Polyimide, and production method and use of the same

Abstract

To provide a polyimide capable of forming a transparent film high in heat resistance, and low in dielectric characteristics and water absorption.SOLUTION: A polyimide is produced through a process of preparing a liquid polyimide precursor including a polyamic acid of a reaction product of a diamine constituent including a diamine having a 9,9-bisaryl fluorine skeleton, and a tetracarboxylic acid dianhydride constituent including a compound expressed by formula (2) where, in the formula, X3 indicates a bond expressed by a direct bond, -O-, -CO-, -S-, -SO2- or -O-X4-O- (in the formula, X4 is a bivalent organic group), R4 and R5 are independently a substituent, and s1 and s2 are independently an integer of 0 to 3, and a solvent, and having a polyamic acid concentration of 30 mass% or less; a process of drying the liquid polyimide precursor; and a process of heating the polyimide precursor at 400°C or lower so as to obtain polyimide.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyimide having a 9,9-bisarylfluorene skeleton, and a method for producing the same and uses thereof. [Background technology]

[0002] Polyimide films have excellent heat resistance and transparency, and are expected to be a substitute for glass in optical materials for smartphones, etc. However, polyimide films have high water absorption and dielectric constant, so there is a demand for reducing these.

[0003] Japanese Patent Laid-Open Publication No. 2014-159519 (Patent Document 1) discloses a polyimide resin that uses a fluorene-skeleton diamine such as 9,9-bis(4-aminophenyl)fluorene, as a polyimide resin that has excellent solvent solubility while having a glass transition temperature exceeding 400°C and a resin decomposition temperature exceeding 500°C, which were previously considered difficult to achieve.

[0004] Furthermore, Japanese Patent Laid-Open Publication No. 2008-74991 (Patent Document 2) discloses a polyimide or polyamideimide having a unit composed of 9,9-bis(3-fluoro-4-aminophenyl)fluorene as a polyimide or polyamideimide having low water absorption, thermal expansion coefficient, birefringence and high glass transition temperature.

[0005] Furthermore, JP 2022-83786 A (Patent Document 3) discloses a polyimide film having structural units derived from tetracarboxylic dianhydrides such as 4,4'-oxydiphthalic dianhydride and structural units derived from diamines such as 9,9-bis(3-fluoro-4-aminophenyl)fluorene, as a polyimide film having excellent transparency, high heat resistance, low retardation characteristics in the thickness direction, and mechanical strength that can be applied to flexible displays. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-159519 A [Patent Document 2] JP 2008-74991 A [Patent Document 3] JP 2022-83786 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, even when polyimide films were produced by the methods described in these patent documents, it was not possible to produce transparent films with low dielectric properties and low water absorption. In particular, even when polyimide films were produced by the method described in Patent Document 3, the obtained polyimide films were brittle and it was difficult to evaluate their physical properties.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a polyimide capable of forming a transparent film having high heat resistance, low dielectric properties and low water absorption, and a method for producing the same and uses thereof. [Means for solving the problem]

[0009] As a result of intensive research to achieve the above object, the present inventors have found that a transparent film having high heat resistance, low dielectric properties and low water absorption can be formed by drying a liquid polyimide precursor having a specific polyamic acid having a fluorene skeleton at a concentration of 30 mass % or less and then heating it at 400° C. or less to obtain a polyimide, thereby completing the present invention.

[0010] That is, the method for producing a polyimide according to aspect [1] of the present invention comprises the steps of: Formula (1):

[0011] [ka]

[0012] (In the formula, Z1 and Z 2 each independently represents an arene ring, X 1 and X 2 each independently represents a halogen atom; n1 and n2 each independently represent an integer of 0 or more; R 1 and R 2 each independently represents a substituent; m1 and m2 each independently represent an integer of 0 or more; R 3 represents a substituent, and k represents an integer of 0 to 8. A diamine component containing a diamine represented by the formula: Formula (2):

[0013] [ka]

[0014] [In the formula, X 3 is a direct bond, -O-, -CO-, -S-, -SO2- or -OX 4 -O-(wherein, X 4 represents a divalent organic group), R 4 and R 5 each independently represents a substituent, and s1 and s2 each independently represent an integer of 0 to 3. a liquid precursor preparation step of preparing a liquid polyimide precursor containing a polyamic acid which is a reaction product with a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride represented by the formula: A drying step of drying the liquid polyimide precursor to obtain a polyimide precursor; and The method includes a polyimide production step of heating the polyimide precursor obtained in the drying step at 400° C. or less to obtain a polyimide.

[0015] The embodiment [2] of the present invention is an embodiment in which the heating temperature in the drying step of the embodiment [1] is 90° C. or lower.

[0016] The embodiment [3] of the present invention is an embodiment in which, in the preparation process of the embodiment [1] or [2], the solvent is a polyamide.

[0017] The embodiment [4] of the present invention is an embodiment in which the preparation process of any one of the embodiments [1] to [3] includes a reaction step of reacting the diamine component with the tetracarboxylic dianhydride component in the presence of a first solvent to obtain a mixed solution containing a polyamic acid, and a concentration adjustment step of adding a second solvent to the mixed solution to adjust the polyamic acid concentration to 30 mass % or less, thereby obtaining the liquid polyimide precursor.

[0018] The fifth aspect of the present invention is directed to a method for adjusting the concentration of the mixture in the fourth aspect, in which the mixture is subjected to a degassing treatment.

[0019] The embodiment [6] of the present invention relates to a compound represented by formula (1) of any one of the embodiments [1] to [5] above, wherein Z 1 and Z 2 is a benzene ring, and X 1 and X 2 is a fluorine atom, and n1 and n2 are 1.

[0020] The embodiment [7] of the present invention relates to a compound represented by formula (2) of any one of the embodiments [1] to [6] above, wherein X 3 is -O-.

[0021] The embodiment [8] of the present invention is an embodiment in which, in any one of the embodiments [1] to [7], the diamine component is solely the diamine represented by the formula (1), and the tetracarboxylic dianhydride component is solely the tetracarboxylic dianhydride represented by the formula (2).

[0022] Aspect [9] of the present invention is any one of aspects [1] to [8] above, wherein the weight average molecular weight of the polyamic acid is 10,000 or more.

[0023] The present invention also includes, as embodiment

[10] , a polyimide obtained by the production method of any one of the above embodiments [1] to [9].

[0024] An embodiment

[11] of the present invention is an embodiment in which the polyimide of the embodiment

[10] is in the form of a film or sheet.

[0025] The present invention includes, as an aspect

[12] , A liquid composition comprising a polyamic acid and a solvent, The polyamic acid concentration is 30% by mass or less, The polyamic acid has the formula (1a):

[0026] [ka]

[0027] (In the formula, X 1 and X 2 each independently represents a halogen atom; n1 and n2 each independently represent an integer of 0 or more; R 1 and R 2 each independently represents a substituent; m1 and m2 each independently represent an integer of 0 or more; R 3 represents a substituent, and k represents an integer of 0 to 8. and a diamine represented by the formula: Formula (2a):

[0028] [ka]

[0029] (In the formula, R 4 and R 5 each independently represents a substituent, and s1 and s2 each independently represent an integer of 0 to 3. and a tetracarboxylic dianhydride represented by the formula: The liquid composition also includes the polyamic acid having a weight average molecular weight of 10,000 or more.

