TWI896753B - Polymer composition, varnish, and polyimide film - Google Patents

Abstract

A polymer composition containing a polymer (X) that contains at least one repeating unit selected from the group consisting of repeating units represented by general formula (1) shown below and repeating units represented by general formula (2) shown below, and a compound (Y) represented by general formula (3) below. (In formula (1), X ¹represents a tetravalent group containing an alicyclic structure or an aromatic ring. In formula (2), X ²represents a tetravalent group containing an alicyclic structure or an aromatic ring, and R ¹and R ²each independently represent a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, or an alkylsilyl group of 3 to 9 carbon atoms. In formula (3), R ³is at least one group selected from the group consisting of alkyl groups of 1 to 30 carbon atoms, a phenyl group, alkoxy groups, an acryloyl group, a methacryloyl group, an acryloyloxyethyl group and a methacryloyloxyethyl group, and n is an integer of 0 to 2).

Description

Polymer composition, varnish, and polyimide film

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

Due to their excellent mechanical properties and heat resistance, polyimide resins have been studied for various applications in electrical and electronic components. For example, polyimide film substrates are being developed to replace the glass substrates used in display devices such as liquid crystal displays and OLED displays, with the goal of replacing them with polyimide film substrates. However, the recent increase in the functionality of electronic devices has necessitated the simultaneous fulfillment of a variety of performance requirements for electronic components. Consequently, attempts are underway to enhance the inherent properties of polyimide resins used in displays by incorporating various additives to enhance them.

For example, Patent Document 1 discloses a polyimide precursor composition containing a specific polyamide and a specific phosphorus compound, with the goal of improving heat resistance and mechanical properties while preventing crystallization and shortening layer formation time. The composition comprises a polyimide precursor containing a specific polyamide and a specific phosphorus compound. By heating the polyamide at a maximum temperature of 300-500°C, a polyimide film with a high water vapor transmission coefficient can be produced. Furthermore, Patent Document 2 discloses a polyimide precursor composition containing a polyimide precursor having specific repeating units and a phosphorus compound containing phosphorus atoms and having a boiling point below its decomposition temperature at 1 atmosphere and 350°C or lower, with the goal of obtaining a polyimide with transparency, heat resistance, and a low linear thermal expansion coefficient. [Prior Art Literature] [Patent Literature]

Patent Document 1: International Publication No. 2016/121817 Patent Document 2: International Publication No. 2015/080139

[The problem that the invention aims to solve]

As mentioned above, polyimide films are required to replace glass substrates, demanding not only mechanical properties and heat resistance but also high colorlessness and transparency. However, achieving both of these properties is difficult. Even with additives to improve heat resistance, preventing yellowing is challenging. In addition, to achieve colorlessness and transparency within the polyimide itself, aliphatic diamines and fluorinated diamines are generally used to inhibit the formation of charge transfer complexes within or between molecules. However, under the harsh conditions of TFT fabrication, such as those at temperatures above 350°C, aliphatic diamines lack the rigidity of aromatic diamines and are therefore less likely to exhibit heat resistance. Furthermore, the colorlessness and transparency of fluorinated diamines deteriorate at high temperatures. Therefore, there is a particular demand for polyimide films with excellent heat resistance and low yellowing. The present invention was made in light of this situation. The object of the present invention is to provide a polymer composition capable of producing a polyimide film having excellent heat resistance and low yellowness, a varnish containing the composition, and a polyimide film having excellent heat resistance and low yellowness. [Means for Solving the Problem]

The inventors of this case discovered that a polymer composition containing repeating units derived from a tetracarboxylic acid having a specific fluorinated diamine and an alicyclic or aromatic ring structure, and a specific phosphorus compound, can solve the above-mentioned problems and thus complete the invention.

That is, the present invention relates to the following [1] to [7]. [1] A polymer composition comprising: a polymer (X) comprising at least one selected from the group consisting of a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2), and a compound (Y) represented by the following general formula (3). [Chemistry 1] (In formula (1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring. In formula (2), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, and ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. In formula (3), ^R3 is at least one selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, and n is 0 to 2.) [2] The polymer composition as described in [1] above, wherein the repeating units represented by the above formula (1) account for 10 mol% or more of the total repeating units of the above polymer (X). [3] A polymer composition as described in [1] or [2] above, wherein the content of the repeating units represented by the formula (2) is 10 mol% or more relative to the total repeating units of the polymer (X). [4] A polymer composition as described in any one of [1] to [3] above, wherein the content of the compound (Y) is 10 ppm or more and 10,000 ppm or less relative to the polymer (X). [5] A varnish formed by dissolving the polymer composition as described in any one of [1] to [4] above in an organic solvent. [6] A polyimide film obtained by coating the varnish as described in [5] above on a support and heating the coating. [7] A method for producing a polyimide film, comprising coating the varnish as described in [5] above on a support. [Effects of the invention]

According to the present invention, a polymer composition capable of obtaining a polyimide film having excellent heat resistance and low yellowness, a varnish containing the composition, and a polyimide film having excellent heat resistance and low yellowness can be provided.

[Polymer composition] The polymer composition of the present invention comprises at least one polymer (X) selected from the group consisting of repeating units represented by the following general formula (1) and repeating units represented by the following general formula (2), and a compound (Y) represented by the following general formula (3). [Chemistry 2] (In formula (1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring. In formula (2), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, and ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. In formula (3), ^R3 is at least one selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, and n is 0 to 2.)

