TWI714944B - Polyamic acid composition with improved storage stability, method for preparing polyimide film by using the same, polyimide film prepared by the same and electronic device - Google Patents

Abstract

The present invention provides a polyamide composition, which utilizes the above polyamide composition A method for preparing a polyimide film, a polyimide film, and an electronic device. The polyimide composition includes an organic solvent and a polyamic acid, and at least a part of the hydroxyl group included in the polyimide and an alcohol This type of additive undergoes alcoholysis reaction and is substituted by an alkoxy group, thereby having excellent storage stability.

Description

Polyamide acid composition with improved storage stability, using it Method for preparing polyimide film, polyimide film and electronic device prepared therewith

The present invention relates to a polyimide composition with improved storage stability, a preparation method of a polyimide film using the above polyimide composition, and a polyimide film prepared by the above preparation method.

Polyimide (PI) is a thermally stable polymer material based on a strong aromatic main chain. Based on the chemical stability of the iminium ring, it has excellent strength, chemical resistance, and weather resistance. , Mechanical properties such as heat resistance.

Moreover, polyimide is favored as a highly functional polymer material that can be widely used in electronics, communications, optics and other industrial fields because of its excellent electrical properties such as insulation properties and low dielectric constant.

Recently, various electronic devices have become thinner, lighter, and smaller. Therefore, many researches are directed towards the use of lightweight and flexible thin polyimide films as insulating materials that can replace circuit boards or glass substrates for displays In the direction of the display substrate.

Generally, the polyimide film is prepared by the following method: a polyimide acid prepared by the polymerization reaction of dianhydride and diamine is coated on a support, and the film is formed into a film form by imidization. Peel off from the support.

However, it is known that polyamic acid includes an amine group and a carboxylic acid group. In particular, the hydroxyl group in the carboxylic acid group reacts with adjacent amine groups and is hydrolyzed, so the storage stability is poor. In addition, it is known that this phenomenon is prominent at a relatively low temperature under the conditions of normal temperature or above.

When the storage stability of polyamic acid is poor, the viscosity will greatly change during the process, and therefore, the coating and imidization of polyamic acid will be unstable. In addition, when the viscosity of polyimide is lowered, the mechanical properties and thermal properties of the polyimide film will be greatly reduced.

Among them, the degradation of the thermal properties of the polyimide film will be particularly unfavorable for preparing display substrates for high-temperature processing.

For example, in the case of an organic light emitting diode (OLED) using a low temperature polysilane (LTPS) process, a process temperature of more than 400°C will be formed. At this high temperature, even Polyimide, which has excellent heat resistance, is also thermally decomposed. It can be said that the thermal characteristics of the polyimide film are a very important factor for realizing a display substrate.

Therefore, there is an urgent need for a polyimide film with excellent storage stability at room temperature and a polyimide film with excellent mechanical and thermal properties.

The purpose of the present invention is to provide an excellent storage stability at room temperature Polyamide acid, a method for preparing a polyimide film with improved mechanical properties and thermal properties using the above polyamide acid, and a polyimide film.

According to an aspect of the present invention, alcohol additives can not only improve the storage stability of polyamide acid, but also reveal the necessary factors for realizing a polyimide film with excellent thermal and mechanical properties.

Alcohol additives can substitute at least a part of the hydroxyl groups included in the polyamide acid with alkoxy groups having relatively low reactivity at room temperature.

This situation minimizes the hydrolysis of polyamic acid at room temperature. As a result, it not only improves the storage stability of polyamic acid, but also inhibits the process of raising the temperature for imidization of polyamic acid. Hydrolysis can play a role in contributing to the realization of a polyimide film having superior physical properties compared to ordinary polyamide containing only hydroxyl groups.

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

In this case, when the heat treatment for forming polyimide is performed, the alkoxy group is quickly released, so that the imidization reaction can proceed relatively quickly. Such a rapid imidization reaction can help increase the rate of change from amidic acid groups to amido groups ("imidization rate)), thereby achieving excellent mechanical and thermal properties. Polyimide film.

In addition, the thermal decomposition temperature of the polyimide film prepared according to the above content may be 550° C. or higher, the tensile strength may be 280 kgf/cm ² or higher, the thermal expansion coefficient may be 40 ppm/° C. or lower, and the elongation rate may be 13% or higher. The polyimide film has the advantages of meeting the mechanical and thermal properties required by the display substrate.

Therefore, the essential object of the present invention is to provide specific examples of the above-mentioned polyimide film.

The present invention provides a polyamide acid composition, which comprises an organic solvent and a polyamide acid. At least a part of the hydroxyl groups included in the polyamide acid undergoes alcoholysis reaction with alcohol additives to be substituted by alkoxy groups. The viscosity change rate calculated by the following formula (1) is above -3% to less than +3%: {(first viscosity-second viscosity)/first viscosity}×100% formula (1)

Here, the first viscosity is the viscosity measured immediately after the preparation of the polyamide acid composition, and the second viscosity is the viscosity measured at a time point of 10 days after storing the polyamide acid composition at room temperature.

In an embodiment of the present invention, the polyamide acid composition is 100 mol% of the polyamide acid group with an amount of 0.07 mol% or more to less than 1.5 mol% Made from alcohol additives.

In an embodiment of the present invention, the alcohol additive is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, benzyl alcohol, ethoxyethanol and butoxyethanol.

