CN115803365A

CN115803365A - Polyamic acid, polyamic acid solution, polyimide film, laminate, method for producing laminate, and electronic device

Info

Publication number: CN115803365A
Application number: CN202180045105.7A
Authority: CN
Inventors: 中山博文
Original assignee: Kaneka Corp
Current assignee: Kaneka Corp
Priority date: 2020-06-23
Filing date: 2021-05-31
Publication date: 2023-03-14
Anticipated expiration: 2041-05-31
Also published as: CN115803365B; JPWO2021261177A1; KR20230027146A; TW202210556A; WO2021261177A1

Abstract

The polyamic acid includes a structural unit represented by the following chemical formula (1). The polyamic acid solution contains a polyamic acid including a structural unit represented by the following chemical formula (1) and an organic solvent. The polyimide is an imide compound of a polyamic acid including a structural unit represented by the following chemical formula (1). The polyimide film contains an imide compound of a polyamic acid containing a structural unit represented by the following chemical formula (1). The laminate comprises a support and a polyimide film containing an imide compound of a polyamic acid containing a structural unit represented by the following chemical formula (1). The electronic device has: a polyimide film containing an imide compound of a polyamic acid containing a structural unit represented by the following chemical formula (1), and a polyimide film disposed on the polyimide filmThe electronic component (c).

Description

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

Technical Field

The present invention relates to polyamic acid, polyamic acid solution, polyimide film, laminate, method for producing laminate, and electronic device. The present invention also relates to a material for electronic devices, 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 EL, electronic paper, or the like), a 3D display, a solar cell, a touch panel, a transparent conductive film substrate, and a material alternative to a member using glass at present, each of which uses polyimide.

Background

With rapid progress in displays such as liquid crystal displays, organic EL displays, and electronic paper, and electronic devices such as solar cells and touch panels, thinning, weight reduction, and flexibility of the devices have been advanced. In these devices, polyimide is used as a substrate material instead of a glass substrate.

In these devices, various electronic components such as a thin film transistor, a transparent electrode, and the like are formed on a substrate, and the formation of these electronic components requires a high-temperature process. Polyimide has heat resistance sufficient to accommodate high-temperature processes, and has a Coefficient of Thermal Expansion (CTE) close to that of a glass substrate or an electronic component, and therefore, internal stress is not easily generated, and it is suitable for a substrate material for a flexible display or the like.

Generally, aromatic polyimides are colored in a yellowish brown color due to intramolecular conjugation and formation of a Charge Transfer (CT) complex, but in top emission organic EL and the like, since 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, when light emitted from a display element is emitted through a substrate, as in a transparent display, a bottom emission type organic EL, or a liquid crystal display, or when a sensor or a camera module is disposed on the back surface of a substrate in order to make a smartphone or the like a full-screen display (without a notch), high optical characteristics (more specifically, transparency or the like) are also required for the substrate.

Against such a background, a material having heat resistance equivalent to that of conventional aromatic polyimide and excellent transparency is required.

In order to reduce coloration of polyimide, there are known a technique of suppressing formation of a CT complex using an aliphatic monomer (patent documents 1 and 2) and a technique of improving transparency using a monomer having a fluorine atom and a sulfur atom (patent document 3).

The polyimides described in patent documents 1 and 2 have high transparency and low CTE, but have an aliphatic structure, so that the polyimide has a low thermal decomposition temperature and is difficult to apply to a high-temperature process for forming an electronic component.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2016-29177

Patent document 2: japanese patent laid-open No. 2012-41530

Patent document 3: japanese patent laid-open No. 2014-70139

Disclosure of Invention

Problems to be solved by the invention

According to the research of the inventor, the following steps are found: the polyimide described in patent document 3 has high transparency, but contains fluorine atoms, and therefore, the surface free energy is reduced, which may result in low adhesion to a barrier film and an electronic component formed on a polyimide substrate, and delamination at the interface with the polyimide in a high-temperature process. In addition, according to the study of the present inventors, it is known that: the polyimide described in patent document 3 may have poor adhesion to a barrier film or an electronic component due to fluorine-based decomposition gas generated in a high-temperature process.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a polyimide which has excellent transparency and high heat resistance and can secure adhesion to an inorganic material (more specifically, a glass substrate, a barrier film, or the like) in a high-temperature process, and a polyamic acid as a precursor thereof. Further, another object is to provide a product or a member which is produced using the polyimide and the polyamic acid and which requires heat resistance and transparency. In particular, an object of the present invention is to provide a product or a member in which the polyimide film of the present invention is formed on the surface of an inorganic substance such as glass, metal oxide, and single crystal silicon.

Means for solving the problems

As a result of intensive studies, the present inventors have found that a polyimide obtained by imidizing a specific polyamic acid having a fluorene skeleton (fluorene structure) is excellent in transparency, has high heat resistance, and can secure adhesion to a glass substrate or a barrier film in a high-temperature process, thereby completing the present invention.

The polyamic acid of the present invention includes a structural unit represented by the following chemical formula (1).

The polyamic acid according to one embodiment of the present invention further includes a structural unit represented by the following general formula (2).

In the general formula (2), X represents a 4-valent organic group different from the tetracarboxylic dianhydride residue in the chemical formula (1).

In one embodiment of the polyamic acid of the present invention, X in the general formula (2) is at least one selected from the group consisting of a 4-valent organic group represented by the following chemical formula (3) and a 4-valent organic group represented by the following chemical formula (4).

In one embodiment of the polyamic acid of the present invention, the content of the structural unit represented by the chemical formula (1) is 1 mol% or more based on the total structural units.

In one embodiment of the polyamic acid of the present invention, the ratio of the amount of the total amount of the tetracarboxylic dianhydride residue divided by the amount of the total amount of the diamine residue is 0.900 or more and less than 1.100.

The polyamic acid solution of the present invention contains the polyamic acid of the present invention and an organic solvent.

The polyimide of the present invention is an imide of the polyamic acid of the present invention.

The polyimide of the present invention preferably has a 1% weight loss temperature of 500 ℃ or higher. The polyimide of the present invention preferably has a glass transition temperature of 400 ℃ or higher.

The polyimide film of the present invention contains the polyimide of the present invention.

The yellow index of the polyimide film of the present invention is preferably 25 or less. The polyimide film of the present invention preferably has a haze of less than 1.0%.

The laminate of the present invention comprises a support and the polyimide film of the present invention.

In the method for producing a laminate of the present invention, the polyamic acid solution of the present invention is applied to a support to form a coating film containing the polyamic acid, and the coating film is heated to imidize the polyamic acid.

The electronic device of the present invention comprises the polyimide film of the present invention and an electronic component disposed on the polyimide film.

ADVANTAGEOUS EFFECTS OF INVENTION

The polyimide produced using the polyamic acid of the present invention is excellent in transparency and heat resistance, and can secure adhesion to an inorganic material in a high-temperature process. Therefore, the polyimide produced using the polyamic acid of the present invention is suitable as a material for electronic devices which require transparency and heat resistance and are produced through a high-temperature process.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

First, terms used in the present specification will be described. "structural unit" means a repeating unit constituting a polymer. The "polyamic acid" is a polymer containing a structural unit represented by the following general formula (5) (hereinafter, may be referred to as "structural unit (5)").

