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

Abstract

To provide a polyimide which has reduced coloration, has excellent transparency and high heat resistance, and can suppress the generation of hydrogen fluoride during a high-temperature process and to provide a polyamide acid composition as a precursor thereof.SOLUTION: There is provided a polyimide acid composition comprising a polyamic acid, a plasticizer and a solvent, wherein the polyamide acid is an adduct of an acid dianhydride and a diamine compound, the polyamide acid contains 1 mol% or more of spiro[11H-difluoro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9 tetoron as an acid dihydride when the total amount of acid dianhydrides is defined as 100 mol% or more and contains 50 mol% or more of 2,2'-bis(trifluoromethyl)benzidine as a diamine compound when the total amount of diamine compounds is defined as 100 mol%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid composition, a polyimide, a polyimide film, a laminate, an electronic device, and a method for producing the polyimide film and the laminate. The present invention also relates to an electronic device material using the polyimide, a thin film transistor (TFT) substrate, a flexible display substrate, a color filter, a printed matter, an optical material, an image display device (more specifically, a liquid crystal display device, an organic electroluminescence (EL) display, an electronic paper, etc.), a 3D display, a solar cell, a touch panel, a transparent conductive film substrate, and a substitute material for components currently using glass. [Background technology]

[0002] Rapid advances in electronic devices, such as displays (LCDs, OLEDs, electronic paper, etc.), solar cells, and touch panels, have led to devices becoming thinner, lighter, and more flexible. In these devices, polyimide is being used as the substrate material instead of glass.

[0003] These devices require various electronic elements, such as thin-film transistors and transparent electrodes, to be formed on the substrate, and high-temperature processes are required to form these electronic elements. Polyimide has sufficient heat resistance to be applicable to high-temperature processes, and its coefficient of thermal expansion (CTE) is close to that of glass substrates and electronic elements, making it less susceptible to internal stress and suitable for use as a substrate material for flexible displays and other applications.

[0004] Aromatic polyimides are generally colored yellowish-brown due to intramolecular conjugation and the formation of charge-transfer (CT) complexes, but in top-emission organic electroluminescence (OLED) and other displays, where light is extracted from the opposite side of the substrate, transparency is not required for the substrate, and conventional aromatic polyimides have been used. However, in cases where light emitted from the display element is emitted through the substrate, such as in transparent displays, bottom-emission organic electroluminescence (OLED) and LCD displays, or when sensors or camera modules are placed on the back of the substrate to make smartphones and other devices full-screen (notchless), high optical properties (more specifically, transparency, etc.) are now required for the substrate as well.

[0005] In light of this, there is a demand for materials that have heat resistance equivalent to that of existing aromatic polyimides, but that are less colored and have excellent transparency.

[0006] To reduce the coloration of polyimides, there are known techniques for suppressing the formation of CT complexes using aliphatic monomers (Patent Documents 1 and 2), and a technique for increasing transparency using monomers containing fluorine atoms or sulfur atoms (Patent Document 3).

[0007] The polyimides described in Patent Documents 1 and 2 have high transparency and low CTE, but because they have an aliphatic structure, they have a low thermal decomposition temperature, making them difficult to apply to high-temperature processes when forming electronic devices. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-29177 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-41530 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-70139 [Patent Document 4] WO2019―195148 Summary of the Invention [Problem to be solved by the invention]

[0009] The polyimides described in Patent Documents 3 and 4 have excellent transparency due to the inclusion of fluorine atoms, but the inventors' investigations have revealed that hydrogen fluoride is generated during high-temperature processes (specifically, heat treatment at 350°C or higher). The generation of hydrogen fluoride can cause poor adhesion between the polyimide and barrier films, etc., and can also cause corrosion of electronic elements provided on the polyimide film.

[0010] The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a polyimide and a polyamic acid composition as its precursor that exhibit reduced coloration, excellent transparency, high heat resistance, and suppresses the generation of hydrogen fluoride during high-temperature processes. Another aim is to provide a product or component that requires heat resistance and transparency and is manufactured using the polyimide and polyamic acid composition. In particular, the present invention aims to provide a product or component in which the polyimide film of the present invention is formed on the surface of an inorganic material such as glass, metal, metal oxide, or single-crystal silicon. [Means for solving the problem]

[0011] As a result of extensive research, the present inventors have found that a polyimide obtained from a composition containing a specific polyamic acid and a plasticizer exhibits reduced coloration, excellent transparency, and high heat resistance, and is capable of suppressing the generation of hydrogen fluoride during high-temperature processes, thereby completing the present invention.

[0012] The polyamic acid composition of the present invention contains a polyamic acid, a plasticizer, and a solvent. The polyamic acid is an adduct of an acid dianhydride and a diamine compound, and is characterized in that, when the total acid dianhydride is taken as 100 mol % or more, the polyamic acid composition contains 1 mol % or more of spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9tetrone as the acid dianhydride, and when the total diamine compounds is taken as 100 mol %, the polyamic acid composition contains 50 mol % or more of 2,2-bis(trifluoromethyl)benzidine as the diamine compound.

[0013] The polyamic acid composition according to the present invention preferably contains one or more acid dianhydrides selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic 2,3:6,7-dianhydride, from the viewpoints of improving Tg (glass transition temperature), improving mechanical strength, and reducing internal stress.

[0014] In the polyamic acid composition according to the present invention, when the total acid dianhydride content is 100 mol % or more, it is preferable from the viewpoint of transparency that the acid dianhydride content be 1 mol % or more and 50 mol % or less of spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9tetrone.

[0015] In the polyamic acid composition according to the present invention, the amount of the plasticizer added is preferably 20 parts by weight or less per 100 parts by weight of the polyamic acid, from the viewpoint of imparting molecular mobility and avoiding the effects of decomposition of the plasticizer itself.

[0016] In the polyamic acid composition according to the present invention, the plasticizer is preferably at least one selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters, from the viewpoints of availability and plasticizing effect.

[0017] In the polyamic acid composition according to the present invention, the solvent is preferably an aprotic solvent.

[0018] The polyimide according to the present invention is an imidized product of the polyamic acid contained in the polyamic acid composition according to the present invention.

[0019] The polyimide according to the present invention is heated in a helium gas flow from an ambient temperature of 60°C to an ambient temperature of 470°C at a heating rate of 10°C / min, and the gas generated from the polyimide is analyzed using a quadrupole mass spectrometer to obtain a mass spectrum at m / z=20. In the mass spectrum, the peak intensity at 470°C is preferably divided by the peak intensity at 470°C of a polyimide obtained from a polyamic acid containing no plasticizer, and the value is preferably 0.8 or less.

[0020] The polyimide film according to the present invention contains the polyimide according to the present invention.

[0021] The polyimide film according to the present invention having a thickness of 10 μm preferably has a transmittance of 30% or more at 400 nm.

[0022] The haze of the polyimide film according to the present invention when the film thickness is 10 μm is preferably 1.0% or less.

[0023] The laminate according to the present invention has a support and the polyimide film according to the present invention.

[0024] The method for producing a laminate according to the present invention comprises applying the polyamic acid composition according to the present invention onto a support to form a coating film containing a polyamic acid and a plasticizer, and then heating the coating film to imidize the polyamic acid.

[0025] The method for producing a polyimide film according to the present invention comprises applying the polyamic acid composition according to the present invention onto a support to form a coating film containing the polyamic acid and the plasticizer, heating the coating film, and peeling off the formed coating film.

