JP5909391B2 - Polyimide solution and polyimide film obtained from the solution - Google Patents

Description

  The present invention relates to a polyimide solution and a polyimide film obtained from the solution. Furthermore, electronic device materials using the polyimide film, TFT substrates, flexible display substrates, color filters, printed materials, optical materials, liquid crystal display devices, organic EL, electronic paper and other image display devices, 3-D displays, solar cells, The present invention relates to a touch panel, a transparent conductive film substrate, and an alternative material for a portion where glass is currently used.

  In recent years, with rapid advances in displays such as liquid crystal, organic EL, and electronic paper, and electronics such as solar cells and touch panels, devices are required to be thinner and lighter, and more flexible. Therefore, instead of a glass substrate, a plastic film substrate that can be made thinner, lighter, and flexible has been studied.

  In these devices, various electronic elements such as a thin film transistor and a transparent electrode are formed on a substrate. However, a high temperature process is required to form these electronic elements. However, plastic films have low heat resistance and low dimensional stability at high temperatures, and are susceptible to thermal deformation such as warpage in the manufacturing process, making alignment difficult and possibly destroying electrical elements. .

  Furthermore, when the light emitted from the display element is emitted through the plastic film substrate (for example, bottom emission type organic EL), the plastic film substrate needs to be transparent. In particular, the light transmittance is required to be high in a wavelength region of 400 nm or less that is a visible light region.

  These device fabrication processes are divided into batch type and roll-to-roll type. When using a roll-to-roll fabrication process, new equipment is required and several problems due to rotation and contact must be overcome. On the other hand, the batch type is a process in which a coating resin solution is applied on a glass substrate, dried, a substrate is formed, and then peeled off. For this reason, the glass substrate process and equipment such as the current TFT can be used, which is advantageous in terms of cost.

  Against this background, there is a strong demand for the development of a coating resin solution that can be applied to existing batch processes and that can provide a heat-resistant and highly dimensionally stable coating film.

  Polyimide has been studied as a material having these requirements. In order to obtain a highly transparent polyimide, an alicyclic monomer or an aromatic monomer containing a fluorine substituent is generally used (Patent Document 1, Patent Document 2). On the other hand, Patent Document 3 is known as a flexible printed wiring board application having a low linear expansion coefficient. In addition, a polyimide containing an amide group or an ester group has been reported as an interlayer insulating film material (Patent Document 4).

JP 2004-252373 A JP 2004-182757 A WO2005 / 113647 JP 2010-106225 A

  When the alicyclic monomer described in Patent Document 1 or 2 is used, although the solubility in an organic solvent is increased, a polyimide having high heat resistance and high dimensional stability cannot be obtained. Polyimides containing fluorine substituents, such as polyimides obtained from 2,2′-bis (trifluoromethyl) benzidine (hereinafter sometimes referred to as TFMB), have excellent heat resistance, solubility in organic solvents, and transparency. However, there have been reports on liquid crystal alignment films and visual compensation films, but there is no description of thermal expansion characteristics and dimensional stability. The polyesterimide described in Patent Document 3 hardly dissolves in a solvent because of its rigid structure. The ester group-containing polyimide and amide group-containing polyimide described in Patent Document 4 have room for improvement in terms of transparency.

  The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to obtain a polyimide that is excellent in transparency, heat resistance, solubility in an organic solvent, and low linear thermal expansion coefficient.

The present invention has the following configuration.
1 A polyimide solution containing a polyimide containing a structure represented by the following general formula (1) and an organic solvent.

(In the formula, R1 to R4 may be the same or different and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, an aryl group, a trifluoromethyl group, and a methoxy group, provided that all of R1 to R4 are hydrogen. Except when

2 R1-R3 is a C1-C5 alkyl group, R4 is hydrogen, The polyimide solution of 1 characterized by the above-mentioned.
3 R1 and R3 are alkyl groups, R2 and R4 are hydrogen, The polyimide solution of 1 characterized by the above-mentioned.
4 The polyimide solution according to any one of 1 to 3, which contains 50 mol% or more of the structure of the general formula (1).
5 The polyimide solution according to any one of 1 to 4, wherein the organic solvent is selected from at least one of an amide solvent, a ketone solvent, and an ether solvent.
6 A polyimide film obtained from the polyimide solution of any one of 1 to 5.
76. A polyimide film obtained by applying the polyimide solution described in 76 to a support.
8. The polyimide film according to 7, wherein the support is a glass substrate.
9 The transmittance | permeability of the light of wavelength 400nm is 50% or more, The polyimide film in any one of 6-8 characterized by the above-mentioned.
10 Linear thermal expansion coefficient is 20 ppm / K or less, The polyimide film in any one of 6-9 characterized by the above-mentioned.
11 A TFT substrate containing any one of 6 to 10 polyimide film.
12 A flexible display substrate containing any one of 6 to 10 polyimide film.
The color filter containing the polyimide film in any one of 13-6-10.
14 An image display device such as an organic EL or electronic paper containing any one of 6 to 10 polyimide films.
15 An optical material containing any one of 6 to 10 polyimide film.
16 Electronic device material containing any one of 6-10 polyimide films.

  Since the polyimide according to the present invention has a low linear thermal expansion coefficient equivalent to various inorganic materials in addition to transparency and heat resistance, heat resistance and low expansion (dimensional stability) are required. It is suitable as a film or coating film for all known members.

  The present invention is described in detail below.

  The polyimide solution manufactured by this invention contains the polyimide and organic solvent which contain the structure represented by following formula (1).

  R1 to R4 in the formula may be the same or different and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, an aryl group, a trifluoromethyl group, and a methoxy group. However, it excludes when all of R1-R4 are hydrogen atoms. Moreover, from the viewpoint of obtaining high transparency and low thermal expansion characteristics, it is preferable that R1 to R3 are alkyl groups and R4 is hydrogen. From the viewpoint of improving transparency, it is preferable that R1 and R3 are alkyl groups and R2 and R4 are hydrogen.

From R1 to R4, at least one of these is preferably an alkyl group having 1 to 5 carbon atoms or a trifluoromethyl group from the viewpoint of low thermal expansion, heat resistance and solubility of the polyimide. More preferred are a tert-butyl group and a trifluoromethyl group. Furthermore, from the viewpoint of availability and production cost, at least one of R1 to R4 is a methyl group, a tert-butyl group or an isobutyl group, and R1 to R4 other than the methyl group, the tert-butyl group and the isobutyl group are hydrogen atoms. It is particularly preferred. Moreover, it is preferable that the sum total of all the carbon numbers of R1-R4 is 3 or more at the point which provides transparency and solubility. The upper limit is preferably 12 or less from the viewpoints of heat resistance and low thermal expansion. That is, for example, when R1 to R3 are —CH ₃ groups and R4 is hydrogen, the total number of carbon atoms of R1 to R4 is 3. When R1 is a —CH (CH ₃ ) CH ₂ CH ₃ group and R2 to R4 are hydrogen, the total number of carbon atoms is 4. That is, R1, R2, and R3 are methyl groups and R4 is hydrogen, or one of R1 to R4 is a tert-butyl group, an isobutyl group, or a 1,1-dimethylpropyl group, and the remaining three are hydrogen The case where R1 to R3 are methyl groups and R4 is hydrogen is most preferable. In this case, the structure is represented by the following formula (2):

It becomes.

