JPH1036506A - New polyimide composition and polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new polyimide composition having a specific water absorbing rate and swelling coefficient with a moisture absorption, excellent in low thermal expandability, low water absorptivity and low swelling ability with water-absorption and suitable as a base film for a flexible printed board, a carrier tape for TAB(Tape Automated Bonding), a resin for a laminated plate, etc. SOLUTION: This polyimide composition has <=1.6% coefficient of water absorption and <=150ppm swelling coefficient with a moisture absorption and obtained by dehydrating and cyclizing compounds of the formula (R1 is biphenyl, naphthyl, etc.; R2 is a divalent organic group; R3 is a tetravalent organic group). The polyimide film is obtained by forming the polyimide into the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel polyimide composition and a polyimide film. More specifically, it has excellent properties such as low thermal expansion, low water absorption, and low moisture expansion, and can be suitably used as a base film for flexible printed circuit boards, a carrier tape for TAB or a resin for laminated boards. The present invention relates to a polyimide composition and a polyimide film.

[0002]

2. Description of the Related Art In general, polyimide films have excellent heat resistance, low temperature characteristics, and
Due to its chemical resistance and electrical properties, it is widely used as a material for electrical and electronic equipment, from the space and aviation fields to the electronic communication field. In particular, recently, it has been required to have not only excellent heat resistance but also various performances depending on the application.

For example, it is desired that a base film for a flexible printed board, a carrier tape for TAB (tape automated bonding), or a resin for a laminated board have a high elastic modulus and a small coefficient of hygroscopic expansion. However, a polyimide film that sufficiently satisfies these properties has not been obtained so far.

[0004]

In order to obtain such a polyimide, it is necessary to make the polyimide main chain as rigid as possible to exhibit low thermal expansion. However, when polyimide is synthesized using pyromellitic dianhydride having the most rigid structure as the raw material constituting the polyimide main chain, high elasticity can be easily expressed,
The polarization of the imide group increases, and low hygroscopicity cannot be exhibited. In order to lower the water absorption, it is conceivable to introduce a fluorine-based resin, but this is not preferable because the production cost is increased and the reactivity of the acid anhydride is expected to decrease.

The present inventors have conducted intensive studies and, as a result, have arrived at a novel polyimide composition obtained by dehydrating and cyclizing a polyamic acid having a specific structure.
The inventors have found that the above-mentioned conventional problems can be solved and the initial object can be achieved, and the present invention has been completed.

[0006]

[Means for Solving the Problems]

The gist of the novel polyimide composition according to the present invention for achieving this object is that the water absorption is 1.6% or less and the coefficient of hygroscopic expansion is 15 ppm or less.

Further, the polyimide composition is represented by the following general formula (1):

[0009]

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Wherein R ₁ is

[0011]

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R ₂ is one or more divalent organic groups, R ₃ is one or more tetravalent organic groups, and R ₄ is CH ₃ -, Cl-, Br
- indicates F-, CH ₃ O-a. ) Is to dehydrate and ring-close the polyamic acid copolymer.

Further, the polyimide composition is represented by the following general formula (1):

[0014]

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Wherein R ₁ is

[0016]

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R ₂ is a divalent organic group selected from
1

[0018]

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A divalent organic group selected from the group consisting of R ₃
Is

[0020]

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Wherein R ₄ is CH ₃ —, Cl—, Br—, F—, CH ₃
O- is shown. L and m each represent an integer of 0 or more, and 0 ≦
m / l, l ≠ 0. ) Is to dehydrate and ring-close the polyamic acid copolymer.

Further, the gist of the polyimide film according to the present invention lies in the use of the polyimide composition according to any one of claims 1 to 3.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide composition according to the present invention is a polyimide composition and a polyimide film having excellent characteristics such as low thermal expansion, low water absorption and low moisture expansion. Specifically, the polyimide composition according to the present invention,
General formula (1)

[0024]

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Wherein R ₁ is

[0026]

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R ₂ is at least one divalent organic group, R ₃ is at least one tetravalent organic group,
R ₄ is _{CH 3 -, Cl-, Br-,} F-, showing a CH ₃ O-. l and m each represent an integer of 1 or more, and 0 ≦ m / l, l
Satisfies ≠ 0. ) Is obtained by dehydration ring closure.

