Polyimide film production method and polyimide film

Abstract

Disclosed is a method for producing an aromatic polyimide film having improved light transmittance. This method for producing a polyimide film comprises: a step (1) for applying, onto a support base material, a polyimide precursor composition that is obtained by reacting a tetracarboxylic acid component which contains an aromatic tetracarboxylic dianhydride and a diamine component which contains an aromatic diamine; a step (2) for removing a solvent from the applied polyimide precursor composition; a step (3) for imidizing the polyimide precursor composition to obtain a polyimide film; and a step (4) for irradiating the polyimide precursor composition and / or the polyimide film with light including a wavelength of 300-500 nm, wherein step (4) is performed simultaneously with at least one step selected from step (1), step (2), and step (3), and / or is performed after at least one step selected from step (1), step (2), and step (3).

Description

Polyimide film manufacturing method and polyimide film

[0001] The present invention relates to a method for producing a polyimide film 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] International Publication No. WO 2012 / 011590 International Publication No. WO 2013 / 179727 International Publication No. WO 2014 / 038715 International Publication No. WO 2022 / 176956

[0006] Compared with the 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. In recent years, film formation methods for thin film transistors (TFTs) have also been improved, and film formation temperatures have been lowered compared to conventional methods, but high-temperature treatment 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, have the advantage of being adaptable to a variety of processes if their heat resistance is further improved.

[0007] 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.

[0008] Therefore, an object of the present invention is to provide a method for producing a polyimide film that has the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient, and also has improved optical transparency. Another object of the present invention is to provide a method for producing a polyimide film / substrate laminate and a flexible electronic device.

[0009] The main disclosures of the present application can be summarized as follows: 1. A method for producing a polyimide film, comprising: step (1) of applying, onto a supporting substrate, a polyimide precursor composition obtained by reacting a tetracarboxylic acid component containing an aromatic tetracarboxylic dianhydride with a diamine component containing an aromatic diamine; step (2) of removing the solvent from the applied polyimide precursor composition; step (3) of imidizing the polyimide precursor composition to obtain a polyimide film; and step (4) of irradiating the polyimide precursor composition and / or the polyimide film with light having a wavelength of 300 nm to 500 nm, wherein step (4) is carried out simultaneously with at least one step selected from steps (1), (2), and (3) and / or after at least one step selected from steps (1), (2), and (3).

[0010] 2. The method for producing a polyimide film according to item 1, wherein the tetracarboxylic acid component contains 50 mol % or more of an aromatic tetracarboxylic dianhydride, and the diamine component contains 50 mol % or more of an aromatic diamine.

[0011] 3. The method for producing a polyimide film according to item 2, wherein the tetracarboxylic acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 70 mol % or more and the diamine component contains p-phenylenediamine in an amount of 70 mol % or more. 3a. The method for producing a polyimide film according to item 2, wherein the tetracarboxylic acid component contains 50 mol % or more of at least one selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone, and the diamine component contains 50 mol % or more of at least one selected from p-phenylenediamine, 4-aminophenyl-4-aminobenzoate, and 4,4'-diaminobenzanilide.

[0012] 4. The light receiving energy in the range of 300 nm to 400 nm on the light receiving surface is 100 J / m ２ The method for producing a polyimide film according to any one of the preceding items, wherein the light irradiation in step (4) is carried out in such a manner as described above.

[0013] 5. The illuminance in the range of 300 nm to 400 nm on the light receiving surface is 10 W / m ２ The method for producing a polyimide film according to any one of the preceding items, wherein the light irradiation in step (4) is carried out in such a manner as described above.

[0014] 6. The method for producing a polyimide film according to any one of the preceding items, wherein the light irradiation in step (4) is carried out simultaneously with the imidization in step (3).

[0015] 7. The method for producing a polyimide film according to item 6, wherein the imidization in step (3) is carried out by infrared radiation heating.

[0016] 8. The method for producing a polyimide film according to any one of the preceding items, wherein the polyimide film obtained by the method for producing a polyimide film is used for a flexible electronic device substrate.

[0017] 9. A method for producing a polyimide film / substrate laminate in which a polyimide film is laminated on a supporting substrate, the method comprising the method for producing a polyimide film according to any one of the preceding items as at least one step, wherein after step (1), steps (2) and (3) are carried out in a state in which a polyimide precursor composition is applied to the supporting substrate, to form a polyimide film on the supporting substrate.

[0018] 10. A method for producing a flexible electronic device, comprising the steps of: producing a polyimide film / substrate laminate by the production method of item 9 above; forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate; and peeling the polyimide film from the supporting substrate.

[0019] 11. A polyimide film obtained from a tetracarboxylic acid component containing 70 mol % or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 70 mol % or more of p-phenylenediamine, the polyimide film having a 450 nm transmittance of 70% or more and a retardation of 2400 nm or less, measured at a thickness of 10 μm. A polyimide film obtained from a tetracarboxylic acid component containing at least one member selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone in an amount of 50 mol % or more, and a diamine component containing at least one member selected from p-phenylenediamine, 4-aminophenyl-4-aminobenzoate, and 4,4'-diaminobenzanilide in an amount of 50 mol % or more, the polyimide film having a transmittance of 70% or more at 450 nm measured at a thickness of 10 μm.

