JP2007063492A - Polyimide film having little defect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film having little gel defects. <P>SOLUTION: This polyimide film obtained by adding/agitating an imide formation-accelerator consisting of a dehydrating agent, an imide-forming catalyst and solvent to the organic solvent solution of a polyamide acid which is a precursor of the polyimide, casting the obtained dope liquid over a supporting body, drying and heat-treating the obtained gel film is characterized by setting 30-75 range weight of the added imide formation-accelerator in the case of setting the weight of the organic solvent solution of the polyamide acid as 100. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyimide film that improves the mixing properties of an organic solvent solution of a polyamic acid and an imidization accelerator and suppresses the occurrence of defects due to poor mixing of the two.

A polyimide film is used as a base film of a flexible printed wiring board (hereinafter also referred to as FPC) because of its heat resistance and insulation. A polyimide film is generally a thermal imidation method in which an organic solvent solution of a polyamic acid as a precursor is cast and applied on a support, and the gel film obtained by volatilizing the solvent to some extent is heat-treated, or polyamide It is often produced by any of chemical imidation methods in which a gel film is similarly prepared and heat treated after adding an imidization accelerator consisting of a dehydrating agent, an imidization catalyst, and a solvent to an organic solvent solution of acid. .
Of these two methods, the chemical imidation method can be preferably used because the production rate can be easily improved by promoting the imidization reaction.

  However, in the chemical imidization method, since an imidization accelerator is added, imidation may proceed faster than intended. Moreover, since a high-viscosity polyamic acid solution and a low-viscosity imidization accelerator are mixed, poor mixing tends to occur. Because of these, the fine particles of polyamic acid that remain without imidization completely, or the fine particles of polyimide that have been locally imidized (hereinafter these Are formed into a gel-like material, and defects caused thereby are called gel defects). When this gel defect exists in the film, it causes a repellency or the like of the adhesive solution when an adhesive for bonding the copper foil to the film is applied.

  The above gel defects are improved by keeping the temperature of the polyamic acid solution and the imidization accelerator at a low temperature to suppress rapid imidization, and increasing the number of revolutions of the stirring mixer that mixes both to improve the stirring efficiency. Is possible. However, increasing the rotation speed of the stirring also leads to an increase in the heat generated by the stirring, so there is a limit to the increase in the rotation speed.

On the other hand, an attempt has been made to reduce gel defects in the film by filtering the solution in which the polyamic acid solution and the imidization accelerator are mixed (see Patent Document 1). However, this method only removes the gel-like substance with a filter, and does not fundamentally suppress the occurrence thereof. For this reason, when a large amount of gel is generated, the filter is clogged, and long-term continuous production of the film becomes difficult.
JP 2002-348388 A

  This invention is made | formed in view of said subject, Comprising: The objective is to provide a polyimide film with few gel defects.

As a result of intensive studies in view of the above-mentioned problems, the present inventors have uniquely found that the occurrence of gel defects can be suppressed by optimizing the mixing ratio of the polyamic acid solution and the imidization accelerator, and complete the present invention. It came to. That is, the above object can be achieved by the following novel polyimide film.
1) Add an imidization accelerator consisting of a dehydrating agent, an imidization catalyst, and a solvent to an organic solvent solution of polyamic acid, which is a polyimide precursor, and cast and dry the resulting dope solution on a support. When the weight of the polyamic acid organic solvent solution is 100, the weight of the imidization accelerator to be added is in the range of 30 to 75. A polyimide film characterized by
2) The polyimide film according to 1), wherein the viscosity of the organic solvent solution of the polyamic acid is 1000 to 3500 poise.
3) The number of moles of the dehydrating agent used for the imidization accelerator is 1.0 to 3.5 with respect to 1 mole of the amic acid unit present in the organic solvent solution of the polyamic acid. The polyimide film as described in 1) or 2).
4) The number of moles of the imidization catalyst used for the imidization accelerator is 0.3 to 1.5 with respect to the number of moles 1 of the amic acid unit present in the organic solvent solution of the polyamic acid. The polyimide film according to 1) to 3).
5) The polyimide film as described in 1) to 4), wherein the number of defects caused by poor mixing of the polyamic acid organic solvent solution and imidization accelerator is 2/1000 m ² or less.

