Polyimide resin precursor composition and polyimide film

Abstract

Provided are a polyimide resin precursor composition capable of providing a polyimide film excellent in heat resistance and transparency even after high-temperature treatment, and a polyimide film excellent in heat resistance and transparency even after high-temperature treatment.　This polyimide resin precursor composition contains a polyimide resin precursor containing a repeating unit represented by formula (1), a silsesquioxane compound, and an organic solvent.　In formula (1), X1 and X2 are each independently a hydrogen atom, a C1-6 alkyl group or a C3-9 alkylsilyl group; A1 contains a tetravalent group represented by formula (2); B1 contains a bivalent group represented by formula (3); in formula (3), Y1 and Y2 are each independently -COO- or -OCO-; and k is 0 or 1.

Description

Polyimide resin precursor composition and polyimide film

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

[0002] Polyimide resins are being considered for various uses in fields such as electrical and electronic components. In particular, in recent years, they have been considered for use as transparent flexible substrates, taking advantage of their lightweight and flexible properties, replacing the glass substrates traditionally used in the field of display materials. To apply polyimide resins as transparent flexible substrates, they must have not only transparency but also heat resistance and mechanical strength. To meet these requirements, attempts have been made to synthesize semi-aromatic polyimides by tweaking the raw materials, tetracarboxylic acids and diamines.

[0003] For example, Patent Document 1 discloses a method for producing a polyimide by reacting 1,2,3,4-cyclobutanetetracarboxylic dianhydride with bis(4-aminophenyl)terephthalate to obtain a polyamic acid, and then imidizing the polyamic acid, with the aim of obtaining a polyimide that is colorless and transparent, has excellent heat resistance, a low linear expansion coefficient, and toughness.

[0004] JP 2010-077184 A

[0005] As mentioned above, polyimides used in the field of display materials require high transparency. Recently, polyimides have also been used in the manufacture of TFT substrates. However, for example, the process temperature for TFT device types such as LTPS (low-temperature polysilicon TFT) exceeds 400°C. Polyimides used in such applications require not only heat resistance but also transparency after exposure to high temperatures. Thus, higher heat resistance and higher transparency than conventional polyimides are required, and there has also been a demand for polyimides that exhibit high transparency after high-temperature treatment. The present invention has been made in light of these circumstances. The object of the present invention is to provide a polyimide resin precursor composition capable of producing a polyimide film that exhibits excellent heat resistance and transparency even after high-temperature treatment, and a polyimide film that exhibits excellent heat resistance and transparency even after high-temperature treatment.

[0006] The present inventors have found that the above-mentioned problems can be solved by a polyimide resin precursor composition containing a polyimide resin precursor having specific structural units and a silsesquioxane compound, and have thus completed the present invention.

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

[12] : [1] A polyimide resin precursor composition containing a polyimide resin precursor having a repeating unit represented by the following formula (1), a silsesquioxane compound, and an organic solvent: (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently -COO- or -OCO-, and k is 0 or 1.) [2] The polyimide resin precursor composition according to [1] above, wherein the mass ratio of the silsesquioxane compound to the polyimide resin precursor (silsesquioxane compound / polyimide resin precursor) is 1 / 99 to 35 / 65. [3] The polyimide resin precursor composition according to [1] above or [2] above, wherein the molecular weight of the silsesquioxane compound is 300 to 6000. [4] B 1 The polyimide resin precursor composition according to any one of [1] to [3] above, further comprising a divalent group represented by the following formula (4): [5] The polyimide resin precursor composition according to any one of [1] to [4], wherein the silsesquioxane compound is a compound represented by the following composition formula (5): [R 1 SiO 1.5 ] n (5) (In formula (5), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and n is 4 to 100. Note that n is an average value.) [6] R 1 [7] The polyimide resin precursor composition according to [5] above, wherein R contains a hydroxy group or an alkoxy group. 1[8] The polyimide resin precursor composition according to [5] or [6] above, wherein A contains an aromatic group. 1 [8] The polyimide resin precursor composition according to any one of [1] to [7] above, further comprising a tetravalent group represented by the following formula (6): [9] A polyimide film obtained by applying the polyimide resin precursor composition according to any one of [1] to [8] above onto a support and heating the composition.

[10] A method for producing a polyimide film, by applying the polyimide resin precursor composition according to any one of [1] to [8] above onto a support and heating the composition.

[11] The polyimide film according to [9] above, which is used for displays.

[12] A method for improving the transparency of a polyimide film, by adding a silsesquioxane compound to a polyimide resin precursor containing a repeating unit represented by the following formula (1), which is a raw material for the polyimide film: (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0008] According to the present invention, it is possible to provide a polyimide resin precursor composition from which a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment can be obtained, and a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment.

[0009] [Polyimide Resin Precursor Composition] The polyimide resin precursor composition of the present invention is a polyimide resin precursor composition containing a polyimide resin precursor having a repeating unit represented by the following formula (1), a silsesquioxane compound, and an organic solvent. (In formula (1), X 1 and X 2 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; A1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0010] The reason why the use of the polyimide resin precursor composition of the present invention enables the production of a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment is unclear, but it is thought to be as follows. It is believed that the polyimide resin precursor containing the repeating unit represented by formula (1) and the polyimide resin obtained therefrom have excellent compatibility with silsesquioxane compounds. Therefore, it is believed that the heat resistance of the silsesquioxane compound alone can be further improved. Furthermore, it is believed that the uniform compatibility between the polyimide resin and the silsesquioxane compound allows the transparency of the silsesquioxane compound to be exhibited, and the resulting polyimide film can have properties that combine heat resistance and transparency.

[0011] <Polyimide Resin Precursor> The polyimide resin precursor contained in the polyimide resin precursor composition of the present invention contains a repeating unit represented by the following formula (1). (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0012] The "repeating unit" in the polyimide resin precursor is an amic acid unit, an amic acid ester unit, or an amic acid silyl ester unit containing a structural unit derived from one tetracarboxylic dianhydride and a structural unit derived from one diamine. 1 and X 2are each independently at least one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, preferably at least one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom.

[0013] In formula (1), A 1 includes a tetravalent group represented by formula (2), and is preferably a tetravalent group represented by formula (2). 1 The phrase "contains a tetravalent group represented by formula (2)" means that a plurality of A 1 is present, some or all of it is a tetravalent group represented by formula (2). The tetravalent group represented by formula (2) is preferably at least one selected from the group consisting of a tetravalent group represented by formula (2s) below, a tetravalent group represented by formula (2a) below, and a tetravalent group represented by formula (2i) below, more preferably at least one selected from the group consisting of a tetravalent group represented by formula (2s) below and a tetravalent group represented by formula (2a) below, and even more preferably a tetravalent group represented by formula (2s) below. 1 By including the tetravalent group represented by formula (2), the heat resistance of the resulting polyimide film can be further improved.

[0014] A 1 From the viewpoint of obtaining a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the tetravalent group represented by formula (2) in is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0015] In formula (1), A 1 Preferably, the compound further contains a tetravalent group represented by the following formula (6): A 1 By including a tetravalent group represented by formula (6), the elongation can be further increased. 1 When A contains a tetravalent group represented by formula (6),1 In the above formula (2), the molar ratio of the tetravalent group represented by formula (2) to the tetravalent group represented by formula (6) (formula (2) / formula (6)) is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45. By using the above molar ratio, heat resistance and transparency can be further improved.

[0016] A 1 The total ratio of the tetravalent groups represented by formula (2) and the tetravalent groups represented by formula (6) is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0017] In formula (1), B 1 includes a divalent group represented by formula (3), and is preferably a divalent group represented by formula (3). 1 The phrase "contains a divalent group represented by formula (3)" means that the precursor contains a plurality of B 1 In the formula (3), when Y is present, a part or all of it is a divalent group represented by the formula (3). 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1. In formula (3), k is 0 or 1, and preferably k is 0. When k is 1, Y 1 is —COO—, and Y 2 is —OCO— or Y 1 is —OCO—, and Y 2 is preferably —COO—, and Y 1 is —OCO—, and Y 2 It is more preferred that is —COO—.

[0018] The divalent group represented by formula (3) is preferably at least one selected from the group consisting of a divalent group represented by formula (31) below, a divalent group represented by formula (32) below, and a divalent group represented by formula (33) below, more preferably at least one selected from the group consisting of a divalent group represented by formula (31) below and a divalent group represented by formula (32) below, and even more preferably a divalent group represented by formula (31) below.

