CN118159588A

CN118159588A - Polyamic acid, polyamic acid composition, polyimide film, laminate, method for producing laminate, and electronic device

Info

Publication number: CN118159588A
Application number: CN202280071739.4A
Authority: CN
Inventors: 中山博文
Original assignee: Kaneka Corp
Current assignee: Kaneka Corp
Priority date: 2021-10-25
Filing date: 2022-10-11
Publication date: 2024-06-07
Also published as: TW202328294A; KR20240089738A; WO2023074350A1; JPWO2023074350A1

Abstract

The polyamic acid has a tetracarboxylic dianhydride residue and a diamine residue. The tetracarboxylic dianhydride residue includes one or more residues selected from the group consisting of 3,3', 4' -biphenyl tetracarboxylic dianhydride residues, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residues, 4 '-oxydiphthalic anhydride residues, spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetralone residues, and 2,3,6, 7-naphthalene tetracarboxylic dianhydride residues. The diamine residues comprise 2,2' -bis (trifluoromethyl) benzidine residues. The content of 2,3,6, 7-naphthalene tetracarboxylic dianhydride residues is 5 mol% or more and 90 mol% or less. The content of 2,2' -bis (trifluoromethyl) benzidine residues is 50 mol% or more.

Description

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

Technical Field

The present invention relates to a polyamic acid, a polyamic acid composition, a polyimide film, a laminate, a method for producing a laminate, and an electronic device. The present invention also relates to an electronic device material using polyimide, a Thin Film Transistor (TFT) substrate, a flexible display substrate, a color filter, a printed matter, an optical material, an image display device (more specifically, a liquid crystal display device, an organic EL, electronic paper, or the like), a 3D display, a solar cell, a touch panel, a transparent conductive film substrate, and a substitute material for a member using glass today.

Background

With rapid progress in electronic devices such as liquid crystal displays, organic EL, electronic paper, solar cells, and touch panels, thinning, weight saving, and flexibility of 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 thin film transistors, transparent electrodes, and the like, are formed on a substrate, and the formation of these electronic components requires a high-temperature process. Polyimide has sufficient heat resistance to cope with high temperature processes, and has a Coefficient of Thermal Expansion (CTE) similar to that of a glass substrate or an electronic component, and therefore, is hardly subjected to internal stress, and is suitable for a substrate material for flexible displays and the like.

Generally, an aromatic polyimide is colored to a yellowish brown color by intramolecular conjugation and formation of a Charge Transfer (CT) complex, but a top emission type organic EL or the like extracts light from the opposite side of a substrate, and therefore transparency is not required for the substrate, and a conventional aromatic polyimide is used. However, in the case of a transparent display, a bottom emission type organic EL, or a liquid crystal display, in which light emitted from a display element is emitted through a substrate, or in the case of disposing a sensor or a camera module on the back surface of a substrate in order to form a full-screen display (without a gap) such as a smart phone, high optical characteristics (more specifically, transparency or the like) are demanded for the substrate.

Against this background, a material having heat resistance equivalent to that of conventional aromatic polyimide, reduced in coloration, and excellent in transparency has been demanded.

In order to reduce the coloration of polyimide, there are known a technique of suppressing the formation of CT complex using an aliphatic monomer (patent documents 1 and 2) and a technique of improving transparency by using a monomer having a fluorine atom (patent document 3). In order to obtain a polyimide having a low CTE, a polyimide having a naphthalene skeleton with high planarity has been studied (patent document 4).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication 2016-2977

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

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

Patent document 4: international publication No. 2016/166961

Disclosure of Invention

Problems to be solved by the invention

The polyimides described in patent documents 1 and 2 have high transparency and low CTE, but have aliphatic structures and low thermal decomposition temperatures, and are difficult to apply to high temperature processes for forming electronic components.

In applications requiring transparency, particularly, blue light (light having a wavelength of around 470 nm) is required to have high transmittance from the viewpoint of color reproducibility and the like, and light having a wavelength of 400nm is required to have high transmittance in practical use. From the studies of the present inventors, it is clear that the polyimide described in patent documents 3 and 4 has a low transmittance of light having a wavelength of 400 nm.

In the techniques described in patent documents 1 to 4, it is difficult to obtain polyimide having excellent heat resistance and high transmittance of light having a wavelength of 400 nm.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a polyimide having excellent heat resistance and high transmittance of light having a wavelength of 400nm, and a polyamic acid as a precursor thereof. Further, it is also an object to provide a product or member which is produced using the polyimide and the polyamic acid and requires heat resistance and transparency. In particular, the polyimide film of the present invention is intended to provide a product or member formed on the surface of an inorganic substance such as glass, metal oxide, monocrystalline silicon, or the like.

Solution for solving the problem

< Mode of the invention >

The present invention includes the following means.

[1] A polyamic acid having a tetracarboxylic dianhydride residue and a diamine residue, wherein the tetracarboxylic dianhydride residue comprises at least one residue selected from the group consisting of a3, 3',4' -biphenyl tetracarboxylic dianhydride residue, a 9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residue, a4, 4 '-oxydiphthalic anhydride residue and a spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetralone residue and a2, 3,6, 7-naphthalene tetracarboxylic dianhydride residue,

The diamine residues comprise 2,2' -bis (trifluoromethyl) benzidine residues,

The content of the 2,3,6, 7-naphthalene tetracarboxylic dianhydride residues is 5 to 90 mol% based on the total amount of the tetracarboxylic dianhydride residues,

The content of the 2,2' -bis (trifluoromethyl) benzidine residue is 50 mol% or more based on the total amount of the diamine residues.

[2] The polyamic acid according to the item [1], wherein, in the case where the diamine residue comprises a diamine residue different from the 2,2 '-bis (trifluoromethyl) benzidine residue, the diamine residue different from the 2,2' -bis (trifluoromethyl) benzidine residue is a residue derived from a diamine having a highest occupied orbital level of-5.20 eV or less.

[3] The polyamic acid according to the above [2], wherein the diamine residue different from the above 2,2' -bis (trifluoromethyl) benzidine residue is at least one residue selected from the group consisting of a 4-aminophenyl-4-aminobenzoate residue, a 9, 9-bis (4-aminophenyl) fluorene residue and a2, 2' -bis (trifluoromethyl) -4,4' -diaminodiphenyl ether residue.

[4] The polyamic acid according to the above [2] or [3], wherein the content of diamine residues different from the 2,2' -bis (trifluoromethyl) benzidine residues is 1 mol% or more and 50 mol% or less with respect to the total amount of the diamine residues.

[5] The polyamic acid according to the item [4], wherein the content of the 3,3', 4' -biphenyltetracarboxylic dianhydride residue is 30 mol% or more and 50 mol% or less with respect to the total amount of the tetracarboxylic dianhydride residues.

[6] The polyamic acid according to any one of the above [1] to [5], wherein the difference between the average value of the lowest orbital levels of tetracarboxylic dianhydride forming the tetracarboxylic dianhydride residue and the average value of the highest occupied orbital levels of diamine forming the diamine residue is 2.25eV or more.

[7] A polyamic acid composition comprising the polyamic acid according to any one of [1] to [6] and an organic solvent.

[8] The polyamic acid composition according to the item [7], which further contains a plasticizer.

[9] The polyamic acid composition according to the above [8], wherein the amount of the plasticizer is 0.001 to 10 parts by weight based on 100 parts by weight of the polyamic acid.

[10] The polyamic acid composition according to the [8] or [9], wherein the plasticizer comprises phosphorus.

[11] A polyimide which is an imide of the polyamic acid according to any one of the above [1] to [6 ].

[12] The polyimide according to item [11], which has a 1% weight loss temperature of 500℃or higher.

[13] A polyimide film comprising the polyimide of the preceding [11] or [12 ].

[14] The polyimide film according to item [13], which has a transmittance of 40% or more for light having a wavelength of 400 nm.

[15] The polyimide film according to the above [13] or [14], which has a haze of 1.0% or less.

[16] A laminate comprising a support and the polyimide film according to any one of [13] to [15 ].

[17] A method for producing a laminate comprising a support and a polyimide film, wherein the polyamic acid composition according to any one of [7] to [10] is applied to the support to form a coating film containing the polyamic acid, and the coating film is heated to imidize the polyamic acid.

[18] An electronic device having the polyimide film of any one of [13] to [15] above and an electronic element disposed on the polyimide film.

ADVANTAGEOUS EFFECTS OF INVENTION

The polyimide produced using the polyamic acid of the present invention has excellent heat resistance and high transmittance of light having a wavelength of 400 nm. Therefore, the polyimide produced using the polyamic acid of the present invention is suitable as a material for electronic devices requiring heat resistance and transparency.

