JP2008184558A - Polyimide precursor having ester group and oxazole structure, polyimide and method for producing the same - Google Patents

Abstract

【化２】

【選択図】なしProvided are a polyimide having a high glass transition temperature, a low linear thermal expansion coefficient close to copper, a low hygroscopic expansion coefficient, sufficient adhesion to metals, particularly copper, and sufficient toughness, a polyimide precursor, and a method for producing a polyimide. To do.
A polyimide having a structure represented by general formula (1) and general formula (2) having an ester group and an oxazole structure in which the ratio of X and Y is 60/40 to 99/1. Polyimide.
[Chemical 1]

[Chemical 2]

[Selection figure] None

Description

  The present invention relates to a polyimide having a high glass transition temperature, a low coefficient of linear thermal expansion, sufficient adhesion with a metal foil, a low hygroscopic expansion coefficient, and a sufficient toughness, a polyimide precursor, and a method for producing a polyimide. FPC) substrate, base material for tape automation bonding (TAB), electrical insulating film and liquid crystal display substrate in various electronic devices, organic electroluminescence (EL) display substrate, electronic paper substrate, solar cell substrate, especially FPC substrate Useful as a material.

Polyimide has not only excellent heat resistance but also characteristics such as chemical resistance, radiation resistance, electrical insulation, and excellent mechanical properties. Therefore, FPC substrates, TAB base materials, semiconductor element protective films, Currently, it is widely used in various electronic devices such as an interlayer insulating film of an integrated circuit. In addition to these properties, polyimide has become increasingly important in recent years because of its simplicity of manufacturing method and extremely high film purity.
As electronic devices become lighter, thinner, and more demanding, the demands on polyimide have become stricter year by year. Not only solder heat resistance, but also the dimensional stability of polyimide film against thermal cycling and moisture absorption, transparency, and adhesion to metal substrates Multifunctional polyimide materials that simultaneously satisfy a plurality of characteristics such as properties, molding processability, and fine processability such as through-holes have been demanded.

  In recent years, the demand for polyimide as an FPC substrate has increased dramatically. The composition of the original fabric of the FPC board (copper-clad laminate, FCCL) is mainly classified into three modes. That is, 1) A three-layer type in which a polyimide film and a copper foil are bonded using an epoxy-based adhesive or the like. 2) A polyimide varnish is applied to a copper foil and then dried or a polyimide precursor (polyamide acid) varnish is applied. Later, drying, imidization, or non-adhesive two-layer type that forms a copper layer on a polyimide film by vapor deposition / sputtering, etc., 3) pseudo-two-layer type using thermoplastic polyimide as the adhesive layer are known Yes. In applications where a high degree of dimensional stability is required for the polyimide film, a two-layer FCCL without an adhesive is advantageous.

Polyimide as an FPC board undergoes dimensional changes when exposed to various thermal cycles in the mounting process. In order to suppress this as much as possible, in addition to the glass transition temperature (Tg) of the polyimide being higher than the process temperature, the coefficient of linear thermal expansion below the glass transition temperature is as low as possible, matching the coefficient of linear thermal expansion of the metal foil. It is desirable that As will be described later, the control of the linear thermal expansion coefficient of the polyimide layer is extremely important from the viewpoint of reducing the residual stress generated during the two-layer FCCL manufacturing process.
Many polyimides are insoluble in organic solvents and do not melt above the glass transition temperature, so it is usually not easy to mold the polyimide itself. Therefore, a polyimide is generally composed of an aromatic tetracarboxylic dianhydride such as pyromellitic anhydride (PMDA) and an aromatic diamine such as 4,4′-oxydianiline (ODA) and a dimethylacetamide (DMAc). First, a polyimide precursor (polyamic acid) having a high degree of polymerization is polymerized in an aprotic polar organic solvent, and this varnish is coated on a copper foil, heated at 250 to 400 ° C., and dehydrated. The film is formed by ring closure (imidization).

Residual stress occurs in the process of cooling the polyimide / metal substrate laminate to room temperature after the imidization reaction at high temperature, and serious problems such as FCCL curling, peeling, and film cracking often occur.
As a measure for reducing thermal stress, it is effective to reduce the thermal expansion of polyimide itself as an insulating film. For most polyimides, the linear thermal expansion coefficient is in the range of 40-100 ppm / K, which is much greater than the linear thermal expansion coefficient of 17 ppm / K for metal substrates, such as copper, so it is close to that of copper, approximately 20 ppm / K Research and development of low thermal expansion polyimides exhibiting a linear thermal expansion coefficient of K or less are being conducted.

At present, as a practical low thermal expansion polyimide material, polyimide formed from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine is best known. This polyimide film shows a very low linear thermal expansion coefficient of 5 to 10 ppm / K (for example, see Non-Patent Document 1), although it depends on the film thickness and production conditions, but does not show a low hygroscopic expansion coefficient.
The dimensional stability of polyimide is required not only for thermal cycling but also for moisture absorption. Conventional polyimide absorbs 2 to 3 wt%. Circuit misalignment due to dimensional changes due to moisture absorption of the insulating layer is a serious problem for high-density wiring and multilayer wiring. Further serious problems may be caused by deterioration of electrical characteristics such as corrosion at the polyimide / conductor interface, ion migration, and dielectric breakdown. Therefore, the polyimide layer as an insulating film is required to have a low hygroscopic expansion coefficient as much as possible.

  In order to realize a low hygroscopic expansion coefficient, for example, a polyimide film containing a repeating unit represented by the following formula (33) in the molecule has been proposed (see Patent Document 1).