[0019] B 1 From the viewpoint of obtaining a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the divalent group represented by formula (3) in is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0020] In formula (1), B 1 Preferably, the compound further contains a divalent group represented by the following formula (4): B 1 By including a divalent group represented by formula (4), the heat resistance and elongation can be further improved. 1 When a divalent group represented by formula (4) is contained in B 1 In the above formula (3), the molar ratio of the divalent group represented by formula (3) to the divalent group represented by formula (4) (formula (3) / formula (4)) is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and still more preferably 65 / 35 to 75 / 25. By using the above molar ratio, it is possible to further improve heat resistance and elongation.

[0021] B 1The total ratio of the divalent groups represented by formula (3) and the divalent groups represented by formula (4) is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0022] <Constituent Units of Polyimide Resin Precursor> The polyimide resin precursor contains a repeating unit represented by general formula (1), and the constituent units that constitute the precursor will be described below.

[0023] The polyimide resin precursor preferably has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine. In the polyimide resin precursor, the structural unit A and the structural unit B form an amic acid structure. Since the polyimide resin precursor contains the repeating unit represented by formula (1), preferably, the structural unit A contains a structural unit (A2) derived from a compound represented by formula (a2) below, and the structural unit B contains a structural unit (B3) derived from a compound represented by formula (b3) below. (In formula (b3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0024] (Structural Unit A) The structural unit A is a structural unit derived from a tetracarboxylic dianhydride, and preferably includes a structural unit (A2) derived from a compound represented by formula (a2) above, and more preferably is a structural unit (A2) derived from a compound represented by formula (a2). The compound represented by formula (a2) is biphenyltetracarboxylic dianhydride (BPDA). The compound represented by formula (a2) is at least one selected from the group consisting of a compound represented by formula (a2s) below, a compound represented by formula (a2a) below, and a compound represented by formula (a2i) below, more preferably at least one selected from the group consisting of a compound represented by formula (a2s) below and a compound represented by formula (a2a) below, and even more preferably a compound represented by formula (a2s) below.

[0025] The compound represented by formula (a2s) is 2,3,3',4'-biphenyltetracarboxylic dianhydride (s-BPDA), and the compound represented by formula (a2a) is 3,3',4,4'-biphenyltetracarboxylic dianhydride (a-BPDA). The compound represented by formula (a2i) is 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA). By using the structural unit (A2) derived from the compound represented by formula (a2) as a structural unit of the polyimide resin precursor, the heat resistance of the obtained polyimide film can be further improved.

[0026] From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the structural unit (A2) in the structural unit A is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0027] Preferably, the structural unit A further includes a structural unit (A6) derived from a compound represented by the following formula (a6): The compound represented by formula (a6) is 4,4'-oxydiphthalic anhydride (ODPA). By including the structural unit (A6) in the structural unit A, elongation can be further increased. When the structural unit A includes the structural unit (A6), the molar ratio of the structural unit (A2) to the structural unit (A6) in the structural unit A ((A2) / (A6)) is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45. By achieving this molar ratio, the heat resistance and transparency of the resulting polyimide film can be further improved.

[0028] The total proportion of the structural unit (A2) and the structural unit (A6) in the structural unit A is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and even more preferably 99 mol% or more and 100 mol% or less.

[0029] The structural unit A may contain a structural unit other than the structural unit (A2) and the structural unit (A6). Examples of such structural units include, but are not limited to, structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A2) and the structural unit (A6), structural units derived from alicyclic tetracarboxylic dianhydrides, and structural units derived from aliphatic tetracarboxylic dianhydrides.

[0030] Examples of aromatic tetracarboxylic dianhydrides that provide structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A2) and the structural unit (A6) include 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), pyromellitic anhydride (PMDA), 4,4-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (BP-TME), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), 2,3,6,7-naphthalenetetracarboxylic 2,3:6,7-dianhydride ( NTCDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 9,9-bis(trifluoromethyl)-9H-xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), hydroquinone diphthalic anhydride (HQDEA), ethylene glycol bis(trimellitate) dianhydride (TMEG), p-phenylene bis(trimellitate) dianhydride (TAHQ), and the like.Alicyclic tetracarboxylic dianhydrides that provide structural units derived from alicyclic tetracarboxylic dianhydrides include dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (H-BPDA), cyclohexane-1,2,4,5-tetracarboxylic dianhydride (HPMDA), cyclohexane-1,2,3,4-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5',6,6'-tetracarboxylic dianhydride (CpODA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3 Examples of the aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclopentanetetracarboxylic acid dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic acid dianhydride, 2,2-propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, and bicyclo[4.4.0]decane-2,3,6,7-tetracarboxylic acid dianhydride. Examples of the aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-butanetetracarboxylic acid dianhydride. The structural unit optionally contained in the structural unit A may be one type or two or more types. In this specification, the term "aromatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more aromatic rings, the term "alicyclic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and the term "aliphatic tetracarboxylic acid dianhydride" refers to 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 preferably includes a structural unit (B3) derived from a compound represented by the formula (b3), and more preferably is a structural unit (B3) derived from a compound represented by the formula (b3). 1 and Y 2are each independently —COO— or —OCO—, and k is 0 or 1. In formula (b3), k is 0 or 1, and preferably k is 0. When k is 1, Y 1 is —COO—, and Y 2 is —OCO— or Y 1 is —OCO—, and Y 2 is preferably —COO—, and Y 1 is —OCO—, and Y 2 It is more preferred that is —COO—.

[0032] The compound represented by formula (b3) is preferably at least one selected from the group consisting of compounds represented by the following formula (b31), compounds represented by the following formula (b32), and compounds represented by the following formula (b33), more preferably at least one selected from the group consisting of compounds represented by the following formula (b31) and compounds represented by the following formula (b32), and even more preferably a compound represented by formula (b31).

[0033] The compound represented by formula (b31) is 4-aminophenyl-4'-aminobenzoate (4-BAAB). The compound represented by formula (b32) is bis(4-aminophenyl)terephthalate (APTP). The compound represented by formula (b33) is 1,4-bis(4-aminobenzoyloxy)benzene (ABHQ).

[0034] From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the proportion of the structural unit (B3) in the structural unit B is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0035] Preferably, the structural unit B further includes a structural unit (B4) derived from a compound represented by the following formula (b4): The compound represented by formula (b4) is p-phenylenediamine (PPD). By including the structural unit (B4) in the structural unit B, heat resistance and elongation can be further improved. When the structural unit B includes the structural unit (B4), the molar ratio of the structural unit (B3) to the structural unit (B4) in the structural unit B [(B3) / (B4)] is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and still more preferably 65 / 35 to 75 / 25. By achieving this molar ratio, the heat resistance and elongation of the resulting polyamide film can be further improved.

[0036] The total proportion of the structural unit (B3) and the structural unit (B4) in the structural unit B is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0037] The structural unit B may contain structural units other than the structural unit (B3) and the structural unit (B4). Examples of such structural units include, but are not limited to, structural units derived from aromatic diamines other than the structural unit (B3) and the structural unit (B4), structural units derived from alicyclic diamines, and structural units derived from aliphatic diamines. Examples of aromatic diamines that provide structural units derived from aromatic diamines other than the structural unit (B3) and the structural unit (B4) include bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS-M), 1,3-bis(3-aminophenoxy)benzene (TPE-M), 1,3-bis[2-(3-aminophenyl)-2-propyl]benzene, 1,3-bis[2-(3-aminophenyl)-2-hexafluoropropyl]benzene, 2,2'-bis(trifluoromethyl) -4,4'-diaminodiphenyl ether (6FODA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFMB), 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-5,5'-diaminobiphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane (HFDA), 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane , 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diamino-2,2'-dimethylbiphenyl (mTB), 9,9 -bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 5-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indane (5-TMDM), 6-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indane (6-TMDM), 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAM), 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAP), 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl (BODA), 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-bis(3-aminophenoxy)benzene, 1 , 4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-diaminobenzanilide, 4-aminobenzoic acid-4-aminophenyl, 3,4-diaminobenzanilide, and the like. Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophoronediamine, bis(aminomethyl)norbornane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane. Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine.

[0038] In this specification, "aromatic diamine" refers to a diamine containing one or more aromatic rings, "alicyclic diamine" refers to a diamine containing one or more alicyclic rings but no aromatic rings, and "aliphatic diamine" refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in structural unit B may be one type or two or more types.

