Polyimide precursor composition and polyimide film

Abstract

The present invention provides a polyimide precursor composition for producing an aromatic polyimide film in which light transmittance and / or heat resistance is improved. The polyimide precursor composition comprises: a polyimide precursor having a repeating unit represented by formula (I); a solvent A selected from among 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N,N-dimethylpropanamide, 1-butyl-2-pyrrolidone, N,N-diphenylformamide, N,N-diethylbenzamide, benzanilide, and 1-phenyl-2-pyrrolidone; and a solvent B selected from among N,N-dimethylpropionamide, N,N-diethylformamide, N,N-diethylacetamide N,N-dimethylisobutylamide, N,N-diethylpropionamide, and tetramethyl urea. (In the formula, R1 and R2 are each a hydrogen atom or the like, and not less than 50 mol% of X1 is an aromatic group and / or not less than 50 mol% of Y1 is an aromatic group.)

Description

Polyimide precursor composition and polyimide film

[0001] The present invention relates to a polyimide precursor composition suitable for use in electronic devices such as substrates for flexible devices, and to a polyimide film having excellent heat resistance.

[0002] Polyimide films have been widely used in fields such as electrical and electronic devices and semiconductors due to their excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability. Meanwhile, with the advent of an advanced information society in recent years, the development of optical materials such as optical fibers and optical waveguides in the optical communications field, and liquid crystal alignment films and protective films for color filters in the display device field has progressed. Particularly in the display device field, there has been active research into lightweight and highly flexible plastic substrates as an alternative to glass substrates, and the development of displays that can be bent or rolled.

[0003] Displays such as liquid crystal displays and organic electroluminescence displays (EL) displays use semiconductor elements such as thin-film transistors (TFTs) to drive each pixel. Therefore, substrates must have heat resistance and dimensional stability. Polyimide film is a promising substrate for displays because of its excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability.

[0004] Polyimide is generally colored yellowish-brown, which has limited its use in transmission devices such as backlit liquid crystal displays. However, in recent years, polyimide films have been developed that have excellent optical transparency in addition to mechanical and thermal properties, and expectations are growing for polyimide films as substrates for display applications (see Patent Documents 1 to 4).

[0005] N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) are commonly used as solvents for producing polyimides. On the other hand, Patent Document 5 discloses that certain organic solvents are superior to NMP.

[0006] International Publication No. WO 2012 / 011590 International Publication No. WO 2013 / 179727 International Publication No. WO 2014 / 038715 International Publication No. WO 2022 / 176956 International Publication No. WO 2015 / 186782

[0007] Compared with the (semi)alicyclic polyimides described in Patent Documents 1 to 4, aromatic polyimides have problems with coloration, but because they generally have excellent heat resistance, they may be usable as substrates for display applications if coloration is reduced as much as possible. While film formation methods for thin film transistors (TFTs) have been improved in recent years, and film formation temperatures have been lowered compared to conventional methods, high-temperature processing is still required in certain processes, and the larger the process margin, the better the yield. Therefore, even aromatic polyimides, which generally have excellent heat resistance, would have the advantage of being adaptable to a variety of processes if their heat resistance were further improved.

[0008] In particular, in smartphones and other devices equipped with under-display cameras, light reaches the camera through the display, so polyimide films for such displays are required to have high light transmittance, especially in the sensor's sensitive range.

[0009] Therefore, an object of the present invention is to provide a polyimide precursor composition for producing a polyimide film that has improved optical transparency and / or heat resistance, and preferably both, while maintaining the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient. Another object of the present invention is to provide a polyimide film, a polyimide film / substrate laminate, and the like, obtained from this polyimide precursor, for use in flexible electronic devices, particularly as a flexible display substrate.

[0010] The main disclosures of this application can be summarized as follows:

[0011] 1. A polyimide precursor composition comprising: a polyimide precursor having a repeating unit represented by the following general formula (I): at least one solvent A selected from the group consisting of 1,3-dimethyl-2-imidazolidinone (DMI), 3-methoxy-N,N-dimethylpropanamide (MPA), 1-butyl-2-pyrrolidone (NBP), N,N-diphenylformamide, N,N-diethylbenzamide, benzanilide, and 1-phenyl-2-pyrrolidone; and at least one solvent B selected from the group consisting of N,N-dimethylpropionamide (DMPA), N,N-diethylformamide (DEF), N,N-diethylacetamide (DEAc), N,N-dimethylisobutyramide (DMIB), N,N-diethylpropionamide (DEPA), and tetramethylurea (TMU).

[0012] (In general formula I, １ is a tetravalent aliphatic or aromatic group, and Y １ is a divalent aliphatic or aromatic group, and R １ and R ２ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, provided that X １ 50 mol % or more of the aromatic group and / or Y １ At least 50 mol % of the groups are aromatic groups.

[0013] 2. X １ are structures represented by formula (II-1) and / or formula (II-2), and Y １ 50 mol % or more of the polyimide precursor composition according to item 1 is a structure represented by formula (III).

[0014]

[0015] 3. The polyimide precursor composition according to item 1 or 2, wherein the total amount of solvent A and solvent B is 80 mass % or more based on the total mass of the solvents.

[0016] 4. The polyimide precursor composition according to any one of the preceding paragraphs, wherein the mass of solvent A relative to the total mass of solvent A and solvent B is in the range of more than 1 mass % and not more than 90 mass %.

[0017] 5. The polyimide precursor composition according to any one of the preceding paragraphs, wherein solvent A and solvent B are selected from the following combinations (a) to (g): (a) Solvent A contains 1,3-dimethyl-2-imidazolidinone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (b) Solvent A contains 1-butyl-2-pyrrolidone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (c) Solvent A contains 3-methoxy-N,N-dimethylpropanamide, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (d) Solvent A contains 1-phenyl-2-pyrrolidone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (e) Solvent A contains N,N-diphenylformamide, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (f) (g) Solvent A contains benzanilide and solvent B contains N,N-dimethylpropionamide, tetramethylurea or N,N-dimethylisobutyramide.

[0018] 6. The polyimide precursor composition according to any one of the preceding paragraphs, wherein the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition is higher than the following (i) and (ii), or higher than (ii) when solvent A is solid at 25°C: (i) the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition using a solvent containing only solvent A, and (ii) the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition using a solvent containing only solvent B.

[0019] 7. The polyimide precursor composition according to any one of the preceding paragraphs, wherein a 10 μm thick polyimide film obtained from the polyimide precursor composition has a light transmittance at 450 nm that is higher than the following (i) and (ii), or, when solvent A is solid at 25° C., higher than (ii): (i) the light transmittance at 450 nm of a polyimide film obtained from a polyimide precursor composition prepared using a solvent containing only solvent A; and (ii) the light transmittance at 450 nm of a polyimide film obtained from a polyimide precursor composition prepared using a solvent containing only solvent B.

[0020] 8. A polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs.

[0021] 9. A polyimide film / substrate laminate comprising: a polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs; and a supporting substrate.

[0022] 10. The polyimide film / substrate laminate according to item 9, wherein the supporting substrate is a glass substrate.

[0023] 11. A method for producing a polyimide film / substrate laminate, comprising: (a) applying the polyimide precursor composition according to any one of the preceding paragraphs onto a supporting substrate; and (b) heat-treating the polyimide precursor on the supporting substrate, and laminating a polyimide film on the supporting substrate.

[0024] 12. The method according to item 11, wherein the supporting substrate is a glass substrate.

[0025] 13. A flexible electronic device comprising the polyimide film according to item 10 or the polyimide film / substrate laminate according to items 11 or 12.

[0026] 14. A method for producing a flexible electronic device, comprising: (a) applying the polyimide precursor composition according to any one of the preceding paragraphs onto a supporting substrate; (b) heat-treating the polyimide precursor on the supporting substrate to produce a polyimide film / substrate laminate in which a polyimide film is laminated on the supporting substrate; (c) forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate; and (d) peeling the supporting substrate and the polyimide film from each other.

[0027] 15. The manufacturing method according to item 14, wherein the supporting substrate is a glass substrate.

[0028] According to the present invention, there is provided a polyimide precursor composition for producing a polyimide film that has improved optical transparency and / or heat resistance while maintaining the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient. Furthermore, the present invention provides a polyimide film and a polyimide film / substrate laminate obtained from the polyimide precursor.

[0029] According to another aspect of the present invention, there are provided a polyimide film and a polyimide film / substrate laminate obtained by using the polyimide precursor composition. According to another aspect of the present invention, there are provided a method for producing a flexible electronic device using the polyimide precursor composition, and a flexible electronic device.

