Polyamic acid, polyimide, and use thereof

Abstract

Provided is a polyamic acid that is a copolymerization reaction product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group, wherein the silsesquioxane compound A is obtained by reacting: a thiol group of a condensate B of a thiol-group-containing trialkoxysilane a1 represented by the general formula: R1Si(OR2)3 (in the formula, R1 represents an organic group such as a C1-8 aliphatic hydrocarbon group in which at least 1 hydrogen is substituted by a thiol group, and R2 each independently represent a hydrogen atom, a C1-8 aliphatic hydrocarbon group, etc.) and a thiol-group-free trialkoxysilane a2; and a reactive group composed of a vinyl group, etc., in a dicarboxylic anhydride C having the reactive group.

Description

Polyamic acid, polyimide, and their uses

[0001] The present invention relates to a polyamic acid containing a novel silsesquioxane compound as a copolymerization component, a polyimide obtained by imidizing the polyamic acid, and uses thereof. Examples of the uses include polyimide films, laminates thereof, and flexible electronic devices.

[0002] Polyimide films have excellent heat resistance, good mechanical properties, and are widely used in the electrical and electronic fields as flexible materials. However, because ordinary polyimide films are colored yellowish-brown, they cannot be used in areas where light transmission is required, such as display devices.

[0003] Meanwhile, display devices are becoming thinner and lighter, and there is a demand for them to be even more flexible. To address this, attempts are underway to replace glass substrates with flexible polymer film substrates. However, colored polyimide films cannot be used as substrate materials for liquid crystal displays, which display images by turning light transmission on and off. Therefore, they have only been used in a few applications, such as peripheral circuits such as TAB and COF on which display device driver circuits are mounted, and the back side of reflective or self-emissive display devices.

[0004] In view of this, development of colorless and transparent polyimide films has been progressing. When polyimide films are used as flexible electronic circuit substrates, they are required to have not only colorless transparency, a low coefficient of linear expansion (CTE), and a low retardation (Rth), but also resistance to bending and mechanical strength under high temperature conditions during circuit formation, and therefore, they are required to have a high modulus of elasticity, mechanical strength, and a high glass transition temperature (Tg).

[0005] A typical example is the attempt to develop a colorless and transparent polyimide film using a fluorinated polyimide resin or a semi-alicyclic or fully alicyclic polyimide resin (Patent Documents 1 to 3). These films are less colored and have transparency, but they do not have as high mechanical strength as colored polyimide films, and when industrial production or applications involving exposure to high temperatures are considered, thermal decomposition or oxidation reactions occur, so the colorlessness and transparency are not necessarily maintained.

[0006] From this perspective, a method of heat treatment while spraying gas with a specified oxygen content has been proposed (Patent Document 4), but the manufacturing cost is high in an environment where the oxygen concentration is less than 18%, making industrial production extremely difficult.

[0007] Furthermore, as a means of further improving the properties of organic materials, there is a so-called organic-inorganic hybridization technology in which organic materials are combined with inorganic materials to impart inorganic properties such as high heat resistance, chemical resistance, and high surface hardness. For example, it is known that combining transparent polyimide with silica nanoparticles can improve CTE, Rth, and Tg while maintaining transparency. However, as the amount of silica nanoparticles mixed increases, the film becomes more rigid and brittle, resulting in a decrease in mechanical strength.

[0008] On the other hand, RSiO ３／２ Silsesquioxanes represented by the formula (I) can be easily used to provide organic-inorganic hybrid cured products by providing R with a substituent that can react with organic materials, and so their practical application is being investigated (see, for example, Patent Document 5). Attempts have been made to improve heat resistance and processability by combining flexible silsesquioxanes with polyimides. It is known that the charge-transfer interaction between the imide moiety of polyimide and silsesquioxane increases the thermal decomposition temperature (see, for example, Non-Patent Document 1).

[0009] Japanese Patent Laid-Open No. 11-106508 Japanese Patent Laid-Open No. 2002-146021 Japanese Patent Laid-Open No. 2002-348374 WO2008 / 146637 Japanese Patent No. 3653976

[0010] Thermochimica Acta 2004, 417, pp.133-142European Polymer Journal 2011, 47 (6), pp. 1328-1337

[0011] However, since the flexible silsesquioxane structure reduces the rigidity of the polyimide, silsesquioxane composite polyimides usually have the problem of exhibiting a relatively low modulus of elasticity and a low Tg (Non-Patent Document 2).

[0012] As described above, it is extremely difficult to produce a colorless, transparent polyimide film that has a low coefficient of linear expansion, high heat resistance, and high mechanical strength. Increasing the amount of monomer components having an alicyclic structure in semi-alicyclic or fully alicyclic polyimides improves colorless transparency, but reduces mechanical strength, making film production difficult. On the other hand, introducing aromatic monomers increases toughness and improves the mechanical properties of the film, but makes it more susceptible to coloration and reduces colorless transparency. Introducing a filler (inorganic component) with a refractive index close to that of the resin component improves heat resistance and colorless transparency, further lowers the coefficient of linear expansion, and improves processability, but makes the resin hard and brittle, resulting in reduced mechanical properties.

[0013] Therefore, there is a trade-off between practical properties such as heat resistance and mechanical properties and colorlessness (transparency or whiteness), and there has been a demand for a method for producing a polyimide film that has improved toughness while maintaining the other main properties.

[0014] Therefore, an object of the present invention is to provide a polyamic acid that is useful as a raw material for producing a polyimide film having improved toughness while maintaining other main properties. Another object of the present invention is to provide a polyamic acid composition containing such a polyamic acid and a polyimide obtained by imidizing the polyamic acid.

[0015] Furthermore, another object of the present invention is to provide a polyimide film having improved toughness while maintaining other main properties, a laminate thereof, a flexible electronic device using the polyimide film, and a method for producing the same.

[0016] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by using a polyamic acid containing, as a copolymerization component, a novel silsesquioxane compound into which a dicarboxylic acid anhydride group has been introduced by reaction with a thiol group, and have thereby completed the present invention.

[0017] That is, the present invention includes the following:

[0018] [1] A polyamic acid which is a copolymerization reaction product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group, wherein the silsesquioxane compound A is represented by the general formula: R １ Si(OR ２ ) ３ and a thiol group-containing trialkoxysilane a1 represented by the formula (wherein R １ represents an organic group in which at least one hydrogen atom of an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms has been substituted with a thiol group; R ２ and each independently represent a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.) A polyamic acid which is a silsesquioxane compound A obtained by reacting a trialkoxysilane a2 having no thiol group with a thiol group of a condensation product B of: and a reactive group of a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group.

[0019] [2] A polyamic acid that is a copolymerization reaction product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group, wherein the silsesquioxane compound A has structural units represented by the following general formulas (1) and (2):

[0020]

[0021] (In the formula, Q １ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms; Q２ represents a single bond, a hydrocarbon group having 1 to 8 carbon atoms, an organic group in which one or more carbon atoms of a hydrocarbon group having 1 to 8 carbon atoms are substituted with oxygen, or a carbonyl group; X represents a carbon-carbon bond, or an aliphatic ring having 4 to 10 carbon atoms, an aromatic ring having 6 to 10 carbon atoms, or a heterocycle in which some of the carbon atoms constituting these rings are substituted with oxygen or sulfur, and one or more hydrogen atoms bonded to these rings may be substituted with a hydrocarbon group; and 1.0≦m≦2.0 and 1.4≦n≦1.6.

[0022] (In the formula, Q ３ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms, and 1.4≦n≦1.6.) [3] The polyamic acid according to [1] or [2], wherein the molar ratio of the trialkoxysilane a2 in the silsesquioxane compound A ([number of moles of a2] / [number of moles of a1+number of moles of a2]) or the molar ratio of the structural unit represented by general formula (2) ([structural unit (2)] / [structural unit (1)+structural unit (2)]) is 0.1 or more and 0.7 or less.

[0023] [4] The polyamic acid according to [1] or [3], wherein the dicarboxylic acid anhydride C is a compound represented by a chemical formula selected from the following:

[0024]

[0025] (wherein Rx represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.) [5] The polyamic acid according to any one of [1] to [4], wherein the molar content of the structural units derived from the silsesquioxane compound A based on the divalent monomer: (nA / (nA+nD))×100 (wherein nA is the total number of moles of the structural units derived from the silsesquioxane compound A divided by the total number of the dicarboxylic acid anhydride groups and multiplied by two, and nD is the number of moles of the structural units derived from the carboxylic acids) is 0.01 to 10.0 mol %.

[0026] [6] The polyamic acid according to any one of [1] to [5], wherein the carboxylic acids are one or more compounds represented by a chemical formula selected from the following: [7] The polyamic acid according to any one of [1] to [6], wherein the diamines include 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) or 4,4'-diaminobenzanilide (DABA).

[0027] [8] A polyamic acid composition comprising the polyamic acid according to any one of [1] to [7] and a solvent.

[0028] [9] A polyimide obtained by imidizing the polyamic acid according to any one of [1] to [7].

[0029]

[10] A polyimide film containing the polyimide according to [9].

[0030]

[11] The polyimide film according to

[10] , having a linear expansion coefficient of 40 ppm / K or less and −20 ppm / K or more.

[0031]

[12] The polyimide film according to

[10] or

[11] , which has a tensile product in a tensile test of 1,000 MPa·% or more and 10,000 MPa·% or less.

[0032]

[13] A laminate comprising the polyimide film according to any one of

[10] to

[12] and an inorganic substrate.

[0033]

[14] A method for producing a flexible electronic device, comprising the steps of forming an electronic device on the polyimide film surface of the laminate according to

[13] , and peeling off the inorganic substrate.

[0034]

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

[10] to

[12] and an electronic device formed on the polyimide film.

[0035] According to the present invention, there is provided a polyamic acid useful as a raw material for producing a polyimide film having improved toughness while maintaining other main properties, a polyamic acid composition containing such a polyamic acid, and a polyimide obtained by imidizing the polyamic acid.

[0036] Furthermore, the present invention can provide a polyimide film having improved toughness while maintaining other main properties, a laminate thereof, a flexible electronic device using the polyimide film, and a method for producing the same.

[0037] SQ109 (PGMEA solution) used in Synthesis Example 2-1 １ H NMR (CDCl ３ ) spectrum of PGMEA. １ H NMR (CDCl ３ ) spectrum. Note that δ=2.2 is a peak derived from acetone for cleaning instruments. １ H NMR (CDCl ３ ) spectrum. Note that δ=2.2 is a peak derived from acetone used for cleaning instruments. １ H NMR (CDCl ３ ) spectrum of silsesquioxane SQ2 having an acid anhydride group obtained in Synthesis Example 2-2. １ H NMR (CDCl ３ ) spectrum of silsesquioxane SQ3 having an acid anhydride group obtained in Synthesis Example 2-3. １ H NMR (DMSO-d ６ ) spectrum of silsesquioxane SQ4 having an acid anhydride group obtained in Synthesis Example 2-4. １ H NMR (DMSO-d ６ ) spectrum of silsesquioxane SQ5 having an acid anhydride group obtained in Synthesis Example 2-5. １ H NMR (DMSO-d ６ ) spectrum of silsesquioxane SQ6 having an acid anhydride group obtained in Synthesis Example 2-6. １H NMR (DMSO-d ６ ) spectrum of silsesquioxane SQ7 having an acid anhydride group obtained in Synthesis Example 2-7. １ H NMR (DMSO-d ６ ) spectrum of silsesquioxane SQ8 having an acid anhydride group obtained in Synthesis Example 2-8. １ H NMR (DMSO-d ６ ) spectrum.

[0038] The present invention will be described in detail below, but these are only embodiments of the present invention and the present invention is not limited to these details.

[0039] The polyamic acid of the present invention is a copolymerization reaction product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group. These will be explained below.

[0040] <Silsesquioxane Compound A Having a Dicarboxylic Acid Anhydride Group> The novel silsesquioxane compound A is a silsesquioxane compound having a dicarboxylic acid anhydride group (hereinafter, may be simply referred to as an "acid anhydride group"), and is a silsesquioxane compound obtained by reacting a thiol group of a condensate B, which is a thiol group-containing silsesquioxane compound, with a reactive group of a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group.

[0041] The condensate B is represented by the general formula: R １ Si(OR ２ ) ３ and a thiol group-containing trialkoxysilane a1 represented by the formula (wherein R １ represents an organic group in which at least one hydrogen atom of an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms has been substituted with a thiol group; R ２ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.) A condensation product B of a trialkoxysilane a2 having no thiol group.

[0042] Here, since both the thiol group-containing trialkoxysilanes a1 and the trialkoxysilanes a2 have three reactive alkoxy groups, the resulting product has a three-dimensionally complex structure, and it is not realistic to specify the entire structure by chemical formula. For this reason, the product invention is specified in the form of a manufacturing process limitation (product-by-process).

[0043] However, it is possible to partially specify the structure as two repeating units. That is, the novel silsesquioxane compound A preferably has structural units represented by the following general formulas (1) and (2).

[0044]

[0045] (In the formula, Q １ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms; Q ２ represents a single bond, a hydrocarbon group having 1 to 8 carbon atoms, an organic group in which one or more carbon atoms of a hydrocarbon group having 1 to 8 carbon atoms are substituted with oxygen, or a carbonyl group; X represents a carbon-carbon bond, or an aliphatic ring having 4 to 10 carbon atoms, an aromatic ring having 6 to 10 carbon atoms, or a heterocycle in which some of the carbon atoms constituting these rings are substituted with oxygen or sulfur, and one or more hydrogen atoms bonded to these rings may be substituted with a hydrocarbon group; and 1.0≦m≦2.0 and 1.4≦n≦1.6.

[0046] (In the formula, Q ３ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms, and 1.4≦n≦1.6.) In another aspect, the novel silsesquioxane compound A is not limited to being specified by the above-mentioned production method, but can be specified as having structural units represented by the following general formulas (1) and (2) as two repeating units:

[0047] The novel silsesquioxane compound A can be suitably produced, for example, by a production method including the following steps in order.

[0048] General formula: R １ Si(OR ２ ) ３ and a thiol group-containing trialkoxysilane a1 represented by the formula (wherein R １ represents an organic group in which at least one hydrogen atom of an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms has been substituted with a thiol group; R ２ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.) A first step of hydrolyzing trialkoxysilanes a2 having no thiol group with water using an acidic catalyst to obtain a reaction mixture x; a second step of removing the acidic catalyst from the reaction mixture x to obtain a reaction mixture y; a third step of mixing the reaction mixture y with a polar solvent containing a basic catalyst and condensing the mixture to obtain a condensate B having a thiol group; and a fourth step of reacting the condensate B with a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group.