However, since the resulting polyimide film is feared to deteriorate the adhesiveness with the copper foil, it is difficult to use it as a base material for two-layer FCCL. For example, pretreatment for improving adhesion and application of an adhesive layer are required.
In addition, a polyimide film using an aromatic diamine having a benzoxazole structure has been reported to improve the adhesion between the copper foil and the substrate (see Patent Document 2). The benzoxazole structure has a rigid structure and high heat resistance, and can be expected to improve adhesion. However, depending on the content of the oxazole structure, the resulting polyimide film has a very low linear thermal expansion coefficient of 5-9 ppm / K, depending on the film thickness and production conditions, and is controlled to a thermal expansion coefficient equivalent to that of copper foil. Difficult to do. Furthermore, there is a concern about the deterioration of the hygroscopic expansion coefficient due to the presence of oxygen atoms and nitrogen atoms in the ring structure of the oxazole structure.

Low linear thermal expansion coefficient, low hygroscopic expansion coefficient (less than 8ppm /% RH, 10-80% RH), high toughness, solder heat resistance, and copper foil, close to copper, while maintaining polymerization reactivity and film forming processability It is not easy in molecular design to obtain a polyimide that satisfies the adhesive properties, and at present, practical materials satisfying such required properties are hardly known.
Macromolecules, 29, 7897 (1996). JP 2006-328407 A JP 2005-131918 A

  The present invention has a high glass transition temperature, a low linear thermal expansion coefficient close to copper, a low hygroscopic expansion coefficient, a sufficient adhesiveness with metals, particularly copper, and a sufficient toughness, which has been difficult with conventional polyimides. It aims at providing the manufacturing method of a polyimide, a polyimide precursor, and a polyimide.

As a result of intensive research in view of the above problems, a polyimide precursor varnish having a structure represented by the following general formula (1) and general formula (2) is applied to a conductive substrate such as copper foil and dried. A polyimide film having a structure represented by the following general formula (14) and general formula (15) formed by imidizing the film thermally or using a dehydrating reagent is used in the industrial field. It has been found that the material is extremely useful, and the present invention has been completed.
That is, the present invention is as follows.
1. A polyimide precursor having a structure represented by the following general formula (1) and the following general formula (2), the ratio of X and Y being 60/40 to 99/1, having an ester group and an oxazole structure Polyimide precursor.

Here, A ₁ and A ₂ are tetravalent aromatic groups selected from the formulas (3) to (6), and may be the same or different. The two carboxyl groups bonded to A ₁ and A ₂ are not limited to the cis configuration, and a cis configuration and a trans configuration may be mixed. R ₁ represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, or hydrogen.

Here, B is selected from divalent aromatic groups represented by formula (7) to formula (10), R _{2 to} R ₆ represent an alkyl group having 1 to 4 carbon atoms, a methoxy group, and hydrogen, R _{2 to} R ₄ may be the same or different. In A ₁ , A ₂ , and B, at least one selected from Formula (3), Formula (4), Formula (7), Formula (8), and Formula (9) having an ester group is selected.

Here, D is selected from divalent aromatic groups represented by the formulas (11) to (13), Ar ₁ represents a phenyl group, a biphenyl group, or a naphthyl group, and Ar ₂ represents a phenyl group or a biphenyl group. Represents.

2. It is a polyimide which has a structure represented by the following general formula (14) and the following general formula (15), Comprising: It has an ester group and oxazole structure whose ratio of X and Y is a ratio of 60 / 40-99 / 1. Polyimide.

Here, A ₁ and A ₂ are tetravalent aromatic groups selected from the formulas (3) to (6), and may be the same or different. The two carboxyl groups bonded to A ₁ and A ₂ are not limited to the cis configuration, and a cis configuration and a trans configuration may be mixed. R ₁ represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, or hydrogen.

Here, B is selected from divalent aromatic groups represented by formula (7) to formula (10), R _{2 to} R ₆ represent an alkyl group having 1 to 4 carbon atoms, a methoxy group, and hydrogen, R _{2 to} R ₄ may be the same or different. In A ₁ , A ₂ , and B, at least one selected from Formula (3), Formula (4), Formula (7), Formula (8), and Formula (9) having an ester group is selected.

Here, D is selected from divalent aromatic groups represented by the formulas (11) to (13), Ar ₁ represents a phenyl group, a biphenyl group, or a naphthyl group, and Ar ₂ represents a phenyl group or a biphenyl group. Represents.

3. The method for producing a polyimide according to 2, wherein the polyimide precursor having an ester group and an oxazole structure according to 3.1 is subjected to a cyclization reaction (imidization) by heating or using a dehydrating reagent.
4.1. A varnish containing, as a main component, a polyimide precursor having an ester group and an oxazole structure described in 4.1 is coated on a metal foil, dried, and then imidized by heating or using a dehydrating reagent. The manufacturing method of the laminated board of the resin layer comprised from the metal layer and the polyimide of 2.
The manufacturing method of a flexible printed wiring board characterized by etching the metal layer of the laminated board as described in 5.4.

  According to the present invention, a polyimide having an ester group and an oxazole structure having a high glass transition temperature, a low linear thermal expansion coefficient close to copper, a low hygroscopic expansion coefficient, sufficient adhesion to metal and sufficient toughness, and a polyimide precursor The manufacturing method of a body and a polyimide can be provided. Polyimides with these characteristics include flexible printed wiring (FPC) substrates, tape automation bonding (TAB) substrates, electrical insulation films and liquid crystal display substrates in various electronic devices, organic electroluminescence (EL) display substrates, It is useful as an electronic paper substrate, a solar cell substrate, particularly an FPC substrate material.

