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

Abstract

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

Description

Technology Field

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

[0002] Polyimide resins are being considered for various applications in fields such as electrical and electronic components. For example, there is a demand to replace glass substrates used in image display devices, such as liquid crystal displays or OLED displays, with plastic substrates for the purpose of making the devices lighter or more flexible, and research is being conducted on polyimide films suitable as such plastic substrates. Transparency is required for polyimide films used for these purposes.

[0003] Furthermore, as a required characteristic of the polyimide film, it is required that the phase difference due to birefringence be small and the retardation be low (good optical isotropy).

[0004] Patent Document 1 discloses a polyimide resin that provides a film with reduced birefringence, wherein the polyimide resin is obtained using a diamine (e.g., metaphenylenediamine) in which at least one of the amino groups of the diamine is bonded to a meta position relative to the main chain.

[0005] Patent document 2 discloses a polyimide resin that provides a film with excellent heat resistance, transmittance, low coefficient of linear expansion, and low retardation, comprising a tetracarboxylic acid residue and a diamine residue of a specific structure, and a tetracarboxylic acid residue and / or a diamine residue having a refractive site. Specifically, a polyimide resin obtained using 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-bicyclohexanetetracarboxylic acid dianhydride, pyromellitic anhydride, 2,2'-bis(trifluoromethyl)benzidine, and 4,4'-diaminodiphenylsulfone is disclosed. Prior art literature

[0006] Japanese Patent Publication No. H8-134211, International Publication No. 2015 / 125895 The problem to be solved

[0007] As described above, good optical properties, such as transparency and optical isotropy, are required for polyimide films. On the other hand, since polyimide has a rigid and rigid molecular structure, breakage due to shrinkage during film manufacturing or breakage when used in products with moving parts (e.g., flexible displays) has been a problem. In order to suppress breakage and improve ductility, for example, if a highly flexible component is introduced into the molecule, optical properties generally deteriorate. Thus, there has been a demand for a polyimide film that possesses good optical properties and ductility.

[0008] Accordingly, the objective of the present invention is to provide a polyimide resin, a polyimide resin composition, a polyimide varnish, and a polyimide film capable of forming a film having excellent transparency and optical isotropy and excellent flexibility. means of solving the problem

[0009] The inventors have discovered that a polyimide resin comprising a combination of specific constituent units and a resin composition comprising said polyimide resin and a specific polymer can solve the above problem, and have thus completed the invention.

[0010] That is, the present invention relates to [1] to [8] below.

[0011] [1]

[0012] A polyimide resin having a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, wherein constituent unit A comprises at least one constituent unit selected from the group consisting of a constituent unit (A1) derived from a compound represented by the following formula (a1) and a constituent unit (A2) derived from a compound represented by the following formula (a2), and constituent unit B comprises at least one constituent unit (B1) selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b11), a constituent unit derived from a compound represented by the following formula (b12), and a constituent unit derived from a compound represented by the following formula (b13), and at least one constituent unit (B2) selected from the group consisting of a constituent unit derived from a compound represented by the following general formula (b21) and a constituent unit derived from a compound represented by the following general formula (b22), and the molar ratio [(B1) / (B2)] of constituent unit (B1) and constituent unit (B2) is 45 / 55~75 / 25, polyimide resin.

[0013] [Chemical Formula 1]

[0014]

[0015] (In equation (b11), R 1 and R 2 represents, respectively, a methyl group or a trifluoromethyl group, and in formulas (b21) and (b22), X 1 ~X 4 Each represents, independently, a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, or -S-, -SO-, -SO2-, -O-, or -CO-.

[0016] [2]

[0017] The polyimide resin described in [1] above, having a breaking point elongation of 10% or more as measured in accordance with JIS K 7127.

[0018] [3]

[0019] A polyimide resin described in either [1] or [2], wherein the constituent unit (B2) comprises at least one constituent unit selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b211), a constituent unit derived from a compound represented by the following formula (b212), and a constituent unit derived from a compound represented by the following formula (b213).

[0020] [Chemical Formula 2]

[0021]

[0022] [4]

[0023] A polyimide resin composition comprising at least one selected from the group consisting of a polyimide resin described in any one of [1] to [3] above, a fluorine-containing polymer, and a silicon-containing polymer.

[0024] [5]

[0025] A polyimide resin composition described in [4], wherein the total content of the fluorine-containing polymer and the silicon-containing polymer is 0.01 to 2 parts by mass per 100 parts by mass of the polyimide resin.

[0026] [6]

[0027] The polyimide resin composition described in [4] or [5], wherein the fluorine-containing polymer is a fluorine-containing acrylic polymer.

[0028] [7]

[0029] A polyimide varnish formed by dissolving the polyimide resin described in any one of [1] to [3] above, or the polyimide resin composition described in any one of [4] to [6] above, in an organic solvent.

[0030] [8]

[0031] A polyimide film comprising a polyimide resin described in any one of [1] to [3] above, or a polyimide resin composition described in any one of [4] to [6] above. Effects of the invention

[0032] According to the present invention, a polyimide resin, a polyimide resin composition, a polyimide varnish, and a polyimide film capable of forming a film having excellent transparency and optical isotropy and excellent flexibility can be provided. Specific details for implementing the invention

[0033] [Polyimide Resin]

[0034] The polyimide resin of the present invention is a polyimide resin having a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, wherein constituent unit A comprises at least one constituent unit selected from the group consisting of a constituent unit (A1) derived from a compound represented by the following formula (a1) and a constituent unit (A2) derived from a compound represented by the following formula (a2), and constituent unit B comprises at least one constituent unit (B1) selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b11) (hereinafter also referred to as constituent unit (B11)), a constituent unit derived from a compound represented by the following formula (b12) (hereinafter also referred to as constituent unit (B13)), a constituent unit derived from a compound represented by the following general formula (b21) (hereinafter also referred to as constituent unit (B21)), and the following It includes at least one constituent unit (B2) selected from the group consisting of constituent units derived from a compound represented by general formula (b22) (hereinafter also referred to as constituent unit (B22)), and the molar ratio [(B1) / (B2)] of constituent unit (B1) and constituent unit (B2) is 45 / 55 to 75 / 25.

[0035] [Chemical Formula 3]

[0036]

[0037] (In equation (b11), R 1 and R 2represents, respectively, a methyl group or a trifluoromethyl group, and in formulas (b21) and (b22), X 1 ~X 4 Each represents, independently, a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, or -S-, -SO-, -SO2-, -O-, or -CO-.

[0038] <Constituent Unit A>

[0039] Constituent unit A is a constituent unit derived from a tetracarboxylic acid dianhydride that occupies the polyimide resin, and constituent unit A comprises at least one constituent unit selected from the group consisting of a constituent unit (A1) derived from a compound represented by the following formula (a1) and a constituent unit (A2) derived from a compound represented by the following formula (a2).

[0040] [Chemical Formula 4]

[0041]

[0042] The compound represented by formula (a1) is 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride.

[0043] By including the constituent unit A (A1), the transparency and optical isotropy of the film can be improved, and furthermore, the heat resistance and thermal stability can also be improved.

[0044] The compound represented by formula (a2) is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride.

