Polyimide resin

Abstract

A polyimide resin having structural units A derived from tetracarboxylic dianhydride and structural units B derived from diamine, wherein structural unit A comprises structural units (A1) derived from a compound represented by formula (a1) and structural units (A2) derived from a compound represented by formula (a2), and structural unit B comprises structural units (B1) derived from a compound represented by formula (b1), wherein the ratio of structural units (A2) in structural unit A is 27 mol% or less, and the polyimide resin does not contain structural element (c). (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

Description

Technical Field

[0001] This invention relates to polyimide resins. Background Technology

[0002] Generally, polyimide resins are obtained by the condensation polymerization of aromatic tetracarboxylic anhydrides and aromatic diamines. Due to their structure, polyimide resins possess molecular rigidity, resonance stabilization, and strong chemical bonds. Therefore, polyimide resins exhibit excellent heat resistance, chemical resistance, mechanical properties, and electrical properties, and are widely used in molding materials, composite materials, electrical / electronic components, optical materials, displays, aerospace, and other fields.

[0003] In recent years, the application of polyimide materials in optical and electronic materials for image display devices has been advancing, requiring properties such as colorless transparency and solvent solubility of polyimide resins. However, most conventional polyimides suffer from problems such as high haze values ​​and high yellowness index (YI). As a solution to this problem, for example, Patent Document 1 proposes a thin film characterized by comprising a fluorinated polyimide layer with a total haze value of 4 or less, a yellowness index of 3 or less, and a total transmittance of 90% or more.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-027146 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Fluorinated polyimides can improve colorlessness, transparency, and solubility; however, as part of compounds belonging to the perfluoroalkyl and polyfluoroalkyl (PFAS) group, they are restricted substances under the European REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulations due to concerns about environmental impact and health-related hazards, with stricter restrictions anticipated in the future. Against this backdrop, the use of perfluoroalkyl and polyfluoroalkyl compounds is sometimes restricted in electronic components.

[0009] If only transparency needs to be improved, it can also be achieved by using aliphatic or alicyclic raw materials. However, this reduces mechanical properties, making it difficult to balance the transparency and mechanical properties of polyimide resins. Therefore, the goal is to find a polyimide resin that is not a PFAS resin but possesses both excellent transparency and mechanical properties.

[0010] The present invention was made in view of the following situation, and the object of the present invention is to provide a polyimide resin with excellent transparency, high elastic modulus and high strength, excellent elongation, and solvent solubility. In particular, the object is to provide a polyimide resin that does not contain perfluoroalkyl or polyfluoroalkyl structures but has the aforementioned properties.

[0011] Methods for solving problems

[0012] The inventors discovered that polyimide resins containing combinations of specific structural units can solve the above-mentioned problems, and thus completed the invention.

[0013] That is, the present invention relates to the following [1]~

[12] .

[0014] [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 comprising a structural unit (A1) derived from a compound represented by formula (a1) and a structural unit (A2) derived from a compound represented by formula (a2), the structural unit B comprising a structural unit (B1) derived from a compound represented by formula (b1), the ratio of structural unit (A2) in structural unit A being 27 mol% or less, and the polyimide resin not comprising the structural element (c) described below.

[0015]

[0016] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0017] [2] According to the polyimide resin described above [1], the ratio of structural units (A1) in structural unit A is 10 to 99 mol.

[0018] [3] According to the polyimide resin described in [1] or [2] above, the molar ratio of structural unit (A1) to structural unit (A2) in structural unit A [(A1) / (A2)] is 73 / 27 to 99 / 1.

[0019] [4] The polyimide resin according to any one of [1] to [3] above, wherein the ratio of structural unit (B1) in structural unit B is 40 to 100 moles.

[0020] [5] The polyimide resin according to any one of [1] to [4] above, wherein the structural unit B further comprises at least one selected from the group consisting of a structural unit (B2) derived from a compound represented by formula (b2), a structural unit (B3) derived from a compound represented by formula (b3), a structural unit (B4) derived from a compound represented by formula (b4), a structural unit (B5) derived from a compound represented by formula (b5), and a structural unit (B6) derived from a compound represented by formula (b6).

[0021]

[0022] (In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.)

[0023] [6] According to the polyimide resin described above [5], the total ratio of structural unit (B2), structural unit (B3), structural unit (B4), structural unit (B5) and structural unit (B6) in structural unit B is less than 50 mol%.

[0024] [7] According to the polyimide resin described in [5] or [6] above, the molar ratio of structural unit (B1) in structural unit B to the total of structural units (B2), structural unit (B3), structural unit (B4), structural unit (B5) and structural unit (B6) [(B1) / ((B2)+(B3)+(B4)+(B5)+(B6))] is 50 / 50 to 99 / 1.

[0025] [8] The polyimide resin according to any one of [1] to [7] above, wherein the ratio of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride contained in the structural unit (A1) is 30 mol% or more in the structural unit (A1).

[0026] [9] A polyimide varnish, which is made by dissolving the polyimide resin described in any one of [1] to [8] above in an organic solvent.

[0027]

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

[0028]

[11] The polyimide film described in

[10] above has a YI of 7.5 or less when the thickness is 50 μm, a total transmittance of 80% or more, a haze of 1.0% or less, and a tensile breakage elongation of 5% or more when subjected to a tensile test at 23°C and 50%RH with a test piece of 50 μm × 10 mm × 120 mm, a tensile speed of 20 mm / min, and a chuck distance of 50 mm. In the stress-strain curve obtained by the tensile test, the tensile modulus calculated based on the slope of the least squares method for the strain range of 0.1 mm to 0.5 mm is 3.7 GPa or more.

[0029]

[12] The polyimide film according to

[10] or

[11] above has a thickness of 5 to 100 μm.

[0030] The effects of the invention

[0031] According to the present invention, a polyimide resin with excellent transparency, high elastic modulus, high strength, and excellent elongation, and which is soluble in solvents, is provided. In particular, a polyimide resin possessing the aforementioned properties without containing perfluoroalkyl or polyfluoroalkyl structures can be provided. Therefore, the polyimide resin of the present invention is useful as an optical material, an electronic material, and especially a material for displays. Detailed Implementation

[0032] [Polyimide resin]

[0033] The polyimide resin of the present invention has a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine. Structural unit A comprises a structural unit (A1) derived from a compound represented by formula (a1) and a structural unit (A2) derived from a compound represented by formula (a2). Structural unit B comprises a structural unit (B1) derived from a compound represented by formula (b1). The ratio of structural unit (A2) in structural unit A is 27 mol% or less. The polyimide resin does not contain the following structural element (c).

[0034] The polyimide resin of the present invention has excellent transparency, high elastic modulus and high strength, and excellent elongation, and is soluble in solvents.

[0035]

[0036] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0037] It should be noted that the reasons why the polyimide resin of the present invention has excellent transparency, high elastic modulus and high strength, excellent elongation and solubility in solvents are not yet clear, but are believed to be as follows.

[0038] The polyimide resin of the present invention, having a cyclohexane structure as an alicyclic structure, exhibits excellent transparency, excellent solubility, and good elongation. Furthermore, due to its rigid structure with substituents, it possesses high elastic modulus, high strength, and good elongation. Moreover, the good packing of the imide rings adjacent to the cyclobutane structure allows the aforementioned properties to be maintained by including a small amount of this structure, resulting in high elastic modulus, high strength, and good elongation. Therefore, the polyimide resin of the present invention exhibits excellent transparency, high elastic modulus, high strength, and excellent elongation, and is soluble in solvents.

[0039] <Structural Unit A>

[0040] Structural unit A is a structural unit derived from tetracarboxylic acid dianhydride in polyimide resin.

[0041] Structural unit A comprises structural units (A1) derived from the compound represented by formula (a1) below and structural units (A2) derived from the compound represented by formula (a2) below, wherein the ratio of structural units (A2) in structural unit A is 27 mol% or less. Furthermore, it does not contain the structural element (c) below.

[0042]

[0043] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0044] By including structural units (A1) and (A2) in structural unit A, the transparency of polyimide resin can be improved without including the perfluoroalkyl and polyfluoroalkyl structures shown in structural element (c), and the elastic modulus and strength are also improved, the elongation is good, and the solvent solubility is also improved.

[0045] The compound shown in formula (a1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA).

[0046] By incorporating structural unit A into structural unit (A1), the transparency of the polyimide resin can be improved, as can its elongation. Additionally, solvent solubility can be enhanced.

[0047] The structural unit (A1) preferably comprises a trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride.

[0048] The trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride refers to the structure of formula (1) below in the backbone of polyimide resin. Furthermore, the structure of formula (2) below is a cis structure and is not included in the aforementioned trans structure.

[0049] It should be noted that the raw material used to obtain the structure of formula (1) is preferably (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, but is not limited to (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride. It can also be a raw material other than (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, such as (1S,2R,4S,5R)-cyclohexanetetracarboxylic dianhydride with a cis structure. That is, the structure of formula (1) is a trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride.