[0020] 12. The polyimide film according to item 11a above, having a retardation of 2,400 nm or less when measured at a thickness of 10 μm. 13. A polyimide film / substrate laminate comprising a supporting substrate and the polyimide film according to any one of the preceding items formed on the supporting substrate.

[0021] 14. The polyimide film / substrate laminate according to item 13, wherein the supporting substrate is a glass substrate.

[0022] 15. A flexible electronic device comprising the polyimide film according to any one of the preceding claims.

[0023] According to the present invention, it is possible to produce a polyimide film that has the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient, while at the same time improving optical transparency. Furthermore, the present invention can provide a polyimide film / substrate laminate and a method for producing a flexible electronic device.

[0024] Furthermore, according to one aspect of the present invention, it is possible to provide a method for producing polyimide having improved phase difference (retardation) in the thickness direction.

[0025] 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.

[0026] The method for producing a polyimide film of the present invention includes at least the following steps (1) to (4): step (1): applying a polyimide precursor composition to a supporting substrate; step (2): removing the solvent from the applied polyimide precursor composition; step (3): imidizing the polyimide precursor composition to obtain a polyimide film; step (4): irradiating the polyimide precursor composition and / or the polyimide film with light having a wavelength of 300 nm to 500 nm.

[0027] The following description will be mainly divided into the sections of <<Polyimide precursor composition>>, <<Production method of polyimide film by steps (1) to (3)>>, and <<Light irradiation by step (4)>>.

[0028] <<Polyimide Precursor Composition>> First, the polyimide precursor composition used in step (1) will be described. The polyimide precursor composition for forming a polyimide film contains a polyimide precursor and a solvent. The polyimide precursor is dissolved in the solvent. The polyimide precursor has a structure obtained by reacting a tetracarboxylic acid component with a diamine component. The tetracarboxylic acid component contains an aromatic tetracarboxylic dianhydride, and the diamine component contains an aromatic diamine compound.

[0029] A preferred specific structure of the polyimide precursor is represented by the following general formula (I):

[0030] (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. １ and R ２ is a polyamic acid in which each of the groups is a hydrogen atom.

[0031] In all repeating units in the polyimide precursor, X １At least a portion of the aromatic groups are aromatic groups, preferably 50 mol% or more (preferably more than 50 mol%), more preferably 60 mol% or more, and even more preferably 70 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, and 95 mol% or more in that order, with the latter range being more preferred, and 100 mol% being also very preferred. In the following similar descriptions, the phrase "the latter range" will be omitted. １ At least a portion of the aromatic groups are aromatic groups, preferably 50 mol% or more (preferably more than 50 mol%), more preferably 60 mol% or more, and even more preferably 70 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, and 95 mol% or more in that order, and 100 mol% is also very preferable.

[0032] X １ preferably contains at least one of the structures represented by the following formula (II-1), formula (II-2) and formula (II-3), and X １ Preferably, 50 mol% or more (preferably more than 50 mol%), more preferably 60 mol% or more of these structures are these structures, and even more preferably 70 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, and 95 mol% or more are these structures in this order, and it is also very preferable that it is 100 mol%. １ contains at least one of the structures represented by formula (II-1) and formula (II-2) in the proportions described above. X other than formula (II-1), formula (II-2) and formula (II-3) １ is also preferably an aromatic group.

[0033]

[0034] Y １ preferably contains at least one of the structures represented by the following formulas (III-1), (III-2) and (III-3), and Y １Preferably, 50 mol % or more (preferably more than 50 mol %), more preferably 60 mol % or more of these structures are present, and even more preferably 70 mol % or more, 80 mol % or more, 85 mol % or more, 90 mol % or more, and 95 mol % or more are present, in that order, and it is also very preferable that the proportion is 100 mol %. １ contains the structure represented by formula (III-1) in the proportion described above. Y other than formula (III-1), formula (III-2) and formula (III-3) １ The structures of formula (III-2) and formula (III-3) also include structures in which the left and right sides are reversed.

[0035]

[0036] 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.

[0037] 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. When the term "derivative" is used for a tetracarboxylic acid component, it means a tetracarboxylic acid derivative. Although not particularly limited, it is convenient to use tetracarboxylic acid dianhydrides in production, and in the following explanation, an example will be described in which tetracarboxylic acid dianhydrides are used as the tetracarboxylic acid component. Furthermore, the diamine component is a diamine having an amino group (-NH ２ ) is a diamine compound having two

[0038] 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."

[0039] <X １ 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.

[0040] X １ When is a tetravalent aromatic group, it is preferably a tetravalent group having an aromatic ring with 6 to 40 carbon atoms.

[0041] Examples of the tetravalent group having an aromatic ring include the following.

[0042] (In the formula, Z １ is a direct bond or a divalent group as follows:

[0043] 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.)

[0044] 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.

