JPS61143434A - Moisture-resistant polyimide - Google Patents

Abstract

PURPOSE:To provide a polyimide of outstanding moisture and heat resistance, high elastic modulus and low linear expansion coefficient, suitable for base film for floppy disc and VTR tape, consisting mainly of two recurring units of each specific structural formula. CONSTITUTION:The objective polyimide consisting mainly of two recurring units of formulae I and II (molar ratio I/II is 70/30-30/70), respectively. These recurring units are constituted by using (A) diamino compound from (i) 30-70mol% of 2.2-bis[4-(4-aminophenoxy)phenyl]-propane of formula III and (ii) 70-30mol% of 3.3'-dimethyl-4,4'-diaminobiphyhenyl of formula IV and (B) biphenyl tetracarboxylic dianhydride (derivative) of formula V.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This invention relates to a moisture-resistant polyimide that has excellent moisture resistance, high elastic modulus and heat resistance, and a low coefficient of linear expansion.

[Background technology]

-a, the polyimide film is made of polyimide obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine.

As this aromatic tetracarboxylic dianhydride, inexpensive pyromellitic dianhydride is widely used, and aromatic tetracarboxylic dianhydride including this pyromellitic dianhydride and various aromatic diamines are used. Various polyimide films obtained in combination with are known. These polyimide films have excellent heat resistance, electrical insulation, chemical resistance, radiation resistance, mechanical strength, etc., and are therefore used for various purposes including surface protection films for semiconductor devices. However, the polyimide film has a drawback of low moisture resistance.

Therefore, we selected biphenyltetracarboxylic dianhydride as the aromatic tetracarboxylic dianhydride and 2,2-bis(4-(4-aminophenoxy)phenyl)propane as the aromatic diamine to absorb moisture. A method for manufacturing a polyimide film with a low expansion coefficient and high moisture resistance has been proposed. However, although this film has an improved moisture absorption expansion coefficient, it has a low elastic modulus and is easily deformed, so it is not suitable for flexible printed distribution boards. When using the film for electrical circuit boards such as the However, it also has disadvantages in that warpage occurs in the laminate obtained by cooling, and dimensional stability during processing for circuit formation deteriorates.

By the way, with the recent increase in the density of magnetic recording media such as floppy disks and VTR tapes, the conventional magnetic coating method (horizontal magnetization) has been replaced by a magnetic material deposition method (vertical magnetization), and these base films As such, the use of polyimide films with excellent elastic properties in place of conventional polyester films is being considered.

However, the polyimide film obtained using the above-mentioned 2,2-bis[4-(4-aminophenoxy)phenyl]propane etc. has the moisture resistance required as the above-mentioned base film, but has a low elastic modulus. , has a high linear expansion coefficient and poor heat resistance (low glass transition point), which causes deformation and deterioration during magnetic material deposition. Therefore, it cannot be applied as is to the above-mentioned base film.

[Purpose of the invention]

This invention aims to increase the elastic modulus and glass transition point of the polyimide obtained using 2,2-bis(4-(4-aminophenoxy)phenyl)propane, etc. without impairing its excellent moisture resistance, and to reduce the expansion coefficient,
The purpose of this invention is to make it suitable for use as a base film for floppy disks and VTR tapes, as well as for use as electric circuit boards such as flexible printed wiring boards.

[Disclosure of the invention]

In order to achieve the above object, the moisture-resistant polyimide of the present invention has repeating units represented by the following general formulas (A) and (B) as main components.

(However, the A/B molar ratio is 70/30 to 30/70.) That is, as seen in general formula B, the above polyimide is composed of 3.3'-dimethyl-4,4'-diaminobiphenyl. Since the structural moieties to be induced are introduced in a specific proportion, 2,2-bis[4-(4-aminophenoxy)
The above-mentioned drawbacks of polyamides obtained using phenyl]propane and the like are overcome without impairing their excellent moisture resistance, and they can be suitably used for base films such as floppy disks and electric circuit boards.

Note that the phrase "the repeating units represented by the general formulas A and B are the main components" also includes the case where the entire unit consists only of the main components.

