WO2011086627A1 - Polyimide film and process for production thereof - Google Patents

Abstract

Provided is a process for the production of a transparent polyimide film which comprises using 3,3',4,4'-biphenyl- tetracarboxylic dianhydride and 2,2'-bis(trifluoromethyl)- benzidine as the monomers and which can produce such a film that exhibits a reduced dimensional change under heat. A polyimide film which exhibits excellent dimensional stability under heat can be obtained by: mixing a polyamic acid solution with a chemical imidating agent to prepare a gel film; baking the gel film at high temperature; and then cooling the resulting film while gradually lowering the temperature of the cooling process.

Description

Polyimide film and method for producing the same

The present invention relates to a polyimide film excellent in transparency and dimensional stability, and a method for producing the same. In particular, it relates to the fact that a transparent polyimide film having excellent dimensional stability can be obtained by lowering the initial temperature of film baking and making the temperature lowering process multistage.

In recent years, with rapid advances in displays such as liquid crystal, organic EL, and electronic paper, and electronics such as solar cells and touch panels, improvement in breakage resistance, thinning and weight reduction, and further flexibility are required. It has come to be. At present, as a base substrate of these devices, a glass-based laminated material in which various electronic elements such as TFTs and transparent electrodes and inorganic films such as a gas barrier layer are formed on a glass plate is used.

However, devices using glass substrates have problems such as being thick, heavy, and easy to break, and plastic film substrates using film materials instead of this glass plate have been studied, making the panel itself thinner and lighter And further flexibility is expected.

Polyimide films have high heat resistance, dimensional stability, chemical resistance, electrical properties, mechanical properties, and other excellent properties, and thus have been applied to semiconductors and electronic components. In particular, polyimides using monomers of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine have high heat resistance and low linear expansion coefficient. It is also excellent in transparency, and there have been several reports so far (Patent Document 1). However, no method has been found for improving the dimensional change during heating of the polyimide film.

JP2007-046054

The present invention has been accomplished in view of the above circumstances, and is a polyimide film prepared using a specific amount of dehydrating agent and a specific amount of an imidizing agent under a specific temperature condition, and is transparent. It aims at providing the manufacturing method with a small dimensional change at the time of the heating of a film.

As a result of intensive studies to solve the above problems, the present inventors have found the present invention having the following configuration.

1). Polyamic acid having a repeating unit represented by the following formula (1) synthesized using a diamine compound and an acid dianhydride, and 0.1 to 2.0 mole equivalent of imide with respect to the carboxylic acid of the polyamic acid The turbidity obtained by preparing a gel film at a temperature of 25 ° C. to 128 ° C. with a composition comprising a dehydrating agent in an amount of 0.6 to 10.0 molar equivalents relative to the carboxylic acid of the polyamic acid and polyamic acid. Polyimide film of 4% or less, YI (yellowness) 20 or less, total light transmittance 80% or more, and heat shrinkage 0.05% or less

(In the formula, R ¹ represents a tetravalent organic group represented by the following general formula (2), and R ² represents a divalent organic group represented by the following general formula (3).)

2). The polyimide film as described in 1), comprising a composition using β-picoline as an imidizing agent and acetic anhydride as a dehydrating agent.

3). Polyamic acid having a repeating unit represented by the following formula (1) synthesized using a diamine compound and an acid dianhydride, and 0.1 to 2.0 mole equivalent of imide with respect to the carboxylic acid of the polyamic acid First, a gel film is prepared at a temperature of 25 ° C. to 128 ° C. using a composition comprising a dehydrating agent in an amount of 0.6 to 10.0 molar equivalents relative to the carboxylic acid of the polyamic acid, and then imidized. The manufacturing method of the polyimide film as described in 1) characterized by the above-mentioned.

(In the formula, R ¹ represents a tetravalent organic group represented by the following general formula (2), and R ² represents a divalent organic group represented by the following general formula (3).)

4). 3) characterized in that when the film imidized by heat drying at 300 ° C. to 420 ° C. is cooled to room temperature, it is continuously cooled or provided with one or more steps lower than the heat drying temperature. The manufacturing method of the polyimide film of description.

According to the present invention, a polyimide film excellent in transparency and dimensional stability during heating can be provided.

