CN113613904A

CN113613904A - Polyamic acid composition and method for producing same, polyamic acid solution, polyimide film, laminate and method for producing same, and flexible device and method for producing same

Info

Publication number: CN113613904A
Application number: CN202080022551.1A
Authority: CN
Inventors: 中山博文; 宇野真理
Original assignee: Kaneka Corp
Current assignee: Kaneka Corp
Priority date: 2019-03-20
Filing date: 2020-03-19
Publication date: 2021-11-05
Also published as: WO2020189759A1; TW202045592A; KR20210138701A; JPWO2020189759A1; JP7539366B2

Abstract

The polyamic acid composition comprises polyamic acid and inorganic particles with average primary particle diameter of less than 200nm, wherein the polyamic acid comprises a structural unit shown in a general formula (1) and a structural unit shown in a general formula (2). Plural R¹Each independently a hydrogen atom, an alkyl group or an aryl group. Plural R²And R³Each is independentThe carbon atom number of the alkyl group is 1 to 3 or the carbon atom number of the aryl group is 6 to 10. X is a 4-valent organic group, and Z is a 2-valent organic group free of silicon atoms. And each Y is independently an alkylene group having 1 to 3 carbon atoms or an arylene group.

Description

Polyamic acid composition and method for producing same, polyamic acid solution, polyimide film, laminate and method for producing same, and flexible device and method for producing same

Technical Field

The present invention relates to a polyamic acid composition, a polyamic acid solution, a polyimide film, and a flexible device using the polyimide film.

Background

For devices such as displays such as liquid crystals, organic EL, and electronic paper, solar cells, touch panels, and lighting devices, thinning, weight reduction, and flexibility are required, and the use of plastic film substrates instead of glass substrates has been studied. In the manufacturing process of an electronic device, electronic elements such as a thin film transistor and a transparent electrode are provided on a substrate. Since the formation of electronic components requires a high-temperature process and the plastic film substrate requires heat resistance adaptable to the high-temperature process, the use of polyimide as a material for the plastic film substrate has been studied.

Manufacturing processes of electronic devices are classified into a batch type and a roll-to-roll type. In the batch process, a resin solution is applied to a glass support and dried to form a laminate of the glass support and a film substrate, and after forming an element thereon, the film substrate is peeled from the glass support. When the film substrate is a polyimide, a polyamic acid solution which is a precursor of the polyimide is applied to the support, and the polyamic acid is heated together with the support to imidize the polyamic acid, thereby obtaining a laminate of the support and the polyimide film.

In an optical device such as a display, light emitted from an element is emitted through a thin film substrate, and thus transparency is required for a substrate material. It is known that a polyimide obtained using a rigid monomer or a fluorine-based monomer has high transparency and low thermal expansion (patent documents 1 and 2). It is known that the use of silicone as a material of polyimide reduces the interfacial stress between the glass support and the polyimide film (patent documents 3 and 4).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2002-

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

Patent document 3: japanese patent laid-open publication No. 2017-226847

Patent document 4: japanese patent No. 5948545

Disclosure of Invention

Problems to be solved by the invention

The polyimide having an organosilicon skeleton (polyorganosiloxane structure) introduced therein for reducing the stress at the interface between the support and the polyimide film has a low thermal decomposition temperature, and when an electronic component is formed, there is a concern that productivity may be reduced due to outgassing from the polyimide film, or contamination of a manufacturing apparatus may occur. The purpose of the present invention is to provide a polyimide film which can reduce stress at the interface with a substrate, has excellent heat resistance and a high thermal decomposition temperature, and a polyamic acid composition which is a precursor of the polyimide film.

Means for solving the problems

One embodiment of the present invention is a polyamic acid composition including a polyamic acid and inorganic fine particles, the polyamic acid including a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2).

In the polyamic acid, the structural unit represented by the general formula (1) preferably includes a structural unit represented by the following general formula (3).

The inorganic fine particles have an average primary particle diameter of 200nm or less. The inorganic fine particles may be silica fine particles. The inorganic fine particles may be surface-treated.

The polyamic acid can be obtained by, for example, reacting tetracarboxylic dianhydride with diamine in an organic solvent. The tetracarboxylic dianhydride and the diamine can be reacted in an organic solvent in which inorganic fine particles are dispersed. The polyamic acid composition obtained by compositing (combining) the polyamic acid with the inorganic fine particles can be obtained by performing a polymerization reaction in a dispersion of the inorganic fine particles.

By using the silicone diamine represented by the following general formula (4) as the diamine, a polyamic acid having a structural unit represented by the general formula (2) can be obtained.

In the general formulae (2) and (4), a plurality of R²And R³Each independently is an alkyl group having 1 to 3 carbon atoms or an aryl group. And each Y is independently an alkylene group having 1 to 3 carbon atoms or an arylene group. m is an integer of 1 or more, preferably 30 or more and less than 300.

In the general formulae (1) to (3), a plurality of R¹Each independently a hydrogen atom, an alkyl group or an aryl group, preferably a hydrogen atom. The 4-valent organic group X is a residue of tetracarboxylic dianhydride. In the polyamic acid, the organic group X may have, for example, a structure of the following (a), (B), or (C).

The block copolymer can be obtained by reacting tetracarboxylic dianhydride with 1 st diamine in an organic solvent to form a polyamic acid segment, and then adding 2 nd diamine. When the 1 st diamine is a diamine containing no silicon atom and the 2 nd diamine is an organosilicon diamine, an ABA type triblock copolymer in which a second segment containing a polyorganosiloxane structure is bonded to both ends of a first segment containing no silicon atom can be obtained. The amount (number of moles) of tetracarboxylic dianhydride added to form the polyamic acid segment (first segment) by the reaction between tetracarboxylic dianhydride and 1 st diamine is preferably 1.001 times or more and less than 1.100 times the amount (number of moles) of 1 st diamine added.

The polyamic acid solution contains the polyamic acid composition and an organic solvent. The polyimide is obtained by dehydrating and cyclizing a polyamic acid. In one embodiment, a polyimide film can be obtained by applying a polyamic acid solution to a support to form a laminate in which a film-shaped polyamic acid is provided on the support, and heating the laminate to imidize the polyamic acid.

The 1% weight loss temperature of the polyimide film is preferably 450 ℃ or higher. The glass transition temperature of the polyimide film is preferably 300 ℃ or higher. The internal stress of the laminate of the support and the polyimide film at room temperature is preferably 25MPa or less.

A flexible device is obtained by forming an electronic component on a polyimide film. The electronic component may be formed on the polyimide film of the laminate in which the polyimide film is provided on the support, and after the electronic component is formed, the polyimide film may be peeled from the support.

ADVANTAGEOUS EFFECTS OF INVENTION

The laminate of the polyimide film and the inorganic support has low internal stress and excellent heat resistance, and is suitable as a substrate material for electronic devices.

Drawings

Fig. 1 is a graph showing the change in the heating weight of the polyimide films of example 2 and comparative example 2.

FIG. 2 is a graph showing the change in the heating weight of the polyimide films of example 3 and comparative example 3.

Fig. 3 is a graph showing changes in the heating weight of the polyimide films of comparative example 1B and comparative example 1C.

Fig. 4 is a cross-sectional TEM image of a polyimide film containing no inorganic fine particles (comparative example 2).

Fig. 5 is a cross-sectional TEM image of a polyimide film (example 2) containing silica particles.

Detailed Description

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

[ Polyamic acid composition ]

One embodiment of the present invention is a polyamic acid composition including a polyamic acid and inorganic fine particles. In the polyamic acid composition, polyamic acid and inorganic fine particles may be compounded. The polyamic acid is a precursor of polyimide, and the polyimide is obtained by a dehydration ring-closure reaction of the polyamic acid.

