JP2018193343A - Diamines and polyimides and their use - Google Patents

Abstract

To provide a polyimide having excellent solution processability.SOLUTION: The present invention provides a diamine and a polyimide having structures represented by formula (1) and formula (3) (R's independently represent a C1-4 alkyl group or alkoxy group; n is an integer of 1-4; Xis at least one of a tetravalent aromatic group and aliphatic group).SELECTED DRAWING: None

Description

  The present invention relates to diamines and polyimides, and their use.

  Currently, glass substrates are used in various display devices such as liquid crystal displays and organic EL displays. A glass substrate is an excellent material in that it has high heat resistance, a low coefficient of linear thermal expansion, and high transparency. On the other hand, these displays are required to be lightweight and flexible, and there is a strong demand for materials that can replace glass. Various polyimide materials have been studied as materials satisfying these requirements.

  Now, polyimide has high heat resistance because of its chemical structure. However, many of polyimides are insoluble in a solvent, and it is difficult to form a uniform film using a polyimide solution coating process. Therefore, a method of uniformly forming a polyamic acid, which is a polyimide precursor soluble in a solvent, into a film and converting it into a polyimide film is widely adopted.

  However, according to such a method, the process of converting from polyamic acid to polyimide requires heating at 300 ° C. or higher, and involves a large reaction shrinkage. Therefore, in this method, there is a problem that not only warpage occurs due to mismatch of the linear thermal expansion coefficient between the inorganic material substrate and the polyimide film, but also a film defect occurs due to by-product water.

  For example, Patent Documents 1 and 2 disclose a polyimide that is soluble and transparent with respect to the above problem.

International Publication No. 2013/121917 Japanese Patent Laying-Open No. 2015-214597

  However, a polyimide having a structure different from the polyimides described in Patent Documents 1 and 2 and having excellent solution processability has been demanded.

  An object of one embodiment of the present invention is to provide a polyimide excellent in solution processability.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, by using a diamine having a specific structure, it has been found that a polyimide having excellent solution processability can be prepared, and the present invention has been completed. It was.

  That is, the diamine according to one embodiment of the present invention has the following formula (1):

(In the formula (1), the substituent R independently represents an alkyl group or alkoxy group having 1 to 4 carbon atoms, n represents the number of the substituent R, and is an integer of 1 to 4). ).

  Moreover, the polyimide which concerns on 1 aspect of this invention is following formula (3):

(In the formula (3), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of the substituent R, and 1 to 4). X ₁ represents at least one of a tetravalent aliphatic group and an aromatic group).

  According to one embodiment of the present invention, it is possible to provide a polyimide that is excellent in solution processability.

6 is a diagram showing an infrared absorption spectrum of a polyimide thin film measured in Example 3. FIG.

  Embodiments of the present invention will be described in detail below, but these are one aspect of the present invention, and the present invention is not limited to these contents.

  In this specification, “solution processability” means excellent processability because of its excellent solubility in organic solvents. For example, when a polyimide film is formed, a solution obtained by dissolving a polyimide in an arbitrary organic solvent is applied to a support and dried, so that excellent solution processability is very important. It is a characteristic.

<1. Diamine>
The diamine according to one embodiment of the present invention is represented by the following formula (1):

(In the formula (1), the substituent R independently represents an alkyl group or alkoxy group having 1 to 4 carbon atoms, n represents the number of the substituent R, and is an integer of 1 to 4). ).

  The diamine has an amide bond in the molecule. Therefore, in the polyimide obtained using the diamine, the main chain structure is likely to be linear, and intermolecular hydrogen bonds are likely to be formed. Therefore, it is considered that a film having a low linear thermal expansion coefficient can be obtained from the polyimide.

  The diamine has a trifluoromethyl group. Since the trifluoromethyl group is sterically bulky, the introduction of the trifluoromethyl group prevents aggregation and crystallization of the polymer chain. Thus, it is considered that solvent molecules can easily enter between polyimide molecular chains, and as a result, a solvent-soluble polyimide can be obtained.

  Furthermore, the polyimide obtained using the diamine has significantly improved solubility in organic solvents as compared to the polyimide obtained using the diamine not containing the substituent R, as shown in Examples below. Is done. This is presumed to be because the dense aggregation of the polymer chains is hindered.

  Each substituent R may be the same or different. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group. Examples of the alkoxy group having 1 to 4 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, and tert-butoxy group. Among these, when the substituent R is a methyl group, it is preferable because both solution processability and heat resistance can be achieved.

  The diamine is represented by the following formula (2):

It may be represented by The polyimide obtained by using the diamine can provide a film with improved transparency due to the bonding position of the trifluoromethyl group. Moreover, when the substituent R is a methyl group, it is preferable from the viewpoint of achieving both solution processability and heat resistance.

  The method for synthesizing the diamine is not limited to this, and examples thereof include a method of obtaining a dinitro compound as a precursor and reducing the dinitro compound with hydrogen in the presence of a catalyst. For example, the diamine represented by the above formula (1) can be obtained by the method represented by the formula (7).

  The dinitro compound as a precursor can be obtained, for example, by reacting 2,2'-bis (trifluoromethyl) benzidine with a chlorinated 4-nitrobenzoic acid derivative having a substituent R. For example, when obtaining the diamine of formula (2), 3-methyl-4-nitrobenzoic acid can be used as the 4-nitrobenzoic acid derivative. For example, the chlorinated product is prepared by adding 3-methyl-4-nitrobenzoic acid to thionyl chloride, further adding N, N-dimethylformamide as a catalyst and refluxing, and then adding benzene to remove excess thionyl chloride. It can be obtained by azeotropic distillation.

