TWI868252B - Polyimide resin, polyimide varnish, and polyimide film - Google Patents

Abstract

A polyimide resin having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A includes a structural unit (A-1) derived from the compound represented by formula (a-1) shown below, and the structural unit B includes a structural unit (B-1) derived from the compound represented by formula (b-1) shown below and a structural unit (B-2) derived from the compound represented by formula (b-2) shown below.

Description

Polyimide resin, polyimide varnish and polyimide film

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

There are studies 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 and OLED displays will be replaced with a plastic substrate, and research on polyimide films suitable as the plastic substrate is underway. In image display devices, when the light emitted from the display element is emitted through the plastic substrate, the plastic substrate is required to be colorless and transparent. When the light passes through a phase difference film or a polarizing plate (such as a liquid crystal display, a touch panel, etc.), in addition to colorless and transparent properties, high optical isotropy (i.e., low Rth) is also required.

In order to satisfy such performance, the development of polyimide resins of various compositions is underway. For example, Patent Document 1 discloses a polyimide film, which is intended to obtain a polyimide film containing a polyimide having good solubility in a solvent and excellent processability, and which is colorless, transparent and has excellent toughness, and includes a structure composed of a combination of 3,3'-diaminodiphenylsulfone and other specific diamines as a diamine component. [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 2016/158825

[The problem that the invention wants to solve]

As mentioned above, polyimide films are required to have good optical properties such as colorless transparency and optical isotropy. Optical isotropy is particularly important for applications such as liquid crystal displays. On the other hand, since polyimide has a rigid and strong molecular structure, cracking becomes a problem when manufacturing films or using them in products with movable parts. If highly flexible components are introduced into the molecules or additives are added to the resin in order to suppress cracking, the optical properties will generally decrease. As such, polyimide films with good optical properties and ductility are required. In addition, chemical resistance is also important. For example, in order to form another resin layer (e.g., color filter, resist) on the polyimide film, when the varnish used to form the resin layer is applied to the polyimide film, the polyimide film is required to be resistant to the solvent contained in the varnish. If the solvent resistance of the polyimide film is insufficient, there is a risk that the film will dissolve and swell and lose its function as a substrate. However, as mentioned above, in order to ensure the optical properties, the polyimide film must be made in the form of a solution, and it is difficult to take these properties into consideration. Thus, there is a need for a polyimide resin that can maintain the optical properties of the obtained polyimide film, especially the optical isotropy, and can obtain a polyimide film having excellent flexibility and chemical resistance. The present invention is to provide a polyimide resin, polyimide varnish, and polyimide film that can form a film having excellent optical isotropy, and also excellent flexibility and chemical resistance. [Means for solving the problem]

The inventors of the present invention have found that a polyimide resin comprising a combination of a constituent unit derived from a specific tetracarboxylic dianhydride and a constituent unit derived from two specific diamines can solve the above-mentioned problems, and have completed 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, wherein the constituent unit A includes a constituent unit (A-1) derived from a compound represented by the following formula (a-1), and the constituent unit B includes a constituent unit (B-1) derived from a compound represented by the following formula (b-1), and a constituent unit (B-2) derived from a compound represented by the following formula (b-2).

[Chemistry 1]

<2> The polyimide resin as described in <1> above, wherein the ratio of the constituent unit (B-1) in the constituent unit B is 5 to 80 mol%, and the ratio of the constituent unit (B-2) in the constituent unit B is 20 to 95 mol%. <3> The polyimide resin as described in <1> or <2>, wherein the molar ratio [(B-1)/(B-2)] of the constituent unit (B-1) to the constituent unit (B-2) in the constituent unit B is 5/95 to 80/20. <4> A polyimide resin as described in any one of <1> to <3> above, wherein the constituent unit A further comprises at least one selected from the group consisting of a constituent unit (A-2-1) derived from a compound represented by the following formula (a-2-1) and a constituent unit (A-2-2) derived from a compound represented by the following formula (a-2-2).

[Chemistry 2]

<5> A polyimide resin as described in any one of <1> to <4> above, wherein the constituent unit B further comprises at least one selected from the group consisting of a constituent unit (B-3-1) derived from a compound represented by the following formula (b-3-1) and a constituent unit (B-3-2) derived from a compound represented by the following formula (b-3-2).

[Chemistry 3] (In formula (b-3-1), ^Z1 and ^Z2 each independently represent a divalent aliphatic group which may contain an oxygen atom, or a divalent aromatic group, ^R1 and ^R2 each independently represent a monovalent aromatic group or a monovalent aliphatic group, ^R3 and ^R4 each independently represent a monovalent aliphatic group, ^R5 and ^R6 each independently represent a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer greater than 1, and the sum of m and n is an integer of 2 to 1000. However, at least one of ^R1 and ^R2 represents a monovalent aromatic group.)

<6> The polyimide resin as described in <5> above, wherein ^R1 and ^R2 in the formula (b-3-1) are phenyl groups. <7> A polyimide varnish obtained by dissolving the polyimide resin as described in any one of <1> to <6> above in an organic solvent. <8> A polyimide film comprising the polyimide resin as described in any one of <1> to <6> above. [Effects of the Invention]

According to the present invention, a polyimide resin, a polyimide varnish and a polyimide film can be provided which can form a film having excellent optical isotropy, and also excellent flexibility and chemical resistance.

[Polyimide resin] The polyimide resin of the present invention has a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from a diamine, wherein the constituent unit A includes a constituent unit (A-1) derived from a compound represented by the following formula (a-1), and the constituent unit B includes a constituent unit (B-1) derived from a compound represented by the following formula (b-1), and a constituent unit (B-2) derived from a compound represented by the following formula (b-2).