In an embodiment of the present invention, the polyamide acid is formed by polymerizing more than one dianhydride monomer and more than one diamine monomer in the organic solvent, and the polyamide acid is 100 mol% Based on the diamine monomer, the input amount of the dianhydride monomer is 99 mol% to 99.9 mol%, and the input amount of the alcohol additive is 0.1 mol% to 1 mol%.

In an embodiment of the present invention, the dianhydride monomer is selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2 ,3,3',4'- One or more of the group consisting of biphenyltetracarboxylic dianhydride (a-BPDA).

In an embodiment of the present invention, the diamine monomer is selected from 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2 , 6-Diaminotoluene and 3,5-Diaminobenzoic acid (DABA) are composed of more than one species.

In an embodiment of the present invention, the first viscosity is 10,000 cP or less.

The present invention provides a preparation method, which is a method for preparing a polyimide film, comprising: (a) putting more than one dianhydride monomer and more than one diamine monomer into an organic solvent for polymerization to prepare a polyimide film. The process of the polyamide acid solution of amino acid; (b) relative to 100 mol% of the amide acid group of the polyamide acid, adding 0.07 mol% or more to less than 1.5 mol% alcohol additives A process of adding to the polyamide acid solution to prepare a polyamide acid composition; (c) a process of drying the polyamide acid composition to form a gel film; and (d) treating the gel The process of obtaining a polyimide film by heat treatment of the film

In an embodiment of the present invention, in the process (b), at least a part of the hydroxyl group included in the polyamide acid reacts with the alcohol additive to be substituted by an alkoxy group; in the process (c) and In the process (d), the hydroxyl group and the alkoxy group respectively react with an amine group to form a plurality of amide groups.

In an embodiment of the present invention, based on 100 mol% of the diamine monomer, the input amount of the dianhydride monomer is 99 mol% to 99.9 mol%, and the alcohol additive is The input amount is 0.1 mol% to 1 mol%.

In an embodiment of the present invention, the dianhydride monomer is selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2 ,3,3',4'-Biphenyltetracarboxylic dianhydride (a-BPDA) is composed of more than one kind, diamine mono The body is selected from 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5- Diaminobenzoic acid (DABA) is composed of more than one species.

In an embodiment of the present invention, the alcohol additive is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, benzyl alcohol, ethoxyethanol and butoxyethanol.

In an embodiment of the present invention, the polyimide film is prepared by a thermal imidization method, and in process (c), drying is performed at a variable temperature in the range of 50°C to 200°C. In the process (d), heat treatment is performed at a variability temperature in the range of 50°C to 600°C.

The present invention provides a polyimide film, which is a polyimide film prepared by the above-mentioned preparation method, and has a thermal decomposition temperature of 550°C or more, a thermal expansion coefficient of 40 ppm/°C or less, and an elongation rate of 13% or more. The tensile strength is 280kgf/cm ² or more.

The present invention provides an electronic device, which includes the above polyimide film.

In an embodiment of the present invention, the electronic device includes a flexible circuit substrate or a display substrate.

The polyamide acid composition of the present invention is characterized in that at least a part of the hydroxyl groups included in the polyamide acid are substituted with alkoxy groups when an alcohol additive is added. The alkoxy group has relatively low reactivity at room temperature without causing modification of the polyamide acid. Therefore, the polyamide acid composition has the advantage of improved storage stability at room temperature. The alkoxy group can also inhibit hydrolysis during the heating process for the imidization of polyamide acid. In this case, it is more advantageous to realize polyimide with excellent physical properties than the case without alkoxy group. The role of the membrane.

The advantage of the preparation method of the present invention is that the polyimide composition obtained by adding alcohol additives to polyamide acid so that at least a part of the hydroxyl group is replaced by alkoxy groups can be prepared with excellent mechanical properties and thermal properties. Characteristic polyimide film.

The reason may be that when the heat treatment is performed for the preparation of the polyimide film, the alkoxy group is rapidly separated and the imidization reaction advances relatively quickly, thereby increasing the imidization rate.

In addition, the polyimide film prepared according to the above content has a thermal decomposition temperature of 550° C. or more, and a tensile strength of 280 kgf/cm ² or more, and can have excellent thermal and mechanical properties required for display substrates.

Hereinafter, the function and effect of the invention will be described in more detail through specific embodiments of the invention. However, these embodiments are only examples of the invention, and do not thereby define the scope of rights of the invention.

The present invention has discovered that at least a part of the hydroxyl groups included in the polyamide acid are substituted by alkoxy groups with alcohol additives, and the obtained polyamide acid composition has excellent storage stability at room temperature.

The present invention also found that if the polyimide film is prepared using the polyimide composition described above, a faster imidization reaction can be induced, and therefore, a polyimide film with excellent mechanical and thermal properties can be realized .

Therefore, in this specification, specific content for realizing the polyimide film described above will be described.

Prior to this, the terms or words used in this specification and the scope of the invention application should not be limitedly interpreted as ordinary meanings or meanings in the dictionary. In order for the inventor to explain his own invention in the best way, he should only be based on The principles of the concepts of terms can be appropriately defined and interpreted as meanings and concepts that conform to the technical idea of the present invention.

