Polyimide precursor composition, polyimide film, polyimide film / substrate layered product, flexible electronic device, and flexible electronic device substrate

Abstract

This polyimide precursor composition contains: a polyimide precursor which contains a repeating unit represented by a formula (1) and satisfies a specific condition (for example, the condition that at least one of all X1 moieties present in the polyimide precursor is a tetravalent aromatic group); and a specific silicon compound such as a silanol compound. [In formula (1), X1 is a tetravalent aromatic group or the like, Y1 is a divalent aromatic group or the like, and R1 and R2 are each independently a hydrogen atom or the like.]

Description

Polyimide precursor compositions, polyimide films, polyimide film / substrate laminates, flexible electronic devices, and flexible electronic device substrates.

[0001] The present invention relates to a polyimide precursor composition, a polyimide film, a polyimide film / substrate laminate, a flexible electronic device, and a flexible electronic device substrate.

[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. In recent years, the use of polyimide films as plastic substrates to replace glass substrates has been explored, particularly in the field of display devices (such as liquid crystal displays and organic EL displays). Research is underway on various types of polyimide precursor compositions (varnishes, etc.) to efficiently manufacture polyimide films for various applications.

[0003] For example, Japanese Patent Publication No. 2013-18806 (Patent Document 1) discloses a polyamic acid composition in its examples and comparative examples that comprises a varnish of polyamic acid and a cage-like partially cleaved structure of silsesquioxane having silanol groups and phenyl groups, wherein the content of the partially cleaved structure of silsesquioxane is 36 parts by mass or 100 parts by mass per 100 parts by mass of polyamic acid.

[0004] Furthermore, International Publication No. 2023 / 120627 (Patent Document 2) discloses a curable resin composition comprising polyimide and silsesquioxane, wherein the polyimide content is 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of silsesquioxane (Note that, with respect to such a curable resin composition, the silsesquioxane content, when converted to an amount per 100 parts by mass of polyimide, is 200 parts by mass or more and 20,000 parts by mass or less).

[0005] Furthermore, in the section of its examples, International Publication No. 2017 / 051827 (Patent Document 3) discloses a composition comprising a polyimide precursor and a silicone-based surfactant, wherein the content of the silicone-based surfactant is 0.025 parts by mass per 100 parts by mass of the polyimide precursor (Examples 35, 39, 41, and 45 of Patent Document 3, etc.).

[0006] Japanese Patent Publication No. 2013-18806, International Publication No. 2023 / 120627, International Publication No. 2017 / 051827

[0007] However, conventional compositions such as those described in Patent Documents 1 to 3 above were not sufficient in terms of storage stability and in achieving both high levels of transparency and high levels of heat resistance.

[0008] The present invention has been made in view of the problems of the prior art described above, and aims to provide a polyimide precursor composition that enables the production of a polyimide film that has high storage stability, as well as high levels of transparency and high levels of heat resistance. Furthermore, the present invention aims to provide a polyimide film obtained using the polyimide precursor composition, as well as a polyimide film / substrate laminate, a flexible electronic device, and a flexible electronic device substrate using the polyimide film.

[0009] As a result of diligent research to achieve the above objective, the present inventors have found that by providing a polyimide precursor composition containing a repeating unit represented by the following formula (1) and satisfying the following (i) and (ii); and at least one silicon compound selected from the group consisting of silanol compounds and silicones; and by setting the content of the silicon compound to 1 to 29 parts by mass when the mass of the polyimide precursor in terms of polyimide is 100 parts by mass, it is possible to provide a composition with high storage stability such that the film does not become cloudy even when the composition is stored for a long period of time of about 30 days and then used to manufacture a film, and moreover, by using this composition, it is possible to manufacture a polyimide film having a high level of transparency and a high level of heat resistance, thus completing the present invention.

[0010] In other words, the present invention provides the following embodiments.

[0011] [1] A polyimide precursor composition comprising: a polyimide precursor containing repeating units represented by the following formula (1) and satisfying the following (i) and (ii); and at least one silicon compound selected from the group consisting of silanol compounds and silicones, wherein the content of the silicon compound is 1 to 29 parts by mass when the mass of the polyimide precursor in terms of polyimide is 100 parts by mass.

[0012]

[0013] [In formula (1), X １ Y is a tetravalent aliphatic group or a tetravalent aromatic group. １ R is a divalent aliphatic group or a divalent aromatic group. １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.

[0014] (i) All X present in the polyimide precursor １ At least one of them is a tetravalent aromatic group.

[0015] (ii) At least one of all Ys present in the polyimide precursor is a divalent aromatic group. １

[0016] [2] The polyimide precursor composition according to [1], wherein the silicon compound is at least one selected from the group consisting of a silanol compound having an aryl group and a silicone having an aryl group and a silanol group.

[0017] [3] In the polyimide precursor, 50 mol% or more of the total amount of X １ is a tetravalent aromatic group represented by the following formula (1-1), and the polyimide precursor composition according to [1] or [2].

[0018]

[0019] [4] In the polyimide precursor, 50 mol% or more of the total amount of Y １ is a p-phenylene group, and the polyimide precursor composition according to any one of [1] to [3].

[0020] [5] The polyimide precursor composition according to any one of [1] to [4], further comprising an imidazole compound.

[0021] [6] In the polyimide precursor, 1 to 30 mol% of the total amount of X １ is a tetravalent aromatic group represented by the following formula (1-2), and the polyimide precursor composition according to any one of [1] to [5].

[0022]

[0023] [In formula (1-2), R １０ and R １１ are each independently a single bond or a divalent organic group. ]

[0024] [7] In the polyimide precursor, 1 to 30 mol% of the total amount of Y １ is a divalent aromatic group represented by the following formula (1-3), and the polyimide precursor composition according to any one of [1] to [6].

[0025]

[0026] [In formula (1-3), R １２ and R １３ Each of these is independently a single-bonded or divalent organic group.

[0027] A polyimide film obtained from the polyimide precursor composition described in any one of items [8], [1], to [7].

[0028] A polyimide film / substrate laminate comprising the polyimide film described in [9] and [8] and a substrate.

[0029] A flexible electronic device comprising the polyimide film described in

[10] and [8].

[0030] A flexible electronic device substrate comprising the polyimide film described in

[11] and [8].

[0031]

[12] A polyimide film obtained from a polyimide precursor composition containing a repeating unit represented by the following formula (1) and a polyimide precursor satisfying the following (i) and (ii), wherein the silicon content in the polyimide film is 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film, and the 0.5% weight loss temperature is 535°C or higher.

[0032]

[0033] [In formula (1), X １ Y is a tetravalent aliphatic group or a tetravalent aromatic group. １ R is a divalent aliphatic group or a divalent aromatic group. １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.

[0034] (i) All X present in the polyimide precursor １ At least one of them is a tetravalent aromatic group.

[0035] (ii) All Y present in the polyimide precursor １ At least one of them is a divalent aromatic group.

[0036] According to the present invention, it is possible to provide a polyimide precursor composition that enables the production of a polyimide film having high storage stability, high levels of transparency, and high levels of heat resistance. Furthermore, according to the present invention, it is possible to provide a polyimide film obtained using the polyimide precursor composition, as well as a polyimide film / substrate laminate, a flexible electronic device, and a flexible electronic device substrate using the polyimide film.

[0037] The present invention will be described in detail below with reference to its preferred embodiments.

[0038] <Polyimide Precursor Composition> The polyimide precursor composition of the present invention contains a polyimide precursor that contains repeating units represented by the above formula (1) and satisfies (i) and (ii) above; and at least one silicon compound selected from the group consisting of silanol compounds and silicones; wherein the content of the silicon compound is 1 to 29 parts by mass when the mass of the polyimide precursor in terms of polyimide is 100 parts by mass (in this specification, "mass of the polyimide precursor in terms of polyimide" means the mass of polyimide obtained when polyimide is produced from the polyimide precursor (total amount) in the composition by completely imidizing all of the repeating units in the polyimide precursor contained in the composition (total mass of polyimide obtained when all of the polyimide precursor contained in the composition is completely ring-closed imidized)). Hereinafter, the polyimide precursor and the silicon compound will be described separately.

[0039] <Polyimide Precursor> The polyimide precursor to be contained in the polyimide precursor composition of the present invention is a repeating unit represented by the following formula (1) (wherein the following formula (1), X １ is a tetravalent aliphatic group or a tetravalent aromatic group, Y １ R is a divalent aliphatic group or a divalent aromatic group. １ and R ２Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group. The polyimide precursor contains and satisfies the above conditions (i) and (ii). Below, regarding the polyimide precursor, we will first explain the repeating unit represented by formula (1) that the polyimide precursor has as an essential repeating unit, and then explain each condition.

[0040]

[0041] (Regarding the repeating unit represented by equation (1)) X in equation (1) １ is a tetravalent aliphatic group or a tetravalent aromatic group. In the present invention, the polyimide precursor must satisfy (i) above. Therefore, in the present invention, a plurality of X contained in the polyimide precursor １ At least one of them will always contain a tetravalent aromatic group. Here, first, multiple X present in the precursor １ The X in formula (1) includes at least one tetravalent aromatic group that is always present among them. １ This section describes the bases that can be selected as such.

[0042] X in equation (1) above １ X is a tetravalent aliphatic group or a tetravalent aromatic group. １ The structure is derived from the tetracarboxylic acid component, which is a monomer component used in the production of polyimide precursors (organic group). The "tetracarboxylic acid component" referred to here is a component that can be used as a raw material monomer when producing polyimide and is also present in the polyimide precursor X １Any compound that can incorporate a tetravalent aliphatic group or a tetravalent aromatic group is acceptable, and the concept includes tetracarboxylic acids, tetracarboxylic dianhydrides, and other tetracarboxylic acid derivatives such as tetracarboxylic silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. The tetracarboxylic acid component is not particularly limited, but since it is convenient to use tetracarboxylic dianhydrides in the production of polyimide precursors, the following explanation will mainly focus on the case where tetracarboxylic dianhydrides are used as the tetracarboxylic acid component. For convenience, tetracarboxylic acids may also be used as examples of compounds that can be used as the tetracarboxylic acid component.

[0043] Such X １ As the tetravalent aliphatic group that can be selected, residues obtained by removing two acid anhydride groups from known aliphatic tetracarboxylic dianhydrides usable in the production of polyimides (this is synonymous with residues obtained by removing four carboxylic acid groups from an aliphatic tetracarboxylic acid) can be suitably used. Such aliphatic tetracarboxylic acids and aliphatic tetracarboxylic dianhydrides are not particularly limited, and known ones can be used as appropriate. For example, tetracarboxylic acids (1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidene diphenoxybisphthalic acid, etc.) and their acid dianhydrides can be listed in paragraph

[0080] of International Publication No. 2024 / 024901. １ If the aliphatic group is a tetravalent aliphatic group, it is preferable that such aliphatic group is a group having an alicyclic structure. １ As for the tetravalent aliphatic group that can be selected, those known in the field of polyimides (for example, those exemplified in International Publication No. 2024 / 024901) may be used as appropriate.

[0044] Also, the above X １As for the tetravalent aromatic group that can be selected, residues obtained by removing two acid anhydride groups from known aromatic tetracarboxylic dianhydrides that can be used in the production of polyimides (this is synonymous with residues obtained by removing four carboxylic acid groups from an aromatic tetracarboxylic acid) can be suitably used. Such aromatic tetracarboxylic acids and aromatic tetracarboxylic dianhydrides are not particularly limited, and known ones can be used as appropriate. For example, aromatic tetracarboxylic dianhydrides disclosed in paragraph

[0028] of Japanese Patent Application Publication No. 2022-190149, tetracarboxylic acids described in paragraph

[0079] of International Publication No. 2024 / 024901, and the like can be cited as examples. Examples of such aromatic tetracarboxylic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), pyromellitic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, and 3,3',4,4'-benzophenone. Examples of such tetravalent aromatic groups include tetracarboxylic dianhydrides, 4,4'-oxydiphthalic acid dianhydrides (ODPA), 3,4'-oxydiphthalic acid dianhydrides, bis(3,4-dicarboxyphenyl)sulfone dianhydrides, m-terphenyl-3,4,3',4'-tetracarboxylic dianhydrides, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydrides, biscarboxyphenyldimethylsilane dianhydrides, bisdicarboxyphenoxydiphenyl sulfide dianhydrides, sulfonyl diphthalic acid dianhydrides, and the like. Such tetravalent aromatic groups may be those known in the field of polyimides (for example, those exemplified in International Publication No. 2024 / 024901). Furthermore, the groups represented by formula (1-1) and formula (1-2) described above can be suitably used as tetravalent aromatic groups.

[0045] Also, Y in formula (1) １is a divalent aliphatic group or a divalent aromatic group. In this invention, the polyimide precursor satisfies (ii) above. Therefore, in this invention, multiple Y present in the polyimide precursor １ At least one of them will contain a divalent aromatic group. Here, first, multiple Y present in the precursor １ Y in formula (1) includes at least one divalent aromatic group that is always present among them. １ We will explain the bases that can be selected as Y. １ The structure is derived from the diamine (diamine component), which is a monomer component used in the production of polyimide precursors, and consists of organic groups.

[0046] This kind of Y １ The divalent aliphatic group that can be selected is not particularly limited, and residues obtained by removing two amino groups from known aliphatic diamines available for the production of polyimides can be suitably used. Such aliphatic diamines are not particularly limited, and known ones can be used as appropriate. Examples include the diamines described in paragraph

[0101] of International Publication No. 2024 / 024901 (1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, etc.) and the diamines having an aliphatic structure described in paragraph

[0034] of Japanese Patent Application Publication No. 2023-034768. １ If the aliphatic group is an aliphatic group, it is preferable that the aliphatic group has an alicyclic structure. As such a divalent aliphatic group, those known in the field of polyimides (for example, those exemplified in International Publication No. 2024 / 024901) may be used as appropriate.

