JP6790756B2 - Polyimide, polyimide precursor, and polyimide film - Google Patents

Description

The present invention relates to a polyimide having high heat resistance, low water absorption, and excellent dielectric properties, a polyimide precursor from which the polyimide can be obtained, and a polyimide film obtained by using them.

Polyimide is widely used in fields such as electrical / electronic device fields, semiconductor fields, and aerospace fields because it is excellent in heat resistance, chemical resistance, mechanical strength, electrical characteristics, dimensional stability, and the like.

In recent years, with the development of an advanced information society, there is a demand for higher functionality, higher performance, and smaller size of electronic devices. For the transmission and processing of large-capacity information, there is a need for materials with excellent high-frequency characteristics as well as ensuring the electrical reliability of printed circuit boards. Specifically, as the frequency increases, it is required to improve the propagation speed, reduce the transmission loss, improve the electrical density, and the like. Among these characteristics, the dielectric constant of the material itself, the reduction of the dielectric loss tangent, and the reduction of water content contribute significantly to the improvement of the propagation speed and the reduction of the transmission loss. Against this background, liquid crystal polymers characterized by low dielectric constant, low dielectric loss tangent, and low water absorption have been used for application in the high frequency range. However, although the liquid crystal polymer has excellent dielectric properties, there is room for improvement in heat resistance and adhesiveness to the metal foil. On the other hand, it is known that a material using polyimide having features such as heat resistance and metal adhesiveness has a high dielectric constant, dielectric loss tangent, and water absorption. As described above, when polyimide is used in the fields of electrical / electronic devices and semiconductors, improvement of water absorption and dielectric properties has been considered to be a major issue.

As a method for reducing water absorption in polyimide, it has been proposed to reduce the amount of hydrophilic functional groups. Also, regarding the dielectric properties, it has been proposed to reduce the amount of polar functional groups and to increase the symmetry of the molecular structure. From the above, as a method for exhibiting low water absorption and excellent dielectric properties, it is used to reduce the imide group concentration or to use a compound having good symmetry.

Patent Documents 1 to 3 disclose polyimides using diamino-p-terphenyl and diamino-p-quarterphenyl, which are compounds having a plurality of aromatic rings, as diamine components.

Japanese Unexamined Patent Publication No. 57-188853 Japanese Unexamined Patent Publication No. 60-22246 Japanese Unexamined Patent Publication No. 60-243120

The technique described in Patent Document 1 proposes a semiconductor device having excellent moisture resistance of a semiconductor device by using a polyimide film having low moisture permeability on the surface of the semiconductor element. The techniques described in Patent Documents 2 and 3 have proposed a substrate for a flexible printed wiring board which is excellent in heat resistance and does not generate curl. However, these patents do not propose means for simultaneously improving the water absorption and dielectric properties of polyimide.

The present invention describes a polyimide having lower water absorption and excellent dielectric properties, heat resistance, chemical resistance, and dimensional stability, a polyimide precursor from which the polyimide can be obtained, and a polyimide obtained by using them. The purpose is to provide a film.

The present invention relates to the following matters.

式中、基Ａは、化学構造中に一般式（２）の化学構造を有する４価の基であり、基Ｂは、化学構造中に一般式（３）の化学構造を有する２価の基である。

式中、Ｘは、直接結合を表すか、又はＯ、Ｓ、ＳＯ_２、Ｃ（ＣＦ_３）_２又はＣ_６Ｈ_４を表す。

1. 1. A polyimide having a repeating unit represented by the general formula (1), having a saturated water absorption rate of 1.5% by mass or less, and a dielectric loss tangent having a frequency of 10 GHz of 0.0045 or less.

In the formula, the group A is a tetravalent group having the chemical structure of the general formula (2) in the chemical structure, and the group B is a divalent group having the chemical structure of the general formula (3) in the chemical structure. Is.

In the formula, X represents a direct bond or represents O, S, SO ₂ , C (CF ₃ ) ₂ or C ₆ H ₄ .

2. The polyimide according to 1 above, wherein X in the general formula (2) is a direct bond.

3. 3. As the group A of the general formula (1), the structure represented by the general formula (2) is contained in the range of 50 to 100 mol%, and as the group B, the structure represented by the general formula (3) is 50 to 100. The polyimide according to any one of 1 and 2 above, which is contained in the range of mol%.

式中、基Ａは、化学構造中に一般式（５）の化学構造を有する４価の基であり、基Ｂは、化学構造中に一般式（６）の化学構造を有する２価の基であり、Ｒ_１はそれぞれ独立に水素原子、炭素数１〜６のアルキル基又は炭素数３〜９のアルキルシリル基である。

式中、Ｘは、直接結合を表すか、又はＯ、Ｓ、ＳＯ_２、Ｃ（ＣＦ_３）_２又はＣ_６Ｈ_４を表す。

4. A polyimide precursor having a structural unit represented by the general formula (4) and used for producing the polyimide according to one of 1 to 3 above.

In the formula, the group A is a tetravalent group having the chemical structure of the general formula (5) in the chemical structure, and the group B is a divalent group having the chemical structure of the general formula (6) in the chemical structure. R ₁ is an independent hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, respectively.

In the formula, X represents a direct bond or represents O, S, SO ₂ , C (CF ₃ ) ₂ or C ₆ H ₄ .

5. A varnish obtained by using the polyimide according to any one of 1 to 3 or the polyimide precursor according to 4.

6. A polyimide film obtained by using the polyimide according to any one of 1 to 3 or the polyimide precursor according to 4.