  If the said polyimide contains the repeating unit represented by the said Formula (1), it will not restrict | limit in particular about another frame | skeleton. For example, tetracarboxylic dianhydrides and diamines other than the skeleton represented by the above formula (1) can be used. The repeating unit of the polyimide of the present invention represented by the above formula (1) is selected depending on the balance between the solubility and the low linear thermal expansion coefficient, but it is 50 mol% or more, preferably 60 mol% or more of the whole polyimide, Preferably it contains 70 mol% or more, and most preferably contains 90 mol% or more. Moreover, the repeating unit of said Formula (1) may be regularly arranged, and may exist in polyimide at random.

  The polyimide containing the repeating unit represented by the above formula (1) includes an ester group-containing tetracarboxylic dianhydride, 2,2′-bis (trifluoromethyl) benzidine and / or 3,3′-. It is preferably produced using bis (trifluoromethyl) benzidine.

  When manufacturing the polyimide containing the repeating unit represented by the above formula (1), other tetracarboxylic dianhydrides that can be used in combination with the ester group-containing tetracarboxylic dianhydride include, for example, ethylene. Tetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) Propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis ( , 4-Dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3 4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, 2 , 2-bis {4- [3- ( , 2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2 -Dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4'-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4'-bis [3- (1,2 -Dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) Phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] Phenyl} s Hong dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfide Anhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2- Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalene tetracarboxylic acid di Anhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride 3,4,9,10-perylenetetracarbo Acid dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like can be mentioned, but are not limited thereto. . These may be used alone or in combination of two or more.

  Specific examples of diamine monomers that can be used in combination include, for example, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′- Diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4, 4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4 '-Diaminodiphenylmethane, , 2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 1,1-di ( 3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) ) Benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis 4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2,6 -Bis (3-aminophenoxy) pyridine, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] Ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl Enyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3- Bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α- Dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl ] Benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4′-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4 ′ -Bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, 4,4 '-Bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4, '-Dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis (3-aminophenoxy) -3,3,3' , 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 1,3 -Bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethylsiloxane, α, ω-bis ( 3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2- Minomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether, 1,2-bis (aminomethoxy) ethane, 1,2- Bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-amino Propyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1 , 6-Diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, trans- 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4- Aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 1,4-diamino -2-fluorobenzene, 1,4-diamino-2,3-difluorobenzene, 1,4-diamino-2,5-difluoro Lobenzene, 1,4-diamino-2,6-difluorobenzene, 1,4-diamino-2,3,5-trifluorobenzene, 1,4-diamino-2,3,5,6-tetrafluorobenzene, 1 , 4-diamino-2- (trifluoromethyl) benzene, 1,4-diamino-2,3-bis (trifluoromethyl) benzene, 1,4-diamino-2,5-bis (trifluoromethyl) benzene, 1,4-diamino-2,6-bis (trifluoromethyl) benzene, 1,4-diamino-2,3,5-tris (trifluoromethyl) benzene, 1,4-diamino-2,3,5 6-tetrakis (trifluoromethyl) benzene, 2-fluorobenzidine, 3-fluorobenzidine, 2,3-difluorobenzidine, 2,5-difluorobenzidine, 2,6 Difluorobenzidine, 2,3,5-trifluorobenzidine, 2,3,6-trifluorobenzidine, 2,3,5,6-tetrafluorobenzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine 2,3'-difluorobenzidine, 2,2 ', 3-trifluorobenzidine, 2,3,3'-trifluorobenzidine, 2,2', 5-trifluorobenzidine, 2,2 ', 6-tri Fluorobenzidine, 2,3 ′, 5-trifluorobenzidine, 2,3 ′, 6, -trifluorobenzidine, 2,2 ′, 3,3′-tetrafluorobenzidine, 2,2 ′, 5,5′- Tetrafluorobenzidine, 2,2 ′, 6,6′-tetrafluorobenzidine, 2,2 ′, 3,3 ′, 6,6′-hexafluorobenzidine, 2,2 ′ 3,3 ′, 5,5 ′, 6,6′-octafluorobenzidine, 2- (trifluoromethyl) benzidine, 3- (trifluoromethyl) benzidine, 2,3-bis (trifluoromethyl) benzidine, 2 , 5-bis (trifluoromethyl) benzidine, 2,6-bis (trifluoromethyl) benzidine, 2,3,5-tris (trifluoromethyl) benzidine, 2,3,6-tris (trifluoromethyl) benzidine 2,3,5,6-tetrakis (trifluoromethyl) benzidine, 2,3′-bis (trifluoromethyl) benzidine, 2,2 ′, 3-bis (trifluoromethyl) benzidine, 2,3,3 '-Tris (trifluoromethyl) benzidine, 2,2', 5-tris (trifluoromethyl) benzidine, 2,2 ', 6-tris (to (Rifluoromethyl) benzidine, 2,3 ′, 5-tris (trifluoromethyl) benzidine, 2,3 ′, 6, -tris (trifluoromethyl) benzidine, 2,2 ′, 3,3′-tetrakis (tri Fluoromethyl) benzidine, 2,2 ′, 5,5′-tetrakis (trifluoromethyl) benzidine, 2,2 ′, 6,6′-tetrakis (trifluoromethyl) benzidine, but are not limited thereto. It is not a thing. These may be used alone or in combination of two or more.

  Polyimide can be obtained from its precursor polyamic acid. This polyamic acid can be obtained, for example, by reacting diamine and tetracarboxylic dianhydride in an organic solvent. Specifically, in an inert atmosphere such as argon or nitrogen, the diamine is dissolved in an organic solvent or dispersed in a slurry to obtain a diamine solution. On the other hand, tetracarboxylic dianhydride may be added to the diamine solution after being dissolved or dispersed in an organic solvent or in a solid state.

  When synthesizing a polyamic acid using the diamine and tetracarboxylic dianhydride, the reaction may be performed using at least one of the diamine and tetracarboxylic dianhydride. At this time, if 1 type of diamine and 1 type of tetracarboxylic dianhydride are substantially equimolar, it will become a polyamic acid of 1 type of tetracarboxylic dianhydride components and 1 type of diamine components. Moreover, when using 2 or more types of tetracarboxylic dianhydride components and 2 or more types of diamine components, the number of moles of the total amount of the plurality of diamine components and the number of moles of the total amount of the plurality of tetracarboxylic acid dianhydride components are substantially If adjusted to an equimolar ratio, a polyamic acid copolymer can be arbitrarily obtained. The temperature condition for the reaction of the diamine and tetracarboxylic dianhydride (polyamide acid synthesis reaction) is not particularly limited, but is preferably 80 ° C. or lower, more preferably 0 to 50 ° C. If the temperature condition of the polyamic acid synthesis reaction is 80 ° C. or lower, the polyamic acid is hardly decomposed, and if the temperature condition of the polyamic acid synthesis reaction is 0 ° C. or higher, the progress of the polymerization reaction is difficult to slow. Moreover, what is necessary is just to set reaction time arbitrarily in the range of 10 minutes-30 hours.

  Furthermore, the organic solvent used for the synthesis reaction of the polyamic acid is not particularly limited as long as it is an organic polar solvent. As the reaction between the diamine and tetracarboxylic dianhydride proceeds, polyamic acid is generated, and the viscosity of the reaction solution increases. Moreover, as will be described later, the polyamic acid solution obtained by synthesizing the polyamic acid can be heated under reduced pressure to simultaneously remove the organic solvent and imidize. Therefore, as the organic solvent, it is advantageous in terms of the process to select an organic solvent that can dissolve the polyamic acid and has a low boiling point as much as possible.