[0047] Also, Y １The divalent aromatic group that can be selected is not particularly limited, and residues obtained by removing two amino groups from known aromatic diamines available for the production of polyimides can be suitably used. Such aromatic diamines are not particularly limited, and known ones can be used as appropriate, for example, diamines described in paragraph

[0096] of International Publication No. 2024 / 024901 (p-phenylenediamine, m-phenylenediamine, benzidine, etc.), aromatic diamines described in paragraph

[0047] of Japanese Patent Application Publication No. 2022-000518 (4,4'-diaminobenzanilide, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)benzidine, 9,9'-bis(4-aminophenyl)fluorene, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminodiphenylsulfone, etc.). Examples of such aromatic diamines include p-phenylenediamine (PPD), 9,9-bis(4-aminophenyl)fluorene (BAFL), m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 2,2'-bis(trifluoromethyl)benzidine, m-tolidine, 3,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, N,N'-p-phenylenebis(p-aminobenzamide), 4-aminophenyl-4-aminobenzoate, 4,4'-diaminodiphenylsulfone (4,4'-DDS), bis(4-aminophenyl)terephthalate, and biphenyl-4,4'-diphenyl Bis(4-aminophenyl) ester rubonate, 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-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((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 Examples include 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, 2,4-bis(4-aminoanilino)-6-anilino-1,3,5-triazine, 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. Such divalent aromatic groups may be those known in the field of polyimides (for example, those exemplified in International Publication No. 2024 / 024901) as appropriate. Furthermore, as such divalent aromatic groups, p-phenylene groups and the divalent aromatic groups represented by the above formulas (1-3) can be suitably used. In formulas (1-3), R, １２ and R １３ This will be discussed later.

[0048] Furthermore, in formula (1) above, R １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group, but from the viewpoint of ease of production, in formula (1) above, R １ and R ２ Preferably, all of these are hydrogen atoms.

[0049] (Conditions for the polyimide precursor, etc.) The polyimide precursor according to the present invention contains repeating units represented by formula (1). Generally, the polyimide precursor containing the repeating units represented by formula (1) is produced by reacting a tetracarboxylic acid component (tetracarboxylic dianhydride) with a diamine, but depending on the reaction conditions used, after the repeating units represented by formula (1) are formed, at least one of the two amide structures (-CONH-) in the structure represented by formula (1) is -COOR in the structure represented by the same formula １ and / or - COOR ２ It reacts with and undergoes chemical ring closure, and at least one of the two amide structures (-CONH-) in formula (1) becomes -COOR １ and / or - COOR ２ It can react with and imide-formed repeating units (hereinafter, depending on the case, simply referred to as "repeating units introduced from the repeating units represented by formula (1)"). Therefore, the polyimide precursor according to the present invention, together with the repeating units represented by formula (1), has at least one of the two amide structures (-CONH-) in formula (1) being -COOR １ and / or - COOR ２ It may include repeating units that react with and imide (repeating units introduced from the repeating unit represented by formula (1) above). All formulas in the structure of the repeating unit represented by formula (1): -COOR(R is R １ or R ２ A repeating unit formed by the ring-closing imidation of a group represented by the formula (2-1) and two structures (groups) represented by the formula: -CONH- is a repeating unit represented by the formula (2-1) below (X in formula (2-1) １ and Y １ These are the X in equation (1) １ and Y １ This is equivalent to the repeating unit of polyimide. Also, one of the two amide structures (-CONH-) in formula (1) is -COOR １The repeating unit that reacts with and partially imides is the repeating unit represented by the following formula (2-2) (X in formula (2-2) １ , Y １ and R ２ These are the X in equation (1) １ , Y １ and R ２ (This is equivalent to) and one of the two amide structures (-CONH-) in formula (1) becomes -COOR ２ The repeating unit that reacts with and partially imides is the repeating unit represented by the following formula (2-3) (X in formula (2-3) １ , Y １ and R １ These are the X in equation (1) １ , Y １ and R １ This is equivalent to:

[0050]

[0051] Therefore, the polyimide precursor according to the present invention preferably consists of at least one polymer selected from the group consisting of: a polymer consisting only of repeating units represented by formula (1) (polyamic acid and its derivatives); and a polymer containing repeating units represented by formula (1) and repeating units introduced from the repeating units represented by formula (1) (at least one repeating unit selected from the group consisting of repeating units represented by formulas (2-1) to (2-3)) (partially imidized polyamic acid and its derivatives in which partial imidization has progressed). Preferably, all of these polymers are reaction products of a tetracarboxylic acid component (tetracarboxylic dianhydride) and a diamine and derivatives thereof, and a tetracarboxylic dianhydride represented by formula (3) (X in formula (3)) described later. １ X in equation (1) above １ This is equivalent to: ) and formula: H ２ N-Y １ -NH ２ Diamine represented by (Y in the formula) １ Y in equation (1) above １It is more preferable that the polyimide precursor is a reaction product of ( ). When the polyimide precursor according to the present invention contains, together with the repeating unit represented by formula (1), a repeating unit introduced from the repeating unit represented by formula (1) (at least one repeating unit selected from the group consisting of the repeating units represented by formulas (2-1) to (2-3)), the imidation rate of the polyimide precursor is preferably 60 mol% or less (more preferably 50 mol% or less). Such an imidation rate is determined by measuring the polyimide precursor composition diluted in a deuterated solvent using a nuclear magnetic resonance spectrometer. １ The 1H-NMR spectrum was measured, and assuming that the structure of formulas (2-1) to (2-3) is not included, i.e., that it is in the state of a complete polyamic acid, the two amide structures (-CONH-) in formula (1) １ With respect to the integral value α of the peak originating from H, the two amide structures (-CONH-) in equation (1) obtained from the aforementioned integral value α are as follows: １ The ratio (%) of α-β, obtained by subtracting the integral value β of the peak derived from H, can be calculated using the following formula: [Imidization rate (%)] = (α-β) ÷ α × 100. Therefore, the "imidization rate" referred to here can be determined as the ratio of the molar amount of the ring-closed imidized structure of the two amide structures (-CONH-) in formula (1) to the molar amount of the two amide structures (-CONH-) in formula (1) assuming a complete polyamic acid state.

[0052] Thus, in this specification, "polyimide precursor" is a concept that includes polyamic acids and their derivatives, and partially imidized polyamic acids and their derivatives in which partial imidization has progressed. Furthermore, in this specification, the term "polyimide precursor" is used to mean a precursor capable of forming polyimides (for example, a precursor capable of forming polyimides in a polyimide film).

[0053] Furthermore, the polyimide precursor according to the present invention is as follows (i): (i) all X present in the polyimide precursor １At least one of them is a tetravalent aromatic group (in the polyimide precursor, the repeating unit represented by the formula (1) and at least one of the two amide structures in the formula (1) is -COOR １ and / or -COOR ２ When there is a repeating unit that reacts and imidizes, all X present in the polyimide precursor １ refers to all X contained in the precursor, including X in the repeating unit represented by the formula (1) and X in the repeating unit that reacts and imidizes with at least one of the two amide structures in the formula (1) being -COOR １ and / or -COOR １ and reacts and imidizes. It is necessary to satisfy this. That is, in the polyimide precursor according to the present invention, at least one of all X contained in the polyimide precursor ２ is a tetravalent aromatic group. Thus, by having at least one of the plurality of X in the polyimide precursor １ be a tetravalent aromatic group, it becomes possible to achieve both heat resistance and transparency. Also, in the polyimide precursor according to the present invention, since a higher effect can be obtained from the above viewpoint, 50 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more of the total amount of X present in the polyimide precursor is preferably a tetravalent aromatic group. The upper limit of the content of the tetravalent aromatic group with respect to the total amount of X １ is not particularly limited and may be 100 mol%. Such X in the formula (1) １ is, as described above, it is sufficient that at least one of the total amount of X in the precursor is a tetravalent aromatic group, and depending on the application, etc., a tetravalent aliphatic group can be appropriately combined with the tetravalent aromatic group and used. In this specification, "the total amount of X present in the polyimide precursor" means X contained in the precursor １ and refers to all X contained in the precursor １ Among them, at least one is a tetravalent aromatic group, so that heat resistance and transparency can be achieved simultaneously. Also, in the polyimide precursor according to the present invention, since a higher effect can be obtained from the above viewpoint, 50 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more of the total amount of X present in the polyimide precursor is preferably a tetravalent aromatic group. The upper limit of the content of the tetravalent aromatic group with respect to the total amount of X １ is not particularly limited and may be 100 mol%. Such X in the formula (1) １ is, as described above, it is sufficient that at least one of the total amount of X in the precursor is a tetravalent aromatic group, and depending on the application, etc., a tetravalent aliphatic group can be appropriately combined with the tetravalent aromatic group and used. In this specification, "the total amount of X present in the polyimide precursor" means X contained in the precursor １ and refers to all X contained in the precursor １ and "the total amount of X" means X contained in the precursor １This refers to the total amount of all structures (groups) represented by the formula (1). For example, if the polyimide precursor consists only of repeating units represented by the formula (1), then the X contained in all the repeating units represented by the formula (1) is the total amount of X. １ X refers to the total amount of X, and if the precursor contains repeating units represented by formula (1) and repeating units introduced from the repeating units represented by formula (1) (for example, repeating units represented by formula (2-1), then X in the repeating units represented by formula (1) １ And X in the repeating unit that is introduced from the repeating unit represented by formula (1) above １ All X contained in the precursor, including １ This refers to the total amount.

[0054] Furthermore, in the polyimide precursor according to the present invention, X １ The tetravalent aromatic group that must be included is not particularly limited, but from the viewpoint of achieving both excellent heat resistance and transparency, the group represented by formula (1-1) above (such a group is the same as the residue obtained by removing two acid anhydride groups from s-BPDA), the group represented by formula (1-2) above, the residue obtained by removing two acid anhydride groups from 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA), and the two acid anhydrides from 4,4'-oxydiphthalic acid dianhydride (ODPA) It is more preferable that the residue is a residue with a group removed, a residue obtained by removing two acid anhydride groups from 3,4'-oxydiphthalic acid dianhydride, or a residue obtained by removing two acid anhydride groups from pyromellitic acid dianhydride; it is even more preferable that the residue is a group represented by formula (1-1), a tetravalent aromatic group represented by formula (1-2), and it is particularly preferable that the residue is a group represented by formula (1-1), or a residue obtained by removing two acid anhydride groups from 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

[0055] Furthermore, the polyimide precursor according to the present invention preferably satisfies the following (iii): (iii) X present in the polyimide precursor １ At least 50 mol% of the total amount consists of tetravalent aromatic groups represented by the following formula (1-1).

[0056]

[0057] X present in the aforementioned polyimide precursor １ By ensuring that the content of the tetravalent aromatic group represented by formula (1-1) is 50 mol% or more relative to the total amount, it is possible to improve the heat resistance based on the 0.5% weight loss temperature. Furthermore, from the same viewpoint, a higher effect can be obtained by using X present in the polyimide precursor. １ The content of the tetravalent aromatic group represented by formula (1-1) relative to the total amount is more preferably 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more. １ There is no particular upper limit on the content of the tetravalent aromatic group represented by formula (1-1) relative to the total amount of X, and it may be, for example, 100 mol%. Therefore, for example, the above X １ Examples of suitable ranges for the content of the tetravalent aromatic group represented by formula (1-1) relative to the total amount include 70 to 100 mol% and 85 to 100 mol%. The polyimide precursor according to the present invention is X １ In the case where the polyimide precursor contains a tetravalent aromatic group represented by formula (1-1), when the tetravalent aromatic group represented by formula (1-1) is combined with other groups, X present in the polyimide precursor １ It is preferable that 1 to 30 mol%, more preferably 3 to 20 mol%, and particularly preferably 5 to 15 mol%, of the total amount are groups other than the tetravalent aromatic group represented by formula (1-1). １ When the content of groups other than the tetravalent aromatic group represented by formula (1-1) relative to the total amount exceeds the upper limit, the heat resistance tends to be lower compared to the case below the upper limit, and it tends to be difficult to achieve both high heat resistance and transparency at a higher level. On the other hand, when it is below the lower limit, the effect of improving transparency tends to be lower compared to the case above the lower limit.

[0058] Furthermore, the polyimide precursor according to the present invention is X present in the polyimide precursor. １It is more preferable that 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 to 15 mol%, of the total amount of tetravalent aromatic groups represented by the following formula (1-2). １ When the content of tetravalent aromatic groups represented by the following formula (1-2) relative to the total amount exceeds the upper limit, the heat resistance tends to decrease compared to the case below the upper limit, making it difficult to achieve both high heat resistance and transparency. On the other hand, when it is below the lower limit, the effect of improving transparency tends to be lower compared to the case above the lower limit.

[0059]

[0060] [R in equation (1-2)] １０ and R １１ Each of these is independently a single-bonded or divalent organic group.

[0061] In equation (1-2), R １０ and R １１ As for the divalent organic group that can be selected, an organic group containing an aromatic ring is preferred, and for example, a group represented by the following formula (1-2-1) can be suitably used.

[0062]

[0063] [In formula (1-2-1), R ２０ and R ２１ Each of them is independently a single bond, -COO-, -OCO-, or -O- (R ２１ When R is bonded to the fluorenyl group, ２０ is -COO-, -OCO- or -O- and R ２１ (Preferably a single bond), n R ３０ Each of these is independently an alkyl group or phenyl group having 1 to 4 carbon atoms (preferably methyl), and n is an integer from 0 to 4 (preferably 1).