[0049] Alternatively, it can also be obtained by reacting a commercially available thiol group-containing silsesquioxane compound (condensate B) with a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group.

[0050] <Condensate B (Thiol Group-Containing Silsesquioxane Compound)> Condensate B is a condensate of a thiol group-containing trialkoxysilane a1 and a thiol group-free trialkoxysilane a2. As the condensate B, for example, organic-inorganic hybrid resin COMPOCELAN SQ (product name: SQ107 or SQ109, Arakawa Chemical Industries, Ltd.) can be used. Alternatively, condensate B synthesized by a method including the above steps 1 to 3 can be used.

[0051] <First Step> The first step is a step of forming a compound represented by the general formula: R １ Si(OR ２ ) ３The reaction mixture x is obtained by hydrolysis of a thiol group-containing trialkoxysilane a1 represented by the following formula (1), a thiol group-free trialkoxysilane a2, and water in the presence of an acid catalyst.

[0052] (In the formula, R １ represents an organic group in which at least one hydrogen atom of an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms has been substituted with a thiol group; R ２ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.) Here, the limitation of the number of carbon atoms, such as "1 to 8 carbon atoms," refers to the total number of carbon atoms in the organic group including the substituents. More specifically, in the above general formula, R １ R represents an organic group in which at least one hydrogen atom of a linear, branched, or aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms and optionally having a hydrocarbon group, has been substituted with a thiol group. １ As the alkyl group, a straight-chain hydrocarbon group is preferred from the viewpoint of imparting flexibility to the polymer chain, and an alicyclic hydrocarbon group or an aromatic hydrocarbon group is preferred from the viewpoint of enhancing heat resistance.

[0053] R ２ R each independently represents a hydrogen atom, a linear or branched hydrocarbon group having 1 to 8 carbon atoms, or an aliphatic ring, or an aromatic hydrocarbon group having 6 to 8 carbon atoms and optionally having a hydrocarbon group. ２ From the viewpoint of reactivity in the hydrolysis reaction, alkyl groups having 1 to 4 carbon atoms are preferred, with methyl and ethyl groups being particularly preferred.

[0054] Specific examples of thiol group-containing trialkoxysilanes a1 (hereinafter referred to as component (a1)) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropyltributoxysilane, 1,4-dimercapto-2-(trimethoxysilyl)butane, 1,4-dimercapto-2-(triethoxysilyl)butane, 1,4-dimercapto-2-(tripropoxysilyl)butane, 1,4-dimercapto-2-(tributoxysilyl)butane, 2-mercaptomethyl Examples of suitable mercaptosilanes include 1,2-dimercaptopropyltrimethoxysilane, 2-mercaptomethyl-3-mercaptopropyltriethoxysilane, 2-mercaptomethyl-3-mercaptopropyltripropoxysilane, 2-mercaptomethyl-3-mercaptopropyltributoxysilane, 1,2-dimercaptoethyltrimethoxysilane, 1,2-dimercaptoethyltriethoxysilane, 1,2-dimercaptoethyltripropoxysilane, and 1,2-dimercaptoethyltributoxysilane. These exemplary compounds may be used alone or in appropriate combination. Among these exemplary compounds, 3-mercaptopropyltrimethoxysilane is particularly preferred because of its high reactivity in hydrolysis reactions and ease of availability.

[0055] The trialkoxysilane a2 (hereinafter referred to as component (a2)) having no thiol group is a compound represented by the general formula: R ３ Si(OR ２ ) ３ (wherein R ３ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms; R ２ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms. ３ represents a linear, branched, or aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms which may have a hydrocarbon group. ２is as described for component (a1), but R ２ may be the same as or different from.

[0056] Specific examples of component (a2) that can be used include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane. Component (a2) can be used alone or in combination of two or more. By using these, the amount of thiol groups can be adjusted, which makes it possible to adjust the degree of crosslinking of the final polyimide or increase the proportion of inorganic components in the polyimide.

[0057] The molar ratio of trialkoxysilane a2 in the alkoxysilanes ([moles of a2] / [moles of a1 + moles of a2]) is preferably 0.1 or more and 0.7 or less, more preferably 0.2 or more and 0.7 or less. The larger this molar ratio, the smaller the amount of thiol groups contained per molecule, and the smaller the value, the larger the amount of thiol groups. When the molar ratio is within this range, the resulting polyimide chains are appropriately crosslinked, and the effect of improving physical properties is also sufficient.

[0058] Condensate B, which is a thiol group-containing silsesquioxane, can be obtained by hydrolyzing and then condensing components (a1) and (a2). In the first step, the alkoxy groups contained in components (a1) and (a2) are converted into silanol groups by the hydrolysis reaction, and an alcohol is produced as a by-product.

[0059] The amount of water required for the hydrolysis reaction is preferably 0.4 to 10, expressed as a molar ratio ([number of moles of water used in the hydrolysis reaction] / [total number of moles of the alkoxy groups contained in component (a1) and component (a2)]). If this molar ratio is 0.4 or more and less than 0.5, some alkoxy groups will remain in the resulting thiol group-containing silsesquioxane, but adhesion to inorganic materials can be improved. Furthermore, if the molar ratio is 0.5 to 10, substantially no alkoxy groups will remain in the resulting thiol group-containing silsesquioxane, making it easy to produce a thick-film cured product.

[0060] In addition to the components (a1) and (a2), it is also possible to further use dialkoxysilanes and / or tetraalkoxysilanes within a range that does not impair the effects of the present invention (for example, 50 mol % or less).

[0061] As the catalyst used in the hydrolysis reaction, any acid catalyst that can function as a conventionally known hydrolysis catalyst can be used. However, since the acid catalyst needs to be substantially removed after the hydrolysis reaction, it is preferable to use one that is easy to remove. Examples of such catalysts include formic acid, which has a low boiling point and can be removed by reducing pressure, and solid acid catalysts, which can be easily removed by methods such as filtration.

[0062] Examples of solid acid catalysts include cation exchange resins, activated clay, and carbon-based solid acids. Among these, cation exchange resins are preferred because they have high catalytic activity and are easily available. As the cation exchange resin, strong acid cation exchange resins and weak acid cation exchange resins can be used. Examples of strong acid ion exchange resins include the Diaion SK series, UBK series, PK series, and HPK25 / PCP series (all trade names manufactured by Mitsubishi Chemical Corporation), Amberlite IR120B, IR124, 200CT, and 252, Amberjet 1020, 1024, 1060, and 1220, and Amberlyst 15DRY, 15JWET, 16WET, 31WET, and 35WET (all trade names manufactured by Organo Corporation). Examples of weak acid ion exchange resins include the Diaion WK series and WK40 (all trade names manufactured by Mitsubishi Chemical Corporation), and Amberlite FPC3500 and IRC76 (all trade names manufactured by Organo Corporation). The type of ion exchange resin to be used can be selected arbitrarily depending on the reaction rate and the suppression of side reactions, but a strongly acidic ion exchange resin is particularly preferred in terms of reactivity.

[0063] The amount of acid catalyst added is preferably 0.1 to 25 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the total of component (a1) and component (a2). An amount of 25 parts by mass or less tends to facilitate removal in a subsequent step, which is economically advantageous. On the other hand, an amount of 0.1 part by mass or more tends to allow the reaction to proceed moderately, and the reaction time tends not to be too long.

[0064] The reaction temperature and time can be set as desired depending on the reactivity of component (a1) and component (a2), but are typically about 0 to 100°C, preferably 20 to 60°C, and about 1 minute to 2 hours. The hydrolysis reaction can be carried out in the presence or absence of a solvent, but it is preferable to use no solvent. When a solvent is used, the type of solvent is not particularly limited, and one or more solvents can be selected and used, but it is preferable to use the same solvent as that used in the condensation reaction described below.

[0065] <Step 2> Step 2 is a step of removing the acid catalyst from the reaction mixture x to obtain a reaction mixture y. That is, after the hydrolysis reaction in Step 1 is completed, the acid catalyst must be substantially removed from the system. If the acid catalyst is not removed, the condensation reaction described below may not proceed, the silanol groups may not be completely consumed, or the system may gel due to abnormally high molecular weight, making it impossible to obtain the desired thiol group-containing silsesquioxane (condensate B).

[0066] The method for removing the acidic catalyst can be appropriately selected from various known methods depending on the catalyst used. For example, as described above, when formic acid is used, the acidic catalyst can be easily removed by reducing pressure, and when a solid acid catalyst is used, the acidic catalyst can be easily removed by a method such as filtration after the completion of the condensation reaction.

[0067] After the hydrolysis reaction is completed and the acid catalyst is removed from the system, or simultaneously with the removal of the acid catalyst, the by-produced alcohol and excess water may be removed by a method such as reducing pressure. Furthermore, by diluting the removed product with the solvent used in the condensation reaction, the hydrolysis reaction product can be easily added to the subsequent condensation reaction.

[0068] <Step 3> Step 3 is a step in which the reaction mixture y is mixed with a polar solvent containing a basic catalyst and condensed to obtain a condensate B having a thiol group. In the condensation reaction, water is by-produced between the silanol groups, and alcohol is by-produced between the silanol groups and the alkoxy groups, forming siloxane bonds. In the condensation reaction, any basic catalyst that can function as a conventionally known dehydration condensation catalyst can be used.

[0069] The basic catalyst is preferably one with high basicity, and specific examples include sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) ２ Examples of suitable basic catalysts include alkali salts such as 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene, organic amines such as 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene, and ammonium hydroxides such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide. These exemplary compounds can be used alone or in appropriate combinations. Among these exemplary compounds, tetramethylammonium hydroxide is particularly preferred because of its high catalytic activity and easy availability. Furthermore, when these basic catalysts are used as aqueous solutions, the hydrolysis reaction also proceeds in the condensation reaction step, so it is necessary to appropriately adjust the amount of water used during hydrolysis, for example by reducing the amount of water contained in the basic catalyst in advance.

[0070] The amount of basic catalyst added is preferably 0.01 to 5 parts by mass, and more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the total of component (a1) and component (a2). If the amount of basic catalyst added is 5 parts by mass or less, the cured product produced using the resulting thiol group-containing silsesquioxane (condensate B) tends to be less likely to be discolored, and the catalyst removal process tends to be easier when it is necessary to remove it. On the other hand, if the amount is 0.01 part by mass or more, the reaction can proceed moderately, and the reaction time tends not to be too long.

[0071] The reaction temperature can be set arbitrarily depending on the reactivity of component (a1) and component (a2), but is usually about 40 to 150° C., preferably about 60 to 100° C. The condensation reaction is preferably carried out in the presence of a polar solvent, and from the viewpoints of the stability of the resulting silsesquioxane compound A and its copolymer, an amic acid solution, and the quality of the resulting film, it is more preferable to avoid the use of a nonpolar solvent such as toluene.

[0072] As the polar solvent, a polar solvent compatible with water is preferred, and glycol ethers are particularly preferred. Furthermore, among glycol ethers, dialkyl glycol ether-based solvents are particularly preferred. Examples of dialkyl glycol ether-based solvents compatible with water include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether. Furthermore, glycol ether acetate-based solvents such as propylene glycol monomethyl ether acetate (PGMEA), dipropylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate can also be used.

[0073] The condensation reaction can be carried out by setting the reaction temperature and sequentially adding a solution containing the hydrolyzate obtained by the hydrolysis reaction to a polar solvent to which a dehydration condensation catalyst has been added. The addition method can be appropriately selected from various known methods. The time required for addition can be set arbitrarily depending on the reactivity of component (a1) and component (a2), but is usually about 30 minutes to 12 hours.

[0074] When the condensation reaction is carried out by the above method, it is preferable to carry out the reaction until unreacted silanol groups are substantially eliminated. If unreacted silanol groups remain, the storage stability and heat resistance of the resulting thiol group-containing silsesquioxane (condensate B) and the composition containing condensate B will be reduced, which is undesirable.

[0075] Furthermore, it is preferable to proceed so that the total molar ratio of unreacted alkoxy groups ([total number of moles of unreacted alkoxy groups] / [total number of moles of each alkoxy group contained in component (a1) and component (a2)]) is 0.2 or less, and it is even more preferable to make it substantially 0. If this molar ratio is greater than 0 but not greater than 0.2, some alkoxy groups will remain in the resulting thiol group-containing silsesquioxane (condensate B), but this is preferable from the viewpoint of improving adhesion to inorganic materials. By making the molar ratio 0, substantially no alkoxy groups will remain, making it easy to prepare a thick-film cured product, and since the cage structure contained in the resulting thiol group-containing silsesquioxane (condensate B) is maximized, this is particularly preferable from the viewpoint of improving the heat resistance of the cured product. Furthermore, if the molar ratio is not 0, the amount of random silsesquioxane contained in the resulting condensate B will be large, and the molecular weight (Mw) of the condensate B will tend to be large.

[0076] The condensation reaction is preferably carried out by diluting with a solvent so that the total concentration of component (a1) and component (a2) is approximately 2 to 80% by mass, more preferably 15 to 75% by mass. Using a solvent with a boiling point higher than that of the water and alcohol produced by the condensation reaction is preferred because it allows these to be distilled off from the reaction system. A concentration of 2% by mass or higher is preferred because a sufficient amount of thiol group-containing silsesquioxane (condensate B) is contained in the resulting curable composition. A concentration of 80% by mass or lower tends to reduce gelation during the reaction and result in a moderate molecular weight for the condensate B produced.

[0077] Removing the catalyst used after the condensation reaction is preferable because it improves the stability of the thiol group-containing silsesquioxane (condensate B) and the polyimide containing condensate B. The removal method can be appropriately selected from various known methods depending on the catalyst used. For example, when tetramethylammonium hydroxide is used, it can be removed after the condensation reaction by adsorption and removal with a cation exchange resin. <Fourth Step> The fourth step is a step of reacting the condensate B with a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group.

[0078] As dicarboxylic acid anhydride C (hereinafter referred to as component (C)), a dicarboxylic acid anhydride having a functional group capable of reacting with a thiol group is used. For example, a dicarboxylic acid anhydride having a vinyl group, an acrylic group, a methacrylic group, an allyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, or an acid chloride group can be used. More preferably, a dicarboxylic acid anhydride having a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, or an acid chloride group can be used. In particular, the following structure is desirable for dicarboxylic acid anhydride C:

[0079] Among these, the following compounds and compounds having an acid chloride group are particularly preferred due to their high reactivity. When using dicarboxylic anhydride C, which has low reactivity, it is difficult to completely proceed with the reaction using UV light alone, so it is preferable to use an oxidation catalyst such as oxygen or iron chloride in combination.