The repeating units represented by the above general formulas A and B are 2,2-bis[4-(4-aminophenoxy)phenyl]propane shown by the following general formula and the difference in the substitution position of the amino group thereof. These diamino It is composed of a compound, biphenyltetracarboxylic dianhydride represented by the following general formula, and its derivatives alone or in combination.

In this case, the mutual ratio of the above 2,2-bis(4-(4-aminophenoxy)phenyl]propane and at least one of its positional isomers and 3,3'-dimethyl-4,4"-diaminobiphenyl As mentioned above, the molar ratio is set to 30/70 to 70/30. That is, 2
,2-bis[4-(4-aminophenoxy)phenyl]
When the proportion of propane is less than 30 mol%, 3.3°
-Dimethyl-4,4゛ -The proportion of diaminobiphenyl becomes relatively high, and the resulting polyimide film has a high hygroscopic expansion coefficient. It loses its flexibility and becomes brittle. Conversely, the above ratio is 7
If it exceeds 0 mol%, 3.3"-dimethyl-4,4"
- The proportion of diaminobiphenyl becomes relatively low, and the resulting polyimide film has a low elastic modulus and glass transition point, and a high linear expansion coefficient. therefore,
2.2-bis(4-(4-aminophenoxy)phenyl)propane etc. and 3.3'-dimethyl-4,4'
-diaminobiphenyl is set at a molar ratio of 30/70 to 70/30, as described above.

In addition, the above 2,2-bis(4-(4-aminophenoxy)phenyl)propane, etc. and 3,3'-dimethyl-4,
The mutual molar ratio with 4'-diaminobiphenyl is 30
3. within the range of /70 to 70/30.
Up to 10 mol% of the amount of 3'-dimethyl-4'-diaminobiphenyl used may be replaced with other diamino compounds other than the above diamino compounds. Examples of the other diamino compounds include 4,4' -bis(4-aminophenoxy)biphenyl, bis(4-(4-7minophenoxy)phenyl)sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, l, 4-bis(4-
aminophenoxy)benzene, 1.3-bis(4-aminophenoxy)benzene, 1.3-bis(3-aminophenoxy)benzene, 1.4-bis(4-aminophenyl)benzene, bis(4-(4-aminophenoxy)benzene, -aminophenoxy)phenyl]ether, bis(3-ethyl-4-aminophenyl)methane, bis(3-methyl-4-aminophenyl)methane, 3.3'-diaminodiphenylsulfone,
4.4'-diaminodiphenylsulfone, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4.
4'-diaminodiphenyl sulfide, 3.3'
-diaminodiphenyl ether, 3,4''-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4゜4゛-diaminodiphenylmethane, 4.4
"-diaminobiphenyl, 2,4-diaminotoluene, p-phenylenediamine, m-phenylenediamine, etc., which may be used alone or in combination. However, if the proportion of the other diamino compounds used is greater than the above value. In this case, the elastic modulus and glass transition point of the obtained polyimide film become low, and the linear expansion coefficient becomes high, so that the amount used is regulated within the above range.

In addition, biphenyltetracarboxylic dianhydride or its derivatives (hereinafter referred to as "biphenyltetracarboxylic dianhydrides") which are the constituent components of the repeating units represented by the general formulas A and B are 3.3' , 4,4"-biphenyltetracarboxylic dianhydride, 2,3.3',
Examples thereof include 4'-biphenyltetracarboxylic dianhydride and derivatives thereof such as acid halides, diesters, and monoesters. Among these compounds, 3,
It is preferable to use 3',4.4'-biphenyltetracarboxylic dianhydride in an amount of 50 mol% or more based on the total amount of biphenyltetracarboxylic dianhydride used, from the viewpoint of mechanical strength of the resulting polyimide. . Note that the above-mentioned biphenyltetracarboxylic dianhydrides and other aromatic tetracarboxylic dianhydrides may be mixed and used together. Other aromatic tetracarboxylic dianhydrides other than those mentioned above include, for example, pyromellitic acid, 3.3
”, 4.4'-benzophenonetetracarboxylic acid,
2.3,6.7-naphthalenetetracarboxylic acid, 1.4
．． 5.8-Naphthalenetetracarboxylic acid, 3.3”, 4
．． Examples include acid dianhydrides such as 4'-diphenyl ether tetracarboxylic acid and derivatives thereof. These acid dianhydrides and their derivatives may be used alone or in combination.