[0030] In this application, the term "flexible (electronic) device" means that the device itself is flexible, and the device is typically completed by forming a semiconductor layer (such as a transistor or diode as an element) on a substrate. A "flexible (electronic) device" is distinguished from devices such as COF (chip-on-film) in which a "rigid" semiconductor element such as an IC chip is mounted on a conventional FPC (flexible printed circuit board). However, there is no problem in mounting or electrically connecting a "rigid" semiconductor element such as an IC chip on a flexible substrate and using the resulting fusion in order to operate or control the "flexible (electronic) device" of this application. Suitable flexible (electronic) devices include display devices such as liquid crystal displays, organic electroluminescence displays, and electronic paper, solar cells, and light-receiving devices such as CMOS.

[0031] The polyimide precursor composition of the present invention will be described below, followed by a description of a method for producing a flexible electronic device.

[0032] <<Polyimide Precursor Composition>> The polyimide precursor composition for forming a polyimide film contains a polyimide precursor and at least two solvents. The polyimide precursor is dissolved in the solvent.

[0033] The polyimide precursor is represented by the following general formula (I):

[0034] (In general formula I, １ is a tetravalent aliphatic or aromatic group, and Y １ is a divalent aliphatic or aromatic group, and R １ and R ２ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. １ and R ２ is a polyamic acid in which each of the groups is a hydrogen atom.

[0035] In all repeating units in the polyimide precursor, X １With regard to Y, preferably 50 mol% or more (preferably more than 50 mol%), more preferably 70 mol% or more are aromatic groups, and further more preferably 80 mol% or more, 90 mol% or more, and 95 mol% or more in that order. In the following description, the phrase "the latter range" will be omitted. １ With regard to the aromatic groups, preferably 50 mol % or more (preferably more than 50 mol %), more preferably 70 mol % or more, further more preferably 80 mol % or more, 90 mol % or more, and 95 mol % or more are aromatic groups in this order.

[0036] X １ is preferably a structure represented by the following formula (II-1) and / or formula (II-2), and Y １ is preferably a structure represented by the following formula (III). １ With regard to X other than formula (II), preferably 50 mol % or more (preferably more than 50 mol %), more preferably 70 mol % or more are structures represented by formula (II-1) and / or formula (II-2), and even more preferably 80 mol % or more, 90 mol % or more, and 95 mol % or more. １ is also preferably an aromatic group.

[0037] Y １ With regard to Y other than the formula (III), preferably 50 mol % or more (preferably more than 50 mol %), more preferably 70 mol % or more are the structure represented by formula (III), and further more preferably 80 mol % or more, 90 mol % or more, and 95 mol % or more in this order. １ is also preferably an aromatic group.

[0038]

[0039] The polyimide precursor composition of the present invention contains at least two types of solvents. Solvent A is at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone (DMI), 3-methoxy-N,N-dimethylpropanamide (MPA), 1-butyl-2-pyrrolidone (NBP), N,N-diphenylformamide, N,N-diethylbenzamide, benzanilide, and 1-phenyl-2-pyrrolidone. Solvent B is at least one selected from the group consisting of N,N-dimethylpropionamide (DMPA), N,N-diethylformamide (DEF), N,N-diethylacetamide (DEAc), N,N-dimethylisobutyramide (DMIB), N,N-diethylpropionamide (DEPA), and tetramethylurea (TMU).

[0040] Regarding the polyimide precursor, X in general formula (I) １ and Y １ The monomers (tetracarboxylic acid component, diamine component, and other components) that give the above formula will be explained, followed by the production method.

[0041] In this specification, the tetracarboxylic acid component includes tetracarboxylic acids, tetracarboxylic dianhydrides, and other tetracarboxylic acid derivatives such as tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides, which are used as raw materials for producing polyimides. Although not particularly limited, it is convenient to use tetracarboxylic acid dianhydrides in production, and in the following description, an example will be described in which tetracarboxylic acid dianhydrides are used as the tetracarboxylic acid component. Furthermore, the diamine component is a compound having an amino group (-NH ２ ) is a diamine compound having two

[0042] In this specification, the term "polyimide film" refers to both a film formed on a supporting (carrier) substrate and present in a laminate, and a film remaining after the substrate is peeled off. The material constituting the polyimide film, i.e., the material obtained by heat-treating (imidizing) a polyimide precursor composition, may also be referred to as a "polyimide material."

[0043] <X１ and tetracarboxylic acid component> As described above, in all repeating units in the polyimide precursor, X １ Preferably, the aromatic group contains an aromatic group, more preferably 50 mol % or more of which are aromatic groups. The aromatic group preferably has four bonds directly bonded to the aromatic ring. In terms of raw materials, a tetracarboxylic acid dianhydride having four -COOH groups directly bonded to the aromatic ring is preferred.

[0044] X １ When is a tetravalent aromatic group, it is preferably a tetravalent group having an aromatic ring with 6 to 40 carbon atoms.

[0045] Examples of the tetravalent group having an aromatic ring include the following.

[0046] (In the formula, Z １ is a direct bond or a divalent group as follows:

[0047] In the formula, Z is either ２ is a divalent organic group, Z ３、 Z ４ are each independently an amide bond, an ester bond, or a carbonyl bond; Z ５ is an organic group containing an aromatic ring.)

[0048] Z ２ Specific examples of the alkyl group include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0049] Z ５ Specific examples of the alkyl group include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0050] As the tetravalent group having an aromatic ring, the following are particularly preferred because they can provide the resulting polyimide film with both high heat resistance and high light transmittance.

[0051] (In the formula, Z １ is a direct bond or a hexafluoroisopropylidene bond.

[0052] Here, the polyimide film obtained has high heat resistance, high light transmittance, and a low linear thermal expansion coefficient, so Z１ is more preferably a direct bond.

[0053] In addition, preferred groups include those in the above formula (9), １ is represented by the following formula (3A):

[0054] Examples of the compound include a compound having a fluorenyl-containing group represented by the formula: １１ and Z １２ are each independently, preferably the same, a single bond or a divalent organic group. １１ and Z １２ As the group, an organic group containing an aromatic ring is preferable, and for example, a group represented by the formula (3A1):

[0055] (Z １３ and Z １４ are each independently a single bond, —COO—, —OCO— or —O—, where Z １４ When is bonded to a fluorenyl group, Z １３ is -COO-, -OCO- or -O- and Z １４ is preferably a single bond; ９１ is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably methyl, and n is an integer of 0 to 4, preferably 1.

[0056] Particularly preferred aromatic groups, as tetracarboxylic acid components, include, for example, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, pyromellitic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 4,4'-oxydiphthalic acid, bis(3,4-dicarboxyphenyl)sulfone, m-terphenyl-3,4,3',4'-tetracarboxylic acid, p-terphenyl-3,4,3',4'-tetracarboxylic acid, biscarboxyphenyldimethylsilane, bisdicarboxyphenoxydiphenyl sulfide, sulfonyldiphthalic acid, and derivatives thereof such as tetracarboxylic acid dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. １ Examples of tetracarboxylic acid components that provide repeating units of general formula (I) in which is a tetravalent group having an aromatic ring containing a fluorine atom include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane and derivatives thereof such as tetracarboxylic acid dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. Furthermore, a preferred compound is (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate). The tetracarboxylic acid components may be used alone or in combination.

[0057] Among these tetracarboxylic acid components, particularly preferred compounds are 3,3',4,4'-biphenyltetracarboxylic acid (and its derivatives, particularly s-BPDA dianhydride) and oxydiphthalic acid (and its derivatives, particularly ODPA dianhydride), which give structures represented by formula (II-1) and formula (II-2). In one preferred embodiment, it is preferred to use a tetracarboxylic acid component containing s-BPDA and / or ODPA in the ratios described for formula (II-1) and / or formula (II-2). In this case, the other tetracarboxylic acid components can be selected from the compounds described above.

[0058]

[0059] In another preferred embodiment, 3,3',4,4'-biphenyltetracarboxylic acid (and its derivatives, particularly the dianhydride s-BPDA) is not selected, but rather the tetracarboxylic acid component can be selected from those listed above.

[0060] X １ When an aliphatic group is selected as , either an alicyclic group or a chain aliphatic group can be used, but a group having an alicyclic structure is preferred. As a tetravalent group having an alicyclic structure, a tetravalent group having an alicyclic structure with 4 to 40 carbon atoms is preferred, and it is more preferred that it has at least one aliphatic 4- to 12-membered ring, more preferably an aliphatic 4-membered ring or an aliphatic 6-membered ring. Preferred tetravalent groups having an aliphatic 4-membered ring or an aliphatic 6-membered ring include the following.

[0061] (In the formula, R ３１ ~R ３８ R are each independently a direct bond or a divalent organic group. ４１ ~R ４７ , and R ７１ ~R ７３ are each independently a group of the formula: -CH ２ -, -CH=CH-, -CH ２ CH ２ R represents one selected from the group consisting of groups represented by -, -O-, and -S-. ４８ is an organic group containing an aromatic ring or an alicyclic structure.