[0045] Z ５ Specific examples of the alkyl group include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0046] 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. Further preferred compounds include tetracarboxylic acid dianhydrides having a fluorene structure such as (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone, as well as free tetracarboxylic acids and ester derivatives thereof. The tetracarboxylic acid component may be used alone or in combination of two or more kinds.

[0047] Among these tetracarboxylic acid components, particularly preferred compounds, in terms of dianhydride, include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), oxydiphthalic dianhydride (ODPA), pyromellitic dianhydride (PMDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (SFDA). More preferred are s-BPDA, ODPA, and SFDA, which give structures represented by formulas (II-1), (II-2), and (II-3), respectively, and in one preferred embodiment, it is preferred to use a tetracarboxylic acid component containing at least one selected from s-BPDA, ODPA, and SFDA in the proportions described for formulas (II-1), (II-2), and (II-3). In this case, the other tetracarboxylic acid component can be selected from the compounds described above.

[0048] In other embodiments, s-BPDA, ODPA, and SFDA (and their tetracarboxylic acids, derivatives thereof) may not be selected, and the tetracarboxylic acid component may be selected from the tetracarboxylic acid components described above.

[0049] 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 the 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 the group has at least one 4- to 12-membered aliphatic ring, more preferably a 4-membered or 6-membered aliphatic ring.

[0050] Examples of the alicyclic tetracarboxylic dianhydride include norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (abbreviation: CpODA), 2,2'-binorbornane-5,5',6,6'-tetracarboxylic dianhydride (abbreviation: BNBDA), monocyclic alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride and cyclohexane-1,2,4,5-tetracarboxylic dianhydride, and [1,1'-bi(cyclohexane)]-3,3',4,4'- Tetracarboxylic acid dianhydride, [1,1'-bi(cyclohexane)]-2,3,3',4'-tetracarboxylic acid dianhydride, [1,1'-bi(cyclohexane)]-2,2',3,3'-tetracarboxylic acid dianhydride, 4,4'-methylenebis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-(propane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-oxybis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-thiobis(cyclohexane-1,2-dicarboxylic acid anhydride), 4,4'-sulfur phenylbis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(dimethylsilanediyl)bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic anhydride), octahydropentalene-1,3,4,6-tetracarboxylic dianhydride, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride, 6-(carboxymethyl)bicyclo[2.2.1]heptane-2,3,5-tricarboxylic 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,8c-dimethanonaphthalene-2c,3c,Examples of such an anhydride include alicyclic tetracarboxylic dianhydrides having two or more rings, such as 6c,7c-tetracarboxylic dianhydride, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2t,3t,6c,7c-tetracarboxylic dianhydride, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic dianhydride, and tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic dianhydride. These may be used alone or in combination of two or more.

[0051] <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.

[0052] 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.

[0053] Examples of the divalent group having an aromatic ring include the following.

[0054] (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.

[0055] 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).

[0056]

[0057] (R in formula (6) ６１ ~R６８ each independently represents a direct bond or a divalent group represented by the formula (5).

[0058] 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 formulas: -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-.

[0059] Another preferred group is W in the above formula (4). １ is a phenylene group, that is, a terphenyldiamine compound, and particularly preferred is a compound in which all the bonds are para-bonded.

[0060] 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.

[0061] 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-aminophenyl-4-aminobenzoate, 4-aminophenone, 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-amino phenoxy)benzene, 1,3-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, 2,4-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.

[0062] Among these diamine components, particularly preferred compounds include p-phenylenediamine (PPD; giving the structure of formula (III-1)), 4-aminophenyl-4-aminobenzoate (4-BAAB; giving the structure of formula (III-2)), 4,4'-diaminobenzanilide (DABAN; giving the structure of formula (III-3)), spiro[fluorene-9,9'-xanthene]-3',6'-diamine (the following formula (SFX1)), and spiro[fluorene-9,9'-xanthene]-3',6'-diamine. and 1-then-2',7'-diamine (formula (SFX2) below). The diamine component preferably contains at least one of these, and in a more preferred embodiment, it preferably contains a diamine compound containing at least one selected from PPD, 4-BAAB, and DABAN in the proportions described for formulas (III-1), (III-2), and (III-3). In this case, the other diamine component can be selected from the compounds described above.

[0063]

[0064] In another preferred embodiment, p-phenylenediamine may not be selected, but may be selected from the diamine components described above.

[0065] Y 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 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.

[0066] Y １ is 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.

[0067] 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.

[0068] Polyimides derived from monomers containing s-BPDA and PPD as their main components have excellent heat resistance, mechanical strength, and thermal properties. Therefore, if the present invention can improve coloration even slightly, it will have a significant practical effect in flexible (electronic) device applications.

[0069] 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. 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 Depending on the chemical structure of the 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.

[0070] 1) The polyamic acid polyimide precursor can be suitably obtained as a polyimide precursor solution by reacting a tetracarboxylic acid 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.

[0071] 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.

