TWI861323B - Polyimide resin, 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 a structural unit (A-1) derived from a compound represented by formula (a-1) shown below and a structural unit (A-2) derived from a compound represented by formula (a-2) shown below, the structural unit B includes a structural unit (B-1) derived from a compound represented by formula (b-1) shown below and a structural unit (B-2) derived from a compound represented by formula (b-2) shown below, and the polyimide resin is capable of forming a film having excellent optical isotropy and superior releasability and chemical resistance. The invention also provides a polyimide varnish and a polyimide film.

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 expected 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 on polyimide films suitable as the plastic substrate is underway. Films used for image display devices require various optical properties. For example, when light emitted from a display element passes through a plastic substrate, the plastic substrate is required to be colorless and transparent. On the other hand, when light passes through a phase difference film or a polarizing plate, such as when used in liquid crystal displays, touch panels, etc., high optical isotropy (i.e., low Rth) is particularly required.

In order to satisfy the above-mentioned properties, polyimide resins of various compositions have been developed. For example, Patent Document 1 discloses a polyimide film having a structure composed of a combination of 3,3'-diaminodiphenylsulfone and other specific diamines as a diamine component in order to obtain a polyimide film having good solubility in solvents and excellent processability, and being colorless, transparent, and having excellent toughness. [Prior Art Document] [Patent Document]

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

[The problem that the invention wants to solve]

As mentioned above, especially for the use of displays, polyimide films with excellent optical isotropy are sought. In addition, polyimide films with high chemical resistance are also sought. For example, in order to form other resin layers (such as color filters, resists) on the polyimide film, when the varnish used to form the resin layer is applied to the polyimide film, the polyimide film needs to be resistant to the solvent contained in the varnish. If the solvent resistance of the polyimide film is insufficient, there is a concern that the film will dissolve and swell, and the meaning of making a substrate will be lost. However, as mentioned above, in order to ensure the optical properties, the polyimide film must be made into a solution when making it, and it is not easy to take these properties into consideration. Furthermore, when a polyimide film is used as a substrate, the film will adhere to a support such as a glass plate during the step of making an electronic circuit on the film. Therefore, after the circuit is made, the polyimide film is also required to be easily peeled off from the support. In this way, a polyimide resin is sought that can maintain the optical properties of the obtained polyimide film, especially the optical isotropy, and can obtain a polyimide film with excellent peeling properties and chemical resistance. Therefore, the subject of the present invention is to provide a polyimide resin that can form a film with excellent optical isotropy, and also excellent peeling properties and chemical resistance, as well as to provide a polyimide varnish and a polyimide film. [Means for Solving the Problem]

The inventors of the present invention have found that a polyimide resin comprising a combination of two specific constituent units derived from tetracarboxylic dianhydride and two specific constituent units derived from diamine can solve the above-mentioned problems, and thus the present invention has been completed.

That is, the present invention relates to the following <1> to <5>. <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 a constituent unit (A-1) derived from a compound represented by the following formula (a-1) and a constituent unit (A-2) derived from a compound represented by the following formula (a-2), and 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).

[Chemistry 1]

<2> The polyimide resin described in <1> above, wherein the ratio of the constituent unit (A-1) in the constituent unit A is 20 to 80 mol%, and the ratio of the constituent unit (A-2) in the constituent unit A is 20 to 80 mol%. <3> The polyimide resin described in <1> or <2> 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%. <4> A polyimide varnish obtained by dissolving the polyimide resin described in any one of <1> to <3> above in an organic solvent. <5> A polyimide film comprising a polyimide resin as described in any one of <1> to <3> above. [Effect 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 peeling property and chemical resistance.

[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 a constituent unit (A-1) derived from a compound represented by the following formula (a-1) and a constituent unit (A-2) derived from a compound represented by the following formula (a-2), and 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).

