TWI875901B - Polyimide resin, polyimide resin composition, polyimide varnish and polyimide film - Google Patents

Abstract

The invention provides a polyimide resin having a structural unit A derived from a tetracarboxylic acid dianhydride and a structural unit B derived from a diamine, wherein the structural unit A includes at least one structural unit selected from the group consisting of a structural unit (A1) derived from the compound represented by formula (a1) shown below and a structural unit (A2) derived from the compound represented by formula (a2) shown below, the structural unit B includes at least one structural unit (B1) selected from the group consisting of structural units derived from a compound represented by formula (b11) shown below, structural units derived from the compound represented by formula (b12) shown below and structural units derived from the compound represented by formula (b13) shown below, and at least one structural unit (B2) selected from the group consisting of structural units derived from a compound represented by formula (b21) shown below and structural units derived from a compound represented by formula (b22) shown below, and the molar ratio [(B1)/(B2]] between the structural unit (B1) and the structural unit (B2) is within a range from 45/55 to 75/25. The invention also provides a polyimide resin and a polyimide resin composition that exhibit excellent transparency and optical isotropy and are capable of forming a film having superior ductility, as well as a polyimide varnish and a polyimide film. (In the formulas, 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 of 1 to 5 carbon atoms, an alkylidene group of 2 to 5 carbon atoms, -S-, -SO-, -SO₂ -, -O- or -CO-.)

Description

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

The present invention relates to a polyimide resin, a polyimide resin composition, a polyimide varnish, and a polyimide film.

There are already discussions on various uses of polyimide resins in the fields of electrical and electronic components. For example, in order to make the device lighter and more flexible, it is hoped that the glass substrate used in image display devices such as liquid crystal displays or OLED displays will be replaced with a plastic substrate, and research is underway on polyimide films suitable as such plastic substrates. Polyimide films for such uses require transparency. In addition, in terms of the required properties of polyimide films, small phase difference due to birefringence and low phase delay (good optical isotropy) are required.

Patent document 1 discloses a polyimide resin obtained by using at least one of the amine groups of a diamine bonded to a diamine (e.g., meta-phenylenediamine) at the meta position relative to the main chain as a polyimide resin for providing a film with reduced birefringence. Patent document 2 discloses a polyimide resin containing tetracarboxylic acid residues and diamine residues of a specific structure, and tetracarboxylic acid residues and/or diamine residues having a bent portion as a polyimide resin for providing a film having excellent heat resistance, transmittance, low linear expansion coefficient, and low phase retardation. Specifically, the polyimide resin is obtained by using 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-bicyclohexanetetracarboxylic dianhydride, pyromellitic anhydride, 2,2'-bis(trifluoromethyl)benzidine, and 4,4'-diaminodiphenylsulfone. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 8-134211 [Patent Document 2] International Publication No. 2015/125895

[The problem that the invention wants to solve]

As described above, polyimide films require good optical properties such as transparency and optical isotropy. On the other hand, polyimide has a straight and strong molecular structure, so the breakage caused by shrinkage during film manufacturing and the breakage when used in products with movable parts (such as flexible displays) will become a problem. In order to suppress the breakage and improve the elongation, for example, if a highly flexible component is introduced into the molecule, the optical properties will generally decrease. Thus, a polyimide film with good optical properties and elongation is required. Therefore, the subject of the present invention is to provide a polyimide resin that can form a film with excellent transparency and optical isotropy and excellent elongation, and to provide a polyimide resin composition, a polyimide varnish, and a polyimide film. [Methods of solving the problem]

The inventors of the present invention have found that a polyimide resin comprising a combination of specific constituent units and a resin composition comprising the polyimide resin and a specific polymer can solve the above-mentioned problems and thus complete the present invention.

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

[Chemistry 1] In formula (b11), ^R1 and ^R2 each independently represent a methyl group or a trifluoromethyl group. In formulas (b21) and (b22), ^X1 to ^X4 each independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms, -S-, -SO-, _-SO2- , -O- or -CO-.

[2] The polyimide resin described in [1] above, wherein the elongation at break point measured in accordance with JIS K 7127 is 10% or more. [3] The polyimide resin described in [1] or [2] above, 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).

[Chemistry 2]

[4] A polyimide resin composition comprising: a polyimide resin as described in any one of [1] to [3] above, and at least one selected from the group consisting of a fluorine-containing polymer and a polysilicone-containing polymer. [5] The polyimide resin composition as described in [4] above, wherein the total content of the fluorine-containing polymer and the polysilicone-containing polymer is 0.01 to 2 parts by weight relative to 100 parts by weight of the polyimide resin. [6] The polyimide resin composition as described in [4] or [5] above, wherein the fluorine-containing polymer is a fluorine-containing acrylic polymer. [7] A polyimide varnish is prepared by dissolving a polyimide resin as described in any one of [1] to [3] above, or a polyimide resin composition as described in any one of [4] to [6] above in an organic solvent. [8] A polyimide film contains a polyimide resin as described in any one of [1] to [3] above, or a polyimide resin composition as described in any one of [4] to [6] above. [Effect of the Invention]

According to the present invention, a polyimide resin, a polyimide resin composition, a polyimide varnish and a polyimide film can be provided which can form a film having excellent transparency, optical isotropy and elongation.