[0072] 2) A polyamic acid ester tetracarboxylic dianhydride is reacted with an 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, a polyimide precursor can be easily obtained by dehydration condensation of a diester dicarboxylic acid and a diamine using a phosphorus-based condensing agent or a carbodiimide condensing agent.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The solvents used in preparing the polyimide precursor are water, N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone (DMI), 3-methoxy-N,N-dimethylpropanamide (MPA), and 1-butyl-2-pyrrolidone (NBP). Solvent B includes N,N-dimethylpropionamide (DMPA), N,N-diethylformamide (DEF), N,N-diethylacetamide (DEAc), N,N-dimethylisobutyramide (DMIB), and N amide solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, cyclic ester solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, phenol solvents such as m-cresol, p-cresol, 3-chlorophenol, 4-chlorophenol, acetophenone, sulfolane, dimethyl sulfoxide, and the like. 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.

[0078] When a solvent is used, it is also preferable to select and use a solvent that is not designated as a substance of concern due to its hazardous properties under the REACH regulation of the European Union (EU). In this regard, in one embodiment of the present invention, it is preferable not to use N,N-dimethylacetamide, N-methylpyrrolidone, N-methylacetamide, or N,N-dimethylformamide, or, if used, to keep the amount to a minimum.

[0079] 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.

[0080] 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.

[0081] <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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] <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.

[0086] 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. －１ The 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.

[0087] 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.

[0088] 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.

[0089] Since the present invention relates to a method for producing a polyimide film for flexible electronic device substrates, the polyimide precursor composition is substantially free of compounds that react sensitively to light irradiation. For example, it does not contain photosensitive compounds such as quinone diazide compounds, polymerizable compounds that undergo addition polymerization such as compounds having an ethylenic double bond, or other compounds that are unstable in themselves, such as radical or ionic polymerization initiators. It is also preferable that the polyimide precursor composition does not contain compounds such as diamines that have liquid crystal alignment properties or compounds having a siloxane structure.

[0090] <<Method for Producing a Polyimide Film by Steps (1) to (3)>> Steps (1) to (3) are not particularly limited, and any known steps for producing a polyimide film can be adopted. In addition to these, the production method of the present invention also includes step (4), which will be described later.

[0091] A typical method for producing a polyimide film, comprising steps (1) to (3), includes casting a polyimide precursor composition onto a supporting substrate (step (1)), followed by heating and imidizing the composition on the substrate to obtain a polyimide film (steps (2) and (3)). This method is suitable for producing flexible electronic devices via a polyimide film / substrate laminate, as will be described below.

[0092] <Production of Polyimide Film / Substrate Laminate and Flexible Electronic Device> According to the production method of the present invention, a polyimide film / substrate laminate can be produced using a polyimide precursor composition. The polyimide film / substrate laminate can be produced by (a) applying a polyimide precursor composition to a supporting substrate (step (1)), 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 (steps (2) and (3)). The production method of a flexible electronic device of the present invention uses the polyimide film / substrate laminate produced in steps (a) and (b) and further comprises the steps of (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.

[0093] 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] In step (b), the polyimide precursor composition is heat-treated on the supporting substrate. Step (b) includes a step (2) of removing the solvent from the coated polyimide precursor composition and a step (3) of imidizing the polyimide precursor composition to obtain a polyimide film. As a result, a polyimide film / substrate laminate having a polyimide film on the supporting substrate is produced.

[0099] The heat treatment conditions are not particularly limited, but for example, heating is first performed in a temperature range of 50°C to 150°C. In this temperature range, the removal of the solvent mainly proceeds, and imidization may also proceed. Therefore, step (2) is mainly performed. Thereafter, it is preferable to perform the treatment by heating to a maximum heating temperature of, for example, 150°C to 600°C, preferably 200°C to 550°C, and more preferably 250°C to 500°C. In this range, the remaining solvent is removed, and imidization proceeds and is completed. Therefore, step (3) is mainly performed. In this way, each step does not need to be clearly separated.

[0100] <<Light Irradiation in Step (4)>> A feature of the present invention is the implementation of step (4). Step (4) may be implemented simultaneously with at least one step selected from steps (1) to (3), or may be implemented after at least one step selected from steps (1) to (3), or may be implemented simultaneously with at least one step selected from steps (1) to (3) and after at least one step selected from steps (1) to (3). Here, "implemented simultaneously" means that step (4) may be implemented during any period during which the selected step (e.g., step (1)) is being implemented; for example, it is not necessary for steps (1) and (4) to start and end simultaneously.

[0101] For example, step (4) can be started during step (1), and step (4) can be continued even after step (1) is completed, and step (4) can be completed before step (2) starts, and step (4) can be performed again during step (3), and any combination thereof can be used.

[0102] Specifically, examples of the method include: - carrying out light irradiation immediately after applying the polyimide precursor composition onto the support substrate in step (1); - carrying out light irradiation in step (2) and / or step (3) while removing the solvent from the applied polyimide precursor composition and / or while allowing imidization to proceed; - carrying out light irradiation after removing the solvent in step (2) (it is not necessary for the solvent to be completely removed) and before completing imidization in step (3); - carrying out light irradiation after completing imidization in step (3).