  In the polyimide film of the present invention, the occurrence of gel defects is suppressed, so that problems such as repellency do not occur during adhesive coating, and a flexible copper-clad laminate can be obtained with high yield.

Embodiments of the present invention will be described below.
The polyimide film used in the present invention is manufactured using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid. Usually, the polyamic acid obtained by dissolving a substantially equimolar amount of an aromatic dianhydride and an aromatic diamine in an organic solvent is obtained. The organic solvent solution is produced by stirring under controlled temperature conditions until the polymerization of the acid dianhydride and the diamine is completed.
As the polymerization method, any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of polyamic acid is the order of addition of the monomers, and the physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any method of adding monomers may be used for the polymerization of polyamic acid. The following method is mentioned as a typical polymerization method. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent and this is reacted with a substantially equimolar amount of an aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Then, the method of superposing | polymerizing using an aromatic diamine compound so that an aromatic tetracarboxylic dianhydride and an aromatic diamine compound may become substantially equimolar in all the processes.
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize.
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar.
5) A method in which a substantially equimolar mixture of aromatic tetracarboxylic dianhydride and aromatic diamine is reacted in an organic polar solvent for polymerization.
And so on. These methods may be used singly or in combination.
In the present invention, the polyamic acid obtained by using any of the above polymerization methods may be used, and the polymerization method is not particularly limited.