[0030] The present invention provides, as an aspect

[13] , a film formed from a cured product of the liquid composition according to the aspect

[12] , The transmittance of light with a wavelength of 380 nm is 10% or more. The dielectric constant at a frequency of 1 GHz is 10 or less, The dielectric tangent at a frequency of 1 GHz is 0.02 or less, Also included are films with a water contact angle of 90° or greater.

[0031] The embodiment

[14] of the present invention is an embodiment in which the film of the embodiment

[13] is a single film having no support.

[0032] In addition, in the present specification and claims, the number of carbon atoms of a substituent is defined as C1, C6, C 10 For example, an alkyl group with one carbon atom is represented as a "C1 alkyl group," and an aryl group with 6 to 10 carbon atoms is represented as a "C 6-10 Aryl group”. Effect of the Invention

[0033] In the present invention, a liquid polyimide precursor having a specific polyamic acid concentration of 30 mass % or less having a fluorene skeleton is dried and then heated at a temperature of 400° C. or less to obtain a polyimide, so that a transparent film having high heat resistance, dielectric properties, and low water absorption can be formed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] [Liquid precursor preparation process] The method for producing a polyimide of the present invention includes a liquid precursor preparation step of preparing a liquid polyimide precursor that contains a polyamic acid, which is a reaction product of a diamine component containing a diamine represented by the formula (1) and a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride represented by the formula (2), and a solvent, and has a polyamic acid concentration of 30 mass % or less.

[0035] The liquid precursor preparation step is not particularly limited as long as it contains the polyamic acid and a solvent and the polyamic acid concentration is adjusted to 30 mass % or less. For example, the liquid precursor preparation step may be a first liquid precursor preparation step or a second liquid precursor preparation step described below.

[0036] First liquid precursor step: A liquid precursor preparation step that involves a two-step process of reacting a diamine component containing the diamine represented by formula (1) with a tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride represented by formula (2) in the presence of a first solvent to obtain a mixed solution containing a polyamic acid, and a concentration adjustment step of adding a second solvent to the mixed solution to adjust the polyamic acid concentration to 30 mass% or less to obtain the liquid polyimide precursor.

[0037] Second liquid precursor step: a liquid precursor preparation step of reacting a diamine component containing the diamine represented by the formula (1) with a tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride represented by the formula (2) in the presence of a solvent to obtain the liquid polyimide precursor having a polyamic acid concentration of 30 mass% or less.

[0038] As the liquid precursor preparation step, a first liquid precursor preparation step in which the reaction step and the adjustment step are combined is preferred, since the concentration of the polyamic acid can be easily adjusted, the productivity is excellent, and film formation can be easily performed.

[0039] (Diamine represented by formula (1)) The diamine component contains a diamine represented by the above formula (1) (hereinafter, may be referred to as "diamine (1)").

[0040] In the formula (1), Z 1 and Z 2 Examples of the arene ring (aromatic hydrocarbon ring) represented by the formula (1) include a monocyclic arene ring such as a benzene ring, a polycyclic arene ring, etc. Examples of the polycyclic arene ring include a condensed polycyclic arene ring (condensed polycyclic aromatic hydrocarbon ring), a ring-assembled arene ring (ring-assembled polycyclic aromatic hydrocarbon ring), etc.

[0041] The fused polycyclic arene ring includes, for example, fused bicyclic arene rings, fused tricyclic arene rings, and other fused bicyclic to tetracyclic arene rings. The fused bicyclic arene ring includes, for example, fused bicyclic C rings such as naphthalene ring and indene ring. 10-16 Examples of the fused tricyclic arene ring include fused tricyclic C arene rings such as anthracene ring and phenanthrene ring. 14-20 A preferred fused polycyclic arene ring is a fused polycyclic C ring such as a naphthalene ring. 10-14 It is an arene ring.

[0042] Examples of the ring assembly arene ring include biarene rings such as biphenyl ring, phenylnaphthalene ring, and binaphthyl ring; and terarene rings such as terphenyl ring. Preferred ring assembly arene rings are C 12-18 This is a biarene ring.

[0043] In the present specification and claims, a "ring assembly arene ring" refers to two or more ring systems (arene ring systems) directly linked by single bonds or double bonds, and the number of bonds directly linking the rings is one less than the number of ring systems. For example, as described above, a phenylnaphthalene ring, a binaphthyl ring, and the like are classified as ring assembly arene rings even though they have a fused polycyclic arene ring skeleton, and are clearly distinguished from "fused polycyclic arene rings" such as a naphthalene ring (non-ring assembly arene ring).

[0044] Preferred Ring Z 1 and Z 2 As for C 6-14 arene rings, and more preferably C rings such as benzene rings, naphthalene rings, and biphenyl rings. 6-12 C such as an arene ring, more preferably a benzene ring or a naphthalene ring 6-10 An arene ring, particularly a benzene ring, is preferred. Ring Z 1 The type of ring is Z 2 may be different, but are preferably the same.

[0045] Ring Z 1 , Z 2 The position of the amino group on the ring Z is not particularly limited. 1 , Z 2 When is a benzene ring, it is preferred that the substituent is at any one of the 2-, 3- or 4-positions, particularly the 3- or 4-position, and particularly the 4-position, of the phenyl group bonded to the 9-position of the fluorene ring.

[0046] Group X 1 and X 2 Examples of the halogen atom represented by the formula (1) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. These halogen atoms can be used alone or in combination of two or more. Among these, a fluorine atom is preferred.

[0047] Group X 1 and X 2 The numbers of substitutions n1 and n2 may each be an integer of 0 or more, and the ring Z 1 , Z 2 n1 and n2 may be different from each other, but are preferably the same. When n1 is 2 or more, X is 2 or more. 1 may be the same or different, and n2 and X 2 The same applies to the group X 1 The type of group is X 2 may be the same as or different from.

[0048] Group X 1 and X 2 The substitution position of ring Z is not particularly limited. 1 and Z 2 In the above formula, the substituent may be a substituent at any position other than the bonding position between the amino group and the 9-position of the fluorene ring, but the 3-position is preferred.

[0049] base R 1 and R 2Examples of the substituent represented by the formula (I) include an alkyl group, an alkoxy group, an acyl group, a nitro group, a cyano group, and a disubstituted amino group.

[0050] The alkyl group includes linear or branched alkyl groups, and C groups such as methyl, ethyl, propyl, isopropyl, n-butyl, and t-butyl groups. 1-10 Alkyl groups, preferably C 1-6 Alkyl groups, more preferably C 1-4 Examples of such groups include alkyl groups.