Hereinafter, the novel polyimide composition and the method for producing a polyimide film according to the present invention will be described in detail.

This polyimide composition can be obtained by dehydrating and ring-closing a polyamic acid copolymer which is a precursor thereof. This polyamic acid solution uses substantially equimolar amounts of an acid anhydride and a diamine component, It is obtained by polymerization in a polar solvent. First, a method for producing a polyamic acid copolymer solution will be described.

First, in an atmosphere of an inert gas such as argon or nitrogen, the general formula (2) H ₂ N—R ₂ —NH ₂ (2) (wherein R ₂ represents a divalent organic group) Is dissolved in an organic solvent or dispersed in a slurry form. This solution was added to the general formula (3)

[0031]

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(Wherein R ₁ represents a divalent organic group) and at least one aromatic diester dianhydride represented by the general formula (4):

[0033]

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(Wherein, R ₃ represents a tetravalent organic group). A mixture of at least one tetracarboxylic dianhydride represented by the following formula: A solution of the acid polymer is obtained.

The reaction temperature at this time is from -20.degree.
° C, desirably 60 ° C or less. The reaction time is
It is about 30 minutes to 12 hours.

In this reaction, contrary to the above-mentioned addition procedure, first, a mixture of ester dianhydride and tetracarboxylic dianhydride is dissolved or diffused in an organic solvent, and the solid of the diamine is dissolved in the solution. Alternatively, a solution or slurry using an organic solvent may be added. In addition, they may be mixed and reacted simultaneously, and the mixing order of the acid dianhydride component and the diamine component is not limited.

The organic solvent used for the polyamic acid formation reaction includes, for example, sulfoxide solvents such as diamityl sulfoxide and diethyl sulfoxide, and N,
Formamide solvents such as N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N,
Acetamide solvents such as N-diethylacetamide, N-
Pyrrolidone-based solvents such as methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol-based solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, and catechol; or hexamethylphosphorus Amides, γ-butyrolactone and the like can be mentioned. These can be used with only one kind of solvent or a mixed solvent of two or more kinds. Further, it is also possible to use a mixture of aromatic hydrocarbons such as xylene and toluene.

A mixed solvent composed of these polar solvents and a non-solvent of polyamic acid can also be used. Examples of the non-solvent for the polyamic acid include acetone, methanol, ethanol, isopropanol, benzene, and methyl cellosolve. Further, a part of aromatic hydrocarbons such as xylene and toluene can be used.

It is desirable from the viewpoint of handling that the polyamic acid is dissolved in the above-mentioned organic polar solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight.

The molecular weight of the polyamic acid to be produced preferably has a number average molecular weight of 10,000 or more and 1,000,000 in order to maintain the strength of the polyimide film. If the average molecular weight is less than 10,000, the resulting film becomes brittle, while
If it exceeds 10,000, the viscosity of the polyamic acid varnish becomes too high and handling becomes difficult, which is not preferable.

In this reaction, the ratio of the acid dianhydride component is determined by the molar ratio of the ester dianhydride represented by the general formula (3) and the tetracarboxylic dianhydride represented by the general formula (4). It is preferred to use such that the ratio is in the range of 10/90 to 100/0.

The diamine represented by the general formula (2) is preferably used in an equimolar amount to the total amount of the acid dianhydride component.

More specifically, the diamine component used in the polyimide composition according to the present invention is represented by the following general formula (2): H ₂ N—R ₂ —NH ₂ (2) (where R ₂ is

[0044]

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A divalent organic group represented by the formula:
₄ represents CH ₃ —, Cl—, Br—, F—, CH ₃ O—. )).

As the acid anhydride used in the polyimide composition according to the present invention, essentially various acid dianhydrides can be used. More specifically, from the balance of various properties, the general formula (3) Chemical formula 18

[0047]

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Wherein R ₁ is

[0049]

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A divalent organic group represented by the formula:
₄ represents CH ₃ —, Cl—, Br—, F—, CH ₃ O—. ), And an aromatic diester dianhydride selected from the group consisting of:

[0051]

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Wherein R ₃ is

[0053]

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And a tetravalent organic group represented by It is preferred to use a tetracarboxylic dianhydride selected from

The acid component monomer used in the present invention may be prepared by reacting trimellitic anhydride chloride with phenols in the presence of pyridine in a solvent such as benzene or toluene, or by reacting trimellitic anhydride in a high boiling solvent. It can be obtained by a method such as a transesterification reaction between an acid and diacetates.