[0103] The irradiating light includes wavelengths in the range of 300 nm to 500 nm. In a preferred embodiment, the irradiating light includes the entire wavelength range of 300 nm to 500 nm. In a different embodiment, the irradiating light may include only a portion of the wavelength range of 300 nm to 500 nm. In one embodiment, the irradiating light preferably includes a wavelength range of 300 nm to 400 nm.

[0104] The intensity of the irradiated light, i.e., the illuminance in the range of 300 nm to 400 nm on the light receiving surface (irradiance: power per unit area), is preferably 10 W / m ２ More preferably, 40 W / m ２ or more, and even more preferably 60 W / m ２ or more, and even more preferably 100 W / m ２ More preferably, it is 10,000 W / m ２ Less than or equal to 5,000 W / m ２ or less, and even more preferably 3,000 W / m ２ The irradiance in the range of 300 nm to 400 nm is expressed as the irradiance spectrum (W / m ２ The light-receiving surface is obtained by integrating the light-receiving wavelength (λ / nm) over a range of 300 to 400 nm. It can be measured conveniently using a measuring device as described below. Here, the light-receiving surface refers to the surface of the polyimide precursor composition and / or polyimide film coated on the supporting substrate that receives light.

[0105] In addition, the received light energy in the range of 300 nm to 400 nm on the light receiving surface (integrated light amount J / m ２ ; Irradiance x time = W / m ２× sec), preferably 1 J / m ２ or more, and further 10 J / m ２ Above, 100J / m ２ Above, 1kJ / m ２ Above, 10kJ / m ２ The above order is more preferable. To ensure the effect, 100 kJ / m ２ Above, 1,000kJ / m ２ Above, 2,000kJ / m ２ Above, 3,000kJ / m ２ Above, 5,000kJ / m ２ Above, 10,000kJ / m ２ or more than 100,000 kJ / m ２ However, since prolonged irradiation is a waste of energy, for example, it is preferable to set the irradiation dose to 10,000,000 kJ / m ２ or less, more preferably 6,000,000 kJ / m ２ or less, and even more preferably 4,500,000 kJ / m ２ Usually, it is 1,000,000 kJ / m or less. ２ Below, 500,000kJ / m ２ Below, 100,000kJ / m ２ or less than 70,000 kJ / m ２ Even if the temperature is less than this, sufficient effects can be obtained.

[0106] The light receiving energy in the range of 310 to 390 nm on the light receiving surface is 20 J / m ２ Above, 200J / m ２ Above, 2kJ / m ２ Above, 20kJ / m ２ Above, 200kJ / m ２ Above, 500kJ / m ２ More than 1,000 kJ / m is preferable, and 1,000 kJ / m is more preferable. ２ Above, 2,000kJ / m ２ More than 20,000kJ / m ２ It is also possible to set it to 2,000,000 kJ / m or more. ２ or less, more preferably 1,000,000 kJ / m ２ or less, and even more preferably 800,000 kJ / m２ Usually, it is 200,000 kJ / m or less. ２ Below, 90,000kJ / m ２ Below, 20,000kJ / m ２ or less than 10,000 kJ / m ２ Even if the temperature is less than this, sufficient effects can be obtained.

[0107] The light receiving energy in the range of 320 to 470 nm on the light receiving surface is 200 J / m ２ Above, 2kJ / m ２ Above, 20kJ / m ２ Above, 200kJ / m ２ Above, 2,000kJ / m ２ Above, 4,000kJ / m ２ Above, 6,000kJ / m ２ Above, 10,000kJ / m ２ Above, 20,000kJ / m ２ or more than 200,000 kJ / m ２ It is also possible to set it to 20,000,000 kJ / m or more. ２ or less, more preferably 12,000,000 kJ / m ２ or less, and even more preferably 9,000,000 kJ / m ２ Usually, it is 2,000,000 kJ / m or less. ２ Below, 1,000,000kJ / m ２ Below, 200,000kJ / m ２ or less or 140,000 kJ / m ２ Even if the temperature is less than this, sufficient effects can be obtained.

[0108] The received light energy (integrated light amount J / m) in these wavelength ranges ２) in the range of 300 nm to 400 nm can be measured or calculated, for example, using a testing device such as the Atlas SUNTEST XLS+ manufactured by Toyo Seiki Seisakusho (or using a photodetector attached to this device). For the range of 310 to 390 nm, it can be measured or calculated using, for example, a UIT250+ photodetector UVD-S365 (center wavelength 365 nm) manufactured by Ushio Inc., and for the range of 320 to 470 nm, it can be measured or calculated using a UIT250+ photodetector UVD-S405 (center wavelength 405 nm) manufactured by Ushio Inc. In other words, in the present invention, the light source (intensity, wavelength) and irradiation time (described below) can be selected so that the above-mentioned received light energy is obtained when measured using at least one of the three measuring devices (photodetectors) exemplified herein.

[0109] The irradiation time can be determined appropriately depending on the illuminance so as to achieve the above-mentioned received light energy, but is, for example, 10 seconds or more, preferably 1 minute or more, more preferably 10 minutes or more. It is usually 30 days or less, preferably 20 days or less. Note that, in the environment during normal polyimide film production and flexible electronic device production, the above-mentioned illuminance and received light energy conditions are not reached.

