JP2017074714A - Production method of multilayer polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing crack which is generated when a metal-clad laminate is formed by arranging a metal foil on a multilayer polyimide film, and further a flexible printed wiring board is continuously manufactured by a roll-to-roll method.SOLUTION: A multilayer polyimide film is formed by laminating a thermoplastic polyimide layer including at least a thermoplastic polyimide on at least one face of a non-thermoplastic polyimide layer including at least a non-thermoplastic polyimide. A production method of the multilayer polyimide film comprises: forming a multilayer liquid film by simultaneously flow casting at least two kinds of solutions containing a polyimide precursor or a polyimide on a support medium; obtaining a multilayer self-supporting film by heat-treating the multilayer liquid film; and subsequently heat-treating the multilayer self-supporting film, in which a heat-treating step in a super-heated steam atmosphere is included.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a multilayer polyimide film. Specifically, the present invention relates to a method for producing a multilayer polyimide film that can suppress cracks that occur in the production process of a flexible printed wiring board when used as a material for producing a flexible printed wiring board.

  2. Description of the Related Art In recent years, electronic devices have been rapidly improved in performance, functionality, and miniaturization, and accordingly, there is an increasing demand for miniaturization and thinning of electronic components used in electronic devices. Further, the cost reduction is progressing, and the manufacturing process of the flexible printed wiring board (hereinafter also referred to as FPC) is changing from the conventional batch type to the roll-to-roll type processing method.

  Specifically, in the conventional FPC manufacturing process, each process such as development, etching treatment, and resist stripping is performed in a batch system. On the other hand, by continuously performing the three steps of development, etching treatment, and resist removal in a roll-to-roll manner, both high productivity and a reduction in personnel can be achieved, and cost reduction can be realized.

  The batch type FPC manufacturing process has the merit that fine conditions can be set for each process, but takes time and effort. On the other hand, in the roll-to-roll method, while cost reduction can be expected, if the processing time of one process becomes long, the processing time of the whole continuous process naturally increases, and it is difficult to make a small turn compared to the batch method, As a result, the thermal burden on the metal-clad laminate is also increased. In addition, the roll-to-roll method has a greater mechanical burden on the substrate than the batch method, such as the need to apply a certain level of tension to the substrate so as not to cause wrinkles during conveyance of the substrate. There is a case. In addition, there is a chemical burden derived from various chemicals in the etching process or the like in FPC processing, and a load is exerted on both a batch type and a roll-to-roll type.

  Conventionally, there have been reports on polyimides (for example, Patent Documents 1 and 2) in which resistance to an alkaline solution used in development, etching, and resist stripping processes is controlled.

  Moreover, in the manufacturing method of FPC, there exists a method of apply | coating and drying a polyimide-type resin to the metal foil with which copper foil is used frequently, obtaining a metal-clad laminated board, and also performing processes, such as an etching, and obtaining FPC. Recently, in the production of this metal-clad laminate, heat treatment with superheated steam has been proposed in place of the conventional heat treatment methods such as hot air drying and infrared drying. (For example, Patent Documents 3 and 4). These methods are recognized to have a certain effect in a casting method in which a metal-clad laminate is obtained by applying a polyimide resin layer to a metal foil and drying it.

Japanese Patent Laid-Open No. 06-120659 JP 2012-186377 A JP 2009-286093 A JP 2009-286095 A

  According to the study by the present inventors, a new problem that did not become a problem in the batch type FPC manufacturing process, that is, a problem that a crack occurs in the polyimide film of the base material in the roll-to-roll type FPC manufacturing process. Was found to occur.

  That is, the materials disclosed in Patent Documents 1 and 2 can withstand the process of continuously manufacturing FPCs by the roll-to-roll method as described above, even if there is no problem in the conventional batch-type FPC manufacturing process. It has been found that such a polyimide material has not been provided, and a polyimide material that does not crack after such a process has not been provided. In addition, the heat treatment method using superheated steam disclosed in Patent Documents 3 and 4 discloses a technique relating to a heat laminating method which is superior in terms of productivity of a metal-clad laminate, etc., than a casting method in which a resin layer is directly laminated on a metal foil. Not.

  That is, in the production of a multilayer polyimide film, (1) when heat treatment sufficient to sufficiently promote imidization of the polyamic acid which is a polyimide precursor is performed, the multilayer polyimide film, particularly the thermoplastic polyimide layer, is caused by an excessive thermal history. There is a problem that the multilayer polyimide film is deteriorated due to the oxidative decomposition reaction, and the adhesion to the metal foil is lowered. On the other hand, (2) when imidization is performed under relatively mild heat treatment conditions in which no oxidative decomposition reaction occurs, the non-thermoplastic polyimide may be insufficiently agglomerated, and as a result, under a tensile load in the FPC manufacturing process. It becomes a factor which the crack in a multilayer polyimide film under an alkaline condition generate | occur | produces.

