JP2007106859A - Aromatic polyamic acid, polyimide and lamination body for wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyimide or a precursor of the same used in electric/electronic fields and the like, expressing low moisture absorption or low hygroscopic expansion and a low dielectric constant to be especially useful as an insulation material for wiring boards and expressing proper elastic modulus. <P>SOLUTION: The aromatic polyimide or the precursor of the same has ≥10 mole% structural unit expressed by general formula (2) (wherein Ar<SB>1</SB>expresses a tetravalent organic group having ≥1 aromatic ring; R expresses a 2-6C hydrocarbon group). The aromatic polyimide is synthesized from an aromatic diamine containing 3, 3'-dialkoxybenzidine or 3, 3'-diphenoxybenzidine and an aromatic tetracarboxylic acid dianhydride. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel aromatic polyamic acid, a novel aromatic polyimide obtained by dehydrating and ring-closing it, and a laminate for a wiring board containing the polyimide in a resin layer. Specifically, a novel aromatic polyamic acid obtained by introducing a monomer unit derived from a diamine having a substituent such as an ethoxy group, a propoxy group, or a phenoxy group into the molecule, and a novel aromatic polyimide obtained by dehydrating and cyclizing it. And a laminate for a wiring board containing the polyimide in a resin layer.

  In general, polyimide resin has excellent heat resistance, chemical resistance, electrical properties, and mechanical properties. Therefore, it is widely used as an electrical and electronic equipment material, especially for electrical insulation materials that require heat resistance. It's being used. Particularly, in recent years, electronic devices have been improved in function, performance, and size, and a polyimide resin that can cope with the reduction in size and weight of electronic components is strongly desired.

  Conventional polyimides are known to have significantly higher moisture absorption, although they have better heat resistance and electrical insulation than other organic polymers. Therefore, it may cause problems such as swelling that occurs when the flexible printed wiring board is immersed in a solder bath, deterioration of electrical characteristics due to moisture absorption in the air, and poor connection of electronic equipment due to dimensional changes after moisture absorption of polyimide. It was. Therefore, characteristics such as low moisture absorption and low humidity expansion are desired. In addition, since the machining process includes many processes that receive stress and processes that undergo humidity changes, it is desirable that the dimensional change due to stress and humidity changes be small. In order to reduce the dimensional change due to stress, it is effective that the film exhibits high elasticity, and in order to reduce the dimensional change due to humidity change, it is effective to reduce the humidity expansion coefficient of the film.

  Conventionally, in order to obtain a highly elastic polyimide film, it is known that it is effective to use a monomer having high linearity. For example, if only a rigid straight chain such as pyromellitic anhydride and paraphenylenediamine is used, a highly elastic polyimide can be synthesized. However, such a structure is very fragile and the moisture absorption rate increases, so that the hygroscopic expansion coefficient also increases.

Japanese Patent Laid-Open No. 02-225522 JP 2001-11177 A JP 08-217877 A JP 2000-63543 A JP-A-01-261421 WO01 / 28767 Publication

  Against this background, in recent years, there has been an increasing demand for polyimide resins having excellent low hygroscopicity and post-moisture dimensional stability, and various studies have been conducted. For example, Patent Document 1 and Patent Document 2 propose a polyimide that improves hydrophobicity and expresses low hygroscopicity by introducing a fluorine-based resin. There is a drawback of poor adhesion. As for other efforts to reduce moisture absorption, as shown in Patent Document 3 and Patent Document 4 and the like, while exhibiting good characteristics such as low moisture absorption and low thermal expansion coefficient, it is possible to maintain high heat resistance. Not.

  Patent Documents 5 and 6 propose monomers having high heat resistance, high elasticity, and low hygroscopicity. However, since the polyimide resin described here is rigid, its elastic modulus is very high. In recent years, laminates used for flexible printed wiring boards having polyimide as an insulating layer are often used for bending applications such as cellular phones. When applied to such applications, an appropriate elastic modulus that is not too rigid is required, and the reliability of the laminate in the above applications is satisfied by balancing with other physical properties. Also, when polyimide resin is used as an insulating layer such as a wiring board, high-speed information transfer may be required. In that case, low dielectric constant and low dielectric loss tangent are required as electrical characteristics of polyimide. Yes. Since polyimide has a strongly polar imide group, most of them have a dielectric constant of 3.5 or more, and development of a material having a lower dielectric constant has been desired.

  Therefore, the present invention solves the above-mentioned conventional problems, has an aromatic polyimide having excellent heat resistance and low moisture absorption, an aromatic polyamic acid as a precursor thereof, and a polyimide containing the same in the resin layer It aims at providing the laminated body for wiring boards which performs.