[0062] R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , R ３６ , R ３７ , R ３８ Specific examples of the bond include a direct bond, an organic group containing an aromatic ring or an alicyclic structure, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an oxygen atom (—O—), a sulfur atom (—S—), a carbonyl bond, an ester bond, and an amide bond. A direct bond is particularly preferred.

[0063] R ３１ ~R ３８ or R ４８ Examples of the organic group containing an aromatic ring include the following:

[0064] (In the formula, W １ is a direct bond or a divalent organic group, and n １１ ~n １３ each independently represents an integer of 0 to 4, R ５１ , R ５２ , R ５３ are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0065] W １ Specific examples of the group include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0066] (R in formula (6) ６１ ~R ６８ each independently represents a direct bond or a divalent group represented by the formula (5).

[0067] As the tetravalent group having an alicyclic structure, a group having a bridged alicyclic structure is preferred, and the following is particularly preferred.

[0068]

[0069] Examples of the alicyclic tetracarboxylic acid dianhydride that gives the group having the alicyclic structure include norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid dianhydride (abbreviation: CpODA), 2,2'-binorbornane-5,5',6,6'-tetracarboxylic acid dianhydride (abbreviation: BNBDA), monocyclic alicyclic tetracarboxylic acid dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride and cyclohexane-1,2,4,5-tetracarboxylic acid dianhydride, [1,1'-bi(cyclohexane)]tetracarboxylic acid dianhydride, and the like. [1,1'-bi(cyclohexane)]-3,3',4,4'-tetracarboxylic dianhydride, [1,1'-bi(cyclohexane)]-2,3,3',4'-tetracarboxylic dianhydride, [1,1'-bi(cyclohexane)]-2,2',3,3'-tetracarboxylic dianhydride, 4,4'-methylenebis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(propane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-oxybis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-thiobis(cyclohexane-1,2-di carboxylic acid anhydride), 4,4'-sulfonylbis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-(dimethylsilanediyl)bis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid anhydride), octahydropentalene-1,3,4,6-tetracarboxylic acid dianhydride, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid dianhydride, 6-(carboxymethyl)bicyclo[2.2.1]heptane-2,3,5-tricarboxylic acid dianhydride carboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-5-ene-2,3,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.02,5]decane-3,4,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.02,5]dec-7-ene-3,4,9,10-tetracarboxylic dianhydride, 9-oxatricyclo[4.2.1.02,5]nonane-3,4,7,8-tetracarboxylic dianhydride (4arH,8acH)-decahydro-1t,4t:5c,Examples of such an anhydride include alicyclic tetracarboxylic acid dianhydrides having two or more rings, such as 8c-dimethanonaphthalene-2c,3c,6c,7c-tetracarboxylic acid dianhydride, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2t,3t,6c,7c-tetracarboxylic acid dianhydride, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, and tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid dianhydride. These may be used alone or in combination of two or more types.

[0070] <Y １ and diamine component> As described above, in all repeating units in the polyimide precursor, Y １ Preferably, the aromatic group comprises aromatic groups, more preferably 50 mol % or more (preferably more than 50 mol %) of which are aromatic groups.

[0071] Y １ When " is a divalent group having an aromatic ring, it is preferably a divalent group having an aromatic ring having 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms.

[0072] Examples of the divalent group having an aromatic ring include the following.

[0073] (In the formula, W １ is a direct bond or a divalent organic group, and n １１ ~n １３ each independently represents an integer of 0 to 4, R ５１ , R ５２ , R ５３ are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0074] W １ Specific examples of the group include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0075]

[0076] (R in formula (6) ６１ ~R ６８ each independently represents a direct bond or a divalent group represented by the formula (5).

[0077] Here, the polyimide obtained has high heat resistance, high light transmittance, and a low linear thermal expansion coefficient, so W １ is particularly preferably one selected from the group consisting of a direct bond or groups represented by the formula: -NHCO-, -CONH-, -COO-, and -OCO-. １ But, R ６１ ~R ６８ is particularly preferably either a direct bond or a divalent group represented by formula (6), which is one selected from the group consisting of groups represented by the formulas: -NHCO-, -CONH-, -COO-, and -OCO-.

[0078] Additionally, preferred groups include those represented by the formula (4): １ is represented by the following formula (3B):

[0079] Examples of the compound include a compound having a fluorenyl-containing group represented by the formula: １１ and Z １２ are each independently, preferably the same, a single bond or a divalent organic group. １１ and Z １２ As the group, an organic group containing an aromatic ring is preferable, and for example, a group represented by the formula (3B1):

[0080] (Z １３ and Z １４ are each independently a single bond, —COO—, —OCO— or —O—, where Z １４ When is bonded to a fluorenyl group, Z １３ is -COO-, -OCO- or -O- and Z １４ is preferably a single bond; ９１ is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably phenyl, and n is an integer of 0 to 4, preferably 1.

[0081] Another preferred group is W in the above formula (4). １is a phenylene group, that is, a terphenyldiamine compound, and particularly preferred is a compound in which all the bonds are para-bonded.

[0082] Another preferred group is W in the above formula (4). １ In the structure of the first phenyl ring of formula (6), R ６１ and R ６２ is a 2,2-propylidene group.

[0083] Still another preferred group is a group represented by the formula (4): １ is the following formula (3B2):

[0084] Examples of the compound include compounds represented by the following formula:

[0085] Particularly preferred aromatic groups, as diamine components, include, for example, p-phenylenediamine, m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, 4,4'-diaminobenzanilide, 3,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, N,N'-p-phenylenebis(p-aminobenzamide), 4-aminophenoxy-4-diaminobenzoate, bis( 4-aminophenyl) terephthalate, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl) ester, p-phenylenebis(p-aminobenzoate), bis(4-aminophenyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, [1,1'-biphenyl]-4,4'-diylbis(4-aminobenzoate), 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-methylenebis(phenylenediamine), 1,3-bis(4-aminophenoxy)benzene, 1,3-bi Bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, bis(4-aminophenyl)sulfone, 3,3'-bis(trifluoromethyl)benzidine, 3,3'-bis((aminophenoxy)phenyl)propane, 2,2'-bis(3-amino-4- hydroxyphenyl)hexafluoropropane, bis(4-(4-aminophenoxy)diphenyl)sulfone, bis(4-(3-aminophenoxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-triazine, 2,Examples include 4-bis(4-aminoanilino)-6-ethylamino-1,3,5-triazine and 2,4-bis(4-aminoanilino)-6-anilino-1,3,5-triazine. １ is a divalent group having an aromatic ring containing a fluorine atom, examples of the diamine component that provides the repeating unit of general formula (I) include 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. Additionally, preferred diamine compounds include 9,9-bis(4-aminophenyl)fluorene, 4,4'-(((9H-fluorene-9,9-diyl)bis([1,1'-biphenyl]-5,2-diyl))bis(oxy))diamine, [1,1':4',1"-terphenyl]-4,4"-diamine, and 4,4'-([1,1'-binaphthalene]-2,2'-diylbis(oxy))diamine. The diamine components may be used alone or in combination of two or more.

[0086] Among these diamine components, one particularly preferred compound is p-phenylenediamine (PPD), which gives a structure represented by formula (III), and in one preferred embodiment, it is preferred to use a diamine component containing p-phenylenediamine in the ratio described for formula (III). In this case, the other diamine components can be selected from the compounds described above.

[0087] In another preferred embodiment, p-phenylenediamine may not be selected, but may be selected from the diamine components listed above.

[0088] Y １When an aliphatic group is selected as , either an alicyclic group or a chain aliphatic group can be used, but a group having an alicyclic structure is preferred. As the divalent group having an alicyclic structure, a divalent group having an alicyclic structure with 4 to 40 carbon atoms is preferred, and it is even more preferred that it has at least one aliphatic 4- to 12-membered ring, more preferably aliphatic 6-membered ring.

[0089] Examples of the divalent group having an alicyclic structure include the following.

[0090] (In the formula, V １ , V ２ are each independently a direct bond or a divalent organic group, and n ２１ ~n ２６ each independently represents an integer of 0 to 4, R ８１ ~R ８６ are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group, and R ９１ , R ９２ , R ９３ are each independently a group of the formula: -CH ２ -, -CH=CH-, -CH ２ CH ２ It is one selected from the group consisting of groups represented by -, -O-, and -S-.

[0091] V １ , V ２ Specific examples of the group include a direct bond and a divalent group represented by the formula (5).

[0092] As the divalent group having an alicyclic structure, the following are particularly preferred because they can provide the resulting polyimide with both high heat resistance and a low coefficient of linear thermal expansion.