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

[Chemistry 3] In formula (b11), ^R1 and ^R2 each independently represent a methyl group or a trifluoromethyl group. In formulas (b21) and (b22), ^X1 to ^X4 each independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms, -S-, -SO-, _-SO2- , -O- or -CO-.

<Constituent unit A> Constituent unit A is a constituent unit derived from tetracarboxylic dianhydride contained in the polyimide resin, wherein constituent unit A comprises at least one constituent unit selected from the group consisting of constituent units (A1) derived from a compound represented by the following formula (a1) and constituent units (A2) derived from a compound represented by the following formula (a2).

[Chemistry 4]

The compound represented by formula (a1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride. By including the constituent unit (A1), the transparency and optical isotropy of the film can be improved, and the heat resistance and thermal stability can be further improved. The compound represented by formula (a2) is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. By including the constituent unit (A2), the transparency of the film can be improved, and the solubility of the polyimide in the organic solvent can be improved.

The constituent unit A may include both the constituent unit (A1) and the constituent unit (A2), but preferably includes either the constituent unit (A1) or the constituent unit (A2), and more preferably includes the constituent unit (A1).

When the constituent unit A includes the constituent unit (A1) and the constituent unit (A2), the total ratio of the constituent units (A1) and (A2) in the 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 total ratio of the constituent units (A1) and (A2) is not particularly limited, that is, 100 mol%.

When the constituent unit A includes the constituent unit (A1), the ratio of the constituent unit (A1) in the constituent unit A is preferably 45 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the ratio is not particularly limited, that is, 100 mol%. Similarly, the ratio of the constituent unit (A1) in the constituent unit A is preferably 45~100 mol%, preferably 70~100 mol%, more preferably 90~100 mol%, and particularly preferably 99~100 mol%. When the constituent unit A includes the constituent unit (A2), the ratio of the constituent unit (A2) in the constituent unit A is preferably 45 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the ratio is not particularly limited, that is, 100 mol%. Similarly, the ratio of the constituent unit (A2) in the constituent unit A is preferably 45-100 mol%, more preferably 70-100 mol%, more preferably 90-100 mol%, and particularly preferably 99-100 mol%.

The constituent unit A may further include a constituent unit (A3) derived from a compound represented by the following formula (a3).

[Chemistry 5]

The compound represented by formula (a3) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride. The constituent unit A includes the constituent unit (A3), which improves the transparency of the film.

When constituent unit A includes constituent unit (A3), the ratio of constituent unit (A3) in constituent unit A is preferably 55 mol% or less, and more preferably 30 mol% or less. Moreover, it is preferably 5 mol% or more. When constituent unit A includes constituent unit (A3), constituent unit A preferably includes constituent unit (A1) and constituent unit (A3), and more preferably is composed of constituent unit (A1) and constituent unit (A3).

The constituent unit A may also contain constituent units other than the constituent units (A1) to (A3) within the scope that does not impair the effect of the present invention. The tetracarboxylic dianhydride providing such a constituent unit is not particularly limited, and examples thereof include: aromatic tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonate tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, and the like. Aromatic tetracarboxylic dianhydrides (but excluding compounds represented by formula (a2)); alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, dicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride (but excluding compounds represented by formula (a1) and compounds represented by formula (a3)); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. In addition, in this specification, aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more alicyclic rings and no aromatic ring, and aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring. Constituent units other than constituent units (A1) to (A3) that constituent unit A may arbitrarily contain may be one type or two or more types. Constituent unit A preferably does not contain constituent units other than the aforementioned constituent units (A1) to (A3).

<Constituent unit B> Constituent unit B is a constituent unit derived from diamine in the polyimide resin, wherein the constituent unit B comprises a constituent unit (B1) and a constituent unit (B2), wherein the constituent unit (B1) is selected from 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 derived from a compound represented by the following formula (b13) The constituent unit (B2) is selected from at least one of the group consisting of a constituent unit (B21) of a compound represented by the following general formula (b21) and a constituent unit (B22) of a compound represented by the following general formula (b22), and the molar ratio [(B1)/(B2)] of the constituent unit (B1) to the constituent unit (B2) is 45/55 to 75/25.

[Chemistry 6]

In formula (b11), ^R1 and ^R2 each independently represent a methyl group or a trifluoromethyl group. In formulas (b21) and (b22), ^X1 to ^X4 each independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms, -S-, -SO-, _-SO2- , -O- or -CO-.

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

[Chemistry 7]

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

Constituent unit B includes at least one constituent unit selected from the group consisting of constituent units (B11) to (B13). Among them, from the viewpoint of improving the elongation of the film, it is more preferable that constituent unit B includes at least one constituent unit selected from the group consisting of constituent units (B11) and constituent units (B12), and it is even more preferable that constituent unit B includes constituent unit (B11). Constituent unit B may also include two or more constituent units (B11) to (B13), preferably including one constituent unit (B11) to (B13). That is, constituent unit B preferably includes constituent unit (B11), constituent unit (B12), or constituent unit (B13).

By including the constituent unit (B1), the transparency and optical isotropy of the film can be maintained, and the stretchability can be improved. In addition, the colorlessness can be improved. The constituent unit (B1) can be one type or two or more types. The constituent unit (B1) is preferably a constituent unit derived from 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

(Constituent unit (B2)) Constituent unit (B2) is at least one constituent unit selected from the group consisting of constituent units (B21) derived from compounds represented by the following general formula (b21) and constituent units (B22) derived from compounds represented by the following general formula (b22).

