KR20160115740A - Polyimide film - Google Patents

Abstract

Provided is a thin polyimide film having a thickness of 1.0-10.0 m. The polyimide film does not have the deterioration of properties caused by the alteration of the film and/or by hydrolysis, even when immersed in an alkaline solution. According to the present invention, when an L value of the polyimide film having a thickness of 1.0-10.0 m is 28-45, and also the molecular weight of a repeat unit of polyimide is in 100%, the molecular weight of imide groups is equal to or less than 40%.

Description

POLYIMIDE FILM [0002]

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

There is provided a process for producing a polyamic acid polymer solution, which comprises polymerizing an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid polymer solution, forming the polyamic acid polymer solution into a film form, thermally and / Since the polyimide film obtained by dehydrating ring closure, that is, by imidation, is excellent in heat resistance, insulation and mechanical properties, it can be used as a base film of an electric insulating material of a wire, a heat insulating material, a flexible printed board (hereinafter abbreviated as FPC) A carrier tape for bonding, a tape for fixing an IC lead frame, a cover lay for the purpose of protecting a conductive circuit or insulating it, and the like.

Among these applications, the FPC has a basic structure in which a circuit pattern is formed on a flexible and thin base film and a cover layer is formed on the surface of the circuit pattern. By virtue of the excellent characteristics such as flexibility, Is widely used in the field. In recent years, due to advancement of mounting technology, wiring density has been increased and FPCs have been made more multilayered. The three-layer type of conventional copper foil / adhesive (acrylic or epoxy resin) / polyimide, as well as the copper foil / copper foil having no adhesive interposed therebetween, which is effective as one of means for improving the bending resistance and miniaturization of the FPC, The two-layer type of polyimide is mainstream.

As a two-layer type method of producing a copper foil / polyimide, there is a casting method in which a polyimide precursor resin is cast on a copper foil, a thermoplastic polyimide film is formed on one side or both sides of a non-thermoplastic polyimide film before heating. A method of applying a solution of an organic solvent of a polyamic acid which is a precursor of polyamic acid and then heating it to obtain a film and then bonding the copper foil; a method of applying a polyamic acid, which is a precursor of a thermoplastic polyimide, on one surface or both surfaces of a non- A method in which an organic solvent solution is applied, and a copper foil is bonded.

As the polyimide film for these FPC applications, a thin film has recently been required, but the film is weakened in strength by thinning, and there is a problem that breakage or deformation of the film tends to occur in the process of manufacturing a film or an FPC . Further, the thinner the thickness, the lower the rigidity of the film, so that the flatness of the film becomes worse, and wrinkles tend to occur at the time of film transportation, and the yield is lowered.

Particularly, when an extremely thin polyimide film having a thickness of 10.0 占 퐉 or less is to be formed, the film is thin due to breakage of the end of the film from the hole fixed by the pin or generation of wrinkles during transportation Tearing and other troubles are very likely to occur, resulting in low productivity.

Problems such as wrinkles at the time of film breakage or transportation during film formation do not easily occur and an extremely thin polyimide film having a thickness of 8.0 탆 or less is used for a film which defines tear propagation resistance and ultrasonic wave transmission rate of the film (Patent Document 1).

As a method for producing an extremely thin polyimide film, there has been reported a method of applying a polyimide resin precursor solution containing a releasing agent on a substrate, peeling the substrate from the substrate after drying and heat treatment, and the like (Patent Document 2).

However, if the thickness of the polyimide film is reduced to 10.0 占 퐉 or less, the durability (resistance) to chemicals tends to decrease. For example, when a dry polyimide film is soaked (immersed) in an alkaline solution as a peeling liquid for a few minutes in the peeling process of the dry resist film in the FPC production process, the change speed of the thin polyimide film becomes faster, The fracture strength, elongation of the elongation, cracks, and the like are generated, thereby greatly deteriorating the reliability of the FPC. Therefore, development of an extremely thin polyimide film excellent in alkali resistance is required.

Japanese Patent Application Laid-Open No. 2014-196467 Japanese Patent Application Laid-Open No. 2009-226632

An object of the present invention is to provide a thin polyimide film having a thickness of 1.0 to 10.0 占 퐉 which does not easily deteriorate due to deterioration and / or hydrolysis of the film even when immersed in an alkali solution.

It is also an object of the present invention to provide a thin polyimide film having a thickness of 1.0 to 10.0 占 퐉, which does not cause breakage or wrinkling in the film production process and is excellent in film forming stability.

As a method for improving the alkali resistance of the polyimide film, various methods such as examinations of the kind and composition (composition) of the monomers forming the polyamic acid can be considered.

However, since the conventional thin film polyimide film having high alkali resistance has a hard, low flexibility, and is liable to be crumpled, the film is damaged during the film transportation, There arises a problem that defects are generated on the surface of the film, the film-forming stability at the time of producing the film is poor, and it is difficult to form the film.