In the general formula (5), a represents a tetracarboxylic dianhydride residue (a 4-valent organic group derived from a tetracarboxylic dianhydride), and B represents a diamine residue (a 2-valent organic group derived from a diamine).

The content of the structural unit (5) relative to the total structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, further preferably 80 mol% or more and 100 mol% or less, further more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

The "1% weight loss temperature" is a measurement temperature at which the weight of the polyimide at a measurement temperature of 150 ℃ is taken as a reference (100 wt%), and the weight is reduced by 1 wt% from the reference weight. The method of measuring the 1% weight loss temperature is the same as or based on the method described in the examples below.

Hereinafter, the compound and its derivatives may be collectively referred to in general terms by adding a "system" to the compound name. When a "system" is added after a compound name to indicate a polymer name, it means that a repeating unit of the polymer is derived from the compound or a derivative thereof. In addition, tetracarboxylic dianhydride is sometimes described as "acid dianhydride".

The polyamic acid of the present embodiment includes a structural unit represented by the following chemical formula (1) (hereinafter, may be referred to as "structural unit (1)").

The structural unit (1) has a partial structure derived from 9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride (hereinafter, sometimes referred to as "BPAF") and a partial structure derived from 4-aminophenyl-4-aminobenzoate (hereinafter, sometimes referred to as "4-bab"). That is, the structural unit (1) has a BPAF residue as A in the above-mentioned general formula (5) and a 4-BAAB residue as B in the general formula (5).

4-BAAB has a rigid structure and is therefore suitable as a raw material (monomer) for polyimide having a high glass transition temperature (excellent heat resistance). Further, 4-BAAB having a rigid structure is also suitable as a raw material (monomer) for polyimide which suppresses the generation of internal stress and has high mechanical strength. BPAF has a bulky fluorene structure, and is therefore suitable as a raw material (monomer) for polyimide having excellent heat resistance and transparency.

In synthesizing the polyamic acid according to the embodiment, a diamine other than 4-BAAB may be used as a monomer within a range not impairing the performance. Examples of diamines other than 4-BAAB include: 1, 4-diaminocyclohexane, p-phenylenediamine, m-phenylenediamine, 4' -oxydianiline, 3,4' -oxydianiline, 2' -bis (trifluoromethyl) -4,4' -diaminodiphenyl ether, 4' -diaminobenzanilide, N, N ' -bis (4-aminophenyl) terephthalamide, 4' -diaminodiphenyl sulfone, m-tolidine, o-tolidine, 4' -bis (aminophenoxy) biphenyl, 2- (4-aminophenyl) -6-aminobenzoxazole, 3, 5-diaminobenzoic acid, 4' -diamino-3, 3' -dihydroxybiphenyl, 4' -methylenebis (cyclohexylamine), 1, 3-bis (3-aminopropyl) tetramethyldisiloxane, and derivatives thereof, which may be used alone or in combination of 2 or more. From the viewpoint of improving heat resistance, improving mechanical strength, and reducing internal stress, the diamine other than 4-BAAB is preferably at least one selected from the group consisting of p-phenylenediamine and 4,4' -diaminobenzanilide, and more preferably p-phenylenediamine. The content of the 4-BAAB residue is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and may be 100 mol% with respect to the total diamine residues constituting the polyamic acid, from the viewpoints of improving transparency, improving heat resistance, improving mechanical strength, and reducing internal stress.

The polyamic acid of the present embodiment preferably further includes a structural unit represented by the following general formula (2) (hereinafter, may be referred to as "structural unit (2)") in addition to the structural unit (1) from the viewpoints of improvement in transparency and reduction in internal stress. When the polyamic acid of the present embodiment includes the structural unit (1) and the structural unit (2), the arrangement of the structural unit (1) and the structural unit (2) in the polyamic acid may be random or block.

In the general formula (2), X represents a 4-valent organic group different from the tetracarboxylic dianhydride residue in the chemical formula (1). X may be 1 species or 2 or more species.

Suitable examples of the acid dianhydride for forming the structural unit (2) (the acid dianhydride represented by X in the general formula (2)) include pyromellitic dianhydride (hereinafter, sometimes referred to as "PMDA"), 3', 4' -biphenyltetracarboxylic dianhydride (hereinafter, sometimes referred to as "BPDA"), p-phenyleneditrimellitate dianhydride (p-phenylenediylbis (trimellitaneanhydride)), 2,3,6, 7-naphthalenetetracarboxylic dianhydride, 1,2,5, 6-naphthalenetetracarboxylic dianhydride, 2', 3' -biphenyltetracarboxylic dianhydride, 3',4,4' -benzophenonetetracarboxylic dianhydride, 4,4' -oxydiphthalic anhydride, 4,4' - (hexafluoroisopropylidene) phthalic anhydride, dicyclohexyl-3,3 ',4,4' -tetracarboxylic dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 2' -oxydisuro [ bicyclo [2.2.1] heptane-2, 1 "-cycloheptane-3, 2" -bicyclo [2.2.1] heptane ] -5,5' -6,6' -tetracarboxylic dianhydride, and derivatives thereof, which may be used alone or in combination of 2 or more.

From the viewpoint of improving heat resistance, improving mechanical strength, and reducing internal stress, the acid dianhydride providing X in the general formula (2) is preferably at least one selected from the group consisting of PMDA and BPDA, and more preferably BPDA. When PMDA is used as the acid dianhydride, X in the general formula (2) is a 4-valent organic group represented by the following chemical formula (3). When BPDA is used as the acid dianhydride, X in the general formula (2) is a 4-valent organic group represented by the following chemical formula (4).

In the case where the polyamic acid of the present embodiment includes at least one of a PMDA residue and a BPDA residue, the total content of the BPAF residue, the PMDA residue, and the BPDA residue is preferably 60 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and may be 100 mol% with respect to all acid dianhydride residues constituting the polyamic acid, from the viewpoints of improving transparency, improving heat resistance, improving mechanical strength, and reducing internal stress.

In particular, the BPAF residue has a bulky structure derived from a fluorene structure, and contributes to improvement of heat resistance, improvement of transparency, and reduction of yellow index, and crystallization of polyimide can be suppressed by including only a small amount of BPAF residue. Therefore, the content of the structural unit (1) including a BPAF residue is preferably 1 mol% or more, more preferably 3 mol% or more, further preferably 5 mol% or more, and further more preferably 10 mol% or more, based on the total structural units of the polyamic acid of the present embodiment. From the viewpoint of reducing the internal stress, the content of the structural unit (1) containing a BPAF residue is preferably 50 mol% or less, more preferably 40 mol% or less, and still more preferably 30 mol% or less, based on the total structural units of the polyamic acid of the present embodiment.

By setting the content of the structural unit (1) in the above range, a polyimide which suppresses the generation of internal stress and has high transparency, a low yellow index, and high heat resistance can be obtained.

