TWI698462B - Polyimide film - Google Patents

Abstract

The subject of the present invention is to provide a thin polyimide film with a thickness of 1.0 to 10.0 μm, which is not prone to deterioration in characteristics caused by film deterioration and/or hydrolysis even if it is immersed in an alkaline solution.

Set the L value of the polyimide film with a thickness of 1.0~10.0μm to 28~45, and when the molecular weight of the polyimide repeating unit is set to 100%, set the molecular weight of the polyimide group to Less than 40%.

Description

Polyimide film

The present invention relates to an extremely thin polyimide film with excellent alkali chemical resistance.

After the aromatic diamine and the aromatic tetracarboxylic dianhydride are polymerized in an organic solvent to obtain a polyamide acid polymer solution, the polyamide acid polymer solution is formed into a film shape and subjected to thermal dehydration The polyimide film obtained by closed loop and/or chemical dehydration closed loop, that is, imidization, is widely used in electrical insulation materials, thermal insulation materials, and electrical insulation materials for electric wires because of its excellent heat resistance, insulation and mechanical properties. Flexible printed circuit board (hereinafter referred to as FPC) base film, IC (Integrated Circuit, integrated circuit) tape carrier film for automatic bonding, IC lead frame fixing tape, conductive circuit protection or insulation In the purpose of covering layer use, etc.

Among these applications, FPC will form a circuit pattern on a soft and thin base film and apply a covering layer on its surface as the basic structure. Due to its excellent properties such as flexibility, it is widely used in electronics. In the technical field. In recent years, due to advances in packaging technology, high-density wiring and multi-layer FPC have been promoted, and high bending resistance has also been required along with this. As one of the means of improving the bending resistance and miniaturization of FPC, thin film is effective. Since the previous three-layer type of copper foil/adhesive (acrylic or epoxy resin)/polyimide, no The two-layer type of copper foil/polyimide inserted with adhesive has become the mainstream.

As a production method of the two-layer type of copper foil/polyimide, in addition to the casting method of casting polyimide precursor resin on the copper foil, the following methods can be cited: non-thermoplastic polyimide before heating One or both sides of the amine film are coated as a thermoplastic polyimide The organic solvent solution of polyamide acid as the precursor is heated to obtain the film, and then the copper foil is laminated; the heated non-thermoplastic polyimide film is coated on one or both sides as a thermoplastic polyamide The organic solvent solution of polyamide acid as the precursor of imine, the method of laminating copper foil, etc.

As these polyimide films for FPC applications, thinning has been sought in recent years, but there is a problem that the strength of the film is weakened due to the thinning, and the film is likely to be broken or deformed during the manufacturing steps of the film or FPC. In addition, the thinner the thickness, the lower the rigidity of the film, so the flatness of the film deteriorates, wrinkles are likely to occur when the film is transported, and the yield is reduced.

In particular, if an ultra-thin polyimide film with a thickness of 10.0 μm or less is to be produced, the following problems exist: because of its thinness, it is very easy to cause rupture at the end of the film from the needle-fixed hole, or when it is transported. Troubles such as winding and breakage of the film caused by the occurrence of wrinkles are low in productivity.

As an ultra-thin polyimide film with a thickness of less than 8.0μm, which is unlikely to cause film breakage or wrinkles during film production, it has been reported that the film has a specified tear resistance expansion resistance or ultrasonic transmission speed. (Patent Document 1).

In addition, as a method for producing ultra-thin polyimide film, a method of coating a polyimide resin precursor solution containing a release agent on a substrate, drying and heat treatment, and peeling from the substrate, etc. ( Patent Document 2).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-196467

[Patent Document 2] Japanese Patent Laid-Open No. 2009-226632

However, if the polyimide film is made as thin as 10.0 μm or less, the durability against chemicals tends to be reduced and it becomes a problem. For example, in the peeling step of the dry resist film in the FPC manufacturing process, when immersed in an alkaline solution as a peeling liquid for several minutes, the thinner the polyimide film, the faster the deterioration rate and the harder it becomes. Become brittle, resulting in its breaking strength or elongation at break The reduction, cracks, etc. greatly damage the reliability of the FPC. Therefore, it is required to develop an extremely thin polyimide film with excellent alkali resistance.

The object of the present invention is to provide a thin polyimide film with a thickness of 1.0 to 10.0 μm, which is not prone to deterioration in characteristics caused by film deterioration and/or hydrolysis even if it is immersed in an alkaline solution.

In addition, the subject of the present invention is also to provide a thin polyimide film with a thickness of 1.0 to 10.0 μm that does not cause breakage or wrinkles in the film manufacturing step, and is excellent in film formation stability.

As a method of improving the alkali resistance of the polyimide film, for example, various methods such as studies on the type or composition of the monomer forming the polyimide acid are conceivable.

However, the previous thin-film polyimide film with higher alkali resistance is hard, less flexible, and brittle. Therefore, during the film manufacturing process, the film is damaged during film transportation, or from damaged film debris. This leads to the problem of defects on the surface of the film, poor film formation stability when manufacturing the film, and difficulty in film formation.

In order to solve the above-mentioned problems, the inventors have made repeated research and found that by adjusting the L value of the polyimide film (furthermore, the ratio of the polyimide group) to a specific range Inside, even if it is a film of 1.0~10.0μm, a polyimide film with alkali resistance (more specifically, film formation stability during film production) can be obtained.

In order to solve the above-mentioned problems, the inventors of the present invention made further and intensive studies, and as a result, completed the present invention.

That is, the present invention relates to the following polyimide film and the like.