[0080] Among the dicarboxylic acid anhydrides C, phthalic anhydride compounds having an aromatic ring structure are desirable from the viewpoint of enhancing the heat resistance of the resulting polyimide and suppressing yellowing under high-temperature conditions, while maleic anhydride and cyclohexanedicarboxylic anhydride, each having an alicyclic structure in their structure, are desirable from the viewpoint of enhancing colorless transparency.

[0081] The reaction between the thiol group-containing silsesquioxane (condensate B) and the dicarboxylic acid anhydride C can be carried out by utilizing a thiol-ene reaction or a reaction between a thiol group and an acid chloride group.

[0082] It is known that the reaction mechanism of the thiol-ene reaction varies depending on the type of carbon-carbon double bond and the presence or absence of a radical polymerization initiator. Specifically, when a compound having a vinyl group or allyl group with low radical polymerizability is used as component (C), only the ene-thiol reaction proceeds, and the thiol group in condensate B reacts with the carbon-carbon double bond in component (C) in a molar ratio of approximately 1:1, which is preferable. On the other hand, when a compound having an acrylic group or methacrylic group with high radical polymerizability is used as component (C), the polymerization reaction of the carbon-carbon double bond in component (C) also proceeds in parallel, particularly when a radical polymerization initiator is used in combination, and the thiol group in condensate B reacts with the carbon-carbon double bond in component (C) in a molar ratio of approximately 1:1 to 100, which may result in insufficient effects of the invention. From the above viewpoints, when component (C) having a vinyl group or allyl group with low radical polymerizability is used, it is preferable to blend them so that the molar ratio ([number of moles of thiol groups contained in condensate B] / [number of moles of carbon-carbon double bonds contained in component (C)]) is 0.9 to 2.5, and more preferably 1.0. When this molar ratio is 0.9 or more, carbon-carbon double bonds are less likely to remain after UV curing, and weather resistance tends to be improved. Furthermore, when it is 2.5 or less, the crosslink density of the cured product becomes sufficient, and heat resistance tends to be improved.

[0083] The initiator for the thiol-ene reaction can be an ultraviolet light source, an organic material, an inorganic material, or oxygen. The ultraviolet light source can be, for example, a high-pressure mercury lamp, a halogen lamp, a xenon lamp, or an ultraviolet LED.

[0084] The initiator that can be used is not particularly limited, and can be selected from conventionally known photocationic initiators, photoradical initiators, oxidizing agents, etc. Examples of photocationic initiators include sulfonium salts, iodonium salts, metallocene compounds, benzoin tosylates, and the like, which are compounds that generate acid upon irradiation with ultraviolet light. Commercially available products thereof include, for example, Cyracure UVI-6970, Cyracure UVI-6974, and Cyracure UVI-6990 (all trade names manufactured by Union Carbide Corporation, USA), Irgacure 264 (manufactured by BASF Corporation), and CIT-1682 (manufactured by Nippon Soda Co., Ltd.). The amount of the photocationic polymerization initiator used is typically about 10 parts by mass or less, preferably 1 to 5 parts by mass, per 100 parts by mass of the composition.

[0085] Examples of photoradical initiators include Darocur 1173, Irgacure 651, Irgacure 184, and Irgacure 907 (all trade names manufactured by BASF), benzophenone, etc., and are used in an amount of about 5 parts by mass or less, preferably 0.1 to 2 parts by mass, per 100 parts by mass of the composition. The reaction can be accelerated by adding an oxidizing agent such as iron oxide or iron chloride. However, for substrate film applications requiring high heat resistance and transparency, it is desirable to carry out the reaction using an ultraviolet light source or oxygen without using a photoinitiator or photosensitizer.

[0086] In the case of a reaction between a thiol group and an acid chloride group, it is preferable to add a dicarboxylic acid anhydride having an acid chloride group in an amount equal to or greater than the sum of the amount of thiol groups and the amount of silanol groups in the silsesquioxane (condensate B). If the amount of dicarboxylic acid anhydride having an acid chloride group added is small, the by-product hydrochloric acid acts as a catalyst, causing condensation between the silanol groups, which tends to lead to gelation. However, if the amount of dicarboxylic acid anhydride added is large, this adverse effect can be reduced. In this case, unreacted acid chloride groups may be copolymerized with polyamic acid to produce polyamideimide.

[0087] Furthermore, in the case of a reaction between a thiol group and an acid chloride group, hydrochloric acid is generated as a by-product, so a base may be added as a pH adjuster. Examples of bases that can be used include organic bases, tertiary amines, and inorganic bases. Examples of organic bases include N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, imidazole, N-methylcaprolactam, imidazole, N,N-dimethylaniline, and N,N-diethylaniline. Examples of tertiary amines include pyridine, collidine, lutidine, and triethylamine. Examples of inorganic bases include potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate. However, for substrate film applications requiring high heat resistance and transparency, it is desirable to use a volatile base for the reaction. By removing the hydrochloric acid by adding a base or by heating the solution, gelation due to excessive reaction of the silsesquioxane can be suppressed.

[0088] Examples of solvents used in the reaction include benzene, toluene, xylene, mesitylene, pentane, hexane, heptane, octane, nonane, decane, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, imidazole, N-methylcaprolactam, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, diethyl sulfone, hexamethylsulfonamide, cresol, phenol, xylenol, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraglyme, propylene glycol monomethyl ether acetate (PGMEA), dioxane, tetrahydrofuran, and γ-butyrolactone. A mixture of at least two of these may also be used. In particular, in consideration of productivity and the optical properties of the film, it is preferable to use N,N-dimethylacetamide, N-methyl-2-pyrrolidone, or γ-butyrolactone as the main component of the organic solvent. In addition to these organic solvents, poor solvents such as toluene and xylene may be used to the extent that the polyimide resin or its precursor does not precipitate.

[0089] The silsesquioxane compound A having an acid anhydride group obtained in the fourth step can be used as a solution after the reaction as is, or it can be used as a powder after filtering out foreign matter and gel-like matter or by distilling off the solvent.

[0090] <Structure of Silsesquioxane Compound A Having Acid Anhydride Group> The silsesquioxane compound A obtainable as described above preferably has structural units represented by the following general formulas (1) and (2), and more preferably has only structural units represented by the general formulas (1) and (2).

[0091]

[0092] (In the formula, Q １ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms; Q ２represents a single bond, a hydrocarbon group having 1 to 8 carbon atoms, an organic group in which one or more carbon atoms of a hydrocarbon group having 1 to 8 carbon atoms are substituted with oxygen, or a carbonyl group; X represents a carbon-carbon bond, or an aliphatic ring having 4 to 10 carbon atoms, an aromatic ring having 6 to 10 carbon atoms, or a heterocycle in which some of the carbon atoms constituting these rings are substituted with oxygen or sulfur, and one or more hydrogen atoms bonded to these rings may be substituted with a hydrocarbon group; and 1.0≦m≦2.0 and 1.4≦n≦1.6.

[0093] (In the formula, Q ３ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms, and 1.4≦n≦1.6. １ represents a linear, branched, or aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms which may have a hydrocarbon group. １ As the alkyl group, a straight-chain hydrocarbon group is preferred from the viewpoint of imparting flexibility to the polymer chain, and an alicyclic hydrocarbon group or an aromatic hydrocarbon group is preferred from the viewpoint of enhancing heat resistance.

[0094] Q １ Specific examples of the group include hydrocarbon groups in which the Si atom and the S atom of the compounds exemplified as the thiol group-containing trialkoxysilanes a1 are bonded, and aromatic hydrocarbon groups.

[0095] Q ２ Q is a hydrocarbon group having 1 to 8 carbon atoms and having a single bond, a straight chain, or a branched chain, an oxygen-containing hydrocarbon group in which one or more carbon atoms are substituted with oxygen, or a carbonyl group. ２ As the alkyl group, a straight-chain hydrocarbon group is preferred from the viewpoint of imparting flexibility to the polymer chain, and a single bond, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group is preferred from the viewpoint of enhancing heat resistance.

[0096] X is a carbon-carbon bond, or an aliphatic ring having 4 to 10 carbon atoms, an aromatic ring having 6 to 10 carbon atoms, or a heterocycle in which some of the carbon atoms constituting these rings are substituted with oxygen or sulfur, and one or more hydrogen atoms bonded to these rings may be substituted with a hydrocarbon group. X is preferably a carbon-carbon bond from the viewpoint of imparting flexibility to the polymer chain, and is preferably a single bond, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group from the viewpoint of enhancing heat resistance. In particular, when X is an aromatic hydrocarbon group, this is preferred from the viewpoints of enhancing heat resistance and suppressing discoloration under high-temperature conditions.

[0097] Q ２ Specific examples of X include the reactive residues of the compounds exemplified as dicarboxylic acid anhydride C excluding the dicarboxylic acid anhydride group. An example of X being a heterocycle in which some of the carbon atoms constituting the aliphatic or aromatic ring are substituted with oxygen or sulfur is shown in the following chemical formula:

[0098] Regarding m, 1.0≦m≦2.0 is satisfied, and from the viewpoint of reducing steric hindrance and increasing the reactivity of the dicarboxylic acid anhydride group, m is preferably 1. When m is 1.0<m<2.0 (i.e., other than an integer), a compound having one thiol group and a compound having two thiol groups are used in combination as component (a1).

[0099] Regarding n, 1.4≦n≦1.6 is satisfied, and from the viewpoint of forming a more uniform three-dimensional structure, n is preferably 1.5. The reason why n is assumed to be other than 1.5 is that it is acceptable for the raw material to contain not only trialkoxysilane but also small amounts of dialkoxysilane and tetraalkoxysilane.

[0100] In addition, Q in general formula (2) ３ represents a linear, branched, or aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms which may have a hydrocarbon group. ３ From the viewpoint of suppressing crystallization and improving heat resistance, short-chain and branched-chain hydrocarbon groups, or aromatic hydrocarbon groups are preferred as Q. ３Specific examples of the group include hydrocarbon groups or aromatic hydrocarbon groups bonded to the Si atoms of the compounds exemplified as trialkoxysilanes a2.

[0101] In a silsesquioxane compound A having structural units represented by general formulas (1) and (2), the molar ratio of the structural units represented by general formula (2) ([structural unit (2)] / [structural unit (1)+structural unit (2)]) is preferably 0.1 or more and 0.7 or less, and more preferably 0.2 or more and 0.7 or less. The larger this molar ratio, the smaller the amount of thioether groups or thioester groups contained per molecule, and the smaller the value, the larger the amount of thioether groups or thioester groups. By keeping the ratio within this range, the resulting polyimide chains are appropriately crosslinked, thereby achieving a sufficient improvement in physical properties.

[0102] The number of acid anhydride groups (number of functional groups) per molecule of the silsesquioxane compound A is preferably 2 to 10, and more preferably 2.5 to 6. When the number of functional groups is within this range, the resulting polyimide chains are appropriately crosslinked, and the physical properties are sufficiently improved.

[0103] The molecular weight of the silsesquioxane compound A is preferably 400 to 5000, more preferably 600 to 3000. When the molecular weight is within this range, the resulting polyimide is less likely to become non-uniform, and a uniform crosslinked structure is more likely to be obtained.

[0104] The general formulas (1) and (2) tend to be randomly bonded, but by bonding them regularly, a cage-type (including double-decker type) or a partially open cage-type or ladder-type silsesquioxane compound can be obtained.

[0105] Methods for obtaining a silsesquioxane compound A having such a structure include a method in which a cage-type, partially open cage-type, or ladder-type silsesquioxane compound is obtained at the stage of condensate B (thiol group-containing silsesquioxane compound), and a method in which a commercially available thiol group-containing silsesquioxane compound having such a structure is used.

[0106] Condensate B can be synthesized by the dehydration condensation of dialkylsilanediol or the dehydrochlorination reaction of dialkylsilanediol and dialkyldichlorosilane. The ratio of specific structures produced can be increased by adjusting the catalyst, solvent, and substrate concentration used. The specific structures can be isolated by purifying the resulting product using methods such as recrystallization, solvent washing, and column separation. While the synthesis method is not particularly limited, methods described in review articles (e.g., (1) "Silicon's Expanding Application Fields and Technical Trends," by Yoshiaki Ono, Chemical Daily; (2) "The Science of Silicon," by Nobuo Matsumoto, Institute of Electronics, Information, and Communication Engineers; (3) "The Latest Silicon Application Technology," edited by Makoto Kumada and Tadashi Wada, CMC Publishing; (4) "Silicon Compound Selection and Optimal Utilization Technology," edited by the Technical Information Association; (5) "Organosilicon Science in the 21st Century," edited by Kohei Tamao, CMC Publishing; and (6) "Chemistry and Application Development of Silsesquioxane Materials," edited by Maki Ito, CMC Publishing) can be used. T, a type of cage structure Ｈ ８ can be synthesized, for example, by hydrolysis of trichlorosilane in the presence of iron chloride (Bull. Chem. Soc. Jpn., 73, 215 (2000)). Ｈ ８ Various derivatives can be synthesized by further chemically modifying the starting material. Ｈ ８ In the case of introducing an organic group by hydrosilylation, the organic group is introduced by reacting an alkenyl compound in the presence of a platinum catalyst. Ｈ ８ If you react it with chlorine, you get T Ｃｌ ８ The double-decker structure T Ｐｈ ４ T Ｐｈ ３ (ONa) ３is produced almost quantitatively when trimethoxy(phenyl)silane is hydrolyzed in the presence of sodium hydroxide. Methods for synthesizing condensate B having a ladder structure include a method in which trichloro(phenyl)silane is hydrolyzed followed by an alkaline equilibration reaction using potassium hydroxide as a catalyst (Chem. Rev., 95, 1409 (1995)), and a method in which trichloro(phenyl)silane is hydrolyzed using a phase transfer catalyst (Silicon Chemistry Society Journal, (8), 16 (1997)).

[0107] In the examples described below, silsesquioxane compounds A having acid anhydride groups are mainly used that have a random structure, which allows the production of polyimide films with improved toughness while maintaining other main properties. The detailed reasons for this are not clear, but it is thought that the relatively flexible (compared to inorganic fillers, etc.) silsesquioxane skeleton forms small domains, making it easier to tolerate deformation of the polyimide base material. Therefore, it is thought that similar effects can be obtained not only when using silsesquioxane compounds A having a random structure, but also when using silsesquioxane compounds A having other structures as described above.