[Chemistry 8]

In formulae (b21) and (b22), X ¹ to X ⁴ independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms, -S-, -SO-, -SO ₂ -, -O- or -CO-.

The compound represented by general formula (b21) has a skeleton in which three benzene rings are linked by ^X1 and ^X2 , and ^X1 and ^X2 are bonded to the 1,3 positions of the central benzene ring. The compound represented by general formula (b22) has a skeleton in which three benzene rings are linked by ^X3 and ^X4 , and ^X3 and ^X4 are bonded to the 1,2 positions of the central benzene ring. By having such a structure, a thin film having excellent stretchability, transparency and optical isotropy can be formed.

In general formula (b21) and (b22), X ¹ to X ⁴ are preferably independently an alkylene group having 3 to 5 carbon atoms, -SO ₂ -, or -O-, preferably an alkylene group having 3 to 5 carbon atoms or -O-, more preferably an isopropylene group or -O-, and even more preferably an isopropylene group. X ¹ and X ² in general formula (b21) may have different groups, but are preferably the same group. Similarly, X ³ and X ⁴ in formula (b22) may have different groups, but are preferably the same group. The amino groups in the general formulae (b21) and (b22) are preferably bonded to the para or meta position of the benzene ring relative to any of X ¹ to X ⁴ bonded to the benzene ring to which each amino group is bonded, and are more preferably bonded to the para position of the benzene ring. The alkylene groups having 2 to 5 carbon atoms represented by X ¹ to X ⁴ in the general formulae (b21) and (b22) include ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, isopentylene, etc. The alkylene group is preferably an alkylene group having 3 to 5 carbon atoms, and is more preferably an isopropylene group.

The constituent unit (B2) preferably includes a constituent unit derived from a compound represented by the above-mentioned 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 general formula (b211), a constituent unit derived from a compound represented by the following general formula (b212), and a constituent unit derived from a compound represented by the following general formula (b213).

[Chemistry 9]

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

Among the compounds represented by formula (b211) to formula (b213), it is 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 it is more preferably the compound represented by formula (b211).

(Other constituent units that constituent unit B may also contain) Constituent unit B may also contain constituent units other than constituent units (B1) and (B2). The diamines that provide such constituent units are not particularly limited, and examples thereof include: 1,4-phenylenediamine, p-phenylenediamine, 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- Aromatic diamines such as 5-amine, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, 1,4-bis(4-aminophenoxy)benzene (but excluding compounds represented by formula (b11) to (b13) and compounds represented by formula (b21) to (b22)); alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine. In addition, in this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings and no aromatic ring, and aliphatic diamine means a diamine containing neither an aromatic ring nor an alicyclic ring. Constituent units other than constituent units (B1) and (B2) that may be arbitrarily included in constituent unit B may be one type or two or more types.

(Structure of component unit B) Component unit B includes component unit (B1) and component unit (B2), and the molar ratio of component unit (B1) to component unit (B2) is 45/55~75/25. The ideal structure is described below.

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

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

(Physical properties of polyimide resin, etc.) The number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 100,000 from the viewpoint of the mechanical strength of the obtained polyimide film. In addition, the number average molecular weight of the polyimide resin can be obtained, for example, by using the standard polymethyl methacrylate (PMMA) conversion value obtained by gel filtration analysis.

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

By using the polyimide resin of the present invention, a film having excellent transparency, optical isotropy and extensibility can be formed, and the ideal physical property values of the film are as follows. When a film having a thickness of 30 μm is made, the total light transmittance is preferably 85% or more, preferably 87% or more, more preferably 88% or more, and more preferably 89% or more. When a film having a thickness of 30 μm is made, the yellowness index (YI) is preferably 6.5 or less, preferably 4.0 or less, more preferably 3.0 or less, more preferably 2.0 or less, and more preferably 1.5 or less. When a film having a thickness of 30 μm is made, the haze is preferably 1.0% or less, preferably 0.5% or less, and more preferably 0.1% or less. When a film having a thickness of 30 μm is made, the thickness phase difference (Rth) is preferably 40 nm or less, preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. In addition, the polyimide resin of the present invention preferably has a breaking point elongation of 10% or more, preferably 18% or more, more preferably 20% or more, and even more preferably 30% or more, as measured in accordance with JIS K 7127. In addition, the above-mentioned physical property values in the present invention can be specifically measured by the method described in the embodiment.

[Production method of polyimide resin] The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component comprising at least one selected from the group consisting of a compound providing the above-mentioned constituent unit (A1) and a compound providing the above-mentioned constituent unit (A2) with a diamine component comprising a compound providing the above-mentioned constituent unit (B1) and a compound providing the above-mentioned constituent unit (B2).

The compound providing the constituent unit (A1) may include compounds represented by formula (a1), but is not limited thereto, and may also be derivatives thereof within the scope of providing the same constituent unit. The derivative may include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a1) and alkyl esters of the tetracarboxylic acids. The compound providing the constituent unit (A1) is preferably a compound represented by formula (a1) (i.e., dianhydride). Similarly, the compound providing the constituent unit (A2) may include compounds represented by formula (a2), but is not limited thereto, and may also be derivatives thereof within the scope of providing the same constituent unit. The derivative may include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a2) and alkyl esters of the tetracarboxylic acids. The compound providing the constituent unit (A2) is preferably a compound represented by formula (a2) (i.e., dianhydride).