[0045] By including constituent unit A as constituent unit (A2), the transparency of the film is improved and the solubility of the polyimide in organic solvents is improved.

[0046] Constituent unit A may include both constituent unit (A1) and constituent unit (A2), preferably including either constituent unit (A1) or constituent unit (A2), and more preferably including constituent unit (A1).

[0047] When constituent unit A includes constituent unit (A1) and constituent unit (A2), the ratio of the total of constituent units (A1) and (A2) in constituent unit A is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the ratio of the total of constituent units (A1) and (A2) is not specifically limited, i.e., 100 mol%.

[0048] When constituent unit A includes constituent unit (A1), the proportion of constituent unit (A1) in constituent unit A is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the proportion is not particularly limited, i.e., 100 mol%. Likewise, the proportion of constituent unit (A1) in constituent unit A is preferably 45 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably 99 to 100 mol%.

[0049] When constituent unit A includes constituent unit (A2), the proportion of constituent unit (A2) in constituent unit A is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the proportion is not particularly limited, i.e., 100 mol%. Likewise, the proportion of constituent unit (A2) in constituent unit A is preferably 45 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably 99 to 100 mol%.

[0050] Constituent unit A may additionally include a constituent unit (A3) derived from a compound represented by the following formula (a3).

[0051] [Chemical Formula 5]

[0052]

[0053] The compound represented by formula (a3) ​​is norbonan-2-spiro-α-cyclopentanone-α'-spiro-2''-norbonan-5,5'',6,6''-tetracarboxylic acid dianhydride. By including constituent unit A as constituent unit (A3), the transparency of the film is improved.

[0054] When constituent unit A includes constituent unit (A3), the proportion of constituent unit (A3) in constituent unit A is preferably 55 mol% or less, more preferably 30 mol% or less. Also, it is preferably 5 mol% or more.

[0055] When constituent unit A includes constituent unit (A3), constituent unit A preferably includes constituent unit (A1) and constituent unit (A3), and more preferably consists of constituent unit (A1) and constituent unit (A3).

[0056] Constituent unit A may include constituent units other than constituent units (A1) to (A3) to the extent that it does not impair the effects of the present invention. The tetracarboxylic acid dianhydrides imparting such constituent units are not particularly limited, but include aromatic tetracarboxylic acid dianhydrides such as pyromellitic acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid anhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, and 2,2',3,3'-biphenyltetracarboxylic acid dianhydride (provided that compounds represented by formula (a2) are excluded); Examples include alicyclic tetracarboxylic acid dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclopentanetetracarboxylic acid dianhydride, bicyclo[2.2.2]octa-7-en-2,3,5,6-tetracarboxylic acid dianhydride, and dicyclohexyltetracarboxylic acid dianhydride (excluding compounds represented by formula (a1) and compounds represented by formula (a3); and aliphatic tetracarboxylic acid dianhydrides such as 1,2,3,4-butanetetracarboxylic acid dianhydride.

[0057] Meanwhile, in the present specification, an aromatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more aromatic rings, an alicyclic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more alicyclic rings and not an aromatic ring, and an aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing neither aromatic rings nor alicyclic rings.

[0058] Constituent units other than constituent units (A1) to (A3) that are optionally included in constituent unit A may be of one type or two or more types.

[0059] It is preferable that constituent unit A does not include constituent units other than the above constituent units (A1) to (A3).

[0060] <Constituent Unit B>

[0061] Constituent unit B is a constituent unit derived from a diamine in a polyimide resin, comprising at least one constituent unit (B1) selected from the group consisting of a constituent unit (B11) derived from a compound represented by the following formula (b11), a constituent unit (B12) derived from a compound represented by the following formula (b12), and a constituent unit (B13) derived from a compound represented by the following formula (b13), and at least one constituent unit (B2) selected from the group consisting of a constituent unit (B21) derived from a compound represented by the following general formula (b21) and a constituent unit (B22) derived from a compound represented by the following general formula (b22).

[0062] The molar ratio [(B1) / (B2)] of the constituent unit (B1) and the constituent unit (B2) is 45 / 55 to 75 / 25.

[0063] [Chemical Formula 6]

[0064]

[0065] In equation (b11), R 1 and R 2 represents, respectively, a methyl group or a trifluoromethyl group, and in formulas (b21) and (b22), X 1 ~X 4 Each represents, independently, a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO2-, -O-, or -CO-.

[0066] (Constituent Unit (B1))

[0067] The constituent unit (B1) is at least one constituent unit selected from the group consisting of a constituent unit (B11) derived from a compound represented by the following formula (b11), a constituent unit (B12) derived from a compound represented by the following formula (b12), and a constituent unit (B13) derived from a compound represented by the following formula (b13).

[0068] [Chemical Formula 7]

[0069]

[0070] The compound represented by formula (b11) is 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane or 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and

[0071] The compound represented by formula (b12) is a 4,4'-diaminodiphenyl ether, and

[0072] The compound represented by formula (b13) is 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene.

[0073] Constituent unit B includes at least one constituent unit selected from the group consisting of constituent units (B11) to (B13). Among these, it is more preferable for constituent unit B to include at least one constituent unit selected from the group consisting of constituent unit (B11) and constituent unit (B12) in order to increase the flexibility of the film, and it is even more preferable for constituent unit B to include constituent unit (B11).

[0074] Constituent unit B may include two or more types of constituent units (B11) to (B13), but it is preferable to include one type of constituent unit among constituent units (B11) to (B13). That is, it is preferable that constituent unit B includes constituent unit (B11), constituent unit (B12), or constituent unit (B13).

[0075] By including constituent unit B as constituent unit (B1), flexibility can be improved while maintaining the transparency and optical isotropy of the film. Additionally, colorlessness can also be improved. Constituent unit (B1) may be one type or two or more types. As constituent unit (B1), a constituent unit derived from 2,2-bis[4-(4-aminophenoxy)phenyl]propane is preferred.

[0076] (Constituent Unit (B2))

[0077] The constituent unit (B2) is at least one constituent unit selected from the group consisting of a constituent unit (B21) derived from a compound represented by the following general formula (b21) and a constituent unit (B22) derived from a compound represented by the following general formula (b22).

[0078] [Chemical Formula 8]

[0079]

[0080] Among equations (b21) and (b22), X 1 ~X 4 Each represents, independently, a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -S-, -SO-, -SO2-, -O-, or -CO-.

[0081] The compound represented by the general formula (b21) is X 1 and X 2 Three benzene rings are connected via , and X at the 1,3 position of the central benzene ring 1 and X 2 A compound having a skeleton formed by the bonding of X and represented by the general formula (b22) is X 3 and X 4 Three benzene rings are connected via , and X at the 1,2 position of the central benzene ring 3 and X 4 It has a combined framework. By having this structure, it becomes possible to form a film that is flexible while possessing excellent transparency and optical isotropy.

[0082] X in general formulas (b21) and (b22) 1 ~X 4 In terms of forming a film with excellent optical isotropy, each independently preferably represents an alkylidene group having 3 to 5 carbon atoms, -SO2-, or -O-, more preferably an alkylidene group having 3 to 5 carbon atoms, or -O-, even more preferably an isopropylidene group, or -O-, and even more preferably an isopropylidene group.