[0039] (Method for Producing Polyimide Resin Precursor) The polyimide resin precursor may be produced by any method, but is preferably produced by the following production method: Specifically, it is preferably produced by a production method in which a tetracarboxylic acid component and a diamine component constituting a polyamic acid containing a repeating unit represented by formula (1) are reacted to obtain a polyimide resin precursor.

[0040] The tetracarboxylic acid component used in this production method preferably contains a compound that provides the structural unit (A2) and may contain a compound that provides the structural unit (A6). It may also contain a tetracarboxylic acid component other than the compound that provides the structural unit (A2) and the compound that provides the structural unit (A6), as long as the effects of the present invention are not impaired. The diamine component used in this production method preferably contains a compound that provides the structural unit (B3) and may also contain a compound that provides the structural unit (B4). It may also contain a diamine component other than the compound that provides the structural unit (B3) and the compound that provides the structural unit (B4), as long as the effects of the present invention are not impaired. The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0041] The method for reacting the tetracarboxylic acid component and the diamine component in this production method is not particularly limited, and known methods can be used. Specific reaction methods include charging a reactor with the tetracarboxylic acid component, the diamine component, a solvent, and, if necessary, an end-capping agent, and stirring the mixture 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 resin precursor does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, allowing for stable production of a polyimide resin precursor that is a polyamic acid.

[0042] The above method provides a polyimide resin precursor solution having a polyamic acid structure dissolved in a solvent, with a concentration of the polyimide resin precursor in the resulting solution being preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0043] The number-average molecular weight of the polyimide resin precursor obtained by the above-described production method is preferably 5,000 to 500,000 from the viewpoint of the mechanical strength of the resulting polyimide film. Also, from the same viewpoint, the weight-average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000. Next, the raw materials used in this production method will be described.

[0044] [Tetracarboxylic Acid Component] The tetracarboxylic acid component used as a raw material in the present production method is preferably the tetracarboxylic acid dianhydride described above in the section (Structural Unit A). The tetracarboxylic acid dianhydride used as the tetracarboxylic acid component in the present production method may be in the form of a dianhydride, a tetracarboxylic acid (free acid), or an alkyl ester of a tetracarboxylic acid, but is preferably a dianhydride. The tetracarboxylic acid component used as a raw material in the present production method contains at least a compound represented by formula (a2) (a compound that provides structural unit (A2)). It may also contain both a compound represented by formula (a2) and a compound represented by formula (a6) (a compound that provides structural unit (A6)). From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the proportion of the compound represented by formula (a2) in the tetracarboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more. The upper limit is 100 mol % or less.

[0045] When the tetracarboxylic acid component contains a compound represented by formula (a6), the molar ratio ((a2) / (a6)) of the compound represented by formula (a2) to the compound represented by formula (a6) in the tetracarboxylic acid component is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. By achieving this molar ratio, the heat resistance and transparency of the resulting polyimide film can be further improved. The total ratio of the compound represented by formula (a2) to the compound represented by formula (a6) in the tetracarboxylic acid component is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%.

[0046] The tetracarboxylic acid component may contain a tetracarboxylic acid component other than the compound represented by formula (a2) and the compound represented by formula (a6). Such tetracarboxylic acid components are not particularly limited, but include aromatic tetracarboxylic acid dianhydrides other than the compound represented by formula (a2) and the compound represented by formula (a6), alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides. Specific examples of tetracarboxylic acid components other than the compound represented by formula (a2) and the compound represented by formula (a6) include the tetracarboxylic acid dianhydrides described above in the section (Structural Unit A). These tetracarboxylic acid dianhydrides may be used alone or in combination of two or more.

[0047] [Diamine Component] The diamine component used as a raw material in this production method is preferably the diamine described in the section (Structural Unit B) above. The diamine used as the diamine component in this production method may be in the form of either a diamine or a diisocyanate corresponding to the diamine, but is preferably a diamine. The diamine component used as a raw material in this production method contains at least a compound represented by formula (b3) (a compound that provides structural unit (B3)). It may also contain both a compound represented by formula (b3) and a compound represented by formula (b4) (a compound that provides structural unit (B4)). From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the compound represented by formula (b3) in the diamine component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

[0048] When the diamine component contains a compound represented by formula (b4), the molar ratio of the compound represented by formula (b3) to the compound represented by formula (b4) in the diamine component ((b3) / (b4)) is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and even more preferably 65 / 35 to 75 / 25. By achieving this molar ratio, the heat resistance and elongation of the resulting polyamide film can be further improved. The total ratio of the compound represented by formula (b3) to the compound represented by formula (b4) in the diamine component is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%.

[0049] The diamine component may contain a diamine component other than the compound represented by formula (b3) and the compound represented by formula (b4). Such diamine components are not particularly limited, but include aromatic diamines other than the compound represented by formula (b3) and the compound represented by formula (b4), alicyclic diamines, and aliphatic diamines. One type of diamine may be used, or two or more types may be used.

[0050] [End-capping Agent] In addition to the tetracarboxylic acid component and diamine component described above, an end-capping agent may also be used in the production of the polyimide resin precursor. Monoamines or dicarboxylic acids are preferred as end-capping agents. The amount of the end-capping agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per mol of the tetracarboxylic acid component. Examples of monoamine end-capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline. Of these, benzylamine and aniline are preferred. Dicarboxylic acids are preferred as dicarboxylic acid end-capping agents, and a portion of these may be 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, 4-cyclohexene-1,2-dicarboxylic acid, etc. Of these, phthalic acid and phthalic anhydride are more preferred.

[0051] [Organic Solvent Used in Producing Polyimide Resin Precursor] The organic solvent used in producing the polyimide resin precursor may be any solvent capable of dissolving the resulting polyimide resin precursor, such as an aprotic solvent, a phenolic solvent, an ether solvent, or a carbonate solvent.

[0052] Specific examples of the aprotic solvent 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.

[0053] 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-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above organic solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above solvents may be used alone or in combination.

[0054] <Organic Solvent> The polyimide resin precursor composition of the present invention contains the polyimide resin precursor, a silsesquioxane compound, and an organic solvent. That is, the polyimide resin precursor and the silsesquioxane compound are dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyimide resin precursor. However, it is preferable to use the above-mentioned compounds alone or in combination of two or more as the solvent used in the production of the polyimide resin precursor. The polyimide resin precursor composition of the present invention may be obtained by adding a silsesquioxane compound to the above-mentioned polyimide resin precursor solution after the production of the polyimide resin precursor, or may be obtained by further mixing a silsesquioxane compound and a dilution solvent with the polyimide resin precursor solution.

[0055] Examples of the organic solvent contained in the polyimide resin precursor composition of the present invention include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0056] Specific examples of the aprotic solvent 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.

[0057] 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-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above organic solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above organic solvents may be used alone or in combination.

[0058] <Silsesquioxane Compound> The polyimide resin precursor composition of the present invention contains a silsesquioxane compound. By including a silsesquioxane compound in the polyimide resin precursor composition of the present invention, a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment can be obtained. The molecular weight of the silsesquioxane compound is preferably 300 to 6,000, more preferably 500 to 6,000, even more preferably 600 to 6,000, even more preferably 700 to 5,000, even more preferably 800 to 5,000, even more preferably 900 to 5,000, even more preferably 1,000 to 4,000, and from the viewpoint of handleability, even more preferably 1,000 to 2,000. By including a silsesquioxane compound in the above range, the resulting polyimide film has excellent transparency.

[0059] In addition, when the silsesquioxane compound has a random structure or a ladder structure, the molecular weight of the silsesquioxane compound is the weight average molecular weight determined by standard polystyrene (PS) conversion by gel filtration chromatography measurement. Furthermore, when the silsesquioxane compound has a cage structure, most of the molecules have a single structure (molecular weight), so the molecular weight of the silsesquioxane compound is the molecular weight calculated from the molecular formula. In the case where the silsesquioxane compound has a random structure or a ladder structure, the molecular weight of the silsesquioxane compound of the random structure or the ladder structure is more preferably 600 to 6000, even more preferably 700 to 5000, even more preferably 800 to 5000, even more preferably 900 to 5000, even more preferably 1000 to 4000, and from the viewpoint of handleability, even more preferably 1000 to 2000. When the silsesquioxane compound has a cage structure, the molecular weight of the silsesquioxane compound having a cage structure is even more preferably 600 to 6000, even more preferably 600 to 4000, even more preferably 600 to 2000, even more preferably 600 to 1500, even more preferably 700 to 1000, and from the standpoint of availability, even more preferably 700 to 900. When the molecular weight of the silsesquioxane compound is within the above range, the resulting polyimide film has excellent transparency.