  This invention is made | formed in view of the said subject, The objective is to provide the multilayer polyimide film suitable for a thermal laminating method in the process of laminating | stacking with metal foil. Another object is to provide a multilayer polyimide film that does not crack even when exposed to the harsh environment in the manufacturing process of FPC. Specifically, when a metal foil is laminated on a multilayer polyimide film to form a metal-clad laminate, and when FPC is continuously produced in a roll-to-roll manner, sufficient adhesion with copper foil can be expressed. it can. In addition, an object of the present invention is to provide a method for producing a multilayer polyimide film capable of suppressing the generation of cracks even under alkaline treatment conditions in a roll-to-roll system.

That is, this invention can solve the said subject with the manufacturing method of the following novel multilayer polyimide films.
1) After a polyimide precursor or a polyimide-containing solution is simultaneously cast on a support to form a multilayer liquid film, the multilayer liquid film is heat-treated to form a multilayer self-supporting film The present invention relates to a method for producing a multilayer polyimide film, which comprises heat-treating the multilayer self-supporting film in a superheated steam atmosphere.
2) At least one of a multilayer self-supporting film having a residual solvent amount of 31 wt% to 150 wt% or a multilayer polyimide film having a residual solvent amount of 0.01 wt% to 30 wt% is heat-treated in a superheated steam atmosphere. The manufacturing method of the multilayer polyimide film characterized by including the process of performing.
3) The multilayer polyimide film is a multilayer polyimide film in which a thermoplastic polyimide layer containing at least a thermoplastic polyimide is laminated on at least one surface of a non-thermoplastic polyimide layer containing at least a non-thermoplastic polyimide. It relates to the manufacturing method.

  The multilayer polyimide film obtained by the production method of the present invention exhibits sufficient adhesion to the metal foil, is tensioned, and does not generate cracks even when exposed to a severe environment under alkaline conditions. If the multilayer polyimide film obtained by the manufacturing method of this invention is used, the productivity in the processing process of FPC using a metal-clad laminated board can be improved.

It is a figure which shows the test piece used by the cracking-resistance test of this invention.

  One embodiment of the present invention will be described below. However, this invention is not limited to this, It can implement in the aspect which added the various deformation | transformation within the described range.

  Unless otherwise specified in this specification, “A to B” indicating a numerical range means “A or more and B or less”.

  The present invention relates to a method for producing a multilayer polyimide film in which a multilayer polyimide film is formed by laminating a thermoplastic polyimide layer containing at least a thermoplastic polyimide on at least one surface of a non-thermoplastic polyimide layer containing at least a non-thermoplastic polyimide.

(Multilayer polyimide film)
The multilayer polyimide film in the present invention refers to a laminate in which a thermoplastic polyimide layer containing at least a thermoplastic polyimide is laminated on at least one surface of a non-thermoplastic polyimide layer containing at least a non-thermoplastic polyimide.

  The non-thermoplastic polyimide in the present invention is a polyimide that retains its shape without wrinkling or stretching when heated at 450 ° C. for 1 minute, when the film obtained when formed alone is formed. Say.

  The thermoplastic polyimide in the present invention refers to a polyimide that does not retain its shape when wrinkled or stretched when heated at 450 ° C. for 1 minute.

(Non-thermoplastic polyimide)
The aromatic dianhydride used as a raw material of the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer of the multilayer polyimide film is not particularly limited. For example, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6 -Naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic 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-dicarboxy Enyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylene bis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid mono Ester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and derivatives thereof, and mixtures thereof alone or in any proportion can be exemplified.

  Among these, from the group consisting of pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride Preferably, it is at least one acid dianhydride selected, and in terms of solvent solubility during production, pyromellitic acid dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride Is more preferable.

  The aromatic diamine used as a raw material for the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer of the multilayer polyimide film is not particularly limited. For example, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 1 , 4-bis (4-aminophenoxy) benzene, p-phenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine (4,4′-diaminobiphenyl), 3,3′- Dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4 ′ -Diaminodiphenyl ether, 1,5-diaminonaphthalene, 4 4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl-N-methylamine, 4,4'-diaminobiphenyl-N -Methylamine, 4,4'-diaminodiphenyl-N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, 2,2-bis [ 4- (4-aminophenoxy) phenyl] propane, 4,4′-bis (4-aminophenoxy) biphenyl, and derivatives thereof are exemplified, and examples thereof include a mixture of these alone or in an arbitrary ratio. be able to.

  Among these, the diamine constituting the non-thermoplastic polyimide is 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenyl ether, 4 in terms of forming a thermoplastic block. , 4′-bis (4-aminophenoxy) biphenyl is preferably used, and p-phenylenediamine is preferably used in terms of controlling the linear expansion coefficient and strength.

  It should be noted that the non-thermoplastic polyimide contains a thermoplastic block component, that is, the polyamic acid that becomes the non-thermoplastic polyimide layer is a polyamic acid that is a precursor of the non-thermoplastic polyimide having a thermoplastic block component in the molecule. A certain thing is preferable at the point which can improve the adhesiveness of a non-thermoplastic polyimide and a thermoplastic polyimide.