[0026] An electronic device according to the present invention comprises the polyimide film according to the present invention and an electronic element disposed on the polyimide film. [Effects of the Invention]

[0027] The polyimide produced using the polyamic acid composition of the present invention exhibits reduced coloration, excellent transparency and heat resistance, and can suppress the generation of hydrogen fluoride during high-temperature processes. Therefore, the polyimide produced using the polyamic acid composition of the present invention is suitable as a material for electronic devices that require low coloration, transparency, and heat resistance and are manufactured through high-temperature processes. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a graph showing the detection intensity of m / z=20 obtained by analyzing the polyimides according to Example 4 and Comparative Example 5 with a quadrupole mass spectrometer when heated to 470° C. DETAILED DESCRIPTION OF THE INVENTION

[0029] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited to these.

[0030] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. In this specification, not only polyamic acid but also polyamic acid esters (polyamic acid alkyl esters, polyamic acid aryl esters, etc.) are referred to as "polyamic acid."

[0031] "m / z" is a measurement value that can be read from the horizontal axis of a mass spectrum, which is the measurement result of mass spectrometry. It is "a dimensionless quantity obtained by dividing the mass of an ion by the unified atomic mass unit (Dalton), and then dividing that quantity by the absolute value of the charge on the ion."

[0032] The term "plasticizer" refers to a material that exists in a liquid state during imidization of polyamic acid and has a plasticizing effect, and is preferably a compound with a boiling point higher than that of the solvent used.

[0033] Hereinafter, the compound name may be followed by "system" to refer to the compound and its derivatives collectively. When the compound name is followed by "system" to refer to the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic dianhydrides may be referred to as "acid dianhydrides."

[0034] The polyamic acid composition of the present invention contains a polyamic acid, a plasticizer, and a solvent. The polyamic acid is an adduct of an acid dianhydride and a diamine compound, and when the total acid dianhydride is taken as 100 mol % or more, the polyamic acid composition contains 1 mol % or more of spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9tetrone (hereinafter sometimes abbreviated as SFAD) as the acid dianhydride. When the total diamine compounds are taken as 100 mol %, the polyamic acid composition contains 50 mol % or more of 2,2-bis(trifluoromethyl)benzidine (hereinafter sometimes abbreviated as TFMB) as the diamine compound.

[0035] SFDA has a bulky fluorene structure in the side chain, which suppresses aggregation between molecules and suppresses the formation of intermolecular CT, giving it high transparency. Furthermore, the formation of a xanthene structure through ether bonds gives it higher linearity and lower CTE than the similarly structured 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.

[0036] TFMB has a rigid structure and exhibits high Tg, low CTE, low internal stress, and excellent mechanical strength. Furthermore, the trifluoromethyl group reduces coloration and provides high transparency.

[0037] The polyamic acid according to the present embodiment may contain an acid dianhydride other than SFDA in order to improve the balance of properties other than transparency (specifically, CTE, internal stress, Tg, etc.).

[0038] Specifically, pyromellitic dianhydride (hereinafter sometimes abbreviated as PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as BPDA), 2,3,6,7-naphthalenetetracarboxylic 2,3:6,7-dianhydride (hereinafter sometimes abbreviated as NTCDA), 1,4-phenylenebis(trimellitate dianhydride), 1,2,5,6-naphthalenetetracarboxylic 1,2:5,6-dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenoxy) Examples of suitable dianhydrides include 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 2'-oxodispiro[bicyclo[2.2.1]heptane-2,1'-cycloheptane-3,2'-bicyclo[2.2.1]heptane]-5,5'-6,6'-tetracarboxylic dianhydride, and acid dianhydrides derived from analogs thereof, and these may be used alone or in combination.

[0039] Among these, PMDA, BPDA and NTCDA are preferable from the viewpoints of heat resistance, improvement of Tg, improvement of mechanical strength and reduction of internal stress.

[0040] From the viewpoints of improving transparency, heat resistance, and Tg, as well as reducing internal stress, the total amount of PMDA, BPDA, NTCDA, and SFDA is preferably 60 mol% or more, more preferably 70 mol%, and even more preferably 80 mol% or more, when the total amount of the dianhydrides constituting the polyamic acid is taken as 100 mol%, and may be 100 mol%.

[0041] In particular, when the total acid dianhydride constituting the polyamic acid is taken as 100 mol%, from the viewpoint of transparency, the SFDA is preferably 1 mol% to 50 mol% or less, more preferably 5 mol% to 45 mol%, and from the viewpoint of reducing internal stress, it is even more preferably 5 mol% to 45 mol%, and particularly preferably 10 mol% to 40 mol%.

[0042] Because PMDA, BPDA, and NTCDA exhibit extremely low CTE and high Tg when combined with rigid diamines, the combined content of PMDA, BPDA, and NTCDA is preferably 30 mol% or more when the total acid dianhydrides constituting the polyamic acid are taken as 100 mol%. From the perspective of the balance between transparency and internal stress, the content is preferably 50 mol% to 99 mol%, more preferably 60 mol% to 95 mol%, and even more preferably 65 mol% to 90 mol%. By keeping the content within the above ranges, a well-balanced physical property of transparency, CTE, and Tg can be obtained.

[0043] In addition, diamine components other than TFMB may be contained within the range that does not impair transparency or other performances. For example, 1,4-diaminocyclohexane, 1,4-phenylenediamine, 1,3-phenylenediamine, 4-aminophenyl-4-aminobenzoate, 9,9-bis(4-aminophenyl)fluorene, 4,4'-oxydianiline, 3,4'-oxydianiline, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'- Examples of suitable amines include diaminodiphenylsulfone, m-tolidine, o-tolidine, 4,4'-bis(aminophenoxy)biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexanamine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and analogs thereof. These may be used alone or in combination. Among these, 1,4-phenylenediamine and 9,9-bis(4-aminophenyl)fluorene are preferred from the viewpoint of improving heat resistance and Tg. 4,4'-oxydianiline and 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether are preferred for improving mechanical properties, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane and analogs thereof are preferred for improving adhesion.

[0044] From the viewpoints of improving transparency, heat resistance, and Tg, as well as reducing internal stress, when the total diamines constituting the polyamic acid is taken as 100 mol %, the content of TFMB is preferably 50 mol % or more, more preferably 70 mol %, and even more preferably 80 mol % or more, and may even be 100 mol %.

[0045] The polyamic acid of the present invention can be synthesized by a known general method, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. Specifically, for example, in an inert atmosphere such as argon or nitrogen, the diamine is dissolved in an organic solvent or dispersed in a slurry form to prepare a diamine solution. Meanwhile, the tetracarboxylic dianhydride may be added to the diamine solution after being dissolved in an organic solvent or dispersed in a slurry form, or in a solid state.

[0046] When synthesizing polyamic acid using a diamine and a tetracarboxylic dianhydride, the total molar amount of the diamine or diamines and the total molar amount of the tetracarboxylic dianhydride can be adjusted to obtain a desired polyamic acid copolymer. Alternatively, blending two polyamic acids can produce a polyamic acid containing multiple tetracarboxylic dianhydrides and diamines. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the polyamic acid synthesis reaction, are not particularly limited, but may be in the range of 25°C to 150°C as needed, and the reaction time may be set arbitrarily within the range of 10 minutes to 30 hours.

[0047] The organic solvent used for the polymerization of polyamic acid must be capable of dissolving at least a portion of the tetracarboxylic dianhydride and diamines used, and is preferably capable of dissolving the polyamic acid to be produced, and more preferably is an aprotic solvent. Examples of organic solvents used in the synthesis reaction of the polyamic acid include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide or sulfone-based solvents such as dimethyl sulfoxide, 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 hexamethylphosphoric triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based 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 alone, but two or more may be used in combination as needed. To enhance the solubility and reactivity of polyamic acid, the organic solvent used in the synthesis reaction of the polyamic acid is preferably selected from amide solvents, ketone solvents, ester solvents, and ether solvents, with aprotic amide solvents such as DMF, DMAC, NMP, and MPA being particularly preferred. Furthermore, an inert atmosphere such as argon or nitrogen is preferred during the reaction.