[0060] The silsesquioxane compound is preferably a compound having a structural unit represented by the following formula (5a): (R 1 SiO 1.5 ) (5a) (In formula (5a), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group.

[0061] In formula (5a), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and preferably R 1 contains a hydroxy group or an alkoxy group, more preferably R1 further comprises an aromatic group, i.e., R 1 Preferably, contains a hydroxy group or an alkoxy group and an aromatic group, and more preferably is a hydroxy group or an alkoxy group and an aromatic group.

[0062] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group, preferably a methoxy group or an ethoxy group, and more preferably an ethoxy group. Examples of the aromatic group include a phenyl group, a tolyl group, and a xylyl group, preferably a phenyl group or a tolyl group, and more preferably a phenyl group.

[0063] The silsesquioxane compound is more preferably a compound represented by the following composition formula (5): The composition formula (5) is a composition formula showing the main skeleton of the silsesquioxane compound, and the molecular terminal of the silsesquioxane compound may have a moiety in which two or three hydroxyl groups, alkoxy groups, or aromatic groups are bonded to a silicon atom. [R 1 SiO 1.5 ] n (5) (In formula (5), R 1 is at least one selected from a hydroxy group, an alkoxy group, and an aromatic group, and n is 4 to 100. n is an average value.

[0064] In formula (5), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and preferably R 1 contains a hydroxy group or an alkoxy group, more preferably R 1 further comprises an aromatic group, i.e., R 1 Preferably, contains a hydroxy group or an alkoxy group and an aromatic group, and more preferably is a hydroxy group or an alkoxy group and an aromatic group.

[0065] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group, preferably a methoxy group or an ethoxy group, and more preferably an ethoxy group. Examples of the aromatic group include a phenyl group, a tolyl group, and a xylyl group, preferably a phenyl group or a tolyl group, and more preferably a phenyl group.

[0066] In formula (5), n is 4 to 100, preferably 7 to 100, more preferably 8 to 80, even more preferably 9 to 80, still more preferably 10 to 70, even more preferably 13 to 50, and still more preferably 13 to 30. When a plurality of silsesquioxane compounds are contained, n is an average value (corresponding to the number average degree of polymerization).

[0067] <Composition and Properties of Polyimide Resin Precursor Composition> The polyimide resin precursor composition of the present invention contains a polyimide resin precursor containing a repeating unit represented by formula (1), a silsesquioxane compound, and an organic solvent. The mass ratio of the silsesquioxane compound to the polyimide resin precursor (silsesquioxane compound / polyimide resin precursor) is preferably 1 / 99 to 35 / 65, more preferably 3 / 97 to 35 / 65, even more preferably 5 / 95 to 35 / 65, still more preferably 10 / 90 to 35 / 65, and even more preferably 15 / 85 to 35 / 65. When the mass ratio of the silsesquioxane compound to the polyimide resin precursor is within the above range, the resulting polyimide film has excellent heat resistance and excellent transparency even after high-temperature treatment. Furthermore, particularly from the viewpoint of further improving the transparency of the resulting polyimide film, the mass ratio of the silsesquioxane compound to the polyimide resin precursor (silsesquioxane compound / polyimide resin precursor) is even more preferably 20 / 80 to 35 / 65, even more preferably 25 / 75 to 35 / 65, and even more preferably 30 / 70 to 35 / 65. Furthermore, particularly from the viewpoint of further improving the elongation of the resulting polyimide film, it is even more preferably 5 / 95 to 30 / 70, even more preferably 5 / 95 to 25 / 75, and even more preferably 10 / 90 to 20 / 80.

[0068] The solids concentration of the polyimide resin precursor composition (total of the polyimide resin precursor and the silsesquioxane compound) is preferably 3 to 50 mass %, more preferably 5 to 45 mass %, even more preferably 10 to 40 mass %, still more preferably 15 to 40 mass %, even more preferably 20 to 35 mass %, and still more preferably 20 to 30 mass %. The polyimide resin precursor is solvent-soluble, so it can be made into a high-concentration solution that is stable at room temperature, and by setting the concentration in this range, a polyimide film with a thickness suitable for display applications can be efficiently obtained.

[0069] The content of the organic solvent contained in the polyimide resin precursor composition is preferably 50 to 97% by mass, more preferably 55 to 95% by mass, even more preferably 60 to 90% by mass, still more preferably 60 to 85% by mass, even more preferably 65 to 80% by mass, and still more preferably 70 to 80% by mass. The polyimide resin precursor is solvent-soluble, so that it can be made into a highly concentrated solution that is stable at room temperature. By adjusting the content of the organic solvent to the above range, a polyimide film having a thickness suitable for display applications can be efficiently obtained.

[0070] The polyimide resin precursor composition of the present invention may further contain an imidization catalyst and a dehydration catalyst from the viewpoint of efficiently proceeding with the imidization of the polyamic acid, which is the polyimide resin precursor. The imidization catalyst may have a boiling point of 40°C or higher. An imidization catalyst with a boiling point of 40°C or higher can avoid the possibility of volatilization before the imidization has progressed sufficiently. Examples of imidization catalysts include amine compounds such as pyridine or picoline; imidazole compounds such as imidazole, 1,2-dimethylimidazole, 1-benzylimidazole, 1-benzyl-2-methylimidazole, and benzimidazole; and the like. The above imidization catalysts may be used alone or in combination of two or more. Examples of dehydration catalysts include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may be used alone or in combination of two or more.

[0071] The viscosity of the polyimide resin precursor composition is preferably 0.1 to 100 Pa·s, more preferably 0.1 to 20 Pa·s. The viscosity of the polyimide resin precursor composition is a value measured at 25°C using an E-type viscometer. The polyimide resin precursor composition of the present invention may also contain various additives, such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brighteners, crosslinking agents, polymerization initiators, and photosensitizers, to the extent that the required properties of the resulting polyimide film are not impaired. The method for producing the polyimide resin precursor composition of the present invention is not particularly limited, and known methods can be applied. For example, the polyimide resin precursor composition can be obtained by adding a silsesquioxane compound to a solution of the polyimide resin precursor obtained by the above-mentioned production method, and adjusting the concentration by adding an additional organic solvent as necessary.

[0072] [Polyimide Film and Method for Producing Polyimide Film] The polyimide film of the present invention is preferably produced using the polyimide resin precursor composition described above. Specifically, the polyimide film of the present invention is preferably a polyimide film obtained by applying the polyimide resin precursor composition to a support and heating the applied composition. Therefore, the polyimide film of the present invention has excellent heat resistance and excellent transparency even after high-temperature treatment.

[0073] The method for producing a polyimide film using the polyimide resin precursor composition is not particularly limited, but is preferably a method in which the polyimide resin precursor composition is applied to a support and heated. Examples of the support include a glass plate, a metal plate, and plastic. The support preferably has a smooth surface. After applying the polyimide resin precursor composition to the support and forming it into a film, organic solvents such as reaction solvents and dilution solvents contained in the polyimide resin precursor composition are removed by heating to obtain a polyamic acid film. The polyamic acid in the polyamic acid film is imidized (dehydration ring closure) by heating, and then peeled off from the support, thereby producing a polyimide film.

[0074] The heating temperature when drying the polyimide resin precursor composition to obtain a polyimide resin precursor (polyamic acid) film is preferably 50 to 150°C. The heating temperature when imidizing the polyimide resin precursor by heating is preferably 350 to 450°C, more preferably 380 to 450°C. The heating time is typically 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 resulting polyimide film are improved. Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, and a nitrogen / hydrogen mixed gas. However, to prevent discoloration of the resulting polyimide resin, nitrogen gas with an oxygen concentration of 100 ppm or less and a nitrogen / hydrogen mixed gas with a hydrogen concentration of 0.5% or less are preferred. The imidization method is not limited to thermal imidization; chemical imidization can also be used.

[0075] 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. It is also 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. It is particularly preferable that the thickness of the polyimide film is 1 μm or more and 20 μm or less. Having a thickness within the above range enables practical use as a free-standing film. The thickness of the polyimide film can be easily controlled by adjusting the solids concentration and viscosity of the polyimide resin precursor composition.