When the polyamic acid of the present embodiment includes the structural unit (1) and the structural unit (2), the total content of the structural unit (1) and the structural unit (2) is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and may be 100 mol% with respect to the total structural units constituting the polyamic acid, from the viewpoints of improvement in transparency, improvement in heat resistance, improvement in mechanical strength, and reduction in internal stress.

In order to obtain a polyimide which is more excellent in transparency and heat resistance and which can more reliably ensure adhesion to an inorganic material in a high-temperature process, the polyamic acid according to the present embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, further preferably satisfies the following condition 3, and further preferably satisfies the following condition 4.

Condition 1: the polyamic acid contains at least one of a PMDA residue and a BPDA residue, and the total content of the BPAF residue, the PMDA residue and the BPDA residue is 100 mol% based on all tetracarboxylic dianhydride residues constituting the polyamic acid.

Condition 2: the content of 4-BAAB residues in the polyamide acid resin composition satisfies the above condition 1, and is 50 mol% or more and 100 mol% or less based on the total diamine residues constituting the polyamide acid.

Condition 3: the content of the structural unit (1) is 1 mol% or more and 30 mol% or less with respect to the total structural units of the polyamic acid while satisfying the above condition 1.

Condition 4: the content of the structural unit (1) is 1 mol% or more and 30 mol% or less based on the total structural units of the polyamic acid while satisfying the condition 2.

From the viewpoint of suppressing the decrease in transparency caused by the remaining of unreacted monomers at the time of polyimide formation, the amount ratio (molar ratio) of the total amount of tetracarboxylic dianhydride residues divided by the total amount of diamine residues is preferably 0.900 or more and less than 1.100, more preferably 0.950 or more and 1.080 or less, and still more preferably 1.000 or more and 1.050 or less. By adjusting the amount ratio of the substances within the above range, a polyimide having excellent transparency can be obtained.

The polyamic acid of the present invention can be synthesized by a known general method, and can be obtained by reacting a diamine and a tetracarboxylic dianhydride in an organic solvent, for example. An example of a specific method for synthesizing a polyamic acid will be described. First, a diamine solution is prepared by dissolving or dispersing a diamine in an organic solvent in an inert gas atmosphere such as argon or nitrogen in the form of a slurry. Then, the tetracarboxylic dianhydride is dissolved in an organic solvent, dispersed in a slurry state, or added to the diamine solution in a solid state.

In the case of synthesizing a polyamic acid using a diamine and a tetracarboxylic dianhydride, a desired polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the amount of the substance of the diamine (the amount of each diamine in the case of using a plurality of diamines) and the amount of the substance of the tetracarboxylic dianhydride (the amount of each tetracarboxylic dianhydride in the case of using a plurality of tetracarboxylic dianhydrides). The mass ratio (molar ratio) of each residue in the polyamic acid is, for example, the same as the mass ratio of each monomer (diamine and tetracarboxylic dianhydride) used for the synthesis of the polyamic acid. Further, by mixing 2 kinds of polyamic acids, a polyamic acid containing a plurality of tetracarboxylic dianhydride residues and a plurality of diamine residues can be obtained. The temperature condition for the reaction between the diamine and the tetracarboxylic dianhydride, that is, the synthesis reaction of the polyamic acid is not particularly limited, and is, for example, in the range of 20 ℃ to 150 ℃. The reaction time of the synthesis reaction of the polyamic acid is, for example, in the range of 10 minutes to 30 hours.

The organic solvent used for the synthesis of the polyamic acid is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the produced polyamic acid. Examples of the organic solvent used for the synthesis of the polyamic acid include urea solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as diphenyl sulfone and tetramethyl sulfone; amide solvents such as N, N-Dimethylacetamide (DMAC), N-Dimethylformamide (DMF), N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), hexamethylphosphoric triamide, and the like; ester solvents such as γ -butyrolactone; halogenated alkyl solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenol solvents such as phenol and cresol; ketone solvents such as cyclopentanone; ether solvents such as tetrahydrofuran, 1, 3-dioxolane, 1, 4-dioxane, dimethyl ether, diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents may be used alone or in combination of 2 or more, as required. In order to improve the solubility and reactivity of the polyamic acid, the organic solvent used in the synthesis reaction of the polyamic acid is preferably at least one solvent selected from the group consisting of an amide solvent, a ketone solvent, an ester solvent, and an ether solvent, and more preferably an amide solvent (more specifically, DMF, DMAC, NMP, and the like). The synthesis reaction of the polyamic acid is preferably performed in an inert gas atmosphere such as argon or nitrogen.

The weight average molecular weight of the polyamic acid of the present embodiment varies depending on the use thereof, and is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 500,000, and still more preferably in the range of 30,000 to 200,000. When the weight average molecular weight is 10,000 or more, polyamic acid or polyimide obtained using polyamic acid can be easily formed into a coating film or a polyimide film (thin film). On the other hand, when the weight average molecular weight is 1,000,000 or less, since sufficient solubility in a solvent is exhibited, a coating film or a polyimide film having a smooth surface and a uniform thickness can be obtained by using a polyamic acid solution described later. The weight average molecular weight used herein refers to a polyethylene oxide equivalent value measured by Gel Permeation Chromatography (GPC).

The polyimide of the present embodiment is an imide compound of the polyamic acid of the present embodiment described above. The polyimide of the present embodiment can be obtained by a known method, and the production method thereof is not particularly limited. An example of a method for obtaining the polyimide of the present embodiment by imidizing the polyamic acid will be described below. Imidization is performed by dehydrating and ring-closing polyamic acid. The dehydration ring closure can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. The imidization of the polyimide from the polyamic acid may be performed at any ratio of 1% to 100%. That is, a polyamic acid partially imidized can be synthesized. In particular, when imidization is performed by heating to raise the temperature, the ring closure reaction of the polyamic acid to the polyimide proceeds simultaneously with hydrolysis of the polyamic acid, and there is a possibility that the molecular weight when the polyimide is produced becomes lower than that of the polyamic acid, or coloring is caused by oxidation of diamine generated by hydrolysis or the like, and therefore, from the viewpoint of improving transparency and mechanical properties, it is preferable to imidize a part of the polyamic acid in the polyamic acid solution in advance before forming a polyimide film described later. In the present specification, a polyamic acid partially imidized may be also referred to as "polyamic acid".

The polyamic acid solution of the present embodiment includes the polyamic acid of the present embodiment described above and an organic solvent. Here, the organic solvent contained in the polyamic acid solution includes the organic solvents exemplified as the organic solvents usable in the synthesis reaction of the polyamic acid, and is preferably at least one solvent selected from the group consisting of an amide solvent, a ketone solvent, an ester solvent, and an ether solvent, and more preferably an amide solvent (more specifically, DMF, DMAC, NMP, and the like). When the polyamic acid is obtained by the above-described method, the reaction solution (solution after the reaction) itself may be used as the polyamic acid solution of the present embodiment. The polyamic acid solution of the present embodiment can be prepared by dissolving solid polyamic acid obtained by removing the solvent from the reaction solution in the solvent. The content of the polyamic acid in the polyamic acid solution according to the present embodiment is not particularly limited, and is, for example, 1 wt% or more and 80 wt% or less with respect to the total amount of the polyamic acid solution.

