibits little change in hue after heat treatment can be obtained.

[0036] The structural unit B may contain a structural unit other than the structural unit (B1). Diamines that provide such a structural unit are not particularly limited, but include 3,5-diaminobenzoic acid (3,5-DABA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4-aminophenyl-4-aminobenzoate (4-BAAB), 1,4-phenylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 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-propyl-2-benzophenone, 1,4 ... aromatic diamines other than the compound represented by formula (b1), such as N,N'-bis(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; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.

[0037] Of the structural units other than the structural unit (B1), it is preferable to include a structural unit (B2) derived from a compound represented by the following formula (b2). [ka] The compound represented by formula (b2) is 9,9-bis(4-aminophenyl)fluorene (BAFL). When the structural unit B contains the structural unit (B2), the molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0038] When the structural unit B includes the structural unit (B1) and the structural unit (B2), from the viewpoints of colorless transparency and heat resistance, the silane compound included in the polyimide resin composition of the present invention is preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) above, compounds represented by the general formula (2-3) above, and compounds represented by the general formula (2-4) above, more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) above and compounds represented by the general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-3).

[0039] In this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings but no aromatic rings, and aliphatic diamine means a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in the structural unit B may be one type, or two or more types.

[0040] (Polyimide manufacturing method) The polyimide contained in the polyimide resin composition of the present invention can be produced by reacting a tetracarboxylic acid component that provides structural unit A and a diamine component that provides structural unit B, which are described above in the section <Structural units of polyimide>.

[0041] 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 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.

[0043] 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, triethylenediamine, 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, a base catalyst is preferred, an organic base catalyst is more preferred, one or more selected from triethylamine and triethylenediamine is even more preferred, and triethylamine is even more preferred.

[0044] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° 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.

[0045] By the above method, a polyimide solution dissolved in a solvent is obtained. The concentration of polyimide in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass. Next, the raw materials used in this production method will be described.

[0046] [Tetracarboxylic acid component] The tetracarboxylic acid component used as a starting material in this production method contains an alicyclic tetracarboxylic acid dianhydride having at least one norbornane skeleton as a compound that provides the structural unit (A1), and an aromatic tetracarboxylic acid dianhydride as a compound that provides the structural unit (A2). Of these, preferred compounds that provide the structural unit (A1) include compounds represented by formula (a1), compounds represented by formula (a2), and compounds represented by formula (a3), with compounds represented by formula (a1) being more preferred. Furthermore, preferred compounds that provide the structural unit (A2) include compounds represented by formula (a4) and compounds represented by formula (a5), with compounds represented by formula (a4) being more preferred. When the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2) are contained, the molar ratio of the compound that provides the structural unit (A1) to the compound that provides the structural unit (A2) [(A1) / (A2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30. The tetracarboxylic acid component may contain other tetracarboxylic acid dianhydrides. Examples of other tetracarboxylic acid dianhydrides include, but are not limited to, alicyclic tetracarboxylic acid dianhydrides and aliphatic tetracarboxylic acid dianhydrides other than the compounds that provide the structural unit (A1). The tetracarboxylic acid component is not limited to tetracarboxylic dianhydride, but may be a derivative thereof. Examples of the derivative include tetracarboxylic acid and alkyl esters of the tetracarboxylic acid. Among these, tetracarboxylic dianhydride is preferred.

[0047] [Diamine component] The diamine component used as a raw material in this production method contains a compound represented by formula (b1) as a compound that provides the structural unit (B1). Among the compounds represented by formula (b1), compounds represented by formula (b11) and compounds represented by formula (b12) are preferred, and compounds represented by formula (b121) are more preferred. The diamine component may contain other diamines. The other diamines are not particularly limited, but include aromatic diamines, alicyclic diamines, and aliphatic diamines other than the compound represented by formula (b1). Among these, the compound represented by formula (b2) is preferred. When the compound represented by formula (b2) is contained, the molar ratio of the compound represented by formula (b1) to the compound represented by formula (b2) [(b1) / (b2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30. The diamine component is not limited to diamine, but may be a derivative thereof. Examples of the derivative include a diisocyanate corresponding to the diamine. Among these, diamine is preferred.

[0048] In the reaction, the ratio of the diamine component to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0049] [End-capping agent] In addition to the tetracarboxylic acid component and diamine component, a terminal blocking agent may be used in the production of the polyimide. The terminal blocking agent is preferably a monoamine or a dicarboxylic acid. The amount of the terminal blocking agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Examples of the monoamine terminal blocking agent 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 preferred. The dicarboxylic acid terminal blocking agent is preferably a dicarboxylic acid, which may be partially ring-closed. Examples include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid. Of these, phthalic acid and phthalic anhydride are more preferred.

[0050] 〔solvent〕 The solvent used in the production of the polyimide may be any solvent capable of dissolving the resulting polyimide, such as aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0051] Specific examples of aprotic solvents include amide solvents such as 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, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone; and ester solvents such as 2-methoxy-1-methylethyl acetate.

[0052] 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 solvents or lactone solvents are preferred, amide solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above reaction solvents may be used alone or in combination of two or more.