[0051] The alkoxy group is a C group such as a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, or a t-butoxy group. 1-10 Examples of the alkyl group include alkoxy groups.

[0052] Acyl groups include C such as acetyl groups. 1-6 Examples include alkyl-carbonyl groups.

[0053] The substituted amino group may be a mono or di-C group such as a monomethylamino group or a dimethylamino group. 1-4 Alkylamino groups; mono- or bis(C 1-4 alkyl-carbonyl)amino groups and the like.

[0054] Typical group R 1 and R 2 Examples of the R group include an alkyl group, an alkoxy group, an acyl group, a nitro group, and a cyano group. 1 and R 2 is an alkyl group, specifically, a C group such as a methyl group. 1-6 Alkyl groups; alkoxy groups, specifically, methoxy groups, etc. 1-4 An alkoxy group is particularly preferred; 1-4 It is an alkyl group.

[0055] The numbers of substitutions m1 and m2 are, for example, integers of 0 to 3, preferably integers of 0 to 2, more preferably 0 or 1, and even more preferably 0. When m1 and m2 are integers of 2 or more, two or more groups R 1 and R 2 The types may be the same or different.

[0056] R 3 Examples of the substituent represented by the formula (I) include a cyano group, a halogen atom, and an alkyl group. Examples of the halogen atom include the group X 1 and X 2 The halogen atoms exemplified as the halogen atoms of the above-mentioned can also be used as the alkyl group. 1 and R 2 Among these substituents, alkyl groups are preferred, and C 1-6 Alkyl groups are more preferred, and C 1-4 Alkyl groups are particularly preferred.

[0057] In addition, the group R 3 When the number of substitutions k is 2 or more, two or more groups R 3 The types of R may be the same or different, and two or more groups R substituted on different benzene rings. 3 The types of may be the same or different. 3 The bonding positions (substitution positions) of are not particularly limited as long as they are positions 1 to 8 of the fluorene ring, and examples thereof include positions 2, 7, and 2,7 of the fluorene ring.

[0058] The number of substitutions k may be, for example, an integer of 0 to 6, and is preferably an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, 0 or 1, stepwise, and most preferably 0. In addition, in the two benzene rings constituting the fluorene ring, the group R 3 The number of substitutions in each of the above may be different from each other, but is preferably the same.

[0059] As the diamine (1), Z 1and Z 2 is a benzene ring, and Z 1 and Z 2 is a benzene ring, and X 1 and X 2 Diamines in which n1 and n2 are 1 and n2 are 1 are particularly preferred.

[0060] Specific examples of diamine (1) include 9,9-bis(aminoaryl)fluorenes such as 9,9-bis(4-aminophenyl)fluorene; 9,9-bis(fluoro-aminoaryl)fluorenes such as 9,9-bis(3-fluoro-4-aminophenyl)fluorene; and the like. Among these, 9,9-bis(fluoro-amino C 6-10 aryl)fluorenes are preferred, with 9,9-bis(3-fluoro-4-aminophenyl)fluorene being particularly preferred.

[0061] (Other diamines) The diamine component may further contain other diamines in addition to the diamine (1).

[0062] The other diamine may be a diamine that does not have a 9,9-bisarylfluorene skeleton (a diamine other than the diamine represented by the formula (1)). Examples of the other diamine include aliphatic diamines, alicyclic diamines, and aromatic diamines. These other diamines may be used alone or in combination of two or more.

[0063] Examples of the aliphatic diamine include alkanediamines and aliphatic diamines having a heteroatom such as an oxygen atom or a sulfur atom.

[0064] Examples of alkanediamines include linear or branched C diamines such as ethylenediamine, trimethylenediamine, propylenediamine, tetramethylenediamine, 2-methyl-1,2-propanediamine, 2-methyl-1,3-propanediamine, pentamethylenediamine, 1,3-pentanediamine, 2,2-dimethyl-1,3-propanediamine, hexamethylenediamine, 2-methylpentamethylenediamine, 2,3-dimethyl-2,3-butanediamine, heptamethylenediamine, octamethylenediamine, 2,5-dimethyl-2,5-hexanediamine, nonamethylenediamine, 2-methyloctamethylenediamine, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, decamethylenediamine, undecamethylenediamine, and dodecamethylenediamine. 2-20 Alkanediamines and the like.

[0065] Examples of the aliphatic diamine having a heteroatom include aliphatic (poly)ether-based diamines, aliphatic sulfide-based diamines, and N,N-bis(aminoalkyl)-alkylamines.

[0066] Examples of the (poly)ether diamines include bis(aminoalkyl) ethers such as bis(2-aminoethyl) ether; and (poly)alkylene glycol bis(aminoalkyl) ethers such as ethylene glycol bis(2-aminoethyl) ether, 1,4-butanediol bis(3-aminopropyl) ether, diethylene glycol bis(3-aminopropyl) ether, triethylene glycol bis(2-aminoethyl) ether, polyethylene glycol diamine, and polypropylene glycol diamine.

[0067] Examples of the sulfide diamines include bis(aminoalkyl)sulfides such as bis(2-aminoethyl)sulfide.

[0068] N,N-bis(aminoalkyl)-alkylamines include N,N-bis(3-aminopropyl)methylamine and the like.

[0069] Examples of the alicyclic diamine include alicyclic diamines having a monocyclic skeleton, and alicyclic diamines having a bridged cyclic or spirocyclic skeleton.

[0070] Examples of alicyclic diamines having a monocyclic skeleton include diamines having a cycloalkane skeleton and diamines having a heterocyclic skeleton.

[0071] Examples of diamines having a cycloalkane skeleton include cycloalkane diamines such as cyclohexane diamine (1,2-cyclohexane diamine, 1,3-cyclohexane diamine, 1,4-cyclohexane diamine); bis(aminoalkyl)cycloalkanes such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; bis(aminocycloalkyl)alkanes such as bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane, isophorone diamine, and menthene diamine.

[0072] Examples of diamines having a heterocyclic skeleton include piperazines such as piperazine, 2-methylpiperazine, 2-ethylpiperazine, 2,5-dimethylpiperazine, and N-(2-aminoethyl)piperazine.

[0073] Examples of alicyclic diamines having a bridged cyclic skeleton include bi- or tricycloalkane diamines such as adamantane-1,3-diamine, 2,5- or 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, bis(aminomethyl)tricyclo[5.2.1.0 2,6 ]decane and other bis(aminoalkyl)bi- or tricycloalkanes.