The dehydration ring-closing of the polyamic acid may be performed by heating the polyamic acid. The method for heating the polyamic acid is not particularly limited, and for example, the polyamic acid solution of the present embodiment may be applied to a support such as a glass substrate, a metal plate, or a PET film (polyethylene terephthalate film), and then the heat treatment of the polyamic acid may be performed at a temperature in the range of 40 ℃ to 500 ℃. According to this method, the laminate of the present embodiment having a support and a polyimide film (specifically, a polyimide film containing an imide product of a polyamic acid of the present embodiment) disposed on the support can be obtained. Alternatively, the dehydration ring-closing of the polyamic acid can also be performed by directly placing the polyamic acid solution in a container subjected to a mold release treatment such as coating with a fluorine-based resin, and heating and drying the polyamic acid solution under reduced pressure. By dehydration ring closure of polyamic acid by these methods, polyimide can be obtained. The heating time of each treatment differs depending on the amount of the polyamic acid solution subjected to the dehydration ring-closing and the heating temperature, and is preferably in the range of 1 to 300 minutes after the treatment temperature reaches the maximum temperature. In order to shorten the heating time and express the characteristics, an imidizing agent and/or a dehydration catalyst may be added to the polyamic acid solution, and the polyamic acid solution to which the imidizing agent and/or the dehydration catalyst is added may be heated by the above-described method to perform imidization.

The imidizing agent is not particularly limited, and a tertiary amine may be used. The tertiary amine is preferably a heterocyclic tertiary amine. Preferable specific examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline, and 1, 2-dimethylimidazole. Preferred examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

The addition amount of the imidizing agent is preferably 0.5 to 5.0 times by mol equivalent, more preferably 0.7 to 2.5 times by mol equivalent, and still more preferably 0.8 to 2.0 times by mol equivalent, based on the amide group of the polyamic acid. The amount of the dehydration catalyst to be added is preferably 0.5 to 10.0 times by mol equivalent, more preferably 0.7 to 5.0 times by mol equivalent, and still more preferably 0.8 to 3.0 times by mol equivalent, based on the amide group of the polyamic acid. In the present specification, the "amide group of a polyamic acid" refers to an amide group formed by a polymerization reaction of a diamine and a tetracarboxylic dianhydride. When the imidizing agent and/or the dehydration catalyst are added to the polyamic acid solution, they may be added as they are without being dissolved in an organic solvent, or they may be added as they are dissolved in an organic solvent. In the method of adding the imide compound as it is insoluble in an organic solvent, the imide compound and/or the dehydration catalyst may react rapidly before diffusing to form a gel. Therefore, it is more preferable to add a solution obtained by dissolving the imidizing agent and/or the dehydration catalyst in the organic solvent to the polyamic acid solution.

The polyimide film of the present embodiment (specifically, a polyimide film including an imide compound of a polyamic acid of the present embodiment) is colorless and transparent, has a low yellow index, and has a glass transition temperature (heat resistance) that can withstand a TFT manufacturing process, and is therefore suitable as a transparent substrate material for a flexible display. The content of the polyimide (specifically, the imide compound of the polyamic acid according to the present embodiment) in the polyimide film according to the present embodiment is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may be 100% by weight, based on the total amount of the polyimide film. Examples of the component other than polyimide in the polyimide film include additives (more specifically, nano silica particles and the like) described later.

The electronic device of the present embodiment includes: the polyimide film of the present embodiment, and an electronic component disposed on the polyimide film. When the electronic device of the present embodiment is manufactured for use as a flexible display, first, an inorganic substrate such as glass is used as a support, and a polyimide film is formed thereon. Then, an electronic element such as a TFT is disposed (formed) on the polyimide film, thereby forming an electronic device on the support. The step of forming the TFT is usually performed in a wide temperature range of 150 ℃ to 650 ℃, but actually, in order to achieve desired performance, an oxide semiconductor layer and an a-Si layer are formed at 300 ℃ or higher, and in some cases, a-Si or the like is crystallized by a laser or the like.

In this case, when the thermal decomposition temperature of the polyimide film is low, there is a possibility that exhaust gas (out gas) is generated during formation of the electronic component, and the exhaust gas adheres to the inside of the oven as a sublimate, which causes contamination in the oven, or an inorganic film (a barrier film and the like described later) formed on the polyimide film and the electronic component are peeled off, and therefore, the 1% weight loss temperature of the polyimide film is preferably 500 ℃. The higher the upper limit of the 1% weight loss temperature of the polyimide, the better, for example, 520 ℃. The 1% weight loss temperature can be adjusted by, for example, changing the content of a residue having a rigid structure (more specifically, a 4-BAAB residue, a BPDA residue, etc.). More specifically, an inorganic film such as a silicon oxide film (SiOx film) or a silicon nitride film (SiNx film) is formed as a barrier film on a polyimide film before formation of the TFT. If the polyimide has low heat resistance, the polyimide and the inorganic film may be peeled off due to volatile components such as decomposition gas of the polyimide in a high-temperature process after the inorganic film is laminated. Therefore, it is desirable that the polyimide not only has a 1% weight loss temperature of 500 ℃ or higher, but also has a weight loss ratio of less than 1% when the polyimide is isothermally held at a temperature in the range of 400 ℃ to 450 ℃.

Further, the present inventors have verified that a polyimide film containing fluorine atoms and a polyimide film containing no fluorine atoms are significantly different in adhesion between the polyimide film and the inorganic film. This is considered to be because the surface free energy of the polyimide film containing fluorine atoms is significantly low. Therefore, in order to suppress peeling between the inorganic film and the polyimide film in the high-temperature process, the polyimide preferably has a low fluorine atom content, and more preferably is derived from a monomer containing no fluorine atom.

In addition, when the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, a positional shift or the like may occur in the formation of an electronic component, and therefore the Tg of the polyimide is preferably 300 ℃ or higher, more preferably 350 ℃ or higher, and further preferably 400 ℃ or higher. The higher the upper limit of the Tg of the polyimide, the better, for example, 450 ℃. In addition, since the glass substrate generally has a smaller thermal expansion coefficient than the resin, internal stress is generated between the glass substrate and the polyimide film. When the internal stress of the laminate of the glass substrate, the electronic component, and the polyimide film used as the support is high, the laminate including the polyimide film expands in the TFT forming step at a high temperature and then contracts when cooled to a normal temperature, causing problems such as warpage and breakage of the glass substrate and peeling of the polyimide film from the glass substrate. Therefore, the internal stress generated in the laminate of the polyimide film and the glass substrate is preferably 30MPa or less, more preferably 25MPa or less, and still more preferably 20MPa or less.

The polyimide of the present embodiment can be suitably used as a material for a display substrate such as a TFT substrate or a touch panel substrate. When polyimide is used for the above applications, the following methods are often used: after forming an electronic component (specifically, an electronic component having an electronic element formed on a polyimide film) on a support as described above, the polyimide film is peeled off from the support. Further, alkali-free glass is suitably used as a material of the support. An example of a method for producing a laminate of a polyimide film and a support will be described in detail below.