[0050]

[0051] The proportion of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride contained in the structural unit (A1) is preferably 30 mol% or more in the structural unit (A1). The ratio of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride in the structural unit (A1) is preferably 35-100 mol%, more preferably 40-100 mol%, even more preferably 50-100 mol%, even more preferably 55-100 mol%, even more preferably 60-100 mol%, even more preferably 70-100 mol%, even more preferably 75-100 mol%, even more preferably 80-100 mol%, even more preferably 85-100 mol%, even more preferably 90-100 mol%, even more preferably 95-100 mol%. The structural unit (A1) may also be composed solely of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, and more preferably the structural unit (A1) is composed solely of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride. The structural unit (A1) can improve the transparency, elastic modulus and strength of the resulting polyimide resin by including the inverse structure.

[0052] That is, the proportion of the structure of formula (1) included in the structural unit (A1) is preferably 30 mol% or more in the structural unit (A1). More preferably, the proportion of the structure of formula (1) included in the structural unit (A1) is 35 to 100 mol%, further preferably 40 to 100 mol%, even more preferably 50 to 100 mol%, even more preferably 55 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 75 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably 85 to 100 mol%, even more preferably 90 to 100 mol%, even more preferably 95 to 100 mol%. The structural unit (A1) may also be composed solely of the structure of formula (1), and more preferably, the structural unit (A1) is composed solely of the structure of formula (1). By including the trans structure, the structural unit (A1) can improve the transparency of the obtained polyimide resin, increase the elastic modulus, and achieve high strength.

[0053] The compound shown in formula (a2) is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0054] By including structural unit (A2) in structural unit A, the elastic modulus of polyimide resin can be improved in particular.

[0055] The ratio of structural unit (A2) in structural unit A is less than 27 mol%.

[0056] The ratio of structural unit (A2) in structural unit A is preferably 25 mol% or less, more preferably 23 mol% or less, and even more preferably 22 mol% or less. The lower limit of the ratio of structural unit (A2) in structural unit A is preferably 0.5 mol% or more. The ratio of structural unit (A2) in structural unit A is preferably 0.5 to 27 mol%, more preferably 1 to 27 mol%, even more preferably 3 to 27 mol%, even more preferably 5 to 27 mol%, even more preferably 10 to 27 mol%, even more preferably 10 to 25 mol%, even more preferably 15 to 25 mol%, even more preferably 15 to 23 mol%, and even more preferably 15 to 22 mol%. By setting the ratio of structural unit (A2) in structural unit A within the above range, the transparency of the obtained polyimide resin can be improved, while also achieving high elastic modulus, strength, and excellent elongation.

[0057] The molar ratio of structural unit (A1) to structural unit (A2) in structural unit A [(A1) / (A2)] is preferably 73 / 27 to 99 / 1, more preferably 73 / 27 to 97 / 3, even more preferably 73 / 27 to 95 / 5, even more preferably 73 / 27 to 90 / 10, even more preferably 75 / 25 to 90 / 10, even more preferably 75 / 25 to 85 / 15, even more preferably 77 / 23 to 85 / 15, and even more preferably 78 / 22 to 85 / 15. By setting the aforementioned molar ratio, the transparency of the obtained polyimide resin can be improved, while also taking into account high elastic modulus, strength, and excellent elongation.

[0058] The ratio of structural units (A1) in structural unit A is preferably 99.5 mol% or less, more preferably 10 to 99.5 mol%, even more preferably 10 to 99 mol%, and still more preferably 50 to 99 mol%, even more preferably 73 to 99 mol%, even more preferably 73 to 97 mol%, even more preferably 73 to 95 mol%, even more preferably 73 to 90 mol%, even more preferably 75 to 90 mol%, even more preferably 75 to 85 mol%, even more preferably 77 to 85 mol%, and still more preferably 78 to 85 mol%. By setting the ratio of structural units (A1) in structural unit A within the above range, the transparency of the obtained polyimide resin can be improved, while also achieving high elastic modulus, strength, and excellent elongation.

[0059] The total ratio of structural units (A1) and structural units (A2) in structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less. Structural unit A may consist only of structural units (A1) and structural units (A2), and structural unit A is even more preferably consisting only of structural units (A1) and structural units (A2). That is, the total ratio of structural units (A1) and structural units (A2) in structural unit A may be 100 mol%, and even more preferably 100 mol%.

[0060] Structural unit A may also include structural units other than structural units (A1) and structural units (A2). There are no particular limitations on the tetracarboxylic dianhydrides that provide such structural units; examples include aromatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and aliphatic tetracarboxylic dianhydrides, excluding those shown in formula (a1) and those shown in formula (a2).

[0061] Examples of aromatic tetracarboxylic dianhydrides other than those mentioned above include 4,4'-oxobisphthalic anhydride (ODPA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), terephthalobisphthalic anhydride (HQDEA), ethylene glycol bis(trimethoxyester) dianhydride (TMEG), 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl=bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (TMPBP-TME), and 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride.

[0062] Examples of alicyclic tetracarboxylic dianhydrides include cyclohexane-1,2,3,4-tetracarboxylic dianhydrides, 1,2,3,4-cyclopentanetetracarboxylic dianhydrides, 1,2,4,5-cyclopentanetetracarboxylic dianhydrides, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydrides, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydrides, decahydro-1,4:5,8-dimethylbridged naphthalene-2,3,6,7-tetracarboxylic dianhydrides (DNDA), and 5,5'-(1,4-phenylene)-bis[hexahydro-4,7-methanoisobenzofuran-1,3-dione](5,5'-(1,4-phenylene)-bis[hexahydro-4,7-Methanoisobenzofuran-1,3-dione](5,5'-(1,4-phenylene)-bis[hexahydro-4,7-Methanoisobenzofuran-1,3-dione]). an-1,3-dione]), 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid-5,5',6,6'-dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2”-norbornane-5,5',6,6'-tetracarboxylic acid anhydride (CpODA), 2,2-propenylidene-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, bicyclo[2.2.2]octane-2,3:5,6-tetracarboxylic acid dianhydride (BODA), bicyclo[4.4.0]decane-2,3,6,7-tetracarboxylic acid dianhydride, etc.

[0063] Examples of aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydrides.

[0064] It should be noted that, in this specification, aromatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more alicyclic rings but not aromatic rings, and aliphatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing neither aromatic rings nor alicyclic rings.

[0065] Structural unit A may contain one or more structural units.

[0066] <Structural Unit B>

[0067] Structural unit B is a diamine-derived structural unit in polyimide resin.

[0068] Structural unit B comprises structural units (B1) derived from the compound shown in formula (b1) below. It does not contain the structural element (c) below.

[0069]

[0070] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0071] By including structural unit (B1) in structural unit B, the transparency and solvent solubility of polyimide resin can be maintained without including the perfluoroalkyl structure and polyfluoroalkyl structure shown in structural element (c), and the elastic modulus and strength can be improved.

[0072] The compound shown in formula (b1) is 2,2'-dimethylbenzidine (mTB).

[0073] The ratio of structural units (B1) in structural unit B is preferably 40-100 mol%, more preferably 50-100 mol%, even more preferably 70-100 mol%, even more preferably 80-100 mol%, even more preferably 85-100 mol%, and even more preferably 85-95 mol%. The ratio of structural units (B1) in structural unit B can be 100 mol%, and structural unit B can be composed solely of structural units (B1).

[0074] Structural unit B may consist of only structural unit (B1), or may include structural units other than structural unit (B1), but preferably, as structural units other than structural unit (B1), it also includes at least one of the following groups: structural unit (B2) derived from the compound shown in formula (b2), structural unit (B3) derived from the compound shown in formula (b3), structural unit (B4) derived from the compound shown in formula (b4), structural unit (B5) derived from the compound shown in formula (b5), and structural unit (B6) derived from the compound shown in formula (b6).

[0075]

[0076] (In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.)

[0077] Structural unit B preferably comprises at least one selected from the group consisting of structural units (B2) derived from the compound represented by formula (b2), structural units (B3) derived from the compound represented by formula (b3), structural units (B4) derived from the compound represented by formula (b4), structural units (B5) derived from the compound represented by formula (b5), and structural units (B6) derived from the compound represented by formula (b6). More preferably, it comprises at least one selected from the group consisting of structural units (B2) derived from the compound represented by formula (b2), structural units (B3) derived from the compound represented by formula (b3), and structural units (B6) derived from the compound represented by formula (b6). Even more preferably, it comprises structural unit (B6) derived from the compound represented by formula (b6).

[0078] The compound represented by formula (b2) is diaminodiphenyl sulfone. Examples of compounds represented by formula (b2) include 4,4'-diaminodiphenyl sulfone (4,4'-DDS) in which all amino groups are located at the 4-position and 3,3'-diaminodiphenyl sulfone (3,3'-DDS) in which all amino groups are located at the 3-position, with 4,4'-diaminodiphenyl sulfone (4,4'-DDS) being preferred.

[0079] By including structural unit (B2) in structural unit B, the transparency of polyimide resin can be improved.

[0080] The compound shown in formula (b3) is octafluorobenzidine (8FBZ).

[0081] By incorporating structural unit B into structural unit (B3), the elastic modulus and elongation of the polyimide resin can be improved.

[0082] The compound shown in formula (b4) is 2,3,5,6-tetrafluorobenzene-1,4-diamine.

[0083] By incorporating structural unit B into structural unit (B4), the elastic modulus and elongation of the polyimide resin can be improved.