  The reaction of 2,2'-bis (trifluoromethyl) benzidine and a chlorinated 4-nitrobenzoic acid derivative can be carried out, for example, by dissolving them in dehydrated tetrahydrofuran and mixing them. At this time, hydrogen chloride generated during the reaction can be removed by allowing a base such as pyridine or triethylamine to coexist as a dehydrochlorinating agent.

  There are various methods for reducing the obtained dinitro compound to diamine, and there is no particular limitation. However, a catalytic reduction method in which hydrogen gas is reacted in the presence of a metal catalyst such as Pd / C or Ni is simple. is there. Examples of the solvent used in this case include 1,4-dioxane, ethanol and tetrahydrofuran.

<2. Polyimide>
The polyimide according to one embodiment of the present invention has the following formula (3):

(In the formula (3), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of the substituent R, and 1 to 4). X ₁ represents at least one of a tetravalent aliphatic group and an aromatic group). In other words, X ₁ may be a tetravalent aliphatic group, a tetravalent aromatic group, or a structure containing both a tetravalent aliphatic group and an aromatic group (for example, 4 A structure in which a valent aliphatic group and a tetravalent aromatic group are linked).

  Since the polyimide has a structure derived from the diamine represented by the formula (1) as described above, it has excellent solution processability and has a low linear thermal expansion coefficient when formed into a film. In addition, the polyimide exhibits high heat resistance due to its chemical structure.

  The polyimide has the following formula (4):

(In formula (4), X ₁ represents at least one of a tetravalent aliphatic group and an aromatic group).

  The tetravalent aliphatic group can be, for example, a structure derived from the following alicyclic tetracarboxylic dianhydride: (1S, 2R, 4S, 5R) -cyclohexanetetracarboxylic dianhydride (cis, cis Cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride), (1S, 2S, 4R, 5R) -cyclohexanetetracarboxylic dianhydride, (1R, 2S, 4S, 5R) -cyclohexanetetra Carboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5 , 6-tetracarboxylic dianhydride, 5- (dioxotetrahydrofuryl-3-methyl) -3-cyclohexene-1,2-dicarboxylic anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl ) -Tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo-3,3 ', 4,4'-tetracarboxylic dianhydride, 1, 2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride Anhydride or 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and the like. That is, the tetravalent aliphatic group can be derived from a structure sandwiched between the acid anhydride groups of these alicyclic tetracarboxylic dianhydrides.

The cause of polyimide coloring yellow or brown is the charge transfer interaction within and / or between the polyimide molecules. In order to obtain a transparent polyimide, it is necessary to suppress these charge transfer interactions. As one means for that purpose, it is effective to select a tetravalent aliphatic group as X ₁ in the formula (4).

Among these, from the viewpoint that the main chain of polyimide can have a more rigid structure, X ₁ is represented by the following formula (5):

It is preferable that it is a tetravalent aliphatic group represented by these. The structure represented by the formula (5) can be introduced into polyimide by using 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

  The tetravalent aromatic group can be, for example, a structure derived from the following aromatic tetracarboxylic dianhydride: 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride or 1,4-bis (Fluoromethyl-2,3,5,6-benzenetetracarboxylic dianhydride) and the like. That is, the tetravalent aromatic group can be derived from a structure sandwiched between the acid anhydride groups of these aromatic tetracarboxylic dianhydrides. Examples of the tetravalent aromatic group include those containing an aromatic ring and at least one selected from the group consisting of a hexafluoroisopropylidene group, a sulfonyl group, an ether bond and an ester bond. When polyimide contains a tetravalent aromatic group, solution processability can be improved.

Among these, from the viewpoint that the solution processability can be further improved without impairing the heat resistance, X ₁ is represented by the following formula (6):

It is preferable that it is a tetravalent aromatic group represented by these. The structure represented by the formula (6) can be introduced into polyimide by using 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride.

  In the polyimide, when the total repeating unit is 100 mol%, the content of the repeating unit represented by the formula (3) is preferably 70 mol% or more, more preferably 80 moll% or more, More preferably, it is 90 mol% or more, and it is especially preferable that it is 100 mol% (the said polyimide consists of a repeating unit represented by Formula (3)). When the content of the repeating unit represented by the formula (3) is 70 mol% or more, it is possible to provide a polyimide having better solution processability, transparency, high heat resistance, and low linear thermal expansion coefficient.

The polyimide is a repeating unit represented by the above formula (3), and X ₁ is a tetravalent aliphatic group represented by the formula (5) (hereinafter also referred to as a repeating unit (a)). And a repeating unit represented by the above formula (3), wherein X ₁ is a tetravalent aromatic group represented by the formula (6) (hereinafter also referred to as repeating unit (b)). And at least two types of repeating units. In this case, transparency can be improved based on the tetravalent aliphatic group of the repeating unit (a), and solution processability can be improved based on the tetravalent aromatic group of the repeating unit (b). Is preferable.

  When the total number of moles of the repeating unit (a) and the repeating unit (b) is 100 mol%, the composition ratio (molar ratio) between the repeating unit (a) and the repeating unit (b), that is, [(a) ] / [(B)] is preferably 95/5 to 5/95, more preferably 90/10 to 10/90, still more preferably 80/20 to 20/80, It is especially preferable that it is 70 / 30-50 / 50. With the above composition ratio, improvement in transparency due to the tetravalent aliphatic group of the repeating unit (a) and improvement in solution processability due to the tetravalent aromatic group of the repeating unit (b) Good balance. For example, when priority is given to the improvement of transparency, [(a)] / [(b)] is preferably 95/5 to 55/45, and 90/10 to 60/40. Is more preferable, and 85/15 to 65/35 is more preferable. On the other hand, when priority is given to improving the solution processability, [(a)] / [(b)] is preferably 5/95 to 50/50, and preferably 10/90 to 40/60. More preferably, it is more preferably 15/85 to 35/65.