[0053] <Silane compounds> The silane compound contained in the polyimide resin composition of the present invention is at least one silane compound selected from the group consisting of compounds represented by the following general formula (2-1), compounds represented by the following general formula (2-2), compounds represented by the following general formula (2-3), and compounds represented by the following general formula (2-4). [ka] (In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. 3 is an alkyl group having 1 to 6 carbon atoms. By including the silane compound, a film having heat resistance and low yellowness can be obtained. The silane compound contained in the polyimide resin composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2), compounds represented by the general formula (2-3), and compounds represented by the general formula (2-4), more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) and compounds represented by the general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-3).

[0054] In formula (2-1), R 1 and R 2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms, and are preferably at least one selected from the group consisting of hydrogen and a phenyl group, and more preferably hydrogen. In formula (2-1), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group. In formula (2-2), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group. In formula (2-3), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably a methyl group. In formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms, and are preferably an alkyl group having 1 to 6 carbon atoms. In formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group.

[0055] The silane compound can be a commercially available product. A preferred commercially available silane compound is KBE9007N (3-isocyanatepropyltriethoxysilane, in formula (2-2), R 3 is an ethyl group), KBM9659 (tris-(trimethoxysilylpropyl) isocyanurate, 3 is a methyl group), KBM573 (N-phenyl-3-aminopropyltrimethoxysilane, 3 is a methyl group), KBE9103P (3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3 is an ethyl group), KBE903 (3-aminopropyltriethoxysilane, in formula (2-3), 3 is an ethyl group), KBM903 (3-aminopropyltrimethoxysilane, 3 is a methyl group).

[0056] The content of the silane compound relative to the polyimide is preferably 10 ppm to 50,000 ppm, more preferably 1,000 ppm to 20,000 ppm, even more preferably 2,000 ppm to 15,000 ppm, even more preferably 3,000 ppm to 12,000 ppm, and even more preferably 3,000 ppm to 8,000 ppm. By using a silane compound in this range, a film can be obtained that has heat resistance and exhibits little change in color even after heat treatment. In this specification, "ppm" refers to parts per million by mass.

[0057] The glass transition temperature of the polyimide resin composition of the present invention is preferably 350° C. or higher, more preferably 380° C. or higher, and even more preferably 400° C. or higher. When the glass transition temperature of the polyimide resin composition is in the above range, a polyimide film having excellent heat resistance and little change in color after heat treatment can be obtained.

[0058] [varnish] The varnish of the present invention contains the polyimide resin composition and an organic solvent, i.e., the polyimide, the silane compound, and an organic solvent, with the polyimide and the silane compound being dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyimide and the silane compound. However, it is preferable to use the compounds described above as solvents used in the production of polyimide, either alone or in combination of two or more. The varnish of the present invention may be the above-mentioned polyimide solution itself in which a silane compound is dissolved, or may be the polyimide solution in which a dilution solvent and a silane compound are further mixed and dissolved.

[0059] The polyimide contained in the varnish of the present invention is solvent-soluble, making it possible to produce a highly concentrated varnish that is stable at room temperature. The varnish of the present invention preferably contains 3 to 40 mass % of polyimide, more preferably 5 to 30 mass %. The viscosity of the varnish is preferably 0.1 to 100 Pa·s, more preferably 0.1 to 20 Pa·s. The viscosity of the varnish is a value measured at 25°C using an E-type viscometer. The varnish of the present invention may also contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, antifoaming agents, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film. The method for producing the varnish of the present invention is not particularly limited, and any known method can be applied. For example, the varnish can be obtained by mixing and dissolving the silane compound in the polyimide solution obtained by the above-mentioned production method, and then adding an additional solvent as necessary to adjust the concentration.

[0060] [Polyimide film and method for producing polyimide film] The polyimide film of the present invention is preferably produced using the above-mentioned varnish.

[0061] The method for producing a polyimide film using the varnish of the present invention is not particularly limited, and any known method can be used. For example, a polyimide film can be produced by applying the varnish of the present invention to a smooth support such as a glass plate, a metal plate, or a plastic plate, or by forming the varnish into a film, and then removing the solvent. That is, the polyimide film of the present invention is preferably a polyimide film obtained by applying the above-mentioned varnish to a support and heating the applied varnish, and the method for producing the polyimide film of the present invention is preferably a method of applying the above-mentioned varnish to a support and heating the applied varnish.

[0062] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. Also, it is preferably 250 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 20 μm or less. A thickness within the above range enables practical use. The thickness of the polyimide film can be easily controlled by adjusting the solid content and viscosity of the varnish.

[0063] The glass transition temperature of the polyimide film of the present invention is preferably 350° C. or higher, more preferably 380° C. or higher, and even more preferably 400° C. or higher. When the glass transition temperature of the polyimide film is in the above range, the polyimide film has excellent heat resistance and undergoes little change in color after heat treatment.

[0064] The polyimide film of the present invention is suitably used as a film for various components such as color filters, flexible displays, semiconductor components, optical components, etc. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays.