[0074] Examples of alicyclic diamines having a spirocyclic skeleton include 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0075] Examples of aromatic diamines include diaminoarenes such as phenylenediamine, toluenediamine, diaminoanisole, naphthalenediamine, benzidine, o-tolidine, dimethoxybenzidine, and 4,4"-diamino-p-terphenyl; aminoaralkylamines such as aminobenzylamine; bis(aminoalkyl)arenes such as xylylenediamine; bis(4-aminophenyl)methane, bis(4-amino-3-methylphenyl)methane, bis(4-amino-3,5-dimethylphenyl)methane, 1,2-bis(4-aminophenyl)ethane, 2,2-bis(4-aminophenyl)propane, and 2,2-bis(4-aminophenyl)hexafluoropropane; bis(aminoaryl)ethers such as bis(4-aminophenyl)ether and 3,4'-diaminodiphenyl ether; and bis( bis(aminoaryl)ketones such as bis(4-aminophenyl)ketone; bis(aminoaryl)sulfides such as bis(4-aminophenyl)sulfide; bis(aminoaryl)sulfones such as bis(4-aminophenyl)sulfone; bis(aminoaryl)amides such as 4,4'-diaminobenzanilide; bis[(aminoaryloxy)aryl]alkanes such as 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane; bis[(aminophenoxy)phenyl]arenes such as 1,4-bis(4-aminophenoxy)benzene and 4,4'-bis(4-aminophenoxy)biphenyl; and bis[(aminoaryloxy)aryl]sulfones such as bis[4-(4-aminophenoxy)phenyl]sulfone.

[0076] These other diamines can be used alone or in combination of two or more. Among these, aromatic diamines are widely used.

[0077] (Composition of diamine component) The diamine component may contain diamine (1), and the proportion of diamine (1) in the total diamine components is preferably 50 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, and most preferably 100 mol %. 1 and Z 2 is a benzene ring, and X 1 and X 2 is a fluorine atom, and n1 and n2 are 1. In particular, the diamine component may be a proportion of diamine (1) in which Z 1 and Z 2 is a benzene ring, and X 1 and X 2 is a fluorine atom, n1 and n2 are 1, and m1, m2 and k are 0. If the proportion of diamine (1) is too small, there is a risk that the dielectric properties and water absorption rate cannot be reduced.

[0078] The proportion of the other diamines in the total diamine components is preferably 50 mol % or less, more preferably 20 mol % or less, even more preferably 10 mol % or less, and most preferably 0 mol %.

[0079] (Tetracarboxylic acid dianhydride represented by formula (2)) The tetracarboxylic dianhydride component contains a tetracarboxylic dianhydride represented by the above formula (2) (hereinafter, may be referred to as "tetracarboxylic dianhydride (2)").

[0080] The group X in the formula (2) 3 In the formula (I), the group -OX 4 -O-X 4 The organic group represented by the formula (I) is usually a group containing a hydrocarbon, and may be, for example, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or a group containing an aromatic ring.

[0081] Aliphatic hydrocarbon groups include C groups such as ethylene, propylene (1,2-propanediyl), trimethylene, 1,2-butanediyl, and tetramethylene. 2-6 An alkylene group is exemplified.

[0082] Examples of alicyclic hydrocarbon groups include C groups such as cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, and cyclododecane-diyl groups. 3-12 Examples thereof include a cycloalkylene group.

[0083] Examples of the group containing an aromatic ring include arylene groups (for example, arylene groups such as phenylene, tolylene, xylylene, and naphthylene; biphenylene groups such as 4,4'-biphenylene and 3,3'-biphenylene; and bisphenol residues such as dimethyldiphenylmethane-4,4'-diyl group (bisphenol A residue), diphenylmethane-4,4'-diyl group (bisphenol-F residue), diphenylcarbonyl-4,4'-diyl group, diphenylsulfonyl-4,4'-diyl group (bisphenol-S residue), diphenylthio-4,4'-diyl group, and diphenyloxy-4,4'-diyl group.

[0084] Group X 3 As the alkyl group, a direct bond, -O-, -CO- and the like are generally used, and -O- (ether bond) is preferable.

[0085] base R 4 and R 5 Examples of the substituent represented by the formula (1) include a halogen atom, an alkyl group, an alkoxy group, an acyl group, a nitro group, a cyano group, and a disubstituted amino group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Other examples of the substituent include the group R 1 and R 2 The halogen atoms and the substituents can be used alone or in combination of two or more. Among these, fluorine atoms, C 1-4 Alkyl group, C 1-4 An alkoxy group is commonly used, with a fluorine atom being preferred.

[0086] The numbers of substitutions s1 and s2 are integers of 0 to 3, preferably integers of 0 to 2, more preferably 0 or 1, and even more preferably 0. When s1 and s2 are integers of 2 or more, two or more groups R 4and R 5 The types may be the same or different.

[0087] The tetracarboxylic dianhydride (2) is, for example, X 3 is preferably a tetracarboxylic dianhydride in which X is an ether bond, 3 Particularly preferred is a tetracarboxylic dianhydride in which s1 is an ether bond and s2 is 0.

[0088] (Other tetracarboxylic dianhydrides) The tetracarboxylic dianhydride component may further contain other tetracarboxylic dianhydrides in addition to the tetracarboxylic dianhydride (2). Examples of the other tetracarboxylic dianhydrides include monocyclic aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, and alicyclic tetracarboxylic dianhydrides such as the tetracarboxylic dianhydride (2) or hydrogenated products of the monocyclic aromatic tetracarboxylic dianhydrides.

[0089] These other tetracarboxylic dianhydrides can be used alone or in combination of two or more. Among these, monocyclic aromatic tetracarboxylic dianhydrides are widely used.

[0090] (Composition of Tetracarboxylic Dianhydride Component) The tetracarboxylic dianhydride component may contain tetracarboxylic dianhydride (2), and the proportion of tetracarboxylic dianhydride (2) in the total tetracarboxylic dianhydride component is preferably 50 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, and most preferably 100 mol %. This proportion is determined by the following formula: 3 In particular, the tetracarboxylic dianhydride component may be a tetracarboxylic dianhydride (2) in which X is an ether bond. 3 It may be a tetracarboxylic dianhydride (2) alone in which s1 is an ether bond and s2 are 0. If the proportion of the tetracarboxylic dianhydride (2) is too small, there is a risk that the dielectric properties and water absorption rate cannot be reduced.

[0091] The proportion of other tetracarboxylic dianhydrides in the entire tetracarboxylic dianhydride component is preferably 50 mol % or less, more preferably 20 mol % or less, even more preferably 10 mol % or less, and most preferably 0 mol %.

[0092] (Molar ratio of diamine component to tetracarboxylic dianhydride component) The molar ratio of the diamine component to the tetracarboxylic dianhydride component can be selected from the range of about diamine component / tetracarboxylic dianhydride component=5 / 1 to 1 / 5, preferably 3 / 1 to 1 / 3, further preferably 2 / 1 to 1 / 2, more preferably 1.5 / 1 to 1 / 1.5, and most preferably 1.2 / 1 to 1 / 1.2, and may be approximately equimolar.

[0093] (solvent) In the reaction step of the first liquid precursor step and the second liquid precursor step, the reaction between the diamine component and the tetracarboxylic dianhydride component may be carried out in the presence of a solvent (first solvent).