[1] A polyimide film with a thickness of 1.0~10.0μm, characterized in that: when the molecular weight of the repeating unit of the polyimide is set to 100%, the molecular weight of the imine group is 40% or less, and The L value of polyimide film is 28~45.

[2] The polyimide film as described in [1] above, wherein the polyimide film is stretched by biaxial stretching in the mechanical transport direction (MD) and the width direction (TD) of the film, and the total film Stretching ratio (MD stretching ratio×TD stretching ratio) is 1.60 or more.

[3] The polyimide film of any one of [1] to [2] above, which is composed of aromatic diamine components selected from p-phenylenediamine, 4,4'-diaminodiphenyl One or more of the group consisting of ether and 3,4'-diaminodiphenyl ether, the aromatic anhydride component is pyromellitic dianhydride and/or 3,3',4,4'-biphenyl Manufactured by polyamide acid of tetracarboxylic dianhydride.

[4] The polyimide film manufacturing method as described in any one of [1] to [3] above, which stretches the gel film that can form the polyimide film to obtain a film at 350~500℃ Heat treatment for 5 to 300 seconds. When the polyimide film has a molecular weight of 100% of the repeating unit of the polyimide film, the molecular weight of the polyimide group is less than 40%.

[5] A polyimide film, characterized in that it comprises the polyimide film (A) as described in any one of [1] to [4] above, and a layer laminated on the polyimide film (A) Polyimide film on one or both sides (B).

[6] The polyimide film according to any one of [1] to [5] above, wherein the form of the polyimide film is a polyimide film roll with a width of 500-3000 mm and a length of 1000 m or more.

According to the present invention, it is possible to obtain a polyimide film with a thickness of 1.0 to 10.0 μm, which is less prone to deterioration in characteristics caused by film deterioration and/or hydrolysis even when immersed in an alkaline solution, and is excellent in alkali resistance.

In addition, according to the present invention, a polyimide film with a thickness of 1.0 to 10.0 μm can be obtained in which the damage or wrinkles of the film in the film forming step are reduced and the film forming stability is excellent.

Furthermore, according to the present invention, it is possible to obtain a product having a thickness of 1.0 to 10.0 μm, excellent alkali resistance, and less failure caused by a decrease in breaking strength or cracks in the peeling step of the dry resist film in the FPC manufacturing step Polyimide film.

Hereinafter, the present invention will be described in detail.

The thickness of the polyimide film of the present invention is usually 1.0 to 10.0 μm, preferably 2.0 to 9.0 μm, and more preferably 3.0 to 8.0 μm.

The L value of the polyimide film of the present invention is usually 28-45, preferably 28-44, more preferably 29-43, and still more preferably 30-42.

The L value can be adjusted by selecting the constituent components of the polyimide or the ratio thereof, the processing conditions (heat treatment conditions, stretching conditions) of the polyimide film (gel film), and the like.

For example, for a gel film, heat treatment is performed as described later, but by selecting such heat treatment conditions (temperature, time, etc.), the degree of crystallization or structural change of polyimide can be adjusted, and the film surface can be adjusted. The degree of oxidation can adjust the L value of the film.

Furthermore, as one of the reasons why a film excellent in alkali resistance (more specifically, film forming stability) can be obtained by selecting the L value in the specific range as described above, for example, the following reasons are conceivable.

By strengthening the heat treatment of the gel film, the crystallization is promoted along with the rearrangement of polymer chains or the formation of a cross-linked structure, and the L value becomes lower. In this way, as the water absorption of the film surface increases, the alkali resistance also increases. Moreover, by further setting the progress of crystallization to an appropriate range (that is, the L value is not too low), the strength and flexibility of the film during the manufacturing step can be guaranteed, and the alkali resistance and excellent manufacturing can be efficiently combined Membrane stability.

If the L value is in the above-mentioned range, even if the thickness of the polyimide film is as thin as 1.0 to 10.0 μm, it is excellent in alkali resistance, which is preferable. In addition, if the range is within this range, even if the thickness of the target polyimide film is as thin as 1.0~10.0μm, the film breakage or wrinkles are reduced during the production process of the polyimide film, and the film formation stability is excellent , So better.

In addition, L value is the value measured by the method described in the Example mentioned later. L value can It is measured by overlapping polyimide films and setting the total thickness to 50-60 μm.

In the polyimide film of the present invention, when the molecular weight of the repeating unit of the polyimine is set to 100%, the molecular weight of the imine group represented by the following formula (1) is usually 40% or less, preferably 39 % Or less, more preferably 38% or less.

Furthermore, "the molecular weight of the repeating unit of polyimine" and "the molecular weight of polyimine" have the same meaning.

If it is in this range, the alkali resistance of the polyimide film is improved, which is preferable. It can be considered that the higher the content of the imine group in the polyimide film, the higher the water absorption. On the other hand, it can be considered that the higher the content of hydrophobic components other than the imine group, the lower the water absorption of the polyimide film and the higher the alkali resistance.

Furthermore, the width of the polyimide film of the present invention is not particularly limited, and is preferably 500 to 3000 mm, more preferably 1000 to 2800 mm, and still more preferably 1500 to 2500 mm.

In addition, the length of the polyimide film of the present invention is not particularly limited, but is preferably 1,000 m or more, more preferably 2,000 to 50,000 m, and still more preferably 3,000 to 30,000 m.

[Polyamide acid]

To obtain the polyimide film of the present invention, first, the aromatic diamine component and the aromatic acid anhydride component are polymerized in an organic solvent to obtain a polyimide acid solution (hereinafter also referred to as polyimide acid solution). Hereinafter, the polyamide acid solution will be described.