However, as the amount used increases, the properties of the resulting polyimide film may be adversely affected.
The amount used is 20% by weight or less, preferably 10% by weight.
It is regulated as below.

The moisture-resistant polyimide of the present invention is manufactured using the above-mentioned raw materials, and is particularly suitable for floppy disks, VT
It is useful as a moisture-resistant polyimide film with uses such as a base film for R tape. For example, such a moisture-resistant polyimide film is produced as follows. That is, first, the above-mentioned aromatic tetracarboxylic acid compound and the above-mentioned diamino compound are reacted in a substantially equimolar organic polar solvent to obtain a polyimide precursor such as polyamic acid. In this case, biphenyltetracarboxylic dianhydrides, 2,2-bis(4-(4-aminophenoxy)phenyl)propanes and 3.3°-dimethyl-4,4′-
The polyimide precursor may be synthesized by charging diamino biphenyl and diamino biphenyl into the same container, or by using two containers and placing one of the two types of diamino compounds and the acid dianhydride in one of the containers. Two types of polyimide precursors may be synthesized by charging the other diamino compound and the acid dianhydride in another container and reacting them, and then mixing these after the synthesis.

Next, a solution of this polyimide precursor is cast onto a smooth flat plate such as a glass plate, stainless steel plate, aluminum plate, copper plate, etc. to form a film, and the solvent is gradually removed from this film by heating to form a polyimide precursor. Form a precursor film. or,
After the solution is poured onto the endless stainless steel belt to form a film, the belt is introduced into a heating furnace and the solvent is gradually removed to form a polyimide precursor film. Next, the film of the polyimide precursor obtained as described above was coated with a film of 100 to 200
The solvent is removed by heating at 200 to 350° C. for about 30 to 300 minutes, and polyimide is formed by heating at 200 to 350° C. for about 30 to 300 minutes. As a result, a heat-resistant polyimide film of the present invention is obtained. The above-mentioned solvent removal and heating for the imidization reaction may be performed continuously, or the latter half of the solvent removal and the first half of the imidization reaction may be performed simultaneously.

In addition, as the organic polar solvent, N-methyl-2-
pyrrolidone, N,N-dimethylformamide, N,N-
Dimethylacetamide, hexamethylphosphortriamide, phenol, m-cresol, p-cresol, p
-chlorophenol, O-chlorophenol, dimethyl sulfoxide, etc., which may be used alone or in combination.

In some cases, a nonpolar solvent such as xylene, toluene, naphtha, benzene, etc. may be used in combination with the above polar solvent.

The amount of the above-mentioned polar solvent (when using a mixture of polar and non-polar solvents, only the polar solvent) should be used so that the concentration of both the above compounds is 5-30%. It is preferable.

To explain in more detail about the production of the polyimide precursor in this solvent, the polyimide precursor is prepared by adding approximately equal moles of both the above compounds to the solvent, usually at a temperature of 0 to 80°C.
It can be obtained by reacting for about 0.5 to 24 hours. This polyimide precursor has a logarithmic viscosity (the obtained polyimide precursor solution is dissolved in N-methyl-2-pyrrolidone).
．． diluted to a concentration of 5 g/dl and measured at 30°C) is 0.5
It is preferable that it is in the range of ~7. Particularly preferred is
It is within the range of 0°8 to 5. If the logarithmic viscosity is too low, the resulting polyimide film will have low mechanical strength, which is not preferable. On the other hand, if the logarithmic viscosity is too high, it will be difficult to cast the polyimide precursor solution onto a glass plate or the like, making it difficult to form a film, which is not preferable.

The above logarithmic viscosity is calculated by the following formula, and the falling time in the formula is measured by a capillary viscometer.

(In the formula, tl is the time for the solution to fall through a constant volume of the capillary tube, and t6 is the time for the solvent to fall.