  Specifically, examples of the organic solvent used in the polyamic acid synthesis reaction include a formamide solvent such as N, N-dimethylformamide, an acetamide solvent such as N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and the like. Examples thereof include pyrrolidone solvents such as N-vinyl-2-pyrrolidone, ester solvents such as γ-butyrolactone, ether solvents such as tetrahydrofuran, dioxane and dioxolane.

  The reaction solvent used for the polymerization of the polyamic acid is preferably one capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably one capable of dissolving the produced polyamic acid. For example, urea solvents such as tetramethylurea, N, N-dimethylethylurea, dimethyl sulfoxide, diphenylsulfone, sulfoxide such as tetramethylsulfone, or sulfone solvents, N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), N, N′-diethylacetamide, N-methyl-2-pyrrolidone (NMP), ester solvents such as γ-butyrolactone, amide solvents such as hexamethylphosphoric triamide, chloroform, chloride Alkyl halide solvents such as methylene, aromatic hydrocarbon solvents such as benzene and toluene, phenol solvents such as phenol and cresol, ketone solvents such as cyclopentanone, tetrahydrofuran, 1,3-dioxolane, 1,4 -Dioxane, di Chirueteru, diethyl ether, p- cresol methyl ether can be mentioned ether solvents such as, typically may be used in appropriate combination of two or more as needed using these solvents alone. In order to increase the solubility and reactivity of the polyamic acid, amide solvents such as DMF, DMAc, and NMP are preferably used.

  Next, a method for imidizing the polyamic acid to obtain a polyimide using the polyamic acid will be described. Imidization is performed by dehydrating and ring-closing the polyamic acid. This dehydration ring closure can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method.

  Dehydration ring closure by a thermal method may be performed by heating the polyamic acid. Alternatively, after polyamic acid is cast or coated on a support such as a glass plate, a metal plate, or PET (polyethylene terephthalate), heat treatment may be performed within a range of 80 ° C to 500 ° C. Furthermore, the polyamic acid can be dehydrated and closed by placing the polyamic acid directly in a container that has been subjected to a release treatment such as coating with a fluororesin and then drying by heating under reduced pressure. Polyimide can be obtained by dehydration and ring closure of polyamic acid by such a thermal method. In addition, although the heating time of each said process changes with the process amount and heating temperature of the polyamic acid solution which performs dehydration ring closure, generally it is performed in the range of 1 minute-5 hours after the processing temperature reaches the maximum temperature. It is preferable. In the azeotropic method using an azeotropic solvent, a solvent that azeotropes with water such as toluene and xylene is added to polyamic acid, and the temperature is raised to 170 to 200 ° C. to actively generate water generated by dehydration ring closure. The reaction may be carried out for about 1 to 5 hours while being removed from the system. After completion of the reaction, it is precipitated in a poor solvent such as alcohol, washed with alcohol or the like as necessary, and then dried to obtain a polyimide.

  On the other hand, dehydration and ring closure by a chemical method is such that after the imidization is completed in the reaction solvent with the polyamic acid to which the dehydration catalyst and the imidizing agent are added, the poor solvent is introduced into the reaction solvent. And a method of obtaining polyimide as a solid material.

  A tertiary amine can be used as the imidizing agent. As the tertiary amine, a heterocyclic tertiary amine is more preferable. Preferable specific examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline and the like. Specific examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and the like.

  As the amount of the imidizing agent or dehydration catalyst added, the imidizing agent is 0.5 to 5.0 times molar equivalent, more preferably 0.7 to 2.5 times molar equivalent, especially the amide group of the polyamic acid. Is preferably 0.8 to 2.0 times molar equivalent. The dehydration catalyst is preferably 0.5 to 10.0 times molar equivalent, more preferably 0.7 to 5.0 times molar equivalent, and particularly preferably 0.8 to 3.0 times molar equivalent.

  When an imidizing agent or a dehydration catalyst is added to the polyamic acid, it may be added directly without being dissolved in a solvent, or a solution dissolved in a solvent may be added. In the direct addition method, the reaction may rapidly proceed before the imidizing agent or the dehydration catalyst diffuses to form a gel. Preferably, the imidizing agent and the dehydration catalyst are dissolved in a solvent, and the solution is mixed with the polyamic acid solution.

  As described above, after adding an imidizing agent or a dehydration catalyst to the polyamic acid and completing imidization in the reaction solvent, this solution may be used as a polyimide solution, or a poor solvent may be used in the reaction solvent. It is good also as a solid-state polyimide. In this case, a method of isolating a solid polyimide or a method of precipitating in a solid state can be used by adding a poor solvent to a polyimide solution containing a polyimide, an imidizing agent and a dehydration catalyst. The isolated polyimide is in a solid state including powder, flakes, and various forms, and the average particle size is preferably 5 mm or less, more preferably 3 mm or less, and particularly preferably 1 mm or less. .

  As the poor solvent for polyimide used in the present invention, a solvent that does not dissolve polyimide and that is miscible with the organic solvent used as the solvent dissolving polyimide can be used. Examples thereof include water, methyl alcohol, ethyl alcohol, 2-propyl alcohol, ethylene glycol, triethylene glycol, 2-butyl alcohol, 2-hexyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, phenol, and t-butyl alcohol. Among the above alcohols, alcohols such as 2-propyl alcohol, 2-butyl alcohol, 2-pentyl alcohol, phenol, cyclopentyl alcohol, cyclohexyl alcohol, and t-butyl alcohol have high stability and imidization rate of the polyimide after isolation. From the viewpoint of becoming, 2-propyl alcohol or water is particularly preferable.

  When a polyimide solution containing a polyimide, an imidizing agent and a dehydration catalyst is put into a poor solvent, the solid content concentration of the polyimide solution is not particularly limited as long as it has a viscosity capable of stirring, but the polyimide particle size is reduced. The concentration is preferably dilute from the point of view, and after the dilution is performed so that the solid content concentration of the polyimide solution is 15% or less, preferably 10% or less, a poor solvent is added to the polyimide solution. Is preferred. Moreover, it is preferable if the solid content concentration of the polyimide solution is 5% or more because the amount of the poor solvent does not increase too much. The amount of the poor solvent to be used is preferably an amount equal to or greater than that of the polyimide solution, and more preferably 2 to 3 times. Here, solid content is all components other than a solvent, and solid content concentration represents weight% concentration of solid content in the whole solution.

  Since the polyimide obtained here contains a small amount of an imidizing agent and a dehydration catalyst, it is preferably washed several times with the above poor solvent, particularly an alcohol solvent such as 2-propyl alcohol.

  The method for drying the polyimide thus obtained may be vacuum drying or hot air drying. In order to completely dry the solvent contained in the polyimide, vacuum drying is desirable, and the drying temperature is preferably in the range of 100 to 200 ° C, particularly preferably 120 to 180 ° C.

  The weight average molecular weight of the polyimide of the present invention is preferably in the range of 5,000 to 500,000, more preferably in the range of 10,000 to 300,000, although it depends on its use. More preferably, it is in the range of 000 to 200,000. When the weight average molecular weight is 5,000 or more, sufficient strength is easily obtained when a coating film or film is formed. On the other hand, when it is 500,000 or less, solubility can be ensured, so that a coating film or film having a smooth surface and a uniform film thickness is easily obtained. The molecular weight used here refers to a value in terms of polyethylene glycol as determined by gel permeation chromatography (GPC), and may be the molecular weight of the polyimide itself or the molecular weight of the polyamic acid that is the precursor.