Next, in order to obtain a polyimide copolymer from the polyamic acid copolymer solution, dehydration ring closure (imidization) is carried out using either a thermal method or a chemical method using a dehydrating agent. )do it.

For example, in the method of chemically dehydrating and ring-closing, first, a dehydrating agent having a stoichiometric amount or more and a catalytic amount of a tertiary amine are added to the above-mentioned polyamic acid copolymer or a solution thereof to form a support. A film is formed by casting or coating on a support such as a plate, an organic film such as PET, a drum or an endless belt, and a self-supporting polyamic acid film is obtained by evaporating the organic solvent. The evaporation of the organic solvent is preferably performed at a temperature of 150 ° C. or less for about 5 to 90 minutes.

Next, this is peeled off from the support and the end is fixed. Then, it is imidized by gradually heating to about 100 ° C. to 500 ° C., and after cooling it is removed to obtain the polyimide film according to the present invention.

In the thermal dehydration and ring closure method, the polyamic acid solution is cast or coated on a support plate, an organic film such as PET, a support such as a drum or an endless belt to form a film, and then chemically. Treat in the same manner as in the case of dehydration.

When the method of thermally imidizing and the method of chemically imidizing are compared, the elongation of the polyimide composition obtained by the chemical method is excellent, and the mechanical strength of the polyimide is low. There are advantages that mechanical properties such as a large one and a small linear expansion coefficient become good, and that a chemical method allows imidization in a short time. In addition, it is also possible to use both the method of thermally imidizing and the method of chemically imidizing together.

Further heating and drying to imidize,
A polyimide film comprising the polyimide polymer of the present invention is obtained. The heating temperature is preferably in the range of 110 ° C to 550 ° C. There is no particular limitation on the rate of temperature rise during heating, but it is preferable that the temperature is gradually increased so that the maximum temperature becomes the above-mentioned temperature. The heating time varies depending on the film thickness and the maximum temperature.
A range from 0 seconds to 10 minutes is preferred. When heating and drying / imidizing a film having self-supporting properties, the film having self-supporting properties is peeled off from the support, and the end portion is fixed and heated in that state to reduce the linear thermal expansion coefficient. A polymer is obtained.

The general formula (1) obtained as described above
In the thermoplastic polyimide polymer represented by the number of repeating block units m, n is an integer of 1 or more, 0 ≤ m
/ L, l ≠ 0.

Examples of the dehydrating agent include aliphatic dianhydrides such as acetic anhydride and aromatic dianhydrides. Examples of the catalyst include aliphatic amines such as triethylamine, aromatic amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline and isoquinoline.

It is well known that polyimide is equivalent to polyisoimide, but it is possible to improve the solvent solubility by selecting an isoimide structure.
In order to obtain a polyisoimide polymer, the above-mentioned chemical ring-closing agent may be replaced with a diimide such as dicyclohexylcarbodiimide (DCC) and / or a carboxylic acid such as trifluoroacetic acid, and then a reaction similar to the formation of the polyimide may be performed. .

Further, an organic additive such as a thermoplastic resin such as nylon, polyvinyl acetate, polytetrafluoroethylene and polymethyl methacrylate, or a glass fiber is added to the polyamic acid copolymer solution which is a precursor of the polyimide film. A film may be obtained by blending such inorganic fillers or various reinforcing agents, and by blending these, it is possible to further improve various properties such as mechanical strength and adhesiveness.

The novel polyimide composition according to the present invention obtained by the above method has excellent properties such as low thermal expansion, low water absorption and low moisture expansion. Specifically, this polyimide composition has a water absorption of 1.6% or less,
Since the coefficient of hygroscopic expansion is 15 ppm or less, a polyimide film using the polyimide composition according to the present invention may be used as a base film for a flexible printed board, a carrier tape for a TAB, or a resin for a laminated board. It can be suitably used as an electronic circuit component material corresponding to the application.