[Chemistry 4]

The reason why the polyimide resin of the present invention can maintain optical isotropy and have excellent flexibility and chemical resistance is not certain, but it is considered that the polyimide resin of the present invention has an alicyclic structure, an ether skeleton and an aromatic group at an appropriate ratio, so it can maintain optical isotropy and have excellent flexibility and chemical resistance. Among them, since the structure contains a small diamine-containing diamine unit, the imide group concentration becomes high, and the optical isotropy can be maintained, and the chemical resistance is very excellent.

<Constituent unit A> Constituent unit A is a constituent unit derived from tetracarboxylic dianhydride contained in the polyimide resin. Constituent unit A includes a constituent unit (A-1) derived from a compound represented by the following formula (a-1).

[Chemistry 5]

The compound represented by formula (a-1) is 4,4'-oxydiphthalic anhydride. When constituent unit A includes constituent unit (A-1), the chemical resistance and toughness of the film can be improved.

The ratio of the constituent unit (A-1) in the constituent unit A is preferably 40 mol% or more, more preferably 50 mol% or more, more preferably 55 mol% or more, and more preferably 60 mol% or more. In view of the toughness of the film, it is more preferably 70 mol% or more. The upper limit of the ratio of the constituent unit (A-1) is not particularly limited, that is, 100 mol%. The constituent unit A may also be composed of only the constituent unit (A-1).

Constituent unit A may also include constituent units other than constituent unit (A-1). Considering the heat resistance, constituent unit A should preferably include, in addition to constituent unit (A-1), at least one constituent unit (A-2) selected from the group consisting of constituent unit (A-2-1) derived from a compound represented by the following formula (a-2-1) and constituent unit (A-2-2) derived from a compound represented by the following formula (a-2-2). That is, constituent unit (A-2-1) and constituent unit (A-2-2) are collectively referred to as constituent unit (A-2).

[Chemistry 6]

The compound represented by formula (a-2-1) is 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride. The compound represented by formula (a-2-2) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid dianhydride. From the viewpoint of improving heat resistance, chemical resistance and optical isotropy, the ratio of the constituent unit (A-2) in the constituent unit A is preferably 10 to 50 mol%, more preferably 15 to 45 mol%, and more preferably 20 to 40 mol%. When the constituent unit A includes the constituent unit (A-2), the molar ratio [(A-1)/(A-2)] of the constituent unit (A-1) to the constituent unit (A-2) in the constituent unit A is preferably 50/50 to 90/10, more preferably 55/45 to 85/15, and even more preferably 60/40 to 80/20, from the viewpoint of improving heat resistance, chemical resistance and optical isotropy.

Constituent unit A may also include constituent units other than constituent units (A-1) and constituent units (A-2). There is no particular limitation on the tetracarboxylic dianhydride that provides such a constituent unit, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (but excluding compounds represented by formula (a-1)); alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride (but excluding compounds represented by formula (a-2-1) and formula (a-2-2)); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. In addition, in this specification, aromatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more alicyclic rings and no aromatic ring, and aliphatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring. The constituent unit arbitrarily included in the constituent unit A may be one type or two or more types.

<Constituent unit B> Constituent unit B is a constituent unit derived from diamine that accounts for a large proportion of the polyimide resin, and includes a constituent unit (B-1) derived from a compound represented by the following formula (b-1) and a constituent unit (B-2) derived from a compound represented by the following formula (b-2).

[Chemistry 7] The compound represented by formula (b-1) is 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether. When constituent unit B includes constituent unit (B-1), the optical isotropy and colorless transparency of the film can be improved.

The compound represented by formula (b-2) is bis(aminomethyl)cyclohexane. Specific examples thereof include 1,3-bis(aminomethyl)cyclohexane represented by formula (b-2a) and 1,4-bis(aminomethyl)cyclohexane represented by formula (b-2b).

[Chemistry 8] Considering the resistance to organic solvents and heat resistance, the cis:inverse ratio of the compound represented by formula (b-2) is preferably 0:100 to 80:20, more preferably 0.1:99.9 to 70:30, more preferably 0.5:99.5 to 60:40, and more preferably 1:99 to 20:80. By including constituent unit (B-2) in constituent unit B, the optical isotropy, flexibility and chemical resistance of the film can be improved.

The ratio of the constituent unit (B-1) in the constituent unit B is preferably 5 to 80 mol%, more preferably 10 to 70 mol%, and more preferably 30 to 60 mol%. The ratio of the constituent unit (B-2) in the constituent unit B is preferably 20 to 95 mol%, more preferably 30 to 90 mol%, and more preferably 40 to 70 mol%. The total ratio of the constituent units (B-1) and (B-2) in the constituent unit B is preferably 50 mol% or more, more preferably 70 mol% or more, and more preferably 90 mol% or more. The upper limit of the total ratio of the constituent units (B-1) and (B-2) is not particularly limited, that is, 100 mol%. The constituent unit B may also be composed of only the constituent unit (B-1) and the constituent unit (B-2). From the viewpoint of improving optical isotropy and drug resistance, the molar ratio [(B-1)/(B-2)] of the constituent unit (B-1) to the constituent unit (B-2) in the constituent unit B is preferably 5/95 to 80/20, more preferably 10/90 to 70/30, and even more preferably 30/70 to 60/40.

Constituent unit B may also include constituent units other than constituent units (B-1) and (B-2). In addition to constituent units (B-1) and (B-2), constituent unit B preferably further includes a constituent unit (B-3) selected from at least one of the group consisting of constituent units (B-3-1) derived from a compound represented by the following formula (b-3-1) and constituent units (B-3-2) derived from a compound represented by the following formula (b-3-2). That is, constituent unit (B-3-1) and constituent unit (B-3-2) are collectively referred to as constituent unit (B-3). Among them, constituent unit B preferably further includes a constituent unit (B-3-1) derived from a compound represented by the following formula (b-3-1).