< Polyamic acid >

The polyamic acid contained in the polyamic acid composition of the present embodiment includes a structural unit represented by the following general formula (1) (hereinafter, sometimes referred to as "structural unit 1") and a structural unit represented by the following general formula (2) (hereinafter, sometimes referred to as "structural unit 2").

The structural unit 1 is formed by the reaction of a diamine having a 2-valent organic group Z containing no silicon atom and a tetracarboxylic dianhydride having a 4-valent organic group X. In the general formula (1), Z is a 2-valent organic group and is a residue of a diamine. For example, when the diamine is 2, 2' -bis (trifluoromethyl) benzidine (TFMB), the structural unit 1 is represented by the following general formula (3).

The structural unit 2 is formed by the reaction of an organosilicon diamine represented by the following general formula (4) with a tetracarboxylic dianhydride having a 4-valent organic group X.

In the general formula (1) and the general formula (2), X isThe organic group having a valence of 4 is a residue of tetracarboxylic dianhydride. Plural R¹Each independently a hydrogen atom, an alkyl group or an aryl group. In polyamic acid obtained by reaction of tetracarboxylic dianhydride and diamine, R¹Is a hydrogen atom. R is obtained by esterifying carboxyl group of polyamic acid¹Polyamic acid (polyamic acid ester) which is an alkyl group or an aryl group. The polyamic acid ester is not easily hydrolyzed, and the solution stability is excellent.

In the general formulae (2) and (4), a plurality of R²And R³Each independently is an alkyl group having 1 to 3 carbon atoms or an aryl group. And each Y is independently an alkylene group having 1 to 3 carbon atoms or an arylene group. m is an integer of 1 or more.

By including the structural unit 2, the internal stress of the polyimide film obtained by imidization of the polyamic acid tends to be reduced. The content of the structural unit represented by the general formula (2) in the polyamic acid is preferably 0.3 to 7 mol%, more preferably 0.5 to 5 mol%, and further preferably 0.7 to 4 mol%.

The polyamic acid has a weight-average molecular weight of, for example, 10000 to 1000000, preferably 30000 to 500000, and more preferably 40000 to 100000. If the weight average molecular weight is 10000 or more, the mechanical strength of the polyimide film can be ensured. When the weight average molecular weight is 1000000 or less, the polyamic acid exhibits sufficient solubility in a solvent, and a coating film or a thin film having a smooth surface and a uniform film thickness can be obtained. The molecular weight is a value in terms of polyethylene oxide based on Gel Permeation Chromatography (GPC).

< tetracarboxylic dianhydride >

In the general formulae (1) to (3), the organic group X is a residue of a tetracarboxylic dianhydride and is a 4-valent organic group derived from a tetracarboxylic dianhydride used for polymerization of a polyamic acid.

Specific examples of the tetracarboxylic acid dianhydride include pyromellitic dianhydride, 3,3 ', 4,4 ' -biphenyltetracarboxylic acid, 1, 4-phenylenebis (trimellitic acid dianhydride), 2,3,6, 7-naphthalenetetracarboxylic acid dianhydride, 1,2,5, 6-naphthalenetetracarboxylic acid dianhydride, 2 ', 3,3 ' -biphenyltetracarboxylic acid dianhydride, 3,3 ', 4,4 ' -benzophenonetetracarboxylic acid dianhydride, 4,4 ' -oxydiphthalic acid dianhydride, 9-bis (3, 4-dicarboxyphenyl) fluorenic acid dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride, dicyclohexyl-3, 3 ', 4,4 ' -tetracarboxylic acid dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic acid dianhydride, cyclobutanetetracarboxylic acid dianhydride, 2 ' -oxydisulfide [2.2.1] heptane-2, 1 '-cycloheptane-3, 2' -bicyclo [2.2.1] heptane-5, 5 '-6, 6' -tetracarboxylic dianhydride, and the like. When a plurality of tetracarboxylic dianhydrides are used, polyamic acids having a plurality of organic groups X can be obtained.

Among the tetracarboxylic dianhydrides exemplified, pyromellitic dianhydride (PMDA) and 3,3 ', 4' -biphenyltetracarboxylic dianhydride (BPDA) are preferable from the viewpoint of improving the heat resistance and mechanical strength of the polyimide film. From the viewpoint of improving the transparency (reducing the yellowness) of the polyimide film, tetracarboxylic dianhydrides having a bent structure such as 9, 9-bis (3, 4-dicarboxyphenyl) fluorenic dianhydride (BPAF), 4 '- (hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4, 4' -oxophthalic dianhydride (OPDA) are preferably used. Among these, BPAF is preferable in terms of being able to reduce the birefringence of the polyimide film.

From the viewpoint of obtaining a polyimide film having excellent heat resistance and low birefringence, PMDA and/or BPDA and BPAF are preferably used as the tetracarboxylic dianhydride. The residue of PMDA is a 4-valent organic group represented by the formula (A), the residue of BPDA is a 4-valent organic group represented by the formula (B), and the residue of BPAF is a 4-valent organic group represented by the formula (C).

That is, in the polyamic acid, the structure derived from the tetracarboxylic dianhydride (the organic group X in the general formulae (1) to (3)) preferably contains 1 or more kinds selected from the group consisting of the organic group having a valence of 4 represented by the formula (a) and the organic group having a valence of 4 represented by the formula (B), and the organic group having a valence of 4 represented by the formula (C). Preferred combinations of tetracarboxylic dianhydrides are combinations of PMDA and BPAF, BPDA and BPAF, and PMDA and BPDA and BPAF.

From the viewpoint of improving the transparency and heat resistance of the polyimide film and reducing birefringence and internal stress, the total amount of PMDA, BPDA, and BPAF is preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, relative to 100 mol% of the total amount of tetracarboxylic dianhydride components of the polyamic acid. The total amount of PMDA, BPDA and BPAF may be 90 mol% or more, or may be 100 mol%.

From the viewpoint of obtaining a polyimide film having low birefringence, the amount of BPAF is preferably 30 mol% or more, more preferably 35 mol% or more, and still more preferably 40 mol% or more, relative to 100 mol% of the total amount of tetracarboxylic dianhydride components of polyamic acid. From the viewpoint of obtaining a polyimide film having excellent heat resistance, the total amount of PMDA and BPDA is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 30 mol% or more, based on 100 mol% of the total amount of tetracarboxylic dianhydride components of polyamic acid.

In the case where the tetracarboxylic dianhydride is a combination of PMDA and BPAF, the amount of BPAF is preferably 30 to 90 mol%, more preferably 35 to 70 mol%, and still more preferably 40 to 60 mol% based on the total amount of PMDA and BPAF, from the viewpoint of obtaining a highly transparent and low birefringent polyimide film. The tetracarboxylic dianhydride is preferably a combination of BPDA and BPAF, and the amount of BPAF is preferably 30 to 90 mol%, more preferably 35 to 70 mol%, and even more preferably 40 to 60 mol% based on the total amount of BPDA and BPAF, from the viewpoint of obtaining a polyimide film having excellent alkali resistance.

< diamine >

As the diamine, diamines containing no silicon atom and silicone diamines can be used. By using a diamine containing no silicon atom, the structural unit 1 having the residue Z having a valence of 2 is formed.