As described above, in order to clarify the usefulness of the novel heat-fusible polyimide polymer composition according to the present invention,
Although one of the application examples has been described, the present invention is not limited to only these examples, and the present invention is based on the knowledge of those skilled in the art without departing from the spirit of the present invention.
The present invention can be implemented in a modified or modified mode.

[0068]

EXAMPLES First, an example of producing an acid component for producing the polyimide composition according to the present invention will be described.

(Production Example 1) Acid component: Synthesis of p-phenylenebis (trimellitic acid monoester anhydride) .4
Mol) and 1000 ml of toluene and stirred at about 80 ° C. 132 g (1.2 mol) of hydroquinone was dissolved in 1200 ml of toluene and 240 ml of pyridine,
It is dripped from the dropping funnel into the neck flask. After the dropwise addition, the mixture was stirred under reflux for about 2 hours. After cooling, the precipitate was separated by filtration to obtain a white solid. The white solid is washed with 3 liters of water, stirred under reflux with acetic anhydride for about 2 hours, and filtered. The white solid obtained by filtration was recrystallized from DMF to obtain 380 g of a white solid.

(Production Example 2) Acid component: Synthesis of p-methylphenylenebis (trimellitic acid monoester acid anhydride) Instead of hydroquinone, methylhydroquinone 14
Except that 7.6 g (1.2 mol) was used, 350 g of a white solid was obtained in the same manner as in Production Example 1.

(Production Example 3) Synthesis of acid component: p- (2,3-dimethylphenylene) bis (trimellitic acid monoester anhydride) Instead of hydroquinone, 165.6 g (1) of 2,3-dimethylhydroquinone (0.2 mol) in the same manner as in Production Example 1 to obtain 400 g of a white solid.

(Production Example 4) Synthesis of acid component: p-biphenylenebis (trimellitic acid monoester anhydride) .4
Mol) and 1000 ml of toluene and stirred at about 80 ° C. 4,4 ^'- dihydroxybiphenyl 223.2g
(1.2 mol) in toluene (1200 ml) and pyridine (24)
Dissolve in 0 ml, and add dropwise to the above three-necked flask from a dropping funnel. After the dropwise addition, the mixture was stirred under reflux for about 2 hours. After cooling,
The precipitate was filtered off to give a white solid. The white solid is washed with 3 liters of water, stirred under reflux with acetic anhydride for about 2 hours, and filtered. The white solid obtained by filtration was recrystallized from DMF to obtain 400 g of a white solid.

(Production Example 5) Acid component: Synthesis of 1,4-naphthalenebis (trimellitic acid monoester dianhydride) Instead of hydroquinone, 192.0 g (1.2 mol) of 1,4-dihydroxynaphthalene 380 g of a white solid was obtained in the same manner as in Production Example 4 except that was used.

(Production Example 6) Acid component: Synthesis of 2,6-naphthalenebis (trimellitic acid monoester anhydride) In place of hydroquinone, 192.0 g (1.2 mol) of 2,6-dihydroxynaphthalene was used. Except for using it, 385 g of a white solid was obtained in the same manner as in Production Example 4.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the scope of these examples. In the examples, ODA is 4,4'-diaminodiphenyl ether, BAPP is 2,2-bis [4- (4-aminophenoxy) phenyl] propane, and BAPB is 4,4'-diaminodiphenyl ether.
^4' -bis (4-aminophenoxy) biphenyl, TPE
-Q is 1,4-bis (4-aminophenoxy) benzene, p-PDA is paraphenylenediamine, PMDA
Represents pyromellitic anhydride and DMF represents dimethylformamide.

Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the scope of these examples. In the examples, ODA is 4,4'-diaminodiphenyl ether, BAPP is 2,2-bis [4- (4-aminophenoxy) phenyl] propane, and BAPB is 4,4'-diaminodiphenyl ether.
^4' -bis (4-aminophenoxy) biphenyl, TPE
-Q is 1,4-bis (4-aminophenoxy) benzene, p-PDA is paraphenylenediamine, PMDA
Represents pyromellitic anhydride and DMF represents dimethylformamide.