[0048] The weight-average molecular weight of the polyamic acid according to the present invention is preferably in the range of 10,000 to 1,000,000, more preferably 20,000 to 500,000, and even more preferably 30,000 to 200,000. Furthermore, when applying a polyamic acid solution to a substrate using a slit coater or the like to form a film, it is important from the viewpoint of productivity that the viscosity and solids concentration of the polyamic acid solution be within the optimal range. By achieving these ranges, a polyamic acid solution or polyimide solution with optimal viscosity and solids concentration can be obtained. A weight-average molecular weight of 10,000 or greater allows the polyamic acid and polyimide to be formed into a coating or film. On the other hand, a weight-average molecular weight of 1,000,000 or less exhibits sufficient solubility in solvents, resulting in a coating or film with a smooth surface and uniform thickness from the polyamic acid solution and polyimide solution described below. The molecular weight used here refers to the value calculated as polyethylene glycol by gel permeation chromatography (GPC).

[0049] Alternatively, molecular weight can be controlled by using an excess of either the acid dianhydride or the diamine, or by quenching the reaction by reacting with a monofunctional acid anhydride or amine 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 as long as the molar ratio of the acid dianhydride charged divided by the molar ratio of the diamine charged is between 0.95 and 1.05.

[0050] Next, we discuss the effect of the plasticizer in this invention. In principle, transparent polyimide films can be obtained by designing a polyimide with a large HOMO / LUMO band gap. Therefore, TFMB, with its low electron donating properties, is effective for achieving transparent polyimide films. However, the diamine's low nucleophilicity slows the reaction rate, which is expected to slow the imidization rate. In our study, we compared the imidization rates of a typical colored polyimide made from BPDA and 1,4-phenylenediamine with those of transparent polyimides made from PMDA or BPDA and TFMB. The colored polyimide was over 90% imidized at 300°C and nearly 100% imidized at 350°C, whereas the transparent polyimide made with TFMB was only 75% imidized at 300°C and only about 80% imidized at 350°C, demonstrating a clear difference in imidization rate.

[0051] The driving force during the dehydration ring closure of polyamic acid to polyimide by thermal imidization is largely due to the molecular motion caused by heat and the plasticizing effect of the solvent, so to achieve complete imidization, it is desirable to treat at a higher temperature or above the glass transition temperature of the polyimide. However, the glass transition temperature of the combination of rigid acid dianhydrides such as PMDA and TFMB exceeds 400°C, and depending on the monomer combination, the glass transition temperature may be higher than the heat treatment temperature during film formation.

[0052] Under the conditions described above, imidization may not proceed completely, and furthermore, recombination after depolymerization during thermal imidization may not occur sufficiently. As a result, during the display manufacturing process (e.g., dehydrogenation of TFT elements), moisture may be generated due to the progress of imidization, decomposition of polyamic acid may occur, and outgassing may occur due to the generation of low-molecular-weight components, which may result in peeling of the barrier film or adverse effects on the TFT elements.

[0053] The plasticizer according to the present invention imparts sufficient mobility during thermal imidization, inhibits depolymerization of polyamic acid, and reduces the amount of residual solvent, thereby reducing the amount of outgassing during high-temperature processes such as TFT processes.

[0054] The plasticizer of the present invention is preferably soluble in the solvent used in the polymerization of polyamic acid and remains liquid during imidization. It is also necessary that the plasticizer does not volatilize at low temperatures to provide sufficient mobility during imidization. Therefore, the boiling point of the plasticizer of the present invention is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 150°C or higher, and it is desirable that the decomposition temperature does not fall below the boiling point.

[0055] The amount of plasticizer added varies depending on the compatibility between the plasticizer and polyamic acid and the desired physical properties. From the viewpoint of imparting molecular mobility and avoiding the effects of decomposition of the plasticizer itself, the amount of plasticizer added is preferably 0.001 to 20 parts by weight, more preferably 0.01 to 15 parts by weight, and even more preferably 0.1 to 10 parts by weight, per 100 parts by weight of polyamic acid.

[0056] The plasticizer of the present invention not only improves molecular motion during dehydration ring closure of polyamic acid to polyimide, but also can impart functions such as adjusting the glass transition temperature and providing flame retardancy and antioxidant properties, and known plasticizers can be used. Examples of the plasticizer include phosphorus-based compounds (phosphorus-containing compounds), polyalkylene glycols such as polyethylene glycol and polypropylene glycol, aliphatic tribasic acid esters such as citrate esters, aliphatic dibasic acid esters such as adipate esters, phthalates, trimellitates, polyesters, and epoxy-based plasticizers, and low-molecular-weight organic compounds and thermoplastic resins may also be used.

[0057] Among these, one or more selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters are preferred from the viewpoints of availability and plasticizing effect. The phosphorus-based compounds used in the present invention are not particularly limited, but it is preferable to use phosphoric acids, phosphorous acids, phosphonic acids, phosphinic acids, phosphines, phosphine oxides, phosphoranes, phosphazenes, etc. These phosphorus-based compounds may be in the form of esters or condensates thereof, may contain a cyclic structure, or may form salts with amines, etc. Furthermore, some of these phosphorus-based compounds are in a tautomeric relationship, such as phosphorous acids and phosphonic acids, and may exist in either form.

[0058] Specific examples of phosphorus-based phosphates include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris(isopropylphenyl) phosphate, tris(phenylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl(2-ethylhexyl) phosphate, di(isopropylphenyl) phosphate, (phenyl)phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dimelamine phosphate, melamine pyrophosphate, triphenylphosphine oxide, tricresyl phosphine oxide, diphenyl methanephosphonate, diethyl phenylphosphonate, resorcinol bis(diphenyl) bis(triphenyl phosphate), bisphenol A bis(diphenyl phosphate), phosphaphenanthrene, tris(β-chloropropyl)phosphate, 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, di Phenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, trilauryl trithiophosphite, diethyl hydrogen phosphite, bis(2-ethylhexyl) hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite, tetraphenyl dipropylene glycol diphosphite, tetra(C12 to C15 alkyl)-4,4-isopropylidene diphenyl diphosphite, 4,Examples include 4-butylidenebis(3-methyl-6-t-butylphenyl ditridecyl phosphite), bis(decyl)pentaerythritol diphosphite, bis(tridecyl)pentaerythritol diphosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, and tris(2,4-di-tert-butylphenyl)phosphite.

[0059] Examples of condensates include trialkyl polyphosphate, resorcinol polyphenyl phosphate, resorcinol poly(di-2,6-xylyl) phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., trade name PX-200), hydroquinone poly(2,6-xylyl) phosphate, resorcinol polyphenyl phosphate (trade name CR-733S), bisphenol A polycresyl phosphate (trade name CR-741), aromatic condensed phosphate ester (trade name CR747), resorcinol polyphenyl phosphate, bisphenol A polycresyl phosphate (trade names FP-600, FP-700), etc. These phosphorus-based compounds can be used singly or in combination.

[0060] Examples of phosphazenes include phenoxycyclophosphazene (trade name: FP-110, manufactured by Fushimi Pharmaceutical Co., Ltd.) and cyclic cyanophenoxyphosphazene (trade name: FP-300, manufactured by Fushimi Pharmaceutical Co., Ltd.).