（式中、Ar₁は芳香環を1個以上有する4価の有機基であり、Rは炭素数2〜6の炭化水素基である。） That is, this invention is an aromatic polyamic acid characterized by having 10 mol% or more of a structural unit represented by the following general formula (1).

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and R is a hydrocarbon group having 2 to 6 carbon atoms.)

（式中、Ar₁は芳香環を1個以上有する4価の有機基であり、Rは炭素数2〜6の炭化水素基である。） Furthermore, this invention is an aromatic polyimide characterized by having 10 mol% or more of structural units represented by the following general formula (2).

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and R is a hydrocarbon group having 2 to 6 carbon atoms.)

  Furthermore, the present invention is the laminate for a wiring board, wherein at least one of the polyimide resin layers is the aromatic polyimide in a laminate having a metal foil on one or both sides of the polyimide resin layer.

  Hereinafter, the present invention will be described in more detail.

  A polyamic acid having a structural unit represented by the general formula (1) (hereinafter also referred to as the present polyamic acid) is a polyimide having a structural unit represented by the general formula (2) by curing and imidizing the polyamic acid. (Hereinafter also referred to as the present polyimide), it can be referred to as a precursor of the present polyimide.

In the structural units represented by the general formulas (1) and (2), Ar ₁ is a tetravalent organic group having one or more aromatic rings, such as an aromatic tetracarboxylic acid or an acid dianhydride thereof. An aromatic tetracarboxylic acid residue generated from Therefore, Ar ₁ is understood by describing the aromatic tetracarboxylic acid used. Usually, when synthesizing this polyimide or the polyamic acid having the structural unit, so that the aromatic tetracarboxylic acid dianhydride is used frequently, the preferred Ar ₁ using an aromatic tetracarboxylic dianhydride This will be described below.

  It does not specifically limit as said aromatic tetracarboxylic dianhydride, A well-known thing can be used. Specific examples include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 2 , 3,3 ', 4'-Benzophenonetetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride , Naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3 , 5,6,7-hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2, 7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphth Len-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 3,3 ', 4 , 4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3, 3 '', 4,4 ''-p-terphenyltetracarboxylic dianhydride, 2,2``, 3,3 ''-p-terphenyltetracarboxylic dianhydride, 2,3,3 ' ', 4' '-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) ) -Propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, Bis (2,3-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) Nyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, perylene-2,3 , 8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5, 6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1 , 2,9,10-Tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine -2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, and the like. Moreover, these can be used individually or in mixture of 2 or more types.

  Among these, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1, 4,5,8-tetracarboxylic dianhydride, 3,3 ", 4,4" -p-terphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3'4 At least one aromatic tetracarboxylic dianhydride selected from 4,4′-benzophenone tetracarboxylic dianhydride or bis (2,3-dicarboxyphenyl) sulfone dianhydride is preferred. More preferably, pyromellitic dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic dianhydride (NTCDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA). In selecting tetracarboxylic dianhydride, it is preferable to select a suitable one by specifically measuring the thermal expansion coefficient, thermal decomposition temperature, glass transition temperature, etc. of polyimide obtained by polymerization and heating.

The diamine used in the synthesis of the present polyamic acid or the present polyimide having the structural unit represented by the general formula (1) or (2) is an aromatic diamine represented by the following general formula (3) (hereinafter referred to as the present aromatic). Also referred to as a diamine).

  R has the same meaning as R in formula (1) or (2) and is a hydrocarbon group having 2 to 6 carbon atoms, preferably an alkyl group having 2 to 4 carbon atoms or a phenyl group. More preferably, they are an ethyl group n-propyl group or a phenyl group.

  The present polyamic acid or the present polyimide can be advantageously obtained by reacting an aromatic tetracarboxylic dianhydride with a diamine containing 10 mol% or more of the present aromatic diamine.

  The aromatic diamine represented by the general formula (3) can be synthesized through the following steps. For example, with respect to those in which R has a hydrocarbon having 3 to 6 carbon atoms, a step of etherifying the corresponding nitrophenol to synthesize alkoxynitrobenzene or allyloxynitrobenzene (hereinafter abbreviated as step-I) and the corresponding alkoxy Nitrobenzene or allyloxynitrobenzene can be obtained from a step (hereinafter abbreviated as Step-II) of benzidine rearrangement via a hydrazo compound to obtain the desired aromatic diamine.