Detailed Description

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

First, description will be made with respect to terms used in the present specification. "structural unit" refers to the repeating units that make up the polymer. "polyamic acid" is a polymer comprising a structural unit represented by the following general formula (1) (hereinafter sometimes referred to as "structural unit (1)").

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

The content of the structural unit (1) 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, still more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol% or less.

"1% Weight loss temperature" means: the measured temperature was a temperature at which the weight of polyimide at the measured temperature of 150℃was reduced by 1% by weight relative to the weight of polyimide at the reference (100% by weight). The method for measuring the 1% weight loss temperature is the same method as or based on the following examples.

"Plasticizer" refers to a material that exists as a liquid upon imidization of at least a portion of the polyamic acid.

Hereinafter, the term "system" is sometimes given after the name of a compound to collectively refer to the compound and its derivatives. When the name of a compound is followed by a "system" to denote the name of the polymer, it is meant that the repeating units of the polymer originate from the compound or derivative thereof. In addition, the tetracarboxylic dianhydride is sometimes referred to as "acid dianhydride". The components, functional groups, and the like exemplified in the present specification may be used alone or in combination of two or more unless otherwise specified.

< Preferred embodiment of the invention >

The polyamic acid (hereinafter, sometimes referred to as "polyamic acid (1)") of the present embodiment has a tetracarboxylic dianhydride residue and a diamine residue.

In the polyamide acid (1), the tetracarboxylic dianhydride residue contains at least one residue selected from the group consisting of 3,3', 4' -biphenyl tetracarboxylic dianhydride residue, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residue, 4 '-oxydiphthalic anhydride residue, and spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetralone residue, and 2,3,6, 7-naphthalene tetracarboxylic dianhydride residue. That is, the polyamic acid (1) contains, as tetracarboxylic dianhydride residues, at least one residue selected from the group consisting of 3,3', 4' -biphenyltetracarboxylic dianhydride residues, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residues, 4 '-oxydiphthalic anhydride residues, and spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetralone residues, and 2,3,6, 7-naphthalene tetracarboxylic dianhydride residues.

In addition, in the polyamic acid (1), the diamine residue includes a2, 2' -bis (trifluoromethyl) benzidine residue. That is, the polyamic acid (1) contains a2, 2' -bis (trifluoromethyl) benzidine residue as a diamine residue.

The 3,3', 4' -biphenyltetracarboxylic dianhydride residue is a partial structure derived from 3,3', 4' -biphenyltetracarboxylic dianhydride (hereinafter, may be referred to as "BPDA"). The 9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residue is a partial structure derived from 9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride (hereinafter, sometimes referred to as "BPAF"). The 4,4 '-oxydiphthalic anhydride residue is a partial structure derived from 4,4' -oxydiphthalic anhydride (hereinafter, sometimes referred to as "ODPA"). The spiro [ 11H-difuran [3,4-b:3',4' -i ] xanthene-11, 9'- [9H ] fluorene ] -1,3,7, 9-tetraone residue is a partial structure derived from spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetraone (hereinafter sometimes referred to as "SFDA"). The 2,3,6, 7-naphthalene tetracarboxylic dianhydride residue is a partial structure derived from 2,3,6, 7-naphthalene tetracarboxylic dianhydride (hereinafter, may be referred to as "NTCDA"). The 2,2 '-bis (trifluoromethyl) benzidine residue is a partial structure derived from 2,2' -bis (trifluoromethyl) benzidine (hereinafter, sometimes referred to as "TFMB"). The SFDA residue is a 4-valent organic group represented by the following chemical formula (2).

In the polyamide acid (1), the content of the NTCDA residues is 5 mol% or more and 90 mol% or less relative to the total amount of the tetracarboxylic dianhydride residues. Further, in the polyamide acid (1), the content of TFMB residues is 50 mol% or more with respect to the total amount of diamine residues.

In general, polyimide obtained from polyamic acid having an NTCDA residue and a TFMB residue is derived from their rigid structure, has a high 1% weight loss temperature (TD 1) (excellent heat resistance), has a low CTE, and can reduce internal stress (hereinafter, sometimes simply referred to as "internal stress") generated when a polyimide film is formed on a support to obtain a laminate. Polyimide using NTCDA as the acid dianhydride monomer tends to have a higher transmittance of light having a wavelength of 400nm (hereinafter, may be referred to as "400nm transmittance") than polyimide using pyromellitic dianhydride as the acid dianhydride monomer. However, the use of polyimide obtained from polyamic acid having only an NTCDA residue as a tetracarboxylic dianhydride residue and only a TFMB residue as a diamine residue for the purpose of requiring high transparency is insufficient.

The present inventors have conducted intensive studies and as a result, have found that polyimide obtained from a polyamide acid (1)) having at least one residue selected from the group consisting of a BPDA residue, a BPAF residue, an ODPA residue and an SFDA residue (hereinafter, sometimes referred to as a "specific acid dianhydride residue"), an NTCDA residue and a TFMB residue, and having a content of the NTCDA residue and the TFMB residue in a specific range, has excellent heat resistance and high transmittance at 400 nm. Specifically, in the polyamide acid (1), the content of NTCDA residues is 5 mol% or more and 90 mol% or less relative to the total amount of tetracarboxylic dianhydride residues, and the content of TFMB residues is 50 mol% or more relative to the total amount of diamine residues.

In order to obtain polyimide having excellent heat resistance by increasing the glass transition temperature (Tg), the content of NTCDA residues is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1). In order to obtain polyimide capable of reducing internal stress, the content of NTCDA residues is preferably 85 mol% or less, more preferably 80 mol% or less, based on the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1).

In order to obtain a polyimide having excellent heat resistance and a transmittance of 400nm or higher, the content of the specific acid dianhydride residue is preferably 10 mol% or more and 95 mol% or less, more preferably 10 mol% or more and 90 mol% or less, and still more preferably 10 mol% or more and 80 mol% or less, with respect to the total amount of the tetracarboxylic dianhydride residues constituting the polyamic acid (1). When the polyamide acid (1) has a plurality of specific acid dianhydride residues, the "content of the specific acid dianhydride residues" means the total content of the plurality of specific acid dianhydride residues.

In order to obtain polyimide having more excellent heat resistance, a BPDA residue is preferable as the specific acid dianhydride residue. In order to obtain a polyimide having more excellent transparency, one or more residues selected from the group consisting of a BPAF residue, an ODPA residue and an SFDA residue are preferable as the specific acid dianhydride residue.

In order to obtain polyimide having a transmittance of 400nm, one or more residues selected from the group consisting of BPAF residues and SFDA residues are preferable as the specific acid dianhydride residues. In order to obtain a polyimide having a transmittance of 400nm or higher, the content of at least one residue selected from the group consisting of a BPAF residue and an SFDA residue (in the case of both a BPAF residue and an SFDA residue, the total content of these residues) is preferably 10 mol% or more and 50 mol% or less, more preferably 20 mol% or more and 50 mol% or less, and still more preferably 30 mol% or more and 50 mol% or less, with respect to the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1).

When the polyamic acid (1) has a BPDA residue, the content of the BPDA residue is preferably 5 mol% or more and 90 mol% or less, more preferably 5 mol% or more and 70 mol% or less, and still more preferably 5 mol% or more and 50 mol% or less, based on the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1), in order to obtain a polyimide having more excellent heat resistance while improving transparency.

When the polyamic acid (1) has a BPAF residue, the content of the BPAF residue is preferably 1 mol% or more and 50 mol% or less, more preferably 1 mol% or more and 40 mol% or less, and still more preferably 1 mol% or more and 30 mol% or less, with respect to the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1), in order to obtain a polyimide having more excellent transparency while improving heat resistance.

When the polyamide acid (1) has an ODPA residue, the content of the ODPA residue is preferably 5 mol% or more and 30 mol% or less, more preferably 5 mol% or more and 20 mol% or less, and still more preferably 5 mol% or more and 10 mol% or less, with respect to the total amount of tetracarboxylic dianhydride residues constituting the polyamide acid (1), in order to obtain a polyimide having more excellent transparency while improving heat resistance.

When the polyamide acid (1) has an SFDA residue, the content of the SFDA residue is preferably 1 mol% or more and 50 mol% or less, more preferably 1 mol% or more and 40 mol% or less, and still more preferably 1 mol% or more and 30 mol% or less, with respect to the total amount of tetracarboxylic dianhydride residues constituting the polyamide acid (1), in order to obtain a polyimide having more excellent transparency while improving heat resistance.

In order to obtain a polyimide having more excellent heat resistance and a transmittance of 400nm, the content of TFMB residues is preferably 55 mol% or more, more preferably 60 mol% or more, still more preferably 65 mol% or more, still more preferably 70 mol% or more, and may be 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol% with respect to the total amount of diamine residues constituting the polyamic acid (1).