[Chemistry 9]

In formula (b-3-1), ^Z1 and ^Z2 each independently represent a divalent aliphatic group which may contain an oxygen atom, or a divalent aromatic group, ^R1 and ^R2 each independently represent a monovalent aromatic group or a monovalent aliphatic group, ^R3 and ^R4 each independently represent a monovalent aliphatic group, ^R5 and ^R6 each independently represent a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer greater than 1, and the sum of m and n is an integer of 2 to 1000. However, at least one of ^R1 and ^R2 represents a monovalent aromatic group. In formula (b-3-1), the two or more different repeating units described in [ ] are irrelevant to the order of [ ], and may be repeated in any form and order of random, alternating or block.

In formula (b-3-1), the divalent aliphatic group or divalent aromatic group in ^Z1 and ^Z2 may be substituted by a fluorine atom. As the divalent aliphatic group, there can be mentioned a divalent saturated or unsaturated aliphatic group having 1 to 20 carbon atoms, and an aliphatic group containing an oxygen atom. The carbon number of the divalent aliphatic group is preferably 3 to 20. As the divalent saturated aliphatic group, there can be mentioned an alkylene group having 1 to 20 carbon atoms, such as methylene, ethylene, propylene, trimethylene, tetramethylene, hexamethylene, octamethylene, decamethylene, dodecamethylene, etc. As the divalent unsaturated aliphatic group, there can be mentioned an alkenylene group having 2 to 20 carbon atoms, such as vinylene, propenylene, and an alkylene group having an unsaturated double bond at the end. As the aliphatic group containing an oxygen atom, an alkoxy group and an aliphatic group having an ether bond can be listed. As the alkoxy group, a propyloxy group and a trimethyleneoxy group can be listed. As the divalent aromatic group, an aryl group having 6 to 20 carbon atoms and an arylalkyl group having 7 to 20 carbon atoms can be listed. As specific examples of the aryl group having 6 to 20 carbon atoms in ^Z1 and ^Z2 , o-phenylene, m-phenylene, p-phenylene, 4,4'-biphenylene, 2,6-naphthylene and the like can be listed. As for ^Z1 and ^Z2 , trimethylene and p-phenylene are particularly preferred, and trimethylene is more preferred.

In formula (b-3-1), as the monovalent aliphatic group in R ¹ to R ⁶ , a monovalent saturated or unsaturated aliphatic group can be mentioned. As the monovalent saturated aliphatic group, an alkyl group having 1 to 22 carbon atoms can be mentioned, for example, a methyl group, an ethyl group, a propyl group, etc. As the monovalent unsaturated aliphatic group, an alkenyl group having 2 to 22 carbon atoms can be mentioned, for example, a vinyl group, a propenyl group, etc. These groups may also be substituted with a fluorine atom. As the monovalent aromatic group in R ¹ , R ² , R ⁵ and R ⁶ in formula (b-3-1), an aryl group having 6 to 20 carbon atoms, an aryl group having 7 to 30 carbon atoms and substituted with an alkyl group, an aralkyl group having 7 to 30 carbon atoms, etc. can be mentioned. As the monovalent aromatic group, an aryl group is preferred, and a phenyl group is more preferred. At least one of ^R1 and ^R2 represents a monovalent aromatic group, preferably both ^R1 and ^R2 are monovalent aromatic groups, more preferably ^{both R1} and ^R2 are phenyl groups. ^R3 and ^R4 are preferably alkyl groups having 1 to 6 carbon atoms, more preferably methyl groups. ^R5 and ^R6 are preferably monovalent aliphatic groups, more preferably methyl groups.

As described above, among the compounds represented by the formula (b-3-1), the compounds represented by the following formula (b-3-11) are preferred.

[Chemistry 10] (In formula (b-3-11), m and n are synonymous with m and n in formula (b-3-1), and their ideal ranges are also the same.)

In formula (b-3-1) and formula (b-3-11), m represents the number of repetitions of siloxane units bonded to at least one monovalent aromatic group, and in formula (b-3-1) and formula (b-3-11), n represents the number of repetitions of siloxane units bonded to a monovalent aliphatic group. In formula (b-3-1) and formula (b-3-11), m and n each independently represent an integer greater than 1, and the sum of m and n (m+n) represents an integer of 2 to 1000. The sum of m and n is preferably an integer of 3 to 500, more preferably 3 to 100, and even more preferably 3 to 50. The ratio of m/n in formula (b-3-1) and formula (b-3-11) is preferably 5/95 to 50/50, more preferably 10/90 to 40/60, and even more preferably 20/80 to 30/70.

The functional group equivalent (amine equivalent) of the compound represented by formula (b-3-1) is preferably 150 to 5,000 g/mol, more preferably 400 to 4,000 g/mol, and even more preferably 500 to 3,000 g/mol. In addition, the functional group equivalent refers to the mass of the compound represented by formula (b-3-1) per 1 mol of functional group (amine group).

Among the compounds represented by the formula (b-3-1), those available as commercial products include "X-22-9409", "X-22-1660B", "X-22-161A", and "X-22-161B" manufactured by Shin-Etsu Chemical Co., Ltd.

When the constituent unit B includes the constituent unit (B-3-1), the colorless transparency, optical isotropy and flexibility of the film can be improved.

Formula (b-3-2) is 4,4'-diaminodiphenylsulfone. When the constituent unit B includes the constituent unit (B-3-2), the colorless transparency, toughness and chemical resistance of the film can be improved.

When constituent unit B includes constituent unit (B-1), constituent unit (B-2) and constituent unit (B-3), the total ratio of constituent unit (B-1) and constituent unit (B-2) in constituent unit B is preferably 70 mol% or more, more preferably 80 mol% or more, and more preferably 90 mol% or more, and the ratio of constituent unit (B-3) in constituent unit B is preferably 0.1 to 30 mol%, more preferably 1 to 25 mol%, more preferably 2 to 20 mol%, and more preferably 3 to 15 mol%. The total ratio of constituent unit (B-1), constituent unit (B-2) and constituent unit (B-3) in constituent unit B is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total ratio of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3) is not particularly limited, that is, 100 mol%. The constituent unit B may also be composed only of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3).

