KR101949316B1 - Polyamic Acid Composition with Improved Storage Stability, Method for Preparing Polyimide Film by Using the Same and Polyimide Film Prepared by the Same - Google Patents

Abstract

The present invention provides: a polyamic acid composition containing an organic solvent and a polyamic acid, wherein at least part of a hydroxyl group contained in the polyamic acid is substituted with an alkoxy group by conducting an alcohol decomposition reaction with an alcohol additive, thereby having excellent storage stability; a method for manufacturing a polyimide film by using the same; and the polyimide film.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyamic acid composition having improved storage stability, a process for producing a polyimide film using the same, and a polyimide film prepared using the same. [0002] Polyamic Acid Composition with Improved Storage Stability,

The present invention relates to a polyamic acid composition having improved storage stability, a method for producing a polyimide film using the same, and a polyimide film produced thereby.

Polyimide (PI) is a polymer material with thermal stability based on a rigid aromatic backbone, and has mechanical properties such as excellent strength, chemical resistance, weather resistance, and heat resistance based on the chemical stability of the imide ring.

In addition, polyimide is attracting attention as a high-functional polymer material applicable to a wide range of industrial fields such as electronic, communication, and optical due to excellent electrical properties such as insulation property and low dielectric constant.

In recent years, various electronic devices have become thinner, lighter, and smaller, and research has been conducted to use a thin and lightweight polyimide film having excellent flexibility as a display substrate that can replace an insulating material of a circuit substrate or a glass substrate for a display .

Generally, a polyimide film is prepared by applying a polyamic acid prepared by polymerization reaction of dianhydride and diamine on a support and imidizing it to form a film, and peeling it from the support.

However, it is known that the polyamic acid contains both an amine group and a carboxylic acid group, and in particular, a hydroxyl group in a carboxylic acid group can be hydrolyzed by reacting with an adjacent amine group, resulting in poor storage stability. It is also known that such a phenomenon becomes noticeable at room temperature or higher than at low temperature.

If the storage stability of the polyamic acid is poor, the viscosity during the process may be greatly changed, and the application and imidization of the polyamic acid may proceed unstably. In addition, when the viscosity of the polyamic acid is lowered, the mechanical and thermal properties of the polyimide film may be significantly lowered.

The degradation of the thermal properties of the dual polyimide film can be particularly negative for the manufacture of display substrates involving high temperature processes.

For example, an organic light emitting diode (OLED) using a low temperature polysilane (LTPS) process can be formed at a process temperature of 400 ° C or higher. Even at such a high temperature, polyimide having excellent heat resistance can be pyrolyzed, The thermal characteristics of the mid-film are very important factors for realizing the display substrate.

Therefore, there is a high demand for polyamic acid having excellent storage stability at room temperature and polyimide film having excellent mechanical and thermal characteristics.

An object of the present invention is to provide a polyamic acid having excellent storage stability at room temperature, a method of producing a polyimide film having improved mechanical and thermal characteristics by using the polyamic acid, and a polyimide film.

According to one aspect of the present invention, an alcoholic additive not only improves the storage stability of a polyamic acid but also is disclosed as an essential factor for realizing a polyimide film having excellent thermal and mechanical properties.

The alcoholic additive may replace at least a part of the hydroxyl groups contained in the polyamic acid with an alkoxy group having relatively low reactivity at room temperature.

This minimizes the phenomenon of hydrolysis of polyamic acid at room temperature. As a result, not only can the storage stability of polyamic acid be improved, but also the hydrolysis is suppressed even in the course of elevating temperature to imidize polyamic acid, It can be advantageous in realizing a polyimide film having excellent physical properties compared to polyamic acid.

According to another aspect of the present invention, a polyamic acid-containing composition in which at least a part of a hydroxyl group is substituted with an alkoxy group by an alcohol-based additive may be used in order to produce a polyimide film having excellent mechanical and thermal properties.

In this case, the imidization reaction can proceed relatively quickly due to the rapid dislocation of the alkoxy group during the heat treatment for polyimide formation. This rapid imidization reaction can contribute to improvement of the conversion ratio ('imidization ratio') from an amic acid group to an imide group, and thus a polyimide film having excellent mechanical and thermal characteristics can be realized.

The polyimide film produced according to the above may have a thermal decomposition temperature of 550 ° C or more, a tensile strength of 280 kgf / cm ² or more, a thermal expansion coefficient of 40 ppm / ° C or less, and an elongation of 13% or more. Such a polyimide film has an advantage of satisfying the mechanical and thermal properties required for the display substrate.

Therefore, the present invention has a practical purpose to provide a specific embodiment thereof.

The present invention has found that a polyamic acid composition in which an alcoholic additive has at least a part of a hydroxyl group contained in a polyamic acid substituted with an alkoxy group has excellent storage stability at room temperature.

The present invention has also found that it is possible to induce a faster imidization reaction and to realize a polyimide film having excellent mechanical and thermal characteristics when the polyimide film is produced using the polyimide film.