[0108] <Polyamic Acid> The polyamic acid of the present invention is a copolymerization product of at least the silsesquioxane compound A having an acid anhydride group, a carboxylic acid, and a diamine, as described above.

[0109] In particular, when a silsesquioxane compound having more than two acid anhydride groups is used as the silsesquioxane compound A, it can form a crosslinked structure in the polyimide as a copolymerization component.

[0110] In general, polyimides have a trade-off relationship between practical properties such as heat resistance and mechanical properties and colorlessness (transparency or whiteness). Therefore, there has been a demand for a method for producing polyimide films that have improved toughness while maintaining the other main properties.

[0111] The polyamic acid of the present invention is particularly useful as a raw material for producing a polyimide film having improved toughness while maintaining other main properties by using a polyamic acid containing a silsesquioxane compound A as a copolymerization component. The polyimide film can be obtained, for example, by a process including a step of synthesizing the polyamic acid in a solution, a step of forming the polyamic acid solution into a film, and a step of imidizing the polyamic acid.

[0112] <Synthesis of Polyamic Acid> Polyamic acid can be synthesized, for example, by reacting at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic acid anhydride group in a solvent. That is, at least carboxylic acids and diamines can be used as monomer components other than the silsesquioxane compound A.

[0113] The carboxylic acids are not particularly limited, and alicyclic tetracarboxylic anhydrides, aromatic tetracarboxylic anhydrides, tricarboxylic acids, dicarboxylic acids, etc., commonly used in polyimide synthesis, polyamideimide synthesis, and polyamide synthesis can be used. From the viewpoint of heat resistance, aromatic acids are preferred, and from the viewpoint of transparency, alicyclic acids are preferred. These may be used alone or in combination of two or more.

[0114] Examples of the alicyclic tetracarboxylic acid anhydride in the present invention include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]oct-7-ene-2,3,5, 6-tetracarboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-no norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2 -spiro-2'-cyclohexanone-6'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclooctanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2''-norbornane-5,5'',6 ,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2''-norbornane-5,5'', ,6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, and norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, and tetracarboxylic acids such as these acid anhydrides. Among these, dianhydrides having two acid anhydride structures are preferred, and in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, with 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetracarboxylic dianhydride being more preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride being even more preferred. These may be used alone or in combination of two or more.

[0115] Examples of the aromatic tetracarboxylic acid anhydride in the present invention include 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid)1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2 -dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4-isopropyl-toluene] 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1, 1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]diphthalic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]diphthalic acid, and other tetracarboxylic acids and acid anhydrides thereof. The aromatic tetracarboxylic acids may be used alone or in combination of two or more.

[0116] Examples of tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalenetricarboxylic acid, diphenylether-3,3',4'-tricarboxylic acid, and diphenylsulfone-3,3',4'-tricarboxylic acid, as well as hydrogenated products of the above aromatic tricarboxylic acids such as hexahydrotrimellitic acid, alkylene glycol bistrimellitates such as ethylene glycol bistrimellitate, propylene glycol bistrimellitate, 1,4-butanediol bistrimellitate, and polyethylene glycol bistrimellitate, and monoanhydrides and esterified products thereof. Among these, monoanhydrides having one acid anhydride structure are preferred, with trimellitic anhydride and hexahydrotrimellitic anhydride being particularly preferred. These may be used alone or in combination.

[0117] Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid, as well as hydrogenated versions of these aromatic dicarboxylic acids such as 1,6-cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecadioic acid, dodecanedioic acid, and 2-methylsuccinic acid, as well as acid chlorides and esters thereof. Among these, aromatic dicarboxylic acids and hydrogenated versions thereof are preferred, with terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid being particularly preferred. The dicarboxylic acids may be used alone or in combination.

[0118] The carboxylic acids are preferably one or more compounds represented by the following chemical formulas:

[0119]

[0120] The diamines used in the present invention are not particularly limited, and aromatic diamines, aliphatic diamines, and alicyclic diamines commonly used in polyimide synthesis, polyamideimide synthesis, and polyamide synthesis can be used. From the viewpoint of heat resistance, aromatic diamines are preferred, and from the viewpoint of transparency, alicyclic diamines are preferred. The diamines may be used alone or in combination of two or more.

[0121] Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4 -(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4, 4'-Diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl] 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis( 4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4- Bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)pheno hydroxy}phenyl] sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene , 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4, 4'-diviphenoxybenzophenone, 4,4'-diamino-5,5'-diviphenoxybenzophenone, 3,4'-diamino-4,5'-diviphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 4 , 4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, 5-amino-2-(p-aminophenyl)fluorene nyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d: 5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, etc. In addition, some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine may be substituted with halogen atoms, alkyl or alkoxy groups having 1 to 3 carbon atoms, or cyano groups, and further some or all of the hydrogen atoms of the alkyl or alkoxy groups having 1 to 3 carbon atoms may be substituted with halogen atoms.

[0122] Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine), 9,10-bis(4-aminophenyl)adenine, and dimethyl 2,4-bis(4-aminophenyl)cyclobutane-1,3-dicarboxylate.

[0123] The diamines preferably include 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) or 4,4'-diaminobenzanilide (DABA), and more preferably 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) or 4,4'-diaminobenzanilide (DABA).

[0124] The molar content of the structural units derived from the silsesquioxane compound A based on the divalent monomer: (nA / (nA+nD))×100 (where nA is the total number of moles of the structural units derived from the silsesquioxane compound A divided by the total number of dicarboxylic acid anhydride groups and multiplied by two, and nD is the number of moles of the structural units derived from the carboxylic acids) is preferably 0.01 to 10.0 mol%. When the molar content of the silsesquioxane compound A is 0.01 mol% or more, a complexing effect is obtained, and when the molar content is 10.0 mol% or less, gelation of the polyamic acid solution is unlikely to occur and stability over time is likely to be achieved. For this reason, the molar content is more preferably 0.1 to 5.0 mol%.

[0125] In particular, when the number of acid anhydride groups per molecule of the silsesquioxane compound A is 2 to 5, the molar content is more preferably 0.1 to 10.0 mol %. When the number of acid anhydride groups per molecule of the silsesquioxane compound A is 5 to 10, the molar content is more preferably 0.1 to 5.0 mol %.

[0126] As the solvent used in the synthesis of polyamic acid, any solvent that dissolves polyamic acid and its monomers can be used, and examples thereof include aprotic solvents, phenolic solvents, ether and glycol solvents.

[0127] Specific examples of the aprotic solvent include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as cyclohexanone and methylcyclohexanone; tertiary amine solvents such as picoline and pyridine; and ester solvents such as 2-methoxy-1-methylethyl acetate.

[0128] Examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, etc. Examples of ether and glycol-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, 1,4-dioxane, etc.

[0129] Among these, from the viewpoint of solubility and film-forming properties, the solvent preferably contains, as a main component, N-methyl-2-pyrrolidone, N,N'-dimethylacetamide, or γ-butyrolactone. The above solvents may be used alone or in combination of two or more.

[0130] As for synthesis conditions, the reaction temperature is preferably −30 to 200°C, more preferably 20 to 180°C, and particularly preferably 20 to 100°C. Stirring is continued at room temperature (20 to 25°C) or an appropriate reaction temperature, and the reaction can be terminated when the viscosity of the polyimide precursor becomes constant. The reaction can usually be completed within 3 to 100 hours.

[0131] <Polyamic Acid Composition> The polyamic acid composition of the present invention contains the polyamic acid and a solvent as described above. The polyamic acid composition may contain a solvent different from that used during synthesis, but from the viewpoint of avoiding complication of the production process, it is preferable that the solvent used during synthesis is contained. Therefore, it is preferable that the main component of the solvent contained in the polyamic acid composition is N-methyl-2-pyrrolidone, N,N'-dimethylacetamide, or γ-butyrolactone.

[0132] The content of polyamic acid in the polyamic acid composition is preferably 5 to 30% by mass, more preferably 10 to 20% by mass, from the viewpoint of the film thickness during film formation. When the content is within this range, a thin film having a thickness that is easy to handle can be obtained.

[0133] The polyamic acid composition may further contain optional components such as an adhesion promoter, a surfactant, a leveling agent, an antioxidant, a UV absorber, a chemical imidization agent, a colorant, etc. Furthermore, the polyamic acid composition may further contain a filler, etc., which may be contained in a polyimide film.

[0134] <Polyimide> The polyimide of the present invention is obtained by imidizing the polyamic acid described above. The polyimide can be obtained, for example, by heating the polyamic acid. By heating, the carboxy groups of the polyamic acid are each dehydrated and cyclically closed, and the polyamic acid is imidized to form a polyimide structure.

[0135] Polyimide can be obtained by heating polyamic acid in a solvent. The heating temperature for imidizing polyamic acid in a solvent is preferably 150 to 220°C.

[0136] Furthermore, as will be described later, polyimide can be provided as a membrane-like or film-like molded article by applying a polyamic acid composition containing a solvent to a substrate and heating it. The heating temperature for imidizing polyamic acid is preferably 250 to 400°C when the solvent is at least to a certain extent and in a dry state.

[0137] It is also possible to obtain polyimides by chemical imidization instead of thermal imidization. In this case, it is preferable to use a tertiary amine as the imidization accelerator. As the tertiary amine, a heterocyclic tertiary amine is more preferable. Specific examples of preferable heterocyclic tertiary amines include pyridine, 2,5-diethylpyridine, picoline, quinoline, and isoquinoline.

[0138] <Polyimide Film> The polyimide film of the present invention contains the polyimide described above. When the polyimide film is composed of two or more layers, it is sufficient that at least one layer contains the polyimide of the present invention.

[0139] A polyimide film can be obtained, for example, by casting a polyamic acid solution onto a substrate, heating it to volatilize the solvent, forming a uniform green film with a thickness of 1 to 100 μm, and then imidizing the resulting film. Examples of substrates that can be used to form films by such casting methods include polymer films, glass plates, silicone rubber plates, and metal plates.

[0140] As the polymer film, for example, polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) can be used. To obtain a green film of a predetermined thickness, methods such as adjusting the concentration of the polyamic acid solution, adjusting the gap between coaters, or repeating casting to achieve the desired film thickness can be employed, thereby producing a substrate of the desired film thickness. The resulting green film can then be thermally imidized by heat treatment to obtain a polyimide film.

[0141] The polyimide film may have a single layer structure or a laminate structure of two or more layers. In view of the physical strength of the polyimide film and its ease of peeling from the inorganic substrate, a laminate structure of two or more layers is preferred, and a laminate structure of three or more layers is also acceptable. In this specification, when the polyimide film has a laminate structure of two or more layers, the physical properties (yellowness index, total light transmittance, haze, etc.) refer to the values ​​of the entire polyimide film unless otherwise specified.

[0142] The thickness of the polyimide film is preferably 5 μm or more, more preferably 7 μm or more. There is no particular upper limit to the thickness of the polyimide film, but for use in flexible electronic devices, it is preferably 200 μm or less, more preferably 90 μm or less, and even more preferably 50 μm or less. If the film is too thin, it is difficult to produce and transport the film, and if it is too thick, it becomes difficult to transport it by roll.

[0143] The total light transmittance of the polyimide film in the present invention is preferably 75% or more, more preferably 85% or more, even more preferably 87% or more, and even more preferably 88% or more. There is no particular upper limit to the total light transmittance of the polyimide film, but for use as a flexible electronic device, it is preferably 98% or less, more preferably 97% or less.

[0144] The haze of the polyimide film of the present invention is preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.5 or less, and still more preferably 0.3 or less.

[0145] The yellowness index (hereinafter also referred to as "yellow index" or "YI") of the polyimide film in the present invention is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and still more preferably 5 or less. There is no particular lower limit to the yellowness index of the polyimide film, but for use as a flexible electronic device, it is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more.

[0146] The thickness direction retardation (Rth) of the polyimide film in the present invention is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and even more preferably 100 nm or less. The lower limit of Rth of the polyimide film is not particularly limited, but for use as a flexible electronic device, it is preferably 0.1 nm or more, more preferably 0.5 nm or more.

[0147] The colorless and highly transparent polyimide film of the present invention, which exhibits a high coefficient of linear expansion (CTE), can also be achieved by stretching the polyimide film during its formation. This stretching operation involves applying a polyimide solution to a support for polyimide film preparation, drying the polyimide film to form a polyimide film containing 1 to 50% by mass of solvent, and then stretching the polyimide film containing 1 to 50% by mass of solvent at a high temperature on the support for polyimide film preparation or after peeling it from the support, stretching the polyimide film by 1.5 to 4.0 times in the MD direction and 1.4 to 3.0 times in the TD direction. In this case, using an unstretched thermoplastic polymer film as the support for polyimide film preparation, stretching the thermoplastic polymer film and polyimide film simultaneously, and then peeling the stretched polyimide film from the thermoplastic polymer film, can prevent scratches on the polyimide film, particularly during stretching in the MD direction, and produce a higher-quality, colorless and highly transparent polyimide film.

[0148] The average coefficient of linear expansion (CTE) of the polyimide film between 50°C and 200°C is preferably 40 ppm / K or less, more preferably 35 ppm / K or less. It is also preferably -20 ppm / K or more, and more preferably -10 ppm / K or more. When the CTE is within the above range, the difference in the coefficient of linear expansion from a typical support (inorganic substrate) can be kept small, and peeling between the polyimide film and the inorganic substrate or warping of the support can be avoided even when the polyimide film is subjected to a heat-applying process. Here, CTE is a factor that represents reversible expansion and contraction with temperature. The CTE of the polyimide film is measured according to the method described in the Examples.

[0149] The polyimide film may contain a filler. Examples of fillers include, but are not limited to, silica, carbon, and ceramic, with silica being preferred. These fillers may be used alone or in combination of two or more. Adding a filler provides protrusions to the surface of the polyimide film, thereby improving the slipperiness of the polyimide film surface. Adding a filler also reduces the CTE and Rth of the polyimide film. The average particle size of the filler is preferably 1 nm or more, more preferably 5 nm or more. It is also preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 100 nm or less.