[0093] Among the divalent groups having an alicyclic structure, the following are preferred.

[0094]

[0095] Y １is a divalent group having an alicyclic structure, examples of the diamine component that provides the repeating unit of general formula (I) include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclobutane, 1,4 6,6'-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane. The diamine component may be used alone or in combination of two or more types.

[0096] As the tetracarboxylic acid component and diamine component that provide the repeating unit represented by the general formula (I), any of aliphatic tetracarboxylic acids other than alicyclic (particularly dianhydrides) and / or aliphatic diamines can be used. The content thereof is preferably less than 30 mol%, more preferably less than 20 mol%, less than 10 mol%, less than 5 mol%, and less than 2 mol% (including 0%) relative to 100 mol% in total of the tetracarboxylic acid component and the diamine component.

[0097] Polyimides derived from monomers primarily composed of s-BPDA and PPD are known for their excellent heat resistance, mechanical strength, and thermal properties, and are highly trusted by users. Therefore, if the polyimide precursor composition of the present invention can improve these properties even slightly, or if it can alleviate the weak point of coloration, it will have a significant practical effect in flexible device applications.

[0098] <Solvent> As described above, the solvents contained in the polyimide precursor composition of the present invention include solvent A and solvent B. Solvent A is at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone (DMI), 3-methoxy-N,N-dimethylpropanamide (MPA), 1-butyl-2-pyrrolidone (NBP), N,N-diphenylformamide, N,N-diethylbenzamide, benzanilide, and 1-phenyl-2-pyrrolidone, and solvent B is at least one selected from the group consisting of N,N-dimethylpropionamide (DMPA), N,N-diethylformamide (DEF), N,N-diethylacetamide (DEAc), N,N-dimethylisobutyramide (DMIB), N,N-diethylpropionamide (DEPA), and tetramethylurea (TMU). Solvent A has a higher boiling point than solvent B. It should be noted that even a compound that is solid at room temperature (e.g., 25°C), such as 1-phenyl-2-pyrrolidone, can be used by mixing it with another solvent. For example, when solvent A is a solid compound and solvent B is a liquid, the method of mixing the solvents is not particularly limited. Solvent A may be added as a solid to solvent B and dissolved therein, or solvent A may be heated to a temperature above its melting point to become a liquid, and then mixed with solvent B.

[0099] These solvents are also preferred in that they are not designated as substances of concern due to their harmful effects under the REACH regulations of the EU (European Union).

[0100] The mass ratio of solvent A to solvent B may be any as long as both are present, and the mass of solvent A relative to the total mass of solvent A and solvent B is greater than 0%, preferably greater than 1%, preferably 1.5% or more, more preferably 2% or more, and further preferably 3% or more, 5% or more, and may also be 8% or more, 10% or more, 20% or more, 25% or more, or 30% or more. The upper limit of the mass of solvent A relative to the total mass of solvent A and solvent B is less than 100%, preferably 90% or less, and may be 80% or less, 75% or less, or 70% or less. In one embodiment, from the viewpoint of handling, it may be preferable to have less solvent A and more solvent B, and it may be preferable for the mass of solvent A relative to the total mass of solvent A and solvent B to be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 8% or less. In one embodiment, for example, the ratio is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30. From another perspective, solvent A may be added so that the number of moles per mole of repeating units of the polyimide precursor is 0.5 moles or more, preferably 1 mole or more. The upper limit can be determined from the concentration of the polyimide precursor and the range of the mass ratio of solvent A to solvent B.

[0101] In the polyimide precursor composition, the total amount of solvent A and solvent B is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and most preferably 95% by mass or more, and is also preferably 100% by mass, based on the total amount of solvent.

[0102] The combination of solvent A and solvent B is not particularly limited, and examples of the combination include: (a) solvent A contains DMI, and solvent B contains DMPA, TMU, or DMIB; (b) solvent A contains NBP, and solvent B contains DMPA, TMU, or DMIB; (c) solvent A contains MPA, and solvent B contains DMPA, TMU, or DMIB; (d) solvent A contains 1-phenyl-2-pyrrolidone, and solvent B contains DMPA, TMU, or DMIB; (e) solvent A contains N,N-diphenylformamide, and solvent B contains DMPA, TMU, or DMIB; (f) solvent A contains N,N-diethylbenzamide, and solvent B contains DMPA, TMU, or DMIB; (g) solvent A contains benzanilide, and solvent B contains DMPA, TMU, or DMIB;

[0103] Among these, the combinations of solvent A and solvent B are preferably the following: (a') solvent A contains DMI, and solvent B contains DMPA; (b') solvent A contains NBP, and solvent B contains DMPA, TMU, or DMIB; (c') solvent A contains MPA, and solvent B contains DMPA; (d') solvent A contains 1-phenyl-2-pyrrolidone, and solvent B contains DMPA, TMU, or DMIB; (e') solvent A contains N,N-diphenylformamide, and solvent B contains DMPA; (f') solvent A contains N,N-diethylbenzamide, and solvent B contains DMPA; (g') solvent A contains benzanilide, and solvent B contains DMPA, TMU, or DMIB.

[0104] In each of the above combinations (a) to (g) and (a') to (g'), another solvent A may be used in addition to the specified solvent A. Typically, the mass of the specified solvent A is, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% based on the total mass of solvent A. Similarly, another solvent B may be used in addition to the specified solvent B. Typically, the mass of the specified solvent B is, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% based on the total mass of solvent B.

[0105] In a specific embodiment of the present invention, solvent A comprises 1,3-dimethyl-2-imidazolidinone (DMI), preferably at 50% by weight or more (preferably more than 50% by weight), and may further comprise 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. Solvent A may comprise only DMI. In the same or a different embodiment, solvent B comprises N,N-dimethylpropionamide (DMPA), preferably at 50% by weight or more (preferably more than 50% by weight), and further may comprise 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. Solvent B may comprise only DMPA.

[0106] In a specific embodiment of the present invention, solvent A contains 1,3-dimethyl-2-imidazolidinone, and solvent B contains N,N-dimethylpropionamide. For example, the total mass of the solvents contains 1,3-dimethyl-2-imidazolidinone and N,N-dimethylpropionamide, preferably 80% by mass or more, more preferably 90% by mass or more, or even 100% by mass. The mass ratio of 1,3-dimethyl-2-imidazolidinone to N,N-dimethylpropionamide can be within the range of solvent A to solvent B described above, but may be, for example, in the range of 20 / 80 to 80 / 20.

[0107] A solvent other than solvent A and solvent B (hereinafter referred to as "other solvent") may be contained as the residue, but it is preferable that the other solvent has a lower boiling point than solvent A. Furthermore, the other solvent may have a lower boiling point than solvent B.

[0108] Other solvents include water, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and N-ethyl-2-pyrrolidone, cyclic ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, phenol solvents such as m-cresol, p-cresol, 3-chlorophenol, and 4-chlorophenol, acetophenone, sulfolane, and dimethyl sulfoxide. Further examples include other common organic solvents, such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran, dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, turpentine, mineral spirits, petroleum naphtha-based solvents, etc. As other solvents, a combination of two or more of these solvents may be used.

[0109] When using other solvents, it is recommended to use solvents that are not designated as substances of concern due to their hazardous properties under the REACH regulation of the European Union. In this regard, it is preferable to avoid using N,N-dimethylacetamide, N-methylpyrrolidone, N-methylacetamide, and N,N-dimethylformamide, or to minimize their use if they are used at all.

[0110] The polyimide precursor composition of the present invention can be produced by reacting the above-mentioned tetracarboxylic acid component and diamine component in a solvent, specifically in a solvent containing at least one selected from solvent A and at least one selected from solvent B of the present invention. The polyimide precursor used in the present invention (a polyimide precursor containing at least one repeating unit represented by the formula (I)) is a polyimide precursor containing at least one repeating unit represented by the formula (I) １ and R ２ 1) Polyamic acid (R １ and R ２ is hydrogen), 2) polyamic acid ester (R １ and R ２ wherein at least a portion of the group is an alkyl group), 3) 4) polyamic acid silyl ester (R １ and R ２ and (wherein at least a portion of the groups are alkylsilyl groups). Polyimide precursors can be easily produced by the following production methods for each of these classifications. However, the production methods for the polyimide precursors used in the present invention are not limited to the following production methods.

[0111] 1) Polyamic Acid A polyimide precursor can be suitably obtained as a polyimide precursor solution by reacting a tetracarboxylic dianhydride as a tetracarboxylic acid component with a diamine component in approximately equimolar amounts, preferably at a molar ratio of the diamine component to the tetracarboxylic acid component [number of moles of diamine component / number of moles of tetracarboxylic acid component] of 0.90 to 1.10, more preferably 0.95 to 1.05, in a solvent at a relatively low temperature, for example, 120° C. or lower, while suppressing imidization.