Thus, specific details for its implementation are described herein.

Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, it is to be understood that the constituent features of the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the inventive concepts of the present invention, so that various equivalents and variations It should be understood that examples may exist.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising," "comprising," or "having ", and the like are intended to specify the presence of stated features, But do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

As used herein, "dianhydride" is intended to include its precursors or derivatives, which may not technically be dianhydrides, but nevertheless react with diamines to form polyamic acids And this polyamic acid can be converted back to polyimide.

As used herein, "diamine" is intended to include precursors or derivatives thereof, which, although not technically diamines, will nonetheless react with dianhydride to form a polyamic acid, / RTI >

Where an amount, concentration, or other value or parameter is given herein as an enumeration of ranges, preferred ranges, or preferred upper and lower preferred values, it is understood that any pair of any upper range limits It is to be understood that the present invention specifically discloses all ranges formed by preferred values and any lower range limits or preferred values. Where a range of numerical values is referred to in this specification, unless otherwise stated, the range is intended to include all the integers and fractions within the endpoint and its range. The scope of the present invention is not intended to be limited to the specific values that are mentioned when defining the scope.

First Aspect: Polyamic acid composition

The polyamic acid composition according to the present invention comprises an organic solvent and a polyamic acid, wherein at least a part of the hydroxyl groups contained in the polyamic acid is substituted with an alkoxy group by an alcohol decomposition reaction with an alcoholic additive,

The viscosity change rate according to the following formula (1) is more than -3% and less than + 3%.

{(First viscosity - second viscosity) / first viscosity} X 100% (1)

Here, the first viscosity is a viscosity measured immediately after the preparation of the polyamic acid composition, and the second viscosity is a viscosity measured after 10 days from the storage of the polyamic acid composition at room temperature.

Since the viscosity of polyamic acid is substantially proportional to the molecular weight, the change in viscosity means that the polyamic acid has undergone denaturation, and the degree of change in viscosity is an indicator of the degree of polyamic acid denaturation.

In case of conventional polyamic acid, viscosity change rate of more than ± 10% can be shown when stored at room temperature for about 7 days, which means that considerable degeneration occurs in polyamic acid, which may make it difficult to realize a polyimide film having excellent physical properties.

On the other hand, although the polyamic acid of the present invention is stored at room temperature for 10 days, the viscosity change rate is not so small as less than ± 3%, and thus the storage stability at room temperature is excellent. This may be due to the fact that the alkoxy group at room temperature has relatively low room temperature reactivity with respect to the hydroxyl group.

The first viscosity may be 10,000 cP or less, specifically 7,500 cP or less, more specifically 7,200 cP or less. The polyamic acid composition having such a first viscosity has an advantage of being easy to handle in terms of fluidity and may be advantageous for film formation.

The polyamic acid composition may be prepared by adding an alcoholic additive in an amount of 0.07 mol% to less than 1.5 mol% based on 100 mol% of the amic acid group of the polyamic acid. More specifically, , And 0.1 mol% or more and 1 mol% or less.

When a polyamic acid composition is prepared by adding an alcoholic additive to the above range, it may be difficult to produce a polyimide film having desired physical properties. When the amount falls below the above range, improvement in storage stability may be insignificant , Which is undesirable.

The alcohol-based additive may be at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropyl alcohol, benzyl alcohol, ethoxyethanol and butoxyethanol, but is not limited thereto.

The polyamic acid may be produced by polymerizing at least one dianhydride monomer and at least one diamine monomer in an organic solvent.

The dianhydride monomer that may be used in the preparation of the polyamic acid of the present invention may be an aromatic tetracarboxylic dianhydride.

The aromatic tetracarboxylic dianhydride may be pyromellitic dianhydride (or PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (or BPDA), 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (or a-BPDA), oxydiphthalic dianhydride (or ODPA), diphenylsulfone-3,4,3'4'-tetracarboxylic Dianhydride (or DSDA), bis (3,4-dicarboxyphenyl) sulfide dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3- Hexafluoropropane dianhydride, 2,3,3 ', 4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride (or Bis (3,4-dicarboxyphenyl) propane dianhydride, p-phenylene bis (trimellitic monoester), bis Acid Anna P-biphenylene bis (trimellitic monoester acid anhydride), m-terphenyl-3,4,3 ', 4'-tetracarboxylic dianhydride, p-terphenyl- Bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxy Bis (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) biphenyl dianhydride, 2,2- (BPADA), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4 '- (2,2-hexafluoro Diisopropylidene) diphthalic acid dianhydride, and the like. These dianhydride monomers may be used alone or in combination of two or more thereof as desired. However, dianhydride monomers that can be particularly preferably used in the present invention include pyromellitic dianhydride (PMDA), 3,3 ', 4,4 -Biphenyl tetracarboxylic dianhydride (s-BPDA) and 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (a-BPDA). .