As a molecular design for reducing the thermal expansion of polyimide, it is necessary to make the main chain skeleton as straight and rigid as possible (various conformations are difficult to take due to internal rotation). However, on the other hand, this reduces the entanglement of the polymer chains and may cause the film to become brittle. In addition, excessive introduction of a flexible unit such as an ether structure into the polyimide skeleton greatly contributes to improvement of film toughness and adhesion to metal, but may hinder the expression of low thermal expansion characteristics.
The ester group and oxazole structure focused on in the present invention have a higher internal rotation barrier than the ether structure, and the change in conformation is relatively hindered. Therefore, the ester group and the oxazole structure behave as a rigid structural unit and have a certain amount in the polyimide main chain. It is also expected to give flexibility and give a flexible film.

In addition, since the ester group has a lower polarizability per unit volume than the amide structure or imide structure, a low hygroscopic expansion coefficient is expected by introducing the ester group into polyimide. However, simply increasing the content of the aromatic ester group in the polyimide not only reduces the heat resistance, which is the greatest feature of the polyimide, but also the solubility of the precursor (solution cast film forming property) and polymerization reactivity (polymerization). There is concern about deterioration of adhesiveness with copper foil.
On the other hand, the oxazole structure is expected to increase the interaction with the metal due to the presence of oxygen atoms and nitrogen atoms in the ring structure, and is advantageous for improving the adhesion.
The polyimide precursor according to the present invention is produced by selecting a monomer having an ester group from an ester group-containing acid dianhydride and / or an ester group-containing diamine and using the oxazole structure-containing diamine together.

When polymerizing the polyimide precursor according to the present invention, an ester group-containing tetracarboxylic dianhydride represented by the following formula (16) and formula (17) and / or formula (18) to An ester group-containing diamine represented by the formula (20) is used. Incidentally, the tetracarboxylic dianhydride component A _1, A ₂ may be used or two or more kinds thereof may be used alone. Moreover, the diamine components B and D may each be used alone or in combination of two or more.

(R ₁ represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, or hydrogen.)

(R _{2 to} R ₆ represent an alkyl group having 1 to 4 carbon atoms, a methoxy group, and hydrogen, and R _{2 to} R ₄ may be the same or different.)
When the ester group-containing tetracarboxylic dianhydride represented by formula (16) or formula (17) is used, the monomer of component B is limited to the ester group-containing diamine of formula (18) to formula (20). Alternatively, an aromatic diamine represented by the formula (21) may be selected.

Similarly, when the ester group-containing diamine represented by the formula (18) to the formula (20) is used, the monomers of the A ₁ and A ₂ components contain the ester groups of the formula (16) and the formula (17). The tetracarboxylic dianhydride is not limited to tetracarboxylic dianhydrides, and tetracarboxylic dianhydrides represented by the formulas (22) and (23) may be selected.

  When polymerizing the polyimide precursor according to the present invention, an oxazole structure-containing diamine represented by the following formulas (24) to (26) is used as a monomer having an oxazole structure.

In the formula (24), Ar ₁ represents a phenyl group, a biphenyl group, or a naphthyl group, and in the formula (26), Ar ₂ represents a phenyl group or a biphenyl group.
The polyimide which concerns on this invention is a polyimide which has a structure represented by Formula (14) and Formula (15), Comprising: The ratio of X and Y has an ester group and oxazole structure which are 60 / 40-99 / 1 It has a special feature. The molar ratio of X and Y is 60/40 to 99/1, and preferably 80/20 to 95/5. Thus, the polyimide according to the present invention has a high glass transition temperature, high heat resistance, a low hygroscopic expansion coefficient, a low thermal expansion coefficient equivalent to copper foil, and a metal such as copper, depending on the composition ratio of units having an ester group and an oxazole structure. Of sufficient adhesiveness at the same time. In the polyimide having the structure represented by formula (14) or formula (15), from the viewpoint of the hygroscopic expansion coefficient, the molar ratio of the constituent component having an oxazole structure is preferably less than 40%, and the adhesiveness to the metal From the viewpoint, it is preferably more than 1%.

Moreover, since the polyimide according to the present invention is produced from a monomer containing an ester group and a monomer containing an oxazole structure, a polyimide having the above characteristics can be produced at low cost without using an expensive monomer. be able to.
Embodiments of the present invention will be described in detail below, but these are examples of the embodiments of the present invention and the present invention is not limited to these contents.
In the present invention, at least one kind of ester group-containing acid dianhydride represented by formula (16) or formula (17) or ester group-containing diamine represented by formula (18) to formula (20) is used. By selecting an ester group-containing monomer, selecting at least one oxazole structure-containing diamine represented by the formula (24) to the formula (26), and combining the acid dianhydride and the diamine to cause a polymerization reaction, An extremely useful polyimide having an ester group and an oxazole structure can be provided. When the resin is made into a resin due to the structural characteristics of the monomer having an ester group and an oxazole structure such as rigidity, hydrophobicity, and steric bulk of the substituent, and the composition ratio of the unit having the ester group and the oxazole structure, a copper foil The material should have the same physical properties that could not be obtained with conventional materials, with the same low linear thermal expansion coefficient, low hygroscopic expansion coefficient, sufficient adhesion to metal foil, high glass transition temperature, and high film toughness. Achieved.

<Method for producing polyimide precursor>
The method for producing the polyimide precursor according to the present invention is not particularly limited, and a known method can be applied. More specifically, it is obtained by the following method.
First, diamine is dissolved in a polymerization solvent, tetracarboxylic dianhydride powder is gradually added thereto, and it is 0 to 100 ° C., preferably 20 to 60 ° C., preferably 0.5 to 100 hours using a mechanical stirrer, preferably Stir for 1-24 hours. In this case, the monomer concentration is preferably 5 to 50 wt%, more preferably 10 to 40 wt% from the viewpoint of the degree of polymerization and the solubility of the monomer and the polymer to be produced. From the viewpoint of the toughness of the polyimide film, it is desirable that the degree of polymerization of the polyimide precursor is as high as possible. By performing polymerization in the above monomer concentration range, a uniform and high degree of polyimide precursor solution (varnish) can be obtained. it can. From the viewpoint of polyimide film toughness and varnish handling, the intrinsic viscosity of the polyimide precursor is preferably in the range of 0.1 to 15.0 dL / g, more preferably in the range of 0.5 to 5.0 dL / g. . Further, the polymerization mode is arbitrary, and examples thereof include a random copolymerization mode and a block copolymerization mode.