(Thermoplastic polyimide)
The aromatic dianhydride used as a raw material for the thermoplastic polyimide contained in the thermoplastic polyimide layer is not particularly limited. For example, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6 -Naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic 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-dicarboxy Enyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylene bis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid mono Ester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and derivatives thereof, and mixtures thereof alone or in any proportion can be exemplified.

  Among these, from the group consisting of pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride Preferably, the acid dianhydride is at least one selected, and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used in terms of increasing the copper foil peeling strength of the metal-clad laminate. It is preferable that pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dicarboxylic acid are used in order to improve solder heat resistance while increasing the peeling strength of the copper foil of the metal-clad laminate. It is preferable to use an anhydride in combination.

  The aromatic diamine used as a raw material for the thermoplastic polyimide contained in the thermoplastic polyimide layer is not particularly limited. For example, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 1 , 4-bis (4-aminophenoxy) benzene, p-phenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine (4,4′-diaminobiphenyl), 3,3′- Dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4 ′ -Diaminodiphenyl ether, 1,5-diaminonaphthalene, 4 4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl-N- Phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4, Examples thereof include 4′-bis (4-aminophenoxy) biphenyl and derivatives thereof, and examples thereof include a mixture of these alone or in an arbitrary ratio.

  Among these, 2,2-bis [4- (4-aminophenoxy) phenyl] propane and 4,4′-bis (4-aminophenoxy) biphenyl constituting thermoplastic polyimide are metal foils of metal-clad laminates. This is preferable in terms of improving the peeling strength.

  As the preferred solvent for producing the polyamic acid in the present invention, any solvent that dissolves the polyamic acid can be used. For example, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like can be exemplified. Of these, N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.

In the present invention, any method for adding a monomer may be used for producing the polyamic acid. As typical polymerization methods, the following methods may be mentioned. 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 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. Subsequently, a method of polymerizing with an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps,
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 of polymerizing by reacting a mixture of substantially equimolar aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent,
And so on. These methods may be used singly or in combination.

Especially, it is preferable that the polyamic acid of a non-thermoplastic polyimide layer is obtained by the following process (i)-(iii).
(I) a step of reacting an aromatic acid dianhydride with an excess molar amount of an aromatic diamine in an organic polar solvent to obtain a prepolymer having amino groups at both ends;
(Ii) Subsequently, an additional step of adding an aromatic diamine here,
(Iii) Further, a step of adding and polymerizing the aromatic dianhydride so that the aromatic dianhydride and the aromatic diamine in all steps are substantially equimolar to obtain a polyamic acid solution.

  Among the above methods, the prepolymer obtained in (i) is preferably a thermoplastic block component. Determination of whether a prepolymer is a thermoplastic block component can be performed as follows.

  Correct the acid dianhydride and diamine used in the preparation of the prepolymer to equimolar amounts (if there are multiple types of acid dianhydrides used, the ratio is fixed, and the diamine used is multiple types) (The ratio was fixed.) The obtained polyamic acid solution was cast on an aluminum foil using a comma coater, heated at 130 ° C. for 100 seconds, and then a self-supporting gel film was drawn from the aluminum foil. Remove and fix to metal frame. Then, when it heat-processes at 300 degreeC * 20 second and 450 degreeC * 1 minute, when a film softens or fuse | melts and the external appearance has changed, it determines with a thermoplastic block component.

The method for producing thermoplastic polyamic acid of thermoplastic polyimide is as follows:
(I) a step of reacting an aromatic acid dianhydride with an excess molar amount of an aromatic diamine in an organic polarity to obtain a prepolymer having amino groups at both ends;
(Ii) Subsequently, a process of adding and polymerizing the aromatic acid dianhydride so that the ratio of the aromatic acid dianhydride and the aromatic diamine in the entire process becomes a determined ratio to obtain a polyamic acid solution. ,
Is preferred.
In (ii), there are a method of adding an aromatic acid dianhydride, a method of adding a powder, a method of adding an acid solution in which an acid dianhydride is dissolved in an organic polar solvent in advance, and the reaction is uniform. In view of easy progress, a method of adding an acid solution is preferable.

  The solid component concentration during synthesis of these polyamic acids is preferably 10 to 30% by weight.

  In addition, a filler can be added for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, and corona resistance. The filler is not particularly limited, and preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

  The polyimide is obtained by a dehydration conversion reaction from a polyimide precursor, that is, polyamic acid. As a method for carrying out the dehydration conversion reaction, a thermal curing method using only heat and a chemical curing method using a chemical dehydrating agent are widely known, and these can be selected as appropriate. Since it is excellent in productivity, it is preferable to employ a chemical curing method. In both the thermal curing method and the chemical curing method, it is preferable to use an imidization catalyst in terms of advancing the imidization reaction quickly.

  A chemical dehydrating agent is a dehydrating ring-closing agent for polyamic acid, and the main components thereof are aliphatic acid anhydride, aromatic acid anhydride, N, N′-dialkylcarbodiimide, lower aliphatic halide, halogenated lower fat. An aromatic acid anhydride, an aryl sulfonic acid dihalide, a thionyl halide, or a mixture of two or more thereof can be preferably used. Of these, aliphatic acid anhydrides and aromatic acid anhydrides work particularly well. The imidation catalyst is a component having an effect of promoting the dehydration ring-closing action of the curing agent on the polyamic acid. For example, an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine is used. Can do. Of these, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, or β-picoline are preferred. Furthermore, adding an organic polar solvent to at least one of the chemical dehydrating agent or the imidization catalyst may be appropriately selected.