[0065] [Polyimide precursor composition] The polyimide precursor composition of the present invention contains a polyimide precursor having a repeating unit represented by the following general formula (11) and at least one silane compound selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4). [ka] (In formula (11), X 2 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-. In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. In formula (2-1), formula (2-2), formula (2-3) and formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms.

[0066] In addition to obtaining a polyimide film using the polyimide resin composition as described above, a polyimide film having excellent heat resistance and little change in color after heat treatment can also be obtained by imidizing the polyimide precursor composition of the present invention.

[0067] <Polyimide precursor> The polyimide precursor contained in the polyimide precursor composition of the present invention has a repeating unit represented by the following general formula (11). [ka] (In formula (11), X 2is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-.

[0068] In terms of heat resistance, X in the formula (11) is preferably a single bond. That is, the polyimide precursor contained in the polyimide resin composition of the present invention preferably has a repeating unit represented by the following general formula (11-1). [ka] (In formula (11), X 2 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0069] The repeating unit represented by the general formula (11) contained in the polyimide preferably includes a repeating unit represented by the following general formula (11-2), and more preferably is a repeating unit represented by the following general formula (11-2). [ka] (In formula (11-2), X 2 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-.

[0070] Examples of the repeating unit represented by formula (11-2) contained in the polyimide include repeating units represented by the following formulas (11-2-1) to (11-2-5), and from the viewpoint of heat resistance, the repeating unit represented by formula (11-2-1) is preferred. That is, in the formula (11-2), X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO- and -OCO-, and from the viewpoint of heat resistance, X is preferably a single bond. [ka] (In formulas (11-2-1) to (11-2-5), X 2 is a tetravalent group having at least one alicyclic structure or aromatic ring having a norbornane skeleton, and R 4 and R 5 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0071] In the formula (11), X 2 is a tetravalent group having an alicyclic structure having at least one norbornane skeleton or an aromatic ring. 2 is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride that is the raw material for the structural unit AA derived from a tetracarboxylic acid dianhydride, which will be described later. Similarly, in any of the formulas (11-1), (11-2), (11-2-1), (11-2-2), (11-2-3), (11-2-4), and (11-2-5), X 2 is a tetravalent group having an alicyclic structure having at least one norbornane skeleton or an aromatic ring. 2 is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride that is the raw material for the structural unit AA derived from a tetracarboxylic acid dianhydride, which will be described later.

[0072] X in the formula (11) 2is preferably at least one selected from the group consisting of the following formula (3), the following formula (4), the following formula (5), the following formula (6) and the following formula (7). [ka] (In formula (5), W is at least one selected from the group consisting of a single bond and an organic group having 1 to 16 carbon atoms. In formula (6), Z is at least one selected from the group consisting of a single bond and an organic group having 1 to 13 carbon atoms. In formula (7), each R is independently a methyl group or a trifluoromethyl group, m is 1 or 2, and n is an integer of 0 to 4.

[0073] The organic group having 1 to 16 carbon atoms for W includes an alkenyl group, a phenylene group, -NHCO-, -CONH-, -COO- and -OCO-, each of which may have a substituent. The organic group having 1 to 13 carbon atoms in Z includes an alkenyl group, a phenylene group, -NHCO-, -CONH-, -COO- and -OCO-, each of which may have a substituent.

[0074] Among these, X in the formula (11) 2 is more preferably at least one selected from the group consisting of the following formula (8), the following formula (9) and the following formula (10). [ka]

[0075] In the formula (11), R 4 and R 5 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and are preferably hydrogen.

[0076] <Each structural unit of polyimide precursor> The polyimide precursor contains a repeating unit represented by the general formula (11), and the structural units that constitute the polyimide precursor will be described below. The polyimide precursor has a structural unit AA derived from a tetracarboxylic dianhydride and a structural unit BA derived from a diamine, each of which is the same as the structural unit described above in <Structural units of polyimide>. That is, the structural unit AA derived from a tetracarboxylic dianhydride is the same as the structural unit A derived from a tetracarboxylic dianhydride, and the preferred structural units are also the same, and the structural unit BA derived from a diamine is the same as the structural unit B derived from a diamine, and the preferred structural units are also the same. These are explained in detail below.

[0077] (Structural unit AA) The structural unit AA is a structural unit derived from a tetracarboxylic dianhydride, and is at least one selected from the group consisting of the structural unit (AA1) derived from an alicyclic tetracarboxylic dianhydride having at least one norbornane skeleton and the structural unit (AA2) derived from an aromatic tetracarboxylic dianhydride. From the viewpoint of reducing hue change, the structural unit (AA1) is preferred. From the viewpoint of heat resistance, the structural unit (AA2) is preferred. It is more preferred that the structural unit AA contains both the structural unit (AA1) derived from an alicyclic tetracarboxylic dianhydride having at least one norbornane skeleton and the structural unit (AA2) derived from an aromatic tetracarboxylic dianhydride.

[0078] Examples of tetracarboxylic dianhydrides that provide the structural unit (AA1) derived from a tetracarboxylic dianhydride having at least one norbornane skeleton include compounds represented by the following formula (a1), compounds represented by the following formula (a2), and compounds represented by the following formula (a3). [ka]

[0079] The compound represented by formula (a1) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (CpODA). The compound represented by formula (a2) is 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic dianhydride (BNBDA). The compound represented by formula (a3) ​​is decahydro-1H,3H-4,10:5,9-dimethanonaphtho[2,3-c:6,7-c']difuran-1,3,6,8-tetraone (DNDA).

