JP2008222925A - Low thermally shrinkable highly adhesive polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film having improved thermal shrinkability and simultaneously having improved adhesiveness. <P>SOLUTION: This polyimide film comprising (1) a polyimide obtained from 4,4'-diaminodiphenyl ether and pyromellitic dianhydride, and (2) inorganic particles having particle diameters of 0.01 to 1.5 μm and an average particle diameter of 0.05 to 0.7 μm in an amount of 0.1 to 0.9 wt.% based on the weight of the polyamic acid in a uniformly dispersed state is characterized by having a surface free energy of ≥80 mN/m, when the polyimide film is sequentially subjected to a discharge treatment and a heating treatment in a state constantly keeping the longitudinal tension of the film and then measured on the basis of a contact angle method, and further having a thermal shrinkage degree of ≤0.10% at 200°C for one hour. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyimide film having improved heat shrinkability and at the same time improved adhesion.

  A polyimide film obtained by polycondensation of an aromatic tetracarboxylic dianhydride and an aromatic diamine has been widely used as a base film for a flexible printed circuit board because of its excellent heat resistance, insulation and mechanical properties.

  In order to make a flexible printed circuit board using a polyimide film as a base film, it is necessary to laminate a metal foil such as copper on the film via an adhesive, or to attach the metal directly to the film by vacuum deposition, sputtering, etc. There is. In these processes, since considerable heat is applied to the base film, the polyimide film as the base film is required to have dimensional stability against heat. Furthermore, as a recent trend, fine pitches are being promoted, and a polyimide film with smaller shrinkage due to heat is required.

  As means for meeting such demands, a method is proposed in which a polyimide film is heated in a heating oven under substantially no tension and then cooled (for example, see Patent Document 1). In this method, in order to heat-treat under no tension, the film-wrapped roll is left in a heating oven, or the film is continuously removed in a continuous heating furnace equipped with an unwinder and a winder. Procedures for processing are taken. Such a heat treatment method under no tension can be said to be an effective method because the latent shrinkage stress of the film is relaxed and the shrinkage of the film with respect to heating after the heat treatment is reduced. However, the heat treatment according to the procedure as described above, in any case, will be treated for a long time under no tension, so that the resulting film will be in a state of undulation, which causes the heat shrinkage rate to vary. was there. In particular, in the case of continuous processing, there has been a disadvantage that the film meanders and a complete product roll cannot be obtained.

  Furthermore, in applications such as a base film for flexible printed wiring boards and a carrier tape film for IC tape automated bonding, a polyimide film and a copper foil are usually bonded via various adhesives. However, polyimides often have insufficient adhesion due to their chemical structure and high chemical resistance. In order to improve the shortage of adhesiveness, methods that have been tried in the past include a method of chemically treating the film surface with acid or alkali (for example, see Patent Document 2), and sandblasting. For example, there is a method of performing a physical process (see, for example, Patent Document 3).

  However, since these processes require separate steps such as washing and drying after the process, they have problems in terms of not only productivity, stability and cost but also environmental conservation.

JP 62-41024 JP 2002-294965 A Japanese Patent Laid-Open No. 9-48864

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

  Accordingly, an object of the present invention is to provide a polyimide film having improved heat shrinkability and at the same time improved adhesion.

  According to the present invention for achieving the above object, (1) a polyimide obtained from 4,4′-diaminodiphenyl ether and pyromellitic dianhydride, and (2) a particle size of 0.01 to 1. An inorganic particle having an average particle diameter of 0.05 to 0.7 μm within a range of 5 μm is a polyimide film comprising 0.1 to 0.9% by weight based on the weight of the polyamic acid, The powder is uniformly dispersed in the polyimide film, and the polyimide film is sequentially subjected to a discharge treatment and a heat treatment while keeping the tension in the length direction of the film constant. A polyimide film having a surface free energy of 80 mN / m or more measured based on a contact angle method and a heat shrinkage of 0.10% or less at 200 ° C. for 1 hour Are provided.