As a result of careful examination to solve the above problems, the present inventors have found that by adjusting the L value of the polyimide film (and hence the ratio of the imide group in the polyimide) to a specific range, It is possible to obtain a polyimide film having an alkali resistance (and further, a film-forming stability at the time of producing the film) even if the film thickness is in the range of 10 탆 to 탆.

Means for Solving the Problems The present inventors have conducted extensive studies to solve the above problems, and as a result, they have completed the present invention.

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

[1] A polyimide film, characterized in that the molecular weight of the imide group is 40% or less and the L value of the polyimide film is 28 to 45, when the molecular weight of the repeating unit of the polyimide is 100% Mu m.

(2) The polyimide film is stretched by the biaxial stretching process in the machine direction (MD) and the transverse direction (TD) of the film, and the total stretching ratio of the film (stretching ratio of MD × stretching ratio of TD) Or more based on the weight of the polyimide film.

[3] The process according to [1], wherein the aromatic diamine component is at least one selected from the group consisting of paraphenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether, and the aromatic acid anhydride component is pyromellitic dianhydride The polyimide film according to the above [1] or [2], wherein the polyimide film is prepared from a polyamic acid which is tetracarboxylic dianhydride and / or 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride.

[4] A film obtained by stretching a gel film capable of forming a polyimide film having a molecular weight of the imide group of 40% or less, when the molecular weight of the repeating unit of the polyimide is 100% A process for producing a polyimide film according to any one of [1] to [3], wherein the polyimide film is heat-treated for 300 seconds.

[5] A polyimide film (A) according to any one of the above [1] to [4] and a polyimide film (B) laminated on one side or both sides of the polyimide film (A) Lt; / RTI >

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

According to the present invention, a polyimide film having a thickness of 1.0 to 10.0 탆 and excellent in alkaline resistance can be obtained, which does not readily deteriorate due to deterioration and / or hydrolysis of the film even when immersed in an alkali solution.

Further, according to the present invention, it is possible to obtain a polyimide film having a thickness of 1.0 to 10.0 탆, which is excellent in film-breaking and wrinkling in the film-forming step and in film-forming stability.

Further, according to the present invention, a polyimide film having a thickness of 1.0 to 10.0 占 퐉, excellent alkali resistance, and low in troubles due to cracking, cracking, or the like in the peeling process of the dry resist film during the FPC production process Can be obtained.

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 占 퐉, preferably 2.0 to 9.0 占 퐉, and more preferably 3.0 to 8.0 占 퐉.

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

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

For example, the gel film is usually subjected to heat treatment as described later, but the gel film may be subjected to heat treatment under various conditions such as crystallization (crystallization) of the polyimide, degree of structural change, It is possible to adjust the L value of the film due to the fact that the degree of oxidation of the film surface can be adjusted.

As one of the reasons why a film excellent in alkali resistance (and thus, film-forming stability) can be obtained rather than selecting the L value in the above-mentioned predetermined range, for example, the following reasons can be considered.

By enhancing the heat treatment for the gel film, crystallization is promoted by rearrangement of the polymer chains or formation of the crosslinked structure, and furthermore, the L value is lowered. As a result, the alkali resistance is improved with the improvement of the absorbency of the film surface. In addition, by setting the crystallization progression to a proper range (i.e., not too small), it is possible to secure the strength and flexibility of the film in the manufacturing process, and to achieve both the alkali resistance and the excellent film- have.

When the L value is in the range as described above, even if the thickness of the polyimide film is as small as 1.0 to 10.0 占 퐉, it is preferable because the alkali resistance is excellent. Even if the thickness of the target polyimide film is as small as 1.0 to 10.0 占 퐉 in this range, the occurrence of breakage or wrinkling of the film is reduced in the production process of the polyimide film, Do.

The L value is a value measured by the method described in the following example. The L value can be measured by superposing a polyimide film and setting the total thickness to 50 to 60 mu m.

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

The " molecular weight of repeating unit of polyimide " and " molecular weight of polyimide "

Such a range is preferable because the alkali resistance of the polyimide film is improved. It is considered that the polyimide film has a higher absorbability as the content of the imide group is larger. On the other hand, it is considered that the more the content of the hydrophobic component other than the imide is, the lower the absorbability of the polyimide film is, and the alkali resistance is improved.

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

The length of the polyimide film of the present invention is not particularly limited, but is preferably 1000 m or more, more preferably 2000 to 50000 m, and still more preferably 3000 to 30000 m.

[Polyamic acid]

In order to obtain the polyimide film of the present invention, first, a polyamic acid solution (hereinafter also referred to as a polyamic acid solution) is obtained by polymerizing an aromatic diamine component and an aromatic acid anhydride component in an organic solvent. Hereinafter, the polyamic acid solution will be described.

In the present invention, the polyamic acid solution can be obtained by polymerizing an aromatic diamine component of a raw material and an aromatic acid anhydride component, or a chemical substance containing both of them as an essential component in an organic solvent.

Examples of the aromatic diamine component include para-phenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4 , 4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3 '-Dimethoxybenzidine, 1,4-bis (3-methyl-5-aminophenyl) benzene, and amide-forming derivatives thereof. These may be used alone or in combination of two or more.