[0094] Examples of the solvent (first solvent) include cyclic ethers such as tetrahydrofuran and 1,4-dioxane; esters such as ethyl acetate; chain ketones such as acetone and methyl ethyl ketone; cyclic ketones such as cyclohexanone; halogenated hydrocarbons such as dichloromethane and chloroform; amides such as dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone (NMP); nitriles such as acetonitrile and propionitrile; and sulfoxides such as dimethyl sulfoxide. These solvents can be used alone or in combination of two or more. Among these, amides, halogen-containing solvents, and nitriles are preferred, amides are more preferred, and pyrrolidones such as NMP are most preferred.

[0095] In the reaction step, the proportion of the first solvent is, for example, 10 to 10,000 parts by mass, preferably 30 to 1,000 parts by mass, further preferably 50 to 500 parts by mass, more preferably 100 to 300 parts by mass, and most preferably 150 to 250 parts by mass, relative to 100 parts by mass in total of the diamine component and the tetracarboxylic dianhydride component.

[0096] In the second liquid precursor step, the solvent ratio can be selected depending on the desired polyamic acid concentration.

[0097] (Other ingredients) In the reaction step of the first liquid precursor step and the second liquid precursor step, other components may be blended in addition to the diamine component and the tetracarboxylic dianhydride component during the reaction. Examples of the other components include reaction accelerators, reaction retarders, and stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, light resistance stabilizers, etc.). These other components may be used alone or in combination of two or more. The total proportion of the other components may be 30 parts by mass or less (for example, 0.1 to 30 parts by mass) relative to 100 parts by mass of the total amount of the diamine component and the tetracarboxylic dianhydride component, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less.

[0098] (Reaction conditions) In the reaction step of the first liquid precursor step and the second liquid precursor step, the diamine component and the tetracarboxylic dianhydride component may be reacted in an atmosphere of an inert gas, for example, nitrogen gas; or a rare gas such as helium or argon, and it is preferable to react them in an atmosphere of an inert gas such as argon gas.

[0099] The diamine component and the tetracarboxylic dianhydride component may be reacted under normal pressure or under reduced pressure. The reaction temperature may be selected from the range of about 0 to 100°C, and is preferably 5 to 50°C, more preferably 10 to 40°C, more preferably 15 to 35°C, and most preferably 20 to 30°C, or may be room temperature. The reaction time is, for example, 1 to 100 hours, preferably 5 to 50 hours, more preferably 10 to 30 hours, and more preferably 15 to 25 hours.

[0100] In the reaction step of the first liquid precursor step, the total amount of the diamine component and the tetracarboxylic dianhydride component may be 25% by mass or more in the total amount of the first solvent, the diamine component, and the tetracarboxylic dianhydride component, for example, 25 to 70% by mass, preferably 28 to 50% by mass, more preferably 30 to 45% by mass, and even more preferably 32 to 40% by mass. If the total amount of the diamine component and the tetracarboxylic dianhydride component is too small, the film-forming property may decrease, making it difficult to form a film or to form a thin film, or bubbles or cracks may occur in the polyimide production process due to poor solvent volatilization in the drying step.

[0101] On the other hand, in the second liquid precursor step, the diamine component and the tetracarboxylic dianhydride component can be used in such a ratio that the polyamic acid concentration in the mixed liquid after the reaction becomes a target concentration.

[0102] (Polyamic acid) In the reaction step of the first liquid precursor step and the second liquid precursor step, the weight average molecular weight Mw of the polyamic acid which is the reaction product of the diamine component and the tetracarboxylic dianhydride component may be 10,000 or more, for example, 10,000 to 1,000,000, preferably 30,000 to 800,000, further preferably 50,000 to 500,000, more preferably 100,000 to 300,000, and most preferably 150,000 to 250,000. If the weight average molecular weight of the polyamic acid is too small, it may be difficult to form it into a film.

[0103] In this specification and claims, the weight average molecular weight of the polyamic acid can be measured by gel permeation chromatography (GPC) using polystyrene as a standard substance, and in detail, can be measured by the method described in the examples below.

[0104] (Adjustment of polyamic acid concentration) In the first liquid precursor process, the mixed liquid obtained in the reaction process has a polyamic acid concentration adjusted to a higher concentration than a target concentration, and in the concentration adjustment process, the polyamic acid concentration is adjusted to 30 mass % or less by adding a second solvent to the mixed liquid.

[0105] Examples of the second solvent include the solvents exemplified as the first solvent used in the reaction step. The solvents can be used alone or in combination of two or more. Among the solvents, amides, halogen-containing solvents, and nitriles are preferred, amides are more preferred, and pyrrolidones such as N-methyl-2-pyrrolidone are most preferred. This solvent may be different from the solvent used in the reaction step, but is preferably the same solvent.

[0106] On the other hand, in the second liquid precursor step, a solvent can be used as a reaction solvent in such a ratio that the concentration of polyamic acid in the mixed liquid after the reaction becomes a target concentration.

[0107] (Defoaming treatment) In the preparation step, it is preferable to subject the mixed liquid containing the polyamic acid to a degassing treatment. In the production method of the present invention, by subjecting the mixed liquid to a degassing treatment, a film having excellent mechanical properties can be easily formed.

[0108] In the first liquid precursor step, the mixed liquid obtained in the reaction step may be degassed, or the mixed liquid in which the polyamic acid concentration has been adjusted to 30 mass % or less in the concentration adjustment step may be degassed. Of these, it is preferable to degas the mixed liquid obtained in the reaction step and in which the polyamic acid concentration has not been adjusted to 30 mass % or less.

[0109] In the second liquid precursor step, it is preferable to subject the obtained mixed liquid (mixed liquid having a polyamic acid concentration of 30 mass % or less) to a degassing treatment.

[0110] As the defoaming treatment, a conventional defoaming treatment can be used. Examples of the conventional defoaming treatment include vacuum (reduced pressure) defoaming treatment, ultrasonic defoaming treatment, centrifugal defoaming treatment, stirring defoaming treatment, and static defoaming treatment. Among these, vacuum (reduced pressure) defoaming treatment is preferred.

[0111] The defoaming treatment may be performed by heating. The heating temperature is, for example, 40 to 80° C., and preferably 50 to 70° C. The defoaming treatment may be performed while increasing the temperature from room temperature to the above temperature.

[0112] (Liquid polyimide precursor) The liquid polyimide precursor obtained in the preparation step (first liquid precursor step or second liquid precursor step) has a polyamic acid concentration adjusted to 30% by mass or less in the liquid polyimide precursor, for example, 5 to 30% by mass, preferably 10 to 28% by mass, further preferably 15 to 25% by mass, more preferably 17 to 25% by mass, and most preferably 18 to 23% by mass. If the polyamic acid concentration is too high, the film formability may decrease, making film formation or thinning difficult, or foaming or cracking may occur in the polyimide production process due to poor solvent volatilization in the drying step.

[0113] In this liquid polyimide precursor, examples of the solvent include the solvents exemplified as the first solvent. The solvents can be used alone or in combination of two or more. The solvent may be two or more solvents, such as when different types of solvents are used as the first and second solvents in the first liquid precursor process, but a single solvent is preferred. Furthermore, among the solvents, amides, halogen-containing solvents, and nitriles are preferred, amides are more preferred, and pyrrolidones such as NMP are most preferred.

