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

Abstract

The present invention is a polyimide resin which has a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, wherein: the constituent unit A contains at least one constituent unit that is selected from the group consisting of a constituent unit (A1) derived from a compound represented by formula (a1) and a constituent unit (A2) derived from a compound represented by formula (a2); the constituent unit B contains at least one constituent unit (B1) that is selected from the group consisting of a constituent unit derived from a compound represented by formula (b11), a constituent unit derived from a compound represented by formula (b12) and a constituent unit derived from a compound represented by formula (b13), and at least one constituent unit (B2) that is selected from the group consisting of a constituent unit derived from a compound represented by general formula (b21) and a constituent unit derived from a compound represented by general formula (b22); and the molar ratio of the constituent unit (B1) to the constituent unit (B2), namely (B1) / (B2) is from 45 / 55 to 75 / 25. The present invention provides: a polyimide resin which is capable of forming a film that has excellent transparency and optical isotropy, while exhibiting excellent ductility; a polyimide resin composition; a polyimide varnish; and a polyimide film. (In the formulae, each of R1 and R2 independently represents a methyl group or a trifluoromethyl group; and each of X1 to X4 independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO2-, -O- or –CO-.)

Description

[Technical field]

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

[0002] Various applications of polyimide resins are being considered in the fields of electric and electronic components. For example, it is desirable to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with plastic substrates in order to make the devices lighter and more flexible, and research on polyimide films suitable for such plastic substrates is ongoing. Polyimide films for such applications are required to be transparent. Furthermore, the polyimide film is required to have a small phase difference due to birefringence and a low retardation (good optical isotropy).

[0003] Patent Document 1 discloses a polyimide resin obtained by using a diamine (e.g., metaphenylenediamine) in which at least one of the amino groups of the diamine is bonded to the meta position relative to the main chain, as a polyimide resin that provides a film with reduced birefringence. Patent Document 2 discloses a polyimide resin containing tetracarboxylic acid residues and diamine residues of specific structures, and tetracarboxylic acid residues and / or diamine residues having bending sites, as a polyimide resin that provides a film excellent in heat resistance, transmittance, low linear expansion coefficient, and low retardation. Specifically, the document discloses a polyimide resin obtained using 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-bicyclohexanetetracarboxylic acid dianhydride, pyromellitic anhydride, 2,2'-bis(trifluoromethyl)benzidine, and 4,4'-diaminodiphenyl sulfone. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-134211 [Patent Document 2] International Publication No. 2015 / 125895 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, polyimide films are required to have good optical properties such as transparency and optical isotropy. However, because polyimide has a rigid and strong molecular structure, problems include breakage due to shrinkage during film production and breakage when used in products with moving parts (such as flexible displays). For example, when a highly flexible component is introduced into the molecule to suppress breakage and improve ductility, the optical properties generally deteriorate. Thus, there has been a demand for polyimide films that have good optical properties and ductility. Therefore, an object of the present invention is to provide a polyimide resin, a polyimide resin composition, a polyimide varnish, and a polyimide film which are capable of forming a film having excellent transparency, optical isotropy, and ductility. [Means for solving the problem]

[0006] The present inventors have discovered that a polyimide resin containing a specific combination of structural units and a resin composition containing the polyimide resin and a specific polymer can solve the above problems, and have completed the invention.

[0007] That is, the present invention relates to the following [1] to [8]. [1] A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A comprises at least one structural unit selected from the group consisting of a structural unit (A1) derived from a compound represented by the following formula (a1), and a structural unit (A2) derived from a compound represented by the following formula (a2); the structural unit B comprises at least one structural unit (B1) selected from the group consisting of a structural unit derived from a compound represented by the following formula (b11), a structural unit derived from a compound represented by the following formula (b12), and a structural unit derived from a compound represented by the following formula (b13), and at least one structural unit (B2) selected from the group consisting of a structural unit derived from a compound represented by the following general formula (b21), and a structural unit derived from a compound represented by the following general formula (b22); and the molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is 45 / 55 to 75 / 25.

[0008] [ka] (In formula (b11), R 1 and R 2 each independently represents a methyl group or a trifluoromethyl group; in formulas (b21) and (b22), X 1 ~X 4 each independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO 2 -, -O- or -CO-.

[0009] [2] The polyimide resin according to [1] above, which has an elongation at break of 10% or more as measured in accordance with JIS K 7127. [3] The polyimide resin according to either of the above [1] or [2], wherein the structural unit (B2) includes at least one structural unit selected from the group consisting of a structural unit derived from a compound represented by the following formula (b211), a structural unit derived from a compound represented by the following formula (b212), and a structural unit derived from a compound represented by the following formula (b213):

[0010] [ka]

[0011] [4] A polyimide resin composition comprising the polyimide resin according to any one of the above [1] to [3], and at least one selected from the group consisting of a fluorine-containing polymer and a silicone-containing polymer. [5] The polyimide resin composition according to the above item [4], wherein the total content of the fluorine-containing polymer and the silicone-containing polymer is 0.01 to 2 parts by mass per 100 parts by mass of the polyimide resin. [6] The polyimide resin composition according to the above [4] or [5], wherein the fluorine-containing polymer is a fluorine-containing acrylic polymer. [7] A polyimide varnish obtained by dissolving the polyimide resin according to any one of the above [1] to [3] or the polyimide resin composition according to any one of the above [4] to [6] in an organic solvent. [8] A polyimide film comprising the polyimide resin according to any one of the above [1] to [3] or the polyimide resin composition according to any one of the above [4] to [6]. Effect of the Invention

[0012] According to the present invention, it is possible to provide a polyimide resin, a polyimide resin composition, a polyimide varnish, and a polyimide film which are capable of forming a film having excellent transparency, optical isotropy, and ductility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Polyimide resin] The polyimide resin of the present invention is a polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, in which the structural unit A includes at least one structural unit selected from the group consisting of a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from a compound represented by the following formula (a2), and the structural unit B includes a structural unit derived from a compound represented by the following formula (b11) (hereinafter also referred to as structural unit (B11)), a structural unit derived from a compound represented by the following formula (b12) (hereinafter also referred to as structural unit (B12)), .) and a structural unit derived from a compound represented by the following formula (b13) (hereinafter also referred to as structural unit (B13)), and at least one structural unit (B2) selected from the group consisting of a structural unit derived from a compound represented by the following general formula (b21) (hereinafter also referred to as structural unit (B21)) and a structural unit derived from a compound represented by the following general formula (b22) (hereinafter also referred to as structural unit (B22)), and the molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is 45 / 55 to 75 / 25.

