JPH05320379A - Polyimide film and its production - Google Patents

Abstract

PURPOSE:To obtain a polyimide film having a specific structural unit, good in the balance of physical properties such as elasticity and linear thermal expansion coefficient, etc., by adding 4, 4'-oxydiphthalic anhydride to a straight-line diamine followed by addition of acid dianhydride(s) and then performing dehydrating ring closure. CONSTITUTION:4,4'-oxydiphthalic anhydride is added to a straight-line diamine of e.g. formula I followed by addition of acid dianhydride(S) of formula II and/or formula III so as to be equimolar for the acid dianhydride(s) and the diamine to obtain a polyamic acid copolymer, which is, in turn, thermally dehydrated to effect ring closure, thus obtaining the objective film having a structural unit of formula IV (R1 is straight-line diamine residue; R2 is of formula V or VI; n is >=1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film having excellent heat resistance and mechanical properties, an appropriate coefficient of linear expansion and low hygroscopicity, and a method for producing the same.

[0002]

2. Description of the Related Art Polyimide resins have excellent heat resistance and electrical insulation properties, and have been widely used as industrial materials such as electrical equipment. The polyimide resin is
As described above, it has various excellent properties as compared with other polymers, but with the progress of technology, the required properties required for polyimide resins will also become higher, and it is desired to have various performances depending on the application. There is.

In particular, in recent years, it has been increasingly used in electric and electronic materials for which the tendency of miniaturization and refinement has become remarkable, so that the dimensional stability of the polyimide used is strongly desired. There is. Among them, film applications include many processes in which stress is applied and processes in which temperature is changed, and therefore, it is desired that dimensional changes due to stress and temperature changes are small.

To reduce the dimensional change due to stress, it is effective that the film has a high elastic modulus, and to reduce the dimensional change due to temperature change, it is effective that the film has a small linear expansion coefficient. However, polyimide is mainly used for films such as flexible printed circuit board, TAB base film, and copper wire coating, and these are all composites with metal such as copper or glass. Therefore, it is not preferable for practical use that the coefficient of linear expansion is extremely smaller than that of metal such as copper or glass. Further, when the polyimide film absorbs moisture in the air, the electrical characteristics are deteriorated, so that the polyimide film is desired to have low hygroscopicity.

It has been conventionally known that it is effective to use a highly linear monomer in order to obtain a highly elastic polyimide film. For example, a highly elastic polyimide can be synthesized by using only a rigid straight chain such as pyromellitic anhydride and paraphenylenediamine. However, such a structure is very brittle, the coefficient of linear expansion becomes too small, and the moisture absorption rate becomes large.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyimide film having excellent heat resistance and mechanical properties, having an appropriate linear expansion coefficient and low hygroscopicity, and a method for producing the same.

[0007]

In order to solve the above problems, the inventors of the present invention have diligently studied the molecular structure of polyimide, and as a result, an aromatic polyimide film having a repeating unit of a specific structure has excellent heat resistance, Excellent mechanical properties,
The present invention was completed by finding out that it has an appropriate linear expansion coefficient and low hygroscopicity.

That is, the first aspect of the present invention is that

[0009]

[Chemical 9]

(Wherein R ₁ is at least one linear diamine residue, and R ₂ is

[0011]

[Chemical 10]

It is at least one acid dianhydride residue selected from, and n represents an integer of 1 or more. ] The polyimide film characterized by having the structural unit represented by these.

A second aspect of the invention is the addition of 4,4'-oxydiphthalic anhydride to at least one linear diamine, and then the following:

[0014]

[Chemical 11]

At least one acid dianhydride selected from the above is added so that the total molar amounts of the acid dianhydrides and the diamines are substantially equimolar amounts to obtain a polyamic acid copolymer. And a method for producing a polyimide film, which comprises subjecting the polyamic acid copolymer to dehydration ring closure to obtain a polyimide film having the following structural unit.