[0114] A suitable liquid polyimide precursor may be a liquid composition containing a polyamic acid and a solvent, the polyamic acid having a concentration of 30 mass % or less, the polyamic acid being a reaction product of the polyamic acid represented by the formula (1a) and the tetracarboxylic dianhydride represented by the formula (2a), and the polyamic acid having a weight average molecular weight of 10,000 or more. This liquid composition may be a liquid composition that has been subjected to a degassing treatment.

[0115] In the formula (1a), X 1 and X 2 Halogen atoms represented by R 1 ~R 3 Any of the substituents represented by the formula (1) including preferred embodiments thereof may be selected from the halogen atoms and substituents described in the formula (1) above. Any of the numbers of substitutions n1, n2, m1, m2, and k may be selected from the numbers of substitutions described in the formula (1) above including preferred embodiments thereof.

[0116] In the formula (2a), R 4 and R 5 The substituents represented by the formula (2) can be selected from those described in the formula (2) above, including preferred embodiments. The numbers of substitutions s1 and s2 can also be selected from those described in the formula (2) above, including preferred embodiments.

[0117] The liquid polyimide precursor may further contain a polyimide. The polyimide may be a polyimide different from the polyimide obtained by heating the polyamic acid in the next step (e.g., a polyimide having a different molecular weight, etc.), or preferably the same polyimide. The proportion of the polyimide may be 100 parts by mass or less, for example, 1 to 100 parts by mass, preferably 5 to 50 parts by mass, relative to 100 parts by mass of the polyamic acid.

[0118] The liquid polyimide precursor may further contain other components. Examples of the other components include crosslinking or curing agents, defoamers, coating improvers, thickeners, lubricants, stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, light resistance stabilizers, etc.), dyes, pigments, antistatic agents, flame retardants, flame retardant assistants, antiblocking agents, fillers, gelling agents, etc. These other components may be used alone or in combination of two or more. The total proportion of the other components may be 30 parts by mass or less (for example, 0.1 to 30 parts by mass) relative to 100 parts by mass of polyamic acid, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less.

[0119] The liquid polyimide precursor can be used as a liquid composition (varnish or coating composition) for producing a polyimide.

[0120] [Drying process] The method for producing a polyimide of the present invention includes a drying step of drying the liquid polyimide precursor obtained in the preparation step to obtain a polyimide precursor.

[0121] The method for drying the liquid polyimide precursor is not particularly limited, and may be natural drying, but from the standpoint of productivity, etc., a method of drying by heating is preferred.

[0122] In the method of drying by heating, the heating temperature may be 150° C. or lower, preferably 100° C. or lower, and from the viewpoint of easiness in forming a film, more preferably 90° C. or lower, for example, 40 to 90° C., preferably 50 to 90° C., more preferably 60 to 85° C., and more preferably 70 to 85° C. If the heating temperature is too high, it may be difficult to form a film.

[0123] The drying time can be appropriately selected depending on the heating temperature and the like, and is, for example, 1 to 180 minutes, preferably 5 to 120 minutes, further preferably 10 to 60 minutes, and even more preferably 20 to 40 minutes.

[0124] The shape of the liquid polyimide precursor subjected to the drying step can be appropriately selected depending on the shape of the target molded product. For example, when a film or sheet is produced, the shape may be a coating film obtained by coating the liquid polyimide precursor on a substrate. Conventional coating methods can be used. Conventional coating methods include flow coating, spin coating, spray coating, screen printing, casting, bar coating, curtain coating, roll coating, gravure coating, dipping, and slit methods.

[0125] [Polyimide manufacturing process] The method for producing a polyimide of the present invention includes a polyimide production step of heating the polyimide precursor obtained in the drying step at 400° C. or less to obtain a polyimide. The polyimide production step may be a thermosetting step, and the obtained polyimide may be a cured product (thermosetting product) of a liquid polyimide precursor. In the present invention, a transparent film having low dielectric properties and low water absorption can be produced by heating the polyimide precursor at a temperature of 400° C. or less.

[0126] The temperature for curing the polyimide precursor is, for example, 150 to 400° C., preferably 200 to 390° C., further preferably 300 to 380° C., further preferably 330 to 370° C., and most preferably 340 to 360° C. If the curing temperature is too high, it may be difficult to produce a transparent film with low dielectric properties and water absorption.

[0127] The pressure conditions for curing may be normal pressure or reduced pressure (or under vacuum), or normal pressure or increased pressure, with reduced pressure (or under vacuum) being preferred.

[0128] The curing time is, for example, 10 minutes to 2 hours, preferably 20 minutes to 1.5 hours, and more preferably 30 minutes to 1.2 hours.

[0129] [Polyimide] The polyimide of the present invention obtained by the above-mentioned production method has excellent transparency. In the polyimide of the present invention, the light transmittance at a wavelength of 360 nm may be 0.5% or more, for example, 0.5 to 10%, preferably 1 to 8%, further preferably 2 to 7%, and further preferably 2.5 to 5%.

[0130] The light transmittance at a wavelength of 380 nm may be 10% or more, for example, 10 to 90%, preferably 20 to 80%, further preferably 30 to 70%, more preferably 40 to 60%, and most preferably 50 to 55%.

[0131] The light transmittance at a wavelength of 400 nm may be 30% or more, for example, 30 to 99%, preferably 40 to 95%, further preferably 50 to 90%, even more preferably 60 to 80%, and most preferably 70 to 75%.

[0132] The light transmittance at a wavelength of 600 nm may be 40% or more, for example, 40 to 99.9%, preferably 50 to 99%, further preferably 70 to 98%, more preferably 80 to 95%, and most preferably 85 to 90%.

[0133] The light transmittance at a wavelength of 800 nm may be 40% or more, for example, 40 to 99.9%, preferably 50 to 99%, further preferably 70 to 98%, more preferably 80 to 95%, and most preferably 85 to 90%.

[0134] In the present specification and claims, the light transmittance can be measured for a film having a thickness of 20 to 35 μm using an ultraviolet-visible spectrophotometer, and in detail, can be measured by the method described in the examples below.

[0135] The polyimide of the present invention has excellent electrical properties, and exhibits a low relative dielectric constant and a low dielectric loss tangent. The relative dielectric constant at a frequency of 1 GHz is, for example, 10 or less, preferably 6 or less, more preferably 2 to 5.5, more preferably 3 to 5, and most preferably 3.5 to 4.5. The dielectric loss tangent at a frequency of 1 GHz is, for example, 0.02 or less, preferably 0.001 to 0.015, more preferably 0.003 to 0.01, more preferably 0.004 to 0.008, and most preferably 0.005 to 0.0075.