[0080] Of these, the compound represented by formula (a1) is preferred, and the structural unit AA preferably contains a structural unit derived from the compound represented by formula (a1). By using a structural unit derived from the compound represented by formula (a1) as a structural unit of the polyimide precursor, a polyimide film with little change in hue can be obtained.

[0081] Examples of tetracarboxylic dianhydrides that provide the structural unit (AA2) derived from an aromatic tetracarboxylic dianhydride include biphenyltetracarboxylic dianhydride (BPDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenonetetracarboxylic dianhydride. Among these, from the viewpoint of achieving both heat resistance and reduced hue change, at least one selected from the group consisting of compounds represented by the following formula (a4) and compounds represented by the following formula (a5) is preferred, and the compound represented by the following formula (a4) is more preferred. That is, the structural unit AA preferably contains at least one selected from the group consisting of a structural unit derived from a compound represented by the following formula (a4) and a structural unit derived from a compound represented by the following formula (a5), and more preferably contains a structural unit derived from a compound represented by the following formula (a4): [ka]

[0082] The compound represented by formula (a4) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a4s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a4a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a4i). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a4s) is preferred. [ka]

[0083] The compound represented by formula (a5) is 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). When the structural unit A contains the structural unit (AA1) and the structural unit (AA2), the molar ratio of the structural unit (AA1) to the structural unit (AA2) [(AA1) / (AA2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0084] When the structural unit AA contains a structural unit derived from the compound represented by formula (a4), the silane compound contained in the polyimide precursor composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-1), compounds represented by general formula (2-3), and compounds represented by general formula (2-4), more preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-3) and compounds represented by general formula (2-4), and even more preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-3).

[0085] Furthermore, when the structural unit AA contains a structural unit derived from the compound represented by formula (a5), the silane compound contained in the polyimide precursor composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-2), compounds represented by general formula (2-3), and compounds represented by general formula (2-4), more preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-2) and compounds represented by general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of compounds represented by general formula (2-3).

[0086] The structural unit AA may contain a structural unit other than the structural unit described above. The tetracarboxylic acid dianhydride that provides such a structural unit is not particularly limited, but examples include alicyclic tetracarboxylic acid dianhydrides and aliphatic tetracarboxylic acid dianhydrides that provide structural units other than the structural unit (AA1). Examples of alicyclic tetracarboxylic dianhydrides that provide structural units other than the structural unit (AA1) include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride. Examples of aliphatic tetracarboxylic dianhydrides that provide structural units derived from aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride. The structural unit AA may optionally contain one type of structural unit, or two or more types of structural units. In this specification, aromatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.

[0087] (Block BA) The structural unit BA is a structural unit derived from a diamine, and includes a structural unit (BA1) derived from a compound represented by formula (b1). By including the structural unit (BA1) in the structural unit BA, excellent heat resistance is achieved, and particularly when combined with a silane compound, the effect of reducing yellowness is excellent. [ka] (In formula (b1), X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, COO—, and —OCO—.)

[0088] The structural unit (BA1) preferably includes a structural unit (BA11) derived from a compound represented by the following formula (b11). [ka]

[0089] Furthermore, the structural unit (BA1) preferably includes a structural unit (BA12) derived from a compound represented by the following formula (b12). [ka] (In formula (b12), X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, COO—, and —OCO—.)

[0090] The structural unit (BA12) comprises at least one selected from the group consisting of a structural unit (BA121) derived from a compound represented by the following formula (b121), a structural unit (BA122) derived from a compound represented by the following formula (b122), and a structural unit (BA123) derived from a compound represented by the following formula (b123). Of these, from the viewpoint of heat resistance, the structural unit (BA121) derived from a compound represented by the following formula (b121) is preferred, and the structural unit (BA121) derived from a compound represented by the following formula (b121) is more preferred. [ka]

[0091] The compound represented by formula (b121) is 2,2'-bis(trifluoromethyl)benzidine (TFMB). By including the structural unit (BA1) in the structural unit BA, it is possible to obtain a polyimide film that is excellent in heat resistance and exhibits little change in hue after heat treatment.

[0092] The structural unit BA may contain a structural unit other than the structural unit (BA1). Diamines that provide such a structural unit include, but are not limited to, 3,5-diaminobenzoic acid (3,5-DABA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4-aminophenyl-4-aminobenzoate (4-BAAB), 1,4-phenylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 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-propyl-2-benzophenone, 1,4-diaminobenzanilide ... aromatic diamines other than the compound represented by formula (b1), such as N,N'-bis(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; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.

[0093] Of the structural units other than the structural unit (BA1), it is preferable to include a structural unit (BA2) derived from a compound represented by the following formula (b2). [ka] The compound represented by formula (b2) is 9,9-bis(4-aminophenyl)fluorene (BAFL). When the structural unit BA contains the structural unit (BA2), the molar ratio of the structural unit (BA1) to the structural unit (BA2) [(BA1) / (BA2)] is preferably 50 / 50 to 90 / 10, more preferably 50 / 50 to 80 / 20, and even more preferably 50 / 50 to 70 / 30.