  The reaction of Step-I is described in T. Sala, MV Sargent J. Chem. Soc., Perkin I, pages 2593 to (1979) and RB Bates, KD Janda J. Org. Chem., 47, pages 4374 to (1982). It is well known in the literature, and it is possible to obtain alkoxynitrobenzene or allyloxynitrobenzene with a very good yield in a reaction time of about 15 hours. When R is ethyl, since nitrophenetole as a raw material is commercially available, it can also be used, and can be synthesized from nitrophenol in the same manner. In the reaction of Step-II, by using a known reaction described in RB Carlin J. Am. Chem. Soc., Vol. 67, pages 928 to (1945), formation of isomers of semizine and diphenylin type is observed. The benzidine skeleton can be obtained without any problems.

  These aromatic diamines having a benzidine skeleton can be obtained with high purity by performing recrystallization with a methanol: water mixed solvent.

  In this invention, 90 mol% or less of other diamine other than that can be used with this aromatic diamine represented by the said General formula (3). And it can be set as copolymerization type polyamic acid or a polyimide by it. The structural unit represented by the general formula (1) or (2) is contained in the polyamic acid or the polyimide in an amount of 10 to 100 mol%, preferably 50 to 100 mol%, more preferably 80 to 100 mol%. Good.

  In addition to the aromatic diamine that gives the structural unit represented by the general formula (1) or (2), the diamine used in the copolymerization is not particularly limited. -Dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4 , 4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl Sulfides, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3 , 3'-dimethoxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t- Butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) Benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t- Til) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine and the like can be mentioned.

  Among these, 4,4′-diaminodiphenyl ether (DAPE), 1,3-bis (4-aminophenoxy) benzene (TPE-R) and the like are preferably used. Moreover, when using these diamines, the preferable usage rate is the range of 0-50 mol% of all the diamine, More preferably, it is the range of 0-20 mol%.

  The polyamic acid can be produced by a known method in which the aromatic diamine component and the aromatic tetracarboxylic dianhydride component shown above are used in substantially equimolar amounts and polymerized in an organic polar solvent. That is, it is obtained by dissolving an aromatic diamine in an organic polar solvent such as N, N-dimethylacetamide under a nitrogen stream, adding aromatic tetracarboxylic dianhydride, and reacting at room temperature for about 3 hours.

  And this polyimide is obtained by heating and imidating this polyamic acid obtained by making it above. For imidization, use an applicator on an arbitrary substrate such as copper foil, and after pre-drying at a temperature of 150 ° C or lower for 2 to 20 minutes, usually 130 to 360 ° C for solvent removal and imidization. The heat treatment is performed at a temperature of about 2 to 30 minutes.

  The degree of polymerization of the present polyamic acid and the present polyimide is 50,000 to 800,000, preferably 60,000 to 120,000, as the weight average molecular weight (Mw) of the polyamic acid solution. The weight average molecular weight can be measured by GPC.

  The polyamic acid of the present invention can be dehydrated and cyclized to give a polyimide having excellent heat resistance and low hygroscopicity / low hygroscopic expansion. That is, the polyimide of the present invention has a heat resistance of 430 ° C. or higher (thermal decomposition temperature Td 5%), an elastic modulus of 4 to 8 GPa at 23 ° C., a moisture absorption rate of 0.7% or less, and a dielectric constant of 3.2. Since it is possible to show the following, it is excellent in heat resistance, dimensional stability and elastic modulus, and can have excellent properties such as low hygroscopicity and low dielectric property. The polyimide of the present invention can be used in various fields including the electric / electronic field by taking advantage of these characteristics, and is particularly useful as an insulating material for a wiring board.

  Hereinafter, the content of the present invention will be specifically described based on examples, but the present invention is not limited to the scope of these examples.

Abbreviations used in Examples and the like are shown below.
-PMDA: pyromellitic dianhydride-BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride-o-MOB: 3,3'-dimethoxybenzidine-o-NPOB: 3,3' -Di-n-propyloxybenzidine, o-PHOB: 3,3'-diphenoxybenzidine, TPE-R: 1,3-bis (4-aminophenoxy) benzene, DMF: N, N-dimethylformamide, DMAc: N, N-dimethylacetamide

  In addition, measurement methods and conditions for various physical properties in the examples are shown below.

[Glass transition temperature (Tg), storage modulus E ']
The dynamic viscoelasticity of the polyimide film (10mm x 22.6mm) obtained in each example was measured at a rate of 5 ° C / min from 20 ° C to 500 ° C using a dynamic thermal analyzer, and the glass transition The temperature (tan δ maximum value) and the storage elastic modulus (E ′) at 23 ° C. were determined.