The structural unit 2 having a polyorganosiloxane structure is formed by using an organosilicon diamine represented by the general formula (4) as a diamine. The silicone diamine represented by the general formula (4) is a diamine derived from an organosilicon compound (both terminal amino group-modified silicone). Specific examples of Y in the general formulae (2) and (4) include ethylene, propylene and phenylene, and among them, propylene is preferable. As R²And R³Examples thereof include methyl, ethyl, propyl and phenyl groups. From the viewpoint of suppressing the decrease in heat resistance of the polyimide, R is preferred²And R³At least one of them is an alkyl group, and among them, a methyl group is preferable.

The number m of repeating units in the siloxane structure is preferably 30 or more, more preferably 40 or more, and still more preferably 51 or more. When the structural unit 2 has a polyorganosiloxane structure in which the number m of repeating units is 30 or more, a domain is easily formed, and the internal stress of the polyimide film tends to be reduced by the stress relaxation effect. On the other hand, if the number of repeating units m is too large, the compatibility between the structural unit 1 and the structural unit 2 may be too low, and the haze of the polyimide film may be increased. Therefore, the number m of repeating units is preferably less than 300, more preferably less than 250, and further preferably less than 200. m may be less than 160, less than 100, or less than 80.

Specific examples of the silicone diamine include double-terminal amino group-modified methylphenylsilicones (for example, "X22-1660B-3" (number average molecular weight 4400), "X22-9409" (number average molecular weight 1300) manufactured BY shin-Etsu chemical Co., Ltd.), double-terminal amino group-modified dimethylsilicones (for example, "X22-161A" (number average molecular weight 1600), "X22-161B" (number average molecular weight 3000), "KF-8010" (number average molecular weight 860), "KF-8012" (number average molecular weight 4400) and "KF-8008" (number average molecular weight 11400), "BY 16-835U" (number average molecular weight 900) manufactured BY DOW Co., Ltd., and "Silaplane FM-3321" (number average molecular weight 5000) manufactured BY CHISSO Co., Ltd.). From the viewpoint of reducing the internal stress of the laminate of the polyimide film and the inorganic support, the amino group-modified dimethylsilicone having both terminals is preferable.

The amount of the silicone diamine represented by the general formula (4) is preferably 0.3 to 7 mol%, more preferably 0.5 to 5 mol%, and still more preferably 0.7 to 4 mol% based on 100 mol% of the total amount of the diamine component of the polyamic acid. The copolymerization ratio of the silicone diamine is preferably in the range of 2 to 30% by mass, more preferably 5 to 25% by mass, and still more preferably 10 to 20% by mass, based on the mass of the polyamic acid (the total amount of the tetracarboxylic dianhydride and the diamine). If the amount of the silicone diamine is in the above range, the internal stress of a laminate of a polyimide film obtained by imidization of a polyamic acid and an inorganic substrate such as glass tends to be small.

By including the structural unit 1, the characteristics such as transparency, heat resistance, and mechanical strength of a polyimide film obtained by imidization of a polyamic acid can be controlled. The 2-valent organic group Z in the structural unit 1 is preferably a fluorine-containing aromatic group from the viewpoint of obtaining a polyimide which is less colored and has high transparency. Examples of the diamine having a fluorine-containing aromatic group include fluoroalkyl-substituted benzidine.

Fluoroalkyl-substituted benzidines have fluoroalkyl groups on one or both phenyl rings of benzidine (4, 4' diaminobiphenyl). The fluoroalkyl group is preferably a trifluoromethyl group. Among fluoroalkyl-substituted biphenylamines, trifluoromethyl-substituted biphenylamines having 1 or more trifluoromethyl groups on each of the two benzene rings are preferable, and among these, 2' -bis (trifluoromethyl) biphenylamine (TFMB) is particularly preferable from the viewpoint of obtaining a polyimide having high transparency. As described above, the polyamic acid using TFMB as a diamine has a structure represented by the general formula (3) as the structural unit 1.

The amount of TFMB is preferably 60 to 99.7 mol%, more preferably 70 to 99.5 mol%, and still more preferably 80 to 99.3 mol% based on 100 mol% of the total amount of diamine components in the polyamic acid. The content of the structural unit represented by the general formula (3) in the polyamic acid is preferably 60 to 99.7 mol%, more preferably 70 to 99.5 mol%, and still more preferably 80 to 99.3 mol%.

In the polyamic acid, as the structural unit 1, a structure other than the general formula (3) may be included. That is, as the diamine component of the polyamic acid, a diamine containing no silicon atom other than TFMB may be used. Examples of the diamine containing no silicon atom include 1, 4-diaminocyclohexane, 1, 4-phenylenediamine, 1, 3-phenylenediamine, 4 '-oxydianiline, 3, 4' -oxydianiline, 2 '-bis (trifluoromethyl) -4, 4' -diaminodiphenyl ether, 4 '-diaminobenzanilide, 4' -aminophenyl-4-aminobenzene, 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), and the like.

< sequence of Polyamic acid >

The arrangement of the structural unit 1 and the structural unit 2 in the polyamic acid may be random or block. The polyamic acid may be a block copolymer having a first segment including the structural unit 1 but not the structural unit 2 and a second segment including the structural unit 2. Examples of the arrangement of blocks in the block copolymer include an AB type in which a second segment is bonded to one end of a first segment, an ABA type in which second segments are bonded to both ends of a first segment, and (AB) in which first segments and second segments are alternately arranged_nType, etc. The block copolymer is preferably an ABA type triblock structure in terms of ease of polymerization of polyamic acid and ease of formation of a block structure.

The first segment is a segment formed by repeating the structural unit 1. When only TFMB and a silicone diamine are used as the diamine component of the polyamic acid, the first segment is a segment formed of the repeating unit of the general formula (3). When a diamine other than TFMB and the silicone diamine is used as the diamine component, the proportion of the structure of the general formula (3) in the first segment is preferably 60 mol% or more, more preferably 70 mol% or more, and still more preferably 80 mol% or more.

The second segment may be formed of only the structural unit 2, or may include the structural unit 1 and the structural unit 2. When the silicone diamine has a high molecular weight (for example, m in the general formula (4) is 30 or more), a domain having the same block structure can be formed even when the structural units 2 are not continuous in the polymer sequence.

When a polyamic acid containing a polysiloxane structure as a structural unit 2 is imidized on an inorganic support such as glass to form a polyimide film, the internal stress in a laminate of the inorganic support and the polyimide film tends to be small. The detailed mechanism is not clear, but it is considered that: if the silicone (polyorganosiloxane) -derived domain is present in the polyimide film, when stress is generated in the polyimide film, the silicone-derived domain undergoes micro plastic deformation to relax the stress, and thus the internal stress of the entire polyimide film is reduced.

Particularly, in the case where the polyamic acid and the polyimide are block copolymers, which include domains (second segments) and a continuous phase (first segments), and the domains and the continuous phase have a difference in elastic modulus, it is considered that stress concentrates to the domains formed by the second segments, thereby effectively relaxing the stress. When the compatibility between the components constituting the domain and the components constituting the continuous phase is high, the following tendency is present: no distinct interface is formed, and stress concentration is less likely to occur in the domain due to partial compatibility, and the stress relaxation effect is reduced. Further, since the glass transition temperature of the silicone is low, if the domain of the second segment is partially compatible with the continuous phase, the glass transition temperature (Tg) tends to shift to the low temperature side. Therefore, it is preferable that the silicone-derived domain (second segment) has low compatibility with the continuous phase of the polyamic acid and the polyimide. As described above, it can be considered that: if the polyamic acid is a block copolymer having a first segment that does not include the structural unit 2, the compatibility of the first segment with a second segment is low, and a phase separation structure is easily formed by microdomains, thereby promoting stress relaxation.