In the synthesis of the polyamide acid (1), an acid dianhydride other than NTCDA and a specific acid dianhydride may be used as the monomer within a range not to impair the performance. Examples of the acid dianhydride other than the NTCDA and the specific acid dianhydride include: the pyromellitic dianhydride, the p-phenylene bistrimellitic dianhydride, the 1,2,5, 6-naphthalene tetracarboxylic dianhydride, the 2,2', 3' -biphenyl tetracarboxylic dianhydride, the 3,3', 4' -benzophenone tetracarboxylic dianhydride, the 4,4 '-dioxydiphthalic anhydride, the dicyclohexyl-3, 3',4 '-tetracarboxylic dianhydride, the 1,2,4, 5-cyclohexane tetracarboxylic dianhydride, the 1,2,3, 4-cyclobutane tetracarboxylic dianhydride, the 2' -oxydispiro [ bicyclo [2.2.1] heptane-2, 1 '-cyclopentane-3', 2 "-bicyclo [2.2.1] heptane ] -5,6:5", the 6 "-tetracarboxylic dianhydride and their derivatives may be used singly or in combination of two or more.

In order to obtain a polyimide having more excellent heat resistance and a transmittance of 400nm, the total content of the NTCDA residues and the specific acid dianhydride residues is preferably 70 mol% or more, more preferably 75 mol% or more, still more preferably 80 mol% or more, still more preferably 85 mol% or more, and may be 90 mol% or more, 95 mol% or more, or 100 mol% based on the total amount of the tetracarboxylic dianhydride residues constituting the polyamic acid (1).

In the synthesis of the polyamic acid (1), a diamine other than TFMB may be used as a monomer within a range that does not impair the performance. Examples of diamines other than TFMB include p-phenylenediamine, 4-aminophenyl-4-aminobenzoate (hereinafter, sometimes referred to as "BAAB"), 9-bis (4-aminophenyl) fluorene (hereinafter, sometimes referred to as "BAFL"), 2' -bis (trifluoromethyl) -4,4' -diaminodiphenyl ether (hereinafter, sometimes referred to as "6 FODA"), 1, 4-cyclohexanediamine, 4' -diaminobenzanilide, metaphenylene diamine, 4' -oxydiphenylamine, 3,4' -oxydiphenylamine, N, N ' -bis (4-aminophenyl) terephthalamide, 4' -diaminodiphenyl sulfone, m-tolidine, o-tolidine, 4' -bis (4-aminophenoxy) biphenyl, 2- (4-aminophenyl) -6-aminobenzoxazole, 3, 5-diaminobenzoic acid, 4' -diamino-3, 3' -dihydroxybiphenyl, 4' -methylenebis (cyclohexane amine), 1, 3-bis (3-aminopropyl) tetramethyldisiloxane and derivatives thereof may be used singly or as mixtures of two or more thereof.

When the polyamic acid (1) has a diamine residue (hereinafter, sometimes referred to as "any diamine residue") different from the TFMB residue, the diamine-derived residue having a highest occupied orbital level (hereinafter, sometimes referred to as "HOMO") of-5.20 eV or less, more preferably-5.30 eV or less, still more preferably-5.40 eV or less, and still more preferably-5.50 eV or less, is preferable as the optional diamine residue in order to obtain a polyimide having a higher transmittance at 400 nm. In addition, when the polyamic acid (1) has an arbitrary diamine residue, in order to obtain a polyimide having a transmittance of 400nm or higher, the polyamic acid (1) preferably has only a diamine-derived residue having a HOMO of-5.20 eV or less as an arbitrary diamine residue. In order to enhance the reactivity of the monomer at the time of synthesizing the polyamic acid (1), any diamine residue is preferably a diamine-derived residue having a HOMO of-6.20 eV or more.

Examples of the diamine-derived residue having a HOMO of-5.20 eV or less include BAAB residues, BAFL residues, and 6FODA residues. That is, when the polyamic acid (1) has any diamine residue, one or more residues selected from the group consisting of BAAB residues, BAFL residues and 6FODA residues are preferable as any diamine residue in order to obtain a polyimide having a higher transmittance at 400 nm. In addition, when the polyamic acid (1) has an arbitrary diamine residue, in order to obtain a polyimide having a transmittance of 400nm or higher, the polyamic acid (1) preferably has only one or more residues selected from the group consisting of BAAB residues, BAFL residues and 6FODA residues as an arbitrary diamine residue.

When the polyamic acid (1) has any diamine residue, the content of any diamine residue (the total content when a plurality of any diamine residues are present) is preferably 1 mol% or more and 50 mol% or less, more preferably 1 mol% or more and 40 mol% or less, still more preferably 1 mol% or more and 30 mol% or less, still more preferably 1 mol% or more and 20 mol% or less, or 1 mol% or more and 15 mol% or less, based on the total amount of diamine residues constituting the polyamic acid (1), in order to obtain a polyimide having excellent heat resistance and a transmittance of 400 nm.

When the polyamide acid (1) has any diamine residue and the content of any diamine residue (the total content when a plurality of any diamine residues are present) is 1 mol% or more and 50 mol% or less with respect to the total amount of diamine residues constituting the polyamide acid (1), the content of BPDA residues is preferably 30 mol% or more and 50 mol% or less with respect to the total amount of tetracarboxylic dianhydride residues constituting the polyamide acid (1) in order to obtain a polyimide having more excellent heat resistance.

In order to obtain a polyimide having a transmittance of 400nm or higher, the difference between the average value of the lowest orbital levels of tetracarboxylic dianhydride forming the tetracarboxylic dianhydride residue in the polyamic acid (1) (hereinafter, referred to as "LUMO" in some cases) and the average value of HOMO of diamine forming the diamine residue in the polyamic acid (1) (hereinafter, referred to as "average level difference" in some cases) is preferably 2.25eV or more, more preferably 2.30eV or more, still more preferably 2.35eV or more, and may be 2.40eV or more. The LUMO of the tetracarboxylic dianhydride and the HOMO of the diamine are both values calculated by the density functional method (DFT). The average energy level difference is a value calculated by the formula "average energy level difference=average value of LUMOs of tetracarboxylic dianhydride-average value of HOMO of diamine".

The "average value of LUMOs of tetracarboxylic dianhydrides" is a value obtained by summing up a value obtained by multiplying LUMOs of NTCDA by a mole fraction of NTCDA, a value obtained by multiplying LUMOs of specific acid dianhydrides by a mole fraction of specific acid dianhydrides (each value in the case of using a plurality of specific acid dianhydrides), and a value obtained by multiplying LUMOs of other acid dianhydrides, which are used if necessary, by mole fractions of other acid dianhydrides (each value in the case of using a plurality of other acid dianhydrides). For example, in the case of example 1 described later, 90 mol% of NTCDA (LUMO: -3.80 eV) was used, and 10 mol% of BPAF (LUMO: -3.19 eV) as a specific acid dianhydride was used, so that the average value of LUMO of the tetracarboxylic dianhydride used in example 1 was (-3.80) ×0.9+ (-3.19) ×0.1= -3.739eV. The "average HOMO value of diamine" is also calculated by the same method as the calculation method of the aforementioned "average LUMO value of tetracarboxylic dianhydride".

In order to improve the reactivity of the monomer at the time of synthesizing the polyamic acid (1), the average energy level difference is preferably 2.80eV or less, more preferably 2.70eV or less, and further preferably 2.60eV or less.

In order to obtain a polyimide having more excellent heat resistance and a higher transmittance of light having a wavelength of 400nm, the polyamic acid (1) preferably satisfies the following condition 1, more preferably satisfies the following condition 2, and even more preferably satisfies the following condition 3.

Condition 1: the content of NTCDA residues is 10 to 90 mol% relative to the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1), and the content of TFMB residues is 90 to 100 mol% relative to the total amount of diamine residues constituting the polyamic acid (1).

Condition 2: the above condition 1 is satisfied, and the specific acid dianhydride residue is one or more residues selected from the group consisting of BPAF residues and SFDA residues.

Condition 3: the content of at least one residue selected from the group consisting of a BPAF residue and an SFDA residue (the total content of both the BPAF residue and the SFDA residue when present) satisfying the above condition 2 is 10 mol% or more and 50 mol% or less relative to the total amount of tetracarboxylic dianhydride residues constituting the polyamic acid (1).

The polyamic acid (1) can be synthesized by a known general method, and can be obtained, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. An example of a specific synthesis method of the polyamic acid (1) will be described. First, a diamine solution is prepared by dissolving or dispersing a diamine in a slurry form in an organic solvent in an inert gas atmosphere such as argon or nitrogen. Then, the tetracarboxylic dianhydride is dissolved in an organic solvent or dispersed in a slurry form, or is added to the diamine solution in a solid state.