The polymer composition of the present invention is an excellent raw material for polyimide films. The reason why the resulting polyimide films exhibit excellent heat resistance and low yellowness is unclear, but is believed to be as follows. The polymer composition of the present invention contains a specific phosphorus compound. It is believed that by coordinating the phosphorus compound to the ends of the polyimide obtained by imidization of the polymer, or by reacting the ends of the polyimide with the phosphorus compound, side reactions and decomposition degradation at the ends, particularly at high temperatures, can be suppressed. Furthermore, the removal of fluorine from the fluorinated diamine can be suppressed, resulting in both heat resistance and low yellowness.

<Polymer (X)> The polymer (X) contained in the polymer composition of the present invention contains at least one selected from the group consisting of repeating units represented by the following general formula (1) and repeating units represented by the following general formula (2). [Chemistry 3] (In formula (1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring. In formula (2), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, and ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.)

The repeating units represented by the above general formula (1) contained in the polymer (X) are preferably repeating units represented by the following general formula (1-1). [Chemical 4] (In formula (1-1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring.)

The repeating units represented by the above general formula (2) contained in the polymer (X) are preferably repeating units represented by the following general formula (2-1). [Chemistry 5] (In formula (2-1), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, and ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.)

The polymer (X) contains at least one selected from the group consisting of the repeating units represented by the above-mentioned general formula (1) and the repeating units represented by the above-mentioned general formula (2). It may contain only one of the repeating units represented by the above-mentioned general formula (1) or the repeating units represented by the above-mentioned general formula (2), or it may contain both. That is, the polymer composition of the present invention may be a polyamic acid composition containing: a polyimide containing the repeating units represented by the following general formula (1) and a compound (Y) represented by the following general formula (3), [Chemistry 6] (In formula (1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring. In formula (3), ^R3 is at least one selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, and n is 0 to 2.) It may also be a polyamide composition comprising: a polyamide containing a repeating unit represented by the following general formula (2), and a compound (Y) represented by the following general formula (3). [Chemistry 7] (In formula (2), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. In formula (3), ^R3 is at least one selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, and n is 0 to 2.)

The polymer (X) preferably contains the repeating unit represented by the above general formula (1), and more preferably contains both the repeating unit represented by the above general formula (1) and the repeating unit represented by the above general formula (2).

In the above formula (1), X ¹ is a tetravalent group having an alicyclic structure or an aromatic ring. X ¹ is preferably a group obtained by removing two dianhydride moieties (four carboxyl groups) from tetracarboxylic dianhydride, which is a raw material for the structural unit A from tetracarboxylic dianhydride described below. In the above formula (2), X ² is a tetravalent group having an alicyclic structure or an aromatic ring. X ² is preferably a group obtained by removing two dianhydride moieties (four carboxyl groups) from tetracarboxylic dianhydride, which is a raw material for the structural unit A from tetracarboxylic dianhydride described below. In the above formula (2), R ¹ and R ² are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and are preferably hydrogen.

(Structure of Polymer (X)) As described above, polymer (X) contains at least one member selected from the group consisting of repeating units represented by the above-mentioned general formula (1) and repeating units represented by the above-mentioned general formula (2). It may contain only the repeating units represented by the above-mentioned general formula (1) or the repeating units represented by the above-mentioned general formula (2), or both. In particular, from the viewpoint of reducing yellowness and improving transparency, the repeating units represented by the above-mentioned formula (1) are preferably present in an amount of 10 mol% or more, more preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, even more preferably 90 mol% or more, and not more than 100 mol%. Furthermore, from the perspective of maintaining low yellowness while also improving heat resistance, the content of the repeating units represented by the above formula (2) relative to the total repeating units of the above polymer (X) is preferably 10 mol% or more, more preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, even more preferably 90 mol% or more, and not more than 100 mol%. In addition, when both the repeating units represented by the above general formula (1) and the repeating units represented by the above general formula (2) are contained, the molar ratio [(1)/(2)] of the repeating units represented by the above general formula (1) to the repeating units represented by the above general formula (2) is preferably 10/90 to 70/30, more preferably 20/80 to 60/40, and even more preferably 25/75 to 55/45.

<Structural Units of Polymer (X)> Polymer (X) contains at least one type selected from the group consisting of the repeating units represented by the above-mentioned general formula (1) and the repeating units represented by the above-mentioned general formula (2). The structural units constituting the polymer are described below.

The polymer (X) has a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from a diamine. Furthermore, although in the repeating unit represented by the general formula (1), the structural units A and B form an imide structure, and in the repeating unit represented by the general formula (2), the structural units A and B form an amide structure, in both cases, the structural units derived from tetracarboxylic dianhydride are collectively referred to as structural units A, and the structural units derived from diamine are collectively referred to as structural units B.

(Structural Unit A) Structural Unit A is a tetracarboxylic dianhydride-derived structural unit, and is at least one selected from the group consisting of structural units derived from alicyclic tetracarboxylic dianhydrides and structural units derived from aromatic tetracarboxylic dianhydrides. From the perspective of low yellowness and transparency, structural units derived from alicyclic tetracarboxylic dianhydrides are preferred, while from the perspective of heat resistance, structural units derived from aromatic tetracarboxylic dianhydrides are preferred.

Examples of the alicyclic tetracarboxylic dianhydride providing a structural unit derived from an alicyclic tetracarboxylic dianhydride include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, bicyclo[2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyltetracarboxylic dianhydride, 5,5'-(1,4-phenylene)-bis[hexahydro-4,7-methylisobenzofuran-1,3-dione], 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic dianhydride, or positional isomers thereof. Among these, compounds represented by the following formula (a1) are preferred from the viewpoint of low yellowness and transparency, and structural unit A preferably contains structural unit (A1) derived from the compound represented by formula (a1). [Chemistry 8] The compound represented by formula (a1) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride.

