Polyamide acid, polyamide acid solution, polyimide, polyimide substrate and laminate, and method for manufacturing the same

Abstract

The present application aims to provide a polyimide having high heat resistance and high transparency, and improved adhesion to an inorganic film, a polyamic acid as a precursor thereof, a polyimide substrate and a laminate, and a method for producing the same. The above problems can be solved by a polyamic acid which is a polyaddition product of a diamine and a tetracarboxylic dianhydride, the diamine containing 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride containing 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, a polyimide obtained therefrom, a polyimide substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to a polyamic acid, a polyamic acid solution, a polyimide, a polyimide substrate, and a laminate, and a method for producing the same. BACKGROUND

[0002] In electronic devices such as displays, touch panels, and solar cells, thinness, lightness, and flexibility are required, and resin thin film substrates are used instead of glass substrates.

[0003] In these devices, various electronic elements such as thin film transistors and transparent electrodes are formed on the substrate, and high temperature processes are required in the formation of these electronic elements. A general aromatic polyimide has sufficient heat resistance to adapt to the high temperature processes only, and the linear thermal expansion coefficients (CTEs) of the glass substrate and the electronic elements are also close, and internal stress is not easily generated, and thus, the general aromatic polyimide is suitable as a substrate material for flexible displays and the like.

[0004] Generally, aromatic polyimides are colored brown due to intramolecular conjugation and formation of charge transfer (CT) complexes. In organic EL and the like of a top emission type, light is extracted from the side opposite to the substrate side, and thus, transparency is not required for the substrate, and thus, the general aromatic polyimide has been used in the past. However, in the case where light emitted from a display element is emitted through a substrate, such as in transparent displays, organic EL of a bottom emission type, and liquid crystal displays, and in the case where a sensor and a camera component are disposed on the back surface of a substrate in order to form a full-surface display (without a notch) for a smartphone and the like, high optical properties are also required for the substrate.

[0005] Against this background, a material having heat resistance equivalent to that of the existing aromatic polyimide and further excellent transparency is sought.

[0006] It is reported that in order to reduce the coloring of polyimides, the formation of CT complexes can be suppressed by using an aliphatic monomer (Patent Document 1, Patent Document 2). In addition, it is known that it is not a technique for reducing the coloring of polyimides, but by adding a silicone oil to a polyamic acid which is a polyimide precursor and imidizing, a polyimide film obtained thereby shows high adhesion to a substrate (Patent Document 3).

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2012-041530

[0010] Patent Document 2: Japanese Patent No. 5660249

[0011] Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2015-229691 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, the above-described prior art has room for improvement in terms of having high heat resistance and further excellent transparency. The polyimides described in Patent Documents 1 and 2 also have high transparency and low CTE, but have low thermal decomposition temperature due to the presence of aliphatic structures, and cannot be adapted to high-temperature processes for forming electronic components.

[0014] In addition, organic EL light-emitting elements have low moisture resistance, and black spot generation, leakage current generation, and non-lighting occur due to moisture intrusion from the outside. If a resin is used as a substrate, moisture cannot be completely blocked. Therefore, in order to improve the barrier properties of the substrate, an inorganic film such as a silicon oxide film and a silicon nitride film is used as an intermediate layer of each polyimide layer of a two-layer polyimide film or on a film for forming a two-layer polyimide film. However, there is a problem in that the adhesion of the inorganic film to the polyimide film is low, and peeling or floating occurs at the interface between the inorganic film and the polyimide film in the process.

[0015] In view of the above, the object of the present application is to provide a polyimide having high heat resistance and high transparency, further improved adhesion to an inorganic film, a polyamic acid as a precursor thereof, a polyimide substrate and a laminate, and a method for producing the same.

[0016] MEANS FOR SOLVING THE PROBLEMS

[0017] The present inventors et al. have found that a polyimide and a polyamic acid as a precursor thereof satisfying the above-described characteristics are obtained by introducing a rigid structure in a polymer skeleton and further using a monomer component having a siloxane bond. One embodiment of the present application forms the following configuration.

[0018] A polyamic acid is a polyadduct of a diamine and a tetracarboxylic dianhydride, the diamine includes 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride includes 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.

[0019] EFFECTS OF THE INVENTION

[0020] The present application can provide a polyimide having high heat resistance and high transparency, and improved adhesion to an inorganic film, and a polyamic acid as a precursor thereof. They are suitable as a substrate material for electronic devices. DETAILED DESCRIPTION

[0021] The polyamic acid of one embodiment of the present invention is a polyamic acid that is a polyaddition product of a diamine and a tetracarboxylic dianhydride, the diamine includes 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride includes 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.

[0022] The polyimide obtained from the polyamic acid of the present embodiment has a siloxane bond in the resin, and thus has improved affinity for an inorganic film such as a silicon oxide film, and is expected to have improved adhesion to the inorganic film. On the other hand, when the repeating unit of the siloxane bond is long, the glass transition temperature (Tg) of the resin can be greatly reduced, or the heat resistance can be reduced due to the occurrence of cyclic siloxane based on intramolecular condensation, or the equipment can be contaminated, and thus the repeating unit of the siloxane bond is preferably small. Specifically, by using 1,3-bis(3-aminopropyl)tetramethyldisiloxane, a polyimide having high adhesion to an inorganic film and high heat resistance can be obtained. From the viewpoint of balancing adhesion and heat resistance, the ratio of 1,3-bis(3-aminopropyl)tetramethyldisiloxane is preferably 0.1 to 10.0 mol%, more preferably 0.15 to 1.0 mol%, and further preferably 0.2 to 0.5 mol%, based on 100 mol% of the total of all diamines. By being within the above range, the polyimide obtained from the polyamic acid can have sufficient adhesion to an inorganic film such as a silicon oxide film and heat resistance that can withstand high-temperature processes.