In the present invention, the polyamide acid solution can be obtained by polymerizing the aromatic diamine component and the aromatic anhydride component, or a chemical substance containing the two as main components, in an organic solvent.

Examples of aromatic diamine components include p-phenylenediamine, m-phenylenediamine, benzidine, p-xylylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diamine Diphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodi Phenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis(3-methyl-5-aminophenyl)benzene and these amides Formative derivatives. These may be used individually by 1 type, and may mix and use 2 or more types.

The aromatic diamine component is preferably selected from the group consisting of p-phenylenediamine and 4,4'-diaminodiphenyl from the viewpoint of the obtained polyimide film being excellent in low thermal expansion and flexibility, etc. One or more of the group consisting of phenylether and 3,4'-diaminodiphenyl ether, and more preferably a combination of p-phenylenediamine and 4,4'-diaminodiphenyl ether.

In the present invention, as a raw material for forming a polyamide acid solution, other diamine components other than the above-mentioned aromatic diamine components may be contained within a range that does not hinder the effects of the present invention.

二唑、2,2-雙(4-胺基苯基)六氟丙烷、N-(3-胺基苯基)-4-胺基苯甲醯胺、4-胺基苯基-3-胺基苯甲酸酯等。該等可單獨使用1種，亦可將2種以上混合使用。 Examples of the above-mentioned other diamine components include: 3,3'-diaminodiphenyl ether, m-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,4'-diamino Diphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-di Amino diphenylmethane, benzidine, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide Ether, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 2,6-diaminopyridine, Bis-(4-aminophenyl)diethylsilane, 3,3'-dichlorobenzidine, bis-(4-aminophenyl)ethyl phosphine oxide, bis-(4-aminophenyl) Phenylphosphine oxide, bis-(4-aminophenyl)-N-phenylamine, bis-(4-aminophenyl)-N-methylamine, 1,5-diaminonaphthalene, 3, 3'-dimethyl-4,4'-diaminobiphenyl, 3,4'-dimethyl-3',4-diaminobiphenyl-3,3'-dimethoxybenzidine, 2,4-bis(p-β-amino-tertiary butylphenyl) ether, bis(p-β-amino-tertiary butylphenyl) ether, p-bis(2-methyl-4- Aminopentyl)benzene, p-bis-(1,1-dimethyl-5-aminopentyl)benzene, m-xylylenediamine, p-xylylenediamine, 1,3-diamine pyridine, 3 ,3'-Diamino-1,1'-Diamine Fundmantane, 3,3'-Diaminomethyl-1,1'-Diadamantane, Bis(p-aminocyclohexyl)methane, Hexa Methylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, 3-methyl heptamethylene diamine, 4,4'- Dimethylheptamethylene diamine, 2,11-diaminododecane, 1,2-bis(3-aminopropoxy)ethane, 2,2-dimethylpropanediamine, 3 -Methoxyhexamethylene diamine, 2,5-dimethylhexamethylene diamine, 2,5-dimethylheptamethylene diamine, 5-methylnonamethylene diamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, 2,5-diamino-1,3,4-

Diazole, 2,2-bis(4-aminophenyl)hexafluoropropane, N-(3-aminophenyl)-4-aminobenzamide, 4-aminophenyl-3-amine Base benzoate and so on. These may be used individually by 1 type, and may mix and use 2 or more types.

Specific examples of the above-mentioned aromatic acid anhydride components include, for example, pyromellitic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3',3,4'-biphenyltetracarboxylic acid , 3,3',4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalene tetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl) ether, pyridine -2,3,5,6-tetracarboxylic acid and aromatic tetracarboxylic anhydride components such as amide-forming derivatives. These may be used individually by 1 type, and may mix and use 2 or more types.

The aromatic acid anhydride component is preferably selected from the group consisting of pyromellitic dianhydride and 3,3',4,4' from the viewpoint of the obtained polyimide film being excellent in heat resistance and low water absorption. -One or more of the group consisting of biphenyltetracarboxylic dianhydride.

In the present invention, as a raw material for forming a polyamide acid solution, an acid anhydride component other than the above-mentioned aromatic acid anhydride component may be contained within a range that does not impair the effects of the present invention.

Examples of the above-mentioned other acid anhydride components include: 2,3',3,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2, 3,6,7-naphthalene dicarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6-tetracarboxylic dianhydride, 1, 2, 4,5-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,4,5,8-decahydronaphthalenetetracarboxylic dianhydride, 4,8-dimethyl -1,2,5,6-hexahydronaphthalenetetracarboxylic dianhydride, 2,6-dichloro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,7-dichloro-1,4 ,5,8-Naphthalenetetracarboxylic dianhydride, 2,3,6,7-tetrachloro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,8,9,10- Phenanthrene tetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1- Bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(3, 4-Dicarboxyphenyl) bismuth dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 3,4,3',4'-benzophenone tetracarboxylic dianhydride, etc. These may be used individually by 1 type, and may mix and use 2 or more types.

In the present invention, as a particularly preferable combination of an aromatic diamine component and an aromatic acid anhydride component, from the viewpoints that the obtained polyimide film is excellent in heat resistance, low water absorption, low thermal expansion, and flexibility, etc. Examples include: 4,4'-diaminodiphenyl ether as an aromatic diamine component, or p-phenylenediamine and 4,4'-diaminodiphenyl ether, and benzene as an aromatic anhydride component Pyromellitic dianhydride, or a combination of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Among them, a combination of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is particularly preferred.