The diamine monomers that can be used in the production of the polyamic acid of the present invention are aromatic diamines, which can be categorized as follows.

(1) A method of producing a polyimide precursor composition comprising: 1, 4-diaminobenzene (or paraphenylenediamine, PDA), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, Diamines having one benzene nucleus structurally, such as acacia (" DABA "), etc .; diamines of relatively rigid structure;

2) diaminodiphenyl ethers such as 4,4'-diaminodiphenyl ether (or oxydianiline, ODA) and 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (Methylenediamine), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'- diaminobiphenyl, 2,2'-bis (trifluoromethyl ) -4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane , 3,3 ', 5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis (4-aminophenyl) sulfide, 4,4'- diaminobenzanilide, Dimethylbenzidine (or o-tolidine), 2,2'-dimethylbenzidine (or m-tolidine), 3,3'-dimethoxybenzidine, 2,2'-dimethoxy Benzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylsulfide, 3,4 ' -Diaminodiphenylsulfide, 4,4'-diamino Phenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4 ' -Diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenyl Bis (3-aminophenyl) propane, 2,2-bis (4-amino Phenyl) propane, 2,2-bis (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis , 1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenylsulfoxide, 3,4'-diaminodiphenylsulfoxide, 4,4'-diaminodiphenylsulfoxide A diamine having two benzene nuclei in structure;

(3) aminophenyl) benzene, 1,4-bis (3-aminophenyl) benzene, Bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene (or TPE- Benzene (or TPE-Q), 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 3,3'-diamino- , 3'-diamino-4,4'-di (4-phenylphenoxy) benzophenone, 1,3-bis (3-aminophenylsulfide) benzene, Benzene, 1,4-bis (4-aminophenylsulfide) benzene, 1,3-bis (3-aminophenylsulfone) benzene, 1,3- Benzene, 1,4-bis [2- (3-aminophenyl) isopropyl] benzene, 1,4- Benzene having three structural benzene nuclei, such as bis [2- (4-aminophenyl) isopropyl] benzene, Amine;

4) bisphenols such as 3,3'-bis (3-aminophenoxy) biphenyl, 3,3'-bis (4-aminophenoxy) biphenyl, 4,4'- (4-aminophenoxy) phenyl] ether, bis [4- (aminophenoxy) phenyl] (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, bis [3- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- , Bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) (4-aminophenoxy) phenyl] sulfone, bis [3- (4-aminophenoxy) (3-aminophenoxy) phenyl] methane, bis [3- (4-aminophenoxy) phenyl] methane, bis [4- Phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 2,2-bis [3- Phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2- (BAPP), 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2- -Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] Such as 3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, Diamine with four benzene nuclei in structure.

These diamines can be used singly or in combination of two or more kinds as desired. The diamine monomers that can be particularly preferably used in the present invention include 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD ), 2,4-diaminotoluene, 2,6-diaminotoluene, and 3,5-diaminobenzoic acid (DABA).

In the polyamic acid composition, the diamine monomer and the dianhydride monomer may be substantially equimolarly charged. More specifically, the amount of the dianhydride monomer may be from 99 mol% to 101 Mol, and more specifically, the amount of the dianhydride monomer may be 99 mol% to 99.9 mol% based on 100 mol% of the diamine monomer.

When the amount of the dianhydride monomer added is less than or equal to the above range, polymerization is terminated before a desired molecular weight is reached, or a polyamic acid capable of forming a polyimide film by generating a large number of low molecular weight oligomers it's difficult.

Second aspect: Production method of polyimide film and polyimide film

The method for producing a polyimide film according to the present invention comprises:

(a) introducing at least one dianhydride monomer and at least one diamine monomer into an organic solvent and polymerizing to prepare a polyamic acid solution containing a polyamic acid;

(b) adding an alcoholic additive in an amount of from 0.07 mol% to less than 1.5 mol% based on 100 mol% of the amic acid group of the polyamic acid to a polyamic acid solution to prepare a polyamic acid composition; And

(c) drying the polyamic acid composition to form a gel film;

(d) heat treating the gel film to obtain a polyimide film.

An advantage of the manufacturing method according to the present invention is that,

In the step (b), at least a part of the hydroxyl groups contained in the polyamic acid is reacted with the alcohol-based additive to replace with an alkoxy group;

In the above processes (c) and (d), each of the hydroxyl group and the alkoxy group may react with an amine group to form a plurality of imide groups. At this time, the alkoxy group acts as a good leaving group, This is because the hydrogenation reaction can be promoted.

In summary, the alkoxy group has a low reactivity with respect to a hydroxyl group at room temperature, which is preferable for polyamic acid in terms of storage stability and can act as an excellent leaving group at a high temperature for producing a polyimide film to promote the imidization reaction of polyamic acid. It can be a significant advantage for both mica and polyimide films. Also from this advantage, a high imidization rate polyimide film can be realized.