Among the tetracarboxylic acid components, the total content of the compound providing the constituent unit (A1) and the compound providing the constituent unit (A2) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound providing the constituent unit (A1) and the compound providing the constituent unit (A2) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may also be composed only of the compound providing the constituent unit (A1) and the compound providing the constituent unit (A2).

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 a constituent unit (A1) or the compound that provides a constituent unit (A2) preferably contains 45 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more. The upper limit of the content of the compound that provides a constituent unit (A1) or the compound that provides a constituent unit (A2) is not limited, that is, 100 mol%. The tetracarboxylic acid component may also be composed only of a compound that provides a constituent unit (A1) or a compound that provides a constituent unit (A2), preferably only of a compound that provides a constituent unit (A1).

The tetracarboxylic acid component may also include a compound that provides the above-mentioned constituent unit (A3) within the scope that does not impair the optical isotropy and elongation. The compound that provides the constituent unit (A3) may be a compound represented by formula (a3), but is not limited thereto. It may also be a derivative thereof within the scope that can provide the same constituent unit. The derivative may be a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by formula (a3) and an alkyl ester of the tetracarboxylic acid. The compound that provides the constituent unit (A3) is preferably a compound represented by formula (a3) (i.e., dianhydride).

When the tetracarboxylic acid component includes a compound providing a constituent unit (A3), the compound providing a constituent unit (A3) preferably includes 55 mol% or less, more preferably includes 30 mol% or less. In addition, it is preferably included at least 5 mol%. When the tetracarboxylic acid component includes a compound providing a constituent unit (A3), it is preferably composed only of a compound providing a constituent unit (A1) and a compound providing a constituent unit (A3).

The tetracarboxylic acid component may also contain compounds other than the compounds providing the constituent units (A1), the compounds providing the constituent units (A2), and the compounds providing the constituent units (A3), and the compounds may include the above-mentioned aromatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, aliphatic tetracarboxylic dianhydrides, and their derivatives (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.). The tetracarboxylic acid component may contain one or more compounds other than the compounds providing the constituent units (A1) to (A3).

The compound providing the constituent unit (B1) can be exemplified as follows: the compound providing the constituent unit (B11), i.e., the compound represented by the general formula (b11), the compound providing the constituent unit (B12), i.e., the compound represented by the general formula (b12), and the compound providing the constituent unit (B13), i.e., the compound represented by the general formula (b13), but the present invention is not limited thereto and may be a derivative thereof within the scope of providing the same constituent unit. The derivative can be exemplified as a diisocyanate corresponding to the compound represented by the general formula (b11), the compound represented by the general formula (b12), and the compound represented by the general formula (b13). The compound providing the constituent unit (B1) is preferably at least one compound (i.e., a diamine) selected from the group consisting of the compound represented by the general formula (b11), the compound represented by the general formula (b12), and the compound represented by the general formula (b13).

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

The compound providing the constituent unit (B2) may include compounds represented by the general formula (b21) and compounds represented by the general formula (b22), but the present invention is not limited thereto and may be derivatives thereof within the scope of providing the same constituent unit. The derivative may include diisocyanates corresponding to the compounds represented by the general formula (b21) and compounds represented by the general formula (b22). The compound providing the constituent unit (B2) is preferably at least one compound (i.e., diamine) selected from the group consisting of compounds represented by the general formula (b21) and compounds represented by the general formula (b22).

The compound providing the constituent unit (B2) preferably includes a compound represented by the general formula (b21), and more preferably includes at least one compound selected from the group consisting of a compound represented by the formula (b211), a compound represented by the formula (b212), and a compound represented by the formula (b213). It is even more preferably includes at least one compound selected from the group consisting of a compound represented by the formula (b211) and a compound represented by the formula (b212). The compound represented by the formula (b211) is particularly preferred.

The total content of the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2) in the constituent unit B is preferably 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. 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, and is preferably 100 mol%. It is even more preferred that the diamine component is composed only of the compound providing the constituent unit (B1) and the compound providing the constituent unit (B2).

The molar ratio [(B1)/(B2)] of the compound providing the constituent unit (B1) to the compound providing the constituent unit (B2) is preferably 45/55-75/25 from the viewpoint of improving transparency, optical isotropy and elongation, and is preferably 45/55-70/30 from the viewpoint of transparency, optical isotropy and colorlessness, more preferably 45/55-65/35, more preferably 45/55-60/40, and even more preferably 45/55-55/45. Furthermore, from the viewpoint of improving the elongation, it is preferably 45/55-75/25, more preferably 50/50-75/25, more preferably 55/45-75/25, more preferably 60/40-75/25, and even more preferably 65/35-75/25.

The diamine component may also contain compounds other than the compounds providing the constituent unit (B1) and the compounds providing the constituent unit (B2), and the compounds may include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, and their derivatives (diisocyanates, etc.). The compounds other than the compounds providing the constituent unit (B1) and the compounds providing the constituent unit (B2) that the diamine component may optionally contain may be one or more.