[0064] Furthermore, the tetravalent aromatic group represented by formula (1-2) is R in the formula. １０ and R １１Groups in which both are single bonds are more preferable, and tetravalent aromatic groups represented by the following formula (1-2A) are particularly preferred. Such tetravalent aromatic groups represented by formula (1-2A) can be efficiently introduced by using BPAF as the tetracarboxylic acid component (tetracarboxylic dianhydride) used in the production of polyimide precursors.

[0065]

[0066] Furthermore, in the polyimide precursor according to the present invention, X １ It is preferable to include a combination of the groups represented by formula (1-1) and formula (1-2). １ Even when the groups represented by formula (1-1) and formula (1-2) are combined and included, other groups may also be further combined and included. In that case, the amount of such other groups is determined from the viewpoint of achieving both heat resistance and transparency, and the amount of X present in the polyimide precursor is considered. １ The amount is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, relative to the total amount.

[0067] Furthermore, the polyimide precursor according to the present invention is as follows (ii): (ii) all Y present in the polyimide precursor １ At least one of them is a divalent aromatic group (Note that the polyimide precursor contains a repeating unit represented by formula (1) and at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ If there are repeating units that react with and imide, all Y present in the polyimide precursor １ Y in the repeating unit represented by formula (1) above. １ And, at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ Y in the repeating unit reacts with and imidizes １ All Y contained in the precursor, including １This refers to ( ). It must satisfy the following conditions. That is, the polyimide precursor according to the present invention is all Y contained in the polyimide precursor １ At least one of them is a divalent aromatic group. In this way, all Y present in the polyimide precursor １ By having at least one of them be a divalent aromatic group, it is possible to achieve both heat resistance and transparency. Furthermore, in the polyimide precursor according to the present invention, a higher effect can be obtained from the above viewpoint, and the Y present in the polyimide precursor １ It is preferable that 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more of the total amount are divalent aromatic groups. １ There is no particular upper limit on the content of divalent aromatic groups relative to the total amount, and it may be 100 mol%. In formula (1), Y １ As mentioned above, Y １ At least one of the total amount of divalent aromatic groups is sufficient, and depending on the application, divalent aromatic groups can be used in combination with divalent aliphatic groups as appropriate. In this specification, "Y present in the polyimide precursor" refers to Y １ "Total amount" means the amount of Y contained in the precursor. １ This refers to the total amount of all structures (groups) represented by the formula (1). For example, if the polyimide precursor consists only of repeating units represented by the formula (1), then the amount of Y contained in all repeating units represented by the formula (1) is the total amount of Y. １ This refers to the total amount of Y in the repeating unit represented by formula (1), and if the precursor contains a repeating unit represented by formula (1) and a repeating unit introduced from the repeating unit represented by formula (1) (for example, a repeating unit represented by formula (2-1), etc.), then Y in the repeating unit represented by formula (1) １ And, Y in the repeating unit that is introduced from the repeating unit represented by formula (1) above １ All Y contained in the precursor, including １ This refers to the total amount.

[0068] In the polyimide precursor according to the present invention, Y １ The divalent aromatic group that is always included is preferably a p-phenylene group, a divalent aromatic group represented by formula (1-3), a residue obtained by removing two amino groups from m-phenylenediamine, a residue obtained by removing two amino groups from 4-aminophenyl-4-aminobenzoate, a residue obtained by removing two amino groups from bis(4-aminophenyl)sulfone, a residue obtained by removing two amino groups from 2,2'-bis(trifluoromethyl)benzidine, or a residue obtained by removing two amino groups from 4,4'-DDS. It is more preferably a p-phenylene group, a group represented by formula (1-3), and particularly preferably a p-phenylene group, a residue obtained by removing two amino groups from BAFL.

[0069] Furthermore, the polyimide precursor according to the present invention preferably satisfies the following (iv): (iv) Y present in the polyimide precursor １ More than 50 mol% of the total amount consists of p-phenylene groups.

[0070] Y in the aforementioned polyimide precursor １ By setting the p-phenylene group content to 50 mol% or more relative to the total amount, it is possible to improve the heat resistance based on the 0.5% weight loss temperature. Furthermore, from the same viewpoint, a higher effect can be obtained, so Y present in the polyimide precursor. １ The content of p-phenylene groups relative to the total amount is more preferably 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more. The Y in the polyimide precursor １ There is no particular upper limit on the content of p-phenylene groups relative to the total amount of Y, and it may be, for example, 100 mol%. Therefore, for example, Y １ Suitable ranges for the p-phenylene group content relative to the total amount include 70-100 mol% and 85-100 mol%. The polyimide precursor according to the present invention is Y １ For example, when a p-phenylene group is included, and when the p-phenylene group is combined with other groups, Y present in the polyimide precursor１ It is preferable that 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 to 15 mol%, of the total amount of groups other than p-phenylene groups. １ When the content of groups other than p-phenylene groups relative to the total amount exceeds the upper limit, the heat resistance tends to be lower compared to when it is below the upper limit, making it difficult to achieve both high heat resistance and transparency. On the other hand, when it is below the lower limit, the effect of improving transparency tends to be lower compared to when it is above the lower limit.

[0071] Furthermore, the polyimide precursor according to the present invention is preferably one that satisfies the following (vi): (vi) Y present in the polyimide precursor １ 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 to 15 mol%, of the total amount are divalent aromatic groups represented by the following formula (1-3).

[0072] Y present in polyimide precursors １ When the content of repeating units, which are tetravalent aromatic groups represented by the following formula (1-3), relative to the total amount exceeds the upper limit, the heat resistance tends to decrease compared to the case below the upper limit, making it difficult to achieve both high heat resistance and transparency. On the other hand, when it is below the lower limit, the effect of improving transparency tends to be lower compared to the case above the lower limit.

[0073]

[0074] [R in equation (1-3)] １２ and R １３ Each of these is independently a single-bonded or divalent organic group.

[0075] In equations (1-3), R １２ and R １３ As for the divalent organic group that can be selected, an organic group containing an aromatic ring is preferred, and for example, a group represented by the following formula (1-3-1) can be suitably used.

[0076]

[0077] [In formula (1-3-1), R ２２ and R ２３Each of them is independently a single bond, -COO-, -OCO-, or -O- (R ２３ When R is bonded to the fluorenyl group, ２２ is -COO-, -OCO- or -O- and R ２３ (Preferably a single bond), n R ３１ Each of these is independently an alkyl group or phenyl group having 1 to 4 carbon atoms (preferably methyl), and n is an integer from 0 to 4 (preferably 1).

[0078] Furthermore, the divalent aromatic group represented by formula (1-3) is R in the formula. １２ and R １３ Groups in which all are single bonds are more preferable, and tetravalent aromatic groups represented by the following formula (1-3A) are particularly preferred. Such tetravalent aromatic groups represented by formula (1-3A) can be efficiently introduced by using BAFL as the diamine used in the production of polyimide precursors.

[0079]

[0080] In the polyimide precursor according to the present invention, Y １ It is preferable to include a combination of a p-phenylene group and a group represented by the above formula (1-3). １ Even when p-phenylene groups and the groups represented by formula (1-3) are combined and included, other groups may be further combined and included. In that case, the content of such other groups shall be determined from the viewpoint of achieving both heat resistance and transparency, Y １ The amount is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, relative to the total amount.

[0081] Furthermore, the polyimide precursor according to the present invention contains repeating units represented by formula (1) from the viewpoint of heat resistance, and X present in the polyimide precursor. １ Preferably, all of these are tetravalent aromatic groups represented by the above formula (1-1), and from the viewpoint of achieving both heat resistance and transparency, it is preferable that they contain repeating units represented by formula (1) and X present in the polyimide precursor. １70 to 99 mol% (more preferably 80 to 97 mol%, particularly preferably 85 to 95 mol%) of the total amount is a tetravalent aromatic group represented by the above formula (1-1), and X is present in the polyimide precursor. １ It is preferable that 1 to 30 mol% (more preferably 3 to 20 mol%, particularly preferably 5 to 15 mol%) of the total amount are tetravalent aromatic groups represented by the above formula (1-2).

[0082] Furthermore, from the viewpoint of heat resistance, the polyimide precursor according to the present invention contains repeating units represented by formula (1), and Y present in the polyimide precursor. １ Preferably, all of these are p-phenylene groups, and from the viewpoint of achieving both heat resistance and transparency, it is preferable that it contains repeating units represented by formula (1) and Y present in the polyimide precursor. １ 70 to 99 mol%, more preferably 80 to 97 mol%, and even more preferably 85 to 95 mol%, of the total amount are p-phenylene groups, and Y present in the polyimide precursor １ It is preferable that 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 mol% to 15 mol% of the total amount are tetravalent aromatic groups represented by the above formula (1-2).

[0083] Furthermore, such polyimide precursors are easy to manufacture and are tetracarboxylic dianhydrides represented by the following formula (3) (X in formula (3)). １ X in equation (1) above １ This is equivalent to: ) and formula: H ２ N-Y １ -NH ２ Diamine represented by (Y in the formula) １ Y in equation (1) above １ It is synonymous with ) and preferably an addition polymerization product (reactant) of ).

[0084]

[0085] The polyimide precursor is a tetracarboxylic dianhydride represented by formula (3) (X in formula (3)). １ X in equation (1) above １ This is equivalent to: ) and formula: H ２ N-Y１ -NH ２ Diamine represented by (Y in the formula) １ Y in equation (1) above １ This is synonymous with ). When it is an addition polymer (polyaddition reaction product) of ), the tetracarboxylic dianhydride represented by formula (3) is X such that the resulting precursor satisfies (i) above. １ It is necessary to use a compound that contains a tetravalent aromatic group, a tetracarboxylic dianhydride, and the obtained precursor must satisfy the above (ii), as shown in the formula: H ２ N-Y １ -NH ２ As a diamine represented by Y, １ It is necessary to use one that contains an aromatic diamine, which is a divalent aromatic group. Here, if the polyimide precursor satisfies, for example, (iii) and (iv), a polyimide precursor of the desired design can be efficiently produced by using a reaction product (addition polymer) of a tetracarboxylic dianhydride represented by formula (3) containing 50 mol% or more of s-BPDA (tetracarboxylic acid component) and a diamine containing 50 mol% or more of PPD (diamine component). Thus, as the polyimide precursor that satisfies (iii) and (iv), a reaction product (addition polymer) of a tetracarboxylic dianhydride represented by formula (3) containing 50 mol% or more of s-BPDA (tetracarboxylic acid component) and a diamine containing 50 mol% or more of PPD (diamine component) can be cited as a suitable example. A polyimide precursor consisting of such an addition polymer is a so-called polyamic acid (R １ and R ２ These are polyimide precursors, each consisting of a hydrogen atom.

[0086] Furthermore, when the polyimide precursor is a reaction product (addition polymer) of a tetracarboxylic dianhydride represented by formula (3) containing 50 mol% or more of s-BPDA (tetracarboxylic acid component) and a diamine containing 50 mol% or more of PPD (diamine component), it is more preferable that the s-BPDA content in the tetracarboxylic acid component be 70 mol% or more (more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more), and it is more preferable that the PPD content in the diamine component be 70 mol% or more (more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more). Furthermore, preferred components to be included in combination with s-BPDA in the tetracarboxylic acid component are BPAF, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 3,4'-oxydiphthalic acid dianhydride, and pyromellitic acid dianhydride, with BPAF being more preferred. In that case, the content of components other than s-BPDA in the tetracarboxylic acid component is preferably 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 to 15 mol%.

[0087] Furthermore, when the polyimide precursor is a reaction product (addition polymer) of a tetracarboxylic dianhydride represented by formula (3) containing 50 mol% or more of s-BPDA (tetracarboxylic acid component) and a diamine containing 50 mol% or more of PPD (diamine component), the components to be included in combination with PPD in the diamine component are preferably BAFL, m-phenylenediamine, 4-aminophenyl-4-aminobenzoate, bis(4-aminophenyl)sulfone, 2,2'-bis(trifluoromethyl)benzidine, and 4,4'-DDS, more preferably BAFL and 4,4'-DDS, and even more preferably BAFL. In that case, the content of components other than PPD in the diamine component is preferably 1 to 30 mol%, more preferably 3 to 20 mol%, and even more preferably 5 to 15 mol%. Furthermore, the method for obtaining the addition polymer is not particularly limited, and any method known in the field of polyimides may be used as appropriate, and the method described later in the method for producing polyamic acid may be used as appropriate.

[0088] Furthermore, the polyimide precursor of the present invention has R in the repeating unit represented by formula (1) above. １ and R ２ Depending on the type, it can be classified into the following 1) to 3). 1) Polyamic acid (R １ and R ２ 1) Polyimide precursors, all of which are hydrogen atoms; 2) Polyamic acid esters (R １ and R ２ 3) Polyimide precursors in which at least a portion is alkyl group, 3) Silyl polyamic acid esters (R １ and R ２ (Polyimide precursors in which at least a portion is an alkylsilyl group) Below, preferred methods for producing each classification of polyimide precursors will be described. The methods for producing such polyimide precursors in the present invention are not limited to the following methods.

[0089] 1) Method for producing polyamic acid When the polyimide precursor is polyamic acid, a method can be employed in which polyamic acid is produced in a solvent by reacting a tetracarboxylic dianhydride represented by formula (3) and the diamine in approximately equimolar proportions (preferably a proportion where the molar ratio of diamine to tetracarboxylic dianhydride [number of moles of diamine / number of moles of tetracarboxylic dianhydride] is 0.90 to 1.10, more preferably a proportion where the molar ratio is 0.95 to 1.05) at a relatively low temperature (for example, a temperature of 120°C or lower) while basically suppressing imidation. When such a method is employed, the polyimide precursor can be obtained in the form of a polyimide acid solution (polyimide precursor solution). In other words, a polyimide precursor solution can be produced efficiently by such a method. During the production of such polyimide precursors (polyamic acids), the repeating unit represented by formula (1) is basically formed, but depending on the reaction conditions, after the repeating unit represented by formula (1) is formed, at least one of the two amide structures (-CONH-) in formula (1) becomes -COOR １ and / or - COOR ２ This can lead to a reaction, and partially imidized repeating units may also be formed.