  Next, the polyimide film of the present invention will be described. The polyimide film in the present invention is a polyimide molded body having a thickness of 5 to 50 μm and may contain a solvent. The polyimide film can be obtained from a precursor polyamic acid or a polyimide solution. In order to obtain a lower linear expansion coefficient, it is better to form a film after melting polyimide or dissolving it in an organic solvent, rather than forming a film obtained by thermal imidization after forming a film of polyamic acid. preferable.

  Below, the method to obtain a polyimide film from a polyimide solution is demonstrated. The polyimide solution of the present invention can be obtained by dissolving the polyimide obtained by the above-described method in an arbitrary organic solvent. The organic solvent to be used is not particularly limited, but amide solvents such as dimethylformamide (DMF), dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP), acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) It is preferable to select at least one of ketone solvents such as cyclopentanone and cyclohexanone, and ether solvents such as tetrahydrofuran (THF), 1,3-dioxolane and 1,4-dioxane. Further, it is particularly preferable that the solvent is dissolved in all of the amide solvent, ketone solvent and ether solvent from the viewpoint that a solvent suitable for the support to be coated can be selected each time. The concentration of the polyimide solution of the present invention is preferably 5 to 40% by weight, and more preferably 5 to 20% by weight.

  Although the viscosity of a polyimide solution is selected at any time according to the thickness to be applied and the coating environment, it is preferably 0.1 to 50 Pa · s, more preferably 0.5 to 30 Pa · s. When the viscosity of the polyimide solution is 0.1 Pa · s or more, the viscosity is sufficient for film formation, so that sufficient film thickness accuracy can be ensured. When the viscosity of the polyimide solution is 50 Pa · s or less, there is an appropriate fluidity, the film thickness accuracy can be ensured, a portion that dries immediately after coating does not occur, and appearance defects such as gel defects do not occur. The above viscosity is a kinematic viscosity at 23 ° C. measured using an E-type viscometer.

  The polyimide film of the present invention can be produced by applying a polyimide solution to a support and drying it.

  As the support on which the polyimide solution is applied, a glass substrate, a metal substrate such as SUS or a metal belt, a plastic film such as polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate, and triacetyl cellulose is used. It is not limited to. In order to adapt to the current batch type device manufacturing process, it is preferable to use a glass substrate.

  Regarding the drying temperature at the time of manufacturing the polyimide film, it is possible to select conditions according to the process, and there is no particular limitation as long as the characteristics are not affected.

  The transparency of the polyimide film is expressed by, for example, the total light transmittance or haze according to JIS K7105-1981. The total light transmittance is 85% or more, more preferably 87% or more. The haze is 2.0% or less, more preferably 1.0% or less. In the application of the present invention, it is required that the transmittance is high in the entire wavelength region. In particular, polyimide tends to absorb light on the short wavelength side, and the film itself is often colored yellow. In order to be used for the application of the present invention, the light transmittance at a wavelength of 400 nm is preferably 50% or more, and more preferably 60% or more. The light transmission at 400 nm is measured by an ultraviolet-visible spectrophotometer. Thus, by providing transparency, it can be used as a transparent substrate for glass replacement applications and the like. Since the polyimide film of the present invention is particularly excellent in heat resistance and linear thermal expansion coefficient, it can be suitably used as a transparent substrate for glass replacement applications and the like.

  The polyimide film of the present invention thus produced is characterized by low thermal expansion characteristics and dimensional stability before and after heating. For example, when measuring these values by thermomechanical analysis (TMA), 10 mm × The average linear thermal expansion coefficient in the range of 100 to 200 ° C. is 20 ppm / K or less, more preferably 15 ppm / when a weight of 3.0 g is applied to a 3 mm film sample and the rate of temperature increase is 10 ° C./min. A polyimide film having K or less can be obtained.

  The glass transition temperature is preferably as high as possible from the viewpoint of heat resistance. However, in the differential scanning calorimetry (DSC) or dynamic viscoelasticity analysis (DMA), the glass transition temperature is measured at a temperature rising rate of 10 ° C./min. The glass transition temperature is preferably 200 ° C. or higher, and more preferably 250 ° C. or higher in that the heat treatment temperature can be increased.

  The polyimide according to the present invention may be used as it is for a coating or molding process for producing a product or member as it is, but the polyimide molded into a film can be further subjected to a treatment such as coating to be used as a laminate. In order to provide a coating or molding process, the polyimide is dissolved or dispersed in a solvent as necessary, and further, a light or thermosetting component, a non-polymerizable binder resin other than the polyimide according to the present invention, and other components are blended. Thus, a polyimide composition may be prepared.

  In order to impart processing characteristics and various functionalities to the polyimide composition according to the present invention, various other organic or inorganic low-molecular or high-molecular compounds may be blended. For example, dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  In the polyimide composition according to the present invention, the polyimide represented by the formula (1) is usually contained within a range of 60 to 99.9% by weight with respect to the entire solid content of the composition. 99.9% by weight means substantially all of them. Further, the blending ratio of other optional components is preferably in the range of 0.1 wt% to 95 wt% with respect to the entire solid content of the polyimide composition. When it is 0.1% by weight or more, the effect of adding the additive is easily exhibited, and when it is 95% by weight or less, the characteristics of the composition are easily reflected in the final product. In addition, solid content of a polyimide composition is all components other than a solvent, and a liquid monomer component is also contained in solid content.

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

  Since the polyimide film according to the present invention has high dimensional stability and high solubility in an organic solvent in addition to the original characteristics of polyimide such as heat resistance and insulation, fields in which these characteristics are effective It may be used for products such as printed materials, color filters, flexible displays, optical films, liquid crystal display devices, organic EL and electronic paper and other image display devices, 3-D displays, touch panels, transparent conductive film substrates or solar cells. More preferably, it is more preferable to use an alternative material for the portion where glass is currently used. That is, the polyimide containing the structure represented by the general formula (1) according to the present invention, preferably R1 to R3 are methyl groups, R4 is hydrogen, and the trifluoromethyl group is in the 2,2 ′ position. A general formula (2)

The polyimide film containing polyimide represented by is particularly suitable as an image display device such as a TFT substrate, a flexible display substrate, a color filter, organic EL, and electronic paper, an optical material, and an electronic device material.

(Evaluation method)
The material characteristic values and the like described in the present specification are obtained by the following evaluation methods.
(1) Molecular weight of polyimide The weight average molecular weight (Mw) was determined under the conditions shown in Table 1. The evaluation results are shown in Table 2.

(2) Solubility test of polyimide in organic solvent For 0.5 g of polyimide, 9.5 g of organic solvent shown in Table 2 (solid content concentration 5%) was put in a sample tube and stirred with a magnetic stirrer. A sample completely dissolved at room temperature was marked with ◎, a sample melted by heating was marked with ◯, a sample with some undissolved residue was marked with Δ, and a sample insoluble was marked with ×. The evaluation results are shown in Table 2.