The polyamic acid used for the production of the polyimide film of the present invention is a polyamic acid having a repeating unit represented by the general formula (1). This polyamic acid can be synthesized using an acid dianhydride and a diamine compound.

The acid dianhydride used preferably has an aromatic group, and the aromatic group may have a substituent. The substituent is preferably an alkyl group having 1 to 10 carbon atoms, and the alkyl group may have a branch or a halogen. Among the substituents, a preferred embodiment is an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. When it has a substituent, the number is preferably 1 to 3, more preferably 1 or 2. Moreover, 2 or more types can be used together as needed.

Specifically, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride represented by the general formula (2) can be given. The total amount of the acid dianhydride is preferably used as the acid dianhydride component, but it does not exceed 70 mol%, preferably 50 mol% of the total acid dianhydride, depending on the desired physical properties. Other acid dianhydrides may be used in the range. Moreover, when using multiple types including the case where other acid dianhydrides are used, they may be regularly arranged or may be present in the polyamic acid at random.

Specific examples of other acid dianhydrides that can be used in combination with an acid dianhydride having an organic group represented by the general formula (2) include, for example, ethylenetetracarboxylic dianhydride, butanetetracarboxylic acid Anhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetra Carboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4- Dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis ( 2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3 , 3,3-hexafluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3- Bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- ( 1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4 -(1,2-dicarboxy) phenoxy] Enyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} Ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone Anhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1 , 1,1 3,3,3-hexaflupropane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane Dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, etc. Is mentioned.

On the other hand, the diamine compound that can be used in the present invention has at least one aromatic group, at least one of which has a substituent, or a branched or straight chain alkyl group having a plurality of aromatic groups. It is preferable that it has the structure couple | bonded by.

Specifically, 2,2′-bis (trifluoromethyl) benzidine and / or a derivative thereof represented by the general formula (3) can be given.

The diamine compound used in the present invention can be used in combination of two or more as required. The total amount of 2,2′-bis (trifluoromethyl) benzidine and / or its derivative is preferably used as the diamine compound, but it is 70 mol%, preferably 50 mol%, based on the target physical properties. Other diamines may be used within a range not exceeding. Moreover, when using multiple types of diamine compounds, they may be arranged regularly and may exist in polyamic acid at random.

Specific examples of other diamines that can be used in combination with the diamine compound having an organic group represented by the general formula (3) include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, and 3,3 ′. -Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3 '-Diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3, 3'-Diaminodiphenylmethane, 4,4'-diamy Diphenylmethane, 3,4'-diaminodiphenylmethane, 2,2-di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl)- 1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) ) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4- Bis (4-Ami Phenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4 -Aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis ( 3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) ) Benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4, 4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) Phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino Nophenoxy) phenyl] ether, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4 -Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- ( 4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [ -(3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α) , Α-dimethylbenzyl) phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxyben Phenone, 6,6′-bis (3-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3, 3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3- Aminopropyl) ether, bis (2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl ] Ether, 1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2 -(2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3- Diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-dia Nocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2 -Aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2 .1] Heptane can be raised.

In the composition comprising the polyamic acid, the imidizing agent and the dehydrating agent used in the present invention, a solvent for dissolving them can be used. The solvent that can be used is preferably an aprotic solvent.

Specific examples of the aprotic polar solvent that can be used in the present invention include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP). , Dimethyl sulfoxide (DMSO), hexamethylphosphorylamide, acetonitrile, acetone, tetrahydrofuran and the like are used alone or as a mixture, but preferably N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) Can be mentioned.

The aprotic polar solvent mentioned here is a solvent having high polarity and no acidic hydrogen. The high polarity means that the dielectric constant is preferably 5 or more, for example.

The total amount of the solvent that can be used in the present invention is preferably an aprotic polar solvent, but an aromatic solvent or an ether solvent may be used as an auxiliary solvent.

Examples of the auxiliary solvent include xylene, toluene, benzene, diethylene glycol ethyl ether, 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), 1,2-bis- (2-methoxyethoxy) ethane (triglyme), Bis- (2-methoxyethyl) ether, butyl cellosolve, butyl cellosolve acetate, propylene glycol methyl ether and propylene glycol methyl ether acetate. The auxiliary solvent can be used in an amount of less than 50% by weight of the aprotic polar solvent used, further less than 30% by weight, particularly less than 15% by weight.