  In the low heat shrinkable and highly adhesive polyimide film of the present invention, the elastic modulus of the polyimide film is 3 to 4 GPa, the linear expansion coefficient at 50 to 200 ° C. is 25 to 30 ppm / ° C., and the humidity expansion It is preferable that the coefficient is 30 ppm /% RH or less and the water absorption is 4% or less.

  Further, in the low heat shrinkable and highly adhesive polyimide film of the present invention, after the polyimide film is formed, a discharge treatment is performed, and then a heat treatment is performed while keeping the tension in the length direction of the polyimide film constant. It is preferable that the heat treatment be performed while keeping the tension in the length direction of the film in a range of 1 kg / m or more and 10 kg / m or less, and that the discharge treatment is a plasma discharge treatment.

  ADVANTAGE OF THE INVENTION According to this invention, the polyimide film which improved adhesiveness while improving the shrinkability with respect to a heat | fever can be obtained. That is, the low heat-shrinkage and high-adhesion polyimide film of the present invention has excellent dimensional stability against heat, small shrinkage due to heat, and markedly improved adhesion to copper foil.

  Hereinafter, the low heat shrinkable and highly adhesive polyimide film of the present invention will be described in detail.

  First, a procedure for obtaining polyimide will be described. A polyimide can be obtained from the polyimide acid which is the precursor. Preferred polyamic acids in the present invention can be prepared from an anhydride to an aromatic diamine component and an aromatic tetracarboxylic acid. In the present invention, polyamic acid is obtained by polymerizing 4,4'-diaminodiphenyl ether as an aromatic diamine component and pyromellitic dianhydride as an aromatic tetracarboxylic dianhydride component. The resulting polyamic acid is then converted to polyimide.

  Polyimide acid is formed from 100 mol% 4,4'-diaminodiphenyl ether as aromatic diamine and 100 mol% pyromellitic dianhydride as aromatic tetracarboxylic dianhydride.

  Any method known in the art can be used as a method for obtaining polyimide. 1) Amidation in which an aromatic tetracarboxylic dianhydride component and an aromatic diamine component are reacted to form a polyamic acid. It is preferable to prepare by a method including a step and 2) an imidization step in which an amide and a carboxylic acid in a polyamic acid are reacted to form a polyimide.

Any method known in the art can be used as the amidation step for forming the polyamic acid. Although any known method can be used as the amidation method, the following methods are preferable as the amidation method. That is,
(1) A method in which an aromatic diamine component is dissolved in an organic polar solvent, and a substantially equimolar amount of the aromatic tetracarboxylic dianhydride component is added thereto for polymerization.
(2) An aromatic tetracarboxylic dianhydride component is reacted with a small molar amount of an aromatic diamine component in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, a method of polymerizing the prepolymer solution by adding the diamine component so that the aromatic tetracarboxylic dianhydride component and the aromatic diamine component are substantially equimolar in all steps;
(3) An aromatic tetracarboxylic dianhydride component and an excess molar amount of an aromatic diamine component are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. An aromatic diamine component is additionally added to the prepolymer solution, and then the aromatic tetracarboxylic dianhydride component and the aromatic diamine component are substantially equimolar in all steps. A method of polymerizing by adding a carboxylic dianhydride component;
(4) A method in which an aromatic tetracarboxylic dianhydride component is dissolved and / or dispersed in an organic polar solvent, and then a substantially equimolar amount of an aromatic diamine component is added and polymerized; or (5) A method such as a method in which a mixture of a substantially equimolar amount of an aromatic tetracarboxylic dianhydride component and an aromatic diamine component is reacted in an organic polar solvent for polymerization.

  In the present invention, for example, an organic solvent solution of a substantially equimolar amount of an aromatic tetracarboxylic dianhydride component and an aromatic diamine component is added to the aromatic tetracarboxylic dianhydride under controlled temperature conditions. A polyamic acid solution can be produced by stirring until the reaction between the component and the aromatic diamine component is complete.