According to the present invention, a polyimide having high heat resistance, low water absorption, and excellent dielectric properties, a polyimide precursor from which the polyimide can be obtained, and a polyimide film obtained by using them. Is provided.

It will be described based on the preferred embodiment used for the polyimide of the present invention. The polyimide of the present invention is composed of a repeating unit represented by the general formula (1). The component represented by the group A in the general formula (1) has a structure including the general formula (2), and the component represented by the group B has a structure including the general formula (3). The polyimide of the present invention has a saturated water absorption rate of 1.5% by mass or less and a dielectric loss tangent at a frequency of 10 GHz of 0.0045 or less.

Group A is a residue obtained by removing four COOH groups from a tetracarboxylic acid (i.e., from the tetracarboxylic acid dianhydride two carboxylic acid anhydride groups (CO) residues obtained by removing 2 _O). Group B is a component obtained by removing two NH ₂ groups from diamine. Hereinafter, the tetracarboxylic acid and dianhydride used for polyimide will be referred to as a tetracarboxylic acid component, and diamines will be referred to as a diamine component. The groups A and B in the general formula (1) and the general formula (4) are derived from the tetracarboxylic acid component and the diamine component, respectively, and are contained in the polyimide and the polyimide precursor.

The polyimide precursor and the raw materials used for the polyimide will be described below, and the method for producing the polyimide precursor and the polyimide will be described.

X in the general formula (2) represents a direct bond or a linking group. When X is a linking group, examples of the linking group include O, S, SO ₂ , C (CF ₃ ) _{2 and} C ₆ H ₄ . Specific examples of the tetracarboxylic acid component represented by the general formula (2) are 3,3', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3', 4 '-Biphenyltetracarboxylic dianhydride (a-BPDA), 2,2', 3,3'-biphenyltetracarboxylic dianhydride (i-BPDA), oxydiphthalic acid dianhydride, diphenylsulfone-3,4 , 3', 4'-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfide dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1, 3,3,3-Hexafluoropropane dianhydride, m-terphenyl-3,4,3', 4'-tetracarboxylic dianhydride, p-terphenyl-3,4,3', 4'- Examples include tetracarboxylic dianhydride.

As the tetracarboxylic acid component, the general formula (2) may be used alone, or a plurality of types may be used in combination.

As other tetracarboxylic acid components that can be used in the present invention, aromatic and aliphatic ones can be used. Specific examples of aromatic tetracarboxylic acid components include pyromellitic dianhydride, 2,3,3', 4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-benzophenone. Tetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, p-phenylene bis (trimeritic acid mono) (Esteric dianhydride), p-biphenylenebis (trimellitic acid monoesteric dianhydride), 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4- Dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) biphenyl dianhydride, 2,2-bis [(3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4'-(2,2-hexafluoroisopropyridene) diphthalic acid dianhydride An anhydride and the like can be mentioned.

Specific examples of the aliphatic tetracarboxylic acid component include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, cyclohexane-1,2,4,5-tetracarboxylic acid dianhydride, [1, 1'-bi (cyclohexane)]-3,3', 4,4'-tetracarboxylic acid dianhydride, [1,1'-bi (cyclohexane)]-2,3,3', 4'-tetracarboxylic Acid dianhydride, [1,1'-bi (cyclohexane)]-2,2', 3,3'-tetracarboxylic acid dianhydride, 4,4'-methylenebis (cyclohexane-1,2-dicarboxylic acid dianhydride) (Anhydrous), 4,4'-(propane-2,2-diyl) bis (cyclohexane-1,2-dicarboxylic acid dianhydride), 4,4'-oxybis (cyclohexane-1,2-dicarboxylic acid dianhydride) , 4,4'-thiobis (cyclohexane-1,2-dicarboxylic acid dianhydride), 4,4'-sulfonylbis (cyclohexane-1,2-dicarboxylic acid dianhydride), 4,4'-( Dimethylsilanediyl) bis (cyclohexane-1,2-dicarboxylic acid dianhydride), 4,4'-(tetrafluoropropane-2,2-diyl) bis (cyclohexane-1,2-dicarboxylic acid dianhydride), Octahydropentalene-1,3,4,6-tetracarboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid dianhydride, 6- (carboxymethyl ) Bicyclo [2.2.1] heptane-2,3,5-tricarboxylic acid dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo [2.2.2] 2.2.2] Octa-5-ene-2,3,7,8-tetracarboxylic acid dianhydride, norbornan-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane 5 , 5'', 6,6''-tetracarboxylic acid dianhydride and the like can be mentioned.

Specific examples of the general formula (3) include 2,2'''-diamino-p-quarterphenyl, 2,3'''-diamino-p-quarterphenyl, 2,4'''-diamino-p-. Examples thereof include quarter phenyl, 3,3'''-diamino-p-quarter phenyl, 3,4'''-diamino-p-quarter phenyl, and 4,4'''-diamino-p-quarter phenyl.

As the diamine component, the general formula (3) may be used alone, or a plurality of types may be used in combination.

Other diamine components that can be used in the present invention include aromatic and aliphatic ones. Specific examples of the aromatic diamine component include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,4-bis (β-amino-tertiary butyl) toluene, and bis-p- ( 1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylene diamine, p-xylylene diamine, 4,4'-diaminodiphenyl ether, 4,4 '-Diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3' -Dimethyl-4,4'-biphenyldiamine, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylpropane, bis (4) -Amino-3-carboxyphenyl) methane, bis (p-β-amino-t-butylphenyl) ether, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene , Bis (p-β-methyl-6-aminophenyl) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 4, Examples thereof include 4'-bis (4-aminophenoxy) biphenyl and the like.

