Polyamic acid, polyamic acid composition, polyimide, polyimide film, laminate, method for producing laminate, and electronic device

Abstract

This polyamic acid has a tetracarboxylic acid dianhydride residue and a diamine residue. The diamine residue includes a divalent organic group represented by general formula (1) and a divalent organic group represented by general formula (2). In general formula (1): R1 and R2 each independently represent a trifluoromethoxy group, a pentafluoroethoxy group, or a heptafluoropropoxy group; a represents an integer from 1 to 4; b represents an integer from 0 to 4; when a represents an integer from 2 to 4, the plurality of R1s may be the same or different; when b represents an integer from 2 to 4, the plurality of R2s may be the same or different; and m represents an integer from 0 to 3. In general formula (2): R3 and R4 each independently represent a divalent hydrocarbon group; and n represents an integer from 1 to 5.

Description

Polyamic acid, polyamic acid composition, polyimide, polyimide film, laminate, method for manufacturing laminate, and electronic device

[0001] The present invention relates to polyamic acid, polyamic acid compositions, polyimides, polyimide films, laminates, methods for producing laminates, and electronic devices.

[0002] With the rapid advancements in displays such as liquid crystal displays, organic EL displays, and electronic paper, as well as electronic devices such as solar cells and touch panels, devices are becoming thinner, lighter, and more flexible. In these devices, polyimide is being used as the substrate material instead of glass.

[0003] These devices have various electronic elements, such as thin-film transistors (TFTs) and transparent electrodes, formed on the substrate, and the formation of these electronic elements requires high-temperature processes. Polyimide has sufficient heat resistance to withstand high-temperature processes, making it suitable as a substrate material for flexible displays and the like.

[0004] Generally, aromatic polyimides are colored yellowish-brown due to intramolecular conjugation and the formation of charge transfer (CT) complexes. However, in top-emission organic EL displays, light is extracted from the opposite side of the substrate, so transparency is not required, and conventional aromatic polyimides have been used. However, in cases where light emitted from display elements passes through the substrate, such as in transparent displays, bottom-emission organic EL displays, and liquid crystal displays, or when sensors and camera modules are placed on the back of the substrate to create a full-screen (notch-less) display in smartphones, high optical properties (more specifically, transparency, etc.) are now required for the substrate.

[0005] Against this backdrop, there is a need for a material that has the same heat resistance as existing aromatic polyimides, but with reduced coloration and superior transparency.

[0006] To reduce the coloration of polyimides, techniques are known to suppress the formation of CT complexes using aliphatic monomers (Patent Documents 1 and 2), and to improve transparency by using monomers containing fluorine or sulfur atoms (Patent Document 3). In addition, although not relating to a technique for reducing the coloration of polyimides, it is known that by adding silicone oil to polyamic acid as a polyimide precursor and performing imidization, the resulting polyimide film exhibits high adhesion to inorganic materials (Patent Document 4).

[0007] Japanese Patent Publication No. 2016-29177, Japanese Patent Publication No. 2012-41530, Japanese Patent Publication No. 2014-70139, Japanese Patent Publication No. 2015-229691

[0008] However, the technologies described in Patent Documents 1 to 4 have room for improvement in obtaining polyimides that have excellent adhesion to inorganic materials while increasing transparency.

[0009] This invention was made in view of the above circumstances and aims to provide a polyimide and a polyamic acid as its precursor that exhibit high transparency and excellent adhesion to inorganic materials. Furthermore, this invention also aims to provide a product or component requiring transparency, manufactured using the polyimide and polyamic acid.

[0010] <Aspects of the Invention> The present invention includes the following aspects.

[0011] [1] A polyamic acid having a tetracarboxylic dianhydride residue and a diamine residue, wherein the diamine residue includes a divalent organic group represented by the following general formula (1) and a divalent organic group represented by the following general formula (2).

[0012]

[0013] In the above general formula (1), R １ and R ２ Each independently represents a trifluoromethoxy group, a pentafluoroethoxy group, or a heptafluoropropoxy group, where a represents an integer between 1 and 4, b represents an integer between 0 and 4, and when a represents an integer between 2 and 4, multiple R １The elements may be the same or different from each other, and if b represents an integer between 2 and 4, then there may be multiple R ２ R may be the same or different from each other, and m represents an integer between 0 and 3. In the general formula (2) above, R ３ and R ４ Each of these independently represents a divalent hydrocarbon group, and n represents an integer between 1 and 5.

[0014] [2] The polyamic acid according to [1], wherein the content of the divalent organic group represented by the general formula (1) is 1 mol% or more and 10 mol% or less with respect to the total amount of the diamine residue.

[0015] [3] The polyamic acid according to [1] or [2], wherein the content of the divalent organic group represented by the general formula (2) is 0.1 mol% or more and 1.0 mol% or less with respect to the total amount of the diamine residue.

[0016] [4] The polyamic acid according to any one of [1] to [3], wherein the tetracarboxylic dianhydride residue comprises a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue.

[0017] [5] The polyamic acid according to [4], wherein the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residue is 90 mol% or more of the total amount of the tetracarboxylic dianhydride residue.

[0018] [6] The polyamic acid according to any one of [1] to [5], wherein the diamine residue further comprises a p-phenylenediamine residue.

[0019] [7] The polyamic acid according to [6], wherein the content of the p-phenylenediamine residue is 90 mol% or more of the total amount of the diamine residue.

[0020] [8] A polyamic acid composition comprising the polyamic acid described in any one of [1] to [7] above and an organic solvent.

[0021] [9] The polyamic acid composition according to [8], further comprising one or more compounds selected from the group consisting of tertiary amines, phosphorus-containing compounds, and phenolic compounds.

[0022]

[10] The polyamic acid composition according to [9], wherein the amount of one or more compounds selected from the group consisting of tertiary amines, phosphorus-containing compounds, and phenolic compounds is 0.001 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the polyamic acid.

[0023]

[11] A polyimide which is an imide of a polyamic acid according to any one of [1] to [7] above.

[0024]

[12] The polyimide according to

[11] , wherein the 1% weight loss temperature is 550°C or higher and the 5% weight loss temperature is 590°C or higher.

[0025]

[13] A polyimide film containing the polyimide described in

[11] or

[12] above.

[0026]

[14] The polyimide film according to

[13] , wherein the transmittance of light with a wavelength of 450 nm is 70% or more.

[0027]

[15] A laminate having a support and the polyimide film described in

[13] or

[14] .

[0028]

[16] A method for manufacturing a laminate having a support and a polyimide film, comprising: applying a polyamic acid composition according to any one of [8] to

[10] onto a support to form a coating film containing the polyamic acid; and heating the coating film to imide the polyamic acid.

[0029]

[17] An electronic device having a polyimide film as described in

[13] or

[14] above, and an electronic element disposed on the polyimide film.

[0030] According to the present invention, it is possible to provide a polyimide that exhibits excellent adhesion to inorganic materials while enhancing transparency, and a polyamic acid as its precursor. Furthermore, according to the present invention, it is also possible to provide a product or component that requires transparency, manufactured using the polyimide and polyamic acid.

[0031] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. Furthermore, all academic and patent documents cited herein are incorporated herein by reference.

[0032] First, the terms used in the present specification will be explained. The "structural unit" refers to a repeating unit constituting a polymer. "Polyamic acid" is a polymer comprising a structural unit represented by the following general formula (3) (hereinafter may be referred to as "structural unit (3)").

[0033]

[0034] In the general formula (3), A １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from tetracarboxylic dianhydride), and A ２ represents a diamine residue (a divalent organic group derived from diamine).

[0035] The content of the structural unit (3) relative to all structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, still more preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0036] The "1% weight loss temperature" is a measurement temperature obtained when the weight of polyimide at a measurement temperature of 150°C is used as the reference (100% by weight), and the weight is reduced by 1% by weight relative to the reference weight. The "5% weight loss temperature" is a measurement temperature obtained when the weight of polyimide at a measurement temperature of 150°C is used as the reference (100% by weight), and the weight is reduced by 5% by weight relative to the reference weight. The measurement methods for the 1% weight loss temperature and the 5% weight loss temperature are both the same methods as those in the examples described later or equivalent methods thereto.