The high imidation rate is a major factor in causing the polyimide film to exhibit excellent thermal and mechanical properties, so that the advantages of the manufacturing method of the present invention can be sufficiently expected.

The preparation of the polyamic acid solution in the present invention can be carried out, for example,

(1) a method in which the whole amount of the diamine monomer is put into a solvent, and then the dianhydride monomer is added so as to be substantially equimolar with the diamine monomer, and the mixture is polymerized;

(2) a method in which the whole amount of the dianhydride monomer is put into a solvent, and then, the diamine monomer is added so as to be substantially equimolar with the dianhydride monomer and polymerized;

(3) After adding some of the components of the diamine monomer into the solvent, a part of the dianhydride monomer is mixed with the reaction component in a ratio of about 95 to 105 mol%, and then the remaining components of the diamine monomer are added. A method in which a dianhydride monomer component is added to polymerize the diamine monomer and the dianhydride monomer so that they are substantially equimolar;

(4) After adding the dianhydride monomer into the solvent, the dianhydride monomer component is added to the reaction component in a proportion of 95 to 105 mol%, and then the remaining diamine monomer component To thereby polymerize the diamine monomer and the dianhydride monomer so that the diamine monomer and the dianhydride monomer are substantially equimolar;

(5) reacting one or more of the diamine monomer component and the part of the dianhydride monomer component in an excess to form a first composition, and in the other solvent, adding a part of the diamine monomer component and a part of the dianhydride monomer component A method of mixing a first and a second composition to complete a polymerization, wherein, when the first composition is formed, if the diamine monomer component is excessive, In the case where the dianhydride monomer component is excessive in the first composition and the diamine monomer component is excessive in the second composition when the dianhydride monomer component is excessive in the second composition, So that the total diamine monomer component and the dianhydride monomer component used in the step And the like over the polymerization method.

However, the polymerization method is not limited to the above examples, and any known method may be used.

The dianhydride monomer may be appropriately selected from the examples described above, and specifically includes pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride ( s-BPDA) and 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (a-BPDA) can be preferably used.

The dianhydride monomer may be appropriately selected from the examples described above and specifically includes 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzoic acid (DABA), and the like can be preferably used.

The alcohol-based additive may be at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropyl alcohol, benzyl alcohol, ethoxy ethanol and butoxy ethanol, but the scope of the present invention is not limited thereto .

The amount of the dianhydride monomer may be 99 mol% to 99.9 mol% based on 100 mol% of the diamine monomer, and the amount of the alcohol-based additive may be 0.1 mol% to 1 mol%.

When the amount of the dihydride monomer to be added is more than or less than the above range, the polymerization is terminated before the desired molecular weight is reached, or a large number of low molecular weight oligomers are produced, and a polyimide film is formed A problem that can not be solved can occur.

When the alcohol-based additive is added in an amount exceeding the above range, it may be difficult to produce a polyimide film having desired physical properties. If the alcohol-based additive is below the above range, improvement in storage stability of the polyamic acid solution may be insignificant, It is not preferable.

In the production process of the present invention, the polyimide film can be produced through thermal imidation. The thermal imidization method is a method in which a chemical catalyst is excluded and a imidization reaction is induced by a heat source such as hot air or an infrared drier.

For reference, there is a possibility that at least a part of the added alcoholic additive remains in the process (b) in which the alkoxylation reaction is carried out by introducing the alcoholic additive, and water is generated as a byproduct of the alkoxylation reaction, Can remain in the mixed acid solution. The water remaining in the polyamic acid solution may lose the function of the anhydride catalyst used as a chemical catalyst in the imidization process. Therefore, the thermal imidization method not using a chemical catalyst may be preferable for the implementation of the polyimide film contemplated in the present invention, because the imidization reaction may not proceed effectively even when a chemical catalyst is used.

The thermal imidization method may include the step (d). In the step (d), the gel film is heat-treated at a variable temperature ranging from 50 ° C to 600 ° C to remove an amic acid group present in the gel film It can be imidated.

However, even in the step (c) of forming the gel film, a part (about 0.1 to 10 mol%) of amic acid may be imidized, and in this step (c) The polyamic acid composition can be dried at a variable temperature, and this can also be included in the category of the thermal imidation process.

The polyimide film of the present invention produced according to the above production method has a thermal decomposition temperature (Td) of 550 DEG C or more, a thermal expansion coefficient of 40 ppm / DEG C or less, an elongation of 13% or more, a tensile strength of 280 kgf / cm < ² >.

The present invention also provides an electronic device comprising the polyimide film, wherein the electronic device may be an electronic device including a flexible circuit board or a display substrate.

The polyamic acid composition according to the present invention is characterized in that at least a part of the hydroxyl groups contained in the polyamic acid is substituted with an alkoxy group by the addition of an alcoholic additive. The alkoxy group has relatively low reactivity at room temperature and does not cause denaturation of the polyamic acid, and thus the polyamic acid composition has an advantage of improving storage stability at room temperature. The alkoxy group can also inhibit hydrolysis even in the course of elevating the temperature to imidize the polyamic acid, which can be advantageous for realizing a polyimide film having better physical properties than the case without alkoxy groups.