  When manufacturing the said polyimide, you may use other diamine other than the diamine represented by Formula (1). Examples of other diamines include p-phenylene diamine, m-phenylene diamine, o-phenylene diamine, 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, , 2-Di (3-amino Enyl) 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] sulfide, bi Sus [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino Phenoxy) 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] ben Zen, 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-4,4′-dibiphenoxyben Zophenone, 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-aminomethoxy) ethyl ] Ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminopropoxy) 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-aminopropyl) 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-diamino Hexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminono 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-fluoro Benzene, 1,4-diamino-2,3-difluorobenzene, 1,4-diamino-2,5-difluorobenzene, 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 (trifluoro Methyl) 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-trifluorobenzidine 2,3 ′, 5-trifluorobenzidine, 2,3 ′, 6, -trifluorobenzidine, 2,2 ′, 3,3′-tetrafluorobenzidine, 2,2 ′, 5,5′-tetrafluoro Benzidine, 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 (trifluoromethyl) benzene 2,3 ′, 5-tris (trifluoromethyl) benzidine, 2,3 ′, 6-tris (trifluoromethyl) benzidine, 2,2 ′, 3,3′-tetrakis (trifluoromethyl) benzidine, Examples include, but are not limited to, 2,2 ′, 5,5′-tetrakis (trifluoromethyl) benzidine and 2,2 ′, 6,6′-tetrakis (trifluoromethyl) benzidine.

  The weight average molecular weight of the polyimide is preferably in the range of 20,000 to 500,000, more preferably in the range of 30,000 to 300,000, although it depends on the application. More preferably, it is in the range of 200,000. If the weight average molecular weight is 20,000 or more, a film having sufficient strength can be obtained. On the other hand, if the weight average molecular weight is 500,000 or less, there is no significant deterioration in handling during coating due to an increase in the solution viscosity, and good solution processability can be maintained. A uniform film can be obtained. In this specification, a weight average molecular weight molecular weight means the value of polyethylene glycol conversion by gel permeation chromatography (GPC). When the polyimide is insoluble in the solvent used for GPC measurement, the molecular weight of the polyamic acid that is the precursor can be used instead of the molecular weight of the polyimide itself.

  Moreover, it is preferable that the intrinsic viscosity of a polyimide is 0.3-10 dL / g, and it is more preferable that it is 0.5-10 dL / g. If the intrinsic viscosity is 0.3 dL / g or more, since it has a sufficient molecular weight, a film having sufficient strength can be obtained. On the other hand, if the intrinsic viscosity is 10 dL / g or less, there is no significant deterioration in handling during coating due to an increase in solution viscosity, and good solution processability can be maintained, so the surface is smooth and the film thickness is uniform. Can be obtained. In addition, an intrinsic viscosity can be measured by the method as described in the below-mentioned Example.

  The manufacturing method of the said polyimide is not specifically limited, It can obtain using a well-known method. For example, the polycarboxylic acid dianhydride represented by the formula (8) and the diamine represented by the formula (1) are stirred and polymerized in a solvent to obtain a precursor polyamic acid, and further imidized. By doing so, the polyimide can be obtained.

  Examples of the tetracarboxylic dianhydride represented by the formula (8) include the above-described alicyclic tetracarboxylic dianhydrides and / or aromatic tetracarboxylic dianhydrides.

  When the diamine represented by the formula (1) and another diamine are used in combination (that is, copolymerization), the content of the diamine represented by the formula (1) when the total amount of diamine is 100 mol% is The higher the content, the better in the order of 10 mol% or more, 50 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, and 100 mol%.

  The solvent at the time of polymerization is not limited as long as it can dissolve the polyamic acid and the polyimide uniformly and does not inhibit the reaction. Examples of the solvent include amide solvents and cyclic ester solvents. Examples of the amide solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and hexamethylphosphoramide. Examples of the cyclic ester solvent include γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone.

  The imidization method is not particularly limited, and known methods (chemical imidization method and thermal imidization method) can be applied.

  First, a method for producing polyimide by chemical imidization will be described. A polyimide precursor varnish obtained by polymerization, or a polyimide precursor varnish moderately diluted with the same solvent used for polymerization, and under stirring, comprises an organic acid anhydride and a tertiary amine as a catalyst. A chemical imidizing agent is added dropwise. The imidization reaction can be completed easily by stirring the varnish at 0 to 100 ° C., preferably 20 to 50 ° C. for 0.5 to 48 hours.

  The organic acid anhydride is not particularly limited, and examples thereof include acetic anhydride, propionic anhydride, maleic anhydride, and phthalic anhydride. Of these, acetic anhydride is preferably used from the viewpoint of cost and ease of post-treatment (removal). Moreover, it does not specifically limit as a tertiary amine, A pyridine, a triethylamine, N, N- dimethylaniline etc. are mentioned. Of these, pyridine is preferably used from the viewpoint of safety.

  The amount of the organic acid anhydride in the chemical imidizing agent to be added is not particularly limited, but is in the range of 1 to 10 moles of the theoretical dehydration amount of the polyimide precursor. From the viewpoint of completion of the reaction, reaction rate, and post-treatment. It is preferably in the range of ˜5 times mole. The amount of tertiary amine used as a catalyst is not particularly limited, but is 0.1 to 1 mol per mol of the organic acid anhydride from the viewpoint of completion of the reaction, reaction rate, and post-treatment (ease of removal). It is preferable that it is the range of these.