When the polyamide acid is synthesized using diamine and tetracarboxylic dianhydride, the desired polyamide acid (polymer of diamine and tetracarboxylic dianhydride) can be obtained by adjusting the amount of diamine (amount of diamine in the case of using a plurality of diamines) and the amount of tetracarboxylic dianhydride (amount of tetracarboxylic dianhydride in the case of using a plurality of tetracarboxylic dianhydrides). The mole fraction of each residue in the polyamic acid (1) corresponds to, for example, the mole fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of the polyamic acid (1). In addition, by mixing two kinds of polyamic acids, polyamic acid (1) containing a plurality of tetracarboxylic dianhydride residues and a plurality of diamine residues can also be obtained. The reaction between diamine and tetracarboxylic dianhydride, that is, the synthesis reaction of polyamide acid (1), is not particularly limited, and the temperature is, for example, in the range of 20℃to 150 ℃. The reaction time of the synthesis reaction of the polyamic acid (1) is, for example, in the range of 10 minutes to 30 hours.

The organic solvent used for the synthesis of the polyamic acid (1) is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the polyamic acid (1) produced. Examples of the organic solvent used for the synthesis of the polyamic acid (1) include urea solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as diphenyl sulfone and tetramethylsulfone; amide solvents such as N, N-Dimethylacetamide (DMAC), N-Dimethylformamide (DMF), N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 3-methoxy-N, N-dimethylpropane amide (MPA), and hexamethylphosphoric triamide; ester solvents such as gamma-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 generally singly or in combination of two or more kinds as needed. In order to improve the solubility and reactivity of the polyamic acid (1), the organic solvent used in the synthesis reaction of the polyamic acid (1) is preferably one or more solvents selected from the group consisting of an amide-based solvent, a ketone-based solvent, an ester-based solvent, and an ether-based solvent, and more preferably an amide-based solvent (more specifically, DMF, DMAC, NMP, MPA and the like). The synthesis reaction of the polyamic acid (1) is preferably performed under an inert gas atmosphere such as argon or nitrogen.

The weight average molecular weight of the polyamic acid (1) also varies depending on the application, and is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 500,000, still more preferably in the range of 30,000 to 200,000. When the weight average molecular weight is 10,000 or more, the polyamic acid (1) or polyimide obtained by using the polyamic acid (1) can be easily formed into a coating film or polyimide film (thin film). On the other hand, when the weight average molecular weight is 1,000,000 or less, the solvent is sufficiently soluble, and therefore, a coating film or polyimide film having a smooth surface and a uniform thickness can be obtained by using the polyamide acid composition described later. The weight average molecular weight as used herein refers to a polyethylene oxide equivalent measured using Gel Permeation Chromatography (GPC).

In addition, as a method for controlling the molecular weight of the polyamic acid (1), there is mentioned: a method of excess of either one of an acid dianhydride and a diamine; a method of quenching the reaction by reacting with a monofunctional acid anhydride such as phthalic anhydride or aniline, or an amine. When either one of the acid dianhydride and the diamine is polymerized in an excessive amount, a polyimide film having sufficient strength can be obtained if the molar ratio of the addition of the acid dianhydride and the diamine is in the range of 0.95 to 1.05. The above-mentioned molar ratio of the total amount of diamine used for synthesizing the polyamic acid (1) to the total amount of acid dianhydride used for synthesizing the polyamic acid (1) (the total amount of diamine/the total amount of acid dianhydride). Further, by capping with phthalic anhydride, maleic anhydride, aniline, or the like, the coloration of the polyimide obtained by using the polyamic acid (1) can be further reduced.

The polyamic acid composition of the present embodiment contains a polyamic acid (1) and an organic solvent. The organic solvent contained in the polyamic acid composition according to the present embodiment is exemplified as an organic solvent that can be used in the synthesis reaction of the polyamic acid (1), and is preferably one or more solvents selected from the group consisting of an amide-based solvent, a ketone-based solvent, an ester-based solvent, and an ether-based solvent, and more preferably an amide-based solvent (more specifically, DMF, DMAC, NMP, MPA, etc.). In the case of obtaining the polyamic acid (1) by the above-mentioned method, the reaction solution (the solution after the reaction) itself may be used as the polyamic acid composition of the present embodiment. The polyamic acid composition of the present embodiment can be prepared by dissolving the solid polyamic acid (1) obtained by removing the solvent from the reaction solution in an organic solvent. The content of the polyamic acid (1) in the polyamic acid composition according to the present embodiment is not particularly limited, and is, for example, 1% by weight or more and 80% by weight or less relative to the total amount of the polyamic acid composition.

In addition, the polyamic acid composition according to the present embodiment may contain an imidization accelerator and/or a dehydration catalyst in order to shorten the heating time and to exhibit characteristics.

The imidization accelerator is not particularly limited, and tertiary amines may be used. As the tertiary amine, a heterocyclic tertiary amine is preferable. Preferred specific examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline, imidazole, and the like. The dehydration catalyst may be exemplified by acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and the like.

The amount of the imidization accelerator is preferably 0.1 parts by weight or more and 10 parts by weight or less, more preferably 0.5 parts by weight or more and 5 parts by weight or less, relative to 100 parts by weight of the polyamic acid (1), from the viewpoint of shortening the heating time and exhibiting characteristics. From the viewpoint of shortening the heating time and exhibiting the characteristics, the amount of the dehydration catalyst is preferably 0.1 parts by weight or more and 10 parts by weight or less, more preferably 0.5 parts by weight or more and 5 parts by weight or less, relative to 100 parts by weight of the polyamic acid (1).

As the imidization accelerator, imidazoles are preferable. In the present specification, imidazoles refer to compounds having a 1, 3-diazole ring (1, 3-diazole ring structure). Examples of imidazoles that can be added to the polyamic acid composition according to the present embodiment include, but are not particularly limited to, 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1, 2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, and the like. 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 imidazoles 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 still more preferably 0.015 mol or more and 0.050 mol or less, based on 1 mol of amide groups of the polyamic acid (1). The polyimide film strength and transparency can be improved by containing 0.005 mol or more of imidazole, and the heat resistance can be improved while maintaining the storage stability of the polyamic acid (1) by setting the imidazole content to 0.1 mol or less. In the present specification, the term "amide group of the polyamic acid (1)" refers to an amide group formed by a polymerization reaction of a diamine and a tetracarboxylic dianhydride.

The method for mixing the polyamic acid (1) and the imidazoles is not particularly limited. From the viewpoint of easiness of molecular weight control of the polyamic acid (1), it is preferable to add imidazoles to the polymerized polyamic acid (1). In this case, the imidazole may be directly added to the polyamic acid (1), or the imidazole may be dissolved in a solvent in advance, and the solution may be added to the polyamic acid (1), and the method of addition is not particularly limited. The polyamic acid composition of the present embodiment can be prepared by adding imidazoles to a solution (a solution after reaction) containing the polymerized polyamic acid (1).

Various organic or inorganic low-molecular compounds or high-molecular compounds may be blended as additives in the polyamic acid composition according to the present embodiment. As the additive, for example, a plasticizer, an antioxidant, a dye, a surfactant, a leveling agent, a silicone, microparticles, a sensitizer, and the like can be used. The fine particles include organic fine particles formed of polystyrene, polytetrafluoroethylene, or the like; inorganic fine particles formed of colloidal silica, carbon, layered silicate, or the like, and the like may have a porous structure or a hollow structure. The function and morphology of the fine particles are not particularly limited, and may be, for example, pigment, filler, or fibrous particles.

The effect of the plasticizer that can be compounded in the polyamic acid composition of the present embodiment will be described. In general, when a transparent polyimide film is desired, polyimide having large band gaps of HOMO and LUMO is designed in principle, and therefore TFMB having low electron donating property is effective for obtaining a transparent polyimide film. On the other hand, TFMB with low electron donating property is predicted to have low reaction rate due to low nucleophilicity, and imidization rate is also predicted to be low. The inventors of the present invention studied the imidization ratio and as a result, obtained the following findings. That is, when the imidization rate of a general colored polyimide obtained from BPDA and p-phenylenediamine is compared with that of a transparent polyimide obtained from PMDA, BPDA and TFMB, the imidization rate of the colored polyimide is 90% or more at the imidization temperature of 300 ℃ and is close to 100% at the imidization temperature of 350 ℃, but the imidization rate of the transparent polyimide is 75% or so at the imidization temperature of 300 ℃ and is only 80% or so at the imidization temperature of 350 ℃, and a significant difference is observed in imidization rate.