[0023] In order to obtain a polyimide having low internal stress, the ratio of 3,3,4,4-biphenyltetracarboxylic dianhydride is preferably 70 to 99 mol%, more preferably 75 to 98 mol%, more preferably 75 to 97 mol%, more preferably 75 to 96 mol%, more preferably 75 to 95 mol%, and further preferably 80 to 90 mol%, based on 100 mol% of the total of all tetracarboxylic dianhydrides, in the polyamic acid.

[0024] 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride is derived from its bulky structure to inhibit the formation of charge transfer complexes, and thus is effective for the transparency of the polyimide derived from the aforementioned polyamic acid. On the other hand, the bulky structure hinders the packing of the molecular chains, and thus there is a tendency that the internal stress of the polyimide derived from the aforementioned polyamic acid becomes large. Therefore, from the viewpoint of balancing the transparency and the moderate internal stress, the aforementioned polyamic acid is preferably a polyamic acid in which the ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride is 1 to 30 mol% when the total of the four carboxylic dianhydrides is 100 mol%, more preferably 5 to 25 mol%, and further preferably 10 to 20 mol%. By being in the above range, the increase in the internal stress of the polyimide derived from the polyamic acid is inhibited, and the internal stress occurring when a laminate is formed with a glass substrate or the like can be reduced. Therefore, in the manufacturing process of the laminate using the polyimide derived from the polyamic acid or the electronic device using the laminate, a material excellent in process suitability can be obtained without warping of the laminate.

[0025] The polyamic acid of the present embodiment can contain other diamine components other than 1,4-phenylenediamine and other than 1,3-bis(3-aminopropyl)tetramethyldisiloxane within a range not impairing the properties thereof. As the aforementioned other diamine components, for example, 1,4-diaminocyclohexane, 1,3-phenylenediamine, 4,4'-oxydianiline, 3,4'-oxydianiline, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-diaminodiphenyl sulfone, 4-(aminophenyl) 4-aminobenzoate, m-xylylenediamine, o-xylylenediamine, 4,4'-bis(aminophenoxy) biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'dihydroxybiphenyl, 4,4'-methylenebis(cyclohexylamine), and the like can be given, and they can be used alone or in combination of two or more. Among them, 4-(aminophenyl) 4-aminobenzoate or the like is ideal in terms of the improvement in Tg and transparency.

[0026] The polyamide acid of the present embodiment can contain other acid dianhydride components other than 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride within a range not impairing the properties thereof. As the aforementioned other acid dianhydride components, for example, there can be mentioned pyromellitic dianhydride, 1,4-phenylene bis(trimellitic acid dianhydride), 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxyphthalic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, 2'-oxodispiro[bicyclo[2.2.1]heptane-2,1'-cyclopentane-3',2"-bicyclo[2.2.1]heptane]-5,6:5",6"-tetracarboxylic dianhydride, and the like, which can be used alone or in combination of two or more.

[0027] [Synthesis of polyamide acid and polyimide]

[0028] The polyimide containing the aforementioned structure is obtained by a known method. The polyimide can be synthesized by a synthesis method via a precursor such as a polyamide acid and a polyimide ester, and a synthesis method not via a precursor. The polyimide is preferably synthesized by imidization of a polyamide acid as a precursor, in terms of availability of monomers and ease of polymerization.

[0029] The polyamide acid containing the aforementioned structure is obtained by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. For example, a diamine solution can be prepared by dissolving a diamine in an organic solvent or dispersing it in the organic solvent in a slurry state, and a tetracarboxylic dianhydride solution or a solid in which a tetracarboxylic dianhydride is dissolved in an organic solvent or dispersed in the organic solvent in a slurry state can be added to the aforementioned diamine solution in this state. A diamine can be added to a tetracarboxylic dianhydride solution. The dissolution and reaction of the diamine and the tetracarboxylic dianhydride are preferably performed in an atmosphere of an inactive gas such as argon or nitrogen.

[0030] In the synthesis of the aforementioned polyamide acid, the number of moles of the total amount of the diamine component and the number of moles of the total amount of the tetracarboxylic dianhydride component are preferably adjusted to be substantially equal moles. By using a plurality of diamines and / or a plurality of tetracarboxylic dianhydrides, a polyamide acid having a plurality of structural units is obtained. In addition, by blending polyamide acids having different structures, a blend of polyamide acids having a plurality of structural units having different structures can also be obtained.

[0031] The organic solvent used in the synthesis reaction of the aforementioned polyamic acid is not particularly limited. The aforementioned organic solvent is preferably one that can dissolve the tetracarboxylic dianhydride and diamine to be used, and can dissolve the polyamic acid produced by polymerization. As specific examples of the aforementioned organic solvent, there can be mentioned urea-based solvents such as tetramethyl urea, N,N-dimethylethyl urea, and the like; sulfoxide or sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, tetramethyl sulfone, and the like; amide-based solvents such as N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), and the like; ester-based solvents such as γ-butyrolactone and the like; amide-based solvents such as hexamethylphosphoric acid triamide and the like; halogenated alkane-based solvents such as chloroform, dichloromethane, and the like; aromatic hydrocarbon-based solvents such as benzene, toluene, and the like; phenol-based solvents such as phenol, cresol, and the like; ketone-based solvents such as cyclopentanone and the like; ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, p-cresyl methyl ether, and the like. Two or more kinds of organic solvents can be combined as needed and used. In order to improve the solubility and reactivity of the polyamic acid, the organic solvent used in the synthesis of the polyamic acid is preferably selected from amide-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, and particularly preferably amide-based solvents such as DMF, DMAC, NMP, and the like.

[0032] The temperature conditions of the aforementioned synthesis reaction of the polyamic acid are not particularly limited. From the viewpoint of suppressing a decrease in the molecular weight of the polyamic acid based on depolymerization, the reaction temperature is preferably 80°C or lower. From the viewpoint of allowing the polymerization reaction to proceed moderately, the reaction temperature is more preferably 0 to 50°C. The reaction time can be arbitrarily set within a range of 10 minutes to 30 hours.