Specific examples of the aliphatic diamine component include 1,4-diaminobutane, 1,3-diaminopentane, 1,5-diaminopentane, 1,6-diaminohexane (hexamethylenediamine), and 1,7-diamino. Examples thereof include aliphatic diamines having 4 to 10 carbon atoms such as heptane, 1,8-diaminooctane, 1,9-diaminononane and 1,10-diaminodecane.

The polyimide precursor of the present invention is a raw material for giving the polyimide of the present invention, and is represented by the general formula (4). In the general formula (4), the group A is a tetravalent group having the chemical structure of the general formula (5) in the chemical structure. Group B is a divalent group having the chemical structure of the general formula (6) in its chemical structure. The chemical structures of the general formulas (5) and (6) are the same as the chemical structures of the general formulas (2) and (3) described above. Therefore, with respect to the chemical structures of the general formulas (5) and (6), the description of the chemical structures of the general formulas (2) and (3) is similarly applied. Further, R ₁ of the general formula (4) is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. The type of functional group and the introduction rate of the functional group of R ₁ can be changed by the production method described later.

When R ₁ is a hydrogen atom, the polyimide tends to be easily produced. On the other hand, when R ₁ is an alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, the storage stability of the polyimide precursor tends to be excellent. In this case, R ₁ is more preferably a methyl group or an ethyl group.

Further, when R ₁ is an alkylsilyl group having 3 to 9 carbon atoms, the solubility of the polyimide precursor tends to be excellent. In this case, R ₁ is more preferably a trimethylsilyl group or a t-butyldimethylsilyl group.

Introduction rate of functional groups is not particularly limited, when introducing an alkyl group or an alkylsilyl group, each R ₁ is 25% or more, preferably 50% or more, more preferably an alkyl group or an alkylsilyl 75% or more Can be the basis. Polyimide precursors of the present invention, the chemical _{structure wherein R 1} is taken, 1) a polyamic acid _{(R 1} is a hydrogen atom), 2) a polyamic acid ester (at least some alkyl groups of _{R 1),} 3) 4) Polyamide It can be classified as an acid silyl ester (at least a part of R ₁ is an alkylsilyl group). The polyimide precursor of the present invention can be easily produced by the following production methods for each of these categories. However, the method for producing the polyimide precursor of the present invention is not limited to the following production methods.

1) Polyimide The polyimide precursor of the present invention contains approximately equimolar tetracarboxylic dianhydride as a tetracarboxylic dian component and a diamine component in a solvent, preferably the molar ratio of the diamine component to the tetracarboxylic acid component [diamine]. The number of moles of the component / the number of moles of the tetracarboxylic acid component] is preferably at a ratio of 0.99 to 1.10, more preferably 0.95 to 1.05, for example, imidization at a relatively low temperature of 120 ° C. or lower. By reacting while suppressing the above, a polyimide precursor solution composition can be suitably obtained.

More specifically, the diamine is dissolved in an organic solvent, and the tetracarboxylic dianhydride is gradually added to the solution while stirring the solution, preferably 0 to 120 ° C., more preferably 5 to 80 ° C. A polyimide precursor can be obtained by stirring in the temperature range of 1 to 72 hours. When the reaction is carried out at 80 ° C. or higher, the molecular weight fluctuates depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so that the polyimide precursor may not be stably produced. It is preferable to add the diamine and the tetracarboxylic dianhydride in the above-mentioned order in the above-mentioned production method from the viewpoint that the molecular weight of the polyimide precursor is easily improved. It is also possible to reverse the order of addition of the diamine and the tetracarboxylic dianhydride in the above production method, which is preferable from the viewpoint of reducing the precipitate.

When the molar ratio of the tetracarboxylic acid component to the diamine component is excessive, a carboxylic acid derivative in an amount substantially corresponding to the excess molar number of the diamine component is added as necessary, and the tetracarboxylic acid component and the diamine are added. The molar ratio of the components can be brought close to the equivalent amount. The carboxylic acid derivative here is a tetracarboxylic acid that does not substantially increase the viscosity of the polyimide precursor solution, that is, does not substantially participate in the extension of the molecular chain, or a tricarboxylic acid and its anhydride that function as a terminal terminator. Dicarboxylic acids and their anhydrides are suitable.

2) Polyamic acid ester Tetracarboxylic acid dianhydride is reacted with an arbitrary alcohol to obtain a diester dicarboxylic acid, which is then reacted with a chlorination reagent (thionyl chloride, oxalyl chloride, etc.) to obtain a diester dicarboxylic acid chloride. A polyimide precursor can be obtained by stirring the diester dicarboxylic acid chloride and diamine preferably in the range of -20 to 120 ° C., more preferably -5 to 80 ° C. for 1 to 72 hours. When the reaction is carried out at 80 ° C. or higher, the molecular weight fluctuates depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so that the polyimide precursor may not be stably produced. A polyimide precursor can also be easily obtained by dehydrating and condensing a diesterdicarboxylic acid and a diamine using a phosphorus-based condensing agent, a carbodiimide condensing agent, or the like.

Since the polyimide precursor obtained by this method is stable, purification such as reprecipitation can be performed by adding a solvent such as water or alcohol.