In general, in order to achieve complete imidization, it is preferable to perform a treatment at a temperature equal to or higher than the glass transition temperature of polyimide, because the molecular motion due to heat and the plasticizing effect due to a solvent are large due to the driving force when the polyimide is dehydrated and closed by thermal imidization. However, in the combination of a rigid acid dianhydride such as NTCDA and TFMB, the glass transition temperature of the obtained polyimide may exceed 400 ℃, and the glass transition temperature may be higher than the heat treatment temperature at the time of film formation. Therefore, in imidization reaction of a rigid acid dianhydride such as NTCDA with TFMB, imidization may not be completely performed. Therefore, for example, in a high-temperature process using a polyimide film (for example, dehydrogenation treatment of a TFT element, etc.), imidization of unreacted portions in the polyimide film proceeds, and outgas (for example, hydrogen fluoride, etc.) due to the generation of low molecular weight components from the polyimide film is generated, which may cause peeling of a barrier film, corrosion of a TFT, etc. In contrast, by blending the plasticizer in the polyamic acid composition, sufficient molecular motion can be imparted at the time of imidization of the polyamic acid (1), and not only the imidization is completely performed, but also depolymerization of the polyamic acid (1) is suppressed, and generation of outgas (particularly hydrogen fluoride) can be suppressed. Further, by adding a plasticizer to the polyamic acid composition, molecular motion is imparted to the polyamic acid (1), and thus the solvent is also easily removed, the amount of residual solvent in the film (polyimide film) is reduced, and the coloring of the film is also reduced.

As the plasticizer usable in the present embodiment, a material which is dissolved in a solvent used at the time of imidization of the polyamic acid (1) is preferable. In addition, in order to impart sufficient molecular mobility to the polyamic acid (1) at the time of imidization, the plasticizer is preferably not volatilized at a low temperature. Thus, the boiling point of the plasticizer is preferably 50℃or higher, more preferably 100℃or higher, and still more preferably 150℃or higher. In order to impart sufficient molecular mobility to the polyamic acid (1) at the time of imidization, the plasticizer preferably has no decomposition temperature at a boiling point or lower.

From the viewpoint of avoiding decomposition of the plasticizer itself, the amount of the plasticizer is preferably 10 parts by weight or less with respect to 100 parts by weight of the polyamic acid (1). In addition, from the viewpoint of imparting sufficient molecular mobility to the polyamic acid (1) and avoiding decomposition of the plasticizer itself, the amount of the plasticizer is preferably 0.001 parts by weight or more and 10 parts by weight or less, more preferably 0.01 parts by weight or more and 10 parts by weight or less, still more preferably 0.01 parts by weight or more and 8 parts by weight or less, and still more preferably 0.1 parts by weight or more and 6 parts by weight or less, relative to 100 parts by weight of the polyamic acid (1).

In order to further suppress the generation of hydrogen fluoride when used in a high-temperature process, one or more selected from the group consisting of a phosphorus-containing compound (phosphorus-containing compound), a polyalkylene glycol, and an aliphatic dibasic acid ester is preferable as the plasticizer.

The phosphorus-containing compound may be represented by the following general formulae (3-1) to (3-10). In the following general formulae (3-1) to (3-10), R ⁵、R⁶ and R ⁷ each independently represent a hydrogen atom, a monovalent organic group or a polyvalent organic group, R ⁸ represents a polyvalent organic group, and n represents a degree of polymerization.

Preferable examples of the phosphorus-containing compound include phosphoric acid-based compounds, phosphorous acid-based compounds, phosphonic acid-based compounds, phosphinic acid-based compounds, phosphine oxide-based compounds, phosphane-based compounds, phosphazene-based compounds, and the like. The phosphorus-containing compound may be an ester of the above-listed compounds or a condensate thereof, may contain a cyclic structure, or may form a salt with an amine or the like. Among these phosphorus-containing compounds, there are also those which exhibit a tautomeric relationship like a phosphite compound and a phosphonate compound, and may be present in any state.

Specific examples of the phosphoric acid-based compound include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris (2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, triisopropylphenyl phosphate, trinaphthalenyl phosphate, cresyl diphenyl phosphate, diphenyl (2-ethylhexyl) phosphate, di (isopropylphenyl) phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dicyandiamide phosphate, bisphenol a bis (diphenyl phosphate), and tris (. Beta. -chloropropyl) phosphate.

Specific examples of the phosphorous acid-based compound include triphenyl phosphite, trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, triisobutyl phosphite, tris (2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, diethyl phosphite, dibutyl phosphite, dimethyl phosphite, diphenyl mono (2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono (tridecyl) phosphite, trilauryl tritolyl phosphite, diethyl hydrogen phosphite, bis (2-ethylhexyl) phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite, tetraphenyl dipropylene glycol diphosphite, bis (decyl) pentaerythritol diphosphite, bis (tridecyl) pentaerythritol diphosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, tris (2, 4-di-tert-butylphenyl) phosphite, tris (3, 4-di-tert-butyl) phosphite, and 3, 9-3-diisobutyl-3, 9-3-diisobutyl-9-5-tetraoxa-2, 4-diphosphonate.

Examples of the condensed product include condensed phosphoric esters. Specific examples of the condensed phosphoric acid ester include trialkyl polyphosphoric acid ester, resorcinol polyphenyl phosphoric acid ester, resorcinol poly (di-2, 6-xylyl) phosphoric acid ester, hydroquinone poly (2, 6-xylyl) phosphoric acid ester, and the like. Examples of the commercial products of the condensed phosphoric ester include "CR-733S" manufactured by Daba chemical industry Co., ltd., "CR-741" manufactured by Daba chemical industry Co., ltd., and "PX-200" manufactured by Daba chemical industry Co., ltd., and "FP-600" manufactured by ADEKA Co., ltd.

Specific examples of the phosphazene-based compound include phenoxycyclophosphazene ("FP-110" manufactured by Vol. Co., ltd.), and cyclic cyanophenoxyphosphazene ("FP-300" manufactured by Vol. Co., ltd.).

Specific examples of the polyalkylene glycol include polypropylene glycol and polyethylene glycol.

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

The plasticizer may be a low-molecular organic compound or a thermoplastic resin as long as it exhibits plasticizing effect. The low-molecular organic compound includes, for example, an organic compound having a molecular weight of about 1,000 or less, and a phenolic compound; phthalimide compounds such as phthalimide, N-phenylphthalimide, N-glycidyl phthalimide, N-hydroxy phthalimide, and cyclohexylthio-phthalimide; maleimide compounds such as N, N-p-phenylene bismaleimide and 2,2' - (ethylenedioxy) bis (ethylmaleimide). Examples of the thermoplastic resin include polyimide and polyamide having an asymmetric structure.

In addition, the polyamic acid composition according to the present embodiment may contain a silane coupling agent in order to exhibit appropriate adhesion to a support. The type of the silane coupling agent is not particularly limited, and a known type can be used, and from the viewpoint of reactivity with the polyamic acid (1), an amino group-containing compound is particularly preferable.

The blending ratio of the silane coupling agent to 100 parts by weight of the polyamic acid (1) 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 still more preferably 0.01 part by weight or more and 0.05 part by weight or less. The effect of suppressing the self-supporting body peeling can be sufficiently exhibited by setting the blending ratio of the silane coupling agent to 0.01 part by weight or more, and the embrittlement of the polyimide film can be suppressed by setting the blending ratio of the silane coupling agent to 0.50 part by weight or less, thereby suppressing the decrease in molecular weight of the polyamic acid (1).

The polyimide of the present embodiment is an imide compound of the polyamide acid (1). The polyimide according to the present embodiment can be obtained by a known method, and the method for producing the polyimide is not particularly limited. An example of a method for obtaining the polyimide of the present embodiment by imidizing the polyamic acid (1) will be described below. Imidization is performed by dehydrating and ring-closing the polyamic acid (1). The dehydration ring closure may be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. The imidization of the polyamide acid (1) to the polyimide may be performed at any ratio of 1% to 100%. In other words, the partially imidized polyamic acid (1) can be synthesized. In particular, in the case where imidization is performed by heating and raising the temperature, since the ring-closure reaction of the polyamic acid (1) to polyimide and the hydrolysis of the polyamic acid (1) are performed simultaneously, the molecular weight at the time of producing polyimide may be lower than that of the polyamic acid (1), and therefore, from the viewpoint of improving mechanical properties, it is preferable to imidize a part of the polyamic acid (1) in the polyamic acid composition in advance before forming a polyimide film described later. In the present specification, the partially imidized polyamic acid is sometimes referred to as "polyamic acid".