(Multilayer polyimide film)
The multilayer polyimide film of the present invention may have any number of layers and is not particularly limited. For example, the outermost layer of a multilayer polyimide film used for a metal-clad laminate is preferably a thermoplastic polyimide so that a metal foil can be laminated. Moreover, in order to suppress the heat shrinkage rate of the multilayer polyimide film and make it comparable to metal, it is preferable that the layers other than the outermost layer of the multilayer polyimide film are non-thermoplastic polyimides, but they are limited to these structures. is not. Moreover, it is preferable to keep the total number of layers in the multilayer polyimide film to a minimum from the viewpoint of equipment, cost, and productivity. In order to suppress curling of the multilayer polyimide film, it is preferable to have three layers. As a result of these, a multilayer polyimide film having a three-layer structure in which thermoplastic polyimide is disposed on both sides of a non-thermoplastic polyimide can produce a metal-clad laminate, particularly a double-sided metal-clad laminate, and reduce the weight and size of the FPC. This is particularly preferable in terms of realizing high density.

  The thickness of the multilayer polyimide film is preferably 7.5 μm to 125 μm. The thickness of the thermoplastic polyimide layer on at least one side of the non-thermoplastic polyimide layer in the multilayer polyimide film is preferably 1.7 μm to 35 μm. If the thickness of the thermoplastic polyimide layer is within this range, the adhesion to the surface of the metal foil will be good, and the dimensional change rate when producing FPC by etching the metal foil after forming the metal-clad laminate will also be good. Become. The thickness of the thermoplastic polyimide layer is more preferably 1.7 μm to 10 μm, further preferably 1.7 μm to 8 μm.

(Manufacturing method of multilayer polyimide film)
The production method of the multilayer polyimide film in the present invention is not particularly limited as long as an intended product can be produced, and various methods can be mentioned. For example,
(A) A polyimide precursor or a solution containing polyimide is simultaneously cast on a support to form a multilayer liquid film,
(B) After heat-treating the multilayer liquid film to form a multilayer self-supporting film,
(C) The manufacturing method of the multilayer polyimide film which heat-processes the said multilayer self-supporting film is mentioned.

(Formation of multilayer liquid film)
The step of forming a multilayer liquid film by casting (a) a polyimide precursor or a polyimide-containing solution on the support at the same time in the present invention will be described.

  As a method for producing a multilayer polyimide film, it is preferable to simultaneously cast several types of polyamic acid solutions on a support by a multilayer coextrusion die to form a multilayer liquid film.

  As the multilayer coextrusion die, those having various structures can be used. For example, a multilayer T die capable of creating a multilayer film can be used. In addition, any conventionally known structure can be suitably used, and feed block T dies and multi-manifold T dies are exemplified as particularly suitable ones.

  In the step (a) in the present invention, a solution in which at least one of a chemical dehydrating agent or an imidization catalyst is mixed as necessary with a solution containing polyamic acid which is a polyimide precursor is obtained, and this solution is used as a support. It is cast and coated on top to obtain a multilayer liquid film.

(Formation of multilayer self-supporting film)
In the present invention, (b) a step of heat-treating the multilayer liquid film to form a multilayer self-supporting film will be described.

  The multilayer liquid film is cast on a support such as a drum or an endless belt, and then subjected to a heat treatment temperature on the support to obtain a multilayer self-supporting film.

  The heat treatment temperature on the support is preferably 100 ° C. to 160 ° C., although it depends on the thickness of the resulting multilayer liquid film. Thereafter, the gel film in a liquid film state from which the solvent has been removed to some extent is peeled from the support to obtain a multilayer self-supporting film.

The self-supporting film peeled off from the support is in an intermediate stage of curing from polyamic acid to polyimide and has self-supporting properties. Moreover, Formula (1)
(AB) × 100 / B (1)
In formula (1), A and B represent the following.
A: Weight of the multilayer film B: The residual solvent amount calculated from the weight after heating the multilayer film at 350 ° C. for 10 minutes is preferably 5% by weight to 150% by weight, and 10% by weight to 100% by weight. More preferably, it is more preferably 30% by weight to 80% by weight. By setting the volatile content within this range, it is preferable in that it is possible to suppress problems such as film breakage, uneven color tone of the film due to uneven drying, and variation in characteristics. Further, for the purpose of improving the melt fluidity of the thermoplastic polyimide layer, the imidization rate may be intentionally lowered or the solvent may be left.

(Process to heat treat multilayer self-supporting film)
In the present invention, (c) the step of heat-treating the multilayer self-supporting film to advance an imidization reaction to obtain a multilayer polyimide film will be described.