3) Polyamic acid silyl ester (indirect method)
A diamine is reacted with a silylating agent in advance to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or the like. Then, the silylated diamine is dissolved in the dehydrated solvent, and the tetracarboxylic dianhydride is gradually added while stirring, preferably at 0 to 120 ° C, more preferably 5 to 80 ° C. A polyimide precursor can be obtained by stirring in the range for 1 to 72 hours. When the reaction is carried out at 80 ° C. or higher, the molecular weight fluctuates depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so that the polyimide precursor may not be stably produced.

As the silylating agent used here, it is preferable to use a silylating agent that does not contain chlorine from the viewpoint that it is not necessary to purify the silylated diamine. Examples of the chlorine atom-free silylating agent include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable because they do not contain a fluorine atom and are low in cost.

In the silylation reaction of diamine, an amine-based catalyst such as pyridine, piperidine, or triethylamine can be used to accelerate the reaction. This catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

4) Polyamic acid silyl ester (direct method)
The polyimide precursor is obtained by mixing the polyamic acid solution obtained by the method 1) above with a silylating agent and stirring the mixture in a range of preferably 0 to 120 ° C, more preferably 5 to 80 ° C for 1 to 72 hours. Is obtained. When the reaction is carried out at 80 ° C. or higher, the molecular weight fluctuates depending on the temperature history at the time of polymerization, and imidization proceeds due to heat, so that the polyimide precursor may not be stably produced.

As the silylating agent used here, it is preferable to use a silylating agent that does not contain chlorine from the viewpoint that it is not necessary to purify the silylated polyamic acid or the obtained polyimide. Examples of the chlorine atom-free silylating agent include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable because they do not contain a fluorine atom and are low in cost.

Since all of the above-mentioned production methods can be preferably carried out in an organic solvent, as a result, the varnish of the polyimide precursor of the present invention can be easily obtained.

Solvents used in preparing the polyimide precursor are, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide. Etc., an aprotic solvent is preferable. In particular, N, N-dimethylacetamide and N-methyl-2-pyrrolidone are preferable. However, as long as the raw material monomer component and the generated polyimide precursor are dissolved, any kind of solvent can be used without any problem, so that the structure is not particularly limited. As the solvent, an amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone , Cyclic ester solvents such as α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, m-cresol, p-cresol, 3-chlorophenol, 4-chlorophenol. Such as phenolic solvent, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like are preferably adopted. In addition, other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methylcellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran. , Dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methylisobutylketone, diisobutylketone, cyclopentanone, cyclohexanone, methylethylketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, tarpen, mineral spirit, petroleum A naphtha-based solvent or the like can also be used. A plurality of types of solvents can be used in combination.

When the molar ratio of the tetracarboxylic acid component to the diamine component is excessive, a carboxylic acid derivative in an amount substantially corresponding to the excess molar number of the diamine component is added as necessary, and the tetracarboxylic acid component and the diamine component are added. The molar ratio of can be brought close to the equivalent amount. The carboxylic acid derivative here is a tetracarboxylic acid that does not substantially increase the viscosity of the polyimide precursor solution, that is, does not substantially participate in the extension of the molecular chain, or a tricarboxylic acid and its anhydride that function as a terminal terminator. Dicarboxylic acids and their anhydrides are suitable.

The logarithmic viscosity of the polyimide precursor is not particularly limited, but the logarithmic viscosity in an N, N-dimethylacetamide solution having a concentration of 0.5 g / dL at 30 ° C. is preferably 0.2 dL / g or more, more preferably 0.3 dL. / G or more, particularly preferably 0.4 dL / g or more. By setting the logarithmic viscosity to 0.2 dL / g or more, the molecular weight of the polyimide precursor is high, and the mechanical strength and heat resistance of the obtained polyimide are excellent.

The varnish of the polyimide precursor contains at least the polyimide precursor of the present invention and the solvent, and the total amount of the tetracarboxylic acid component and the diamine component is preferable with respect to the total amount of the solvent, the tetracarboxylic acid component and the diamine component. Is 3% by mass or more, more preferably 5% by mass or more, and more preferably 7% by mass or more. The upper limit is usually preferably 60% by mass or less, more preferably 50% by mass or less. The total concentration of the tetracarboxylic acid component and the diamine component is a concentration close to the solid content concentration due to the polyimide precursor, but if this concentration is too low, for example, a polyimide film obtained when producing a polyimide film is obtained. It may be difficult to control the film thickness.

The viscosity (rotational viscosity) of the varnish of the polyimide precursor is not particularly limited, but the rotational viscosity measured at a temperature of 25 ° C. and a shear rate of 20 sec ^-1 using an E-type rotational viscometer is 0.01 to 1000 Pa · sec. It is preferably 0.1 to 250 Pa · sec, more preferably 0.1 to 250 Pa · sec. The varnish can also be given thixotropic properties as needed. With a viscosity in the above range, it is easy to handle when coating or forming a film, repelling is suppressed, and the leveling property is excellent, so that a good film can be obtained.

The polyimide precursor varnish of the present invention contains imidization catalysts, organic phosphorus-containing compounds, chemical imidizing agents (cyclization catalysts, dehydrating agents), inorganic particles, antioxidants, fillers, dyes, pigments, as required. Coupling agents such as silane coupling agents, primers, flame retardant materials, defoaming agents, leveling agents, polyimide control agents (fluid aids), release agents and the like can be added.