[0076] The polyimide film of the present invention preferably has the following physical properties. The glass transition temperature (Tg) is preferably 470°C or higher, more preferably 480°C or higher, even more preferably 485°C or higher, and even more preferably 490°C or higher. The 5% weight loss temperature (Td5%) is preferably 550°C or higher, more preferably 560°C or higher, even more preferably 570°C or higher, and even more preferably 580°C or higher. The total light transmittance when the polyimide film has a thickness of 10 μm is preferably 80% or higher, more preferably 81% or higher, even more preferably 83% or higher, and even more preferably 85% or higher. The tensile elongation at 23°C and 50% RH when the polyimide film has a thickness of 10 μm is preferably 8% or higher, more preferably 9% or higher, even more preferably 10% or higher, even more preferably 11% or higher, and even more preferably 13% or higher. The above-mentioned physical properties in the present invention can be specifically measured by the methods described in the examples.

[0077] As described above, the polyimide film of the present invention has excellent heat resistance and excellent transparency even after high-temperature treatment, and is therefore useful as a film for displays. Therefore, the polyimide film of the present invention is preferably used for displays.

[0078] [Method for Improving Transparency of Polyimide Film] The method for improving the transparency of the polyimide film of the present invention is a method of adding a silsesquioxane compound to a polyimide resin precursor containing a repeating unit represented by the following formula (1), which is a raw material for the polyimide film: (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0079] A polyimide film obtained by imidizing a polyimide resin precursor containing a repeating unit represented by formula (1), adding a silsesquioxane compound to the polyimide resin precursor containing a repeating unit represented by formula (1), and then imidizing the polyimide resin precursor, will have higher transparency. Therefore, in this method, when producing a polyimide film from a polyimide resin precursor, a silsesquioxane compound is added to increase the transparency of the resulting polyimide film. The polyimide film can preferably be obtained by adding a silsesquioxane compound to a polyimide resin precursor to obtain a mixture, applying the mixture to a support, and heating the mixture. X in formula (1) 1 , X 2 , A 1 , B 1 , Y in formula (3) 1 , Y 2 The values ​​of k are the same as those described above in the section on the polyimide resin precursor, and the preferred ranges are also the same. The values ​​of the silsesquioxane compound are the same as those described above in the section on the silsesquioxane compound, and the preferred ranges are also the same. Details are described below.

[0080] <Polyimide Resin Precursor> The polyimide resin precursor used in this method contains a repeating unit represented by the following formula (1). (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0081] The "repeating unit" in the polyimide resin precursor is an amic acid unit, an amic acid ester unit, or an amic acid silyl ester unit containing a structural unit derived from one tetracarboxylic dianhydride and a structural unit derived from one diamine. 1 and X 2 are each independently at least one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, preferably at least one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom.

[0082] In formula (1), A 1 includes a tetravalent group represented by formula (2), and is preferably a tetravalent group represented by formula (2). The tetravalent group represented by formula (2) is preferably at least one selected from the group consisting of a tetravalent group represented by formula (2s) below, a tetravalent group represented by formula (2a) below, and a tetravalent group represented by formula (2i) below, more preferably at least one selected from the group consisting of a tetravalent group represented by formula (2s) below and a tetravalent group represented by formula (2a) below, and even more preferably a tetravalent group represented by formula (2s) below. 1 By including the tetravalent group represented by formula (2), the heat resistance of the resulting polyimide film can be further improved.

[0083] A 1 From the viewpoint of obtaining a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the tetravalent group represented by formula (2) in is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0084] In formula (1), A 1 Preferably, the compound further contains a tetravalent group represented by the following formula (6): A 1By including a tetravalent group represented by formula (6), the elongation can be further increased. 1 When A contains a tetravalent group represented by formula (6), 1 In the above formula (2), the molar ratio of the tetravalent group represented by formula (2) to the tetravalent group represented by formula (6) (formula (2) / formula (6)) is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45. By using the above molar ratio, heat resistance and transparency can be further improved.

[0085] A 1 The total ratio of the tetravalent groups represented by formula (2) and the tetravalent groups represented by formula (6) is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0086] In formula (1), B 1 contains a divalent group represented by formula (3), and is preferably a divalent group represented by formula (3). 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1. In formula (3), k is 0 or 1, and preferably k is 0. When k is 1, Y 1 is —COO—, and Y 2 is —OCO— or Y 1 is —OCO—, and Y 2 is preferably —COO—, and Y 1 is —OCO—, and Y 2 It is more preferred that is —COO—.

[0087] The divalent group represented by formula (3) is preferably at least one selected from the group consisting of a divalent group represented by formula (31) below, a divalent group represented by formula (32) below, and a divalent group represented by formula (33) below, more preferably at least one selected from the group consisting of a divalent group represented by formula (31) below and a divalent group represented by formula (32) below, and even more preferably a divalent group represented by formula (31) below.

[0088] B 1 From the viewpoint of obtaining a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the divalent group represented by formula (3) in is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0089] In formula (1), B 1 Preferably, the compound further contains a divalent group represented by the following formula (4): B 1 By including a divalent group represented by formula (4), the heat resistance and elongation can be further improved. 1 When a divalent group represented by formula (4) is contained in B 1 In the above formula (3), the molar ratio of the divalent group represented by formula (3) to the divalent group represented by formula (4) (formula (3) / formula (4)) is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and still more preferably 65 / 35 to 75 / 25. By using the above molar ratio, it is possible to further improve heat resistance and elongation.

[0090] B 1The total ratio of the divalent groups represented by formula (3) and the divalent groups represented by formula (4) is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0091] <Constituent Units of Polyimide Resin Precursor> The polyimide resin precursor contains a repeating unit represented by general formula (1), and the constituent units that constitute the precursor will be described below.

[0092] The polyimide resin precursor preferably has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine. In the polyimide resin precursor, the structural unit A and the structural unit B form an amic acid structure. Since the polyimide resin precursor contains the repeating unit represented by formula (1), preferably, the structural unit A contains a structural unit (A2) derived from a compound represented by formula (a2) below, and the structural unit B contains a structural unit (B3) derived from a compound represented by formula (b3) below. (In formula (b3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

[0093] (Structural Unit A) The structural unit A is a structural unit derived from a tetracarboxylic dianhydride, and preferably includes a structural unit (A2) derived from a compound represented by formula (a2) above, and more preferably is a structural unit (A2) derived from a compound represented by formula (a2). The compound represented by formula (a2) is biphenyltetracarboxylic dianhydride (BPDA). The compound represented by formula (a2) is at least one selected from the group consisting of a compound represented by formula (a2s) below, a compound represented by formula (a2a) below, and a compound represented by formula (a2i) below, more preferably at least one selected from the group consisting of a compound represented by formula (a2s) below and a compound represented by formula (a2a) below, and even more preferably a compound represented by formula (a2s) below.

[0094] The compound represented by formula (a2s) is 2,3,3',4'-biphenyltetracarboxylic dianhydride (s-BPDA), and the compound represented by formula (a2a) is 3,3',4,4'-biphenyltetracarboxylic dianhydride (a-BPDA). The compound represented by formula (a2i) is 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA). By using the structural unit (A2) derived from the compound represented by formula (a2) as a structural unit of the polyimide resin precursor, the heat resistance of the obtained polyimide film can be further improved.

[0095] From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the structural unit (A2) in the structural unit A is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0096] Preferably, the structural unit A further includes a structural unit (A6) derived from a compound represented by the following formula (a6): The compound represented by formula (a6) is 4,4'-oxydiphthalic anhydride (ODPA). By including the structural unit (A6) in the structural unit A, elongation can be further increased. When the structural unit A includes the structural unit (A6), the molar ratio of the structural unit (A2) to the structural unit (A6) in the structural unit A ((A2) / (A6)) is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45. By achieving this molar ratio, the heat resistance and transparency of the resulting polyimide film can be further improved.

[0097] The total proportion of the structural unit (A2) and the structural unit (A6) in the structural unit A is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and even more preferably 99 mol% or more and 100 mol% or less.

[0098] The structural unit A may contain a structural unit other than the structural unit (A2) and the structural unit (A6). Examples of such structural units include, but are not limited to, structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A2) and the structural unit (A6), structural units derived from alicyclic tetracarboxylic dianhydrides, and structural units derived from aliphatic tetracarboxylic dianhydrides.