  In the present invention, the multilayer self-supporting film obtained in the step (b) is peeled off from the support, and the end of the multilayer self-supporting film is fixed by a gripping member such as a clip, a chuck or a pin. While avoiding shrinkage in the width direction of the film, it is transported through a heating furnace to remove residual solvent, water, chemical dehydrating agent, imidization catalyst, etc., and the remaining amic acid is completely imidized to form a multilayer polyimide film. obtain.

  As the heat treatment method in the step (c), a known method can be applied to remove the solvent remaining in the multilayer self-supporting film as long as the polyimidization can proceed from the polyamic acid. Examples thereof include hot air drying and infrared drying.

  At this time, the method and conditions for obtaining the multilayer polyimide film by firing the multilayer self-supporting film are not particularly limited, and any method or condition that allows the self-supporting film to be effectively heat-treated and fired into the multilayer polyimide film. That's fine. For example, a method in which hot air is sprayed from the upper surface or lower surface of the film, or both surfaces to heat the film, or a method in which far infrared rays are irradiated on the film can be suitably used. The firing temperature in the firing step is not particularly limited as long as the necessary minimum imidization can be completed and the remaining components can be sufficiently removed, but is preferably 200 ° C to 400 ° C. . The firing time is not particularly limited, and the firing can be performed within a conventionally known range.

  Moreover, the imidation process can also be performed in the form of post-baking in a separate process from the manufacturing process of a normal multilayer polyimide film. Examples of the heating method include a method in which a sheet that has been drawn out and cut into a sheet is placed in a batch-type oven, a method in which the material is heated while being conveyed again into a heat treatment furnace by roll-to-roll, and the like. However, the present invention can be carried out within a conventionally known range.

(Heat treatment under superheated steam atmosphere)
In the present invention, at least two kinds of polyimide precursors or polyimide-containing solutions are simultaneously cast on a support to form a multilayer liquid film, and the multilayer liquid film is heat treated to produce a multilayer self-supporting film. After that, a method for producing a multilayer polyimide film in which the multilayer self-supporting film is heat-treated, which includes a step of performing a heat treatment in a superheated steam atmosphere. In any step, heat treatment can be performed in a superheated steam atmosphere, but the amount of residual solvent is 31% by weight to 150% by weight, or the amount of residual solvent is 0.01% by weight. It is preferable to heat-treat at least one of the multilayer polyimide film of ˜30 wt% in a superheated steam atmosphere. In the case of a multilayer self-supporting film, it is more preferably 35% by weight to 100% by weight, and further preferably 40% by weight to 80% by weight. When the amount of the remaining solvent is within this range, if heat treatment is performed in a superheated steam atmosphere, it is possible to suppress a decrease in molecular weight or the like with respect to the properties of polyimide that is easily hydrolyzed. In the case of a multilayer polyimide film, it is more preferably 0.1% by weight to 20% by weight, further preferably 0.5% by weight to 10% by weight, and 1% by weight to 5% by weight. Is particularly preferred. When the residual solvent amount is in this range, the heat treatment in the superheated steam atmosphere makes it possible to promote the agglomeration of the polyimide more efficiently.

  By appropriately selecting the conditions for the film-forming process, the deterioration of the original physical properties derived from the primary structure of the polyimide is prevented, and by controlling the higher-order structure due to the agglomeration of the polyimide in the heat treatment process, continuous A multilayer polyimide film in which the generation of cracks is suppressed even when it is used for the production of an FPC can be obtained. The conventionally known method of introducing superheated steam in the production process of a metal-clad laminate is for a single-layer polyimide film, and is effective for pre-treatment of thermocompression bonding and efficient drying and removal of residual solvent in the film. In contrast, the present invention performs heat treatment in a superheated steam atmosphere for the purpose of controlling the higher-order structure of the polyimide of the multilayer polyimide film.

  In the present invention, the temperature of the heat treatment step in the superheated steam atmosphere is set higher than the maximum temperature of the other steps of peeling the multilayer self-supporting film and transporting the inside of the heating furnace among the manufacturing steps of the multilayer polyimide film. It is preferable to do. In the case where the temperature of the heat treatment step in the superheated steam atmosphere is set high, a temperature that is 20 ° C. to 120 ° C. higher than other temperatures transported in the heating furnace can be exemplified, although it depends on the multilayer polyimide film to be handled. Alternatively, it is preferable to set the time of the heat treatment step in the superheated steam atmosphere longer than the time of peeling off the multilayer self-supporting film and heating in another step of transporting the inside of the heating furnace. When setting the time of the heat treatment step in the superheated steam atmosphere to be long, depending on the multilayer polyimide film to be handled and the heating temperature, the time is 0.1 to 90 minutes longer than the other time of transporting in the heating furnace. it can. 0.1 to 60 minutes is more preferable, and 0.1 to 30 minutes is particularly preferable.

  The effect of the heat treatment process in the superheated steam atmosphere is the effect of the co-extrusion method especially in the multilayer polyimide film having the thermoplastic polyimide layer, which has restrictions on the film forming conditions such as the temperature in the film forming process cannot be extremely high. In the multilayer polyimide film manufactured and formed using it, it is remarkably exhibited.