In the present invention, it is also preferable to use a polymerization method for obtaining a prepolymer using a diamine component having a rigid structure typified by paraphenylenediamine or substituted benzidine. By using this method, a polyimide film having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained. The molar ratio of the diamine having a rigid structure and the acid dianhydride used in preparing the prepolymer in the present method is 100: 70 to 100: 99 or 70: 100 to 99: 100, and further 100: 75 to 100: 90 or 75: 100-90: 100 is preferable. When this ratio is less than the above range, it is difficult to obtain the effect of improving the elastic modulus and the hygroscopic expansion coefficient, and when it exceeds the above range, there are cases where the linear expansion coefficient becomes too small or the tensile elongation becomes small.
Here, the material used for the polyamic acid composition concerning this invention is demonstrated. Suitable acid dianhydrides that can be used in the present invention are pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetra Carboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride , Bis (3,4-dicarboxyphenyl) propane 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) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (Trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and the like, these alone or Any proportion of the mixture can be preferably used.
Among these acid dianhydrides, especially pyromellitic dianhydride and / or 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and It is preferable to use 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride.
Among these acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and / or 3,3 ′, 4,4 The preferred amount of '-biphenyltetracarboxylic dianhydride is 60 mol% or less, preferably 55 mol% or less, more preferably 50 mol% or less, based on the total acid dianhydride. 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and / or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride If the amount of use exceeds this range, the glass transition temperature of the polyimide film becomes too low, or the storage elastic modulus at the time of heating becomes too low and the film formation itself becomes difficult, which is not preferable.
Moreover, when using pyromellitic dianhydride, the preferable usage-amount is 40-100 mol%, More preferably, it is 45-100 mol%, Most preferably, it is 50-100 mol%. By using pyromellitic dianhydride in this range, the glass transition temperature and the storage elastic modulus at the time of heating can be easily maintained in a range suitable for use or film formation.
Suitable diamines that can be used in the polyimide precursor polyamic acid composition according to the present invention include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 3, 3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 4, 4'-diaminodiphenyl sulfone, 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane 4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphineoxy 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2- Diaminobenzene, bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′- Bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1, 3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone and the like Something similar.
If these diamines are classified into so-called rigid diamines such as diaminobenzenes and benzidines and diamines having flexible structures such as ether groups, sulfone groups, ketone groups and sulfide groups, rigid structures and flexible diamines are considered. The use ratio of the structural diamine is 80/20 to 20/80, preferably 70/30 to 30/70, particularly preferably 60/40 to 30/70, in molar ratio. If the use ratio of the rigid diamine exceeds the above range, the tensile elongation of the resulting film tends to be small, and if it falls below this range, the glass transition temperature becomes too low or the storage modulus during heat decreases. This is not preferable because it may cause adverse effects such as difficulty in film formation.
The polyimide film used in the present invention is obtained by appropriately determining the type and blending ratio of the aromatic dianhydride and aromatic diamine so as to be a film having desired characteristics within the above range. Can do.
As the preferred solvent for synthesizing the polyamic acid, any solvent can be used as long as it dissolves the polyamic acid. However, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N- Examples thereof include methyl-2-pyrrolidone, and N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.
Regarding the concentration of the polyamic acid solution at the time of synthesis, a lower concentration is preferable because the amount of the solvent contained in the polyamic acid solution increases and the mixing property with the imidization accelerator is improved. However, if the concentration is too low, it is difficult to produce a thick film. The concentration of the polyamic acid solution is preferably 5 to 30 wt%, and more preferably 10 to 20 wt%.
Moreover, about the viscosity of a polyamic-acid solution, since the lower one improves a miscibility with an imidation promoter, it is preferable. However, lowering the viscosity leads to lowering the molecular weight of the polyamic acid, so that the obtained fill may not exhibit desired physical properties. In consideration of ensuring both film properties and mixing properties, the viscosity of the polyamic acid solution is preferably 1000 to 3500 poise, and more preferably 1500 to 3000 poise. On the other hand, the viscosity of polyamic acid depends on the concentration. If the molecular weight is the same, the lower the concentration, the lower the viscosity. For this reason, the concentration of the polyamic acid may be adjusted to achieve a desired viscosity. However, in order to obtain a film having sufficient strength, the weight average molecular weight of the polyamic acid is preferably at least 100,000 or more.
In addition, a filler can be added for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.
The particle size of the filler is not particularly limited because it is determined by the film characteristics to be modified and the kind of filler to be added, but generally the average particle size is 0.05 to 100 μm, preferably 0.1. It is -75 micrometers, More preferably, it is 0.1-50 micrometers, Most preferably, it is 0.1-25 micrometers. If the particle size is below this range, the modification effect is less likely to appear. If the particle size is above this range, the surface properties may be greatly impaired or the mechanical properties may be greatly deteriorated. Further, the number of added parts of the filler is not particularly limited because it is determined by the film properties to be modified, the filler particle diameter, and the like. Generally, the addition amount of the filler is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight with respect to 100 parts by weight of the polyimide. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired. Addition of filler
1. 1. A method of adding to a polymerization reaction solution before or during polymerization 2. A method of kneading fillers using three rolls after completion of polymerization. Any method such as preparing a dispersion containing filler and mixing it with a polyamic acid organic solvent solution may be used. However, a method of mixing a dispersion containing filler with a polyamic acid solution, particularly mixing immediately before film formation. This method is preferable because the contamination by the filler in the production line is minimized. When preparing a dispersion containing a filler, it is preferable to use the same solvent as the polymerization solvent for the polyamic acid. Further, in order to disperse the filler satisfactorily and stabilize the dispersion state, a dispersant, a thickener and the like can be used within a range not affecting the film physical properties.
As a method for producing a polyimide film from these polyamic acid solutions, conventionally known methods can be used, and examples thereof include a thermal imidization method and a chemical imidation method. Is better.