As the aromatic diamine component, the polyimide film to be obtained is preferably a polyimide film comprising a group consisting of paraphenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether from the viewpoints of excellent low- , And a combination of paraphenylenediamine and 4,4'-diaminodiphenyl ether is more preferable.

In the present invention, the raw materials used for forming the polyamic acid solution may contain diamine components other than the aromatic diamine component within a range not hindering the effect of the present invention.

Examples of the other diamine component include 3,3'-diaminodiphenyl ether, metaphenylenediamine, 4,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylpropane, 3,3'- 3'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, benzidine, 4,4'-dia Aminodiphenylsulfide, 3,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenyl Sulfone, 3,3'-diaminodiphenylsulfone, 2,6-diaminopyridine, bis- (4-aminophenyl) diethylsilane, 3,3'-dichlorobenzidine, bis- Phosphine oxide, bis- (4-aminophenyl) phenylphosphine oxide, bis- (4-aminophenyl) -N-phenylamine, bis- Diminaphthalene, 3,3'-dimethyl-4,4'-diaminophenyl, 3,4'-dimethyl-3 ', 4-diaminophenyl-3,3'-dimethoxybenzidine, (p-β-amino-tert-butylphenyl) ether, bis (p- , 1-dimethyl-5-aminopentyl) benzene, m-xylenediamine, p-xylenediamine, 1,3-diaminoamantane, 3,3'- diamino- , 3'-diaminomethyl-1,1'-diadamantane, bis (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 3-methyl Heptamethylenediamine, 4,4'-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis (3-aminopropoxy) ethane, 2,2-dimethylpropylenediamine, 3-methoxyhexa But are not limited to, ethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-diaminocyclohexane, Diamino-1,3,4-oxadiazole, 2,2-bis (4-aminophenyl) hex Include fluoro propane, N- (3- Amino-phenyl) -4-amino-benzamide, 4-amino-3-aminobenzoate. These may be used alone or in combination of two or more.

Specific examples of the aromatic acid anhydride component include pyromellitic acid, 3,3 ', 4,4'-biphenyltetracarboxylic acid, 2,3', 3,4'-biphenyltetracarboxylic acid, 3 , 3 ', 4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine- And aromatic tetracarboxylic anhydride components such as 5,6-tetracarboxylic acid and amide-forming derivatives thereof. These may be used alone or in combination of two or more.

As the aromatic acid anhydride component, the polyimide film to be obtained is selected from the group consisting of pyromellitic dianhydride and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride from the viewpoint of excellent heat resistance and low water absorption property. Is preferably 1 or more.

In the present invention, the raw material used for forming the polyamic acid solution may contain an acid anhydride component other than the aromatic acid anhydride component within a range not hindering the effect of the present invention.

Examples of the other acid anhydride component include 2,3 ', 3,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,3 , 6,7-naphthalenedicarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6-tetracarboxylic dianhydride, 5-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,4,5,8-decahydronaphthalene tetracarboxylic 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-naphthalene Tetracarboxylic dianhydride, 2,3,6,7-tetrachloro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,8,9,10-phenanthrene tetracarboxylic dianhydride, 2, Bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane imine Water, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis 3,4-dicarboxyphenyl) sulfone dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 3,4,3 ', 4'-benzophenone tetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more.

In the present invention, the combination of the aromatic diamine component and the aromatic acid anhydride component in the present invention is preferably a combination of the aromatic diamine component and the aromatic acid anhydride component in terms of heat resistance, low water absorption, low heat expansion and flexibility, Diaminodiphenyl ether, or 4,4'-diaminodiphenyl ether with paraphenylenediamine, pyromellitic acid dianhydride as the aromatic acid anhydride component, or pyromellitic dianhydride with 3,3 ', 4,4' -Biphenyltetracarboxylic dianhydride can be exemplified. Among them, a combination of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is particularly preferable.

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

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

In the present invention, specific examples of the organic solvent used for forming the polyamic acid solution include sulfoxide-based solvents such as dimethylsulfoxide and diethylsulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, and N, N-diethylacetamide; organic solvents such as N-methyl-2-pyrrolidone, N-vinyl- Phenol, o-, m-, or phenol-based solvents such as p-cresol, xylenol, halogenated phenol and catechol, as well as hexamethylphosphoramide, And aprotic polar solvents such as lactone. These may be used alone or in combination of two or more, and may be used in combination with aromatic hydrocarbons such as xylene and toluene.

The polymerization method of the polyamic acid solution may be any known method. For example,

(1) First, all the aromatic diamine component is added to the solvent, and then the aromatic acid anhydride component is added to the total amount of the aromatic diamine component.

(2) First, all the aromatic acid anhydride components are put into a solvent, and then the aromatic diamine component is added so as to be equivalent to the aromatic acid anhydride component.

(3) After one aromatic diamine component is added to the solvent, the reaction mixture is mixed for a period of time necessary for the reaction so that one aromatic acid anhydride component accounts for 95 to 105 mol%, and the other aromatic diamine component is added , And then adding the other aromatic acid anhydride component so that the total aromatic diamine component and the entire aromatic acid anhydride component are approximately equivalent.