The dehydration and ring closure of the polyamic acid (1) may be performed by heating the polyamic acid (1). The method for heating the polyamic acid (1) is not particularly limited, and for example, the polyamic acid composition of the present embodiment is applied to a support such as a glass substrate, a metal plate, or a PET film (polyethylene terephthalate film), and then the polyamic acid (1) is heat-treated at a temperature in the range of 40 ℃ to 500 ℃. According to this method, a laminate of the present embodiment including a support and a polyimide film (specifically, a polyimide film including an imide compound of the polyamic acid (1)) disposed on the support can be obtained. Alternatively, the polyamide acid (1) may be dehydrated and closed by directly charging the polyamide acid composition into a container subjected to a mold release treatment such as coating with a fluorine-based resin, and heating and drying the polyamide acid composition under reduced pressure. By the dehydration ring closure of the polyamic acid (1) based on these methods, polyimide can be obtained. The heating time for each treatment varies depending on the amount of the polyamide acid composition to be treated for dehydration and ring closure and the heating temperature, and is preferably in the range of 1 to 300 minutes after the treatment temperature reaches the maximum temperature.

The polyimide film of the present embodiment (specifically, the polyimide film containing the imide compound of the polyamic acid (1)) is colorless and transparent, has a low yellow color, and has a glass transition temperature (heat resistance) that can withstand the TFT manufacturing process, and thus is suitable for a transparent substrate material of a flexible display. The content of polyimide (more specifically, imide compound of polyamide acid (1)) in the polyimide film of 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 the above-mentioned additives (more specifically, particles and the like).

The electronic device (more specifically, a flexible device or the like) of the present embodiment includes: the polyimide film of the present embodiment, and an electronic component directly or indirectly disposed on the polyimide film. In the case of manufacturing the electronic device according to the present embodiment 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 arranged (formed) on the polyimide film, whereby an electronic device is formed on the support. The process of forming a TFT is usually performed in a wide temperature range of 150 ℃ to 650 ℃, but in practice, 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 and the like are crystallized by laser light and the like.

In this case, when the thermal decomposition temperature of the polyimide film is low, there is a possibility that outgas may occur during formation of the electronic component and the polyimide film may adhere to the inside of the oven as sublimates to cause contamination in the oven, or the inorganic film (barrier film or the like described later) formed on the polyimide film and the electronic component may be peeled off, and therefore, the 1% weight loss temperature of the polyimide is preferably 500 ℃. The higher the upper limit of the 1% weight loss temperature of polyimide, the better, for example, 600 ℃. The 1% weight loss temperature can be adjusted by, for example, changing the content of residues having a rigid structure (more specifically, NTCDA residues, BPDA residues, etc.). To explain in more detail, 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 the polyimide film before forming the TFT. In this case, when the polyimide has low heat resistance, imidization is not completely performed, or when a large amount of solvent remains, the polyimide may be peeled from the inorganic film due to volatile components such as decomposed gas of the polyimide in a high-temperature process after lamination of the inorganic film. It is therefore desirable that: the polyimide 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 ℃ inclusive, with the weight loss ratio of 1% being 500 ℃ or higher.

In addition, when the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, positional shift or the like may occur during formation of the electronic component, and therefore, the Tg of the polyimide is preferably 300 ℃ or higher, more preferably 350 ℃ or higher, further preferably 400 ℃ or higher, and still further preferably 420 ℃ or higher. The higher the upper limit of Tg of the polyimide, the better, for example 500 ℃. In addition, in general, the glass substrate has a smaller thermal expansion coefficient than the resin, and thus, internal stress is generated between the glass substrate and the polyimide film. If the internal stress of the laminate of the glass substrate, the electronic element, and the polyimide film used as the support is high, the laminate including the polyimide film expands in the TFT forming step at high temperature and then contracts when cooled to 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 between the polyimide film and the glass substrate is preferably 40MPa or less, more preferably 35MPa or less, further preferably 30MPa or less, and still further preferably 25MPa or less. The method for measuring the internal stress is the same method as or based on the examples described later.

If there is a floating at the interface between the polyimide film and the support (e.g., glass substrate), there is a possibility that the polyimide film may be peeled off during the formation of the electronic component or the yield may be lowered when the polyimide film is peeled off after the formation of the electronic component. The term "floating" refers to a state in which adhesion between the polyimide film and other material layers (more specifically, glass substrates, barrier films, and the like) is poor due to subcomponents and residual solvents generated during imidization. Specific examples of the "floating" include a state in which the polyimide film floats from the glass substrate, a state in which a part of the polyimide film is broken to cause interlayer peeling between the polyimide film and the other material layer, and a state in which the barrier film floats from the polyimide film. In general, a polyimide film obtained from a polyamic acid having a BPDA residue and BAAB residue has a molecular chain that is densely packed and has poor outgassing, and thus tends to float at the interface with a support (e.g., a glass substrate). According to the study of the present inventors, it was found that floating can be prevented by introducing a bulky structure or a soft structure into the molecular chain or the terminal of the polyamic acid. Among them, when polyamic acid having a BPAF residue and an SFDA residue is used, it is possible to achieve both good gas discharge properties and high glass transition temperature due to its bulky structure.

The polyimide of the present embodiment can be suitably used as a material for display substrates such as TFT substrates and touch panel substrates. When polyimide is used for the above-mentioned applications, a method of peeling the polyimide film from the support after forming an electronic device (more specifically, an electronic device in which an electronic element is formed on the polyimide film) on the support is often employed as described above. In addition, 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 composition according to the present embodiment is coated (cast) on a support to form a laminate comprising a coating film comprising the polyamic acid (1) and a coating film comprising the support. Next, the laminate containing the coating film is heated, for example, at a temperature of 40 ℃ or higher and 200 ℃ or lower. The heating time at this time is, for example, 3 minutes to 120 minutes. The multi-stage heating step may be provided, for example, by heating the laminate containing the coating film at a temperature of 50 ℃ for 30 minutes and then at a temperature of 100 ℃ for 30 minutes. Next, in order to imidize the polyamic acid (1) in the coating film, the laminate containing the coating film is heated under conditions such that the maximum temperature is 200 ℃ to 500 ℃. The heating time (heating time at the highest temperature) at this time is, for example, 1 minute to 300 minutes. In this case, the temperature is preferably gradually increased from a low temperature to a maximum temperature. The temperature rise rate is preferably 2 to 10 ℃ per minute, more preferably 4 to 10 ℃ per minute. The maximum temperature is preferably 250 ℃ to 450 ℃. If the maximum temperature is 250 ℃ or higher, imidization is sufficiently performed, and if the maximum temperature is 450 ℃ or lower, thermal degradation and coloring of polyimide can be suppressed. In addition, the temperature may be maintained at any temperature for any time until the maximum temperature is reached. The imidization reaction may be performed under air, under reduced pressure, or under an inert gas such as nitrogen, and is preferably performed under reduced pressure or under an inert gas such as nitrogen in order to exhibit higher transparency. As the heating device, a known device such as a hot air oven, an infrared oven, a vacuum oven, an inert oven, or a heating plate can be used. Through these steps, the polyamic acid (1) in the coating film is imidized, and a laminate of the support and the polyimide film (film containing the imidized product of the polyamic acid (1)), that is, the laminate of the present embodiment, can be obtained.

The polyimide film may be peeled from the laminate of the obtained support and polyimide film by a known method. For example, the peeling may be performed by hand, or may be performed using a mechanical device such as a driving roller or a robot. Further, a method of providing a release layer between the support and the polyimide film may be employed; a method of forming a silicon oxide film on a support having a plurality of grooves, forming a polyimide film using the silicon oxide film as a base layer, and peeling the polyimide film by immersing a silicon oxide etching solution between the support and the silicon oxide film. In addition, a method of separating a polyimide film by irradiating a laser may be used.

The transparency of the polyimide film can be evaluated by using the total light transmittance (TT) based on JIS K7361-1:1997 and the haze based on JIS K7136-2000. When a polyimide film is used for applications requiring high transparency, the total light transmittance of the polyimide film is preferably 75% or more, more preferably 80% or more. In the case of using a polyimide film for applications requiring high transparency, the haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, still more preferably 1.0% or less, and may be 0%. The haze can be adjusted by changing the content of TFMB residues in the polyamic acid (1), for example. In applications requiring high transparency, polyimide films are required to have high transmittance in all wavelength regions, but polyimide films tend to absorb light on the short wavelength side easily, and the films themselves often become yellow in color. In order to use the polyimide film in applications requiring high transparency, it is preferable that the coloring of the polyimide film be reduced. Specifically, in order to use the polyimide film for applications requiring high transparency, the Yellowness (YI) of the polyimide film is preferably 25 or less, more preferably 20 or less, and may be 0.YI can be measured according to JIS K7373-2006. In this way, the polyimide film having reduced coloration and imparted with transparency is suitable for a transparent substrate for glass substitution use or the like, and a substrate having a sensor or a camera module provided on the back surface thereof.