An advantage of the production process according to the present invention is that a polyimide film having excellent mechanical and thermal properties can be produced by using a polyimide composition in which an alcoholic additive is added to a polyamic acid to replace at least a part of the hydroxyl groups with an alkoxy group will be.

This may be due to the fact that the imidization reaction proceeds relatively quickly due to the rapid dislocation of the alkoxy group during the heat treatment for producing the polyimide film, and thus the imidization rate is improved.

In addition, the polyimide film produced according to the above can have excellent thermal and mechanical properties required for a display substrate, with a pyrolysis temperature of 550 ° C or higher and a tensile strength of 280 kgf / cm ² or higher.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

The abbreviations used in Examples and Comparative Examples are as follows.

- biphenyl tetracarboxylic acid dianhydride: BPDA

- pyromellitic dianhydride: PMDA

- para-phenylenediamine: PPD

- N-methylpyrrolidone: NMP

≪ Example 1 >

824 g of NMP was introduced into a 1000 ml reactor equipped with a stirrer and a nitrogen inlet / outlet tube, and the temperature of the reactor was set at 35 ° C. Then, 40.5 g of PPD and 101.4 g of BPDA were added to completely dissolve and react Stir until stirring. After the completion of the reaction, 2.85 g of BPDA was dissolved in NMP in an amount of 10% by weight, and the solution was added thereto at 10 minutes intervals until the viscosity reached 8000 cP at 23 ° C. Thereafter, the temperature of the reactor was set at 50 캜, and 0.1 mol of methanol was added to 100 mol of PPD. After sufficiently stirring until the reaction was completed, a polyimide precursor composition (viscosity at 23 캜: 7,100 cP) was prepared.

The viscosity was measured by measuring Brookfield viscometer (RVDV-II + P) twice at 50 rpm using a 7 scandal at 25 ° C.

≪ Example 2 >

The polyamic acid composition was prepared in the same manner as in Example 1 except that the molar ratio of BPDA to methanol was changed as shown in Table 1, and the first viscosity was measured. The measured viscosity was about 6,900 cP.

≪ Example 3 >

A polyamic acid composition was prepared and the first viscosity was measured in the same manner as in Example 1, except that ethanol was added at a molar ratio shown in Table 1 instead of methanol. The measured viscosity was 6,970 cP.

<Example 4>

A polyamic acid composition was prepared and the first viscosity was measured in the same manner as in Example 1, except that n-propanol was used instead of methanol in the molar ratio shown in Table 1 below. The measured viscosity was 6,950 cP.

&Lt; Example 5 >

PPD, BPDA, and PMDA were added to NMP in the molar ratio shown in Table 1 while maintaining the inside of the reaction system at 25 占 폚 and polymerization was carried out to prepare a polyamic acid solution. Methanol was added to the polyamic acid solution thus prepared at the molar ratio shown in Table 1 below to prepare a polyamic acid composition and the first viscosity was measured. The measured viscosity was about 5,300 cP.

&Lt; Example 6 >

The polyamic acid composition was prepared and the first viscosity was measured in the same manner as in Example 5, except that the molar ratio of BPDA to methanol was changed as shown in Table 1 below. The measured viscosity was about 5,150 cP.

&Lt; Comparative Example 1 &

PPD and BPDA were added to NMP in the molar ratio shown in Table 1 while maintaining the inside of the reaction system at 25 ° C and polymerization was carried out to prepare a polyamic acid solution and the first viscosity was measured. The measured viscosity was about 7,100 cP.

&Lt; Comparative Example 2 &

The polyamic acid composition was prepared in the same manner as in Example 1 except that the molar ratio of BPDA to methanol was changed as shown in Table 1, and the first viscosity was measured. The measured viscosity was about 6,780 cP.

&Lt; Comparative Example 3 &

The polyamic acid composition was prepared and the viscosity was measured in the same manner as in Example 1, except that the molar ratio of BPDA to methanol was changed as shown in Table 1 below. The measured viscosity was about 6,950 cP.

&Lt; Comparative Example 4 &

The polyamic acid composition was prepared and the first viscosity was measured in the same manner as in Example 1 except that ethanol was used instead of methanol, and the molar ratio of BPDA to ethanol was changed as shown in Table 1 below. The measured viscosity was 7,050 cP.

&Lt; Comparative Example 5 &

Except that n-propanol was used instead of methanol, and the molar ratio of BPDA and n-propanol was changed as shown in Table 1, and the first viscosity was measured by preparing the polyamic acid composition in the same manner as in Example 1. The measured viscosity was 7,000 cP.

&Lt; Comparative Example 6 >

The polyamic acid composition was prepared and the viscosity was measured in the same manner as in Example 5, except that the molar ratio of BPDA to methanol was changed as shown in Table 1 below. The measured viscosity was about 5,400 cP.