When constituent unit B includes constituent unit (B-1), constituent unit (B-2) and constituent unit (B-3-1), the total ratio of constituent unit (B-1) and constituent unit (B-2) in constituent unit B is preferably 70 mol% or more, more preferably 80 mol% or more, and more preferably 90 mol% or more, and the ratio of constituent unit (B-3-1) in constituent unit B is preferably 0.1 to 30 mol%, more preferably 1 to 25 mol%, more preferably 2 to 20 mol%, more preferably 3 to 15 mol%, and more preferably 3 to 10 mol%. The total ratio of constituent unit (B-1), constituent unit (B-2) and constituent unit (B-3-1) in constituent unit B is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total ratio of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3-1) is not particularly limited, that is, 100 mol%. The constituent unit B may also be composed only of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3-1).

When constituent unit B includes constituent unit (B-1), constituent unit (B-2) and constituent unit (B-3-2), the total ratio of constituent unit (B-1) and constituent unit (B-2) in constituent unit B is preferably 70 mol% or more, more preferably 80 mol% or more, and more preferably 90 mol% or more. Considering the colorless transparency, toughness and chemical resistance of the film, the ratio of constituent unit (B-3-2) in constituent unit B is preferably 2-30 mol%, more preferably 3-30 mol%, more preferably 10-30 mol%, more preferably 15-30 mol%, and more preferably 15-25 mol%. The total ratio of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3-2) in the constituent unit B is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total ratio of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3-2) is not particularly limited, that is, 100 mol%. The constituent unit B may also be composed only of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3-2).

The constituent unit (B-3) may be only the constituent unit (B-3-1), only the constituent unit (B-3-2), or a combination of the constituent unit (B-3-1) and the constituent unit (B-3-2).

Constituent unit B may also include constituent units other than constituent units (B-1), (B-2) and (B-3). The diamines that provide the constituent units are not particularly limited, and examples thereof include: 1,4-phenylenediamine, p-phenylenediamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'- Aromatic diamines such as bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, and 9,9-bis(4-aminophenyl)fluorene (but excluding compounds represented by formula (b-1), compounds represented by formula (b-3-1), and compounds represented by formula (b-3-2)); alicyclic diamines (but excluding compounds represented by formula (b-2)); and aliphatic diamines such as ethylenediamine and hexamethylenediamine. In this specification, aromatic diamine refers to a diamine containing one or more aromatic rings, alicyclic diamine refers to a diamine containing one or more alicyclic rings and no aromatic ring, and aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The constituent units arbitrarily included in the constituent unit B other than the constituent units (B-1), (B-2) and (B-3) may be one or more.

<Characteristics of polyimide resin> From the perspective of the mechanical strength of the obtained polyimide film, the number average molecular weight of the polyimide resin is preferably 5,000 to 300,000. 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 may also contain structures other than the polyimide chain (a structure formed by imide bonds between constituent units A and B). As for structures other than the polyimide chain that may be contained in the polyimide resin, for example, structures containing amide bonds may be cited. The polyimide resin preferably contains a polyimide chain (a structure formed by imide bonds between constituent units A and B) as a main structure. Therefore, the ratio of the polyimide chain in the polyimide resin should be 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably 99% by mass or more.

The polyimide resin composition of the present invention containing the above-mentioned polyimide resin can form a film having colorless transparency, optical isotropy and excellent chemical resistance. The ideal physical property values of the film are as follows.

When a film with a thickness of 10 μm is made, the total light transmittance is preferably 88% or more, more preferably 88.5% or more, and more preferably 89% or more. When a film with a thickness of 10 μm is made, the yellowness index (YI) is preferably 4.5 or less, more preferably 3.0 or less, more preferably 2.0 or less, and more preferably 1.5 or less. When a film with a thickness of 10 μm is made, the absolute value of the thickness retardation (Rth) is preferably 70 nm or less, more preferably 60 nm or less, and more preferably 50 nm or less.

In addition, the film formed by using the above-mentioned polyimide resin has good mechanical properties and heat resistance, and has the following ideal physical property values. The film formed by using the polyimide resin of the present invention has good mechanical properties and heat resistance, and has the following ideal physical property values. The tensile strength is preferably 70MPa or more, more preferably 80MPa or more, and more preferably 90MPa or more. The tensile modulus is preferably 2.0GPa or more, more preferably 2.5GPa or more, and more preferably 3.0GPa or more. The elongation at break is preferably 8% or more, more preferably 10% or more, and more preferably 15% or more. The glass transition temperature (Tg) is preferably 200°C or more, more preferably 230°C or more, and more preferably 250°C or more. Furthermore, the above-mentioned physical property values in the present invention can be specifically measured by the methods described in the examples.

<Production method of polyimide resin> In the present invention, the polyimide resin can be produced by reacting a tetracarboxylic acid component containing a compound providing the above-mentioned constituent unit (A-1) with a diamine component containing a compound providing the above-mentioned constituent unit (B-1) and a compound providing the above-mentioned constituent unit (B-2).

As for the compound providing the constituent unit (A-1), the compound represented by formula (a-1) can be listed, but it is not limited thereto, and its derivatives can also be listed within the scope of providing the same constituent unit. As for the derivative, the tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by formula (a-1) (i.e., 4,4'-oxydiphthalic acid) and the alkyl ester of the tetracarboxylic acid can be listed. Among them, the tetracarboxylic dianhydride represented by formula (a-1) is preferred.

The tetracarboxylic acid component preferably contains 40 mol% or more of the compound providing the constituent unit (A-1), more preferably 50 mol% or more, and even more preferably 70 mol% or more. The upper limit of the content of the compound providing the constituent unit (A-1) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may also consist only of the compound providing the constituent unit (A-1).

The tetracarboxylic acid component may contain compounds other than the compounds providing the constitutional unit (A-1).