[ inorganic Fine particles ]

As described above, by introducing the structural unit 2 derived from the silicone diamine into the polyamic acid, the internal stress in the laminate of the polyimide film and the substrate tends to be reduced. On the other hand, introduction of a polysiloxane structure tends to lower the heat resistance of polyimide and lower the thermal decomposition temperature. In the present embodiment, the heat resistance of a polyimide having a polyorganosiloxane structure can be improved by preparing a polyamic acid composition having a polyamic acid having a structural unit 1 derived from a diamine containing no silicon atom and a structural unit 2 derived from an organosilicon diamine and having inorganic fine particles having an average primary particle diameter of 200nm or less, and imidizing the polyamic acid in the composition.

The material of the inorganic fine particles is preferably an insulating material such as silica, zirconia, titania, alumina, magnesia, barium titanate, or silicon nitride. The inorganic fine particles may be montmorillonite, bentonite, phyllosilicate, etc. Among these, silica is preferable as the material of the inorganic fine particles in terms of high transparency and excellent effect of improving heat resistance by interaction with polyamic acid having a polyorganosiloxane structure.

From the viewpoint of maintaining the transparency of the polyimide, the average particle diameter of the inorganic fine 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 inorganic fine particles is preferably 5nm or more, more preferably 10nm or more, from the viewpoint of securing dispersibility.

The inorganic fine particles may be surface-treated for the purpose of improving dispersibility, increasing interaction with polyamic acid and polyimide, and the like. As the surface treatment, various known treatments can be applied. For example, the nano silica particles may be surface-treated with a silane coupling agent or the like. As the silane coupling agent used for the surface treatment of the nano silica, an alkoxysilane compound having an amino group, a glycidyl group or the like as a functional group can be suitably used, and among them, from the viewpoint of improving the interaction with the polyamic acid and the polyimide, an amino group-containing alkoxysilane is preferable. 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-aminophenyltrimethoxysilane. Among them, 3-aminopropyltriethoxysilane is preferable from the viewpoint of raw material stability. For example, the surface treatment can be performed by adding a silane coupling agent to a dispersion of amorphous nano silica (organic silica sol) and stirring the mixture at 20 to 80 ℃ for about 1 to 10 hours. A catalyst may be used for the purpose of promoting the reaction and the like.

The content of the inorganic fine particles in the polyamic acid composition is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, based on 100 parts by weight of polyamic acid. If the content of the inorganic fine particles is 1 part by weight or more, it can contribute to improvement of heat resistance. If the content of the inorganic fine particles is 30 parts by weight or less, adverse effects on the mechanical properties and transparency of the polyimide film can be suppressed.

The polyamic acid composition including the polyamic acid and the inorganic fine particles can be prepared by, for example, adding the inorganic fine particles to the polyamic acid solution. The diamine and the tetracarboxylic dianhydride may be added to a dispersion liquid in which inorganic fine particles are dispersed in an organic solvent, and the polymerization of the polyamic acid may be performed in the dispersion liquid. The polyamic acid composition obtained by compositing the polyamic acid and the inorganic fine particles can be prepared by polymerizing in a dispersion of the inorganic fine particles. By using a composition obtained by compositing a polyamic acid and inorganic fine particles, the heat resistance of a polyimide obtained by dehydrating the polyimide tends to be improved.

[ polymerization of Polyamic acid ]

The polyamic acid is obtained by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. For example, the diamine may be dissolved or dispersed in an organic solvent to prepare a diamine solution, and the tetracarboxylic dianhydride may be added to the diamine solution in a solution or solid state dissolved or dispersed in an organic solvent to prepare a slurry. Diamines may also be added to the tetracarboxylic dianhydride solution.

The organic solvent used in the polymerization of the polyamic acid is not particularly limited. The organic solvent is preferably capable of dissolving the tetracarboxylic dianhydride and diamine used and of dissolving the polyamic acid produced by the polymerization. Specific examples of the organic solvent used for the polymerization of polyamic acid include urea solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxide or sulfone solvents such as dimethyl sulfoxide, diphenyl sulfone and tetramethyl sulfone; ester solvents such as N, N-Dimethylacetamide (DMAC), N-Dimethylformamide (DMF), N' -diethylacetamide, N-methyl-2-pyrrolidone (NMP), and γ -butyrolactone; amide solvents such as hexamethylphosphoric triamide; 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, and p-cresol methyl ether. In general, these solvents may be used alone, or 2 or more kinds thereof may be appropriately combined as necessary. In order to improve the solubility and reactivity of the polyamic acid, the organic solvent used in the polymerization of the polyamic acid is preferably selected from amide solvents, ketone solvents, ester solvents, and ether solvents, and particularly preferably an amide solvent such as DMF, DMAC, NMP, and the like. In order to improve the stability of the solution, an ether solvent such as diethylene glycol or tetrahydrofuran may be added.

As described above, in the dispersion liquid in which the inorganic fine particles are dispersed in the organic solvent, the tetracarboxylic dianhydride and the diamine are reacted to synthesize the polyamic acid. In this case, it is preferable to select an organic solvent which can dissolve the tetracarboxylic dianhydride and the diamine and has excellent dispersibility of the inorganic fine particles.

When the polyamic acid is prepared by polymerizing a diamine and a tetracarboxylic dianhydride, a polyamic acid copolymer having a plurality of kinds of structural units can be obtained by using a plurality of kinds of one or both of the diamine and the tetracarboxylic dianhydride and adjusting the amounts of the diamine and the tetracarboxylic dianhydride. For example, a diamine containing no silicon atom such as TFMB and a silicone diamine are used as the diamine, whereby a polyamic acid having a structural unit 1 and a structural unit 2 can be obtained. The ratio of the structural unit 1 to the structural unit 2 in the polyamic acid can be arbitrarily adjusted by changing the ratio of the diamine. Similarly, by using a plurality of tetracarboxylic dianhydrides, polyamic acids having a plurality of organic groups X can be obtained. For example, by using PMDA and BPAF as tetracarboxylic dianhydride, a polyamic acid having structure (a) and structure (C) as organic group X having a valence of 4 can be obtained, and by using BPDA and BPAF, a polyamic acid having structure (B) and structure (C) as organic group X having a valence of 4 can be obtained. Also, 2 or more kinds of polyamic acids may be blended to obtain a polyamic acid containing a plurality of tetracarboxylic dianhydrides and diamines.

The diamine and the tetracarboxylic dianhydride are preferably dissolved and reacted in an inert gas atmosphere such as argon or nitrogen. The temperature condition for the reaction of the diamine and the tetracarboxylic dianhydride is not particularly limited, and is, for example, 25 to 150 ℃, preferably 40 to 150 ℃, and more preferably 60 to 120 ℃ from the viewpoint of sufficiently performing the reaction of the silicone diamine and suppressing the decomposition of the polyamic acid. The reaction time may be arbitrarily set, for example, within a range of 10 minutes to 30 hours. As the reaction proceeds, the molecular weight of the polyamic acid increases, and the viscosity of the reaction solution increases.

The reaction rate of a fluorine-containing diamine such as TFMB is lower than that of a fluorine-free aromatic diamine. The reaction rate can be increased by increasing the concentration of the tetracarboxylic dianhydride and the diamine in the reaction solution. The charging concentration of the raw materials (diamine and tetracarboxylic dianhydride) in the reaction solution is preferably 15 to 30% by weight.

An ABA type triblock copolymer in which second segments are bonded to both ends of a first segment can be obtained by preparing a polyamic acid having a first segment having an acid anhydride group at the end and adding a silicone diamine. First, a first segment is formed by reacting a tetracarboxylic dianhydride with a 1 st diamine in an organic solvent. The 1 st diamine is a diamine containing no silicon atom, and is a component other than the silicone diamine among the diamines constituting the polyamic acid. The 1 st diamine is, for example, TFMB. The 1 st diamine may comprise a diamine other than TFMB.