Aromatic tetracarboxylic dianhydrides having structural units derived from aromatic tetracarboxylic dianhydrides include, for example, biphenyltetracarboxylic dianhydride (BPDA), 9,9-bis(3,4-dicarboxyphenyl)fluoran anhydride (BPAF), pyromelitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfonate tetracarboxylic dianhydride, 3,3',4,4'-diphenylketone tetracarboxylic dianhydride, and 2,2',3,3'-diphenylketone tetracarboxylic dianhydride. Among these, from the perspective of achieving both heat resistance and low yellowness, at least one compound selected from the group consisting of compounds represented by the following formula (a2) and compounds represented by the following formula (a3) is preferred, and the compound represented by the following formula (a2) is more preferred. That is, the structural unit A preferably contains at least one selected from the group consisting of the structural unit (A2) derived from the compound represented by the following formula (a2) and the structural unit (A3) derived from the compound represented by the following formula (a3), and more preferably contains the structural unit (A2) derived from the compound represented by the following formula (a2). [Chemistry 9]

The compound represented by formula (a2) is biphenyltetracarboxylic dianhydride (BPDA). Specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by formula (a2s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by formula (a2a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by formula (a2i). Among them, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by formula (a2s) is preferred. [Chemical 10]

The compound represented by formula (a3) is 9,9'-bis(3,4-dicarboxyphenyl)fluoranic anhydride (BPAF).

Structural unit A may contain structural units other than aromatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides. The tetracarboxylic dianhydrides providing such structural units are not particularly limited, and examples include aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. The structural units optionally contained in structural unit A may be one or two or more. In this specification, aromatic tetracarboxylic dianhydrides refer to tetracarboxylic dianhydrides containing one or more aromatic rings; alicyclic tetracarboxylic dianhydrides refer to tetracarboxylic dianhydrides containing one or more alicyclic rings and no aromatic rings; and aliphatic tetracarboxylic dianhydrides refer to tetracarboxylic dianhydrides containing neither aromatic nor alicyclic rings.

(Structural unit B) Structural unit B is a structural unit derived from a diamine and contains a structural unit (B1) derived from a compound represented by formula (b1). Due to the inclusion of structural unit (B1) in structural unit B, heat resistance is excellent, and in particular, when combined with compound (Y), the effect of reducing yellowness is excellent. The ratio of structural unit (B1) in structural unit B is preferably 45 mol% or more, more preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of this ratio is not particularly limited and is 100 mol% or less. [Chemical 11]

The structural unit (B1) preferably contains a structural unit (B11) derived from a compound represented by the following formula (b11). The structural unit (B1) preferably contains a structural unit (B11) derived from a compound represented by the following formula (b11). [Chemical 12]

The compound represented by formula (b11) is 2,2'-bis(trifluoromethyl)-4,4'-diaminediphenyl ether (6FODA). By including structural unit (B11) in structural unit B, particularly when combined with compound (Y), the yellowness is significantly reduced.

Structural unit B may contain structural units other than structural unit (B1). There are no particular restrictions on the diamines that provide such structural units, and examples thereof include 4-aminophenyl-4-aminobenzoic acid (4-BAAB), 3,5-diaminobenzoic acid (3,5-DABA), 9,9-bis(4-aminophenyl)fluorene, 1,4-phenylenediamine, p-xylylenediamine, 1,5-naphthalenediamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)- Aromatic diamines such as bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzamide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)-p-phenylamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.

Among these, the compound represented by the following formula (b2) is preferred, and the structural unit B preferably contains a structural unit (B2) derived from the compound represented by formula (b2). [Chemistry 13] The compound represented by formula (b2) is 4-aminophenyl-4-aminobenzoic acid (4-BAAB).

In this specification, an aromatic diamine refers to a diamine containing one or more aromatic rings; an alicyclic diamine refers to a diamine containing one or more alicyclic rings and no aromatic rings; and an aliphatic diamine refers to a diamine containing neither aromatic nor alicyclic rings. The structural units optionally contained in structural unit B may be one or more.

(Production Method of Polymer (X)) Polymer (X) can be produced by any method, but the following method is preferred. As described above, polymer (X) contains either or both of the repeating units represented by general formula (1) (i.e., the imide moiety) and the repeating units represented by general formula (2) (i.e., the amide moiety). This can be adjusted by varying the production method. Specifically, in the production method (production method of an imide-amide copolymer) when both the repeating unit represented by formula (1) and the repeating unit represented by formula (2) are contained, by using only the step of producing the portion (polyimide portion) containing the repeating unit represented by formula (1) as the main component, a polymer (X) (polyamide) substantially composed of the repeating unit represented by formula (1) can be obtained; by using only the step of producing the portion (polyamide portion) containing the repeating unit represented by formula (2) as the main component, a polymer (X) (polyamide) substantially composed of the repeating unit represented by formula (2) can be obtained.

A polymer (X) containing both the repeating unit represented by formula (1) and the repeating unit represented by formula (2) (hereinafter also referred to as an imide-amide copolymer) is preferably prepared by a method comprising the following steps 1 and 2. Step 1: A step of reacting a tetracarboxylic acid component constituting the imide portion with a diamine component to obtain an imide oligomer. Step 2: A step of reacting the imide oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the amide portion to obtain an imide-amide copolymer.