In addition to providing compounds constituting unit (A-1), the tetracarboxylic acid component may also contain compounds providing constituent unit (A-2). As for the compounds providing constituent unit (A-2), compounds represented by formula (a-2-1) and compounds represented by formula (a-2-2) may be listed, but they are not limited thereto and may also be derivatives thereof within the scope of providing the same constituent unit. As for the derivatives, tetracarboxylic acids corresponding to the compounds represented by formula (a-2-1) and formula (a-2-2) and alkyl esters of the tetracarboxylic acids may be listed. As for the compounds providing constituent unit (A-2), compounds represented by formula (a-2-1) and formula (a-2-2) (i.e., dianhydrides) are preferred.

When the tetracarboxylic acid component contains a compound providing the structural unit (A-2), the tetracarboxylic acid component preferably contains 10 to 50 mol %, more preferably 15 to 45 mol %, and even more preferably 20 to 40 mol % of the compound providing the structural unit (A-2).

The compounds arbitrarily contained in the tetracarboxylic acid component other than the compound providing the constituent unit (A-1) are not limited to the compounds providing the constituent unit (A-2). As such arbitrary compounds, the above-mentioned aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydride, and their derivatives (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.) can be listed. The compounds arbitrarily contained in the tetracarboxylic acid component other than the compound providing the constituent unit (A-1) and the compound providing the constituent unit (A-2) may be one or more.

As for the compound providing the constituent unit (B-1), the compound represented by formula (b-1) can be listed, but it is not limited to them, and its derivatives can also be provided within the scope of providing the same constituent unit. As for the derivative, the diisocyanate corresponding to the compound (diamine) represented by formula (b-1) can be listed. Among them, the compound represented by formula (b-1) (i.e., diamine) is preferred. Similarly, as for the compound providing the constituent unit (B-2), the compound represented by formula (b-2) can be listed, but it is not limited to them, and its derivatives can also be provided within the scope of providing the same constituent unit. As for the derivative, the diisocyanate corresponding to the compound (diamine) represented by formula (b-2) can be listed. As for the compound providing the constituent unit (B-2), the compound represented by formula (b-2) (i.e., diamine) is preferred.

The diamine component preferably contains 5 to 80 mol% of the compound providing the constituent unit (B-1), more preferably 10 to 70 mol%, and more preferably 30 to 60 mol%. The diamine component preferably contains 20 to 95 mol% of the compound providing the constituent unit (B-2), more preferably 30 to 90 mol%, and more preferably 40 to 70 mol%. The diamine component preferably contains 50 mol% or more, more preferably 70 mol% or more, and more preferably 90 mol% or more of the total of the compound providing the constituent unit (B-1) and the compound providing the constituent unit (B-2). The upper limit of the total content of the compound providing the constituent unit (B-1) and the compound providing the constituent unit (B-2) is not particularly limited, that is, 100 mol%. The diamine component may be composed only of a compound providing the constitutional unit (B-1) and a compound providing the constitutional unit (B-2).

The diamine component may contain compounds other than the compound providing the constitutional unit (B-1) and the compound providing the constitutional unit (B-2).

In addition to the compounds that provide the constituent unit (B-1) and the compounds that provide the constituent unit (B-2), the diamine component may also contain compounds that provide the constituent unit (B-3). As for the compounds that provide the constituent unit (B-3), the compounds represented by formula (b-3-1) and the compounds represented by formula (b-3-2) can be listed, but they are not limited to them. Derivatives thereof can also be listed within the scope of providing the same constituent unit. As for the derivatives, diisocyanates corresponding to the diamine represented by formula (b-3-1) and diisocyanates corresponding to the diamine represented by formula (b-3-2) can be listed. As for the compounds that provide the constituent unit (B-3), the compounds represented by formula (b-3-1) and the compounds represented by formula (b-3-2) (i.e., diamines) are preferably used.

The compound constituting unit (B-3) may be only the compound represented by formula (b-3-1), only the compound represented by formula (b-3-2), or a combination of a compound represented by formula (b-3-1) and a compound represented by formula (b-3-2).

When the diamine component contains a compound providing a constituent unit (B-3), the diamine component preferably contains 0.1 to 30 mol% of the compound providing a constituent unit (B-3), more preferably 1 to 25 mol%, and more preferably 5 to 25 mol%. When the diamine component contains a compound providing a constituent unit (B-3), the total of the compound providing a constituent unit (B-1), the compound providing a constituent unit (B-2), and the compound providing a constituent unit (B-3) in the diamine component preferably contains 80 mol% or more, more preferably 90 mol% or more, and more preferably 99 mol% or more. The upper limit of the total content of the compound providing a constituent unit (B-1), the compound providing a constituent unit (B-2), and the compound providing a constituent unit (B-3) is not particularly limited, that is, 100 mol%. The diamine component may be composed only of a compound providing a constitutional unit (B-1), a compound providing a constitutional unit (B-2), and a compound providing a constitutional unit (B-3).

The compounds arbitrarily contained in the diamine component other than the compounds providing the constituent unit (B-1) and the compounds providing the constituent unit (B-2) are not limited to the compounds providing the constituent unit (B-3). As such arbitrary compounds, the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, and their derivatives (diisocyanates, etc.) can be listed. The compounds arbitrarily contained in the diamine component other than the compounds providing the constituent unit (B-1) and the compounds providing the constituent unit (B-2) can 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.

In addition, in the present invention, in the production of the polyimide resin, in addition to the aforementioned tetracarboxylic acid component and diamine component, a capping agent may also be used. The capping agent is preferably a monoamine or a dicarboxylic acid. The amount of the introduced capping agent is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, relative to 1 mol of the tetracarboxylic acid component. As for the monoamine capping agent, for example: methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc., preferably benzylamine, aniline. As for the dicarboxylic acid capping agent, it is preferably a dicarboxylic acid, and a part of it may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are listed, preferably phthalic acid and phthalic anhydride.