The solid content concentration of the polyamic acid solution used in the present invention is preferably 5 to 50% by weight, more preferably 10 to 35% by weight from the viewpoint of handling.

It is preferable that the diamine compound and the acid dianhydride used in the production of the polyamic acid solution are substantially the same amount (molar ratio). As the monomer ratio of the diamine compound and the acid dianhydride, for example, the diamine component is 92.0 to 99.5 mol%, further 95.0 to 99.0 mol% with respect to 100 mol% of the acid dianhydride component. preferable. When the diamine component is small, a sufficient viscosity cannot be obtained, and the mechanical properties of the polyimide film synthesized from the polyamic acid are unlikely to be sufficient.

The monomer ratio with respect to the acid dianhydride component when the diamine component is 100 mol% is also preferably in the same range as described above. If the molecular weight of the polyamic acid is not high to some extent, it is difficult to obtain sufficient mechanical properties of the polyimide obtained as described above. Polyamic acid is an unstable compound, and as a simple method instead of grasping the polymerization state by molecular weight measurement, a method of grasping the polymerization state from the viscosity of the obtained polyamic acid solution is used. It is preferable to determine the polymerization conditions such that the viscosity of the polyamic acid solution is 500 to 4500 poise, further 850 to 4000 poise, particularly 1000 to 3500 poise at 23 ° C.

When the solution viscosity is high, handling becomes difficult, and when the solution viscosity is low, the mechanical properties of the polyimide film synthesized from polyamic acid are not sufficient. The solution viscosity also varies depending on the solid content concentration. When the molecular weight is the same, the higher the solid content concentration, the higher the solution viscosity. It is preferable to determine the polymerization conditions so that the viscosity of the polyamic acid solution is within the range of the solid content concentration.

The reaction temperature when polymerizing the polyamic acid used in the present invention is preferably 0 to 35 ° C, more preferably 3 to 30 ° C. When the reaction temperature is low, there is a possibility that the reaction time becomes long or the solubility of the raw material is lowered and the molar ratio becomes abnormal. Further, when the reaction temperature is high, the decomposition reaction of the polyamic acid is also promoted, so that the viscosity may not increase.

During the polyamic acid polymerization, an aliphatic carboxylic acid having 15 or less carbon atoms may be added. The amount of the aliphatic carboxylic acid having 15 or less carbon atoms is in the range of 0.5 to 35% by weight of the total amount of the solvent including the carboxylic acid, more preferably 0.7 to 33% by weight, particularly 1.0 to 31% by weight Can be added. It is preferable to use the aliphatic carboxylic acid so that the amount of the aliphatic carboxylic acid is within these ranges, since the polymerization rate of the polyamic acid can be improved and the generated polyamic acid can be prevented from being decomposed.

The aliphatic carboxylic acid having 15 or less carbon atoms is preferably an alkyl group having 15 or less carbon atoms, and the alkyl group may have a branch. Among aliphatic carboxylic acids having 15 or less carbon atoms, carboxylic acids having 10 or less carbon atoms, more preferably 5 or less, and particularly 3 or less are preferable. Polyvalent carboxylic acids can also be used, but monovalent carboxylic acids are preferred. Specific examples include formic acid, acetic acid, propionic acid, n-butyric acid, and iso-butyric acid. Of these, formic acid, acetic acid, and propionic acid are preferable, and acetic acid is more preferable.

In the polymerization of the polyamic acid solution, the diamine compound and the acid dianhydride to be used may be added at once (including adding the entire amount of the other to the other). A method may be used in which the prepolymer (precursor) is polymerized first without using all the components, and the remaining components are added later. The ratio of the diamine compound and acid dianhydride used for the polymerization of the polyamic acid of the present invention can be the ratio described above. When the prepolymer is polymerized, the prepolymer is first polymerized in a state where the diamine compound is large. There are a method of using the remaining acid dianhydride and a method of polymerizing the prepolymer in a state where the acid dianhydride is large and then using the remaining diamine compound.