[0083] X in general formula (b21) 1 and X 2 Each may have a different group, but it is preferable that they be the same group. Likewise, X in formula (b22) 3 and X 4 Each may have a different energy, but it is desirable that they have the same energy.

[0084] In general formulas (b21) and (b22), the amino group is X bonded to the benzene ring to which each amino group is bonded. 1 ~X 4 For any one of them, it is preferable to bond to the para or meta position of this benzene ring, and it is more preferable to bond to the para position of this benzene ring.

[0085] X in general formulas (b21) and (b22) 1 ~X 4 Examples of the alkylidene groups having 2 to 5 carbon atoms represented by α include ethylidene groups, propylidene groups, isopropylidene groups, butylidene groups, isobutylidene groups, pentylidene groups, isopentylidene groups, etc. Among these alkylidene groups, alkylidene groups having 3 to 5 carbon atoms are preferred, and isopropylidene groups are more preferred.

[0086] The constituent unit (B2) preferably includes a constituent unit derived from a compound represented by the general formula (b21), and more preferably includes at least one constituent unit selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b211), a constituent unit derived from a compound represented by the following formula (b212), and a constituent unit derived from a compound represented by the following formula (b213).

[0087] [Chemical Formula 9]

[0088]

[0089] The compound represented by formula (b211) is 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, and

[0090] The compound represented by formula (b212) is 1,3-bis(4-aminophenoxy)benzene, and

[0091] The compound represented by formula (b213) is 1,3-bis(3-aminophenoxy)benzene.

[0092] Among the compounds represented by formulas (b211) to (b213), preferably at least one compound selected from the group consisting of the compound represented by formula (b211) and the compound represented by formula (b212), and more preferably, the compound represented by formula (b211).

[0093] (Other constituent units that may be included in constituent unit B)

[0094] Constituent unit B may include constituent units other than constituent units (B1) and (B2). Diamines providing such constituent units are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 3,4'-diaminodiphenyl ether, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene-5-amine, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, Examples include aromatic diamines such as 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 9,9-bis(4-aminophenyl)fluorene, 1,4-bis(4-aminophenoxy)benzene (excluding compounds represented by formulas (b11) to (b13) and compounds represented by formulas (b21) to (b22); alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.

[0095] Meanwhile, in this specification, an aromatic diamine means a diamine containing one or more aromatic rings, a diamine alicyclic means a diamine containing one or more alicyclic rings and not an aromatic ring, and an aliphatic diamine means a diamine that does not contain either an aromatic ring or alicyclic rings.

[0096] The constituent units other than constituent units (B1) and (B2) optionally included in constituent unit B may be of one type or two or more types.

[0097] (Composition of Constituent Unit B)

[0098] Constituent unit B includes constituent unit (B1) and constituent unit (B2), and the molar ratio of constituent unit (B1) and constituent unit (B2) is 45 / 55 to 75 / 25. A suitable composition is described below.

[0099] The ratio of the sum of constituent unit (B1) and constituent unit (B2) in constituent unit B is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more. The upper limit of the ratio of the sum of constituent unit (B1) and constituent unit (B2) is not particularly limited, but is preferably 100 mol%. It is even more preferable that constituent unit B consists only of constituent unit (B1) and constituent unit (B2).

[0100] The molar ratio [(B1) / (B2)] of constituent unit (B1) and constituent unit (B2) is 45 / 55 to 75 / 25 in terms of improving transparency, optical isotropy, and ductility, and in terms of transparency, optical isotropy, and colorlessness, it is preferably 45 / 55 to 70 / 30, more preferably 45 / 55 to 65 / 35, even more preferably 45 / 55 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. In addition, in terms of improving ductility, it is preferably 45 / 55 to 75 / 25, more preferably 50 / 50 to 75 / 25, even more preferably 55 / 45 to 75 / 25, even more preferably 60 / 40 to 75 / 25, and even more preferably 65 / 35 to 75 / 25.

[0101] A combination of constituent unit B is preferably one in which constituent unit (B1) is derived from a compound represented by formula (b11) as constituent unit (B1), and constituent unit (B2) is derived from a compound represented by formula (b211). A polyimide resin of the present invention is preferably one in which constituent unit A is derived from a compound represented by formula (a1), and constituent unit B is a constituent unit having the above combination.

[0102] (Physical properties of polyimide resin, etc.)

[0103] The number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 100,000 in terms of the mechanical strength of the polyimide film obtained. Meanwhile, the number average molecular weight of the polyimide resin can be obtained, for example, from the standard polymethyl methacrylate (PMMA) equivalent value by gel filtration chromatography measurement.

[0104] The polyimide resin of the present invention may include a structure other than a polyimide chain (a structure formed by the imide bonding of constituent unit A and constituent unit B). Examples of structures other than a polyimide chain that may be included in the polyimide resin include a structure including an amide bond.

[0105] The polyimide resin of the present invention preferably comprises a polyimide chain (a structure formed by the imide bonding of constituent unit A and constituent unit B) as the main structure. Accordingly, the proportion of the polyimide chain included in the polyimide resin of the present invention is preferably 50 mass% or more, more preferably 70 mass% or more, even more preferably 90 mass% or more, and particularly preferably 99 mass% or more.

[0106] By using the polyimide resin of the present invention, a film having excellent transparency and optical isotropy and excellent flexibility can be formed, and the favorable physical properties of the film are as follows.

[0107] The total light transmittance is preferably 85% or more when using a film with a thickness of 30 μm, more preferably 87% or more, even more preferably 88% or more, and even more preferably 89% or more.

[0108] The yellow index (YI) is preferably 6.5 or less when the film is 30 μm thick, more preferably 4.0 or less, even more preferably 3.0 or less, even more preferably 2.0 or less, and even more preferably 1.5 or less.

[0109] When using a film with a thickness of 30 μm, the haze is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

[0110] The thickness phase difference (Rth) is preferably 40 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, and even more preferably 18 nm or less when the film is 30 μm thick.

[0111] In addition, the polyimide resin of the present invention has a fracture point elongation measured in accordance with JIS K 7127, preferably 10% or more, more preferably 18% or more, even more preferably 20% or more, and even more preferably 30% or more.

[0112] Meanwhile, the above-described physical property values ​​in the present invention can be specifically measured by the method described in the examples.

[0113] [Method for manufacturing polyimide resin]

[0114] The polyimide resin of the present invention can be prepared by reacting a tetracarboxylic acid component comprising at least one selected from the group consisting of a compound providing the aforementioned constituent unit (A1) and a compound providing the aforementioned constituent unit (A2), with a diamine component comprising a compound providing the aforementioned constituent unit (B1) and a compound providing the aforementioned constituent unit (B2).

[0115] Examples of compounds that impart the constituent unit (A1) include compounds represented by formula (a1), but are not limited thereto and may also be derivatives thereof within the scope of imparting the same constituent unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic acid dianhydride represented by formula (a1) and alkyl esters of said tetracarboxylic acids. As for the compound imparting the constituent unit (A1), the compound represented by formula (a1) (i.e., the dianhydride) is preferred.