Further, C is the concentration of the polymer in grams in the solution 100111. ) It is known that this logarithmic viscosity is directly related to the molecular weight of the polymer.

Note that the moisture-resistant polyimide film can be produced not only by the above method but also by the following method. That is, a solution of a polyimide precursor obtained in the same manner as the above method was cast onto a flat plate such as a glass plate, and 10
A film is formed by heating and drying at 0 to 150°C for 30 to 120 minutes, and this film is immersed in a mixed solution of pyridine and acetic anhydride to simultaneously remove the solvent and imidize the polyimide precursor. Viscosity (measured at 3°0°C at a concentration of 0.5 g/d1 in concentrated sulfuric acid (usually 98-t% concentration)) is 0°5
It can also be produced by using a polyimide of .about.7. Polyimides obtained by this method generally have a higher elastic modulus (stronger) than those obtained by the above-mentioned method obtained by imidization using only heating. This is because when heated to high temperatures, the molecular weight decreases due to decomposition of the main chain. However, in the case of imidization by chemical treatment as described above, molecular weight reduction does not occur.

The polyimide film of the present invention obtained as described above has a thickness of, for example, 25μ, usually
Tensile modulus at 23℃ is 250-400kg/Tsuru2
The hygroscopic expansion rate after being left in an atmosphere of 100% R0H0 at 25°C for 24 hours is 0.1% or less, and is 50 to 25%.
The average linear expansion coefficient at 0°C is t, axto-'~4.
3 x 10-'1/'Ill: approximately. Further, the glass transition point is 270 to 330°C.

The above hygroscopic expansion coefficient refers to a sample film (a: 80 m, b: 10 (ln, c: 10 m)) having the shape shown in the drawing that has been dried for 24 hours in a hot air circulation dryer at 50°C.
℃, 100% R, H, left for 24 hours,
The dimensions of the front and rear bases are measured using a profile projector or the like, and the value is calculated from the following equation based on the change.

Coefficient of Hygroscopic Expansion (%) Furthermore, the linear expansion coefficient described above is expressed as Δ1/l, assuming that the length of a material of length l at temperature T changes by Δβ due to a temperature change of 1°C.

In addition, the average coefficient of linear expansion means that the measurement temperature is 50 to 250°C.
It is expressed as the average value of linear expansion coefficient between

In contrast, the conventional moisture-resistant polyimide film (rBPDA-BAPP polyimide film) obtained from biphenyltetracarboxylic dianhydride and 2,2-bis(4-(4-aminophenoxy)phenyl)propane (hereinafter referred to as rBPDA-BAPP polyimide film) ) is usually 25 μm thick.
Tensile modulus at 3℃ is 170-240kg/1m"
degree, the hygroscopic expansion coefficient under the same conditions as above is 0.05% or less, and the average linear expansion coefficient at 50 to 250°C is 5 ×
It is about 10-5 to 7.3 x 10-'1/''C, and the glass transition point is 240 to 250°C.

That is, the film made from polyimide of the present invention has a low and excellent hygroscopic expansion coefficient close to that of the above-mentioned BPDA-BAPP polyimide film.
It has a higher modulus of elasticity, a higher glass transition point, and a lower coefficient of linear expansion than other systems.

This polyimide film has the above excellent properties,
It can be suitably used for applications such as base films for floppy disks and VTR tapes, and electric circuit boards.

As mentioned above, since the polyimide of the present invention has repeating units represented by the general formulas A and B as its main components, the logarithmic viscosity measured at 30°C at a concentration of 0.5 g/d1 in concentrated sulfuric acid is 0. 5 to 7, the hygroscopic expansion coefficient is 0.1% or less, and the glass transition point is 270°C or higher.