[Chemistry 2]

The reason why the polyimide resin of the present invention maintains optical isotropy and has excellent peeling property and chemical resistance is unknown, but it is believed that the polyimide resin of the present invention has a sulfonyl structure and an alicyclic structure in addition to an ether structure, so it has excellent optical isotropy, and also has excellent peeling property and chemical resistance.

<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) and a constituent unit (A-2) derived from a compound represented by the following formula (a-2).

[Chemistry 3]

The compound represented by formula (a-1) is 4,4'-oxydiphthalic anhydride. By including the constituent unit (A-1), the chemical resistance, optical isotropy, and transparency of the constituent unit A can be improved. The compound represented by formula (a-2) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride. By including the constituent unit (A-2), the solubility of the obtained polyimide resin in the varnish can be improved, and the chemical resistance and optical isotropy can be improved.

The ratio of the constituent unit (A-1) in the constituent unit A is preferably 20 to 80 mol%, preferably 30 to 70 mol%, and more preferably 40 to 60 mol%. The ratio of the constituent unit (A-2) in the constituent unit A is preferably 20 to 80 mol%, preferably 30 to 70 mol%, and more preferably 40 to 60 mol%. The total ratio of the constituent units (A-1) and (A-2) in the constituent unit A is preferably 50 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more. The upper limit of the total ratio of the constituent units (A-1) and (A-2) is not particularly limited, that is, 100 mol%. The constituent unit A may also be composed of only the constituent units (A-1) and (A-2). In the polyimide resin of the present invention, the constituent unit A comprises both constituent units (A-1) and (A-2), so that not only are the optical isotropy, peeling property, and chemical resistance all excellent as described above, but also the polymer generated by the imidization reaction during the manufacture of the polyimide resin has a high solubility in the solvent, and a transparent varnish and film can be obtained. 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 20/80 to 80/20, more preferably 30/70 to 70/30, and even more preferably 40/60 to 60/40 from the viewpoint of improving the optical isotropy and chemical resistance.

The constituent unit A may include constituent units other than the constituent unit (A-1) and the constituent unit (A-2). The tetracarboxylic dianhydride providing such a constituent unit is not particularly limited, 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, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (but excluding compounds represented by formula (a-2)); 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. The constituent unit A may contain one or more constituent units.

<Constituent unit B> Constituent unit B is a constituent unit derived from diamine in 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 4]

The compound represented by formula (b-1) is 4,4'-diaminodiphenylsulfonium. By including the constituent unit (B-1), the toughness and peeling properties of the film can be improved, and the heat resistance can be further improved.

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

[Chemistry 5] The cis:trans 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 even more preferably 1:99 to 20:80, from the viewpoint of resistance to organic solvents and heat resistance. By including the constituent unit (B-2), the colorless transparency and optical isotropy 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%, preferably 10 to 70 mol%, more preferably 30 to 70 mol%, more preferably 45 to 70 mol%, and more preferably 45 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%, more preferably 30 to 70 mol%, more preferably 30 to 55 mol%, and more preferably 40 to 55 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). In the polyimide resin of the present invention, the constituent unit B contains both the constituent units (B-1) and (B-2), so that not only the optical isotropy, the peeling property, and the chemical resistance are all excellent as mentioned above, but also when the polyimide resin is manufactured, the solubility of the polymer generated by the imidization reaction in the solvent is also high, and a transparent varnish and film can be obtained. 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, from the viewpoint of improving optical isotropy and chemical resistance, more preferably 30/70 to 70/30 from the viewpoint of heat resistance, more preferably 45/55 to 70/30 from the viewpoint of toughness, and more preferably 45/55 to 60/40.

Constituent unit B may also include constituent units other than constituent units (B-1) and (B-2). Considering the viewpoints of heat resistance and colorless transparency, constituent unit B preferably includes, in addition to constituent units (B-1) and (B-2), a constituent unit (B-3) derived from a compound represented by the following formula (b-3).

[Chemistry 6] The compound represented by formula (b-3) is 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether.