(4) One of the aromatic acid anhydride components is added to the solvent, and then the mixture is mixed for a period of time necessary for the reaction so that one aromatic diamine component accounts for 95 to 105 mol% of the reaction component. Then, the other aromatic acid anhydride component is added And then adding the other aromatic diamine component so that the total aromatic diamine component and the total aromatic acid anhydride component are approximately equivalent.

(5) The polyamic acid solution (A) is prepared by reacting one of the aromatic diamine component and the aromatic acid anhydride component in a solvent so that one of the aromatic diamine component and the aromatic acid anhydride component is excessively present. In the other solvent, either one of the aromatic diamine component and the aromatic acid anhydride component To give an excess of polyamic acid solution (B). A method in which each of the polyamic acid solution (A) and the solution (B) thus obtained is mixed and the polymerization is completed. At this time, when the aromatic diamine component is excessive in preparing the polyamic acid solution (A), the aromatic acid anhydride component is excessively used in the polyamic acid solution (B), and the aromatic acid anhydride component in the polyamic acid solution (A) In the case of excess, in the polyamic acid solution (B), the aromatic diamine component is excessive, and the polyamic acid solution (A) and the solution (B) are mixed, and the total aromatic diamine component and the entire aromatic acid anhydride component And the like.

The polymerization method is not limited to these, and other known methods may be used.

In the present invention, the aromatic acid anhydride component and the aromatic diamine component constituting the polyamic acid are polymerized in such a ratio that their molar numbers are approximately equal, but one of them is, for example, 10 mol%, preferably 5 mol% May be excessively blended to the other side within the range of < RTI ID = 0.0 >

The polymerization reaction is preferably carried out with stirring in an organic solvent. The polymerization temperature is not particularly limited, but is usually carried out at an internal temperature of 0 to 80 캜 of the reaction solution. The polymerization time is not particularly limited, but it is preferably carried out continuously for 10 minutes to 30 hours. The polymerization reaction may be carried out by dividing the polymerization reaction, increasing the temperature or lowering the temperature if necessary. The order of adding the two reactants is not particularly limited, but it is preferable to add an aromatic acid anhydride to the solution of the aromatic diamine component. Vacuum defoaming during the polymerization reaction is an effective method for producing an organic solvent solution of high quality polyamic acid. The polymerization reaction may be controlled by adding a small amount of a terminal sealing agent to the aromatic diamines before the polymerization reaction. The terminal sealing agent is not particularly limited and a known one can be used.

The polyamic acid solution thus obtained contains a solid content of usually 5 to 40% by weight, preferably 10 to 30% by weight. The viscosity is a value measured by a Brookfield viscometer, and is not particularly limited, but is usually from 10 to 2000 Pa · s, and preferably from 100 to 1000 Pa · s for stable liquid feeding. The polyamic acid in the organic solvent solution may be partially imidized.

In addition, the polyamic acid solution may contain chemically inert organic fillers such as titanium oxide, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate and polyimide filler, and inorganic fillers, if necessary. The content of the filler is not particularly limited as long as it does not hinder the effect of the present invention.

The polyamic acid solution used herein may be a pre-polymerized polyamic acid solution or may be a solution obtained by sequentially polymerizing the filler particles.

In addition, the polyamic acid solution may contain one or more compounds other than the filler. Examples of the compound other than the filler include carbon oxides, metal oxides such as alumina and titania, and boron compounds such as boron nitride.

Next, a method of producing the polyimide film of the present invention will be described.

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

Examples of the method for producing the polyimide film include a method of casting a polyamic acid solution into a film form and thermally depolarizing and desolvating the polyimide film to obtain a polyimide film; and a method of mixing a polyamic acid solution with a cyclization catalyst and a dehydrating agent, A method of producing a polyimide film by preparing a film and heating and removing the solvent therefrom is exemplified, but the latter method is preferable.

In the method of chemically de-catalyzing, the polyamic acid solution is first prepared. The polyamic acid solution may contain a cyclization catalyst (imidization catalyst), a dehydrating agent and a gelling retarder.

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 heterocyclic compounds such as isoquinoline, pyridine, Tertiary amines, etc. These may be used alone or in combination of two or more. Among them, the use of at least one heterocyclic tertiary amine is preferable.

Specific examples of the dehydrating agent used in the present invention include an aliphatic carboxylic acid anhydride such as acetic anhydride, propionic anhydride, and butyric anhydride, and an aromatic carboxylic anhydride such as an anhydrous benzoic acid. Of these, acetic anhydride and / desirable.

As a method for producing a polyimide film from a polyamic acid solution, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent is flow cast onto a support from a mouthpiece having slits formed therein, molded into a film form, After forming a gel film having self-supporting property, the film is peeled off from the support, heat-dried / imidized, and heat-treated.

The polyamic acid solution is passed through a slit type mouthpiece to be formed into a film shape, flow cast on a heated support, subjected to thermal cyclization reaction on a support, and made into a gel film having self-supportability and peeled from the support.