Example 1 NM was placed in a separable flask.
Two equivalents of P and p-PDA and one equivalent of ODA were taken and stirred well at room temperature until the diamine compound was completely dissolved. Next, 2.85 equivalents of p-phenylenebis (trimellitic acid monoester anhydride) shown in Production Example 1 was added as a powder, and the mixture was stirred for 40 minutes. Then, 0.15 equivalents of p-phenylenebis (trimellitic acid monoester anhydride) was dissolved in NMP, gradually added, and then cooled and stirred for 1 hour to obtain a NMP solution of polyamic acid.
Was used so that the concentration of the charged monomer in the aromatic tetracarboxylic dianhydrides was 18% by weight than in the diamines.

Next, the polyamic acid solution was treated with acetic anhydride, β
Mix with picoline, apply by casting on a glass plate,
After drying at about 5 ° C. for about 5 minutes, the polyamic acid coating film was peeled off from the glass plate, and the coating film was fixed on a support frame.
For about 5 minutes, at about 200 ° C. for about 5 minutes, at about 300 ° C. for about 5 minutes, heated at about 400 ° C. for about 5 minutes, and dehydrated and ring-closed to obtain a polyimide film of about 50 μm. Table 1 shows the physical properties of the obtained polyimide film.

The coefficient of thermal expansion was measured at 100 ° C. to 200 ° C. measured by TMA 8140 manufactured by Rigaku Denki in a nitrogen stream.
Refers to the coefficient of thermal expansion in ° C. The water absorption is 150
The weight but was dried for 30 minutes at ℃ City W _1, 24
After immersion in distilled water for a long time and wiping off water droplets on the surface, the weight is defined as W ₂ and calculated by the following equation. Water absorption (%) = (W ₂ −W ₁ ) ÷ W ₁ × 100

The coefficient of hygroscopic expansion was measured by leaving the film in an environmental tester at 50 ° C. and 30% Rh for 24 hours, measuring the film dimensions (L ₁ ), and then placing the film in an environmental tester at 50 ° C. and 80% Rh for 24 hours. Leave to stand, measure film dimensions (L
₂ ) Calculate from the following formula. Hygroscopic expansion coefficient (ppm) = (L ₂ −L ₁ ) {L ₁ } (8
0-30) × 10 ⁶

The elastic modulus is according to ASTM D882.

[0082]

[Table 1]

(Example 2) Instead of ODA, BAPP
A polyamic acid was obtained in the same manner as in Example 1 except that 1 equivalent was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

(Embodiment 3) Instead of ODA, BAPB
A polyamic acid was obtained in the same manner as in Example 1 except that 1 equivalent was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 4 Instead of ODA, TPE-
A polyamic acid was obtained in the same manner as in Example 1 except that 1 equivalent of Q was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 5 Production Example 2 was used instead of p-phenylenebis (trimellitic acid monoester anhydride).
Example 1 was repeated except that 3 equivalents of p-methylphenylenebis (trimellitic acid monoester anhydride) were used.
A polyamic acid was obtained in the same manner as in Example 1, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 6 Production Example 3 was repeated in place of p-phenylenebis (trimellitic acid monoester anhydride).
A polyamic acid was obtained in the same manner as in Example 1 except that 3 equivalents of p- (2,3-dimethylphenylene) bis (trimellitic acid monoester acid anhydride) shown in, were used. Was performed to obtain a polyimide film of about 50 μm. Table 1 shows the physical properties of the obtained polyimide film.

Example 7 Production Example 4 was used instead of p-phenylenebis (trimellitic acid monoester anhydride).
4,4 ^'shown in - biphenylene bis (trimellitic acid monoester acid dianhydride) 2.85 but using an equivalent amount, to obtain a polyamic acid in the same manner as in Example 1, Example 1
A polyimide film of about 50 μm was obtained in the same manner as described above. Table 1 shows the physical properties of the obtained polyimide film.