[0150] The filler content in the polyimide film is preferably adjusted according to the average particle size of the filler. When the filler particle size is 30 nm or more, it is preferably 0.01 to 5 mass%, more preferably 0.01 to 3 mass%, even more preferably 0.01 to 2 mass%, and particularly preferably 0.01 to 1 mass%. On the other hand, when the average particle size is less than 30 nm, it is preferably 0.01 to 50 mass%, more preferably 0.01 to 40 mass%, even more preferably 0.01 to 30 mass%, and particularly preferably 0.01 to 20 mass%. By adjusting the content within the above range, the slipperiness of the polyimide film surface can be maintained high without impairing the transparency of the polyimide film, and the CTE and Rth of the polyimide film can be reduced.

[0151] The method for adding a filler to a polyimide film is not particularly limited, but examples thereof include a method in which the filler is added as a powder during or after the preparation of the polyamic acid (polyimide precursor) solution, or a method in which the filler is added in the form of a filler / solvent (slurry), and among these, the method in which the filler is added as a slurry is particularly preferred. The slurry is not particularly limited, but examples thereof include a slurry in which silica having an average particle size of 10 nm is dispersed in N,N-dimethylacetamide (DMAC) at a concentration of 20% by mass (e.g., "Snowtex (registered trademark) DMAC-ST" manufactured by Nissan Chemical Industries, Ltd.), a slurry in which silica having an average particle size of 80 nm is dispersed in N,N-dimethylacetamide (DMAC) at a concentration of 20% by mass (e.g., "Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.), and a slurry in which silica having an average particle size of 10 nm is dispersed in N-methylpyrrolidone (NMP) at a concentration of 20% by mass (e.g., "Snowtex (registered trademark) NMP-ST" manufactured by Nissan Chemical Industries, Ltd.). The polyimide film may contain a colorant. For example, mixing a blue colorant into a pale yellow polyimide film can reduce the YI of the film. Examples of colorants include organic pigments, inorganic pigments, and dyes. However, organic pigments and inorganic pigments are preferred in order to improve the heat resistance, reliability, and light resistance of the colored film. Examples of organic pigments include diketopyrrolopyrrole pigments; azo pigments such as azo, disazo, and polyazo; phthalocyanine pigments such as copper phthalocyanine, halogenated copper phthalocyanine, and metal-free phthalocyanine; anthraquinone pigments such as aminoanthraquinone, diaminodianthraquinone, anthrapyrimidine, flavanthrone, anthanthrone, indanthrone, pyranthrone, and violanthrone; quinacridone pigments; dioxazine pigments; perinone pigments; perylene pigments; thioindigo pigments; isoindoline pigments; isoindolinone pigments; quinophthalone pigments; threne pigments; and metal complex pigments.Examples of inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, white lead, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, Prussian blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet. Examples of dyes include azo dyes, anthraquinone dyes, condensed polycyclic aromatic carbonyl dyes, indigoid dyes, carbonium dyes, phthalocyanine dyes, methine dyes, and polymethine dyes.

[0152] The tensile strength at break of the polyimide film is preferably 60 MPa or more, more preferably 120 MPa or more, and even more preferably 160 MPa or more. The upper limit of the tensile strength at break is not particularly limited, but is practically less than about 1000 MPa. A tensile strength at break of 60 MPa or more can prevent the polyimide film from breaking when peeled from the inorganic substrate. The tensile strength at break of the polyimide film is measured by the method described in the Examples. Even when the film is prepared by applying the film to a glass substrate using a casting applicator, the two orthogonal directions, parallel and perpendicular to the application of the casting applicator, are defined as the MD direction and the TD direction, respectively. The same applies to the tensile elongation at break and the tensile modulus of elasticity below.

[0153] The tensile elongation at break of the polyimide film is preferably 1% or more, more preferably 5% or more, and even more preferably 10% or more. When the tensile elongation at break is 5% or more, the polyimide film has excellent handleability. The tensile elongation at break of the polyimide film is measured by the method described in the Examples.

[0154] The tensile modulus of the polyimide film is preferably 2 GPa or more, more preferably 3 GPa or more, and even more preferably 4 GPa or more. When the tensile modulus is 3 GPa or more, the polyimide film undergoes little elongation deformation when peeled from an inorganic substrate, resulting in excellent handleability. The tensile modulus is preferably 20 GPa or less, more preferably 12 GPa or less, and even more preferably 10 GPa or less. When the tensile modulus is 20 GPa or less, the polyimide film can be used as a flexible film. The tensile modulus of the polyimide film is measured according to the method described in the Examples.

[0155] The polyimide film has improved toughness while maintaining a certain level of tensile modulus, and therefore has an improved tensile product, which is the product of tensile strength and elongation, compared to conventional polyimide films. That is, the tensile product of the polyimide film of the present invention in a tensile test is preferably 1,000 MPa·% or more, and more preferably 1,200 MPa·% or more. Although no upper limit is particularly set, from the viewpoint of film handleability, the tensile product in a tensile test is preferably 10,000 MPa·% or less.

[0156] The polyimide film is preferably obtained in the form of a rolled long polyimide film having a width of 300 mm or more and a length of 10 m or more during production, and more preferably in the form of a rolled polyimide film wound around a winding core. When the polyimide film is wound in a roll, it can be easily transported in the form of a rolled polyimide film.

[0157] In order to ensure the handleability and productivity of the polyimide film, it is preferable to add or contain about 0.03 to 3 mass % of a lubricant (particles) having a particle diameter of about 10 to 1000 nm to the polyimide film, thereby imparting fine irregularities to the surface of the polyimide film and ensuring slipperiness.

[0158] Furthermore, when a polyimide film has a laminated structure of two or more layers, the difference in CTE between each layer is undesirable because it can cause warping. Therefore, the difference in CTE between the first polyimide film layer in contact with the inorganic substrate and the second polyimide film layer adjacent to the first polyimide film without contacting the inorganic substrate is preferably 40 ppm / K or less, more preferably 30 ppm / K or less, and even more preferably 15 ppm / K or less. In particular, it is preferable that the thickest layer of the second polyimide film be within the above range. Furthermore, it is preferable that the polyimide film has a symmetrical structure in the thickness direction, as this makes it less likely to warp.

[0159] In the polyimide film having a laminated structure of two or more layers, the thickness of the mixture at the interface between the first polyimide film layer in contact with the inorganic substrate and the second polyimide film layer adjacent to the first polyimide film layer (hereinafter simply referred to as the "second polyimide film layer") is not particularly limited as long as it is less than the sum of the thickness of one layer of the first polyimide film layer and the thickness of one layer of the second polyimide film layer. However, it is preferably 99% or less, more preferably 80% or less, and even more preferably 50% or less of the sum of the thickness of one layer of the first polyimide film layer and the thickness of one layer of the second polyimide film layer. There is also no particular limitation on the lower limit, but from an industrial perspective, a thickness of 10 nm or more is acceptable, and even 20 nm or more is acceptable. Note that when there is a significant difference in the functions of the layers and it is necessary to fully utilize the respective functions without canceling each other out, the mixture area in each layer is preferably limited to 50% or less, more preferably 30% or less, and even more preferably 10% or less.

[0160] Although there are no particular limitations on the means for forming a layer with minimal intermixing, it is preferable to first prepare either the first or second polyimide film layer, then perform a heating process, and then prepare the next layer, rather than simultaneously preparing two layers, the first and second polyimide film layers, by solution casting. This includes both intermediate and completed heating processes. Preparing the next layer after the heating process is complete results in a layer with minimal intermixing, but the surface of the completed film often has already lost its reactivity, and the lack of functional groups on the surface can weaken the adhesion between the two layers, potentially causing practical problems. Therefore, even when intermixing is minimal, an interface with intermixing of 10 nm or more is desirable.

[0161] By using two layers of materials (resins) with different physical properties, it is possible to produce a film with a variety of properties. Furthermore, by laminating the layers symmetrically in the thickness direction (e.g., first polyimide film layer / second polyimide film layer / first polyimide film layer), the CTE of the entire film can be well balanced, resulting in a film that is less prone to warping. Furthermore, by making one of the layers absorb ultraviolet or infrared light, it is possible to impart distinctive spectral characteristics, or to control the incidence and emission of light using layers with different refractive indices. Furthermore, by adding a lubricant to the first polyimide film layer, the overall optical and thermal properties of the film can be maintained similar to those of the second polyimide film layer, while improving the film's slipperiness. In this case, the polymer compositions of the first polyimide film layer and the second polyimide film layer may be the same or different.

[0162] There are various methods that can be considered for producing a film with a layer structure of two or more layers, such as simultaneous coating using a T-die that can simultaneously eject two or more layers, sequential coating in which one layer is coated and then the next layer is coated, a method in which one layer is coated and then dried before coating the next layer, a method in which one layer is formed into a film and then the next layer is coated, or multi-layering by heat lamination by adding a thermoplastic layer, and in this patent, various existing coating methods and multi-layering techniques can be incorporated as appropriate.

[0163] <Laminate> The laminate of the present invention includes the polyimide film and an inorganic substrate as described above. In the laminate, when the polyimide film is composed of two or more layers, it is sufficient that at least one layer contains the polyimide of the present invention. In addition to the polyimide film, a transparent, highly heat-resistant film other than the polyimide film may be laminated.

[0164] Examples of the transparent, highly heat-resistant film include PET, PEN, PVC, acrylic, polystyrene, polycarbonate, etc. The transparent, highly heat-resistant film can be used on either side of the polyimide film.

[0165] A silane coupling agent layer, an adhesive layer, a pressure-sensitive adhesive layer, etc. may be further included between the polyimide film and the inorganic substrate. In addition, a wiring layer, a conductive film layer, a metal layer, etc. may be included on the surface of the polyimide film.

[0166] <Inorganic Substrate> The inorganic substrate may be any plate-like substrate that can be used as a substrate made of an inorganic material, and examples thereof include those that are mainly made of a glass plate, a ceramic plate, a semiconductor wafer, a metal, or the like, and composites of these glass plates, ceramic plates, semiconductor wafers, and metals, such as laminates of these plates, composites in which these plates are dispersed, and composites in which fibers of these plates are contained.

[0167] Examples of the glass plate include quartz glass, high silicate glass (96% silica), soda-lime glass, lead glass, aluminoborosilicate glass, borosilicate glass (Pyrex (registered trademark)), borosilicate glass (alkali-free), borosilicate glass (microsheet), aluminosilicate glass, etc. Among these, those having a linear expansion coefficient of 5 ppm / K or less are desirable, and commercially available products such as liquid crystal glass "Corning (registered trademark) 7059", "Corning (registered trademark) 1737", and "EAGLE" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10, OA11G" manufactured by Nippon Electric Glass Co., Ltd., and "AF32" manufactured by Schott GmbH are desirable.

[0168] The semiconductor wafer is not particularly limited, but examples include wafers of silicon wafers, germanium, silicon-germanium, gallium-arsenic, aluminum-gallium-indium, nitrogen-phosphorus-arsenic-antimony, SiC, InP (indium phosphide), InGaAs, GaInNAs, LT, LN, ZnO (zinc oxide), CdTe (cadmium telluride), ZnSe (zinc selenide), etc. Among these, the wafers that are preferably used are silicon wafers, and particularly preferred are mirror-polished silicon wafers having a size of 8 inches or more.

[0169] Examples of the metal include single-element metals such as W, Mo, Pt, Fe, Ni, and Au, as well as alloys such as Inconel, Monel, nimonic, copper carbon, Fe-Ni-based Invar alloys, and Super Invar alloys. Multilayer metal plates formed by adding other metal layers or ceramic layers to these metals are also included. In this case, Cu, Al, etc. can also be used for the main metal layer as long as the overall coefficient of linear expansion (CTE) with the additional layers is low. The metal used for the additional metal layer is not limited as long as it has properties such as strong adhesion to the high-heat-resistant film, no diffusion, and good chemical and heat resistance. Suitable examples include Cr, Ni, TiN, and Mo-containing Cu.

[0170] The ceramic plate in the present invention includes substrate ceramics such as Al2O3, Mullite, AlN, SiC, crystallized glass, Cordierite, Spodumene, Pb-BSG+CaZrO3+Al2O3, Crystallized glass+Al2O3, Crystallized Ca-BSG, BSG+Quartz, BSG+Quartz, BSG+Al2O3, Pb-BSG+Al2O3, Glass-ceramic, and Zerodur material.

[0171] The planar portion of the inorganic substrate is preferably sufficiently flat. Specifically, the P-V value of the surface roughness is 50 nm or less, more preferably 20 nm or less, and even more preferably 5 nm or less. If the surface is rougher than this, the peel strength between the polyimide film layer and the inorganic substrate may be insufficient.

[0172] The thickness of the inorganic substrate is not particularly limited, but from the viewpoint of ease of handling, it is preferably 10 mm or less, more preferably 3 mm or less, and even more preferably 1.3 mm or less. The lower limit of the thickness is not particularly limited, but it is preferably 0.07 mm or more, more preferably 0.15 mm or more, and even more preferably 0.3 mm or more. If it is too thin, it will be easily broken and difficult to handle. If it is too thick, it will be heavy and difficult to handle.

[0173] <Laminate Formation> The laminate of the present invention is preferably one in which the polyimide film and the inorganic substrate are laminated together substantially without the use of an adhesive. When the polyimide film has a laminate structure of two or more layers, it preferably contains the first polyimide film in contact with the inorganic substrate and a second polyimide film layer adjacent to the first polyimide film layer without contacting the inorganic substrate. The second polyimide film may further have a multi-layer structure. Furthermore, the laminate may have a structure in which both ends in the thickness direction are inorganic substrates (e.g., inorganic substrate / first polyimide film / second polyimide film / first polyimide film / inorganic substrate). In this case, the polyimide film and inorganic substrate at both ends are bonded substantially without the use of an adhesive.

[0174] The laminate may be formed by laminating a polyimide film on an inorganic substrate after preparation, or by forming a polyimide film on an inorganic substrate directly or via another layer. When forming via another layer, it is preferable to interpose an easily peelable layer such as a silane coupling agent layer. In addition, the inorganic substrate may be surface-treated to control the peel strength to an appropriate level.

[0175] The shape of the laminate is not particularly limited, and may be square or rectangular. A rectangular shape is preferred, with the long side preferably being 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more. There is no particular upper limit, but it is desirable that it can replace substrates of the size and material used industrially. A length of 20,000 mm or less is sufficient, and a length of 10,000 mm or less is acceptable.