[0014] [ka] (In formula (b11), R 1 and R 2 each independently represents a methyl group or a trifluoromethyl group; in formulas (b21) and (b22), X 1 ~X 4 each independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO 2 -, -O- or -CO-.

[0015] <Constituent unit A> The structural unit A is a structural unit derived from a tetracarboxylic dianhydride contained in the polyimide resin, and includes at least one structural unit selected from the group consisting of a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from a compound represented by the following formula (a2):

[0016] [ka]

[0017] The compound represented by formula (a1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride. When the structural unit A contains the structural unit (A1), the transparency and optical isotropy of the film can be improved, and further, the heat resistance and thermal stability are also improved. The compound represented by formula (a2) is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. When the structural unit A contains the structural unit (A2), the transparency of the film is improved, and the solubility of the polyimide in organic solvents is improved.

[0018] The structural unit A may contain both the structural unit (A1) and the structural unit (A2), but preferably contains either the structural unit (A1) or the structural unit (A2), and more preferably contains the structural unit (A1).

[0019] When the structural unit A contains the structural unit (A1) and the structural unit (A2), the total ratio of the structural units (A1) and (A2) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to the total ratio of the structural units (A1) and (A2), i.e., 100 mol%.

[0020] When the structural unit A contains the structural unit (A1), the ratio of the structural unit (A1) in the structural unit A is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, that is, it is 100 mol%. Similarly, the ratio of the structural unit (A1) in the structural unit A is preferably 45 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably 99 to 100 mol%. When the structural unit A contains the structural unit (A2), the ratio of the structural unit (A2) in the structural unit A is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, that is, it is 100 mol%. Similarly, the ratio of the structural unit (A2) in the structural unit A is preferably 45 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably 99 to 100 mol%.

[0021] The structural unit A may further contain a structural unit (A3) derived from a compound represented by the following formula (a3).

[0022] [ka]

[0023] The compound represented by formula (a3) ​​is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride. When the structural unit A contains the structural unit (A3), the transparency of the film is improved.

[0024] When the structural unit A contains the structural unit (A3), the proportion of the structural unit (A3) in the structural unit A is preferably 55 mol % or less, more preferably 30 mol % or less, and further preferably 5 mol % or more. When the structural unit A contains the structural unit (A3), the structural unit A preferably contains the structural unit (A1) and the structural unit (A3), and more preferably consists of the structural unit (A1) and the structural unit (A3).

[0025] The structural unit A may contain structural units other than the structural units (A1) to (A3) as long as the effects of the present invention are not impaired. The tetracarboxylic dianhydride that provides such a structural unit is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, and 2,2',3,3'-biphenyltetracarboxylic dianhydride. carboxylic dianhydrides (excluding the compound represented by formula (a2)); alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride (excluding the compound represented by formula (a1) and the compound represented by formula (a3)); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. 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. The structural units other than the structural units (A1) to (A3) optionally contained in the structural unit A may be of one type, or of two or more types. It is preferable that the structural unit A does not contain any structural units other than the structural units (A1) to (A3) described above.

[0026] <Structural unit B> The structural unit B is a structural unit derived from a diamine in a polyimide resin, and includes at least one structural unit (B1) selected from the group consisting of a structural unit (B11) derived from a compound represented by the following formula (b11), a structural unit (B12) derived from a compound represented by the following formula (b12), and a structural unit (B13) derived from a compound represented by the following formula (b13), and at least one structural unit (B2) selected from the group consisting of a structural unit (B21) derived from a compound represented by the following general formula (b21), and a structural unit (B22) derived from a compound represented by the following general formula (b22): The molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is 45 / 55 to 75 / 25.

[0027] [ka]

[0028] In formula (b11), R 1 and R 2 each independently represents a methyl group or a trifluoromethyl group; in formulas (b21) and (b22), X 1 ~X 4 each independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO 2 It represents -, -O- or -CO-.

[0029] (Structural unit (B1)) The structural unit (B1) is at least one structural unit selected from the group consisting of a structural unit (B11) derived from a compound represented by the following formula (b11), a structural unit (B12) derived from a compound represented by the following formula (b12), and a structural unit (B13) derived from a compound represented by the following formula (b13).

[0030] [ka]

[0031] The compound represented by formula (b11) is 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane or 2,2-bis[4-(4-aminophenoxy)phenyl]propane, The compound represented by formula (b12) is 4,4'-diaminodiphenyl ether, The compound represented by formula (b13) is 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene.

[0032] The structural unit B contains at least one structural unit selected from the group consisting of the structural units (B11) to (B13). From the viewpoint of increasing the ductility of the film, it is more preferable that the structural unit B contains at least one structural unit selected from the group consisting of the structural units (B11) and (B12), and it is even more preferable that the structural unit B contains the structural unit (B11). The structural unit B may contain two or more of the structural units (B11) to (B13), but preferably contains one of the structural units (B11) to (B13). In other words, the structural unit B preferably contains the structural unit (B11), the structural unit (B12), or the structural unit (B13).

[0033] By including the structural unit (B1) in the structural unit B, the film transparency and optical isotropy can be maintained while improving the ductility. In addition, colorlessness can also be improved. The structural unit (B1) may be one type or two or more types. As the structural unit (B1), a structural unit derived from 2,2-bis[4-(4-aminophenoxy)phenyl]propane is preferred.

[0034] (Structural unit (B2)) The structural unit (B2) is at least one structural unit selected from the group consisting of a structural unit (B21) derived from a compound represented by the following general formula (b21) and a structural unit (B22) derived from a compound represented by the following general formula (b22).