  In the polymerization of the polyimide precursor having the structure represented by the formula (1) and the formula (2) within a range not impairing the required characteristics of the polyimide film according to the present invention and the polymerization reactivity of the polyimide precursor, the formula (22 ) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride represented by formula (23) Examples of the aromatic tetracarboxylic dianhydride include, but are not limited to, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4 ′. -Biphenyl ether tetracarboxylic dianhydride, 3,3 ', 4,4'-biphenylsulfone tetracarboxylic dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid Anhydride, 2,2'-bis (3,4-carboxyphenyl) propanoic acid dianhydride, such as 1,4,5,8-naphthalene tetracarboxylic acid dianhydride as an example. Two or more of these may be used.

  As long as the required characteristics of the polyimide film according to the present invention and the polymerization reactivity of the polyimide precursor are not impaired, the usable aliphatic tetracarboxylic dianhydride is not particularly limited, but bicyclo [2.2.2] octane -7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (dioxotetrahydrofuryl-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 4- (2, 5-Dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo-3,3 ′, 4,4 ′ -Tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, etc. That. It is also possible to use two or more of these.

  In addition to the p-phenylenediamine represented by the formula (21), the aromatic diamine that can be partially used is particularly limited within the range in which the polymerization reactivity of the polyimide precursor according to the present invention and the required characteristics of the polyimide are not significantly impaired. Without limitation, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-diaminodiphenylmethane, 4,4′- Methylene bis (2-methylaniline), 4,4'-methylene bis (2-ethylaniline), 4,4'-methylene bis (2,6-dimethylaniline), 4,4'-methylene bis (2,6-diethylaniline) 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diamino Benzanilide, benzidine, 3,3′-dihydroxybenzidine, 3,3′-dimethoxybenzidine, o-tolidine, m-tolidine, 2,2′-bis (trifluoromethyl) benzidine, 1,4-bis (4- Aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis (4- ( 3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) Examples include hexafluoropropane and p-terphenylenediamine. Two or more of these may be used in combination.

  The aliphatic diamine that can be partially used is not particularly limited as long as the polymerization reactivity of the polyimide precursor according to the present invention and the required properties of the polyimide are not significantly impaired. For example, 4,4′-methylenebis (cyclohexylamine) ), Isophoronediamine, trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1]. ] Heptane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropyl Bread, 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1 , 9-nonamethylenediamine and the like. Two or more of these may be used in combination.

  As a solvent used in the polymerization reaction, there is no problem as long as the raw material monomer and the polyimide precursor to be generated are dissolved, and the structure is not particularly limited. Specifically, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε -Cyclic ester solvents such as caprolactone, 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-chloro Examples thereof include phenol solvents such as phenol, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like. From the viewpoint of solubility, aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and 1,3-dimethyl-2-imidazolidinone are preferable. .

Other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran , Dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpene, mineral spirit, petroleum naphtha solvents, etc. Can also be used.
The polyimide precursor according to the present invention can be isolated as a powder by dropping, filtering and drying the polymerization solution in a large amount of poor solvent such as water or methanol.

<Production method of polyimide>
The polyimide according to the present invention can be produced by subjecting the polyimide precursor obtained by the above method to a dehydration ring-closing reaction (imidation reaction). Usable forms of the obtained polyimide are a film, a metal foil / polyimide film laminate, a powder, a molded product and a solution.
First, a method for producing a polyimide film will be described.
A polymerization solution (varnish) of a polyimide precursor is cast on a substrate such as glass, copper, aluminum, or silicon and dried in an oven at 40 to 180 ° C., preferably 50 to 150 ° C. The obtained polyimide precursor film is heated at 200 to 430 ° C., preferably 250 to 400 ° C. in vacuum, in an inert gas such as nitrogen, or in the air on the substrate. Can be manufactured. From the viewpoint of the ring-closing reaction of imidization, it is 200 ° C. or higher, and from the viewpoint of thermal stability of the produced polyimide film, it is 430 ° C. or lower. The imidization is desirably performed in a vacuum or in an inert gas, but may be performed in air if the imidization temperature is not too high.

In addition, the imidization reaction is replaced with the above heat treatment, and a tertiary amine such as pyridine or triethylamine is added to the polyimide precursor polymerization solution to prepare a polyimide precursor film containing a tertiary amine. It is also possible to perform chemical imidization while heating at ~ 300 ° C, or by immersing the polyimide precursor film in a solution containing a dehydrating reagent such as acetic anhydride in the presence of a tertiary amine such as pyridine or triethylamine. is there.
Here, although the manufacturing method of the polyimide film from a polyimide precursor varnish was described, it is not limited to this, The polyimide precursor film dried by heat or the isolated polyimide precursor is heated, or a dehydrating reagent is used. The polyimide may be produced by cyclization reaction. When polyimide is insoluble in a solvent, crystalline polyimide powder can also be obtained as a precipitate.