[0033] The aforementioned polyamic acid solution containing the polyamic acid and the organic solvent is obtained by polymerizing the aforementioned diamine and the aforementioned tetracarboxylic dianhydride in the aforementioned organic solvent. This polymerization solution can be used directly as a polyamic acid solution. In addition, the concentration of the polyamic acid and the viscosity of the solution can also be adjusted by removing a part of the solvent from the polymerization solution, or by adding a solvent. The solvent to be added can be different from the solvent used in the polymerization of the polyamic acid. In addition, a polyamic acid solution can also be prepared by dissolving the solid polyamic acid resin obtained by removing the solvent from the polymerization solution in a solvent. As the organic solvent of the polyamic acid solution, one having a high solubility of the polyamic acid is preferred, and the aforementioned exemplary organic solvents used in the synthesis of the polyamic acid can be used. Among them, amide-based solvents such as DMF, DMAC, NMP, and the like are preferred.

[0034] The imidization is performed by dehydration and ring closure of the aforementioned polyamic acid. The dehydration and ring closure is performed by an azeotropic method using an azeotropic solvent, a thermal method or a chemical method. In the case of performing the imidization in a solution state, it is preferable to add an imidization agent and / or a dehydration catalyst to the aforementioned polyamic acid solution, and perform chemical imidization. The aforementioned imidization agent is not particularly limited, and a tertiary amine is preferably used, and among them, a heterocyclic tertiary amine is more preferable. As the aforementioned heterocyclic tertiary amine, pyridine, methylpyridine, quinoline, isoquinoline, imidazoles and the like can be given. As the aforementioned dehydration catalyst, acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, γ-valerolactone and the like can be given.

[0035] In the case of removing the solvent from the aforementioned polyamic acid solution to perform the imidization, it is preferable to perform thermal imidization by dehydration and ring closure by heating. The method of heating the aforementioned polyamic acid is not particularly limited, and for example, it is possible to perform heat treatment in the range of 80°C to 500°C after coating the aforementioned polyamic acid solution on a support such as a glass plate, a metal plate, PET (polyethylene terephthalate) or the like. The heating time varies depending on the amount of the polyamic acid solution to be treated and the heating temperature, but generally, it is preferable to perform heating for 1 minute to 5 hours after the treatment temperature reaches the maximum temperature. It is also possible to add an imidization agent and / or a dehydration catalyst to the polyamic acid solution, and perform the imidization by heating in the aforementioned method.

[0036] When the aforementioned polyamic acid is subjected to thermal imidization, the decomposition of the polyamic acid is suppressed by simultaneously generating the imidization reaction and the decomposition of the polyamic acid, and thus it is possible to reduce the generation of terminal groups, or to obtain a polyimide film having excellent transparency. As the method of suppressing the decomposition of the aforementioned polyamic acid, esterification of the polyamic acid, silyl esterification, a method of accelerating the reaction rate and the like can be given, but any method can be used. Specifically, by adding a small amount of a tertiary amine such as imidazoles, it is possible to accelerate the imidization speed at the time of thermal imidization, and to obtain a polyimide film having excellent transparency. As the aforementioned imidazoles, 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-pentadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-phenylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole and the like can be given. Among them, 1,2-dimethylimidazole is preferable.

[0037] The content of the imidazole compound in the aforementioned polyamic acid solution is preferably 0.005 to 0.100 mol, more preferably 0.010 to 0.080 mol, further preferably 0.015 to 0.050 mol, relative to 1.000 mol of the amide group of the polyamic acid. The "amide group of the polyamic acid" refers to an amide group generated by the polycondensation of a diamine and a tetracarboxylic dianhydride. When the aforementioned imidazole compound is added in the above range, improvement in the transparency and low internal stress of the polyimide film can be expected.

[0038] When the aforementioned imidazole compound is added, it is preferable to add it after the polymerization of the polyamic acid. The aforementioned imidazole compound can be added directly to the polyamic acid solution, or can be added as an imidazole solution to the polyamic acid solution.

[0039] The imidization from the aforementioned polyamic acid to polyimide can be performed at an arbitrary rate of 1 to 100% of the imidization rate, or a part of the imidized polyamic acid can be synthesized. When the imidization from the polyamic acid to polyimide is performed, there is a tendency for the solubility in organic solvents and the change in the viscosity of the solution. In addition, it is not generally easy to stop the imidization at a specific imidization rate. In the case of forming a thin film by the coating and drying of a solution, the viscosity and thixotropy of the solution have an influence on the uniformity of the film thickness. Therefore, if the stability of the process is taken into consideration, it is preferable not to add an imidization agent and a dehydration catalyst to the aforementioned polyamic acid, and to perform the coating of the aforementioned polyamic acid solution on a support at an imidization rate of 0%, and to perform the removal of the solvent and the imidization by heating on the support.

[0040] [Use of polyamic acid and polyimide]

[0041] The polyamic acid and polyimide of one embodiment of the present application can be directly used for the production of articles and members. Alternatively, a composition can be formed by adding a thermosetting component, a photocurable component, a non-polymerizable adhesive resin, a dye, a surfactant, a leveling agent, a plasticizer, a silane coupling agent, a fine particle, a sensitizer, or the like, to the aforementioned polyamic acid and the aforementioned polyimide. The compounding ratio of any of these components is preferably in the range of 0.1 to 95% by mass, relative to the entire solid content of the aforementioned polyimide. Note that the solid content of the composition refers to all components other than an organic solvent, and a liquid monomer component is also included in the solid content.