[0061] If the molecular weight of polyethylene glycol or polypropylene glycol is high, its compatibility with polyamic acid and polyimide is low, and there is a risk of phase separation being induced during thermal imidization, resulting in whitening of the film. Therefore, the number average degree of polymerization is preferably 200 or more and 10,000 or less, more preferably 300 or more and 6,000 or less, and even more preferably 400 or more and 4,000 or less.

[0062] Specific examples of aliphatic dibasic acid esters include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisonyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl]adipate, bis(2-ethylhexyl)azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, and diethyl succinate.

[0063] Furthermore, low-molecular-weight organic compounds and thermoplastic resins may be used as long as they exhibit a plasticizing effect. The low-molecular-weight organic compounds in the present invention generally have a molecular weight of about 1,000 or less, and examples thereof include phthalimides such as phthalimide, N-phenylphthalimide, N-glycidylphthalimide, N-hydroxyphthalimide, and cyclohexylthiophthalimide, and maleimides such as N,Np-phenylenebismaleimide and 2,2-(ethylenedioxy)bis(ethylmaleimide). Examples of thermoplastic resins include polyimides and polyamides having an asymmetric structure.

[0064] As described above, the polyamic acid composition according to this embodiment contains a plasticizer, which provides sufficient molecular motion during imidization, ensuring complete imidization and suppressing depolymerization of the polyamic acid. This reduces outgassing during high-temperature processes, and the molecular mobility imparted to the resin facilitates solvent removal, reducing the amount of residual solvent in the film, potentially reducing discoloration and outgassing of the film itself. Therefore, the polyamic acid composition according to this embodiment can, for example, inhibit corrosion of the barrier film formed on the polyimide film and the glass supporting substrate during the manufacturing process of a flexible display, thereby improving the reliability (resistance to failure) of the flexible display. The plasticizer may remain in the polyimide film, or it may be decomposed and removed from the polyimide film during the imidization process.

[0065] The polyimide of the present invention can be obtained by known methods, and its production method is not particularly limited. Due to the availability of monomers and ease of polymerization, the polyimide of the present invention is preferably obtained from its precursor, polyamic acid. A method for imidizing the polyamic acid to obtain a polyimide using polyamic acid will be described below. Imidation is performed by dehydration ring-closing the polyamic acid. This dehydration ring-closing can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. Furthermore, the imidization ratio of polyamic acid to polyimide can be any ratio between 1 and 100%. In other words, a partially imidized polyamic acid may be synthesized. In particular, when imidization is performed by heating, the ring-closing reaction from polyamic acid to polyimide and the hydrolysis of polyamic acid proceed simultaneously, which may result in a polyimide with a lower molecular weight than the polyamic acid itself, or coloration due to oxidation of terminal diamines generated by hydrolysis. Therefore, a partially imidized polyamic acid solution is preferred from the viewpoint of transparency and mechanical properties.

[0066] In this specification, a solution containing polyamic acid and an organic solvent is referred to as a polyamic acid solution. The organic solvent contained in the polyamic acid solution can be the same as the organic solvent used in the synthesis reaction of the polyamic acid. Among these, an organic solvent selected from amide solvents, ketone solvents, ester solvents, and ether solvents is more preferably used, and aprotic amide solvents such as DMF, DMAC, and NMP are particularly preferably used. When polyamic acid is obtained by the above-described method, the synthesis reaction solution itself may also be referred to as a polyamic acid solution.

[0067] The dehydration ring closure can be carried out by heating the polyamic acid. The method for heating the polyamic acid is not particularly limited. For example, a polyamic acid solution can be cast or coated onto a support such as a glass plate, a metal plate, or PET (polyethylene terephthalate), followed by heat treatment at a temperature ranging from 80°C to 500°C. Alternatively, the polyamic acid solution can be directly placed in a container that has been treated with a release agent such as a fluorine-based resin coating, and the polyamic acid solution can be heated and dried under reduced pressure to carry out the dehydration ring closure of the polyamic acid. Polyimide can be obtained by this method of dehydration ring closure of the polyamic acid. The heating time for each of the above treatments varies depending on the amount of the polyamic acid solution to be dehydrated and the heating temperature, but is generally preferably carried out within a range of 1 minute to 5 hours after the treatment temperature reaches its maximum. To shorten the heating time or to enhance properties, an imidizing agent and / or a dehydration catalyst can be added to the polyamic acid solution, and the polyamic acid solution containing the imidizing agent and / or the dehydration catalyst can be heated by the above method to effect imidization.

[0068] The imidizing agent is not particularly limited, but a tertiary amine can be used. A heterocyclic tertiary amine is more preferred as the tertiary amine. Specific preferred examples of the heterocyclic tertiary amine include pyridine, picoline, isoquinoline, and 1,2-dimethylimidazole. Specific preferred examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0069] The amounts of the imidizing agent and dehydration catalyst added are preferably 0.5 to 5.0 molar equivalents, more preferably 0.7 to 2.5 molar equivalents, and particularly preferably 0.8 to 2.0 molar equivalents, relative to the amide groups of the polyamic acid. Furthermore, the dehydration catalyst is preferably 0.5 to 10.0 molar equivalents, more preferably 0.7 to 5.0 molar equivalents, and particularly preferably 0.8 to 3.0 molar equivalents, relative to the amide groups of the polyamic acid. The imidizing agent and / or dehydration catalyst may be added directly to the polyamic acid solution without dissolving in an organic solvent, or may be added after dissolving in an organic solvent. Direct addition without dissolving in an organic solvent may result in the reaction proceeding too rapidly before the imidizing agent and / or dehydration catalyst diffuse, resulting in the formation of a gel. It is more preferable to dissolve the imidizing agent and / or dehydration catalyst in an organic solvent and mix the resulting solution with the polyamic acid solution.

[0070] As described above, the polyimide film produced from the polyamic acid according to the present embodiment is colorless, transparent, and has low yellowness, and has Tg and heat resistance that can withstand the TFT fabrication process, and is therefore suitable for use in transparent substrates of flexible displays.

[0071] When manufacturing a flexible display, a flexible substrate is formed on an inorganic film such as glass as a support, and electronic elements such as TFTs are then formed on top of that (flexible device). The process of forming TFTs is generally carried out over a wide temperature range of 150°C to 650°C, but to actually achieve the desired performance, oxide semiconductors or a-Si are formed at temperatures above 300°C, and in some cases the a-Si is further crystallized using a laser or other means to form LTPS (Low Temperature Polysilicone).

[0072] In this case, if the thermal decomposition temperature of the polyimide film is low, outgassing occurs during device formation, and the sublimated material adheres to the inside of the oven, causing contamination inside the furnace and possibly peeling off of the inorganic film or device formed on the polyimide film. Therefore, the 1% weight loss temperature of the polyimide film is preferably 500°C or higher, and the higher the temperature, the better.

[0073] More specifically, before TFT fabrication, SiOx, SiNx, or the like is formed on the polyimide film as a barrier film. If the polyimide has low heat resistance, if imidization is not complete, if a large amount of low-molecular-weight components are generated by depolymerization, or if there is a large amount of residual solvent, peeling can occur at the interface between the polyimide and the barrier film due to volatile components such as polyimide decomposition gases during high-temperature processes after laminating the inorganic film, such as the dehydrogenation process of LTPS.

[0074] In particular, when fluorine-containing monomers such as TFMB are used, hydrogen fluoride is generated during high-temperature processes, corroding the barrier film and TFT, reducing the reliability of the display, and causing the polyimide film itself to yellow, making it insufficient for applications requiring transparency.