  In addition, by adding and stirring a dehydrating reagent such as N, N-dicyclohexylcarbodiimide or trifluoroacetic anhydride into the polyimide precursor solution and reacting at 0 to 100 ° C, preferably 0 to 60 ° C, The polyisoimide which is a body is produced | generated. After polyisoimide varnish is formed in the same procedure as described above, it can be easily converted to polyimide by heat treatment at 250 to 450 ° C., preferably 270 to 400 ° C. The isoimidization reaction can also be performed by immersing the polyimide precursor film in a solution containing the dehydrating reagent.

When the polyimide is dissolved in the solvent used for the polymerization of the precursor, the polyimide precursor polymerization solution is heated as it is at 150 to 200 ° C. as it is or after being appropriately diluted with the same solvent. The solution (varnish) can be easily produced. At this time, toluene, xylene, or the like may be added in order to azeotropically distill off water which is a by-product of imidization. In addition, a base such as γ-picoline can be added as a catalyst. The obtained polyimide varnish can be dropped and filtered in a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. Alternatively, the polyimide powder can be redissolved in the polymerization solvent to obtain a polyimide varnish.
A polyimide film can also be formed by applying the polyimide varnish obtained as described above onto a substrate and drying at 40 to 400 ° C., preferably 100 to 300 ° C.
Moreover, the polyimide molded body can be produced by heat-compressing the obtained polyimide powder at 200 to 450 ° C., preferably 250 to 430 ° C.

<Manufacturing method of laminated board>
The polyimide precursor varnish according to the present invention is applied onto a metal foil, for example, a copper foil, dried, and then imidized under the above-described conditions. A laminated board (FCCL) can be obtained.
Various metal foils can be used as the metal layer of the FPC board, and preferably, an aluminum foil, a copper foil, a stainless steel foil, and the like can be given. These metal foils may be subjected to surface treatment such as mat treatment, plating treatment, chromate treatment, aluminum alcoholate treatment, aluminum chelate treatment, silane coupling agent treatment, and the like.
Although the thickness of metal foil is not specifically limited, Preferably it is 35 micrometers or less, More preferably, it is 6-18 micrometers.

FCCL can be manufactured as follows.
First, the polyimide precursor varnish according to the present invention is applied (coated) on a metal foil using a blade coater, a lip coater, a gravure coater, and the like, and then dried to form a polyimide precursor layer. The coating thickness is affected by the solid content concentration of the polyimide precursor varnish, but the polyimide precursor layer is thermally imidized at 200 to 400 ° C. in an inert atmosphere such as nitrogen, helium or argon. Thus, a polyimide resin (insulating) layer can be formed. The thickness of the polyimide resin (insulating) layer is 100 μm or less, preferably 50 μm or less, and more preferably 3 to 25 μm.

Furthermore, an adhesive-free flexible printed wiring board is manufactured by etching the metal layer of the laminated board obtained as described above into a desired circuit shape using an etching solution such as ferric chloride aqueous solution. can do.
Additives such as an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a photopolymerization initiator, and a sensitizer are added to the polyimide and the precursor thereof according to the present invention as necessary. be able to.
Additives such as an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a photopolymerization initiator, and a sensitizer are added to the polyimide and the precursor thereof according to the present invention as necessary. be able to.

    The polyimide according to the present invention has a low linear thermal expansion coefficient equivalent to that of metal foil, particularly copper foil, in particular, sufficient adhesion to copper foil, low hygroscopic expansion coefficient, high glass transition temperature, and high film toughness. It can be used for electrical insulating films and flexible printed wiring boards, display boards, electronic paper boards, solar cell boards, etc. in various electronic devices, and is particularly useful as a flexible printed wiring board material.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited to these Examples. In addition, the physical-property value in an Example was measured with the following method.
<Infrared absorption spectrum>
Using a Fourier transform infrared spectrophotometer (Avatar 360 FT-IR manufactured by Thermo Nicolet), the infrared absorption spectrum of the polyimide film (25 μm thick) was measured by the total reflection method.
<Intrinsic viscosity: h>
A 0.5 wt% polyimide precursor solution was measured at 30 ° C. using an Ostwald viscometer.
<Glass transition temperature: Tg>
By using a thermomechanical analyzer (TMA-50) manufactured by Shimadzu Corporation, a thermal load of 5 g, a heating rate of 10 ° C./min, under a nitrogen atmosphere (flow rate of 20 ml / min), and a temperature range of 50 to 450 ° C. The test piece elongation was measured, and the glass transition temperature of the polyimide film (thickness 25 μm) was determined from the inflection point of the obtained curve.

<Linear thermal expansion coefficient: CTE>
By using a thermomechanical analyzer (TMA-50) manufactured by Shimadzu Corporation, a thermal load of 5 g, a heating rate of 10 ° C./min, under a nitrogen atmosphere (flow rate of 20 ml / min), and a temperature range of 50 to 450 ° C. The test piece elongation was measured, and the linear thermal expansion coefficient of the polyimide film (25 μm thickness) was determined as an average value in the range of 50 to 200 ° C.
<Hygroscopic expansion coefficient: CHE>
Using a thermomechanical analyzer (TM-9400) and a humidity atmosphere controller (HC-1) manufactured by ULVAC-RIKO, Inc., a film having a width of 3 mm, a length of 30 mm (a length between chucks of 15 mm), and a thickness of 20 to 25 μm is obtained. From the elongation of the test piece when the humidity was changed from 10% RH to 80% RH at 23 ° C. and a load of 5 g, the hygroscopic expansion coefficient of the polyimide film was determined as an average value in 10% RH to 80% RH.