[0042] The polyimide of one embodiment of the present application is excellent in transparency and heat resistance, and thus can be used as a transparent substrate for glass-substituting applications and the like, and application to a substrate for electronic devices such as a TFT substrate and an electrode substrate is expected. In the aforementioned electronic devices, use as a substrate for devices such as a liquid crystal display device, an organic EL element, electronic paper, and a touch panel, which require light transmission, is preferable. The polyimide of one embodiment of the present application can also be used as an optical member such as a color filter, an antireflection film, and a hologram, a building material, and a material for structures. Various inorganic thin films such as a metal oxide and a transparent electrode can be formed on the surface of the polyimide of one embodiment of the present application. The aforementioned inorganic thin films are formed by, for example, a PVD method such as a sputtering method, a vacuum evaporation method, and an ion plating method, and a dry process such as a CVD method.

[0043] [Production of polyimide substrate and electronic device]

[0044] The polyimide of one embodiment of the present application is excellent in adhesion to a support in addition to heat resistance and transparency, and thus is preferably used as a substrate for electronic devices manufactured by a batch process. In the batch process, a polyimide film (substrate) is formed on a support, and an electrode and / or an electronic element are formed thereon, followed by separation of the polyimide substrate on which the electrode and / or the electronic element are formed from the support, whereby an electronic device is obtained.

[0045] Thus, one embodiment of the present application further includes a polyimide substrate formed of the aforementioned polyimide, a laminate of the polyimide substrate and a support, and an electronic device provided with an electrode and / or an electronic element on the aforementioned polyimide substrate. In addition, one embodiment of the present application includes a method for manufacturing a laminate of a polyimide substrate and a support, in which a polyimide acid solution is cast on a support and imidized, whereby a polyimide substrate is formed on the aforementioned support.

[0046] The aforementioned polyimide substrate has a thickness of about 1 to 200 μm, preferably about 5 to 100 μm.

[0047] In one embodiment of the present application, in order to improve the barrier property of the aforementioned polyimide substrate, an inorganic film such as a silicon oxide film and a silicon nitride film can be used as an intermediate layer of each of the polyimide layers of a polyimide film formed of two layers or on a film of a polyimide film formed of two layers.

[0048] As a specific example, for example, after coating the aforementioned polyamide acid solution on a support, performing drying and imidization based on heating, the polyimide film formed on the aforementioned support is subjected to CVD vapor deposition of an inorganic film. Subsequently, the aforementioned polyamide acid solution is again coated on the inorganic film, and drying and imidization based on heating are performed, thereby obtaining a polyimide film (polyimide substrate) in which the inorganic film is laminated on the aforementioned support. This example is an example of a polyimide substrate in which the inorganic film is used as an intermediate layer of each polyimide layer of the polyimide film formed in two layers.

[0049] As the support on which the aforementioned polyamide acid solution is coated, a glass substrate (glass plate); a metal substrate or a metal band such as SUS; a resin film such as polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate, triacetyl cellulose, and the like can be given. In order to be applicable to the existing batch-type device manufacturing process, a glass substrate (glass plate) is more preferably used as the support.

[0050] When the aforementioned polyamide acid solution is coated on the aforementioned support such as glass and heated, imidization of the polyamide acid is started together with evaporation of the solvent, and the organic solvent and water generated by imidization (dehydration of the polyamide acid) are volatilized from the polyamide acid solution. At this time, a part of the water and / or the organic solvent does not volatilize and remains between the aforementioned support and the aforementioned resin film in the imidization, and becomes a cause of peeling at the interface of the aforementioned support and the aforementioned resin film. The water and / or the organic solvent remaining at the interface of the aforementioned support and the aforementioned resin film are discharged through the polyimide film in the process of heating at a high temperature thereafter, and a bubble remains in the portion where peeling or floating has occurred. If such a bubble is generated, a defective situation occurs when an element is formed on the polyimide substrate. In particular, in a device that is thinned or miniaturized, even a fine peeling or floating has a large influence on the formation or mounting of an element or the like.

[0051] The polyamide acid and the polyimide of one embodiment of the present application having a siloxane structure have high adhesion to glass, and also have high adhesion to an inorganic film used as an intermediate layer or the like, and thus peeling or floating caused by the retention of an organic solvent and water at the interface of a glass support and a resin film is less likely to occur at the time of drying and imidization of the solvent on a support. Thus, the formation and mounting of an element on a polyimide substrate in which an inorganic film is laminated on a support can be accurately performed.

[0052] A polyimide film made using the polyamide acid solution of one embodiment of the present application has high heat resistance and high transparency, and also has improved adhesion to an inorganic film.

[0053] The 90° peeling strength of the polyimide film (polyimide substrate) laminated on the aforementioned support from the aforementioned support is preferably 0.08 N / cm to 5.00 N / cm, more preferably 0.09 N / cm to 4.00 N / cm, and further preferably 0.10 N / cm to 3.50 N / cm. In the case where the polyimide film (polyimide substrate) laminated on the aforementioned support has the aforementioned adhesiveness, peeling from the aforementioned support is less likely to occur in the process of forming and mounting a device, and peeling from the aforementioned support after the formation and mounting of the device is easy. The 90° peeling strength can be measured according to the method described in the Examples below.

[0054] For the transparency of the aforementioned polyimide or the aforementioned polyimide film, a high transmittance in the entire wavelength region of visible light is required in applications such as displays. The yellow index (YI) of the aforementioned polyimide or the aforementioned polyimide film is preferably 20 or less, and more preferably 18 or less. The YI can be measured according to JIS K7373-2006. Such a polyimide film having high transparency can be used as a transparent substrate for applications such as glass replacement.

[0055] The internal stress generated between the aforementioned polyimide substrate and the aforementioned support is preferably 30 MPa or less, more preferably 25 MPa or less, and further preferably 20 MPa or less. The internal stress generated between the aforementioned polyimide substrate and the aforementioned support can be measured according to the method described in the Examples below. If the aforementioned internal stress is 30 MPa or less, the aforementioned laminate does not warp in the manufacturing process of an electronic device, and thus, the polyimide substrate has the advantage of excellent process suitability.