&Lt; Comparative Example 7 &

The polyamic acid composition was prepared and the viscosity was measured in the same manner as in Example 5, except that the molar ratio of BPDA to methanol was changed as shown in Table 1 below. The measured viscosity was about 5,010 cP.

PPD
(mole%) PMDA
(mole%) BPDA
(mole%) Methanol
(mole%) ethanol
(mole%) n-propanol
(mole%) First viscosity
(cP) Example 1 100 - 99.9 0.1 - - 7,100 Example 2 100 - 99 One - - 6,900 Example 3 100 - 99.9 - 0.1 - 6,970 Example 4 100 - 99.9 - - 0.1 6,950 Example 5 100 50 49.9 0.1 - - 5,300 Example 6 100 50 49 One - - 5,150 Comparative Example 1 100 - 100 - - - 7,100 Comparative Example 2 100 - 98.5 1.5 - - 6,780 Comparative Example 3 100 - 99.95 0.05 - - 6,950 Comparative Example 4 100 - 99.95 - 0.05 - 7,050 Comparative Example 5 100 - 99.95 - - 0.05 7,000 Comparative Example 6 100 50 49.95 0.05 - - 5,400 Comparative Example 7 100 50 48.5 1.5 - - 5,010

EXPERIMENTAL EXAMPLE 1: Evaluation of storage stability [

The polyamic acid compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 7 were allowed to stand at room temperature for 10 days. Thereafter, the second viscosity was measured by the viscosity measurement method described in Example 1, and the rate of change in viscosity was calculated according to the following equation (1), and it is shown in Table 2 below.

{(First viscosity - second viscosity) / first viscosity} X 100% (1)

First viscosity
(cP) Second viscosity
(cP) Viscosity change rate
(%) Example 1 7,100 7,210 + 1.55% Example 2 6,900 7,070 + 2.46% Example 3 6,970 7,100 + 1.86% Example 4 6,950 7,100 + 2.16% Example 5 5,150 5,250 + 1.32% Example 6 5,300 5,420 + 2.26% Comparative Example 1 7,100 8,030 + 13.10% Comparative Example 2 6,780 6,120 -10.78% Comparative Example 3 6,950 7,670 + 10.36% Comparative Example 4 7,050 7,850 + 11.35% Comparative Example 5 7,000 7,890 + 12.71% Comparative Example 6 5,400 6,030 + 11.67% Comparative Example 7 5,010 4,520 -10.84%

As shown in Table 2, the polyamic acid compositions of Examples 1 to 6, in which the alcoholic additive was added within the range of the present invention, did not significantly change the viscosity even after 10 days passed.

From the above results, it can be seen that the polyamic acid composition of the present invention is excellent in storage stability at room temperature.

This is because at least a part of the hydroxyl groups capable of inducing a modifying reaction such as hydrolysis at room temperature is substituted with an alkoxy group in an appropriate amount of the alcoholic additive within the scope of the present invention and as a result, And that the reaction was not induced.

On the other hand, in Comparative Example 1 in which no alcoholic additive was added at all, a remarkable decrease in viscosity of the polyamic acid was caused. It is expected that the hydroxyl group of the polyamic acid of Comparative Example 1 promotes the modification reaction such as hydrolysis and thus the viscosity is greatly changed as shown in Table 2. [

On the other hand, in the case of Comparative Examples 2 to 7, a large viscosity change was accompanied by the addition of an alcohol-based additive. This clearly shows that the effect of improving the storage stability is not manifested even if the content of the alcoholic additive is too small or too large to be used beyond the scope of the present invention.

&Lt; Example 7 >

The polyimide precursor composition of Example 1 was bubbled through a high-speed rotation of 1,500 rpm or more. Thereafter, the defoamed polyimide precursor composition was applied to the glass substrate using a spin coater. Thereafter, the resultant was dried in a nitrogen atmosphere at 120 ° C. for 30 minutes, heated to 450 ° C. at a rate of 2 ° C./min, heat-treated at 450 ° C. for 60 minutes, cooled to 30 ° C. at a rate of 2 ° C./min To prepare a polyimide film. Thereafter, the film was dipped in distilled water and the polyimide film was peeled from the glass substrate. The thickness of the produced polyimide film was 15 1 탆.

The thickness of the polyimide film was measured using an electric film thickness tester manufactured by Anritsu.

&Lt; Example 8 >

A polyimide film having a thickness of 15 탆 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Example 2 was used.

&Lt; Example 9 >

A polyimide film having a thickness of 15.5 占 퐉 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Example 3 was used.

&Lt; Example 10 >

A polyimide film having a thickness of 15.4 占 퐉 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Example 4 was used.

&Lt; Example 11 >

A polyimide film having a thickness of 14.8 占 퐉 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Example 5 was used.

&Lt; Example 12 >

A polyimide film having a thickness of 14.6 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Example 6 was used.