(3) Linear thermal expansion coefficient of polyimide film The average linear expansion coefficient at 100 to 200 ° C. was measured using a Bruker-AXS TMA4000 (sample size 5 mm wide, 15 mm long), and the load was film thickness (μm) × 0.5 g, once raised to 150 ° C. at 5 ° C./min (first rise), then cooled to 20 ° C., and further raised at 5 ° C./min (second rise) It calculated from the TMA curve at the time of the second temperature increase.
(4) Glass transition temperature of polyimide film Using TMA4000 manufactured by Bruker-AXS, the measurement length (measurement jig interval) is set to 15 mm, a load (amplitude 15 g) is applied sinusoidally, dynamic viscoelasticity measurement is performed, and the loss energy is maximum. This temperature was defined as the glass transition temperature.
(5) Total light transmittance of polyimide film: Measured by Nippon Denshoku Industries Co., Ltd. integrating sphere haze meter 300A according to the method described in JIS K7105-1981.
(6) Haze of polyimide film Measured by a method described in JIS K7105-1981 using an integrating sphere haze meter 300A manufactured by Nippon Denshoku Industries Co., Ltd.
(7) Transmittance of polyimide film Using a UV-Vis near-infrared spectrophotometer (V-650) manufactured by JASCO Corporation, the transmittance of the polyimide film at 200-800 nm is measured, and the transmittance at a wavelength of 400 nm. Was used as an index. Further, the wavelength (cutoff wavelength) at which the transmittance was 0.5% or less was also determined.
(8) FT-IR spectrum measurement of ester group-containing tetracarboxylic dianhydride Using an FT-IR5300 manufactured by JASCO Corporation, the number of integration was measured 16 times in the range of 4000 cm ^{-1 to} 400 cm ^-1 .
(9) ¹ H-NMR spectrum measurement of ester group-containing tetracarboxylic dianhydride Using JNM-ECP400 manufactured by JOEL, about 5 mg of sample is put in a measuring tube, and deuterated solvent containing TMS (DMSO-d ₆ ) is added. Measurement was carried out at 400 MHz on a measurement sample that was adjusted to a height of 4 cm in the measurement tube.
(10) Melting | fusing point of ester group containing tetracarboxylic dianhydride It measured by the method as described in JISK-7121 by DSC3100 by Bruker-AXS.

(Synthesis Example 1)
<Synthesis of ester group-containing tetracarboxylic dianhydride (following formula (3))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod equipped with a four-blade stirring blade on a polytetrafluoroethylene sealing stopper and a nitrogen inlet tube, and trimellitic anhydride chloride 4 .6 g (22.0 mmol) was added, and 4.0 ml of tetrahydrofuran (hereinafter referred to as THF) was added and dissolved so that the solution concentration was 56.6 wt% to prepare Solution A. In another container, 1.5 g (10.0 mmol) of trimethylhydroquinone was added and dissolved in 4.0 ml of THF so that the solution concentration was 30.0 wt%, and 3.2 ml (40.0 mmol) of pyridine was used as a deoxidizer. Was added to prepare Solution B.

In an ice bath, solution B was slowly added dropwise with stirring to solution A, and the mixture was stirred for 3 hours, and then stirred at room temperature for 18 hours. The precipitate was filtered off, and the resulting precipitate was washed with 10 ml of THF, and then further washed with ion-exchanged water until chloride ions were removed. Removal of chloride ions was confirmed by dropping several drops of a 1 wt% aqueous silver nitrate solution into the washing filtrate. The washed precipitate was vacuum dried at 150 ° C. for 12 hours to obtain a white product in a yield of 2.7 g and a yield of 53.1%. In FT-IR, peaks of 1857 cm ⁻¹ , 1781 cm ⁻¹ (acid anhydride group C═O stretching vibration), 1734 cm ⁻¹ (ester group C═O stretching vibration), and ¹ H-NMR, δ2. 12 ppm (m, CH ₃ , 9H), δ 8.70 ppm (m, on phthalimide, 5 and 6 position C _arom H, 4H), δ 8.31 ppm (dd, on phthalimide, 3 position C _arom H, 2H), δ7. Since a peak of 22 ppm (s, on central phenyl, C _arom H, 1H) could be confirmed, an ester group-containing tetracarboxylic dianhydride represented by the above formula (3) was obtained. It was confirmed. It was 245 degreeC when melting | fusing point of this compound was measured by DSC.

(Synthesis Example 2)
<Polyimide polymerization (following formula (2))>

A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 11.9 g of 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) and polymerized. 170.0 g of dehydrated N, N-dimethylformamide (hereinafter referred to as DMF) was added as a solvent for stirring and stirred, and then the ester group-containing tetracarboxylic dianhydride having the structure of the formula (3) synthesized in Synthesis Example 1 was added to this solution. 18.1 g of product was added and stirred at room temperature for 7 hours to obtain a polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 15 weight% with respect to all the reaction liquids.

  DMF was added to the above solution to adjust the solid concentration to 10% by weight, and 5.8 g of pyridine was added as an imidization catalyst to completely disperse. 9.1 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water to obtain a powdered polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 100 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 3)
<Synthesis of ester group-containing tetracarboxylic dianhydride (following formula (4))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod equipped with a four-blade stirring blade on a polytetrafluoroethylene sealing stopper and a nitrogen introducing tube, and trimellitic anhydride chloride 8 .8 g (42.0 mmol) was added, and 20.0 ml of THF was added and dissolved so that the solution concentration was 33.2 wt% to prepare Solution A. Further, in another container, 4.3 g (19.6 mmol) of 2,5-ditert-butylhydroquinone was added and dissolved in 15.4 ml of THF so that the solution concentration was 24.1 wt%, and pyridine 4 was used as a deoxidizer. Solution B was prepared by adding 2 ml (52.0 mmol).

In an ice bath, solution B was slowly added dropwise with stirring to solution A, and the mixture was stirred for 3 hours, and then stirred at room temperature for 16 hours. The precipitate was filtered off, and the resulting precipitate was washed with 10 ml of THF, and then further washed with ion-exchanged water until chloride ions were removed. Removal of chloride ions was confirmed by dropping several drops of a 1 wt% aqueous silver nitrate solution into the washing filtrate. The washed precipitate was vacuum-dried at 160 ° C. for 12 hours to obtain a white product in a yield of 4.8 g and a yield of 43.0%. The crude crystals were recrystallized from a toluene / γ-gutyrolactone = 20/1 (weight ratio) solution and dried under vacuum at 180 ° C. for 12 hours to obtain a purified product. In FT-IR, peaks of 1828 cm ⁻¹ , 1780 cm ⁻¹ (acid anhydride group C═O stretching vibration), 1747 cm ⁻¹ (ester group C═O stretching vibration), and ¹ H-NMR, δ1. 26 ppm (s, tert-Bu, 18H), δ 7.41 ppm (s, on central phenyl, C _arom H, 2H) δ 8.33 ppm (m, on phthalimide, 5-position C _arom H, 2H), δ 8.61 ppm (dd On the phthalimide, the peak at the 3-position C _arom H, 2H) δ 8.70 ppm (m, on the phthalimide, the 6-position C _arom H, 2H) was confirmed. It was confirmed that an ester group-containing tetracarboxylic dianhydride shown in FIG.

(Synthesis Example 4)
<Polymerization polymerization (following formula (10))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 9.7 g of TFMB, and 170.0 g of dehydrated DMF as a polymerization solvent was charged and stirred. Then, 20.3 g of an ester group-containing tetracarboxylic dianhydride having the structure of the formula (4) synthesized in Synthesis Example 3 was added and stirred at room temperature for 7 hours to obtain a polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 15 weight% with respect to all the reaction liquids.