In addition, as described above, in applications requiring transparency, it is particularly required that the transmittance of blue light (light having a wavelength of around 470 nm) is high from the viewpoint of color reproducibility and the like, and the transmittance of light having a wavelength of 400nm (400 nm transmittance) is high in practical use. The 400nm transmittance of the polyimide film is preferably 40% or more, more preferably 45% or more, from the viewpoint of color reproducibility and the like. The upper limit of the 400nm transmittance of the polyimide film is not particularly limited and may be 100%.

In addition, the light extraction method of the flexible display includes both a top emission method of extracting light from the front surface side of the TFT and a bottom emission method of extracting light from the back surface side of the TFT. Since light is not blocked by the TFT in the top emission method, the aperture ratio is easily improved and a high definition image quality is obtained, and the bottom emission method has a feature that the TFT and the pixel electrode are easily aligned and easily manufactured. If the TFT is transparent, the aperture ratio can be increased even in the bottom emission method, and thus there is a tendency to adopt the bottom emission method which is easy to manufacture in a large-sized display. The polyimide film of the present embodiment has low YI and excellent heat resistance, and thus can be applied to any of the above light extraction systems.

In addition, in the batch-type device manufacturing process, the adhesion between the support and the polyimide film is preferably excellent, and the batch-type device manufacturing process is: the polyamic acid composition is applied to a support such as a glass substrate, heated to imidize the composition, and then the polyimide film is peeled off after forming an electronic device or the like. The adhesion referred to herein means adhesion strength. In a manufacturing process in which the polyimide film on the support is peeled off from the support after the electronic component or the like is formed, if the adhesion between the polyimide film and the support is excellent, the electronic component or the like can be formed or mounted more accurately. In a manufacturing process in which an electronic component or the like is disposed on a support with a polyimide film interposed therebetween, the higher the peel strength between the support and the polyimide film is, the better from the viewpoint of improvement in productivity. Specifically, the peel strength is preferably 0.05N/cm or more, more preferably 0.1N/cm or more.

In the above-described production 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 laser light, the cut-off wavelength of the polyimide film needs to be longer than the wavelength of the laser light used for the peeling. Since a XeCl excimer laser 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, more preferably 330nm or more. On the other hand, if the cutoff wavelength is long, the polyimide film tends to be colored yellow, and therefore the cutoff wavelength of the polyimide film is preferably 390nm or less. From the viewpoint of both transparency (low yellowness) and processability in laser lift-off, the cutoff wavelength of the polyimide film is preferably 320nm to 390nm, more preferably 330nm to 380 nm. 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 composition and polyimide according to the present embodiment can be used directly in a coating and molding process for producing a product or a member, or can be used as a material for coating a molded article molded into a film shape. For use in a coating or molding process, the polyamic acid composition or polyimide may be dissolved or dispersed in an organic solvent as needed, and further, a photocurable component, a thermosetting component, a non-polymerizable binder resin, and other components may be compounded as needed to prepare a composition containing the polyamic acid (1) or polyimide.

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 according to the present embodiment. The method for forming the inorganic thin film is not particularly limited, and examples thereof include PVD methods such as sputtering, vacuum deposition, ion plating, and CVD methods.

The polyimide film of the present embodiment is preferably used in fields and products in which these characteristics can be exhibited because the polyimide film can ensure adhesion to an inorganic material in a high-temperature process because the polyimide film generates small internal stress when forming a laminate with a glass substrate, in addition to heat resistance, low thermal expansion, and transparency. 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 electronic paper, a printed matter, a color filter, a flexible display, an optical thin 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, preferably 5 μm or more and 100 μm or less. The thickness of the polyimide film can be measured using a laser holographic micrometer (Laser Hologage).

The polyamic acid composition according to the present embodiment can be suitably used in a batch-type device manufacturing process, which is: the polyamide acid composition is coated on a support, heated and imidized to form an electronic component, and then the polyimide film is peeled off. Therefore, the present embodiment also includes a method for manufacturing an electronic device, which includes a step of applying the polyamic acid composition onto a support, heating the applied composition to imidize the applied composition, and forming an electronic device 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 element or the like is formed from the support.

Examples

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

< Method for measuring physical Properties >

First, a method for measuring physical properties of polyimide (polyimide film) will be described.

[ Transmittance at 400nm ]

The polyimide films in each of the laminated bodies obtained in examples and comparative examples described later were measured for transmittance of light having a wavelength of 400nm (400 nm transmittance) using an ultraviolet-visible near-infrared spectrophotometer (manufactured by Japanese spectroscopy Co., ltd. "V-650"). When the transmittance at 400nm was 40% or more, it was evaluated as "the transmittance of light having a wavelength of 400nm was high". On the other hand, when the transmittance at 400nm was less than 40%, it was evaluated as "the transmittance of light having a wavelength of 400nm was not high".

[ Yellowness (YI) ]

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

[ Total light transmittance (TT) ]

Polyimide films peeled from each of the laminates obtained in examples and comparative examples described later were subjected to JISK 7361-1 by using an integrating sphere haze meter (HM-150N, manufactured by Toku color technology Co., ltd.): the method described in 1997 determines the total light transmittance (TT).

[ Haze ]

The polyimide films peeled from the respective laminates obtained in examples and comparative examples described later were measured for haze by the method described in JIS K7136-2000 using an integrating sphere haze meter (HM-150N manufactured by Country color technology research).

[ Internal stress ]

The polyamide acid compositions prepared in examples and comparative examples described below were applied to a glass substrate (material: alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm) made by Corning, whose warpage amount was measured in advance, 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. Mu.m 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 warpage amount of the laminate was measured in a nitrogen atmosphere at 25℃using a film stress measuring apparatus (FLX-2320-S manufactured by KLA-Tencor). And, the internal stress generated between the glass substrate and the polyimide film is calculated using Stoney formula from the amount of warpage of the glass substrate before forming the polyimide film and the amount of warpage of the laminate.

[1% Weight loss temperature (TD 1) ]

The polyimide films obtained in examples and comparative examples (specifically, polyimide films obtained by sampling from each laminate so that the weight thereof became 10 mg) were each used as a measurement sample, and a differential thermal weight simultaneous measurement apparatus ("TG/DTA 7200" manufactured by hitachi high-tech sciences corporation) was used, and the temperature was raised from 25 ℃ to 650 ℃ under a nitrogen atmosphere at 20 ℃/min, and the weight of the sample at the measurement temperature of 150 ℃ was used as a reference, and the measurement temperature at which the weight of the reference was reduced by 1% was used as a 1% weight loss temperature (TD 1). When TD1 was 500℃or higher, it was evaluated as "excellent in heat resistance". On the other hand, when TD1 is lower than 500 ℃, it is evaluated as "not excellent in heat resistance".

[ Glass transition temperature (Tg) ]

Polyimide films each having a width of 3mm and a length of 10mm were sampled from each laminate obtained in examples and comparative examples described later, and used as samples for Tg measurement. A TMA curve was obtained by heating the sample from 20℃to 470℃at 10℃per minute under a load of 98.0mN using a thermal analysis apparatus (TMA/SS 7100, manufactured by Hitachi Ltd.) and plotting the temperature and the strain (elongation). The temperature at the inflection point of the obtained TMA curve (the temperature corresponding to the peak in the differential curve of the TMA curve) was taken as the glass transition temperature (Tg).

< Preparation of polyimide film >

Hereinafter, a method for producing a polyimide film (laminate) of examples and comparative examples will be described. Hereinafter, the compounds and reagents will be described simply. The preparation of the polyamic acid composition for producing a polyimide film was carried out under a nitrogen atmosphere. Table 1 shows LUMO (calculated value based on DFT) of each acid dianhydride used as a monomer, and table 2 shows HOMO (calculated value based on DFT) of each diamine used as a monomer.

NMP: n-methyl-2-pyrrolidone

NTCDA:2,3,6, 7-naphthalene tetracarboxylic dianhydride

PMDA: pyromellitic dianhydride

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

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

ODPA:4,4' -Oxyphthalic anhydride

DODA:4,4' -Dioxydiphthalic anhydride

SFDA: spiro [ 11H-difuran [3,4-b:3',4' -i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetraketone

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

BAAB: 4-aminophenyl-4-aminobenzoate

BAFL:9, 9-bis (4-aminophenyl) fluorene

6FODA:2,2 '-bis (trifluoromethyl) -4,4' -diaminodiphenyl ether

PDA: para-phenylenediamine

PX-200: resorcinol poly (di-2, 6-xylyl) phosphate manufactured by Daba chemical industries, inc

TPPi: triphenyl phosphite

TABLE 1

	LUMO[eV]
		PMDA	-4.32
NTCDA	-3.80
		BPDA	-3.47
BPAF	-3.19
		ODPA	-3.43
DODA	-3.60
		SFDA	-3.24

TABLE 2

	HOMO[eV]
		PDA	-5.02
TFMB	-6.04
		BAAB	-5.63
BAFL	-5.55
		6FODA	-5.94

Example 1

A300 mL glass-made removable flask equipped with a stirrer equipped with a stainless steel stirring bar and a nitrogen inlet tube was charged with 40.0g of NMP as an organic solvent for polymerization. Then, 5.272g of TFMB was placed in the flask while stirring the flask contents, and dissolved. Then, after adding 3.973g of NTCDA and 0.755g of BPAF to the flask content, the flask content was stirred for 24 hours under an atmosphere at a temperature of 25℃to obtain a polyamic acid composition. The obtained polyamic acid composition was applied onto a glass substrate (alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm, manufactured by Corning) using 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 (laminate of example 1) having a polyimide film with a thickness of 10. Mu.m on the glass substrate.