[0112] More specifically, although not limited to, a polyimide precursor is obtained by dissolving a diamine in a solvent, gradually adding a tetracarboxylic dianhydride to the solution while stirring, and stirring for 1 to 72 hours at a temperature ranging from 0 to 120°C, preferably from 5 to 80°C. Reactions at temperatures above 80°C may result in fluctuations in molecular weight depending on the temperature history during polymerization, and imidization may progress due to heat, potentially making it difficult to stably produce a polyimide precursor. The order of addition of the diamine and tetracarboxylic dianhydride in the above production method is preferred because it facilitates an increase in the molecular weight of the polyimide precursor. Furthermore, the order of addition of the diamine and tetracarboxylic dianhydride in the above production method may be reversed, which is preferred because it reduces precipitates.

[0113] 2) Polyamic Acid Esters: Tetracarboxylic dianhydride is reacted with any alcohol to obtain a diester dicarboxylic acid, which is then reacted with a chlorinating agent (e.g., thionyl chloride, oxalyl chloride) to obtain a diester dicarboxylic acid chloride. This diester dicarboxylic acid chloride and diamine are stirred in a solvent at temperatures ranging from −20 to 120°C, preferably −5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor. Reactions at temperatures above 80°C can result in fluctuations in molecular weight depending on the temperature history during polymerization, and imidization can progress due to heat, potentially making it difficult to stably produce a polyimide precursor. Alternatively, polyimide precursors can be easily obtained by dehydration condensation of diester dicarboxylic acid and diamine using a phosphorus-based condensing agent or a carbodiimide condensing agent.

[0114] 3) Polyamic Acid Silyl Ester (Indirect Method) A diamine and a silylating agent are reacted in advance to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or other methods. The silylated diamine is then dissolved in a dehydrated solvent, and a tetracarboxylic acid dianhydride is gradually added while stirring. The mixture is stirred at a temperature ranging from 0 to 120°C, preferably from 5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor. If the reaction is carried out at temperatures above 80°C, the molecular weight varies depending on the temperature history during polymerization, and imidization proceeds due to heat, potentially making it impossible to stably produce a polyimide precursor.

[0115] 4) Polyamic Acid Silyl Ester (Direct Method) A polyimide precursor is obtained by mixing the polyamic acid solution obtained by method 1) with a silylating agent and stirring the mixture for 1 to 72 hours at a temperature ranging from 0 to 120° C., preferably from 5 to 80° C. If the reaction is carried out at 80° C. or higher, the molecular weight varies depending on the temperature history during polymerization, and imidization proceeds due to heat, which may make it impossible to stably produce the polyimide precursor.

[0116] The use of a chlorine-free silylating agent as the silylating agent used in methods 3) and 4) is preferable because it is not necessary to purify the silylated polyamic acid or the resulting polyimide. Examples of silylating agents that do not contain chlorine atoms include N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(trimethylsilyl)acetamide, and hexamethyldisilazane. N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and are low cost.

[0117] In the silylation reaction of the diamine in method 3), an amine catalyst such as pyridine, piperidine, or triethylamine can be used to accelerate the reaction. This catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

[0118] In the production of the polyimide precursor, although not particularly limited, the monomer and solvent are charged at a concentration such that the solids concentration of the polyimide precursor (mass concentration in terms of polyimide) is, for example, 5 to 45 mass %, and the reaction is carried out.

[0119] The logarithmic viscosity of the polyimide precursor is not particularly limited, but it is preferably 0.2 dL / g or more, more preferably 0.3 dL / g or more, and particularly preferably 0.4 dL / g or more, in an N-methyl-2-pyrrolidone solution having a concentration of 0.5 g / dL at 30° C. When the logarithmic viscosity is 0.2 dL / g or more, the molecular weight of the polyimide precursor is high, and the resulting polyimide has excellent mechanical strength and heat resistance.

[0120] <Imidazole Compound> The polyimide precursor composition preferably contains at least one imidazole compound. The imidazole compound is not particularly limited as long as it is a compound having an imidazole skeleton, and examples thereof include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole, and benzimidazole. From the viewpoint of storage stability of the polyimide precursor composition, 2-phenylimidazole and benzimidazole are preferred. A plurality of imidazole compounds may be used in combination.

[0121] The content of the imidazole compound in the polyimide precursor composition can be appropriately selected taking into consideration the balance between the effect of addition and the stability of the polyimide precursor composition. The amount of the imidazole compound is preferably more than 0.0001 mol and not more than 2 mol per mol of repeating units of the polyimide precursor. The addition of the imidazole compound is effective in improving the light transmittance, the coefficient of linear thermal expansion, and / or the mechanical properties, and within this content range, it is also effective in improving the storage stability of the polyimide precursor composition.

[0122] The content of the imidazole compound is more preferably 0.0005 mol or more, even more preferably 0.0008 mol or more, even more preferably 0.001 mol or more, and more preferably 1.0 mol or less, even more preferably 0.5 mol or less, even more preferably 0.1 mol or less, even more preferably 0.05 mol or less, and most preferably 0.01 mol or less, relative to 1 mol of the repeating unit.

[0123] Furthermore, when an imidazole compound is added, the storage stability of the polyimide precursor composition is improved, which may be particularly advantageous in terms of transportation, distribution, and inventory storage. For example, when the polyimide equivalent mass concentration (solid content concentration) is high, particularly when the composition is applied to a solution having a solid content concentration of 10 mass % or more, preferably 15 mass % or more, the storage stability may be particularly improved.

[0124] <Characteristics of Polyimide Precursor Composition> The concentration of the polyimide precursor in the polyimide precursor composition is not particularly limited, but is typically 5 to 45 mass %, preferably 8 to 25 mass %, and more preferably 10 to 20 mass %, in terms of polyimide-equivalent mass concentration (hereinafter sometimes referred to as solids concentration). Here, the polyimide-equivalent mass refers to the mass when all repeating units are completely imidized. Typically, a tetracarboxylic acid component and a diamine component are reacted in predetermined amounts in a solvent, and the resulting polyimide precursor composition is used as is. Therefore, the solids concentration of the polyimide precursor composition is approximately equal to the amounts of the tetracarboxylic acid component and the diamine component charged. The concentration can be adjusted by dilution or concentration, as necessary.

[0125] The viscosity (rotational viscosity) of the polyimide precursor composition is not particularly limited, but may be measured using an E-type rotational viscometer at a temperature of 25° C. and a shear rate of 50 sec. －１The rotational viscosity measured by is preferably 0.01 to 1000 Pa sec, more preferably 0.1 to 100 Pa sec, more preferably 0.5 to 20 Pa sec, and even more preferably 1 to 10 Pa sec. Thixotropy can also be imparted as necessary. With a viscosity within the above range, the composition is easy to handle when coating or forming a film, and repellency is suppressed, resulting in excellent leveling, and a good coating film can be obtained.

[0126] Although the details of film production will be described later, a polyimide film is formed by casting a polyimide precursor composition onto a supporting substrate and imidizing and removing the solvent by heat treatment, thereby obtaining a laminate of the supporting substrate and the polyimide film (polyimide film / substrate laminate).

[0127] When forming films in device production, coaters with narrow slits as discharge ports are used, such as slit coaters. Generally, excessively high viscosity can lead to difficult discharge and slower coating speeds, resulting in reduced production takt time. Conversely, excessively low viscosity can make stable casting difficult. Therefore, polyimide precursor compositions used in industrial device manufacturing processes must have an appropriate viscosity to match the slit spacing, and the viscosity affects the cast coating film thickness. Meanwhile, since the thickness of a polyimide film depends on the product of the solids concentration of the polyimide precursor composition and the cast film thickness, if the concentration is too low when the viscosity is adjusted to an appropriate level for coating, a polyimide film of the desired thickness cannot be produced. In the present invention, a mixed solvent selected from "Solvent A and Solvent B of the present invention" can be used to achieve an appropriate viscosity and solids concentration.

[0128] The polyimide precursor composition using this mixed solvent also has excellent viscosity stability. Viscosity changes can cause changes in the cast coating film thickness, resulting in a change in the thickness of the polyimide film, or can require major changes in the coating machine conditions, creating practical problems. The polyimide precursor composition using this mixed solvent is more stable than compositions using only solvent A or only solvent B, and is preferably more stable than compositions using only solvent A and compositions using only solvent B. For example, if a composition containing only solvent A is more stable than a composition containing only solvent B, a composition using a mixed solvent containing both solvents A and B will exhibit stability equal to or greater than that of a composition containing only solvent A. Viscosity stability can be evaluated, for example, by measuring the viscosity after 30 days based on the viscosity immediately after production of the polyimide precursor composition.