[0116] Likewise, the compound imparting the constituent unit (A2) may be a compound represented by formula (a2), but is not limited thereto and may be a derivative thereof within the scope of imparting the same constituent unit. Examples of such derivatives include a tetracarboxylic acid corresponding to the tetracarboxylic acid dianhydride represented by formula (a2) and an alkyl ester of the said tetracarboxylic acid. The compound imparting the constituent unit (A2) is preferably a compound represented by formula (a2) (i.e., a dianhydride).

[0117] The tetracarboxylic acid component comprises, in total, a compound providing a constituent unit (A1) and a compound providing a constituent unit (A2), preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound providing a constituent unit (A1) and the compound providing a constituent unit (A2) is not specifically limited, i.e., 100 mol%. The tetracarboxylic acid component may consist only of a compound providing a constituent unit (A1) and a compound providing a constituent unit (A2).

[0118] When the tetracarboxylic acid component includes a compound that provides a constituent unit (A1) or a compound that provides a constituent unit (A2), the compound that provides the constituent unit (A1) or the compound that provides the constituent unit (A2) preferably contains 45 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more. The upper limit of the content of the compound that provides the constituent unit (A1) or the compound that provides the constituent unit (A2) is not limited, i.e., 100 mol%. The tetracarboxylic acid component may consist only of the compound that provides the constituent unit (A1) or the compound that provides the constituent unit (A2), and it is preferable that it consists only of the compound that provides the constituent unit (A1).

[0119] The tetracarboxylic acid component may include a compound that imparts the constituent unit (A3) described above within a range that does not impair optical isotropy and ductility.

[0120] Examples of compounds that impart the constituent unit (A3) include compounds represented by formula (a3), but are not limited thereto and may also be derivatives thereof within the scope of imparting the same constituent unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic acid dianhydride represented by formula (a3) ​​and alkyl esters of said tetracarboxylic acids. As for the compound imparting the constituent unit (A3), the compound represented by formula (a3) ​​(i.e., the dianhydride) is preferred.

[0121] When the tetracarboxylic acid component includes a compound that provides a constituent unit (A3), the compound that provides the constituent unit (A3) is preferably included in an amount of 55 mol% or less, more preferably 30 mol% or less. Additionally, it is preferably included in an amount of 5 mol% or more. When the tetracarboxylic acid component includes a compound that provides a constituent unit (A3), it is preferable that it consists only of the compound that provides the constituent unit (A1) and the compound that provides the constituent unit (A3).

[0122] The tetracarboxylic acid component may include compounds other than the compound providing the constituent unit (A1), the compound providing the constituent unit (A2), and the compound providing the constituent unit (A3), and the compounds may include the aromatic tetracarboxylic acid dianhydride, the alicyclic tetracarboxylic acid dianhydride, and the aliphatic tetracarboxylic acid dianhydride described above, and their derivatives (tetracarboxylic acid, alkyl ester of tetracarboxylic acid, etc.).

[0123] Compounds other than the compound that imparts the constituent units (A1) to (A3) optionally included in the tetracarboxylic acid component may be one type or two or more types.

[0124] Compounds that provide the constituent unit (B1) may include a compound represented by general formula (b11) that provides the constituent unit (B11), a compound represented by general formula (b12) that provides the constituent unit (B12), and a compound represented by general formula (b13) that provides the constituent unit (B13), but are not limited thereto and may also be derivatives thereof within the scope of providing the same constituent unit. Examples of such derivatives may include diisocyanates corresponding to the compound represented by general formula (b11), the compound represented by general formula (b12), and the compound represented by general formula (b13). As for the compound that provides the constituent unit (B1), at least one compound (i.e., a diamine) selected from the group consisting of the compound represented by general formula (b11), the compound represented by general formula (b12), and the compound represented by general formula (b13) is preferred.

[0125] The diamine component may include a compound that provides two or more of the constituent units (B11) to (B13), but it is preferable to include a compound that provides one of the constituent units (B11) to (B13). That is, it is preferable that constituent unit B includes a compound that provides constituent unit (B11), a compound that provides constituent unit (B12), or a compound that provides constituent unit (B13).

[0126] Examples of compounds that impart the constituent unit (B2) include compounds represented by general formula (b21) and compounds represented by general formula (b22), but are not limited thereto and may also be derivatives thereof within the scope of imparting the same constituent unit. Examples of such derivatives include diisocyanates corresponding to compounds represented by general formula (b21) and compounds represented by general formula (b22). As for the compound imparting the constituent unit (B2), at least one compound (i.e., a diamine) selected from the group consisting of compounds represented by general formula (b21) and compounds represented by general formula (b22) is preferred.

[0127] As for the compound providing the constituent unit (B2), it is preferable to include a compound represented by the general formula (b21), more preferable to include at least one compound selected from the group consisting of a compound represented by formula (b211), a compound represented by formula (b212), and a compound represented by formula (b213), even more preferable to include at least one compound selected from the group consisting of a compound represented by formula (b211) and a compound represented by formula (b212), and particularly preferable to include a compound represented by formula (b211).

[0128] The compound providing the constituent unit (B1) and the compound providing the constituent unit (B2) among the constituent unit B are included in total, preferably at least 70 mol%, more preferably at least 80 mol%, even more preferably at least 90 mol%, and even more preferably at least 95 mol%. The upper limit of the total content of the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2) is not particularly limited, but is preferably 100 mol%. It is even more preferable that the diamine component consists only of the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2).

[0129] The molar ratio [(B1) / (B2)] of the content of the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2) is preferably 45 / 55 to 75 / 25 in terms of improving transparency, optical isotropy and ductility, and in terms of transparency, optical isotropy and colorlessness, it is preferably 45 / 55 to 70 / 30, more preferably 45 / 55 to 65 / 35, even more preferably 45 / 55 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. In addition, in terms of improving ductility, it is preferably 45 / 55 to 75 / 25, more preferably 50 / 50 to 75 / 25, even more preferably 55 / 45 to 75 / 25, even more preferably 60 / 40 to 75 / 25, and even more preferably 65 / 35 to 75 / 25.

[0130] The diamine component may include compounds other than the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2), and examples of such compounds include the aromatic diamine, alicyclic diamine, and aliphatic diamine described above, and their derivatives (diisocyanates, etc.).

[0131] Compounds other than the compound that provides the constituent unit (B1) optionally included in the diamine component and the compound that provides the constituent unit (B2) may be one type or two or more types.

[0132] In the present invention, the ratio of the input amounts of the tetracarboxylic acid component and the diamine component used in the manufacture of the polyimide resin is preferably 0.9 to 1.1 moles of the diamine component per 1 mole of the tetracarboxylic acid component.

[0133] In addition, in the present invention, in addition to the aforementioned tetracarboxylic acid component and diamine component, a terminal encapsulant may be used in the manufacture of the polyimide resin. Monoamines or dicarboxylic acids are preferred as terminal encapsulants. The amount of terminal encapsulant introduced is preferably 0.0001 to 0.1 mole per 1 mole of tetracarboxylic acid component, and particularly preferably 0.001 to 0.06 mole. Examples of monoamine terminal encapsulants include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. Among these, benzylamine and aniline may be suitably used. As for dicarboxylic acid terminal encapsulating agents, dicarboxylic acids are preferred, and some of them may have closed rings. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are suggested. Among these, phthalic acid and phthalic anhydride can be used appropriately.