In the present invention, the molar ratio of p-phenylenediamine and 4,4'-diaminodiphenyl ether is preferably 40/60~0/100, more preferably 30/70~0/100.

In the present invention, the molar ratio of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride is preferably 100/0~40/60, more preferably 100/0~65 /35.

Furthermore, in the present invention, specific examples of the organic solvent used to form the polyamide acid solution include, for example, sulfinous solvents such as dimethyl sulfene and diethyl sulfin; N,N-dimethyl Formamide solvents such as formamide and N,N-diethylformamide; acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide; N -Methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and other pyrrolidone solvents; phenol, o-cresol, m-cresol or p-cresol, xylenol, halogenated phenol, o-benzene Phenolic solvents such as diphenols; aprotic polar solvents such as hexamethylphosphamide and γ-butyrolactone. These can be used alone or in combination of two or more, and can be used in combination with aromatic hydrocarbons such as xylene and toluene.

The polymerization method of the polyamide acid solution can be carried out by any known method, for example, the following methods can be mentioned.

(1) First put the total amount of aromatic diamine components into the solvent, and then combine with the aromatic diamine The total amount of diamine components is a method in which aromatic acid anhydride components are added in an equal amount to perform polymerization.

(2) A method in which the total amount of aromatic acid anhydride components is first put into a solvent, and then the aromatic diamine component is added in an equivalent amount to the aromatic acid anhydride component to perform polymerization.

(3) After putting a part of the aromatic diamine component in the solvent, the part of the aromatic acid anhydride component is 95~105 mol% relative to the reaction component, and after mixing for the time required for the reaction, add another part of the aromatic A method in which all the aromatic diamine components and all the aromatic acid anhydride components are then added in such a way that all of the aromatic diamine components and all the aromatic acid anhydride components are substantially equal to each other to carry out polymerization.

(4) After putting a part of the aromatic acid anhydride component in the solvent, the ratio of the part of the aromatic diamine component to the reaction component is 95~105 mol% after mixing for the time required for the reaction, and then adding another part of the aromatic A method of polymerization by adding another part of the aromatic diamine component so that all the aromatic diamine components and all the aromatic acid anhydride components become approximately equal amounts.

(5) A part of the aromatic diamine component and the aromatic anhydride component are reacted in a solvent such that either one becomes excessive to prepare a polyamide acid solution (A), and another part of the aromatic diamine component is made in another solvent It reacts with an aromatic acid anhydride component so that any one becomes excessive, and the polyamide acid solution (B) is prepared. The polyamic acid solutions (A) and (B) thus obtained are mixed to complete the polymerization method. At this time, when the aromatic diamine component is excessive in the preparation of the polyamide acid solution (A), the aromatic acid anhydride component is excessive in the polyamide acid solution (B), and the polyamide acid solution ( When the aromatic acid anhydride component is excessive in A), make the aromatic diamine component excessive in the polyamic acid solution (B), mix the polyamic acid solution (A) and (B), and use them for the reaction All aromatic diamine components and all fully aromatic anhydride components are prepared in roughly equal amounts.

In addition, the polymerization method is not limited to this, and other known methods may be used.

In the present invention, the aromatic acid anhydride component and the aromatic diamine component constituting the polyamide acid are It is polymerized so that the respective molar numbers become approximately equal proportions, and one of them may be over-adjusted relative to the other in the range of, for example, 10 mol%, preferably 5 mol%.

The polymerization reaction is preferably carried out while stirring in an organic solvent. The polymerization temperature is not particularly limited, and it is usually carried out at the internal temperature of the reaction solution from 0 to 80°C. The polymerization time is not particularly limited, but it is preferably continuously performed for 10 minutes to 30 hours. The polymerization reaction may be divided into sections or the temperature may be increased or decreased as necessary. The order of addition of the two reactants is not particularly limited, but it is preferable to add an aromatic anhydride to the solution of the aromatic diamine component. In terms of producing high-quality organic solvent solutions of polyamide acid, vacuum defoaming during polymerization is an effective method. Furthermore, by adding a small amount of a blocking agent to the aromatic diamines before the polymerization reaction, the polymerization reaction can also be controlled. The said blocking agent is not specifically limited, A well-known thing can be used.

The polyamide acid solution thus obtained usually contains 5-40% by weight, preferably 10-30% by weight of solid content. In addition, the viscosity is a measured value obtained by using a Brookfield viscometer, and is not particularly limited. It is usually 10~2000Pa‧s. In order to achieve stable infusion, it is preferably 100~1000Pa‧s. Furthermore, the polyamic acid in the organic solvent solution can also be partially imidized.

In addition, the polyamide acid solution may contain chemically inactive organic or inorganic fillers such as titanium oxide, silicon oxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, and polyimide fillers as needed. The content of the filler is not particularly limited as long as it does not impair the effect of the present invention.

The polyamide acid solution used here may be a polyamide acid solution prepared by polymerization in advance, or may be a polyamide acid solution obtained by sequential polymerization when it contains filler particles.

In addition, the polyamide acid solution may contain one or more compounds other than the filler. Examples of compounds other than fillers include metal oxides such as carbon, aluminum oxide or titanium dioxide, and boron compounds such as boron nitride.

Hereinafter, the manufacturing method of the polyimide film of the present invention will be described.

The polyimide film of the present invention is produced by heating the above polyimide acid solution, It will be described in detail below.