The production process of the polyimide film by the chemical imidization method particularly preferable in the present invention is as follows.
a) a step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution;
b) a step of casting a dope solution containing the polyamic acid solution and the imidization accelerator on a support;
c) a step of peeling the gel film from the support after heating on the support;
d) further heating to imidize and dry the remaining amic acid,
It is preferable to contain.
In the above step, the imidization accelerator comprises a dehydrating agent typified by an acid anhydride, an imidization catalyst typified by a tertiary amine, and a solvent for dilution.
Examples of the dehydrating agent include aliphatic acid anhydrides, aromatic acid anhydrides, N, N′-dialkylcarbodiimides, lower aliphatic halides, halogenated lower aliphatic halides, halogenated lower fatty acid anhydrides, and arylphosphonic acid dihalogens. , Thionyl halides and the like can be used. Of these, aliphatic anhydrides such as acetic anhydride, propionic anhydride, and acetic anhydride can be preferably used.
As the imidization catalyst, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, or the like can be used. Among them, those selected from heterocyclic tertiary amines can be particularly preferably used. Specifically, quinoline, isoquinoline, β-picoline, pyridine and the like are preferably used.
The solvent for dilution is not particularly limited as long as both the dehydrating agent and the imidization catalyst are soluble, but the same solvent as used for the polymerization of the polyamic acid is used from the viewpoint of the miscibility with the polyamic acid solution. It is preferable to use it.
A dope solution is obtained by mixing the polyamic acid solution and the imidization accelerator, and a polyimide film is obtained by casting and drying the solution on a support. There is no particular limitation on the apparatus used when mixing the polyamic acid solution and the imidization accelerator, but in order to prevent defects such as perforations from occurring in the resulting film due to the mixing of bubbles, a closed mixer is used. It is preferable to use it. About the mixer rotation speed at the time of mixing, what is necessary is just to adjust suitably with the capacity | capacitance of a mixer and the flow rate of a varnish, but it keeps at the rotation speed of the grade which imidation is not accelerated | stimulated by heat of stirring.
When a high-viscosity solution and a low-viscosity solution are mixed, the larger the ratio of the low-viscosity solution, the lower the viscosity of the solution after mixing, so that the mixing tends to be easier. However, as a result of intensive studies, the present inventors have found that when the polyamic acid solution and the imidization accelerator are mixed, if the ratio of the low-viscosity solution exceeds a certain ratio, the mixture does not mix uniformly in time, It has been found that poor mixing tends to occur.
Here, the defect caused by the poor mixing in the present invention is, as described above, the fine particles of the polyamic acid remaining without the complete imidization or the local imidization first. It is the fine grain of the polyimide which has been done.
That is, in the present invention, in order to improve the mixing property of the polyamic acid and the imidization accelerator, the weight of the imidization accelerator to be added is 30 to 75 when the weight of the polyamic acid organic solvent solution is 100. It is important to keep it within range. Furthermore, it is preferable to suppress the weight of the imidization accelerator in the range of 45 to 70, and it is particularly preferable to suppress the weight in the range of 50 to 65. When the ratio of the imidization accelerator is less than the above range, the amount of the dehydrating agent or catalyst contained in the imidization accelerator is small, and thus imidation may not sufficiently proceed in the film baking step. Or, since the solvent is reduced without reducing the amount of the dehydrating agent and the catalyst, the concentration of the imidization accelerator is too high, the imidization proceeds locally, and the resulting polyimide film has gel defects. It may occur frequently or solidify in the worst case. On the contrary, when the ratio of the imidization accelerator is larger than the above range, the time required for mixing with the polyamic acid solution becomes long, so that the dope solution that is not uniformly mixed is cast on the support, and thus obtained. Gel defects may occur frequently in the polyimide film.
Regarding the amount of the dehydrating agent used for the imidization accelerator, the number of moles of the dehydrating agent is 1.0 to 3.5 with respect to the number of moles of the amic acid unit existing in the organic solvent solution of the polyamic acid. It is preferable to set it as 1.5-3.0. When the amount of the dehydrating agent is less than the above range, imidization does not proceed sufficiently and may break during firing or mechanical strength may decrease. When the dehydrating agent is added, the viscosity of the polyamic acid solution tends to increase. Therefore, if the amount of the dehydrating agent exceeds the above range, the viscosity of the dope solution increases excessively, resulting in poor mixing and resulting polyimide. Gel defects may occur frequently in the film.
Regarding the amount of the catalyst used for the imidization accelerator, the number of moles of the catalyst may be 0.3 to 1.5 with respect to the number of moles 1 of the amic acid unit present in the organic solvent solution of the polyamic acid. Preferably, it is 0.4 to 1.0. When the amount of the catalyst is less than the above range, imidization does not proceed sufficiently, and it may break during firing or mechanical strength may decrease. On the other hand, if the above range is exceeded, the imidization reaction proceeds rapidly even during mixing, and the accompanying gel defects may occur, or in the worst case, the dope solution may solidify and become impossible to cast. As for the imidation catalyst, the catalyst capacity varies depending on the structure, so the optimum addition amount varies depending on the type of catalyst, but no matter what catalyst is used, if the addition amount is adjusted to be within the above range, there is no problem. It is possible to use.
Hereafter, the preferable manufacturing process of the polyimide film in this invention is demonstrated. However, the present invention is not limited to the following examples. The film forming conditions and heating conditions can vary depending on the type of polyamic acid, the thickness of the film, and the like.
First, a film-forming dope is obtained by mixing an imidization accelerator in a polyamic acid solution at a low temperature. Subsequently, this film-forming dope is cast into a film on a support such as a glass plate, an aluminum foil, an endless stainless steel belt, or a stainless drum, and the temperature on the support is 80 ° C. to 200 ° C., preferably 100 ° C. to 180 ° C. By heating in the region, the dehydrating agent and imidization catalyst are activated to partially cure and / or dry and then peel from the support to obtain a polyamic acid film (hereinafter referred to as a gel film).
The gel film is in the intermediate stage of curing from polyamic acid to polyimide, has self-supporting properties, and has the formula (1)
(AB) × 100 / B (1)
(In Formula (1), A and B represent the following.
A: Weight of the gel film B: Weight after heating the gel film at 450 ° C. for 20 minutes)
The volatile content calculated from is in the range of 5 to 500% by weight, preferably 5 to 200% by weight, more preferably 5 to 150% by weight. It is preferable to use a film in this range. If the film deviates from this range, problems such as film breakage, film color unevenness due to uneven drying, and characteristic variations may occur in the baking process.