[0035] [ka]

[0036] In formulas (b21) and (b22), X 1 ~X 4 each independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO 2 It represents -, -O- or -CO-.

[0037] The compound represented by the general formula (b21) is X 1 and X 2 Three benzene rings are connected via 1 and X 2 The compound represented by the general formula (b22) has a skeleton to which X 3 and X 4 Three benzene rings are connected via X, and the central benzene ring has X at the 1- and 2-positions. 3 and X 4 By having such a structure, it is possible to form a film that is excellent in transparency and optical isotropy while having ductility.

[0038] X in general formulae (b21) and (b22) 1 ~X 4 From the viewpoint of forming a film having excellent optical isotropy, each of the groups independently preferably represents an alkylidene group having 3 to 5 carbon atoms, —SO 2 It represents - or -O-, more preferably an alkylidene group having 3 to 5 carbon atoms or -O-, still more preferably an isopropylidene group or -O-, and still more preferably an isopropylidene group. X in general formula (b21) 1 and X 2 may each have a different group, but is preferably the same group. 3 and X 4 may each have a different group, but preferably has the same group. In the general formulae (b21) and (b22), the amino group is bonded to a benzene ring to which each amino group is bonded. 1 ~X 4 It is preferable that the aryl group is bonded to the para or meta position of the benzene ring relative to either of the above, and it is more preferable that the aryl group is bonded to the para position of the benzene ring. X in general formulae (b21) and (b22) 1 ~X 4 Examples of the alkylidene group having 2 to 5 carbon atoms include an ethylidene group, a propylidene group, an isopropylidene group, a butylidene group, an isobutylidene group, a pentylidene group, an isopentylidene group, etc. As the alkylidene group, an alkylidene group having 3 to 5 carbon atoms is preferable, and an isopropylidene group is more preferable.

[0039] The structural unit (B2) preferably contains a structural unit derived from a compound represented by general formula (b21) above, and more preferably contains at least one structural unit selected from the group consisting of a structural unit derived from a compound represented by formula (b211) below, a structural unit derived from a compound represented by formula (b212) below, and a structural unit derived from a compound represented by formula (b213) below.

[0040] [ka]

[0041] The compound represented by formula (b211) is 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, The compound represented by formula (b212) is 1,3-bis(4-aminophenoxy)benzene, The compound represented by formula (b213) is 1,3-bis(3-aminophenoxy)benzene.

[0042] Of the compounds represented by formulas (b211) to (b213), at least one compound selected from the group consisting of the compounds represented by formula (b211) and the compounds represented by formula (b212) is preferred, and the compound represented by formula (b211) is more preferred.

[0043] (Other structural units that may be included in structural unit B) The structural unit B may contain a structural unit other than the structural units (B1) and (B2). Diamines that provide such structural units are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 3,4'-diaminodiphenylether, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, N, Examples of the diamines include aromatic diamines such as N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, and 1,4-bis(4-aminophenoxy)benzene (excluding the compounds represented by the formulae (b11) to (b13) and the compounds represented by the formulae (b21) to (b22)); alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine. In this specification, an aromatic diamine refers to a diamine containing one or more aromatic rings, an alicyclic diamine refers to a diamine containing one or more alicyclic rings but no aromatic rings, and an aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural units other than the structural units (B1) and (B2) optionally contained in the structural unit B may be of one type, or of two or more types.

[0044] (Configuration of structural unit B) The structural unit B contains a structural unit (B1) and a structural unit (B2), and the molar ratio of the structural unit (B1) to the structural unit (B2) is from 45 / 55 to 75 / 25, with preferred structures being described below.

[0045] The total ratio of the structural unit (B1) and the structural unit (B2) in the structural unit B is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more. The upper limit of the total ratio of the structural unit (B1) and the structural unit (B2) is not particularly limited, but is preferably 100 mol%. It is even more preferable that the structural unit B is composed of only the structural unit (B1) and the structural unit (B2).

[0046] The molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is 45 / 55 to 75 / 25 from the viewpoint of improving transparency, optical isotropy, and ductility, but is preferably 45 / 55 to 70 / 30, more preferably 45 / 55 to 65 / 35, even more preferably 45 / 55 to 60 / 40, and even more preferably 45 / 55 to 55 / 45 from the viewpoint of improving transparency, optical isotropy, and colorlessness. Also, from the viewpoint of improving ductility, it is preferably 45 / 55 to 75 / 25, more preferably 50 / 50 to 75 / 25, even more preferably 55 / 45 to 75 / 25, even more preferably 60 / 40 to 75 / 25, and even more preferably 65 / 35 to 75 / 25. The structural unit B preferably includes a structural unit (B11) derived from a compound represented by formula (b11) as the structural unit (B1), and a structural unit derived from a compound represented by formula (b211) as the structural unit (B2). The polyimide resin of the present invention preferably includes a structural unit (A1) derived from a compound represented by formula (a1) as the structural unit A, and a structural unit having the above combination as the structural unit B.

[0047] (Physical properties of polyimide resin, etc.) From the viewpoint of the mechanical strength of the resulting polyimide film, the number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 100,000. The number average molecular weight of the polyimide resin can be determined, for example, from a standard polymethyl methacrylate (PMMA)-equivalent value measured by gel filtration chromatography.

[0048] The polyimide resin of the present invention may contain a structure other than a polyimide chain (a structure formed by imide bonding between the structural unit A and the structural unit B). Examples of structures other than a polyimide chain that can be contained in the polyimide resin include structures containing amide bonds. The polyimide resin of the present invention preferably contains, as a main structure, a polyimide chain (a structure formed by imide bonding between the structural unit A and the structural unit B). Therefore, the ratio of the polyimide chain in the polyimide resin of the present invention is preferably 50 mass % or more, more preferably 70 mass % or more, even more preferably 90 mass % or more, and particularly preferably 99 mass % or more.