Alternatively, by reacting the entire tetracarboxylic acid component with the diamine component in step 1, a polymer (X) (polyimide) consisting essentially of repeating units represented by formula (1) can be obtained. Specifically, the method for producing a polymer (X) (polyimide) consisting essentially of repeating units represented by formula (1) is to interpret step 1 as "a step of reacting the tetracarboxylic acid component constituting the polyimide with the diamine component to obtain the polyimide." Alternatively, by reacting the entire tetracarboxylic acid component with the diamine component in step 2 without performing step 1, a polymer (X) (polyamide) consisting essentially of repeating units represented by formula (2) can be obtained. Specifically, the method for producing a polymer (X) (polyamide) substantially composed of repeating units represented by formula (2) is to interpret the above-mentioned step 2 as "a step of reacting a tetracarboxylic acid component constituting polyamide with a diamine component to obtain polyamide."

[Step 1] Step 1 is a step of reacting a tetracarboxylic acid component constituting the imide moiety with a diamine component to obtain an imide oligomer. The tetracarboxylic acid component used in Step 1 preferably contains a compound that provides structural unit (A1), and is preferably used in its entirety in Step 1. It may also contain a tetracarboxylic acid component other than the compound that provides structural unit (A1). The tetracarboxylic acid component other than the compound that provides structural unit (A1) is preferably a compound that provides structural unit (A2) or a compound that provides structural unit (A3). The diamine component used in Step 1 preferably contains a compound that provides structural unit (B1). It may also contain a diamine component other than the compound that provides structural unit (B1) as long as it does not impair the effects of the present invention. The tetracarboxylic acid component other than the compound providing structural unit (B1) is preferably a compound providing structural unit (B2). In step 1, the diamine component is preferably present in an amount of 1.01 to 2 mol, more preferably 1.05 to 1.9 mol, and even more preferably 1.1 to 1.7 mol relative to the tetracarboxylic acid component. In addition, when obtaining a polymer (X) (polyimide) substantially composed of repeating units represented by formula (1), the diamine component is preferably present in an amount of 0.9 to 1.1 mol relative to the tetracarboxylic acid component.

The method for reacting the tetracarboxylic acid component and the diamine component to obtain the imide oligomer in step 1 is not particularly limited, and a known method can be used. Specific reaction methods include: (1) a method in which the tetracarboxylic acid component, the diamine component, and the reaction solvent are charged into a reactor, stirred at 10 to 110°C for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which the diamine component and the reaction solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged, stirred at 10 to 110°C for 0.5 to 30 hours as needed, and then the temperature is raised to carry out the imidization reaction; (3) a method in which the tetracarboxylic acid component, the diamine component, and the reaction solvent are charged into a reactor, and the temperature is directly raised to carry out the imidization reaction.

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

In the above-mentioned imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include alkaline catalysts and acid catalysts. Examples of alkaline catalysts include organic alkaline catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic alkaline catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate. Examples of acid catalysts include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. These imidization catalysts may be used alone or in combination of two or more. Among these, from the perspective of operability, base catalysts are preferred, more preferably organic base catalysts, more preferably at least one selected from triethylamine and triethylenediamine, and even more preferably triethylamine.

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

The imide oligomer obtained in step 1 preferably has an imide repeating structural unit formed from a compound providing structural unit (A1) and a compound providing structural unit (B1). The above method can produce a solution containing the imide oligomer dissolved in a solvent. The solution containing the imide oligomer obtained in step 1 may contain at least a portion of the components used as the tetracarboxylic acid component and the diamine component in step 1 as unreacted monomers, as long as the effects of the present invention are not impaired.

[Step 2] Step 2 of the production method of the present invention involves reacting the imide oligomer obtained in Step 1 with a tetracarboxylic acid component and a diamine component constituting the amide portion to produce an imide-amide copolymer.

The tetracarboxylic acid component used in Step 2 preferably contains a compound that provides structural unit (A1), and the entire amount thereof is preferably used in Step 1. It may also contain a tetracarboxylic acid component other than the compound that provides structural unit (A1). The tetracarboxylic acid component other than the compound that provides structural unit (A1) is preferably a compound that provides structural unit (A2) or a compound that provides structural unit (A3). The diamine component used in Step 2 preferably contains a compound that provides structural unit (B1). It may also contain a diamine component other than the compound that provides structural unit (B1) as long as the effects of the present invention are not impaired. The tetracarboxylic acid component other than the compound that provides structural unit (B1) is preferably a compound that provides structural unit (B2). In addition, when a polymer (X) (polyamide) substantially composed of repeating units represented by formula (2) is obtained by performing only step 2, the diamine component is preferably set to 0.9 to 1.1 mol relative to the tetracarboxylic acid component.

In step 2, the method for reacting the tetracarboxylic acid component and the diamine component with the imide oligomer obtained in step 1 is not particularly limited, and a known method can be used. Specific reaction methods include (1) a method in which the imide oligomer obtained in step 1, the tetracarboxylic acid component, the diamine component, and the solvent are charged into a reactor and stirred at a temperature in the range of 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours; (2) a method in which the imide oligomer obtained in step 1 and the solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component and the diamine component are charged and stirred at a temperature in the range of 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out below 80°C, the molecular weight of the copolymer obtained in step 2 does not vary depending on the temperature history during polymerization. Furthermore, the progress of thermal imidization is suppressed, enabling stable production of the copolymer.