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 to 80°C for 0.5 to 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 added, and if necessary, stirred at 0 to 80°C for 0.5 to 30 hours, 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.

The reaction solvent used in the production of polyimide resin can be any solvent that does not hinder the imidization reaction and can dissolve the generated polyimide. Examples include: aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, etc.

Specific examples of aprotic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone (GBL) 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, cyclohexanone, and methylcyclohexanone; amine solvents such as methylpyridine 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, methyl ethyl carbonate, ethyl carbonate, propyl carbonate, etc. Among the above reaction solvents, aprotic solvents are preferred, and amide solvents and lactone solvents are more preferred. The above reaction solvents may be used alone or in combination of two or more.

In the imidization reaction, it is preferable to use a Dean-Stark apparatus or the like to carry out the reaction 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. As for the imidization catalyst, alkali catalysts or acid catalysts can be listed. As for the alkali catalyst, organic alkali catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline, etc.; inorganic alkali catalysts such as potassium hydroxide or sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, etc. can be listed. In addition, as for the acid catalyst, there can be listed: 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 imidization catalyst can be used alone or in combination of two or more. Considering the operability, it is preferable to use an alkali catalyst among the above, and it is more preferable to use an organic alkali catalyst, and it is more preferable to use triethylamine.

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

[Polyimide varnish] The polyimide varnish of the present invention is obtained by dissolving the polyimide resin 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 and an organic solvent, and the polyimide resin is dissolved in the organic solvent. The organic solvent is not particularly limited as long as it can dissolve the polyimide resin. The above compounds are preferably used as reaction solvents for the production of the polyimide resin, either alone or in combination of two or more. The polyimide varnish of the present invention may be a polyimide solution obtained by dissolving a polyimide resin obtained by a polymerization method in a reaction solvent, or may be a polyimide solution obtained by further adding a solvent and diluting the polyimide solution.

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 more preferably contains 10 to 30% by mass. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, and more preferably 1 to 100 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 manufacturing method of 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. Therefore, the optical isotropy, flexibility and chemical resistance of the polyimide film of the present invention are excellent. The ideal physical properties 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 applied 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 diluting solvent contained in the varnish is removed by heating.

As for the coating method, known coating methods such as spin coating, slit coating, and knife coating can be listed. Among them, slit coating is preferred from the viewpoint of controlling the molecular orientation and improving the chemical resistance and workability. As for the method of removing the organic solvent contained in the varnish by heating, it is preferred to evaporate the organic solvent at a temperature below 150°C and make it non-viscous, and then dry it at a temperature above the boiling point of the organic solvent (not particularly limited, preferably 200-500°C). In addition, it is preferred to dry it in an air environment or a nitrogen environment. The pressure of the drying environment can be any of reduced pressure, normal pressure, and pressurized. The method for peeling the polyimide film formed on the support from the support is not particularly limited, and examples thereof include a laser peeling method, a method using a sacrificial layer for peeling (a method in which a peeling agent is pre-coated on the surface of the support), and a method of adding a peeling agent.

In addition, the polyimide film of the present invention can also be produced using a polyimide varnish in which polyimide is dissolved 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 addition polymerization of the tetracarboxylic acid component of the compound providing the aforementioned constituent unit (A-1) and the diamine component of the compound providing the aforementioned constituent unit (B-1) and the compound providing the constituent unit (B-2). By subjecting this polyimide to imidization (dehydration and ring closure), the polyimide resin of the present invention can be obtained as the final product. As for the organic solvent contained in the aforementioned polyamide varnish, the organic solvent contained in the polyimide varnish of the present invention can be used. In the present invention, the polyamide varnish can be a polyamide solution itself obtained by allowing a tetracarboxylic acid component and a diamine component to undergo an addition polymerization reaction in a reaction solvent, or can be a polyamide solution obtained by further adding a solvent and diluting 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 coated on a smooth support such as a glass plate, a metal plate, or a plastic, or formed into a film, and the organic solvents such as the reaction solvent and the 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 for drying the polyamide varnish and obtaining the polyamide film is preferably 50 to 120°C. The heating temperature for imidizing the polyamide by heating is preferably 200 to 400°C. In addition, the imidization method is not limited to thermal imidization, and chemical imidization can also be used.

The thickness of the polyimide film of the present invention can be appropriately selected according to the application, and is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, more preferably 8 to 80 μm, and more preferably 10 to 80 μm. With a thickness of 1 to 250 μm, it can be used as a self-supporting film in practical applications. 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 is particularly suitable for use 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 embodiments, but the present invention is not limited to these embodiments.

<Thin film properties and evaluation> The physical properties of the thin films obtained in the examples and comparative examples were measured using the methods shown below.

(1) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

(2) Tensile strength, tensile modulus, and tensile elongation at break (tensile elongation at break is an evaluation of flexibility) Tensile strength, tensile modulus, and tensile elongation at break were measured in accordance with JIS K7127:1999 using a tensile testing machine "STROGRAPH VG-1E" manufactured by Toyo Seiki Co., Ltd. The distance between the clamps was set to 50 mm, the specimen size was set to 10 mm × 70 mm, and the test speed was set to 20 mm/min.

(3) Glass transition temperature (Tg) Thermomechanical analyzer "TMA/SS6100" manufactured by Hitachi High-Tech Science Co., Ltd. was used to remove residual stress in the tensile mode with a sample size of 2mm×20mm, a load of 0.1N, and a heating rate of 10℃/min. The sample was heated to a temperature sufficient to remove residual stress and then cooled to room temperature. Thereafter, the elongation of the test piece was measured under the same conditions as the above-mentioned treatment for removing residual stress, and the glass transition temperature was obtained when the inflection point of the elongation was observed.