[0049] By using the polyimide resin of the present invention, a film excellent in transparency, optical isotropy, and ductility can be formed, and the preferable physical properties of the film are as follows. The total light transmittance, when made into a film having a thickness of 30 μm, is preferably 85% or more, more preferably 87% or more, even more preferably 88% or more, and still more preferably 89% or more. The yellow index (YI), when formed into a film having a thickness of 30 μm, is preferably 6.5 or less, more preferably 4.0 or less, even more preferably 3.0 or less, still more preferably 2.0 or less, and even more preferably 1.5 or less. The haze, when formed into a film having a thickness of 30 μm, is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.1% or less. The thickness retardation (Rth) is preferably 40 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, and still more preferably 18 nm or less, when made into a film having a thickness of 30 μm. Furthermore, the polyimide resin of the present invention has an elongation at break measured in accordance with JIS K 7127 of preferably 10% or more, more preferably 18% or more, even more preferably 20% or more, and still more preferably 30% or more. The above-mentioned physical properties in the present invention can be specifically measured by the methods described in the Examples.

[0050] [Manufacturing method of polyimide resin] The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component containing at least one selected from the group consisting of a compound that provides the above-mentioned structural unit (A1) and a compound that provides the above-mentioned structural unit (A2), with a diamine component containing a compound that provides the above-mentioned structural unit (B1) and a compound that provides the above-mentioned structural unit (B2).

[0051] Compounds that provide the structural unit (A1) include compounds represented by formula (a1), but are not limited thereto, and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a1) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A1) are preferably compounds represented by formula (a1) (i.e., dianhydrides). Similarly, examples of compounds that provide the structural unit (A2) include compounds represented by formula (a2), but are not limited thereto and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a2) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A2) are preferably compounds represented by formula (a2) (i.e., dianhydrides).

[0052] The tetracarboxylic acid component contains a compound that gives the structural unit (A1) and a compound that gives the structural unit (A2) in a total amount of preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound that gives the structural unit (A1) and the compound that gives the structural unit (A2) is not particularly limited, that is, it is 100 mol%. The tetracarboxylic acid component may be composed only of a compound that gives the structural unit (A1) and a compound that gives the structural unit (A2).

[0053] When the tetracarboxylic acid component contains a compound that gives the structural unit (A1) or a compound that gives the structural unit (A2), the compound that gives the structural unit (A1) or the compound that gives the structural unit (A2) is preferably contained in an amount of 45 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more. The upper limit of the content of the compound that gives the structural unit (A1) or the compound that gives the structural unit (A2) is not limited, that is, it is 100 mol%. The tetracarboxylic acid component may be composed only of a compound that gives the structural unit (A1) or a compound that gives the structural unit (A2), and preferably consists only of a compound that gives the structural unit (A1).

[0054] The tetracarboxylic acid component may contain a compound that provides the above-mentioned structural unit (A3) to the extent that optical isotropy and ductility are not impaired. Compounds that provide the structural unit (A3) include, but are not limited to, compounds represented by formula (a3), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a3) ​​and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A3) are preferably compounds represented by formula (a3) ​​(i.e., dianhydrides).

[0055] When the tetracarboxylic acid component contains a compound that gives the structural unit (A3), it preferably contains 55 mol % or less, more preferably 30 mol % or less, of the compound that gives the structural unit (A3). It is also preferable that it contains 5 mol % or more. When the tetracarboxylic acid component contains a compound that gives the structural unit (A3), it is preferable that it consists only of a compound that gives the structural unit (A1) and a compound that gives the structural unit (A3).

[0056] The tetracarboxylic acid component may contain a compound other than the compound that provides the structural unit (A1), the compound that provides the structural unit (A2), and the compound that provides the structural unit (A3). Examples of such compounds include the above-mentioned aromatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides, as well as derivatives thereof (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.). The compound other than the compound that gives the structural units (A1) to (A3) that is optionally contained in the tetracarboxylic acid component may be one type, or two or more types.

[0057] Examples of compounds that provide the structural unit (B1) include compounds represented by general formula (b11) that provide the structural unit (B11), compounds represented by general formula (b12) that provide the structural unit (B12), and compounds represented by general formula (b13) that provide the structural unit (B13), but are not limited thereto and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the compounds represented by general formula (b11), the compounds represented by general formula (b12), and the compounds represented by general formula (b13). As a compound that provides the structural unit (B1), at least one compound (i.e., a diamine) selected from the group consisting of the compounds represented by general formula (b11), the compounds represented by general formula (b12), and the compounds represented by general formula (b13) is preferred.

[0058] The diamine component may contain a compound that provides two or more of the structural units (B11) to (B13), but preferably contains a compound that provides one of the structural units (B11) to (B13). In other words, it is preferable for the structural unit B to contain a compound that provides the structural unit (B11), a compound that provides the structural unit (B12), or a compound that provides the structural unit (B13).

[0059] Compounds that provide the structural unit (B2) include compounds represented by general formula (b21) and compounds represented by general formula (b22), but are not limited thereto and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the compounds represented by general formula (b21) and the compounds represented by general formula (b22). Compounds that provide the structural unit (B2) are preferably at least one compound (i.e., diamines) selected from the group consisting of compounds represented by general formula (b21) and compounds represented by general formula (b22).

[0060] The compound providing structural unit (B2) preferably includes a compound represented by general formula (b21), more preferably includes at least one compound selected from the group consisting of compounds represented by formula (b211), compounds represented by formula (b212), and compounds represented by formula (b213), even more preferably includes at least one compound selected from the group consisting of compounds represented by formula (b211) and compounds represented by formula (b212), and particularly preferably includes a compound represented by formula (b211).

[0061] The total content of the compound giving the structural unit (B1) and the compound giving the structural unit (B2) in the structural unit B is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more. The upper limit of the total content of the compound giving the structural unit (B1) and the compound giving the structural unit (B2) is not particularly limited, but is preferably 100 mol%. It is even more preferable that the diamine component is composed only of the compound giving the structural unit (B1) and the compound giving the structural unit (B2).