[0136] The relative dielectric constant at a frequency of 10 GHz is, for example, 10 or less, preferably 6 or less, more preferably 2 to 5.5, more preferably 3 to 5, and most preferably 3.5 to 4.5. The dielectric loss tangent at a frequency of 10 GHz is, for example, 0.03 or less, preferably 0.001 to 0.03, more preferably 0.003 to 0.025, more preferably 0.005 to 0.02, and most preferably 0.01 to 0.015. If the relative dielectric constant or dielectric loss tangent is too high, there is a risk that applications will be limited from the viewpoint of electrical properties.

[0137] In this specification and claims, the dielectric constant and dielectric loss tangent can be measured in accordance with ASTM D 2520 (cavity resonator perturbation method), and more specifically, can be measured by the method described in the examples below.

[0138] The polyimide of the present invention has a low water absorption rate and exhibits high hydrophobicity. The water contact angle of the polyimide of the present invention may be 90° or more, for example, 90 to 120°, preferably 95 to 115°, and more preferably 100 to 110°.

[0139] In the present specification and claims, the water contact angle can be measured using a contact angle meter, and more specifically, can be measured by the method described in the examples below.

[0140] The polyimide of the present invention has excellent heat resistance. The decomposition initiation temperature of the polyimide of the present invention may be 500° C. or higher, for example, 500 to 700° C., preferably 530 to 650° C., and more preferably 550 to 600° C. The remaining amount of the polyimide of the present invention at 600° C. may be 50% or higher, for example, 50 to 99%, preferably 60 to 95%, and more preferably 80 to 90%.

[0141] In the present specification and claims, the decomposition starting temperature and the residual amount at 600° C. can be measured in accordance with JIS K 7120, and more specifically, can be measured by the method described in the examples below.

[0142] The polyimide of the present invention has a high molecular weight and is excellent in mechanical properties and moldability (productivity), and can be used as molded articles of various shapes. The shape of the molded article formed from the polyimide of the present invention can be selected according to the application, and may be, for example, a one-dimensional structure (such as a fiber), a two-dimensional structure (such as a film, sheet, or plate), or a three-dimensional structure (such as a tube, rod, hollow, housing, or casing). Among these, two-dimensional structures such as a film or sheet are preferred from the viewpoint of productivity. The thickness of the film-shaped polyimide molded article can be selected from a wide range of about 0.01 μm to 50 mm, and is, for example, 5 to 45 μm, preferably 10 to 40 μm, and more preferably 20 to 35 μm. EXAMPLES

[0143] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Details of the materials used in the examples and the evaluation methods used in the examples are as follows.

[0144] [material] (Diamine component) BOFAF: 9,9-bis(4-amino-3-fluorophenyl)fluorene, CAS.127926-65-2, manufactured by Osaka Gas Chemicals Co., Ltd. BAF: 9,9-bis(4-aminophenyl)fluorene, CAS.15499-84-0, manufactured by Osaka Gas Chemicals Co., Ltd. PDA: Paraphenylenediamine, CAS.106-50-3, Fujifilm Wako Pure Chemical Industries, Ltd.

[0145] (Tetracarboxylic acid dianhydride component) OPDA: 4,4'-oxydiphthalic anhydride, CAS.1823-59-2, manufactured by Tokyo Chemical Industry Co., Ltd. (TCI) 6FDA: 4,4'-(Hexafluoroisopropylidene)diphthalic anhydride, CAS.1107-00-2), manufactured by TCI PMDA: Pyromellitic anhydride, CAS.89-32-7, manufactured by TCI

[0146] (solvent) NMP: 1-methyl-2-pyrrolidone, CAS.872-50-4, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0147] [Weight average molecular weight Mw] The weight average molecular weight of the resulting polyamic acid was measured using the following measuring instrument under the following measuring conditions.

[0148] (Measuring equipment) Chromatography system: GPC (Shodex "GPC-104") Pump: LC-10ADvp (Shimadzu Corporation) Detector: Shodex RI-71 (Showa Denko Co., Ltd.) Column: Shodex GPC KF-806L, KF-802 (Showa Denko K.K.), column temperature: 50°C Eluent: NMP (with lithium bromide and phosphoric acid (30 mmol / L each) added) Standard material: polystyrene Flow rate: 0.8mL / min.

[0149] (Measurement conditions) The sample was adjusted to a concentration of 0.2 w / v%, pretreated with a membrane filter, and then measured.

[0150] [Film formability] The film-forming properties of the polyimide film were evaluated according to the following criteria.

[0151] ○: A film with excellent mechanical properties was formed. △: Although a film was formed, it was brittle and could not be used for evaluation testing. ×: Film formation was not possible.

[0152] [UV-vis transmittance (%T)] The transmittance of the polyimide film was measured using a UV-visible spectrophotometer V-630 (manufactured by JASCO Corporation).

[0153] [Dielectric properties] Test pieces (L80 (mm) × W1.5 (mm) × t0.01~0.03 (mm)) were prepared using polyimide film, and the dielectric constant and dielectric loss tangent at 1 GHz and 10 GHz were measured in a test environment of 23℃±1℃ and 50% RH±5% RH in accordance with ASTM D2520 (cavity resonator perturbation method) using the following measuring equipment.

[0154] (Measuring equipment) PNA network analyzer N5222B (Keysight Technologies, Inc.) Cavity resonator for 1GHz: CP431 (manufactured by Kanto Electronics Application Development Co., Ltd.) Cavity resonator for 10 GHz: CP431 (manufactured by Kanto Electronics Application Development Co., Ltd.).

[0155] [Water contact angle (hydrophobicity evaluation)] 1.0 μL of ultrapure water was dropped onto the polyimide film, and the water drop angle was measured using a contact angle meter DMo-501 (Kyowa Interface Science Co., Ltd.) Six measurements were taken, and the average of the four results excluding the maximum and minimum measurements was taken as the water contact angle.

[0156] [Decomposition temperature and residual amount at 600℃ (TG-DTA)] The measurements were carried out in accordance with JIS K 7120 using a thermogravimetry-differential thermal analyzer (TG-DTA) ("TG-DTA 8122" manufactured by Rigaku Corporation).

[0157] Example 1 The reactor was dried under reduced pressure and replaced with argon, and BOFAF (7.7123 g, 0.02 mol) and 29 g of NMP were added so that the concentration of the resulting polyamic acid was 33% by mass, followed by stirring. OPDA (6.3312 g, 0.02 mol) was added at 0 to 15°C, and the mixture was reacted at 25°C for 20 hours to synthesize polyamic acid A (BOFAF / OPDA, weight average molecular weight 210,000), and a mixed solution containing polyamic acid A was obtained.

[0158] The obtained mixture containing polyamic acid A was subjected to a degassing treatment under vacuum (reduced pressure), and NMP was added so that the polyamic acid concentration became 20% by mass, to prepare a polyimide precursor. The polyimide precursor was applied to a heat-resistant glass plate using an applicator, dried at 80°C for 30 minutes, and then heated at 350°C for 1 hour to obtain a polyimide film (thickness 30 μm). The obtained polyimide film could be obtained as an independent single film even when peeled off from the glass plate.