Examples of the imidization catalyst include a substituted or unsubstituted nitrogen-containing heterocyclic compound, an N-oxide compound of the nitrogen-containing heterocyclic compound, a substituted or unsubstituted amino acid compound, an aromatic hydrocarbon compound having a hydroxyl group, or an aromatic compound. Examples include heterocyclic compounds. In particular, lower alkyl imidazoles such as 1,2-dimethylimidazole, N-methylimidazole, N-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 5-methylbenzimidazole, N-benzyl. Substituted pyridines such as benzimidazole such as -2-methylimidazole, isoquinoline, 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine and 4-n-propylpyridine Etc. can be preferably used. The amount of the imidization catalyst used is preferably 0.01 to 2 times equivalent, particularly about 0.02 to 1 times equivalent with respect to the amic acid unit of the polyamic acid. By using an imidization catalyst, the physical properties of the obtained polyimide film, particularly elongation and edge crack resistance, may be improved.

Examples of the organic phosphorus-containing compound include monocaproyl phosphate, monooctyl phosphate, monolauryl phosphate, monomyristyl phosphate, monocetyl phosphate, monostearyl phosphate, and triethylene glycol monotridecyl. Ether monophosphate, tetraethylene glycol monolauryl ether monophosphate, diethylene glycol monostearyl ether monophosphate, dicaproyl phosphate, dioctyl phosphate, dicapryl phosphate, dilauryl phosphate, dimyristyl phosphate, Disetyl phosphate, distearyl phosphate, tetraethylene glycol mononeopentyl ether diphosphate, triethylene glycol monotridecyl ether diphosphate, tetraethylene glycol monolauryl ether diphosphate, diethylene glycol monostearyl ether Examples thereof include phosphoric acid esters such as diphosphate ester and amine salts of these phosphoric acid esters. Ammonia, monomethylamine, monoethylamine, monopropylamine, monobutylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, monoethanolamine, diethanolamine, triethanolamine And so on.

Examples of the cyclization catalyst include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as isoquinoline, pyridine, α-picoline and β-picoline. And so on.

Examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride.

Examples of the inorganic fine particles include fine-grained titanium dioxide powder, silicon dioxide (silica) powder, magnesium oxide powder, aluminum oxide (alumina) powder, zinc oxide powder and other inorganic oxide powder, fine-grained silicon nitride powder, and titanium nitride powder. Examples thereof include inorganic nitride powders such as silicon carbide powder, inorganic carbide powders such as silicon carbide powder, and inorganic salt powders such as fine-grained calcium carbonate powder, calcium sulfate powder, and barium sulfate powder. Two or more kinds of these inorganic fine particles may be used in combination. The method for uniformly dispersing these inorganic fine particles is not particularly limited, and a known method can be applied.

The polyimide of the present invention is a polyimide obtained from the above-mentioned tetracarboxylic acid component and diamine component used for obtaining the polyimide precursor of the present invention. The polyimide of the present invention can be suitably produced by subjecting the polyimide precursor of the present invention as described above to a dehydration ring closure reaction (imidization reaction). The imidization method is not particularly limited, and a known thermal imidization or chemical imidization method can be preferably applied.

In the present invention, the logarithmic viscosity of polyimide is not particularly limited, but the logarithmic viscosity in an N, N-dimethylacetamide solution having a concentration of 0.5 g / dL at 30 ° C. is preferably 0.2 dL / g or more, more preferably 0. .3 dL / g or more, more preferably 0.4 dL / g or more. By setting the logarithmic viscosity to 0.2 dL / g or more, a polyimide having excellent mechanical strength and heat resistance can be obtained.

In the present invention, the polyimide varnish contains at least the polyimide and the solvent of the present invention, and the polyimide is 3% by mass or more, preferably 5% by mass or more, more preferably 7% by mass, based on the total amount of the solvent and the polyimide. The above ratio is preferable. If the concentration of polyimide is too low, it may be difficult to control the film thickness of the polyimide film obtained, for example, when producing a polyimide film.

The solvent used for the polyimide varnish of the present invention has no problem as long as the polyimide is dissolved, and its structure is not particularly limited. As the solvent, the solvent used for the varnish of the polyimide precursor of the present invention can be similarly used.

In the present invention, the viscosity (rotational viscosity) of the polyimide varnish is not particularly limited, but the rotational viscosity measured with an E-type rotational viscometer at a temperature of 25 ° C. and a shear rate of 20 sec ^-1 is 0.01 to 1000 Pa. sec is preferable, and 0.1 to 250 Pa · sec is more preferable. In addition, thixotropic properties can be imparted as needed. With a viscosity in the above range, it is easy to handle when coating or forming a film, repelling is suppressed, and the leveling property is excellent, so that a good film can be obtained.

The polyimide varnish of the present invention can be used as a coupling agent such as an antioxidant, a filler, a dye, a pigment, a silane coupling agent, a primer, a flame retardant, a defoaming agent, a leveling agent, and a rheology control agent, if necessary. Flow aid), release agent, etc. can be added.

The polyimide obtained from the polyimide precursor of the present invention and the polyimide of the present invention have an extremely low saturated water absorption rate of 1.5% by mass or less, preferably 0.8% by mass or less when formed into a film. .. In order to set the saturated water absorption rate to the above-mentioned value or less, for example, the above-mentioned raw material for polyimide may be used, or the above-mentioned method may be adopted as a method for producing polyimide. The method for measuring the saturated water absorption rate will be described in Examples described later.