The amount of the tetracarboxylic dianhydride (total number of moles) charged in the formation of the first segment is preferably larger than the amount of the 1 st diamine (total number of moles). By increasing the amount of the tetracarboxylic dianhydride charged, a polyamic acid (first segment) having an acid anhydride group at the end is formed. On the other hand, if the amount of the tetracarboxylic dianhydride charged is too large, the molecular weight of the first segment may not be sufficiently increased. In the formation of the first segment, the total molar number of the tetracarboxylic dianhydride is preferably 1.001 times or more and less than 1.100 times, more preferably 1.01 to 1.09 times, and still more preferably 1.03 to 1.08 times the total molar number of the 1 st diamine.

When the first segment is formed by the reaction of tetracarboxylic dianhydride and the 1 st diamine and the 2 nd diamine is added, the acid anhydride group at the end of the first segment reacts with the 2 nd diamine, and a polyamic acid having the 2 nd diamine residue at both ends can be obtained. When a part of the tetracarboxylic dianhydride remains unreacted in forming the first segment, the second segment is extended at both ends of the first segment by the reaction of the unreacted tetracarboxylic dianhydride and the 2 nd diamine. After the first segment is formed, tetracarboxylic dianhydride may be additionally added in addition to the 2 nd diamine.

If the 2 nd diamine contains an organosilicon diamine, a block copolymer in which a second segment containing the structural unit 2 is bonded to both ends of a first segment not containing the structural unit 2 can be obtained. The 2 nd diamine may be only an organosilicon diamine, or may contain a diamine other than an organosilicon diamine. The second segment may contain a structure derived from a 1 st diamine remaining unreacted at the time of forming the first segment, in addition to a polysiloxane structure derived from an organosilicon diamine.

[ solution of Polyamide acid ]

The polyamic acid solution used in the preparation of the inorganic fine particle-containing polyimide contains the above polyamic acid composition (polyamic acid and inorganic fine particles) and a solvent. A solution obtained by reacting a diamine and a tetracarboxylic dianhydride in a dispersion of inorganic fine particles can be used as it is as a polyamic acid solution containing inorganic fine particles. Inorganic fine particles may also be added to the polyamic acid solution. The concentration of the polyamic acid and the viscosity of the solution can also be adjusted by removing a part of the solvent from the polymerization solution or adding a solvent. The solvent added may be different from the solvent used in the polymerization of the polyamic acid. Alternatively, the polyamic acid solution may be prepared by dissolving a solid polyamic acid resin obtained by removing the solvent from the polymerization solution in the solvent. The organic solvent of the polyamic acid solution is preferably an amide solvent, a ketone solvent, an ester solvent, or an ether solvent, and particularly preferably an amide solvent such as DMF, DMAC, or NMP.

For the purpose of imparting processing characteristics, various functions, and the like, an organic or inorganic low-molecular or high-molecular compound may be blended into the polyamic acid solution. Examples of the additive include dyes, pigments, surfactants, leveling agents, plasticizers, silicones, silane coupling agents, sensitizers, and fillers. The polyamic acid solution may contain resin components such as a photocurable component, a thermosetting component, and a non-polymerizable resin, in addition to the polyamic acid.

For the purpose of promoting imidization reaction and the like, an imidizing agent and/or a dehydrating agent may be added to the polyamic acid solution. The imidizing agent is not particularly limited, and tertiary amines are preferably used, and among them, heterocyclic tertiary amines are preferable. Examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, and isoquinoline. Examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

Imidazoles may be added to the polyamic acid solution. Imidazoles include compounds having a 1, 3-oxadiazole ring structure such as 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 them, 1, 2-dimethylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl 2-phenylimidazole are preferable, and 1, 2-dimethylimidazole and 1-benzyl-2-methylimidazole are particularly preferable.

The amount of the imidazole to be added is preferably about 0.005 to 0.1 mol, more preferably 0.01 to 0.08 mol, and still more preferably 0.015 to 0.050 mol based on 1 mol of the amide group of the polyamic acid. The "amide group of polyamic acid" refers to an amide group generated by addition polymerization of a diamine and a tetracarboxylic dianhydride. When the amount of the imidazole to be added is in the above range, it is expected that the heat resistance of the polyimide film is improved and the internal stress of the laminate of the inorganic support and the polyimide film is reduced in addition to the improvement of the storage stability of the polyamic acid solution.

When imidazole is added, it is preferable to add the imidazole after polymerizing the polyamic acid. The imidazole may be added directly to the polyamic acid solution or may be added as an imidazole solution to the polyamic acid solution.

[ polyimide and polyimide film ]

The polyimide is obtained by dehydration ring closure of polyamic acid. The dehydration ring closure can be performed by an azeotropic method, a thermal method or a chemical method using an azeotropic solvent. The imidization of the polyamic acid to the polyimide may be performed at an arbitrary ratio of 1 to 100%, and a partially imidized polyamic acid may be synthesized.

In order to obtain a polyimide film, it is preferable to apply a polyamic acid solution to a support such as a glass plate, a metal plate, or a PET (polyethylene terephthalate) film in the form of a film, and then heat the film to dehydrate the polyamic acid for ring closure. In order to shorten the heating time and to exhibit the characteristics, an imidizing agent and/or a dehydration catalyst may be added to the polyamic acid solution as described above. In order to accommodate a batch type device manufacturing process, a glass substrate is preferably used as a support, and alkali-free glass may be suitably used.

In the formation of the polyimide film on the support, first, a polyamic acid solution containing inorganic fine particles is applied to the support to form a coating film, and the laminate of the support and the coating film of polyamic acid is heated at a temperature of 40 to 200 ℃ for 3 to 120 minutes to remove the solvent. For example, the drying may be performed at two or more stages at a temperature of 50 ℃ for 30 minutes, and then at 100 ℃ for 30 minutes.

A laminate of a support and a polyamic acid is heated at a temperature of 200-400 ℃ for 3-300 minutes to dehydrate and ring-close the polyamic acid, thereby obtaining a laminate in which a polyimide film containing microparticles is provided on the support. In this case, the temperature is preferably gradually increased from the low temperature to the high temperature and then increased to the maximum temperature. The temperature rise rate is preferably 2 to 10 ℃/min, more preferably 4 to 10 ℃/min. The highest temperature is preferably 250-400 ℃. If the maximum temperature is 250 ℃ or higher, imidization can be sufficiently performed, and if the maximum temperature is 400 ℃ or lower, thermal deterioration and coloring of polyimide can be suppressed. In the heating for imidization, it may be kept at an arbitrary temperature for an arbitrary time until the maximum temperature is reached.

The heating atmosphere may be under air, under reduced pressure, or in an inert gas such as nitrogen. In order to exhibit higher transparency, heating under reduced pressure or in an inert gas is preferable. Examples of the heating device include a hot air oven, an infrared oven, a vacuum oven, an inert oven, and a hot plate.

[ Properties and uses of polyimide ]

The polyimide can be directly used for coating and forming processes for manufacturing products and components. As described above, the polyimide may be formed into a polyimide film shaped into a film. Various inorganic thin films such as metal oxides and transparent electrodes can be formed on the surface of the polyimide film. 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 has heat resistance and transparency, and therefore, can be used as a substitute material for glass, and can be applied to printed matter, color filters, flexible displays, optical films, liquid crystal display devices, image display devices such as organic EL and electronic paper, 3D displays, touch panels, transparent conductive film substrates, solar cells, and the like. In these applications, the thickness of the polyimide film is, for example, about 1 to 200 μm, preferably about 5 to 100 μm.