[0099] Examples of aromatic tetracarboxylic dianhydrides that provide structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (A2) and the structural unit (A6) include 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), pyromellitic anhydride (PMDA), 4,4-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (BP-TME), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), 2,3,6,7-naphthalenetetracarboxylic 2,3:6,7-dianhydride ( NTCDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 9,9-bis(trifluoromethyl)-9H-xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), hydroquinone diphthalic anhydride (HQDEA), ethylene glycol bis(trimellitate) dianhydride (TMEG), p-phenylene bis(trimellitate) dianhydride (TAHQ), and the like.Alicyclic tetracarboxylic dianhydrides that provide structural units derived from alicyclic tetracarboxylic dianhydrides include dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (H-BPDA), cyclohexane-1,2,4,5-tetracarboxylic dianhydride (HPMDA), cyclohexane-1,2,3,4-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5',6,6'-tetracarboxylic dianhydride (CpODA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3 Examples of the aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclopentanetetracarboxylic acid dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic acid dianhydride, 2,2-propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, and bicyclo[4.4.0]decane-2,3,6,7-tetracarboxylic acid dianhydride. Examples of the aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-butanetetracarboxylic acid dianhydride. The structural unit optionally contained in the structural unit A may be one type or two or more types. In this specification, the term "aromatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more aromatic rings, the term "alicyclic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and the term "aliphatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.

[0100] (Structural Unit B) The structural unit B is a structural unit derived from a diamine, and preferably includes a structural unit (B3) derived from a compound represented by the formula (b3), and more preferably is a structural unit (B3) derived from a compound represented by the formula (b3). 1 and Y 2are each independently —COO— or —OCO—, and k is 0 or 1. In formula (b3), k is 0 or 1, and preferably k is 0. When k is 1, Y 1 is —COO—, and Y 2 is —OCO— or Y 1 is —OCO—, and Y 2 is preferably —COO—, and Y 1 is —OCO—, and Y 2 It is more preferred that is —COO—.

[0101] The compound represented by formula (b3) is preferably at least one selected from the group consisting of compounds represented by the following formula (b31), compounds represented by the following formula (b32), and compounds represented by the following formula (b33), more preferably at least one selected from the group consisting of compounds represented by the following formula (b31) and compounds represented by the following formula (b32), and even more preferably a compound represented by formula (b31).

[0102] The compound represented by formula (b31) is 4-aminophenyl-4'-aminobenzoate (4-BAAB). The compound represented by formula (b32) is bis(4-aminophenyl)terephthalate (APTP). The compound represented by formula (b33) is 1,4-bis(4-aminobenzoyloxy)benzene (ABHQ).

[0103] From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the proportion of the structural unit (B3) in the structural unit B is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, with the upper limit being 100 mol% or less.

[0104] Preferably, the structural unit B further includes a structural unit (B4) derived from a compound represented by the following formula (b4): The compound represented by formula (b4) is p-phenylenediamine (PPD). When structural unit B contains structural unit (B4), heat resistance and elongation can be further improved. When structural unit B contains structural unit (B4), the molar ratio of structural unit (B3) to structural unit (B4) in structural unit B ((B3) / (B4)) is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and still more preferably 65 / 35 to 75 / 25. By achieving this molar ratio, the heat resistance and elongation of the resulting polyamide film can be further improved.

[0105] The total proportion of the structural unit (B3) and the structural unit (B4) in the structural unit B is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, and still more preferably 99 mol% or more and 100 mol% or less.

[0106] The structural unit B may contain structural units other than the structural unit (B3) and the structural unit (B4). Examples of such structural units include, but are not limited to, structural units derived from aromatic diamines other than the structural unit (B3) and the structural unit (B4), structural units derived from alicyclic diamines, and structural units derived from aliphatic diamines. Examples of aromatic diamines that provide structural units derived from aromatic diamines other than the structural unit (B3) and the structural unit (B4) include bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS-M), 1,3-bis(3-aminophenoxy)benzene (TPE-M), 1,3-bis[2-(3-aminophenyl)-2-propyl]benzene, 1,3-bis[2-(3-aminophenyl)-2-hexafluoropropyl]benzene, 2,2'-bis(trifluoromethyl) -4,4'-diaminodiphenyl ether (6FODA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFMB), 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-5,5'-diaminobiphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane (HFDA), 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane , 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diamino-2,2'-dimethylbiphenyl (mTB), 9,9 -bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 5-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indane (5-TMDM), 6-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indane (6-TMDM), 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAM), 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAP), 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl (BODA), 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-bis(3-aminophenoxy)benzene, 1 , 4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-diaminobenzanilide, 4-aminobenzoic acid-4-aminophenyl, 3,4-diaminobenzanilide, and the like. Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophoronediamine, bis(aminomethyl)norbornane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane. Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine.

[0107] In this specification, "aromatic diamine" refers to a diamine containing one or more aromatic rings, "alicyclic diamine" refers to a diamine containing one or more alicyclic rings but no aromatic rings, and "aliphatic diamine" refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in structural unit B may be one type or two or more types.

[0108] (Method for Producing Polyimide Resin Precursor) The polyimide resin precursor may be produced by any method, but is preferably produced by the following production method: Specifically, it is preferably produced by a production method in which a tetracarboxylic acid component and a diamine component constituting a polyamic acid containing a repeating unit represented by formula (1) are reacted to obtain a polyimide resin precursor.

[0109] The tetracarboxylic acid component used in this production method preferably contains a compound that provides the structural unit (A2) and may contain a compound that provides the structural unit (A6). It may also contain a tetracarboxylic acid component other than the compound that provides the structural unit (A2) and the compound that provides the structural unit (A6), as long as the effects of the present invention are not impaired. The diamine component used in this production method preferably contains a compound that provides the structural unit (B3) and may also contain a compound that provides the structural unit (B4). It may also contain a diamine component other than the compound that provides the structural unit (B3) and the compound that provides the structural unit (B4), as long as the effects of the present invention are not impaired. The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0110] The method for reacting the tetracarboxylic acid component and the diamine component in this production method is not particularly limited, and known methods can be used. Specific reaction methods include charging a reactor with the tetracarboxylic acid component, the diamine component, a solvent, and, if necessary, an end-capping agent, and stirring the mixture 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 resin precursor does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, allowing for stable production of a polyimide resin precursor that is a polyamic acid.

[0111] The above method provides a polyimide resin precursor solution having a polyamic acid structure dissolved in a solvent, with a concentration of the polyimide resin precursor in the resulting solution being preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0112] The number-average molecular weight of the polyimide resin precursor obtained by the above-described production method is preferably 5,000 to 500,000 from the viewpoint of the mechanical strength of the resulting polyimide film. Also, from the same viewpoint, the weight-average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000. Next, the raw materials used in this production method will be described.

[0113] [Tetracarboxylic Acid Component] The tetracarboxylic acid component used as a raw material in the present production method is preferably the tetracarboxylic acid dianhydride described above in the section (Structural Unit A). The tetracarboxylic acid dianhydride used as the tetracarboxylic acid component in the present production method may be in the form of a dianhydride, a tetracarboxylic acid (free acid), or an alkyl ester of a tetracarboxylic acid, but is preferably a dianhydride. The tetracarboxylic acid component used as a raw material in the present production method contains at least a compound represented by formula (a2) (a compound that provides structural unit (A2)). It may also contain both a compound represented by formula (a2) and a compound represented by formula (a6) (a compound that provides structural unit (A6)). From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the proportion of the compound represented by formula (a2) in the tetracarboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more. The upper limit is 100 mol % or less.

[0114] When the tetracarboxylic acid component contains a compound represented by formula (a6), the molar ratio of the compound represented by formula (a2) to the compound represented by formula (a6) in the tetracarboxylic acid component [(a2) / (a6)] is preferably 40 / 60 to 80 / 20, more preferably 40 / 60 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. By achieving this molar ratio, the heat resistance and transparency of the resulting polyimide film can be further improved. The total ratio of the compound represented by formula (a2) to the compound represented by formula (a6) in the tetracarboxylic acid component is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%.

[0115] The tetracarboxylic acid component may contain a tetracarboxylic acid component other than the compound represented by formula (a2) and the compound represented by formula (a6). Such tetracarboxylic acid components are not particularly limited, but include aromatic tetracarboxylic acid dianhydrides other than the compound represented by formula (a2) and the compound represented by formula (a6), alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides. Specific examples of tetracarboxylic acid components other than the compound represented by formula (a2) and the compound represented by formula (a6) include the tetracarboxylic acid dianhydrides described above in the section (Structural Unit A). These tetracarboxylic acid dianhydrides may be used alone or in combination of two or more.