The amount of the acid dianhydride or diamine compound used later is preferably 3 to 15 mol%, more preferably 4 to 10 mol%, based on the total amount of the acid dianhydride or diamine compound. The solution viscosity of the prepolymer is preferably 1 to 200 poise, preferably 2 to 150 poise, particularly preferably 3 to 100 poise at 23 ° C. Moreover, in order to suppress foreign material mixing in the obtained polyimide film, it may be filtered once at the prepolymer stage. Any known method can be applied as a prepolymer filtration method.

It is possible to produce a polyimide film by imidizing the polyamic acid solution, and the resulting polyimide film is useful as a flexible substrate. In embodiment of this invention, it can use as a board | substrate of an inorganic film laminated | multilayer film. In particular, it can be applied to various uses required in the electronics field. That is, it can be used for gas barrier films for displays and solar cells, transparent conductive films, interlayer insulating films, wiring coating films, optical circuits, antireflection films, holograms, and the like.

As a method for imidization, a method in which a polyamic acid is mixed with a dehydrating agent or an imidizing agent, cast on a base material, and then dried by heating to obtain a polyimide film is preferable. As the imidizing agent that can be used, a tertiary amine is preferable, and among them, a heterocyclic tertiary amine is preferable. Specific examples include pyridine, 3,5-diethylpyridine, picoline, quinoline, and isoquinoline.

As the dehydrating agent, acid anhydrides are preferred, and specific examples include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride, with acetic anhydride being the most preferred. preferable.

In the present invention, as the molar amount of the imidizing agent added to the carboxylic acid of the polyamic acid is increased, the linear expansion coefficient and dimensional stability of the resulting film tend to be improved. On the other hand, if imidization proceeds too quickly with a large amount of imidizing agent, it becomes insoluble before filming, which causes problems such as inability to cast. 0.1 to 2.0 times molar equivalent, more preferably 0.25 to 1.8 times molar equivalent, and even more preferably 0.5 to 1.5 times molar equivalent to the carboxylic acid group of the polyamic acid. As the casting method, a method of casting or coating on an endless belt, or a method of casting or coating on a substrate having a predetermined size can be employed.

In addition, although there is an upper limit for saturation of the dehydrating agent, increasing the amount to be added tends to easily balance the physical properties of the film. Moreover, there exists a tendency which becomes easy to peel a cast film from a base material. From these tendencies, the dehydrating agent is added in an amount of 0.6 to 10.0 times molar equivalent, more preferably 1.0 to 8.0 times molar equivalent to the carboxylic acid group of the polyamic acid. Is preferably 1.5 to 6.0 times the molar equivalent. In addition, the said preferable range of an imidating agent and a dehydrating agent can be used in combination as appropriate.

The polyimide film according to the present invention can be obtained by adding a specific amount of an imidizing agent and a specific amount of a dehydrating agent to a polyamic acid having a specific structure and forming a gel film at a specific temperature. In addition, after the gel film is imidized by baking and then cooled to room temperature, a transparent polyimide film having good dimensional stability during heating can be obtained by employing specific cooling conditions.

The film is mixed with polyamic acid with a dehydrating agent or imidizing agent, cast onto a base material, then heated and dried to cause partial imidization to produce a gel film, which is then peeled off from the base material, pins, clips, etc. A method of obtaining a polyimide film by fixing to a substrate and further drying by heating. After casting only polyamic acid on a substrate, heat drying is performed to produce a gel film, which is peeled off from the substrate and / or dehydrated together with the substrate. Examples of the method include a method of obtaining a polyimide film by immersing in an agent or an imidizing agent, peeling off from a base material, fixing to a pin or clip, and drying by heating.

Of these, the former method is preferable because the entire film can be imidized uniformly and the characteristic variation can be reduced. In the latter method, it takes time for the dehydrating agent or imidizing agent to penetrate into the gel film. Therefore, the film is imidized non-uniformly, resulting in characteristic variations, and the film formation speed is increased to ensure the penetration time. In some cases, it may not be possible to increase the productivity.

The temperature for obtaining the gel film is preferably 25 ° C to 128 ° C, more preferably 60 ° C to 125 ° C. When the baking temperature at the time of gel film preparation is high, the obtained polyimide film becomes cloudy and transparency is lowered, and when it is low, it takes a lot of time to prepare the gel film.