[0037] The "phenolic compound" refers to a compound having a benzene ring in which a part of hydrogen atoms are substituted with hydroxyl groups.

[0038] Hereinafter, the term "based" added after a compound name may collectively refer to the compound and its derivatives. Unless otherwise specified, when a polymer name is expressed by adding "based" after a compound name, it means that the repeating units of the polymer are derived from the compound or a derivative thereof. In addition, tetracarboxylic dianhydride may be referred to as "diacid anhydride". Unless otherwise specified, the components, functional groups and the like exemplified in the present specification may be used alone or in combination of two or more kinds.

[0039] <Preferred Embodiment of the Present Invention> The polyamic acid according to the present embodiment (hereinafter sometimes referred to as "specific polyamic acid") has tetracarboxylic dianhydride residues and diamine residues.

[0040] In the specific polyamic acid, the diamine residues include a divalent organic group represented by the following general formula (1) and a divalent organic group represented by the following general formula (2). In other words, the specific polyamic acid contains, as diamine residues, a divalent organic group represented by the following general formula (1) and a divalent organic group represented by the following general formula (2).

[0041]

[0042] In the general formula (1), R １ and R ２ each independently represent a trifluoromethoxy group, a pentafluoroethoxy group or a heptafluoropropoxy group; a represents an integer of 1 to 4; b represents an integer of 0 to 4; when a represents an integer of 2 to 4, a plurality of R １ may be the same as or different from each other; when b represents an integer of 2 to 4, a plurality of R ２ may be the same as or different from each other; m represents an integer of 0 to 3. Note that in general formula (1), a and b may be the same as or different from each other. In addition, in the general formula (2), R ３ and R ４ each independently represent a divalent hydrocarbon group, and n represents an integer of 1 to 5.

[0043] Hereinafter, a divalent organic group represented by general formula (1) may be referred to as "residue (1)". Similarly, a divalent organic group represented by general formula (2) may be referred to as "residue (2)".

[0044] Polyimides produced using specific polyamic acids exhibit enhanced transparency while maintaining excellent adhesion to inorganic materials. The reason for this is presumed to be as follows:

[0045] The specific polyamic acid contains a residue (1) with a fluorine atom. Therefore, the formation of CT complexes is suppressed in polyimides produced using this specific polyamic acid. Consequently, polyimides produced using this specific polyamic acid exhibit excellent transparency.

[0046] Furthermore, because the specific polyamic acid contains a residue (2) having an Si-O-Si bond, the polyimide produced using this specific polyamic acid exhibits excellent adhesion to inorganic materials.

[0047] To obtain a polyimide with higher transparency and superior adhesion to inorganic materials, R in general formula (1) １ and R ２ It is preferable that represents a trifluoromethoxy group. In order to obtain a polyimide with improved transparency and superior adhesion to inorganic materials, it is preferable that a in general formula (1) be 1 or 2, and more preferably 1. In order to obtain a polyimide with improved transparency and superior adhesion to inorganic materials, it is preferable that b in general formula (1) be an integer between 0 and 2, and more preferably 0 or 1.

[0048] In order to increase the solubility of a specific polyamic acid in an organic solvent while reducing the thermal expansion coefficient of the resulting polyimide, it is preferable that m in general formula (1) be 1 or 2, and more preferably 1.

[0049] In order to obtain a polyimide that is more transparent and has better adhesion to inorganic materials, the residue (1) is preferably one or more selected from the group consisting of a residue derived from 2,2'-bis(trifluoromethoxy)benzidine (hereinafter sometimes referred to as "TFMOB"), a residue derived from 3,3'-bis(trifluoromethoxy)benzidine, and a residue derived from 2,3'-bis(trifluoromethoxy)benzidine, with the TFMOB residue being more preferred.

[0050] In residue (1), the fluoroalkyl group is bonded to the aromatic ring via an oxygen atom. Therefore, even when polyimides produced using specific polyamic acids are exposed to high-temperature environments, hydrogen fluoride is less likely to be generated. Thus, polyimides produced using specific polyamic acids can suppress the generation of hydrogen fluoride during high-temperature processes.

[0051] To obtain a polyimide with superior adhesion to inorganic materials, R in general formula (2) ３ and R ４ In each case, an alkylene group having 1 to 5 carbon atoms is preferred, and an alkylene group having 2 to 4 carbon atoms is more preferred. Furthermore, in order to obtain a polyimide with superior adhesion to inorganic materials, n in general formula (2) is preferably an integer between 1 and 3, and more preferably 1.

[0052] To obtain a polyimide with particularly excellent adhesion to inorganic materials, residue (2) is preferably a residue of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter sometimes referred to as "PAM-E").

[0053] When synthesizing a specific polyamic acid, it is also possible to use a diamine monomer other than a diamine (another diamine) to form residue (1) and residue (2). Other diamines include, for example, p-phenylenediamine (hereinafter sometimes referred to as "PDA"), 4-aminophenyl-4-aminobenzoate, 9,9-bis(4-aminophenyl)fluorene, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, m-phenylenediamine, 4,4'-oxydianiline, 3,4'-oxydianiline, N,N'-bis(4-aminophenyl)terephthalamide, m-tolidine, o-tolidine, 4,4'-bis(4-aminophenoxy)biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexaneamine), and derivatives thereof, which may be used individually or in combination of two or more.

[0054] To obtain a polyimide with excellent heat resistance, PDA is preferred as the other diamine. In other words, to obtain a polyimide with excellent heat resistance, it is preferable that the specific polyamic acid has a PDA residue as a diamine residue.

[0055] To obtain a polyimide with superior heat resistance, the content of PDA residues is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more, relative to the total amount (100 mol%) of diamine residues constituting the specific polyamic acid.

[0056] To obtain a polyimide with improved transparency and superior adhesion to inorganic materials, the content of residue (1) is preferably 0.5 mol% to 10 mol%, more preferably 1 mol% to 10 mol%, even more preferably 1 mol% to 8 mol%, and even more preferably 1 mol% to 5 mol%, relative to the total amount of diamine residues constituting the specific polyamic acid (100 mol%).

[0057] In order to obtain a polyimide with improved transparency and superior adhesion to inorganic materials, the content of residue (2) is preferably 0.1 mol% to 2.0 mol%, more preferably 0.1 mol% to 1.0 mol%, and even more preferably 0.2 mol% to 0.8 mol%, relative to the total amount (100 mol%) of diamine residues constituting the specific polyamic acid.

[0058] In order to obtain a polyimide with improved heat resistance and transparency, as well as superior adhesion to inorganic materials, it is preferable that the total content of PDA residue, residue (1), and residue (2) be 80 mol% to 100 mol%, and more preferably 90 mol% to 100 mol%, relative to the total amount (100 mol%) of diamine residues constituting the specific polyamic acid.

[0059] Examples of acid dianhydrides that can be used when synthesizing specific polyamic acids include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter sometimes referred to as "s-BPDA"), spiro[11H-difluoro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetron (hereinafter sometimes referred to as "SFDA"), 4,4'-oxydiphthalic acid anhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, and 9,9-bis(3,4-dicarboxyphenyl) Examples include ruolene dianhydride, 3,4'-oxydiphthalic acid anhydride, pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, p-phenylenebis(trimellitate anhydride), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, and derivatives thereof, which may be used individually or in combination of two or more.

[0060] To obtain a polyimide with excellent heat resistance, s-BPDA is preferred as the acid dianhydride. In other words, to obtain a polyimide with excellent heat resistance, it is preferable that the specific polyamic acid has an s-BPDA residue as an acid dianhydride residue.

[0061] To obtain a polyimide with superior transparency, SFDA is preferred as the acid dianhydride. In other words, to obtain a polyimide with superior transparency, it is preferable that the specific polyamic acid has an SFDA residue as an acid dianhydride residue. The SFDA residue is a tetravalent organic group represented by the following chemical formula (4).

[0062]

[0063] To obtain a polyimide with superior heat resistance, the content of s-BPDA residues is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more, relative to the total amount (100 mol%) of tetracarboxylic dianhydride residues constituting the specific polyamic acid.

[0064] To obtain a polyimide with superior transparency, the content of SFDA residues is preferably 1 mol% to 10 mol%, and more preferably 3 mol% to 7 mol%, relative to the total amount (100 mol%) of tetracarboxylic dianhydride residues constituting the specific polyamic acid.