[0016]

[Chemical 12]

(Wherein R ₁ is at least one linear diamine residue and R ₂ is

[0018]

[Chemical 13]

It is at least one acid dianhydride residue selected from, and n represents an integer of 1 or more. )

A third aspect of the present invention is the addition of at least one linear diamine to:

[0021]

[Chemical 14]

At least one acid dianhydride selected from the following is added, and then 4,4'-oxydiphthalic anhydride is added so that the total molar amount of each of the acid dianhydride and the diamine is substantially equimolar. To obtain a polyamic acid copolymer, further dehydration ring closure of the polyamic acid copolymer, to obtain a polyimide film having the following structural unit .

[0023]

[Chemical 15]

(Wherein R ₁ is at least one linear diamine residue, and R ₂ is

[0025]

[Chemical 16]

It is at least one acid dianhydride residue selected from, and n represents an integer of 1 or more. )

The present invention will be described in detail below. The polyimide film of the present invention can be obtained from a polyamic acid copolymer solution which is its precursor, and this polyamic acid copolymer solution can be produced by a known method. That is,
It is obtained by polymerizing in a polar organic solvent using substantially equimolar amounts of the tetracarboxylic dianhydride component and the diamine component.

The linear diamine used in the present invention is
The main chain does not include a bending group such as an ether group, a methylene group, an isopropylidene group, a hexafluoroisopropylidene group, and a carbonyl group, and the nitrogen atoms of two amino groups and the carbon atom to which they are bound are aligned. A diamine compound having a lined structure. For example,

[0029]

[Chemical 17]

(However, X is F, Cl, Br, CH ₃ ,
Indicates CH ₃ O or CF ₃ . ) Etc. can be illustrated.

In order to achieve the object of the present invention, 4,4 '
-It is necessary to use oxydiphthalic anhydride,
The water absorption of the polyimide film obtained by using this acid dianhydride can be suppressed to a low level, for example, 2%.
The following is also possible. This is because the electron-donating ether group contained in the 4,4'-oxydiphthalic anhydride residue suppresses the polarizability of the imide group to a low level, and as a result, the amount of water molecules adsorbed on the imide group is reduced. Probably the cause. In the present invention, 4,4'-oxydiphthalic anhydride is represented by the following formula

[0032]

[Chemical 18]

It may be used in any ratio in combination with one or more tetracarboxylic dianhydrides selected from the above, but preferably 4,4'-oxydiphthalic anhydride is 50% of the total acid dianhydride component. ˜99 mol%, at least one tetracarboxylic acid dianhydride selected from the above is 1 to 50 mol% of the total acid dianhydride component, and more preferably 4,4 ′.
-Oxydiphthalic anhydride is a total acid dianhydride component of 75 ~
95 mol%, at least one tetracarboxylic dianhydride selected from the above is 5 to 25 mol of the total acid dianhydride component
% Used. If the ratio of 4,4'-oxydiphthalic anhydride is larger than this, the polyimide film becomes brittle, and if the ratio of 4,4'-oxydiphthalic anhydride is smaller than this, the water absorption becomes large. It is more preferable to use para-phenylenediamine as the linear diamine. Paraphenylenediamine does not have an aliphatic substituent, etc., and is therefore excellent in heat resistance.

The average molecular weight of this polyamic acid is 100.
It is desirable that it is from 0 to 1,000,000. If the average molecular weight is less than 10,000, the obtained film becomes brittle,
On the other hand, if it exceeds 1,000,000, the viscosity of the polyamic acid varnish, which is the polyimide precursor, becomes too high, and the handling becomes difficult. It is also possible to combine various organic additives, inorganic fillers, or various reinforcing materials with this polyimide film.