[0062] The molar ratio of the compound that gives the structural unit (B1) and the compound that gives the structural unit (B2) [(B1) / (B2)] is preferably 45 / 55 to 75 / 25 from the viewpoint of improving transparency, optical isotropy, and ductility, and is preferably 45 / 55 to 70 / 30, more preferably 45 / 55 to 65 / 35, even more preferably 45 / 55 to 60 / 40, and even more preferably 45 / 55 to 55 / 45 from the viewpoint of improving transparency, optical isotropy, and colorlessness. Also, from the viewpoint of improving ductility, it is preferably 45 / 55 to 75 / 25, more preferably 50 / 50 to 75 / 25, even more preferably 55 / 45 to 75 / 25, even more preferably 60 / 40 to 75 / 25, and even more preferably 65 / 35 to 75 / 25.

[0063] The diamine component may contain a compound other than the compound that provides the structural unit (B1) and the compound that provides the structural unit (B2). Examples of such compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, as well as their derivatives (diisocyanates, etc.). The compound optionally contained in the diamine component other than the compound providing the structural unit (B1) and the compound providing the structural unit (B2) may be one type, or two or more types.

[0064] In the present invention, the ratio of the amounts of the tetracarboxylic acid component and the diamine component used in the production of the polyimide resin is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

[0065] In the present invention, in addition to the above-mentioned tetracarboxylic acid component and diamine component, a terminal blocking agent may be used in the production of the polyimide resin. As the terminal blocking agent, monoamines or dicarboxylic acids are preferred. The amount of the terminal blocking agent to be introduced is preferably 0.0001 to 0.1 moles per mole of the tetracarboxylic acid component, and particularly preferably 0.001 to 0.06 moles. As the monoamine terminal blocking agent, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are recommended. Among these, benzylamine and aniline are preferably used. As the dicarboxylic acid terminal blocking agent, dicarboxylic acids are preferred, and a part of them may be ring-closed. For example, 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. are recommended. Of these, phthalic acid and phthalic anhydride are preferably used.

[0066] The method for reacting the tetracarboxylic acid component and the diamine component is not particularly limited, and any known method can be used. Specific reaction methods include (1) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the mixture is stirred at 0 to 80°C for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which a diamine component and a reaction solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged, and the mixture is stirred at 0 to 80°C for 0.5 to 30 hours as necessary, and then the temperature is raised to carry out the imidization reaction; and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

[0067] The reaction solvent used in the production of the polyimide resin may be any solvent that does not inhibit the imidization reaction and can dissolve the resulting polyimide. Examples of the solvent include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0068] Specific examples of aprotic solvents include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone-based solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide-based solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone-based solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone; amine-based solvents such as picoline and pyridine; and ester-based solvents such as (2-methoxy-1-methylethyl) acetate.

[0069] Specific examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above reaction solvents, amide-based solvents and lactone-based solvents are preferred. The above reaction solvents may be used alone or in combination of two or more.

[0070] In the imidization reaction, it is preferable to carry out the reaction while removing water generated during the production using a Dean-Stark apparatus, etc. By carrying out such an operation, it is possible to further increase the degree of polymerization and the imidization rate.

[0071] In the above imidization reaction, a known imidization catalyst can be used, such as a base catalyst or an acid catalyst. Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more kinds. Among the above, from the viewpoint of handleability, it is preferable to use a base catalyst, it is more preferable to use an organic base catalyst, it is even more preferable to use one or more selected from triethylamine and triethylenediamine, and it is particularly preferable to use triethylamine or a combination of triethylamine and triethylenediamine.

[0072] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoints of reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

[0073] [Polyimide resin composition] The polyimide resin composition of the present invention contains the polyimide resin of the present invention and at least one selected from the group consisting of a fluorine-containing polymer and a silicone-containing polymer. By containing at least one selected from the group consisting of a fluorine-containing polymer and a silicone-containing polymer, it is possible to significantly improve ductility while maintaining high transparency and optical isotropy. Among the fluorine-containing polymers and silicone-containing polymers, the fluorine-containing polymer is preferred.

[0074] <Fluorine-containing polymer> The fluorine-containing polymer in the polyimide resin composition of the present invention is preferably a polymer having structural units derived from a monomer containing fluorine, and more preferably a polymer having structural units derived from a monomer containing a fluorinated alkyl group. The fluorine-containing polymer in the present invention is preferably a fluorine-containing acrylic polymer.

[0075] The fluorine-containing acrylic polymer preferably contains a structural unit derived from an acrylic monomer containing fluorine, and more preferably contains a structural unit derived from an acrylic monomer containing fluorine and a structural unit derived from an acrylic monomer having a hydrophilic group.

[0076] As the fluorine-containing acrylic monomer, a monomer having a perfluoroalkyl group is preferable. Examples of acrylic monomers having a hydrophilic group include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylates, polyalkylene glycol (meth)acrylates, acrylamides, and methacrylamides. The fluorine-containing acrylic polymer may contain an acrylic monomer having a hydrophobic group. Examples of the acrylic monomer having a hydrophobic group include alkyl (meth)acrylate, silicone-containing (meth)acrylate, and aryl (meth)acrylate. Here, "(meth)acrylate" means "acrylate or methacrylate". The fluorine-containing acrylic monomer may be copolymerized with another monomer having a vinyl group.

[0077] Commercially available fluorine-containing polymers include "LE-605", "LE-607", "LE-605DM", and "LE-607DM" manufactured by Kyoeisha Chemical Co., Ltd.

[0078] <Silicone-containing polymer> The silicone-containing polymer in the polyimide resin composition of the present invention may be a modified silicone having a side chain or an end of an organic modifying group introduced into the main chain of a silicone skeleton, or a silicone-containing acrylic polymer having a silicone side chain introduced into the main chain of an acrylic polymer, with a silicone-containing acrylic polymer being preferred.

[0079] Examples of modified silicones include polyether-modified silicones in which a polyether group has been introduced into a side chain or terminal, and polyester-modified silicones in which a polyester group has been introduced, with polyether-modified silicones being preferred. Examples of the polyether group of the polyether-modified silicone include a polyethylene glycol group and a polypropylene glycol group, with the polyethylene glycol group being preferred. The main chain of the silicone skeleton of the modified silicone is preferably polydimethylsiloxane.