The end of the gel film is fixed and dried while avoiding shrinkage during curing, water, residual solvent, residual dehydrating agent and imidization catalyst are removed, and the remaining amic acid is completely imidized, The polyimide film of the invention is obtained.
At this time, it is preferable to finally heat at a temperature of 400 to 650 ° C. for 5 to 400 seconds. Above this temperature and / or for a long time, the film may suffer from thermal degradation and may cause problems. Conversely, if the temperature is lower than this temperature and / or the time is shorter, the predetermined effect may not be exhibited.
Moreover, in order to relieve the internal stress remaining in the film, heat treatment can be performed under the minimum tension necessary for transporting the film. This heat treatment may be performed in the film manufacturing process, or may be provided separately. The heating conditions vary depending on the characteristics of the film and the apparatus used, and therefore cannot be determined in general. The internal stress can be relaxed by heat treatment at a temperature of 450 ° C. or lower for 1 to 300 seconds, preferably 2 to 250 seconds, particularly preferably 5 to 200 seconds.

The polyimide film in the present invention can reduce the number of gel defects in the obtained polyimide film by optimizing the polyamic acid solution and the imidization accelerator as described above. Specifically, the number of gel defects generated can be 2/1000 m ² or less. Thereby, generation | occurrence | production of malfunctions, such as an adhesive repellency, can be suppressed in a subsequent adhesive agent coating process, and it becomes easy to process into CCL with a sufficient yield.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

  In addition, the evaluation method of the defect number of a polyimide film, a tensile elasticity modulus, a linear expansion coefficient, and adhesive repellency in an Example and a comparative example is as follows.

(Number of film defects)
The long film was run while illuminating with an incandescent lamp, and defects were confirmed through the polarizing plate. Among the confirmed defects, defects that appear dark (dark defects) are excluded because they are derived from foreign matters such as iron powder, and the details of the defects that appear bright (bright defects) were confirmed, and the number of gel defects was counted.