The polyimide obtained from the polyimide precursor of the present invention and the polyimide of the present invention have extremely excellent dielectric properties. Specifically, the polyimide obtained from the polyimide precursor of the present invention and the polyimide of the present invention have a dielectric loss tangent of 0.0045 or less, preferably 0.0040 or less, more preferably 0.0040 or less when formed into a film. Is 0.0038 or less.

In order to set the above-mentioned dielectric loss tangent within the above-mentioned range, for example, the above-mentioned one may be used as a raw material for polyimide, or the above-mentioned method may be adopted as a method for producing polyimide. Further, the method for measuring the dielectric loss tangent will be described in Examples described later.

The film made of the polyimide of the present invention has a thickness of preferably 1 to 250 μm, more preferably 1 to 150 μm, still more preferably 1 to 125 μm, and having a tetracarboxylic acid component and a diamine component, although it depends on the application. When a plurality of them are included, they may be random copolymerized or block copolymerized.

Next, an example of a polyimide film / base material laminate and a method for producing a polyimide film using the polyimide precursor of the present invention will be described. However, the method is not limited to the following.

For example, the varnish of the polyimide precursor of the present invention is cast on a base material such as ceramic (glass, silicon, alumina), metal (copper, aluminum, stainless steel), heat-resistant plastic film (polyimide), and in vacuum, nitrogen, etc. It is dried in an inert gas or in air using hot air or infrared rays, preferably in a temperature range of 20 to 180 ° C, more preferably 20 to 150 ° C. Next, the obtained polyimide precursor film was peeled off from the substrate or the polyimide precursor film was peeled off from the substrate, and the end portion of the film was fixed in a vacuum or in an inert gas such as nitrogen. Alternatively, a polyimide film / substrate laminate or a polyimide film can be produced by heating imidizing in air at a temperature of preferably 200 to 600 ° C., more preferably 250 to 550 ° C. using hot air or infrared rays. Can be done. In order to prevent the obtained polyimide film from being oxidatively deteriorated, it is desirable that the heating imidization is carried out in vacuum or in an inert gas. If the temperature of heating imidization is not too high, it may be performed in air.

Further, in the imidization reaction of the polyimide precursor, instead of the heat imidization by the heat treatment as described above, the polyimide precursor contains a dehydration cyclization reagent such as anhydrous acetic acid in the presence of a tertiary amine such as pyridine or triethylamine. It is also possible to carry out by chemical treatment such as immersing in a solution. Further, these dehydration cyclization reagents are put into the varnish of the polyimide precursor in advance and stirred, and then cast and dried on the substrate to prepare a partially imidized polyimide precursor. It can also be obtained, and by further heat-treating it as described above, a polyimide film / substrate laminate or a polyimide film can be obtained. Further, a functional layer or a heat-sealing layer may be provided on the surface of the polyimide.

The polyimide film / base material laminate thus obtained and the polyimide film can obtain a flexible conductive substrate by forming a conductive layer on one side or both sides thereof.

The flexible conductive substrate can be obtained by, for example, the following method. That is, as a first method, a conductive substance (metal or metal oxide) is subjected to sputtering, vapor deposition, printing or the like on the surface of the polyimide film without peeling the polyimide film from the base material of the polyimide film / base material laminate. , Conductive organic material, conductive carbon, etc.) to form a conductive layer / polyimide film / base material conductive laminate. After that, if necessary, the conductive layer / polyimide film laminate is peeled off from the base material to form a flexible conductive layer / polyimide film laminate and a conductive layer / polyimide film laminate / conductive layer. A substrate can be obtained.

As a second method, the polyimide film is peeled off from the base material of the polyimide film / base material laminate to obtain a polyimide film, and a conductive substance (metal or metal oxide, conductive organic substance, conductive) is formed on the surface of the polyimide film. A conductive layer made of (sexual carbon, etc.) can be formed in the same manner as in the first method to obtain a flexible conductive substrate made of a conductive layer / polyimide film laminate.

In the first method and the second method, if necessary, before forming a conductive layer on the surface of the polyimide film, a gas barrier layer such as water vapor or oxygen, light by sputtering, vapor deposition, a gel-sol method, or the like. An inorganic layer such as an adjusting layer may be formed.

Further, the conductive layer is preferably formed with a circuit by a method such as a photolithography method, various printing methods, or an inkjet method.

The polyimide film thus obtained has high heat resistance, low water absorption, and excellent dielectric properties, so that a material having excellent high frequency characteristics is more required. It is suitably used as a wiring board material in the fields of electronic devices and semiconductors.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "mass%". The meanings of the abbreviations used in the following examples and comparative examples are as follows.
s-BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride ODPA: oxydiphthalic acid dianhydride PMDA: pyromellitic dianhydride DAQP: 4,4'''-diamino-p-quarter Phenyl ODA: 4,4'-diaminodiphenyl ether DATP: 4,4''-diaminoterphenyl ADA: 9,10-bis (4-aminophenyl) anthracene

In each of the following examples, the evaluation was performed by the following method.

[Saturated water absorption rate]
The polyimide film is dried under heating and vacuum drying until it reaches a constant weight, and the film mass C at the time of drying is measured. Then, the film is immersed in pure water at 23 ° C. for 24 hours, pulled up, the water adhering to the polyimide film is wiped off, and then the film mass D at the time of wetting is measured. The saturated water absorption rate (%) was calculated by the following formula.
Saturated water absorption rate (mass%) = [(DC) / C] x 100

[Relative permittivity and dielectric loss tangent]
The polyimide film was normally adjusted to an environment of 22 ± 1 ° C. and 60 ± 5% RH for 72 hours or more, and then measured by a cylindrical cavity resonator method (frequency: 10 GHz).