As a method of manufacturing a polyimide film, there can be mentioned: a method of casting a polyimide acid solution into a film shape and thermally dering and removing the solvent to obtain a polyimide film; and mixing the ring in the polyimide acid solution The chemical catalyst and dehydrating agent are chemically decyclized to make a gel film, which is heated to remove the solvent to obtain a polyimide film; the latter is preferred.

In the method of chemical decyclization, the above-mentioned polyamide acid solution is first prepared. The above-mentioned polyamide acid solution may contain a cyclization catalyst (imidation catalyst), a dehydrating agent, a gelation retarder, and the like.

Specific examples of the cyclization catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and isoquinoline, Heterocyclic tertiary amines such as pyridine and β-picoline can be used alone or in combination of two or more kinds. Among them, it is preferable to use at least one heterocyclic tertiary amine.

Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic anhydrides such as benzoic anhydride. Among them, acetic anhydride and/or Benzoic anhydride.

As a method for producing polyimide film from polyamide acid solution, a polyimide acid solution containing a cyclization catalyst and a dehydrating agent is cast onto a support from a nozzle with a slit to be shaped into a film. After the body is partially imidized to form a self-supporting gel film, it is peeled off from the support, and is heated to dry/imide and heat treatment.

The above-mentioned polyamide acid solution is formed into a film through a slit-shaped nozzle, and is cast on a heated support, and a thermal closed loop reaction is performed on the support to become a self-supporting gel film. Peel off.

The above-mentioned support is a metal rotating drum or an endless belt, the temperature of which is controlled by a liquid or gas heat medium, and/or radiant heat from an electric heater.

The above-mentioned gel film is heated to 30~200℃, preferably 40~150℃ by heating from the support and/or heating from the heat source such as hot air or electric heater. Volatile components such as organic solvents are dried to become self-supporting and peel off from the support. At this time, by using a support with a diameter of 10 to 100 μm in the concave and convex part existing on the surface of the support, the number of concave and convex parts is 500 to 1500 per 1 cm ² , and the maximum roughness of the concave and convex part is 1 to 5 μm. It can also be peeled off well in the production of thin polyimide film of 10μm or less.

The gel film peeled from the above-mentioned support is usually stretched in the traveling direction by a rotating roller while restricting the traveling speed. The extension in the traveling direction is preferably performed in multiple stages by rotating rollers. Especially in the stretching of thin polyimide film below 10μm, it is better to prevent the film from wrinkles by setting the rotating roller as an S-wrap, or using nip rollers and suction rollers to control the tension in multiple stages. The extension in the traveling direction is usually performed at a temperature below 140° C. with a magnification of 1.01 to 1.90 times, preferably 1.05 to 1.60 times, and more preferably 1.10 to 1.50 times. The gel film stretched in the traveling direction is introduced into the tenter device, and the two ends in the width direction are held by the tenter clip, one side runs with the tenter clip, and the other side extends in the width direction.

Regarding the extension of the gel film, it is preferable that the total extension ratio of the film (the extension ratio in the mechanical transport direction (MD) × the extension ratio in the width direction (TD)) of the film is 1.60 or more, more preferably 1.70~3.00, and more Preferably, it is 1.80~2.60. If the stretching ratio is higher, the alignment of the molecular chain of the polyimide becomes higher, so it is considered that the film becomes less hydrolyzed and the alkali resistance is improved, which is preferable.

The thickness of the polyimide film can be adjusted by adjusting the stretching ratio of MD and TD.

The stretched gel film is usually heated by wind, infrared heater, etc. for 15 seconds to 30 minutes. Then, with hot air and/or electric heaters, the heat treatment is usually performed at a temperature of 250 to 500°C for 5 seconds to 30 minutes. The heat treatment temperature and time can be appropriately changed according to the thickness of the obtained polyimide film.

The heat treatment temperature is usually 250 to 500°C, preferably 300 to 500°C, more preferably 350 to 500°C, and still more preferably 370 to 490°C.

The heat treatment time is usually 5 seconds to 30 minutes, preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and even more preferably 5 seconds to 300 seconds.

In addition, the thickness of the polyimide film can be adjusted by adjusting the traveling speed during heat treatment of the gel film.

It is preferable to further subject the polyimide film thus obtained to annealing treatment. The method of annealing treatment is not particularly limited, as long as it follows a common method.

The annealing temperature is not particularly limited, but is preferably 200°C or higher and 600°C or lower, more preferably 200°C or higher and 550°C or lower, and particularly preferably 210°C or higher and 500°C or lower. Specifically, it is preferable to perform annealing treatment by advancing the film under low tension in a furnace heated to the above-mentioned temperature range. The time the film stays in the furnace becomes the processing time, which is controlled by changing the traveling speed, preferably a processing time of 5 seconds to 5 minutes. Moreover, the film tension during travel is preferably 10-50 N/m, more preferably 20-30 N/m.

In addition, the polyimide film obtained as described above is preferably subjected to plasma surface treatment such as atmospheric piezoelectric plasma or vacuum plasma surface treatment on the surface of the film. The method of plasma surface treatment is not particularly limited.

The form of the polyimide film of the present invention is not particularly limited, and it is preferably a roll shape.

The polyimide film roll can be obtained by winding the polyimide film onto a roll core. In the present invention, the method of winding onto the core is not particularly limited.

The material of the above-mentioned core is not particularly limited, and previously known materials can be used. Examples include: paper; plastics such as vinyl chloride; a combination of glass fiber and epoxy resin, paper and phenol resin, carbon fiber and epoxy resin, etc. Fiber reinforced plastics (FRP) formed by other materials; metals such as stainless steel; those obtained by impregnating resin in a paper core; or those obtained by forming a resin layer on the surface of such materials.