Therefore, the configuration of the embodiment described in this specification is only the best embodiment of the present invention, and does not represent all the technical ideas of the present invention. Therefore, it should be understood that from the perspective of this application, there may be possible Replace various equivalents and modifications of the above-mentioned embodiments.

In this specification, as long as other meanings are not clearly expressed in the text, the expression of the singular number includes the expression of the plural number. In this specification, it should be understood that the terms "include", "have" or "have" indicate the existence of implemented features, numbers, steps, constituent elements, or combinations thereof, and do not preclude one or more other features, numbers, The existence or additional possibilities of steps, constituent elements, or combinations thereof.

In this specification, "dianhydride" refers to those including its precursors or derivatives, which may not be dianhydrides technically, but even so, they also react with diamine to form polyamide acid. The above-mentioned polyamide can be converted into polyimide again.

In this specification, "diamine" refers to those including its precursors or derivatives, which may not be diamines technically, but even so, they also react with dianhydrides to form polyamide acid. The amino acid can be converted into polyimide again.

In this specification, when an amount, concentration, other value or parameter is listed as a range, a preferred range or a preferred upper limit and a preferred lower limit, it should be understood as Regardless of whether the ranges are separately disclosed, all ranges formed by any pair of arbitrary upper range limit values or preferred values and arbitrary lower range limit values or preferred values are specifically disclosed. When the range of a numerical value is mentioned in this specification, unless otherwise stated, the range means the end point and all integers and fractions within the range. The scope of the present invention is not limited to the specific values mentioned when defining the scope.

First embodiment: Polyamide acid composition

The polyamide acid composition of the present invention is characterized in that it includes an organic solvent and polyamide acid, and at least a part of the hydroxyl groups included in the polyamide acid undergoes alcoholysis reaction with alcohol additives to be substituted by alkoxy groups. The viscosity change rate calculated by the following formula (1) is above -3% to less than +3%.

{(First viscosity-Second viscosity)/First viscosity}×100% formula (1)

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

The viscosity of polyamic acid is substantially proportional to the molecular weight. Therefore, the change in viscosity means that the polyamic acid is modified. The degree of viscosity change can be understood as an index indicating the degree of modification of the polyamic acid.

Normal polyamic acid exhibits a viscosity change rate of ±10% or more when stored at room temperature for about 7 days. This situation means that polyamic acid undergoes a very large modification, which makes it difficult to achieve excellent results. Physical properties of polyimide film.

On the contrary, even if the polyamide acid of the present invention is stored at room temperature for 10 days, the viscosity change rate is less than ±3% and is not large, and the storage stability at room temperature is very excellent. The reason may be that at room temperature, the alkoxy group has relatively lower room temperature reactivity than the hydroxyl group.

The above-mentioned first viscosity can be less than 10,000cP, specifically 7,500cP Hereinafter, in more detail, it is less than 7,200cP. The polyamide acid composition with such a first viscosity has the advantage of being easy to handle in terms of fluidity, and is also beneficial to film formation.

The polyamide acid composition can be prepared by adding 0.07 mol% or more to less than 1.5 mol% alcohol additives relative to 100 mol% of the amide acid group of the polyamide acid. In detail, The alcohol additive can be 0.1 mol% or more and 1 mol% or less based on 100 mol% of the diamine monomer.

In the case of preparing a polyimide composition by adding alcohol additives in a manner greater than the above range, it is difficult to prepare a polyimide film having the desired physical properties. In the case of less than the above range, storage stability is improved Will be very small, so it is not good.

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

The above-mentioned polyamide acid can be produced by polymerizing more than one dianhydride monomer and more than one diamine monomer in an organic solvent.

The dianhydride monomer that can be used to prepare the polyamide acid of the present invention may be an aromatic tetracarboxylic dianhydride.

The above-mentioned aromatic tetracarboxylic dianhydride can include pyromellitic dianhydride (or PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (or s-BPDA), 2,3,3 ',4'-Biphenyltetracarboxylic dianhydride (or a-BPDA), oxydiphthalic dianhydride (or ODPA), diphenyl sulfide-3,4,3',4'-tetracarboxylic acid 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 BTDA) , Bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylene bis(trimellitic acid monoester anhydride), P-biphenyl bis(trimellitic acid mono Ester anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, 1,3- Bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy) Base) biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1 ,4,5,8-Naphthalenetetracarboxylic dianhydride, 4,4'-(2,2-hexafluoroisopropylidene) diphthalic dianhydride, etc. These can be used singly or in combination of two or more as desired. However, in the present invention, the dianhydride monomer that can be preferably used can be selected from pyromellitic dianhydride (PMDA), 3,3' ,4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) are composed of more than one species.

The diamine monomers that can be used to prepare the polyamide acid of the present invention can be classified and listed as aromatic diamines as follows.