The support is a metal rotary drum or endless belt, the temperature of which is controlled by the heat of the liquid or gas, and / or the radiant heat of the electric heater or the like.

The gel film is heated to 30 to 200 캜, preferably 40 to 150 캜, by a heat ray from a support and / or a heat source such as hot air or an electric heater to perform a ring-closing reaction, By drying the volatile matter, it becomes self-supporting, and is peeled from the support. At this time, the diameter of the uneven portion 10~100 ㎛ present on the support surface, and the number 500-1500 convex parts per 1 cm ² dogs, also using the support is uneven portion maximum roughness 1~5 ㎛, 10 It is possible to satisfactorily peel off even in the production of a thin polyimide film having a thickness of not more than 2 mu m.

The gel film peeled off from the support is stretched (stretched) in the running direction while regulating the traveling speed by a rotary roll. It is preferable that the stretching in the running direction is performed in multiple stages by the rotating roll. Particularly, in the case of stretching in a thin polyimide film having a thickness of 10 탆 or less, it is possible to prevent the wrinkles of the film by controlling the tension in a multistage manner by using a rotating roll as an S-shaped wrap or a nip roll and a suction roll More preferable. The stretching in the running direction is usually carried out at a temperature of 140 DEG C or lower at a magnification of 1.01 to 1.90, preferably 1.05 to 1.60, and more preferably 1.10 to 1.50. The gel film stretched in the running direction is introduced into the tenter device and gripped at both ends in the width direction in the tenter clip and is stretched in the width direction while traveling together with the tenter clip.

The stretching of the gel film is preferably 1.60 or more, more preferably 1.70 to 3.00, and more preferably 1.80 (a stretching magnification in a machine direction (MD) ≪ / RTI > If the stretching magnification is high, orientation of the molecular chains of the polyimide becomes high, which makes it difficult for the film to be hydrolyzed and the alkali resistance is considered to be improved, which is preferable.

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

The stretched gel film is usually heated by a wind, infrared heater or the like for 15 seconds to 30 minutes. Heat treatment is then performed at a temperature of usually 250 to 500 占 폚 for 5 seconds to 30 minutes by hot air and / or an electric heater. The heat treatment temperature and time may be appropriately changed according to the thickness of the obtained polyimide film.

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

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 still more preferably 5 seconds to 300 seconds.

In addition, the thickness of the polyimide film can be adjusted by adjusting the running speed when the gel film is heat-treated.

It is preferable that the polyimide film thus obtained is further subjected to an annealing treatment. The annealing treatment method is not particularly limited and may be carried out by a conventional method.

The temperature of the annealing treatment is not particularly limited, but is preferably 200 ° C to 600 ° C, more preferably 200 ° C to 550 ° C, and particularly preferably 210 ° C to 500 ° C. Concretely, it is preferable that the film is run in a furnace heated to the above-mentioned temperature range under a storage force and annealing is performed. The time during which the film remains in the furnace is the processing time, but it is preferably controlled by changing the running speed so that the processing time is 5 seconds to 5 minutes. The film tension at the time of running is preferably 10 to 50 N / m, more preferably 20 to 30 N / m.

In the polyimide film thus obtained, it is preferable that the surface of the film is subjected to a plasma surface treatment such as an atmospheric pressure plasma or a vacuum plasma surface treatment. The plasma surface treatment method is not particularly limited.

The form of the polyimide film of the present invention is not particularly limited, but a roll type film is preferable.

The polyimide film roll can be obtained by winding a polyimide film on a core. In the present invention, there is no particular limitation on the method of winding the core.

The material for the crimping is not particularly limited and conventionally known ones can be used. Examples of the material include plastics such as paper and vinyl chloride, combinations of glass fiber and epoxy resin, paper and phenol resin, carbon fiber and epoxy resin A fiber reinforced plastic (FRP) formed of a metal or the like, a metal such as stainless steel, a paper core impregnated with a resin, or a resin layer formed on the surface thereof.

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

An organic solvent solution of polyamic acid which is a precursor of polyimide is applied to one side or both sides of the polyimide film (A) of the present invention obtained as described above, followed by heating and drying to laminate the polyimide film (B) A polyimide film usable as a base film for an FPC or the like can be obtained. The coating, heating and drying methods are not particularly limited.

Examples of the polyamic acid include polyamic acid composed of 1,3-bis- (4-aminophenoxy) benzene and 4,4'-dioxydiphthalic anhydride, 2,2'-dimethyl- And polyamide acid composed of 4'-diaminophenyl and pyromellitic dianhydride. The polyamic acid may be used alone or in combination of two or more.

Examples of the organic solvent include, but are not particularly limited to, one or more kinds selected from organic solvents usable for forming the above-mentioned polyamic acid solution, other organic solvents capable of dissolving thermoplastic polyimide and polyamide acid Etc. may be used.

In the organic solvent solution of the polyamic acid, the solid content concentration of the polyamic acid is not particularly limited, but is, for example, 10 to 30% by weight based on the total amount of the organic solvent solution.