[0176] The laminate of the present invention preferably has a warpage of 10 mm or less when heated at 300° C. To improve heat resistance, the warpage is more preferably 8 mm or less, and even more preferably 6 mm or less. There are no particular restrictions on the lower limit of the warpage, but from an industrial perspective, a warpage of 0.01 mm or more is sufficient, and even 0.1 mm or more is acceptable.

[0177] <Adhesive> It is preferable that substantially no adhesive layer is interposed between the inorganic substrate and the polyimide film. Here, the adhesive layer referred to in the present invention refers to one containing less than 10% by mass of Si (silicon) component (less than 10 mass%). Furthermore, "substantially not used (not interposed)" means that the thickness of the adhesive layer interposed between the inorganic substrate and the polyimide film is preferably 0.4 μm or less, more preferably 0.1 μm or less, even more preferably 0.05 μm or less, particularly preferably 0.03 μm or less, and most preferably 0 μm.

[0178] <Silane Coupling Agent (SCA)> In the laminate, a silane coupling agent layer is preferably present between the polyimide film and the inorganic substrate. In the present invention, the silane coupling agent refers to a compound containing 10% by mass or more of silicon (Si). Furthermore, it is preferable that the silane coupling agent has an alkoxy group in its structure. Furthermore, it is desirable that the silane coupling agent does not contain a methyl group. The use of a silane coupling agent layer allows the intermediate layer between the polyimide film and the inorganic substrate to be thin, resulting in fewer outgassing components during heating, less leaching even in wet processes, and even if leaching does occur, it is limited to trace amounts. The silane coupling agent preferably contains a large amount of silicon oxide components to improve heat resistance, and is particularly preferable to have heat resistance at temperatures around 400°C. The thickness of the silane coupling agent layer is preferably less than 0.2 μm. For use in flexible electronic devices, a thickness of 100 nm or less (0.1 μm or less) is preferred, more preferably 50 nm or less, and even more preferably 10 nm. Conventional fabrication results in a thickness of approximately 0.10 μm or less. In addition, in processes where it is desired to use as little silane coupling agent as possible, a thickness of 5 nm or less can be used. If the thickness is 1 nm or less, the peel strength may decrease or there may be areas where the silane coupling agent does not adhere, so a thickness of 1 nm or more is preferable.

[0179] The silane coupling agent in the present invention is not particularly limited, but is preferably one having an amino group or an epoxy group. Specific examples of silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- Glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, tris-(3- trimethoxysilylpropyl) isocyanurate, chloromethylphenethyltrimethoxysilane, chloromethyltrimethoxysilane, etc.Among these, preferred ones include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, aminophenylaminomethylphenethyltrimethoxysilane, etc. When heat resistance is required in the process, those in which Si and the amino group are linked by an aromatic group are desirable.

[0180] The peel strength between the polyimide film and the inorganic substrate must be 0.3 N / cm or less. This makes it very easy to peel the polyimide film from the inorganic substrate after forming a device on the polyimide film. This allows for the production of mass-produced device assemblies, facilitating the production of flexible electronic devices. The peel strength is preferably 0.25 N / cm or less, more preferably 0.2 N / cm or less, even more preferably 0.15 N / cm or less, and particularly preferably 0.12 N / cm or less. It is also preferably 0.03 N / cm or more. Since this prevents the laminate from peeling when forming a device on the polyimide film, the peel strength is more preferably 0.06 N / cm or more, even more preferably 0.08 N / cm or more, and particularly preferably 0.1 N / cm or more. The peel strength is the value of the laminate after bonding the polyimide film and the inorganic substrate and then heat-treating it at 100°C for 10 minutes in an air atmosphere (initial peel strength). Furthermore, it is preferable that the peel strength of the laminate after the initial peel strength measurement is further heat-treated at 300° C. for 1 hour in a nitrogen atmosphere is also within the above range (peel strength after heat treatment at 300° C.).

[0181] The laminate of the present invention can be produced, for example, by the following procedure. A laminate can be obtained by first treating at least one surface of an inorganic substrate with a silane coupling agent, then superimposing a polyimide film on the silane coupling agent-treated surface, and laminating the two under pressure. Alternatively, a laminate can be obtained by first treating at least one surface of a polyimide film with a silane coupling agent, then superimposing the silane coupling agent-treated surface on an inorganic substrate, and laminating the two under pressure. When the polyimide film has a laminate structure of two or more layers, it is preferable to superimpose a first polyimide film on the inorganic substrate. Examples of pressurization methods include ordinary pressing or lamination in air or pressing or lamination in vacuum. However, in order to obtain stable peel strength over the entire surface, lamination in air is preferable for large-sized laminates (e.g., greater than 200 mm). In contrast, pressing in a vacuum is preferable for small-sized laminates of approximately 200 mm or less. A vacuum of approximately 10 Torr or less is sufficient using a conventional oil-sealed rotary pump. The preferred pressure is 1 MPa to 20 MPa, more preferably 3 MPa to 10 MPa. High pressure may damage the substrate, while low pressure may result in areas of poor adhesion. The preferred temperature is 90°C to 500°C, more preferably 100°C to 400°C. High temperatures may damage the film, while low temperatures may result in weak adhesion.

[0182] <Method for manufacturing a flexible electronic device> The method for manufacturing a flexible electronic device of the present invention includes the steps of forming an electronic device on the polyimide film surface of the laminate of the present invention and peeling off the inorganic substrate. In this way, a flexible electronic device having an electronic device formed on the polyimide film surface can be manufactured.

[0183] Therefore, the flexible electronic device of the present invention includes the polyimide film of the present invention and an electronic device formed on the polyimide film.

[0184] The laminate can be used to easily fabricate a flexible electronic device using existing equipment and processes for manufacturing electronic devices. Specifically, the flexible electronic device can be fabricated by forming an electronic device on the polyimide film of the laminate and peeling the polyimide film from the laminate.

[0185] In this specification, the term "electronic device" refers to a wiring substrate having a single-sided, double-sided, or multi-layer structure that carries electrical wiring, an electronic circuit including active elements such as transistors and diodes, and passive devices such as resistors, capacitors, and inductors, as well as sensor elements that sense pressure, temperature, light, humidity, etc., biosensor elements, light-emitting elements, image display elements such as liquid crystal displays, electrophoretic displays, and self-luminous displays, wireless and wired communication elements, computing elements, memory elements, MEMS elements, solar cells, thin-film transistors, etc.

[0186] This wiring board also includes an interposer function, which is an electrode that penetrates the polyimide. By roughly penetrating the polyimide, the process of later creating a through electrode after peeling off the inorganic substrate is largely eliminated. Known methods can be used to create the through holes. For example, through holes are drilled in a polyimide film using a UV nanolaser. Next, the through holes are filled with conductive metal by applying standard methods used for through holes in double-sided printed wiring boards or via holes in multilayer printed wiring boards, and then metal wiring patterns are formed as needed.

[0187] In the case of polyimide film, it is possible to form through-hole electrodes as described above before laminating the film to an inorganic substrate. It is also possible to create through-hole electrodes after laminating the inorganic substrate and polyimide film. It is also possible to form through-holes in the polyimide film and metallize the holes, but it is also possible to drill holes on one side of the polyimide film and metallize the holes on the opposite surface without penetrating the film.

[0188] <Step of Peeling Off Inorganic Substrate> The method for producing a flexible electronic device of the present invention includes a step of forming an electronic device on the polyimide film surface of the laminate and then peeling off the inorganic substrate. When peeling off the inorganic substrate, it is possible to peel off the inorganic substrate at the interface between the polyimide film and the inorganic substrate, peel off one or more layers of a polyimide film composed of two or more layers, or peel off the inorganic substrate together with any other layer.

[0189] When peeling at the interface between the polyimide film and the inorganic substrate, i.e., the method for peeling the polyimide film with the device from the inorganic substrate, is not particularly limited, but may include, for example, peeling from the edge using tweezers, making an incision in the polyimide film and then applying adhesive tape to one side of the incision and then peeling from the tape, or vacuum-adsorbing one side of the incision in the polyimide film and then peeling from that part. Note that, if a small curvature occurs at the incision in the polyimide film during peeling, stress will be applied to the device in that area, potentially destroying the device. Therefore, peeling with as large a curvature as possible is desirable. For example, it is desirable to wind the film while winding it around a roll with a large curvature, or to wind it using a machine configured so that a roll with a large curvature is positioned at the peeling area.

[0190] Methods for making incisions in the polyimide film include, but are not limited to, a method of cutting the polyimide film with a cutting tool such as a blade, a method of cutting the polyimide film by scanning a laser relative to a laminate, a method of cutting the polyimide film by scanning a water jet relative to a laminate, and a method of cutting the polyimide film while cutting slightly into the glass layer using a semiconductor chip dicing device.For example, when employing the above-mentioned methods, it is also possible to appropriately employ a method of superimposing ultrasonic waves on the cutting tool, or a method of adding reciprocating or up-and-down motion to improve cutting performance.

[0191] Another useful method is to attach another reinforcing substrate to the area to be peeled and peel off the reinforcing substrate together. When the flexible electronic device to be peeled off is a backplane of a display device, it is also possible to attach a frontplane of the display device to the inorganic substrate in advance, integrate the two together on the inorganic substrate, and then peel off the two at the same time to obtain a flexible display device.

[0192] Furthermore, when peeling an inorganic substrate together with one or more layers of a polyimide film consisting of two or more layers, the peel strength at the interface of the polyimide film consisting of two or more layers is adjusted so that the peel strength is lighter than the interface with the inorganic substrate, and the film can be peeled in the same manner as described above. The adjustment of the peel strength at the interface of the polyimide film can be adjusted by the type of polyimide in each layer and the degree of imidization of the lower layer when applying the upper layer.

[0193] When peeling off the inorganic substrate together with any other layer, an adhesive layer or the like having a higher adhesion to the inorganic substrate and an adjusted peel strength from the polyimide film may be provided, and the layers may be peeled off in the same manner as described above.

[0194] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Note that the various physical properties in the synthesis examples and examples were measured by the following methods.

[0195] <Measurement of Polyimide Film Thickness> The film thickness was measured using a micrometer (Militron 1245D, manufactured by Fine Leaf Co., Ltd.) The same measurement was carried out three times, and the arithmetic average value was used.

[0196] <Total Light Transmittance> The total light transmittance (TT) of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. The same measurement was performed three times, and the arithmetic average value was used.

[0197] <Haze> The haze of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. The same measurement was performed three times, and the arithmetic average value was used.

[0198] <Yellow Index> Using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source, the tristimulus values ​​X, Y, and Z of the film were measured in accordance with ASTM D1925, and the yellowness index (YI) was calculated using the following formula: The same measurement was performed three times, and the arithmetic average value was used.

[0199] YI = 100 × (1.28X - 1.06Z) / Y <Glass transition temperature (Tg), coefficient of linear expansion (CTE)> Measured using a TMA (TMA4000S, BRUKER AXIS). The film was cut into a strip of 15 mm wide x 2 mm long and set in the device with a chuck distance of 10 mm and a load of 5 gf. Under an argon atmosphere, the temperature was raised to 250 ° C at a heating rate of 20 ° C / min, and then lowered to 30 ° C at a rate of 5 ° C / min. Thereafter, the temperature was raised at 10 ° C / min to a temperature (Td1-20 ° C) at which thermal decomposition did not occur. The CTE was calculated from the slope of the 200 ° C to 50 ° C section during the temperature drop, and the inflection point during the second heating was taken as Tg.

[0200] <Tensile Modulus, Tensile Strength, Elongation, Tensile Product> Tests were carried out using a Tensilon (Autograph AG-IS, Shimadzu Corporation) as follows. Test pieces were prepared by cutting the film into strips measuring 5 mm x 50 mm in length in the machine direction (MD) during application. 30 mm of each strip was held in an air jaw chuck, and the tensile modulus, tensile strength at break, and elongation at break in the MD were determined at room temperature at a pulling rate of 50 mm / min. The tensile modulus was determined from the initial elastic gradient of the strain-stress curve. Measurements were carried out at N=5 for each level, and the average value of three points excluding the maximum and minimum values ​​was treated as data. The product of the tensile strength at break and the elongation at break was taken as the tensile product.

[0201] <Silsesquioxane compound having an acid anhydride group １ H NMR measurement: Each sample was measured under the following conditions: １ H NMR measurement was carried out. Apparatus: DPX400 manufactured by Bruker Biospin (Examples 1 and 2) or 400MR manufactured by Agilent (Examples 3 to 9). Solvent: deuterated chloroform (CDCl ３ ) (Examples 1 and 2) or deuterated DMSO (DMSO-d ６) (Examples 3 to 9) Sample concentration: 3 mg / 1 mL Measurement temperature: room temperature (24°C) Resonance frequency: 400 MHz Number of accumulations: 32

[0202] Synthesis Example 1-1: Synthesis of thiol group-containing silsesquioxane compound 1 A reaction apparatus equipped with a stirrer, a condenser, a water divider, a thermometer, a dropping funnel, and a nitrogen inlet was charged with 11.8 g (60.0 mmol) of 3-mercaptopropyltrimethoxysilane, 2.72 g (20.0 mmol) of methyltrimethoxysilane ([number of moles of component (a2)] / [total number of moles of component (a1) and component (a2)]=0.25), 1.9 g of ion-exchanged water ([number of moles of water used in the hydrolysis reaction] / [total number of moles of alkoxy groups contained in components (a1) and (a2)] (molar ratio)=0.45), and 1.0 g of cation exchange resin, and the hydrolysis reaction was carried out at room temperature for 30 minutes. After the reaction, the cation exchange resin was filtered off and then diluted with 5 g of ethylene glycol dimethyl ether (DMG) to obtain a hydrolyzate solution.

[0203] Next, 9 g of DMG and 0.05 g of a 25% aqueous solution of tetramethylammonium hydroxide were charged into a separate reaction vessel and heated to 80°C. The hydrolyzate solution was then added dropwise over 2 hours and 30 minutes. During the dropwise addition, the tetramethylammonium hydroxide dissolved, and the reaction solution became clear. After the dropwise addition, the reaction was continued for another 15 minutes at 80°C, after which it was cooled to 25°C. 0.5 g of cation exchange resin was added and stirred at room temperature for 4 hours. The tetramethylammonium hydroxide was adsorbed during stirring, and the reaction solution became clear. The cation exchange resin was filtered off to obtain a solution of thiol group-containing silsesquioxane (average number of thiol groups per molecule = 6). Toluene was added, and the mixture was heated to 70°C under reduced pressure to distill off the methanol and water generated by hydrolysis, as well as a portion of the toluene. Toluene was added as needed to adjust the final solids concentration to 72%.