&Lt; Comparative Example 8 >

A polyimide film having a thickness of 15.3 占 퐉 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Comparative Example 1 was used.

&Lt; Comparative Example 9 &

A polyimide film having a thickness of 15.7 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Comparative Example 2 was used.

&Lt; Comparative Example 10 &

A polyimide film having a thickness of 15.5 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Comparative Example 3 was used.

&Lt; Comparative Example 11 &

A polyimide film having a thickness of 15.5 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Comparative Example 4 was used.

&Lt; Comparative Example 12 >

A polyimide film having a thickness of 15.4 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Comparative Example 5 was used.

&Lt; Comparative Example 13 &

A polyimide film having a thickness of 15.3 占 퐉 was obtained in the same manner as in Example 7 except that the polyamic acid composition of Comparative Example 6 was used.

&Lt; Comparative Example 14 >

A polyimide film having a thickness of 15 탆 was obtained in the same manner as in Example 7, except that the polyamic acid composition of Comparative Example 7 was used.

<Experimental Example 2: Evaluation of physical properties>

Physical properties of the polyimide films prepared in Examples 7 to 10 and Comparative Examples 8 to 12 were measured by the following method, and the results are shown in Table 3 below.

(1) Pyrolysis temperature

The pyrolysis temperature was measured using a TGA measuring apparatus of Perkin Elmer. The polyimide film was cut into a size of 3 mm x 3 mm, pre-treated, placed on a weighed fan, adiabatically treated at 110 ° C for 30 minutes, cooled to room temperature and then heated to 600 ° C at a rate of 5 ° C per minute Were measured. The pyrolysis temperature was estimated to be 1% of the weight of the first loaded polyimide film.

(2) Tensile strength

The tensile strength was measured by a method based on KS6518.

(3) Coefficient of thermal expansion (CTE)

Using a TA thermomechanical analyzer Q400 model, the polyimide film was cut to a width of 2 mm and a length of 10 mm. The film was stretched at a rate of 10 ° C / min under a nitrogen atmosphere at a rate of 0.05 N And then the slope of the temperature range from 100 ° C to 400 ° C was measured while cooling at a rate of 10 ° C / min again.

Pyrolysis temperature
(° C) The tensile strength
(kgf / cm ² ) CTE
(ppm / DEG C) Example 7 564 372 4.5 Example 8 564 375 5.6 Example 9 563 353 7.2 Example 10 563 360 3.3 Comparative Example 8 554 278 33.4 Comparative Example 9 538 - - Comparative Example 10 545 248 22.8 Comparative Example 11 543 253 24.7 Comparative Example 12 543 255 26.9

It is necessary to pay attention to Example 7 and Comparative Example 8 in which the monomer composition is similar to the above results.

The polyimide film of Example 7 was produced from a polyamic acid composition in which an alcoholic additive was added to a polyamic acid, and it was confirmed that the polyimide film had a relatively excellent thermal decomposition temperature and tensile strength.

On the other hand, the polyimide film of Comparative Example 8 was produced from a polyamic acid to which no alcohol-based additive was added, and it was confirmed that the polyimide film had a significantly lower thermal decomposition temperature and tensile strength than Example 7.

Generally, at high temperatures, which are formed to form polyimide, among the alkoxy group and the hydroxy group, the alkoxy group can react with the adjacent amine group at a higher reaction rate. This is expected to be due to the fact that the alkoxy group belongs to the leaving group, which is relatively better than the hydroxy group, at the temperature for the imidization.

Thus, it is expected that when imidization at the same time, the polyamic acid composition containing the alkoxy group could be converted to a polyimide film with a higher imidization ratio, and in comparable Example 7, Mechanical properties, whereas comparative example 8, which does not comply with this, is presumed to have relatively poor thermal and mechanical properties.

Likewise, when comparing Examples 8, 9, 10 and Comparative Examples 8, 10, 11, 12 having similar monomer compositions, all of the examples showed better thermal decomposition temperatures and tensile strengths, Proves clearly.

It should also be noted that the thermal expansion coefficients measured in Examples and Comparative Examples.

The polyimide film preferably has a thermal expansion coefficient of 15 ppm / ° C, more specifically 10 ppm / ° C or less in view of dimensional stability at a high temperature. Particularly, in order to use the polyimide film as a display substrate, It is important that the dimensions do not change even in a high-temperature process of more than 10 占 폚, and it may be preferable to have a thermal expansion coefficient of 10 ppm / 占 폚 or less.

Therefore, in the embodiments falling within the scope of the present invention, it can be considered that the thermal expansion coefficient is 8 ppm / ° C or less and the dimensional stability at a high temperature is excellent. Thus, various electronic fields requiring such characteristics, such as a display substrate and a flexible circuit Can be preferably used.

On the other hand, in the comparative example, the coefficient of thermal expansion was remarkably high, which means that the dimensional stability at a high temperature is poor and thus it is difficult to apply to the above-mentioned electronic field.