(4) Total light transmittance and yellowness index (YI) Total light transmittance and YI were measured in accordance with JIS K7136 using the color-turbidity simultaneous tester "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

(5) Haze The measurement was carried out in accordance with JIS K7361-1 using the color-turbidity simultaneous tester "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

(6) Thickness phase difference (Rth) (Evaluation of optical isotropy) The thickness phase difference (Rth) is measured using an elliptical polarimeter "M-220" manufactured by JASCO Corporation. The thickness phase difference is measured at a wavelength of 590nm. In addition, Rth is expressed by the following formula when the largest refractive index in the plane of the polyimide film is nx, the smallest is ny, the refractive index in the thickness direction is nz, and the thickness of the film is d. Rth is also calculated by converting the film thickness to 10μm. Rth={[(nx+ny)/2]-nz}×d

(7) Solvent resistance (evaluation of chemical resistance) The polyimide film formed on a glass plate was immersed in a solvent at room temperature to check whether there was any change on the film surface. Propylene glycol monomethyl ether acetate (PGMEA) was used as a solvent. The evaluation criteria for solvent resistance are as follows. ○: No change on the film surface. △: Some microcracks on the film surface. ×: Cracks occurred on the film surface, or the film surface was dissolved.

<Abbreviations of components, etc.> The tetracarboxylic acid components and diamine components used in the Examples and Comparative Examples, and their abbreviations are as follows.

(Tetracarboxylic acid component) ODPA: 4,4'-oxydiphthalic anhydride (manufactured by MANAC Co., Ltd.; compound represented by formula (a-1)) HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.; compound represented by formula (a-2-1)) CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (manufactured by JXTG energy Co., Ltd.; compound represented by formula (a-2-2)) 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride

(Diamine component) 6FODA: 4,4'-diamino-2,2'-bistrifluoromethyl diphenyl ether (manufactured by ChinaTech Chemical (Tianjin) Co., Ltd.; compound represented by formula (b-1)) 1,3-BAC: 1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.; compound represented by formula (b-2a)) 1,4-BAC: 1,4-bis(aminomethyl)cyclohexane (compound represented by formula (b-2b); cis ratio 40%) 1,4-BACT: 1,4-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.; compound represented by formula (b-2b); Cis ratio 85%) X-22-9409: (Shin-Etsu Chemical Co., Ltd.; compound represented by formula (b-3-1)) 4,4’-DDS: 4,4’-diaminodiphenyl sulfone (SEIKA Co., Ltd.; compound represented by formula (b-3-2)) 3,3’-DDS: 3,3’-diaminodiphenyl sulfone (SEIKA Co., Ltd.) TFMB: 2,2’-bis(trifluoromethyl)benzidine (SEIKA Co., Ltd.)

<Production of polyimide resin, varnish and polyimide film> Example 1 16.812 g (0.0500 mol) of 6FODA, 7.113 g (0.0500 mol) of 1,4-BACT and 65.935 g of γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) were added to a 300 mL 5-necked 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, and stirred at a temperature of 70°C in a nitrogen environment at a rotation speed of 200 rpm to obtain a solution. After adding 31.021g (0.100 mol) of ODPA and 16.484g of γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) to the solution at once, 0.506g of triethylamine (Kanto Chemical Co., Ltd.) was added as an imidization catalyst, and the temperature in the reaction system was raised to 190°C in about 20 minutes using a heating jacket. The distilled components were collected, and the rotation speed was adjusted according to the increase in viscosity. At the same time, the temperature in the reaction system was maintained at 190°C and refluxed for about 5 hours. Then, 208.517 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) was added so that the solid content concentration became 15% by mass, and the temperature in the reaction system was cooled to 100°C, and then stirred for about 1 hour to make it uniform, thereby obtaining a polyimide varnish. Then, the obtained polyimide varnish was applied on a glass plate by spin coating, and maintained at 80°C for 20 minutes using a heating plate, and then heated at 300°C for 30 minutes (heating rate 5°C/min) in a hot air dryer under a nitrogen environment to evaporate the solvent and obtain a film.

Example 2 The amount of ODPA was changed from 31.021 g (0.100 mol) to 24.817 g (0.080 mol), and 7.688 g (0.020 mol) of CpODA was added. In addition, a polyimide varnish was prepared by the same method as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 1.

Example 3 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 16.429 g (0.04886 mol), the amount of 1,4-BACT was changed from 7.113 g (0.0500 mol) to 6.950 g (0.04886 mol), and 2.941 g (0.00228 mol) of X-22-9409 was added. In addition, a polyimide varnish was prepared by the same method as in Example 2 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 1.

Example 4 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 16.012 g (0.04762 mol), the amount of 1,4-BACT was changed from 7.113 g (0.0500 mol) to 6.774 g (0.04762 mol), and 6.140 g (0.00476 mol) of X-22-9409 was added. In addition, a polyimide varnish was prepared by the same method as in Example 2 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 1.

Example 5 The amount of ODPA was changed from 31.021g (0.100 mol) to 15.511g (0.050 mol), and 19.219g (0.050 mol) of CpODA was added. The amount of 6FODA was changed from 16.812g (0.0500 mol) to 15.980g (0.04753 mol), and the amount of 1,4-BACT was changed from 7.113g (0.0500 mol) to 6.760g (0.04753 mol), and 6.386g (0.00495 mol) of X-22-9409 was added. In addition, a polyimide varnish was prepared by the same method as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. Using the obtained polyimide varnish, a film was obtained by the same method as in Example 1.

Example 6 The amount of ODPA was changed from 31.021 g (0.100 mol) to 15.511 g (0.050 mol), and HPMDA 11.209 g (0.050 mol) was added. In addition, a polyimide varnish was prepared by the same method as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 1.