[0080] The silicone-containing acrylic polymer preferably contains a structural unit derived from an acrylic monomer containing silicone, and more preferably contains a structural unit derived from an acrylic monomer containing silicone and a structural unit derived from an acrylic monomer having a hydrophilic group.

[0081] As the silicone-containing acrylic monomer, a monomer having a polydimethylsiloxane group is preferred. Examples of acrylic monomers having a hydrophilic group include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylates, polyalkylene glycol (meth)acrylates, acrylamides, and methacrylamides. The silicone-containing acrylic polymer may contain an acrylic monomer having a hydrophobic group. Examples of the acrylic monomer having a hydrophobic group include alkyl (meth)acrylate, silicone-containing (meth)acrylate, and aryl (meth)acrylate. Here, "(meth)acrylate" means "acrylate or methacrylate". The silicone-containing acrylic monomer may be copolymerized with other monomers having a vinyl group.

[0082] Commercially available silicone-containing polymers include "LE-302", "LE-304", and "KL-700" manufactured by Kyoeisha Chemical Co., Ltd., and "BYK-378" manufactured by BYK Japan KK.

[0083] In the polyimide resin composition of the present invention, the total content of the fluorine-containing polymer and the silicone-containing polymer is preferably 0.01 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, even more preferably 0.2 to 1.2 parts by mass, and even more preferably 0.5 to 1.0 parts by mass, relative to 100 parts by mass of the polyimide resin. Note that the total content is the content of the fluorine-containing polymer when only the fluorine-containing polymer is contained, and is the content of the silicone-containing polymer when only the silicone-containing polymer is contained.

[0084] [Polyimide varnish] The polyimide varnish of the present invention is obtained by dissolving the polyimide resin of the present invention or the polyimide resin composition of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention or the polyimide resin composition of the present invention and an organic solvent, and the polyimide resin or the polyimide resin composition is dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyimide resin and the fluorine-containing polymer and silicone-containing polymer contained in the polyimide resin composition. However, it is preferable to use the above-mentioned compounds as a reaction solvent used in the production of a polyimide resin, either alone or in combination of two or more kinds. The polyimide varnish of the present invention may be a polyimide solution itself in which a polyimide resin obtained by polymerization is dissolved in a reaction solvent, or may be a polyimide solution to which a dilution solvent is further added. Also, the polyimide varnish may be a polyimide solution in which a polyimide resin obtained by polymerization is dissolved in a reaction solvent, in which the fluorine-containing polymer, the silicone-containing polymer, or a mixture thereof is dissolved, or a dilution solvent may be further added. The polyimide varnish of the present invention may be prepared by dissolving the polyimide resin of the present invention in a low-boiling solvent having a boiling point of 130° C. or less. By using the low-boiling solvent as the organic solvent, the heating temperature during the production of the polyimide film described below can be lowered. Examples of the low-boiling solvent include carbon tetrachloride, dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, and acetone, and among these, dichloromethane is preferred.

[0085] Since the polyimide resin of the present invention has solvent solubility, it can be made into a highly concentrated varnish that is stable at room temperature. The polyimide varnish of the present invention preferably contains 5 to 40 mass %, more preferably 10 to 30 mass %, of the polyimide resin of the present invention. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, more preferably 5 to 150 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer. In addition, the polyimide varnish of the present invention may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film. The method for producing the polyimide varnish of the present invention is not particularly limited, and any known method can be applied.

[0086] [Polyimide film] The polyimide film of the present invention contains the polyimide resin of the present invention or the polyimide resin composition of the present invention. Therefore, the polyimide film of the present invention is excellent in transparency and optical isotropy, and further, in ductility. The preferable physical properties of the polyimide film of the present invention are as described above. The method for producing the polyimide film of the present invention is not particularly limited, and known methods can be used. For example, the polyimide varnish of the present invention is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and then the organic solvents contained in the varnish, such as a reaction solvent or a dilution solvent, are removed by heating. If necessary, a release agent may be applied to the surface of the support in advance. The following method is preferred as a method for removing the organic solvent contained in the varnish by heating. That is, it is preferred to evaporate the organic solvent at a temperature of 120°C or less to form a self-supporting film, peel the self-supporting film from the support, fix the ends of the self-supporting film, and dry at a temperature equal to or higher than the boiling point of the organic solvent used to produce a polyimide film. It is also preferred to dry under a nitrogen atmosphere. The pressure of the drying atmosphere may be reduced pressure, normal pressure, or pressurized. The heating temperature when drying the self-supporting film to produce a polyimide film is not particularly limited, but is preferably 200 to 400°C. When the organic solvent contained in the polyimide varnish of the present invention is a low-boiling point solvent having a boiling point of 130° C. or less, the heating temperature of the self-supporting film is preferably 100 to 180° C. Furthermore, it is preferable to perform an annealing treatment in which the polyimide film obtained by removing the low-boiling point solvent is further heated at a temperature equal to or higher than the glass transition temperature.

[0087] The polyimide film of the present invention can also be produced by using a polyamic acid varnish prepared by dissolving a polyamic acid in an organic solvent. The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin of the present invention, and is a product of a polyaddition reaction between a tetracarboxylic acid component containing at least one selected from the group consisting of a compound that gives the above-mentioned structural unit (A1) and a compound that gives the above-mentioned structural unit (A2), and a diamine component containing a compound that gives the above-mentioned structural unit (B1) and a compound that gives the above-mentioned structural unit (B2). The polyamic acid is imidized (dehydration ring closure) to obtain the polyimide resin of the present invention, which is the final product. As the organic solvent contained in the polyamic acid varnish, the organic solvent contained in the polyimide varnish of the present invention can be used. In the present invention, the polyamic acid varnish may be a polyamic acid solution itself obtained by subjecting a tetracarboxylic acid component containing at least one selected from the group consisting of a compound which provides the above-mentioned structural unit (A1) and a compound which provides the above-mentioned structural unit (A2) to a polyaddition reaction in a reaction solvent with a diamine component which contains a compound which provides the above-mentioned structural unit (B1) and a compound which provides the above-mentioned structural unit (B2), or may be a polyamic acid solution to which a dilution solvent has been further added.