First, the polyamic acid solution of the present embodiment is applied to a support to form a coating film containing a polyamic acid and a laminate containing the coating film of the support. Next, the laminate containing the coating film is heated at a temperature of, for example, 40 ℃ to 200 ℃. The heating time in this case is, for example, 3 minutes to 120 minutes. For example, a multi-stage heating step may be provided, such as heating the laminate including the coating film at 50 ℃ for 30 minutes and then heating the laminate at 100 ℃ for 30 minutes. Next, in order to progress imidization of the polyamic acid in the coating film, the laminate containing the coating film is heated, for example, at a maximum temperature of 200 ℃ to 500 ℃. The heating time at this time (heating time at the highest temperature) is, for example, 1 minute or more and 300 minutes or less. In this case, the temperature is preferably gradually increased from the low temperature to the maximum temperature. The temperature increase rate is preferably 2 ℃/min to 10 ℃/min, more preferably 4 ℃/min to 10 ℃/min. The maximum temperature is preferably in the range of 250 ℃ to 450 ℃. If the maximum temperature is 250 ℃ or higher, imidization proceeds sufficiently, and if the maximum temperature is 450 ℃ or lower, thermal deterioration and coloring of polyimide can be suppressed. Alternatively, the temperature may be maintained at an arbitrary temperature for an arbitrary time until the maximum temperature is reached. The imidization reaction may be carried out under air, under reduced pressure, or in an inert gas such as nitrogen, but in order to obtain higher transparency, it is preferably carried out under reduced pressure or in an inert gas such as nitrogen. As the heating device, a known device such as a hot air oven, an infrared oven, a vacuum oven, an inert (inert) oven, or a hot plate can be used. Through these steps, the polyamic acid in the coating film is imidized, and a laminate of the support and the polyimide film (imide of polyamic acid) can be obtained. In order to shorten the heating time and express the characteristics, an imidizing agent and a dehydration catalyst may be added to the polyamic acid solution, and the solution may be heated and imidized in the above-described method.

A known method can be used for peeling the polyimide film from the laminate of the obtained support and polyimide film. For example, peeling may be performed by hand, or may be performed using a mechanical device such as a driving roller or a robot. Further, the following method may be adopted: a method in which a release layer is provided between a support and a polyimide film; a method of forming a silicon oxide film on a substrate having a plurality of grooves, forming a polyimide film using the silicon oxide film as a base layer, and immersing an etching solution of silicon oxide between the substrate and the silicon oxide film to thereby peel off the polyimide film. In addition, a method of separating the polyimide film by irradiation with a laser beam may be employed.

If the interface between the polyimide film and the support (for example, a glass substrate) has a bump, there is a possibility that the polyimide film is peeled off during the formation of the electronic component or the yield is lowered when the polyimide film is peeled off after the formation of the electronic component. The term "bulge" refers to a state in which: the polyimide film and other material layers (more specifically, glass substrates, barrier films, etc.) are in a state of poor adhesion due to the auxiliary components (more specifically, release components, etc.) generated during imidization and the remaining solvent. Specific "bumps" include: a state where the polyimide film is raised from the glass substrate, a state where a part of the polyimide film is broken and interlayer peeling occurs between the polyimide film and another material layer, a state where the barrier film is raised from the polyimide film, and the like. For example, in the case of polyimide comprising BPDA and 4-BAAB, highly oriented molecular chains are densely packed, and the outgassing of subcomponents produced during imidization is poor, so that swelling is likely to occur. According to the studies of the present inventors, it has been found that the formation of a bulky structure in a molecular chain or at a terminal can prevent the formation of a bulge. Further, according to the studies of the present inventors, it has been found that a good exhaust property and a high Tg can be achieved at the same time by using a combination of BPAF and 4-BAAB having a structure with a large volume and a low rotational degree of freedom. According to the polyamic acid of the present embodiment, generation of swelling can be suppressed because of having the structural unit (1) containing the BPAF residue and the 4-BAAB residue. Therefore, according to the polyamic acid of the present embodiment, adhesion to an inorganic material in a high-temperature process can be ensured.

The transparency of the polyimide film can be measured by the following method in accordance with JIS K7361-1:1997 total light transmittance (TT) and haze according to JIS K7136-2000. When the polyimide film is used in applications where high transparency is required, the total light transmittance of the polyimide film is preferably 75% or more, more preferably 80% or more. When a polyimide film is used for applications requiring high transparency, the haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, even more preferably less than 1.0%, and may be 0%. In applications where high transparency is required, a polyimide film is required to have high transmittance over the entire wavelength range, and the polyimide film tends to easily absorb light on the short wavelength side, and the film itself is often colored yellow. In order to use the polyimide film in applications where high transparency is required, the Yellow Index (YI) of the polyimide film is preferably 25 or less, more preferably 20 or less, further preferably 15 or less, and may be 0.YI can be measured according to JIS K7373-2006. The polyimide film thus provided with transparency is suitable for a transparent substrate for glass replacement or the like, and a substrate having a sensor or a camera module provided on the back surface thereof.

Further, the light extraction method of the flexible display includes 2 types, i.e., a top emission method in which light is extracted from the TFT element side and a bottom emission method in which light is extracted from the rear surface side of the TFT element. The top emission type is characterized in that light is not blocked by the TFT element, and therefore, an aperture ratio is easily increased, and high-definition image quality is obtained, and the bottom emission type is characterized in that alignment between the TFT element and the pixel electrode is easily performed, and manufacturing is easily performed. When the TFT element is transparent, the aperture ratio can be increased even in the bottom emission type, and therefore, the bottom emission type which is easy to manufacture tends to be adopted for a large-sized display. The polyimide film of the present embodiment has a low YI and excellent heat resistance, and thus can be applied to any of the light extraction methods described above.

In addition, in a batch-type device fabrication process, the adhesion between the support and the polyimide film is more preferably excellent, and the batch-type device fabrication process is characterized in that: the polyimide film is peeled off after applying a polyamic acid solution to a support such as a glass substrate, heating the solution to imidize the solution to form an electronic component or the like. The adhesion referred to herein means adhesion strength. In a manufacturing process in which a polyimide film on a support is formed into an electronic component or the like and then the polyimide film on which the electronic component or the like is formed is peeled from the support, if the polyimide film has excellent adhesion to the support, the electronic component or the like can be formed or mounted more accurately. In a production process in which an electronic component or the like is disposed on a support via a polyimide film, the higher the peel strength between the support and the polyimide film, the better the productivity. Specifically, the peel strength is preferably 0.05N/cm or more, more preferably 0.1N/cm or more.