[0084] The compound shown in formula (b5) is 2,4,5,6-tetrafluorobenzene-1,3-diamine.

[0085] By incorporating structural unit B into structural unit (B5), the elastic modulus and elongation of the polyimide resin can be improved.

[0086] In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.

[0087] Each of R is independently a hydrogen atom or a methyl group, preferably a hydrogen atom, and more preferably both R are hydrogen atoms.

[0088] n can be 0 or 1, preferably 0.

[0089] In formula (b6), when both R are hydrogen atoms and n is 0, the compound shown in formula (b6) is 4,4'-diaminobenzoylaniline (DABA).

[0090] By incorporating structural units derived from 4,4'-diaminobenzoylaniline (DABA) in structural unit B, the high elastic modulus and strength of polyimide resin can be maintained, while transparency and elongation can be improved.

[0091] In formula (b6), when n is 1, the compound shown in formula (b6) contains Y as a divalent group with 12 to 30 carbon atoms.

[0092] Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, preferably a divalent group containing 12 to 26 carbon atoms of an aromatic ring.

[0093] Among the compounds shown in formula (b6), the preferred compounds when n is 1 include the compounds shown in formula (b61), formula (b62), formula (b63), and formula (b64).

[0094] The compound represented by formula (b6) is preferably selected from at least one of the group consisting of the compound represented by formula (b61), the compound represented by formula (b62), the compound represented by formula (b63), and the compound represented by formula (b64). More preferably, it is selected from at least one of the group consisting of the compound represented by formula (b61), the compound represented by formula (b62), and the compound represented by formula (b63). Even more preferably, it is selected from at least one of the group consisting of the compound represented by formula (b61) and the compound represented by formula (b63). Still more preferably, it is the compound represented by formula (b61).

[0095]

[0096] The compound shown in formula (b61) is N,N'-(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[4-amino-3-methylbenzamide] (AMB-mTOL).

[0097] By incorporating structural units (B6) into structural units derived from the compound shown in formula (b61), the high elastic modulus and strength of polyimide resin can be maintained, while transparency and elongation can be improved.

[0098] The compound shown in formula (b62) is N,N'-[(octahydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c']dipyrrole-2,6(1H,3H)-diyl)bis(3-methoxy-4,1-phenylene)]bis[4-amino-benzamide](AB-MP-HPMDI).

[0099] By incorporating structural units (B6) into structural units derived from the compound shown in formula (b62), the high elastic modulus and strength of polyimide resin can be maintained, while transparency and elongation can be improved.

[0100] The compound shown in formula (b63) is N,N'-(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[4-amino-benzamide](AB-mTOL).

[0101] By incorporating structural units (B6) containing structural units derived from the compound shown in formula (b63), it is possible to maintain the high elastic modulus and strength of polyimide resins, and to improve transparency and elongation.

[0102] The compound shown in formula (b64) is N,N'-(oxydi-4,1-phenylene)bis[4-amino-benzamide](AB-44ODA).

[0103] By incorporating structural units (B6) into structural units derived from the compound shown in formula (b64), the high elastic modulus and strength of polyimide resin can be maintained, while transparency and elongation can be improved.

[0104] As described above, by including structural unit (B6) in structural unit B, it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of polyimide resin.

[0105] The total ratio of structural units (B2), (B3), (B4), (B5), and (B6) in structural unit B is preferably 50 mol% or less.

[0106] The total ratio of structural units (B2), (B3), (B4), (B5), and (B6) in structural unit B is more preferably 1 to 50 mol%, more preferably 1 to 40 mol%, even more preferably 1 to 30 mol%, even more preferably 3 to 25 mol%, even more preferably 3 to 20 mol%, even more preferably 5 to 20 mol%, and even more preferably 5 to 15 mol%. By ensuring that the total ratio of structural units (B2), (B3), (B4), (B5), and (B6) in structural unit B is within the above range, the high elastic modulus and strength of the obtained polyimide resin can be maintained, and the transparency and elongation can be improved.

[0107] The molar ratio of structural unit (B1) in structural unit B relative to the total of structural units (B2), (B3), (B4), (B5), and (B6) [(B1) / ((B2)+(B3)+(B4)+(B5)+(B6))] is preferably 50 / 50 to 99 / 1, more preferably 60 / 40 to 99 / 1, even more preferably 70 / 30 to 99 / 1, even more preferably 75 / 25 to 97 / 3, even more preferably 80 / 20 to 97 / 3, even more preferably 80 / 20 to 95 / 5, and even more preferably 85 / 15 to 95 / 5. By setting the molar ratio of structural unit (B1) in structural unit B relative to the total of structural units (B2), (B3), (B4), (B5), and (B6) within the range described above, it is possible to maintain the high elastic modulus and strength of the obtained polyimide resin, and improve its transparency and elongation.

[0108] The total ratio of structural units (B1), (B2), (B3), (B4), (B5), and (B6) in structural unit B is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less. Structural units B may also include only structural units (B1), (B2), (B3), (B4), (B5), and (B6).

[0109] Structural unit B may also include structural units other than structural units (B1), (B2), (B3), (B4), (B5), and (B6). There are no particular limitations on the diamines that provide such structural units; examples include aromatic diamines, alicyclic diamines, and aliphatic diamines other than those shown in formula (b1), formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6).

[0110] Examples of aromatic diamines other than the aforementioned compounds include bis(4-aminophenyl) terephthalate (APTP), 1,4-bis(4-aminobenzoyloxy)benzene, 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, and 4,4'-diaminodiphenylsulfonium. Ethers, 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 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(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-( [3-Aminophenoxy)phenyl]one, bis[4-(4-aminophenoxy)phenyl]one, 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, bis[4-(4-aminophenoxy)phenyl] sulfone, 4,4-diaminobenzoylaniline, 4-aminobenzoic acid-4-aminophenyl ester, 3,4-diaminobenzoylaniline, etc.

[0111] Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophorone diamine, bis(aminomethyl)norbornene, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane.

[0112] Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine.

[0113] It should be noted that, in this specification, aromatic diamines refer to diamines containing one or more aromatic rings, alicyclic diamines refer to diamines containing one or more alicyclic rings but not aromatic rings, and aliphatic diamines refer to diamines containing neither aromatic nor alicyclic rings.

[0114] Structural unit B may contain one or more structural units.

[0115] <Structure and Properties of Polyimide Resins>

[0116] The polyimide resin of the present invention does not contain the following structural element (c).

[0117]

[0118] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0119] The structural element (c) in this invention will be described in detail below. It should be noted that the structural element (c) in the polyimide resin, its manufacturing method, polyimide varnish, and polyimide film of this invention all have the same meaning.

[0120] In formula (c), the carbon atom other than X bonded to the CF2 group can be a secondary, tertiary, or quaternary carbon atom. It can be a carbon atom that constitutes an aromatic ring, or it can be replaced by an atom other than hydrogen and carbon. Examples of atoms other than hydrogen and carbon include halogens, nitrogen atoms, and oxygen atoms.

[0121] When X is a carbon atom, the carbon atom of X can be a primary carbon, secondary carbon, tertiary carbon, or quaternary carbon. It can be a carbon atom that forms an aromatic ring, or it can be replaced by an atom other than hydrogen or carbon. Examples of atoms other than hydrogen and carbon include halogens, nitrogen atoms, and oxygen atoms.

[0122] Structural element (c) is a perfluoroalkyl structure or a polyfluoroalkyl structure. Examples of polyimide resins containing the above-mentioned structural elements include those having structural units derived from tetracarboxylic dianhydrides listed below and structural units derived from diamines listed below. That is, the polyimide resins of the present invention do not have structural units derived from tetracarboxylic dianhydrides listed below or structural units derived from diamines listed below.

[0123] Examples of tetracarboxylic dianhydrides include 9,9-bis(trifluoromethyl)-9H-xanthon-2,3,6,7-tetracarboxylic dianhydride (6FCDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, and 4,4'-(hexafluoroisopropylidene)bisphthalic anhydride (6FDA).

[0124] Examples of diamines mentioned above include 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, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP).

[0125] From the viewpoint of the mechanical strength of the obtained polyimide film, the number-average molecular weight of the polyimide resin is preferably 5,000 to 300,000. It should be noted that the number-average molecular weight of the polyimide resin can be determined, for example, by conversion of the standard polymethyl methacrylate (PMMA) value based on gel filtration chromatography.

[0126] Polyimide resins may contain structures other than polyimide chains (structures formed by imide bonding of structural unit A and structural unit B). Examples of structures other than polyimide chains that may be included in polyimide resins include structures containing amide bonds. However, structures other than polyimide chains do not contain structural element (c).

[0127] The polyimide resin preferably comprises polyimide chains (a structure formed by imide bonding of structural unit A and structural unit B) as its main structure. Therefore, the proportion of polyimide chains in the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and even more preferably 99% by mass or more. Additionally, it is preferably 100% by mass or less. More preferably, the polyimide resin may consist solely of polyimide chains, which is 100% by mass.

[0128] <Manufacturing Method of Polyimide Resin>

[0129] The method for manufacturing the polyimide resin of the present invention is not particularly limited, but preferably a method in which the polyimide resin is obtained by reacting a tetracarboxylic dianhydride providing the above-described structural unit A with a diamine providing the above-described structural unit B. According to this method, the polyimide resin is directly obtained from the tetracarboxylic dianhydride and the diamine. The manufacturing method shown below is preferred.