[0088] The method for producing a polyimide film using the polyamic acid varnish is not particularly limited, and a known method can be used. For example, the polyamic acid varnish is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and the organic solvent contained in the varnish, such as a reaction solvent or a dilution solvent, is removed by heating to obtain a polyamic acid film, and the polyamic acid in the polyamic acid film is imidized by heating, thereby producing a polyimide film. The heating temperature when the polyamic acid varnish is dried to obtain a polyamic acid film is preferably 50 to 120° C. The heating temperature when the polyamic acid is imidized by heating is preferably 200 to 400° C. The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[0089] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and even more preferably 10 to 80 μm. When the thickness is in the above range, practical use as a free-standing film becomes possible. The thickness of the polyimide film can be easily controlled by adjusting the solids concentration and viscosity of the polyimide varnish.

[0090] The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, optical members, etc. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays. EXAMPLES

[0091] The present invention will be described in detail below with reference to examples, although the present invention is not limited to these examples in any way. The solids concentration of the varnishes and the physical properties of the films obtained in the examples and comparative examples were measured by the methods described below.

[0092] (1) Solid content concentration The solids concentration of the varnish was measured by heating the sample at 280°C for 120 min in a small electric furnace "MMF-1" manufactured by AS ONE Corporation, and calculating from the mass difference of the sample before and after heating. (2) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

[0093] (3) Total light transmittance, haze (transparency evaluation) and yellow index (YI) The total light transmittance, haze and YI were measured using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd. The total light transmittance and YI were measured in accordance with JIS K7361-1:1997, and the haze was measured in accordance with JIS K7136:2000. (4) Thickness retardation (Rth) (evaluation of optical isotropy) The thickness retardation (Rth) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. The thickness retardation value was measured at a measurement wavelength of 550 nm. Rth is expressed by the following formula, where the maximum in-plane refractive index of the polyimide film is nx, the minimum is ny, the refractive index in the thickness direction is nz, and the thickness of the film is d. Rth = [{(nx + ny) / 2}-nz] × d

[0094] (5) Elongation at break (evaluation of ductility) The elongation at break was measured by a tensile test (measurement of elongation) in accordance with JIS K 7127. The test pieces used were 10 mm wide and 10 to 60 μm thick. (6) Ductility (Evaluation of ductility) The polyimide films obtained in the examples and comparative examples were cut into test pieces with a width of 10 mm and a thickness of 10 to 60 μm, and subjected to a tensile test (test speed: 50 mm / min) in accordance with JIS K 7127 to evaluate ductility. From the viewpoint of preventing breakage during production and in products, ductility is preferable. As a result of the test, those in which plastic deformation occurred beyond the yield point were judged to have ductility, and those in which the film broke in the elastic region were judged to have no ductility. (7) Appearance The presence or absence of defects (unevenness and voids) on the surface of the polyimide films obtained in the Examples and Comparative Examples was evaluated according to the following criteria. A: No defects are found on the film surface. B: Slight defects are observed on the film surface (no problem in practical use). C: Defects are clearly observed on the film surface (problems in practical use).

[0095] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, as well as their abbreviations, are as follows: <Tetracarboxylic acid component> HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Company, Inc.; compound represented by formula (a1)) <Diamine component> BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane (manufactured by Wakayama Seika Kogyo Co., Ltd., a compound represented by formula (b11)) BisAM: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene (manufactured by Mitsui Fine Chemicals, Inc., a compound represented by formula (b211))

[0096] Details of the solvents and catalysts used in the examples and comparative examples are as follows. γ-Butyrolactone (Mitsubishi Chemical Corporation) N,N-Dimethylacetamide (Mitsubishi Gas Chemical Company, Inc.) Triethylenediamine (Tokyo Chemical Industry Co., Ltd.) Triethylamine (Kanto Chemical Co., Ltd.)

[0097] <Example 1> A 0.3L 5-neck glass round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark apparatus equipped with a cooling tube, a thermometer, and a glass end cap was used as a reaction apparatus. In the round-bottom flask, 28.858g (0.070 mol) of BAPP, 10.373g (0.030 mol) of BisAM, 52.2g of γ-butyrolactone, and 0.056g of triethylenediamine and 5.060g of triethylamine were placed in the flask, and the mixture was heated to 80°C under a nitrogen atmosphere while stirring at 150 rpm to obtain a solution. 22.439g (0.100 mol) of HPMDA and 23.0g of γ-butyrolactone were added in one lump to this solution, and then heated with a mantle heater to raise the temperature in the reaction system to 190°C over about 20 minutes. The distilled components were collected, and the temperature in the reaction system was maintained at 190° C. for 1 hour and 45 minutes. After adding 156.4 g of N,N-dimethylacetamide, the mixture was stirred at about 100° C. for about 1 hour to obtain a homogeneous polyimide varnish (1) with a solid content concentration of 20 mass %.

[0098] The polyimide varnish (1) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a transparent, self-supporting primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0099] <Example 2> Using the same reaction apparatus as in Example 1, 24.641 g (0.060 mol) of BAPP, 13.831 g (0.040 mol) of BisAM, 49.4 g of γ-butyrolactone, and 10.12 g of triethylamine as a catalyst were placed in a round-bottom flask, and the temperature was raised to 80 ° C. while stirring at 150 rpm under a nitrogen atmosphere to obtain a solution. 22.439 g (0.100 mol) of HPMDA and 11.4 g of γ-butyrolactone were added to this solution in one lump, and then the solution was heated with a mantle heater to raise the temperature in the reaction system to 190 ° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190 ° C. for 4.5 hours. After adding 168.1 g of N,N-dimethylacetamide, the mixture was stirred at about 100 ° C. for about 1 hour to obtain a uniform polyimide varnish (2) with a solid content concentration of 20% by mass.