In the above-described manufacturing process, when the polyimide film is peeled from the laminate of the support and the polyimide film, the polyimide film is often peeled from the support by laser irradiation. In this case, since the polyimide film needs to absorb the laser light, the cut-off wavelength of the polyimide film is required to be longer than the wavelength of the laser light used for the peeling. Since XeCl excimer laser light having a wavelength of 308nm is often used for laser lift-off, the cut-off wavelength of the polyimide film is preferably 312nm or more, and more preferably 330nm or more. On the other hand, since the polyimide film tends to be colored yellow when the cutoff wavelength is long, the cutoff wavelength of the polyimide film is preferably 390nm or less. The cutoff wavelength of the polyimide film is preferably 320nm or more and 390nm or less, and more preferably 330nm or more and 380nm or less, from the viewpoint of compatibility between transparency (low yellowness index) and processability by laser lift-off. The cutoff wavelength in the present specification means a wavelength at which the transmittance measured by an ultraviolet-visible spectrophotometer is 0.1% or less.

The polyamic acid and polyimide according to the present embodiment can be used as they are in coating and molding processes for producing products and members, or can be used as materials for further processing such as coating of a molded product molded into a film shape. For use in the coating or molding process, the polyamic acid or polyimide may be dissolved or dispersed in an organic solvent as necessary, and further, a photocurable component, a thermosetting component, a non-polymerizable binder resin, and other components may be blended as necessary to prepare a polyamic acid composition or a polyimide resin composition.

In order to impart processing characteristics and various functionalities to the polyamic acid and polyimide according to the present embodiment, various organic or inorganic low-molecular compounds or high-molecular compounds may be blended as additives. As the additive, for example, a dye, a surfactant, a leveling agent, a plasticizer, silicone, microparticles, a sensitizer, or the like can be used. The microparticles include: organic fine particles formed of polystyrene, polytetrafluoroethylene, or the like; the inorganic fine particles made of colloidal silica, carbon, layered silicate, or the like may have a porous structure or a hollow structure. The function and form of the fine particles are not particularly limited, and they may be, for example, pigments, fillers, or fibrous particles.

In order to maintain the transparency of the polyimide film and to improve the heat resistance, the polyamic acid and the nano silica particles may be compounded using the nano silica particles as the additive. From the viewpoint of maintaining the transparency of the polyimide film, the average primary particle diameter of the nano silica particles is preferably 200nm or less, more preferably 100nm or less, further preferably 50nm or less, and may be 30nm or less. On the other hand, the average primary particle diameter of the nano silica particles is preferably 5nm or more, more preferably 10nm or more, from the viewpoint of securing dispersibility in polyamic acid. As a method for combining polyamic acid and nano silica particles, a known method can be used, and for example, a method using an organic silica sol in which nano silica particles are dispersed in an organic solvent can be mentioned. As a method of combining polyamic acid and nano-silica particles using an organic silica sol, polyamic acid may be synthesized, and then the synthesized polyamic acid and organic silica sol may be mixed, and in order to more highly disperse nano-silica particles in polyamic acid, it is preferable to synthesize polyamic acid in the organic silica sol.

In addition, in order to improve the interaction with the polyamic acid, the nano silica particles may be surface-treated with a surface treatment agent. As the surface treatment agent, a known surface treatment agent such as a silane coupling agent can be used. As the silane coupling agent, an alkoxysilane compound having an amino group, a glycidyl group, or the like as a functional group is widely known and can be appropriately selected. In order to further enhance the interaction with the polyamic acid, an amino group-containing alkoxysilane is preferable as the silane coupling agent. Examples of the amino group-containing alkoxysilane include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 2-aminophenyltrimethoxysilane, and 3-aminopropyltriethoxysilane is preferably used from the viewpoint of stability of the raw material. As a method for surface treatment of the nano silica particles, a method in which a mixture obtained by adding a silane coupling agent to a dispersion liquid (organic silica sol) is stirred at an atmospheric temperature of 20 ℃ to 80 ℃. The stirring time in this case is, for example, 1 hour or more and 10 hours or less. In this case, a catalyst or the like for promoting the reaction may be added.

The polyamic acid composition containing nano silica particles, which is obtained by compositing polyamic acid and nano silica particles, preferably contains nano silica particles in a range of 1 part by weight or more and 30 parts by weight or less, more preferably in a range of 1 part by weight or more and 20 parts by weight or less, with respect to 100 parts by weight of polyamic acid. When the content of the nano silica particles is 1 part by weight or more, the heat resistance of the polyimide containing the nano silica particles can be improved and the internal stress can be sufficiently reduced, and when the content of the nano silica particles is 30 parts by weight or less, the adverse effect on the mechanical properties and transparency of the polyimide containing the nano silica particles can be suppressed.

Imidazole may be added to the polyamic acid of the present embodiment as an additive for imparting functionality. In the present specification, imidazole means a compound having a 1, 3-diazole ring (1, 3-diazole ring structure). The imidazole to be added to the polyamic acid of the present embodiment is not particularly limited, and examples thereof include 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1, 2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. Among these, 1, 2-dimethylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl-2-phenylimidazole are preferable, and 1, 2-dimethylimidazole and 1-benzyl-2-methylimidazole are more preferable.

The content of the imidazole compound is preferably 0.005 mol or more and 0.1 mol or less, more preferably 0.01 mol or more and 0.08 mol or less, and further preferably 0.015 mol or more and 0.050 mol or less based on 1 mol of the amide group of the polyamic acid. The film strength and transparency of polyimide can be improved by containing 0.005 mol or more of imidazole, and Tg and heat resistance can be improved while maintaining storage stability of polyamic acid by containing 0.1 mol or less of imidazole. To explain the improvement of transparency, it is known that a polymerization solvent such as NMP forms a complex based on carboxyl groups and hydrogen bonds of a polyamic acid, and when the imidization rate is low, NMP or the like remains in a polyimide film, and is oxidized and decomposed, which may cause coloring. It is considered that, when imidazoles are added, the imidazoles coordinate with the carboxyl group of the polyamic acid to promote imidization, so that NMP or the like is less likely to remain in the polyimide film, and decomposition of the polyamic acid in the thermal imidization process is also suppressed, thereby improving transparency.

The method of mixing the polyamic acid and the imidazole is not particularly limited. From the viewpoint of ease of controlling the molecular weight of the polyamic acid, it is preferable to add an imidazole to the polyamic acid after polymerization. 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 to the polyamic acid, and the method of addition is not particularly limited. The polyamic acid solution (solution containing polyamic acid and imidazole) according to the present embodiment can be prepared by adding imidazole to the solution containing polyamic acid after polymerization (solution after reaction).

The polyamic acid solution of the present embodiment may contain a silane coupling agent in order to exhibit appropriate adhesion to the support. The type of the silane coupling agent is not particularly limited, and a known silane coupling agent can be used, and a compound containing an amino group is particularly preferable from the viewpoint of reactivity with polyamic acid.

The blending ratio of the silane coupling agent to 100 parts by weight of the polyamic acid is preferably 0.01 part by weight or more and 0.50 part by weight or less, more preferably 0.01 part by weight or more and 0.10 part by weight or less, and further preferably 0.01 part by weight or more and 0.05 part by weight or less. The effect of suppressing peeling of the support can be sufficiently exhibited by setting the compounding ratio of the silane coupling agent to 0.01 parts by weight or more, and the embrittlement of the polyimide film can be suppressed by setting the compounding ratio of the silane coupling agent to 0.50 parts by weight or less, since the decrease in the molecular weight of the polyamic acid is suppressed.