In the present invention, the feed ratio of the tetracarboxylic acid component to the diamine component used in the production of the polyimide resin is preferably 0.9 to 1.1 mol of the diamine component relative to 1 mol of the tetracarboxylic acid component.

Furthermore, in the present invention, in addition to using the aforementioned tetracarboxylic acid component and diamine component, an end-capping agent may also be used when manufacturing the polyimide resin. The end-capping agent is preferably a monoamine or a dicarboxylic acid. The feed amount of the introduced end-capping agent is preferably 0.0001 to 0.1 mole, and is particularly preferably 0.001 to 0.06 mole relative to 1 mole of the tetracarboxylic acid component. Monoamine end-capping agents are recommended, for example: methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. Among them, benzylamine and aniline can be used ideally. The dicarboxylic acid end-capping agent is preferably a dicarboxylic acid, and a part of it can also be ring-closed. 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. Among them, phthalic acid and phthalic anhydride are preferably used.

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

The reaction solvent used in the production of the polyimide resin may be any solvent that can dissolve the generated polyimide without hindering the imidization reaction. Examples of such solvents include aprotic solvents, phenolic solvents, etheric solvents, and carbonate solvents.

Specific examples of aprotic solvents include: amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactone, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphatamide and hexamethylphosphotriamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and cyclobutane sulfone; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl cyclohexanone; amine solvents such as picolinyl and pyridine; ester solvents such as acetic acid (2-methoxy-1-methylethyl ester), and the like.

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. Specific examples of etheric 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. Specific examples of carbonate-based solvents include diethyl carbonate, ethyl methyl carbonate, ethyl carbonate, propyl carbonate, etc. Among the above reaction solvents, amide solvents or lactone solvents are preferred. The above reaction solvents may be used alone or in combination of two or more.

The imidization reaction is preferably carried out using a Dean-Stark apparatus or the like, while removing water generated during the production. By carrying out such an operation, the degree of polymerization and the imidization rate can be further increased.

In the above-mentioned imidization reaction, a known imidization catalyst can be used. The imidization catalyst can be a base catalyst or an acid catalyst. The base catalyst can be: pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-dipicoline, 2,6-dipicoline, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline and other organic base catalysts; potassium hydroxide, or sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate and other inorganic base catalysts. In addition, the acid catalyst can be exemplified by: crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, etc. The above-mentioned imidization catalyst can be used alone or in combination of two or more. Among the above, considering the operability, it is preferable to use an alkaline catalyst, and it is more preferable to use an organic alkaline catalyst, and it is even more preferable to use one or more selected from triethylamine and triethylenediamine, and it is particularly preferable to use triethylamine or a combination of triethylamine and triethylenediamine.

The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoint of reaction rate and inhibition of gelation. The reaction time is preferably 0.5 to 10 hours after the distillation of generated water begins.

[Polyimide resin composition] The polyimide resin composition of the present invention contains: the polyimide resin of the present invention and at least one selected from the group consisting of fluorine-containing polymers and polysilicone-containing polymers. By containing at least one selected from the group consisting of fluorine-containing polymers and polysilicone-containing polymers, high transparency and optical isotropy can be maintained, and at the same time, the elongation can be significantly improved. Among the fluorine-containing polymers and polysilicone-containing polymers, the fluorine-containing polymer is preferably used.

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

The fluorine-containing acrylic polymer preferably includes constituent units derived from a fluorine-containing acrylic monomer, and more preferably includes constituent units derived from a fluorine-containing acrylic monomer and constituent units derived from an acrylic monomer having a hydrophilic group.

The fluorine-containing acrylic monomer is preferably a monomer having a perfluoroalkyl group. Examples of acrylic monomers having a hydrophilic group include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylate, polyalkylene glycol (meth)acrylate, acrylamide, methacrylamide, etc. The fluorine-containing acrylic polymer may also include an acrylic monomer having a hydrophobic group. Examples of acrylic monomers having a hydrophobic group include alkyl (meth)acrylate, (meth)acrylate containing polysilicone, aryl (meth)acrylate, etc. Here, "(meth)acrylate" means "acrylate or methacrylate". Other monomers having a vinyl group may also be copolymerized in the fluorine-containing acrylic monomer.

Commercially available products of fluorine-containing polymers include "LE-605", "LE-607", "LE-605DM", "LE-607DM" and the like manufactured by Kyoeisha Chemical Co., Ltd.

<Polysilicone-containing polymer> The polysilicone-containing polymer in the polyimide resin composition of the present invention can be exemplified as: modified polysilicone formed by introducing various side chains of organic modification groups or various ends of organic modification groups into the main chain of the polysilicone skeleton, and polysilicone-containing acrylic polymer formed by introducing polysilicone side chains into the main chain of acrylic polymer, preferably polysilicone-containing acrylic polymer.

Modified polysilicone includes polyether-modified polysilicone with polyether group introduced into the side chain or the end, polyester-modified polysilicone with polyester group introduced, etc., preferably polyether-modified polysilicone. The polyether group of polyether-modified polysilicone includes polyethylene glycol group and polypropylene glycol group, preferably polyethylene glycol group. The main chain of the polysilicone skeleton of the modified polysilicone is preferably polydimethylsiloxane.