  These polyamic acid solutions are usually obtained at a concentration of 5 to 35% by mass, preferably 10 to 30% by mass. By setting the concentration within such a range, a polyamic acid having an appropriate molecular weight can be obtained. Moreover, it becomes possible to provide a polyamic acid solution having a solution viscosity within a range suitable for the subsequent treatment.

  In the present invention, the polyamic acid obtained by using any of the above methods may be used, and the polymerization method is not particularly limited. Among these methods, from the viewpoint of stably controlling the process, all of the aromatic diamine components used in all the processes are dissolved in an organic solvent, and then the aromatic tetramolar amount is adjusted so as to be a substantially equimolar amount. It is preferable to use the method (1) in which a carboxylic dianhydride component is added to conduct a polymerization reaction.

  In the present invention, pyromellitic dianhydride is used as the aromatic tetracarboxylic dianhydride component, but other aromatic tetracarboxylic dianhydrides can be used in combination as long as they are 40 mol% or less. Other aromatic tetracarboxylic dianhydrides that can be used in combination include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2 , 2′-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, Bis (3,4-carboxyphenyl) ether dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, decahydro Naphthalene-1,4,5,8-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid Dianhydride, 2 6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7- Tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, 1,1-bis (2,3-dicarboxyphenyl) Ethane dianhydride, 1,1-bis (3,4-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′-benzophenonetetracarboxylic acid Two anhydrous , Or the like can be given a mixture of two or more thereof.

  In addition, 4,4'-diaminodiphenyl ether is used as the aromatic diamine component, but another aromatic diamine can be used in combination as long as it is 40 mol% or less. Other aromatic diamines that can be used in combination include 1,4-phenylenediamine (p-phenylenediamine), 3,4'-diaminodiphenyl ether, 1,3-phenylenediamine (m-phenylenediamine), 2,2-bis ( 4-aminophenyl) propane, 4,4′-diaminodiphenylmethane, benzidine, 4,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 2,6-diaminopyridine Bis (4-aminophenyl) diethylsilane, bis (4-aminophenyl) diphenylsilane, 3,3′-dichlorobenzidine, bis (4-aminophenyl) ethylphosphine oxide, bis (4-aminophenyl) phenylphosphine Oxide, N, N-bis (4-aminophenyl) Nyl) -N-phenylamine, N, N-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 (2-amino-1,1-dimethylethyl) toluene, bis (4- (2-amino-1 , 1-dimethylethyl) phenyl) ether, 1,4-bis (2-methyl-4-aminopentyl) benzene, 1,4-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,3- Bis (aminomethyl) benzene (m-xylylenediamine), 1,4-bis (aminomethyl) benzene (p-xylylenediamine), 1,3-diaminoadamantane, 3,3′-diamino 1,1′-diadamantane, bis (4-aminocyclohexyl) methane, hexamethylenediamine, peptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 3-methylheptane-1,7-diamine, 4 , 4-dimethylheptane-1,7-diamine, 2,11-diaminododecane, 1,2-bis- (3-aminopropyloxy) ethane, 2,2-dimethylpropane-1,3-diamine, 3-methoxy Hexane-1,6-diamine, 2,5-dimethylhexane-1,6-diamine, 5-methylnonane-1,9-diamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, 2,5-diamino -1,3,4-oxadiazole, 2,2-bis (4-aminophenyl) hexafluoro Examples thereof include propane, N- (3-aminophenyl) -4-aminobenzamide, 4-aminophenyl-3-aminobenzoate and the like.

  Organic solvents that can be used in the amidation step to form the polyamic acid are N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N-diethylformamide, N, N- Diethylacetamide, N-dimethylmethoxyacetamide, N-methyl-ε-caprolactam, dimethyl sulfoxide, N-methyl-2-pyrrolidone, tetramethylurea, pyridine, dimethylsulfone, hexamethylphosphoramide, tetramethylenesulfone, formamide, N -Organic polar solvents such as methylformamide and γ-butyrolactone are included. These organic polar solvents can be used alone or in combination, or can be used in combination with solvents having poor solubility such as benzene, benzonitrile, dioxane, xylene, toluene and cyclohexane.