Various inorganic thin films such as a metal oxide thin film and a transparent electrode can be formed on the surface of the polyimide film of the present embodiment. The method for forming these inorganic thin films is not particularly limited, and examples thereof include PVD methods such as CVD, sputtering, vacuum deposition, and ion plating.

The polyimide film of the present embodiment is preferably used in a field and a product in which these properties are considered effective, because the polyimide film has heat resistance, low thermal expansion properties, transparency, and small internal stress generated when forming a laminate with a glass substrate and can secure adhesion to an inorganic material in a high-temperature process. For example, the polyimide film of the present embodiment is preferably used for a liquid crystal display device, an image display device such as an organic EL or an electronic paper, a printed matter, a color filter, a flexible display, an optical film, a 3D display, a touch panel, a transparent conductive film substrate, a solar cell, or the like, and is more preferably used as a substitute material for a portion where glass is currently used. In these applications, the thickness of the polyimide film is, for example, 1 μm or more and 200 μm or less, and preferably 5 μm or more and 100 μm or less. The thickness of the polyimide film can be measured using a Laser holography micrometer (Laser Hologlace).

The polyamic acid solution according to the present embodiment can be suitably used in a batch-type device fabrication process in which: a polyamic acid solution is applied to a support, and after heating and imidization to form an electronic component or the like, the polyimide film is peeled off. Therefore, the present embodiment also includes a method for manufacturing an electronic device including the steps of applying a polyamic acid solution to a support, heating the polyamic acid solution to imidize the polyamic acid solution, and forming an electronic element or the like on a polyimide film formed on the support. The method for manufacturing an electronic device may further include a step of peeling the polyimide film on which the electronic component and the like are formed from the support.

Examples

Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples.

< methods for measuring and evaluating physical Properties >

First, a method of measuring physical properties of polyimide and a method of evaluating the same will be described.

[ Yellow Index (YI) ]

The polyimide films obtained in examples and comparative examples described below were measured for transmittance of light having a wavelength of 200nm to 800nm using an ultraviolet-visible near-infrared spectrophotometer ("V-650" manufactured by japan spectrographs), and the Yellowness Index (YI) of the polyimide film was calculated according to the formula described in JIS K7373-2006.

[ haze ]

The polyimide films obtained in examples and comparative examples described below were measured for haze by the method described in JIS K7136-2000 using an integrating sphere haze meter ("HM-150N", manufactured by murakamura color technology research institute).

[ internal stress ]

Each of the polyamic acid solutions prepared in examples and comparative examples described below was applied to a glass substrate (material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) made by Corning Incorporated, which was measured for warpage in advance, by a spin coater, and then heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate. In order to eliminate the influence of water absorption of the polyimide film, the laminate was dried at 120 ℃ for 10 minutes, and then the amount of warpage of the laminate in a nitrogen atmosphere at 25 ℃ was measured using a thin film stress measuring apparatus ("FLX-2320-S" manufactured by KLA-Tencor). Then, the internal stress generated between the glass substrate and the polyimide film was calculated from the warpage amount of the glass substrate before the polyimide film was formed and the warpage amount of the laminate by the Stoney formula.

[ glass transition temperature (Tg) ]

The polyimide films obtained in examples and comparative examples described below were sampled to have a width of 3mm and a length of 10mm, to obtain samples for measuring Tg. The obtained sample was subjected to a load of 98.0mN using a thermal analyzer ("TMA/SS 7100" manufactured by Hitachi High-Tech Science Co., ltd.), and the temperature was raised from 20 ℃ to 450 ℃ at 10 ℃/min, and the temperature and the strain amount (elongation) were plotted to obtain a TMA curve. The temperature at the inflection point of the obtained TMA curve (temperature corresponding to the peak in the differential curve of the TMA curve) was taken as the glass transition temperature (Tg).

[1% weight loss temperature (TD 1) ]

The polyimide films (samples) obtained in examples and comparative examples described later were heated from 25 ℃ to 650 ℃ under a condition of 20 ℃/min in a nitrogen atmosphere using a differential thermal gravimetric simultaneous measurement apparatus ("TG/DTA 7200" manufactured by Hitachi High-Tech Science), and the measurement temperature at which the weight of the sample at the measurement temperature of 150 ℃ was reduced by 1 wt% with respect to the reference weight was defined as the 1% weight loss temperature (TD 1).

[ Presence or absence of protrusion between glass substrate and polyimide film ]

Each of the polyamic acid solutions prepared in examples and comparative examples described below was applied to a glass substrate (material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) made by Corning Incorporated by means of a spin coater, heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate. The presence or absence of a bump between the glass substrate and the polyimide film was visually confirmed with respect to the obtained laminate.

[ Presence or absence of a bump between the SiOx film and the polyimide film ]

Each of the polyamic acid solutions prepared in examples and comparative examples described below was applied to a glass substrate (material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) made by Corning Incorporated by means of a spin coater, heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, thereby forming a polyimide film having a thickness of 10 μm on the glass substrate. Next, a SiOx film (thickness: 1 μm) was laminated on the obtained polyimide film by a plasma CVD method, and the obtained laminate was heated at 430 ℃ for 60 minutes in a nitrogen atmosphere. Then, the heated laminate was visually checked for the presence or absence of a bulge between the SiOx film and the polyimide film.

< preparation of polyimide film >

The following describes a method for producing a polyimide film (laminate) in examples and comparative examples. Hereinafter, compounds and reagents will be described in brief. In addition, in each of examples and comparative examples, the synthesis of polyamic acid was performed in a nitrogen atmosphere.

NMP: n-methyl-2-pyrrolidone

BPAF:9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride

BPDA:3,3'-4,4' -Biphenyltetracarboxylic dianhydride

And (3) PMDA: pyromellitic dianhydride

4-BAAB: 4-aminophenyl-4-aminobenzoic acid ester

PDA: p-phenylenediamine

And (4) TFMB:2,2' -bis (trifluoromethyl) benzidine

DMI:1, 2-dimethylimidazole

[ example 3]

In a 300mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen introduction tube, 39.6g of NMP was placed as an organic solvent for polymerization. Next, 3.030g of 4-BAAB was placed in the flask and dissolved while the flask contents were stirred. Subsequently, 0.183g of BPAF was added to the flask contents, and 3.788g of BPDA was added thereto, and the flask contents were stirred at a temperature of 25 ℃ for 24 hours to obtain a polyamic acid solution. The obtained polyamic acid solution was applied to a glass substrate (made by Corning Incorporated, material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) by means of a spin coater, and heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate.

[ example 4]

In a 300mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen introduction tube, 39.6g of NMP was placed as an organic solvent for polymerization. Next, 3.030g of 4-BAAB was placed in the flask and dissolved while stirring the flask contents. Subsequently, 0.183g of BPAF was added to the flask contents, and 3.788g of BPDA was added thereto, and the flask contents were stirred at a temperature of 25 ℃ for 24 hours. Subsequently, 1 part by weight of DMI was added to the flask relative to 100 parts by weight of polyamic acid in the flask content to obtain a polyamic acid solution. The obtained polyamic acid solution was applied to a glass substrate (made by Corning Incorporated, material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) by a spin coater, heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate.