The diameter of the core is not particularly limited, for example, 50~250mm, preferably 70 ~200mm.

The polyimide film (A) of the present invention obtained as described above is coated with an organic solvent solution of polyimide acid as a precursor of polyimide on one side or both sides, and heated and dried The laminated polyimide film (B) can obtain a polyimide film that can be used as a base film for FPC. The coating, heating, and drying methods are not particularly limited.

As the above-mentioned polyamic acid, for example, polyamic acid containing 1,3-bis-(4-aminophenoxy)benzene and 4,4'-dioxydiphthalic anhydride, or Polyamide acid containing 2,2'-dimethyl-4,4'-diaminobiphenyl and pyromellitic dianhydride, etc. One type or two or more types of polyamide can be used.

The above-mentioned organic solvent is not particularly limited. For example, it is possible to use one selected from the above-mentioned organic solvents that can be used to form polyamide acid solutions, and other organic solvents that can dissolve thermoplastic polyimide or polyamide acid. One type or two or more types, etc.

In addition, in the organic solvent solution of the polyamide acid, the solid content concentration of the polyamide acid is not particularly limited, and is, for example, 10 to 30% by weight relative to the total amount of the organic solvent solution.

In addition, the polyimide film of the present invention can be used in applications such as a base film for FPC, an insulating film for capacitors, and an insulating tape.

[Example]

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples. In addition, the evaluation methods and evaluation criteria of each characteristic explained in the above description and the following examples are as follows.

(1) Breaking strength and breaking elongation

The breaking strength is the strength and elongation when the sample breaks at an elongation speed of 300mm/min using a TENSILON type extension test machine manufactured by ORIENTEC at room temperature according to JIS-K7113. The size of the test piece is 10mm wide×250mm long, the distance between the clamps is set to 100mm, and the measurement is performed under an environment of 25°C and 60%RH.

(2) Film thickness

Overlap 10 films, measure the film thickness using a digital micrometer M-30 manufactured by SONY, and divide the thickness value by 10 to round to the first decimal place, and use the obtained value as the film thickness.

(3) Film L value

The film L value was measured using SM-7-CH manufactured by SUGA TEST INSTRUMENTS. A film of 100 mm×100 mm was divided into 5 in the film width direction, and the center position of each sample was measured and set as the average of the 5 points. Regarding the L value, if the film thickness becomes thinner, the sensitivity of the detector becomes dull and accurate evaluation cannot be performed. Therefore, the total thickness of the stack reaches the minimum number of pieces of 50 μm or more and the measurement is performed. Especially for films with a thickness of 10μm or less, the value measured by overlapping the films so that the total thickness reaches 50-60μm.

(4) Alkali resistance

Under the state of heating 5% sodium hydroxide aqueous solution to 50°C, immerse the film cut into 200mm×200mm in it, take it out after 30 minutes, and measure its breaking strength and breaking elongation. The breaking strength and breaking elongation before alkali immersion were each set to 100%, and the retention rates after alkali immersion were calculated to evaluate alkali resistance. The case where both the retention of breaking strength and breaking elongation were 80% or more was judged to be excellent in alkali resistance (○), and the case where it was less than 80% was judged to be poor in alkali resistance (×).

(5) Film forming properties (film forming stability)

The case where there is no film damage caused by wrinkles or cracks during continuous film production with a film length of 5000m is regarded as ○, and the case where occurrence is regarded as ×.

(Synthesis example 1)

Prepare pyromellitic dianhydride (molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22)/4, in a molar ratio of 65/35/82/18 4'-diaminodiphenyl ether (molecular weight 200.24)/p-phenylenediamine (molecular weight 108.14), prepared as a 20% by weight solution in DMAC (N,N-dimethylacetamide) and polymerized to obtain 3800 poise of polyamide acid solution at 25°C. In this polyamic acid solution, the mixing is 2.0 mol relative to the polyamic acid unit The dried N,N-dimethylacetamide, 4.0 mol of acetic anhydride relative to the polyamide acid unit, and 4.0 mol of β-picoline relative to the polyamide acid unit to prepare polyamide Amino acid solution.

(Synthesis example 2)

Prepare pyromellitic dianhydride (molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22)/4 in the molar ratio of 65/35/75/25 4'-diaminodiphenyl ether (molecular weight 200.24)/p-phenylenediamine (molecular weight 108.14), prepared as a 20% by weight solution in DMAC (N,N-dimethylacetamide) and polymerized to obtain 3800 poise of polyamide acid solution at 25°C. In the polyamide acid solution, 2.0 mol of dried N,N-dimethylacetamide relative to the polyamide acid unit and 4.0 mol of acetic anhydride relative to the polyamide acid unit were mixed , 4.0 mol of β-picoline relative to the polyamide unit to prepare a polyamide acid solution.

(Synthesis example 3)

Prepare pyromellitic dianhydride (molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22)/4 in the molar ratio of 65/35/67/33. 4'-diaminodiphenyl ether (molecular weight 200.24)/p-phenylenediamine (molecular weight 108.14), prepared as a 20% by weight solution in DMAC (N,N-dimethylacetamide) and polymerized to obtain 3800 poise of polyamide acid solution at 25°C. In the polyamide acid solution, 2.0 mol of dried N,N-dimethylacetamide relative to the polyamide acid unit and 4.0 mol of acetic anhydride relative to the polyamide acid unit were mixed , 4.0 mol of β-picoline relative to the polyamide unit to prepare a polyamide acid solution.