[0130] A preferred method for manufacturing polyimide resin includes the following steps: imidizing a tetracarboxylic dianhydride comprising the compounds shown in formula (a1) and (a2) with a diamine comprising the compound shown in formula (b1) in the presence of an organic solvent comprising a base catalyst and a lactone-based solvent. The preferred manufacturing method is described below.

[0131] (Tetracarboxylic acid dianhydride)

[0132] The aforementioned tetracarboxylic dianhydride includes the compound shown in formula (a1) and the compound shown in formula (a2).

[0133] In addition, it is preferable not to include the following structural element (c).

[0134]

[0135] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0136] By including the compounds shown in formula (a1) and formula (a2) in the tetracarboxylic dianhydride, the transparency of the polyimide film (polyimide resin) can be improved without including the perfluoroalkyl structure and polyfluoroalkyl structure shown in structural element (c). It can also improve the elastic modulus, strength, elongation, and solvent solubility.

[0137] By incorporating the tetracarboxylic dianhydride into the compound represented by formula (a1), the transparency of the polyimide film (polyimide resin) can be improved, as well as its elongation. Additionally, solvent solubility can also be improved.

[0138] The compound represented by formula (a1) preferably contains the compound represented by formula (a11) below. The compound represented by formula (a11) below is (1R,2S,4S,5R)-cyclohexanetetracarboxylic acid dianhydride.

[0139] (1R,2S,4S,5R)-cyclohexanetetracarboxylic acid dianhydride has a trans configuration. The compound shown in formula (a12) below has a cis configuration and is not included in the compound shown in formula (a11) below.

[0140]

[0141] The proportion of the compound represented by formula (a1) in the compound represented by formula (a1) is preferably 30 mol% or more.

[0142] Regarding the ratio of the compound of formula (a1) contained in the compound of formula (a1), it is preferably 30 to 100 mol%, more preferably 35 to 100 mol%, even more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, even more preferably 95 to 100 mol%, and may also be 100 mol%, even more preferably 100 mol%. The compound of formula (a1) may consist only of the compound of formula (a1), and it is even more preferably that the compound of formula (a1) consists only of the compound of formula (a1).

[0143] By including the compound shown in formula (a1) in the compound shown in formula (a11), the transparency of the obtained polyimide film (polyimide resin) can be improved, and the elastic modulus can be increased. It should be noted that, as the compound shown in formula (a1), even if only the compound shown in formula (a12) is used, a trans structure can be introduced into the obtained polyimide resin depending on the manufacturing conditions. However, by using the compound shown in formula (a11), a trans structure can be introduced into the polyimide resin more reliably, and therefore it is preferred.

[0144] The elastic modulus of polyimide films (polyimide resins) can be particularly improved by including the tetracarboxylic dianhydride in the compound shown in formula (a2).

[0145] The ratio of the compound represented by formula (a2) in the tetracarboxylic dianhydride is preferably 27 mol% or less.

[0146] The proportion of the compound represented by formula (a2) in tetracarboxylic dianhydride is more preferably 25 mol% or less, more preferably 23 mol% or less, and even more preferably 22 mol% or less. The lower limit of the proportion of the compound represented by formula (a2) in tetracarboxylic dianhydride is preferably 0.5 mol% or more. The proportion of the compound represented by formula (a2) in tetracarboxylic dianhydride is preferably 0.5 to 27 mol%, more preferably 1 to 27 mol%, even more preferably 3 to 27 mol%, even more preferably 5 to 27 mol%, even more preferably 10 to 27 mol%, even more preferably 10 to 25 mol%, even more preferably 15 to 25 mol%, even more preferably 15 to 23 mol%, and even more preferably 15 to 22 mol%. By setting the proportion of the compound represented by formula (a2) in tetracarboxylic dianhydride within the above range, the transparency of the obtained polyimide film (polyimide resin) can be improved, while also achieving high elastic modulus, strength, and excellent elongation.

[0147] The molar ratio of the compound represented by formula (a1) to the compound represented by formula (a2) in the tetracarboxylic dianhydride [(a1) / (a2)] is preferably 73 / 27 to 99 / 1, more preferably 73 / 27 to 97 / 3, even more preferably 73 / 27 to 95 / 5, even more preferably 73 / 27 to 90 / 10, even more preferably 75 / 25 to 90 / 10, even more preferably 75 / 25 to 85 / 15, even more preferably 77 / 23 to 85 / 15, and even more preferably 78 / 22 to 85 / 15. By setting the aforementioned molar ratio, the transparency of the obtained polyimide resin can be improved, while also taking into account high elastic modulus, strength, and excellent elongation.

[0148] The proportion of the compound represented by formula (a1) in the tetracarboxylic dianhydride is preferably 99.5 mol% or less, more preferably 10 to 99.5 mol%, even more preferably 10 to 99 mol%, and still more preferably 50 to 99 mol%, even more preferably 73 to 99 mol%, even more preferably 73 to 97 mol%, even more preferably 73 to 95 mol%, even more preferably 73 to 90 mol%, even more preferably 75 to 90 mol%, even more preferably 75 to 85 mol%, even more preferably 77 to 85 mol%, and still more preferably 78 to 85 mol%. By setting the proportion of the compound represented by formula (a1) in the tetracarboxylic dianhydride within the above range, the transparency of the obtained polyimide resin can be improved, while also achieving high elastic modulus, strength, and excellent elongation.

[0149] The total ratio of the compounds represented by formula (a1) and (a2) in the tetracarboxylic dianhydride is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less. The tetracarboxylic dianhydride may contain only the compounds represented by formula (a1) and (a2), and preferably only the compounds represented by formula (a1) and (a2).

[0150] Tetracarboxylic dianhydrides may include tetracarboxylic dianhydrides other than those shown in formula (a1) and formula (a2). There are no particular limitations on such tetracarboxylic dianhydrides; examples include aromatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and aliphatic tetracarboxylic dianhydrides other than those shown in formula (a1) and formula (a2).

[0151] Examples of aromatic tetracarboxylic dianhydrides other than those mentioned above include 4,4'-oxobisphthalic anhydride (ODPA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), terephthalobisphthalic anhydride (HQDEA), ethylene glycol bis(trimethoxyester) dianhydride (TMEG), 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl=bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (TMPBP-TME), and 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride.

[0152] Examples of alicyclic tetracarboxylic dianhydrides include cyclohexane-1,2,3,4-tetracarboxylic dianhydrides, 1,2,3,4-cyclopentanetetracarboxylic dianhydrides, 1,2,4,5-cyclopentanetetracarboxylic dianhydrides, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydrides, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydrides, decahydro-1,4:5,8-dimethylbridged naphthalene-2,3,6,7-tetracarboxylic dianhydrides (DNDA), and 5,5'-(1,4-phenylene)-bis[hexahydro-4,7-methanoisobenzofuran-1,3-dione](5,5'-(1,4-phenylene)-bis[hexahydro-4,7-Methanoisobenzofuran-1,3-dione](5,5'-(1,4-phenylene)-bis[hexahydro-4,7-Methanoisobenzofuran-1,3-dione]). an-1,3-dione]), 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid-5,5',6,6'-dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2”-norbornane-5,5',6,6'-tetracarboxylic acid anhydride (CpODA), 2,2-propenylidene-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, bicyclo[2.2.2]octane-2,3:5,6-tetracarboxylic acid dianhydride (BODA), bicyclo[4.4.0]decane-2,3,6,7-tetracarboxylic acid dianhydride, etc.

[0153] Examples of aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydrides.

[0154] It should be noted that, in this specification, aromatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more alicyclic rings but not aromatic rings, and aliphatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing neither aromatic rings nor alicyclic rings.

[0155] The optional tetracarboxylic acid dianhydride can be one type or two or more types.

[0156] (Diamine)

[0157] The aforementioned diamine comprises a structural unit (B1) derived from a compound represented by formula (b1) below. Furthermore, it is preferable that it does not contain the structural element (c) below.

[0158]

[0159] (In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.)

[0160] By including the diamine in the compound shown in formula (b1), it is possible to maintain the transparency and solvent solubility of polyimide resin without including the perfluoroalkyl or polyfluoroalkyl structure shown in structural element (c), and to improve the elastic modulus and strength.

[0161] The proportion of the compound represented by formula (b1) in the diamine is preferably 40 to 100 mol%, more preferably 50 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably 85 to 100 mol%, and even more preferably 85 to 95 mol%. The diamine may also contain only the compound represented by formula (b1).

[0162] The diamine may contain only the compound shown in formula (b1), or it may contain diamines other than the compound shown in formula (b1). Preferably, the diamine other than the compound shown in formula (b1) further contains at least one of the compounds selected from the group consisting of the compound shown in formula (b2), the compound shown in formula (b3), the compound shown in formula (b4), the compound shown in formula (b5), and the compound shown in formula (b6).

[0163]

[0164] (In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.)