(Tensile modulus)
The tensile elastic modulus of the polyimide film was measured according to ASTM D882. In addition, the measurement was performed with respect to MD direction of a core film.
Sample measurement range: width 15mm, distance between grips 100mm
Tensile speed: 200 mm / min
(Linear expansion coefficient)
The linear expansion coefficient of the polyimide film is as follows: a thermomechanical analyzer manufactured by SII Nanotechnology, Inc., trade name: TMA / SS6100, once heated from 0 ° C. to 400 ° C., cooled to 10 ° C., and further 10 ° C./min. The average value within the range of 100 to 200 ° C. at the time of the second temperature increase was determined. In addition, the measurement was performed with respect to MD direction and TD direction of the core film.
Sample shape: width 3mm, length 10mm
Load: 29.4 mN
Measurement temperature range: 0 to 400 ° C
Temperature increase rate: 10 ° C / min
(Adhesive repellent)
In the film defect inspection, a flag serving as a mark was attached to the end of the film where the gel defect was confirmed.
Epicoat 1032H60 (manufactured by oil-based shell epoxy) was dissolved in tetrahydrofuran so as to have a solid concentration of 20% to prepare an epoxy solution.
The epoxy solution was continuously applied to the film with the above flag using a die coater, and the film was dried by passing through a hot air oven at 50 ° C. for 2 minutes.
About the obtained coating film, the presence or absence of the adhesive agent repelling of the location which the gel defect has generate | occur | produced was confirmed. The confirmation method was the same as the gel defect inspection.

(Synthesis Example 1: Synthesis of polyamic acid solution)
In a state where the reaction system was kept at 5 ° C., 10 mol% of 3,4′-diaminodiphenyl ether (hereinafter also referred to as 3,4′-ODA) was added to N, N-dimethylformamide (hereinafter also referred to as DMF). And 40 mol% of bis {4- (4-aminophenoxy) phenyl} propane (hereinafter also referred to as BAPP) were added and stirred. After visually confirming dissolution, 20 mol% of benzophenone tetracarboxylic dianhydride (hereinafter also referred to as BTDA) and 25 mol% of pyromellitic dianhydride (hereinafter also referred to as PMDA) were added for 30 minutes. Stirring was performed.

  Subsequently, 50 mol% of p-phenylenediamine (hereinafter also referred to as p-PDA) was added and stirred for 40 minutes. Subsequently, 52 mol% of PMDA was added and stirred for 30 minutes.

  Finally, a solution in which 3 mol% of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity. The polymerization was terminated when the viscosity of the polymer reached 2500 poise. The raw materials were added so that the solid content concentration of the solution was 17%.

Example 1 Synthesis of polyimide film
In the polyamic acid solution obtained in Synthesis Example 1, the number of moles of acetic anhydride and β-picoline was 2.2 and 0.6, respectively, relative to the number of moles of amic acid units, and the entire imidization accelerator Add an imidization accelerator with the amount of DMF adjusted so that the amount is 55% by weight with respect to the polyamic acid solution, continuously stir with a mixer, extrude from the T die and run 20 mm below the die. Cast on a stainless steel endless belt. This resin film is heated at 125 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 50% by weight) and fixed to a tenter clip, 230 ° C. × 30 seconds, 350 ° C. × 30 Second and 450 ° C. × 30 seconds to dry and imidize to obtain a polyimide film having a thickness of 18 μm.

Example 2 Synthesis of Polyimide Film
In the polyamic acid solution obtained in Synthesis Example 1, the number of moles of acetic anhydride and β-picoline was 2.2 and 0.6, respectively, relative to the number of moles of amic acid units, and the entire imidization accelerator Add an imidization accelerator with the amount of DMF adjusted so that the amount is 70% by weight with respect to the polyamic acid solution, continuously stir with a mixer, extrude from the T die and run 20 mm below the die. Cast on a stainless steel endless belt. The resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 50% by weight) and fixed to the tenter clip, 230 ° C. × 30 seconds, 350 ° C. × 30 Second and 450 ° C. × 30 seconds to dry and imidize to obtain a polyimide film having a thickness of 18 μm.

Example 3 Synthesis of polyimide film
In the polyamic acid solution obtained in Synthesis Example 1, the number of moles of acetic anhydride and β-picoline is 2.0 and 0.4, respectively, with respect to the number of moles of the amic acid unit, and the entire imidization accelerator Add an imidization accelerator with the amount of DMF adjusted so that the amount is 40% by weight with respect to the polyamic acid solution, continuously stir with a mixer, extrude from the T die and run 20 mm below the die. Cast on a stainless steel endless belt. This resin film is heated at 110 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 50% by weight) and fixed to a tenter clip, 230 ° C. × 30 seconds, 350 ° C. × 30 Second and 450 ° C. × 30 seconds to dry and imidize to obtain a polyimide film having a thickness of 18 μm.