[0065] To obtain a polyimide with superior heat resistance and transparency, the total content of s-BPDA residues and SFDA residues is preferably 80 mol% to 100 mol%, and more preferably 90 mol% to 100 mol%, relative to the total amount (100 mol%) of tetracarboxylic dianhydride residues constituting the specific polyamic acid.

[0066] To obtain a polyimide with even greater transparency and superior adhesion to inorganic materials, the specific polyamic acid preferably satisfies condition 1 below, and more preferably satisfies condition 2 below. Furthermore, to obtain a polyimide with even greater heat resistance, superior adhesion to inorganic materials, and superior transparency, the specific polyamic acid preferably satisfies condition 3 below. Condition 1: The specific polyamic acid has a TFMOB residue as residue (1) and a PAM-E residue as residue (2). Condition 2: The specific polyamic acid satisfies condition 1 above, and the content of the TFMOB residue is 1 mol% or more and 10 mol% or less relative to the total amount of diamine residues constituting the specific polyamic acid (100 mol%), and the content of the PAM-E residue is 0.1 mol% or more and 1.0 mol% or less relative to the total amount of diamine residues constituting the specific polyamic acid (100 mol%). Condition 3: The specific polyamic acid satisfies condition 2 above, and has an s-BPDA residue and a PDA residue.

[0067] Specific polyamic acids can be synthesized by known general methods, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. An example of a specific synthesis method for specific polyamic acids is described below. First, in the first method, a diamine solution is prepared by dissolving or dispersing a diamine in an organic solvent in an inert gas atmosphere such as argon or nitrogen. Then, the tetracarboxylic dianhydride is added to the diamine solution after being dissolved or dispersed in an organic solvent in a slurry state, or in a solid state. Second, in the second method, a tetracarboxylic dianhydride solution is prepared by dissolving or dispersing a tetracarboxylic dianhydride in an organic solvent in an inert gas atmosphere such as argon or nitrogen. Then, the diamine is added to the tetracarboxylic dianhydride solution after being dissolved or dispersed in an organic solvent in a slurry state, or in a solid state. Note that when producing specific polyamic acids, the order of addition of monomers is not limited to the order shown in the above methods.

[0068] When synthesizing a specific polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired specific polyamic acid (a polymer of diamine and tetracarboxylic dianhydride) can be obtained by adjusting the amount of substance of the diamine (or the amount of each diamine if multiple diamines are used) and the amount of substance of the tetracarboxylic dianhydride (or the amount of each tetracarboxylic dianhydride if multiple tetracarboxylic dianhydrides are used). The mole fraction of each residue in the specific polyamic acid is, for example, the same as the mole fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the specific polyamic acid. Furthermore, by blending two types of polyamic acids, it is also possible to obtain a specific polyamic acid containing multiple types of tetracarboxylic dianhydride residues and multiple types of diamine residues. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the synthesis reaction of the specific polyamic acid, are not particularly limited, but are, for example, in the range of 20°C to 150°C. The reaction time for the synthesis reaction of the specific polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0069] The organic solvent used in the synthesis of the specific polyamic acid is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the specific polyamic acid produced. Examples of organic solvents used in the synthesis of specific polyamic acids include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide-based solvents such as dimethyl sulfoxide; sulfone-based solvents such as diphenyl sulfone and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 3-methoxy-N,N-dimethylpropanamide (MPA), and hexamethylphosphate triamide; ester-based solvents such as γ-butyrolactone; alkyl halogenated solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents are usually used individually, but two or more may be used in appropriate combinations as needed. To enhance the solubility and reactivity of specific polyamic acids, the organic solvent used in the synthesis reaction of specific polyamic acids is preferably one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, with amide solvents (more specifically, DMF, DMAC, NMP, MPA, etc.) being more preferred. Furthermore, the synthesis reaction of specific polyamic acids is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0070] The weight-average molecular weight of the specific polyamic acid is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 500,000, and even more preferably in the range of 30,000 to 200,000, depending on its application. If the weight-average molecular weight is 10,000 or more, it becomes easy to form the specific polyamic acid, or the polyimide obtained using the specific polyamic acid, into a coated film or polyimide film. On the other hand, if the weight-average molecular weight is 1,000,000 or less, it exhibits sufficient solubility in the solvent, so a coated film or polyimide film with a smooth surface and uniform thickness can be obtained using the polyamic acid composition described later. The weight-average molecular weight used here refers to the polyethylene oxide equivalent value measured using gel permeation chromatography (GPC).

[0071] Furthermore, methods for controlling the molecular weight of specific polyamic acids include using an excess of either the acid dianhydride or the diamine, or quenching the reaction by reacting it with monofunctional acid anhydrides or amines such as phthalic anhydride or aniline. When polymerizing with an excess of either the acid dianhydride or the diamine, a polyimide film with sufficient strength can be obtained if the molar ratio of these components is between 0.95 and 1.05. The above molar ratio is the ratio of the total amount of diamine used in the synthesis of the specific polyamic acid to the total amount of acid dianhydride used in the synthesis of the specific polyamic acid (total amount of diamine / total amount of acid dianhydride). In addition, the coloration of the polyimide obtained using the specific polyamic acid can be further reduced by end-capturing with phthalic anhydride, maleic anhydride, aniline, etc.

[0072] The polyamic acid composition according to this embodiment contains a specific polyamic acid and an organic solvent. Examples of organic solvents that can be used in the synthesis reaction of the specific polyamic acid include those exemplified above. Preferably, one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents are used, with amide solvents (more specifically, DMF, DMAC, NMP, MPA, etc.) being more preferred. When the specific polyamic acid is obtained by the method described above, the reaction solution (the solution after the reaction) itself may be used as the polyamic acid composition according to this embodiment. Alternatively, the solid specific polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare the polyamic acid composition according to this embodiment. The content of the specific polyamic acid in the polyamic acid composition according to this embodiment is not particularly limited, but for example, it is 1% by weight or more and 80% by weight or less based on the total amount of the polyamic acid composition.

[0073] The polyamic acid composition according to this embodiment may further contain one or more compounds selected from the group consisting of tertiary amines, phosphorus-containing compounds, and phenolic compounds (hereinafter sometimes referred to as "specific additives"). In this specification, the specific additive is a compound different from the polyamic acid and the solvent. When the polyamic acid composition according to this embodiment contains a specific additive, sufficient molecular motion is imparted to the specific polyamic acid during imidation. As a result, the imidation of the specific polyamic acid proceeds rapidly, and the depolymerization of the specific polyamic acid is suppressed, further suppressing the generation of outgassing (especially hydrogen fluoride). Furthermore, when the polyamic acid composition according to this embodiment contains a specific additive, the imidation of the specific polyamic acid proceeds rapidly, making it easier to obtain a polyimide with superior adhesion to inorganic materials. In order to obtain a polyimide with superior adhesion to inorganic materials, it is preferable that the specific additive be one or more compounds selected from the group consisting of tertiary amines and phenolic compounds, and it is more preferable that the polyamic acid composition according to this embodiment contains both tertiary amines and phenolic compounds as specific additives.

[0074] To further enhance the molecular mobility of the specific polyamic acid during imidation, compounds with a molecular weight of 1500 or less are preferred as the specific additive. To further enhance the molecular mobility of the specific polyamic acid during imidation, compounds that dissolve in the organic solvent in the polyamic acid composition are preferred as the specific additive.

[0075] Furthermore, in order to further enhance the molecular mobility of the specific polyamic acid during imidation, the specific additive is preferably a compound with a boiling point of 150°C or higher, more preferably a compound with a boiling point of 200°C or higher, and even more preferably a compound with a boiling point of 250°C or higher. In order to further enhance the molecular mobility of the specific polyamic acid during imidation, the specific additive is preferably a compound that does not have a decomposition temperature within a temperature range below its boiling point. In order to further enhance the molecular mobility of the specific polyamic acid during imidation, it is preferable that the boiling point of the specific additive is higher than the boiling point of the organic solvent in the polyamic acid composition.