Since the polyimide film of the present embodiment has a small internal stress in a laminate with a glass support, the following batch-type device fabrication process can be applied: the polyimide film is peeled from the support after the polyimide film is formed on the polyimide film of the laminate by applying a polyamic acid solution to the support and heating the polyamic acid solution to perform imidization.

In the batch-type device fabrication process, the application of the polyamic acid solution to the support and the imidization by heating are performed by the above-described method, and a laminate in which a polyimide film is closely laminated on the support is formed. An electronic element such as a TFT is formed on the polyimide film of the laminate. In forming a TFT element, an oxide semiconductor, amorphous silicon, or the like is usually formed at a high temperature of 300 ℃.

When the thermal decomposition temperature of the polyimide film is low, outgassing from the polyimide film occurs due to heating at the time of forming the device, and this may cause a reduction in performance of the device formed on the polyimide film or peeling. Therefore, the 1% weight loss temperature Td1 of the polyimide film is preferably 450 ℃. Td1 may be 460 ℃ or higher, 465 ℃ or higher, 470 ℃ or higher, or 475 ℃ or higher.

When the glass transition temperature of the polyimide film is lower than the process temperature for forming the electronic component, stress may be generated at the interface between the support and the polyimide film due to dimensional change during the formation of the component and during cooling after the formation of the component, which may cause warpage and breakage. Therefore, the Tg of the polyimide film is preferably 300 ℃ or higher, more preferably 350 ℃ or higher, and still more preferably 380 ℃ or higher. The Tg may be 390 ℃ or higher, 395 ℃ or higher or 400 ℃ or higher.

As described above, the polyimide having a polyorganosiloxane structure derived from an organosilicon diamine generally tends to have a lower heat resistance than a polyimide having no polyorganosiloxane structure, and as shown by the change in the heating weight in fig. 1 (comparative example 2) and 2 (comparative example 3), a weight loss can be observed in the vicinity of 200 to 300 ℃.

Fig. 4 is a Transmission Electron Microscope (TEM) image of a cross section of a polyimide film (comparative example 2 described later) containing no inorganic fine particles, and it is seen that a silicone domain (white island-like region) is formed. When a polyimide having a polyorganosiloxane structure is heated, cyclic siloxane is easily generated by condensation between adjacent siloxane bonds, and this is considered to be one of the main causes of thermal decomposition (thermal weight loss) at around 200 to 300 ℃.

Fig. 5 is a cross-sectional TEM image of a polyimide film containing silica microparticles (example 2 described later), and the same white island-like regions as in fig. 4 and black regions were observed. It is known that the black region is a silica particle, and the silica particle is dispersed in such a manner as to enter between the domains of the silicone. In this manner, since the inorganic fine particles are dispersed between the silicone domains, the adjacent domains are prevented from approaching each other, and therefore, the generation of cyclic siloxane by heating can be suppressed, and the increase in the thermal decomposition temperature is estimated.

As described above, the stress of the polyimide film having polyorganosiloxane domains is easily dispersed, and the internal stress tends to be reduced. It can be considered that: in the present embodiment, since the polyimide having a polyorganosiloxane structure is compounded with the inorganic fine particles, thermal decomposition due to condensation cyclization of siloxane or the like is suppressed while maintaining the stress relaxation effect by the polyorganosiloxane domain, and therefore, the polyimide film has low internal stress and excellent heat resistance.

In general, since glass has a smaller thermal expansion coefficient than resin, stress is generated at the interface between the support and the polyimide film laminate due to temperature changes caused by heating and cooling after the formation of an electronic component. If stress remains at the interface between the support and the polyimide film formed on the support, problems such as warpage of the laminate, breakage of the glass support, and peeling of the flexible substrate (polyimide film) from the glass support may occur when the polyimide film shrinks when the polyimide film is cooled to room temperature after being heated to a high temperature in a process for forming an electronic component.

As described above, the polyimide film produced using the polyamic acid solution containing inorganic fine particles according to the present embodiment can reduce the internal stress in the laminate with the glass support in addition to the heat resistance, transparency, and low thermal expansion property. The internal stress of the laminate of the support and the polyimide film is preferably 30MPa or less, more preferably 25MPa or less, and still more preferably 20MPa or less.

In the batch type device fabrication process, in order to accurately form or mount electronic components or the like on the polyimide film, it is preferable that the adhesion between the support and the polyimide film is high. The polyimide film that is tightly laminated on the support preferably has a 90 ℃ peel strength of 0.05N/cm or more, more preferably 0.1N/cm or more, when peeled from the support. On the other hand, the peel strength is preferably 0.25N/cm or less from the viewpoint of workability when peeling the polyimide film from the support after mounting.

The method for peeling the polyimide film from the support is not particularly limited. For example, peeling may be performed by hand, or a peeling device such as a driving roller or a robot may be used. Peeling can be performed by reducing the adhesion between the support and the polyimide film. For example, a polyimide film may be formed on the support provided with the release layer. The silicon oxide film may be formed on a substrate having a plurality of grooves, and the substrate may be immersed in an etching solution to promote the peeling. The peeling may also be performed by laser irradiation.

When the polyimide film is peeled from the support by laser irradiation, the polyimide film needs to absorb the laser light, and therefore, the cut-off wavelength (wavelength having a transmittance of 0.1% or less) of the polyimide film is required to be longer than the wavelength of the laser light used for peeling. Since XeCl excimer laser light having a wavelength of 308nm is often used for laser lift-off, the cutoff wavelength of the polyimide film is preferably 320nm 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 is preferably 390nm or less. The polyimide film preferably has a cutoff wavelength of 320 to 390nm, more preferably 330 to 380nm, from the viewpoint of compatibility between transparency (low yellowness) and laser lift-off processability.

The transparency of the polyimide film can be evaluated by the total light transmittance and haze based on JIS K7105-1981. The total light transmittance of the polyimide film is preferably 80% or more, more preferably 85% or more. The haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, and further preferably 1.0% or less. In applications such as displays, high transmittance in all wavelength regions of visible light is required. The polyimide film preferably has a Yellowness Index (YI) of 15 or less, more preferably 10 or less. YI can be measured according to JIS K7373-2006. As described above, a polyimide film having high transparency can be used as a transparent substrate for glass replacement applications and the like.

Examples of flexible devices using a polyimide film as a substrate include organic EL displays and organic EL lighting. The organic EL device has two types, a bottom emission type in which light is extracted from the substrate side and a top emission type in which light is extracted from the opposite surface of the substrate. A transparent polyimide film having high visible light transmittance and low YI is also suitable as a substrate material for a bottom emission organic EL device.

In the bottom emission type organic EL device, since light is emitted through the substrate, the substrate material is required to have optical isotropy and a small retardation in the thickness direction (Rth) due to birefringence in some cases from the viewpoint of improvement of visibility in addition to transparency. Similarly, the touch panel substrate is also required to have a small Rth. Specifically, the Rth is preferably 300nm or less, more preferably 200nm or less, further preferably 100nm or less, and particularly preferably 50nm or less, based on the thickness of the polyimide film of 10 μm. Rth is the product of thickness and birefringence (difference between in-plane average refractive index and thickness-direction refractive index) in the thickness direction. That is, the birefringence of the polyimide film in the thickness direction is preferably 0.03 or less, more preferably 0.02 or less, still more preferably 0.01 or less, and particularly preferably 0.005 or less.

Examples

The present invention is not limited to the following examples, which are described for illustrative purposes.