[0056] One embodiment of the present application can have the following configuration.

[0057] 1) A polyamic acid which is a polycondensation product of a diamine and a tetracarboxylic dianhydride, the diamine comprising 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride comprising 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.

[0058] 2) The polyamic acid according to 1), wherein the ratio of 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 0.1 mol% to 10.0 mol% relative to the total amount of the diamine.

[0059] 3) The polyamic acid according to 1) or 2), wherein the ratio of 3,3,4,4-biphenyltetracarboxylic dianhydride is 70 mol% to 99 mol% relative to the total amount of the tetracarboxylic dianhydride.

[0060] 4) A polyamic acid solution containing the polyamic acid according to any one of 1) to 3) and an organic solvent.

[0061] 5) The polyamic acid solution according to 4), further containing an imidazole.

[0062] 6) The polyamic acid solution according to 5), wherein the content of the aforementioned imidazole is 0.10 mol or less per 1 mol of amide group of the aforementioned polyamic acid.

[0063] 7) A polyimide which is an imidized product of the polyamic acid solution according to any one of 4) to 6).

[0064] 8) The polyimide according to 7), having a yellow index (YI) of 20 or less at a film thickness of 10 μm.

[0065] 9) A method for producing a laminate, which is a method for producing a laminate of a polyimide substrate and a support, wherein the polyamic acid solution according to any one of 4) to 6) is cast on a support and imidized, thereby forming a polyimide substrate on the aforementioned support.

[0066] 10) A laminate, which is a laminate of a polyimide substrate and a support formed of the polyimide according to 7) or 8).

[0067] 11) The laminate according to 10), wherein the internal stress generated between the aforementioned polyimide substrate and the aforementioned support is 30 MPa or less.

[0068] 12) An electronic device provided with an electrode and / or an electronic component on the polyimide substrate according to 10) or 11).

[0069] The present application is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means respectively disclosed in the different embodiments are also included in the scope of the present application.

[0070] Examples

[0071] (Evaluation method)

[0072] The material property values and the like described in the present specification are obtained according to the following methods.

[0073] (1) Peel strength

[0074] For the laminate of the glass sheet (alkali-free glass) and the polyimide film, and the laminate of the glass sheet on which a silicon oxide film (inorganic film) is formed and the polyimide film, 90° peeling strength from the glass sheet and the glass sheet on which a silicon oxide film (inorganic film) is formed, respectively, was measured in accordance with the ASTM D1876-01 standard. A 10 mm wide notch was introduced in the polyimide film with a cutter, and a 90° peeling test was performed at a tensile speed of 50 mm / min and a peeling length of 50 mm with a Strograph VES1D (manufactured by Toyo Seiki Kenki K.K.) under conditions of 23°C and 55% RH, and the average value of the peeling strength was taken as the peeling strength.

[0075] Here, for the aforementioned laminate of the glass sheet (alkali-free glass) and the polyimide film, the same was produced as in the [production of the polyimide film] described later. In addition, for the aforementioned laminate of the glass sheet on which a silicon oxide film (inorganic film) is formed and the polyimide film, the glass sheet on which a silicon oxide film (inorganic film) is formed was used as the glass sheet, and the same was produced as in the [production of the polyimide film] described later, except for this. The glass sheet on which a silicon oxide film (inorganic film) is formed was produced by CVD vapor deposition of a silicon oxide film on a glass sheet.

[0076] (2) Measurement of internal stress

[0077] The polyamide acid solution produced in the examples and comparative examples was applied to an alkali-free glass (thickness 0.7 mm, 100 mm x 100 mm) of Corning Incorporated, on which the amount of warping had been measured in advance, with a spin coater, and the aforementioned glass sheet on which the polyamide acid solution was applied was baked at 120°C for 30 minutes in air and at 430°C for 30 minutes in a nitrogen atmosphere, to obtain a laminate of a glass substrate and a polyimide film having a film thickness of 10 μm. The amount of warping of the laminate of the glass substrate and the polyimide film was measured with a film stress measuring device FLX-2320-S (manufactured by Tencor), and the internal stress generated between the glass substrate and the polyimide film at 25°C in a nitrogen atmosphere was evaluated. Note that, in order to avoid water absorption of the polyimide film, the laminate of the glass substrate and the polyimide film was measured immediately after baking or after drying at 120°C for 10 minutes.

[0078] (3) 1% weight loss temperature (TD1)

[0079] The polyimide film was heated at 20°C / min from 25°C to 650°C in a N2 atmosphere with a TG / DTA / 7200 (manufactured by Hitachi High-Tech Corporation). The weight of the polyimide film at 150°C was taken as the reference, and the temperature at which the weight decreased by 1% from this was taken as the TD1 of the polyimide film, taking into account the effect of moisture.

[0080] (4) Yellow index (YI) of polyimide film

[0081] The yellow index (YI) as an index of yellow color was calculated from the formula described in JIS K 7373 using a UV-VIS-NIR spectrophotometer (V-650) manufactured by Shimadzu Corporation, measuring the light transmittance of the polyimide film at 200 to 800 nm.