Examples of the organic polar solvent used in the reaction for producing the polyamic acid copolymer include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide such as N, N-dimethylformamide and N, N-diethylformamide. System solvent; acetamide system solvent such as N, N-dimethylacetamide, N, N-diethylacetamide; N-methyl-2-pyrrolidone,
Pyrrolidone-based solvents such as N-vinyl-2-pyrrolidone;
Phenol-based solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, and catechol; or hexamethylphosphoramide, γ-butyrolactone, and the like, which may be used alone or in combination of two or more. However, it is also possible to use a part of an aromatic hydrocarbon such as xylene or toluene.

A method for synthesizing a polyamic acid copolymer solution will be specifically exemplified. An organic polar solvent and at least one linear diamine are placed in a container, and the mixture is cooled and stirred. 4,4'-oxydiphthalic anhydride is added to the above reaction solution, and the mixture is preferably cooled and stirred for 20 minutes or more. As the acid dianhydride component of the shortage so that the molar amount of the linear diamine and the molar amount of all acid dianhydride components are equal, the following formula

[0037]

[Chemical 19]

At least one acid dianhydride selected from the above can be slowly added with cooling and stirring to obtain the polyamic acid copolymer solution. It is also desirable from the viewpoint of handling that the polyamic acid copolymer is dissolved in the organic polar solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight.

In order to obtain the polyimide film of the present invention from this aromatic polyamic acid copolymer solution, either a thermal method of thermally dehydrating or a chemical method using a dehydrating agent may be used. According to the method, the resulting polyimide film has excellent mechanical properties such as elongation and tensile strength, which is preferable.

An example of producing a polyimide film will be described below. A solution obtained by adding a stoichiometric or more stoichiometric dehydrating agent and a catalytic amount of a tertiary amine to the above polyamic acid polymer or a solution thereof is cast or coated on a drum or an endless belt to form a film. It is dried at a temperature of not higher than 0 ° C for about 5 to 90 minutes to obtain a self-supporting polyamic acid film. Then, this is peeled off from the support and the end is fixed. Then, it is imidized by gradually heating to about 100 to 500 ° C., cooled, and then removed from the drum or endless belt to obtain the polyimide film of the present invention.

Examples of the dehydrating agent here include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as benzoic anhydride. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline. These are used alone or in combination of two or more.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following description, ODA is 4,4'-diaminodiphenyl ether, p-PDA is paraphenylenediamine, PMDA is pyromellitic dianhydride, ODPA.
Is 4,4'-oxydiphthalic anhydride, BTDA is 3,
3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride, DMF represents N, N-dimethylformamide.

Example 1 DMF and p-PDA (4 equivalents) were placed in a separable flask, stirred well at room temperature until the diamino compound was completely dissolved, and then cooled with ice. Next, 3 equivalents of ODPA were added, and the mixture was cooled and stirred for 40 minutes. Then, 1 equivalent of BTDA is D
It was dissolved in MF, gradually added, and then cooled and stirred for 1 hour to obtain a DMF solution of polyamic acid. The amount of DMF used was such that the monomer charge concentration of the diamino compound and the aromatic tetracarboxylic acid compound was 18% by weight. The polyamic acid solution is cast on a glass plate, dried at about 100 ° C. for about 30 minutes, the polyamic acid coating film is peeled off from the glass plate, the coating film is fixed to a supporting frame, and then about 1
About 30 minutes at 00 ° C, about 60 minutes at about 200 ° C, about 30 minutes
It was heated at 0 ° C. for about 60 minutes and dehydrated and ring-closed dried to obtain a polyimide film of about 25 μm. The physical properties of the obtained polyimide film are shown in Table 1.

Example 2 Eight equivalents of DMF and p-PDA were placed in a separable flask, well stirred at room temperature until the diamino compound was completely dissolved, and then cooled with ice. Next, 7 equivalents of ODPA was added, and the mixture was cooled and stirred for 40 minutes. Then, 1 equivalent of BTDA is D
It was dissolved in MF, gradually added, and then cooled and stirred for 1 hour to obtain a DMF solution of polyamic acid. Next, this polyamic acid solution was baked in the same manner as in Example 1 to obtain a polyimide film. The physical properties of the obtained polyimide film are shown in Table 1.