[ evaluation method ]

< yellowness >

The transmittance at 200 to 800nm of the polyimide film was measured using an ultraviolet-visible near-infrared spectrophotometer ("V-650" manufactured by Nihon Spectroscopy), and the Yellowness Index (YI) was calculated from the formula described in JIS K7373.

< haze >

The measurement was carried out by the method described in JIS K7136 using an integrating sphere type haze meter ("HM-150N" manufactured by color technology research in village).

< internal stress >

The polyamic acid solutions prepared in examples and comparative examples were applied to alkali-free glass (thickness 0.7mm, 100mm × 100mm) manufactured by CONING, which was previously measured for an excessive warpage amount, by a spin coater, and heated at 80 ℃ for 30 minutes in air and 380 ℃ for 60 minutes in a nitrogen atmosphere, to obtain a laminate having a polyimide film with a thickness of 10 μm on a 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 at 25 ℃ in a nitrogen atmosphere was measured using a thin film stress measuring apparatus ("FLX-2320-S" manufactured by TENCOR corporation), to evaluate the internal stress between the glass substrate and the polyimide film.

< retardation (Rth) >

The retardation in the thickness direction Rth with respect to a light having a wavelength of 590nm was measured using a phase difference meter "OPTIPRO" manufactured by SHITEC, and the retardation in the thickness direction Rth (10) at a thickness of 10 μm was calculated from the film thickness D (μm) of the sample according to the following equation.

Rth(10)＝Rth×10/D

< glass transition temperature (Tg) >

A specimen having a width of 3mm and a length of 10mm was subjected to a load of 98.0mN using a thermomechanical analyzer ("TMA/SS 7100" manufactured by Hitachi high-tech Co., Ltd.), and the temperature and the amount of strain (elongation) were plotted (TMA curve) at a temperature of 10 ℃/min from 20 ℃ to 450 ℃. The glass transition temperature was defined as the intersection point obtained by extending the tangent of the TMA curve before and after the change in slope.

< 1% weight loss temperature (Td1) >

The temperature was raised from 25 ℃ to 500 ℃ at 20 ℃/min in a nitrogen atmosphere (550 ℃ in comparative examples 1B and 1C) using "TG/DTA/7200" manufactured by SII-Nano Technologies, and the temperature at which the weight was reduced by 1% was defined as Td1 of the polyimide film.

[ abbreviation of Compounds and reagents ]

Hereinafter, the compounds and reagents will be described in the following brief descriptions.

< solvent >

NMP: 1-methyl-2-pyrrolidone

DGDE: diethylene glycol diethyl ether

< tetracarboxylic dianhydride >

And (3) PMDA: pyromellitic dianhydride

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

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

< diamine >

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

< organosilicon diamine: both-end-modified organosilicon produced by the Beacon chemical industry >

X-22-1660B-3: r in the general formula (4)²Is methyl, R³A compound having a phenyl group and a phenyl group content of 25 mol% and m ═ 40; mw 4400

KF-8012: r in the general formula (4)²And R³A compound wherein m is 57 to 65; mw is 4400 to 5000

< others >

APS: 3-aminopropyltriethoxysilane

[ example 1]

< preparation of polyamic acid solution >

(surface treatment of Nano-silica)

Into a 300mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen gas inlet tube, an organic silica sol (NMP-ST-R2, manufactured by Nissan chemical Co., Ltd.; NMP dispersion having an average primary particle diameter of nano-silica of 10 to 15nm and a nano-silica content of 30 wt%): 4.6g and NMP: 37.1g, and stirring was performed. Thereafter, 4.2g of a 3 wt% NMP solution of APS was added thereto, and the mixture was stirred at 25 ℃ for 1 hour to carry out surface treatment of nano silica.

(polymerization of Polyamic acid)

To the above NMP solution of surface treated nano silica particles was added TFMB: 7.012g, and stirring. To this solution was added PMDA: 3.244g, stirring for more than 10 minutes, adding BPAF: 3.764g, stirred at room temperature for 12 hours. To this solution, NMP was added to dilute the solution so that the polyamic acid concentration became 15% by weight, and after heating the solution in an oil bath at 80 ℃ for 5 minutes, 2.0g of a 10% DGDE solution of KF-8012 was slowly added dropwise. After the dropwise addition, the mixture was stirred at 80 ℃ for 30 minutes and quenched with ice water to obtain a uniform and transparent polyamic acid solution. The polyamic acid solution contains 10 parts by weight of nano silica per 100 parts by weight of the total amount of tetracarboxylic dianhydride (PMDA and BPAF) and diamine (TFMB).

Comparative example 1A

56.0g of NMP was charged as a solvent into the separable flask, and the organic silica sol and APS were not added. Except for this, a polyamic acid solution containing no inorganic fine particles was prepared in the same manner as in example 1.

Comparative example 1B

Surface treatment of nano silica was carried out in the same manner as in example 1, and TFMB, PMDA and BPAF were added to an NMP solution of the surface-treated nano silica particles in this order, and after stirring at room temperature for 12 hours, the mixture was diluted with NMP to prepare a polyamic acid solution having a concentration of 15 wt%. No reaction with the silicone diamine was carried out.

Comparative example 1C

Without adding the organic silica sol and APS, TFMB, PMDA, and BPAF were added to 56.0g of NMP in this order, and after stirring at room temperature for 12 hours, the mixture was diluted with NMP to prepare a polyamic acid solution containing no inorganic fine particles. No reaction with the silicone diamine was carried out.

Examples 2 and 3 and example 4C

A polyamic acid solution containing nano silica was prepared in the same manner as in example 1, except that the type and amount of tetracarboxylic dianhydride and the type of silicone diamine used in the polymerization of polyamic acid were changed as shown in table 1.

Examples 4A, 4B and 4D

The amount of the organic silica sol added in the surface treatment of the nano silica was changed so that the amount of the nano silica was 3 parts by weight, 5 parts by weight, and 20 parts by weight with respect to 100 parts by weight of the total of the tetracarboxylic dianhydride and the diamine, and the amount of the APS added was changed accordingly. Except for this, in the same manner as in example 4C, a polyamic acid solution containing nano silica was prepared.

[ comparative examples 2 to 4]

A polyamic acid solution containing no inorganic fine particles was prepared in the same manner as in comparative example 1A, except that the type and amount of tetracarboxylic dianhydride and the type of silicone diamine used in the polymerization of polyamic acid were changed as shown in table 1.

[ production of polyimide film ]

The polyamic acid solutions of the examples and comparative examples were applied to a glass plate by a spin coater, and heated at 80 ℃ for 30 minutes in air and 380 ℃ for 1 hour in a nitrogen atmosphere to obtain a polyimide film having a thickness of 10 to 15 μm.

The compositions of polyamic acids and the evaluation results of the properties of polyimide films of examples and comparative examples are shown in table 1. Further, TG-DTA spectra of the polyimide films of example 2 and comparative example 2 are shown in fig. 1, TG-DTA spectra of the polyimide films of example 3 and comparative example 3 are shown in fig. 2, TG-DTA spectra of the polyamide films of comparative example 1B and comparative example 1C are shown in fig. 3, and cross-sectional TEM images of the polyimide films of comparative example 2 and example 2 are shown in fig. 4 and 5.

The amount (mol%) of tetracarboxylic dianhydride in table 1 is a value of 100 mol% relative to the total amount of diamine, and the amounts (phr) of silicone diamine and nanosilica are values of 100 parts by weight relative to the total amount of diamine and tetracarboxylic dianhydride charged. The polyimide films of any of the examples and comparative examples had a haze of less than 1% and a YI of 10 or less.