Example 7 CpODA 7.688g (0.020 mol) was replaced with HPMDA 4.483 (0.020 mol). In addition, a polyimide varnish was prepared in the same manner as in Example 2 to obtain a polyimide varnish having a solid content of 15% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Example 8 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 6.725 g (0.020 mol), and the amount of 1,4-BACT was changed from 7.113 g (0.0500 mol) to 11.380 g (0.080 mol). In addition, a polyimide varnish was prepared by the same method as in Example 6 to obtain a polyimide varnish having a solid content concentration of 15% by mass. Then, the obtained polyimide varnish was applied on a glass plate by spin coating, maintained at 80°C for 20 minutes using a heating plate, and then heated at 240°C for 60 minutes in an air environment in a hot air dryer to evaporate the solvent and obtain a film.

Example 9 In addition to changing 1,4-BACT 7.113 g (0.0500 mol) to 1,3-BAC 7.113 g (0.0500 mol), a polyimide varnish was prepared in the same manner as in Example 1 to obtain a polyimide varnish having a solid content of 15% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Example 10 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 13.450 g (0.0400 mol), and the amount of 1,4-BACT was changed from 7.113 g (0.0500 mol) to 8.535 g (0.0600 mol). In addition, a polyimide varnish was prepared by the same method as in Example 6 to obtain a polyimide varnish having a solid content concentration of 15% by mass. Then, the obtained polyimide varnish was applied on a glass plate by spin coating, maintained at 80°C for 20 minutes using a heating plate, and then heated at 260°C for 30 minutes in an air environment in a hot air dryer to evaporate the solvent and obtain a film.

Example 11 In addition to changing 1,4-BACT 7.113 g (0.0500 mol) to 1,4-BAC 7.113 g (0.0500 mol), a polyimide varnish was prepared in the same manner as in Example 6 to obtain a polyimide varnish having a solid content of 15% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 10.

Example 12 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 10.087 g (0.0300 mol), and 4,4'-DDS 4.966 g (0.0200 mol) was added. In addition, a polyimide varnish was prepared by the same method as in Example 6 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 10.

Comparative Example 1 In addition to changing 6FODA 16.812 g (0.0500 mol) to TFMB 16.012 g (0.0500 mol), a polyimide varnish was prepared in the same manner as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. A film was obtained using the obtained polyimide varnish in the same manner as in Example 1.

Comparative Example 2 The amount of 6FODA was changed from 16.812 g (0.0500 mol) to 33.624 g (0.100 mol), and the amount of 1,4-BACT was changed from 7.113 g (0.0500 mol) to 0 g (0 mol). In addition, a polyimide varnish was prepared by the same method as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. Using the obtained polyimide varnish, a film was obtained by the same method as in Example 1.

Comparative Example 3 In addition to changing 6FODA 16.812 g (0.0500 mol) to 3,3'-DDS 12.415 g (0.0500 mol), a polyimide varnish was prepared in the same manner as in Example 9 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Comparative Example 4 In addition to changing ODPA 31.021 g (0.100 mol) to 6FDA 44.424 g (0.100 mol), a polyimide varnish was prepared in the same manner as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. A film was obtained using the obtained polyimide varnish in the same manner as in Example 1.

Comparative Example 5 In addition to changing ODPA 31.021g (0.100 mol) to HPMDA 22.417g (0.100 mol), changing the amount of 6FODA from 16.812g (0.0500 mol) to 33.624g (0.100 mol), and changing the amount of 1,4-BACT from 7.113g (0.0500 mol) to 0g (0 mol), a polyimide varnish was prepared by the same method as in Example 1 to obtain a polyimide varnish having a solid content concentration of 15% by mass. The obtained polyimide varnish was used to obtain a film by the same method as in Example 10.

The above-mentioned physical property measurements and evaluations were performed on the polyimide films obtained in the Examples and Comparative Examples. The results are shown in Table 1.

[Table 1]

As shown in Table 1, it can be seen that the polyimide film of the embodiment has good optical isotropy, and also has excellent flexibility and chemical resistance.

Claims (7)

A polyimide resin comprises a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from a diamine, wherein the constituent unit A comprises a constituent unit (A-1) derived from a compound represented by the following formula (a-1), the constituent unit B comprises a constituent unit (B-1) derived from a compound represented by the following formula (b-1), and a constituent unit (B-2) derived from a compound represented by the following formula (b-2), the total ratio of the constituent units (B-1) and (B-2) in the constituent unit B is 70 mol% to 100 mol%, the ratio of the constituent unit (B-1) in the constituent unit B is 5-80 mol%, and the ratio of the constituent unit (B-2) in the constituent unit B is 20-95 mol%.

The polyimide resin of claim 1, wherein the molar ratio [(B-1)/(B-2)] of the constituent unit (B-1) to the constituent unit (B-2) in the constituent unit B is 5/95 to 80/20. The polyimide resin of claim 1 or 2, wherein the constituent unit A further comprises at least one selected from the group consisting of a constituent unit (A-2-1) derived from a compound represented by the following formula (a-2-1) and a constituent unit (A-2-2) derived from a compound represented by the following formula (a-2-2),

The polyimide resin of claim 1 or 2, wherein the constituent unit B further comprises at least one selected from the group consisting of a constituent unit (B-3-1) derived from a compound represented by the following formula (b-3-1) and a constituent unit (B-3-2) derived from a compound represented by the following formula (b-3-2),

In formula (b-3-1), ^Z1 and ^Z2 each independently represent a divalent aliphatic group which may contain an oxygen atom, or a divalent aromatic group, ^R1 and ^R2 each independently represent a monovalent aromatic group or a monovalent aliphatic group, ^R3 and ^R4 each independently represent a monovalent aliphatic group, ^R5 and ^R6 each independently represent a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer greater than 1, and the sum of m and n is an integer of 2 to 1000, provided that at least one of ^R1 and ^R2 represents a monovalent aromatic group. The polyimide resin of claim 4, wherein R ¹ and R ² in the formula (b-3-1) are phenyl groups. A polyimide varnish is prepared by dissolving a polyimide resin as described in any one of claims 1 to 5 in an organic solvent. A polyimide film comprising a polyimide resin as described in any one of claims 1 to 5.