(Synthesis example 4)

Prepare pyromellitic dianhydride (molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22)/4 in a molar ratio of 45/55/67/33. 4'-diaminodiphenyl ether (molecular weight 200.24)/p-phenylenediamine (molecular weight 108.14), prepared as a 20% by weight solution in DMAC (N,N-dimethylacetamide) and polymerized to obtain 3800 poise of polyamide at 25℃ Acid solution. In the polyamide acid solution, 2.0 mol of dried N,N-dimethylacetamide relative to the polyamide acid unit and 4.0 mol of acetic anhydride relative to the polyamide acid unit were mixed , 4.0 mol of β-picoline relative to the polyamide unit to prepare a polyamide acid solution.

(Example 1)

The polyamide acid solution of Synthesis Example 1 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm. The ratio of the support speed/the nozzle ejection speed was set to 10.6, and the solution was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller on one side extending 1.22 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds to dry the gel film first fixed. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.40 times in the width direction, blow 250℃ air in the tenter for about 20 seconds to dry it, and then use an electric heater After performing heat treatment for about 30 seconds to bring the film surface temperature to 450°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.6 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 35.0. In addition, the alkali resistance was evaluated. As a result, the retention of breaking strength was 96% and the retention of elongation at break was 97%.

(Example 2)

The polyamide acid solution of Synthesis Example 1 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm. The ratio of the support speed/the nozzle ejection speed was set to 10.6, and the solution was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller on one side extending 1.22 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, Continue to pierce the needle plate on the chain to fix the gel film, and blow 250℃ air on the needle plate for 5-10 seconds to dry and fix the end of the gel film. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.40 times in the width direction, blow 250℃ air in the tenter for about 20 seconds to dry it, and then use an electric heater After performing heat treatment for about 30 seconds to bring the film surface temperature to 475°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.6 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 31.3. In addition, the alkali resistance was evaluated. As a result, the retention of breaking strength was 94% and the retention of elongation at break was 101%.

(Example 3)

The polyamide acid solution of Synthesis Example 2 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 8.6, and cast to a rotating metal at 80°C On the support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and it was transported with a roller while extending 1.31 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds to fix the end of the gel film. Department is dry. After the gel film on the two ends of the needle plate fixed with needles is stretched to 1.62 times in the width direction, blow 250℃ air in the tenter for about 25 seconds to dry it, and then use an electric heater After performing heat treatment for about 35 seconds to bring the film surface temperature to 435°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.4 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 38.3. In addition, the alkali resistance was evaluated. As a result, the breaking strength retention rate was 109%, and the breaking elongation retention rate was 116%.

(Example 4)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 9.0, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller while extending 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle board fixed with the needles is extended to 1.59 times in the width direction, the air of 250℃ is blown in the tenter for 25 seconds to dry it, and then the electric heater is used for implementation. After heat treatment for about 35 seconds to bring the surface temperature of the film to 435°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 38.5. In addition, the alkali resistance was evaluated. As a result, the breaking strength retention rate was 90%, and the breaking elongation retention rate was 100%, which were good values.

(Example 5)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 9.0, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller while extending 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.59 times in the width direction, blow 250℃ air in the tenter for about 20 seconds to dry it, and then use an electric heater Perform heat treatment for about 30 seconds to make After the film surface temperature reached 465°C, it was allowed to relax while cooling to room temperature. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value of the obtained film (measured by overlapping 7 sheets) was 32.5. In addition, the alkali resistance was evaluated. As a result, the retention rate of breaking strength was 94%, and the retention rate of breaking elongation was 100%.

(Example 6)

The polyamide acid solution of Synthesis Example 4 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 9.1, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller while extending 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate of the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds to dry the ends of the gel film first fixed. After the gel film on the two ends of the needle plate fixed with needles is stretched to 1.55 times in the width direction, blow 250℃ air in the tenter for about 25 seconds to dry it, and then use an electric heater After performing heat treatment for about 30 seconds to bring the film surface temperature to 415°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 41.5. In addition, when the alkali resistance was evaluated, the breaking strength retention rate was 92%, and the breaking elongation retention rate was 97%.

(Example 7)

The polyamide acid solution of Synthesis Example 4 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 9.1, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. will The gel film was continuously peeled off from the support, and was transported with a roller on one side extended to 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle plate fixed with needles is stretched to 1.55 times in the width direction, blow 250℃ air in the tenter for about 25 seconds to dry it, and then use an electric heater After performing heat treatment for about 35 seconds to bring the film surface temperature to 445°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 36.7. In addition, the alkali resistance was evaluated. As a result, the retention of breaking strength was 91% and the retention of elongation at break was 88%.

(Example 8)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 14.2, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller while extending 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 240℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.62 times in the width direction, blow 240℃ air in the tenter for about 20 seconds to dry it, and then use an electric heater After performing a heat treatment for about 30 seconds to bring the film surface temperature to 435°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 5.0 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value of the obtained film (measured by overlapping 10 sheets) was 36.5. In addition, the alkali resistance was evaluated. As a result, the breaking strength retention rate was 90%, and the breaking elongation retention rate was 92%, which were good values.

(Example 9)

The polyamide acid solution of Synthesis Example 1 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 6.0, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller on one side extending 1.22 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.45 times in the width direction, blow 250℃ air in the tenter for about 40 seconds to dry it, and then use an electric heater After performing heat treatment for about 60 seconds to bring the film surface temperature to 400°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 10.0 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 5 sheets) of the obtained film was 42.5. In addition, the alkali resistance was evaluated. As a result, the retention of breaking strength was 98% and the retention of elongation at break was 98%, which were good values.