When the constituent unit B includes the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3), the total ratio of the constituent unit (B-1) to the constituent unit (B-2) in the constituent unit B is preferably 50 mol% or more, preferably 60 mol% or more, and more preferably 70 mol% or more, and the ratio of the constituent unit (B-3) in the constituent unit B is preferably 1 to 50 mol%, preferably 5 to 40 mol%, and more preferably 10 to 30 mol%. The total ratio of the constituent unit (B-1), the constituent unit (B-2) and the constituent unit (B-3) in the constituent unit B is preferably 80 mol% or 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).

Constituent unit B may also include constituent units other than constituent units (B-1), (B-2) and (B-3). The diamines that provide such 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-diisopropyl Aromatic diamines such as benzene, N,N'-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) and compounds represented by formula (b-3)); alicyclic diamines (but excluding compounds represented by formula (b-2)); 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 unit (B-1) and constituent unit (B-2) that constituent unit B may arbitrarily contain may be one type or two or more types.

<Characteristics of polyimide resin> The number average molecular weight of the polyimide resin is preferably 5,000 to 300,000 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, from 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). Examples of structures other than the polyimide chain that may be contained in the polyimide resin include structures containing amide bonds, etc. 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 proportion of the polyimide chain in the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 99% by mass or more, and may also be 100% by mass.

The polyimide resin composition of the present invention containing the above-mentioned polyimide resin can form a film having excellent optical isotropy, peeling properties and chemical resistance, and 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, preferably 88.5% or more, and even 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, preferably 3.0 or less, preferably 2.0 or less, and even 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, preferably 50 nm or less, preferably 40 nm or less, and even more preferably 30 nm or less.

In addition, the thin film formed using the above-mentioned polyimide resin also has good mechanical properties and heat resistance, and has the following ideal physical property values. The tensile strength is preferably 70 MPa or more, preferably 90 MPa or more, and even more preferably 100 MPa or more. The tensile elastic modulus is preferably 1.5 GPa or more, preferably 2.0 GPa or more, and even more preferably 2.5 GPa or more. The tensile elongation at break is preferably 5% or more, preferably 6% or more, and even more preferably 7% or more. The glass transition temperature (Tg) is preferably 200°C or more, preferably 230°C or more, and even more preferably 250°C or more. In addition, the above-mentioned physical property values in the present invention can be specifically measured by the method described in the embodiment.

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

The compound providing the constituent unit (A-1) may include compounds represented by formula (a-1), 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 (a-1) (i.e., 4,4'-oxydiphthalic acid) and alkyl esters of the tetracarboxylic acid. Among them, the tetracarboxylic dianhydride represented by formula (a-1) is preferred. Similarly, the compound providing the constituent unit (A-2) may include compounds represented by formula (a-2), 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 (a-2) (i.e., 1,2,4,5-cyclohexanetetracarboxylic acid) and alkyl esters of the tetracarboxylic acid. Among them, tetracarboxylic dianhydride represented by formula (a-2) is preferred.

Among the tetracarboxylic acid components, the compound providing the constituent unit (A-1) preferably contains 20 to 80 mol%, preferably 30 to 70 mol%, and more preferably 40 to 60 mol%. Among the tetracarboxylic acid components, the compound providing the constituent unit (A-2) preferably contains 20 to 80 mol%, preferably 30 to 70 mol%, and more preferably 40 to 60 mol%. Among the tetracarboxylic acid components, the compound providing the constituent unit (A-1) and the compound providing the constituent unit (A-2) preferably contain 50 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more. The upper limit of the total content of the compound providing the constituent unit (A-1) and the compound providing the constituent unit (A-2) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may also be composed only of a compound providing a constituent unit (A-1) and a compound providing a constituent unit (A-2). The molar ratio [(A-1)/(A-2)] of the compound providing a constituent unit (A-1) to the compound providing a constituent unit (A-2) in the tetracarboxylic acid component is preferably 20/80 to 80/20, more preferably 30/70 to 70/30, and even more preferably 40/60 to 60/40.