[0090] The method for producing such polyamic acid is not particularly limited, but it is preferable to use a method in which a diamine is dissolved in an organic solvent or water, and a tetracarboxylic dianhydride is gradually added to this solution while stirring, and the mixture is stirred at 0 to 120°C, more preferably 5 to 80°C, for 1 to 72 hours to obtain polyamic acid (polyimide precursor). When the reaction is carried out at a temperature higher than 80°C, the molecular weight fluctuates depending on the temperature history during polymerization, and imidation may proceed due to heat, so depending on the type of monomer (tetracarboxylic dianhydride, diamine) used, it may be difficult to stably produce a polyimide precursor of the desired design. Furthermore, when employing such a method, the order of addition of the diamine and tetracarboxylic dianhydride is preferable from the viewpoint of keeping the molecular weight of the polyimide precursor to an appropriate size, but from the viewpoint of reducing precipitates, the order of addition may be reversed. The method for producing polyamic acid is not limited to the above method, and known methods can be appropriately adopted.

[0091] 2) Method for producing polyamic acid esters When the polyimide precursor is a polyamic acid ester, the method for producing it can be, for example, to react the tetracarboxylic dianhydride with any alcohol to obtain a diester dicarboxylic acid, then react it with a chlorinating agent (thionyl chloride, oxalyl chloride, etc.) to obtain a diester dicarboxylic acid chloride, and then react this diester dicarboxylic acid chloride with a diamine at a temperature of -20 to 120°C, preferably -5 to 80°C, while stirring for 1 to 72 hours to produce the polyamic acid ester. When the reaction is carried out at a temperature higher than 80°C, the molecular weight fluctuates depending on the temperature history during polymerization, and imidation proceeds due to heat, so depending on the type of monomer (tetracarboxylic dianhydride, diamine) used, it tends to be difficult to stably produce a polyimide precursor with the desired properties. Alternatively, the polyimide precursor can be produced by dehydrating the diester dicarboxylic acid and diamine obtained as described above using a phosphorus-based condensing agent or a carbodiimide condensing agent, and in this case as well, a polyimide precursor can be easily obtained. The polyimide precursors obtained by these methods are stable and can be purified by adding solvents such as water or alcohol to reprecipitation. The methods for producing such polyamic acid esters are not limited to the above methods, and known methods can be used as appropriate.

[0092] 3) Method for producing silyl polyamic acid esters The method for producing silyl polyamic acid esters will be described below, divided into the so-called indirect method and the so-called direct method.

[0093] 3-1) Method for Producing Silyl Polyamic Acid Esters (Indirect Method) As a method for producing silyl polyamic acid esters, for example, the following procedure can be used. First, a diamine is reacted with a silylating agent to obtain a silylated diamine. At this point, the silylated diamine is purified by distillation or other means as needed. Next, a tetracarboxylic dianhydride is gradually added to the solution obtained by dissolving the silylated diamine in a dehydrated solvent while stirring, and the mixture is stirred at a temperature of 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor, which is a silyl polyamic acid ester. In such a method, when the reaction is carried out at a temperature higher than 80°C, the molecular weight fluctuates depending on the temperature history during polymerization, and imidation proceeds due to heat. Therefore, depending on the type of monomer used (tetracarboxylic dianhydride, diamine), it tends to be difficult to stably produce a polyimide precursor with the desired properties.

[0094] 3-2) Method for Producing Silyl Polyamic Acid Esters (Direct Method) As a method for producing silyl polyamic acid esters, for example, a method can be employed in which the polyamic acid solution obtained by the method described in 1) above is mixed with a silylating agent, and the mixture is stirred at a temperature of 0 to 120°C, preferably 5 to 80°C or lower, for 1 to 72 hours to obtain silyl polyamic acid esters. In such a method, when the reaction is carried out at a temperature higher than 80°C, the molecular weight fluctuates depending on the temperature history during polymerization, and imidation proceeds due to heat. Therefore, depending on the type of monomer used (tetracarboxylic dianhydride, diamine), it tends to be difficult to stably produce a polyimide precursor with the desired properties.

[0095] As the "silylation agent" used in the methods described in 3-1) and 3-2) above, it is preferable to use a chlorine-free silylation agent because it is not necessary to purify the obtained silylated polyamic acid. Examples of such chlorine-free silylation agents include N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(trimethylsilyl)acetamide, and hexamethyldisilazane. Furthermore, from the viewpoint of not containing fluorine atoms and being low-cost, N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane are particularly preferred as the silylation agent.

[0096] Furthermore, there are no particular limitations on the solvent that can be used when reacting the tetracarboxylic dianhydride with the diamine in the solvent. Any known solvent that can be used in the production of polyamic acids and polyimides can be used as appropriate. For example, those exemplified as "solvents used when preparing polyimide precursors" in International Publication No. 2024 / 024901 (such as aprotic solvents like N-methyl-2-pyrrolidone (NMP)) can be used as appropriate. Any type of solvent that dissolves the raw material monomer components and the resulting polyimide precursor can be used without any problems, and there are no particular limitations on its structure, but an aprotic solvent is preferred. Furthermore, suitable aprotic solvents include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, N,N-diethylacetamide, N,N-dimethylisobutylamide, N,N-diethylpropionamide, 3-methoxy-N,N-dimethylpropanamide, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, tetramethylurea, dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, and dimethyl sulfoxide. Such solvents may be used individually or in combination of two or more.

[0097] Furthermore, when a polyimide precursor is obtained by reacting the tetracarboxylic dianhydride with the diamine in a solvent, the solid content concentration of the polyimide precursor (concentration based on the mass in terms of polyimide) is not particularly limited, but it is preferable to charge the monomer and solvent at a concentration such that the solid content concentration is 5 to 45% by mass and carry out the reaction.

[0098] Furthermore, while the logarithmic viscosity of the polyimide precursor is not particularly limited, it is preferable that the logarithmic viscosity in a 0.5 g / dL N-methyl-2-pyrrolidone solution at 30°C is 0.2 dL / g or higher, more preferably 0.3 dL / g or higher, and particularly preferably 0.4 dL / g or higher. When the logarithmic viscosity is 0.2 dL / g or higher, the molecular weight of the polyimide precursor increases, which tends to result in a polyimide with superior mechanical strength and heat resistance.

[0099] Furthermore, the average molecular weight (weight average) of the polyimide precursor is preferably 20,000 to 1,000,000, more preferably 50,000 to 500,000, in order to improve the mechanical strength and heat resistance of the polyimide film obtained using the polyimide precursor composition while making the viscosity of the composition appropriate and easy to handle. Such an average molecular weight can be measured using gel permeation chromatography (GPC).

[0100] <Silicon Compounds> The silicon compounds according to the present invention are at least one compound selected from the group consisting of silanol compounds and silicones. Below, silanol compounds and silicones will be explained separately.

[0101] <Silanol Compounds> In this specification, "silanol compounds" that can be selected as silicon compounds mean compounds having a structure in which a hydroxyl group (OH group) is bonded to silicon and that do not have a siloxane bond (-Si-O-) (in this specification, compounds having a silanol group and a siloxane bond (-Si-O-) in their structure correspond to silicones as described later).

[0102] Such silanol compounds are not particularly limited, but include those with the following formula: (R ａ ) ４－ｎ Si(OH) ｎ (In the formula, n is an integer from 1 to 4, and R ａ Compounds represented by (where each is independently a hydrocarbon group) can be suitably used. ａ The group may be any hydrocarbon group, but it is especially preferable that it be a hydrocarbon group having 12 or fewer carbon atoms (more preferably 6 to 12 carbon atoms) (more preferably an alkyl group or aryl group, even more preferably an aryl group). Furthermore, in the above formula, n is preferably 2 to 4, and more preferably 2 or 3. Furthermore, the silanol compound may be a silanol compound having an aryl group (R ａ A silanol compound represented by the above formula, in which at least one of the groups is an aryl group, is preferred. Furthermore, from the viewpoint of preventing a decrease in heat resistance, a phenyl group and a naphthyl group are preferred as such an aryl group, and a phenyl group is more preferred. In addition, diarylsilanediol and arylsilanetriol are preferred as the silanol compound.

[0103] Furthermore, examples of such silanol compounds include trimethylsilanol (Me ３ SiO), dimethylsilanediol (Me ２ Si(OH) ２ ), triethylsilanol (Et ３ SiOH), methylphenylsilanediol (MePhSi(OH) ２ ), dimethylphenylsilanol (Me ２ PhSiO), methyldiphenylsilanol (MePh ２ SiOH), phenylsilanetriol (PhSi(OH) ３ ), diphenylsilanediol (Ph ２ Si(OH) ２ ), triphenylsilanol (Ph ３ SiOH), silanetetraol (Si(OH) ４ ), tri-tert-butoxysilanol ((t-BuO) ３Examples include SiO(1-naphthylsilanetriol), di(1-naphthyl)silanediol, and tri(1-naphthyl)silanol.

[0104] Furthermore, among such silanol compounds, phenylsilanetriol, methylphenylsilanediol, diphenylsilanediol, silanetetraol, 1-naphthylsilanetriol, and di(1-naphthyl)silanediol are preferred from the viewpoint of achieving both heat resistance and permeability, and compatibility with polyimide precursors, with phenylsilanetriol and 1-naphthylsilanetriol being more preferred, and phenylsilanetriol being particularly preferred. The method for producing such silanol compounds is not particularly limited, and known methods can be used as appropriate, for example, by hydrolysis of alkoxysilane. In addition, commercially available silanol compounds may be used.

[0105] <Silicone> The silicone that can be selected as the silicon compound is not particularly limited, and various known siloxane-based polymers can be used as appropriate. From the viewpoint of preventing a decrease in the heat resistance of the polyimide film, it is preferable that such a silicone is a component other than those used as so-called silicone-based surfactants.

[0106] Furthermore, from the viewpoint of compatibility with polyimide, an organopolysiloxane having two or more siloxane bonds (-Si-O-) and an organic group bonded to at least one silicon atom in the siloxane bond can be suitably used as the silicone. Among such organopolysiloxanes that can be used as silicone, silsesquioxane is particularly preferred from the viewpoint of achieving both heat resistance and transparency, and compatibility with polyimide. Here, silsesquioxane is defined as obtained by hydrolysis of a trifunctional silanol compound and a subsequent condensation reaction, with formula: R ｂ SiO ３／２ Structural units represented by (repeating units: R) ｂThis refers to a network-type polymer or polyhedral cluster having an organic group. The structure of such silsesquioxane is not particularly limited and may be any known structure, such as a random structure, ladder-type structure, cage-type structure, incomplete cage-type structure, or double-decker-type structure. Therefore, such silsesquioxane (SQ) may be a ladder-type or random-type polysilsesquioxane (polySQ), or a cage-type, incomplete cage-type, or double-decker-type oligosilsesquioxane (oligoSQ). Among such silsesquioxanes (SQ), polySQ is more preferred from the viewpoint of compatibility with polyimide and improved transmittance due to improved compatibility.

[0107] Furthermore, any known silsesquioxane (for example, the silsesquioxane described in Japanese Patent Publication No. 2015-104843, the silsesquioxane described in International Publication No. 02-059208, etc.) can be used as appropriate, and there are no particular limitations. Examples of such silsesquioxanes include disilanol isobutyl POSS, trisilanol ethyl POSS, trisilanol isobutyl POSS, trisilanol isooctyl POSS, trisilanol phenyl POSS, tetrasilanol phenyl POSS, polySQ (polyphenylsilsesquioxane), which is a condensate of phenylsilanetriol, and polymethylphenylsilsesquioxane (POSS indicates "Polyhedral Oligomeric SilSesquioxane").

[0108] Furthermore, while there are no particular limitations on the organic group in the organopolysiloxane (more preferably silsesquioxane) that is suitable as the silicone, from the viewpoint of compatibility with polyimide and heat resistance of the silicone, it is preferably an aryl group, more preferably a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, and particularly preferably a phenyl group. Thus, as the silicone, a silicone having the aryl group is more preferred.

[0109] As such a silicone, a silicone that is a condensate of the silanol compound (more preferably silsesquioxane) can be suitably used.

[0110] Furthermore, from the viewpoint of heat resistance, such silicones are preferably silicones having aryl groups and silanol groups. Among such silicones, silsesquioxanes having aryl groups and silanol groups, obtained by hydrolysis and condensation reactions of a trifunctional silanol compound (aryltrihydroxysilane) having aryl groups, are more preferable. Thus, silsesquioxanes having aryl groups and silanol groups are more preferable as the silicones. The aryl groups are preferably phenyl groups, 1-naphthyl groups, and 2-naphthyl groups, with phenyl groups being particularly preferred.

[0111] Furthermore, as silsesquioxanes having such an aryl group and a silanol group, trisilanolphenyl POSS, polyphenylsilsesquioxane, and polymethylphenylsilsesquioxane are preferred. Among these, the compound represented by the following formula (I) (where n indicates the number of repetitions) and the compound represented by the following formula (II) are more preferred.

[0112]

[0113] Furthermore, there are no particular restrictions on the method for manufacturing such silicones, and known methods can be used as appropriate. In addition, commercially available silicones may be used as appropriate. Examples of commercially available silicones include the SR series products from Konishi Chemical Industry Co., Ltd., Trisilanolphenyl POSS from Construal Chemical Co., Ltd., and the DOWSIL series products from Dow Toray Industries, Inc.