Example 8 Instead of ODA, BAPP
A polyamic acid was obtained in the same manner as in Example 7, except that one equivalent was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

(Embodiment 9) Instead of ODA, BAPB
A polyamic acid was obtained in the same manner as in Example 7, except that one equivalent was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 10 Instead of ODA, TPE
A polyamic acid was obtained in the same manner as in Example 7 except that -Q1 equivalent was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 11 Instead of p-phenylenebis (trimellitic acid monoester acid anhydride), 1,4-naphthalenebis (trimellitic acid monoester acid dianhydride) 2 shown in Production Example 5 was used. Except that .85 equivalents are used.
Polyamic acid was obtained in the same manner as in Example 1, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

(Example 12) Instead of p-phenylenebis (trimellitic acid monoester acid anhydride), 2,6-naphthalenebis (trimellitic acid monoester acid dianhydride) 2 shown in Production Example 6 was used. Except that .85 equivalents are used.
Polyamic acid was obtained in the same manner as in Example 1, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

(Examples 13 to 24) The amide acid solution used in Examples 1 to 12 was cast and applied on a Teflon-coated SUS plate and dried at about 100 ° C. for about 30 minutes. Peel off from the glass plate, fix the coating on the support frame, and then heat at about 100 ° C for about 30 minutes, about 200 ° C for about 60 minutes, about 300 ° C for about 60 minutes, and about 400 ° C.
For about 30 minutes, followed by dehydration ring-closing and drying to obtain a polyimide film of about 50 μm. Table 1 shows the physical properties of the obtained polyimide film.

(Example 25) Separable plush was added with N
Two equivalents of MP and p-PDA and one equivalent of BAPP were taken, and stirred at room temperature until the diamine compound was completely dissolved. Next, as shown in Production Example 4 4,4 ^'- biphenylene bis (trimellitic acid monoester acid dianhydride) 2 equivalents slowly added a powder, followed by stirring for 40 minutes. PMDA0.
85 equivalents were gradually added as a powder, and then stirred for 40 minutes.
Then, 0.15 equivalents of PMDA is dissolved in NMP, gradually added, and then cooled for 1 hour.
A liquid was obtained. The amount of NMP used was such that the concentration of charged monomers of diamines and aromatic tetracarboxylic dianhydrides was 18% by weight. A polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Example 26 A polyamide was prepared in the same manner as in Example 25 except that 0.85 equivalent of oxydiphthalic acid (ODPA) was added as a powder and 0.15 equivalent as an NMP solution instead of PMDA. An NMP solution of the acid was obtained. From this NMP solution of polyamic acid, a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Comparative Example 1 A polyimide film was obtained in the same manner as in Example 1 except that PMDA and ODA were used in equimolar amounts. Table 1 shows the physical properties of the obtained polyimide film.

[0098]

As described above, as shown in the specific embodiments,
The polyimide composition according to the present invention is obtained from a polyamic acid using a specific ester anhydride, and a polyimide film using the same has a high elasticity, an appropriate linear expansion coefficient, an appropriate flexibility, and a low hygroscopic expansion property. Thus, a useful polyimide film having low hygroscopicity can be obtained.

Claims (4)

[Claims] 1. A novel polyimide composition having a water absorption of 1.6% or less and a hygroscopic expansion coefficient of 15 ppm or less. 2. The method according to claim 1, wherein the polyimide composition has a general formula (1)
Chemical formula 1 Chemical formula 1 (Wherein, R ₁ is R ₂ is one or more divalent organic groups, R ₃ is one or more tetravalent organic groups, and
Wherein R ₄ is CH ₃ —, Cl—, Br—, F—, CH
Shows ₃ O-. 2. The novel polyimide composition according to claim 1, wherein the polyamic acid copolymer represented by the formula) is dehydrated and ring-closed. 3. The method according to claim 1, wherein the polyimide composition has the general formula (1)
Chemical formula 3 Chemical formula 3 (Wherein R ₁ is R ₂ is a divalent organic group selected from Wherein R ₃ is a divalent organic group selected from Wherein R ₄ is C _{4
H 3 -, Cl-, Br-,} F-, showing a CH ₃ O-. L and m each represent an integer of 0 or more, and 0 ≦ m / l, l ≠ 0
Meet. 3. The novel polyimide composition according to claim 1, wherein the polyamic acid copolymer represented by the formula (1) is dehydrated and ring-closed. 4. A polyimide film comprising the polyimide composition according to claim 1.