The above method can produce a copolymer solution containing an imide-amidite copolymer dissolved in a solvent. Alternatively, by performing only step 1, a polyimide solution containing polyimide can be obtained, and by performing only step 2, a polyamidite solution containing polyamidite can be obtained. The copolymer concentration in the resulting solution is generally 1-50% by mass, preferably 3-35% by mass, and more preferably 5-30% by mass. The polyimide resin concentration in the resulting solution is generally 1-50% by mass, preferably 3-35% by mass, and more preferably 5-30% by mass. Furthermore, the concentration of polyamine in the resulting solution is generally 1-50% by mass, preferably 3-35% by mass, and more preferably 5-30% by mass.

The number average molecular weight of the imide-amidite copolymer obtained by the above production method is preferably 5,000 to 500,000 from the perspective of the mechanical strength of the resulting polyimide film. Furthermore, the weight average molecular weight (Mw) is preferably 10,000 to 800,000, and more preferably 100,000 to 300,000. The number average molecular weight and weight average molecular weight of the copolymer can be determined, for example, by converting the values to standard polymethyl methacrylate (PMMA) measured by gel filtration chromatography. The number average molecular weight of the polyimide obtained by the above production method is preferably 5,000 to 500,000 from the perspective of the mechanical strength of the resulting polyimide film. Furthermore, from the same perspective, the weight-average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000. The number-average molecular weight of the polyamide obtained by the above production method is preferably 5,000 to 500,000 from the perspective of the mechanical strength of the resulting polyimide film. Furthermore, from the same perspective, the weight-average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000. Next, the raw materials used in this production method are described.

[Tetracarboxylic Acid Component] The tetracarboxylic acid component used as a raw material in this production method can be, for example, a compound represented by formula (a1), but is not limited thereto. A derivative thereof can also be used within the scope of providing the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the compound represented by formula (a1) and alkyl esters of such tetracarboxylic acids. The compound providing the structural unit (A1) is preferably a compound represented by formula (a1). Similarly, the compound providing the structural unit (A2) can be, for example, a compound represented by formula (a2), but is not limited thereto. A derivative thereof can also be used within the scope of providing the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the compound represented by formula (a2) and alkyl esters of such tetracarboxylic acids. The compound providing the structural unit (A2) is preferably a compound represented by formula (a2). Furthermore, the compound providing the structural unit (A3) may be, for example, a compound represented by formula (a3), but is not limited thereto and may also be a derivative thereof within the scope of providing the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the compound represented by formula (a3) and alkyl esters of such tetracarboxylic acids. The compound providing the structural unit (A3) is preferably a compound represented by formula (a3).

[Diamine Component] The diamine component used as a raw material in this production method can be, for example, a diamine, but is not limited to this, and can also be a derivative thereof within the scope of providing the same structural unit. Examples of such derivatives include diisocyanates corresponding to diamines. The compound providing structural unit (B1) is preferably a diamine. Similarly, the compound providing structural unit (B2) can be, for example, a diamine, but is not limited to this, and can also be a derivative thereof within the scope of providing the same structural unit. Examples of such derivatives include diisocyanates corresponding to diamines. The compound providing structural unit (B2) is preferably a diamine.

In the present invention, the feed ratio of the tetracarboxylic acid component and the diamine component used in all steps of the copolymer production including step 1 and step 2 is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

[End-capping agent] In addition to the aforementioned tetracarboxylic acid component and diamine component, an end-capping agent may also be used in the production of polymer (X). When both steps 1 and 2 are performed, the end-capping agent is preferably used in step 2. The end-capping agent is preferably a monoamine or a dicarboxylic acid. The amount of the end-capping agent introduced is preferably 0.0001 to 0.1 mol, particularly preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Recommended monoamine end-capping agents include, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline. Among these, benzylamine and aniline are preferably used. The dicarboxylic acid end-capping agent is preferably a dicarboxylic acid, some of which may be ring-closed. Recommended examples include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-diphenyl ketone dicarboxylic acid, 3,4-diphenyl ketone dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid. Among these, phthalic acid and phthalic anhydride are particularly suitable.

[Solvent] The solvent used in the production method of polymer (X) can be any solvent capable of dissolving the resulting imide-amide copolymer. Examples include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

Specific examples of aprotic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphamide and hexamethylphosphinotriamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and cyclobutane sulfone; ketone solvents such as acetone, butanone, cyclohexanone, and methylcyclohexanone; and ester solvents such as 2-methoxy-1-methylethyl acetic acid.

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, and 3,5-xylenol. 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, and 1,4-dioxane. Specific examples of carbonate-based solvents include ethyl carbonate, methyl ethyl carbonate, ethyl carbonate, and propyl carbonate. Among the above-mentioned reaction solvents, amide solvents or lactone solvents are preferred, amide solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above-mentioned reaction solvents may be used alone or in combination of two or more.

<Compound (Y)> The compound (Y) contained in the polymer composition of the present invention is represented by the following general formula (3). (In formula (3), R ³ is at least one selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, and n is 0 to 2.) By containing compound (Y), a film having heat resistance and low yellowness can be obtained, and the transparency of the film can be improved.

In formula (3), R ³ is at least one member selected from the group consisting of an alkyl group having 1 to 30 carbon atoms, a phenyl group, an alkoxy group, an acryl group, a methacryl group, an acryloxyethyl group, and a methacryloxyethyl group, preferably an alkyl group having 1 to 30 carbon atoms. A plurality of R ³ s may be the same or different, preferably the same. n is 0 to 2, preferably 1 to 2.