The aforementioned silicone-containing acrylic polymer preferably includes constituent units derived from silicone-containing acrylic monomers, and more preferably includes constituent units derived from silicone-containing acrylic monomers and constituent units derived from acrylic monomers having a hydrophilic group.

The acrylic monomer containing polysilicone is preferably a monomer having a polydimethylsiloxyalkyl group. Examples of acrylic monomers having a hydrophilic group include acrylic acid, methacrylic acid, hydroxyalkyl (meth)acrylate, polyalkylene glycol (meth)acrylate, acrylamide, methacrylamide, etc. The acrylic polymer containing polysilicone may also include an acrylic monomer having a hydrophobic group. Examples of acrylic monomers having a hydrophobic group include alkyl (meth)acrylate, (meth)acrylate containing polysilicone, aryl (meth)acrylate, etc. Here, "(meth)acrylate" means "acrylate or methacrylate". Other monomers having a vinyl group may also be copolymerized in the acrylic monomer containing polysilicone.

Commercially available products of silicone-containing polymers include "LE-302", "LE-304", "KL-700" manufactured by Kyoei Chemical Co., Ltd., and "BYK-378" manufactured by BYK Co., Ltd.

In the polyimide resin composition of the present invention, the total content of the fluorine-containing polymer and the polysilicone-containing polymer is preferably 0.01 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, more preferably 0.2 to 1.2 parts by mass, and even more preferably 0.5 to 1.0 parts by mass, relative to 100 parts by mass of the polyimide resin. In addition, the above-mentioned total content is the content of the fluorine-containing polymer when only the fluorine-containing polymer is contained, and is the content of the polysilicone-containing polymer when only the polysilicone-containing polymer is contained.

[Polyimide varnish] The polyimide varnish of the present invention is prepared by dissolving the polyimide resin of the present invention or the polyimide resin composition of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention or the polyimide resin composition of the present invention and an organic solvent, and the polyimide resin or the polyimide resin composition is dissolved in the organic solvent. The organic solvent is not particularly limited as long as it can dissolve the polyimide resin and the fluorine-containing polymer and polysilicone-containing polymer contained in the polyimide resin composition. It is preferable to use the above-mentioned reaction solvent compounds used for the production of the polyimide resin alone or in combination of two or more. The polyimide varnish of the present invention may be a polyimide solution itself obtained by dissolving a polyimide resin obtained by a polymerization method in a reaction solvent, or may be obtained by adding a diluting solvent to the polyimide solution. Furthermore, it may be a polyimide solution obtained by dissolving a polyimide resin obtained by a polymerization method in a reaction solvent, and dissolving the aforementioned fluorine-containing polymer, the aforementioned polysilicone-containing polymer, or a mixture thereof, or it may be a solution obtained by adding a diluting solvent. The polyimide varnish of the present invention may also be a solution obtained by dissolving the polyimide resin of the present invention in a low-boiling-point solvent having a boiling point of 130°C or less. By using the low-boiling-point solvent as an organic solvent, the heating temperature during the production of the polyimide film described later can be reduced. Examples of the low-boiling-point solvent include carbon tetrachloride, dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, acetone, etc., among which dichloromethane is preferred.

The polyimide resin of the present invention has solvent solubility, so 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% by mass of the polyimide resin of the present invention, and preferably contains 10 to 30% by mass. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, and preferably 5 to 150 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer. Furthermore, the polyimide varnish of the present invention may also contain various additives such as inorganic fillers, adhesion promoters, stripping agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, defoaming agents, fluorescent whitening agents, crosslinking agents, polymerization initiators, and photosensitizers within the range that the required properties of the polyimide film are not impaired. The method for preparing the polyimide varnish of the present invention is not particularly limited, and a known method can be used.

[Polyimide film] The polyimide film of the present invention contains the polyimide resin of the present invention or the polyimide resin composition of the present invention. Therefore, the polyimide film of the present invention has excellent transparency and optical isotropy, and also excellent elongation. The ideal physical property values of the polyimide film of the present invention are as described above. The method for manufacturing the polyimide film of the present invention is not particularly limited, and a known method can be used. For example, the polyimide varnish of the present invention is coated on a smooth support such as a glass plate, a metal plate, or a plastic, or after forming it into a film, the organic solvent such as a reaction solvent and a dilution solvent contained in the varnish is removed by heating. The surface of the aforementioned support may also be coated with a release agent in advance as needed. As for the method of removing the organic solvent contained in the varnish by heating, the following method is preferred. That is, it is preferred to evaporate the organic solvent at a temperature below 120°C to make a self-supporting film, then peel the self-supporting film from the support, fix the end of the self-supporting film, and then dry it at a temperature above the boiling point of the organic solvent used to make a polyimide film. In addition, it is preferred to dry it in a nitrogen environment. The pressure of the drying environment can be any of reduced pressure, normal pressure, and pressurized. There is no particular restriction on the heating temperature when drying the self-supporting film to make a polyimide film, and it is preferably 200~400°C. When the organic solvent contained in the polyimide varnish of the present invention is a low-boiling point solvent having a boiling point of 130° C. or less, the heating temperature of the self-supporting film is preferably 100-180° C. In addition, the polyimide film obtained by removing the low-boiling point solvent is preferably subjected to an annealing treatment by further heating the polyimide film at a temperature above the glass transition temperature.