1) Such as 1,4-diaminobenzene (or p-phenylenediamine, PPD), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3, 5-diaminobenzoic acid (or DABA) and other diamines that have a relatively strong structure as a diamine with a benzene nucleus; 2) such as 4,4'-diaminodiphenyl ether (or oxygen Diphenylamine, ODA), 3,4'-diaminodiphenyl ether and other diaminodiphenyl ethers, 4,4'-diaminodiphenylmethane (methylene diamine), 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'-diaminobenzaniline , 3,3'-Dichlorobenzidine, 3,3'-Dimethylbenzidine (or o-tolidine), 2,2'-Dimethylbenzidine (or m-tolidine), 3,3 '-Dimethoxybenzidine, 2,2'-Dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'- Diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide Ether, 3,3'-diaminodiphenyl chloride, 3,4'-diaminodiphenyl chloride, 4,4'-diaminodiphenyl chloride, 3,3'-diaminodiphenyl Benzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4 '-Dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2 -Bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3 ,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfene , 3,4'-diaminodiphenyl sulfene, 4,4'-diaminodiphenyl sulfene and other diamines with two benzene nuclei in the structure; 3) such as 1,3-bis (3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl) Phenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene (or TPE-Q), 1,4-bis(4 -Aminophenoxy)benzene (or TPE-Q), 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-( 4-phenyl)phenoxybenzophenone, 3,3'-diamino-4,4'-bis(4-phenylphenoxy)benzophenone, 1,3-bis(3- Aminophenyl sulfide)benzene, 1,3-bis(4-aminophenylsulfide)benzene, 1,4-bis(4-aminophenylsulfide)benzene, 1,3-bis(3 -Aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(2-( 4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-bis[2-(4-aminophenyl) )Isopropyl]benzene and other diamines with 3 benzene nuclei in the structure; 4) such as 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4- Aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-( 3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, double [4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ketone, bis[3-(4-aminophenoxy)phenyl ] Ketone, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy) base) Phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4 -Aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, double [4-(3-Aminophenoxy)phenyl] chrysene, bis[4-(4-aminophenoxy)phenyl] chrysene, bis[3-(3-aminophenoxy)phenyl ]Methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy) Yl)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane , 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2, 2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy) Yl)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3 ,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, etc. on the structure Diamine with 4 benzene nuclei.

These can be used alone or in combination of two or more as desired, but in the present invention, the diamine monomer that can be preferably used can be selected from 1,4-diaminobenzene (PPD), 1, One or more of the group consisting of 3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, and 3,5-diaminobenzoic acid (DABA).

The polyamide acid composition can be substantially charged with equal moles of the diamine monomer and dianhydride monomer. Specifically, based on 100 mole% of the diamine monomer, the amount of the dianhydride monomer is The input amount can be 99 mol% to 101 mol%. More specifically, based on 100 mol% of the above-mentioned diamine monomer, the input amount of the above dianhydride monomer can be 99 mol% to 99.9 mol%. ear%.

When the input amount of the above-mentioned dianhydride monomer is larger or smaller than the above-mentioned range, the polymerization is terminated before reaching the desired molecular weight, or low-molecular-weight oligomers are mostly formed. Therefore, it is difficult to realize the formation of polyimide film. The polyamide acid.

Second embodiment: Preparation method of polyimide film and polyimide film

The preparation method of the polyimide film of the present invention may include: (a) adding more than one dianhydride monomer and more than one diamine monomer to an organic solvent for polymerization to prepare a polyamide including polyamide acid The process of acid solution; (b) Adding 0.07 mol% or more to less than 1.5 mol% alcohol additives to the polyamide acid solution relative to 100 mol% of the amide acid group of the above-mentioned polyamide acid , To prepare the polyimide composition; (c) to dry the polyamide composition to form a gel film; and (d) to heat the gel film to obtain a polyimide film the process of.

The advantages of the preparation method of the present invention are as follows: in the above process (b), at least a part of the hydroxyl group included in the polyamide acid reacts with the alcohol additive to be substituted by an alkoxy group; in the above process (c) and In the process (d), the above-mentioned hydroxyl group and alkoxy group can respectively react with the amine group to form multiple amide groups. In this case, the alkoxy group can act as an excellent leaving group to promote the Imidization reaction.

In summary, the above-mentioned alkoxy groups are less reactive than hydroxyl groups at room temperature and are better for polyamic acid in terms of storage stability. They can be used as excellent leaving groups at high temperatures for preparing polyimide films. It acts to promote the imidization reaction of polyamide acid. Therefore, it can act on polyamide acid and polyimide film with many advantages. In addition, a polyimide film with a high imidization rate can be realized by virtue of this advantage.

The high imidization rate is the main factor that makes the polyimide film exhibit excellent thermal and mechanical properties, and therefore, the advantages of the preparation method of the present invention can be fully estimated.

In the present invention, the preparation of the polyamide acid solution can include, for example, the following methods Method: (1) Put the entire amount of the diamine monomer into the solvent, and then add the dianhydride monomer so that it is substantially equal to the diamine monomer and polymerize it; (2) The dianhydride monomer The entire amount of the body is put into the solvent, and thereafter the diamine monomer is added in such a way that it is substantially equal to the dianhydride monomer to polymerize; (3) a part of the diamine monomer is put into After the solvent, a part of the dianhydride monomer is mixed at a ratio of about 95 mol% to 105 mol% relative to the reaction components, and then the remaining diamine monomer components are added, and the remaining dianhydride is continuously added here The monomer component makes the diamine monomer and the dianhydride monomer substantially equal moles to polymerize; (4) After the dianhydride monomer is put into the solvent, the reaction component is subjected to 95 moles Part of the components in the diamine compound is mixed at a ratio of ear% to 105 mol%, and then other dianhydride monomer components are added, and the remaining diamine monomer components are continuously added to make the diamine monomer and the dianhydride monomer substantially become (5) A part of the diamine monomer component and a part of the dianhydride monomer component are excessively reacted in a solvent to form the first composition, and a part of the diamine monomer The monomer component and a part of the dianhydride monomer component are excessively reacted in another solvent to form the second composition, and then the first composition and the second composition are mixed to complete the polymerization. At this time, In the case where the diamine monomer component is excessive when the first composition is formed, the dianhydride monomer component is excessive in the second composition, and the dianhydride monomer component is excessive in the first composition. The first composition and the second composition are mixed in such a way that the diamine monomer component is excessive, and the overall diamine monomer component and the dianhydride monomer component used for the reaction are substantially equal-molar for polymerization. method.