[ Table 1]

The polyimide film of comparative example 1C containing no silicone diamine had Td1 of 500 ℃ or higher and exhibited excellent heat resistance, but the internal stress of the laminate exceeded 50 MPa. In comparative example 1A in which a polyorganosiloxane structure was introduced by the reaction with the organic silicon diamine, the internal stress was reduced to half or less of that of comparative example 1A, and accordingly, the birefringence of the polyimide film was also reduced. However, in comparative example 1A, Td1 was greatly reduced as compared with comparative example 1C. From these results, it can be seen that: although a polyimide film produced using a polyamic acid into which a polysiloxane structure has been introduced by reaction with a silicone diamine can reduce internal stress in a laminate with a substrate, the introduction of a polysiloxane structure tends to reduce heat resistance.

In example 1 in which polyamic acid having the same composition as in comparative example 1A was synthesized in a dispersion of nano silica, Td1 was raised by 20 ℃ as compared with comparative example 1A while maintaining the same low internal stress as in comparative example 1A. From the comparison of comparative example 2 with example 2, the comparison of comparative example 3 with example 3, and the comparison of comparative example 4 with examples 4A to 4D, it can be seen that: by forming a composite with the inorganic fine particles, the internal stress is kept low and the heat resistance is improved. In examples 4A to 4D, Td1 and Tg tended to increase as the amount of the inorganic fine particles added increased.

From these results, it can be seen that: the laminate of the polyimide film and the substrate, which is produced using the polyamic acid that has been introduced into the polysiloxane structure by the reaction with the silicone diamine and has been complexed with the inorganic fine particles, has a low internal stress and is excellent in heat resistance.

In fig. 1, weight loss was observed at 210 to 300 ℃ in comparative example 2, whereas weight loss in this temperature range was suppressed in example 2 containing inorganic fine particles. In fig. 2, in comparative example 3, weight loss occurred from around 270 ℃, whereas in example 3 containing inorganic fine particles, almost no weight loss was observed up to around 400 ℃, and the 1% weight loss temperature Td1 was increased as compared with comparative example 3. From these results, it can be seen that: by including the inorganic fine particles, thermal decomposition at low temperature is suppressed, and the 1% weight loss temperature Td1 is increased. Furthermore, it can be seen that: in examples 2 and 3, weight loss (thermal decomposition) was also suppressed in a high temperature region of 400 ℃ or higher, as compared with comparative examples 2 and 3.

Regarding the polyimide containing no polysiloxane structure, in comparative example 1B and comparative example 1C in which the comparison with inorganic fine particles was performed, although Td1 was slightly higher in comparative example 1B compared with comparative example 1C, the weight loss tendency of both was not significantly different in fig. 3, and the thermal weight loss in the vicinity of 200 to 300 ℃ as in comparative example 2 (fig. 1) and comparative example 3 (fig. 2) was not observed in comparative example 1C in which inorganic fine particles were not contained. From these results, it can be said that: the improvement of heat resistance by using inorganic fine particles is an effect unique to polyimide having a polysiloxane structure.

From the comparison of comparative example 1A with comparative example 1C (difference in heat resistance due to the presence or absence of the silicone diamine) and the weight loss plots shown in FIGS. 1 to 3, it can be considered that: the reduction of the thermal weight loss of the polyimide containing no inorganic fine particles at around 200 to 300 ℃ and the reduction of Td1 associated therewith are caused by the introduction of a polysiloxane structure. As shown by comparison of the examples with the comparative examples, it is considered that: since thermal decomposition due to a polysiloxane structure is suppressed by compounding a polyimide having a polysiloxane structure introduced therein with inorganic fine particles, heat resistance is specifically improved by combining a polyimide having a polysiloxane structure with inorganic fine particles.

In fig. 4 (cross-sectional TEM image of the polyimide film of comparative example 2), white island-like regions were observed. This is considered to be a domain of the silicone (polysiloxane structure) and is presumed to have a function of reducing the internal stress, but on the other hand, it is a cause of the weight loss in the vicinity of 200 to 300 ℃. In fig. 5 (cross-sectional TEM image of the polyimide film of example 2), a black region was observed in addition to a white region. The black regions can be considered as silica particles. The black regions (silica particles) are dispersed so as to enter between white domains (silicone domains), and it is considered that: the silica particles have an effect of hindering or suppressing an interaction between domains (for example, generation of cyclic siloxane by a reaction of siloxanes with each other based on heating), which may contribute to improvement of heat resistance.

Claims

1. A polyamic acid composition comprising a polyamic acid and inorganic fine particles having an average primary particle diameter of 200nm or less, the polyamic acid comprising a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2),

plural R¹Each independently a hydrogen atom, an alkyl group or an aryl group,

plural R²And R³Each independently an alkyl group having 1 to 3 carbon atoms or an aryl group,

x is an organic group having a valence of 4,

z is a 2-valent organic group containing no silicon atom,

y's are each independently an alkylene group having 1 to 3 carbon atoms or an arylene group,

m is an integer of 1 or more.

2. The polyamic acid composition according to claim 1, wherein the structural unit represented by the general formula (1) comprises a structural unit represented by the following general formula (3),

3. the polyamic acid composition according to claim 1 or 2, wherein X in the general formula (1) and the general formula (2) comprises 1 or more selected from the group consisting of 4-valent organic groups represented by the following formulas (A), (B) and (C),

4. the polyamic acid composition according to any one of claims 1 to 3, wherein the inorganic fine particles are silica particles.

5. The polyamic acid composition according to any one of claims 1 to 4, wherein the inorganic fine particles are contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the polyamic acid.

6. The method for producing a polyamic acid composition according to any one of claims 1 to 5, wherein,

in an organic solvent in which the inorganic fine particles are dispersed, a tetracarboxylic dianhydride is reacted with a diamine.

7. The method for producing a polyamic acid composition according to claim 6, wherein a tetracarboxylic dianhydride is reacted with a 1 st diamine in an organic solvent to form a polyamic acid segment, and then a 2 nd diamine is added,

the 1 st diamine contains a diamine containing no silicon atom, the 2 nd diamine is an organosilicon diamine represented by the following general formula (4),

wherein R in the general formula (4)²、R³Y, and m are as defined for R in the general formula (2)²、R³Y and m are the same.

8. The method for producing a polyamic acid composition according to claim 7, wherein the 1 st diamine comprises 2, 2' -bis (trifluoromethyl) benzidine.

9. The method for producing a polyamic acid composition according to claim 7 or 8, wherein the total molar number of the tetracarboxylic dianhydride is 1.001 times or more and less than 1.100 times the total molar number of the 1 st diamine.

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

11. An inorganic fine particle-containing polyimide obtained by subjecting the polyamic acid in the polyamic acid composition according to any one of claims 1 to 5 to dehydrate and cyclize.

12. A polyimide film comprising the inorganic microparticle-containing polyimide according to claim 11.

13. The polyimide film according to claim 12, having a 1% weight loss temperature of 450 ℃ or higher.

14. The polyimide film according to claim 12 or 13, which has a glass transition temperature of 300 ℃ or higher.

15. A laminate comprising the polyimide film according to any one of claims 12 to 14 provided on a support.

16. A method for producing a laminate, comprising applying the polyamic acid solution according to claim 10 to a support to form a film-like polyamic acid on the support, and imidizing the polyamic acid by heating to form a polyimide film on the support.

17. A flexible device having the polyimide film described in any one of claims 12 to 14, and an electronic component formed on the polyimide film.

18. A method for manufacturing a flexible device, wherein a laminate is formed by the method according to claim 16, and after an electronic component is formed on the polyimide film of the laminate, the polyimide film is peeled from the support.