  The polyimide can also be obtained by imidization (thermal imidization) by a thermal method. Imidization by a thermal method may be performed by heating a polyamic acid solution. Alternatively, the polyamic acid solution may be cast or applied to a support such as a glass plate, a metal plate, or PET (polyethylene terephthalate), and then heat treatment may be performed within a range of 80 ° C to 500 ° C. Furthermore, the polyamic acid solution can be directly dehydrated and ring-closed by placing the polyamic acid solution directly into a container that has been subjected to a release treatment such as coating with a fluororesin, and then drying by heating under reduced pressure. A polyimide resin can be obtained by dehydration 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, it is generally performed in the range of 1 minute-5 hours after the processing temperature reaches the maximum temperature. It is preferable.

  In addition, when using an azeotropic method using an azeotropic solvent, a solvent that azeotropes with water such as toluene or xylene is added to the polyamic acid solution, the temperature is raised to 170 to 200 ° C., and water generated by dehydration ring closure The reaction may be carried out for about 1 to 5 hours while positively removing from the system. After completion of the reaction, the reaction solution is dropped into a poor solvent such as alcohol to precipitate the polyimide, and after washing with alcohol or the like as necessary, drying can be performed to obtain a polyimide resin.

  The poor solvent used in the precipitation operation is not particularly limited as long as it does not dissolve polyimide. As the poor solvent, for example, water, methanol, ethanol, n-propanol or isopropanol, or a mixed solvent thereof is preferably used from the viewpoint of miscibility with the reaction solvent and the chemical imidizing agent and ease of removal by drying. Used.

  When a polyimide solution containing polyimide, a chemical imidizing agent or an azeotropic agent is dropped 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 particle size is reduced. From the viewpoint of achieving this, it is preferable that the concentration be dilute. However, if the concentration is too dilute, a large amount of poor solvent is used to precipitate the polyimide, which is not preferable. From these viewpoints, it is preferable to add a poor solvent dropwise to the polyimide solution after dilution so that the solid content concentration of the polyimide solution is 15% by weight or less, preferably 10% by weight or less. The amount of the poor solvent to be used is preferably an amount equal to or more than the equivalent amount of the polyimide solution, and more preferably 2 to 3 times. Since the polyimide obtained here contains a small amount of a chemical imidizing agent and / or an azeotropic agent, it is preferably washed several times with the above poor solvent.

  The method for drying the polyimide thus obtained by the chemical imidization method or the thermal imidization method may be vacuum drying or hot air drying. Vacuum drying is desirable to completely dry the solvent contained in the resin. The drying temperature is preferably in the range of 80 to 200 ° C. from the viewpoint of preventing decomposition of the residual solvent and deterioration of the resin due to the residual solvent. The drying time is arbitrary as long as the solvent contained in the resin can be completely dried, but is preferably 15 hours or less from the viewpoint of manufacturing process cost, and 8 hours from the viewpoint of sufficiently drying the residual solvent. The above is preferable.

<3. Varnish>
The varnish which concerns on one Embodiment of this invention contains 5 weight% or more of solid content concentration of the polyimide which concerns on one Embodiment of this invention. If solid content concentration is 5 weight% or more, the smoothness of the film obtained by coating of varnish can be ensured. The solid content concentration is preferably 5 to 40% by weight, and more preferably 10 to 25% by weight.

  The varnish can be obtained by uniformly dissolving the above polyimide in an organic solvent. The organic solvent is not particularly limited, and examples thereof include amide solvents, ketone solvents, ether solvents, ester solvents, dimethyl sulfoxide, symmetric glycol diethers and ethers. These organic solvents may be used in combination.

  Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone. Examples of ether solvents include tetrahydrofuran, 1,3-dioxolane and 1,4-dioxane. Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, γ-butyrolactone, α-acetolactone, β-propiolactone, and δ-valerolactone. Symmetric glycol diethers include methyl monoglyme (1,2-dimethoxyethane), methyl diglyme (bis (2-methoxyethyl) ether), methyltriglyme (1,2-bis (2-methoxyethoxy) ethane ), Methyltetraglyme (bis [2- (2-methoxyethoxyethyl)] ether), ethylmonoglyme (1,2-diethoxyethane), ethyldiglyme (bis (2-ethoxyethyl) ether) and butyldigly And lime (bis (2-butoxyethyl) ether). Examples of ethers include dipropylene glycol methyl ether, tripropylene glycol methyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripylene glycol n- Examples include propyl ether, propylene glycol phenyl ether, dipropylene glycol dimethyl ether, 1,3-dioxolane, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and ethylene glycol monoethyl ether.

  It is preferable that at least one organic solvent is selected from these. Furthermore, it is particularly preferable that the polyimide is dissolved in all of the amide solvent, the ketone solvent, and the ether solvent because a solvent suitable for the substrate to be coated can be selected each time. Among them, as an organic solvent, an amide solvent and a ketone are used from the viewpoint of preventing defects such as whitening, non-uniformity, and solidification due to moisture absorption during coating during drying. A mixed solvent with a system solvent or an ether solvent is preferable, and a ketone solvent or an ether solvent alone or a mixed solvent thereof is more preferable. Among them, particularly preferred amide solvents include dimethylformamide, dimethylacetamide and N-methylpyrrolidone. Particularly preferred ketone solvents include methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone. Particularly preferred ether solvents include methylmonoglyme (1,2-dimethoxyethane), methyldiglyme (bis (2-methoxyethyl) ether) and methyltriglyme (1,2-bis (2-methoxyethoxy) ethane). Etc.