Example 3 4 equivalents of DMF and p-PDA were placed in a separable flask, stirred well at room temperature until the diamino compound was completely dissolved, and then cooled with ice. Next, 3 equivalents of ODPA were added, and the mixture was cooled and stirred for 40 minutes. And PMDA1 equivalent is D
It was dissolved in MF, gradually added, and then cooled and stirred for 1 hour to obtain a DMF solution of polyamic acid. Next, this polyamic acid solution was baked in the same manner as in Example 1 to obtain a polyimide film. The physical properties of the obtained polyimide film are shown in Table 1.

Example 4 Eight equivalents of DMF and p-PDA were placed in a separable flask, well stirred at room temperature until the diamino compound was completely dissolved, and then cooled with ice. Next, 7 equivalents of ODPA was added, and the mixture was cooled and stirred for 40 minutes. And PMDA1 equivalent is D
It was dissolved in MF, gradually added, and then cooled and stirred for 1 hour to obtain a DMF solution of polyamic acid. Next, this polyamic acid solution was baked in the same manner as in Example 1 to obtain a polyimide film. The physical properties of the obtained polyimide film are shown in Table 1.

Comparative Example 1 In the same manner as in Example 1, a polyimide film was obtained using PMDA and ODA in equimolar amounts. The physical properties of the obtained polyimide film are shown in Table 1.

Comparative Example 2 DMF and p-PDA (1 equivalent) were placed in a separable flask, stirred well at room temperature until the diamino compound was completely dissolved, and then cooled with ice. Next, 2 equivalents of PMDA were added, and the mixture was cooled and stirred for 40 minutes. Then, 1 equivalent of ODA is DM
Dissolve in F, add slowly, then stir for 1 hour with cooling,
A DMF solution of polyamic acid was obtained. Next, this polyamic acid solution was baked in the same manner as in Example 1 to obtain a polyimide film. The physical properties of the obtained polyimide film are shown in Table 1.

[0049]

[Table 1] 1) 100 measured by Rigaku Denki TMA 8140
Thermal expansion coefficient of ~ 200 ℃

[0050]

As described above, by copolymerizing 4,4'-oxydiphthalic anhydride with a linear diamine and a specific acid dianhydride, high elasticity, an appropriate linear expansion coefficient, and an appropriate flexibility are obtained. A polyimide film having low hygroscopicity can be obtained.

[Chemical 20]

Claims (4)

[Claims] 1. The following formula: (However, R ₁ is at least one linear diamine residue, and R ₂ is At least one acid dianhydride residue selected from
n represents an integer of 1 or more. ) A polyimide film having a structural unit represented by: 2. The polyimide film according to claim 1, which has a water absorption of 2% or less. 3. At least one linear diamine,
4,4'-oxydiphthalic anhydride was added and then: At least one acid dianhydride selected from the above is added so that the total molar amount of each of the acid dianhydrides and the diamines becomes substantially equimolar amount to obtain a polyamic acid copolymer. A process for producing a polyimide film, which comprises subjecting a polyamic acid copolymer to dehydration ring closure to obtain a polyimide film having the following structural unit. [Chemical 4] (However, R ₁ is at least one linear diamine residue, and R ₂ is At least one acid dianhydride residue selected from
n represents an integer of 1 or more. ) 4. At least one linear diamine, wherein: At least one acid dianhydride is added, and then 4,4'-oxydiphthalic anhydride is added so that the total molar amount of each of the acid dianhydride and the diamine is substantially equimolar. To obtain a polyamic acid copolymer, which is further dehydrated and cyclized to obtain a polyimide film having the following structural unit. [Chemical 7] (However, R ₁ is at least one linear diamine residue, and R ₂ is At least one acid dianhydride residue selected from
n represents an integer of 1 or more. )