The firing temperature of the polyimide film is preferably from 100 ° C. to 420 ° C., and it is preferable that the temperature is raised stepwise or continuously, and the temperature is preferably lowered stepwise or continuously. When the firing temperature is too high, the polyimide film undergoes thermal decomposition, and when it is too low, the solvent remains in the polyimide film. Further, when the temperature is raised to the maximum firing temperature, it is preferable to take at least 20 seconds, preferably 100 seconds or more, and more preferably 200 seconds or more. When the temperature is raised in a short time, the film may be broken with rapid drying.

When cooling after firing, it is preferable to cool by providing a step of continuously cooling or holding the film in an atmosphere lower than at least one maximum firing temperature.

As the cooling step, it is preferable to continuously cool from the highest firing temperature to room temperature. When cooling in stages, the cooling temperature at which the stages are provided varies depending on the conditions of the maximum firing temperature. For example, when the maximum firing temperature is 300 to 420 ° C., the temperature of each stage is decreased in order according to the following formula. It is preferable to cool it while keeping it in this state.
The number of stages of the cooling process is N, and the desired stage (in order from the highest temperature) is n. In this case, N can be applied to 1 to 4, preferably 1 to 3.

High temperature to nth stage temperature (° C.) = (Maximum firing temperature / (N + 1)) ± 70 / n
About each time to hold | maintain at these temperature, 40 to 300 second, Furthermore, 50 to 250 second is preferable. About these cooling conditions, it can select suitably, when keeping together the heat shrinkage rate and turbidity of a film of this application with the belt temperature at the time of making the above-mentioned gel film. Specifically, the heat shrinkage rate of the film of the present application is appropriately selected such that it is 0.05% or less, preferably 0.03% or less, and the turbidity is 4% or less, preferably 3% or less. To do.

It is also possible to obtain a polyimide film having a tensile elastic modulus of 3 to 15 GPa, preferably 4 to 13 GPa, more preferably 5 to 10 GPa. If it is too high or too low, handling of the film can be difficult.

Also, it is possible to obtain a polyimide film having a tensile strength of 100 to 500 MPa, preferably 150 to 450 MPa, more preferably 200 to 400 MPa. If it is too high or too low, handling of the film can be difficult.

Also, it is possible to obtain a polyimide film having a tensile elongation of 5 to 200%, preferably 10 to 150%, more preferably 15 to 100%. If it is too high or too low, handling of the film can be difficult.

The residual solvent amount of the obtained polyimide film is 2000 ppm or less, preferably 1000 ppm or less, more preferably 500 ppm or less. If the amount of residual solvent is too large, deformation may occur as the solvent evaporates during heating.

It is also possible to obtain a polyimide film having a linear expansion coefficient of −1.0 to 20 ppm / ° C., preferably −0.5 to 10 ppm / ° C., more preferably 0 to 5 ppm / ° C. When the linear expansion coefficient is high, there is a possibility that an inorganic compound having a low linear expansion coefficient cannot be laminated. It is also possible to obtain a polyimide film having a small thermal hysteresis. Thermal hysteresis is a dimensional change before and after heating and cooling. In the present invention, a polyimide film having a small thermal hysteresis can be obtained. In the thermal hysteresis test method shown in the examples, it is also possible to obtain a polyimide film having a thermal hysteresis of 0.01 to 5 μm, further 0.05 to 3.5 μm, particularly 0.06 to 1.8 μm.

It is also possible to obtain a polyimide film having a total light transmittance of 80% or more, preferably 83% or more, and more preferably 85% or more. In addition, a polyimide film having a YI (yellowness) of 20 or less can be obtained.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

[Linear expansion coefficient and thermal hysteresis]
Measured with TMA120C manufactured by Seiko Instruments Inc. A tensile stress of 6 gf was applied to one end in the longitudinal direction of a 10 mm long and 3 mm wide film piece, the temperature was raised from 20 ° C. to 210 ° C. at a temperature rising rate of 10 ° C./min, and then 20 ° C. at a temperature falling rate of 10 ° C./min. The temperature was lowered. This was defined as one cycle, and two-cycle measurement was performed. The linear expansion coefficient was determined from the amount of change in the film piece at 100 ° C. to 200 ° C. in the second cycle. In addition, the film piece used for a measurement was cut out so that the casting direction at the time of film preparation might become vertical.