[0165] The diamine preferably comprises at least one of the compounds selected from the group consisting of the compound shown in formula (b2), the compound shown in formula (b3), the compound shown in formula (b4), the compound shown in formula (b5), and the compound shown in formula (b6), more preferably comprising at least one of the group consisting of the compound shown in formula (b2), the structural unit (B3) derived from the compound shown in formula (b3), and the compound shown in formula (b6), further preferably comprising at least one of the group consisting of the compound shown in formula (b2) and the compound shown in formula (b6), and even more preferably comprising the compound shown in formula (b6).

[0166] Examples of compounds represented by formula (b2) include 4,4'-diaminodiphenyl sulfone (4,4'-DDS) in which all amino groups are present at the 4-position, and 3,3'-diaminodiphenyl sulfone (3,3'-DDS) in which all amino groups are present at the 3-position, with 4,4'-diaminodiphenyl sulfone (4,4'-DDS) being preferred.

[0167] The transparency of polyimide resins can be improved by including compounds represented by the diamine formula (b2).

[0168] By including the compound represented by formula (b3) in the diamine, the elastic modulus, strength, and elongation of the polyimide resin can be improved.

[0169] By including the diamine in the compound shown in formula (b4), the elastic modulus, strength, and elongation of the polyimide resin can be improved.

[0170] By including the compound represented by formula (b5) in the diamine, the elastic modulus, strength, and elongation of the polyimide resin can be improved.

[0171] In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.

[0172] Each of R is independently a hydrogen atom or a methyl group, preferably a hydrogen atom, and more preferably both R are hydrogen atoms.

[0173] n can be 0 or 1, preferably 0.

[0174] In formula (b6), when both R are hydrogen atoms and n is 0, the compound shown in formula (b6) is 4,4'-diaminobenzoylaniline (DABA).

[0175] By including the structural unit derived from 4,4'-diaminobenzoylaniline (DABA) in the compound shown in formula (b6) with diamine, it is possible to maintain the high elastic modulus and strength of polyimide resin, and improve its colorless transparency and elongation.

[0176] In formula (b6), when n is 1, the compound shown in formula (b6) contains Y as a divalent group with 12 to 30 carbon atoms.

[0177] Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, preferably a divalent group containing 12 to 26 carbon atoms of an aromatic ring.

[0178] Among the compounds shown in formula (b6), the preferred compounds when n is 1 include the compounds shown in formula (b61), formula (b62), formula (b63), and formula (b64).

[0179] The compound represented by formula (b6) is preferably selected from at least one of the group consisting of the compound represented by formula (b61), the compound represented by formula (b62), the compound represented by formula (b63), and the compound represented by formula (b64). More preferably, it is selected from at least one of the group consisting of the compound represented by formula (b61), the compound represented by formula (b62), and the compound represented by formula (b63). Even more preferably, it is selected from at least one of the group consisting of the compound represented by formula (b61) and the compound represented by formula (b63). Still more preferably, it is the compound represented by formula (b61).

[0180]

[0181] The compound shown in formula (b61) is N,N'-(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[4-amino-3-methylbenzamide] (AMB-mTOL).

[0182] By including the compound of formula (b61) in the diamine, it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of polyimide resin.

[0183] The compound shown in formula (b62) is N,N'-[(octahydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c']dipyrrole-2,6(1H,3H)-diyl)bis(3-methoxy-4,1-phenylene)]bis[4-amino-benzamide](AB-MP-HPMDI).

[0184] By including the compound represented by formula (b62) in the diamine, it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of polyimide resin.

[0185] The compound shown in formula (b63) is N,N'-(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[4-amino-benzamide](AB-mTOL).

[0186] By including the compound represented by formula (b63) in the diamine, it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of the polyimide resin.

[0187] The compound shown in formula (b64) is N,N'-(oxydi-4,1-phenylene)bis[4-amino-benzamide](AB-44ODA).

[0188] By including the compound represented by formula (b64) in the diamine, it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of the polyimide resin.

[0189] As described above, by including the diamine in the compound represented by formula (b6), it is possible to improve transparency and elongation while maintaining the high elastic modulus and strength of the polyimide resin.

[0190] The total ratio of the compounds shown in formula (b2), (b3), (b4), (b5), and (b6) in the diamine is preferably 50 mol% or less.

[0191] The total ratio of the compounds represented by formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6) in the diamine is more preferably 1 to 50 mol%, more preferably 1 to 40 mol%, even more preferably 1 to 30 mol%, even more preferably 3 to 25 mol%, even more preferably 3 to 20 mol%, even more preferably 5 to 20 mol%, and even more preferably 5 to 15 mol%. By setting the total ratio of the compounds represented by formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6) in the diamine to the above range, the high elastic modulus and strength of the obtained polyimide resin can be maintained, and the transparency and elongation can be improved.

[0192] The molar ratio of the compound of formula (b1) in the diamine to the total molar ratio of the compounds of formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6) [(b1) / ((b2)+(b3)+(b4)+(b5)+(b6))] is preferably 50 / 50 to 99 / 1, more preferably 60 / 40 to 99 / 1, further preferably 70 / 30 to 99 / 1, even more preferably 75 / 25 to 97 / 3, even more preferably 80 / 20 to 97 / 3, even more preferably 80 / 20 to 95 / 5, and even more preferably 85 / 15 to 95 / 5. By setting the total molar ratio of the compound shown in formula (b1) to the total molar ratio of the compounds shown in formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6) in the diamine within the range described above, it is possible to maintain the high elastic modulus and strength of the obtained polyimide resin, and improve its transparency and elongation.

[0193] The total ratio of the compounds shown in formula (b1), (b2), (b3), (b4), (b5), and (b6) in the diamine is preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and preferably 100 mol% or less. The diamine may be only the compounds shown in formula (b1), (b2), (b3), (b4), (b5), and (b6).

[0194] Diamines may include diamines other than those shown in formula (b1), formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6). There are no particular limitations on such diamines; examples include aromatic diamines, alicyclic diamines, and aliphatic diamines other than those shown in formula (b1), formula (b2), formula (b3), formula (b4), formula (b5), and formula (b6).

[0195] Examples of aromatic diamines other than the aforementioned compounds include bis(4-aminophenyl) terephthalate (APTP), 1,4-bis(4-aminobenzoyloxy)benzene, 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, and 4,4'-diaminodiphenylsulfonium. Ethers, 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 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(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-( [3-Aminophenoxy)phenyl]one, bis[4-(4-aminophenoxy)phenyl]one, 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, bis[4-(4-aminophenoxy)phenyl] sulfone, 4,4-diaminobenzoylaniline, 4-aminobenzoic acid-4-aminophenyl ester, 3,4-diaminobenzoylaniline, etc.

[0196] Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophorone diamine, bis(aminomethyl)norbornene, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane.

[0197] Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine.

[0198] It should be noted that, in this specification, aromatic diamines refer to diamines containing one or more aromatic rings, alicyclic diamines refer to diamines containing one or more alicyclic rings but not aromatic rings, and aliphatic diamines refer to diamines containing neither aromatic nor alicyclic rings.

[0199] The diamine may be one type or two or more types.

[0200] (Alkali catalyst)

[0201] Examples of such base catalysts include organic base catalysts such as pyridine, quinoline, isoquinoline, α-methylpyridine, β-methylpyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline, as well as inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0202] The above-mentioned alkaline catalysts can be used alone or in combination of two or more.

[0203] From an operational point of view, an organic base catalyst is preferred, and at least one of the group consisting of triethylamine and triethylenediamine is even more preferred. More preferably, both triethylamine and triethylenediamine are used.

[0204] The amount of alkaline catalyst used in this process is preferably less than 100 mol% relative to the amount of the aforementioned tetracarboxylic acid dianhydride, more preferably 1 to 100 mol%, even more preferably 1 to 60 mol%, even more preferably 5 to 60 mol%, even more preferably 10 to 60 mol%, even more preferably 30 to 60 mol%, even more preferably 40 to 60 mol%.

[0205] In order to increase the proportion of the structural unit (A1) of the obtained polyimide resin derived from the trans structure of (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, the amount of base catalyst is preferably used to be at least 30 mol% relative to the amount of the aforementioned tetracarboxylic dianhydride.

[0206] The amount of triethylamine used in this process is preferably less than 100 mol% relative to the amount of the aforementioned tetracarboxylic acid dianhydride, more preferably 1 to 90 mol%, even more preferably 1 to 60 mol%, even more preferably 5 to 60 mol%, even more preferably 10 to 60 mol%, even more preferably 10 to 55 mol%, even more preferably 30 to 55 mol%, even more preferably 40 to 55 mol%.

[0207] When using both triethylamine and triethylenediamine, the amount of triethylenediamine relative to the aforementioned tetracarboxylic acid dianhydride is preferably 50 mol% or less, more preferably 1 to 50 mol%, even more preferably 1 to 20 mol%, even more preferably 1 to 10 mol%, even more preferably 1 to 7 mol%, even more preferably 1 to 6 mol%, even more preferably 2 to 6 mol%, even more preferably 3 to 6 mol%.

[0208] The amount of alkaline catalyst used in this process is preferably the same as the amount of diamine relative to the amount of tetracarboxylic dianhydride.

[0209] Therefore, the amount of alkaline catalyst used in this process is preferably less than 100 mol% relative to the amounts of the aforementioned tetracarboxylic dianhydride and the aforementioned diamine, more preferably 1 to 100 mol%, even more preferably 1 to 60 mol%, even more preferably 5 to 60 mol%, even more preferably 10 to 60 mol%, even more preferably 30 to 60 mol%, even more preferably 40 to 60 mol%.