  The viscosity of the varnish is selected as needed depending on the thickness to be applied and the coating environment, but is preferably 0.1 to 50 Pa · s, and more preferably 0.5 to 30 Pa · s. When the viscosity of the varnish is 0.1 Pa · s or more, a sufficient viscosity can be secured, and as a result, a sufficient film thickness accuracy can be secured. Moreover, if the viscosity of the varnish is 50 Pa · s or less, it is possible to ensure the film thickness accuracy and more reliably prevent the appearance defects such as gel defects due to the occurrence of a portion that dries immediately after coating. it can. The viscosity is a kinematic viscosity at 23 ° C. measured using an E-type viscometer.

  The varnish may further contain a photocurable component or a thermosetting component, a non-polymerizable binder resin other than polyimide, or other components.

  In order to impart processing characteristics or various functionalities to the varnish, various organic or inorganic low molecular compounds or high molecular compounds may be blended. For example, a dye, a surfactant, a leveling agent, a plasticizer, fine particles, or a sensitizer 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. They may be porous or hollow structures. Moreover, a pigment or a filler is mentioned as a function of the said low molecular or high molecular compound. The form of the low molecular weight or high molecular compound may be a fiber.

<4. Film>
The film (polyimide film) according to one embodiment of the present invention is obtained by drying the varnish (polyimide varnish) according to one embodiment of the present invention. The film can be produced by applying a varnish on a substrate and drying it. A film can also be obtained by applying polyamic acid, which is a polyimide precursor, to a substrate, heating the resulting film, imidizing and drying. From the viewpoint of thermal expansion characteristics and dimensional stability of the obtained film, a method of applying the polyimide varnish described above and drying is more preferable.

  Examples of the substrate on which the varnish is applied include 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. It is not limited. 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 film production, it is possible to select conditions suitable for the process, and there is no particular limitation as long as the properties are not affected.

  Various inorganic thin films such as a metal oxide or a transparent electrode may be formed on the surface of the film. The method for producing these inorganic thin films is not particularly limited, and examples thereof include a CVD method, and a PVD method such as a sputtering method, a vacuum deposition method, and an ion plating method.

<5. Use of polyimide>
The polyimide according to an embodiment of the present invention exhibits extremely useful characteristics such as a low linear thermal expansion coefficient and excellent solution processability and transparency in addition to the original characteristics of polyimide such as heat resistance and insulation.

  Therefore, the polyimide according to an embodiment of the present invention may be used in fields and products in which these characteristics are effective, for example, substrates, color filters, printed materials, optical materials, electronic devices, image display devices, and the like. More preferably, it is more preferable to use a substitute material for a portion where glass or a transparent material is currently used. Accordingly, it is possible to provide a substrate, an image display device, an optical material, and an electronic device that have characteristics such as lightness and flexibility that are not found in glass and high definition.

  Examples of the substrate include a plastic substrate for an image display device (for example, a flexible display substrate), a TFT substrate, and a transparent conductive film substrate. The image display device is a flexible display, liquid crystal display device, organic EL, electronic paper, 3-D display, or the like. The optical material is an optical film or the like. The electronic device is a touch panel, a solar cell, or the like. For example, a plastic substrate for an image display device according to an embodiment of the present invention may include a film according to an embodiment of the present invention, and includes a film according to an embodiment of the present invention. May be.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can also be configured as follows.

  <1> The following formula (1):

(In formula (1), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of substituents R, and an integer of 1 to 4) is there).

  <2> The following formula (2):

<1> represented by the diamine.

  <3> The following formula (3):

(In formula (3), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of substituents R, 4 is an integer, and X ₁ represents at least one of a tetravalent aliphatic group and an aromatic group).

  <4> Formula (4) below:

In polyimide according to <3> having a repeating unit represented (in the formula (4), X ₁ represents at least one tetravalent aliphatic and aromatic groups).

<5> X ₁ is the following formula (5):

<3> or <4>, wherein the polyimide is a tetravalent aliphatic group represented by the formula:

<6> X ₁ is the following formula (6):

<3> or <4>, wherein the polyimide is a tetravalent aromatic group represented by the formula:

  <7> A varnish containing the polyimide according to any one of <3> to <6> at a solid content concentration of 5% by weight or more.

  <8> A film obtained by drying the varnish described in <7>.

  <9> A plastic substrate for an image display device, comprising the film according to <8>.

[Evaluation of physical properties]
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited to these Examples. The physical property values in the following examples were measured by the following methods.

<Infrared absorption (FT-IR) spectrum>
The infrared absorption spectrum of diamine was measured by a KBr method using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, FT-IR4100). Further, the infrared absorption spectra of the polyimide precursor and polyimide were separately measured by a transmission method by preparing a thin film having a thickness of about 4 to 5 μm.

^<1 H-NMR spectrum>
The ¹ H-NMR spectrum of the diamine and the polyimide powder was measured using an NMR spectrophotometer (manufactured by JEOL Ltd., ECP400) using deuterated dimethyl sulfoxide (DMSO-d ₆ ) as a solvent.

<Differential scanning calorimetry (melting point and melting curve)>
The melting point and melting curve of diamine were measured at a heating rate of 5 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (manufactured by Netch Japan Co., Ltd., DSC3100).

<Intrinsic viscosity (η _inh )>
The reduced viscosities of the polyimide precursor (PAA) and the polyimide (PI) were measured using an Ostwald viscometer at a solid content concentration of 0.5% by weight at 30 ° C. This value can be regarded as the intrinsic viscosity, and the higher the value, the higher the molecular weight.