[0075] The detection intensity obtained from mass spectrometry can be used as an indicator of the amount of hydrogen fluoride gas generated when an imidized polyamic acid (polyimide according to the present embodiment) is used in a high-temperature process. Specifically, the polyimide is first heated in a helium gas flow from an ambient temperature of 60°C at a heating rate of 10°C / min until the ambient temperature reaches 470°C. The gas generated from the polyimide is analyzed using a quadrupole mass spectrometer. The detection intensity of the m / z=20 peak (hereinafter sometimes referred to as the "20 peak intensity"), which is presumed to be due to hydrogen fluoride, is then read from the resulting mass spectrum (specifically, a mass spectrum showing the results of analyzing the components of the gas generated from the polyimide when the ambient temperature reaches 470°C). The 20 peak intensity tends to increase as the amount of hydrogen fluoride generated increases. The flow rate of helium gas used in the quadrupole mass spectrometer analysis may be set so that the gas generated from the polyimide can be analyzed in real time by the quadrupole mass spectrometer. For example, the flow rate is in the range of 50 mL / min to 150 mL / min, and preferably in the range of 80 mL / min to 120 mL / min. In the present example, the flow rate was 100 mL / min.

[0076] As a result of our investigations, we found that imidization in the presence of a plasticizer reduces the amount of residual solvent in the film and significantly reduces the amount of outgassing. In particular, when TFMB is used as a monomer, imidization in the presence of a plasticizer suppresses the amount of hydrogen fluoride gas generated when the resulting polyimide is used in a high-temperature process (Figure 1).

[0077] As a result of investigations by the present inventors, it was found that when a laminate consisting of a fluorine-containing polyimide film formed on a glass substrate and a barrier film formed thereon is heat-treated as in Reference Examples 1 and 2 shown in the Examples section, there is a very high correlation between the adhesion between the barrier film and the polyimide film and the coloration of the polyimide film, and the 20 peak intensity.

[0078] When a laminate of glass and a polyimide film was heated at 470°C with a 1 μm SiOx film formed on it by plasma CVD, the laminate using a polyimide film obtained from a polyamic acid containing a plasticizer did not peel off and the coloring of the polyimide film itself was suppressed (Reference Example 1).On the other hand, the laminate using a polyimide film obtained from a polyamic acid containing no plasticizer corroded the SiOx after heating, causing peeling over the entire surface and discoloring of the polyimide film itself (Reference Example 2).

[0079] 20 peak intensity at 470℃ (I 470The smaller the value of (2), the less hydrogen fluoride is generated. Even when polyamic acids have the same resin composition, the inclusion of a plasticizer reduces the 20-peak intensity, thereby suppressing the amount of hydrogen fluoride generated. Specifically, the 20-peak intensity at 470°C of a polyimide obtained from a polyamic acid containing a plasticizer is divided by the 20-peak intensity at 470°C of a polyimide obtained from a polyamic acid containing no plasticizer, and this value is defined as the 20-peak intensity reduction ratio. This value is preferably 0.8 or less, more preferably 0.6 or less, and even more preferably 0.4 or less. Within the above range, the effect of the plasticizer in suppressing hydrogen fluoride generation can be determined to be sufficient. Therefore, poor adhesion between the polyimide film and the barrier film can be suppressed, suppressing corrosion of electronic devices, making the film suitable for use as a substrate for electronic devices such as TFTs.

[0080] Furthermore, as a result of the inventors' investigations, it was found that a laminate consisting of a polyimide film and an inorganic film or glass lowers the temperature at which hydrogen fluoride begins to be generated and increases the amount of hydrogen fluoride generated compared to a single-layer structure consisting of a polyimide film. This is presumably because the laminate prevents components containing radicals generated by heat from volatilizing, accelerating the autoxidation cycle of the polyimide.

[0081] Although it depends on the device fabrication process, in addition to a 1% weight loss temperature of 500°C or higher, low outgassing is required when maintained isothermally at 400-500°C. Specifically, after forming an inorganic film such as SiOx on a polyimide film, it is desirable that there be no peeling between the polyimide film and the inorganic film when maintained at 400°C for one hour. Since the higher the processing temperature, the better the performance of TFTs, so it is more desirable that there be no peeling at 430°C, and even more desirable that there be no peeling at 470°C.

[0082] Furthermore, if the Tg is significantly lower than the process temperature, misalignment or other issues may occur during element formation. Therefore, the Tg of the polyimide film used as a flexible substrate is preferably 300°C or higher, more preferably 350°C or higher, and even more preferably 400°C or higher. Furthermore, if the internal stress generated in the glass substrate used as a support, electronic elements, and polyimide film is high, problems such as warping or breakage of the glass substrate and peeling of the flexible substrate from the glass substrate may occur when the polyimide film expands during the high-temperature TFT process and then contracts upon cooling to room temperature. Generally, the thermal expansion coefficient of the glass substrate is smaller than that of resin, so internal stress is generated between the polyimide film and the flexible substrate. Therefore, the internal stress generated between the polyimide film and the glass substrate is preferably 50 MPa or lower, more preferably 40 MPa or lower, and most preferably 30 MPa or lower.

[0083] The polyimide of the present invention can be suitably used as a display substrate material, such as a TFT substrate or a touch panel substrate. When used in the above applications, a manufacturing method is often used in which a laminate of a support and polyimide is manufactured, electronic elements are formed thereon, and finally the polyimide layer is peeled off. Furthermore, alkali-free glass is suitably used as the support. Below, we will specifically describe a manufacturing method for a laminate of polyimide and a support, and a manufacturing method for polyimide via the laminate. These are examples of manufacturing methods for polyimide, and the methods are not limited to the following.

[0084] First, the polyamic acid solution is cast onto a support, and the laminate of the support and polyamic acid is preferably heated at a temperature of 40 to 200°C for 3 to 120 minutes. Alternatively, drying may be performed in two stages, for example, at 50°C for 30 minutes and then at 100°C for 30 minutes. Next, to promote imidization, the laminate of the support and polyamic acid is heated at a temperature of 200 to 470°C for 3 to 300 minutes to obtain a laminate of the support and polyimide. The temperature is preferably gradually increased from a low temperature to a maximum temperature. The rate of temperature increase is preferably 2°C / min to 10°C / min, more preferably 4°C / min to 10°C / min. The maximum temperature is preferably in the range of 250 to 470°C. A maximum temperature of 250°C or higher allows for sufficient imidization, while a maximum temperature of 450°C or lower can suppress thermal degradation and discoloration of the polyimide. The temperature may be maintained at any desired temperature for any desired time before reaching the maximum temperature. The heating atmosphere can be air, reduced pressure, or an inert gas such as nitrogen, but to achieve higher transparency, it is preferable to perform the heating under reduced pressure or an inert gas such as nitrogen. Furthermore, known heating devices such as hot air ovens, infrared ovens, vacuum ovens, inert ovens, and hot plates can be used. Furthermore, to shorten the heating time and improve the properties, an imidizing agent or a dehydration catalyst can be added to the polyamic acid solution, and the solution can be heated and imidized by the method described above. In other words, a laminate of a partially or completely imidized polyamic acid and a support can also be obtained by the same method.

[0085] The polyimide layer can be peeled from the resulting laminate of the support and polyimide by any known method. For example, the peeling may be performed by hand, or by using a mechanical device such as a drive roll or a robot. Furthermore, a method of providing a peeling layer between the substrate and the polyimide layer, or a method of forming a silicon oxide film on a substrate having a large number of grooves and infiltrating an etching solution to peel the film can also be used. Separation by irradiation with laser light can also be used.