[0082] (5) Appearance after heating test (high-temperature film formation step stability)

[0083] A polyamide acid solution prepared in the Examples and Comparative Examples was applied to an alkali-free glass (thickness 0.7 mm, 100 mm x 100 mm) manufactured by Corning Incorporated using a spin coater, and the glass substrate on which the polyamide acid solution was applied was fired at 120°C for 30 minutes in air and at 430°C for 30 minutes in a nitrogen atmosphere to obtain a laminate of the glass substrate and a polyimide film having a thickness of 10 μm. A SiOx layer was laminated on the polyimide film of the laminate by a PE-CVD method to a thickness of 1 μm, and the laminate was fired by raising the temperature at 5°C / minute from room temperature to 470°C in a nitrogen atmosphere, and after reaching 470°C, the temperature was maintained for 10 minutes, and then it was visually confirmed whether or not there was floating between the SiOx or the glass substrate and the polyimide film. The case where there was no floating was recorded as O (good), the case where there was floating of 1 or more but less than 5 was recorded as Δ (ordinary), the case where there was floating of 5 or more was recorded as X (poor), and the case where there was film damage due to thermal decomposition was recorded as XX (very poor).

[0084] [Preparation of polyamide acid solution]

[0085] Example 1

[0086] A 300 mL glass separable flask equipped with a stirrer having a stainless steel stirring blade and a nitrogen gas inlet tube was charged with 3,3',4,4'-diphenyltetracarboxylic dianhydride (BPDA) 8.68 g, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF) 2.55 g, and N-methyl-2-pyrrolidone (NMP) 85.0 g, and stirring and dissolution were performed at room temperature (23°C). After 30 minutes, 1,3-bis(3-aminopropyl)tetramethyldisiloxane (PAM-E) 0.009 g was added to the resulting solution, and further stirring was performed. To this solution, 1,4-phenylenediamine (PDA) 3.76 g was added, and stirring was performed at room temperature for 5 hours to obtain a polyamide acid solution. The input concentration of the diamine and the tetracarboxylic dianhydride in the reaction solution was 15% by weight relative to the total amount of the reaction solution. Further, 1,2-dimethylimidazole (DMI) was added to the solution so that the concentration of DMI relative to the polyamide acid (resin component) became 1% by weight.

[0087] Example 2

[0088] The input amount of BPDA was changed to 8.68 g, the input amount of BPAF was changed to 2.55 g, the input amount of PAM-E was changed to 0.013 g, and the input amount of PDA was changed to 3.76 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0089] Example 3

[0090] The input amount of BPDA was changed to 8.68 g, the input amount of BPAF was changed to 2.55 g, the input amount of PAM-E was changed to 0.017 g, and the input amount of PDA was changed to 3.76 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0091] Example 4

[0092] The input amount of BPDA was changed to 8.69 g, the input amount of BPAF was changed to 2.55 g, the input amount of PAM-E was changed to 0.026 g, and the input amount of PDA was changed to 3.74 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0093] Example 5

[0094] The input amount of BPDA was changed to 8.68 g, the input amount of BPAF was changed to 2.55 g, the input amount of PAM-E was changed to 0.043 g, and the input amount of PDA was changed to 3.73 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0095] Example 6

[0096] The input amount of BPDA was changed to 8.67 g, the input amount of BPAF was changed to 2.54 g, the input amount of PAM-E was changed to 0.086 g, and the input amount of PDA was changed to 3.70 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0097] Example 7

[0098] The input amount of BPDA was changed to 10.085 g, the input amount of BPAF was changed to 0.993 g, the input amount of PAM-E was changed to 0.018 g, and the input amount of PDA was changed to 3.904 g. Other than this, a polyamic acid solution was obtained in the same manner as in Example 1.

[0099] Example 8

[0100] The input amount of BPDA was changed to 9.370 g, the input amount of BPAF was changed to 1.784 g, the input amount of PAM-E was changed to 0.018 g, the input amount of PDA was changed to 3.829 g, and a polyamic acid solution was obtained in the same manner as in Example 7, except for these.

[0101] Example 9

[0102] The input amount of BPDA was changed to 9.366 g, the input amount of BPAF was changed to 1.784 g, the input amount of PAM-E was changed to 0.026 g, the input amount of PDA was changed to 3.823 g, and a polyamic acid solution was obtained in the same manner as in Example 1, except for these.

[0103] Example 10

[0104] The input amount of BPDA was changed to 8.681 g, the input amount of BPAF was changed to 2.546 g, the input amount of PAM-E was changed to 0.017 g, the input amount of PDA was changed to 3.756 g, and a polyamic acid solution was obtained in the same manner as in Example 7, except for these.

[0105] Example 11

[0106] The input amount of BPDA was changed to 8.629 g, the input amount of BPAF was changed to 2.551 g, the input amount of PAM-E was changed to 0.043 g, the input amount of PDA was changed to 3.766 g, and a polyamic acid solution was obtained in the same manner as in Example 7, except for these.

[0107] Example 12

[0108] The input amount of BPDA was changed to 8.018 g, the input amount of BPAF was changed to 3.279 g, the input amount of PAM-E was changed to 0.017 g, the input amount of PDA was changed to 3.686 g, and a polyamic acid solution was obtained in the same manner as in Example 7, except for these.

[0109] Example 13

[0110] The input amount of BPDA was changed to 8.015 g, the input amount of BPAF was changed to 3.278 g, the input amount of PAM-E was changed to 0.025 g, the input amount of PDA was changed to 3.681 g, and a polyamic acid solution was obtained in the same manner as in Example 1, except for these.

[0111] Example 14

[0112] The input amount of BPDA was changed to 7.543 g, the input amount of BPAF was changed to 3.871 g, the input amount of PAM-E was changed to 0.025 g, the input amount of PDA was changed to 3.651 g, and a polyamic acid solution was obtained in the same manner as in Example 1, except for the above.

[0113] Example 15

[0114] The input amount of BPDA was changed to 8.587 g, the input amount of BPAF was changed to 2.549 g, the input amount of PAM-E was changed to 0.173 g, the input amount of PDA was changed to 3.692 g, and a polyamic acid solution was obtained in the same manner as in Example 1, except for the above.

[0115] Example 16

[0116] The input amount of BPDA was changed to 4.548 g, the input amount of BPAF was changed to 7.087 g, the input amount of PDA was changed to 3.342 g, and PAM-E was changed to 0.023 g, and a polyamic acid solution was obtained in the same manner as in Example 1, except for the above.