[0159] Example 2 The reactor was dried under reduced pressure and replaced with argon, and BAF (6.9794 g, 0.02 mol) and 53 g of NMP were added so that the concentration of the resulting polyamic acid was 20% by mass, followed by stirring. OPDA (6.3312 g, 0.02 mol) was added at 0 to 15°C, and the mixture was allowed to react at 25°C for 20 hours to synthesize polyamic acid B (BAF / OPDA, weight average molecular weight 110,000), and a polyimide precursor was obtained.

[0160] The polyimide precursor was applied onto a heat-resistant glass plate using an applicator, dried at 80° C. for 30 minutes, and then heated at 350° C. for 1 hour to obtain a polyimide film (thickness: 33 μm). The obtained polyimide film could be obtained as an independent film even when peeled off from the glass plate.

[0161] Comparative Example 1 The reactor was dried under reduced pressure and replaced with argon, and PDA (3.3456 g, 0.03 mol) and 51 g of NMP were added so that the concentration of the resulting polyamic acid was 20 mass%, and the mixture was stirred at 50° C. OPDA (9.4976 g, 0.03 mol) was added at 0 to 15° C., and the mixture was reacted at 25° C. for 20 hours to synthesize polyamic acid C (PDA / OPDA, weight average molecular weight 51,000), and a polyimide precursor was obtained.

[0162] The polyimide precursor was applied onto a heat-resistant glass plate using an applicator, dried at 80° C. for 30 minutes, and then heated at 350° C. for 1 hour to obtain a polyimide film (thickness: 19 μm).

[0163] Comparative Example 2 A mixed solution containing the polyamic acid A synthesized in Example 1 at a concentration of 30% by mass was applied onto a heat-resistant glass plate using an applicator, dried at 80°C for 10 minutes, and then heated at 300°C for 1 hour under vacuum conditions, but a polyimide film could not be obtained.

[0164] Comparative Example 3 A mixed liquid containing the polyamic acid A synthesized in Example 1 at a concentration of 30% by mass was degassed in a vacuum (reduced pressure), applied to a heat-resistant glass plate using an applicator, dried at 80°C for 30 minutes, and then heated at 350°C under vacuum conditions for 1 hour to obtain a polyimide film.

[0165] In Examples 1 and 2 and Comparative Examples 1 to 3, the conditions for producing the polyimides are shown in Table 1, and the evaluation results are shown in Table 2.

[0166] [Table 1]

[0167] [Table 2]

[0168] As is clear from the results in Table 2, transparent films having excellent dielectric properties, high hydrophobicity and heat resistance were obtained in the Examples. In particular, the polyimide film of Example 1 was highly excellent in transparency and hydrophobicity. In contrast, the polyimide film of Comparative Example 1 had low transparency and was colored.

[0169] On the other hand, in Comparative Example 2, it was not possible to form a film, and in Comparative Example 3, the obtained polyimide film was too brittle to be taken out as a single film, and therefore could not be subjected to evaluation tests. [Industrial Applicability]

[0170] The polyimide of the present invention can be suitably used for applications requiring high transparency and heat resistance, such as substrates for flexible display devices such as displays for organic electroluminescent devices (OLEDs), displays for liquid crystal devices, TFT substrates, flexible printed circuit boards, flexible OLED surface lighting substrates, and substrate materials for electronic paper, as well as protective films and resins for machine parts or devices (automobiles, aerospace materials, sensors, sliding members, etc.).

Claims

1. Formula (1): 【Chemistry 1】 (In the formula, Z １ and Z ２ each independently represents an arene ring, X １ and X ２ each independently represents a halogen atom; n1 and n2 each independently represent an integer of 0 or more; R １ and R ２ each independently represents a substituent; m1 and m2 each independently represent an integer of 0 or more; R ３ represents a substituent, and k represents an integer of 0 to 8. A diamine component containing a diamine represented by the formula: Formula (2): 【Chemistry 2】 [In the formula, X ３ represents a direct bond, -O-, -CO-, -S-, or -SO ２ -or-O-X ４ -O- (wherein, X ４ represents a divalent organic group), R ４ and R ５ each independently represents a substituent, and s1 and s2 each independently represent an integer of 0 to 3. a liquid precursor preparation step of preparing a liquid polyimide precursor comprising a polyamic acid which is a reaction product of a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride represented by the formula: A drying step of drying the liquid polyimide precursor to obtain a polyimide precursor; and a polyimide production step of heating the polyimide precursor obtained in the drying step at 400° C. or less to obtain a polyimide.

2. The method according to claim 1, wherein the heating temperature in the drying step is 90° C. or lower.

3. 3. The process according to claim 1, wherein the solvent is an amide.

4. 3. The method according to claim 1, wherein the preparing step comprises: a reaction step of reacting the diamine component with the tetracarboxylic dianhydride component in the presence of a first solvent to obtain a mixed solution containing a polyamic acid; and a concentration adjusting step of adding a second solvent to the mixed solution to adjust a concentration of the polyamic acid to 30 mass% or less to obtain the liquid polyimide precursor.

5. The method according to claim 4 , wherein the mixed liquid is subjected to a degassing treatment in the concentration adjusting step.

6. In the formula (1), Z １ and Z ２ is a benzene ring, and X １ and X ２ The process according to claim 1 or 2, wherein n1 and n2 are each a fluorine atom and n2 is 1.

7. In the formula (2), X ３ The method according to claim 1 or 2, wherein is -O-.

8. 3. The method according to claim 1, wherein the diamine component is the diamine represented by the formula (1) alone, and the tetracarboxylic dianhydride component is the tetracarboxylic dianhydride represented by the formula (2) alone.

9. 3. The method according to claim 1, wherein the polyamic acid has a weight average molecular weight of 10,000 or more.

10. A polyimide obtained by the process according to claim 1 or 2.

11. The polyimide according to claim 10, which is in the form of a film or sheet.

12. A liquid composition comprising a polyamic acid and a solvent, The polyamic acid concentration is 30% by mass or less, The polyamic acid has the formula (1a): 【Chemistry 3】 (In the formula, X １ and X ２ each independently represents a halogen atom; n1 and n2 each independently represent an integer of 0 or more; R １ and R ２ each independently represents a substituent; m1 and m2 each independently represent an integer of 0 or more; R ３ represents a substituent, and k represents an integer of 0 to 8. and a diamine represented by the formula: Formula (2a): 【Chemistry 4】 (In the formula, R ４ and R ５ each independently represents a substituent, and s1 and s2 each independently represent an integer of 0 to 3. and a tetracarboxylic dianhydride represented by the formula: The liquid composition, wherein the polyamic acid has a weight average molecular weight of 10,000 or more.

13. A film formed from a cured product of the liquid composition according to claim 12, The transmittance of light having a wavelength of 380 nm is 10% or more, The dielectric constant at a frequency of 1 GHz is 10 or less, The dielectric tangent at a frequency of 1 GHz is 0.02 or less, A film having a water contact angle of 90° or more.

14. 14. The film according to claim 13, which is a single film having no support.

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