In addition, the polyimide film of the present invention can also be produced using a polyimide varnish obtained by dissolving polyimide in an organic solvent. The polyimide contained in the aforementioned polyimide varnish is a precursor of the polyimide resin of the present invention, and is a product of an addition polymerization reaction of at least one tetracarboxylic acid component selected from the group consisting of a compound providing the above-mentioned constituent unit (A1) and a compound providing the above-mentioned constituent unit (A2) and a diamine component including a compound providing the above-mentioned constituent unit (B1) and a compound providing the above-mentioned constituent unit (B2). By subjecting the polyimide to imidization (dehydration and ring closure), the final product, i.e., the polyimide resin of the present invention, can be obtained. The organic solvent contained in the aforementioned polyamide varnish may be the organic solvent contained in the polyimide varnish of the present invention. In the present invention, the polyamide varnish may be a polyamide solution itself obtained by subjecting a tetracarboxylic acid component comprising at least one selected from the group consisting of the compound providing the aforementioned constituent unit (A1) and the compound providing the aforementioned constituent unit (A2) and a diamine component comprising the compound providing the aforementioned constituent unit (B1) and the compound providing the aforementioned constituent unit (B2) to addition polymerization in a reaction solvent, or may be obtained by adding a diluting solvent to the polyamide solution.

The method of using polyamide varnish to produce polyimide film is not particularly limited, and a known method can be used. For example, polyamide varnish can be applied on a smooth support such as a glass plate, a metal plate, or a plastic, or formed into a film, and organic solvents such as a reaction solvent and a dilution solvent contained in the varnish can be removed by heating to obtain a polyamide film, and then the polyamide in the polyamide film can be imidized by heating to produce a polyimide film. The heating temperature when drying the polyamide varnish to obtain the polyamide film is preferably 50 to 120°C. The heating temperature when heating the polyamide to imidize the polyamide is preferably 200 to 400°C. In addition, the imidization method is not limited to thermal imidization, and chemical imidization may also be used.

The thickness of the polyimide film of the present invention can be appropriately selected according to the application, etc., preferably 1 to 250 μm, more preferably 5 to 100 μm, and even more preferably 10 to 80 μm. When the thickness is within the aforementioned range, it can be practically used as a self-supporting film. The thickness of the polyimide film can be easily controlled by adjusting the solid component concentration and viscosity of the polyimide varnish.

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

The present invention is described in detail below using examples. However, the present invention is not limited by these examples. The solid content concentration of the varnish obtained in the examples and comparative examples and the various physical properties of the film were measured using the method shown below.

(1) Solid content concentration The solid content concentration of the varnish was measured by heating the sample at 280℃×120min using a small electric furnace "MMF-1" manufactured by AS ONE Co., Ltd. and calculating the mass difference of the sample before and after heating. (2) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

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

(5) Elongation at break (evaluation of elongation) The elongation at break is measured by a tensile test (elongation measurement) in accordance with JIS K 7127. The test piece used is 10 mm wide and 10 to 60 μm thick. (6) Elongation (evaluation of elongation) The polyimide film obtained in the embodiment and the comparative example is made into a test piece with a width of 10 mm and a thickness of 10 to 60 μm, and a tensile test (test speed 50 mm/min) in accordance with JIS K 7127 is carried out, and the elongation is evaluated. From the perspective of suppressing the breakage during manufacturing or in the product, it is preferable to have elongation. The results of the above test are evaluated as having elongation if the film exceeds the yield point and undergoes plastic deformation, and as having no elongation if the film breaks in the elastic region. (7) Appearance The following criteria were used to evaluate whether the polyimide films obtained in the examples and comparative examples had surface defects (unevenness and voids). A: No defects were observed on the film surface. B: Slight defects were observed on the film surface (no problem in actual use). C: Clear defects were observed on the film surface (problem in actual use).

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

The details of the solvents and catalysts used in the examples and comparative examples are as follows. γ-Butyrolactone (Mitsubishi Chemical Co., Ltd.) N,N-dimethylacetamide (Mitsubishi Gas Chemical Co., Ltd.) Triethylenediamine (Tokyo Chemical Industry Co., Ltd.) Triethylamine (Kanto Chemical Co., Ltd.)

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

Then, the obtained polyimide varnish (1) was coated on a PET substrate and maintained at 100°C for 20 minutes to evaporate the solvent to obtain a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in air for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

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

Then, the obtained polyimide varnish (2) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

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

Then, the obtained polyimide varnish (3) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Example 4> Into the polyimide varnish (3) obtained in Example 3, 0.1 parts by mass (calculated as effective ingredient) of a fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to 100 parts by mass of the polyimide resin to obtain a polyimide varnish (4).

Then, the obtained polyimide varnish (4) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Example 5> Into the polyimide varnish (3) obtained in Example 3, 0.5 parts by mass (calculated as effective ingredient) of a fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to 100 parts by mass of the polyimide resin to obtain a polyimide varnish (5).