[Measurement of thermal decomposition temperature (Td5%)]
The weight change when a polyimide film weighing 10-20mg was heated from 30 ° C to 550 ° C at a constant rate with a thermogravimetric analysis (TG) device was measured, and 5% weight loss temperature (Td5% )

[Measurement of moisture absorption rate]
After drying 4cm x 20cm polyimide films (each 3 sheets) at 120 ° C for 2 hours, leave it in a constant temperature and humidity room at 23 ° C / 50% RH for more than 24 hours. Asked.
Moisture absorption rate (%) = [(weight after moisture absorption−weight after drying) / weight after drying] × 100

[Measurement of humidity expansion coefficient (CHE)]
An etching resist layer was provided on a copper foil of a polyimide / copper foil laminate of 35 cm × 35 cm, and this was formed into a pattern in which 12 points with a diameter of 1 mm were arranged at intervals of 10 cm on four sides of a 30 cm square. The exposed portion of the copper foil in the opening portion of the etching resist was etched to obtain a polyimide film for CHE measurement having 12 copper foil remaining points. This film was dried at 120 ° C for 2 hours, then left at 23 ° C / 30% RH / 50% RH constant temperature and humidity chamber for at least 24 hours at each humidity, and measured at each humidity measured by a two-dimensional measuring machine. It calculated | required from the dimensional change between copper foil points.

First, the synthesis example of the diamine component used for manufacture of the polyimide which concerns on this invention is demonstrated.
Synthesis example 1
Step-1 Synthesis of 2-n-propyloxynitrobenzene Under a nitrogen atmosphere, 44 g of o-nitrophenol was added to a three-necked flask containing a stirring bar and dissolved in 317 ml of DMF. Potassium carbonate (53 g) and 1-iodopropane (37 ml) were sequentially added, and the reaction was performed at room temperature for 13 hours. The reaction was stopped by adding 200 ml of a saturated aqueous ammonium chloride solution, and the mixture was extracted with 300 ml of a mixed solvent of hexane: ethyl acetate 3: 1. After removing the solvent, purification by column chromatography was performed to obtain 57 g of a light yellow liquid substance. It was.

Step-2 Synthesis of azo compound To a three-necked flask containing a stirrer, 57 g of 2-n-propyloxynitrobenzene obtained in Step-1, 312 ml of ethyl alcohol, 156 ml of 30% by weight sodium hydroxide aqueous solution and 61 g of zinc powder were sequentially added. The reaction was carried out at the boiling temperature for 3 hours. After the ethyl alcohol was almost distilled off, the zinc powder was removed. After extraction with toluene, the solvent was distilled off to recover 45 g of a brown solid.

Step-3 Synthesis of hydrazo compound To a three-necked flask containing a stirrer, 45 g of the reaction product obtained in Step-2, 142 ml of ethyl alcohol and 14 ml of acetic acid were added and heated to the boiling temperature, and then 20 g of zinc powder was added. After confirming that the orange color in the system immediately faded, the reaction contents were poured into a 0.1 wt% sodium sulfite aqueous solution at 70 ° C. The zinc powder was removed by filtration, and ethyl alcohol was almost distilled off, followed by extraction with toluene. By distilling off the solvent, 45 g of a pale yellow to brown solid was recovered.

Step-4 Synthesis of rearrangement reaction product After adding 45 g of the reaction product obtained in Step-3 and 625 ml of diethyl ether to a three-necked flask containing a stir bar and cooling to 0 ° C, 37% concentrated hydrochloric acid: distilled water (volume ratio) 50:50) cold hydrochloric acid 156 ml was added dropwise. When the reaction was performed in an ice bath for 2 hours, precipitation of solid matter was gradually observed. The reaction was stopped by slowly dropping 130 ml of a 20% by weight aqueous sodium hydroxide solution to make it alkaline with a pH of 11 or more. After extraction with toluene and removal of the solvent, recrystallization was performed with a methanol: water mixed solvent to obtain 9.4 g of a white powdery substance. The final yield of the product thus obtained was 20% in 4 steps, and the melting point of this product was 136-138 ° C.

  From the NMR measurement result of the obtained product, it was confirmed that the product was 3,3′-di-n-propyloxybenzidine (o-NPOB).

Synthesis example 2
Step-1 Synthesis of 2-phenoxynitrobenzene Under a nitrogen atmosphere, 73 g of 1,2-dinitrobenzene was added to a three-necked flask containing a stirring bar and dissolved in 433 ml of DMF. 61 g of phenol and 120 g of potassium carbonate were sequentially added, and the temperature was raised from room temperature to 150 ° C. over 2 hours. The reaction solution was cooled to room temperature, insoluble potassium nitrate was removed by filtration, extracted with toluene, the solvent was distilled off, and purification by column chromatography was performed to obtain 84 g of a white solid substance.