[0134] There are no particular restrictions on the method of reacting the aforementioned tetracarboxylic acid component and diamine component, and known methods may be used.

[0135] Specific reaction methods include: (1) a method of introducing a tetracarboxylic acid component, a diamine component, and a reaction solvent into a reactor, stirring at 0 to 80°C for 0.5 to 30 hours, and then raising the temperature to carry out an imidation reaction; (2) a method of introducing a diamine component and a reaction solvent into a reactor and dissolving them, then introducing a tetracarboxylic acid component, stirring at 0 to 80°C for 0.5 to 30 hours as needed, and then raising the temperature to carry out an imidation reaction; and (3) a method of introducing a tetracarboxylic acid component, a diamine component, and a reaction solvent into a reactor and immediately raising the temperature to carry out an imidation reaction.

[0136] The reaction solvent used in the manufacture of polyimide resins only needs to be capable of dissolving the resulting polyimide without inhibiting the imidization reaction. Examples include aprotic solvents, phenolic solvents, etheric solvents, carbonate solvents, etc.

[0137] Specific examples of aprotic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, tetramethylurea, lactone solvents such as γ-butyrolactone, γ-valerolactone, phosphorus-containing amide solvents such as hexamethylphosphoricamide, hexamethylphosphintriamide, sulfur-containing solvents such as dimethylsulfone, dimethyl sulfoxide, sulfolane, ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, methylcyclohexanone, amine solvents such as picoline, pyridine, and ester solvents such as acetic acid (2-methoxy-1-methylethyl).

[0138] Specific examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, etc.

[0139] Specific examples of ether-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, 1,4-dioxane, etc.

[0140] Specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, etc.

[0141] Among the above reaction solvents, amide-based solvents or lactone-based solvents are preferred. The above reaction solvents may be used alone or in a mixture of two or more types.

[0142] In the imidation reaction, it is preferable to carry out the reaction while removing water generated during manufacturing using a Dean Stark apparatus or the like. By performing such operations, the degree of polymerization and the imidation rate can be further increased.

[0143] In the above imidation reaction, a known imidation catalyst may be used. Examples of imidation catalysts include base catalysts or acid catalysts.

[0144] Examples of base catalysts include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-rutidine, 2,6-rutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline, and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0145] In addition, examples of acid catalysts include crotonic acid, acrylic acid, trans-3-hexanoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxycyanoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more types.

[0146] Among the above, from the perspective of handling, it is preferable to use a base catalyst, more preferable to use an organic base catalyst, more preferable to use one or more selected from triethylamine and triethylenediamine, and particularly preferable to use triethylamine or a combination of triethylamine and triethylenediamine.

[0147] The temperature of the imidation reaction is preferably 120 to 250°C, more preferably 160 to 200°C, in terms of the reaction rate and inhibition of gelation. In addition, the reaction time is preferably 0.5 to 10 hours after the start of the discharge of the generated water.

[0148] [Polyimide Resin Composition]

[0149] The polyimide resin composition of the present invention comprises the polyimide resin of the present invention and at least one selected from the group consisting of a fluorine-containing polymer and a silicon-containing polymer. By including at least one selected from the group consisting of a fluorine-containing polymer and a silicon-containing polymer, ductility can be significantly improved while maintaining high transparency and optical isotropy. Among the fluorine-containing polymer and the silicon-containing polymer, the fluorine-containing polymer is preferred.

[0150] Fluorine-containing polymers

[0151] In the polyimide resin composition of the present invention, the fluorine-containing polymer is preferably a polymer having a constituent unit derived from a monomer containing fluorine, and more preferably a polymer having a constituent unit derived from a monomer containing a fluorinated alkyl group.

[0152] In the present invention, the fluorine-containing polymer is preferably a fluorine-containing acrylic polymer.

[0153] The above fluorine-containing acrylic polymer preferably contains a constituent unit derived from an acrylic monomer containing fluorine, and more preferably contains a constituent unit derived from an acrylic monomer containing fluorine and a constituent unit derived from an acrylic monomer having a hydrophilic group.

[0154] As for the fluorine-containing acrylic monomer, a monomer having a perfluoroalkyl group is preferred.

[0155] Examples of acrylic monomers having hydrophilic groups include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylate, polyalkylene glycol (meth)acrylate, acrylamide, and methacrylamide.

[0156] Fluorine-containing acrylic polymers may contain acrylic monomers having hydrophobic groups. Examples of acrylic monomers having hydrophobic groups include alkyl (meth)acrylates, silicon-containing (meth)acrylates, aryl (meth)acrylates, etc.

[0157] Here, "(meth)acrylate" means "acrylate or methacrylate."

[0158] In fluorine-containing acrylic monomers, other monomers having vinyl groups may be copolymerized.

[0159] Commercially available fluorine-containing polymers include “LE-605”, “LE-607”, “LE-605DM”, and “LE-607DM” manufactured by Kyoeisha Chemical Co., Ltd.

[0160] Silicon-containing polymer

[0161] The silicon-containing polymer in the polyimide resin composition of the present invention may be a modified silicon in which a side chain of various organic modifiers or a terminal of various organic modifiers is introduced to the main chain of a silicon backbone, or a silicon-containing acrylic polymer in which a silicon side chain is introduced to the main chain of an acrylic polymer, and it is preferred to be a silicon-containing acrylic polymer.

[0162] Examples of modified silicones include polyether-modified silicones in which polyether groups are introduced to the side chains or ends, and polyester-modified silicones in which polyester groups are introduced, and polyether-modified silicones are preferred.

[0163] Examples of polyether groups of polyether-modified silicone include polyethylene glycol groups and polypropylene glycol groups, and polyethylene glycol groups are preferred.

[0164] Polydimethylsiloxane is preferred as the main chain of the silicon backbone of the modified silicone.

[0165] The above-mentioned silicone-containing acrylic polymer preferably contains a constituent unit derived from an acrylic monomer containing silicone, and more preferably contains a constituent unit derived from an acrylic monomer containing silicone and a constituent unit derived from an acrylic monomer having a hydrophilic group.

[0166] As for the silicone-containing acrylic monomer, a monomer having a polydimethylsiloxane group is preferred.

[0167] Examples of acrylic monomers having hydrophilic groups include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylate, polyalkylene glycol (meth)acrylate, acrylamide, and methacrylamide.

[0168] The silicone-containing acrylic polymer may contain an acrylic monomer having a hydrophobic group. Examples of acrylic monomers having a hydrophobic group include alkyl (meth)acrylates, silicone-containing (meth)acrylates, aryl (meth)acrylates, etc.

[0169] Here, "(meth)acrylate" means "acrylate or methacrylate."

[0170] In the acrylic monomer containing silicone, other monomers having vinyl groups may be copolymerized.

[0171] Commercially available silicon-containing polymers include "LE-302," "LE-304," and "KL-700" manufactured by Kyoeisha Chemical Co., Ltd., and "BYK-378" manufactured by Big Chem Japan Co., Ltd.