[0129] The polyimide precursor composition of the present invention may contain, as necessary, a chemical imidizing agent (an acid anhydride such as acetic anhydride, or an amine compound such as pyridine or isoquinoline), an antioxidant, an ultraviolet absorber, a filler (inorganic particles such as silica), a dye, a pigment, a coupling agent such as a silane coupling agent, a primer, a flame retardant, an antifoaming agent, a leveling agent, a rheology control agent (flow aid), and the like.

[0130] When an imidazole compound is contained, the polyimide precursor composition can be prepared by adding the imidazole compound or a solution of the imidazole compound to the polyimide precursor composition obtained after the reaction and mixing them. Alternatively, the tetracarboxylic acid component and the diamine component may be reacted in the presence of the imidazole compound.

[0131] <<Uses of Polyimide Precursor Composition and Film Properties>> Polyimides and polyimide films can be produced using the polyimide precursor composition of the present invention. The production method is not particularly limited, and any known imidization method can be suitably applied. Suitable forms of the obtained polyimide include films, laminates of polyimide films with other substrates, coating films, powders, beads, molded products, and foams.

[0132] Although it depends on the application, the thickness of the polyimide film is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more, and for example, 250 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0133] The polyimide film of the present invention is excellent in optical transparency, mechanical properties, thermal properties, and heat resistance (glass transition temperature, thermal decomposition resistance), with at least one of optical transparency and thermal decomposition resistance being particularly improved, and in preferred embodiments, both. "Heat resistance" can be classified into two categories: one related to phase change (indicated by glass transition temperature or melting temperature) and the other related to thermal decomposition (indicated by weight loss). Since these are different phenomena, there is no direct relationship between them. The polyimide and polyimide film of the present invention are excellent in both glass transition temperature (Tg) and thermal decomposition resistance.

[0134] Known types of TFTs used in displays such as liquid crystal displays and organic electroluminescence displays include amorphous silicon TFTs (a-Si TFTs), low-temperature polysilicon TFTs (LTPS TFTs), high-temperature polysilicon TFTs, and oxide TFTs. High-temperature film formation is particularly advantageous for forming semiconductor layers with high charge mobility. Amorphous silicon TFTs, which can be formed at relatively low temperatures, require a film formation temperature of 300°C to 400°C, while low-temperature polysilicon TFTs require a film formation temperature of 600°C or lower (for example, around 500°C).

[0135] If the thermal decomposition resistance of a polyimide film is insufficient, for example, during the TFT formation process, outgassing due to polyimide decomposition or the like can cause swelling between the polyimide film and the barrier film or contaminate the manufacturing equipment. For flexible electronic device substrates, materials that are stable at high temperatures, i.e., films that have excellent thermal decomposition resistance at process temperatures and generate very little gas, are preferred. From the perspective of process margins, films with a high thermal decomposition (onset) temperature are preferred, even if only slightly higher (for example, by about 2°C).

[0136] The thermal decomposition resistance of a polyimide film (or the polyimide constituting the polyimide film) can be evaluated, for example, at the 0.5% weight loss temperature, 1% weight loss temperature, 5% weight loss temperature, etc. When even a slight amount of outgassing is problematic, it is generally preferable to evaluate at the 0.5% weight loss temperature or 1% weight loss temperature, etc., as an index showing a small weight loss.

[0137] In one embodiment of the present application, the 0.5% weight loss temperature of the example using the mixed solvent of solvent A and solvent B of the present invention is preferably 1°C or more, more preferably 2°C or more, and even more preferably 3°C or more higher than the example using solvent A alone and / or (preferably "and") solvent B alone. However, if other evaluation items, such as 450 nm transmittance, are excellent, the 0.5% weight loss temperature of the example of this mixed solvent may be similar to the example using solvent A alone or solvent B alone, and even if it is about 2°C lower, it may be acceptable. The 1% weight loss temperature can be evaluated in a similar manner. When solvent A is solid at room temperature (e.g., 25°C), it is preferable to achieve the above improvement over the example using solvent B alone.

[0138] Furthermore, compared to the example in which NMP was used alone as the solvent, it is preferable that the 0.5% weight loss temperature of the example in which a mixed solvent of solvent A and solvent B was used be improved by the same temperature difference as above. However, since not using NMP is a significant effect, the 0.5% weight loss temperature of the example in which this mixed solvent was used may be acceptable compared to the example in which NMP was used alone. For example, it is preferable that the decrease be about 5°C, preferably 3°C, and more preferably 2°C. The 1% weight loss temperature can also be evaluated in a similar manner.

[0139] In one embodiment of the present invention, for example, in a system using DMI and DMPA in combination, the 0.5% weight loss temperature is preferably above 553° C., more preferably 554° C. or higher, and even more preferably 555° C. or higher. Also, the 1% weight loss temperature is preferably above 575° C., more preferably 576° C. or higher, and even more preferably 577° C. or higher.

[0140] The polyimide film of the present invention has an extremely low coefficient of linear thermal expansion. In one embodiment of the present invention, the coefficient of linear thermal expansion (CTE) of the polyimide film from 150°C to 250°C, when measured on a 10 μm thick film, is preferably 20 ppm / K or less, more preferably less than 20 ppm, even more preferably 15 ppm / K or less, and even more preferably 11 ppm / K or less.

[0141] In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting the polyimide film) is preferably 300° C. or higher, more preferably 310° C. or higher, and even more preferably 320° C. or higher.

[0142] In one embodiment of the present application, when measured on a 10 μm thick film, the 450 nm light transmittance of the polyimide film using the mixed solvent of solvent A and solvent B of the present invention is improved by preferably 1% or more, more preferably 2% or more, compared to the example using solvent A alone and / or (preferably "and") solvent B alone. However, when other evaluation items, such as thermal decomposition resistance (0.5% weight loss temperature), are excellent, the 450 nm light transmittance of the example of this mixed solvent may be approximately the same as the example using solvent A alone or solvent B alone, and even a value about 2% lower may be acceptable. When solvent A is a solid at room temperature (e.g., 25° C.), it is preferable to achieve the above improvement compared to the example using solvent B alone.

[0143] Furthermore, compared to an example in which NMP was used alone as the solvent, it is preferable that the 450 nm light transmittance of the example in which a mixed solvent of solvent A and solvent B was used be improved at the same temperature difference as above. However, since not using NMP is a significant effect, the 450 nm light transmittance of the example in which this mixed solvent was used may be the same as that of the example in which NMP was used alone, and a decrease of up to 3%, preferably up to 2%, more preferably up to 1% may be acceptable in some cases.

[0144] In one embodiment of the present invention, for example, in a system using DMI and DMPA in combination, the 450 nm light transmittance of a 10 μm thick film is preferably 68% or more, more preferably 69% or more, and even more preferably 70% or more. Furthermore, when measured on a 10 μm thick film, the yellowness index (YI) of the polyimide film is preferably 40 or less, more preferably 35 or less, even more preferably 33 or less, and even more preferably 32 or less. Usually, a value of 0 or more is preferred.

[0145] In one embodiment of the present invention, the haze value of the polyimide film, when measured on a 10 μm thick film, is preferably less than 1.0%, more preferably 0.8% or less, and even more preferably 0.7% or less. For example, if the haze value exceeds 1%, the film becomes cloudy to the naked eye, making it unsuitable for optical applications.

[0146] Furthermore, in one embodiment of the present invention, the elongation at break of the polyimide film, when measured on a film having a thickness of 10 μm, is preferably more than 10%, more preferably 15% or more, and even more preferably 20% or more, 25% or more, and 30% or more in that order.

[0147] In another preferred embodiment of the present invention, the breaking strength of the polyimide film is preferably 150 MPa or more, more preferably 200 MPa or more, even more preferably 220 MPa or more, even more preferably 250 MPa or more, and even more preferably 280 MPa or more. The breaking strength can be, for example, a value obtained from a film having a thickness of about 5 to 100 μm.

[0148] It is particularly preferable that the polyimide film has all of the above desirable properties simultaneously.

[0149] Polyimide films can be produced by known methods. A typical method involves casting a polyimide precursor composition onto a supporting substrate, followed by heating and imidizing the composition on the substrate to obtain a polyimide film. This method will be described later in connection with the production of a polyimide film / substrate laminate. Alternatively, a polyimide film can be obtained by casting a polyimide precursor composition onto a supporting substrate, heating and drying the composition to produce a self-supporting film, peeling the self-supporting film from the substrate, and then holding the film with, for example, a tenter and heating and imidizing the film while allowing degassing from both sides of the film.