Examples 1, 5, 7, 9 and 11

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 3, except that the charge ratio of BPAF to BPDA was changed to the ratio described in table 1. In examples 1, 5, 7, 9 and 11, the total amount of acid dianhydride was the same as in example 3.

[ examples 2, 6, 8, 10 and 12]

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 4, except that the charge ratio of BPAF to BPDA was changed to the ratio described in table 1. In examples 2, 6, 8, 10 and 12, the total amount of acid dianhydride was the same as in example 4.

[ examples 13 and 15]

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 3, except that the charge ratios of BPAF and BPDA were changed to the ratios shown in Table 1 and that 4-BAAB and PDA were used as diamines for synthesizing polyamic acid in the ratios shown in Table 1. In examples 13 and 15, the total amount of acid dianhydride and the total amount of diamine were the same as in example 3.

[ examples 14 and 16]

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 4, except that the charge ratios of BPAF and BPDA were changed to the ratios shown in Table 1 and that 4-BAAB and PDA were used as diamines for synthesizing polyamic acid in the ratios shown in Table 1. In examples 14 and 16, the total amount of acid dianhydrides and the total amount of diamines were the same as in example 4.

[ example 17]

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 4, except that PMDA was used instead of BPDA, and BPAF and PMDA were used at the charge ratios shown in table 1. The total amount of the acid dianhydrides used in example 17 is the same as the total amount of the acid dianhydrides used in example 4.

Comparative example 1

In a 300mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen introduction tube, 39.6g of NMP was placed as an organic solvent for polymerization. Next, 3.058g of 4-BAAB was put into the flask and dissolved while stirring the flask contents. Next, 3.942g of BPDA was added to the flask contents, and the flask contents were stirred at a temperature of 25 ℃ for 24 hours to obtain a polyamic acid solution. The obtained polyamic acid solution was applied to a glass substrate (made by Corning Incorporated, material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) by a spin coater, and heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate.

Comparative example 2

In a 300mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen introduction tube, 39.6g of NMP was placed as an organic solvent for polymerization. Next, 3.058g of 4-BAAB was put into the flask and dissolved while stirring the flask contents. Next, 3.942g of BPDA was added to the flask contents, and the flask contents were stirred at a temperature of 25 ℃ for 24 hours. Next, 1 part by weight of DMI was added to the flask relative to 100 parts by weight of the polyamic acid in the flask contents to obtain a polyamic acid solution. The obtained polyamic acid solution was applied to a glass substrate (made by Corning Incorporated, material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) by a spin coater, and heated at 120 ℃ for 30 minutes in air, and then heated at 430 ℃ for 30 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on the glass substrate.

Comparative example 3

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in comparative example 1, except that PDA was used in place of 4-BAAB. The amount of PDA used in comparative example 3 was the same as the amount of 4-BAAB used in comparative example 1.

Comparative example 4

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in comparative example 2, except that TFMB was used instead of 4-BAAB. The amount of TFMB used in comparative example 4 was the same as the amount of 4-BAAB used in comparative example 2.

Comparative example 5

A laminate having a polyimide film of 10 μm thickness on a glass substrate was obtained in the same manner as in example 4, except that TFMB was used instead of 4-bab, and the input ratio of BPAF to BPDA was changed to the ratio described in table 1. The amount of TFMB used in comparative example 5 was the same as the amount of 4-BAAB used in example 4. The amount of the total amount of acid dianhydrides used in comparative example 5 is the same as the amount of the total amount of acid dianhydrides used in example 4.

The materials used and their proportions are shown in table 1, and the physical properties and evaluations are shown in table 2 for examples 1 to 17 and comparative examples 1 to 5, respectively. In table 1, "-" means that this component is not used. In Table 1, the numerical value in the column of "acid dianhydride" is the content (unit: mol%) of each acid dianhydride relative to the total amount of the acid dianhydrides used. The numerical value in the column of "diamine" is the content (unit: mol%) of each diamine with respect to the total amount of the diamines used. The column of "additive" indicates the amount of additive added (unit: part by weight) per 100 parts by weight of polyamic acid in the flask content.

[ Table 1]

[ Table 2]

As described above, in the present example using the polyamic acid having the structural unit (1), all the conditions of the following (1) to (4) are satisfied.

(1) TD1 exceeds 500 ℃.

(2) YI is 25 or less.

(3) The internal stress is 30MPa or less.

(4) Tg is above 400 ℃.

In comparative examples 1 and 2, tg and TD1 were high, but haze was high, and a bump was generated between the glass substrate and the polyimide film. In comparative example 3, although Tg and TD1 were high, YI was high, and a bump was formed between the glass substrate and the polyimide film. In examples 1 to 17, tg and TD1 were high, and YI and haze were low. In examples 1 to 17, there was no protrusion between the glass substrate and the polyimide film, and there was no protrusion between the SiOx film and the polyimide film.

In comparative examples 4 and 5 containing fluorine atoms, though the yi was low, a bump was generated between the SiOx film and the polyimide film.

From the above results, it was shown that: the polyimide obtained from the polyamic acid of the present invention is excellent in transparency and heat resistance, and can secure adhesion to an inorganic material in a high-temperature process.

Claims

1. A polyamic acid comprising a structural unit represented by the following chemical formula (1),

2. the polyamic acid according to claim 1, further comprising a structural unit represented by the following general formula (2),

3. The polyamic acid according to claim 2, wherein X in the general formula (2) is at least one selected from the group consisting of a 4-valent organic group represented by the following chemical formula (3) and a 4-valent organic group represented by the following chemical formula (4),

4. the polyamic acid according to any one of claims 1 to 3, wherein a content of the structural unit represented by the chemical formula (1) is 1 mol% or more based on the total structural units.

5. The polyamic acid according to any one of claims 1 to 4, wherein the quantitative ratio of a substance obtained by dividing the amount of the total substance of the tetracarboxylic dianhydride residues by the amount of the total substance of the diamine residues is 0.900 or more and less than 1.100.

6. A polyamic acid solution comprising the polyamic acid according to any one of claims 1 to 5 and an organic solvent.

7. A polyimide which is an imide compound of the polyamic acid according to any one of claims 1 to 5.

8. The polyimide according to claim 7, having a 1% weight loss temperature of 500 ℃ or higher.

9. The polyimide according to claim 7 or 8, which has a glass transition temperature of 400 ℃ or higher.

10. A polyimide film comprising the polyimide according to any one of claims 7 to 9.

11. The polyimide film according to claim 10, having a yellow index of 25 or less.

12. The polyimide film according to claim 10 or 11, having a haze of less than 1.0%.

13. A laminate having a support and the polyimide film according to any one of claims 10 to 12.

14. A method for producing a laminate comprising a support and a polyimide film,

wherein the polyamic acid solution according to claim 6 is applied to a support to form a coating film comprising the polyamic acid, and the coating film is heated to imidize the polyamic acid.

15. An electronic device, having: the polyimide film according to any one of claims 10 to 12, and an electronic component disposed on the polyimide film.