[0116] [Diamine Component] The diamine component used as a raw material in this production method is preferably the diamine described in the section (Structural Unit B) above. The diamine used as the diamine component in this production method may be in the form of either a diamine or a diisocyanate corresponding to the diamine, but is preferably a diamine. The diamine component used as a raw material in this production method contains at least a compound represented by formula (b3) (a compound that provides structural unit (B3)). It may also contain both a compound represented by formula (b3) and a compound represented by formula (b4) (a compound that provides structural unit (B4)). From the viewpoint of obtaining a polyimide film that has excellent heat resistance and excellent transparency even after high-temperature treatment, the ratio of the compound represented by formula (b3) in the diamine component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

[0117] When the diamine component contains a compound represented by formula (b4), the molar ratio of the compound represented by formula (b3) to the compound represented by formula (b4) in the diamine component [(b3) / (b4)] is preferably 50 / 50 to 90 / 10, more preferably 60 / 40 to 90 / 10, even more preferably 65 / 35 to 80 / 20, and even more preferably 65 / 35 to 75 / 25. By achieving this molar ratio, the heat resistance and elongation of the resulting polyamide film can be further improved. The total ratio of the compound represented by formula (b3) to the compound represented by formula (b4) in the diamine component is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, even more preferably 95 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%.

[0118] The diamine component may contain a diamine component other than the compound represented by formula (b3) and the compound represented by formula (b4). Such diamine components are not particularly limited, but include aromatic diamines other than the compound represented by formula (b3) and the compound represented by formula (b4), alicyclic diamines, and aliphatic diamines. One type of diamine may be used, or two or more types may be used.

[0119] [End-capping Agent] In addition to the tetracarboxylic acid component and diamine component described above, an end-capping agent may also be used in the production of the polyimide resin precursor. Monoamines or dicarboxylic acids are preferred as end-capping agents. The amount of the end-capping agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per mol of the tetracarboxylic acid component. Examples of monoamine end-capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline. Of these, benzylamine and aniline are preferred. Dicarboxylic acids are preferred as dicarboxylic acid end-capping agents, and a portion of these may be 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, 4-cyclohexene-1,2-dicarboxylic acid, etc. Of these, phthalic acid and phthalic anhydride are more preferred.

[0120] [Organic Solvent Used in Producing Polyimide Resin Precursor] The organic solvent used in producing the polyimide resin precursor may be any solvent capable of dissolving the resulting polyimide resin precursor, such as an aprotic solvent, a phenolic solvent, an ether solvent, or a carbonate solvent.

[0121] Specific examples of the aprotic solvent 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.

[0122] 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-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above organic solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above solvents may be used alone or in combination.

[0123] <Silsesquioxane Compound> The silsesquioxane compound used in this method will now be described. The molecular weight of the silsesquioxane compound is preferably 300 to 6,000, more preferably 500 to 6,000, even more preferably 600 to 6,000, still more preferably 700 to 5,000, even more preferably 800 to 5,000, even more preferably 900 to 5,000, even more preferably 1,000 to 4,000, and from the standpoint of handleability, even more preferably 1,000 to 2,000. When the molecular weight of the silsesquioxane compound is within the above range, the resulting polyimide film will have excellent transparency.

[0124] In addition, when the silsesquioxane compound has a random structure or a ladder structure, the molecular weight of the silsesquioxane compound is the weight average molecular weight determined by standard polystyrene (PS) conversion by gel filtration chromatography measurement. Furthermore, when the silsesquioxane compound has a cage structure, most of the molecules have a single structure (molecular weight), so the molecular weight of the silsesquioxane compound is the molecular weight calculated from the molecular formula. In the case where the silsesquioxane compound has a random structure or a ladder structure, the molecular weight of the silsesquioxane compound of the random structure or the ladder structure is more preferably 600 to 6000, even more preferably 700 to 5000, even more preferably 800 to 5000, even more preferably 900 to 5000, even more preferably 1000 to 4000, and from the viewpoint of handleability, even more preferably 1000 to 2000. When the silsesquioxane compound has a cage structure, the molecular weight of the silsesquioxane compound having a cage structure is even more preferably 600 to 6000, even more preferably 600 to 4000, even more preferably 600 to 2000, even more preferably 600 to 1500, even more preferably 700 to 1000, and from the standpoint of availability, even more preferably 700 to 900. When the molecular weight of the silsesquioxane compound is within the above range, the resulting polyimide film has excellent transparency.

[0125] The silsesquioxane compound is preferably a compound having a structural unit represented by the following formula (5a): (R 1 SiO 1.5 ) (5a) (In formula (5a), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group.

[0126] In formula (5a), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and preferably R 1 contains a hydroxy group or an alkoxy group, more preferably R 1 contains an aromatic group, i.e., R 1 Preferably, contains a hydroxy group or an alkoxy group and an aromatic group, and more preferably is a hydroxy group or an alkoxy group and an aromatic group.

[0127] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group, preferably a methoxy group or an ethoxy group, and more preferably an ethoxy group. Examples of the aromatic group include a phenyl group, a tolyl group, and a xylyl group, preferably a phenyl group or a tolyl group, and more preferably a phenyl group.

[0128] The silsesquioxane compound is more preferably a compound represented by the following formula (5): [R 1 SiO 1.5 ] n (5) (In formula (5), R 1 is at least one selected from a hydroxy group, an alkoxy group, and an aromatic group, and n is 4 to 100. n is an average value.

[0129] In formula (5), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and preferably R 1 contains a hydroxy group or an alkoxy group, more preferably R 1 further comprises an aromatic group, i.e., R 1Preferably, contains a hydroxy group or an alkoxy group and an aromatic group, and more preferably is a hydroxy group or an alkoxy group and an aromatic group.

[0130] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group, preferably a methoxy group or an ethoxy group, and more preferably an ethoxy group. Examples of the aromatic group include a phenyl group, a tolyl group, and a xylyl group, preferably a phenyl group or a tolyl group, and more preferably a phenyl group.

[0131] In formula (5), n is 4 to 100, preferably 7 to 100, more preferably 8 to 80, even more preferably 9 to 80, still more preferably 10 to 70, even more preferably 13 to 50, and still more preferably 13 to 30. When a plurality of silsesquioxane compounds are contained, n is an average value (corresponding to the number average degree of polymerization).

[0132] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples in any way.

[0133] <Physical Properties and Evaluation of Polyimide Films> The physical properties of the films obtained in the examples and comparative examples were measured by the following methods. (1) Film Thickness: Film thickness was measured using a micrometer manufactured by Mitutoyo Corporation. (2) Glass Transition Temperature (Tg): Using a thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Corporation, the elongation of a test piece was measured in tensile mode under the following conditions: sample size 3 mm x 20 mm, load 50 mN, nitrogen gas flow (flow rate 200 mL / min), and heating rate 10°C / min. The point at which an inflection point of elongation was observed was determined as the glass transition temperature. (3) 5% Weight Loss Temperature (Td5%): Using a thermogravimetric simultaneous differential thermal analyzer "TG / DTA6200" manufactured by Hitachi High-Tech Science Corporation. The sample was heated from 40°C to 150°C at a heating rate of 10°C / min and held at 150°C for 30 minutes to remove absorbed moisture. The sample was then further heated to 600°C. The temperature at which the weight decreased by 5% compared to the weight at 150°C was defined as the 5% weight loss temperature (Td5%). The higher the weight loss temperature, the better the heat resistance. (4) Total Light Transmittance: Total light transmittance was measured in accordance with JIS K7105:1981 using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd. The higher the total light transmittance, the higher the transparency after heat treatment and the better the heat resistance. (5) Tensile Elongation: Tensile elongation was measured in accordance with JIS K7127:1999 using a tensile testing machine "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. The distance between chucks was 50 mm, the test piece size was 10 mm x 70 mm, and the test speed was 20 mm / min. The larger the tensile elongation, the higher the bending performance and the better the flexibility when used as a substrate.