The tetracarboxylic acid component may also contain compounds other than the compounds providing the constituent unit (A-1) and the compounds providing the constituent unit (A-2). Such arbitrary compounds include the above-mentioned aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydride, and their derivatives (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.). The compounds other than the compounds providing the constituent unit (A-1) and the compounds providing the constituent unit (A-2) that the tetracarboxylic acid component may arbitrarily contain may be one or more.

The compound providing the constituent unit (B-1) may include compounds represented by formula (b-1), but is not limited thereto. It may also be a derivative thereof within the scope of providing the same constituent unit. The derivative may include a diisocyanate corresponding to the compound represented by formula (b-1). The compound providing the constituent unit (B-1) is preferably a compound represented by formula (b-1) (i.e., a diamine). Similarly, the compound providing the constituent unit (B-2) may include compounds represented by formula (b-2), but is not limited thereto. It may also be a derivative thereof within the scope of providing the same constituent unit. The derivative may include a diisocyanate corresponding to the compound represented by formula (b-2). The compound providing the constituent unit (B-2) is preferably a compound represented by formula (b-2) (i.e., a diamine).

Among the diamine components, the compound providing the constituent unit (B-1) preferably contains 5 to 80 mol%, preferably 10 to 70 mol%, more preferably 30 to 70 mol%, more preferably 45 to 70 mol%, and more preferably 45 to 60 mol%. Among the diamine components, the compound providing the constituent unit (B-2) preferably contains 20 to 95 mol%, preferably 30 to 90 mol%, more preferably 30 to 70 mol%, more preferably 30 to 55 mol%, and more preferably 40 to 55 mol%. Among the diamine components, the compound providing the constituent unit (B-1) and the compound providing the constituent unit (B-2) preferably contain 50 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more. 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 also be composed only of the compound providing the constituent unit (B-1) and the compound providing the constituent unit (B-2). The molar ratio [(B-1)/(B-2)] of the compound providing the constituent unit (B-1) to the compound providing the constituent unit (B-2) in the diamine component is preferably 5/95 to 80/20, more preferably 10/90 to 70/30, from the viewpoint of improving optical isotropy and chemical resistance, more preferably 30/70 to 70/30 from the viewpoint of heat resistance, more preferably 45/55 to 70/30 from the viewpoint of toughness, and more preferably 45/55 to 60/40.

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

In addition to compounds that provide constituent unit (B-1) and compounds that provide constituent unit (B-2), the diamine component may also include compounds that provide constituent unit (B-3). The compound that provides constituent unit (B-3) may be a compound represented by formula (b-3), but is not limited thereto and may be a derivative thereof within the scope of providing the same constituent unit. The derivative may be a diisocyanate corresponding to the compound represented by formula (b-3). The compound that provides constituent unit (B-3) is preferably a compound represented by formula (b-3) (i.e., a diamine).

In the diamine component, the compound providing the constituent unit (B-3) preferably contains 1 to 50 mol%, preferably contains 5 to 40 mol%, and even more preferably contains 10 to 30 mol%. When the diamine component contains the compound providing the constituent unit (B-3), in the diamine component, the compound providing the constituent unit (B-1), the compound providing the constituent unit (B-2), and the compound providing the constituent unit (B-3) preferably contain 80 mol% or more in total, preferably contain 90 mol% or more, and even more preferably contain 99 mol% or more. There is no particular upper limit on the total content of the compound providing the constituent unit (B-1), the compound providing the constituent unit (B-2), and the compound providing the constituent unit (B-3), which is 100 mol%. The diamine component may be composed only of a compound providing the constitutional unit (B-1), a compound providing the constitutional unit (B-2), and a compound providing the constitutional unit (B-3).