Thermal hysteresis indicates the change in film dimensions at 50 ° C. when heated from 20 ° C. to 210 ° C. and then cooled to 20 ° C. in the second cycle of the linear expansion coefficient test, and (thermal hysteresis) = (50 at cooling) The length was calculated from (length in ° C)-(length at 50 ° C when heated).

[Viscosity measurement]
The solution viscosity at 23 ° C. was measured using an E-type viscometer RE550 manufactured by Toki Sangyo Co., Ltd.

[Measure turbidity / total light transmittance]
The turbidity and total light transmittance of the film were measured using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd.

[YI (yellowness) measurement]
The YI of the film was measured using NR-3000 manufactured by Nippon Denshoku Industries Co., Ltd.

[Measurement of heat shrinkage]
A test shape of 100 mm in length, 100 mm in width, and a film thickness of about 50 μm was allowed to stand in a constant temperature and humidity chamber at 23 ° C. and 55% for 24 hours, and then 80 mm in length with a printed board processing machine Eleven T manufactured by Mits. Then, four holes were made at intervals of 80 mm across, and the hole intervals were measured with a measuring microscope MF-A1720H manufactured by Mitutoyo Corporation. The film was heated in a hot air oven at 200 ° C. for 30 minutes and allowed to stand in a constant temperature and humidity chamber at 23 ° C. and 55% for 24 hours, and then the hole interval was measured again. Based on the hole interval before and after heating, (heat shrinkage rate) = {(hole interval after heating) − (hole interval before heating)} / (hole interval before heating) × 100 Calculated.

[Residual solvent amount measurement]
The amount of solvent produced by heating the film at 350 ° C. for 30 minutes with a TurboMatrix ATD manufactured by Perkin Elmer was measured by GCMS manufactured by Agilent Technologies.

[Synthesis example]
In a 2000 ml separable flask, 179.0 g (559.1 mmol) of 2,2′-bis (trifluoromethyl) benzidine was added and dissolved in 1381 g of N, N-dimethylacetamide. Thereto, 166.4 g (565.5 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added and stirred at room temperature for 48 hours to obtain a polyamic acid solution. The solution viscosity at 23 ° C. of the polyamic acid solution thus obtained was 2130 poise.

Example 1
To 80 g of the above polyamic acid solution, 3.6 g (38.7 mmol) of β-picoline, 20.0 g (194.4 mmol) of acetic anhydride and 4.4 g of N, N-dimethylacetamide were added and mixed. After defoaming with a centrifuge, it was cast on an aluminum sheet and a gel film was produced at 80 ° C. The gel film is peeled off from the aluminum sheet and fixed to the pin frame, and dried at 150 ° C for 4 minutes, 200 ° C for 5 minutes, 250 ° C for 3 minutes, 300 ° C for 2 minutes 30 seconds, and 380 ° C for 2 minutes went. Further, after being held at 150 ° C. for 60 seconds during cooling, it was returned to room temperature to obtain a polyimide film 1.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 1 was 0.9 ppm / ° C., and the thermal hysteresis was 0.2 μm. YI was 15.9, turbidity was 1.6%, total light transmittance was 86%, and the residual solvent amount was 218 ppm. Furthermore, the heat shrinkage rate of the film was 0.02%. The film thickness was 53 μm.

(Example 2)
A gel film was prepared in the same manner as in Example 1. Heat drying was performed at 150 ° C. for 4 minutes, 200 ° C. for 5 minutes, 250 ° C. for 3 minutes, 300 ° C. for 2 minutes 30 seconds, and 350 ° C. for 2 minutes. Furthermore, after holding at 200 ° C. for 60 seconds or more and 100 ° C. for 60 seconds or more during cooling, the temperature was returned to room temperature to obtain a polyimide film 2.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 2 was 0.3 ppm / ° C., and the thermal hysteresis was 0.1 μm. YI was 19.4, turbidity was 3.0%, total light transmittance was 85%, and the amount of residual solvent was not detected. Furthermore, the heat shrinkage rate of the film was 0.01%. The film thickness was 50 μm.