[0117] Comparative Example 1

[0118] In a 300 mL glass separable flask equipped with a stirrer having a stainless steel stirring blade and a nitrogen gas inlet tube, BPDA 8.70 g, BPAF 2.55 g, and NMP 85.0 g were charged, and stirring and dissolution were performed at room temperature (23°C). After 30 minutes, PDA 3.75 g was added to the solution, and stirring was performed at room temperature for 5 hours, to obtain a polyamic acid solution. Further, 1,2-dimethylimidazole was added to the solution so as to be 1% by weight with respect to the polyamic acid (resin component).

[0119] Comparative Example 2

[0120] The input amount of BPDA was changed to 9.478 g, the input amount of BPAF was changed to 1.641 g, the input amount of PDA was changed to 3.881 g, and 1,2-dimethylimidazole was not added, and a polyamic acid solution was obtained in the same manner as in Comparative Example 1, except for the above.

[0121] Comparative Example 3

[0122] The input amount of BPDA was changed to 8.107 g, the input amount of BPAF was changed to 3.158 g, the input amount of PDA was changed to 3.734 g, and 1,2-dimethylimidazole was not added, and a polyamic acid solution was obtained in the same manner as in Comparative Example 1, except for the above.

[0123] Comparative Example 4

[0124] The input amount of BPDA was changed to 10.950 g, the input amount of BPAF was changed to 0 g, the input amount of PDA was changed to 4.023 g, PAM-E was changed to 0.028 g, and otherwise, a polyamic acid solution was obtained in the same manner as in Example 1.

[0125] <Comparative Example 5>

[0126] The input amount of BPDA was 8.643 g, the input amount of BPAF was 2.565 g, the input amount of PDA was 3.792 g, PAM-E was 0 g, 3-aminopropyltriethoxysilane (APS) was added in a manner so as to be 0.05% by weight, and otherwise, a polyamic acid solution was obtained in the same manner as in Comparative Example 2.

[0127] <Comparative Example 6>

[0128] APS was added in a manner so as to be 0.2% by weight, and otherwise, a polyamic acid solution was obtained in the same manner as in Comparative Example 5.

[0129] <Comparative Example 7>

[0130] APS was added in a manner so as to be 0.3% by weight, and otherwise, a polyamic acid solution was obtained in the same manner as in Comparative Example 5.

[0131] <Comparative Example 8>

[0132] In a 300 mL glass detachable flask equipped with a stirrer having a stainless steel stirring blade and a nitrogen gas introduction tube, trans-1,4-cyclohexanediamine (CHDA) 4.166 g, PAM-E 0.046 g, and NMP 85 g were put in, and stirring and dissolution were performed at room temperature (23°C). After 30 minutes, BPDA 10.788 g was added, and after heating at 80°C for 30 minutes, it was cooled to room temperature, stirred for 5 hours, and a polyamic acid solution was obtained. Further, 1,2-dimethylimidazole was added to the solution in a manner so as to be 1% by weight with respect to the polyamic acid (resin component).

[0133] [Production of polyimide film]

[0134] NMP was added to the polyamic acid solutions obtained in the above examples and comparative examples to dilute the polyamic acid concentration to 10.0% by weight. Using a spin coater, the diluted polyamic acid solution was cast onto a 10mm × 10mm square alkali-free glass plate (Corning EAGLE XG, 0.7mm thick) to a thickness of 10 μm after drying. The glass plate with the cast diluted polyamic acid solution was dried in a hot air oven at 120°C for 30 minutes, and then heated at 430°C for 30 minutes under a nitrogen atmosphere to perform imidization, resulting in a laminate of a 10 μm thick polyimide film and the glass plate. The polyimide film was peeled off from the glass substrate of the resulting laminate, and its properties were evaluated.

[0135] The composition of the polyamic acid solutions of each example and comparative example, and the evaluation results of the polyimide films, are shown in Table 1. The composition in Table 1 is expressed as a total of 100 mol% for both tetracarboxylic dianhydride and diamine. The amount of 1,2-dimethylimidazole (DMI) added is relative to 100 parts by weight of polyamic acid (resin component). In the table, "Stress" indicates the internal stress generated between the polyimide film and the support. Additionally, "-" in the table indicates that no measurement was performed.

[0136] [Table 1]

[0137]

[0138] As shown in Table 1, the polyimide films obtained in Examples 1 to 16 using the following polyamic acid have the following properties, wherein the polyamic acid is an addition polymerization product of a diamine and a tetracarboxylic dianhydride, wherein the diamine comprises 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride comprises 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride.

[0139] • Adhesion to glass is above 0.10 N / cm

[0140] • Its adhesion to SiO2 is above 0.05 N / cm.

[0141] ·YI is below 20

[0142] Further, by introducing 1,3-bis(3-aminopropyl)tetramethyldisiloxane in a polyamic acid in which the ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride is 70 to 99 mol% and the ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorene dicarboxylic dianhydride is 1 to 30 mol% with respect to a total of 100 mol% of all tetracarboxylic dianhydrides, and further using 1,4-phenylenediamine as a diamine, a polyimide film having the following properties is obtained.

[0143] • Adhesion to glass is 0.10 N / cm or more

[0144] • Adhesion to SiO2 is 0.05 N / cm or more

[0145] • Internal stress is 30 MPa or less

[0146] • YI is 20 or less

[0147] Judgment: The polyimide film of Example 16 in which the ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride is 50 mol% and the ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorene dicarboxylic dianhydride is 50 mol% with respect to a total of 100 mol% of all tetracarboxylic dianhydrides has excellent adhesion to glass and a silicon oxide film, and the value of YI is also small, but the internal stress is higher than that of the other examples.