<Copper foil adhesive strength>
About the sample preparation method and measuring method of adhesive strength, it carried out according to JIS C6471 standard. A copper foil with a polyimide film coated with a polyimide precursor on a copper foil and imidized in a drier is cut into a size of 15 cm long × 1 cm wide, leaving a center width of 3 mm, and a ferric chloride solution. Etched with. The obtained sample was left to dry in a dryer at 105 ° C. for 1 hour or more, and then attached to a FR-4 substrate having a thickness of 3 mm with a double-sided adhesive tape. A conductor having a width of 3 mm was peeled off at the interface with the polyimide film and attached to an aluminum tape to make a grip allowance.
The sample produced as described above was fixed to a Shimadzu Corporation tensile tester (Autograph AG-10KNI). When fixing, a jig was attached in order to surely peel off in the direction of 90 °. The load at the time of peeling 50 mm at a speed of about 50 mm per minute was measured and calculated as the adhesive strength per 1 cm.

<Solder heat resistance evaluation>
A copper foil with a polyimide film obtained by applying a polyimide precursor onto a copper foil and imidized in a drier is cut into a size of 3 cm in length and 3 cm in width, leaving a center of 2.5 cm × 2.5 cm, and an outer periphery. The copper foil was etched with a ferric chloride solution. After putting the obtained sample in a dryer and leaving it to stand at 105 ° C. for 1 hour or more and drying, the sample was left on the surface of the solder bath for 2 minutes in a solder bath set at 300 ° C. so that the copper foil side is in contact with the sample. , Took out. Changes in the appearance such as swelling in the copper foil and polyimide film and the presence or absence of wrinkles in the copper foil were evaluated by visual observation, and a case where no change in the appearance was observed was regarded as a good result (◯).

<Boiled solder heat resistance evaluation>
A polyimide film-coated copper foil coated with a polyimide precursor on a copper foil and imidized in a drier is cut into a size of 3 cm long × 3 cm wide, leaving a central portion of 2.5 cm × 2.5 cm, and an outer peripheral portion. The copper foil was etched with a ferric chloride solution. Purified water was put into a container with a reflux condenser, and the obtained sample was immersed and allowed to stand at 100 ° C. for 2 hours. Thereafter, samples were put into purified water at room temperature, each sample was taken out one by one, and moisture on both sides was wiped off with a paper towel. Then, after leaving still on the solder bath surface for 2 minutes so that the copper foil side might contact in the solder bath set to 280 degreeC, it took out. Changes in the appearance such as swelling in the copper foil and polyimide film and the presence or absence of wrinkles in the copper foil were evaluated by visual observation, and a case where no change in the appearance was observed was regarded as a good result (◯).
Synthesis Example 1 Synthesis 1 of Oxazole Structure-Containing Diamine 1
In a 2 L Separa flask, 1000 g of polyphosphoric acid and 200 mmol of 3,3′-dihydroxy-4,4′-diaminobiphenyl (manufactured by Wakayama Seika Kogyo Co., Ltd.) are placed and stirred at 150 ° C. for 2 hours in a nitrogen atmosphere. It was. Thereafter, 400 mmol of p-aminobenzoic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and reacted at 200 ° C. for 5 hours. The reaction solution was allowed to reach room temperature, then dropped into purified water, and the resulting yellow-green precipitate was collected by filtration and then vacuum dried at 125 ° C. to obtain crude crystals. Thereafter, the crude crystals were dissolved in N-methylpyrrolidone at around 100 ° C., and the solution allowed to cool to room temperature was filtered to remove insoluble components. Then, a 3 wt% aqueous sodium carbonate solution was added dropwise to the obtained filtrate to obtain a solid. Precipitated. The precipitated solid was collected by filtration, washed 2 to 3 times with purified water, and then vacuum-dried at 125 ° C. to obtain an oxazole structure-containing diamine represented by the following formula (27) (hereinafter referred to as OXA). Got.

Synthesis Example 2 Synthesis 2 of Oxazole Structure-Containing Diamine 2
Instead of 3,3′-dihydroxy-4,4′-diaminobiphenyl, 2,4-diaminophenol dihydrochloride (trade name Amidol, manufactured by Wako Pure Chemical Industries, Ltd.) was used and 2,4-diaminophenol dihydrochloride was used. The oxazole represented by the following formula (28) was subjected to a dehydration ring-closing reaction and separation / purification in polyphosphoric acid in the same manner as in Synthesis Example 1 except that the molar ratio charged to p-aminobenzoic acid was equivalent. A structure-containing diamine (hereinafter referred to as BOXA) was obtained.

Synthesis Example 3 Synthesis of Oxazole Structure-Containing Diamine 3
In place of 3,3′-dihydroxy-4,4′-diaminobiphenyl, 2,4-diaminophenol dihydrochloride (trade name Amidol, manufactured by Wako Pure Chemical Industries, Ltd.), terephthalic acid instead of p-aminobenzoic acid An oxazole structure-containing diamine represented by the following formula (29) is obtained by performing dehydration ring-closing reaction and separation / purification in polyphosphoric acid in the same manner as in Synthesis Example 1 except that (Wako Pure Chemical Industries, Ltd.) is used. (Hereinafter referred to as PBOXA).

(Example 1)
<Polymerization of polyimide precursor, imidization and evaluation of polyimide film characteristics>
In a well-dried sealed reaction vessel with a stirrer, 28 mmol of an ester group-containing diamine (hereinafter referred to as APAB) represented by the formula (30) and 7.2 mmol of OXA represented by the formula (27) were placed, and N-methyl-2 -After dissolving in 145 mL of pyrrolidone, 35.8 mmol of a powder of ester group-containing tetracarboxylic dianhydride (hereinafter referred to as TAMHQ) represented by the formula (31) was gradually added to this solution. After 30 minutes, the solution viscosity increased rapidly.