[0100] The polyimide varnish (2) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0101] <Example 3> Using the same reaction apparatus as in Example 1, 20.534 g (0.050 mol) of BAPP, 17.289 g (0.050 mol) of BisAM, 49.1 g of γ-butyrolactone, and 10.13 g of triethylamine as a catalyst were placed in a round-bottom flask, and the temperature was raised to 80 ° C. while stirring at 150 rpm under a nitrogen atmosphere to obtain a solution. 22.439 g (0.100 mol) of HPMDA and 11.1 g of γ-butyrolactone were added to this solution in one lump, and then the solution was heated with a mantle heater to raise the temperature in the reaction system to 190 ° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190 ° C. for 7 hours. After adding 166.1 g of N,N-dimethylacetamide, the mixture was stirred at about 100 ° C. for about 1 hour to obtain a uniform polyimide varnish (3) with a solid content concentration of 20% by mass.

[0102] The polyimide varnish (3) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0103] <Example 4> A fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to the polyimide varnish (3) obtained in Example 3 in an amount of 0.1 parts by mass (effective component) per 100 parts by mass of the polyimide resin to obtain a polyimide varnish (4).

[0104] The polyimide varnish (4) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0105] <Example 5> A fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to the polyimide varnish (3) obtained in Example 3 in an amount of 0.5 parts by mass (effective component) per 100 parts by mass of the polyimide resin to obtain a polyimide varnish (5).

[0106] The polyimide varnish (5) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0107] <Comparative Example 1> Using the same reaction apparatus as in Example 1, 16.427 g (0.040 mol) of BAPP, 20.747 g (0.060 mol) of BisAM, 48.5 g of γ-butyrolactone, and 10.10 g of triethylamine as a catalyst were placed in a round-bottom flask, and the temperature was raised to 80 ° C. while stirring at 150 rpm under a nitrogen atmosphere to obtain a solution. 22.439 g (0.100 mol) of HPMDA and 11.0 g of γ-butyrolactone were added to this solution in one lump, and then the mixture was heated with a mantle heater to raise the temperature in the reaction system to 190 ° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190 ° C. for 7.5 hours. After adding 164.2 g of N,N-dimethylacetamide, the mixture was stirred at about 100° C. for about 1 hour to obtain a homogeneous polyimide varnish (6) having a solid content concentration of 20 mass %.

[0108] The polyimide varnish (6) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0109] <Comparative Example 2> A fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 0.1 parts by mass (effective component) per 100 parts by mass of the polyimide resin to obtain a polyimide varnish (7).

[0110] The polyimide varnish (7) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0111] <Comparative Example 3> A fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 0.5 parts by mass (effective component) per 100 parts by mass of polyimide resin to obtain a polyimide varnish (8).

[0112] The polyimide varnish (8) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0113] <Comparative Example 4> A fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 1.0 part by mass (effective component) per 100 parts by mass of the polyimide resin to obtain a polyimide varnish (9).

[0114] The polyimide varnish (9) was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting, transparent, primary dried film. The film was then fixed onto a stainless steel frame and dried at 260°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0115] <Comparative Example 5> Using the same reaction apparatus as in Example 1, 43.745 g (0.107 mol) of BAPP, 81.4 g of γ-butyrolactone, and 0.54 g of triethylamine as a catalyst were placed in a round-bottom flask, and the mixture was heated to 70 ° C. under a nitrogen atmosphere while stirring at 150 rpm to obtain a solution. 23.887 g (0.107 mol) of HPMDA and 20.3 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added to this solution in one lump, and then the mixture was heated with a mantle heater to raise the temperature in the reaction system to 190 ° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190 ° C. for 4.0 hours. After adding 154.2 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation), the mixture was stirred at about 100 ° C. for about 1 hour to obtain a uniform polyimide varnish (10) with a solid content concentration of 20 mass%. The polyimide varnish (10) obtained was then applied onto a PET substrate and held at 100°C for 20 minutes to evaporate the solvent, yielding a self-supporting transparent primary dried film. The film was then fixed onto a stainless steel frame and dried at 210°C for 20 minutes in an air atmosphere to remove the solvent, yielding a film. The evaluation results of this polyimide film are shown in Table 1.

[0116] [Table 1]

[0117] As shown in Table 1, the polyimide films of the examples are excellent in transparency and optical isotropy, as well as in ductility.

Claims

1. A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, The structural unit A includes a structural unit (A1) derived from a compound represented by the following formula (a1): The structural unit B is a structural unit (B1) derived from a compound represented by the following formula (b11): It includes at least one structural unit (B2) selected from the group consisting of a structural unit derived from a compound represented by the following formula (b211), a structural unit derived from a compound represented by the following formula (b212), and a structural unit derived from a compound represented by the following formula (b213): The ratio of the structural unit (A1) in the structural unit A is 100 mol %, the molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] is 60 / 40 to 75 / 25; A polyimide resin in which the total proportion of the structural unit (B1) and the structural unit (B2) in the structural unit B is 70 to 100 mol %. 【Chemistry 1】 (In formula (b11), R 1 and R 2 each independently represents a methyl group or a trifluoromethyl group.

2. 2. The polyimide resin according to claim 1, which has an elongation at break measured in accordance with JIS K 7127 of 10% or more and 43.8% or less.

3. A polyimide resin composition comprising the polyimide resin according to claim 1 or 2, and at least one selected from the group consisting of a fluorine-containing polymer and a silicone-containing polymer.

4. 4. The polyimide resin composition according to claim 3, wherein the total content of the fluorine-containing polymer and the silicone-containing polymer is 0.01 to 2 parts by mass based on 100 parts by mass of the polyimide resin.

5. The polyimide resin composition according to claim 3 or 4, wherein the fluorine-containing polymer is a fluorine-containing acrylic polymer.

6. 6. A polyimide varnish comprising the polyimide resin according to claim 1 or 2, or the polyimide resin composition according to any one of claims 3 to 5, dissolved in an organic solvent.

7. A polyimide film comprising the polyimide resin according to claim 1 or 2, or the polyimide resin composition according to any one of claims 3 to 5.

Images