Steps 2 to 4 Synthesis of 3,3'-diphenoxybenzidine Using 53 g of the obtained 2-phenoxynitrobenzene, the same reaction as in Steps 2 to 4 of Synthesis Example 1 is carried out to obtain the final target product. 16 g of white powdery material (o-PHOB) was obtained. The final product yield was 32% in 4 steps and the melting point of this product was 125-127 ° C.

  From the NMR measurement results of the obtained product, it was confirmed that the product was the desired 3,3′-diphenoxybenzidine (o-PHOB).

Examples 1-7
In order to synthesize the polyamic acids A to G, the diamines shown in Table 1 were dissolved in the solvent DMAc with stirring in a 100 ml separable flask under a nitrogen stream. Subsequently, the tetracarboxylic dianhydride shown in Table 1 was added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a yellow-brown viscous solution of polyamic acids A to G to be polyimide precursors. The weight average molecular weight (Mw) of each polyamic acid solution was in the range of 60,000 to 120,000, and it was confirmed that a polyamic acid having a high degree of polymerization was produced. The solid content and solution viscosity of the polyamic acid are shown in Table 1. Here, the solid content is a weight ratio of the polyamic acid to the total amount of the polyamic acid and the solvent. The solution viscosity was measured using an E-type viscometer.

Comparative Example 1
Polyamic acid H was synthesized in the same manner as in Examples 1 to 7, except that the raw material composition was changed as shown in Table 1, and the same measurement was performed. The results are summarized in Table 1.

Examples 8-14
In order to produce a polyimide film, each of the polyamic acid solutions A to G was applied on a copper foil using an applicator so that the film thickness after drying was about 15 μm, and after drying at 130 ° C. for 3 minutes, Further, stepwise heat treatment was performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C. and 360 ° C. for 2 to 12 minutes to form a polyimide layer on the copper foil.

  The results of structural analysis of each polyimide film by IR are shown in FIGS. Also, copper foil is etched away using ferric chloride aqueous solution to create a polyimide film of A to G, glass transition temperature (Tg), storage elastic modulus (E '), 5% weight loss temperature (Td5% ), Moisture absorption, hygroscopic expansion coefficient (CHE), and dielectric constant. In addition, the polyimide film of A-G means that it was obtained from the polyamic acid of A-G.

Comparative Example 2
The polyimide amic acid solution of H was imidized in the same manner as in Examples 8 to 14 to prepare a polyimide film of H and evaluated.

Table 2 shows the measurement results of Examples and Comparative Examples.

  The polyimides of Examples 8 to 14 have the heat resistance required for insulating resin applications such as flexible printed laminates, that is, the 5% weight loss temperature (Td5%) of 450 ° C. or higher while maintaining the object of the present invention. The moisture absorption coefficient and humidity expansion coefficient can be lowered, and the elastic modulus and dielectric constant can also be lowered. The polyimide of Comparative Example 2 has a high moisture absorption rate and humidity expansion coefficient.

IR spectrum of polyimide film A IR spectrum of polyimide film B IR spectrum of polyimide film C IR spectrum of polyimide film D IR spectrum of polyimide film E IR spectrum of polyimide film F IR spectrum of polyimide film G

Claims (6)

An aromatic polyamic acid comprising 10 mol% or more of a structural unit represented by the following general formula (1).

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and R is a hydrocarbon group having 2 to 6 carbon atoms.) An aromatic polyimide comprising 10 mol% or more of a structural unit represented by the following general formula (2).

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and R is a hydrocarbon group having 2 to 6 carbon atoms.) In the general formula (2), at least a part of Ar ₁ is pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, naphthalene-2,3,6,7- Tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, 3,3 ", 4,4" -p-terphenyltetracarboxylic dianhydride, 4,4'- Of at least one aromatic tetracarboxylic acid selected from oxydiphthalic dianhydride, 3,3'4,4'-benzophenonetetracarboxylic dianhydride and bis (2,3-dicarboxyphenyl) sulfone dianhydride The aromatic polyimide according to claim 2, which is a residue.   The aromatic polyimide according to claim 2, having an elastic modulus at 23 ° C of 4 to 8 GPa, a moisture absorption rate of 0.7 wt% or less, and a humidity expansion coefficient of 30 to 50% RH of 10 ppm /% RH or less.   3. The method for producing an aromatic polyimide according to claim 2, wherein the aromatic polyamic acid according to claim 1 is imidized.   A laminate having a metal foil on one or both sides of a polyimide resin layer, wherein at least one of the polyimide resin layers is the aromatic polyimide according to claim 2.

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