[0076] In order to further enhance the molecular mobility of the specific polyamic acid during imidation while suppressing the deterioration of polyimide properties due to the decomposition of the specific additive, the amount of the specific additive is preferably 0.001 parts by weight or more and 20 parts by weight or less, more preferably 0.01 parts by weight or more and 15 parts by weight or less, and even more preferably 0.02 parts by weight or more and 10 parts by weight or less, per 100 parts by weight of the specific polyamic acid.

[0077] The method of mixing the specific polyamic acid and the specific additive is not particularly limited, but from the viewpoint of ease of controlling the molecular weight of the specific polyamic acid, it is preferable to add the specific additive to the specific polyamic acid after polymerization. In this case, the specific additive may be added directly to the specific polyamic acid, or the specific additive may be dissolved in a solvent beforehand and this solution added to the specific polyamic acid; the method of addition is not particularly limited. The polyamic acid composition according to this embodiment may also be prepared by adding the specific additive to a solution containing the specific polyamic acid after polymerization (a solution after the reaction).

[0078] The tertiary amine used as a specific additive coordinates to the carboxyl group of the specific polyamic acid and therefore also functions as an imidation accelerator, as described later. By including 0.001 parts by weight or more of the tertiary amine per 100 parts by weight of the specific polyamic acid, it is possible to increase the strength and transparency of the resulting polyimide film while reducing its coefficient of thermal expansion. Examples of tertiary amines include alkylamine compounds such as triethylamine, diisopropylamine, dibutylamine, and N,N-dimethylbutylamine; and heterocyclic compounds such as pyridine, 3,5-lutidine, and imidazole compounds.

[0079] In particular, imidazole compounds readily coordinate to the carboxyl group of specific polyamic acids. Therefore, using an imidazole compound as a tertiary amine allows the imidation of the specific polyamic acid to proceed more rapidly. This reduces the likelihood of organic solvents such as NMP remaining in the polyimide film during thermal imidation, and simultaneously suppresses the decomposition of the specific polyamic acid, thus further improving the transparency of the resulting polyimide film.

[0080] In this specification, the term "imidazole compound" refers to a compound having a 1,3-diazole ring (1,3-diazole ring structure). The imidazole compounds that can be added to the polyamic acid composition according to this embodiment are not particularly limited, but examples include 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. Among these, 2-phenylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole are preferred, and 2-phenylimidazole, 1,2-dimethylimidazole, and 1-benzyl-2-methylimidazole are more preferred.

[0081] Examples of phosphorus-containing compounds include those represented by the following general formulas (5-1) to (5-10). In the following general formulas (5-1) to (5-10), R ５ , R ６ and R ７ Each of these independently represents a hydrogen atom, a monovalent organic group, or a polyvalent organic group, R ８ represents a polyvalent organic group, and x represents the degree of polymerization.

[0082]

[0083] Preferred examples of phosphorus-containing compounds include phosphate compounds, phosphite compounds, phosphonic acid compounds, phosphinic acid compounds, phosphine compounds, phosphine oxide compounds, phosphorane compounds, and phosphazene compounds. The phosphorus-containing compounds may be esters or condensates thereof of the compounds listed above, may contain cyclic structures, or may form salts with amines, etc. Furthermore, some of these phosphorus-containing compounds, such as phosphite compounds and phosphonic acid compounds, are tautomers, but they may exist in either state.

[0084] Specific examples of phosphate compounds include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris(isopropylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl(2-ethylhexyl) phosphate, di(isopropylphenyl)phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dimelamine phosphate, bisphenol A bis(diphenyl phosphate), tris(β-chloropropyl) phosphate, and the like.

[0085] Specific examples of phosphite compounds include triphenyl phosphite, trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, triisobutyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, tris(tridecyl) phosphite, diphenyl phosphite, diethyl phosphite, dibutyl phosphite, dimethyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, trilauryl trithiophosphite, diethylhydrogen phosphite, and bis(2-ethylhexyl) phosphite. Examples include hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite, tetraphenyl dipropylene glycol diphosphite, bis(decyl)pentaerythritol diphosphite, bis(tridecyl)pentaerythritol diphosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, triisodecyl phosphite, and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0086] Examples of the above-mentioned condensates include condensed phosphate esters. Specific examples of condensed phosphate esters include trialkyl polyphosphates, resorcinol polyphenyl phosphates, resorcinol poly(di-2,6-xylyl) phosphates, and hydroquinone poly(2,6-xylyl) phosphates. Examples of commercially available condensed phosphate esters include "CR-733S," "CR-741," and "PX-200" from Daihachi Chemical Industry Co., Ltd., and "FP-600" from ADEKA Corporation.

[0087] Specific examples of phosphazene compounds include phenoxycyclophosphazene (FP-110, manufactured by Fushimi Pharmaceutical Co., Ltd.) and cyclic cyanophenoxyphosphazene (FP-300, manufactured by Fushimi Pharmaceutical Co., Ltd.).

[0088] Phenolic compounds function as antioxidants and also have the effect of suppressing the discoloration of polymers, making them suitable for applications where transparency is required. In this embodiment, it is desirable that the phenolic compound be in liquid form during imidation. From the viewpoint of suppressing the discoloration of the film, it is desirable that it remain present during imidation, so the boiling point of the phenolic compound is preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher, and it is desirable that it does not have a decomposition temperature below its boiling point.

[0089] Examples of phenolic compounds include hindered, semi-hindered, and less-hindered types. Specifically, these include dibutylhydroxytoluene, ethylenebis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate) (product name: Irganox245), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione (product name: AO-20), 4,4 ',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol) (product name: AO-30), 6,6'-di-tert-butyl-4,4'-butylidenedi-m-cresol (product name: AO-40), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name: AO-50), pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (product name: AO-60) , 2,2'-dimethyl-2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropane-1,1'-diyl=bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate] (product name: GA-80), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylmethyl)-2,4,6-trimethylbenzene (product name: AO-330), 1'-hydroxy(2,2'-ethylidenebis(4,6-bis( Examples include 1,1-dimethylpropyl)benzene))-1-yl (product name: Smirizer GS), 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl=acrylate (product name: Smirizer GM), and 2-tert-butyl-6-methyl-4-{3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin-6-yl)oxy]propyl}phenol (product name: Smirizer GP).To obtain a polyimide with superior adhesion to inorganic materials, it is preferable to use one or more phenolic compounds selected from the group consisting of GA-80, Smirizer GS, Smirizer GP, and Smirizer GM.

[0090] Phenolic compounds primarily function as primary antioxidants, scavenging peroxyl radicals and converting them to hydroperoxides, thereby suppressing the auto-oxidation of polymers. This effectively inhibits discoloration caused by polymer oxidation. Furthermore, combining them with phosphite esters, which act as secondary antioxidants converting hydroperoxides into stable alcohol compounds, can yield even greater synergistic effects. For example, using approximately 10 to 150 equivalents of phosphite esters in addition to a phenolic compound efficiently suppresses radical generation and reduces polymer discoloration.

[0091] To obtain a polyimide with superior adhesion to inorganic materials, the amount of the phenolic compound is preferably 0.001 parts by weight or more and 10 parts by weight or less, more preferably 0.01 parts by weight or more and 5 parts by weight or less, and even more preferably 0.02 parts by weight or more and 1 part by weight or less, per 100 parts by weight of the specific polyamic acid.

[0092] Furthermore, the polyamic acid composition according to this embodiment may contain an imidation accelerator and / or a dehydration catalyst to shorten the heating time and enhance the properties.

[0093] The above-mentioned imidation accelerator is not particularly limited, but tertiary amines can be used. Heterocyclic tertiary amines are preferred. Preferred specific examples of heterocyclic tertiary amines include pyridine, picoline, quinoline, isoquinoline, and imidazole compounds. Preferred specific examples of the above-mentioned dehydration catalysts include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0094] The amount of imidization accelerator added is preferably 0.5 to 5.0 molar equivalents relative to the amide group of the specific polyamic acid, more preferably 0.7 to 2.5 molar equivalents, and even more preferably 0.8 to 2.0 molar equivalents. The amount of dehydration catalyst added is preferably 0.5 to 10.0 molar equivalents relative to the amide group of the specific polyamic acid, more preferably 0.7 to 5.0 molar equivalents, and even more preferably 0.8 to 3.0 molar equivalents. In this specification, "amide group of specific polyamic acid" refers to the amide group produced by the polymerization reaction of a diamine and a tetracarboxylic dianhydride. When adding the imidization accelerator and / or dehydration catalyst to the polyamic acid composition, they may be added directly without dissolving them in an organic solvent, or they may be added after being dissolved in an organic solvent. In methods where the imidation accelerator and / or dehydration catalyst are added directly without dissolving them in an organic solvent, the reaction may proceed rapidly before the imidation accelerator and / or dehydration catalyst can diffuse, potentially leading to gel formation. Therefore, it is preferable to add a solution obtained by dissolving the imidation accelerator and / or dehydration catalyst in an organic solvent to the polyamic acid composition.