Furthermore, it stirred at 80 degreeC for 4 hours, and obtained the polyimide precursor solution which has a transparent, uniform and viscous ester group and an oxazole structure. This polyimide precursor solution (varnish) did not precipitate or gel at all even when allowed to stand at room temperature and 20 ° C. for one month, and showed high solution storage stability. The intrinsic viscosity of the polyimide precursor measured with an Ostwald viscometer in N-methyl-2-pyrrolidone at a concentration of 0.5% by weight at 30 ° C. was 0.72 dL / g.
Next, a 12 μm-thick copper foil (NIPPON ELECTRIC CO., LTD. USLP foil) was placed on a metal coating table so that the matte surface was the surface. The surface temperature of the coating table was set to 90 ° C., and the obtained polyimide precursor solution was applied to the copper foil mat surface using a doctor blade. Then, it left still for 30 minutes on the coating stand, and also left still for 30 minutes at 100 degreeC in dryer. A polyimide precursor film (thickness: 45 μm) having no tackiness was obtained. Subsequently, a polyimide precursor film was attached to a metal plate made of SUS, and heated in a hot air dryer under a nitrogen atmosphere at a rate of temperature increase of 5 ° C./minute, 150 ° C. for 30 minutes, 200 ° C. for 1 hour, 400 ° C. And allowed to stand for 1 hour for imidization. A film with copper foil without curling was obtained. This film with copper foil was etched with a ferric chloride solution to obtain a light brown polyimide film having a thickness of 25 μm.

This polyimide film did not break by the 180 ° bending test and showed flexibility. Moreover, it did not show solubility in organic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide. This polyimide film showed 20 ppm / K (average value between 50 ° C. and 200 ° C.) and a low linear thermal expansion coefficient equivalent to copper foil by TMA measurement. When the hygroscopic expansion coefficient was measured, it was 4.4 ppm /% RH (an average value between 10% RH and 80% RH) and an extremely low hygroscopic expansion coefficient. When the 90 ° copper foil adhesive strength was measured, it showed an extremely high adhesiveness of 1.2 kg / cm. Moreover, the high glass transition temperature of 414 degreeC was shown.
Table 1 summarizes the physical property values. The infrared absorption spectrum of the obtained polyimide film is shown in FIG.

(Example 2)
In the same manner as in Example 1, 26 mmol of APAB and 1.4 mmol of OXA were placed in a well-dried sealed reaction vessel with a stirrer, dissolved in 110 mL of N-methyl-2-pyrrolidone, and then 28 mmol of TAMHQ was added to the solution to obtain a composition ratio. Except for the change, according to the method described in Example 1, the polyimide precursor was polymerized, formed into a film and imidized to produce a polyimide film, and physical properties were evaluated. The copolymer composition (molar ratio) is APAB: OXA = 95: 5. This polyimide film did not break even in the 180 ° bending test and showed flexibility. It was not soluble in organic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide. It showed high glass transition temperature, low linear thermal expansion coefficient equivalent to copper foil, low hygroscopic expansion coefficient, high adhesion with copper foil, and good solder heat resistance. The physical property values are shown in Table 1. The infrared absorption spectrum of the obtained polyimide film is shown in FIG.

(Example 3)
It described in Example 1 except having used ester group containing tetracarboxylic dianhydride (henceforth TAHQ) represented by Formula (32) as an ester group containing tetracarboxylic dianhydride instead of TAMHQ. According to the method, the polyimide precursor was polymerized, formed into a film and imidized to produce a polyimide film, and the physical properties were evaluated. The copolymer composition (molar ratio) is APAB: OXA = 80: 20. This polyimide film did not break even in the 180 ° bending test and showed flexibility. It was not soluble in organic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide. It exhibited high glass transition temperature, low linear thermal expansion coefficient equivalent to copper foil, extremely low low hygroscopic expansion coefficient, sufficient adhesion with copper foil, and good solder heat resistance. The physical property values are shown in Table 1. The infrared absorption spectrum of the obtained polyimide film is shown in FIG.

Example 4
Except for using BOXA as the oxazole structure-containing diamine, a polyimide precursor was polymerized, formed into a film and imidized in accordance with the method described in Example 1, and a polyimide film was prepared. Similarly, physical properties were evaluated. The copolymer composition (molar ratio) is APAB: BOXA = 80: 20. This polyimide film did not break even in the 180 ° bending test and showed flexibility. It was not soluble in organic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide. It exhibited high glass transition temperature, low linear thermal expansion coefficient equivalent to copper foil, extremely low low hygroscopic expansion coefficient, sufficient adhesion with copper foil, and good solder heat resistance. The physical property values are shown in Table 1. The infrared absorption spectrum of the obtained polyimide film is shown in FIG.

(Example 5)
Except for using PBOXA as the oxazole structure-containing diamine, a polyimide precursor was polymerized, formed into a film and imidized in accordance with the method described in Example 1, and a polyimide film was prepared. Similarly, physical properties were evaluated. The copolymer composition (molar ratio) is APAB: PBOXA = 80: 20. This polyimide film did not break even in the 180 ° bending test and showed flexibility. It was not soluble in organic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide. It exhibited high glass transition temperature, linear thermal expansion coefficient close to copper, low hygroscopic expansion coefficient, high adhesion to copper foil, good solder heat resistance, and film toughness. The physical property values are shown in Table 1. The infrared absorption spectrum of the obtained polyimide film is shown in FIG.

(Comparative Example 1)
In the same manner as in Example 1, except that TAMHQ was used as the acid dianhydride and the composition ratio of APAB and OXA was changed, the polyimide precursor was polymerized according to the method described in Example 1 to form a film and imidize. A polyimide film was prepared and similarly evaluated for physical properties. The copolymer composition (molar ratio) is APAB: OXA = 50: 50. Although linear thermal expansion coefficient close to copper, high adhesion with copper foil, high glass transition temperature, and film toughness were exhibited, the hygroscopic expansion coefficient was a high value of 10 ppm /% RH. The physical property values are shown in Table 1.