[Imide group concentration]
The imide group concentration (mass%) of the polyimide film was calculated by the following formula.
Imide group concentration (% by mass) = [(Molecular weight of imide group x number of imide groups per unit unit constituting polyimide) / (molecular weight per unit unit constituting polyimide)] x 100

[Tension modulus, breaking point stress and breaking point elongation]
A polyimide film is punched into a dumbbell shape of IEC-540 (S) standard to make a test piece (width: 4 mm), and using ORIENTEC's TENSILON, the chuck distance is 30 mm, the tensile speed is 2 mm / min, and the initial tensile elastic modulus. , Break point stress and break point elongation were measured.

Two main methods are known as methods for synthesizing the diamine of the general formula (3). In U.S. Pat. No. 4,709,082, quarter-phenyl is dinitrated and the nitro group is reduced to obtain a diamine. Color. Technol. 2007,123, p. In 34-38, biphenyl was halogenated and subsequently nitrated to obtain a dinitro compound by the Ulmann coupling reaction, and then a diamine was obtained by a reduction reaction of the nitro group. According to International Publication No. 2007/104361, a diamine is obtained by a Suzuki coupling reaction between an aromatic boron compound having an amino group and a bishalogenated aromatic compound. The DAQP used in this example is synthesized by the Suzuki coupling method, but any synthesis method does not affect the effect of the present invention.

A specific method for synthesizing DAQP will be described below.
DAQP is synthesized by two steps. In the first step, 4,4'-dibromo-1,1'-biphenyl and tert-butyl (4- (4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) phenyl) ) Di-tert-butyl [1,1': 4', 1'' ,: 4'', 1'''-quarterphenyl] -4,4'''-diyldi by Suzuki coupling reaction with carbamate Carbamate was synthesized. In the second step, di-tert-butyl [1,1': 4', 1'',: 4'', 1'''-quarterphenyl] -4,4'''' obtained in the first step -The deprotection reaction of diyldicarbamate was carried out to synthesize DAQP. Hereinafter, as reference example 1, as the first step, di-tert-butyl [1,1': 4', 1'',: 4'', 1'''-quarterphenyl] -4,4'''- The procedure for synthesizing diyldicarbamate and the procedure for synthesizing DAQP as Reference Example 2 are shown.

[Reference Example 1 Synthesis of di-tert-butyl [1,1': 4', 1'',: 4'', 1'''-quarterphenyl] -4,4'''-diyldicarbamate]
In a 10 L four-necked flask, under an argon atmosphere, 12,4'-dibromo-1,1'-biphenyl 123.9 g (397 mmol), tert-butyl (4- (4,4,5,5-tetramethyl-1) , 3,2-Dioxaborolan-2-yl) phenyl) carbamate 266.2 g (833 mmol) was added, dissolved in 5942 mL of N, N-dimethylformamide and the solution was bubbled with argon. To the solution was added 1485 mL of an aqueous solution containing 126.1 g (1.19 mol) of sodium carbonate, and bubbling with argon. Then added _{Pd (PPh 3) 4 14g (} 0.011mmol), and stirred at 100 ° C. 20 hours. The reaction solution is filtered, the filtrate is washed with THF and ion-exchanged water, dried by heating under vacuum, and di-tert-butyl [1,1': 4', 1'' ,: 4'as a gray solid. ', 1'''-Quarterphenyl] -4,4'''-Diyldicarbamate 186.1 g was obtained (acquisition yield 87%).

The physical property values of di-tert-butyl [1,1': 4', 1'',: 4'', 1'''-quarterphenyl] -4,4'''-diyldicarbamate were as follows. ..
^{1 1} H-NMR (DMSO-d6 _, σ (ppm)); 1.50 (s, 2H), 7.53-7.68 (m, 8H), 7.71-7.83 (m, 8H), 9.47 (s, 2H)
ESI-MS (m / z); 537 (M + 1)

[Reference Example 2 Synthesis of DAQP]
Di-tert-butyl [1,1': 4', 1'' ,: 4'', 1'''-quarterphenyl] -4,4'''-in a 5 L four-necked flask under an argon atmosphere 196.4 g (365 mmol) of diyldicarbamate was suspended in 1510 mL of dichloromethane, 1269 mL (7.47 mol) of trifluoroacetic acid was added, and the mixture was stirred at room temperature for 20 hours. 10.4 L of a 2 mol / L sodium hydroxide aqueous solution was added to the solution after completion of the reaction, and the precipitated solid was filtered. The filter was washed with ion-exchanged water, followed by THF and dichloromethane. The obtained solid was heated and dried under vacuum to obtain 86.0 g of a crude DAQP as a gray solid. Subsequently, 180 g of the DAQP crude obtained in the same manner was sublimated and purified to obtain 134 g of DAQP as a pale yellow solid with a purity of 99% or more of 1H-NMR (di-tert-butyl [1,1': 4). ', 1'' ,: 4'', 1'''-quarter phenyl] -4,4'''-diyl dicarbamate standard acquisition yield 52%).