[0095] The polyamic acid composition according to this embodiment may contain various organic or inorganic low-molecular-weight compounds or high-molecular-weight compounds as additives other than the specified additives described above. Examples of additives other than the specified additives include antioxidants other than phenolic compounds, plasticizers, dyes, surfactants, leveling agents, silicones, microparticles, sensitizers, etc. The microparticles include organic microparticles made of polystyrene, polytetrafluoroethylene, etc., and inorganic microparticles made of colloidal silica, carbon, layered silicates, etc., which may have a porous or hollow structure. Furthermore, the function and form of the microparticles are not particularly limited; for example, they may be pigments, fillers, or fibrous particles.

[0096] To improve the heat resistance while maintaining the transparency of the resulting polyimide film, nanosilica particles may be used as the additive, and the specific polyamic acid and nanosilica particles may be compounded. From the viewpoint of further improving the transparency of the polyimide film, the average primary particle diameter of the nanosilica particles is preferably 200 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, and may also be 30 nm or less. On the other hand, from the viewpoint of ensuring dispersibility in the specific polyamic acid, the average primary particle diameter of the nanosilica particles is preferably 5 nm or more, and more preferably 10 nm or more. As a method for compounding the specific polyamic acid and nanosilica particles, known methods can be used, for example, a method using an organosilica sol in which nanosilica particles are dispersed in an organic solvent. As a method for compounding the specific polyamic acid and nanosilica particles using an organosilica sol, a method may be used in which the specific polyamic acid is synthesized and then mixed with the synthesized specific polyamic acid and the organosilica sol, but in order to disperse the nanosilica particles more highly in the specific polyamic acid, it is preferable to synthesize the specific polyamic acid in the organosilica sol.

[0097] Furthermore, to enhance the interaction with specific polyamic acids, nanosilica particles can be surface-treated with a surface treatment agent. Known surface treatment agents such as silane coupling agents can be used. Among silane coupling agents, alkoxysilane compounds having an amino group or a glycidyl group as a functional group are widely known and can be selected as appropriate. To further enhance the interaction with specific polyamic acids, an amino group-containing alkoxysilane is preferred as the silane coupling agent. Examples of amino group-containing alkoxysilanes include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 2-aminophenyltrimethoxysilane, and 3-aminophenyltrimethoxysilane, but from the viewpoint of raw material stability, 3-aminopropyltriethoxysilane is preferred. One method for surface treatment of nanosilica particles is to stir a mixture of a dispersion (organosilica sol) and a silane coupling agent under an ambient temperature of 20°C to 80°C. The stirring time is, for example, 1 hour to 10 hours. At this time, a catalyst or the like may be added to accelerate the reaction.

[0098] A nanosilica-polyamic acid composite, formed by compounding a specific polyamic acid with nanosilica particles, preferably contains nanosilica particles in an amount of 1 to 30 parts by weight, and more preferably 1 to 20 parts by weight, per 100 parts by weight of the specific polyamic acid. When the nanosilica particle content is 1 part by weight or more, the heat resistance of the nanosilica particle-containing polyimide can be improved and internal stress can be sufficiently reduced. When the nanosilica particle content is 30 parts by weight or less, adverse effects on the mechanical properties and transparency of the nanosilica particle-containing polyimide can be suppressed.

[0099] Furthermore, the polyamic acid composition according to this embodiment may contain a silane coupling agent to achieve appropriate adhesion to the support. While any known silane coupling agent can be used without particular limitation, compounds containing an amino group are particularly preferred from the viewpoint of reactivity with the specific polyamic acid.

[0100] The blending ratio of the silane coupling agent to 100 parts by weight of the specific polyamic acid is preferably 0.01 parts by weight or more and 0.50 parts by weight or less, more preferably 0.01 parts by weight or more and 0.10 parts by weight or less, and even more preferably 0.01 parts by weight or more and 0.05 parts by weight or less. By blending the silane coupling agent at a ratio of 0.01 parts by weight or more, the peeling inhibitory effect on the support is sufficiently exhibited, and by blending the silane coupling agent at a ratio of 0.50 parts by weight or less, the decrease in molecular weight of the specific polyamic acid is suppressed, thereby suppressing the embrittlement of the polyimide film.

[0101] The polyimide according to this embodiment is an imidized product of the specific polyamic acid described above. The polyimide according to this embodiment can be obtained by known methods, and the method of production is not particularly limited. Below, an example of a method for obtaining the polyimide according to this embodiment by imidizing the specific polyamic acid will be described. Imidization is carried out by dehydration and cyclization of the specific polyamic acid. This dehydration and cyclization can be carried out by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. Furthermore, the imidization from the specific polyamic acid to the polyimide can be any ratio of 1% to 100%. In other words, a specific polyamic acid that is partially imidized may be synthesized. In particular, when imidization is carried out by heating and increasing the temperature, the cyclization reaction from the specific polyamic acid to the polyimide and the hydrolysis of the specific polyamic acid proceed simultaneously, and the molecular weight of the resulting polyimide may be lower than the molecular weight of the specific polyamic acid. Therefore, from the viewpoint of improving mechanical properties, it is preferable to pre-imidize a portion of the specific polyamic acid in the polyamic acid composition before forming the polyimide film described later. In this specification, a polyamic acid that is partially imidized may also be referred to as "polyamic acid".

[0102] Dehydration and ring closure of the specific polyamic acid can be performed by heating the specific polyamic acid. The method of heating the specific polyamic acid is not particularly limited, but for example, the polyamic acid composition according to this embodiment described above can be applied to a support such as a glass substrate, a metal plate, or a PET film (polyethylene terephthalate film), and then the specific polyamic acid can be heat-treated at a temperature of 40°C to 500°C. This method yields a laminate according to this embodiment having a support and a polyimide film (more specifically, a polyimide film containing an imidized product of the specific polyamic acid) disposed on the support. Alternatively, the polyamic acid composition can be directly placed in a container that has been subjected to a release treatment such as a coating with a fluororesin, and the polyamic acid composition can be heated and dried under reduced pressure to perform dehydration and ring closure of the specific polyamic acid. Polyimide can be obtained by dehydration and ring closure of the specific polyamic acid using these methods. The heating time for each of the above processes varies depending on the amount of polyamic acid composition to be dehydrated and closed, as well as the heating temperature. However, it is generally preferable to set the heating time to a range of 1 minute to 300 minutes after the processing temperature reaches its maximum temperature.

[0103] The polyimide film according to this embodiment (more specifically, a polyimide film containing an imidized compound of a specific polyamic acid) is colorless and transparent, has low yellowness, and has a glass transition temperature (heat resistance) that can withstand the TFT manufacturing process, making it suitable as a transparent substrate material for flexible displays. The polyimide content (more specifically, an imidized compound of a specific polyamic acid) in the polyimide film according to this embodiment is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may be 100% by weight, based on the total amount of the polyimide film. Examples of components other than polyimide in the polyimide film include the additives mentioned above (more specifically, fine particles, etc.).

[0104] The electronic device according to this embodiment (more specifically, a flexible device, etc.) comprises a polyimide film according to this embodiment and electronic elements directly or indirectly disposed on the polyimide film. When manufacturing the electronic device according to this embodiment for use in a flexible display, first, an inorganic substrate such as glass is used as a support, and a polyimide film is formed on it. Then, an electronic device is formed on the support by arranging (forming) electronic elements such as TFTs on the polyimide film. The process of forming TFTs is generally carried out in a wide temperature range of 150°C to 650°C, but in order to actually achieve the desired performance, an oxide semiconductor layer or an a-Si layer is formed at 300°C or higher, and in some cases, the a-Si may be further crystallized with a laser or the like.