[0110] Examples of light irradiation equipment that can be used include xenon lamps, halogen lamps, sunshine carbon arc lamps (open-flame carbon arc lamps), low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and gallium lamps. When the heat treatment for solvent removal in step (2) and / or imidization in step (3) is performed by infrared radiation heating, an infrared heater containing a predetermined intensity of wavelengths in the range of 300 nm to 500 nm can be used, or a separate light source emitting light in the range of 300 nm to 500 nm can be added in addition to the infrared heater to perform step (4) simultaneously with solvent removal and / or imidization. When using these light sources, it is also preferable to use a filter, as necessary, to cut out unnecessary or undesirable wavelength ranges.

[0111] 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 by 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.

[0112] 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 ２ Examples 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Next, in step (d), the support substrate and the polyimide film are peeled off by a mechanical peeling method in which physical peeling is performed by applying an external force, or by a so-called laser peeling method in which peeling is performed by irradiating the substrate surface with laser light.

[0121] 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.

[0122] 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.

[0123] <Other Manufacturing Methods of Polyimide Film> As another manufacturing method, a method for manufacturing a polyimide film via a self-supporting film can also be applied. This method is preferably applied to a method for continuously manufacturing a polyimide film, preferably in a long form. In this method, a polyimide precursor composition is cast onto a supporting substrate (step (1)), and the self-supporting film is manufactured by heating and drying (step (2) is the main step, but step (3) also proceeds). The self-supporting film is then peeled off from the substrate, and the film is held, for example, by a tenter and heated and imidized in a state in which degassing is possible from both sides of the film to obtain a polyimide film (from the final stage of step (2) to the completion of imidization in step (3)).

[0124] <Properties of Polyimide Film> 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 may be unable to withstand stress and break when used, for example, as a flexible electronic device substrate. 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 be difficult to thin the flexible device. To achieve a thinner polyimide film while maintaining sufficient durability for a flexible device, the thickness of the polyimide film is preferably 2 to 50 μm.

[0125] The polyimide films produced by the present invention are excellent in optical properties, mechanical properties, thermal properties, and heat resistance (glass transition temperature, thermal decomposition resistance). Compared to conventional polyimide films having the same composition, the polyimide films produced by the production method of the present invention have improved light transmittance in particular. The term "heat resistance" includes those related to phase change (indicated by glass transition temperature or melting temperature) and those related to thermal decomposition (indicated by weight loss). Since these are different phenomena, there is no direct relationship between them. The polyimides and polyimide films of the present invention are excellent in both glass transition temperature (Tg) and thermal decomposition resistance.

[0126] The polyimide film produced in one embodiment of the present invention has a 5% weight loss temperature of preferably more than 580°C, more preferably 590°C or higher, even more preferably 595°C or higher, even more preferably 600°C or higher, and even more preferably higher than 600°C.

[0127] The polyimide film produced in one embodiment of the present invention has an extremely low coefficient of linear thermal expansion (CTE) of preferably 20 ppm / K or less, more preferably less than 20 ppm, even more preferably 15 ppm / K or less, even more preferably 10 ppm / K or less, even more preferably 5 ppm / K or less, and even more preferably less than 5 ppm / K, when measured on a 10 μm thick film from 150° C. to 250° C.

[0128] 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.

[0129] In one embodiment of the present invention, the 450 nm light transmittance of a 10 μm thick polyimide film produced by the production method of the present invention, which includes step (4), is improved by preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and even more preferably 4% or more, compared to a production method that does not include step (4).

[0130] In the description of this application, when the invention of a polyimide film is referred to in terms of the film properties of a 10 μm thick film, this means that the properties are exhibited when a 10 μm thick film is produced using the same composition and method, or when converted to a thickness of 10 μm for convenience. It is intended that polyimide films having thicknesses other than 10 μm also be encompassed by this invention.

[0131] In one embodiment of the present invention, the 450 nm light transmittance of a 10 μm thick polyimide film is preferably 69% or more, more preferably 70% or more, even more preferably 71% or more, and even more preferably 72% or more. Furthermore, when measured on a 10 μm thick film, the yellowness index (YI) of the polyimide film is preferably 30 or less, more preferably 28 or less, even more preferably 24 or less, and even more preferably 23 or less. It is usually 0 or more.

[0132] In one embodiment of the present invention, the thickness direction retardation of a 10 μm thick polyimide film produced by the production method of the present invention, which includes step (4), is improved by preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more, compared to a production method that does not include step (4).

[0133] In one embodiment of the present invention, the absolute value of the phase difference (retardation) in the thickness direction of a 10 μm thick polyimide film is preferably 2450 nm or less, more preferably 2400 nm or less, and even more preferably 2300 nm or less, 2200 nm or less, 2100 nm or less, and 2050 nm or less in that order.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] It is particularly preferable that the polyimide film simultaneously satisfy all of the desirable properties. A preferred polyimide film, at a film thickness of 10 μm, has, for example, a 5% weight loss temperature of 600°C or higher (or higher than 600°C), a linear thermal expansion coefficient of 5 ppm / K or lower (or lower than 5 ppm / K), and a 450 nm light transmittance of 70% or higher (or higher than 70%). A preferred polyimide film also preferably has a thickness direction retardation of 2300 nm or lower (or less). It is also preferable that these properties fall within the above-mentioned even better ranges. In addition to these properties, a preferred polyimide film also preferably has higher levels of the optical properties, such as yellowness index and haze value, and mechanical properties, such as elongation at break and strength at break.