  Any method known in the art can be used for the imidization step in the present invention. For example, the imidization step can be performed by drying and heat-treating the polyamic acid in the presence or absence of an additive. Although imidization can be performed without adding a catalyst, in the present invention, it is preferable to perform imidization by adding a conversion agent. The conversion agent generally comprises a catalyst and a dehydrating agent. In the present invention, it is preferable to perform imidization by adding the following catalyst and dehydrating agent.

  As the catalyst that can be used in the present invention, tertiary amines are desirably used. Specific examples of these amines include trimethylamine, triethylamine, N, N-diethyl-N-cyclohexylamine, N, N- Dimethyl-N-cyclohexylamine, N, N-dimethyl-N-benzylamine, N, N-dimethyl-N-dodecylamine, N-ethylmorpholine, N-methylmorpholine, triethylenediamine, pyridine, 2-ethylpyridine 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 4-isopropylpyridine, 4-benzylpyridine, 4-benzoylpyridine, 2,4-lutidine, 2,6-lutidine, 3,4-lutidine, 3 , 5-lutidine, 2,4,6-collidine, and isoquinoline Including sexual amine, and the like.

  Examples of the dehydrating agent include organic carboxylic acid anhydrides, N, N-dialkylcarbodiimides, lower fatty acid halides, halogenated lower fatty acid halides, halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, and thionyl halides. .

Specifically, an organic carboxylic acid anhydride that can be used as a dehydrating agent is:
(A) anhydrides and mixed acid anhydrides of aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid;
(B) Benzoic acid, naphthoic acid (including isomers), toluic acid (including isomers), m-ethylbenzoic acid, p-ethylbenzoic acid, p-propylbenzoic acid, p-isopropylbenzoic acid, anisic acid , Nitrobenzoic acid (including isomers), monohalobenzoic acid (including isomers), dibromobenzoic acid (including isomers), dichlorobenzoic acid (including isomers), tribromobenzoic acid (including isomers) Fragrances such as trichlorobenzoic acid (including isomers), dimethylbenzoic acid (including isomers such as 3,4-xylylic acid and isoxysilylic acid), mesitylene acid, veratromic acid, trimethoxybenzoic acid, and biphenylcarboxylic acid Group monocarboxylic acid anhydrides and mixed acid anhydrides;
(C) a mixed acid anhydride of an aliphatic monocarboxylic acid and an aromatic monocarboxylic acid;
(D) Mixed acid anhydride of carbonic acid or formic acid and monocarboxylic acid (including aliphatic and aromatic); and (e) Mixture of fatty acid ketene (including ketene and dimethylketene) and the above acid anhydride (Acetic anhydride and ketenes are preferred)
including.

  N, N′-dialkylcarbodiimides are represented by the formula: R—N═C═N—R, wherein R can be different alkyl groups but are generally the same, preferably R groups Is a lower alkyl group of 1 to 8 carbon atoms.

  Lower fatty acid halides that can be used as dehydrating agents are acetyl chloride, acetyl bromide, acetyl iodide, acetyl fluoride, propionyl chloride, propionyl bromide, propionyl iodide, propionyl fluoride, isobutyryl chloride, isobutyryl bromide N-butyryl chloride, n-butyryl bromide, and valeryl chloride.

  Halogenated lower fatty acid halides that can be used as dehydrating agents include monochloroacetyl chloride, dichloroacetyl chloride, trichloroacetyl chloride, and bromoacetyl bromide.

  Halogenated lower fatty acid anhydrides that can be used as dehydrating agents include chloroacetic anhydride and trifluoroacetic anhydride.

  Arylphosphonic dihalides that can be used as dehydrating agents include phenylphosphonic dichloride.

  Thionyl halides that can be used as dehydrating agents include thionyl chloride, thionyl bromide, thionyl fluoride, and thionyl chlorofluoride.