[0105] In this case, if the thermal decomposition temperature of the polyimide film is low, outgassing may occur during the formation of electronic elements, causing sublimation to adhere to the inside of the oven and leading to furnace contamination, or the inorganic film (such as the barrier film described later) or electronic elements formed on the polyimide film may peel off. Therefore, it is preferable that the 1% weight loss temperature and the 5% weight loss temperature of the polyimide be 500°C or higher and 550°C or higher, respectively. The upper limits for the 1% weight loss temperature and the 5% weight loss temperature of the polyimide are, for example, 600°C and 650°C, respectively. To explain in more detail, before TFT formation, an inorganic film such as a silicon oxide film (SiOx film) or a silicon nitride film (SiNx film) is formed on the polyimide film as a barrier film. In this case, if the heat resistance of the polyimide is low, if the imidation has not progressed completely, or if there is a large amount of residual solvent, the polyimide and the inorganic film may peel off in the high-temperature process after the inorganic film lamination due to volatile components such as polyimide decomposition gases. Therefore, it is desirable that the 1% weight loss temperature of the polyimide is 500°C or higher, and that the weight loss rate when the polyimide is kept isothermally within the range of 400°C to 450°C is less than 1%.

[0106] Furthermore, in order to obtain a polyimide with excellent heat resistance, it is preferable that the 1% weight loss temperature of the polyimide is 550°C or higher, and the 5% weight loss temperature of the polyimide is 590°C or higher. The 1% weight loss temperature and the 5% weight loss temperature can be adjusted, for example, by changing the content of residues having a rigid structure (more specifically, PDA residues, s-BPDA residues, etc.).

[0107] Furthermore, if the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, misalignment may occur during the formation of electronic elements. Therefore, the Tg of the polyimide is preferably 300°C or higher, more preferably 350°C or higher, even more preferably 400°C or higher, and even more preferably 420°C or higher. The upper limit of the polyimide's Tg is better the higher it is, for example, 470°C. In addition, since the coefficient of thermal expansion of glass substrates is generally smaller than that of resins, internal stress is generated between the glass substrate and the polyimide film. If the internal stress of the laminate of the glass substrate or electronic elements used as a support and the polyimide film is high, the laminate containing the polyimide film will expand during the high-temperature TFT formation process and then contract when cooled to room temperature, causing problems such as warping or breakage of the glass substrate and delamination of the polyimide film from the glass substrate. Therefore, in a laminate having a glass substrate (support) and a polyimide film (a laminate according to this embodiment), the internal stress between the polyimide film and the glass substrate is preferably -20 MPa to 40 MPa, more preferably -15 MPa to 30 MPa, even more preferably -10 MPa to 20 MPa, and even more preferably -10 MPa to 10 MPa. The method for measuring the internal stress is the same as or similar to the method used in the embodiments described later.

[0108] The polyimide according to this embodiment can be suitably used as a material for display substrates such as TFT substrates and touch panel substrates. When using polyimide for the above applications, as described above, an electronic device (more specifically, an electronic device in which electronic elements are formed on a polyimide film) is often formed on a support, and then the polyimide film is peeled off from the support. Alkali-free glass is suitably used as the material for the support.

[0109] Furthermore, after forming an inorganic film on the support, a polyimide film may be formed on the inorganic film. In other words, the laminate according to this embodiment may further include an inorganic film interposed between the support and the polyimide film (more specifically, a polyimide film containing an imidized compound of a specific polyamic acid). In this case, the polyimide film and the inorganic film may be in contact. As described above, the polyimide film containing an imidized compound of a specific polyamic acid has excellent adhesion to inorganic materials. Therefore, even if the polyimide film and the inorganic film are in contact, the interlayer adhesion can be improved. To obtain a laminate with even better adhesion to inorganic materials, it is preferable that the adhesion strength measured by the method described in the examples below is 0.04 N / cm or more.

[0110] Examples of the inorganic films mentioned above include inorganic oxide films such as silicon oxide films and aluminum oxide films; and inorganic nitride films such as silicon nitride films. To further improve adhesion with inorganic materials, inorganic oxide films are preferred as the inorganic film.

[0111] The thickness of the inorganic film is not particularly limited, but for example, it is between 100 nm and 1000 nm. Examples of methods for forming the inorganic film include sputtering and plasma chemical vapor deposition (plasma CVD). When using a silicon oxide film as the inorganic film, a film containing SiOx (where x is a real number between 1.3 and less than 2.0) is preferred. To further improve adhesion with the inorganic material, a silicon oxide film containing SiOx (where x is a real number between 1.3 and less than 2.0) at a content of 90% to 100% by weight of the total film amount (hereinafter sometimes simply referred to as "SiOx film") is preferred.

[0112] Next, an example of a method for manufacturing the laminate according to this embodiment will be described in detail. First, the polyamic acid composition according to this embodiment is applied (cast) onto a support directly or via an inorganic film to form a coated film-containing laminate having a coated film containing a specific polyamic acid and a support. Next, the coated film-containing laminate is heated under conditions such as a temperature of 40°C to 200°C. The heating time in this case is, for example, 3 minutes to 120 minutes. Note that a multi-stage heating process may be provided, such as heating the coated film-containing laminate at 50°C for 30 minutes and then at 100°C for 30 minutes. Next, in order to promote the imidization of the specific polyamic acid in the coated film, the coated film-containing laminate is heated under conditions such as a maximum temperature of 200°C to 500°C. The heating time in this case (heating time at the maximum temperature) is, for example, 1 minute to 300 minutes. In this case, it is preferable to gradually raise the temperature from a low temperature to the maximum temperature. The heating rate is preferably 2°C / min to 10°C / min, and more preferably 3°C / min to 10°C / min. The maximum temperature is preferably in the range of 250°C to 480°C. If the maximum temperature is 250°C or higher, imidation proceeds sufficiently, and if the maximum temperature is 480°C or lower, thermal degradation of the polyimide can be suppressed. The temperature may also be held at any temperature for any time before reaching the maximum temperature. The imidation reaction can be carried out in air, under reduced pressure, or in an inert gas such as nitrogen, but to achieve higher transparency, it is preferable to carry it out under reduced pressure or in an inert gas such as nitrogen. Known heating devices such as hot air ovens, infrared ovens, vacuum ovens, inert ovens, and hot plates can be used. Through these steps, the specific polyamic acid in the coated film is imidized, and a laminate having a support and a polyimide film (a film containing the imidized product of the specific polyamic acid) can be obtained (i.e., the laminate according to this embodiment).

[0113] A known method can be used to peel off the polyimide film from the resulting laminate. For example, it may be peeled off by hand, or it may be peeled off using mechanical devices such as drive rolls or robots. Furthermore, a method can be employed in which a release layer is provided between the support and the polyimide film, or a method can be employed in which a silicon oxide film is formed on a substrate having numerous grooves, a polyimide film is formed using the silicon oxide film as a base layer, and the polyimide film is peeled off by impregnating the substrate and the silicon oxide film with a silicon oxide etching solution. In addition, a method can be employed in which the polyimide film is separated by irradiation with laser light.

[0114] The transparency of a polyimide film can be evaluated by its total light transmittance (TT) according to JIS K7361-1:1997 and its haze according to JIS K7136-2000. When a polyimide film is used in an application requiring high transparency, the total light transmittance of the polyimide film is preferably 75% or higher, and more preferably 80% or higher. Furthermore, when a polyimide film is used in an application requiring high transparency, the haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, and may even be 0%. In applications requiring high transparency, the polyimide film is required to have high transmittance across the entire wavelength range, but polyimide films tend to absorb light on the short-wavelength side, and the film itself often becomes yellowish. In order to use a polyimide film in an application requiring high transparency, it is preferable that the coloration of the polyimide film is reduced. Specifically, for polyimide films to be used in applications requiring high transparency, the yellowness (YI) of the polyimide film is preferably 20 or less, more preferably 15 or less, and may even be 0. YI can be measured according to JIS K7373-2006. Polyimide films with reduced coloration and improved transparency are suitable for transparent substrates such as glass substitutes, and substrates on which sensors or camera modules are mounted on the back.