[0134] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, as well as their abbreviations, are as follows: <Tetracarboxylic acid components> s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation; compound represented by formula (a2s)) ODPA: 4,4'-oxydiphthalic anhydride (manufactured by Manac Corporation; compound represented by formula (a6)) <Diamine components> 4-BAAB: 4-aminophenyl-4'-aminobenzoate (manufactured by Nihon Junryo Pharmaceutical Co., Ltd.; compound represented by formula (b31)) APTP: bis(4-aminophenyl)terephthalate (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b32)) ABHQ: 1,4-bis(4-aminobenzoyloxy)benzene (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b33)) PPD: p-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b4))

[0135] The silsesquioxane compounds used in the examples and comparative examples are as follows: Silsesquioxane compound 1: Random structure. R in formula (5) 1 are hydroxy groups and phenyl groups, and the molecular weight is 1,300. Silsesquioxane compound 2: random structure. R in formula (5) 1 are a hydroxy group, an ethoxy group, and a phenyl group, and the molecular weight is 1000. Silsesquioxane compound 3: a random structure. R in formula (5) 1 are a hydroxy group, an ethoxy group, and a phenyl group, and the molecular weight is 2400. Silsesquioxane compound 4: a random structure. R in formula (5) 1 are hydroxy groups, ethoxy groups, and phenyl groups, and the molecular weight is 4100. Silsesquioxane compound 5: cage structure. The molecular formula is C ３０ H ２８ O １５ Si ８ R in formula (5) 1 are hydroxy groups and phenyl groups, the ratio of the number of hydroxy groups to the number of phenyl groups (hydroxy groups / phenyl groups) is 3 / 5, and the molecular weight is 853.29. Silsesquioxane compound 6: cage structure. The molecular formula is C２４ H ２４ O １６ Si ８ R in formula (5) 1 are hydroxy groups and phenyl groups, the ratio of the number of hydroxy groups to the number of phenyl groups (hydroxy groups / phenyl groups) is 1 / 1, and the molecular weight is 793.19. The molecular weights of silsesquioxane compound 1, silsesquioxane compound 2, silsesquioxane compound 3, and silsesquioxane compound 4 are weight-average molecular weights calculated as standard polystyrene (PS) values ​​by gel filtration chromatography measurement under the following conditions:

[0136] (Gel Filtration Chromatography Measurement Conditions) The silsesquioxane compound was diluted with the mobile phase solvent shown below to a silsesquioxane compound concentration of 0.1 mass % to prepare a measurement solution. Using the measurement solution, gel filtration chromatography measurement was performed under the following conditions to determine the weight average molecular weight of the silsesquioxane compound as a polystyrene (PS) equivalent value. Apparatus: Shodex 101 Column: TSKgel G2000H ＸＬ &TSKgel G4000H ＸＬ Column temperature: 40°C Mobile phase: THF Mobile phase flow rate: 1.0 mL / min Molecular weight standard: polystyrene (PS) (manufactured by Tosoh Corporation)

[0137] The abbreviations for the solvents and catalysts used in the examples and comparative examples are as follows: NMP: N-methyl-2-pyrrolidone (manufactured by Tokyo Pure Chemical Industries, Ltd.) TEA: Triethylamine (manufactured by Kanto Chemical Co., Ltd.)

[0138] <Production of Polyimide Resin Precursor Composition and Polyimide Film> Example 1 26.212 g (0.115 mol) of 4-BAAB and 144.000 g of NMP were placed in a 300 mL 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. The mixture was stirred at 200 rpm under a nitrogen atmosphere at a system temperature of 50°C to obtain a solution. 33.788 g (0.115 mol) of s-BPDA and 96.000 g of NMP were then added to the solution, and the mixture was heated with a mantle heater to raise the reaction system temperature to 70°C and stirred for 5 hours to obtain a solution containing a polyimide resin precursor (polyamic acid). 12.000 g (20% by mass based on the polyimide resin precursor) of silsesquioxane compound 1 was added to the resulting solution to obtain a polyimide resin precursor composition. The resulting polyimide resin precursor composition was then spin-coated onto a glass plate, held on a hot plate at 80°C for 20 minutes, and then heated in an air atmosphere in a hot air dryer at 450°C for 20 minutes to evaporate the solvent, yielding a polyimide film. The physical properties and evaluation results of the polyimide film are shown in Table 1.

[0139] Examples 2 to 9 Polyimide resin precursor compositions were obtained in the same manner as in Example 1, except that the amount or type of silsesquioxane compound in Example 1 was changed as shown in Table 1. Polyimide films were obtained using the obtained polyimide resin precursor compositions in the same manner as in Example 1. The physical properties and evaluation results of the polyimide films are shown in Table 1.

[0140] Examples 10 to 14 and Comparative Example 4 Polyimide resin precursor compositions were obtained in the same manner as in Example 1, except that the amounts and types of the tetracarboxylic acid component and diamine component in Example 1 were changed as shown in Table 2. Using the obtained polyimide resin precursor compositions, polyimide films were obtained in the same manner as in Example 1. The physical properties and evaluation results of the polyimide films are shown in Table 2.

[0141] Comparative Example 1 A polyimide resin precursor composition was obtained in the same manner as in Example 1, except that the silsesquioxane compound was not used. Using the obtained polyimide resin precursor composition, a polyimide film was obtained in the same manner as in Example 1. The physical properties and evaluation results of the polyimide film are shown in Table 2.

[0142] Comparative Example 2 A polyimide resin precursor composition was obtained in the same manner as in Example 10, except that the silsesquioxane compound was not used. Using the obtained polyimide resin precursor composition, a polyimide film was obtained in the same manner as in Example 10. The physical properties and evaluation results of the polyimide film are shown in Table 2.

[0143] Comparative Example 3 A polyimide resin precursor composition was obtained in the same manner as in Example 11, except that the silsesquioxane compound in Example 11 was not used. Using the obtained polyimide resin precursor composition, a polyimide film was obtained in the same manner as in Example 11. The physical properties and evaluation results of the polyimide film are shown in Table 2.

[0144] Comparative Example 5 A polyimide resin precursor composition was obtained in the same manner as in Example 12, except that the silsesquioxane compound in Example 12 was not used. Using the obtained polyimide resin precursor composition, a polyimide film was obtained in the same manner as in Example 12. The physical properties and evaluation results of the polyimide film are shown in Table 2.

[0145]

[0146]

[0147] As shown in Tables 1 and 2, the polyimide films obtained using the polyimide resin precursor compositions of the Examples have a total light transmittance of 80% or more, demonstrating excellent transparency, even after treatment at a high temperature of 450°C. This shows that the polyimide resin precursor composition of the present invention can produce polyimide films that have excellent heat resistance and excellent transparency even after high-temperature treatment, and is useful as a raw material for display films. Furthermore, the polyimide films of the present invention have excellent heat resistance and excellent transparency even after high-temperature treatment, making them useful as display films.

[0148] According to the present invention, there can be provided a polyimide resin precursor composition capable of producing a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment, and a polyimide film having excellent heat resistance and excellent transparency even after high-temperature treatment. Because the polyimide film has the properties described above, the polyimide resin precursor composition of the present invention is useful as a raw material for display films.

Claims

1. A polyimide resin precursor composition containing a polyimide resin precursor having a repeating unit represented by the following formula (1), a silsesquioxane compound, and an organic solvent: (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

2. The polyimide resin precursor composition according to claim 1, wherein the mass ratio of the silsesquioxane compound to the polyimide resin precursor (silsesquioxane compound / polyimide resin precursor) is 1 / 99 to 35 / 65.

3. The polyimide resin precursor composition according to claim 1 or 2, wherein the molecular weight of the silsesquioxane compound is 300 to 6,000.

4. B 1 The polyimide resin precursor composition according to any one of claims 1 to 3, further comprising a divalent group represented by the following formula (4):

5. The polyimide resin precursor composition according to any one of claims 1 to 4, wherein the silsesquioxane compound is a compound represented by the following composition formula (5): [R 1 SiO 1.5 ] n (5) (In formula (5), R 1 is at least one selected from the group consisting of a hydroxy group, an alkoxy group, and an aromatic group, and n is 4 to 100. Note that n is an average value.

6. R 1 The polyimide resin precursor composition according to claim 5 , wherein contains a hydroxy group or an alkoxy group.

7. R 1 The polyimide resin precursor composition according to claim 5 or 6, wherein contains an aromatic group.

8. A 1 The polyimide resin precursor composition according to any one of claims 1 to 7, further comprising a tetravalent group represented by the following formula (6):

9. A polyimide film obtained by applying the polyimide resin precursor composition according to any one of claims 1 to 8 onto a support and heating the applied composition.

10. A method for producing a polyimide film, which comprises applying the polyimide resin precursor composition according to any one of claims 1 to 8 onto a support and heating the applied composition.

11. The polyimide film according to claim 9, which is used for a display.

12. A method for increasing the transparency of a polyimide film, comprising adding a silsesquioxane compound to a polyimide resin precursor containing a repeating unit represented by the following formula (1), which is a raw material for the polyimide film: (In formula (1), X 1 and X 2 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; A 1 contains a tetravalent group represented by formula (2), and B 1 contains a divalent group represented by formula (3), and in formula (3), Y 1 and Y 2 are each independently —COO— or —OCO—, and k is 0 or 1.

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