[0094] When the structural unit BA includes the structural unit (BA1) and the structural unit (BA2), from the viewpoints of colorless transparency and heat resistance, the silane compound included in the polyimide precursor composition of the present invention is preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) above, compounds represented by the general formula (2-3) above, and compounds represented by the general formula (2-4) above, more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) above and compounds represented by the general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-3).

[0095] In this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings but no aromatic rings, and aliphatic diamine means a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit BA may optionally contain one type of structural unit, or two or more types of structural units.

[0096] (Method of producing polyimide precursor) The polyimide precursor contained in the polyimide precursor composition of the present invention can be produced by reacting a tetracarboxylic acid component that provides the structural unit AA and a diamine component that provides the structural unit BA. That is, it can be produced by reacting a tetracarboxylic acid component that provides the structural unit A and a diamine component that provides the structural unit B, as explained in the section <Structural Units of Polyimide>. The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0097] In the present production method, the method for reacting the tetracarboxylic acid component with the diamine component is not particularly limited, and any known method can be used. Specific examples of the reaction method include a method in which a tetracarboxylic acid component, a diamine component, a solvent, and, if necessary, an end-capping agent are charged into a reactor and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out at 80°C or less, the molecular weight of the polyimide precursor does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so that the polyimide precursor, which is a polyamic acid, can be produced stably.

[0098] By the above method, a polyimide precursor solution having a polyamic acid structure dissolved in a solvent can be obtained. The concentration of the polyimide precursor in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0099] <Silane Compound (Silane Compound Contained in Polyimide Precursor Composition)> The silane compound contained in the polyimide precursor composition of the present invention is at least one silane compound selected from the group consisting of compounds represented by the following general formula (2-1), compounds represented by the following general formula (2-2), compounds represented by the following general formula (2-3), and compounds represented by the following general formula (2-4). [ka] (In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. 3 is an alkyl group having 1 to 6 carbon atoms. By including the silane compound, a film having heat resistance and low yellowness can be obtained. The silane compound contained in the polyimide precursor composition of the present invention is, from the viewpoints of colorless transparency and heat resistance, preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2), compounds represented by the general formula (2-3), and compounds represented by the general formula (2-4), more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-2) and compounds represented by the general formula (2-3), and even more preferably at least one silane compound selected from the group consisting of compounds represented by the general formula (2-3).

[0100] In formula (2-1), R 1 and R 2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms, and are preferably at least one selected from the group consisting of hydrogen and a phenyl group, and more preferably hydrogen. In formula (2-1), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group. In formula (2-2), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group. In formula (2-3), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably a methyl group. In formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms, and are preferably an alkyl group having 1 to 6 carbon atoms. In formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms, and is preferably at least one selected from the group consisting of a methyl group and an ethyl group, more preferably an ethyl group.

[0101] The silane compound can be a commercially available product. A preferred commercially available silane compound is KBE9007N (3-isocyanatepropyltriethoxysilane, in formula (2-2), R 3 is an ethyl group), KBM9659 (tris-(trimethoxysilylpropyl) isocyanurate, 3 is a methyl group), KBM573 (N-phenyl-3-aminopropyltrimethoxysilane, 3 is a methyl group), KBE9103P (3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3 is an ethyl group), KBE903 (3-aminopropyltriethoxysilane, in formula (2-3), 3 is an ethyl group), KBM903 (3-aminopropyltrimethoxysilane, 3 is a methyl group).

[0102] The content of the silane compound relative to the polyimide precursor is preferably 10 ppm to 50,000 ppm, more preferably 1,000 ppm to 20,000 ppm, even more preferably 2,000 ppm to 15,000 ppm, even more preferably 3,000 ppm to 12,000 ppm, and even more preferably 3,000 ppm to 8,000 ppm. By using a silane compound in this range, a film can be obtained that has heat resistance and exhibits little change in color even after heat treatment. In this specification, "ppm" refers to parts per million by mass.

[0103] [Varnish (Varnish Containing Polyimide Precursor Composition)] The varnish of the present invention contains the polyimide precursor composition described above and an organic solvent, i.e., the polyimide precursor, the silane compound, and an organic solvent, and the polyimide precursor and the silane compound are dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyimide precursor and the silane compound. However, it is preferable to use the above-mentioned compounds as the solvent used in producing the polyimide precursor, either alone or in combination of two or more. The varnish of the present invention may be prepared by dissolving a silane compound in the above-mentioned polyimide precursor solution itself, or by further mixing the polyimide precursor solution with a dilution solvent and a silane compound and dissolving the mixture therein.

[0104] The varnish of the present invention may further contain a dehydration catalyst. Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; etc. These may be used alone or in combination of two or more.