  Next, the inorganic particles contained in the film of the present invention will be described. The inorganic powder that can be used in the present invention is an inorganic particle having a particle diameter in the range of 0.01 to 1.5 μm and an average particle diameter of 0.05 to 0.7 μm. An average particle size of 0.05 μm or less is not preferable because the slipperiness effect of the film is reduced, and an average particle size of 0.70 μm or more is not preferable because it is locally present as large particles. The range of a preferable average particle diameter is 0.1-0.6 micrometer, and a more preferable range is 0.3-0.5 micrometer. Furthermore, regarding the particle size distribution, it is preferable that 0.15 to 0.6 μm is contained in an amount of 80% by weight or more based on the total particles.

  The kind of the inorganic particles of the present invention is not particularly limited. For example, titanium oxide, silicon dioxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, alumina and the like are common. Of these, silicon dioxide is preferred. The method for producing silicon dioxide is not particularly limited, but a production method in which silicates are used as starting materials for hydrolysis is particularly preferred from the viewpoint of impurity content, particle size, and particle size distribution.

  In order to obtain the effect of the present invention, it is necessary to uniformly disperse the inorganic powder in the film at a ratio of 0.1 to 0.9% by weight with respect to the weight of the polyamic acid. A more preferable addition amount is in the range of 0.3 to 0.8% by weight.

  In order to facilitate the dispersion of the inorganic powder, for example, the inorganic powder is uniformly dispersed in a polar solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, or n-methylpyrrolidone. The slurried slurry can be used. This method is also preferable from the viewpoint of preventing aggregation of the inorganic powder. In addition, since the particle size of the inorganic particles is very small, the slurry has a low sedimentation rate and is stable, and even if it settles, it can be easily redispersed by re-stirring.

  Next, the method for forming the polyimide film of the present invention will be described. The method for forming the polyimide film is not particularly limited, but the following procedure is generally adopted. First, a polyamic acid solution is obtained by mixing and reacting a diamine component and a tetracarboxylic dianhydride component (in the present invention, 4,4′-diaminodiphenyl ether and pyromellitic dianhydride) in an appropriate solvent. Next, an inorganic powder is added to the polyamic acid solution and stirred, and further a catalyst and a dehydrating agent are added and stirred. The resulting solution is cast or extruded into a film. Next, imidation is performed by drying and heat-treating this film.

  Drying and heat treatment can be achieved by passing the polyamic acid solution cast or cast into a film through a dry heat treatment zone maintained in a high temperature atmosphere of 200 to 550 ° C, preferably 250 to 500 ° C.

  In the present invention, it is desirable to adjust the film thickness to be 5 to 150 μm, preferably 7 to 125 μm.

  The polyimide film of the present invention is formed from 100 mol% 4,4'-diaminodiphenyl ether as an aromatic diamine and 100 mol% pyromellitic dianhydride as an aromatic tetracarboxylic dianhydride.

  The polyimide film of the present invention is characterized in that the surface free energy measured based on the contact angle method is 80 mN / m or more.

  Here, when the surface free energy of the polyimide film is less than 80 mN / m, the effect of improving the adhesiveness becomes insufficient, which is not preferable. When the surface free energy condition satisfies the above range, a polyimide film excellent in adhesiveness with the copper foil can be obtained.

  Further, the polyimide film of the present invention preferably has a thermal shrinkage rate of 0.10% or less, more preferably 0.05% or less under a heating condition of 200 ° C./1 hour.

  When the thermal shrinkage rate exceeds 0.10%, the effect of improving the shrinkability to heat is reduced, which is not preferable.

  Furthermore, the polyimide film of the present invention has an elastic modulus of 3 to 4 GPa, a linear expansion coefficient at 50 to 200 ° C. of 25 to 30 ppm / ° C., a humidity expansion coefficient of 30 ppm /% RH or less, and a water absorption rate. Is preferably 4% or less.

  The polyimide film of the present invention satisfying the above characteristics is formed by forming a polyimide having the above composition, and then subjecting the polyimide film to a discharge treatment, and then subjecting the polyimide film to a heat treatment while maintaining a constant tension in the length direction of the film. Can be manufactured.