[0114] Furthermore, the silicones according to the present invention are not particularly limited to those described above. For example, in addition to compounds such as the silsesquioxanes mentioned above, silicones consisting of a combination of trifunctional groups (T units) and tetrafunctional groups (Q units) can also be suitably used.

[0115] Such silicones are preferably those with a weight-average molecular weight of 500 to 50,000 g / mol, more preferably 600 to 10,000 g / mol, and even more preferably 700 to 5,000 g / mol. When the weight-average molecular weight is above the lower limit, a greater effect in terms of storage stability tends to be obtained, while when it is below the upper limit, a greater effect in terms of solubility in solvents and compatibility with polyimides tends to be obtained. Such weight-average molecular weight can be measured using GPC.

[0116] <Regarding preferred conditions for silicon compounds, etc.> The silicon compound according to the present invention may be at least one compound selected from the group consisting of the silanol compound and the silicone, and is not particularly limited. However, from the viewpoint of being able to produce a film with higher performance in terms of heat resistance, it is preferable to use a silanol compound, and from the viewpoint of being able to produce a film with higher performance in terms of transparency, it is preferable to use a silicone.

[0117] Furthermore, from the viewpoint of compatibility with polyimide and heat resistance of silicone, the silicon compound according to the present invention is more preferably at least one selected from the group consisting of silanol compounds having an aryl group and silicones having an aryl group and a silanol group. Among these, phenylsilanetriol and its condensate silicone are even more preferred, and polySQ (polyphenylsilsesquioxane), a condensate of phenylsilanetriol, is particularly preferred.

[0118] <Composition and Properties of the Polyimide Precursor Composition> The polyimide precursor composition of the present invention is a composition containing the polyimide precursor and the silicon compound. In the present invention, the content of the silicon compound in the composition must be between 1 and 29 parts by mass, when the polyimide equivalent mass of the polyimide precursor is taken as 100 parts by mass (as mentioned above, "polyimide equivalent mass of the polyimide precursor" refers to the mass of polyimide obtained when polyimide is produced from the total amount of polyimide precursor in the composition by completely imidizing all the repeating units in the polyimide precursor contained in the composition (the total mass of polyimide obtained when all the polyimide precursor contained in the composition is completely ring-closed imidized)). If the content of the silicon compound is below the lower limit, the transparency of the film made using the composition tends to be insufficient, while if it exceeds the upper limit, problems such as the film becoming cloudy when the film is made using the composition occur, making it difficult to distribute the composition in its original state. The polyimide precursor composition of the present invention can be stored for a long period (at least 30 days) and can be distributed in its compositional form, as the resulting film does not become cloudy even when used in film production after being stored for 30 days.

[0119] Furthermore, in the polyimide precursor composition of the present invention, the content of the polyimide precursor is not particularly limited, but is preferably 5 to 45% by mass, and more preferably 10 to 30% by mass, relative to the total amount of the polyimide precursor composition. If the content of the polyimide precursor in the composition is below the lower limit, the uniformity of the film thickness tends to decrease, while if it exceeds the upper limit, it tends to become difficult to suppress the phase separation of the polyimide and the silicon compound, depending on the type of monomer and silicon compound.

[0120] Furthermore, the polyimide precursor composition of the present invention preferably further contains an imidazole compound. Such an imidazole compound is not particularly limited and may be any compound having an imidazole skeleton. Examples of such imidazole compounds include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 1-phenylimidazole, imidazole, and benzimidazole. Among such imidazole compounds, 1,2-dimethylimidazole and 2-phenylimidazole are particularly preferred. Such imidazole compounds may be used individually or in combination of two or more. The method for producing such imidazole compounds is not particularly limited and known methods can be appropriately employed. Furthermore, commercially available imidazole compounds may be used.

[0121] Furthermore, from the viewpoint of further improving transparency, the content of the imidazole compound in the polyimide precursor composition is preferably such that the ratio of the molar amount of the imidazole compound to the total molar amount of repeating units of the polyimide precursor [= ([molar amount of imidazole compound] / [total molar amount of repeating units]) × 100] is 0.1 mol% or more, more preferably 0.5 mol% or more. Also, from the viewpoint of balancing transparency and linear thermal expansion coefficient, the content of the imidazole compound in the composition is preferably such that the ratio of the molar amount of the imidazole compound to the total molar amount of repeating units of the polyimide precursor is 50 mol% or less, more preferably 10 mol% or less.

[0122] Furthermore, the polyimide precursor composition of the present invention preferably further contains a solvent. By including a solvent in this way, the polyimide precursor composition of the present invention can be suitably used as a so-called varnish (resin solution) for the manufacture of polyimide films and the like. Such a solvent can be any solvent capable of dissolving the polyimide precursor, and is not particularly limited; the solvents described as those used in the manufacture of the polyimide precursor can be used. Moreover, such a solvent is preferably an aprotic solvent, and N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, N,N-diethylacetamide, N,N-dimethylisobutylamide, N,N-diethylpropionamide, 3-methoxy-N,N-dimethylpropanamide, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, tetramethylurea, dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, and dimethyl sulfoxide can be used more suitably. Such solvents may be used individually or in combination of two or more. For example, when a polyimide precursor solution (e.g., a polyamic acid solution) is obtained by producing the precursor in a solvent during the production of the polyimide precursor, that solution may be used as is in the production of the composition (it may be further diluted with a solvent or concentrated as needed), and the solvent in such polyimide precursor solution may be used as is as the solvent in the composition.

[0123] Furthermore, if the polyimide precursor composition of the present invention contains a solvent, the solvent content is not particularly limited, but it is preferably 50 to 90% by mass, and more preferably 70 to 90% by mass.

[0124] Furthermore, the polyimide precursor composition of the present invention may optionally contain various additives in addition to the imidazole compound and solvent. Such additives can be any known compounds that can be used in the production of polyimides, and are not particularly limited. For example, chemical imidizing agents (acid anhydrides such as acetic anhydride, or amine compounds such as pyridine and isoquinoline), antioxidants, ultraviolet absorbers, fillers (inorganic particles such as silica), dyes, pigments, coupling agents such as silane coupling agents, primers, flame retardants, defoaming agents, leveling agents, rheology control agents (flow aids), etc., can be used as appropriate.

[0125] The polyimide precursor composition of the present invention is not particularly limited, but can be measured using an E-type rotational viscometer at a temperature of 25°C and a shear rate of 20 sec. －１ A composition having a viscosity (rotational viscosity) of 0.01 to 1000 Pa·sec, more preferably 0.1 to 100 Pa·sec, as measured under the specified conditions, is preferred. Thixotropy can also be imparted as needed. By setting the viscosity of the polyimide precursor composition within the above range, handling becomes easier during coating and film formation, and repulsion is suppressed, resulting in excellent leveling properties, which makes it possible to efficiently produce a better coating.

[0126] Furthermore, the polyimide precursor composition of the present invention has a viscosity retention rate of preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more. This viscosity retention rate is the ratio of the viscosity of the composition after 30 days to the viscosity of the composition after 24 hours of storage at room temperature (approximately 23°C) under atmospheric pressure after preparation of the polyimide precursor composition. The viscosity of the composition is measured using a TVE-25 E-type viscometer manufactured by Toki Sangyo Co., Ltd., with a measurement temperature of 25°C.

[0127] Furthermore, it is preferable that the polyimide precursor composition of the present invention retains its fluidity even after being stored at atmospheric pressure and room temperature (approximately 23°C) for 30 days after preparation. The fluidity of the composition can be determined by tilting the storage container containing the composition at a 45° angle after 30 days of standing at atmospheric pressure and room temperature (approximately 23°C) and visually checking whether the composition in the container flows.

[0128] Furthermore, the method for producing the polyimide precursor composition of the present invention is not particularly limited, as long as it is a method capable of producing a composition containing the polyimide precursor and the silicon compound. For example, a method can be suitably adopted in which a composition containing the polyimide precursor and the silicon compound is obtained by adding and mixing the silicon compound to the polyimide precursor solution obtained as described above. In such a method, the composition will contain a solvent. In addition, when adopting such a method, the step of adding and mixing an imidazole compound or a solution of an imidazole compound at either the time before or after adding and mixing the silicon compound may be further carried out so that the final composition obtained is a polyimide precursor composition in the form of a polyimide precursor composition containing the polyimide precursor, the silicon compound and the imidazole compound. In this case, in order to add the imidazole compound, it is preferable to prepare a solution in which the imidazole compound is dissolved in a solvent in advance and add this solution to the polyimide precursor solution. When using such an imidazole compound solvent, it is preferable that the solid content concentration of the imidazole compound in the solvent be 0.1 to 50% by mass. In the preparation of the polyimide precursor solution, a polyimide precursor composition containing the polyimide precursor, the silicon compound, and the imidazole compound may be produced by reacting a tetracarboxylic dianhydride with a diamine in the presence of an imidazole compound to prepare a polyimide precursor solution containing the imidazole compound, and then adding and mixing the silicon compound to this solution.

[0129] Various forms of polyimides can be produced using the polyimide precursor composition of the present invention. The method for producing such polyimides is not particularly limited, and any known imidation method can be suitably applied. Furthermore, suitable forms of the resulting polyimides include films, coatings, powders, beads, molded articles, and foams.

[0130] Furthermore, the polyimide precursor composition of the present invention can also be used to produce a film made of so-called all-aromatic polyimide. In this case, it is possible to obtain a polyimide film that has the advantages of all-aromatic polyimide while simultaneously achieving a high level of transparency to light at a wavelength of 450 nm and a high level of heat resistance.

[0131] Furthermore, the polyimide precursor composition of the present invention can be suitably used as a composition for "flexible electronic device substrates (particularly preferably flexible display substrates; the same applies hereinafter)." In this specification, when the term "for flexible electronic device substrates" is used for a polyimide precursor composition, it means a polyimide precursor composition that is applied directly onto a substrate when manufacturing a flexible electronic device (a composition for directly manufacturing a polyimide film as a flexible electronic device substrate from such a composition), as described below.

[0132] <Polyimide film, polyimide film / substrate laminate, flexible electronic device, and flexible electronic device substrate> In describing the polyimide film, polyimide film / substrate laminate, flexible electronic device, and flexible electronic device substrate of the present invention, we will first explain the terms used in this specification.

[0133] In this specification, "flexible (electronic) device" means a device that is flexible itself. Typically, such a "flexible (electronic) device" can be obtained by forming a semiconductor layer (such as transistors and diodes as elements) on a flexible substrate. However, the "flexible (electronic) device" referred to herein is distinguished from conventional devices such as COF (Chip On Film), in which "rigid" semiconductor elements such as IC chips are mounted on a conventional FPC (flexible printed circuit board). There is no problem in using the "flexible (electronic) device" referred to herein in conjunction with the "rigid" semiconductor elements such as IC chips by mounting them on a flexible substrate or electrically connecting them to operate or control the "flexible (electronic) device". Examples of "flexible (electronic) devices" that can be suitably used include flexible displays such as liquid crystal displays and organic EL displays, display devices such as electronic paper, solar cells, and light-receiving devices such as CMOS.

[0134] Furthermore, the term "flexible (electronic) device substrate" in this specification does not include flexible wiring boards (also referred to as flexible circuit boards, flexible printed circuit boards, etc.). Copper (or metal) clad laminates are used to manufacture flexible wiring boards (flexible circuit boards, flexible printed circuit boards), therefore, copper (or metal) clad laminates are also not included in the term "flexible (electronic) device substrate" as used herein.

[0135] Furthermore, when the terms "for flexible electronic device substrates" and "for flexible display substrates" are used in this specification in reference to polyimide films, it means that the polyimide film itself is a major component (or the substrate itself) of the substrate present in the final product (flexible electronic device), and does not refer to films and layers that are not present in the final product, or auxiliary layers laminated to the substrate. To give a specific example, a release layer is not a substrate.

[0136] Furthermore, when the terms "for flexible (electronic) device substrates" and "for flexible display substrates" are used in this specification for polyimide precursor compositions, such terms mean that the composition is a polyimide precursor composition used to directly manufacture a polyimide film for substrates. Therefore, a polyimide film for "flexible (electronic) device substrates (including for flexible display substrates; the same applies hereinafter)" is obtained by coating the polyimide precursor composition onto a substrate and imidizing it. For example, when two or more polyimide precursor compositions (intermediate compositions) are mixed and used to manufacture a polyimide film, each individual polyimide precursor composition is not a "for flexible (electronic) device substrates" composition as defined herein. This is because the structure of the resulting polyimide film depends on the structure of the polyimide precursor composition used to directly manufacture the polyimide film.

[0137] Furthermore, as mentioned above, copper (or metal) clad laminates are not used to manufacture flexible (electronic) devices; therefore, polyimide precursor compositions for copper clad laminate manufacturing are not polyimide precursor compositions for "flexible (electronic) device substrates." The definitions of these terms may be explained in more detail below.

[0138] <Polyimide Film and Polyimide Film / Substrate Laminate> One embodiment of the present invention is a polyimide film obtained from the polyimide precursor composition of the present invention described above. Hereinafter, a polyimide film of this embodiment (a polyimide film obtained from the polyimide precursor composition of the present invention described above), a polyimide film / substrate laminate using the same, a flexible electronic device, and a flexible electronic device substrate will be described, and then another embodiment of the polyimide film of the present invention will be described.

[0139] Such a polyimide film of the present invention is obtained from the polyimide precursor composition of the present invention described above. Furthermore, the polyimide film / substrate laminate of the present invention comprises the polyimide film of the present invention and a substrate.