(Comparative Example 1; synthesis of polyimide film)
In the polyamic acid solution obtained in Synthesis Example 1, the number of moles of acetic anhydride and β-picoline was 2.2 and 0.6, respectively, relative to the number of moles of amic acid units, and the entire imidization accelerator Add an imidization accelerator with the amount of DMF adjusted so that the amount is 80% by weight with respect to the polyamic acid solution, continuously stir with a mixer, extrude from the T die and run 20 mm below the die. Cast on a stainless steel endless belt. The resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 50% by weight) and fixed to the tenter clip, 230 ° C. × 30 seconds, 350 ° C. × 30 Second and 450 ° C. × 30 seconds to dry and imidize to obtain a polyimide film having a thickness of 18 μm.

(Comparative Example 2: Synthesis of polyimide film)
In the polyamic acid solution obtained in Synthesis Example 1, the number of moles of acetic anhydride and β-picoline was 2.2 and 0.6, respectively, relative to the number of moles of amic acid units, and the entire imidization accelerator Add an imidization accelerator with the amount of DMF adjusted so that the amount is 25% by weight with respect to the polyamic acid solution, continuously stir with a mixer, extrude from the T die and run 20 mm below the die. Cast on a stainless steel endless belt. This resin film is heated at 125 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 50% by weight) and fixed to a tenter clip, 230 ° C. × 30 seconds, 350 ° C. × 30 Second and 450 ° C. × 30 seconds to dry and imidize to obtain a polyimide film having a thickness of 18 μm. However, at 1 hour after the start of casting, the dope solution abnormally thickened and casting was impossible, and a long film sufficient to confirm gel defects could not be obtained.

  Table 1 shows the results of evaluating the properties of the polyimide films obtained in each of the examples and comparative examples.

比較例１ならびに２に示すように、イミド化促進剤の重量比が適切でない場合、フィルム物性に問題がなくても、ゲル欠陥が多発したり、長尺フィルムが得られないという問題が生じた。これに対し、実施例１〜３では、ゲル欠陥の発生を抑えたフィルムを得ることが出来た。

As shown in Comparative Examples 1 and 2, when the weight ratio of the imidization accelerator is not appropriate, there is a problem that gel defects occur frequently or a long film cannot be obtained even if there is no problem in film physical properties. . On the other hand, in Examples 1-3, the film which suppressed generation | occurrence | production of a gel defect was able to be obtained.

  Moreover, since the adhesive repellency occurred at the location where the gel defect occurred, the adhesive repellency occurred frequently in the film of Comparative Example 1 having a large number of gel defects. On the other hand, in the films of Examples 1 to 3 in which the number of gel defects generated was small, generation of cissing could be suppressed.

Claims (5)

Obtained by adding an imidization accelerator consisting of a dehydrating agent, an imidization catalyst and a solvent to an organic solvent solution of polyamic acid, which is a polyimide precursor, and casting and drying the resulting dope solution on a support. A polyimide film obtained by heat-treating a gel film, wherein the weight of the imidization accelerator to be added is in the range of 30 to 75 when the weight of the polyamic acid organic solvent solution is 100. And a polyimide film. The polyimide film according to claim 1, wherein the viscosity of the organic solvent solution of the polyamic acid is 1000 to 3500 poise. The number of moles of the dehydrating agent used for the imidization accelerator is 1.0 to 3.5 with respect to the number of moles of 1 of the amic acid unit present in the organic solvent solution of the polyamic acid. Item 3. The polyimide film according to Item 1 or 2. The number of moles of the imidization catalyst used for the imidization accelerator is 0.3 to 1.5 with respect to the number of moles of the amic acid unit present in the organic solvent solution of the polyamic acid, The polyimide film according to claim 1. 5. The polyimide film according to claim 1, wherein the number of defects caused by poor mixing of the polyamic acid organic solvent solution and imidization accelerator is 2/1000 m ² or less.