<Glass transition temperature (T _g )>
The glass transition temperature (T _g ) of the polyimide film (about 20 μm thick) is a loss energy curve at a frequency of 0.1 Hz and a heating rate of 5 ° C./min using a thermomechanical analyzer (manufactured by Netch Japan, TMA4000). It was determined from the peak temperature. T as _g is high, indicating that high physical heat resistance.

<Linear thermal expansion coefficient (CTE)>
The CTE of the polyimide film (about 20 μm thick) is based on the elongation of the test piece at a heating rate of 5 ° C./min per 0.5 g load / 1 μm film thickness using a thermomechanical analyzer (manufactured by Netch Japan, TMA4000). And an average value in the range of 100 to 200 ° C. The closer the CTE value is to 0, the better the thermal dimensional stability.

<5% weight loss temperature (T _d ⁵ )>
The 5% weight reduction temperature (T _d ⁵ ) of the polyimide film (about 20 μm thick) was measured in nitrogen (N ₂ ) and air (air) using a thermogravimetric analyzer (TG-DTA2000) manufactured by Netch Japan. In the temperature rising process at a temperature rising rate of 10 ° C./min, the weight of the polyimide film (20 μm thickness) was obtained from the temperature when the initial weight decreased by 5%. The higher the T _d ⁵ value, the higher the chemical heat resistance (thermal stability).

<Tensile modulus, elongation at break, strength at break>
The mechanical properties of the polyimide film (about 20 μm thick) were evaluated using an A & D tensile tester (Tensilon UTM-II). A test piece (30 mm length × 3 mm width × about 20 μm thickness) was prepared, and a tensile test (stretching speed: 8 mm / min) was performed. From the initial gradient of the stress-strain curve, tensile modulus (E), stress at break From the breaking strength (σ _b ), the breaking elongation (ε _b ) was determined from the elongation at break. The higher the elongation at break, the higher the toughness of the film. The elongation at break showed an average value (ave) and a maximum value (max).

<Transparency of polyimide film: light transmittance, cut-off wavelength, yellowness index, haze>
The transparency of the polyimide film was evaluated from the following optical characteristics. Using a UV-visible spectrophotometer (V-530) manufactured by JASCO Corporation, the light transmittance curve of a polyimide film (about 20 μm thick) was measured in the wavelength range of 200 to 800 nm, and the light transmittance at a wavelength of 400 nm (T ₄₀₀ ) And a wavelength at which the light transmittance is practically zero (cut-off wavelength (λ _cut )). Based on this spectrum, a yellowness index (YI value) was determined based on the ASTM E313 standard using a color calculation program (JASCO). Furthermore, a total light transmittance (T _tot ) and turbidity (haze) were determined using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS K7361-1 and JIS K7136 standards.

<Thickness direction birefringence (Δn _th )>
Abbe refractometer 4T with eyepiece with polarizing plate (manufactured by ATAGO), NaD line (589.3 nm) as a light source, and methylene iodide solution as an intermediate solution saturated with sulfur (n ^D = 1.72 to 1) .80) and a test piece (n ^D = 1.72), the _in- plane refractive index n _in and the out-of-plane refractive index n _{out of} the polyimide film are measured, and the thickness direction birefringence Δn _th (= n _in −n _out ).

<Solution processability>
Solution processability was evaluated based on solubility in solvents. The polyimide powder was added to a 99-fold weight solvent, stirred for 5 minutes using a test tube mixer, and the dissolved state was visually confirmed. Here, when the polyimide powder was uniformly dissolved in the solvent, it was evaluated as “showing excellent solubility”.

〔abbreviation〕
3-Methyl-4-nitrobenzoic acid = 3M4NB
3M4NB chlorinated compound = 3M4NBC
N, N-dimethylformamide = DMF
Tetrahydrofuran = THF
2,2′-bis (trifluoromethyl) benzidine = TFMB
N, N-dimethylacetamide = DMAc
1,2,3,4-cyclobutanetetracarboxylic dianhydride = CBDA
N-methyl-2-pyrrolidone = NMP
Dimethyl sulfoxide = DMSO
4,4 ′-(Hexafluoroisopropylidene) diphthalic anhydride = 6FDA
γ-butyrolactone = GBL.

[Example 1]
<Synthesis of diamine>
The diamine according to one embodiment of the present invention represented by the above formula (2) (hereinafter referred to as M-ABMB) is a synthesized dinitro compound (hereinafter referred to as M-NBMB) which is a precursor of M-ABMB. And synthesized by reducing the nitro group. Specifically, the procedure was as follows.

  First, M-NBMB was synthesized as follows. In a three-necked flask, 10.86 g (60 mmol) of 3M4NB (manufactured by Tokyo Chemical Industry) and 50 mL of thionyl chloride were placed. Three drops of DMF as a catalyst was further added to the flask and refluxed at 80 ° C. for 3 hours. Benzene was added to this solution, and excess thionyl chloride was distilled off azeotropically under reduced pressure, followed by vacuum drying at room temperature for 12 hours to obtain yellow 3M4NBC (melting point: 32 ° C.).