However, the above-mentioned polymerization method is not limited to the above-mentioned example, and of course any known method can be used.

The above-mentioned dianhydride monomer can be appropriately selected from the examples described above. In detail, it can be preferably selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetra One or more of the group consisting of carboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA).

The above-mentioned diamine monomer can be appropriately selected from the examples described above. In detail, it can be preferably selected from 1,4-diaminobenzene (PPD) and 1,3-diaminobenzene (MPD). , 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5-diaminobenzoic acid (DABA) group consisting of more than one kind.

The aforementioned alcohol additives may be one or more selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, benzyl alcohol, ethoxyethanol and butoxyethanol, but the scope of the present invention is not limited to this.

Based on 100 mol% of the above diamine monomer, the input amount of the above dianhydride monomer can be 99 mol% to 99.9 mol%, and the input amount of the alcohol additive is 0.1 mol% to 1 mol% %.

When the input amount of the above dianhydride monomer is greater or less than the above range, the following problems may arise: the polymerization is terminated before reaching the desired molecular weight, or most of the low molecular weight oligomers are formed, so that the preparation cannot be used. The polyamide acid forms a polyimide film.

It is difficult to prepare a polyimide film with the desired physical properties when the alcohol additives above the above range are added, and when it is less than the above range, the storage stability of the polyimide acid solution will be little improved , Therefore not good.

In the preparation method of the present invention, the polyamide can be prepared by the thermal imidization method. Imine film. The above-mentioned thermal imidization method refers to a method of inducing an imidization reaction using a heat source such as hot air or an infrared dryer while excluding a chemical catalyst.

For reference, in the above process (b) in which alcohol additives are added to cause an alkoxylation reaction, there is a possibility that at least a part of the alcohol additives added does not react and remains, and water is produced as a result of the alkoxylation reaction. The by-product remains in the polyamic acid solution. The water remaining in the polyamide acid solution will cause the anhydride catalyst used as a chemical catalyst in the imidization process to lose its function. Therefore, even if a chemical catalyst is used, there is a possibility that the imidization reaction cannot be carried out effectively. Therefore, in terms of realizing the polyimide film intended by the present invention, it may be preferable not to use a chemical catalyst. The above-mentioned thermal imidization method of medium.

The above-mentioned thermal imidization method may include the above-mentioned process (d). In the above-mentioned process (d), the gel film may be heat-treated at a variable temperature in the range of 50°C to 600°C so as to be present in the gel. The amide group of the film is imidized.

However, in the process (c) of forming the above-mentioned gel film, part of the amide acid (about 0.1 mol% to 10 mol%) can also be imidized. For this reason, in the above process (c) The polyamide composition can be dried at a variable temperature ranging from 50°C to 200°C, and this situation can also be included in the category of the above-mentioned thermal imidization method.

The thermal decomposition temperature (Td) of the polyimide film of the present invention prepared according to the above-mentioned preparation method can be 550°C or more, the thermal expansion coefficient is 40ppm/°C or less, the elongation is 13% or more, and the tensile strength is 280kgf /cm ² or more.

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

Hereinafter, the compound names of the abbreviations used in Examples and Comparative Examples are as follows.

-Biphenyltetracarboxylic dianhydride: BPDA

-Pyromellitic dianhydride: PMDA

-P-phenylenediamine: PPD

-N-Methylpyrrolidone: NMP

<Example 1>

To the equipped with agitator and nitrogen injection. Nitrogen was injected into the 1000 ml reactor of the discharge pipe, and 824 g of NMP was charged. The temperature of the reactor was set to 35°C. Then, 40.5 g of PPD and 101.4 g of BPDA were charged and stirred until they were completely dissolved and reacted. After the completion of the reaction, 2.85 g of BPDA was dissolved in NMP at 10% by weight, and then added at intervals of 10 minutes until the viscosity at 23° C. became 8000 cP. After that, after setting the temperature of the reactor to 50°C, 0.1 mol of methanol was added to 100 mol of PPD. Stirring was sufficiently performed until the reaction was completed, and then a polyimide precursor composition (viscosity at 23°C: 7,100 cP) was prepared.

Viscosity is measured using Brookfield viscometer (RVDV-II+P) at 25°C using No. 7 scandal at 50 rpm twice to determine the average value.

<Example 2>

Except changing the molar ratio of BPDA and methanol as shown in Table 1 below, the polyamide composition was prepared by the same method as Example 1, and the first viscosity was measured. The measured viscosity is about 6,900 cP.

<Example 3>

Except that ethanol was added in place of methanol according to the molar ratio shown in Table 1 below, a polyamide acid composition was prepared by the same method as in Example 1, and the first viscosity was measured. The measured viscosity is 6,970 cP.