  Heat transfer by hot air such as air or nitrogen gas in the atmosphere is limited to convection heat transfer and is heated in order from the surface, so when paying attention to the film surface, as a result of thermal decomposition due to excessive heating, copper foil and There is a possibility that the adhesion strength of the material will decrease. On the other hand, heat treatment with superheated steam is not limited to convective heat transfer, but is based on a composite heat transfer of radiant heat transfer and heat of condensation of water vapor, and has high thermal efficiency. Above all, considering that the high-temperature water vapor that touched the film surface is condensed and turned into water, the film surface is kept at a temperature of about 100 ° C. It is considered that the thermal decomposition of is suppressed as much as possible.

(Metal-clad laminate)
The multilayer polyimide film of the present invention suppresses cracking when a metal foil is laminated thereon to form a metal-clad laminate, and further when FPC is continuously produced in a roll-to-roll manner using the metal-clad laminate. be able to. When the multilayer polyimide film is a film in which a thermoplastic polyimide layer is formed on at least one surface of a non-thermoplastic polyimide layer, a metal-clad laminate can be produced particularly easily and continuously.

  The metal foil used in the present invention is not particularly limited, and any metal foil can be used. For example, copper, stainless steel, nickel, aluminum, and alloys of these metals can be suitably used. In general metal-clad laminates, copper foils such as rolled copper foil and electrolytic copper foil are frequently used. However, it is preferable to use these in the present invention.

  Moreover, the said metal foil can select what has various characteristics, such as surface treatment and surface roughness, according to the objective. Furthermore, a rust preventive layer, a heat resistant layer or an adhesive layer may be applied to the surface of the metal foil. The thickness of the metal foil is not particularly limited, and may be any thickness that can exhibit a sufficient function depending on the application.

  The thickness of the metal foil used in the metal-clad laminate is not particularly limited as long as it can be used as an FPC. For example, it is preferable to use a metal foil having a thickness of 1 μm to 25 μm.

  As a method for laminating the multilayer polyimide film and the metal foil, for example, a hot roll laminating apparatus having a pair of metal rolls or a continuous process using a double belt press (DBP) can be used. Among these, it is preferable to use a hot roll laminating apparatus having a pair of metal rolls because the apparatus configuration is simple and advantageous in terms of maintenance cost.

  In order to obtain the metal-clad laminate according to the present invention, it is preferable to use a thermal laminating apparatus that continuously press-bonds the material to be laminated while heating. Further, in this thermal laminating apparatus, a laminated material feeding means for feeding the laminated material may be provided before the thermal laminating means, or a laminated material winding for winding the laminated material is taken after the thermal laminating means. Means may be provided. By providing these means, the productivity of the thermal laminating apparatus can be further improved.

(Manufacturing of FPC)
In order to continuously produce FPCs using the metal-clad laminate thus obtained, the main three steps of the development step, the etching treatment step, and the resist stripping step are continuously performed in a roll-to-roll manner. The developer used in the development process varies depending on the type of resist, but a sodium carbonate-based alkaline aqueous solution is generally used. The developing operation is performed by spraying the solution, and the spray nozzle is uniformly applied to the resist surface by shaking left and right. In the etching process, it is common to dissolve the metal by spraying the etchant from the top and bottom of the circuit board, but again here, iron chloride, copper chloride, and alkaline solutions are mainly used as the etchant. The The stripping process is also performed by spraying a stripping solution as in the development and etching, and an alkaline aqueous solution is used as the stripping solution.

  In this way, in the FPC manufacturing process adopted in recent years, polyimide is in contact with alkali for a long time, and the substrate is tensioned in the longitudinal direction. Further, the circuit board is sprayed with the chemical solution in each process. In this state, repeated stress is applied in the thickness direction. The multilayer polyimide film of the present invention is suitable for continuously producing FPC because cracks do not occur even when these harsh processes are passed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In addition, the lamination | stacking method and evaluation method of a multilayer polyimide film and metal foil in a synthesis example, an Example, and a comparative example are as follows.

(Non-thermoplastic / thermoplastic determination of polyimide)
The polyamic acid solution obtained in each synthesis example was cast on an aluminum foil using a comma coater and heated at 130 ° C. for 100 seconds. Thereafter, the single-layer self-supporting film was peeled off from the aluminum foil and fixed to the metal frame. If heat treatment is performed at 300 ° C. for 20 seconds and 450 ° C. for 1 minute, the film does not melt and the appearance does not deform, it is determined that it is a non-thermoplastic polyimide. It was determined that it was a plastic polyimide.

(Method for producing metal-clad laminate)
A 12 μm electrolytic copper foil (3EC-M3S-HTE (K); manufactured by Mitsui Mining & Mining) on both sides of the multilayer polyimide film, and protective materials (Apical 125 NPI; manufactured by Kaneka) are arranged on both sides. Thus, a metal-clad laminate was produced by continuous thermal lamination under conditions of a lamination temperature of 360 ° C., a lamination pressure of 265 N / cm (27 kgf / cm), and a lamination speed of 1.0 m / min.