Next, 5.15 g (27 mmol) of the above 3M4NBC was dissolved in dehydrated THF in an eggplant flask and sealed with a septum cap to obtain a solution A. Next, in another eggplant flask, 3.20 g (10 mmol) of TFMB was dissolved in dehydrated THF (15 mL), and 2.5 mL (31 mmol) of pyridine was further added as a dehydrochlorinating agent, which was sealed with a septum cap to obtain a solution B. While liquid B was cooled in an ice bath, liquid A was slowly added to liquid B with a syringe. The resulting mixture of liquid A and liquid B was further stirred at room temperature for 12 hours. Thereafter, a large amount of water was poured into the obtained reaction solution to deposit a blackish yellow precipitate. This was filtered off, washed with water, and vacuum dried at 120 ° C. for 12 hours to obtain a crude product. In order to remove the black residue, this crude product was dissolved in ethyl acetate and passed through a silica gel column to obtain an eluate. The eluate was concentrated with an evaporator to precipitate a precipitate. The precipitate was filtered off, washed with ethyl acetate, and dried at 120 ° C. for 12 hours to obtain a pale yellow product in a yield of 76% (melting point: 236 ° C.). From the FT-IR and ¹ H-NMR spectrum, it was confirmed that the obtained product was the target dinitro compound (M-NBMB).

  Next, M-NBMB was reduced as follows. In a three-necked flask, 4.69 g (7.25 mmol) of M-NBMB was dissolved in 1,4-dioxane, Pd / C (0.475 g) was added as a catalyst, and the mixture was refluxed at 80 ° C. for 10 hours in a hydrogen atmosphere. did. Completion of the reduction reaction was confirmed by thin layer chromatography. After completion of the reaction, the reaction mixture was filtered hot to remove the catalyst, and the filtrate was dropped into a large amount of ion-exchanged water to precipitate a precipitate. This precipitate was separated by filtration and vacuum-dried at 120 ° C. for 12 hours to obtain a white product with a reduction reaction yield of 85%.

The analysis result of this white product is as follows. FT-IR (KBr, cm ⁻¹ ): 3368/3226 (amine, NH), 3111/3050 (aromatic C—H), 2959 (CH ₃ , C—H), 1627/1525 (amide, C) = O), 1500 (1,4- _{phenylene), 1320/1255 (CF 3} , CF). ¹ H-NMR (400 MHz, DMSO-d ₆ , δ, ppm): 10.15 (s, 2 H, NHCO), 8.52 (dd, 2 H, J = 8.4, 2.0 Hz, central biphenyl group 5,5′-proton), 8.33 (sd, 2H, J = 2.1 Hz, 3,3′-proton of central biphenyl group), 7.68-7.64 (m, 4H, terminal anilino group) 3,3′-proton + 5,5′-proton), 7.32 (d, 2H, J = 8.5 Hz, 6,6′-proton in the central biphenyl group), 6.68 (d, 2H, J = 8.5 Hz, 6,6′-proton of the terminal anilino group), 5.62 (s, 4H, NH ₂ ), 2.14 (s, 6H, CH ₃ ). Elemental analysis _{(C 30 H 24 O 2 N} 4 F 6, molecular weight 586.54): estimate C; 61.43%, H; 4.12 %, N; 9.55%, analytical values C; 61.35 %, H; 4.26%, N; 9.53%. From these analysis results, it was confirmed that this product was the target diamine (M-ABMB) represented by the formula (1).

[Example 2]
<Polymerization of polyimide precursor, chemical imidization, film formation and film physical properties>
In the reaction vessel, 1.1731 g (2 mmol) of the diamine (M-ABMB) described in Example 1 was dissolved in dehydrated DMAc. To the resulting solution, 0.3922 g (2 mmol) of CBDA powder was added little by little and sealed. The solid content concentration at the beginning of the reaction was 30% by weight. When stirring was continued at room temperature, the polymerization reaction proceeded, the solution viscosity increased, and stirring became difficult. Therefore, DMAc was gradually added to the reaction vessel, and after stirring for 72 hours, the solution was diluted until the solid concentration was 18% by weight. After stirring for 72 hours, a viscous uniform polyimide precursor solution was obtained. The intrinsic viscosity of the obtained polyimide precursor was 1.75 dL / g.

The polyimide precursor solution was appropriately diluted with DMAc (in this case, diluted to 6.0% by weight). While stirring the diluted polyimide precursor solution, a mixed solution of acetic anhydride (20 mmol) and pyridine (volume ratio of acetic anhydride and pyridine: 7/3) as a chemical imidizing agent was slowly dropped at room temperature, After completion of the dropwise addition, the mixture was further stirred in a sealed container for 24 hours. The reaction solution was appropriately diluted with DMAc and then added dropwise to a large amount of water to precipitate a white precipitate. The white precipitate was filtered off, washed thoroughly with water and methanol, and dried in vacuo at 100 ° C. for 12 hours. The obtained powder was dissolved in deuterated DMSO, and a ¹ H-NMR spectrum was measured. As a result, both NHCO proton signals and COOH proton signals derived from the polyimide precursor were completely eliminated, confirming the completion of chemical imidization.

The obtained fibrous polyimide powder was redissolved in DMAc at a solid concentration of 10% by weight to obtain a uniform solution. This was cast on a glass substrate and dried in a hot air dryer at 60 ° C. for 2 hours. Furthermore, it was dried in vacuum at 200 ° C. for 1 hour and then at 300 ° C. for 1 hour. Thereafter, the obtained film was peeled off from the substrate, and heat treated at 330 ° C. for 1 hour in vacuum to obtain a flexible and cloudy polyimide film. When the physical properties of this film were evaluated, it showed an extremely low CTE value (3.6 ppm / K) and high heat resistance (T _g = 325 ° C.). Other physical property values are shown in Table 1. The chemically imidized polyimide powder showed excellent solubility in NMP and DMAc at room temperature. In addition, Example 2 is corresponded to the Example which used 100 mol% of CBDA as tetracarboxylic dianhydride.