[0138] 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.

[0139] In the following examples, evaluation was carried out by the following methods.

[0140] <Evaluation of Polyimide Film> [Light Transmittance at 450 nm and 800 nm, b*] Using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation), the light transmittance at 450 nm and 800 nm of a polyimide film having a thickness of approximately 10 μm was measured. In addition, b* was calculated.

[0141] [Yellowness Index (YI)] The YI of the polyimide film was measured using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation) in accordance with the standard of ASTEM E313. The light source was D65 and the viewing angle was 2°.

[0142] [5% Weight Loss Temperature] A polyimide film having a thickness of approximately 10 μm was used as a test piece, and the temperature was increased from 25° C. to 600° C. at a rate of 10° C. / min in a nitrogen stream using a calorimeter (Q5000IR) manufactured by TA Instruments Co., Ltd. From the obtained weight curve, the 5% weight loss temperature was determined, with the weight at 150° C. being 100%.

[0143] [Coefficient of Linear Thermal Expansion (CTE)] A polyimide film with a thickness of approximately 10 μm was cut into a strip with a width of 3 mm to prepare a test piece, and the test piece was heated to 500° C. using a TMA / SS6100 (manufactured by SII NanoTechnology Inc.) with a chuck length of 15 mm, a load of 2 g, and a heating rate of 20° C. / min. The coefficient of linear thermal expansion from 50° C. to 300° C. was determined from the obtained TMA curve.

[0144] [Retardation in the thickness direction of the film (Rth)] A polyimide film having a thickness of 10 μm was used as a test piece, and Re and Rth were measured using a retardation measurement device (KOBRA-WR) manufactured by Oji Measurement Instruments Co., Ltd. The retardation measurement of the film was carried out with an Rth incident angle of 40°. From the obtained retardation, the retardation in the thickness direction of the film having a thickness of 10 μm was calculated.

[0145] <Raw Materials> The abbreviations for the raw materials used in the following examples are as follows.

[0146] [Diamine component] PPD: p-phenylenediamine 4,4'-DDS: 4,4'-diaminodiphenyl sulfone BAFL: 9,9-bis(4-aminophenyl)fluorene 4-BAAB: 4-aminophenyl-4-aminobenzoate

[0147] [Tetracarboxylic acid components] s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride PMDA: pyromellitic dianhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride SFDA: spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone

[0148]

[0149] [Solvent] NMP: N-methyl-2-pyrrolidone

[0150] Examples and Comparative Examples Preparation of Polyimide Precursor Composition A 10.8 g (0.1 mol) of PPD was placed in a reaction vessel purged with nitrogen gas, and N-methyl-2-pyrrolidone (NMP) was added as a solvent. The mass of the solvent was 292.9 g, an amount that would result in a total mass of charged monomers (total of diamine components and carboxylic acid components) of 12 mass%. Stirring was then carried out 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 A.

[0151] [Production of Polyimide Film / Steps (1), (2), and (3)] A 6-inch Corning Eagle-XG (registered trademark) glass substrate (500 μm thick) was used. Polyimide precursor composition A was applied to the glass substrate, and the substrate was heated from room temperature to 450°C in a nitrogen atmosphere (oxygen concentration 200 ppm or less) to thermally imidize the polyimide film, yielding a polyimide film / substrate laminate. The laminate was immersed in 40°C water (e.g., at a temperature ranging from 20°C to 100°C) to peel the polyimide film from the glass substrate. After drying, a sample was cut out and the properties of the polyimide film before light irradiation were measured. The thickness of the polyimide film was approximately 10 μm. The results are shown in Table 1 (Comparative Example A1).

[0152] [Light Irradiation / Step (4)] The obtained polyimide film was irradiated with light using a xenon lamp as a light source (the test equipment was a tabletop xenon accelerated weathering tester: Atlas SUNTEST XLS+ manufactured by Toyo Seiki Seisakusho). The illuminance in the range of 300 nm to 400 nm on the light-receiving surface of the polyimide film was 40 W / m ２ After the predetermined times (24 hours, 48 ​​hours, 72 hours, 96 hours, 192 hours, and 384 hours) had elapsed, the physical properties of the polyimide film were measured. The results are shown in Table 1 (Examples A1 to A6).

[0153]

[0154] From the results in Table 1, it was found that the transmittance at 450 nm was clearly improved by light irradiation. ｔｈ ) was also confirmed to be improved by light irradiation.

[0155] [Preparation of Polyimide Precursor Compositions B to H] Polyimide precursor compositions B to H were prepared in the same manner as polyimide precursor composition A, except that the tetracarboxylic acid component and diamine component were changed to the compounds shown in Tables 2 and 3. In the tables, the polyimide precursor composition is simply referred to as "composition." Composition A' is a repeat experiment of polyimide precursor composition A, but was used in an experiment in which the irradiance was changed as shown below.