The polyimide of the present invention exhibits excellent properties not only as a film but also as a laminate or a molded product. The production of such laminates and molded products is performed, for example, in the following manner. That is, a solution of the polyimide precursor is prepared in the same manner as above, impregnated with the solution into glass fiber cloth, carbon fiber cloth, etc., heated to gradually remove the solvent, and then further heated to carry out the imidization reaction. . Then, a highly moisture-resistant polyimide laminate is manufactured by laminating several sheets of the obtained polyimide-impregnated glass fiber cloth or carbon fiber cloth and pressing them with a hot press. In addition, the polyimide precursor was reprecipitated with methanol from the same polyimide precursor solution as above and filtered to obtain a fine powder of about 1 to 30 μm, and this fine polyimide precursor powder was further heated at 250°C for about 2 hours. A polyimide fine powder is produced by drying and complete imidization, and a polyimide molded article is produced by press-molding this polyimide fine powder at 300 to 350° C. using a mold. The laminates and molded products thus obtained can be applied to various fields as materials in place of metals. Furthermore, it can also be used as an insulating material, including as an interlayer insulating film for LSIs, in addition to the above applications.

〔Effect of the invention〕

As described above, the moisture-resistant polyimide of the present invention is composed of biphenyltetracarboxylic dianhydride and 2゜2-bis(4-
(4-aminophenoxy)phenyl]propanes, and the above general formula A repeating unit derived from the above acid dianhydrides and 3,3'-dimethyl-4,4'-diaminobiphenyl. Since the repeating unit of formula B is the main component, it has excellent moisture resistance similar to polyimide synthesized from biphenyltetracarboxylic dianhydride and 2,2-bis(4-(4-aminophenoxy)phenyl)propane. Furthermore, it far exceeds that of the above-mentioned polyimide in terms of elastic modulus, '4FA coefficient of expansion, and heat resistance.Therefore, when used as a base film for floppy disks and VTR tapes, its excellent heat resistance This prevents deformation and deterioration of the film during vapor deposition (perpendicular magnetization) of the magnetic material.Also, because the coefficient of hygroscopic expansion and coefficient of linear expansion is low, after forming it on the base film of a floppy disk or VTR tape, etc. It becomes possible to achieve higher density and higher image quality without causing memory errors due to changes in humidity.

Furthermore, when this moisture-resistant polyimide is used for electric circuit boards such as flexible printed wiring boards, it does not cause any difficulty in bonding with copper foil because of its high elastic modulus. In addition, because the coefficient of linear expansion is low, good results can be obtained in terms of warping of laminates obtained by heating bonding with copper foil and dimensional stability during processing for circuit formation. Due to the above-mentioned low and excellent hygroscopic expansion coefficient, good results can be obtained in terms of moisture resistance of circuit boards. Moreover, the film from the polyimide of this invention)
The properties of 5M do not vary significantly depending on the imidization method. That is, biphenyltetracarboxylic dianhydride is used as the acid dianhydride, and 3.3"-
A film of polyimide (represented by the above-mentioned general formula (B)) obtained by reacting with dimethyl-4,4'-diaminobiphenyl has properties that vary greatly depending on the imidization method. That is, as a method for imidization, a polyamic acid solution obtained by the above combination is cast onto a glass plate, etc. to form a dry coating film, and then immersed in a mixed solution of pyridine and acetic anhydride to remove the solvent and imidize it. When chemical imidization is carried out by performing a reaction, the resulting polyimide film has a high elastic modulus and is strong. However, when heat imidization is performed, in which the above coating film is dried and imidized by heating, the molecular weight decreases due to heating, and the resulting polyimide film becomes inflexible and brittle, making it unsuitable for practical use. .

On the other hand, the polyimide F film of the present invention uses the above-mentioned 3,3''-dimethyl-4,
Rather than using 4′-diaminobiphenyl alone, it and 2,2-bis(4-(4-aminophenoxy)
By using phenyl]propanes in combination, a repeating unit of general formula A is introduced in addition to a repeating unit of general formula B, so even if it is obtained by imidization by heating, it is highly effective due to the coexistence of both. It has elastic modulus and is strong. As described above, the properties of the polyimide film of the present invention do not vary significantly depending on the imidization method, and are therefore extremely useful in practice without being limited by the imidization method.

Next, examples will be described together with comparative examples.