[0150] <<Production of Polyimide Film / Substrate Laminate and Flexible Electronic Device>> A polyimide film / substrate laminate can be produced using the polyimide precursor composition of the present invention. The polyimide film / substrate laminate can be produced by (a) applying the polyimide precursor composition to a supporting substrate, and (b) heat-treating the polyimide precursor on the supporting substrate to produce a laminate (polyimide film / substrate laminate) in which a polyimide film is laminated on the supporting substrate. The method for producing a flexible electronic device of the present invention uses the polyimide film / substrate laminate produced in steps (a) and (b) and further includes steps: (c) forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate, and (d) peeling the polyimide film from the substrate.

[0151] First, in step (a), a polyimide precursor composition is cast onto a substrate, and a polyimide film is formed by imidization and solvent removal through heat treatment, thereby obtaining a laminate of a supporting substrate and the polyimide film (polyimide film / substrate laminate).

[0152] As the support substrate, a heat-resistant material is used, for example, a plate- or sheet-like substrate such as a ceramic material (glass, alumina, etc.), a metal material (iron, stainless steel, copper, aluminum, etc.), a semiconductor material (silicon, compound semiconductor, etc.), or a film- or sheet-like substrate such as a heat-resistant plastic material (polyimide, etc.). Generally, a flat and smooth plate-like substrate is preferred, and generally, glass substrates such as soda-lime glass, borosilicate glass, alkali-free glass, sapphire glass, etc.; semiconductor (including compound semiconductor) substrates such as silicon, GaAs, InP, GaN, etc.; and metal substrates such as iron, stainless steel, copper, aluminum, etc. are used.

[0153] A glass substrate is particularly preferred as the support substrate. Flat, smooth, and large-area glass substrates have been developed and are readily available. The thickness of a plate-like substrate such as a glass substrate is not limited, but from the viewpoint of ease of handling, it is, for example, 20 μm to 4 mm, preferably 100 μm to 2 mm. The size of the plate-like substrate is also not particularly limited, but one side (the long side in the case of a rectangle) is, for example, about 100 mm to 4000 mm, preferably about 200 mm to 3000 mm, and more preferably about 300 mm to 2500 mm.

[0154] The substrate such as a glass substrate may have an inorganic thin film (for example, a silicon oxide film) or a resin thin film formed on the surface.

[0155] The method for casting the polyimide precursor composition onto the substrate is not particularly limited, and examples thereof include conventionally known methods such as slit coating, die coating, blade coating, spray coating, inkjet coating, nozzle coating, spin coating, screen printing, bar coater method, and electrodeposition.

[0156] In step (b), the polyimide precursor composition is heat-treated on the supporting substrate to convert it into a polyimide film, thereby obtaining a polyimide film / substrate laminate. The heat-treatment conditions are not particularly limited, but for example, after drying at a temperature in the range of 50°C to 150°C, the maximum heating temperature is, for example, 150°C to 600°C, preferably 200°C to 550°C, and more preferably 250°C to 500°C.

[0157] The thickness of the polyimide film is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more. If the thickness is less than 1 μm, the polyimide film will not maintain sufficient mechanical strength, and when used, for example, as a flexible electronic device substrate, it may not be able to withstand stress and may be broken. Furthermore, the thickness of the polyimide film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less. If the polyimide film is too thick, it may become difficult to thin the flexible device. To achieve a thinner film while maintaining sufficient durability for a flexible device, the thickness of the polyimide film is preferably 2 to 50 μm.

[0158] In the present invention, it is preferable that the polyimide film / substrate laminate has little warpage. Measurement details are described in Japanese Patent No. 6798633. In one embodiment, when the properties of the polyimide film are evaluated based on the residual stress between the polyimide film and the silicon substrate in a polyimide film / silicon substrate (wafer) laminate, the residual stress is preferably less than 27 MPa. However, this assumes that the polyimide film is stored in a dry state at 23°C.

[0159] The polyimide film in the polyimide film / substrate laminate may have a second layer such as a resin film or an inorganic film on its surface. That is, after forming a polyimide film on a substrate, a flexible electronic device substrate may be formed by laminating a second layer thereon. It is preferable to have at least an inorganic film, and it is particularly preferable to have one that functions as a barrier layer against water vapor, oxygen (air), etc. As the water vapor barrier layer, for example, silicon nitride (SiN ｘ ), silicon oxide (SiO ｘ ), silicon oxynitride (SiO ｘ N ｙ ), aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), zirconium oxide (ZrO ２Examples of suitable inorganic films include inorganic films containing an inorganic substance selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides, such as SiO 2 , SiO 3 , SiO 4 , and SiO 5 . Generally, known methods for forming these thin films include physical vapor deposition methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (chemical vapor deposition methods) such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). This second layer may be a multi-layer structure.

[0160] When the second layer is a multi-layer structure, it is also possible to combine a resin film and an inorganic film. For example, a three-layer structure of a barrier layer / polyimide layer / barrier layer may be formed on the polyimide film in a polyimide film / substrate laminate.

[0161] In step (c), at least one layer selected from a conductive layer and a semiconductor layer is formed on a polyimide film (including a polyimide film having a second layer such as an inorganic film laminated on its surface) using the polyimide / substrate laminate obtained in step (b). These layers may be formed directly on the polyimide film (including a polyimide film having a second layer laminated on its surface) or may be formed indirectly on top of other layers required for the device.

[0162] The conductive layer and / or the semiconductor layer are selected appropriately according to the elements and circuits required for the target electronic device. When at least one of a conductive layer and a semiconductor layer is formed in step (c) of the present invention, it is also preferable to form at least one of a conductive layer and a semiconductor layer on a polyimide film having an inorganic film formed thereon.

[0163] The conductive layer and the semiconductor layer may be formed on the entire surface of the polyimide film or on a part of the polyimide film. In the present invention, the process may proceed to the step (d) immediately after the step (c), or may proceed to the step (d) after forming at least one layer selected from the conductive layer and the semiconductor layer in the step (c) and then forming a device structure.

[0164] When manufacturing a TFT liquid crystal display device as a flexible device, for example, metal wiring, amorphous silicon or polysilicon TFTs, and transparent pixel electrodes are formed on a polyimide film having an inorganic film formed on the entire surface as needed. The TFT includes, for example, a gate metal layer, a semiconductor layer such as an amorphous silicon film, a gate insulating layer, and wiring connected to the pixel electrodes. Further structures required for the liquid crystal display can be formed on top of this by known methods. Transparent electrodes and color filters may also be formed on the polyimide film.

[0165] In the case of producing an organic EL display, for example, a transparent electrode, a light-emitting layer, a hole transport layer, an electron transport layer, etc., and optionally a TFT can be formed on a polyimide film having an inorganic film formed on the entire surface as required.

[0166] The polyimide film preferred in the present invention is excellent in various properties such as heat resistance and toughness, and therefore there are no particular limitations on the method for forming circuits, elements and other structures required for devices.

[0167] Next, in step (d), the polyimide film is peeled from the supporting substrate by a mechanical peeling method in which the film is physically peeled by applying an external force, or by a laser peeling method in which the film is peeled by irradiating the substrate surface with a laser beam.

[0168] After the support substrate is peeled off, the (semi-)product having the polyimide film as the substrate is further formed with or incorporated with structures or parts required for the device to complete the device.

[0169] As a different method for producing a flexible electronic device, after producing a polyimide film / substrate laminate by the above-mentioned step (b), the polyimide film can be peeled off, and at least one layer selected from a conductive layer and a semiconductor layer and a necessary structure can be formed on the polyimide film as in the above-mentioned step (c), thereby producing a (semi-)finished product using the polyimide film as a substrate.

[0170] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0171] In the following examples, evaluation was carried out by the following methods.

[0172] <Evaluation of Polyimide Film> [Light Transmittance at 450 nm] The light transmittance at 450 nm of a polyimide film having a thickness of about 10 μm was measured using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation).

[0173] [0.5%, 1%, and 5% Weight Loss Temperatures] A polyimide film having a thickness of approximately 10 μm was used as a test piece, and the temperature was raised from 25° C. to 600° C. at a heating rate of 10° C. / min in a nitrogen stream using a calorimeter measuring device (Q5000IR) manufactured by TA Instruments Co., Ltd. From the obtained weight curve, the 0.5%, 1%, and 5% weight loss temperatures were determined, with the weight at 150° C. being 100%.

[0174] <Evaluation of Polyimide Precursor Composition (Varnish)>

[0175] [Viscosity Measurement of Polyimide Precursor Composition] The rotational viscosity of the polyimide precursor composition (varnish) was measured using a TV-22 E-type rotational viscometer manufactured by Toki Sangyo Co., Ltd. at a temperature of 25°C and a shear rate of 50 sec. －１ The viscosity after storage at 23°C for 30 days was divided by the viscosity of the varnish immediately after production to obtain the "viscosity retention rate (%)" and evaluate the "viscosity stability." For samples in which a significant decrease in viscosity was observed before 30 days, the viscosity stability was evaluated based on the viscosity retention rate at that time (evaluated as "poor viscosity stability").