(Reference example 1)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm, and the ratio of support speed/nozzle ejection speed was set to 8.3, and it was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled off from the support, and was transported with a roller while extending 1.28 times in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. Fix the gel at both ends with needles on the needle board After the film is stretched to 1.59 times in the width direction, air at 250°C is blown in the tenter for about 35 seconds to dry it, and then an electric heater is used to perform heat treatment for about 35 seconds to make the film surface temperature reach After 500°C, cool to room temperature while relaxing it. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. However, after the above conditions were met, the film was formed for 600 m and the end of the film was removed from the needle when the film was broken, resulting in film breakage. The L value of the film immediately before the film breakage (measured by overlapping 7 sheets) was 27.1. The alkali resistance was evaluated. As a result, the retention rate of breaking strength was 96%, and the retention rate of breaking elongation was 101%.

(Reference example 2)

The polyamide acid solution of Synthesis Example 1 was extruded from a T-die with a nozzle slit width of 1.3 mm and a length of 2000 mm. The ratio of the support speed/the nozzle ejection speed was set to 10.6, and the solution was cast to a rotating temperature of 80°C. On the metal support, a self-supporting gel film is obtained. The gel film was continuously peeled from the support, and was transported with a roller while extending 1.22 times the length of the film in the longitudinal direction of the film in a room at 70°C. While pressing the two ends of the gel film with a roller, the needle plate on the chain is continuously pierced to fix the gel film, and air of 250℃ is blown on the needle plate for 5-10 seconds, thereby firstly removing the ends of the gel film Dry and fix. After the gel film on the two ends of the needle plate fixed with needles is extended to 1.40 times in the width direction, blow 250℃ air in the tenter for about 20 seconds to dry it, and then use an electric heater After performing a heat treatment for about 30 seconds to bring the film surface temperature to 400°C, it was cooled to room temperature while being relaxed. Then, the end of the film was removed from the needle, and the edge of the end of the film was cut to obtain a polyimide film with a width of 2100 mm and a thickness of 7.5 μm. There is no wrinkles or cracks in the film during film production, and the film can be stably formed with a length of 5000m or more. The L value (measured by overlapping 7 sheets) of the obtained film was 45.2. In addition, the alkali resistance was evaluated, and as a result, it was confirmed that the breaking strength retention rate deteriorated to 69%, and the breaking elongation rate retention rate deteriorated to 34%.

【Table 1】

As shown by the results of Examples 1-9, the polyimide film of the present invention with an L value of 28 to 45, even if the thickness is as thin as 5.0 to 10.0 μm, is that the breaking strength or breaking elongation is not easy to be immersed in alkaline It is reduced in the solution and excellent in alkali resistance.

Furthermore, the polyimide film of the present invention having an L value of 28 to 45 has excellent film formability even if the thickness is as thin as 5.0 to 10.0 μm.

In addition, the polyimide film of the present invention of Examples 1 to 9 has sufficient breaking strength and breaking elongation even if the thickness is as thin as 5.0 to 10.0 μm.

In addition, from the results of Examples 1-9, when the molecular weight of the repeating unit of the polyimine is set to 100%, the molecular weight of the imine group in the polyimine is set to 40% or less , And become a polyimide film with excellent alkali resistance even as thin as 5.0~10.0μm.

On the other hand, the polyimide film of Reference Example 1 in which the L value was less than 28 was fragile and easy to break, with poor film forming properties.

In addition, the polyimide film of Reference Example 2 with an L value greater than 45 has poor alkali resistance and strong fracture The degree and elongation at break are reduced by immersion in an alkaline solution.

As described above, the thin film polyimide film with an L value of 28 to 45 and a thickness of 1.0 to 10.0 μm can be both alkali resistance and film forming properties.

[Industrial availability]

Although the polyimide film of the present invention is an extremely thin film with a thickness of 1.0~10.0μm, it is also excellent in alkali resistance, and it is not easy to be damaged during the film production step, and has good film stability, so it can be preferably used as The basic film of FPC that requires thinness.

Claims (7)

A polyimide film with a thickness of 1.0~10.0μm, characterized in that when the molecular weight of the repeating unit of the polyimide is set to 100%, the molecular weight of the polyimide group is 40% or less, and the polyimide The L value of the imine film is 28~42.5. Such as the polyimide film of claim 1, wherein the polyimide film is stretched by biaxial stretching in the mechanical conveying direction (MD) and the width direction (TD) of the film, and the total stretching ratio (MD The extension ratio × TD extension ratio) is 1.60 or more. Such as the polyimide film of claim 1, which is composed of aromatic diamine components selected from p-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl One or more of the group consisting of base ethers, the aromatic anhydride component is pyromellitic dianhydride and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride polyamide acid . A method for manufacturing a polyimide film, which is the method for manufacturing a polyimide film according to any one of claims 1 to 3, which is obtained by extending a gel film that can form a polyimide film The film is heated at 350-500°C for 5 to 300 seconds. When the molecular weight of the repeating unit of the polyimine film is set to 100%, the molecular weight of the imine group is 40%. The following. A polyimide film, characterized in that it comprises a polyimide film (A) as in any one of claims 1 to 3, and a polyimide film (A) laminated on one or both sides of the polyimide film (A) Polyimide film (B). Such as the polyimide film of any one of claims 1 to 3, wherein the form of the polyimide film is a polyimide film roll with a width of 500-3000mm and a length of 1000m or more. Such as the polyimide film of any one of claims 1 to 3, which is used for flexible printed circuit boards.