Further, the polyimide film of the present invention can be used for applications such as base films for FPCs, insulating films for capacitors, insulating tapes and the like.

[Example]

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. In addition, evaluation methods and evaluation criteria of each characteristic described in the above-described technique and the following embodiments are as follows.

(1) Breaking strength and elongation at break

The breaking strength was determined by the tensile tester type tensile tester manufactured by ORIENTEC at room temperature in accordance with JIS-K7113, and the strength and elongation at break of the sample at a tensile rate of 300 mm / min. The size of the test piece was 10 mm wide × 250 mm long, and the distance between chucks was 100 mm, and measurement was carried out under an atmosphere of 25 ° C and 60% RH.

(2) Film thickness

The film thickness was measured using a Digital Micrometer M-30 manufactured by SONY Corporation, and the value obtained by dividing the thickness value by 10 was rounded off to the first digit of the decimal point as the film thickness .

(3) Film L value

The film L value was measured using SM-7-CH manufactured by Suga Tester. A film of 100 mm x 100 mm was divided into five in the film width direction, and the center position of each sample was measured, and the average value of the five points was determined. The L value was measured by superimposing the minimum number of films having a total thickness of 50 占 퐉 or more because the sensitivity of the detector was lowered and the film could not be evaluated properly when the film thickness was reduced. Particularly, for a film having a thickness of 10 占 퐉 or less, values obtained by superimposing the films so as to have a total thickness of 50 to 60 占 퐉 were employed.

(4) Alkali resistance

A film cut into 200 mm x 200 mm was immersed in a 5% aqueous solution of sodium hydroxide heated to 50 占 폚 and withdrawn after 30 minutes, and the breaking strength and elongation at break thereof were measured. The alkali resistance was evaluated by calculating the retention ratios after alkali immersion, with the rupture strength and the elongation at break before alkali immersion set at 100%, respectively. Both of the fracture strength and the retention of the elongation at break were 80% or more in terms of excellent alkali resistance (O) and 80% or less in alkaline resistance (X).

(5) Film-forming property (film-forming stability)

"&Amp; cir & ", and" x "when film breakage due to wrinkling or tearing did not occur during the continuous film formation with a film length of 5000 m.

(Synthesis Example 1)

(Molecular weight 218.12) / 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (molecular weight 200.24) / paraphenylene Diamine (molecular weight: 108.14) was prepared at a molar ratio of 65/35/82/18 and polymerized as a 20 wt% solution in DMAC (N, N-dimethylacetamide) and polymerized at 3800 poise at 25 캜. ≪ / RTI > was obtained. 2.0 mol of dry N, N-dimethylacetamide was added to the polyamic acid solution, 4.0 mol of acetic anhydride was added to the polyamic acid unit, 4.0 mol of? -Picoline per polyamic acid unit And mixed to prepare a polyamic acid solution.

(Synthesis Example 2)

(Molecular weight 218.12) / 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (molecular weight 200.24) / paraphenylene Diamine (molecular weight: 108.14) at a molar ratio of 65/35/75/25 was polymerized as a 20 wt% solution in DMAC (N, N-dimethylacetamide) To obtain an acid solution. 2.0 mol of dry N, N-dimethylacetamide was added to the polyamic acid solution, 4.0 mol of acetic anhydride was added to the polyamic acid unit, 4.0 mol of? -Picoline per polyamic acid unit And mixed to prepare a polyamic acid solution.

(Synthesis Example 3)

(Molecular weight 218.12) / 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (molecular weight 200.24) / paraphenylene Diamine (molecular weight: 108.14) was prepared at a molar ratio of 65/35/67/33 and polymerized as a 20 wt% solution in DMAC (N, N-dimethylacetamide) To obtain an acid solution. 2.0 mol of dry N, N-dimethylacetamide was added to the polyamic acid solution, 4.0 mol of acetic anhydride was added to the polyamic acid unit, 4.0 mol of? -Picoline per polyamic acid unit And mixed to prepare a polyamic acid solution.

(Synthesis Example 4)

(Molecular weight 218.12) / 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (molecular weight 200.24) / paraphenylene Diamine (molecular weight: 108.14) was prepared at a molar ratio of 45/55/67/33 and polymerized as a 20 wt% solution in DMAC (N, N-dimethylacetamide) To obtain an acid solution. 2.0 mol of dry N, N-dimethylacetamide was added to the polyamic acid solution, 4.0 mol of acetic anhydride was added to the polyamic acid unit, 4.0 mol of? -Picoline per polyamic acid unit And mixed to prepare a polyamic acid solution.

(Example 1)

The polyamic acid solution of Synthesis Example 1 was extruded from a T die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of the supporter speed to the mouthpiece discharge speed to 10.6, To give a self-supporting gel film. This gel film was continuously peeled off from the support and conveyed by a roll while being stretched to 1.22 times in the longitudinal direction of the film in a room at 70 캜. The both ends of the gel film were pressed with a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate by a factor of 1.40, and then dried by spraying air of 250 DEG C for about 20 seconds in the tenter, and then the film surface temperature was 450 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the end of the film was peeled off from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.6 탆. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 35.0. Further, when the alkali resistance was evaluated, the rupture strength retention was 96% and the rupture elongation retention was 97%.