Then, the obtained polyimide varnish (5) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Comparative Example 1> Using the same reaction apparatus as Example 1, 16.427 g (0.040 mol) of BAPP, 20.747 g (0.060 mol) of BisAM, 48.5 g of γ-butyrolactone, and 10.10 g of triethylamine as a catalyst were placed in a round-bottom flask, and the temperature was raised to 80°C while stirring at 150 rpm in a nitrogen environment to obtain a solution. After adding 22.439 g (0.100 mol) of HPMDA and 11.0 g of γ-butyrolactone to the solution at once, the solution was heated using a heating pack to raise the temperature in the reaction system to 190°C in about 20 minutes. The distilled components were collected and the temperature in the reaction system was maintained at 190°C for 7.5 hours. After adding 164.2 g of N,N-dimethylacetamide, the mixture was stirred at about 100°C for about 1 hour to obtain a uniform polyimide varnish (6) having a solid content of 20 mass %.

Then, the obtained polyimide varnish (6) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Comparative Example 2> To the polyimide varnish (6) obtained in Comparative Example 1, 0.1 parts by mass (calculated as active ingredient) of a fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to 100 parts by mass of the polyimide resin to obtain a polyimide varnish (7).

Then, the obtained polyimide varnish (7) was coated on a PET substrate and maintained at 100°C for 20 minutes to allow the solvent to evaporate, thereby obtaining a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in an air environment for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Comparative Example 3> To the polyimide varnish (6) obtained in Comparative Example 1, 0.5 parts by mass (calculated as active ingredient) of a fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added to 100 parts by mass of the polyimide resin to obtain a polyimide varnish (8).

Then, the obtained polyimide varnish (8) was coated on a PET substrate and maintained at 100°C for 20 minutes to evaporate the solvent to obtain a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in air for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

<Comparative Example 4> To the polyimide varnish (6) obtained in Comparative Example 1, 1.0 mass part (calculated as active ingredient) of a fluorine-containing polymer (LE-607DM, manufactured by Kyoeisha Chemical Co., Ltd., 30% dimethylacetamide solution) was added relative to 100 mass parts of the polyimide resin to obtain a polyimide varnish (9).

Then, the obtained polyimide varnish (9) was coated on a PET substrate and maintained at 100°C for 20 minutes to evaporate the solvent to obtain a self-supporting transparent primary dried film. The film was then fixed on a stainless steel frame and dried at 260°C in air for 20 minutes to remove the solvent and obtain a film. The evaluation results of the polyimide film are shown in Table 1.

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

[Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Polyimide and polyimide composition Tetracarboxylic acid component (mol%) HPMDA (a1) 100 100 100 100 100 100 100 100 100 100 Diamine content (mol%) BAPP (b11) 70 60 50 50 50 40 40 40 40 100 BisAM (b211) 30 40 50 50 50 60 60 60 60 - Fluorinated polymers ^* LE-607DM - - - 0.1 0.5 - 0.1 0.5 1.0 - Film Evaluation Film thickness μm 51.7 25.3 30.0 30.7 27.7 35.3 30.3 21.3 30.0 33.0 Total light transmittance % 88.12 89.30 89.38 89.32 88.99 89.35 89.15 89.18 88.30 89.70 YI 6.22 1.46 1.36 1.70 2.10 1.50 2.60 2.26 3.57 1.69 Fog % 0.48 0.13 0.08 0.08 0.75 0.15 0.13 0.34 3.43 0.32 R nm 41.5 26.1 17.5 15.7 19.5 9.5 - - - 79.5 Elongation at breaking point % 37.8 29.8 10.5 27.1 43.8 6.7 6.4 6.4 6.8 76.1 Extensibility have have have have have without without without without have Appearance B B B A A C A A A B *) The amount of fluorinated polymer is relative to 100 parts by mass of polyimide (parts by mass)

As shown in Table 1, the polyimide film of the embodiment has excellent transparency and optical isotropy, and also excellent elongation.

Claims (8)

A polyimide resin comprises a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from a diamine; the 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); the constituent unit B comprises a constituent unit (B1) and a constituent unit (B2); the constituent unit (B1) is at least one constituent unit 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); The constituent unit (B2) is at least one selected from the group consisting of constituent units derived from a compound represented by the following general formula (b21) and constituent units derived from a compound represented by the following general formula (b22), and the molar ratio of the constituent unit (B1) to the constituent unit (B2) [(B1)/(B2)] is 45/55 to 75/25; In formula (b11), ^R1 and ^R2 each independently represent a methyl group or a trifluoromethyl group. In formulas (b21) and (b22), ^X1 to ^X4 each independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms, -S-, -SO-, _-SO2- , -O- or -CO-. The polyimide resin of claim 1, wherein the elongation at break measured in accordance with JIS K 7127 is 10% or more. The polyimide resin of claim 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); . A polyimide resin composition comprising: The polyimide resin of any one of claims 1 to 3, and At least one selected from the group consisting of a fluorine-containing polymer and a polysilicone-containing polymer. The polyimide resin composition of claim 4, wherein the total content of the fluorine-containing polymer and the polysilicone-containing polymer is 0.01-2 parts by weight relative to 100 parts by weight of the polyimide resin. The polyimide resin composition of claim 4 or 5, wherein the fluorine-containing polymer is a fluorine-containing acrylic polymer. A polyimide varnish is prepared by dissolving a polyimide resin as described in any one of claims 1 to 3 or a polyimide resin composition as described in any one of claims 4 to 6 in an organic solvent. A polyimide film comprises the polyimide resin of any one of claims 1 to 3 or the polyimide resin composition of any one of claims 4 to 6.