Compound (Y) is a phosphorus compound. Specific examples of compound (Y) include at least one selected from the group consisting of acidic phosphates and phosphoric acid, preferably an acidic phosphate. Examples of acidic phosphates include isotridecyl acid phosphate and dibutyl phosphate, preferably isotridecyl acid phosphate.

The content of compound (Y) relative to polymer (X) is preferably from 10 ppm to 10,000 ppm, more preferably from 100 ppm to 5,000 ppm, and even more preferably from 500 ppm to 2,000 ppm. When the amount of compound (Y) is within this range, a heat-resistant film with low yellowing can be obtained, and the transparency of the film can be improved. In this specification, "ppm" means parts per million by mass.

[Varnish] The varnish of the present invention is formed by dissolving the aforementioned polymer composition in an organic solvent. Specifically, the varnish of the present invention is formed by dissolving polymer (X) and compound (Y) in an organic solvent. The varnish of the present invention contains polymer (X), compound (Y), and an organic solvent, with polymer (X) and compound (Y) dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves polymer (X) and compound (Y). The solvent used in the production of polymer (X) is preferably a single solvent or a mixture of two or more of the aforementioned compounds. The varnish of the present invention may be obtained by mixing and dissolving compound (Y) in the aforementioned polymer (X) solution, or by further adding a diluting solvent.

When the polymer (X) contained in the varnish of the present invention contains a repeating unit (amidine moiety) represented by formula (2), from the perspective of efficiently progressing the imidization of the imidization moiety, an imidization catalyst and a dehydration catalyst may be further contained. The imidization catalyst can be any one having a boiling point of 40°C to 180°C, and an amine compound having a boiling point of 180°C or less is suitable. If the imidization catalyst has a boiling point of 180°C or less, there is no risk of the film being stained or deteriorating in appearance during high-temperature drying after film formation. In addition, if the imidization catalyst has a boiling point of 40°C or more, the possibility of volatilization before sufficient imidization can be avoided. Examples of amine compounds suitable for use as imidization catalysts include pyridine and picoline. These imidization catalysts may be used alone or in combination of two or more. Examples of dehydration catalysts include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may also be used alone or in combination of two or more.

The polymer (X) contained in the varnish of the present invention is solvent-soluble, allowing it to be formed into a high-concentration varnish. The varnish of the present invention preferably contains 3-40% by mass of polymer (X), more preferably 5-40% by mass, and even more preferably 10-30% by mass. The viscosity of the varnish is preferably 0.1-100 Pa·s, more preferably 0.1-20 Pa·s. The viscosity of the varnish is measured at 25°C using an E-type viscometer. Furthermore, the varnish of the present invention may contain various additives, such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoaming agents, fluorescent brighteners, crosslinking agents, polymerization initiators, and photosensitizers, as long as the required properties of the polyimide film are not compromised. The production method of the varnish of the present invention is not particularly limited, and known methods may be used.

[Polyimide Film and Method for Producing Polyimide Film] When polymer (X) contains a repeating unit (amidite moiety) represented by formula (2), the polyimide film of the present invention contains a polyimide resin formed by imidizing the amino acid moiety of polymer (X) and compound (Y). Furthermore, when polymer (X) is a polyimide, the film contains the polyimide, or a polyimide resin whose molecular weight is adjusted by further heating, and compound (Y). Therefore, the polyimide film of the present invention has excellent heat resistance and low yellowness. The polyimide film of the present invention can be produced using the above-mentioned varnish.

The method for producing a polyimide film using the varnish of the present invention is not particularly limited, but the following method is preferably used. That is, preferably, the varnish is applied to a support and then heated. Specifically, a varnish formed by dissolving the polymer (X) and the compound (Y) in an organic solvent is applied to the support and then heated. Furthermore, the polyimide film of the present invention is preferably a polyimide film obtained by applying the varnish described above to a support and then heating. Specifically, a varnish formed by dissolving the polymer (X) and the compound (Y) in an organic solvent is applied to the support and then heated.

The support may be a smooth glass plate, metal plate, or plastic. After applying a varnish onto the support or forming it into a film, the varnish is heated to remove organic solvents such as the reaction solvent and diluent solvent, thereby forming a polymer film. If the polymer contained in the polymer film contains an amide moiety, the amide moiety undergoes imidization (dehydration and ring closure) by heating and is then peeled off from the support, thereby producing a polyimide film. The weight-average molecular weight (Mw) of the polyimide resin contained in the polyimide film of the present invention is preferably 10,000 to 800,000, more preferably 30,000 to 500,000, more preferably 50,000 to 400,000, and even more preferably 100,000 to 300,000, from the perspective of the mechanical strength of the film. The weight-average molecular weight of the copolymer can be determined, for example, by converting the value to standard polymethyl methacrylate (PMMA) measured by gel filtration chromatography.

The heating temperature for drying the varnish of the present invention to obtain a polymer film is preferably 50-150°C. The heating temperature for imidization of the polymer is preferably 200-500°C, more preferably 250-450°C, and even more preferably 300-400°C. Furthermore, the heating time is generally 1 minute to 6 hours, preferably 5 minutes to 2 hours, and even more preferably 15 minutes to 1 hour. The heating gas environment may include air, nitrogen, oxygen, hydrogen, or a nitrogen/hydrogen mixture. To prevent coloration of the resulting polyimide resin, nitrogen with an oxygen concentration of 100 ppm or less and nitrogen/hydrogen mixtures with a hydrogen concentration of 0.5% or less are preferred. In addition, the imidization method is not limited to thermal imidization; chemical imidization can also be used.