In addition, in Table 1 below, 5-BPDA is 3.3"
, 4,4”-biphenyltetracarboxylic dianhydride,
a-BPDA is 2.3.3',4'-biphenyltetracarboxylic dianhydride, PMDA is pyromellitic dianhydride, and BTDA is 3,3''.

4.4′-benzophenonetetracarboxylic dianhydride, BAPP is 2,2-bis(4-(4-aminophenoxy)phenyl]propane, DDBP is 3.3′-dimethyl-4,4′-diaminobiphenyl, DDE is 4.
4“-diaminodiphenyl ether, BAPD is 4,
4”-bis(4-aminophenoxy)biphenyl, 1,
4.4-BAPB represents 1,4-bis(4-aminophenoxy)benzene, and ri-PDA represents p-phenylenediamine.

In addition, the logarithmic viscosity is 0.5 in N-methyl-2-pyrrolidone.
Values measured at 30°C at a concentration of g/d1.

[Examples 1 to 11] N-methyl-2-pyrrolidone and a diamino compound shown in Table 1 below were placed in a separable flask (No. 11) and mixed well at room temperature until the diamino compound was completely dissolved.

The amount of N-methyl-2-pyrrolidone used was such that the monomer concentration of the diamino compound and the aromatic tetracarboxylic acid compound would be 18% electrolytic corrosion.

Next, an aromatic tetracarboxylic acid compound shown in the same table was gradually added to the flask while suppressing the temperature rise of the solution. After that, the reaction was carried out at room temperature for 2 hours with stirring,
A solution of polyamic acid having the logarithmic viscosity shown in the same table was obtained.

This polyamic acid solution was cast onto a glass plate to form a film, and this film was dried by heating at 120°C for 60 minutes in a hot air dryer, and then heated at 200°C for 120 minutes to form a film.
A polyimide film having a thickness of 50±5 μm was obtained by imidizing the mixture by heating at 350° C. for 60 minutes and then at 350° C. for 30 minutes. When the IR spectrum of this film was measured, no characteristic absorption of amic acid was observed, but characteristic absorption of imide group was observed around 1780 cm<-1 >.

[Comparative Examples 1 to 5] Polyimide films were obtained in the same manner as Examples 1 to 11 using diamino compounds and aromatic tetracarboxylic acid compounds shown in Table 1 below. When the IR spectrum of this film was measured, the characteristic absorption of amic acid was not observed in Comparative Example 2.3, and the characteristic absorption of imide group was observed near 1780 (J-'; There was no formation ability and some characteristic absorption of amic acid remained.

The properties of the polyimide films obtained in the above Examples and Comparative Examples were investigated as follows, and the results are also shown in Table 1 below.

Tensile modulus, elongation rate> Measured at 23°C in accordance with the tensile test method of ASTM-D-882-80.

<Hygroscopic expansion coefficient> After drying the polyimide film in a hot air dryer at 50°C for 24 hours, sample it in the trapezoid shape, measure the base dimension with a profile projector, and then dry it at 25°C, too%RHL 1f11. After leaving it in a desiccator with adjusted temperature for 24 hours, the dimensions were measured in the same way.
The hygroscopic expansion coefficient was determined from the dimensional change.

Average coefficient of linear expansion〉 Thermomechanical analyzer (TMA; manufactured by Seiko Electronics Co., Ltd.,
5SC580 type) under the condition of 2g load.
The average value of the coefficient of linear expansion at 0°C was determined.

As is clear from the above results, the polyimide film of the present invention has almost the same low hygroscopic expansion coefficient as the BPDA-BAPP polyimide film, and
-It can be seen that it has a higher practical elastic modulus and glass transition point and a lower practical linear expansion coefficient than the BAPP polyimide film.

[Brief explanation of the drawing]

The drawing is an explanatory view of a sample piece for measuring the coefficient of hygroscopic expansion.

Claims (1)

[Claims] (1) A moisture-resistant polyimide whose main component is a repeating unit represented by the following general formulas (A) and (B). ▲There are mathematical formulas, chemical formulas, tables, etc.▼...A ▲There are mathematical formulas, chemical formulas, tables, etc.▼...B (However, the A/B molar ratio is 70/30 to 30/70.)