<Example 4>

Except for adding n-propanol instead of methanol according to the molar ratio shown in Table 1 below, the polyamide composition was prepared by the same method as in Example 1, and the first viscosity was measured. The measured viscosity is 6,950 cP.

<Example 5>

While keeping the inside of the reaction system at 25°C, PPD, BPDA, and PMDA were introduced into NMP in accordance with the molar ratio shown in Table 1 below, and polymerized to prepare a polyamide acid solution. The polyamic acid solution prepared as described above was poured into methanol according to the molar ratio shown in Table 1 below to prepare a polyamic acid composition, and the first viscosity was measured. The measured viscosity is about 5,300 cP.

<Example 6>

Except that the molar ratio of BPDA and methanol was changed as shown in Table 1 below and charged, the polyamide composition was prepared by the same method as in Example 5, and the first viscosity was measured. The measured viscosity is about 5,150 cP.

<Comparative Example 1>

While keeping the inside of the reaction system at 25°C, PPD and BPDA were injected into NMP according to the molar ratio shown in Table 1 below to polymerize to prepare a polyamic acid solution, and the first viscosity was measured. The measured viscosity is about 7,100 cP.

<Comparative Example 2>

Except changing the molar ratio of BPDA and methanol as shown in Table 1 below, the polyamide composition was prepared by the same method as in Example 1, and the first viscosity was measured. The measured viscosity is about 6,780 cP.

<Comparative Example 3>

The molar ratio of BPDA and methanol was changed as shown in Table 1 below and added, except that the polyamide acid composition was prepared by the same method as in Example 1, and measured The first viscosity. The measured viscosity is about 6,950 cP.

<Comparative Example 4>

Ethanol was used instead of methanol, and the molar ratio of BPDA to ethanol was changed as shown in Table 1 below. Except that, the polyamide composition was prepared by the same method as in Example 1, and the first viscosity was measured. . The measured viscosity was 7,050 cP.

<Comparative Example 5>

Instead of methanol, n-propanol was used, and the molar ratio of BPDA and n-propanol was changed as shown in Table 1 below, except that the polyamide composition was prepared by the same method as in Example 1, and Determine the first viscosity. The measured viscosity was 7,000 cP.

<Comparative Example 6>

Except that the molar ratio of BPDA and methanol was changed as shown in Table 1 below and charged, the polyamide composition was prepared by the same method as in Example 5, and the first viscosity was measured. The measured viscosity is about 5,400 cP.

<Comparative Example 7>

Except for changing the molar ratio of BPDA and methanol as in Table 1 below, the polyamide composition was prepared by the same method as in Example 5, and the first viscosity was measured. The measured viscosity is about 5,010 cP.

<Experimental Example 1: Storage Stability Evaluation>

The polyamide acid composition prepared in Example 1 to Example 6, and Comparative Example 1 to Comparative Example 7 was placed at room temperature for 10 days. After that, the second viscosity was measured by the viscosity measurement method described in Example 1, and the viscosity change rate was calculated according to the following formula (1) and shown in Table 2 below.

{(First viscosity-Second viscosity)/First viscosity}×100% formula (1)

As shown in Table 2, the implementation of adding alcohol additives within the scope of the present invention The viscosity of the polyamide acid composition of Example 1 to Example 6 did not change significantly after 10 days.

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

It is presumed that the reason is that an appropriate amount of alcohol additives within the scope of the present invention replaces at least a part of the hydroxyl groups that can induce a reforming reaction such as hydrolysis at room temperature with alkoxy groups. As a result, the reactivity at room temperature is low The alkoxy group on the hydroxyl group does not initiate the modification reaction.

In contrast, Comparative Example 1 in which no alcohol additives were added at all resulted in a significant decrease in the viscosity of polyamide acid. It is considered that this is because the hydroxyl group in the polyamide acid of Comparative Example 1 promotes reforming reactions such as hydrolysis, and therefore, the viscosity greatly changes as shown in Table 2.

On the other hand, in the case of Comparative Example 2 to Comparative Example 7, even if an alcohol additive was added, a large viscosity change occurred. This situation clearly illustrates the situation that even if the alcohol additive is used in an excessively small or excessive content outside the scope of the present invention, the effect of improving storage stability is not shown.

<Example 7>

The air bubbles in the polyimide precursor composition of Example 1 were removed by high-speed rotation at 1,500 rpm or more. After that, the defoamed polyimide precursor composition was applied to the glass substrate using a spin coater. Thereafter, it was dried for 30 minutes at a temperature of 120°C in a nitrogen atmosphere, heated to 450°C at a rate of 2°C/min, heat-treated at 450°C for 60 minutes, and cooled to 30°C at a rate of 2°C/min. Preparation of polyimide film. After that, it was dipped in distilled water to peel off the polyimide film from the glass substrate. The thickness of the prepared polyimide film was 15.1 μm.

Use Anritsu's film thickness tester (electric film thickness tester (Electric Film thickness tester)) The thickness of the prepared polyimide film is measured.

<Example 8>

Except that the polyimide composition of Example 2 was used, a 15 μm thick polyimide film was obtained by the same method as that of Example 7.

<Example 9>

Except for using the polyimide composition of Example 3, a 15.5 μm thick polyimide film was obtained by the same method as in Example 7.

<Example 10>

Except for using the polyimide composition of Example 4, a 15.4 μm thick polyimide film was obtained by the same method as that of Example 7.