[0204] Synthesis Example 1-2: Synthesis of thiol group-containing silsesquioxane compound 2 Synthesis was performed in the same manner as in Synthesis Example 1-1, except that the following were used: 8.83 g (45.0 mmol) of 3-mercaptopropyltrimethoxysilane, 5.44 g (40.0 mmol) of methyltrimethoxysilane ([number of moles of component (a2)] / [total number of moles of component (a1) and component (a2)]=0.47), and 2.0 g of ion-exchanged water ([number of moles of water used in hydrolysis reaction] / [total number of moles of alkoxy groups contained in components (a1) and (a2)] (molar ratio)=0.45). The average number of thiol groups per molecule of the resulting thiol group-containing silsesquioxane was 4.5, and the final solids concentration was 72% by mass.

[0205] Synthesis Example 1-3 Synthesis of Thiol Group-Containing Silsesquioxane Compound 3 Synthesis was performed in the same manner as in Synthesis Example 1-1, except that the following were used: 4.91 g (25.0 mmol) of 3-mercaptopropyltrimethoxysilane, 6.81 g (50.0 mmol) of methyltrimethoxysilane ([number of moles of component (a2)] / [total number of moles of component (a1) and component (a2)]=0.67), and 1.8 g of ion-exchanged water ([number of moles of water used in hydrolysis reaction] / [total number of moles of alkoxy groups contained in components (a1) and (a2)] (molar ratio)=0.45). The average number of thiol groups per molecule of the resulting thiol group-containing silsesquioxane was 2.5, and the final solids concentration was 72% by mass.

[0206] Synthesis Example 2-1 Synthesis of Silsesquioxane SQ1 Having Acid Anhydride Groups 10 g of the following thiol group-containing silsesquioxane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) (thiol group amount: 16.7 mmol) and 2.74 g (16.7 mmol) of norbornene anhydride were placed in a reaction vessel and irradiated with ultraviolet light (Spotcure SP-11, USHIO Corporation) for 20 minutes while stirring, thereby obtaining silsesquioxane SQ1 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups and norbornene had reacted. The resulting solution was filtered through a PTFE filter (pore size: 10 μm) and then used in the synthesis of the polyamic acid solutions described below (the same applies to SQ3 to SQ9).

[0207] Compoceran SQ-109: condensation product of methyltrimethoxysilane and 3-mercaptopropyltrimethoxysilane, molar ratio (former / (former+latter))=2 / 8, solvent PGMEA, solids concentration 25% by mass.

[0208] The molar ratio and the average number of thiol groups per molecule were calculated as follows: １ In the HNMR measurement, the molar ratio of methyltrimethoxysilane to 3-mercaptopropyltrimethoxysilane was calculated from the integral ratio of protons derived from methyl groups (δ = around 0.0 to 0.2, 3H) and protons derived from propylthiol groups (δ = around 0.2 to 0.8, 2H). The average number of thiol groups per molecule was calculated based on the ratio of the thiol groups to the methyl groups, the molecular weight per structural unit (SiO １．５ Me=67.1, SiO １．５ C ３ H ６ The thiol equivalent weight was calculated from the SH of the solution (600 g / eq.), the thiol equivalent weight of the solution (600 g / eq.), and the solid content concentration of 25% by mass.

[0209] For reference, the results of NMR measurement are shown in Figures 1 to 4. Figure 1 shows SQ-109 (PGMEA solution), Figure 2 shows PGMEA, Figure 3 shows norbornene anhydride, and Figure 4 shows the reaction mixture after the reaction. １ H NMR (CDCl ３ 4. In FIG. 4, the peaks (δ=6.3, etc.) derived from the double bond of norbornene anhydride disappear, which suggests that the reaction between the thiol group and the double bond has progressed.

[0210] Synthesis Example 2-2 Synthesis of Silsesquioxane SQ2 Having Acid Anhydride Groups 10 g of a thiol group-containing silsesquioxane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) (thiol group amount: 16.7 mmol), 2.74 g (16.7 mmol) of norbornene anhydride, and 1 mg of iron(III) chloride were placed in a reaction vessel and stirred for 10 minutes to obtain silsesquioxane SQ2 having acid anhydride groups as a pale yellow solution (the yellow color is believed to be derived from iron chloride). NMR and IR measurements confirmed that the thiol groups and norbornene had reacted.

[0211] For reference, the results of NMR measurement are shown in FIG. 5. １ H NMR (CDCl ３ In FIG. 5, the peaks (δ=6.3, etc.) derived from the double bond of norbornene anhydride disappear, which suggests that the reaction between the thiol group and the double bond has progressed.

[0212] Synthesis Example 2-3 Synthesis of silsesquioxane SQ3 having acid anhydride groups 20 g of the solution of thiol group-containing silsesquioxane compound 1 obtained in Synthesis Example 1-1 (thiol group amount 97.0 mmol), 15.9 g (97.0 mmol) of norbornene anhydride, and 10.0 g of PGMEA were placed in a reaction vessel, and the mixture was irradiated with ultraviolet light (Spot Cure SP-11, manufactured by USHIO Corporation) for 20 minutes while stirring to obtain silsesquioxane SQ3 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups and norbornene had reacted.

[0213] Synthesis Example 2-4 Synthesis of Silsesquioxane SQ4 Having Acid Anhydride Groups 20 g of the solution of thiol group-containing silsesquioxane compound 2 obtained in Synthesis Example 1-2 (thiol group amount 77.9 mmol), 12.8 g (77.9 mmol) of norbornene anhydride, and 10.0 g of PGMEA were placed in a reaction vessel, and the mixture was irradiated with ultraviolet light (Spot Cure SP-11, manufactured by USHIO Corporation) for 20 minutes while stirring to obtain silsesquioxane SQ4 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups and norbornene had reacted.

[0214] Synthesis Example 2-5 Synthesis of Silsesquioxane SQ5 Having Acid Anhydride Groups 20 g of the solution of thiol group-containing silsesquioxane compound 3 obtained in Synthesis Example 1-3 (thiol group amount 54.5 mmol), 8.95 g (54.5 mmol) of 5-norbornene-2,3-dicarboxylic anhydride, and 10.0 g of PGMEA were placed in a reaction vessel, and the mixture was irradiated with ultraviolet light (Spot Cure SP-11, manufactured by USHIO Corporation) for 20 minutes while stirring to obtain silsesquioxane SQ5 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups had reacted with the 5-norbornene-2,3-dicarboxylic anhydride.

[0215] Synthesis Example 2-6 Synthesis of Silsesquioxane SQ6 Having Acid Anhydride Groups 6 g of a thiol group-containing trialkoxysilane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) (thiol group amount 10.0 mmol) and 1.40 g (10.0 mmol) of allylsuccinic anhydride were placed in a reaction vessel and irradiated with ultraviolet light (Spotcure SP-11, USHIO Corporation) for 20 minutes while stirring, thereby obtaining silsesquioxane SQ6 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups had reacted with the allylsuccinic anhydride.

[0216] Synthesis Example 2-7 Synthesis of Silsesquioxane SQ7 Having Acid Anhydride Groups 6 g of a thiol group-containing trialkoxysilane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) (thiol group amount: 10.0 mmol) and 1.66 g (10.0 mmol) of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride were placed in a reaction vessel and irradiated with ultraviolet light (Spot Cure SP-11, USHIO Corporation) for 20 minutes while stirring, thereby obtaining Silsesquioxane SQ7 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups had reacted with exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride.

[0217] Synthesis Example 2-8 Synthesis of Silsesquioxane SQ8 Having Acid Anhydride Groups 3 g of a thiol group-containing trialkoxysilane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) (thiol group amount 5.0 mmol), 0.94 g (5.0 mmol) of 5,6-dihydro-1,4-dithiine-2,3-dicarboxylic anhydride, and γ-butyrolactone (5 mL) were placed in a reaction vessel and irradiated with ultraviolet light (Spot Cure SP-11, USHIO Corporation) for 20 minutes while stirring to obtain Silsesquioxane SQ8 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups had reacted with the 5,6-dihydro-1,4-dithiine-2,3-dicarboxylic anhydride.

[0218] Synthesis Example 2-9: Synthesis of silsesquioxane SQ9 having acid anhydride groups 6 g (thiol group amount 10.0 mmol) of a thiol group-containing trialkoxysilane solution (Arakawa Chemical Industries, Ltd., Compoceran SQ-109) was placed in a reaction vessel, and 2.10 g (10.0 mmol) of trimellitic anhydride chloride was slowly added with stirring. Stirring was continued at room temperature for 24 hours to obtain silsesquioxane SQ9 having acid anhydride groups as a colorless, transparent solution. NMR and IR measurements confirmed that the thiol groups and acid chloride groups had reacted.

[0219] Comparative Synthesis Example 2-1: Synthesis of terminal dicarboxylic acid anhydride silsesquioxane SQN1 (thioether moiety-free) Using the method described in Example 1 of International Publication WO 2010 / 095329 A1, thioether moiety-free silsesquioxane SQN1 having a structure represented by the following chemical formula was synthesized.

[0220] Comparative Synthesis Example 2-2: Synthesis of terminal dicarboxylic acid anhydride silsesquioxane SQN2 (thioether moiety-free) Silsesquioxane SQN2 having a structure represented by the following chemical formula and containing no thioether moiety was synthesized by the method described in Example 2 of International Publication WO 2010 / 095329 A1.

[0221] [Example A: Synthesis of Polyamic Acid Solution A] 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 5.88 g), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 9.74 g), and SQ1 solution (0.655 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while passing nitrogen through the reactor. The mixture was dissolved in N,N-dimethylacetamide (DMAc, 125.0 g) and stirred at 25 ° C. for 24 hours to obtain polyamic acid solution A (molar ratio of CBDA / SQ1 / TFMB = 0.985 / 0.015 / 1.00). Here, the molar ratio of SQ1 is a value calculated based on the divalent acid anhydride group. Specifically, it is calculated by dividing the total number of moles of unit structures derived from silsesquioxane compound A by the total number of dicarboxylic acid anhydride groups and multiplying the result by two (the same applies to the molar ratios below).

[0222] Example B: Synthesis of Polyamic Acid Solution B Into a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 5.88 g), 4,4′-diaminobenzanilide (DABA, 6.92 g), and SQ1 solution (0.655 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 133.7 g). The mixture was then stirred at 25° C. for 24 hours to obtain Polyamic Acid Solution B (molar ratio of CBDA / SQ1 / DABA=0.985 / 0.015 / 1.00).

[0223] Example Ca: Synthesis of Polyamic Acid Solution Ca Pyromellitic dianhydride (PMDA, 3.27 g), 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 4.88 g), and SQ1 solution (0.328 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 67.0 g) and stirred at 25° C. for 24 hours to obtain polyamic acid solution Ca (molar ratio of PMDA / SQ1 / TFMB=0.985 / 0.015 / 1.00).

[0224] Example Cb: Synthesis of Polyamic Acid Solution Cb Pyromellitic dianhydride (PMDA, 3.27 g), 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 4.90 g), and SQ3 solution (0.227 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N-methyl-2-pyrrolidone (NMP, 66.0 g) and stirred at 25° C. for 24 hours to obtain polyamic acid solution Cb (molar ratio of PMDA / SQ3 / TFMB=0.98 / 0.02 / 1.00).

[0225] [Example Cc: Synthesis of Polyamic Acid Solution Cc] Pyromellitic dianhydride (PMDA, 3.27 g), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 4.90 g), and SQ4 solution (0.258 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N-methyl-2-pyrrolidone (NMP, 66.0 g) and stirred at 25°C for 24 hours to obtain polyamic acid solution Cc (molar ratio of PMDA / SQ4 / TFMB = 0.98 / 0.02 / 1.00).

[0226] [Example Cd: Synthesis of Polyamic Acid Solution Cd] Pyromellitic dianhydride (PMDA, 3.27 g), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 4.90 g), and SQ5 solution (0.325 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N-methyl-2-pyrrolidone (NMP, 66.0 g) and stirred at 25°C for 24 hours to obtain polyamic acid solution Cd (molar ratio of PMDA / SQ5 / TFMB = 0.98 / 0.02 / 1.00).

[0227] [Example Ce: Synthesis of Polyamic Acid Solution Ce] Pyromellitic dianhydride (PMDA, 3.27 g), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 4.90 g), and SQ9 solution (0.354 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N-methyl-2-pyrrolidone (NMP, 66.0 g) and stirred at 25°C for 24 hours to obtain polyamic acid solution Ce (molar ratio of PMDA / SQ9 / TFMB = 0.985 / 0.015 / 1.00).

[0228] Example D: Synthesis of Polyamic Acid Solution D Pyromellitic dianhydride (PMDA, 3.27 g), 4,4′-diaminobenzanilide (DABA, 3.47 g), and SQ1 solution (0.328 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 63.0 g). The mixture was then stirred at 25° C. for 24 hours to obtain Polyamic Acid Solution D (molar ratio of PMDA / SQ1 / DABA=0.985 / 0.015 / 1.00).

[0229] Comparative Example A1: Synthesis of Polyamic Acid Solution A1 Into a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 19.6 g) and 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 32.3 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 279.0 g). The mixture was then stirred at 25° C. for 24 hours to obtain Polyamic Acid Solution A1 (molar ratio of CBDA / TFMB=1.00 / 1.00).

[0230] Comparative Example B1: Synthesis of Polyamic Acid Solution B1 Into a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 3.98 g) and 4,4′-diaminobenzanilide (DABA, 4.58 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 76.0 g). The mixture was then stirred at 25° C. for 24 hours to obtain Polyamic Acid Solution B1 (molar ratio of CBDA / DABA=1.00 / 1.00).

[0231] Example B2 Synthesis of Polyamic Acid Solution B2 While nitrogen was being passed through a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 2.94 g), 4,4′-diaminobenzanilide (DABA, 3.54 g), and SQ1 solution (1.00 g) were placed in the reactor and dissolved in N,N-dimethylacetamide (DMAc, 90 g). The mixture was then stirred at 25° C. for 24 hours to obtain polyamic acid solution B2 (molar ratio of CBDA / SQ1 / DABA=0.955 / 0.045 / 1.00).

[0232] Comparative Example B4: Synthesis of Polyamic Acid Solution B4 In a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 3.98 g) and 4,4'-diaminobenzanilide (DABA, 4.55 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 76.0 g) and stirred for 24 hours at 25° C. Thereafter, SQ-109 (0.546 g) was added, and the mixture was stirred for an additional 24 hours to obtain Polyamic Acid Solution B4 (molar ratio of CBDA / DABA / SQ-109 = 1.00 / 1.00 / 0.01).