[0210] In order to increase the proportion of the structural unit (A1) of the compound represented by formula (a1) derived from the trans structure of (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride in the obtained polyimide resin, the amount of base catalyst is preferably used to be at least 30 mol% relative to the amounts of the aforementioned tetracarboxylic dianhydride and the diamine.

[0211] The amount of triethylamine used in this process is preferably less than 100 mol% relative to the amounts of the aforementioned tetracarboxylic dianhydride and the aforementioned diamine, more preferably 1 to 90 mol%, even more preferably 1 to 60 mol%, even more preferably 5 to 60 mol%, even more preferably 10 to 60 mol%, even more preferably 10 to 55 mol%, even more preferably 30 to 55 mol%, even more preferably 40 to 55 mol%.

[0212] When using both triethylamine and triethylenediamine, the amount of triethylenediamine relative to the amounts of the aforementioned tetracarboxylic dianhydride and the aforementioned diamine is preferably 50 mol% or less, more preferably 1 to 50 mol%, further preferably 1 to 20 mol%, even more preferably 1 to 10 mol%, even more preferably 1 to 7 mol%, even more preferably 1 to 6 mol%, even more preferably 2 to 6 mol%, and even more preferably 3 to 6 mol%.

[0213] It should be noted that "relative to the amounts of the aforementioned tetracarboxylic dianhydride and the aforementioned diamine" means "relative to the amounts of the aforementioned tetracarboxylic dianhydride, and also the same relative to the amounts of the aforementioned diamine."

[0214] (Organic solvents)

[0215] The aforementioned organic solvent used in this manufacturing method preferably includes a lactone-based solvent.

[0216] Examples of lactone-based solvents include γ-butyrolactone (GBL) and γ-valerolactone, with γ-butyrolactone (GBL) being preferred.

[0217] The ratio of lactone solvent in the aforementioned organic solvent to the total organic solvent is preferably 10-100% by mass, more preferably 30-100% by mass, even more preferably 50-100% by mass, even more preferably 70-100% by mass, even more preferably 90-100% by mass, even more preferably 95-100% by mass, and even more preferably 99-100% by mass. The aforementioned organic solvent may consist of only lactone solvent.

[0218] The aforementioned organic solvents may include organic solvents other than lactone-based solvents. There are no particular limitations on such organic solvents; examples include aprotic solvents other than lactone-based solvents and phenolic solvents.

[0219] Examples of nonprotic solvents other than lactone solvents include amide solvents, glycol solvents, phosphorus-containing amide solvents, sulfur-containing solvents, ketone solvents, amine solvents, ester solvents, ether solvents, and carbonate solvents.

[0220] Examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, 1,3-dimethylimidazolinone, tetramethylurea, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

[0221] Examples of diethanol solvents include diethylene glycol dimethyl ether, triethylene glycol, and triethylene glycol dimethyl ether.

[0222] Examples of phosphorus-containing amide solvents include hexamethylphosphoramide and hexamethylphosphine triamide.

[0223] Examples of sulfur-containing solvents include dimethyl sulfone, dimethyl sulfoxide, and sulfolane.

[0224] Examples of ketone solvents include acetone, cyclopentanone, cyclohexanone, and methylcyclohexanone.

[0225] Examples of amine solvents include methylpyridine and pyridine.

[0226] Examples of ester solvents include acetic acid (2-methoxy-1-methylethyl).

[0227] 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.

[0228] Examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.

[0229] Examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol.

[0230] Among the organic solvents other than the lactone-based solvents mentioned above, aprotic solvents are preferred, and amide-based solvents are more preferred. Furthermore, the aforementioned organic solvents can be used alone or in mixtures of two or more.

[0231] By including an amide solvent in addition to a lactone solvent in the organic solvent, it is possible to increase the proportion of the trans structure of the structural unit (A1) of the compound represented by formula (a1) derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride in the obtained polyimide resin.

[0232] Examples of lactone-based solvents include γ-butyrolactone (GBL) and γ-valerolactone, with γ-butyrolactone (GBL) being preferred.

[0233] Examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, 1,3-dimethylimidazolinone, tetramethylurea, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide, with N,N-dimethylacetamide being the preferred choice.

[0234] (Imidization conditions)

[0235] This manufacturing method includes a step of imidizing the aforementioned tetracarboxylic dianhydride and the aforementioned diamine in the presence of the aforementioned alkaline catalyst and the aforementioned organic solvent, preferably under the following conditions.

[0236] In this process, the preferred ratio of tetracarboxylic dianhydride to diamine is 0.9 to 1.1 moles of diamine for every 1 mole of tetracarboxylic dianhydride.

[0237] In addition to tetracarboxylic dianhydride and diamine, a capping agent may also be used in this process. Monoamines or dicarboxylic acids are preferred as capping agents. The amount of capping agent introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, relative to 1 mol of tetracarboxylic dianhydride. Examples of monoamine capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline, with benzylamine and aniline being preferred. Dicarboxylic acids are preferred as capping agents, and a portion of them may be ring-closed. Examples include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid, with phthalic acid and phthalic anhydride being preferred.

[0238] There are no particular restrictions on the method for reacting tetracarboxylic dianhydride with diamine; known methods can be used.

[0239] Specific reaction methods include: (1) adding tetracarboxylic acid dianhydride, diamine and organic solvent into a reactor, stirring at 0~80℃ for 0.5~30 hours, and then heating to carry out an imidization reaction; (2) adding diamine and organic solvent into a reactor and dissolving them, then adding tetracarboxylic acid dianhydride, stirring at 0~80℃ for 0.5~30 hours as needed, and then heating to carry out an imidization reaction; (3) adding tetracarboxylic acid dianhydride, diamine and organic solvent into a reactor, and immediately heating to carry out an imidization reaction, etc.

[0240] In the imidization reaction, a Dean-Stark apparatus or similar device is preferred, where the reaction is carried out while removing water generated during manufacturing. This operation allows for further improvement in the degree of polymerization and the imidization rate.

[0241] From the viewpoints of reaction rate and inhibition of gelation, the temperature for the imidization reaction is preferably 120–250 °C, more preferably 160–200 °C. Furthermore, the reaction time is preferably 0.5–10 hours after the distillation of water begins.

[0242] [Polyimide varnish]

[0243] The polyimide varnish of the present invention is formed by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention comprises the polyimide resin of the present invention and an organic solvent, wherein the polyimide resin is dissolved in the organic solvent.

[0244] The organic solvent can be any solvent that dissolves the polyimide resin, and there are no particular limitations. As the organic solvent used in the manufacture of polyimide resin, it is preferred to use one or more of the above-mentioned compounds alone or in combination.

[0245] The polyimide varnish of the present invention may be a solution of polyimide resin obtained by polymerization and imidization in an organic solvent as described above, or it may be obtained by further diluting the polyimide solution with an organic solvent.

[0246] The polyimide resin of the present invention is solvent-soluble, thus enabling the preparation of a high-concentration varnish stable at room temperature. The polyimide varnish of the present invention preferably contains 5-40% by mass of the polyimide resin of the present invention, more preferably 8-30% by mass, and even more preferably 10-20% by mass. The viscosity of the polyimide varnish is preferably 1-200 Pa·s, more preferably 1-100 Pa·s. The viscosity of the polyimide varnish is a value measured using an E-type viscometer at 25°C.

[0247] In addition, the polyimide varnish of the present invention may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, antioxidants, surfactants, leveling agents, defoamers, fluorescent whitening agents, crosslinking agents, polymerization initiators, and photosensitizers within a range that does not impair the required properties of the polyimide resin and the polyimide film.

[0248] The manufacturing method of the polyimide varnish of the present invention is not particularly limited, and known methods can be used.

[0249] The organic solvent can be any solvent that dissolves the polyimide resin and is not particularly limited. It is preferable to use one or more of the above-mentioned compounds alone or in combination as the organic solvent used in the manufacture of the polyimide resin. Preferably, it is selected from at least one of the group consisting of lactone-based solvents and amide-based solvents, more preferably lactone-based solvents, and even more preferably containing both lactone-based and amide-based solvents. More preferably, it is selected from at least one of the group consisting of γ-butyrolactone (GBL) and N,N-dimethylacetamide, even more preferably γ-butyrolactone (GBL), and even more preferably containing both γ-butyrolactone (GBL) and N,N-dimethylacetamide. By containing the above-mentioned solvents, the solubility and coatability of the polyimide resin are improved.

[0250] As an organic solvent contained in the polyimide varnish, it may contain only γ-butyrolactone. The polyimide varnish preferably contains more than 20% by mass of γ-butyrolactone relative to the total amount of the polyimide varnish, more preferably 20 to 90% by mass, even more preferably 20 to 70% by mass, even more preferably 20 to 60% by mass, even more preferably 20 to 50% by mass, even more preferably 30 to 50% by mass, and even more preferably 30 to 45% by mass.

[0251] In addition, relative to the total amount of organic solvents, the organic solvents contained in the polyimide varnish preferably include 30% by mass or more of γ-butyrolactone, more preferably 30 to 95% by mass, even more preferably 30 to 80% by mass, even more preferably 30 to 70% by mass, even more preferably 35 to 60% by mass, and even more preferably 35 to 50% by mass.