On the other hand, the polyimide film of Comparative Example 9 exhibited a brittle characteristic even though it was in the form of a film, so that it was impossible to measure the tensile strength.

This suggests that the physical properties of the polyimide film may be significantly deteriorated when using an excessive alcohol-based additive which is outside the scope of the present invention.

&Lt; Experimental Example 3: Evaluation of Film Outline >

The appearance of the polyimide films prepared in Examples 11 and 12 and Comparative Examples 13 and 14 was visually observed and judged whether they could be used commercially or not, and the results are shown in Table 4.

For example, when it is a good film, it is represented by 'O', and when it is judged to be defective by having no self-supporting property or brittleness property, it is expressed as 'X'.

Appearance evaluation Example 11 O Example 12 O Comparative Example 13 X Comparative Example 14 X

From the results in Table 4, it can be seen that the polyimide film is not produced as a good product when excessive or too little alcoholic additive is used to deviate from the scope of the present invention.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

Claims (16)

An organic solvent and a polyamic acid,
Wherein at least a part of the hydroxyl groups contained in the polyamic acid is subjected to an alcohol decomposition reaction with an alcoholic additive to be substituted with an alkoxy group,
A polyamic acid composition having a viscosity change rate according to the following formula (1) is more than -3% and less than + 3%

{(First viscosity - second viscosity) / first viscosity} X 100% (1)

Here, the first viscosity is a viscosity measured immediately after the preparation of the polyamic acid composition, and the second viscosity is a viscosity measured after 10 days from the storage of the polyamic acid composition at room temperature. The method according to claim 1,
Wherein the polyamic acid composition is prepared by adding an alcoholic additive in an amount of 0.07 mol% or more to less than 1.5 mol% based on 100 mol% of an amic acid group of the polyamic acid. The method according to claim 1,
Wherein the alcoholic additive is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropyl alcohol, benzyl alcohol, ethoxy ethanol and butoxy ethanol. The method according to claim 1,
Wherein the polyamic acid is produced by polymerization of at least one dianhydride monomer and at least one diamine monomer in an organic solvent,
Wherein the amount of the dianhydride monomer is 99 mol% to 99.9 mol% based on 100 mol% of the diamine monomer, and the amount of the alcohol-based additive is 0.1 mol% to 1 mol%. 5. The method of claim 4,
Wherein the dianhydride monomer is selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3', 4 ' -Biphenyltetracarboxylic dianhydride (a-BPDA). The polyamic acid composition of claim 1, 5. The method of claim 4,
Wherein the diamine monomer is at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5- (DABA). &Lt; / RTI &gt; The method according to claim 1,
Wherein the first viscosity is 10,000 cP or less. A method for producing a polyimide film,
(a) introducing at least one dianhydride monomer and at least one diamine monomer into an organic solvent and polymerizing to prepare a polyamic acid solution containing a polyamic acid;
(b) adding an alcoholic additive in an amount of from 0.07 mol% to less than 1.5 mol% based on 100 mol% of the amic acid group of the polyamic acid to a polyamic acid solution to prepare a polyamic acid composition; And
(c) drying the polyamic acid composition to form a gel film;
(d) heat treating the gel film to obtain a polyimide film. 9. The method of claim 8,
In the step (b), at least a part of the hydroxyl groups contained in the polyamic acid is reacted with the alcohol-based additive to replace with an alkoxy group;
Wherein in the steps (c) and (d), the hydroxyl group and the alkoxy group each react with an amine group to form a plurality of imide groups. 9. The method of claim 8,
Wherein the amount of the dianhydride monomer is 99 mol% to 99.9 mol% based on 100 mol% of the diamine monomer, and the amount of the alcohol-based additive is 0.1 mol% to 1 mol%. 9. The method of claim 8,
Wherein the dianhydride monomer is selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3', 4 ' - biphenyltetracarboxylic dianhydride (a-BPDA), and at least one selected from the group consisting of biphenyltetracarboxylic dianhydride
Wherein the diamine monomer is at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5- (DABA). &Lt; / RTI &gt; 9. The method of claim 8,
Wherein the alcoholic additive is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropyl alcohol, benzyl alcohol, ethoxyethanol and butoxyethanol. 9. The method of claim 8,
The polyimide film is produced through thermal imidization,
Is dried at a variable temperature in the range of 50 DEG C to 200 DEG C in the step (c)
Treated at a variable temperature ranging from 50 캜 to 600 캜 in the step (d). A polyimide film produced by the production method according to claim 8,
When the thermal decomposition temperature (Td) is 550 DEG C or higher,
The thermal expansion coefficient is 40 ppm / 占 폚 or less,
The elongation is 13% or more,
A polyimide film having a tensile strength of 280 kgf / cm ² or more. An electronic device comprising a polyimide film according to claim 14. 16. The electronic device of claim 15, wherein the electronic device comprises a flexible circuit board or a display substrate.