[0172] In the polyimide resin composition of the present invention, the total content of the fluorine-containing polymer and the silicon-containing polymer is preferably 0.01 to 2 parts by mass per 100 parts by mass of the polyimide resin, more preferably 0.1 to 1.5 parts by mass, even more preferably 0.2 to 1.2 parts by mass, and even more preferably 0.5 to 1.0 parts by mass. Meanwhile, the total content is the content of the fluorine-containing polymer when only the fluorine-containing polymer is included, and the content of the silicon-containing polymer when only the silicon-containing polymer is included.

[0173] [Polyimide Varnish]

[0174] The polyimide varnish of the present invention is formed by dissolving the polyimide resin of the present invention or the polyimide resin composition of the present invention in an organic solvent. That is, the polyimide varnish of the present invention comprises the polyimide resin of the present invention or the polyimide resin composition of the present invention and an organic solvent, wherein the polyimide resin or the polyimide resin composition is dissolved in the organic solvent.

[0175] The organic solvent may be one that dissolves the fluorine-containing polymer and the silicon-containing polymer included in the polyimide resin and the polyimide resin composition, and is not particularly limited, but it is preferable to use the compounds described above as a reaction solvent used in the manufacture of the polyimide resin, either alone or in a mixture of two or more.

[0176] The polyimide varnish of the present invention may be the polyimide solution itself in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or it may be a polyimide solution to which a diluent solvent is further added. Additionally, the fluorine-containing polymer, the silicon-containing polymer, or a mixture thereof may be dissolved in the polyimide solution in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, and furthermore, a diluent solvent may be added.

[0177] The polyimide varnish of the present invention may be formed by dissolving the polyimide resin of the present invention in a low-boiling point solvent with a boiling point of 130°C or lower. By using the said low-boiling point solvent as an organic solvent, the heating temperature when manufacturing the polyimide film described later can be lowered. Examples of said low-boiling point solvents include carbon tetrachloride, dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, acetone, etc., among which dichloromethane is preferred.

[0178] Since the polyimide resin of the present invention has solvent solubility, it can be made into a high-concentration varnish that is stable at room temperature. The polyimide varnish of the present invention preferably contains 5 to 40 mass% of the polyimide resin of the present invention, and more preferably contains 10 to 30 mass%. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, and more preferably 5 to 150 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer.

[0179] In addition, the polyimide varnish of the present invention may include various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoaming agents, fluorescent whitening agents, crosslinking agents, polymerization initiators, and photosensitive agents, to the extent that the required characteristics of the polyimide film are not impaired.

[0180] The method for manufacturing the polyimide varnish of the present invention is not particularly limited, and known methods may be applied.

[0181] [Polyimide Film]

[0182] The polyimide film of the present invention comprises the polyimide resin of the present invention or the polyimide resin composition of the present invention. Accordingly, the polyimide film of the present invention has excellent transparency and optical isotropy, and furthermore, excellent flexibility. The suitable physical properties of the polyimide film of the present invention are as described above.

[0183] There are no particular limitations on the method for manufacturing the polyimide film of the present invention, and known methods may be used. For example, methods may include applying the polyimide varnish of the present invention onto a smooth support such as a glass plate, metal plate, or plastic, or forming it into a film, and then removing organic solvents such as reaction solvents or diluents contained in the varnish by heating. If necessary, a release agent may be applied to the surface of the support in advance.

[0184] The following method is preferred for removing the organic solvent contained in the varnish by heating. Specifically, it is preferable to evaporate the organic solvent at a temperature of 120°C or lower to form a self-supporting film, peel the self-supporting film from the support, fix the end of the self-supporting film, and dry it at a temperature above the boiling point of the organic solvent used to produce a polyimide film. Additionally, it is preferable to dry under a nitrogen atmosphere. The pressure of the drying atmosphere may be reduced pressure, atmospheric pressure, or increased pressure. The heating temperature when drying the self-supporting film to produce the polyimide film is not particularly limited, but 200 to 400°C is preferred.

[0185] When the organic solvent included in the polyimide varnish of the present invention is a low-boiling point solvent with a boiling point of 130°C or lower, the heating temperature of the self-supporting film is preferably 100 to 180°C. Furthermore, it is preferable to perform an annealing treatment by heating the polyimide film obtained by removing the low-boiling point solvent at a temperature above the glass transition temperature.

[0186] In addition, the polyimide film of the present invention may also be manufactured using a polyamide acid varnish formed by dissolving a polyamide acid in an organic solvent.

[0187] The polyamide acid included in the above polyamide acid varnish is a product of a heavy addition reaction between a tetracarboxylic acid component comprising at least one selected from the group consisting of a compound providing the aforementioned constituent unit (A1) and a compound providing the aforementioned constituent unit (A2), and a diamine component comprising a compound providing the aforementioned constituent unit (B1) and a compound providing the aforementioned constituent unit (B2), as a precursor of the polyimide resin of the present invention. By imidizing (dehydrating and cloning) this polyamide acid, the polyimide resin of the present invention, which is the final product, is obtained.

[0188] As the organic solvent included in the above polyamide acid varnish, the organic solvent included in the polyimide varnish of the present invention may be used.

[0189] In the present invention, the polyamide acid varnish may be the polyamide acid solution itself obtained by adding a tetracarboxylic acid component comprising at least one selected from the group consisting of a compound providing the aforementioned constituent unit (A1) and a compound providing the aforementioned constituent unit (A2), and a diamine component comprising a compound providing the aforementioned constituent unit (B1) and a compound providing the aforementioned constituent unit (B2) in a reaction solvent, or it may be a polyamide acid solution to which a diluent solvent has been additionally added.

[0190] There are no particular limitations on the method for manufacturing a polyimide film using a polyamide acid varnish, and known methods may be used. For example, a polyamide acid varnish may be applied or formed into a film on a smooth support such as a glass plate, a metal plate, or plastic, and an organic solvent such as a reaction solvent or a diluent contained in the varnish may be removed by heating to obtain a polyamide acid film, and a polyimide film may be manufactured by imidizing the polyamide acid in the polyamide acid film by heating.

[0191] The heating temperature for obtaining a polyamide film by drying the polyamide varnish is preferably 50 to 120°C. The heating temperature for imidizing the polyamide by heating is preferably 200 to 400°C.

[0192] Meanwhile, the imidation method is not limited to thermal imidation, and chemical imidation may also be applied.

[0193] The thickness of the polyimide film of the present invention can be appropriately selected according to the application, etc., preferably in the range of 1 to 250 μm, more preferably in the range of 5 to 100 μm, and even more preferably in the range of 10 to 80 μm. Since the thickness is within the above range, practical use as a self-supporting film becomes possible.

[0194] The thickness of the polyimide film can be easily controlled by adjusting the solid content or viscosity of the polyimide varnish.

[0195] The polyimide film of the present invention is suitably used as a film for various components such as color filters, flexible displays, semiconductor components, and optical components. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays or OLED displays.

[0196] Examples

[0197] The present invention will be specifically explained below by way of examples. However, the present invention is not limited in any way by these examples.

[0198] The solid content concentration of the varnish and each physical property of the film obtained in the examples and comparative examples were measured by the method described below.