[0233] Comparative Example B5: Synthesis of Polyamic Acid Solution B5 In a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 3.98 g) and 4,4'-diaminobenzanilide (DABA, 4.55 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 76.0 g) and stirred for 24 hours at 25° C. Thereafter, SQ-109 (8.19 g) was added, and the mixture was stirred for an additional 24 hours to obtain Polyamic Acid Solution B5 (molar ratio of CBDA / DABA / SQ-109 = 1.00 / 1.00 / 0.15).

[0234] Comparative Example B6: Synthesis of Polyamic Acid Solution B6 In a reactor equipped with a nitrogen inlet tube and a stirring blade, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA, 3.98 g) and 4,4'-diaminobenzanilide (DABA, 4.55 g) were placed while passing nitrogen through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 76.0 g) and stirred for 24 hours at 25° C. Thereafter, SQ-109 (27.3 g) was added, and the mixture was stirred for an additional 24 hours to obtain Polyamic Acid Solution B6 (molar ratio of CBDA / DABA / SQ-109 = 1.00 / 1.00 / 0.50).

[0235] Comparative Example C1: Synthesis of Polyamic Acid Solution C1 Pyromellitic dianhydride (PMDA, 6.54 g) and 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 9.61 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 164.0 g) and stirred at 25° C. for 24 hours to obtain polyamic acid solution C1 (molar ratio of PMDA / TFMB=1.00 / 1.00).

[0236] Comparative Example C2: Synthesis of Polyamic Acid Solution C2 Pyromellitic dianhydride (PMDA, 3.27 g), 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 4.85 g), and SQN1 (0.070 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 67.0 g) and stirred at 25° C. for 24 hours to obtain polyamic acid solution C2 (molar ratio of PMDA / SQN1 / TFMB=0.99 / 0.01 / 1.00).

[0237] Comparative Example C3: Synthesis of Polyamic Acid Solution C3 Pyromellitic dianhydride (PMDA, 3.27 g), 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB, 4.85 g), and SQN2 (0.081 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 67.0 g) and stirred at 25° C. for 24 hours to obtain polyamic acid solution C3 (molar ratio of PMDA / SQN2 / TFMB=0.99 / 0.01 / 1.00).

[0238] Comparative Example D1: Synthesis of Polyamic Acid Solution D1 Pyromellitic dianhydride (PMDA, 3.27 g) and 4,4′-diaminobenzanilide (DABA, 3.41 g) were placed in a reactor equipped with a nitrogen inlet tube and a stirring blade while nitrogen was being passed through the reactor, and the mixture was dissolved in N,N-dimethylacetamide (DMAc, 63.0 g). The mixture was then stirred at 25° C. for 24 hours to obtain Polyamic Acid Solution D1 (PMDA / DABA molar ratio=1.00 / 1.00).

[0239] The polyamic acid solutions obtained in the above Examples and Comparative Examples were formed into films by the following method, and the optical, thermal and mechanical properties were measured.

[0240] Example 1 Polyamic acid solution A was applied to a polyester film (A4100, manufactured by Toyobo) using a casting applicator and heated at 100°C for 18 minutes in a nitrogen atmosphere. The resulting green film was cut with a cutter, peeled off from the polyester film, and fixed to a metal frame. Thermal imidization was carried out by sequentially heating at 200°C for 10 minutes, 250°C for 10 minutes, 300°C for 10 minutes, and 350°C for 10 minutes in a nitrogen atmosphere while gradually increasing the temperature at a rate of 10°C / min. After allowing to cool, the film was removed from the metal frame to obtain a polyimide film.

[0241] [Examples 2 to 5] Polyimide films were obtained in the same manner as in Example 1, except that polyamic acid solutions B, Ca to Ce, D, and B2 were used instead of polyamic acid solution A. The components used and the evaluation results are shown in Table 1.

[0242] [Comparative Examples 1 to 9] Polyimide films were obtained in the same manner as in Example 1, except that polyamic acid solutions A1, B1, B4, B5, B6, C1, C2, C3, and D1 were used instead of polyamic acid solution A. The components used and the evaluation results are shown in Table 1.

[0243] As shown in Table 1, the polyimide films containing 1 mol % of SQ1 in their structure (Examples 1, 2, 3a, and 4) exhibited approximately the same total light transmittance, haze, yellow index, Tg, and CTE as the polyimide films (Comparative Examples 1, 2, 6, and 9) that had the same composition but did not contain SQ1, and also exhibited an increased tensile product.

[0244] Comparing Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5, when SQ-109, which does not have an acid anhydride group, was mixed in place of SQ1, which has an acid anhydride group at the terminal, the polyamic acid solution and polyimide film became cloudy as the addition amount was increased to 1%, 15%, and 50%. Furthermore, when SQ-109 was mixed, no increase in tensile product was observed, and the film became brittle as the addition amount was increased.

[0245] Comparing Examples 3a to 3e with Comparative Examples 6, 7, and 8, it was found that Examples 3a to 3e had improved tensile products compared to Comparative Example 6, while Comparative Examples 7 and 8 had tensile products comparable to that of Comparative Example 6. Example 3a, Comparative Example 7, and Comparative Example 8 are all polyimides containing silsesquioxanes with the same acid anhydride group (norbornene anhydride) in their structures, but SQ1 used in Example 3a contains a thioether group between the acid anhydride group and the silsesquioxane structure, while SQN1 and SQN2 used in Comparative Examples 7 and 8 do not contain a thioether group. This suggests that copolymerization of silsesquioxanes containing a thioether group in their structures is useful for improving the tensile product. (Application Example 1) A dispersion of colloidal silica dispersed in NMP as a lubricant ("Snowtex (registered trademark) NMP-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) was added to the solution of Example Ca so that the amount of colloidal silica (lubricant) was 0.3 mass % of the total polymer solid content in the polyamic acid solution, and the mixture was stirred at room temperature for 24 hours. This was designated Example Ca2 solution.

[0246] Next, the Example Ca2 solution was applied to the non-slip surface of a polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) using a comma coater to a final film thickness of 1.5 μm. The Example Ca solution was then applied to the Example Ca2 solution using a die coater to a final film thickness of 22 μm. This was dried at 110°C for 10 minutes. After drying, the self-supporting polyamic acid film was peeled from the A4100 film that had been used as the support, passed through a pin tenter equipped with a pin sheet, and the film edge was gripped by inserting it into the pins. The pin sheet spacing was adjusted to prevent film breakage and unnecessary slack. The film was then heated at 200°C for 3 minutes, 250°C for 3 minutes, 300°C for 3 minutes, and 400°C for 3 minutes to allow the imidization reaction to proceed. The film was then cooled to room temperature over 2 minutes, and the poorly flat portions at both ends of the film were cut off with a slitter. The film was then wound up into a roll, yielding 500 m of polyimide film A1 with a width of 450 mm. (Application Example 2) First, the polyimide film obtained in Example 3a (PMDA / TFMB / SQ1) was cut into a rectangular shape measuring 360 mm x 460 mm. Next, the film surface was treated with UV / O. ３ Using an irradiator (SKR1102N-03 manufactured by LAN Technical), UV / O ３ The UV / O irradiation was carried out for 3 minutes. ３ The distance between the lamp and the film was 30 mm.

[0247] A display glass (glass substrate of 370 mm × 470 mm, thickness 0.7 mm: OA10G manufactured by Nippon Electric Glass Co., Ltd.) was coated with 3-aminopropyltrimethoxysilane (KBM-903 manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent using a spray coater. The glass substrate was washed with pure water, dried, and then irradiated with UV / O ３ The substrate was irradiated with an irradiator (SKR1102N-03 manufactured by LAN Technical) for 1 minute and then dry-cleaned before use.

[0248] Next, the glass substrate coated with the silane coupling agent was set on a roll laminator equipped with a silicone rubber roller, and 500 ml of pure water was first dripped onto the silane coupling agent-coated surface using a dropper so that the water spread over the entire substrate, wetting the substrate.

[0249] The surface-treated surface of the polyimide film that has undergone the surface treatment is placed on the silane coupling agent coated surface of the glass substrate, that is, the surface that has been wetted with pure water, and the pure water between the polyimide film and the glass substrate is pushed out sequentially from one side of the glass substrate by a rotating roll, and the glass substrate and the polyimide film are laminated together to obtain a provisional laminate.The laminator used is a laminator manufactured by MCK Corporation with an effective roll width of 650 mm, and the bonding conditions are: air source pressure: 0.5 MPa, lamination speed: 50 mm / sec, roll temperature: 22 ° C, ambient temperature 22 ° C, humidity 55% RH.

[0250] The resulting temporary laminate was heat-treated in a clean oven at 200° C. for 10 minutes to obtain a laminate consisting of a polyimide film and a glass substrate.

[0251] A tungsten film (75 nm thick) was formed on the polyimide film surface of the obtained laminate by the following process, and then a silicon oxide film (150 nm thick) was laminated as an insulating film without exposure to the atmosphere. Next, a silicon oxynitride film (100 nm thick) was formed as an underlying insulating film by plasma CVD, and then an amorphous silicon film (54 nm thick) was laminated thereon without exposure to the atmosphere.

[0252] The amorphous silicon film thus obtained was used to fabricate TFT elements. First, the amorphous silicon thin film was patterned to form silicon regions of a predetermined shape, followed by the formation of a gate insulating film, a gate electrode, the formation of source and drain regions by doping into the active region, the formation of an interlayer insulating film, the formation of source and drain electrodes, and an activation process, to fabricate an array of P-channel TFTs.

[0253] The polyimide film was burned off with a UV-YAG laser along a 0.5 mm radius inside the TFT array perimeter, and then peeled off from the edge of the cut using a thin razor blade, yielding a flexible A3-sized TFT array. Peeling was possible with minimal force, and it was possible to peel off without damaging the TFTs. The resulting flexible TFT array maintained its excellent properties even when wrapped around a 5 mm diameter rod, with no degradation in performance.

[0254] As described above, the polyimide film of the present invention has been shown to have good mechanical properties while maintaining optical and thermal properties at the same level as those of a polyimide film not containing a silsesquioxane compound. The polyimide film of the present invention has excellent optical properties, colorless transparency, excellent mechanical properties, and a relatively low CTE. Therefore, the film can be laminated to a flat, rigid inorganic substrate such as glass, and various electronic device processing processes can be performed on the film, and finally, the film can be peeled off from the inorganic substrate to produce a flexible electronic device.

Claims

1. A polyamic acid which is a copolymerization product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group, The silsesquioxane compound A is General formula: R １ Si(OR ２ ) ３ and a thiol group-containing trialkoxysilane a1 represented by the formula: (In the formula, R １ represents an organic group in which at least one hydrogen atom of an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms has been substituted with a thiol group; R ２ each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms. Trialkoxysilanes a2 having no thiol group; A thiol group of the condensation product B of a dicarboxylic acid anhydride C having at least one reactive group selected from a vinyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an acid chloride group, The polyamic acid is a silsesquioxane compound A obtained by reacting the above.

2. A polyamic acid which is a copolymerization product of at least carboxylic acids, diamines, and a silsesquioxane compound A having a dicarboxylic anhydride group, The silsesquioxane compound A is a polyamic acid having structural units represented by the following general formulas (1) and (2). 【Chemistry 1】 (In the formula, Q １ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms; Q ２ is a single bond, a hydrocarbon group having 1 to 8 carbon atoms, an organic group in which one or more carbon atoms of a hydrocarbon group having 1 to 8 carbon atoms are substituted with oxygen, or a carbonyl group; X is a carbon-carbon bond, or an aliphatic ring having 4 to 10 carbon atoms, an aromatic ring having 6 to 10 carbon atoms, or a heterocycle in which some of the carbons constituting these rings are substituted with oxygen or sulfur, and one or more hydrogen atoms bonded to these rings may be substituted with a hydrocarbon group; 1.0≦m≦2.0, and 1.4≦n≦1.

6. 【Chemistry 2】 (In the formula, Q ３ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms, and 1.4≦n≦1.

6.

3. 2. The polyamic acid according to claim 1, wherein the molar ratio of the trialkoxysilane a2 in the silsesquioxane compound A ([molar number of a2] / [molar number of a1+molar number of a2]) is 0.1 or more and 0.7 or less.

4. 3. The polyamic acid according to claim 2, wherein the molar ratio of the structural unit represented by the general formula (2) in the silsesquioxane compound A ([structural unit (2)] / [structural unit (1)+structural unit (2)]) is 0.1 or more and 0.7 or less.

5. 2. The polyamic acid according to claim 1, wherein the dicarboxylic anhydride C is a compound represented by a chemical formula selected from the following: 【Chemistry 3】 (In the formula, Rx represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 4 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms.)

6. 2. The polyamic acid according to claim 1, wherein the molar content of the structural units derived from the silsesquioxane compound A based on a divalent monomer: (nA / (nA+nD))×100 (wherein nA is a number obtained by dividing the total number of moles of the structural units derived from the silsesquioxane compound A by the total number of the dicarboxylic acid anhydride groups and multiplying the result by two, and nD is the number of moles of the structural units derived from the carboxylic acids) is 0.01 to 10.0 mol %.

7. 2. The polyamic acid according to claim 1, wherein the carboxylic acid is one or more compounds represented by a chemical formula selected from the following: 【Chemistry 4】

8. 2. The polyamic acid of claim 1, wherein the diamines include 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) or 4,4'-diaminobenzanilide (DABA).

9. A polyamic acid composition comprising the polyamic acid according to any one of claims 1 to 8 and a solvent.

10. A polyimide obtained by imidizing the polyamic acid according to any one of claims 1 to 8.

11. A polyimide film comprising the polyimide according to claim 10.

12. The polyimide film according to claim 11, having a linear expansion coefficient of 40 ppm / K or less and −20 ppm / K or more.

13. 12. The polyimide film according to claim 11, which has a tensile product in a tensile test of 1,000 MPa·% or more and 10,000 MPa·% or less.

14. A laminate comprising the polyimide film according to claim 11 and an inorganic substrate.

15. A method for producing a flexible electronic device, comprising the steps of: forming an electronic device on a surface of the polyimide film of the laminate according to claim 14; and peeling off the inorganic substrate.

16. A flexible electronic device comprising the polyimide film according to claim 11 and an electronic device formed on the polyimide film.

Images