  In the present invention, it is preferable to perform a heat treatment after the discharge treatment. By performing the treatment in this order, the film has appropriate slipperiness, and wrinkles and the like when wound are reduced.

  As the discharge treatment in the present invention, plasma treatment is typical.

  The pressure of the atmosphere in which the plasma treatment is performed is not particularly limited, but is usually in the range of 13.3 to 1330 kPa, preferably 13.3 to 133 kPa (100 to 1000 Torr), more preferably 80.0 to 120 kPa (600 to 900 Torr). ) Is preferably selected.

The atmosphere in which the plasma treatment is performed contains an inert gas at least 20 mol%, preferably 50 mol% or more, more preferably 80 mol% or more, and most preferably 90 mol% or more. Inert gases that can be used include He, Ar, Kr, Xe, Ne, Rn, N ₂ and mixtures of two or more thereof. A particularly preferred inert gas is Ar. Furthermore, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane, etc. are added to the aforementioned inert gas. You may mix. This is because by mixing these gases, generation of active groups containing oxygen, chlorine, nitrogen or halogen is promoted. Preferred mixed gas combinations used as the plasma treatment atmosphere of the present invention are argon / oxygen, argon / ammonia, argon / helium / oxygen, argon / carbon dioxide, argon / nitrogen / carbon dioxide, argon / helium / nitrogen, argon / Helium / nitrogen / carbon dioxide, argon / helium, helium / air, argon / helium / monosilane, argon / helium / disilane and the like.

The treatment power density when performing the plasma treatment is preferably 200 W · min / m ² or more, more preferably 500 W · min / m ² or more, and most preferably 1000 W · min / m ² or more. The plasma irradiation time for performing the plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of the plasma treatment can be sufficiently exhibited without accompanying film deterioration.

  The gas type, gas pressure, and treatment density of the plasma treatment are not limited to the above conditions, and may be performed in the atmosphere.

  In the heat treatment according to the present invention, the obtained polyimide film is heat-treated at a relatively low temperature and in a relatively short time while maintaining the tension in the length direction of the film at 1 kg / m or more and 10 kg / m or less. This is very important.

  In heat treatment, the lower the tension, the lower the heat shrinkable film. However, under complete tension, the film meanders when the film is wound, particularly when continuous winding is performed. Furthermore, under complete no tension, in addition to such meandering of the film, wrinkles and undulations occur in the film, and there is a tendency that the variation in the heat shrinkage rate increases. For this reason, the tension in the heat treatment needs to be 1 kg / m or more. On the other hand, if the tension exceeds 10 kg / m, it is not preferable because the desired heat-shrinkable film in the present invention cannot be obtained. A more preferable range of tension is 2 kg / m to 7 kg / m.

  As a preferable means of heating at the time of heat treatment, a method of irradiating far infrared rays or a method of blowing hot air is included. The polyimide film has an absorption peak in the far-infrared region, and heat treatment can be performed in a very short time by irradiating far-infrared rays including this absorption wavelength. Moreover, in addition to far-infrared irradiation or hot air spraying, a radiation heater can be used in combination, and heat treatment can be performed using only the radiation heater.

  Although heat processing temperature is not specifically limited, 300-500 degreeC is preferable, More preferably, it is 350-450 degreeC.

  The heat treatment time is preferably about 1 second to 10 minutes. If the treatment time is longer than this, the characteristics such as film flatness may be deteriorated.

  In the present invention, the polyimide film that has been subjected to the discharge treatment and the heat treatment is wound up after having a specified width, for example, by slitting the end portion.

  The polyimide film of the present invention obtained as described above has excellent dimensional stability against heat, small shrinkage due to heat, and much improved adhesiveness with copper foil than before. For this reason, taking advantage of these characteristics, TAB (Tape Automated Bonding), which is a base material used for flexible printed wiring boards (FPC) such as electronic components, COF (Chip On Flex) base insulating films, or semiconductors It can be usefully used as a LOC tape that is a support member in the apparatus.

  Hereinafter, the present invention will be described specifically by way of examples. Each characteristic of the polyimide film in an Example was evaluated with the following method.