[0156] [Preparation of Polyimide Films Using Polyimide Precursor Compositions A', B to H, and Light Irradiation] Polyimide films with a thickness of approximately 10 μm were prepared using polyimide precursor compositions A', B to H in the same manner as in Comparative Example A1 and Examples A1 to A6. A xenon lamp (Atlas SUNTEST XLS+ manufactured by Toyo Seiki Seisakusho) was used as the light source, and the illuminance in the range of 300 nm to 400 nm on the light-receiving surface of the film was 60 W / m ２ The polyimide film was irradiated with light at an intensity adjusted to 72 hours or 144 hours. After a predetermined time (72 hours or 144 hours), the physical properties of the polyimide film were measured. The results are shown in Tables 2 and 3.

[0157] Furthermore, in Tables 2 and 3, the received light energy (integrated light amount) in the light irradiation test is shown as follows: for the range of 300 nm to 400 nm, the measured value is shown using a light receiver attached to the testing machine, Atlas SUNTEST XLS+ manufactured by Toyo Seiki Seisaku-sho; for the range of 310 to 390 nm, the measured value is shown using a UIT250+ light receiving unit UVD-S365 (center wavelength 365 nm) manufactured by Ushio Inc.; and for the range of 320 to 470 nm, the measured value is shown using a UIT250+ light receiving unit UVD-S405 (center wavelength 405 nm) manufactured by Ushio Inc.

[0158]

[0159]

[0160] It was confirmed that the transmittance at 450 nm was also improved by light irradiation in the polyimide precursor compositions B to H.

[0161] 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 method for producing a polyimide film, comprising: step (1) of applying a polyimide precursor composition obtained by reacting a tetracarboxylic acid component containing an aromatic tetracarboxylic dianhydride with a diamine component containing an aromatic diamine onto a supporting substrate; step (2) of removing the solvent from the applied polyimide precursor composition; step (3) of imidizing the polyimide precursor composition to obtain a polyimide film; and step (4) of irradiating the polyimide precursor composition and / or the polyimide film with light having a wavelength of 300 nm to 500 nm, wherein step (4) is carried out simultaneously with at least one step selected from steps (1), (2), and (3) and / or after at least one step selected from steps (1), (2), and (3).

2. The method for producing a polyimide film according to claim 1, wherein the tetracarboxylic acid component contains 50 mol % or more of an aromatic tetracarboxylic dianhydride, and the diamine component contains 50 mol % or more of an aromatic diamine.

3. The method for producing a polyimide film according to claim 2, wherein the tetracarboxylic acid component contains at least one selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone in an amount of 50 mol % or more, and the diamine component contains at least one selected from p-phenylenediamine, 4-aminophenyl-4-aminobenzoate, and 4,4'-diaminobenzanilide in an amount of 50 mol % or more.

4. The light receiving energy in the range of 300 nm to 400 nm on the light receiving surface is 100 J / m ２ The method for producing a polyimide film according to claim 1 , wherein the light irradiation in step (4) is carried out so as to achieve the above.

5. The illuminance in the range of 300 nm to 400 nm on the light receiving surface is 10 W / m ２ The method for producing a polyimide film according to claim 1 , wherein the light irradiation in step (4) is carried out so as to achieve the above.

6. The method for producing a polyimide film according to claim 1, wherein the light irradiation in step (4) is carried out simultaneously with the imidization in step (3).

7. The method for producing a polyimide film according to claim 6, wherein the imidization in step (3) is carried out by infrared radiation heating.

8. The method for producing a polyimide film according to claim 1, wherein the polyimide film obtained by the method for producing a polyimide film is used as a substrate for a flexible electronic device.

9. A method for producing a polyimide film / substrate laminate in which a polyimide film is laminated on a supporting substrate, the method comprising the method for producing a polyimide film according to claim 1 as at least one step, and after step (1), carrying out steps (2) and (3) in a state in which a polyimide precursor composition is applied to the supporting substrate to form a polyimide film on the supporting substrate.

10. A method for producing a flexible electronic device, comprising the steps of: producing a polyimide film / substrate laminate by the production method of claim 9; forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate; and peeling the supporting substrate and the polyimide film.

11. A polyimide film obtained from a tetracarboxylic acid component containing 50 mol% or more of at least one selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone, and a diamine component containing 50 mol% or more of at least one selected from p-phenylenediamine, 4-aminophenyl-4-aminobenzoate, and 4,4'-diaminobenzanilide, the polyimide film having a transmittance of 70% or more at 450 nm measured at a thickness of 10 μm.

12. The polyimide film according to claim 11, which has a retardation of 2,400 nm or less when measured at a thickness of 10 μm.

13. A polyimide film / substrate laminate comprising a supporting substrate and the polyimide film according to claim 11 or 12 formed on the supporting substrate.

14. The polyimide film / substrate laminate according to claim 13, wherein the supporting substrate is a glass substrate.

15. A flexible electronic device comprising the polyimide film according to claim 11 or 12.

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