[0140] Such polyimide films can be efficiently manufactured, for example, by forming a coating of the polyimide precursor composition of the present invention on a substrate and then heat-treating it. In this case, a polyimide film / substrate laminate is obtained simultaneously with the manufacture of the polyimide film. As such, it is preferable that the polyimide film of the present invention be a film made from a heat-treated polyimide precursor composition, since it can be easily manufactured by heat-treating after coating formation.

[0141] The thickness of such a 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 cannot maintain sufficient mechanical strength, and for example, when used as a substrate for a flexible electronic device, it may break due to inability to withstand stress. 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 thickness of the polyimide film is too thick, it may become difficult to make the flexible device thinner. To make the film thinner while maintaining sufficient durability as a flexible device, the thickness of the polyimide film is preferably 2 to 50 μm.

[0142] Furthermore, as mentioned above, such polyimide films can be obtained in the form of a polyimide film / substrate laminate, which has a polyimide film and a substrate, by forming a polyimide film on a substrate. In addition, such polyimide films can be applied to various uses in their laminate form.

[0143] Furthermore, the polyimide film / substrate laminate of the present invention may have the polyimide film of the present invention (a polyimide film obtained from the polyimide precursor composition of the present invention) and a substrate, and for example, other layers such as an inorganic thin film may be laminated on the surface of the polyimide film. The substrate and other layers will be described together with the method for manufacturing the laminate. The polyimide film of the present invention obtained from the polyimide precursor composition of the present invention has excellent heat resistance, for example, and can be used appropriately for work at high temperatures, and layers (for example, inorganic thin films) can be easily formed on the polyimide film according to the application. Therefore, polyimide film / substrate laminates in the form of various layers can be easily formed, and such laminates can be appropriately applied to various applications.

[0144] Furthermore, there are no particular limitations on the method for producing the polyimide film / substrate laminate, which is a laminate of the polyimide film and substrate of the present invention. However, it is possible to suitably employ a method that includes steps (a) to (b): (a) a step of applying a polyimide precursor composition (or "polyimide precursor composition for flexible electronic device substrates" if the resulting polyimide film is to be used for flexible electronic device substrates) onto a substrate; and (b) a step of heat-treating the coating film of the polyimide precursor composition on the substrate to produce a laminate (polyimide film / substrate laminate) in which the polyimide film is laminated on the substrate. After producing the polyimide film / substrate laminate, a step (b2) of forming an inorganic thin film on the surface of the polyimide film may be added to further produce a laminate in which the inorganic thin film / polyimide film / substrate are laminated in that order.

[0145] Step (a) is a step of coating a polyimide precursor composition onto a substrate. The substrate used in such a step is not particularly limited, but it is preferable to use a heat-resistant material. For example, plate-shaped or sheet-shaped substrates such as ceramic materials (glass, alumina, etc.), metal materials (iron, stainless steel, copper, aluminum, etc.), and semiconductor materials (silicon, compound semiconductors, etc.), or film-shaped or sheet-shaped substrates such as heat-resistant plastic materials (polyimide, etc.) can be suitably used. Furthermore, such substrates are preferably flat and smooth plate-shaped. Moreover, from the viewpoint of heat resistance, glass substrates such as soda-lime glass, borosilicate glass, alkali-free glass, and sapphire glass; semiconductor substrates (including compound semiconductors) such as silicon, GaAs, InP, and GaN; and metal substrates such as iron, stainless steel, copper, and aluminum are more preferable.

[0146] Furthermore, glass substrates are particularly preferred as such substrates because they are flat, smooth, and have a large surface area, and are readily available. The thickness of such plate-shaped substrates, such as glass substrates, is not particularly limited, but from the viewpoint of ease of handling, for example, it is preferably 20 μm to 4 mm, more preferably 100 μm to 2 mm. The size of the plate-shaped substrate is not particularly limited, but one side (the longer side in the case of a rectangle) is preferably about 100 mm to 4000 mm, more preferably about 200 mm to 3000 mm, and even more preferably about 300 mm to 2500 mm. Such substrates, such as glass substrates, may have an inorganic thin film (for example, a silicon oxide film) or a resin thin film formed on their surface.

[0147] Furthermore, in step (a), the method for applying the polyimide precursor composition onto the substrate is not particularly limited, but conventionally known methods such as slit coating, die coating, blade coating, spray coating, inkjet coating, nozzle coating, spin coating, screen printing, bar coating, and electrodeposition can be used as appropriate.

[0148] Furthermore, step (b) is a step of heat-treating a coating film of the polyimide precursor composition on a substrate to produce a laminate in which a polyimide film is laminated on the substrate. By such heat treatment, the coating film of the polyimide precursor composition can be converted into a polyimide film, thereby obtaining a polyimide film / substrate laminate. The conditions for such heat treatment are not particularly limited, but for example, it is preferable to dry the coating film in a temperature range of 50 to 150°C, and then treat it with a maximum heating temperature in the range of 150 to 600°C, more preferably 200 to 550°C, and even more preferably 250 to 500°C.

[0149] In the present invention, it is preferable that the polyimide film / substrate laminate exhibits minimal warping. This warping characteristic can be evaluated by the residual stress between the polyimide film and the silicon substrate in the polyimide film / silicon substrate (wafer) laminate. Such residual stress will be described later.

[0150] Furthermore, as described above, the polyimide film / substrate laminate of the present invention may have a second layer, such as an inorganic thin film, on the surface of the polyimide film. When manufacturing a laminate having such a second layer, it is preferable to further perform step (b2). That is, from the viewpoint of obtaining a laminate having a desired laminate structure, the method for manufacturing the polyimide film / substrate laminate may further include, for example, a step (b2) of forming an inorganic thin film on the surface of the polyimide film formed on the substrate, in addition to steps (a) and (b).

[0151] Such inorganic thin films are preferably those that function as a barrier layer against water vapor, oxygen (air), etc. Examples of water vapor barrier layers include silicon nitride (SiN). ｘ ), silicon dioxide (SiO ｘ ), silicon oxynitride (SiO ｘ N ｙ ), aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), zirconium oxide (ZrO ２Examples include inorganic thin films containing inorganic substances selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides. Generally, known methods for depositing these thin films include physical deposition methods such as vacuum deposition, sputtering, and ion plating, and chemical deposition methods (CVD: chemical vapor deposition) such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). In these deposition methods, including the CVD method, the film is densified by high-temperature annealing at, for example, 350°C to 450°C after deposition in order to improve the barrier function. In this specification, "inorganic thin film" refers to both the state before and after annealing. If it refers to only one state, it will be explicitly indicated or will be clear from the context. Similarly, "polyimide film / substrate laminate" refers to both those having an "inorganic thin film" and those not having one.

[0152] Such a second layer can consist of multiple layers. In this case, different types of inorganic thin films may be formed, or a resin film and an inorganic thin film may be combined. An example of the latter is the formation of a three-layer structure of a barrier layer / polyimide layer / barrier layer on a polyimide film in a polyimide film / substrate laminate.

[0153] Furthermore, after obtaining the polyimide film / substrate laminate in this manner, the polyimide film can be peeled off the substrate to obtain only the polyimide film. When manufacturing a single polyimide film (consisting only of polyimide film, not a laminate), the manufacturing method is not particularly limited, and known manufacturing methods can be used as appropriate. In addition to the method of obtaining a single polyimide film by peeling off the polyimide film from the substrate after obtaining the polyimide film / substrate laminate, for example, a method may be employed in which a polyimide precursor composition is applied to a substrate, the coating is heated and dried to produce a self-supporting film, the self-supporting film is peeled off the substrate, and the film is held in a tenter, for example, and heated and imidized from both sides of the film in a state where degassing is possible to obtain a polyimide film. The properties of the polyimide film of the present invention will be described later.

[0154] <Flexible Electronic Device and Flexible Electronic Device Substrate> The flexible electronic device of the present invention comprises the polyimide film of the present invention. The flexible electronic device substrate of the present invention is made of the polyimide film of the present invention.

[0155] The flexible electronic device of the present invention may be any device comprising the polyimide film of the present invention, and other configurations are not particularly limited. For example, other than comprising a substrate made of the polyimide film of the present invention as the flexible electronic device substrate, any configuration known in the field of flexible electronic devices can be appropriately adopted.

[0156] The method for manufacturing such a flexible electronic device of the present invention is not particularly limited, but a method can be suitably employed that includes (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 substrate from the polyimide film, using the polyimide film / substrate laminate manufactured in the above-described steps (a) and (b) (preferably further step (b2)). In the method for manufacturing a flexible electronic device, the polyimide precursor composition applied to the substrate in step (a) is a polyimide precursor composition for flexible electronic device substrates.

[0157] Step (c) is the step of forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film (including a polyimide film with a second layer, such as an inorganic thin film, laminated on its surface) of the polyimide film / substrate laminate obtained in step (b). These layers may be formed directly on the polyimide film (including the one with the second layer laminated on it), or they may be formed on (i.e., indirectly) on top of other layers required for the device after those other layers have been laminated.

[0158] The conductive layer and / or semiconductor layer are selected to match the elements and circuits required by the target electronic device. In such a step (c), when forming at least one of the conductive layer and semiconductor layer, it is also preferable to form at least one of the conductive layer and semiconductor layer on a polyimide film on which an inorganic film has been formed.

[0159] The conductive layer and semiconductor layer include both those formed over the entire surface of the polyimide film and those formed on a portion of the polyimide film. The present invention may proceed immediately to step (d) after step (c), or it may be possible to form at least one layer selected from the conductive layer and semiconductor layer in step (c), then further form a device structure, and then proceed to step (d).

[0160] Furthermore, when manufacturing a TFT liquid crystal display device as a flexible electronic device, the device may be manufactured by forming, for example, metal wiring, TFTs made of amorphous silicon or polysilicon, and transparent pixel electrodes on a polyimide film (polyimide film for flexible display substrates) on which an inorganic film may be formed over the entire surface as needed. The term "TFT" here includes, for example, a gate metal layer, a semiconductor layer such as an amorphous silicon film, a gate insulating layer, wiring connected to the pixel electrodes, etc. Also, when manufacturing a TFT liquid crystal display device, structures necessary for a liquid crystal display can be formed on the TFT by known methods. In addition, transparent electrodes and color filters may be formed on the polyimide film.

[0161] Furthermore, when manufacturing an organic EL display as a flexible electronic device, for example, an organic EL display may be manufactured by forming a transparent electrode, light-emitting layer, hole transport layer, electron transport layer, etc., in addition to a TFT as necessary, on a polyimide film (polyimide film for flexible display substrates) on which an inorganic film is formed over the entire surface as necessary.

[0162] Since the polyimide film of the present invention has excellent heat resistance, the method for forming the circuits, elements, and other structures required for the device is not particularly limited.

[0163] Step (d) is a step of separating the substrate from the polyimide film. As such a separation method, a mechanical peeling method that physically separates the film by applying external force may be used, but it is particularly preferable to use a so-called laser peeling method, which involves irradiating the substrate surface of the polyimide film / substrate laminate with laser light to separate the film, as this method allows for relatively easy separation even when the polyimide film exhibits high adhesion.

[0164] Alternatively, the polyimide film after the substrate has been peeled off may be used as a substrate for a (semi-)product, and the necessary structures or components for the device may be formed or incorporated into it to complete the device.

[0165] As described above, when a flexible electronic device containing a polyimide film is completed, the polyimide film functions as a flexible electronic device substrate within the flexible electronic device. By manufacturing the flexible electronic device of the present invention in this way, it is possible to manufacture a device equipped with a flexible electronic device substrate made of a polyimide film.

[0166] The method for manufacturing flexible electronic devices is not limited to the above method. For example, after manufacturing a polyimide film / substrate laminate by step (b) above, the polyimide film may be peeled off from the laminate, and then, using the same steps as in step (c) above, at least one layer selected from a conductive layer and a semiconductor layer and a necessary structure may be formed on the polyimide film, thereby manufacturing a (semi)product using the polyimide film as a substrate.

[0167] (Regarding the properties of the polyimide film) The properties of the polyimide film of the present invention (the polyimide film obtained from the polyimide precursor composition of the present invention described above) will be explained below. In the following, for each property of the polyimide film, multiple numerical ranges will be described (listed) in the order of the first range, second range, third range, ..., nth range, and it will be indicated that these first to nth ranges become more preferable in that order (as the numerical value from 1 to n increases).

[0168] The polyimide film (or polyimide constituting the present invention) has excellent heat resistance, with a 0.5% weight loss temperature of 535°C or higher. Furthermore, such a 0.5% weight loss temperature is more preferably 540°C or higher (first range), 545°C or higher (second range), and 550°C or higher (third range), in that order.

[0169] Furthermore, the temperature at which the polyimide film (or the polyimide constituting it) of the present invention loses 1% of its weight is preferably 555°C or higher (first range), and more preferably 560°C or higher (second range), 565°C or higher (third range), and 570°C or higher (fourth range).

[0170] In this specification, the 0.5% weight loss temperature and the 1% weight loss temperature are determined by using a polyimide film with a thickness of approximately 10 μm as a test specimen, and measuring the weight curve obtained by heating the film from 25°C to 600°C at a heating rate of 10°C / min in a nitrogen stream, with the weight at 150°C being 100%, and measuring the temperatures at which the weight loss reaches 0.5% and 1%, respectively.

[0171] The silicon content in the polyimide film of the present invention is preferably 0.5 to 5.0 parts by mass (first range) per 100 parts by mass of polyimide film, and more preferably in the order of 2.0 to 4.2 parts by mass (second range), 2.5 to 4.0 parts by mass (third range), and 3.0 to 3.5 parts by mass. In this specification, the silicon content in the polyimide film is determined by placing the polyimide film and acid in a decomposition container, sealing it tightly, irradiating it with microwaves for thermal decomposition, and then adding ultrapure water to a fixed volume. The solution obtained is used as the test solution and measured using an ICP-AES / ICPE9820 (manufactured by Shimadzu Corporation).