The physical property values of DAQP were as follows.
^{1 1} H-NMR (DMSO-d6, σ (ppm)); 5.27 (s, 4H), 6.67 (d, J = 8.5Hz, 4H), 7.42 (d, J = 8.5Hz) , 4H), 7.63 (d, J = 8.5Hz, 2H), 7.69 (d, J = 8.5Hz, 2H)
DI-MS (m / z); 337 (M + 1)

[Example 1]
After 6.1 g (20.8 mmol) of s-BPDA is placed in the polymerization tank, N-methylpyrrolidone, which is an organic solvent, is added to make the total mass of the charged monomers (total of diamine component and tetracarboxylic acid component) 10%. The mixture was added and stirred at 25 ° C. under a nitrogen atmosphere. 7 g (20.8 mmol) of DAQP was gradually added to this solution, and the mixture was stirred to obtain a uniform and viscous polyimide precursor solution (polyamic acid solution) E. The obtained polyimide precursor solution E was cast into a thin film on a glass plate and heated to 490 ° C. to proceed with imidization to obtain a polyimide film having a thickness of 25 μm. The mechanical properties of the obtained film were a tensile elastic modulus of 6.5 GPa, a breaking point stress of 387 MPa, and a breaking point elongation of 39%.

[Example 2]
After placing 9.5 g (28.3 mmol) of DAQP and 1 g (5.0 mmol) of ODA in a polymerization tank, a mixed organic solvent of N-methylpyrrolidone: dimethylacetamide = 1: 1 (mass ratio) was added as a monomer. The total mass (total of diamine component and tetracarboxylic acid component) was added so as to be 13%, and the mixture was stirred at 25 ° C. under a nitrogen atmosphere. 9.8 g (33.3 mmol) of s-BPDA was gradually added to this solution, and the mixture was stirred to obtain a uniform and viscous polyimide precursor solution F. The obtained polyimide precursor solution F was cast into a thin film on a glass plate and heated to 490 ° C. to proceed with imidization to obtain a polyimide film having a thickness of 25 μm.

[Example 3]
In this example, ODPA was used instead of s-BPDA used in Example 2. A polyimide film was obtained in the same manner as in Example 2 except for this.

[Comparative Example 1]
In this comparative example, PMDA was used instead of s-BPDA used in Example 1. The reaction was carried out in the same manner as in Example 1 except for this. However, the solution gelled and a uniform polyimide precursor solution could not be obtained.

[Comparative Example 2]
In this comparative example, DATP was used instead of DAQP used in Example 1. In addition, dimethylacetamide was used instead of N-methylpyrrolidone. Dimethylacetamide was added so that the total mass of the charged monomers (total of diamine component and tetracarboxylic acid component) was 18%. A polyimide film was obtained in the same manner as in Example 1 except for these. The mechanical properties of the obtained film were a tensile elastic modulus of 7.1 GPa, a breaking point stress of 342 MPa, and a breaking point elongation of 24%.

[Comparative Example 3]
In this comparative example, ADA was used instead of the DAQP used in Example 1. In addition, dimethylacetamide was used instead of N-methylpyrrolidone. Dimethylacetamide was added so that the total mass of the charged monomers (the sum of the diamine component and the tetracarboxylic acid component) was 10%. A polyimide film was obtained in the same manner as in Example 1 except for these. The mechanical properties of the obtained film were a tensile elastic modulus of 5.2 GPa, a breaking point stress of 246 MPa, and a breaking point elongation of 14%.

[Comparative Example 4]
In this comparative example, PMDA was used instead of s-BPDA used in Example 2. A polyimide film was obtained in the same manner as in Example 2 except for this.

As is clear from the results shown in Table 1, the polyimide films obtained in each example had a lower saturated water absorption rate and smaller relative permittivity and dielectric loss tangent values than the polyimide films obtained in the comparative examples, and were excellent. It can be seen that it exhibits dielectric properties. The polyimide film of the present invention can be suitably used as a wiring board material in the fields of electrical and electronic devices and semiconductors, where a material having excellent high frequency characteristics is required more.

Claims (6)

A polyimide having a repeating unit represented by the general formula (1), having a saturated water absorption rate of 1.5% by mass or less, and having a dielectric loss tangent of 0.0045 or less at a frequency of 10 GHz.

In the formula, the group A is a tetravalent group having the chemical structure of the general formula (2) in the chemical structure, and the group B is a divalent group having the chemical structure of the general formula (3) in the chemical structure. Is.

Wherein, X represents either a direct bond, or O, S, an SO ₂ or C _{(CF 3) 2.}

The polyimide according to claim 1, wherein X of the general formula (2) is a direct bond. As the group A of the general formula (1), the structure represented by the general formula (2) is contained in the range of 50 to 100 mol%, and as the group B, the structure represented by the general formula (3) is 50. The polyimide according to claim 1 or 2, which comprises a range of ~ 100 mol%. The polyimide precursor used for producing the polyimide according to any one of claims 1 to 3, which has a repeating unit represented by the general formula (4).

In the formula, the group A is a tetravalent group having the chemical structure of the general formula (5) in the chemical structure, and the group B is a divalent group having the chemical structure of the general formula (6) in the chemical structure. R ₁ is an independent hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, respectively.

Wherein, X represents either a direct bond, or O, S, an SO ₂ or C _{(CF 3) 2.}

A varnish obtained by using the polyimide according to any one of claims 1 to 3 or the polyimide precursor according to claim 4. A polyimide film obtained by using the polyimide according to any one of claims 1 to 3 or the polyimide precursor according to claim 4.