(Example 2)

The polyamic acid solution of Synthesis Example 1 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of supporter speed / mouthpiece discharge speed to 10.6, To obtain a self-supporting gel film. This gel film was continuously peeled off from the support and conveyed by a roll while being stretched to 1.22 times in the longitudinal direction of the film in a room at 70 캜. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate by a factor of 1.40 and dried by spraying air of 250 DEG C for about 20 seconds in the tenter and then dried using an electric heater at a film surface temperature of 475 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the end of the film was peeled off from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.6 탆. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 31.3. Further, when the alkali resistance was evaluated, the rupture strength retention was 94% and the rupture elongation retention was 101%, which was a good value.

(Example 3)

The polyamide acid solution of Synthesis Example 2 was extruded from a T die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of the supporter speed to the mouthpiece discharge speed to 8.6, To obtain a self-supporting gel film. This gel film was continuously peeled off from the support, and was transported by a roll while being stretched at 1.31 times in the longitudinal direction of the film in a room at 70 캜. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate at a ratio of 1.62 times and then air was blown in the tenter at 25O < 0 > C for about 25 seconds to dry the film. Then, using an electric heater, , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.4 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value of the obtained film (measured by superposition of 7 films) was 38.3. Further, when the alkali resistance was evaluated, the fracture strength retention was 109% and the retention elongation at break was 116%, which was a good value.

(Example 4)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of supporter speed / mouthpiece discharge speed to 9.0, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction at 1.59 times on the fin plate, and then air was blown in the tenter at 25O < 0 > C for about 25 seconds to dry. Then, the film surface temperature was 435 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 38.5. Further, when the alkali resistance was evaluated, the fracture strength retention was 90% and the retention elongation at break was 100%, which was a good value.

(Example 5)

The polyamide acid solution of Synthesis Example 3 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of supporter speed / mouthpiece discharge speed to 9.0, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate at a rate of 1.59 times and then dried by spraying air of 250 DEG C for about 20 seconds in the tenter and then dried using an electric heater at a film surface temperature of 465 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 32.5. Further, when the alkali resistance was evaluated, the fracture strength retention was 94% and the retention of elongation at break was 100%, which was a good value.

(Example 6)

The polyamic acid solution of Synthesis Example 4 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to give a ratio of supporter speed / mouthpiece discharge speed of 9.1, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate at a rate of 1.55 times and then dried by spraying air of 250 DEG C for about 25 seconds in the tenter and then dried using an electric heater at a film surface temperature of 415 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 41.5. Further, when the alkali resistance was evaluated, the fracture strength retention was 92% and the retention elongation at break was 97%, which was a good value.

(Example 7)

The polyamic acid solution of Synthesis Example 4 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to give a ratio of supporter speed / mouthpiece discharge speed of 9.1, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate by 1.55 times and then air was blown in the tenter at 25O < 0 > C for about 25 seconds to dry the film. Then, using an electric heater, , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 36.7. Further, when the alkali resistance was evaluated, the fracture strength retention was 91% and the retention elongation at break was 88%, which was a good value.

(Example 8)

The polyamic acid solution of Synthesis Example 3 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to give a ratio of supporter speed / mouthpiece discharge speed of 14.2, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and air of 240 DEG C was sprayed on the pin plate for 5 to 10 seconds to dry and fix the gel film end first. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate at a stretch of 1.62 times and then air was blown at 240 DEG C for about 20 seconds in the tenter to dry the film. Thereafter, the film surface temperature was 435 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the end of the film was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 5.0 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by superposing 10 films) of the obtained film was 36.5. Further, when the alkali resistance was evaluated, the fracture strength retention was 90% and the retention elongation at break was 92%, which was a good value.

(Example 9)

The polyamic acid solution of Synthesis Example 1 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of supporter speed / mouthpiece discharge speed to 6.0, To obtain a self-supporting gel film. This gel film was continuously peeled off from the support and conveyed by a roll while being stretched to 1.22 times in the longitudinal direction of the film in a room at 70 캜. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate with a width of 1.45 times and then dried by spraying air of 250 DEG C for about 40 seconds in the tenter and then dried using an electric heater at a film surface temperature of 400 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 10.0 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value of the obtained film (measured by overlapping five films) was 42.5. Further, when the alkali resistance was evaluated, the fracture strength retention was 98% and the retention elongation at break was 98%, which was a good value.