(Comparative Example 2)
Instead of TAMHQ or TAHQ, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA) having no ester group was used, and OXA and 4,4′-diaminodiphenyl ether (hereinafter referred to as “BPHA”) were used. Except for using ODA), a polyimide precursor was polymerized, formed into a film and imidized in accordance with the method described in Example 1, and a polyimide film was prepared to evaluate physical properties. The copolymer composition (molar ratio) is OXA: ODA = 80: 20. Although it showed a low linear thermal expansion coefficient equivalent to copper foil, high adhesion to copper foil, high glass transition temperature, and film toughness, the hygroscopic expansion coefficient was as high as 10 ppm /% RH. The physical property values are shown in Table 1.

(Comparative Example 3)
Except for using BPDA instead of TAMHQ or TAHQ, using BOXA instead of OXA, and using ODA, the polyimide precursor was polymerized according to the method described in Example 1 to form a film, imidize, and polyimide film Were prepared and the physical properties were evaluated. Although it showed low linear thermal expansion coefficient equivalent to copper foil, high adhesion to copper foil, high glass transition temperature, and film toughness, the hygroscopic expansion coefficient was as high as 12 ppm /% RH. The physical property values are shown in Table 1.

(Comparative Example 4)
A polyimide precursor was polymerized according to the method described in Example 1 except that ODA was used instead of OXA. The intrinsic viscosity of the polyimide precursor measured with an Ostwald viscometer at a concentration of 0.5% by weight in N-methyl-2-pyrrolidone was 0.82 dL / g. According to the method described in Example 1, it formed into a film and imidized, the polyimide film was produced and the physical property was evaluated. As with the polyimides described in Examples 1 to 5, the glass transition temperature, the low linear thermal expansion coefficient equivalent to the copper foil, and the film toughness were exhibited, but the hygroscopic expansion coefficient was as high as 8.3 ppm /% RH. The adhesive strength with the copper foil was also a low value of 0.3 kg / cm. The physical property values are shown in Table 1.

  The polyimide of the present invention is a flexible printed wiring (FPC) substrate, a tape automation bonding (TAB) substrate, an electrical insulating film and a liquid crystal display substrate in various electronic devices, an organic electroluminescence (EL) display substrate, and an electronic paper. It can utilize suitably as a board | substrate, a board | substrate for solar cells, especially FPC board | substrate material.

1 is an infrared absorption spectrum of the polyimide film described in Example 1. FIG. FIG. 2 is an infrared absorption spectrum of the polyimide film described in Example 2. FIG. 3 is an infrared absorption spectrum of the polyimide film described in Example 3. 4 is an infrared absorption spectrum of the polyimide film described in Example 4. FIG. FIG. 5 is an infrared absorption spectrum of the polyimide film described in Example 5.

Claims (5)

A polyimide precursor having a structure represented by the following general formula (1) and the following general formula (2), the ratio of X and Y being 60/40 to 99/1, having an ester group and an oxazole structure Polyimide precursor.

Here, A ₁ and A ₂ are tetravalent aromatic groups selected from the formulas (3) to (6), and may be the same or different. The two carboxyl groups bonded to A ₁ and A ₂ are not limited to the cis configuration, and a cis configuration and a trans configuration may be mixed. R ₁ represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, or hydrogen.

Here, B is selected from divalent aromatic groups represented by formula (7) to formula (10), R _{2 to} R ₆ represent an alkyl group having 1 to 4 carbon atoms, a methoxy group, and hydrogen, R _{2 to} R ₄ may be the same or different. In A ₁ , A ₂ , and B, at least one selected from Formula (3), Formula (4), Formula (7), Formula (8), and Formula (9) having an ester group is selected.

Here, D is selected from divalent aromatic groups represented by the formulas (11) to (13), Ar ₁ represents a phenyl group, a biphenyl group, or a naphthyl group, and Ar ₂ represents a phenyl group or a biphenyl group. Represents.

It is a polyimide which has a structure represented by the following general formula (14) and the following general formula (15), Comprising: It has an ester group and oxazole structure whose ratio of X and Y is a ratio of 60 / 40-99 / 1. Polyimide.

Here, A ₁ and A ₂ are tetravalent aromatic groups selected from the formulas (3) to (6), and may be the same or different. The two carboxyl groups bonded to A ₁ and A ₂ are not limited to the cis configuration, and a cis configuration and a trans configuration may be mixed. R ₁ represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, or hydrogen.

Here, B is selected from divalent aromatic groups represented by formula (7) to formula (10), R _{2 to} R ₆ represent an alkyl group having 1 to 4 carbon atoms, a methoxy group, and hydrogen, R _{2 to} R ₄ may be the same or different. In A ₁ , A ₂ , and B, at least one selected from Formula (3), Formula (4), Formula (7), Formula (8), and Formula (9) having an ester group is selected.

Here, D is selected from divalent aromatic groups represented by the formulas (11) to (13), Ar ₁ represents a phenyl group, a biphenyl group, or a naphthyl group, and Ar ₂ represents a phenyl group or a biphenyl group. Represents.

  The method for producing a polyimide according to claim 2, wherein the polyimide precursor having an ester group and an oxazole structure according to claim 1 is cyclized (imidized) by heating or using a dehydrating reagent.   A varnish containing as a main component a polyimide precursor having an ester group and an oxazole structure according to claim 1 is applied onto a metal foil, dried, and then imidized by heating or using a dehydrating reagent. The manufacturing method of the laminated board of the metal layer and the resin layer comprised from the polyimide of Claim 2.   The manufacturing method of a flexible printed wiring board characterized by etching the metal layer of the laminated board of Claim 4.

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