[0172] Regarding the polyimide film of the present invention, the transmittance of 450 nm light (450 nm light transmittance) of the polyimide film when measured with a thickness of 10 μm is 73% or more. The 450 nm light transmittance of such a polyimide film is more preferably 74% or more (first range) and 75% or more (second range). Such a 450 nm light transmittance can be determined by measuring it using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO).

[0173] Furthermore, regarding the polyimide film of the present invention, the yellowness (YI) of the polyimide film when measured with a thickness of 10 μm is preferably 25 or less (first range), more preferably 24 or less (second range), 23 or less (third range), 22 or less (fourth range), and 21 or less (fifth range), in that order. Also, it is preferable that the yellowness (YI) is 0 or greater. Such a YI value can be determined by measuring a 10 μm thick, 5 cm square polyimide film using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO Corporation) in accordance with the ASTM E313 standard, with a light source of D65 and a field of view of 2°.

[0174] Furthermore, the haze value of the polyimide film of the present invention, when measured with a film thickness of 10 μm, is preferably less than 1.0% (first range), and more preferably in the order of 0.9% or less (second range), 0.8% or less (third range), 0.7% or less (fourth range), and 0.6% or less (fifth range). Such haze values ​​can be determined by measuring them using a turbidimeter (for example, NDH2000 manufactured by Nippon Denshoku Industries) in accordance with the JIS K7136 standard.

[0175] Depending on the application, the polyimide film of the present invention may require high adhesion to the substrate. Such adhesion can be evaluated by peel strength. When the peel strength between the polyimide film and the substrate in a polyimide film / substrate laminate is measured in accordance with JIS K6854-1, the magnitude of the peel strength measured in a 90° peel test at a tensile speed of 2 mm / min is preferably 3 gf / cm (0.29 N / cm) or more (first range), and more preferably 5 gf / cm (0.049 N / cm) or more (second range), and 7 gf / cm (0.069 N / cm) or more (third range). Furthermore, the upper limit of the magnitude of the peel strength is usually 5 kgf / cm (49.0 N / cm) or less, preferably 3 kgf / cm (29.4 N / cm) or less. Peel strength is usually measured in air or atmosphere. Furthermore, this peel strength can be determined by measuring the peel strength in the 90° direction in air under conditions of a tensile speed of 2 mm / min using the TENSILON RTA-500 manufactured by Orientec Co., Ltd.

[0176] Furthermore, in the present invention, as described above, it is preferable that the polyimide film / substrate laminate has little warping, and the properties of the polyimide film can be evaluated by the residual stress between the polyimide film and the silicon substrate in the polyimide film / silicon substrate (wafer) laminate. Details of the measurement are described in Japanese Patent No. 6798633. However, the polyimide film is assumed to be in a dry state and placed at 23°C. The residual stress evaluated in this way is preferably 25 MPa or less (first range), more preferably 20 MPa or less (second range), and more preferably 15 MPa or less (third range).

[0177] The polyimide film of the present invention can have an extremely low coefficient of linear expansion (CTE) depending on the application. In one preferred embodiment of the polyimide film of the present invention, the coefficient of linear expansion of the polyimide film from 100°C to 300°C, measured on a film with a thickness of 10 μm, is preferably 20 ppm / K or less (first range), and more preferably 18 ppm / K or less (second range), 17 ppm / K or less (third range), 16 ppm / K or less (fourth range), and 15 ppm / K or less (fifth range).

[0178] Furthermore, in a preferred embodiment of the polyimide film of the present invention, the coefficient of linear expansion of the polyimide film from 100°C to 400°C, when measured with a film thickness of 10 μm, is preferably 20 ppm / K or less (first range), and more preferably 18 ppm / K or less (second range), 17 ppm / K or less (third range), 16 ppm / K or less (fourth range), and 15 ppm / K or less (fifth range). Such CTE can be determined by cutting a polyimide film with a thickness of approximately 10 μm into strips with a width of 4 mm to make test pieces, and using a TMA / SS6100 (manufactured by SII Nanotechnology Co., Ltd.), cooling from 400°C to 50°C at a chuck length of 15 mm, a load of 2 g, and a cooling rate of 20°C / min, and calculating the coefficient of linear expansion for the above temperature range (100°C to 300°C range and 100°C to 400°C range) from the obtained TMA curve.

[0179] In a preferred embodiment of the polyimide film of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting it) is preferably 280°C or higher, more preferably 290°C or higher, even more preferably 300°C or higher, and even more preferably 310°C or higher. Such a glass transition temperature (Tg) can be determined from the inflection point of the obtained TMA curve using a thermomechanical analyzer (TMA).

[0180] The polyimide film of the present invention can also exhibit a very high modulus of elasticity depending on the application. The modulus of elasticity of such a polyimide film is preferably 6.0 GPa or higher (first range), and more preferably in the order of 6.2 GPa or higher (second range), 6.5 GPa or higher (third range), 7.0 GPa or higher (fourth range), 7.5 GPa or higher (fifth range), 8.0 GPa or higher (sixth range), and 8.5 GPa or higher (seventh range). The modulus of elasticity can be obtained from a film with a thickness of, for example, about 8 to 12 μm.

[0181] Furthermore, in a preferred embodiment of the polyimide film of the present invention, the elongation at the breaking point of the polyimide film is preferably 10% or more (first range) when measured for a film with a thickness of 10 μm, and more preferably 20% or more (second range), 25% or more (third range), and 30% or more (fourth range), in that order.

[0182] Furthermore, in one preferred embodiment of the polyimide film of the present invention, the tensile strength of the polyimide film is preferably 200 MPa or more (first range), and more preferably 300 MPa or more (second range), 350 MPa or more (third range), and 400 MPa or more (fourth range). The tensile strength can be a value obtained from a film with a thickness of, for example, 5 to 100 μm.

[0183] The modulus of elasticity, elongation at break, and breaking strength can each be determined by punching out a dumbbell-shaped test specimen from a polyimide film with a thickness of approximately 10 μm according to the IEC 450 standard, and measuring them using a TENSILON manufactured by ORIENTEC Corporation with a chuck length of 30 mm and a tensile speed of 2 mm / min.

[0184] The polyimide film obtained from the polyimide precursor composition of the present invention and the polyimide film / substrate laminate using the same have been described above. Now, another embodiment of the polyimide film of the present invention will be described below.

[0185] Another embodiment of the polyimide film of the present invention is a polyimide film obtained from a polyimide precursor that contains repeating units represented by the following formula (1) and satisfies the following (i) and (ii) (preferably, a polyimide film obtained from a polyimide precursor composition containing the polyimide precursor), wherein the silicon content in the polyimide film is 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film, and the 0.5% weight loss temperature is 535°C or higher.

[0186]

[0187] [In formula (1), X １ Y is a tetravalent aliphatic group or a tetravalent aromatic group. １ R is a divalent aliphatic group or a divalent aromatic group. １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.

[0188] (i) All X present in the polyimide precursor １ At least one of them is a tetravalent aromatic group (Note that the polyimide precursor contains a repeating unit represented by formula (1) and at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ If there are repeating units that react with and imide-formed, all X present in the polyimide precursor １ X in the repeating unit represented by formula (1) above. １ And, at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ X in the repeating unit reacts with and imidizes １ All X contained in the precursor, including １ (This refers to...)

[0189] (ii) All Y present in the polyimide precursor １At least one of them is a divalent aromatic group (Note that the polyimide precursor contains a repeating unit represented by formula (1) and at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ If there are repeating units that react with and imide, all Y present in the polyimide precursor １ Y in the repeating unit represented by formula (1) above. １ And, at least one of the two amide structures in formula (1) is -COOR １ and / or - COOR ２ Y in the repeating unit reacts with and imidizes １ All Y contained in the precursor, including １ (This refers to...)

[0190] The "polyimide precursor" referred to herein is the same as the "polyimide precursor" described in the polyimide precursor composition of the present invention described above, and its preferred conditions are also the same. Therefore, the repeating unit represented by formula (1), (i) and (ii), and other preferred conditions are all the same as those of the polyimide precursor contained in the polyimide precursor composition of the present invention described above.

[0191] Furthermore, in a polyimide film of this type, it is necessary to satisfy the condition that the silicon content in the polyimide film is 2.0 to 4.2 parts by mass or less per 100 parts by mass of the polyimide film (hereinafter, for convenience, this may be simply referred to as "condition (A)"). By setting the silicon content to 2.0 parts by mass or more, it is possible to greatly improve transparency, and by setting the silicon content to 4.2 parts by mass or less, it is possible to suppress phase separation between the polyimide and the silicon compound. In addition, the silicon content in the polyimide film is preferably 2.5 to 4.0 parts by mass, more preferably 3.0 to 3.5 parts by mass, per 100 parts by mass of the polyimide film.

[0192] Furthermore, a polyimide film of this type must satisfy the condition that the 0.5% weight loss temperature is 535°C or higher (hereinafter, for convenience, this will sometimes be simply referred to as "condition (B)"). By setting the 0.5% weight loss temperature to 535°C or higher, it is possible to make the film exhibit high heat resistance. Moreover, such a 0.5% weight loss temperature is preferably 540°C or higher, more preferably 545°C or higher, and even more preferably 550°C or higher.

[0193] A polyimide film of the present invention that satisfies conditions (A) and (B) is preferably a polyimide film obtained from the polyimide precursor composition of the present invention, from the viewpoint of efficiently satisfying the above conditions. In this case, a polyimide film in a form that satisfies these conditions can be said to be a preferred embodiment of the aforementioned polyimide film of the present invention obtained from the polyimide precursor composition of the present invention. Furthermore, there are no particular limitations on the method for producing a polyimide film in a form that satisfies conditions (A) and (B), but a method similar to the method for producing the aforementioned polyimide film of the present invention (a polyimide film obtained from the polyimide precursor composition of the present invention) can be employed, except that the production conditions are appropriately selected so that the silicon content in the polyimide film is 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film. The conditions for making the silicon content in the polyimide film 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film can be easily adjusted by appropriately changing the heating temperature, heating time, etc., depending on the type of silicon compound contained in the composition and its content when producing a polyimide film using the polyimide precursor composition of the present invention.

[0194] Furthermore, the properties of a polyimide film that satisfies conditions (A) and (B) above are preferably similar to those described in the section "About the properties of polyimide film" above, except that the silicon content in the polyimide film must be 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film (it is also preferable that the conditions for the preferred properties are the same).

[0195] <Regarding the Uses of the Polyimide Film> As described above, the polyimide film of the present invention is suitably usable for flexible electronic devices. The uses of the polyimide film of the present invention are not limited to flexible electronic devices, and it can be appropriately used for other applications, such as films for copper (or metal) clad laminates.

[0196] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0197] <Evaluation Methods for Polyimide Precursor Compositions and Polyimide Films> First, the evaluation methods for the polyimide precursor compositions obtained in the following examples, and for the polyimide films obtained using them, will be explained.

[0198] [Evaluation of Storage Stability] Using the polyimide precursor compositions obtained in each of the following examples, a polyimide film was manufactured by following the "Polyimide Film Manufacturing Process" described below, using the composition after 24 hours of storage at atmospheric pressure and room temperature (approximately 23°C) after manufacturing, and the composition after 30 days of storage at atmospheric pressure and room temperature (approximately 23°C) after manufacturing. The obtained polyimide films were used as test pieces for each example, and the presence or absence of clouding in the appearance of the film was visually checked. In this case, a transparent film without visible clouding was evaluated as "transparent," and a film with visible clouding was evaluated as "cloudy." The results of the storage stability evaluation are shown in Tables 1 to 3 (if the above evaluation was not performed, "-" is indicated in the table). Regarding the evaluation results, if the composition becomes "cloudy" 24 hours after manufacturing, it can be determined that the composition could not be stored stably for 24 hours. If the composition becomes "transparent" both 24 hours after manufacturing and 30 days after manufacturing, it can be determined that the composition has high storage stability.

[0199] <Manufacturing Process for Polyimide Film> A circular glass substrate (Corning, Eagle-XG®) with a diameter of 6 inches (500 μm thickness) was prepared as the substrate. The polyimide precursor compositions obtained in each example (composition after 24 hours and composition after 30 days were used, respectively) were coated onto the glass substrate using a spin coater. Under a nitrogen atmosphere (oxygen concentration of 200 ppm or less), the composition was heated on the glass substrate from room temperature to 450°C to perform thermal imidization, thereby obtaining a polyimide film / substrate laminate. After obtaining the laminate in this way, the laminate was immersed in 40°C water to peel the polyimide film from the glass substrate, and the laminate was dried to obtain a polyimide film. The film thickness of the polyimide films obtained using the compositions obtained in each example was approximately 10 μm (10 μm ± 0.2 μm).

[0200] [450 nm light transmittance] Polyimide films with a thickness of approximately 10 μm (10 μm ± 0.2 μm) obtained using the polyimide precursor composition (the polyimide precursor composition produced in each example) 24 hours after production (the films produced when performing the "evaluation of storage stability" described above) were used as test specimens for each example, and the light transmittance at 450 nm (450 nm light transmittance) was measured using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO). In this application, a 450 nm light transmittance of 70% or more is considered to indicate high level of transparency. The obtained results are shown in Tables 1 to 3.