(Example 3)
A gel film was prepared in the same manner as in Example 1. Heat drying was performed at 150 ° C. for 4 minutes, 200 ° C. for 5 minutes, 250 ° C. for 3 minutes, 300 ° C. for 2 minutes 30 seconds, and 380 ° C. for 2 minutes. Furthermore, after cooling at 260 ° C. for 60 seconds and at 130 ° C. for 60 seconds during cooling, the temperature was returned to room temperature to obtain a polyimide film 3.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 3 was 1.5 ppm / ° C., and the thermal hysteresis was 1.4 μm. YI was 18.0, turbidity was 2.5%, total light transmittance was 85%, and the residual solvent amount was 35 ppm. Furthermore, the heat shrinkage rate of the film was 0.01%. The film thickness was 51 μm.

Example 4
A gel film was prepared in the same manner as in Example 1, using 4.0 g (43.0 mmol) of β-picoline, 22.1 g (216.8 mmol) of acetic anhydride, and 4.4 g of N, N-dimethylacetamide. Heat drying was performed at 150 ° C. for 4 minutes, 200 ° C. for 5 minutes, 250 ° C. for 3 minutes, 300 ° C. for 2 minutes 30 seconds, and 380 ° C. for 2 minutes. Furthermore, after cooling at 260 ° C. for 60 seconds and at 130 ° C. for 60 seconds during cooling, the temperature was returned to room temperature to obtain a polyimide film 4.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 4 was 2.0 ppm / ° C., and the thermal hysteresis was 0.5 μm. YI was 16.5, turbidity was 3.1%, total light transmittance was 86%, and the amount of residual solvent was 28 ppm. Furthermore, the heat shrinkage rate of the film was 0.02%. The film thickness was 50 μm.

(Comparative Example 1)
A gel film was prepared in the same manner as in Example 1. Heat drying was performed at 150 ° C. for 4 minutes, 200 ° C. for 5 minutes, 250 ° C. for 3 minutes, 300 ° C. for 2 minutes 30 seconds, and 350 ° C. for 2 minutes, and then rapidly cooled to room temperature to obtain polyimide film 5.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 5 was −0.1 ppm / ° C., and the thermal hysteresis was 0.3 μm. YI was 18.9, turbidity was 2.9%, total light transmittance was 85%, and the amount of residual solvent was not detected. Furthermore, the heat shrinkage rate of the film was 0.06%. The film thickness was 51 μm.

(Comparative Example 2)
A gel film was prepared at a belt temperature of 130 ° C. Heat drying at 150 ° C for 4 minutes, 200 ° C for 5 minutes, 250 ° C for 3 minutes, 300 ° C for 2 minutes 30 seconds, 350 ° C for 2 minutes, and further hold at 150 ° C for 60 seconds during cooling, then to room temperature It returned and the polyimide film 6 was obtained.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 6 was 0.9 ppm / ° C., and the thermal hysteresis was 0.5 μm. YI was 16.3, turbidity was 4.3% (partially cloudy), total light transmittance was 86%, and no residual solvent was detected. Furthermore, the heat shrinkage rate of the film was 0.02%. The film thickness was 53 μm.

(Comparative Example 3)
80 g of the polyamic acid solution of the synthesis example was cast on a 125 μm-thick PET film (Lumirror, manufactured by Toray), and a gel film was produced at 80 ° C. On the other hand, a solution containing β-picoline and acetic anhydride at a molar ratio of 1: 1 was separately prepared, and the gel film was immersed in this solution for 10 minutes with PET. The gel film was peeled off from the PET, fixed to the pin frame, and heated at 80 ° C. for another 2 minutes. Then, it heat-dried for 30 minutes at 100 degreeC, 150 degreeC, 200 degreeC, and 300 degreeC, respectively, and the polyimide film 7 was obtained.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 7 was 0.3 ppm / ° C., and the thermal hysteresis was 2.0 μm. YI was 21.0, turbidity was 3.5%, total light transmittance was 86%, and residual solvent was not detected. Furthermore, the heat shrinkage rate of the film was 0.07%. The film thickness was 51 μm.