[0252] In the polyimide varnish, the organic solvent contained in the polyimide varnish preferably contains 1% or more of an amide solvent relative to the total amount of the polyimide varnish, more preferably 5 to 70% by mass, even more preferably 20 to 70% by mass, even more preferably 25 to 70% by mass, even more preferably 35 to 70% by mass, even more preferably 35 to 60% by mass, and even more preferably 40 to 60% by mass.

[0253] In addition, relative to the total amount of organic solvents, the organic solvents contained in the polyimide varnish preferably include 1% or more of amide solvents, more preferably 5 to 70% by mass, even more preferably 20 to 70% by mass, even more preferably 30 to 70% by mass, even more preferably 40 to 65% by mass, and even more preferably 50 to 65% by mass.

[0254] [Polyimide film]

[0255] The polyimide film of the present invention comprises the aforementioned polyimide resin. Therefore, the polyimide film of the present invention does not contain perfluoroalkyl or polyfluoroalkyl structures, is colorless and highly transparent, and has a high elastic modulus and excellent elongation.

[0256] The preferred physical properties of the polyimide film of the present invention are as follows.

[0257] The polyimide film of the present invention preferably has a YI of 7.5 or less when the thickness is 50 μm, a total light transmittance of 80% or more, a haze of 1.0% or less, and a tensile elongation at the point of fracture of 5% or more when subjected to a tensile test at 23°C and 50% RH, with a test piece of 50 μm × 10 mm × 120 mm, a tensile speed of 20 mm / min, and a chuck spacing of 50 mm. Furthermore, the tensile modulus of elasticity calculated from the slope of the least squares method in the stress-strain curve obtained from the tensile test is 3.7 GPa or more, representing the strain range of 0.1 mm to 0.5 mm. More detailed description follows.

[0258] When the thickness is 50 μm, YI is preferably 7.5 or less, more preferably 7.2 or less, even more preferably 5.0 or less, even more preferably 4.0 or less, and even more preferably 3.0 or less.

[0259] When the thickness is 50 μm, the total light transmittance is preferably 80% or more, more preferably 85% or more, even more preferably 86% or more, even more preferably 87% or more, and even more preferably 88% or more.

[0260] When the thickness is 50 μm, the haze is preferably 1.0% or less, more preferably 0.9% or less, even more preferably 0.6% or less, even more preferably 0.5% or less, and even more preferably 0.4% or less.

[0261] The tensile elongation at the point of fracture in a tensile test conducted at 23°C and 50%RH, with a test piece size of 50μm × 10mm × 120mm, a tensile speed of 20mm / min, and a chuck spacing of 50mm, is preferably 5% or more, more preferably 6% or more, even more preferably 7% or more, even more preferably 8% or more, even more preferably 9% or more, even more preferably 10% or more, and even more preferably 11% or more.

[0262] In the stress-strain curve obtained by a tensile test conducted at 23°C and 50%RH, with a test piece of 50μm × 10mm × 120mm, a tensile speed of 20mm / min, and a chuck spacing of 50mm, the tensile modulus of elasticity calculated based on the slope of the least squares method for the strain range of 0.1mm to 0.5mm is preferably 3.7GPa or more, more preferably 3.8GPa or more, even more preferably 3.9GPa or more, and even more preferably 4.0GPa or more.

[0263] It should be noted that the above-mentioned physical property values ​​in this invention can be specifically measured by the methods described in the embodiments.

[0264] The polyimide film of the present invention comprises the aforementioned polyimide resin, but does not contain perfluoroalkyl or polyfluoroalkyl structures. It is colorless and highly transparent, possesses high elastic modulus, and exhibits excellent elongation. Therefore, the polyimide film of the present invention is suitable for use as an optical material, electronic material, and especially as a material for displays.

[0265] The thickness of the polyimide film of the present invention is not particularly limited, but is preferably 1 to 250 μm, more preferably 5 to 100 μm, even more preferably 8 to 80 μm, and even more preferably 10 to 80 μm. If the thickness of the film is within the above range, it can be used as an optical material, an electronic material, and especially a material for displays.

[0266] The thickness of the polyimide film can be easily controlled by adjusting the concentration and viscosity of the solid components in the varnish.

[0267] <Manufacturing Method of Polyimide Film>

[0268] The method for manufacturing the polyimide film of the present invention is not particularly limited, and known methods can be used. For example, it can be obtained by coating a support with polyimide varnish and then drying it. Among such methods, the manufacturing method shown below is preferred.

[0269] That is, a preferred method for manufacturing a polyimide film includes the following steps: a coating step in which the aforementioned polyimide varnish is coated onto a support to obtain a coated film; a first drying step in which the aforementioned coated film is dried and peeled off from the support to obtain a self-supporting film; and a second drying step in which the aforementioned self-supporting film is dried at 210°C or higher, preferably 220°C or higher.

[0270] The coating process is the process of applying polyimide varnish onto a support to obtain a coating film.

[0271] As a support, glass plates, metal plates, metal cylinders, metal strips, and plastic films with smooth surfaces are preferred, with glass plates or plastic films being more preferred. Furthermore, from the viewpoint of improving productivity, annular supports such as metal cylinders or metal strips, or long strips of plastic film, are preferred as supports, and the polyimide film is manufactured using a roll-to-roll process.

[0272] Commonly known coating methods include spin coating, slot coating, doctor blade coating, and die coating. Glass rods and coating machines can also be used.

[0273] Regarding the coating thickness, it is preferred that the thickness of the dried polyimide film is 1 to 250 μm, more preferably 5 to 100 μm, even more preferably 8 to 80 μm, and even more preferably 10 to 80 μm.

[0274] A release agent can be pre-applied to the surface of the aforementioned support as needed.

[0275] The drying process involves drying the aforementioned coated film and peeling it off from the support to obtain a self-supporting film.

[0276] The first drying step is a process to remove a portion of the organic solvent in order to obtain a self-supporting film. The organic solvent is removed by heating the coating film on the support.

[0277] The preferred temperature for removing the organic solvent is 50–140°C, more preferably 50–120°C. To prevent prolonged heating, the temperature can be gradually increased. In this case, the initial temperature is preferably 50–90°C, more preferably 50–70°C. The final temperature is preferably 80–140°C, more preferably 90–120°C. The removal of the organic solvent is preferably carried out under a nitrogen atmosphere. The removal of the organic solvent can be carried out under reduced pressure, normal pressure, or increased pressure.

[0278] The resulting film is peeled off from the support. The peeled film is self-supporting.

[0279] The secondary drying process involves drying the aforementioned self-supporting film at a temperature above 210°C.

[0280] The end of the self-supporting film obtained in the previous process is fixed and dried at a temperature above 210°C.

[0281] The secondary drying temperature is preferably 210~300℃, more preferably 210~280℃, even more preferably 210~260℃, even more preferably 220~260℃, and even more preferably 220~240℃. By setting the secondary drying temperature within the above range, the elastic modulus can be increased, thereby achieving a balance between colorless transparency and high elastic modulus.

[0282] Secondary drying is preferably carried out under a nitrogen atmosphere. Secondary drying can be carried out at any pressure, including reduced pressure, atmospheric pressure, and pressurized pressure.

[0283] In addition, the secondary drying time can be adjusted appropriately according to the above temperature, preferably 3 to 60 minutes, more preferably 5 to 60 minutes, further preferably 5 to 30 minutes, and even more preferably 5 to 20 minutes.

[0284] From the viewpoint of further improving colorless transparency, 3 to 30 minutes is preferred, 3 to 20 minutes is more preferred, 3 to 15 minutes is even more preferred, and 5 to 15 minutes is still preferred.

[0285] On the other hand, from the viewpoint of further improving the elastic modulus, 10 to 50 minutes is more preferred, 15 to 40 minutes is even more preferred, and 17 to 28 minutes is even more preferred.

[0286] Cooling is performed after secondary drying, but annealing is also an option.

[0287] Example

[0288] The present invention will now be specifically described through examples. However, the present invention is not limited to these examples.

[0289] [Structure of polyimide resin]

[0290] The structure of the polyimide resins obtained in the examples and comparative examples was analyzed using the methods shown below.

[0291] (1) The ratio of trans structures derived from cyclohexanetetracarboxylic dianhydride

[0292] The ratio of polyimide resins derived from the trans structure of cyclohexanetetracarboxylic dianhydride was determined by measuring the polyimide resin. 1 The H-NMR spectrum was calculated as follows.

[0293] 1 H-NMR spectra were determined using an NMR spectrophotometer (ASC End). TM 500 (manufactured by Bruker Corporation), the determination was performed using a deuterated dimethyl sulfoxide solution of polyimide resin. The ratio of the trans structure derived from the cyclohexanetetracarboxylic acid dianhydride was calculated from the integral value of the peak derived from the cyclohexanetetracarboxylic acid moiety described below.