[0105] The polyimide precursor contained in the varnish of the present invention is solvent-soluble, making it possible to produce a highly concentrated varnish that is stable at room temperature. The varnish of the present invention preferably contains 3 to 40 mass % of the polyimide precursor (polyamic acid), more preferably 5 to 30 mass %. The viscosity of the varnish is preferably 0.1 to 100 Pa·s, more preferably 0.1 to 20 Pa·s. The viscosity of the varnish is a value measured at 25°C using an E-type viscometer. The varnish of the present invention may also contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, antifoaming agents, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film. The method for producing the varnish of the present invention is not particularly limited, and any known method can be applied. For example, the varnish can be obtained by mixing and dissolving the silane compound in the solution of the polyimide precursor obtained by the above-mentioned production method, and then adding an additional solvent as necessary to adjust the concentration.

[0106] [Polyimide film and method for producing a polyimide film using a polyimide precursor composition] The polyimide film of the present invention is preferably produced using the above-mentioned varnish. The polyimide film of the present invention is obtained by imidizing the above-mentioned polyimide precursor, and therefore includes a polyimide containing a repeating unit represented by general formula (1).

[0107] The method for producing a polyimide film using the varnish of the present invention is not particularly limited, and any known method can be used. For example, the varnish of the present invention can be applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and then organic solvents such as reaction solvents and dilution solvents contained in the varnish are removed by heating to obtain a polyamic acid film, and the polyamic acid in the polyamic acid film is imidized (dehydration ring closure) by heating to produce a polyimide film. That is, the polyimide film of the present invention is preferably a film obtained by applying the aforementioned varnish to a support and heating the applied varnish, and the method for producing the polyimide film of the present invention is preferably a method of applying the aforementioned varnish to a support and heating the applied varnish.

[0108] The heating temperature when a varnish containing a polyimide precursor composition is dried to obtain a polyimide precursor (polyamic acid) film is preferably 50 to 150°C. The heating temperature when the polyimide precursor is imidized by heating is preferably 350 to 450°C, and more preferably 380 to 420°C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. By using such a temperature and time, the physical properties of the obtained polyimide film become good. Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, and a nitrogen / hydrogen mixed gas. In order to suppress discoloration of the resulting polyimide resin, nitrogen gas having an oxygen concentration of 100 ppm or less and a nitrogen / hydrogen mixed gas having a hydrogen concentration of 0.5% or less are preferred. The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[0109] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more, and is preferably 250 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 20 μm or less. The thickness of the polyimide film can be easily controlled by adjusting the solid content and viscosity of the varnish.

[0110] The glass transition temperature of the polyimide film of the present invention is preferably 350° C. or higher, more preferably 380° C. or higher, and even more preferably 400° C. or higher. When the glass transition temperature of the polyimide film is in the above range, the polyimide film has excellent heat resistance and undergoes little change in color after heat treatment.

[0111] The polyimide film of the present invention is suitably used as a film for various components such as color filters, flexible displays, semiconductor components, optical components, etc. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays. [Example]

[0112] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples in any way. The physical properties of the films obtained in the examples and comparative examples were measured by the following methods.

[0113] (1) Film thickness The film thickness was measured using a film thickness measuring device Filmetrics F20 (manufactured by Filmetrics Inc.).

[0114] (2) Total light transmittance, yellow index (YI) The total light transmittance and YI were measured in accordance with JIS K7136 and YI ASTM E313-05 (D light source, 65°) using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

[0115] (3) Evaluation of laminated film A laminated film was produced in accordance with the manufacturing process of a display for an image display device, and heat treatment was carried out, and the change in hue after the heat treatment was evaluated visually. The laminated film was produced as follows. Without peeling off the polyimide films obtained in the Examples and Comparative Examples, a 300 nm thick SiO2 film was formed on the polyimide film by sputtering, and a 1230 nm thick ITO (indium tin oxide) film was formed on top of it, followed by annealing (heating) at 400°C for 1 hour. The presence or absence of yellowing (increase in yellow color density) of the laminated film before and after annealing was visually evaluated according to the following criteria. None (no yellowing): No yellowing is observed in the laminated film before and after annealing (no change in hue) Yes (yellowing): Yellowing is observed in the laminated film before and after annealing (hue change). If there is no yellowing, there is little change in color after heat treatment, which is good.

[0116] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, as well as their abbreviations, are as follows: <Tetracarboxylic acid component> CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (manufactured by ENEOS Corporation; compound represented by formula (a1)) s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, a compound represented by formula (a4s)) BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (manufactured by JFE Chemical Corporation; compound represented by formula (a5)) <Diamine component> TFMB: 2,2'-bis(trifluoromethyl)benzidine (manufactured by Seika Corporation; compound represented by formula (b121)) BAFL: 9,9-bis(4-aminophenyl)fluorene (manufactured by JFE Chemical Corporation; compound represented by formula (b2)) <Silane compounds> KBE9007N: 3-isocyanatepropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-2), R 3 is an ethyl group) KBM9659: Tris-(trimethoxysilylpropyl) isocyanurate (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-3), R 3 is a methyl group) KBM573: N-phenyl-3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-1), R 1 is a phenyl group, R 2 is a hydrogen atom, R 3 is a methyl group) KBE9103P: 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-4), R 1 is a methyl group, R 2 is a butyl group, R 3 is an ethyl group) KBE903: 3-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-1), R 1 and R 2 is a hydrogen atom, R 3 is an ethyl group) KBM903: 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., in formula (2-1), R 1 and R 2 is a hydrogen atom, R 3 is a methyl group) TEOS: Tetraethoxysilane <Surface conditioner> BYK-378: Silicone surface conditioner (manufactured by BYK Japan Co., Ltd.)