The compounds other than the compounds providing the constituent unit (B-1) and the compounds providing the constituent unit (B-2) that the diamine component may optionally contain are not limited to the compounds providing the constituent unit (B-3). Such arbitrary compounds 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 (B-1) and the compounds providing the constituent unit (B-2) 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 the aforementioned tetracarboxylic acid component and diamine component, an end-capping agent may also be used in the production of the polyimide resin. The end-capping agent is preferably a monoamine or a dicarboxylic acid. The amount of the introduced end-capping agent is preferably 0.0001 to 0.1 mol, and more preferably 0.001 to 0.06 mol, relative to 1 mol of the tetracarboxylic acid component. Examples of monoamine end-capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc., preferably benzylamine and aniline. The dicarboxylic acid end-capping agent is preferably a dicarboxylic acid, and a portion 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., 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, and 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 fed, and stirred at 0 to 80°C for 0.5 to 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 (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 picolinyl and pyridine; ester solvents such as acetic acid (2-methoxy-1-methylethyl ester), etc.

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. Moreover, specific examples of carbonate-based solvents include diethyl carbonate, ethyl methyl 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.

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 (TEA), 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 imidization catalysts 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 triethylamine.

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.

In the polyimide resin of the present invention, perhaps because the constituent unit A includes the constituent units (A-1) and (A-2), and the constituent unit B includes the constituent units (B-1) and (B-2), the polymer generated by the imidization reaction has a high solubility in the solvent and a transparent varnish can be obtained.

[Polyimide varnish] The polyimide varnish of the present invention is prepared 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. 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 in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or may be a polyimide solution diluted by adding a solvent.

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 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. Therefore, the polyimide film of the present invention is optically isotropic, and has excellent peeling properties and chemical resistance. 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 coating method includes spin coating, slit coating, knife coating and other known coating methods. Among them, slit coating is more ideal from the perspective 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 preferable 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 used (preferably 200-500°C, but not particularly limited). In addition, it is preferable 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 pressure. The method for peeling the polyimide film formed on the support from the support is not particularly limited, and a laser lift-off method or the like can be used.

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 between a tetracarboxylic acid component containing a compound providing the above-mentioned constituent unit (A-1) and a compound providing the above-mentioned constituent unit (A-2) and 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). 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 obtained by subjecting a tetracarboxylic acid component and a diamine component to an addition polymerization reaction in a reaction solvent, or may be a polyamide solution obtained by diluting the polyamide solution by adding a solvent.

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 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, more preferably 8 to 80 μm, and even more preferably 10 to 80 μm. With a thickness of 1 to 250 μm, it can be practically used as a self-supporting film. The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the polyimide varnish. [Example]

Hereinafter, the present invention will be specifically described 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 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) The residual stress was removed by heating the sample to a temperature sufficient to remove the residual stress under the conditions of sample size 2 mm × 20 mm, load 0.1 N, and heating rate 10°C/min in the tensile mode using a thermomechanical analyzer "TMA/SS6100" manufactured by Hitachi High-Tech Science Co., Ltd., and then cooling to room temperature. Thereafter, the elongation of the test piece was measured under the same conditions as the treatment for removing the residual stress, and the inflection point of the elongation was determined as the glass transition temperature.

(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 value is measured at a measuring wavelength of 590nm. 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

(7) Peelability The peelability was evaluated by cutting an 8 cm square incision in the polyimide film formed on the glass plate with a utility knife and peeling the film from the glass plate with tweezers. The film that could be peeled off even without being immersed in water was considered to have good peelability, while the film that could only be peeled off after being immersed in water was considered to have poor peelability. In Table 1, good peelability was rated as "A" and poor peelability was rated as "C". In addition, in the evaluations of (1) to (6) above, when a film immersed in water was used, the film was dried at 90°C for 1 hour before measurement and evaluation.

(8) Solvent 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. In addition, propylene glycol monomethyl ether acetate (PGMEA) was used as the solvent. The evaluation criteria for solvent resistance are as follows. A: No change on the film surface. B: Some microcracks on the film surface. C: There were cracks on the film surface, or the film surface was dissolved.