[0115] Furthermore, in applications where transparency is required, a high transmittance of blue light (light with a wavelength of around 470 nm) is particularly desirable from the viewpoint of color reproducibility, and practically speaking, a high transmittance of light with a wavelength of 450 nm (450 nm transmittance) is required. From the viewpoint of color reproducibility, the 450 nm transmittance of the polyimide film is preferably 70% or more, more preferably 71% or more, even more preferably 72% or more, and even more preferably 73% or more. The upper limit of the 450 nm transmittance of the polyimide film is not particularly limited and may be 100%.

[0116] Furthermore, there are two types of light extraction methods for flexible displays: the top emission method, which extracts light from the front side of the TFT, and the bottom emission method, which extracts light from the back side of the TFT. The top emission method has the advantage of being able to easily increase the aperture ratio and obtain high-definition image quality because the light is not blocked by the TFT, while the bottom emission method has the advantage of being easy to manufacture because the alignment of the TFT and the pixel electrode is easy. If the TFT is transparent, it is possible to improve the aperture ratio even in the bottom emission method, so the bottom emission method, which is easy to manufacture, tends to be adopted for large displays. The polyimide film according to this embodiment has a low YI and excellent heat resistance, so it can be applied to either of the above light extraction methods.

[0117] Furthermore, in a batch-type device manufacturing process in which a polyamic acid composition is applied to a support such as a glass substrate, heated to imide it, and then the polyimide film is peeled off after forming electronic elements, it is preferable that the adhesion between the support and the polyimide film is excellent. Here, adhesion refers to adhesion strength. In a manufacturing process in which electronic elements are formed on a polyimide film on a support and then the polyimide film on which the electronic elements are formed is peeled off the support, excellent adhesion between the polyimide film and the support allows for more accurate formation or mounting of the electronic elements. In a manufacturing process in which electronic elements are placed on a support via a polyimide film, from the viewpoint of improving productivity, the higher the peel strength between the support and the polyimide film, the better. Specifically, the peel strength is preferably 0.05 N / cm or higher, and more preferably 0.1 N / cm or higher.

[0118] In the manufacturing process described above, when peeling a polyimide film from a laminate having a support and a polyimide film, the polyimide film is often peeled from the support by laser irradiation. In this case, since it is necessary for the polyimide film to absorb the laser light, the cutoff wavelength of the polyimide film is required to be longer than the wavelength of the laser light used for peeling. Since a 308 nm wavelength XeCl excimer laser is often used for laser peeling, the cutoff wavelength of the polyimide film is preferably 312 nm or longer, and more preferably 330 nm or longer. On the other hand, if the cutoff wavelength is long, the polyimide film tends to become yellowish, so the cutoff wavelength of the polyimide film is preferably 390 nm or shorter. From the viewpoint of achieving both transparency (low yellowness) and processability for laser peeling, the cutoff wavelength of the polyimide film is preferably 320 nm or longer and 390 nm or shorter, and more preferably 330 nm or longer and 390 nm or shorter. In this specification, the cutoff wavelength refers to the wavelength at which the transmittance, as measured by an ultraviolet-visible spectrophotometer, becomes 0.1% or less.

[0119] The polyamic acid composition and polyimide according to this embodiment may be used as is in coating and molding processes for manufacturing products and components, or they may be used as materials for further coating or other treatments on molded products formed into a film. For use in coating or molding processes, the polyamic acid composition or polyimide may be dissolved or dispersed in an organic solvent as needed, and further, a photocurable component, a thermosetting component, a nonpolymerizable binder resin, and other components may be added as needed to prepare a composition containing a specific polyamic acid or polyimide.

[0120] Various inorganic thin films, such as metal oxide thin films or transparent electrodes, may be formed on the surface of the polyimide film according to this embodiment. The method for forming these inorganic thin films is not particularly limited and includes, for example, PVD methods such as sputtering, vacuum deposition, and ion plating, as well as CVD methods.

[0121] The polyimide film according to this embodiment is preferable for use in fields and products where these properties are beneficial, as it exhibits heat resistance, low thermal expansion, and transparency, as well as low internal stress generated when forming a laminate with a glass substrate and ensures adhesion with inorganic materials during high-temperature processes. For example, the polyimide film according to this embodiment is preferable for use in liquid crystal displays, image display devices such as organic EL and electronic paper, printed materials, color filters, flexible displays, optical films, 3D displays, touch panels, transparent conductive film substrates, solar cells, etc., and is even more preferable as a replacement material for parts where glass is currently used. In these applications, the thickness of the polyimide film is, for example, 1 μm to 200 μm, and preferably 5 μm to 100 μm. The thickness of the polyimide film can be measured using a laser hologaze.

[0122] Furthermore, the polyamic acid composition according to this embodiment can be suitably used in a method for manufacturing a polyimide film, which involves coating the polyamic acid composition onto a support, heating it to imide it, and then peeling the polyimide film from the support. The polyamic acid composition according to this embodiment can also be suitably used in a batch-type device manufacturing process, which involves coating the polyamic acid composition onto a support, heating it to imide it, forming electronic elements on the resulting polyimide film, and then peeling the polyimide film on which the electronic elements are formed from the support. Therefore, this embodiment also includes a method for manufacturing an electronic device that includes the steps of coating the polyamic acid composition onto a support, heating it to imide it, and forming electronic elements on the polyimide film formed on the support. Moreover, such a method for manufacturing an electronic device may further include the step of peeling the polyimide film on which the electronic elements are formed from the support.

[0123] The following describes embodiments of the present invention, but the scope of the present invention is not limited to the embodiments described below.

[0124] <Method for measuring physical properties> First, we will explain the method for measuring the physical properties of polyimide (polyimide film).

[0125] [450nm Transmittance] The transmittance of light at a wavelength of 450 nm (450nm transmittance) was measured for the polyimide films in each laminate obtained in the examples and comparative examples described later, using an ultraviolet-visible-near-infrared spectrophotometer (JASCO Corporation "V-650"). If the 450nm transmittance was 70% or higher, it was evaluated as having "excellent transparency." On the other hand, if the 450nm transmittance was less than 70%, it was evaluated as having "poor transparency."

[0126] [Internal Stress] Each polyamic acid composition prepared in the examples and comparative examples described later was applied to a Corning glass substrate (material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm), whose warpage had been measured in advance, using a spin coater. The laminate was heated in air at 120°C for 30 minutes, and then heated in a nitrogen atmosphere at 430°C for 30 minutes to obtain a laminate with a 10 μm thick polyimide film on the glass substrate. To eliminate the effect of water absorption by the polyimide film, the laminate was dried at 120°C for 10 minutes, and then the warpage of the laminate in a nitrogen atmosphere at 25°C was measured using a thin-film stress measuring device (FLX-2320-S, manufactured by KLA-Tencor). The internal stress generated between the glass substrate and the polyimide film was calculated from the warpage of the glass substrate before polyimide film formation and the warpage of the laminate using Stoney's formula.

[0127] [1% weight loss temperature (TD1) and 5% weight loss temperature (TD5)] Each polyimide film obtained in the examples and comparative examples described later (specifically, polyimide films sampled to a weight of 10 mg) was used as a sample for measurement. Using a differential thermogravimetric analyzer (Hitachi High-Tech Science Corporation's "TG / DTA7200"), the temperature was raised from 25°C to 650°C at a rate of 20°C / min under a nitrogen atmosphere. The sample weight at a measurement temperature of 150°C was used as the reference. The measurement temperature when the sample weight decreased by 1% by weight from this reference weight was defined as the 1% weight loss temperature (TD1), and the measurement temperature when the sample weight decreased by 5% by weight from the reference weight was defined as the 5% weight loss temperature (TD5).

[0128] [Adhesion Strength] A SiOx film (thickness: 600 nm) was laminated onto a Corning glass substrate (product name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) by plasma CVD. Then, the polyamic acid compositions prepared in the examples and comparative examples described later were applied to the SiOx film using a spin coater to obtain a laminate. The obtained laminate was heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 450°C for 10 minutes to obtain a measurement laminate in which the glass substrate, SiOx film, and polyimide film (thickness: 10 μm) were laminated in this order. In accordance with the ASTM D1876-01 standard, a 10 mm wide cut was made in the polyimide film of the obtained measurement laminate using a utility knife. Then, using a tensile testing machine (Strograph VES1D, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the average peel strength was measured when the polyimide film was peeled off by 50 mm under conditions of a temperature of 23°C and a relative humidity of 55%, a tensile speed of 50 mm / min, and a peel angle of 90°. The obtained value was defined as the adhesion strength. If the adhesion strength was 0.04 N / cm or higher, it was evaluated as having "excellent adhesion to inorganic materials." On the other hand, if the adhesion strength was less than 0.04 N / cm, it was evaluated as having "poor adhesion to inorganic materials."