[0117] The abbreviations for the solvents and catalysts used in the examples and comparative examples are as follows: GBL: γ-butyrolactone (Mitsubishi Chemical Corporation) TEA: Triethylamine (Kanto Chemical Co., Ltd.) TEDA: Triethylenediamine (Tokyo Chemical Industry Co., Ltd.)

[0118] Example 1 19.214 g (0.060 mol) of TFMB, 13.938 g (0.040 mol) of BAFL, and 126.903 g of GBL were placed in a 1 L five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at a system temperature of 70°C to obtain a solution. To this solution, 23.063 g (0.060 mol) of CpODA and 11.768 g (0.040 mol) of s-BPDA were added, followed by 31.726 g of GBL and 0.506 g of TEA as an imidization catalyst. The mixture was heated with a mantle heater, and the temperature in the reaction system was raised to 190°C over approximately 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190°C and refluxed for 5 hours while adjusting the rotation speed according to the increase in viscosity. Thereafter, GBL was added so that the solid content concentration became 10% by mass, and the temperature in the reaction system was cooled to 120°C, and then the mixture was further stirred for about 1 hour to be homogenized, thereby obtaining a polyimide varnish.

[0119] To 100 g of the obtained varnish, KBE9007N was added so as to be 5000 ppm relative to the polyimide, and BYK-378 was added so as to be 1000 ppm relative to the polyimide, and the mixture was stirred for 30 minutes to be homogenized, thereby obtaining a polyimide composition varnish. The resulting polyimide composition varnish was then spin-coated onto a glass plate (AGC Corporation, AN-100), held at 80°C for 20 minutes on a hot plate, and then transferred to a hot air dryer where it was heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere. The film was then heated at 400°C for 30 minutes in a nitrogen atmosphere to evaporate the solvent, yielding a polyimide film. The evaluation results are shown in Table 1. All evaluations were performed while the film was attached to the glass plate, and the results include the glass plate.

[0120] Examples 2 to 7 and Comparative Example 2 A polyimide film was obtained in the same manner as in Example 1, except that the silane compounds shown in Table 1 were used in the amounts shown in Table 1 instead of KBE9007N. The results are shown in Table 1. All evaluations were performed in the state where the film was attached to a glass plate, and the results include the glass plate.

[0121] Comparative Example 1 A polyimide film was obtained in the same manner as in Example 1, except that KBE9007N was not used. The results are shown in Table 1. All evaluations were performed in a state where the film was attached to a glass plate, and the results include the glass plate.

[0122] Example 8 17.613 g (0.055 mol) of TFMB, 15.680 g (0.045 mol) of BAFL, and 107.673 g of GBL were placed in a 1 L five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at a system temperature of 70°C to obtain a solution. To this solution, 34.594 g (0.090 mol) of CpODA and 4.584 g (0.010 mol) of BPAF were added, followed by 26.918 g of GBL and 0.506 g of TEA and 0.056 g of TEDA as imidization catalysts. The mixture was heated with a mantle heater, and the temperature in the reaction system was raised to 190°C over approximately 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190°C and refluxed for 5 hours while adjusting the rotation speed according to the increase in viscosity. Thereafter, GBL was added so that the solid content concentration became 10% by mass, and the temperature in the reaction system was cooled to 120°C, and then the mixture was further stirred for about 1 hour to be homogenized, thereby obtaining a polyimide varnish.

[0123] To 100 g of the obtained varnish, KBE9007N was added so as to be 5000 ppm relative to the polyimide, and BYK-378 was added so as to be 1000 ppm relative to the polyimide, and the mixture was stirred for 30 minutes to be homogenized, thereby obtaining a polyimide composition varnish. The resulting polyimide composition varnish was then spin-coated onto a glass plate (AGC Corporation, AN-100), held at 80°C for 20 minutes on a hot plate, and then transferred to a hot air dryer where it was heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere. The film was then heated at 400°C for 30 minutes in a nitrogen atmosphere to evaporate the solvent, yielding a polyimide film. The evaluation results are shown in Table 1. All evaluations were performed while the film was attached to the glass plate, and the results include the glass plate.

[0124] Examples 9 to 11 and Comparative Example 4 A polyimide film was obtained in the same manner as in Example 8, except that the silane compounds shown in Table 1 were used in the amounts shown in Table 1 instead of KBE9007N. The results are shown in Table 1. All evaluations were performed in the state where the film was attached to a glass plate, and the results include the glass plate.

[0125] Comparative Example 3 A polyimide film was obtained in the same manner as in Example 8, except that KBE9007N was not used. The results are shown in Table 1. All evaluations were carried out in a state where the film was attached to a glass plate, and the results include those of the glass plate.