[0086] If there is any lift at the interface between the polyimide and the supporting substrate (e.g., glass), the laminate may peel off during processing, resulting in reduced yields. The lift at the interface between the supporting substrate and the polyimide is influenced by the desorbed components and residual solvents generated during imidization. Highly oriented polyimides, such as BPDA / PDA, have densely packed molecular chains, which make them less gas-escapeable and prone to lifting. Our research has shown that lifting can be prevented by introducing bulky or soft structures into the molecular chain or at the end. Among these, SFDA has a highly linear structure but a bulky side chain, which allows it to achieve both good gas-escape properties and a high glass transition temperature.

[0087] For the purposes of the present invention, polyimides are required to have high transmittance across the entire wavelength range, particularly blue (470 nm) transmittance, and for practical purposes, transmittance at 400 nm is important. The transmittance of polyimides can be determined at each wavelength using ultraviolet-visible spectroscopy. Specifically, the transmittance at 400 nm is preferably 30% or higher, more preferably 40% or higher, and may be even higher. Furthermore, polyimides tend to absorb light at short wavelengths, often resulting in a yellow coloration of the film itself. The yellow index (YI) can be calculated as an index of yellowness using the formula described in JIS K 7373. The YI is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. By imparting transparency in this way, polyimide films can be used as transparent substrates for applications such as replacing glass. Even when sensors or camera modules are installed on the backside of the substrate, the impact on the resolution and color reproducibility of the sensors or camera modules can be minimized.

[0088] The transparency of polyimide can be evaluated by total light transmittance (TT) and haze according to JIS K7361 and JIS K7163. When a polyimide film is used in the applications of the present invention, the total light transmittance of the polyimide is preferably 75% or more, more preferably 80% or more. The haze is preferably 1.5% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

[0089] There are two types of light extraction methods for flexible displays: top-emission, in which light is extracted from the TFT element side, and bottom-emission, in which light is extracted from the back side of the TFT element. The top-emission method is characterized by its ease of increasing the aperture ratio and achieving high-definition image quality because light is not blocked by the TFT element, while the bottom-emission method is characterized by its ease of alignment and ease of manufacturing. If the TFT element 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. Materials with excellent transmittance, transparency, and heat resistance, such as those of the present invention, can be used in both of the above applications.

[0090] Furthermore, in a batch-type device fabrication process in which a polyamic acid solution is applied to a support such as glass, heated to imidize it, and then electronic elements or the like are formed on the polyimide to form a substrate, followed by peeling, good adhesion between the support and the polyimide is preferred. Here, "adhesion" refers to adhesion strength. In this fabrication process, electronic elements or the like are formed on a polyimide film on the support to form a substrate, and then the polyimide substrate on which the electronic elements or the like are formed is peeled from the support. Excellent adhesion to the support allows for more accurate formation or mounting of electronic elements or the like. From the perspective of the fabrication process in which electronic elements or the like are laminated on the support, the higher the peel strength, the better. Specifically, a peel strength of 0.05 N / cm or more is preferred, and 0.1 N / cm or more is even more preferred.

[0091] In the manufacturing process described above, when peeling a polyimide layer from a laminate of a support and polyimide, it is often peeled from the support by laser irradiation. From the viewpoint of the peeling processability, it is necessary for the polyimide to absorb light of the laser wavelength. An excimer laser is often used for laser peeling, and since it is necessary to absorb light of the laser wavelength, the cut-off wavelength is preferably 312 nm or more, more preferably 330 nm or more. Furthermore, since a cut-off wavelength of 390 nm or less can exhibit sufficient transparency, the cut-off wavelength is preferably 320 nm or more and 390 nm or less, more preferably 330 nm or more and 380 nm or less. In this specification, the cut-off wavelength means the wavelength at which the transmittance is 0.1% or less as measured by an ultraviolet-visible spectrophotometer.

[0092] The polyamic acid and polyimide according to the present invention may be directly subjected to coating or molding processes for producing products or components, or may be used as a laminate for further coating or other treatment of a film-shaped product. To be subjected to the coating or molding process, the polyamic acid and polyimide may be dissolved or dispersed in an organic solvent as needed, and further blended with a photo- or thermosetting component, a non-polymerizable binder resin other than the polyamic acid and polyimide according to the present invention, and other components to prepare a polyamic acid and polyimide resin composition.

[0093] In order to impart processing properties and various functionalities to the polyamic acid and polyimide according to the present invention, various organic or inorganic low-molecular-weight or high-molecular-weight compounds may be blended. For example, dyes, surfactants, antioxidants, leveling agents, silicones, fine particles, sensitizers, etc. may be used. Examples of fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, and inorganic fine particles such as colloidal silica, carbon, and layered silicates, which may have a porous or hollow structure. Furthermore, the function or form of the fine particles may be pigments, fillers, fibers, etc.

[0094] Imidazoles can be added to the polyamic acid of the present invention as additives for imparting the aforementioned functionality. In this specification, imidazoles refer to compounds containing a 1,3-diazole ring structure. The imidazoles added to the polyamic acid of the present invention 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. 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole are preferred, with 1,2-dimethylimidazole and 1-benzyl-2-methylimidazole being more preferred.

[0095] The content of imidazoles is preferably 0.005 to 0.1 mol per mole of amide group in polyamic acid, more preferably 0.01 to 0.08 mol, and even more preferably 0.015 to 0.050 mol. A content of 0.005 mol or more is effective in improving the film strength and transparency of the polyimide, while a content of 0.1 mol or less maintains the storage stability of the polyamic acid and improves its Tg and heat resistance. Regarding the improvement in transparency, polymerization solvents such as NMP are known to form complexes with the carboxylic acid of polyamic acid through hydrogen bonding. If the imidization rate is slow, NMP or other solvents may remain in the film and cause discoloration through oxidation or decomposition. Addition of imidazoles coordinates with the carboxylic acid of polyamic acid, promoting imidization. This reduces the likelihood of NMP or other solvents remaining in the film, while also suppressing the decomposition of polyamic acid during the thermal imidization process, which is thought to improve transparency. In this specification, the term "amide group of polyamic acid" refers to an amide group formed by a polyaddition reaction between a diamine and a tetracarboxylic dianhydride.

[0096] The method for adding the imidazole to the polyamic acid is not particularly limited. From the viewpoint of controlling the molecular weight of the polyamic acid, a method of mixing the imidazole with the polyamic acid is preferred. In this case, the imidazole may be added directly to the polyamic acid, or the imidazole may be dissolved in a solvent in advance and the solution may be added, and the method is not particularly limited.

[0097] An antioxidant can be added to the polyamic acid of the present invention to impart the effect of suppressing coloration. The antioxidant in the present invention is preferably dissolved in the solvent used for polymerization of the polyamic acid and exists in a liquid state during imidization. Since it is desirable for the antioxidant to remain during imidization in order to suppress coloration of the film, the boiling point of the antioxidant is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 150°C or higher, and it is desirable for the antioxidant to have a decomposition temperature below the boiling point.