[0199] (1) Solid content concentration

[0200] The solid content of the varnish was measured by heating the sample at 280°C × 120 min in a small electric furnace “MMF-1” manufactured by As One Co., Ltd., and calculating it from the difference in mass of the sample before and after heating.

[0201] (2) Film thickness

[0202] The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

[0203] (3) Total light transmittance, haze (evaluation of transparency) and yellow index (YI)

[0204] Total light transmittance, haze, and YI were measured using the "COH7700" color and turbidity simultaneous meter manufactured by Nippon Color Industry Co., Ltd. The measurements of total light transmittance and YI were in accordance with JIS K7361-1:1997, and the measurement of haze was in accordance with JIS K7136:2000.

[0205] (4) Thickness phase difference (Rth) (Evaluation of optical isotropy)

[0206] The thickness phase difference (Rth) was measured using an ellipsometer “M-220” manufactured by Nippon Spectroscopic Corporation. The value of the thickness phase difference was measured at a measurement wavelength of 550 nm. Meanwhile, Rth is expressed by the following formula, where the maximum refractive index within the plane of the polyimide film is nx, the minimum is ny, the refractive index in the thickness direction is nz, and the thickness of the film is d.

[0207] Rth=[{(nx+ny) / 2}-nz]×d

[0208] (5) Elongation at the point of break (evaluation of ductility)

[0209] The fracture point elongation was determined by a tensile test (measurement of elongation) in accordance with JIS K 7127. Test specimens with a width of 10 mm and a thickness of 10 to 60 μm were used.

[0210] (6) Softness (Evaluation of softness)

[0211] The polyimide films obtained in the examples and comparative examples were prepared as test specimens with a width of 10 mm and a thickness of 10 to 60 μm, and ductility was evaluated by performing a tensile test (test speed 50 mm / min) in accordance with JIS K 7127. It is desirable for the film to be ductile in terms of preventing fracture during manufacturing or in the product. As a result of the above test, if plastic deformation occurred beyond the yield point, it was deemed to be ductile, and if the film fractured in the elastic region, it was deemed to be non-ductile.

[0212] (7) Appearance

[0213] The presence or absence of surface defects (non-uniformity and voids) of the polyimide films obtained in the examples and comparative examples was evaluated according to the following criteria.

[0214] A: No defects are visible on the film surface.

[0215] B: Slight defects are visible on the film surface (no issues with actual use).

[0216] C: Clear defects are visible on the film surface (problems with practical use).

[0217] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, and their abbreviations, etc., are as follows.

[0218] Tetracarboxylic acid component

[0219] HPMDA: 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (Mitsubishi Gas & Chemical Corporation; compound represented by formula (a1))

[0220] <Diamine component>

[0221] BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane (manufactured by Wakayama Seika Kogyo Co., Ltd., compound represented by formula (b11))

[0222] BisAM: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene (compound represented by formula (b211) manufactured by Mitsui Chemical Fine Co., Ltd.)

[0223] The details of the solvents and catalysts used in the examples and comparative examples are as follows.

[0224] γ-Butyrolactone (Mitsubishi Chemical Corporation)

[0225] N,N-Dimethylacetamide (manufactured by Mitsubishi Gas Chemical Co., Ltd.)

[0226] Triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0227] Triethylamine (manufactured by Kanto Chemical Co., Ltd.)

[0228] <Example 1>

[0229] As a reaction apparatus, a 0.3L five-mouthed glass round-bottom flask equipped with a stainless steel crescent-shaped stirring blade, a nitrogen inlet tube, a cooling tube, a thermometer, and a glass end cap was used, and in this round-bottom flask, 28.858g (0.070 mol) of BAPP, 10.373g (0.030 mol) of BisAM, 52.2g of γ-butyrolactone, and as catalysts, 0.056g of triethylenediamine and 5.060g of triethylamine were added, and the temperature was raised to 80℃ while stirring at 150 rpm under a nitrogen atmosphere to obtain a solution. To this solution, 22.439 g (0.100 mol) of HPMDA and 23.0 g of γ-butyrolactone were each added in batches, and then heated with a mantle heater to raise the temperature inside the reaction system to 190°C over approximately 20 minutes. The leached components were collected, and the temperature inside the reaction system was maintained at 190°C for 1 hour and 45 minutes. After adding 156.4 g of N,N-dimethylacetamide, the mixture was stirred at around 100°C for approximately 1 hour to obtain a uniform polyimide varnish (1) with a solid content concentration of 20 mass%.

[0230] Next, the obtained polyimide varnish (1) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C under an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0231] <Example 2>

[0232] Using the same reaction apparatus as in Example 1, 24.641 g (0.060 mol) of BAPP, 13.831 g (0.040 mol) of BisAM, 49.4 g of γ-butyrolactone, and 10.12 g of triethylamine as a catalyst were added to a round-bottom flask, and a solution was obtained by raising the temperature to 80°C while stirring at 150 rpm under a nitrogen atmosphere. To this solution, 22.439 g (0.100 mol) of HPMDA and 11.4 g of γ-butyrolactone were each added in batches, and then heated with a mantle heater to raise the temperature inside the reaction system to 190°C over approximately 20 minutes. The leached components were collected, and the temperature inside the reaction system was maintained at 190°C for 4.5 hours. After adding 168.1g of N,N-dimethylacetamide, the mixture was stirred at around 100°C for about 1 hour to obtain a uniform polyimide varnish (2) with a solid content of 20 mass%.

[0233] Next, the obtained polyimide varnish (2) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0234] <Example 3>

[0235] Using the same reaction apparatus as in Example 1, 20.534 g (0.050 mol) of BAPP, 17.289 g (0.050 mol) of BisAM, 49.1 g of γ-butyrolactone, and 10.13 g of triethylamine as a catalyst were added to a round-bottom flask, and a solution was obtained by raising the temperature to 80°C while stirring at 150 rpm under a nitrogen atmosphere. To this solution, 22.439 g (0.100 mol) of HPMDA and 11.1 g of γ-butyrolactone were each added in batches, and then heated with a mantle heater to raise the temperature inside the reaction system to 190°C over approximately 20 minutes. The leached components were collected, and the temperature inside the reaction system was maintained at 190°C for 7 hours. After adding 166.1g of N,N-dimethylacetamide, the mixture was stirred at around 100°C for about 1 hour to obtain a uniform polyimide varnish (3) with a solid content of 20 mass%.

[0236] Next, the obtained polyimide varnish (3) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0237] <Example 4>

[0238] Polyimide varnish (4) was obtained by adding a fluorine-containing polymer (LE-607DM, manufactured by Kyoei Chemical Co., Ltd., 30% dimethylacetamide solution) to the polyimide varnish (3) obtained in Example 3 in an amount of 0.1 parts by mass (converted to effective content) per 100 parts by mass of polyimide resin.

[0239] Next, the obtained polyimide varnish (4) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0240] <Example 5>

[0241] Polyimide varnish (5) was obtained by adding a fluorine-containing polymer (LE-607DM, manufactured by Kyoei Chemical Co., Ltd., 30% dimethylacetamide solution) to the polyimide varnish (3) obtained in Example 3 in an amount of 0.5 parts by mass (converted to effective content) per 100 parts by mass of polyimide resin.