<Abbreviations of components, etc.> The tetracarboxylic acid components and diamine components used in the embodiments 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)) 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride

(Diamine component) 4,4’-DDS: 4,4’-diaminodiphenyl sulfone (manufactured by SEIKA 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-BACT: 1,4-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.; compound represented by formula (b-2b); trans ratio 85%) 6FODA: 4,4’-diamino-2,2’-bis(trifluoromethyl)diphenyl ether (manufactured by ChinaTech Chemical (Tianjin) Co., Ltd.; compound represented by formula (b-3)) 3,3’-DDS: 3,3’-diaminodiphenyl sulfone (manufactured by SEIKA Co., Ltd.)

<Manufacturing of polyimide resin, varnish, and polyimide film> Example 1 In 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, 12.415 g (0.050 mol) of 4,4'-DDS, 7.113 g (0.050 mol) of 1,4-BACT, and 55.496 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) were added, 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 15.511g (0.050 mol) of ODPA, 11.209g (0.050 mol) of HPMDA, and 13.874g of γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) to the solution at once, 0.506g of triethylamine (Kanto Chemical Co., Ltd.) as an imidization catalyst was added, and the temperature in the reaction system was raised to 190°C in about 20 minutes using a mantle heater. 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 kept at 190°C for about 5 hours of reflux. Then, 101.200 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) was added to make the solid content concentration 20% 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 to a glass plate by spin coating, and 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, thereby obtaining a thin film.

Example 2 The same procedure as in Example 1 was followed except that the amount of 1,4-BACT was changed from 7.113 g (0.050 mol) to 11.380 g (0.080 mol) and the amount of 4,4'-DDS was changed from 12.415 g (0.050 mol) to 4.966 g (0.020 mol) to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Example 3 The same procedure as in Example 1 was followed except that the amount of 1,4-BACT was changed from 7.113 g (0.050 mol) to 8.535 g (0.060 mol) and the amount of 4,4'-DDS was changed from 12.415 g (0.050 mol) to 9.932 g (0.040 mol) to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Example 4 The same procedure as in Example 1 was followed except that the amount of 4,4'-DDS was changed from 12.415 g (0.050 mol) to 4.966 g (0.020 mol) and 10.087 g (0.030 mol) of 6FODA was added to obtain a polyimide varnish having a solid content of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Example 5 Except that 7.113 g (0.050 mol) of 1,4-BACT was replaced with 7.113 g (0.050 mol) of 1,3-BAC, the same procedure as in Example 1 was followed to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Comparative Example 1 Except that 15.511 g (0.050 mol) of ODPA and 11.209 g (0.050 mol) of HPMDA were replaced with 44.424 g (0.100 mol) of 6FDA, the same procedure as in Example 1 was followed to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Comparative Example 2 Except that 11.209 g (0.050 mol) of HPMDA was replaced with 22.212 g (0.050 mol) of 6FDA, the same procedure as in Example 1 was followed to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Comparative Example 3 Except that 12.415 g (0.050 mol) of 4,4'-DDS was replaced with 12.415 g (0.050 mol) of 3,3'-DDS, the same procedure as in Example 1 was followed to obtain a polyimide varnish having a solid content concentration of 20% by mass. The obtained polyimide varnish was used to obtain a film in the same manner as in Example 1.

Comparative Example 4 The imidization reaction was carried out in the same manner as in Example 1 except that HPMDA was not used and the amount of ODPA was changed from 15.511 g (0.050 mol) to 31.021 g (0.100 mol). However, after adding triethylamine, the reaction solution became cloudy during the process of raising the temperature in the reaction system to 190°C, and no varnish was obtained.

Comparative Example 5 Other than not using 1,4-BACT and changing the amount of 4,4'-DDS from 12.415 g (0.050 mol) to 24.830 g (0.100 mol), and not using HPMDA and changing the amount of ODPA from 15.511 g (0.050 mol) to 31.021 g (0.100 mol), the imidization reaction was carried out in the same manner as in Example 1. However, after adding triethylamine, the reaction solution became cloudy during the process of raising the temperature in the reaction system to 190°C, and no varnish was obtained.