Example 2

A300 mL glass-made removable flask equipped with a stirrer equipped with a stainless steel stirring bar and a nitrogen inlet tube was charged with 40.0g of NMP as an organic solvent for polymerization. Then, 5.272g of TFMB was placed in the flask while stirring the flask contents, and dissolved. Next, after adding 3.973g of NTCDA and 0.755g of BPAF to the flask content, the flask content was stirred under an atmosphere at a temperature of 25℃for 24 hours. Next, TPPi as a plasticizer was added to the flask content to obtain a polyamic acid composition. TPPi was added in an amount of 1 part by weight relative to 100 parts by weight of the polyamic acid in the flask content. The obtained polyamic acid composition was applied onto a glass substrate (alkali-free glass, thickness: 0.7mm, size: 100 mm. Times.100 mm, manufactured by Corning) using 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 (laminate of example 2) having a polyimide film with a thickness of 10. Mu.m on the glass substrate.

Examples 3 to 30 and comparative examples 1 to 7

Laminates of examples 3 to 6, 8, 10 to 27 and 29, and comparative examples 1 to 7 were obtained in the same manner as in example 1 except that the acid dianhydride and the addition ratio thereof and the diamine and the addition ratio thereof were as shown in tables 3 and 4. Laminates of examples 7, 9, 28 and 30 were obtained in the same manner as in example 2 except that the acid dianhydride and the ratio of the diamine to be used, and the type of plasticizer were as shown in tables 3 and 4. In addition, in any of examples 3 to 30 and comparative examples 1 to 7, the total amount of the acid dianhydride in the preparation of the polyamic acid composition was the same as that in examples 1 and 2. In addition, in any of examples 3 to 30 and comparative examples 1 to 7, the total amount of diamine in the preparation of the polyamic acid composition was the same as in examples 1 and 2.

The monomers and plasticizers used in examples 1 to 30 and comparative examples 1 to 7 are shown in tables 3 and 4, respectively. In tables 3 and 4, "-" means that the component was not used. In tables 3 and 4, the values in the column "acid dianhydride" are the content (unit: mol%) of each acid dianhydride relative to the total amount of the acid dianhydride used. In tables 3 and 4, the numerical values in the column "diamine" are the content (unit: mol%) of each diamine relative to the total amount of diamine used. In tables 3 and 4, the numerical values in the column of "plasticizer" are the amounts of plasticizer (unit: parts by weight) relative to 100 parts by weight of polyamic acid. In addition, regarding any of examples 1 to 30 and comparative examples 1 to 7, the mole fraction of each residue of polyamic acid in the prepared polyamic acid composition was identical to the mole fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of polyamic acid.

TABLE 3

TABLE 4

< Measurement results of physical Properties >

The average energy level differences and the measurement results of the physical properties of each of examples 1 to 30 and comparative examples 1 to 7 are shown in table 5. In table 5, "-" means not measured.

TABLE 5

The polyamic acid in the polyamic acid compositions prepared in examples 1 to 30 includes at least one residue selected from the group consisting of a BPDA residue, a BPAF residue, an ODPA residue and an SFDA residue, an NTCDA residue and a TFMB residue. The content of NTCDA residues in the polyamic acid compositions prepared in examples 1 to 30 was 5 mol% or more and 90 mol% or less based on the total amount of tetracarboxylic dianhydride residues. In the polyamic acid compositions prepared in examples 1 to 30, the content of TFMB residues was 50 mol% or more based on the total amount of diamine residues.

As shown in table 5, in examples 1 to 30, the 400nm transmittance was 40% or more. Therefore, the polyimide obtained in examples 1 to 30 had a high transmittance of light having a wavelength of 400 nm. In examples 1 to 30, TD1 exceeded 500 ℃. Therefore, the polyimide obtained in examples 1 to 30 was excellent in heat resistance.

The content of NTCDA residues of the polyamic acid in the polyamic acid composition prepared in comparative example 1 exceeds 90 mol% with respect to the total amount of tetracarboxylic dianhydride residues. The polyamic acid in the polyamic acid compositions prepared in comparative example 2, comparative example 4, comparative example 6 and comparative example 7 did not have an NTCDA residue. The content of TFMB residues of the polyamic acid in the polyamic acid compositions prepared in comparative examples 3 and 5 was less than 50 mol% with respect to the total amount of diamine residues.

As shown in Table 5, in comparative examples 1 to 7, the transmittance at 400nm was less than 40%. Therefore, the polyimide obtained in comparative examples 1 to 7 had a low transmittance of light having a wavelength of 400 nm.

From the above results, it was found that the polyimide of the present invention was excellent in heat resistance and high in transmittance of light having a wavelength of 400 nm.

Claims

1. A polyamic acid having a tetracarboxylic dianhydride residue and a diamine residue,

The tetracarboxylic dianhydride residue comprises more than one residue selected from the group consisting of 3,3', 4' -biphenyl tetracarboxylic dianhydride residue, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride residue, 4 '-oxydiphthalic anhydride residue, spiro [ 11H-difuran [3,4-b:3',4'-i ] xanthene-11, 9' - [9H ] fluorene ] -1,3,7, 9-tetralone residue and 2,3,6, 7-naphthalene tetracarboxylic dianhydride residue,

The diamine residues comprise 2,2' -bis (trifluoromethyl) benzidine residues,

2. The polyamic acid according to claim 1, wherein, in the case where the diamine residue comprises a diamine residue different from the 2,2 '-bis (trifluoromethyl) benzidine residue, the diamine residue different from the 2,2' -bis (trifluoromethyl) benzidine residue is a residue derived from a diamine having a highest occupied orbital level of-5.20 eV or less.

3. The polyamic acid according to claim 2, wherein the diamine residue different from the 2,2' -bis (trifluoromethyl) benzidine residue is one or more residues selected from the group consisting of a 4-aminophenyl-4-aminobenzoate residue, a 9, 9-bis (4-aminophenyl) fluorene residue and a2, 2' -bis (trifluoromethyl) -4,4' -diaminodiphenyl ether residue.

4. The polyamic acid according to claim 2, wherein the content of diamine residues different from the 2,2' -bis (trifluoromethyl) benzidine residues is 1 mol% or more and 50 mol% or less with respect to the total amount of the diamine residues.

5. The polyamic acid according to claim 4, wherein the content of the 3,3', 4' -biphenyltetracarboxylic dianhydride residue is 30 mol% or more and 50 mol% or less with respect to the total amount of the tetracarboxylic dianhydride residues.

6. The polyamic acid according to claim 1, wherein the difference between the average value of the lowest orbital level of tetracarboxylic dianhydride forming the tetracarboxylic dianhydride residue and the average value of the highest occupied orbital level of diamine forming the diamine residue is 2.25eV or more.

7. A polyamic acid composition comprising the polyamic acid according to claim 1 and an organic solvent.

8. The polyamic acid composition according to claim 7, further comprising a plasticizer.

9. The polyamic acid composition according to claim 8, wherein the amount of the plasticizer is 0.001 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the polyamic acid.

10. The polyamic acid composition according to claim 8, wherein the plasticizer comprises phosphorus.

11. A polyimide which is the imide of the polyamic acid according to claim 1.

12. The polyimide according to claim 11, which has a 1% weight loss temperature of 500 ℃ or higher.

13. A polyimide film comprising the polyimide of claim 11.

14. The polyimide film according to claim 13, which has a transmittance of 40% or more of light having a wavelength of 400 nm.

15. The polyimide film according to claim 13, which has a haze of 1.0% or less.

16. A laminate having a support and the polyimide film of claim 13.

17. A method for producing a laminate comprising a support and a polyimide film, wherein the polyamic acid composition according to claim 7 is applied to the support to form a coating film comprising the polyamic acid, and the coating film is heated to imidize the polyamic acid.

18. An electronic device having the polyimide film of claim 13 and an electronic component disposed on the polyimide film.