<Example 11>

Except for using the polyimide composition of Example 5, a polyimide film having a thickness of 14.8 μm was obtained by the same method as that of Example 7.

<Example 12>

Except for using the polyimide composition of Example 6, a polyimide film having a thickness of 14.6 μm was obtained by the same method as that of Example 7.

<Comparative Example 8>

Except that the polyimide composition of Comparative Example 1 was used, a 15.3 μm thick polyimide film was obtained by the same method as in Example 7 except that the polyimide composition was used.

<Comparative Example 9>

Except for using the polyimide composition of Comparative Example 2, a polyimide film with a thickness of 15.7 μm was obtained by the same method as in Example 7.

<Comparative Example 10>

Using the polyamide acid composition of Comparative Example 3, in addition, by In the same manner as in Example 7, a 15.5 μm thick polyimide film was obtained.

<Comparative Example 11>

Except for using the polyimide composition of Comparative Example 4, a 15.5 μm thick polyimide film was obtained by the same method as in Example 7.

<Comparative Example 12>

Except for using the polyimide composition of Comparative Example 5, a 15.4 μm thick polyimide film was obtained by the same method as in Example 7.

<Comparative Example 13>

Except that the polyimide composition of Comparative Example 6 was used, a 15.3 μm thick polyimide film was obtained by the same method as in Example 7.

<Comparative Example 14>

Except that the polyimide composition of Comparative Example 7 was used, a 15 μm thick polyimide film was obtained by the same method as in Example 7.

<Experimental Example 2: Evaluation of Physical Properties>

The physical properties of the polyimide films prepared in Example 7 to Example 10 and Comparative Example 8 to Comparative Example 12 were measured in the following manner, and the results are shown in Table 3 below.

(1) Thermal decomposition temperature

The thermal decomposition temperature was measured using a thermogravimetric analyzer (Thermo Gravimetric Analyzer, TGA) measuring device from PerkinElmer. The polyimide film is cut to a size of 3mm×3mm and placed on a pre-processed and weighed fan (Fan), and then heat-insulated at 110°C for 30 minutes to cool to room temperature, and then again every minute It was heated to 600°C at a rate of 5°C to measure the weight loss. The thermal decomposition temperature is calculated when the weight reduction ratio is 1% relative to the weight of the polyimide film initially loaded.

(2) Tensile strength

The tensile strength was measured by the method of Korean Standard (KS) 6518.

(3) Coefficient of Thermal Expansion (CTE)

Using TA’s thermomechanical analyzer (thermomechanical analyzer) model Q400, after cutting the polyimide film to a width of 2mm and a length of 10mm, a tension of 0.05N is applied in a nitrogen environment and the temperature is 10℃/min. The temperature was raised to 500°C, and then cooled again at a rate of 10°C/min to measure the gradient of the interval from 100°C to 400°C.

Regarding the above results, it should be noted that Example 7 and Comparative Example 8 with similar monomer composition.

It can be confirmed that the polyimide film of Example 7 is prepared from a polyimide composition obtained by adding alcohol additives to polyamic acid, and has relatively excellent thermal decomposition temperature and tensile strength.

On the contrary, it can be confirmed that the polyimide film of Comparative Example 8 is prepared from polyamic acid without adding alcohol additives, and has a thermal decomposition temperature and tensile strength significantly lower than that of Example 7.

Generally, at the high temperature created to form polyimide, among the alkoxy group and the hydroxyl group, the alkoxy group can react with the adjacent amine group at a faster reaction rate. The reason for this is believed to be that at the temperature created to achieve imidization, the alkoxy group is a leaving group that is relatively better than the hydroxyl group.

Therefore, it is considered that when the imidization is performed for the same time, the polyimide composition including the alkoxy group will be converted into a polyimide film with a higher imidization rate, and it is assumed that this situation is met Example 7 showed relatively excellent thermal and mechanical properties. On the contrary, Comparative Example 8, which did not meet this situation, showed relatively poor thermal and mechanical properties.

Similarly, when comparing Example 8, Example 9, and Example 10 with similar monomer composition with Comparative Example 8, Comparative Example 10, Comparative Example 11, and Comparative Example 12, all the examples showed better Thermal decomposition temperature and tensile strength, this situation also more clearly proves the content explained before.

Note also the coefficient of thermal expansion measured in the Examples and Comparative Examples.

In terms of dimensional stability at high temperatures, the thermal expansion coefficient of the polyimide film may preferably be 15 ppm/°C, more specifically, 10 ppm/°C or less, especially in order to use the polyimide film as a display For the substrate, it is important that the size of the polyimide film does not change during the high temperature process above 300° C., and it may preferably have a thermal expansion coefficient of 10 ppm/° C. or less.

Therefore, the embodiments within the scope of the present invention have a thermal expansion coefficient of 8 ppm/°C or less, which can be regarded as excellent in dimensional stability at high temperatures, and can be preferably used in various electronic fields requiring such characteristics, such as display substrates or flexible circuits. Wait.

On the contrary, in the comparative example, the coefficient of thermal expansion is significantly higher, and it can be considered that the dimensional stability at high temperature is poor and it is difficult to apply to the above-mentioned electronic fields.

On the other hand, although the polyimide film of Comparative Example 9 was in the form of a film, it exhibited brittle characteristics and the tensile strength could not be measured.