  DMF was added to the above solution to adjust the solid content concentration to 10% by weight, and 4.8 g of pyridine was added as an imidization catalyst to completely disperse. 7.5 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water to obtain a powdered polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 100 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 5)
<Polymerization polymerization (following formula (11))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 10.0 g of TFMB and 70.0 g of dehydrated DMAc as a polymerization solvent was stirred. Then, 15.0 g of an ester group-containing tetracarboxylic dianhydride having the structure of the formula (4) synthesized in Synthesis Example 3 was added, and 3.0 g of naphthalene tetracarboxylic dianhydride having a structure of the formula (5) was further added. After stirring at room temperature for 72 hours, 87.5 g of DMAc was added and diluted to obtain polyamic acid.

  In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 16 weight% with respect to all the reaction liquids. The charging ratio of each monomer is as follows: when TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having a structure of (4): 70 mol%, naphthalene tetracarboxylic dianhydride having a structure of formula (5): 30 mol %.

  To the above solution, 6.0 g of pyridine was added as an imidization catalyst and completely dispersed. 9.2 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water to obtain a powdered polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 100 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 6)
<Polymerization polymerization (following formula (12))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 11.2 g of TFMB and 70.0 g of dehydrated DMAc as a polymerization solvent was stirred. Then, 14.0 g of an ester group-containing tetracarboxylic dianhydride having the structure of formula (4) synthesized in Synthesis Example 3 was added, and 4.8 g of an ester group-containing tetracarboxylic dianhydride having a structure of formula (6) was further added. In addition, after stirring at room temperature for 72 hours, 84.0 g of DMAc was added and diluted to obtain polyamic acid.

  The charged concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 16.3% by weight with respect to the total reaction solution. The charging ratio of each monomer is as follows: when TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having the structure of (4): 70 mol%, ester group-containing tetracarboxylic dianhydride having the structure of formula (6) : It was 30 mol%.

  To the above solution, 5.5 g of pyridine was added as an imidization catalyst and completely dispersed. 8.6 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water to obtain a powdered polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 100 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 7)
<Synthesis of ester group-containing tetracarboxylic dianhydride (following formula (7))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod equipped with a four-blade stirring blade on a polytetrafluoroethylene sealing stopper and a nitrogen introducing tube, and trimellitic anhydride chloride 7 .4 g (35.1 mmol) was added, and 10.0 ml of THF was added and dissolved so that the solution concentration was 45.0 wt% to prepare Solution A. Further, in another container, 2.6 g (15.6 mmol) of tert-butylhydroquinone was dissolved by adding 3.5 ml of THF so that the solution concentration was 46.0 wt%, and 3.4 ml (42.42) of pyridine as a deoxidizer. 0 mmol) was added to prepare solution B.

In an ice bath, solution B was slowly added dropwise over about 10 minutes to solution A with stirring, and then stirred at room temperature for 19 hours. The precipitate was filtered off, and the resulting precipitate was washed with 10 ml of THF, and then further washed with ion-exchanged water until chloride ions were removed. Removal of chloride ions was confirmed by dropping several drops of a 1 wt% aqueous silver nitrate solution into the washing filtrate. The washed precipitate was vacuum-dried at 100 ° C. for 2 hours and further at 160 ° C. for 12 hours to obtain a white product at a yield of 5.3 g and a yield of 66.0%. 20 ml of acetic anhydride is added to the crude crystals and recrystallized by heating and cooling. The precipitated crystals are filtered off, washed with acetic anhydride and toluene, then at 80 ° C. for 2 hours, and further at 160 ° C. Vacuum-dried for 12 hours to obtain a purified product. The recrystallization yield was 47.9%, and the total yield was 31.6%. Since the peaks of 1861 cm ⁻¹ , 1778 cm ⁻¹ (acid anhydride group C═O stretching vibration) and 1740 cm ⁻¹ (ester group C═O stretching vibration) could be confirmed by FT-IR, It was confirmed that an ester group-containing tetracarboxylic dianhydride represented by the above formula (7) was obtained. It was 224 degreeC when melting | fusing point of this compound was measured by DSC.

(Synthesis Example 8)
<Polymerization polymerization (following formula (13))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 11.5 g of TFMB and dehydrated DMAc 214.0 g as a polymerization solvent. 18.5 g of an ester group-containing tetracarboxylic dianhydride having the structure of formula (7) synthesized in Synthesis Example 7 was added, and the mixture was stirred at room temperature for 7 hours to obtain a polyamic acid. The charged concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 12.3% by weight with respect to the total reaction solution.

  DMAc was added to the above solution to adjust the solid content concentration to 7.6% by weight, and 5.7 g of pyridine was added as an imidization catalyst to completely disperse. 8.8 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 9)
<Synthesis of ester group-containing tetracarboxylic dianhydride (following formula (8))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod equipped with a four-blade stirring blade on a polytetrafluoroethylene sealing stopper and a nitrogen introducing tube, and trimellitic anhydride chloride 6 .3 g (30.0 mmol) was added, and 8.6 ml of THF was added and dissolved so that the solution concentration was 45.3 wt% to prepare Solution A. In another container, 2.5 g (10.0 mmol) of diamylhydroquinone was dissolved by adding 6.6 ml of THF so that the solution concentration would be 30.0 wt%, and 4.9 ml (60.0 mmol) of pyridine as a deoxidizer. ) Was added to prepare a solution B.

In an ice bath, Solution B was slowly added dropwise over about 10 minutes with stirring to Solution A, and then stirred at room temperature for 18 hours. The precipitate was separated by filtration, and the resulting precipitate was washed with THF and dilute hydrochloric acid solution, and further washed with ion-exchanged water until chloride ions were removed. Removal of chloride ions was confirmed by dropping several drops of a 1 wt% aqueous silver nitrate solution into the washing filtrate. The washed precipitate was vacuum-dried at 80 ° C. for 2 hours and further at 160 ° C. for 12 hours to obtain a white product with a yield of 3.9 g and a yield of 65.6%. To this crude crystal, 10 ml of 1,4-dioxane was added per 1 g, and recrystallized by heating and cooling, and this operation was repeated three times. The precipitated crystals were separated by filtration and then vacuum dried at 80 ° C. for 2 hours and further at 160 ° C. for 12 hours to obtain a purified product. The recrystallization yield was 56.4%, and the total yield was 40.0%. Since the peaks of 1865 cm ⁻¹ , 1783 cm ⁻¹ (acid anhydride group C═O stretching vibration) and 1743 cm ⁻¹ (ester group C═O stretching vibration) could be confirmed by FT-IR, the purpose It was confirmed that an ester group-containing tetracarboxylic dianhydride represented by the above formula (8) was obtained. The melting point of this compound was measured by DSC and found to be 269.2 ° C.

(Synthesis Example 10)
<Polymerization polymerization (following formula (14))>

  A 500 mL glass separable flask equipped with a stirrer with a stainless steel stir bar and a nitrogen inlet tube was charged with 10.3 g of TFMB, and 70.0 g of dehydrated DMAc as a polymerization solvent was added and stirred. Then, 19.3 g of an ester group-containing tetracarboxylic dianhydride having the structure of the formula (8) synthesized in Synthesis Example 9 was added and stirred at room temperature for 142 hours, and then 153.4 g of DMAc was added for dilution. Got. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 11.7 weight% with respect to all the reaction liquids.