[0294] 1 H NMR (DMSO-d6)

[0295] A = the integral value of the peak in the range of δ2.179ppm to δ2.279ppm (trans-cyclohexanetetracarboxylic acid proton (3-position, 6-position), 4H)

[0296] B = the integral value of the peak in the range of δ2.279ppm to δ2.391ppm (cis-cyclohexanetetracarboxylic acid protons (3-position, 6-position), 4H)

[0297] The ratio of trans structures (mol%) = A / (A+B) × 100

[0298] Evaluation of polyimide films (polyimide resins)

[0299] The physical properties of the polyimide films (polyimide resins) obtained in the examples and comparative examples were determined and evaluated using the methods shown below.

[0300] (1) Polyimide film thickness

[0301] The thickness of the polyimide film was measured using a micrometer manufactured by Mitutoyo Corporation.

[0302] (2) Tensile modulus of elasticity, tensile strength and elongation at break

[0303] Tensile modulus of elasticity, tensile strength, and elongation at break were measured according to JIS K7127:1999 using a tensile testing machine, "Strograph VG-1E," manufactured by Toyo Seiki Co., Ltd. The chuck spacing was 50 mm, the test piece size was 10 mm × 120 mm, the testing speed (tensile speed) was 20 mm / min, and the measurement temperature was set to 23 °C.

[0304] The tensile modulus of elasticity is calculated as the slope of the least squares method in the stress-strain curve obtained by the aforementioned tensile test, from the strain interval of 0.1 mm to 0.5 mm.

[0305] A higher tensile modulus value indicates a higher elastic modulus in the polyimide film (polyimide resin), which is preferred. A higher tensile strength value indicates superior strength in the polyimide film (polyimide resin), which is also preferred. Furthermore, a higher tensile elongation at break value indicates superior elongation in the polyimide film (polyimide resin), which is also preferred.

[0306] (3) Haze, total transmittance, and yellowness index (YI)

[0307] Haze was measured according to JIS K7136:2000, total transmittance according to JIS K7361-1:1997, and yI according to ASTM E313-05 (D light source, 65°). All measurements were performed using a color / turbidity simultaneous measuring instrument (COH7700, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[0308] The lower the haze value, the better the transparency of the polyimide film (polyimide resin). The higher the total transmittance value, the better the transparency of the polyimide film (polyimide resin). The lower the YI value of the polyimide film, the better its colorlessness.

[0309] <Abbreviations for ingredients, etc.>

[0310] The tetracarboxylic dianhydride and diamine used in the examples and comparative examples, and their abbreviations, are described below.

[0311] (Tetracarboxylic acid dianhydride)

[0312] HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (compound represented by formula (a1), manufactured by Mitsubishi Gas Chemical Co., Ltd.)

[0313] CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride (the compound shown in formula (a2))

[0314] (Diamine)

[0315] mTB: 2,2'-dimethylbenzidine (compound represented by formula (b1), manufactured by SEIKA Co., Ltd.)

[0316] 4,4'-DDS: 4,4'-Diaminodiphenylsulfone (In the compound shown in formula (b2), the amino group is at position 4)

[0317] 3,3'-DDS: 3,3'-Diaminodiphenylsulfone (The compound shown in formula (b2) has amino groups at the 3-position, manufactured by SEIKA Corporation)

[0318] 8FBZ: Octafluorobenzidine (the compound shown in formula (b3))

[0319] DABA: 4,4'-Diaminobenzoylaniline (the compound shown in formula (b6), n=0, R are all hydrogen atoms, manufactured by SEIKA Corporation)

[0320] AMB-mTOL: N,N'-(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[4-amino-3-methylbenzamide] (the compound shown in formula (b61))

[0321] The abbreviations for solvents and catalysts used in the examples and comparative examples are described below.

[0322] GBL: γ-Butyrolactone (manufactured by Mitsubishi Chemical Corporation)

[0323] DMAc: N,N-dimethylacetamide

[0324] TEA: Triethylamine (manufactured by Kanto Chemical Co., Ltd.)

[0325] TEDA: Triethylenediamine

[0326] <Manufacturing of polyimide resins, polyimide varnishes, and polyimide films>

[0327] Example 1

[0328] In a 500 mL five-necked round-bottom flask equipped with a stainless steel crescent-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark apparatus with a cooling pipe, a thermometer, and glass end caps, 16.938 g (0.0798 mol) of mTB as a diamine and 64.17 g of GBL were added. The system was heated to 70 °C under a nitrogen atmosphere and stirred at 200 rpm to obtain a solution.

[0329] 14.308 g (0.0638 mol) of HPMDA as a tetracarboxylic acid dianhydride, 3.129 g (0.0160 mol) of CBDA, and 8.02 g of GBL were added to the solution in a single addition. Then, 4.04 g (0.0399 mol) of TEA as an imidization catalyst, 0.447 g (0.0040 mol) of TEDA, and GBL as a solvent were added. The reaction system was heated using a jacketed heater, raising the temperature to 190°C over approximately 20 minutes. While collecting the distilled components, the temperature of the reaction system was maintained at 190°C and refluxed for 1 hour to obtain a solution containing polyimide resin. DMAc was added at a solids concentration of 15% by mass, and the reaction system was cooled to 50°C to obtain a polyimide varnish containing polyimide resin. (The solvent composition (by mass) in the varnish is GBL / DMAc = 38 / 47).

[0330] Next, the obtained polyimide varnish was coated onto a PET (polyethylene terephthalate) substrate, and the coating was held at 60°C for 20 minutes using a hot plate, followed by a further holding at 80°C for 20 minutes. Then, the solvent was evaporated by heating at 220°C for 20 minutes in an air dryer to obtain a polyimide film. The physical properties and evaluation results of the film are shown in Table 1.

[0331] Examples 2-7 and Comparative Examples 1-5

[0332] In Example 1, the types and amounts of diamine and tetracarboxylic dianhydride were changed to those shown in Table 1. Otherwise, a polyimide varnish containing polyimide resin was obtained in the same manner as in Example 1. Furthermore, a polyimide film was obtained in the same manner as in Example 1. The physical properties and evaluation results of the film are shown in Table 1.

[0333] [Table 1]

[0334]

[0335] As shown in Table 1, the polyimide resin (polyimide film) of the embodiments not only has a high tensile modulus of elasticity and high tensile strength, but also a high elongation at the point of tensile break, exhibiting excellent mechanical properties. Furthermore, the polyimide resin (polyimide film) of the embodiments demonstrates particularly excellent haze and high total light transmittance.

[0336] Therefore, it can be seen that the polyimide resin of the present invention has excellent transparency, high elastic modulus and high strength, and also excellent elongation. Furthermore, it is known that the polyimide resin of the present invention is soluble in solvents as a varnish, and is thus solvent-soluble. In particular, it is known that although the polyimide resin of the present invention does not contain perfluoroalkyl or polyfluoroalkyl structures, it possesses the aforementioned properties.

Claims

1. A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, Structural unit A comprises structural unit A1 derived from the compound shown in formula (a1) below and structural unit A2 derived from the compound shown in formula (a2) below. Structural unit B comprises structural unit B1 derived from the compound shown in formula (b1) below. The proportion of structural unit A2 in structural unit A is less than 27 mol%. The polyimide resin does not contain the following structural element (c). In formula (c), X is a fluorine atom, a hydrogen atom, or a carbon atom.

2. The polyimide resin according to claim 1, wherein, The ratio of structural unit A1 in structural unit A is 10~99 moles.

3. The polyimide resin according to claim 1 or 2, wherein, The molar ratio of structural unit A1 to structural unit A2 in structural unit A is 73 / 27 to 99 / 1.

4. The polyimide resin according to any one of claims 1 to 3, wherein, The ratio of structural unit B1 in structural unit B is 40~100 moles.

5. The polyimide resin according to any one of claims 1 to 4, wherein, Structural unit B further comprises at least one selected from the group consisting of structural unit B2 derived from the compound shown in formula (b2), structural unit B3 derived from the compound shown in formula (b3), structural unit B4 derived from the compound shown in formula (b4), structural unit B5 derived from the compound shown in formula (b5), and structural unit B6 derived from the compound shown in formula (b6). In formula (b6), R is independently a hydrogen atom or a methyl group, Y is a divalent group containing 12 to 30 carbon atoms of an aromatic ring, and n is 0 or 1.

6. The polyimide resin according to claim 5, wherein, The total ratio of structural units B2, B3, B4, B5 and B6 in structural unit B is less than 50 mol%.

7. The polyimide resin according to claim 5 or 6, wherein The molar ratio of structural unit B1 to the total of structural units B2, B3, B4, B5 and B6 in structural unit B, B1 / (B2+B3+B4+B5+B6), is 50 / 50~99 / 1.

8. The polyimide resin according to any one of claims 1 to 7, wherein, The proportion of the trans structure derived from (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride contained in structural unit A1 is greater than 30 mol%.

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

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

11. The polyimide film according to claim 10, wherein the YI is 7.5 or less when the thickness is 50 μm, the total light transmittance is 80% or more, the haze is 1.0% or less, and the elongation at the tensile fracture point is 5% or more in a tensile test conducted at 23°C and 50%RH under the conditions of a test piece of 50 μm × 10 mm × 120 mm, a tensile speed of 20 mm / min, and a chuck distance of 50 mm, and the tensile modulus of elasticity calculated based on the least squares method in the stress-strain curve obtained by the tensile test is 3.7 GPa or more.

12. The polyimide film according to claim 10 or 11, wherein the thickness is 5 to 100 μm.

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