[0242] Next, the obtained polyimide varnish (5) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0243] <Comparative Example 1>

[0244] Using the same reaction apparatus as in Example 1, 16.427 g (0.040 mol) of BAPP, 20.747 g (0.060 mol) of BisAM, 48.5 g of γ-butyrolactone, and 10.10 g of triethylamine as a catalyst were added to a round-bottom flask, and a solution was obtained by raising the temperature to 80°C while stirring at 150 rpm under a nitrogen atmosphere. To this solution, 22.439 g (0.100 mol) of HPMDA and 11.0 g of γ-butyrolactone were each added in batches, and then heated with a mantle heater to raise the temperature inside the reaction system to 190°C over approximately 20 minutes. The leached components were collected, and the temperature inside the reaction system was maintained at 190°C for 7.5 hours. After adding 164.2g of N,N-dimethylacetamide, the mixture was stirred at around 100°C for about 1 hour to obtain a uniform polyimide varnish (6) with a solid content of 20 mass%.

[0245] Next, the obtained polyimide varnish (6) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0246] <Comparative Example 2>

[0247] Polyimide varnish (7) was obtained by adding a fluorine-containing polymer (LE-607DM, manufactured by Kyoei Chemical Co., Ltd., 30% dimethylacetamide solution) to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 0.1 parts by mass (converted to effective content) per 100 parts by mass of polyimide resin.

[0248] Next, the obtained polyimide varnish (7) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0249] <Comparative Example 3>

[0250] Polyimide varnish (8) was obtained by adding a fluorine-containing polymer (LE-607DM, manufactured by Kyoei Chemical Co., Ltd., 30% dimethylacetamide solution) to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 0.5 parts by mass (converted to effective content) per 100 parts by mass of polyimide resin.

[0251] Next, the obtained polyimide varnish (8) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0252] <Comparative Example 4>

[0253] Polyimide varnish (9) was obtained by adding a fluorine-containing polymer (LE-607DM, manufactured by Kyoei Chemical Co., Ltd., 30% dimethylacetamide solution) to the polyimide varnish (6) obtained in Comparative Example 1 in an amount of 1.0 mass (converted to effective content) per 100 mass parts of polyimide resin.

[0254] Next, the obtained polyimide varnish (9) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 260°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0255] <Comparative Example 5>

[0256] Using the same reaction apparatus as in Example 1, 43.745 g (0.107 mol) of BAPP, 81.4 g of γ-butyrolactone, and 0.54 g of triethylamine as a catalyst were added to a round-bottom flask, and a solution was obtained by raising the temperature to 70°C while stirring at 150 rpm under a nitrogen atmosphere. To this solution, 23.887 g (0.107 mol) of HPMDA and 20.3 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were each added in batches, and then heated with a mantle heater to raise the temperature inside the reaction system to 190°C over approximately 20 minutes. The leached components were collected, and the temperature inside the reaction system was maintained at 190°C for 4.0 hours. After adding 154.2g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.), the mixture was stirred at around 100°C for about 1 hour to obtain a uniform polyimide varnish (10) with a solid content of 20 mass%.

[0257] Next, the obtained polyimide varnish (10) was applied onto a PET substrate and maintained at 100°C for 20 minutes to volatilize the solvent, thereby obtaining a transparent primary dried film with self-supporting properties. Furthermore, the film was fixed to a stainless steel frame and dried at 210°C in an air atmosphere for 20 minutes to remove the solvent, thereby obtaining a film. The evaluation results of this polyimide film are shown in Table 1.

[0258] [Table 1]

[0259]

[0260] As shown in Table 1, it can be seen that the polyimide film of the example has excellent transparency and optical isotropy, and also has excellent flexibility.

Claims

Claim 1 A polyimide resin having a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, wherein constituent unit A comprises a constituent unit (A1) derived from a compound represented by the following formula (a1), and constituent unit B comprises a constituent unit (B1) derived from a compound represented by the following formula (b11), and at least one constituent unit (B2) selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b211), a constituent unit derived from a compound represented by the following formula (b212), and a constituent unit derived from a compound represented by the following formula (b213), and the molar ratio [(B1) / (B2)] of constituent unit (B1) and constituent unit (B2) is 45 / 55 to 75 / 25. (In equation (b11), R 1 and R 2 Each represents, independently, a methyl group or a trifluoromethyl group. Claim 2 A polyimide resin according to claim 1, wherein the breaking point elongation measured in accordance with JIS K 7127 is 10% or more. Claim 3 delete Claim 4 A polyimide resin composition comprising at least one selected from the group consisting of the polyimide resin described in claim 1, and fluorine-containing polymers and silicone-containing polymers. Claim 5 A polyimide resin composition comprising at least one selected from the group consisting of a polyimide resin having a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, and a fluorine-containing polymer and a silicone-containing polymer, wherein constituent unit A comprises at least one constituent unit selected from the group consisting of a constituent unit (A1) derived from a compound represented by the following formula (a1) and a constituent unit (A2) derived from a compound represented by the following formula (a2), and constituent unit B comprises at least one constituent unit (B1) selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b11), a constituent unit derived from a compound represented by the following formula (b12), and a constituent unit derived from a compound represented by the following formula (b13), and at least one constituent unit (B2) selected from the group consisting of a constituent unit derived from a compound represented by the following general formula (b21) and a constituent unit derived from a compound represented by the following general formula (b22). A polyimide resin composition comprising, wherein the molar ratio [(B1) / (B2)] of the constituent unit (B1) and the constituent unit (B2) is 45 / 55 to 75 / 25, and the total content of the fluorine-containing polymer and the silicon-containing polymer is 0.01 to 2 parts by mass per 100 parts by mass of the polyimide resin. Claim 6 A polyimide resin composition comprising at least one selected from the group consisting of a polyimide resin having a constituent unit A derived from a tetracarboxylic acid dianhydride and a constituent unit B derived from a diamine, and a fluorine-containing polymer and a silicon-containing polymer, wherein constituent unit A comprises at least one constituent unit selected from the group consisting of a constituent unit (A1) derived from a compound represented by the following formula (a1) and a constituent unit (A2) derived from a compound represented by the following formula (a2), and constituent unit B comprises at least one constituent unit (B1) selected from the group consisting of a constituent unit derived from a compound represented by the following formula (b11), a constituent unit derived from a compound represented by the following formula (b12), and a constituent unit derived from a compound represented by the following formula (b13), and at least one constituent unit (B2) selected from the group consisting of a constituent unit derived from a compound represented by the following general formula (b21) and a constituent unit derived from a compound represented by the following general formula (b22). A polyimide resin composition comprising, wherein the molar ratio [(B1) / (B2)] of the constituent unit (B1) and the constituent unit (B2) is 45 / 55 to 75 / 25, and the fluorine-containing polymer is a fluorine-containing acrylic polymer. Claim 7 A polyimide varnish formed by dissolving the polyimide resin described in claim 1 or 2, or the polyimide resin composition described in any one of claims 4 to 6, in an organic solvent. Claim 8 A polyimide film comprising the polyimide resin described in claim 1 or 2, or the polyimide resin composition described in any one of claims 4 to 6.

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