The thickness of the polyimide film of the present invention can be appropriately selected based on the intended application, preferably ranging from 1 to 250 μm, more preferably from 5 to 100 μm, and even more preferably from 5 to 50 μm. A thickness of 1 to 250 μm allows practical use as a self-supporting film. The thickness of the polyimide film can be easily controlled by adjusting the solids concentration and viscosity of the varnish.

The polymer composition of the present invention can produce a polyimide film with excellent heat resistance and low yellowness. The resulting polyimide film has excellent heat resistance and low yellowness. Suitable physical properties of the film are as follows: For a film with a thickness of 10 μm, the total light transmittance is preferably 85% or higher, more preferably 87% or higher, and even more preferably 89% or higher. For a film with a thickness of 10 μm, the yellowness index (YI) is preferably 12 or lower, more preferably 11 or lower. For excellent colorlessness, the YI is preferably 9 or lower, more preferably 8 or lower. Furthermore, the 1% weight loss temperature is preferably 430°C or higher, more preferably 480°C or higher, even more preferably 500°C or higher, and even more preferably 510°C or higher. Here, the 1% weight loss temperature refers to the temperature at which the polyimide film is heated to 40-550°C at a rate of 10°C/min, resulting in a 1% weight loss relative to the film's weight at 300°C. Specifically, the aforementioned physical properties of the present invention can be measured using the methods described in the Examples.

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

The present invention is described in detail below using examples. However, the present invention is not limited to these examples. The physical properties of the films obtained in the examples and comparative examples were measured using the methods described below.

(1) Film Thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Co., Ltd. The film thickness of Example 5 and Comparative Example 6 was measured using a film thickness meter Filmetrics F20 (manufactured by Filmetrics Co., Ltd.).

(2) Total light transmittance and yellowness (YI) Total light transmittance was measured in accordance with JIS K7105:1981, and YI was measured in accordance with ASTM D1925 (illuminant C, 2°) using the COH7700 color and turbidity simultaneous tester manufactured by Nippon Denshoku Industries Co., Ltd.

(3) 1% weight loss temperature (Td1%) A differential thermal and thermogravimetric simultaneous measurement device "NEXTA STA200RV" manufactured by Hitachi High-Tech Science Co., Ltd. was used. The sample was heated to 40-150°C at a heating rate of 10°C/min, maintained at 150°C for 30 minutes, and then heated to 550°C after removing moisture. The temperature at which the weight decreased by 1% was compared with the weight after maintaining at 150°C for 30 minutes. The 1% weight loss temperature was defined as the temperature at which the weight decreased by 1%. The larger the weight loss temperature value, the better.

The tetracarboxylic acid components and diamine components used in Examples and Comparative Examples, and their abbreviations are as follows. <Tetracarboxylic acid component> CpODA: Norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (Compound represented by Formula (a1)) s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi Chemical Co., Ltd., Compound represented by Formula (a2s)) BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluoranic anhydride (JFE Chemical Co., Ltd., Compound represented by Formula (a3)) <Diamine component> 6FODA: 2,2'-bis(trifluoromethyl)-4,4'-diaminediphenyl ether (Compound represented by Formula (b11)) 4-BAAB: 4-aminophenyl-4-aminobenzoic acid (Nippon Junryo Pharmaceutical Co., Ltd., Compound represented by Formula (b2)) <Phosphorus compound> JP-513: Isotridecyl acid phosphate (manufactured by Johoku Chemical Industry Co., Ltd., a 1:1 mixture of a compound wherein ^R3 is isotridecyl and n is 1 in formula (3), and a compound wherein ^R3 is isotridecyl and n is 2) DBP: Dibutyl phosphate (manufactured by Johoku Chemical Industry Co., Ltd., a compound wherein ^R3 is butyl and n is 2 in formula (3)) Phosphoric acid: a compound wherein n is 0 in formula (3) Trimethyl phosphate: a compound wherein ^R3 is methyl and n is 3 in formula (3) Triphenylphosphine: a compound wherein ^R3 is phenyl and n is 3 in formula (3) <Other compounds> Irganox 1010 (antioxidant): Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (manufactured by BASF JAPAN Co., Ltd.) <Surface conditioner> BYK-378: Silicone resin surface conditioner (manufactured by BYK-Chemie Japan Co., Ltd.)

The abbreviations for solvents and catalysts used in the Examples and Comparative Examples are as follows. NMP: N-methyl-2-pyrrolidone (manufactured by Tokyo Junyaku Industries, Ltd.) TEA: triethylamine (manufactured by Kanto Chemical Co., Ltd.)

Example 1 Into a 500 mL, five-necked round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet, a Dean-Stark apparatus with a cooling tube, a thermometer, and glass end caps, 26.899 g (0.0800 mol) of 6FODA and 94.146 g of NMP were added. The mixture was stirred at 200 rpm at a temperature of 50°C under a nitrogen atmosphere to obtain a solution. To this solution, 23.536 g (0.0800 mol) of s-BPDA and 23.536 g of NMP were added at once and stirred for 5 hours at 50°C using a mantle heater. Next, 84.059 g of NMP was added for homogenization, and the mixture was returned to room temperature to obtain a polyamine varnish with a solids concentration of 20% by mass. To 100 g of the resulting varnish were added 0.02 g of JP-513 (1000 ppm relative to polyamine) and 0.02 g of BYK-378 (1000 ppm relative to polyamine), and the mixture was stirred for 30 minutes for homogenization to obtain a polyamine composition varnish. The resulting polyimide composition varnish was then spin-coated onto a glass plate and maintained at 80°C on a hot plate for 20 minutes. The varnish was then transferred to a hot air dryer and heated at a rate of 5°C/min to 420°C under a nitrogen atmosphere. The varnish was then heated in a hot air dryer at 420°C for 60 minutes under a nitrogen atmosphere to evaporate the solvent and achieve imidization, yielding a polyimide film. The results are shown in Table 1.