[0201] [0.5% Weight Loss Temperature] Using the polyimide precursor composition (the polyimide precursor composition produced in each example) 24 hours after production, a polyimide film with a thickness of approximately 10 μm (10 μm ± 0.2 μm) was obtained (the film produced when performing the "Evaluation of Storage Stability" described above). These films were used as test specimens for each example, and a calorimeter (TA Instruments, Q5000IR) was used to measure the weight curve by heating the film from 25°C to 600°C at a heating rate of 10°C / min in a nitrogen stream. From the obtained weight curve, the temperature at which the weight at 150°C decreased by 0.5% (0.5% weight loss temperature) was determined, with the weight at 150°C being 100%. The results are shown in Table 1 or 2. In this application, a 0.5% weight loss temperature of 535°C or higher is considered to indicate high heat resistance. The results are shown in Tables 1 to 3.

[0202] [Silicon content in polyimide film (silicon content)] A polyimide film with a thickness of approximately 10 μm (10 μm ± 0.2 μm) was obtained using the polyimide precursor composition (the polyimide precursor composition produced in each example) 24 hours after production (the film produced when performing the "evaluation of storage stability" described above). These films were used as test specimens for each example. The test specimens and acid were placed in a decomposition container, sealed tightly, and decomposed by heating with microwave irradiation. The solution obtained by adding ultrapure water to a fixed volume was used as the test solution, and the silicon content per 100 parts by mass of the polyimide film was measured using an ICP-AES / ICPE9820 (manufactured by Shimadzu Corporation).

[0203] <Raw Materials> Next, the names and abbreviations of the compounds used as raw materials in the examples and comparative examples will be explained. In the text of the examples and comparative examples and in Tables 1 to 3, the compounds used as raw materials will be expressed using the abbreviations or compound names explained below. [Tetracarboxylic acid dianhydrides] ・s-BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride ・ODPA: 4,4'-oxydiphthalic acid dianhydride ・a-BPDA: 2,3,3',4'-biphenyltetracarboxylic acid dianhydride [Diamines] ・PPD: p-phenylenediamine ・BAFL: 9,9-bis(4-aminophenyl)fluorene ・4,4'-DDS: 4,4'-diaminodiphenylsulfone [Silicon compounds] [Silanol compounds] ・Phenylsilanetriol [Silicones] ・Silsesquioxane(I): TrisilanolphenylPOSS, cage structure, CAS number: 444315-26-8, manufactured by Constr Chemical Co., Ltd.) • Silsesquioxane(II): Manufactured by Konishi Chemical Industry Co., Ltd., product name: SR-23, polysilsesquioxane containing phenyl and silanol groups, random structure, weight-average molecular weight: 800 g / mol, terminal groups: ethoxy group, hydroxyl group [Imidazole compound] • 2-Pz: 2-phenylimidazole • 1,2-DMz: 1,2-dimethylimidazole [Solvent] • NMP: N-methyl-2-pyrrolidone

[0204] (Example 1) First, 1.08 g (10 mmol) of PPD as the diamine was added to a reaction vessel purged with nitrogen gas. Then, 28.17 g of NMP, the solvent, was added so that the total mass of monomers used in the production of the polyimide precursor (sum of diamine and tetracarboxylic dianhydride) was 12.5% ​​by mass. The mixture was stirred at room temperature (approximately 23°C) for 1 hour to obtain a solution of diamine. Next, 2.94 g (10 mmol) of s-BPDA as the tetracarboxylic dianhydride was gradually added to the obtained solution of diamine. The mixture was then stirred at room temperature (approximately 23°C) for 6 hours to react the diamine and tetracarboxylic dianhydride in the solution to form a polyimide precursor (polyamic acid), thereby obtaining a homogeneous and viscous polyimide precursor solution (polyamic acid solution) (precursor solution preparation step).

[0205] Next, phenylsilanetriol was added to the obtained polyimide precursor solution in a ratio of 5 parts by mass when the mass of the polyimide precursor contained in the final composition (in terms of polyimide equivalent) was 100 parts by mass (the total mass of polyimide obtained when polyimide is produced from the total amount of polyimide precursor in the composition by completely imidizing all the repeating units in the polyimide precursor contained in the final composition) was taken as 100 parts by mass, and the mixture was stirred at room temperature for 3 hours to obtain a homogeneous and viscous polyimide precursor composition. The solvent content in the composition was 87.0% by mass.

[0206] (Example 2) First, a uniform and viscous polyimide precursor solution (polyamic acid solution) was obtained by employing the same process as the "precursor solution preparation process" used in Example 1.

[0207] Next, 2-Pz was dissolved in four times its mass of NMP to obtain a homogeneous solution of 2-Pz with a solid content concentration of 20% by mass.

[0208] Next, the imidazole compound solution and the polyimide precursor solution were mixed so that the ratio of the molar amount of the imidazole compound to the total molar amount of repeating units of the polyimide precursor (= ([molar amount of imidazole compound / [total molar amount of repeating units]) × 100, unit: mol%) was as shown in Table 1. The total molar amount of repeating units was calculated from the amount of monomer used.

[0209] Next, phenylsilanetriol was added to the resulting mixture as a silicon compound in a ratio of 5 parts by mass when the total mass of the polyimide precursor in the final composition (in terms of polyimide equivalent) was 100 parts by mass. The mixture was then stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor composition. The solvent content in the composition was 86.7% by mass.

[0210] (Examples 3 and 8) A uniform and viscous polyimide precursor composition was obtained in the same manner as in Example 1, except that the type and / or amount of silicon compound used was changed to have the composition shown in Table 1.

[0211] (Examples 4-7 and 9-19) Except for changing the types and amounts (amounts used) of the components used to obtain the compositions (amounts) shown in Tables 1-2, a uniform and viscous polyimide precursor composition was obtained by employing the same method as described in Example 2.

[0212] Regarding the manufacturing methods employed in each example, for example, Example 5 will be given a specific explanation. In Example 5, instead of using PPD (10 mmol) alone as the diamine in the preparation step of the precursor solution, a mixture of PPD (9 mmol) and BAFL (1 mmol) was used, and the type of silicon compound was changed from phenylsilanetriol to silsesquioxane (I). In addition, the amount of silicon compound used was changed from 5 parts by mass to 10 parts by mass when the mass of the polyimide precursor contained in the final composition in terms of polyimide equivalent is 100 parts by mass. Otherwise, the same method as described in Example 2 was adopted to obtain a uniform and viscous polyimide precursor composition.

[0213] (Comparative Example 1) A uniform and viscous polyimide precursor solution (polyamic acid solution) was prepared using the same process as the "precursor solution preparation step" used in Example 1, and this solution was used as a comparative polyimide precursor composition.

[0214] (Comparative Example 2) A uniform and viscous polyimide precursor composition was obtained by employing the same method as described in Example 2, except that the amount of phenylsilanetriol used was changed from 5 parts by mass to 30 parts by mass when the mass of the polyimide precursor in terms of polyimide was 100 parts by mass.

[0215] (Comparative Example 3) First, a uniform and viscous polyimide precursor solution (polyamic acid solution) was prepared by employing the same process as the "precursor solution preparation process" used in Example 1, except that the type and amount of components used were changed so that the composition (amount of ingredients) was as shown in Table 3.

[0216] Next, 2-Pz was dissolved in 4 times its mass of NMP to obtain a homogeneous solution of 2-Pz with a solid content concentration of 20% by mass. Then, the imidazole compound solution and the polyimide precursor solution were mixed so that the ratio of the molar amount of the imidazole compound to the total molar amount of repeating units of the polyimide precursor (= ([molar amount of imidazole compound / [total molar amount of repeating units]) × 100, unit: mol%) was as shown in Table 3, to obtain a polyimide precursor composition.

[0217] (Comparative Example 4) First, a uniform and viscous polyimide precursor solution (polyamic acid solution) was prepared by employing the same process as the "precursor solution preparation process" used in Example 1, except that the type and amount of components used were changed to achieve the composition (amount of ingredients) shown in Table 3. This solution was then used as the polyimide precursor composition for comparison.

[0218]

[0219]

[0220]

[0221] As is clear from the results shown in Tables 1-2, when the polyimide precursor composition was a composition containing a polyimide precursor and a silicon compound in a proportion of 5 to 25 parts by mass when the mass of the polyimide precursor in terms of polyimide equivalent is 100 parts by mass (Examples 1-19), it was confirmed that the storage stability was high, and a transparent film could be manufactured even when the composition was used after 30 days. Furthermore, the polyimide films obtained using the polyimide precursor compositions obtained in Examples 1-19 (corresponding to the polyimide films of the present invention) all had a transmittance of 70% or more for light at 450 nm (450 nm transmittance) and a 0.5% weight loss temperature of 535°C or higher, indicating a high level of transparency and a high level of heat resistance.

[0222] In contrast, when the polyimide precursor composition did not contain a silicon compound and the polyamic acid solution was used directly as the polyimide precursor composition (Comparative Example 1 and Comparative Example 4), the 450 nm transmittance of the resulting polyimide films was 68% (Comparative Example 1) and 69% (Comparative Example 4), respectively, indicating that the transparency was not sufficient.

[0223] Furthermore, when the polyimide precursor composition was a composition containing a polyimide precursor and a silicon compound in an amount of 30 parts by mass when the polyimide equivalent mass of the polyimide precursor was 100 parts by mass (Comparative Example 2), the resulting film appeared cloudy even after 24 hours, indicating insufficient storage stability. Since the film obtained using the composition after 24 hours appeared cloudy, a test using the composition after 30 days was not conducted when evaluating storage stability. In addition, the polyimide film obtained using the polyimide precursor composition obtained in Comparative Example 2 had a transmittance of 63% at 450 nm, indicating insufficient transparency.

[0224] Furthermore, when the polyimide precursor composition was a composition containing a polyimide precursor and an imidazole compound in which the ratio of the molar amount of the imidazole compound to the total molar amount of repeating units of the polyimide precursor was 1.5 mol%, and which did not contain a silicon compound (Comparative Example 3), the transmittance of the resulting polyimide film at 450 nm was 69%, which was not sufficiently transparent.

[0225] These results show that when the polyimide precursor composition is a composition containing a polyimide precursor and a silicon compound in an amount of 1 to 29 parts by mass when the polyimide equivalent mass of the polyimide precursor is 100 parts by mass, the composition exhibits excellent storage stability, the film does not become cloudy even when manufactured after long-term storage, and moreover, when a film is manufactured using this composition, it is possible to manufacture a polyimide film with a high level of transparency and a high level of heat resistance.

[0226] As described above, the present invention makes it possible to provide a polyimide precursor composition that enables the production of a polyimide film having high storage stability, high levels of transparency, and high levels of heat resistance. Furthermore, the present invention makes it possible to provide a polyimide film obtained using the polyimide precursor composition, as well as a polyimide film / substrate laminate, a flexible electronic device, and a flexible electronic device substrate using the polyimide film.

[0227] Therefore, the polyimide precursor composition of the present invention is particularly suitable for use in the production of polyimide films for flexible electronic devices (for example, flexible displays such as liquid crystal displays and organic EL displays; display devices such as electronic paper; and light-receiving devices such as solar cells and CMOS).

Claims

A polyimide precursor containing repeating units represented by the following formula (1) and satisfying the following (i) and (ii), A silicon compound selected from the group consisting of silanol compounds and silicones, A polyimide precursor composition containing the silicon compound, wherein the content of the silicon compound is 1 to 29 parts by mass when the mass of the polyimide precursor in terms of polyimide is 100 parts by mass. [In formula (1), X １ is a tetravalent aliphatic group or a tetravalent aromatic group, Y １ is a divalent aliphatic group or a divalent aromatic group, R １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group. (i) All X present in the polyimide precursor １ At least one of them is a tetravalent aromatic group. (ii) All Y present in the polyimide precursor １ At least one of them is a divalent aromatic group. 　 The polyimide precursor composition according to claim 1, wherein the silicon compound is at least one selected from the group consisting of silanol compounds having an aryl group and silicones having an aryl group and a silanol group. 　 X present in the aforementioned polyimide precursor １ The polyimide precursor composition according to claim 1, wherein 50 mol% or more of the total amount is a tetravalent aromatic group represented by the following formula (1-1). Y present in the aforementioned polyimide precursor １ The polyimide precursor composition according to claim 1, wherein 50 mol% or more of the total amount is p-phenylene groups. The polyimide precursor composition according to claim 1, further comprising an imidazole compound. 　 X present in the polyimide precursor １ The polyimide precursor composition according to claim 3, wherein 1 to 30 mol% of the total amount of １ is a tetravalent aromatic group represented by the following formula (1-2). [In formula (1-2), R １０ and R １１ Each of these is independently a single-bonded or divalent organic group. Y present in the aforementioned polyimide precursor １ The polyimide precursor composition according to claim 4, wherein 1 to 30 mol% of the total amount is a divalent aromatic group represented by the following formula (1-3). [In formula (1-3), R １２ and R １３ Each of these is independently a single-bonded or divalent organic group. 　 A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 7. 　 A polyimide film / substrate laminate having the polyimide film according to claim 8 and a substrate. 　 A flexible electronic device comprising the polyimide film described in claim 8. 　 A flexible electronic device substrate made of the polyimide film described in claim 8. 　 A polyimide film obtained from a polyimide precursor composition containing a repeating unit represented by the following formula (1) and satisfying the following (i) and (ii), The silicon content in the polyimide film is 2.0 to 4.2 parts by mass per 100 parts by mass of the polyimide film, and A polyimide film having a 0.5% weight loss temperature of 535°C or higher. [In formula (1), X １ is a tetravalent aliphatic group or a tetravalent aromatic group, Y １ is a divalent aliphatic group or a divalent aromatic group, R １ and R ２ Each of these is independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group. (i) All X present in the polyimide precursor １ At least one of them is a tetravalent aromatic group. (ii) All Y present in the polyimide precursor １ At least one of them is a divalent aromatic group.

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