(Surface free energy)
The contact angle was measured five times for each solution with water, ethylene glycol and diiodomethane on the surface of the film subjected to the surface treatment, and the average value of the contact angles for each liquid was determined. From this average value, the surface free energy was determined using FACE CA-W150 of Kyowa Interface Science. A large value indicates good wettability and generally high adhesion.

(Adhesion evaluation)
Three types of epoxy resin adhesives (trade names: Epox AH-357A, AH-357B and AH-357C) manufactured by Mitsui Chemicals Co., Ltd. are used. AH-357A / AH-357B / AH-357C An adhesive mixed in a weight ratio was prepared, and this was applied to each film with a coater. The resulting film was pre-dried at 130 ° C. for 4 minutes. Next, 18 μm rolled copper foil (BHY-22B-T, manufactured by Japan Energy Co., Ltd.) is superimposed on this film, and pressed under 2 MPa under 170 ° C. and 80 minutes press cure conditions to obtain a copper-clad laminate. It was. A 0.8 mm circuit was cut on the obtained laminate and etched with a ferric chloride solution to prepare a sample for evaluation. The force required to peel the obtained 0.8 mm wide metal foil part at a peeling angle of 90 ° and a speed condition of 50 mm / min was measured to obtain an adhesive strength [N / m]. Five samples were measured and the average value was calculated.

(Measurement of heat shrinkage)
The measurement of the heat shrinkage rate is IPC-FC-231 Number 2.2.4. It went according to.

(Young's modulus)
The Young's modulus was measured from the slope of the initial rising portion in a tension-strain curve obtained at a tensile speed of 100 mm / min with a Tensilon type tensile tester manufactured by ORIENREC at room temperature according to JISK7113.

(Linear expansion coefficient)
The linear expansion coefficient is measured by a thermomechanical analyzer TMA-50 manufactured by Shimadzu Corporation under the conditions of a temperature range of 50 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min.

(Water absorption rate)
The water absorption is measured by immersing the polyimide film in distilled water for 48 hours, wiping off the surface moisture, and heating from room temperature to 200 ° C. at a heating rate of 10 ° C./min with a thermomechanical analyzer TGA-50 manufactured by Shimadzu Corporation. It is a value obtained from the weight loss up to 50 to 200 ° C.

(Humidity expansion coefficient)
The humidity expansion coefficient was measured by using a humidity expansion coefficient analysis unit (TM9400, NESLAB-RTE7, HC-1 humidity atmosphere control device, MTS9000) manufactured by ULVAC RICOH Co., Ltd. and a sample (length (L0) 15 mm, width 5 mm) in the furnace The relative humidity is increased from 25% RH to 75% RH, the sample length (L1) when the humidity is 75% RH, the sample length (L2) when the humidity is 25% RH, and the relative humidity difference (50% RH) was measured and calculated by the following formula. The measurement was performed in a room (constant temperature and humidity chamber) having a room temperature of 25 ± 3 ° C. and a relative humidity of 60 ± 5%.
Humidity expansion coefficient (ppm /% RH) = (L1-L2) / (L0 × humidity difference) × 1000000

(Creation of silica slurry)
A silica slurry was obtained by uniformly dispersing in N, N-dimethylacetamide so that the concentration of spherical silica having an average particle size of 0.4 μm and a maximum particle size of 1.2 μm was 5 wt%.

<Example 1>
Put 184 g of N, N-dimethylacetamide in a 500 cc glass flask, add 24 g of 4,4'-diaminodiphenyl ether and 25.4 g of pyromellitic dianhydride, and react at room temperature and pressure for 2 hours. Thus, a polyamic acid solution was obtained.

  To this polyamic acid solution, 3.8 g of silica slurry was added and stirred. The amount of silica added is 0.3% with respect to the polyamic acid. Furthermore, after adding acetic anhydride and isoquinoline as conversion agents and N, N-dimethylacetamide as a solvent and stirring, the solution is extruded onto a heated support (85 ° C.) and partially converted into polyimide to self-support. Sex film was obtained.