[0126] [Table 1]

[0127] As shown in Table 1, it can be seen that the polyimide film obtained from the polyimide resin composition of the present invention has excellent heat resistance, excellent colorlessness after heat treatment, and little change in color.

Claims

1. a polyimide having a repeating unit represented by the following general formula (1); A polyimide resin composition comprising at least one silane compound selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4), The polyimide resin composition comprises a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, and the structural unit A contains both a structural unit (A1) derived from an alicyclic tetracarboxylic dianhydride having a norbornane skeleton, which is at least one selected from the group consisting of the following formula (4) and the following formula (5), and a structural unit (A2) derived from an aromatic tetracarboxylic dianhydride having an aromatic ring, which is at least one selected from the group consisting of the following formula (6) and the following formula (7). 【Chemistry 1】 (In formula (1), X 1 is at least one selected from the group consisting of the following formulas (4), (5), (6), and (7), and X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, —COO—, and —OCO—. In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. In formula (2-1), formula (2-2), formula (2-3) and formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms. 【Chemistry 2】 (In formula (5), W is at least one selected from the group consisting of a single bond and an organic group having 1 to 16 carbon atoms. In formula (6), Z is at least one selected from the group consisting of a single bond and an organic group having 1 to 13 carbon atoms. In formula (7), each R is independently a methyl group or a trifluoromethyl group, m is 1 or 2, and n is an integer of 0 to 4.

2. 2. The polyimide resin composition according to claim 1, wherein the repeating unit represented by the general formula (1) is a repeating unit represented by the following general formula (1-2): 【Transformation 3】 (In formula (1-2), X 1 is the same as above, and X is at least one selected from the group consisting of a single bond, —NHCO—, —CONH—, —COO—, and —OCO—.

3. 3. The polyimide resin composition according to claim 1, wherein X in formula (1) is a single bond.

4. X in the formula (1) 1 The polyimide resin composition according to any one of claims 1 to 3, wherein R is at least one selected from the group consisting of the following formula (8), the following formula (9), and the following formula (10): 【Chemistry 4】

5. 5. The polyimide resin composition according to claim 1, wherein the repeating unit represented by formula (1) accounts for 10 mol % or more of all repeating units of the polyimide.

6. 6. The polyimide resin composition according to claim 1, wherein the total content of the silane compounds is 10 ppm or more and 50,000 ppm or less based on the polyimide.

7. A varnish comprising the polyimide resin composition according to any one of claims 1 to 6 and an organic solvent.

8. A polyimide film obtained by applying the varnish according to claim 7 onto a support and heating the applied varnish.

9. 9. The polyimide film according to claim 8, wherein the polyimide film has a glass transition temperature of 350°C or higher.

10. A method for producing a polyimide film, comprising applying the varnish according to claim 7 onto a support and heating the applied varnish.

11. a polyimide precursor having a repeating unit represented by the following general formula (11); A polyimide precursor composition comprising at least one silane compound selected from the group consisting of a compound represented by the following general formula (2-1), a compound represented by the following general formula (2-2), a compound represented by the following general formula (2-3), and a compound represented by the following general formula (2-4), a polyimide precursor composition, the polyimide precursor having a structural unit AA derived from a tetracarboxylic dianhydride and a structural unit BA derived from a diamine, the structural unit AA containing both a structural unit (AA1) derived from an alicyclic tetracarboxylic dianhydride having a norbornane skeleton, which is at least one selected from the group consisting of the following formula (4) and the following formula (5), and a structural unit (AA2) derived from an aromatic tetracarboxylic dianhydride having an aromatic ring, which is at least one selected from the group consisting of the following formula (6) and the following formula (7): 【Transformation 5】 (In formula (11), X 2 is at least one selected from the group consisting of the following formula (4), the following formula (5), the following formula (6), and the following formula (7), and R 4 and R 5 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and X is at least one selected from the group consisting of a single bond, -NHCO-, -CONH-, COO-, and -OCO-. In formula (2-1) and formula (2-4), R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aminoalkyl group having 1 to 6 carbon atoms. In formula (2-1), formula (2-2), formula (2-3) and formula (2-4), R 3 is an alkyl group having 1 to 6 carbon atoms. 【Transformation 6】 (In formula (5), W is at least one selected from the group consisting of a single bond and an organic group having 1 to 16 carbon atoms. In formula (6), Z is at least one selected from the group consisting of a single bond and an organic group having 1 to 13 carbon atoms. In formula (7), each R is independently a methyl group or a trifluoromethyl group, m is 1 or 2, and n is an integer of 0 to 4.

12. The polyimide precursor composition according to claim 11, wherein the total content of the silane compounds is 10 ppm or more and 50,000 ppm or less based on the polyimide precursor.

13. A varnish comprising the polyimide precursor composition according to claim 11 or 12 and an organic solvent.

14. A polyimide film obtained by applying the varnish according to claim 13 onto a support and heating the applied varnish.

15. 15. The polyimide film according to claim 14, wherein the polyimide film has a glass transition temperature of 350°C or higher.

16. A method for producing a polyimide film, comprising applying the varnish according to claim 13 onto a support and heating the applied varnish.

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