[0098] The antioxidant to be added to the polyamic acid of the present invention is not particularly limited, and examples thereof include dibutylhydroxytoluene, ethylene bis(oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate (trade name: Irganox245), 1,3,5-tris(3,5-ditert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione (trade name: AO-20), 4,4,4-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol), and the like. ol) (trade name: AO-30), 6,6-ditert-butyl-4,4-butylidenedi-m-cresol (trade name: AO-40), octadecyl-3-(3,5-ditert-butyl-4-hydroxyphenyl)propionate (trade name: AO-50), pentaerythritol tetrakis(3-(3,5-ditert-butyl-4-hydroxyphenyl)propionate) (trade name: AO-60), 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2 ,4,8,10-Tetraoxaspiro(5,5)undecane (trade name: GA-80), 1,3,5-tris(3,5-ditert-butyl-4-hydroxyphenylmethyl)-2,4,6-trimethylbenzene (trade name: AO-330), 1-hydroxy(2,2-ethylidenebis(4,6-bis(1,1-dimethylpropyl)benzene))-1-yl acrylate (trade name: Sumilizer GS), 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate (trade name: Sumilizer Examples of suitable antioxidants include phenolic antioxidants such as Sumilizer GM, and 2-tert-butyl-6-methyl-4-(3-((2,4,8,10-tetra-tert-butyldibenzo(d,f)(1,3,2)dioxaphosphepin-6-yl)oxy)propyl)phenol (trade name: Sumilizer GP). Of these, polyamic acid and amide solvents may generate nitrides and oxides as decomposition products, so GA-80, Sumilizer GS, Sumilizer GP, and Sumilizer GM are preferred from the standpoint of resistance to these gases and suppression of discoloration of the phenolic compounds themselves.

[0099] Phenolic compounds function as primary antioxidants, primarily capturing peroxy radicals and converting them to hydroperoxides, thereby inhibiting the autoxidation of polymers, thereby suppressing discoloration caused by polymer oxidation. Furthermore, combining them with phosphites, which function as secondary antioxidants by converting hydroperoxides into stable alcohol compounds, can produce even greater synergistic effects. For example, using an equivalent to 10 equivalents of phosphites relative to the phenolic compound can efficiently suppress radical generation and prevent polymer discoloration.

[0100] In order to obtain sufficient plasticizing and antioxidant effects, the amount of the phenolic compound is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, and even more preferably 0.02 to 1 part by weight, based on 100 parts by weight of polyamic acid.

[0101] The polyamic acid of the present invention may contain a silane coupling agent to achieve appropriate adhesion to the support. Known silane coupling agents can be used without particular limitation, but compounds containing amino groups are particularly preferred in terms of reactivity with the polyamic acid. Examples include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 2-aminophenyltrimethoxysilane, and 3-aminophenyltrimethoxysilane. However, 3-aminopropyltriethoxysilane is preferred in terms of raw material stability.

[0102] The blending ratio of these silane coupling agents to 100 parts by weight of polyamic acid is preferably 0.01 to 0.50 parts by weight, more preferably 0.01 to 0.10 parts by weight, and even more preferably 0.01 to 0.05 parts by weight. By blending the silane coupling agent in a ratio of 0.01 part by weight or more, the effect of suppressing peeling from the support is sufficiently exhibited, and by blending it in a ratio of 0.50 parts by weight or less, the molecular weight of the polyamic acid is sufficiently maintained, so that problems such as embrittlement do not occur.

[0103] The polyimide film according to the present invention may have various inorganic thin films formed on its surface, such as metal oxides and transparent electrodes. The method for forming these inorganic thin films is not particularly limited, and examples thereof include CVD, sputtering, vacuum deposition, ion plating, and other PVD methods.

[0104] The polyimide according to the present invention has heat resistance, low thermal expansion, transparency, and also small internal stress between the polyimide and a glass substrate. Therefore, the polyimide is preferably used in fields and products where these properties are effective, such as printed matter, color filters, flexible displays, optical films, liquid crystal displays, image displays such as organic EL and electronic paper, 3-D displays, touch panels, transparent conductive film substrates, and solar cells, and is even more preferably used as a replacement material for parts where glass is currently used.

[0105] The polyamic acid, polyimide, and polyamic acid solution according to the present invention can be suitably used in a batch-type device fabrication process in which a polyamic acid solution is applied to a support, heated to imidize, electronic elements, etc., formed on the polyimide film to form a substrate, and then peeled off. Therefore, the present invention also includes a method for manufacturing an electronic device, which includes a substrate-forming step in which a polyamic acid solution is applied to a support, heated to imidize, and electronic elements, etc., are formed on the polyimide film formed on the support. Furthermore, such an electronic device fabrication method may further include a step of peeling off the polyimide substrate on which the electronic elements, etc., have been formed from the support after the substrate-forming step.

[0106] The present invention will be described in more detail below with reference to examples, but these are provided for illustrative purposes only and the scope of the present invention is not limited to the following examples. [Example]

[0107] (Evaluation method) The material property values ​​and the like described in this specification were obtained by the following evaluation methods.

[0108] (1) Yellow Index (YI) and 400nm Transmittance The light transmittance of the polyimide film in the range of 200-800 nm was measured using a UV-Vis-Near Infrared Spectrophotometer (V-650) manufactured by JASCO Corporation, and the yellow index (YI) was calculated as an index representing yellowness according to the formula described in JIS K 7373.

[0109] (2) Total light transmittance (TT) of polyimide film Measurement was carried out using an integrating sphere haze meter HM-150N (manufactured by Murakami Color Research Laboratory) according to the method described in JIS K7361.

[0110] (3) Haze of polyimide film Measurement was carried out using an integrating sphere haze meter HM-150N (manufactured by Murakami Color Research Laboratory) according to the method described in JIS K7136.

[0111] (4) Measurement of internal stress The polyamic acid solutions prepared in the Examples and Comparative Examples were applied using a spin coater to Corning alkali-free glass (0.7 mm thick, 100 mm x 100 mm) whose warpage had been measured in advance. The glass substrate and polyimide laminate were then baked in air at 120°C for 30 minutes and in a nitrogen atmosphere at 430°C for 30 minutes to obtain a 10 μm-thick glass substrate and polyimide laminate. The warpage of this glass substrate and polyimide laminate was measured using a Tencor FLX-2320-S thin film stress analyzer to evaluate the internal stress generated between the glass substrate and polyimide film at 25°C in a nitrogen atmosphere. To prevent water absorption by the polyimide film, the glass substrate and polyimide laminate was measured immediately after baking or after drying at 120°C for 10 minutes.

[0112] (5) Analysis of gas generated from polyimide film The gas generated from the polyimide film during heating was analyzed using an analytical device combining a thermogravimetric analyzer (NETZSCH "STA449 F5") and a quadrupole mass spectrometer (JEOL "JMS-Q1500GC"). The analytical procedure is described below.

[0113] First, using perfluorotributylamine as a standard substance, the voltage of the quadrupole mass spectrometer was adjusted so that the detection intensity of the peak at m / z=69 was 800,000. Next, using the thermogravimetric analyzer, each polyimide film obtained in the examples and comparative examples described below (specifically, a polyimide film sampled from each laminate to a mass of 140 mg) was heated from an ambient temperature of 60°C at a heating rate of 10°C / min under a helium gas flow at a flow rate of 100 mL / min. The gas generated from the polyimide film when the ambient temperature reached 470°C was analyzed with the quadrupole mass spectrometer. Note that by using the analyzer to heat the polyimide film under a helium gas flow, the helium gas served as a carrier gas, allowing the gas generated from the polyimide film to be analyzed in real time with the quadrupole mass spectrometer. The gas generated from the polyimide film when the ambient temperature reached 470°C was analyzed using the quadrupole mass spectrometer, and the detected intensity of the peak at m / z = 20 (20 peak intensity) was read from the resulting mass spectrum. The baseline was also adjusted so that the peak intensity at 60°C was 2000±100.