[0148] The polyimide films of Comparative Examples 1 to 3, which do not use 1,3-bis(3-aminopropyl)tetramethyldisiloxane as a monomer, also have low internal stress and high transparency, but have small adhesion to glass and a silicon oxide film, and a large amount of floating occurs between the SiOx or glass substrate and the polyimide film after the heat test.

[0149] The polyimide film of Comparative Example 4, which does not use 9,9-bis(3,4-dicarboxyphenyl)fluorene dicarboxylic dianhydride as a monomer, has excellent adhesion to glass and a silicon oxide film, does not generate floating between the SiOx or glass substrate and the polyimide film after the heat test, and has small internal stress, but has a large value of YI and low transparency.

[0150] The polyimide film of Comparative Example 5, which does not use 1,3-bis(3-aminopropyl)tetramethyldisiloxane as a monomer and contains 3-aminopropyltriethoxysilane (APS) at 0.05 phr, also has low internal stress and high transparency, but has small adhesion to glass and a silicon oxide film, and a large amount of floating occurs between the SiOx or glass substrate and the polyimide film after the heat test.

[0151] The polyimide film of Comparative Examples 6 to 7, which do not use 1,3-bis(3- aminopropyl)tetramethyldisiloxane as a monomer, contain 0.2 phr to 0.3 phr of 3- aminopropyltriethoxysilane (APS), and have low internal stress and high transparency, but have low adhesion to a silicon oxide film, and after a heat test, a float is generated between the SiOx or the glass substrate and the polyimide film.

[0152] The polyimide film of Comparative Example 8, which does not use 9,9-bis(3,4- dicarboxyphenyl)fluorene dicarboxylic acid dianhydride as a monomer and uses CHDA instead of PDA, is damaged by thermal decomposition after a heat test.

[0153] It is confirmed from the results that the polyimide obtained by introducing 1,3-bis(3- aminopropyl)tetramethyldisiloxane into a polyamic acid formed from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dicarboxylic acid dianhydride and 1,4-phenylenediamine in the embodiment of the present application has excellent heat resistance, high adhesion to a glass and a silicon oxide film, and high transparency.

[0154] Further, it is confirmed that the polyimide obtained by introducing 1,3-bis(3- aminopropyl)tetramethyldisiloxane into a polyamic acid formed from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride at a ratio of 70 to 99 mol%, 9,9-bis(3,4-dicarboxyphenyl)fluorene dicarboxylic acid dianhydride at a ratio of 1 to 30 mol%, and further 1,4-phenylenediamine as a diamine at a total of 100 mol% of all tetracarboxylic acid dianhydrides has excellent heat resistance, high adhesion to a glass and a silicon oxide film, low internal stress to an inorganic substrate, and high transparency.

[0155] The present application is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means respectively disclosed in the different embodiments are also included in the scope of the present application. Further, new technical features can be formed by combining the technical means respectively disclosed in the embodiments.

Claims

1. A polyamic acid, which is an addition polymerization product of a diamine and a tetracarboxylic dianhydride, wherein the diamine comprises 1,4-phenylenediamine and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the tetracarboxylic dianhydride comprises 3,3,4,4-biphenyltetracarboxylic dianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride.

2. The polyamic acid according to claim 1, wherein, The ratio of 1,3-bis(3-aminopropyl)tetramethyldisiloxane to the total amount of the diamine is 0.1 mol% to 10.0 mol%.

3. The polyamic acid according to claim 1, wherein, The ratio of 3,3,4,4-biphenyltetracarboxylic acid dianhydride to the total amount of tetracarboxylic acid dianhydride is 70 mol% to 99 mol%.

4. The polyamic acid according to claim 1, wherein, The ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorenic dianhydride to the total amount of tetracarboxylic dianhydride is 1 mol% to 30 mol%.

5. A polyamic acid solution comprising: the polyamic acid of claim 1 and an organic solvent.

6. The polyamic acid solution according to claim 5, wherein, The organic solvent is a urea solvent, a sulfoxide or sulfone solvent, an amide solvent, an ester solvent, a haloalkane solvent, an aromatic hydrocarbon solvent, a phenol solvent, a ketone solvent, an ether solvent, or a combination of two or more thereof.

7. The polyamic acid solution according to claim 5 further contains imidazoles.

8. The polyamic acid solution according to claim 7, wherein, The content of the imidazole group is less than 0.10 mol relative to 1 mol of the amide group of the polyamic acid.

9. A polyimide, which is an imide of the polyamic acid solution according to any one of claims 5 to 8.

10. The polyimide according to claim 9, wherein the yellowness (YI) at a film thickness of 10 μm is 20 or less.

11. A method for manufacturing a laminate, wherein, The polyamic acid solution of any one of claims 5 to 8 is cast onto a support and imidized to form a polyimide substrate on the support.

12. The method for manufacturing a laminate according to claim 11, wherein, The polyamic acid in the polyamic acid solution is thermally imidized.

13. A laminate comprising a polyimide substrate and a support formed from the polyimide of claim 9.

14. The laminate according to claim 13, wherein, The thickness of the polyimide substrate is 1–200 μm.

15. The laminate according to claim 13, wherein, The polyimide substrate is a polyimide film formed in a two-layer manner, with an inorganic film formed as an intermediate layer between each polyimide layer of the polyimide film formed in a two-layer manner, or the inorganic film is formed on the polyimide film formed in a two-layer manner.

16. The laminate according to claim 13, wherein, The internal stress generated between the polyimide substrate and the support is less than 30 MPa.

17. The laminate according to claim 13, wherein, The 90° peel strength of the polyimide substrate from the support is 0.08 N / cm to 5.00 N / cm.

18. The laminate according to claim 15, wherein, The polyimide substrate has a 90° peel strength of 0.05 N / cm or higher when peeled from the inorganic film.

19. An electronic device having electrodes and / or electronic components on a polyimide substrate as claimed in claim 13.

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