  Next, the above self-supporting film was peeled off from the support and subjected to drying and heat treatment to complete the conversion reaction to imide. Drying and heat treatment were carried out by passing through a drying heat treatment zone at 250 to 450 ° C. As a result, a polyimide film having a thickness of 25 μm was prepared and wound on a roll. The resulting film had a heat shrinkage of 0.20.

Next, the polyimide film was subjected to plasma treatment. In the plasma treatment, an electrode whose surface is coated with a dielectric and cooled to 25 ° C. in an atmosphere of 750 Toor containing at least 20 mol% of a rare gas (argon), a dielectric-coated electrode that supports a polyimide film, A high voltage was applied during this period, and the surface of the film was continuously processed at a processing power density of 500 w · min / m ² . The processing time was 2 seconds.

  Thereafter, a polyimide film subjected to plasma treatment was continuously fed into a 400 ° C. tunnel-type infrared irradiation furnace and heat-treated at a tension of 1.0 kg / m. The treatment temperature and treatment time were 30 seconds at 400 ° C., respectively. Next, the heat-treated polyimide film was cooled to room temperature while being wound outside the furnace to obtain a target polyimide film. The film tension during the heat treatment was adjusted by the difference in rotation speed between the feed roller and the take-up roller, and the heat treatment time was adjusted by the relative rotation speed of each roller.

  The polyimide film thus obtained was evaluated for adhesion and heat shrinkage. The results are summarized in Table 1.

<Example 2>
A polyimide film was obtained in the same manner as in Example 1 except that the film thickness was 7.5 μm. The polyimide film was evaluated for adhesion and heat shrinkage. The results are summarized in Table 1.

<Comparative Example 1>
A polyimide film was obtained in the same manner as in Example 1 except that the heat treatment at 400 ° C. was not performed. The polyimide film was evaluated for adhesion and heat shrinkage. The results are summarized in Table 1.

<Comparative example 2>
A polyimide film was obtained in the same manner as in Example 1 except that the plasma treatment was not performed. The polyimide film was evaluated for adhesion and heat shrinkage. The results are summarized in Table 1.

<Comparative Example 3>
A polyimide film was obtained in the same manner as in Example 1 except that the heat treatment at 400 ° C. and the plasma treatment were not performed. The polyimide film was evaluated for adhesion and heat shrinkage. The results are summarized in Table 1.

  The polyimide film of the present invention has excellent dimensional stability against heat, small shrinkage due to heat, and much improved adhesiveness with copper foil. For this reason, taking advantage of these characteristics, TAB (Tape Automated Bonding), which is a base material used for flexible printed wiring boards (FPC) such as electronic components, COF (Chip On Flex) base insulating films, or semiconductors It can be usefully used as a LOC tape that is a support member in the apparatus.

Claims (4)

(1) Polyimide obtained from 4,4′-diaminodiphenyl ether and pyromellitic dianhydride, and (2) The particle diameter is in the range of 0.01 to 1.5 μm and the average particle diameter is 0.00. 0.1 to 0.9% by weight of inorganic particles of 0.5 to 0.7 μm based on the weight of the polyamic acid
A polyimide film comprising:
The powder is uniformly dispersed in the polyimide film,
The polyimide film has a surface free energy of 80 mN / m or more measured based on the contact angle method by sequentially performing discharge treatment and heat treatment while keeping the tension in the film length direction constant. And a polyimide film having a heat shrinkage of 0.10% or less at 200 ° C. for 1 hour.   The polyimide film has an elastic modulus of 3 to 4 GPa, a linear expansion coefficient at 50 to 200 ° C. of 25 to 30 ppm / ° C., a humidity expansion coefficient of 30 ppm /% RH or less, and a water absorption of 4% or less. The polyimide film according to claim 1, wherein:   3. The polyimide film according to claim 1, wherein the heat treatment is a treatment performed while maintaining a tension in a length direction of the film in a range of 1 kg / m to 10 kg / m.   The polyimide film according to claim 1, wherein the discharge treatment is a plasma discharge treatment.