(Reference Example 1)

The polyamic acid solution of Synthesis Example 3 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to give a ratio of supporter speed / mouthpiece discharge speed of 8.3, To obtain a self-supporting gel film. The gel film was continuously peeled off from the support, and was transported by a roll while being stretched in the longitudinal direction of the film at room temperature of 70 ° C by 1.28 times. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction at 1.59 times on the pin plate and then dried by spraying air of 250 DEG C for about 25 seconds in the tenter and then dried using an electric heater at a film surface temperature of 500 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. However, when the film end was removed from the fin after 600 m of film formation after the above-mentioned conditions were reached, the film was torn and film breakage occurred. The L value (measured by overlapping seven films) of the film immediately before the film breakage was 27.1. The alkali resistance was evaluated. As a result, the rupture strength retention was 96% and the rupture elongation retention was 101%.

(Reference Example 2)

The polyamic acid solution of Synthesis Example 1 was extruded from a T-die having a mouthpiece slit width of 1.3 mm and a length of 2000 mm to adjust the ratio of supporter speed / mouthpiece discharge speed to 10.6, To obtain a self-supporting gel film. This gel film was continuously peeled off from the support and conveyed by a roll while being stretched to 1.22 times in the longitudinal direction of the film in a room at 70 캜. The both ends of the gel film were pressed by a roller while continuously sticking to the pin plate on the chain to fix the gel film, and the gel film was first dried and fixed by spraying air at 250 DEG C for 5 to 10 seconds on the pin plate. The gel film having both ends fixed by pins was stretched in the width direction on the fin plate at a stretch of 1.40 times and then dried by spraying air of 250 DEG C for about 20 seconds in the tenter and then dried using an electric heater at a film surface temperature of 400 DEG C , Followed by cooling to room temperature while being relaxed. Thereafter, the film end was removed from the pin, and the edge of the end of the film was cut to obtain a polyimide film having a width of 2100 mm and a thickness of 7.5 占 퐉. During film formation, wrinkles and tearing did not occur in the film, and film formation was stably performed with a length of 5000 m or more. The L value (measured by overlapping seven films) of the obtained film was 45.2. The alkali resistance was evaluated. As a result, the fracture strength retention was 69% and the retention elongation at break was 34%.

[Table 1]

As is clear from the results of Examples 1 to 9, even if the polyimide film of the present invention having an L value of 28 to 45 and having a thickness of 5.0 to 10.0 占 퐉 is thinned, the breaking strength and the elongation at break Hardly deteriorates, and is excellent in alkali resistance.

The polyimide film of the present invention having an L value of 28 to 45 is excellent in film formability even if the thickness is as small as 5.0 to 10.0 占 퐉.

In addition, the polyimide films of Examples 1 to 9 of the present invention have sufficient breaking strength and breaking elongation even when the thickness is as small as 5.0 to 10.0 占 퐉.

From the results of Examples 1 to 9, it was found that when the molecular weight of the imide group in the polyimide is 40% or less and the molecular weight of the repeating unit of the polyimide is 100%, even if the thickness is as small as 5.0 to 10.0 탆, It was found that the polyimide film was excellent in alkalinity.

On the other hand, the polyimide film of Reference Example 1 having an L value of less than 28 was liable to be broken and torn easily, and the film-forming property was poor.

In the polyimide film of Reference Example 2 having an L value of more than 45, the alkali resistance was poor, and the breaking strength and the elongation at break were lowered by immersion in an alkali solution.

As described above, it has been found that the thin film polyimide film having a thickness of 1.0 to 10.0 占 퐉 can be compatible with alkali resistance and film formability by setting the L value to 28 to 45. [

Although the polyimide film of the present invention is an extremely thin film having a thickness of 1.0 to 10.0 占 퐉, it is required to be thin because it has excellent alkali resistance and does not readily generate heat in the process of producing the film and has good film- A base film of an FPC to be used, and the like.

Claims (7)

Wherein the polyimide film has a molecular weight of 40% or less and an L value of the polyimide film is 28 to 45 and a thickness of 1.0 to 10.0 m, when the molecular weight of the repeating unit of the polyimide is 100%. The method according to claim 1,
The polyimide film is stretched by a biaxial stretching process in the machine direction (MD) and the transverse direction (TD) of the film, and the total stretch ratio of the film (stretching ratio of MD x stretching ratio of TD ) Is not less than 1.60. 3. The method according to claim 1 or 2,
Wherein the aromatic diamine component is at least one selected from the group consisting of paraphenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether, and the aromatic acid anhydride component is at least one selected from the group consisting of pyromellitic dianhydride And / or a polyamic acid which is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride. A film obtained by stretching a gel film capable of forming a polyimide film having a molecular weight of the imide group of 40% or less, assuming that the molecular weight of the repeating unit of the polyimide is 100%, is heated at 350 to 500 DEG C for 5 to 300 seconds A process for producing a polyimide film according to any one of claims 1 to 3, 4. The method according to any one of claims 1 to 3,
A polyimide film comprising a polyimide film (A) and a polyimide film (B) laminated on one side or both sides of the polyimide film (A). The method according to any one of claims 1 to 3 and 5,
Wherein the polyimide film is in the form of a polyimide film roll having a width of 500 to 3000 mm and a length of 1000 m or more. The method according to any one of claims 1 to 3 and 5 to 6,
Polyimide film for flexible printed circuit boards.