Example 3
A polyimide precursor was polymerized in the same manner as described in Example 2 except that 95 mol% of CBDA and 5 mol% of 6FDA were used as tetracarboxylic dianhydride, and then a polyimide was obtained by chemical imidization and cast film formation. A film was obtained. FIG. 1 shows an infrared absorption spectrum of a separately prepared polyimide thin film. The infrared absorption spectrum was measured using a Fourier transform infrared spectrophotometer FT / IR-4100 type A (manufactured by JASCO Corporation). Table 1 shows physical property values. Since this film (film thickness of about 20 μm) exhibits a higher T ₄₀₀ value, lower YI value and lower haze value than the film of Example 2, it can be seen that the transparency is improved. This is considered to be a result of the 5 mol% copolymerization of 6FDA, which improved the solvent solubility and hindered aggregation of the main chain during the solvent evaporation process during film formation. In addition to a low CTE value (16.9 ppm / K), high heat resistance (T _g = 348 ° C.) was exhibited. Chemically imidized polyimide powder exhibits excellent solubility in a mixed solvent of DMAc, DMAc / GBL (volume ratio 1/1) and a mixed solvent of DMAc / CPN (volume ratio 1/1), and a solid content concentration of about It was possible to obtain 10% by weight of varnish.

Example 4
As a tetracarboxylic dianhydride, a polyimide precursor was polymerized in the same manner as described in Example 2 except that 70 mol% of CBDA and 30 mol% of 6FDA were used, followed by chemical imidization and casting to form a polyimide. A film was obtained. Table 1 shows physical property values. This film had excellent transparency, as indicated by high T ₄₀₀ values, low YI values and low haze values. In addition to a low CTE value (17.9 ppm / K), high heat resistance (T _g = 334 ° C.) was exhibited. Chemically imidized polyimide powder showed excellent solubility in NMP, DMAc and DMF at room temperature.

Example 5
As a tetracarboxylic dianhydride, a polyimide precursor was polymerized in the same manner as described in Example 2 except that 50 mol% of CBDA and 50 mol% of 6FDA were used, followed by chemical imidization and cast film formation to obtain a polyimide. A film was obtained. Table 1 shows physical property values. The film higher T ₄₀₀ value, lower YI value, lower haze values, had excellent transparency. In addition to a relatively low CTE value (23.6 ppm / K), high heat resistance (T _g = 349 ° C.) was exhibited. The chemically imidized polyimide powder showed excellent solubility in NMP, DMAc, DMF and DMSO at room temperature.

Example 6
As a tetracarboxylic dianhydride, a polyimide precursor was polymerized in the same manner as described in Example 2 except that 6FDA was used instead of CBDA, and a polyimide film was obtained by chemical imidization and cast film formation. It was. Table 1 shows physical property values. The film higher T ₄₀₀ value, lower YI value, lower haze values, had excellent transparency. Further, the chemically imidized polyimide powder showed excellent solubility in NMP, DMAc, DMF, DMSO, GBL, triglyme, cyclopentanone, acetone and THF at room temperature. A stable varnish was obtained at a solid concentration of 15% by weight using GBL as a solvent. When the molecular weight was measured by gel permeation chromatography using THF as an elution solvent, the number average molecular weight (M _n ) = 2.3 × 10 ⁴ and the weight average molecular weight (M _w ) = 5.7 × 10 ⁴ were obtained.

[Comparative Example 1]
In order to investigate the effect of a methyl substituent in a diamine according to an embodiment of the present invention, a polyimide precursor is prepared by using a diamine having no methyl substituent (ABMB) and performing a polyaddition reaction with CBDA by the method described in Example 2. Got the body. ABMB is expressed by the following formula (9).

  When the chemical imidizing agent was dropped into the polyimide precursor solution in the same manner as described in Example 2, it was difficult to carry out chemical imidization because the reaction solution gelled. This is because the solvent solubility of polyimide obtained from CBDA and ABMB is insufficient. This result is in contrast to the result of using the diamine according to one embodiment of the present invention (Example 2), and the presence of the methyl substituent in the diamine according to one embodiment of the present invention contributes to the solubility of the polyimide. This suggests a significant contribution.

[Comparative Example 2]
A polyimide precursor was polymerized in the same manner as described in Example 2 except that TFMB was used instead of M-ABMB as the diamine. When a chemical imidizing agent was dropped into the solution in the same manner as described in Example 2, it was difficult to carry out chemical imidization because the reaction solution gelled. This is because the solvent solubility of polyimide obtained from CBDA and TFMB is insufficient.

  The polyimide which concerns on one Embodiment of this invention is used suitably for a board | substrate, a color filter, printed matter, an optical material, an electronic device, an image display apparatus etc. as a film, for example. Therefore, it can be widely used in these industrial fields.

Claims (9)

Following formula (1):

(In formula (1), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of substituents R, and an integer of 1 to 4) is there). Following formula (2):

The diamine of Claim 1 represented by these. Following formula (3):

(In formula (3), the substituent R independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group, n represents the number of substituents R, 4 is an integer, and X ₁ represents at least one of a tetravalent aliphatic group and an aromatic group). Following formula (4):

Polyimide according to claim 3 having in represented by the repeating units (in the formula (4), X ₁ represents at least one tetravalent aliphatic and aromatic groups). X ₁ is the following formula (5):

The polyimide according to claim 3, wherein the polyimide is a tetravalent aliphatic group represented by the formula: X ₁ is the following formula (6):

The polyimide according to claim 3, wherein the polyimide is a tetravalent aromatic group represented by the formula:   A varnish containing the polyimide according to any one of claims 3 to 6 at a solid content concentration of 5% by weight or more.   A film obtained by drying the varnish according to claim 7.   A plastic substrate for an image display device, comprising the film according to claim 8.

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