Comparative Example 6 Other than not using 1,4-BACT and changing the amount of 4,4'-DDS from 12.415 g (0.050 mol) to 24.830 g (0.100 mol), and not using ODPA and changing the amount of HPMDA from 11.209 g (0.050 mol) to 22.417 g (0.100 mol), the imidization reaction was carried out in the same manner as in Example 1. However, after adding triethylamine, the reaction solution became cloudy during the process of raising the temperature in the reaction system to 190°C, and no varnish was obtained.

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] 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 Comparison Example 6 Polyimide resin Tetracarboxylic acid component (numbers represent molar ratio) ODPA(a-1) 50 50 50 50 50 - 50 50 100 100 - HPMDA(a-2) 50 50 50 50 50 - - 50 - - 100 6FDA - - - - - 100 50 - - - - Diamine content (numbers represent molar ratio) 4,4'-DDS(b-1) 50 20 40 20 50 50 50 - 50 100 100 1,3-BAC(b-2a) - - - - 50 - - - - - - 1,4-BACT(b-2b) 50 80 60 50 - 50 50 50 50 - - 6FODA(b-3) - - - 30 - - - - - - - 3,3'-DDS - - - - - - - 50 - - - Film Evaluation Film thickness [μm] 9.7 5.6 8.5 9.0 9.0 8.9 8.5 9.1 No varnish available No varnish available No varnish available Tensile strength [MPa] 113 102 98 107 117 100 116 134 Tensile elastic modulus [GPa] 2.9 2.0 2.7 2.9 3.4 2.8 2.8 3.7 Tensile elongation at break [%] 8 7 6 8 6 4 8 5 Tg[℃] 266 223 262 267 262 283 279 250 Total light transmittance[%] 88.80 89.50 88.90 89.30 88.50 89.90 89.00 88.70 YI 1.84 1.28 1.60 1.90 2.90 1.60 1.77 2.50 Fog[%] 0.30 0.33 0.20 0.20 0.30 0.30 0.26 0.30 Rth[nm] 34 13 32 35 43 79 104 twenty one Converted to Rth[nm] of 10μm 35 twenty four 38 39 48 89 122 twenty three Separability A A A A A A A C Solvent resistance (PGMEA resistance) A A A A A C A A

As shown in Table 1, the polyimide film of the embodiment has good optical isotropy, and also excellent peeling property and chemical resistance. [Industrial Applicability]

The polyimide film containing the polyimide resin of the present invention has good optical isotropy, and also excellent peeling property and chemical resistance, and can be ideally used as a film for various components such as color filters, flexible displays, semiconductor parts, optical components, etc. The polyimide film containing the polyimide resin of the present invention can be particularly ideally used as a substrate for image display devices such as liquid crystal displays and OLED displays.

Claims (5)

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 a constituent unit (A-1) derived from a compound represented by the following formula (a-1) and a constituent unit (A-2) derived from a compound represented by the following formula (a-2); 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 constituent unit (B-2) of the compound represented by formula (b-2), wherein the molar ratio of the constituent unit (A-1) to the constituent unit (A-2) in constituent unit A [(A-1)/(A-2)] is 20/80 to 80/20, and the molar ratio of the constituent unit (B-1) to the constituent unit (B-2) in constituent unit B [(B-1)/(B-2)] is 5/95 to 80/20;

The polyimide resin of claim 1, wherein the ratio of the constituent unit (A-1) in the constituent unit A is 20 to 80 mol%, and the ratio of the constituent unit (A-2) in the constituent unit A is 20 to 80 mol%. For example, the polyimide resin of claim 1 or 2, 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%. A polyimide varnish is prepared by dissolving a polyimide resin as described in any one of claims 1 to 3 in an organic solvent. A polyimide film comprising a polyimide resin as described in any one of claims 1 to 3.