Examples 2, 3, and Comparative Examples 2-4 Polyimide films were obtained by the same method as in Example 1, except that 0.02 g of each of the phosphorus compounds or other compounds listed in Table 1 (1000 ppm relative to the polyamide) was used in place of 0.02 g of JP-513 (1000 ppm relative to the polyamide). The results are shown in Table 1.

Comparative Example 1 A polyimide film was obtained using the same method as in Example 1, except that JP-513 was not used. The results are shown in Table 1.

Example 4 A polyamide composition varnish was obtained by the same method as in Example 1, except that 0.0800 mol of CpODA was used in place of 23.536 g (0.0800 mol) of s-BPDA. After adding all the raw materials at once, the temperature was maintained at 10°C and stirring was continued for 5 hours. The resulting polyimide composition varnish was then applied to a glass plate by spin coating and maintained at 80°C on a hot plate for 20 minutes. The varnish was then transferred to a hot air dryer and heated at a rate of 5°C/min to 420°C under a nitrogen atmosphere. The film was then heated in the hot air dryer at 420°C for 60 minutes under a nitrogen atmosphere to evaporate the solvent, yielding a polyimide film. The results are shown in Table 1.

Comparative Example 5 A polyimide film was obtained using the same method as in Example 4, except that JP-513 was not used. The results are shown in Table 1.

Example 5 Into a 500 mL, five-necked round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet, a Dean-Stark apparatus equipped with a cooling tube, a thermometer, and glass end caps, 10.087 g (0.030 mol) of 6FODA and 47.017 g of NMP were added. The mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70°C to obtain a solution. To this solution, 9.169 g (0.020 mol) of BPAF and 11.754 g of NMP were added at once. Then, 0.101 g of TEA was added as an imidization catalyst. The reaction system was heated using a heating pack, raising the temperature to 190°C over approximately 20 minutes. The distilled components were collected, and the reaction system was maintained at 190°C under reflux for 1 hour while adjusting the rotational speed according to the viscosity increase. Then, 147.043 g of NMP was added, and the reaction system was cooled to 50°C, yielding a solution containing an oligomer with repeating imide units. To this solution, 23.538 g (0.080 mol) of s-BPDA, 15.978 g (0.070 mol) of 4-BAAB, and 26.386 g of NMP were added all at once, and the mixture was stirred at 50°C for 5 hours. NMP was then added to homogenize the mixture to a solids concentration of approximately 15% by mass, yielding a varnish containing a copolymer having imide repeating structural units and amide structural units (imide-amide copolymer varnish). To 100 g of the resulting varnish were added 0.015 g (1000 ppm relative to the imide-amide copolymer) of JP-513 and 0.015 g (1000 ppm relative to the imide-amide copolymer) of BYK-378. The mixture was stirred for 30 minutes to homogenize the mixture, yielding an imide-amide copolymer composition varnish. The resulting imide-amidite copolymer varnish was then applied to a glass plate by spin coating and maintained at 80°C on a hot plate for 20 minutes. The varnish was then transferred to a hot air dryer and heated at a rate of 5°C/min to 430°C in a nitrogen atmosphere. The varnish was then heated in a hot air dryer at 430°C for 60 minutes in a nitrogen atmosphere to evaporate the solvent and thermally imidize the film, yielding a polyimide film. The results are shown in Table 1.

Comparative Example 6 A polyimide film was obtained by the same method as in Example 5, except that JP-513 was not used. The results are shown in Table 1. Because the polyimide film obtained in Comparative Example 6 could not be peeled off from the glass plate, the total light transmittance and yellowness (YI) of Example 5 and Comparative Example 6 were measured with the glass plate included. Furthermore, the 1% weight loss temperature (Td1%) was not measured for the polyimide film obtained in Comparative Example 6.

[Table 1]

As shown in Table 1, the polyimide film obtained from the polymer composition of the present invention has excellent heat resistance and low yellowness. In addition, the polyimide film obtained from the polymer composition of the present invention also has excellent transparency.

Claims (6)

A polymer composition comprising: a polymer (X) comprising at least one selected from the group consisting of a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2), and a compound (Y) represented by the following general formula (3); In formula (1), ^X1 is a tetravalent group having an alicyclic structure or an aromatic ring; in formula (2), ^X2 is a tetravalent group having an alicyclic structure or an aromatic ring, ^R1 and ^R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms; in formula (3), ^R3 is an alkyl group having 1 to 30 carbon atoms, and n is 0 to 2; the content of compound (Y) is greater than 10 ppm and less than 10,000 ppm relative to polymer (X). The polymer composition of claim 1, wherein the repeating unit represented by formula (1) accounts for 10 mol% or more relative to all repeating units of the polymer (X). The polymer composition of claim 1 or 2, wherein the repeating unit represented by formula (2) accounts for 10 mol% or more relative to all repeating units of the polymer (X). A varnish is formed by dissolving the polymer composition according to any one of claims 1 to 3 in an organic solvent. A polyimide film is obtained by coating the varnish of claim 4 on a support and heating the support. A method for manufacturing a polyimide film comprises coating the varnish of claim 4 on a support and heating the support.