(Stripping strength of metal foil)
According to JIS C6471, “6.5 Peeling Strength”, a sample was prepared, a 1 mm wide metal foil portion was peeled off at a peeling angle of 90 degrees and 50 mm / min, and the load was measured. The peel strength is preferably 10 to 20 N / cm.

(Break resistance test)
The film was cut out from three points at both ends and the center of the film, and each was used as a metal-clad laminate. A metal-clad laminate is cut to a size of 6.0 cm × 5.5 cm square, and a part of the metal foil is etched into a lattice shape (lattice size: 1.3 cm × 1.5 cm) as shown in FIG. A specimen was obtained. The test piece is put in a container containing 800 mL of 4% sodium hydroxide aqueous solution (23 ± 2 ° C.) and shaken at 23 ± 2 ° C. at a shaking speed of 230 rpm (ST). Measured and used as a crack resistance test. After etching, it was confirmed with an optical microscope that the radius of curvature inside each corner of the lattice was 50 μm or less, and a specimen having a radius of 50 μm or less was used. This test piece was put into a sodium hydroxide aqueous solution. The presence or absence of a crack was judged as a crack when shaking was stopped every 100 seconds, light was applied to each container containing the test piece with a light box, and light was transmitted through the test piece. ST is preferably 900 seconds or more in order to suppress cracks in the process of continuously producing FPC.

The abbreviations of the monomers used in the synthesis examples are shown below.
DMF: N, N-dimethylformamide BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane ODA: 4,4′-diaminodiphenyl ether PDA: p-phenylenediamine BAPB: 4,4′-bis (4-Aminophenoxy) biphenyl BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride BTDA: 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride PMDA: pyromellitic acid The dianhydride Below, the synthesis example of a polyamic-acid solution is shown.

(Synthesis Example 1)
BAPP (57.3 g: 0.140 mol) and ODA (18.6 g: 0.093 mol) were dissolved in DMF (1137.4 g) cooled to 10 ° C. BTDA (30.0 g: 0.093 mol) and PMDA (25.4 g: 0.116 mol) were added thereto, and the mixture was stirred uniformly for 30 minutes to obtain a prepolymer. After PDA (25.2 g: 0.233 mol) was dissolved in this solution, PMDA (50.7 g: 0.233 mol) was dissolved, and a 7.2 wt% DMF solution of PMDA prepared separately was carefully added to the solution. 0.5 g (PMDA: 0.023 mol) was added, and the addition was stopped when the viscosity reached about 2500 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution having a rotational viscosity at 23 ° C. of 2600 poise. As a result of the determination of the non-thermoplasticity and thermoplasticity of the single-layer polyimide film using the polyamic acid solution, the film did not melt and the appearance did not deform. Therefore, the polyimide of Synthesis Example 1 is a non-thermoplastic polyimide. It was determined.

  The polyamic acid solution synthesized in equimolar amounts of acid dianhydride and diamine, which was used when producing the prepolymer, was cast on an aluminum foil using a comma coater, and 130 ° C. × 100 seconds. After heating, the self-supporting gel film was peeled off from the aluminum foil and fixed to the metal frame. Thereafter, when heat treatment was performed at 300 ° C. for 20 seconds and 450 ° C. for 1 minute, the film was melted and the appearance was deformed. Therefore, the block component of Synthesis Example 1 was determined to be a thermoplastic block component.

(Synthesis Example 2)
ODA (72.2 g: 0.360 mol) was dissolved in DMF (1639.2 g) cooled to 10 ° C. BPDA (63.6 g: 0.216 mol) and BTDA (34.8 g: 0.108 mol) were added thereto, and the mixture was stirred uniformly for 45 minutes to obtain a prepolymer. After dissolving ODA (8.66 g: 0.043 mol) and PDA (34.3 g: 0.317 mol) in this solution, PMDA (81.7 g: 0.375 mol) was dissolved, and PMDA which was separately prepared was dissolved. Then, 65.5 g (PMDA: 0.022 mol) of 7.2% by weight DMF solution was carefully added, and the addition was stopped when the viscosity reached about 2500 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution having a rotational viscosity at 23 ° C. of 2600 poise. As a result of the determination of non-thermoplasticity and thermoplasticity of the single-layer polyimide film using the polyamic acid solution, the film did not melt and the appearance was not deformed. Therefore, the polyimide of Synthesis Example 2 is a non-thermoplastic polyimide. It was determined.

  The polyamic acid solution synthesized in equimolar amounts of acid dianhydride and diamine, which was used when producing the prepolymer, was cast on an aluminum foil using a comma coater, and 130 ° C. × 100 seconds. After heating, the self-supporting gel film was peeled off from the aluminum foil and fixed to the metal frame. Thereafter, when heat treatment was performed at 300 ° C. for 20 seconds and 450 ° C. for 1 minute, the film was melted and the appearance was deformed. Therefore, the block component of Synthesis Example 2 was determined to be a thermoplastic block component.