[0129] <Preparation of Polyimide Films> The following describes the method for preparing polyimide films (laminated structures) in the examples and comparative examples. In the following, compounds and reagents are referred to by the following abbreviations. The preparation of the polyamic acid compositions used to prepare the polyimide films was carried out under a nitrogen atmosphere. NMP: N-methyl-2-pyrrolidone s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride SFDA: spiro[11H-difluoro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetron PDA: p-phenylenediamine TFMOB: 2,2'-bis(trifluoromethoxy)benzidine PAM-E: 1,3-bis(3-aminopropyl)tetramethyldisiloxane 2PhI: 2-phenylimidazole GA-80: 2,2'-dimethyl-2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropane-1,1'-diyl=bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate] (phenolic compound manufactured by Sumitomo Chemical Co., Ltd.)

[0130] [Example 1] 80.0 g of NMP and 29.071 g of s-BPDA were placed in a 300 mL glass separable flask equipped with a stirrer with a stainless steel stirring rod and a nitrogen inlet tube, and the contents of the flask were stirred for 2 hours at an atmosphere of 80°C. Next, 0.098 g of PAM-E was added to the contents of the flask, and the contents of the flask were stirred for 30 minutes at an atmosphere of 25°C. Next, 10.483 g of PDA, 0.348 g of TFMOB, and 80.0 g of NMP were added to the contents of the flask, and the contents of the flask were stirred for 3 hours at an atmosphere of 50°C. Next, 0.12 g of 2PhI and 0.02 g of GA-80 were added to the contents of the flask, and the mixture was stirred until homogeneous to obtain a polyamic acid composition. The obtained polyamic acid composition was coated onto a glass substrate (Corning Corporation, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater, heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 450°C for 10 minutes to obtain a laminate (laminated body of Example 1) having a 10 μm thick polyimide film on the glass substrate.

[0131] [Examples 2-13, Comparative Example 1 and Comparative Example 2] Laminates of Examples 2-13, Comparative Example 1 and Comparative Example 2 were obtained by the same method as in Example 1, except that the acidic dianhydride used and its charging ratio, the diamine used and its charging ratio, the amount of 2PhI and GA-80 added, and the thickness of the polyimide film were as shown in Table 1. In all of Examples 2-13, Comparative Example 1 and Comparative Example 2, the total amount of acidic dianhydride used when preparing the polyamic acid composition was the same as in Example 1.

[0132] Table 1 shows the acidic dianhydrides used and their charging ratios, the diamines used and their charging ratios, the amounts of 2PhI and GA-80 added, and the thickness of the polyimide film (PI film) for Examples 1 to 13, Comparative Example 1, and Comparative Example 2. In Table 1, "-" means that the component was not used. In Table 1, the values ​​in the "Acidic Dianhydride" column represent the content of each acidic dianhydride relative to the total amount of acidic dianhydrides used (100 mol%) (unit: mol%). In Table 1, the values ​​in the "Diamine" column represent the content of each diamine relative to the total amount of acidic dianhydrides used (100 mol%) (unit: mol%). The values ​​in the "Amount of 2PhI Added" and "Amount of GA-80 Added" columns are both amounts added per 100 parts by weight of polyamic acid (unit: parts by weight). Furthermore, in all of Examples 1 to 13, Comparative Example 1, and Comparative Example 2, the mole fraction of each residue of the polyamic acid in the prepared polyamic acid composition was consistent with the mole fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid.

[0133] Furthermore, Table 2 shows the internal stress, TD1, TD5, 450nm transmittance, and adhesion strength for Examples 1 to 13, Comparative Example 1, and Comparative Example 2.

[0134]

[0135]

[0136] As shown in Table 1, the polyamic acid in the polyamic acid compositions prepared in Examples 1 to 13 had residue (1) (TFMOB residue) and residue (2) (PAM-E residue).

[0137] As shown in Table 2, the transmittance at 450 nm was 70% or higher in Examples 1 to 13. Therefore, the polyimide films obtained in Examples 1 to 13 had excellent transparency. The adhesion strength in Examples 1 to 13 was 0.04 N / cm or higher. Therefore, the polyimide films obtained in Examples 1 to 13 had excellent adhesion to inorganic materials.

[0138] As shown in Table 1, the polyamic acid in the polyamic acid composition prepared in Comparative Example 1 did not have residue (1). The polyamic acid in the polyamic acid composition prepared in Comparative Example 2 did not have residue (2).

[0139] As shown in Table 2, in Comparative Example 1, the transmittance at 450 nm was less than 70%. Therefore, the polyimide film obtained in Comparative Example 1 did not have good transparency. In Comparative Example 2, the adhesion strength was less than 0.04 N / cm. Therefore, the polyimide film obtained in Comparative Example 2 did not have good adhesion to inorganic materials.

[0140] The results above demonstrate that the polyimide obtained from the polyamic acid composition according to the present invention exhibits excellent adhesion to inorganic materials while enhancing transparency.

Claims

1. A polyamic acid having a tetracarboxylic dianhydride residue and a diamine residue, wherein the diamine residue includes a divalent organic group represented by the following general formula (1) and a divalent organic group represented by the following general formula (2). (In the above general formula (1), R １ and R ２ Each independently represents a trifluoromethoxy group, a pentafluoroethoxy group, or a heptafluoropropoxy group, where a represents an integer between 1 and 4, b represents an integer between 0 and 4, and when a represents an integer between 2 and 4, multiple R １ The elements may be the same or different from each other, and if b represents an integer between 2 and 4, then there may be multiple R ２ The elements may be the same or different from each other, m represents an integer between 0 and 3, and in the general formula (2) above, R ３ and R ４ Each of these independently represents a divalent hydrocarbon group, and n represents an integer between 1 and 5 (inclusive).

2. The polyamic acid according to claim 1, wherein the content of the divalent organic group represented by the general formula (1) is 1 mol% or more and 10 mol% or less with respect to the total amount of the diamine residue.

3. The polyamic acid according to claim 1, wherein the content of the divalent organic group represented by the general formula (2) is 0.1 mol% or more and 1.0 mol% or less with respect to the total amount of the diamine residue.

4. The polyamic acid according to claim 1, wherein the tetracarboxylic dianhydride residue comprises a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue.

5. The polyamic acid according to claim 4, wherein the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residue is 90 mol% or more of the total amount of the tetracarboxylic dianhydride residue.

6. The polyamic acid according to claim 1, wherein the diamine residue further comprises a p-phenylenediamine residue.

7. The polyamic acid according to claim 6, wherein the content of the p-phenylenediamine residue is 90 mol% or more of the total amount of the diamine residue.

8. A polyamic acid composition containing the polyamic acid described in claim 1 and an organic solvent.

9. The polyamic acid composition according to claim 8, further comprising one or more compounds selected from the group consisting of tertiary amines, phosphorus-containing compounds, and phenolic compounds.

10. The polyamic acid composition according to claim 9, wherein the amount of one or more compounds selected from the group consisting of tertiary amines, phosphorus-containing compounds, and phenolic compounds is 0.001 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the polyamic acid.

11. A polyimide which is an imidide of a polyamic acid according to claim 1.

12. The polyimide according to claim 11, wherein the temperature at which a 1% weight loss occurs is 550°C or higher, and the temperature at which a 5% weight loss occurs is 590°C or higher.

13. A polyimide film comprising the polyimide described in claim 11.

14. The polyimide film according to claim 13, wherein the transmittance of light with a wavelength of 450 nm is 70% or more.

15. A laminate having a support and a polyimide film according to claim 13.

16. A method for producing a laminate having a support and a polyimide film, comprising: applying the polyamic acid composition described in claim 8 onto the support to form a coating film containing the polyamic acid; and heating the coating film to imide the polyamic acid.

17. An electronic device having a polyimide film according to claim 13 and an electronic element disposed on the polyimide film.

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