  DMAc was added to the above solution to adjust the solid concentration to 4.9% by weight, and 5.2 g of pyridine was added as an imidization catalyst to completely disperse. To the dispersed solution, 8.2 g of acetic anhydride was added and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 11)
<Polymerization polymerization (following formula (15))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen inlet tube was charged with 10.0 g of TFMB, and 120.0 g of dehydrated DMAc as a polymerization solvent was stirred and stirred. 15.6 g of an ester group-containing tetracarboxylic dianhydride having the structure of formula (8) synthesized in Synthesis Example 9 was added, and 3.0 g of naphthalenetetracarboxylic dianhydride having a structure of formula (5) was further added. After stirring at room temperature for 48 hours and diluting to an appropriate viscosity, 54.2 g of DMAc was added and diluted to obtain a polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 14.9 weight% with respect to all the reaction liquids. The charging ratio of each monomer is as follows. When TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having a structure of (8): 70 mol%, naphthalene tetracarboxylic dianhydride having a structure of formula (5): 30 mol %.

  DMAc was added to the above solution to a solid content concentration of 5.5% by weight, and 5.9 g of pyridine was added as an imidization catalyst to completely disperse. 9.1 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 12)
<Polymerization polymerization (following formula (16))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 12.6 g of TFMB, and 76.8 g of dehydrated DMAc as a polymerization solvent was charged and stirred. Then, 9.8 g of an ester group-containing tetracarboxylic dianhydride having the structure of the formula (7) synthesized in Synthesis Example 7 was added, and 10.9 g of an ester group-containing tetracarboxylic dianhydride having a structure of the formula (4) was further added. In addition, after stirring for 72 hours at room temperature, 53.2 g of DMAc was added and diluted to obtain polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 20.2 weight% with respect to all the reaction liquids. The charging ratio of each monomer is as follows: when TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having a structure of (7): 50 mol%, ester group-containing tetracarboxylic dianhydride having a structure of formula (4) : 50 mol%.

  DMAc was added to the above solution to adjust the solid concentration to 6.3% by weight, and 6.0 g of pyridine was added as an imidization catalyst to completely disperse. To the dispersed solution, 9.3 g of acetic anhydride was added and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 13)
<Polymerization polymerization (following formula (17))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 13.1 g of TFMB and 80.7 g of dehydrated DMAc as a polymerization solvent was stirred. 16.8 g of the ester group-containing tetracarboxylic dianhydride having the structure of the formula (7) synthesized in Synthesis Example 7 was added, and 4.7 g of the ester group-containing tetracarboxylic dianhydride having the structure of the formula (4) was further added. In addition, after stirring for 48 hours at room temperature, 56.8 g of DMAc was added and diluted to obtain polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 20.1 weight% with respect to all the reaction liquids. The charging ratio of each monomer is as follows: when TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having the structure of (7): 80 mol%, ester group-containing tetracarboxylic dianhydride having the structure of formula (4) : 20 mol%.

  DMAc was added to the above solution to a solid content concentration of 6.2% by weight, and 6.4 g of pyridine was added as an imidization catalyst to completely disperse. 9.9 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 14)
<Polymerization polymerization (following formula (18))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 18.6 g of TFMB and 78.6 g of dehydrated DMAc as a polymerization solvent was stirred. Then, 13.2 g of an ester group-containing tetracarboxylic dianhydride having the structure of the formula (7) synthesized in Synthesis Example 7 was added, and further an ester group-containing tetracarboxylic acid of the structure of the formula (4) synthesized in Synthesis Example 3 was added. After adding 7.9 g of anhydride and stirring at room temperature for 96 hours, 258.0 g of DMAc was added and diluted to obtain polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 9.1 weight% with respect to all the reaction liquids. The charging ratio of each monomer is such that when TFMB is 100 mol%, ester group-containing tetracarboxylic dianhydride having the structure of (7): 65 mol%, ester group-containing tetracarboxylic dianhydride having the structure of formula (4) : 35 mol%.

  DMAc was added to the above solution to adjust the solid content concentration to 6.8% by weight, and 6.2 g of pyridine was added as an imidization catalyst to completely disperse. 9.6 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Synthesis Example 15)
<Polymerization polymerization (following formula (19))>

  A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 12.4 g of TFMB, and 70.9 g of dehydrated DMAc as a polymerization solvent was stirred. Then, 15.5 g of an ester group-containing tetracarboxylic dianhydride having the structure of formula (4) synthesized in Synthesis Example 3 was added, 2.5 g of pyromellitic dianhydride was added, and the mixture was stirred at room temperature for 92 hours. 120.6 g of DMAc was added and diluted to obtain polyamic acid. In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 13.7 weight% with respect to all the reaction liquids. The charging ratio of each monomer was 70 mol% of ester group-containing tetracarboxylic dianhydride having the structure of (4): 30 mol% and pyromellitic dianhydride: 30 mol% when TFMB was 100 mol%.

  DMAc was added to the above solution to a solid content concentration of 6.2% by weight, and 6.1 g of pyridine was added as an imidization catalyst to completely disperse. 9.5 g of acetic anhydride was added to the dispersed solution and stirred at room temperature for 24 hours. A polyimide solution was dropped and precipitated in 2 L of distilled water / ethanol = 1/1 (volume ratio) mixed solvent to obtain a powdery polyimide. The obtained powdery polyimide was washed three times with distilled water, and then vacuum-dried at 150 ° C. for 12 hours with a vacuum dryer, and taken out as polyimide. Table 2 shows the evaluation results of the obtained polyimide.

(Example 1)
<Preparation of polyimide solution and polyimide film>
Using a DMAc as a solvent, a polyimide solution containing the polyimide synthesized in Synthesis Example 2 at a concentration of 7.3% by weight was prepared. This polyimide solution was applied onto a glass plate with a bar coater and dried at 60 ° C. for 2 hours and at 250 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 2)
<Preparation of polyimide solution and polyimide film>
Using cyclopentanone as a solvent, a polyimide solution containing the polyimide synthesized in Synthesis Example 2 at a concentration of 7% by weight was prepared. This polyimide solution was applied onto a glass plate with a bar coater and dried at 60 ° C. for 2 hours and at 250 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 3)
<Preparation of polyimide solution and polyimide film>
A polyimide solution containing the polyimide synthesized in Synthesis Example 4 at a concentration of 15.0% by weight was prepared using DMAc as a solvent. This polyimide solution was applied onto a glass plate with a bar coater and dried at 60 ° C. for 2 hours and at 250 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

Example 4
<Preparation of polyimide solution and polyimide film>
A cyclopentanone was used as a solvent to prepare a polyimide solution containing the polyimide synthesized in Synthesis Example 5 at a concentration of 8.2% by weight. This polyimide solution was applied onto a glass plate with a bar coater and dried at 60 ° C. for 2 hours and 280 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 5)
<Preparation of polyimide solution and polyimide film>
A cyclopentanone was used as a solvent to prepare a polyimide solution containing the polyimide synthesized in Synthesis Example 6 at a concentration of 8.3% by weight. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours and 220 ° C. for 1 hour, peeled from the glass, and further heat treated at 220 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 6)
<Preparation of polyimide solution and polyimide film>
Using a DMAc as a solvent, a polyimide solution containing the polyimide synthesized in Synthesis Example 8 at a concentration of 10.7% by weight was prepared. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 3 hours, peeled from the glass, and further heat treated at 220 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 7)
<Preparation of polyimide solution and polyimide film>
A polyimide solution containing the polyimide synthesized in Synthesis Example 10 at a concentration of 10.6% by weight was prepared using DMAc as a solvent. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours, peeled from the glass, and further heat treated at 260 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 8)
<Preparation of polyimide solution and polyimide film>
A cyclopentanone was used as a solvent to prepare a polyimide solution containing the polyimide synthesized in Synthesis Example 11 at a concentration of 9.1% by weight. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours, peeled from the glass, and further heat treated at 260 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