This situation suggests that when too many alcohol additives outside the scope of the present invention are used, the physical properties of the polyimide film become very poor.

<Experimental Example 3: Film Shape Evaluation>

The appearance of the polyimide films prepared in Example 11, Example 12, Comparative Example 13, and Comparative Example 14 were visually observed to determine whether they are commercially available. The results are shown in Table 4.

For example, when it is a good film, it is expressed as "○", and when it is judged to be defective due to lack of self-sustainability or brittleness, it is expressed as "×".

According to the results of Table 4, it can be seen that when too much or too little alcohol additives are used in a manner outside the scope of the present invention, the polyimide film cannot be prepared as a good product.

The above description has been made with reference to the embodiments of the present invention, but those with common sense in the technical field to which the present invention belongs can make various applications and modifications within the scope of the present invention based on the above content.

Claims (16)

A polyamide acid composition comprising an organic solvent and polyamide acid, at least a part of the hydroxyl groups included in the polyamide acid undergoes alcoholysis reaction with alcohol additives to be substituted by alkoxy groups by The viscosity change rate calculated by the formula (1) is above -3% to less than +3%: {(first viscosity-second viscosity)/first viscosity}×100% where the first viscosity is The viscosity measured immediately after the preparation of the polyamic acid composition, and the second viscosity is the viscosity measured at a time point of 10 days after storing the polyamic acid composition at room temperature. The polyamide composition according to the first item of the scope of patent application, which is based on 100 mol% of the polyamide acid group with 0.07 mol% or more and less than 1.5 mol% Of the alcohol additives. The polyamide acid composition as described in item 1 of the scope of patent application, wherein the alcohol additive is selected from methanol, ethanol, n-propanol, isopropanol, benzyl alcohol, ethoxyethanol and butoxyethanol More than one kind of ethnic group. The polyamide acid composition according to the first item of the scope of patent application, wherein the polyamide acid is formed by polymerizing more than one dianhydride monomer and more than one diamine monomer in the organic solvent , On the basis of 100 mol% of the diamine monomer, the input amount of the dianhydride monomer is 99 mol% to 99.9 mol%, and the input amount of the alcohol additive is 0.1 mol% to 1 mol%. The polyamide acid composition as described in item 4 of the scope of patent application, wherein the dianhydride monomer is selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyl tetrakis Carboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) More than one of the ethnic groups. The polyamide acid composition according to item 4 of the scope of patent application, wherein the diamine monomer is selected from 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD) , 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5-diaminobenzoic acid (DABA) group consisting of more than one kind. The polyamide acid composition as described in item 1 of the scope of patent application, wherein the first viscosity is less than 10,000 cP. A preparation method of a polyimide film, comprising: (a) putting more than one dianhydride monomer and more than one diamine monomer into an organic solvent for polymerization to prepare a polyimide acid solution including polyimide acid (B) Adding 0.07 mol% or more to less than 1.5 mol% alcohol additives to the polyamide acid relative to 100 mol% of the polyamide acid group Solution to prepare a polyamide composition; (c) drying the polyamide composition to form a gel film; and (d) heat treating the gel film to obtain a polyamide The process of amine film; wherein, in the process (b), the viscosity change rate of the polyamide acid composition calculated by the following formula (1) is above -3% to less than +3%: {( The first viscosity-the second viscosity)/the first viscosity}×100% Formula (1) where the first viscosity is the viscosity measured immediately after the polyamide acid composition is prepared, and the second viscosity is the viscosity stored at room temperature The viscosity of the polyamic acid composition measured at the time of 10 days. The preparation method according to item 8 of the scope of patent application, wherein in the process (b), at least a part of the hydroxyl group included in the polyamide acid reacts with the alcohol additive to be substituted by an alkoxy group; In the process (c) and the process (d), the hydroxyl group and the alkoxy group respectively react with the amine group to form a plurality of amide groups. The preparation method as described in item 8 of the scope of patent application, wherein based on 100 mol% of the diamine monomer, the input amount of the dianhydride monomer is 99 mol% to 99.9 mol%, so The input amount of the alcohol additive is 0.1 mol% to 1 mol%. The preparation method as described in item 8 of the scope of patent application, wherein the dianhydride monomer is selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) consisting of more than one kind, the diamine monomer is selected from 1,4- Diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5-diaminobenzoic acid (DABA) More than one kind of ethnic group. The preparation method as described in item 8 of the scope of patent application, wherein the alcohol additive is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, benzyl alcohol, ethoxyethanol and butoxyethanol More than one of them. The preparation method according to item 8 of the scope of the patent application, wherein the polyimide film is prepared by a thermal imidization method, and in the process (c), the variability temperature in the range of 50°C to 200°C Drying is performed under the following conditions, and in the process (d), the heat treatment is performed at a variable temperature in the range of 50°C to 600°C. A polyimide film, which is a polyimide film prepared by a preparation method as described in item 8 of the scope of patent application, with a thermal decomposition temperature of 550°C or more, a thermal expansion coefficient of 40ppm/°C or less, and an elongation rate It is 13% or more, and the tensile strength is 280kgf/cm ² or more. An electronic device comprising the polyimide film as described in item 14 of the scope of patent application. The electronic device described in item 15 of the scope of patent application includes a flexible circuit substrate or a display substrate.