(Comparative Example 4)
80 g of the polyamic acid solution of the synthesis example was cast on a 125 μm-thick PET film (Lumirror, manufactured by Toray), and a gel film was produced at 80 ° C. On the other hand, a solution containing β-picoline and acetic anhydride at a molar ratio of 1: 5 was separately prepared, and the gel film was immersed in this solution for 10 minutes with PET. The gel film was peeled off from the PET and fixed to the pin frame, dried at 150 ° C for 4 minutes, 200 ° C for 5 minutes, 250 ° C for 3 minutes, 300 ° C for 2 minutes 30 seconds, and 380 ° C for 2 minutes. . Further, after cooling at 150 ° C. for 60 seconds during cooling, the temperature was returned to room temperature to obtain a polyimide film 8.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 8 was 4.7 ppm / ° C., and the thermal hysteresis was 0.2 μm. YI was 25.6, turbidity was 3.6%, total light transmittance was 85%, and residual solvent was not detected. Furthermore, the heat shrinkage rate of the film was 0.05%. The film thickness was 49 μm.

(Comparative Example 5)
To 70 g of the polyamic acid solution of Synthesis Example, 2.8 g (31.0 mmol) of β-picoline and 19.0 g (185.4 mmol) of acetic anhydride were added and mixed. After defoaming with a centrifugal separator, the gel film was cast on a polyethylene naphthalate (PEN) film and heated at 50 ° C. for 10 minutes, at 100 ° C. for 10 minutes, and at 200 ° C. for 10 minutes to produce a gel film. The gel film was peeled off from the PEN and fixed to the pin frame, dried by heating at 300 ° C. for 1 hour, and then returned to room temperature to obtain a polyimide film 9.

The linear expansion coefficient (100-200 ° C.) of the polyimide film 9 was 1.2 ppm / ° C., and the thermal hysteresis was 0.3 μm. YI was 16.2, turbidity was 2.2%, total light transmittance was 86%, and residual solvent was not detected. Furthermore, the heat shrinkage rate of the film was 0.07%. The film thickness was 51 μm.

From the results in Table 1, when the film is rapidly cooled after drying and returned to room temperature, the heat shrinkage rate of the polyimide film becomes high (Comparative Example 1 and Comparative Example 3), and when the gel film preparation temperature is high, the polyimide film The turbidity of is increased (Comparative Example 2). On the other hand, it can be seen that when the gel film is produced at 80 ° C. and the cooling process after drying is maintained at a temperature of at least one stage, the heat shrinkage ratio is low and the dimensional stability is high.

Claims (4)

Polyamic acid having a repeating unit represented by the following formula (1) synthesized using a diamine compound and an acid dianhydride, and 0.1 to 2.0 mole equivalent of imide with respect to the carboxylic acid of the polyamic acid The turbidity obtained by preparing a gel film at a temperature of 25 ° C. to 128 ° C. with a composition comprising a dehydrating agent in an amount of 0.6 to 10.0 molar equivalents relative to the carboxylic acid of the polyamic acid and polyamic acid. Polyimide film of 4% or less, YI (yellowness) 20 or less, total light transmittance 80% or more, and heat shrinkage 0.05% or less

(In the formula, R ¹ represents a tetravalent organic group represented by the following general formula (2), and R ² represents a divalent organic group represented by the following general formula (3).)

The polyimide film according to claim 1, comprising a composition using β-picoline as an imidizing agent and acetic anhydride as a dehydrating agent. Polyamic acid having a repeating unit represented by the following formula (1) synthesized using a diamine compound and an acid dianhydride, and 0.1 to 2.0 mole equivalent of imide with respect to the carboxylic acid of the polyamic acid First, a gel film is prepared at a temperature of 25 ° C. to 128 ° C. using a composition comprising a dehydrating agent in an amount of 0.6 to 10.0 molar equivalents relative to the carboxylic acid of the polyamic acid, and then imidized. The manufacturing method of the polyimide film of Claim 1 or 2 characterized by the above-mentioned.

(In the formula, R ¹ represents a tetravalent organic group represented by the following general formula (2), and R ² represents a divalent organic group represented by the following general formula (3).)

4. The method according to claim 3, wherein when the film imidized by heat drying at 300 ° C. to 420 ° C. is cooled to room temperature, the film is continuously cooled or provided with at least one stage lower than the heat drying temperature. The manufacturing method of the polyimide film of description.