Example 9
<Preparation of polyimide solution and polyimide film>
A cyclopentanone was used as a solvent to prepare a polyimide solution containing the polyimide synthesized in Synthesis Example 12 at a concentration of 13.8% by weight. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours, peeled from the glass, and further heat treated at 230 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 10)
<Preparation of polyimide solution and polyimide film>
Using a DMAc as a solvent, a polyimide solution containing the polyimide synthesized in Synthesis Example 13 at a concentration of 15.5% by weight was prepared. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours, peeled from the glass, and further heat treated at 220 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Example 11)
<Preparation of polyimide solution and polyimide film>
Using cyclopentanone as a solvent, a polyimide solution containing the polyimide synthesized in Synthesis Example 14 at a concentration of 7.5% by weight was prepared. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 2 hours, peeled from the glass, and further heat treated at 230 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

Example 12
<Preparation of polyimide solution and polyimide film>
A cyclopentanone was used as a solvent to prepare a polyimide solution containing the polyimide synthesized in Synthesis Example 15 at a concentration of 7.0% by weight. This polyimide solution was applied onto a glass plate with a bar coater, dried at 60 ° C. for 3 hours and 250 ° C. for 1 hour, peeled from the glass, and further heat treated at 250 ° C. for 1 hour to obtain a polyimide film. Table 3 shows the evaluation results of the polyimide film.

(Synthesis Example 16)
TFMB 9.7 g was placed in a 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring rod equipped with a four-blade stirring blade on a polytetrafluoroethylene sealing stopper and a nitrogen introduction tube, and polymerized. After adding 170 g of dehydrated DMF as a solvent for use and stirring, 20.2 g of an amide group-containing tetracarboxylic dianhydride represented by the following formula (9) was added to the solution, followed by stirring at room temperature to obtain polyamide-amic acid. .

  In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 15 weight% with respect to all the reaction liquids. After stirring for 24 hours, 4.8 g of pyridine was added as an imidization catalyst and completely dispersed. 7.4 g of acetic anhydride was added to the dispersed solution and stirred, and the mixture was stirred at 100 ° C. for 4 hours, and then cooled to room temperature. After 88 g of DMF is added to the cooled reaction solution and stirred, the solution is transferred to a 2 L separable flask, and 600 g of isopropanol is dropped into the solution at a rate of 2 to 3 drops / second to produce the desired product. The product was precipitated. Thereafter, the solution was suction filtered with a Kiriyama funnel and washed with 300 g of isopropanol. This washing was repeated twice and suction-filtered with a Kiriyama funnel and dried overnight in a vacuum oven set at 100 ° C. to obtain a polyimide.

(Comparative Example 1)
<Preparation of polyimide solution and polyimide film>
The polyimide obtained in Synthesis Example 16 was dissolved in DMAc to prepare a polyimide solution containing 7% by weight of polyimide. After coating on a glass plate, drying was performed at 60 ° C. for 10 minutes, and further at 150 ° C. It was dried for 60 minutes at 300 ° C. for 60 minutes. Thereafter, the film was peeled off from the glass plate to obtain a film. The evaluation results of the obtained film are shown in Table 3.

(Comparative Example 2)
A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stir bar and a nitrogen introduction tube was charged with 12.3 g of TFMB, and 170 g of dehydrated DMF as a polymerization solvent was charged and stirred. 17.7 g of an ester group-containing tetracarboxylic dianhydride having the structure of (6) was added and stirred at room temperature for 7 hours to obtain a polyamic acid.

  In addition, the preparation density | concentration of the diamine compound and tetracarboxylic dianhydride in this reaction solution was 15 weight% with respect to all the reaction liquids.

  DMF was added to the above solution to adjust the solid content concentration to 10% by weight, and 6.1 g of pyridine was added as an imidization catalyst to be completely dispersed. Although 9.4 g of acetic anhydride was added to the dispersed solution, gelation occurred after 1 hour, so the subsequent operation was not performed.

  The polyimides of Examples 1 to 12 were excellent in transparency because of high light transmittance at a wavelength of 400 nm as compared with the polyimide of Comparative Example 1, and had a low linear thermal expansion coefficient equivalent to that of inorganic materials. . Moreover, the polyimide of Examples 1-12 was excellent in the solubility to a solvent compared with the polyimide of the comparative example 2, and was able to be supplied as a polyimide solution.

  In the above formula (1), R1 to R3 are alkyl groups having 1 carbon atom, and the polyimide of Example 1 containing only a structure in which R4 is a hydrogen atom has a transmittance of 60% or more at a wavelength of 400 nm and linear heat. The expansion coefficient was 15 ppm / K or less, and it had high transparency and low thermal expansion characteristics.

  In the above formula (1), R1 and R3 are alkyl groups having 3 or more carbon atoms, and the polyimides of Examples 3 and 7 containing only a structure in which R2 and R4 are hydrogen atoms have light transmittance at a wavelength of 400 nm. It was 70% or more and was very excellent in transparency.

  In addition, the polyimides shown in Examples 4, 8 and 12 obtained by copolymerizing naphthalene-structure tetracarboxylic dianhydride or pyromellitic dianhydride with polyimide having the structure of the above formula (1) have a linear thermal expansion coefficient of 16 ppm / It was below K and had low thermal expansion characteristics.

Claims (16)

A polyimide solution containing a polyimide containing a structure represented by the following general formula (1) and an organic solvent.

(In the formula, R1 to R4 may be the same or different and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, an aryl group, a trifluoromethyl group, and a methoxy group, provided that all of R1 to R4 are hydrogen. Except when 2. The polyimide solution according to claim 1, wherein R1 to R3 are alkyl groups having 1 to 5 carbon atoms, and R4 is hydrogen. The polyimide solution according to claim 1, wherein R 1 and R 3 are alkyl groups, and R 2 and R 4 are hydrogen. The polyimide solution according to any one of claims 1 to 3, comprising 50 mol% or more of the structure of the general formula (1). 5. The polyimide solution according to claim 1, wherein the organic solvent is selected from at least one of an amide solvent, a ketone solvent, an ester solvent, and an ether solvent. A polyimide film obtained from the polyimide solution according to claim 1. The polyimide film according to claim 6, wherein the polyimide film is obtained by coating the polyimide solution on a support. The polyimide film according to claim 7, wherein the support is a glass substrate. The polyimide film according to any one of claims 6 to 8, wherein a light transmittance at a wavelength of 400 nm is 50% or more. A linear thermal expansion coefficient is 20 ppm / K or less, The polyimide film as described in any one of Claims 6-9 characterized by the above-mentioned. The TFT substrate containing the polyimide film as described in any one of Claims 6-10. The flexible display board | substrate containing the polyimide film as described in any one of Claims 6-10. The color filter containing the polyimide film as described in any one of Claims 6-10. Image display apparatuses, such as organic EL and electronic paper containing the polyimide film as described in any one of Claims 6-10. The optical material containing the polyimide film as described in any one of Claims 6-10. The electronic device material containing the polyimide film as described in any one of Claims 6-10.