[0176] <Raw Materials> The abbreviations for the raw materials used in the following examples are as follows.

[0177] [Diamine component] PPD: p-phenylenediamine

[0178] [Tetracarboxylic acid component] s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

[0179] [Solvent] DMI: 1,3-dimethyl-2-imidazolidinone NBP: 1-butyl-2-pyrrolidone MPA: 3-methoxy-N,N-dimethylpropanamide DMPA: N,N-dimethylpropionamide NMP: N-methyl-2-pyrrolidone

[0180] Example 1 Preparation of Polyimide Precursor Composition 10.8 g (0.1 mol) of PPD was placed in a reaction vessel purged with nitrogen gas, and solvents A and B were added to form a mixed solvent containing 75% by mass of 1,3-dimethyl-2-imidazolidinone (DMI) as solvent A and 25% by mass of N,N-dimethylpropionamide (DMPA) as solvent B. The total mass of solvents A and B was 292.9 g, which was an amount that resulted in a total mass of charged monomers (the sum of the diamine component and the carboxylic acid component) of 12% by mass. This solution was then stirred at room temperature for 3 hours. 29.1 g (0.1 mol) of s-BPDA was gradually added to this solution. Stirring was continued at room temperature for 12 hours, yielding a uniform and viscous polyimide precursor composition.

[0181] The initial viscosity of the resulting polyimide precursor composition (viscosity immediately after production) was measured, and then the composition was stored at 23°C in a sealed container filled with nitrogen gas. The viscosity after 30 days of storage was divided by the initial viscosity to determine the "viscosity retention rate (%)," which was used as an index of viscosity stability. The results are shown in Table 1.

[0182] [Production of Polyimide Film] A 6-inch Corning Eagle-XG (registered trademark) (500 μm thick) glass substrate was used. The polyimide precursor composition was applied to the glass substrate and heated from room temperature to 430°C in a nitrogen atmosphere (oxygen concentration 200 ppm or less) on the glass substrate to thermally imidize the composition, thereby obtaining a polyimide film / substrate laminate. The laminate was immersed in 40°C water (for example, at a temperature ranging from 20°C to 100°C) to peel the polyimide film from the glass substrate. After drying, the properties of the polyimide film were evaluated. The thickness of the polyimide film was approximately 10 μm. The evaluation results are shown in Table 1.

[0183] Examples 2 to 38, Comparative Examples 1 to 12, and Reference Example 1 In Example 1, the varnish concentration (monomer concentration) was kept the same, but the solvent compositions were changed to those shown in Tables 1 to 7, and polyimide precursor compositions were obtained in the same manner as in Example 1. Polyimide films were then produced in the same manner as in Example 1, and the film properties were evaluated in the same manner. The results are shown in Tables 1 to 7. The values ​​listed in the acid dianhydride column in the tables represent the content of each component relative to 100 mol% of the total amount of acid dianhydride. The values ​​listed in the diamine column in the tables represent the content of each component relative to 100 mol% of the total amount of diamine. The values ​​listed in the solvent column in the tables represent the content of each solvent when the total amount of solvent is taken as 100 mass%. The viscosity stability of the obtained polyimide precursor compositions was evaluated for the examples listed in Table 1 in the same manner as in Example 1.

[0184] Examples 39 to 58, Comparative Examples 13 to 17, Reference Example 2 Polyimide precursor compositions were obtained in the same manner as in Example 1, except that the monomer compositions and solvents used in Example 1 were changed to those shown in Tables 8 to 10. Thereafter, polyimide films were produced in the same manner as in Example 1, and the film properties were evaluated in the same manner. The results are shown in Tables 8 to 10. The values ​​in the tables represent the content of each component, as in Tables 1 to 7.

[0185] <Evaluation Results> In the Examples using the mixed solvents specified in the present application, at least one of the 0.5% weight loss temperature (thermal decomposition resistance) and 450 nm light transmittance was improved compared to the Comparative Examples using a single solvent. In the systems using s-BPDA and PPD as the monomer composition, the Examples (Examples 1 to 3) using DMI as solvent A had superior properties compared to Reference Example 1, which used NMP as the solvent. There were also no problems with viscosity stability. Furthermore, the system using ODPA and PPD as the monomer composition had superior properties compared to Reference Example 2, which used NMP as the solvent.

[0186] Note: The viscosity stability of Comparative Example 2 indicates the viscosity retention rate after 16 days.

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195]

[0196] The present invention can be suitably applied to the manufacture of flexible electronic devices, for example, display devices such as liquid crystal displays, organic EL displays, and electronic paper, as well as light-receiving devices such as solar cells and CMOS.

Claims

1. A polyimide precursor composition comprising: a polyimide precursor whose repeating unit is represented by the following general formula (I); at least one solvent A selected from the group consisting of 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N,N-dimethylpropanamide, 1-butyl-2-pyrrolidone, N,N-diphenylformamide, N,N-diethylbenzamide, benzanilide, and 1-phenyl-2-pyrrolidone; and at least one solvent B selected from the group consisting of N,N-dimethylpropionamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-dimethylisobutyramide, N,N-diethylpropionamide, and tetramethylurea. (In general formula I, X １ is a tetravalent aliphatic or aromatic group, and Y １ is a divalent aliphatic or aromatic group, and R １ and R ２ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, provided that X １ 50 mol % or more of the aromatic group and / or Y １ At least 50 mol % of the groups are aromatic groups.

2. X １ are structures represented by formula (II-1) and / or formula (II-2), and Y １ The polyimide precursor composition according to claim 1 , wherein 50 mol % or more of the structure represented by formula (III) is 3. The polyimide precursor composition according to claim 1, wherein the total mass of solvent A and solvent B is 80 mass % or more based on the total mass of the solvents.

4. The polyimide precursor composition according to claim 1, wherein the mass of solvent A relative to the total mass of solvent A and solvent B is in the range of more than 1 mass % and not more than 90 mass %.

5. The polyimide precursor composition according to claim 1, wherein solvent A and solvent B are selected from the following combinations (a) to (g): (a) Solvent A contains 1,3-dimethyl-2-imidazolidinone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (b) Solvent A contains 1-butyl-2-pyrrolidone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (c) Solvent A contains 3-methoxy-N,N-dimethylpropanamide, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (d) Solvent A contains 1-phenyl-2-pyrrolidone, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (e) Solvent A contains N,N-diphenylformamide, and solvent B contains N,N-dimethylpropionamide, tetramethylurea, or N,N-dimethylisobutyramide. (f) (g) Solvent A contains benzanilide and solvent B contains N,N-dimethylpropionamide, tetramethylurea or N,N-dimethylisobutyramide.

6. The polyimide precursor composition according to claim 1, wherein the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition is higher than the following (i) and (ii), or higher than (ii) when solvent A is solid at 25°C: (i) the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition using a solvent containing only solvent A, and (ii) the 0.5% weight loss temperature of the polyimide obtained from the polyimide precursor composition using a solvent containing only solvent B.

7. The polyimide precursor composition according to claim 1, wherein the light transmittance at a wavelength of 450 nm of a 10 μm thick polyimide film obtained from the polyimide precursor composition is higher than the following (i) and (ii), or when solvent A is solid at 25° C., the light transmittance is higher than (ii): (i) the light transmittance at a wavelength of 450 nm of a polyimide film obtained from a polyimide precursor composition using a solvent containing only solvent A; (ii) the light transmittance at a wavelength of 450 nm of a polyimide film obtained from a polyimide precursor composition using a solvent containing only solvent B.

8. A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 7.

9. A polyimide film / substrate laminate comprising: a polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 7; and a supporting substrate.

10. The polyimide film / substrate laminate according to claim 9, wherein the supporting substrate is a glass substrate.

11. A method for producing a polyimide film / substrate laminate, comprising: (a) applying the polyimide precursor composition described in any one of claims 1 to 7 onto a supporting substrate; and (b) heat-treating the polyimide precursor on the supporting substrate and laminating a polyimide film on the supporting substrate.

12. The manufacturing method according to claim 11, wherein the supporting substrate is a glass substrate.

13. A flexible electronic device comprising the polyimide film of claim 8.

14. A method for producing a flexible electronic device, comprising: (a) applying the polyimide precursor composition according to any one of claims 1 to 7 onto a supporting substrate; (b) heat-treating the polyimide precursor on the supporting substrate to produce a polyimide film / substrate laminate in which a polyimide film is laminated on the supporting substrate; (c) forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate; and (d) peeling the supporting substrate and the polyimide film.

15. The manufacturing method according to claim 14, wherein the supporting substrate is a glass substrate.

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