[0114] The abbreviations of the reagents used are as follows: NMP: 1-methyl-2-pyrrolidone BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride SFDA: spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene] 1,3,7,9 tetrone PMDA: Pyromellitic dianhydride 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride TFMB: 2,2-bis(trifluoromethyl)benzidine TMP: Trimethyl phosphate PX-200: 1,3-phenylenebis(2,6-dimethylphenylene phosphate) TPPi: Triphenyl phosphite DEPi: Diethyl phosphite

[0115] Example 1 A 300 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube was charged with 40.0 g of NMP as the polymerization organic solvent and stirred. 5.065 g of TFMB was added and dissolved. 0.747 g of SFDA and 4.188 g of BPDA were added to this solution and stirred at room temperature for 24 hours. 0.1 g of TMP was then added and stirred for 30 minutes, yielding a homogeneous, transparent polyamic acid solution. The resulting polyamic acid solution was spin-coated and baked at 120°C for 30 minutes in air and at 430°C for 30 minutes under a nitrogen atmosphere. The film was then peeled off from the glass substrate to obtain a 10 μm-thick polyimide film. The properties of the resulting polyimide film are shown in Table 1. (Note that in Table 1, "dianhydride [mol%]" refers to the mol% of each dianhydride relative to 100 mol of the total dianhydride, and "diamine [mol%]" refers to the mol% of each diamine relative to 100 mol of the total diamine.)

[0116] In the table, the m / z=20 reduction ratio of Example 1 is (peak intensity of m / z=20 of Example 1) / (peak intensity of m / z=20 of Comparative Example 3).

[0117] (Examples 2 to 8) A polyimide film was obtained in the same manner as in Example 1, except that the monomers and additives used were changed to those shown in Table 1.

[0118] (Comparative Example 1) A 300 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube was charged with 40.0 g of NMP as the polymerization organic solvent and stirred. 5.212 g of TFMB was added and dissolved. 4.788 g of BPDA was added to this solution and stirred at room temperature for 24 hours, resulting in a homogeneous, transparent polyamic acid solution. The resulting polyamic acid solution was applied using a spin coater and baked in air at 120 °C for 30 minutes and in a nitrogen atmosphere at 430 °C for 30 minutes. The resulting polyimide film was then peeled off from the glass substrate to obtain a 10 μm thick polyimide film. The properties of the resulting polyimide film are shown in Table 2.

[0119] (Comparative Examples 2 to 9) A polyimide film was obtained in the same manner as in Comparative Example 1, except that the monomers and additives used and the amounts added were changed to those shown in Table 1. The properties of the obtained polyimide film are shown in Table 1.

[0120] As described above, polyimides obtained from polyamic acid compositions containing a polyamic acid essentially consisting of a polyadduct of 2,2-bis(trifluoromethyl)benzidine and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9 tetrone and a plasticizer are (1) The amount of outgassing of m / z=20 when heated is suppressed. (2) Transmittance at 400 nm is 30% or more (3) Haze is 1.0% or less.

[0121] Examples 1 to 8 are polyimides obtained from polyamic acid compositions containing a plasticizer, and they generate less hydrogen fluoride than Comparative Examples 3 to 9, which do not contain a plasticizer. Comparative Example 2 contains a plasticizer, which results in less hydrogen fluoride generation than Comparative Example 1, but because it does not contain SFDA, it has high haze and is not suitable for applications requiring transparency.

[0122] From the above results, it was confirmed that the polyimide obtained from the polyamic acid composition containing the polyaddition product of the diamine derived from 2,2-bis(trifluoromethyl)benzidine and the acid dianhydride derived from spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9 tetrone, and the plasticizer, has a reduced amount of hydrogen fluoride generation, a high transmittance at 400 nm, and furthermore, the generation of haze is suppressed. Note that the present invention is not limited to the above-described embodiment and can be practiced with various modifications.

[0123] (Reference examples 1 and 2) The polyamic acid solutions prepared in the Examples and Comparative Examples were spin-coated onto Corning alkali-free glass (0.7 mm thick, 100 mm x 100 mm) and baked at 120°C for 30 minutes in air and at 430°C for 30 minutes in a nitrogen atmosphere to obtain a 10 μm-thick laminate of glass substrate and polyimide. A 1 μm-thick layer of SiOx was then laminated onto this laminate by plasma CVD, and the laminate was baked at 470°C for 10 minutes in a nitrogen atmosphere. The delamination between the SiOx and polyimide film was visually confirmed, and the YI was calculated using a UV-Vis-NIR spectrophotometer. Reference Example 1, which contained a plasticizer, showed no delamination after the heat treatment and almost no change in transparency (specifically, YI). However, Reference Example 2, which did not contain a plasticizer, showed delamination of the SiOx and yellowing of the polyimide film itself, resulting in a YI of over 60. [Table 1] [Table 2]

Claims

1. A polyamic acid composition comprising a polyamic acid, a plasticizer, and a solvent, The polyamic acid is an adduct of an acid dianhydride and a diamine compound, When the total acid dianhydride is taken as 100 mol %, the acid dianhydride contains 1 mol % or more of spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9 tetrone, A polyamic acid composition comprising 2,2-bis(trifluoromethyl)benzidine in an amount of 50 mol % or more as a diamine compound, when the total amount of all diamine compounds is taken as 100 mol %.

2. 2. The polyamic acid composition according to claim 1, wherein the acid dianhydride is one or more acid dianhydrides selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic 2,3:6,7-dianhydride.

3. 3. The polyamic acid composition according to claim 1, wherein the polyamic acid composition contains spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]1,3,7,9tetrone in an amount of 1 mol % to 50 mol % as the acid dianhydride, when the total acid dianhydride is taken as 100 mol %.

4. 4. The polyamic acid composition according to claim 1, wherein the amount of the plasticizer added is 20 parts by weight or less based on 100 parts by weight of the polyamic acid.

5. 5. The polyamic acid composition according to claim 1, wherein the plasticizer is at least one selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters.

6. 6. The polyamic acid composition according to claim 1, wherein the solvent is an aprotic solvent.

7. A polyimide which is an imidized product of the polyamic acid contained in the polyamic acid composition according to any one of claims 1 to 6.

8. 8. The polyimide according to claim 7, wherein the polyimide is heated in a helium gas flow from an ambient temperature of 60°C to an ambient temperature of 470°C at a heating rate of 10°C / min, and the gas generated from the polyimide is analyzed with a quadrupole mass spectrometer to obtain a mass spectrum at m / z = 20, wherein the value obtained by dividing the peak intensity at 470°C by the peak intensity at 470°C of a polyimide obtained from a polyamic acid containing no plasticizer is 0.8 or less.

9. A polyimide film comprising the polyimide according to claim 7 or 8.

10. 10. The polyimide film according to claim 9, wherein the polyimide film has a transmittance of 30% or more at 400 nm when the film thickness is 10 μm.

11. 11. The polyimide film according to claim 9, wherein the haze is 1.0% or less when the film thickness is 10 μm.

12. A laminate comprising a support and the polyimide film according to any one of claims 9 to 11.

13. A method for producing a laminate having a support and a polyimide film, comprising the steps of: A method for producing a laminate, comprising applying the polyamic acid composition according to claim 6 onto a support to form a coating film containing the polyamic acid and the plasticizer, and heating the coating film to imidize the polyamic acid.

14. A method for producing a polyimide film, comprising:

7. A method for producing a polyimide film, comprising: applying the polyamic acid composition according to claim 6 onto a support to form a coating film containing the polyamic acid and the plasticizer; heating the coating film; and peeling off the formed coating film.

15. An electronic device comprising the polyimide film according to any one of claims 9 to 11 and an electronic element disposed on the polyimide film.

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