(Synthesis Example 3)
BAPP (118.6 g: 0.289 mol) was dissolved in 861.2 g of N, N-dimethylformamide (DMF). BPDA (12.8 g: 0.043 mol) was added thereto, heated to 50 ° C., cooled to 10 ° C., and PMDA (50.4 g: 0.231 mol) was added to obtain a prepolymer. Thereafter, 40.5 g (PMDA: 0.013 mol) of a 7% by weight PMDA solution separately prepared was carefully added to obtain a polyamic acid solution having a solid component concentration of about 17% and an 800 poise viscosity at 23 ° C. . Thereafter, DMF was added to obtain a polyamic acid solution having a solid component concentration of 14% by weight. As a result of the determination of the non-thermoplasticity and thermoplasticity of the single-layer polyimide film using the polyamic acid solution, the appearance of the film was melted and the appearance was deformed. Therefore, the polyimide of Synthesis Example 3 was determined to be a thermoplastic polyimide. .

(Synthesis Example 4)
After dissolving BAPB (26.5 g: 0.072 mol) and BPDA (17.6 g: 0.060 mol) in 902.0 g of N, N-dimethylformamide (DMF), BAPP (68.9 g: 0.168 mol) Was dissolved. PMDA (36.6 g: 0.168 mol) was added thereto, and 28.3 g (PMDA: 0.0094 mol) of a 7.2 wt% DMF solution of PMDA, which had been separately prepared, was added carefully to obtain a solid component. A 300 poise polyamic acid solution was obtained at a concentration of about 14% and a viscosity of 23 ° C. As a result of the determination of non-thermoplasticity and thermoplasticity of the single-layer polyimide film using the polyamic acid solution, the appearance of the film was melted and the appearance was deformed. Therefore, the polyimide of Synthesis Example 4 was determined to be a thermoplastic polyimide. .

Example 1
A curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 3.5: 1.0: 7.2) was added to the polyamic acid solution obtained in Synthesis Example 1 at a weight ratio of 50% with respect to the polyamic acid solution. Then, after stirring with a mixer, the three-layer coextrusion die was supplied to the central layer, and the polyamic acid solution obtained in Synthesis Example 3 was supplied to both sides of the central layer. The resin film was extruded through a stainless steel endless belt at 120 ° C. for 80 seconds to obtain a self-supporting film. After peeling off this self-supporting film from the belt, both ends are fixed with pins, dried and imidized at 270 ° C. × 12 seconds, 300 ° C. × 12 seconds, 350 ° C. × 10 seconds, 320 ° C. × 35 seconds, The thickness of the plastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer was 2 μm / 8.5 μm / 2 μm, resulting in a three-layer polyimide film. The amount of residual solvent in the obtained three-layer polyimide film was 1.2% by weight. The obtained three-layer polyimide film was fixed to a metal frame, placed in a superheated steam atmosphere in an oven, and heated at 350 ° C. for 30 minutes. The obtained three-layer polyimide film was processed into a metal-clad laminate. The results are summarized in Table 1.

(Comparative Example 1)
Additional heating was performed in an inert oven under a nitrogen atmosphere instead of under a superheated steam atmosphere. Heated at 350 ° C. for 60 minutes. Other treatments were performed in the same manner as in Example 1. The results are summarized in Table 1.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the additional heating was performed in an air atmosphere. The finally obtained three-layer polyimide film was remarkably changed in appearance and was not worthy of various evaluations.

(Comparative Example 3)
Evaluation was performed in the same manner as in Example 1 without performing additional heating.

(Example 2)
A curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 3.5: 1.0: 7.2) was added to the polyamic acid solution obtained in Synthesis Example 2 at a weight ratio of 50% with respect to the polyamic acid solution. After stirring with a mixer, the mixture was fed to the center layer of the three-layer coextrusion die, and the polyamic acid solution obtained in Synthesis Example 4 was fed to both sides of the center layer. The resin film was extruded through a lip opening of 1.3 mm of a three-layer extrusion die, and this resin liquid film was dried with a stainless steel endless belt at 115 ° C. for 80 seconds to obtain a self-supporting film. After peeling this self-supporting film from the belt, both ends are fixed with pins, dried and imidized at 280 ° C. × 15 seconds, 350 ° C. × 30 seconds, 340 ° C. × 30 seconds, thermoplastic polyimide layer / non-thermal A three-layer polyimide film having a plastic polyimide layer / thermoplastic polyimide layer thickness of 2 μm / 8.5 μm / 2 μm was obtained. The amount of residual solvent in the obtained three-layer polyimide film was 1.3% by weight. The obtained three-layer polyimide film was fixed to a metal frame and heated in a nano steam oven at 300 ° C. for 60 minutes. The obtained three-layer polyimide film was processed into a metal-clad laminate. The results are summarized in Table 1.

(Comparative Example 4)
Additional heating was carried out under a nitrogen atmosphere using an inert oven instead of under a superheated steam atmosphere. Other treatments were performed in the same manner as in Example 2. The results are summarized in Table 1.

(Comparative Example 5)
The same procedure as in Example 2 was performed except that the additional heating was performed in an air atmosphere. The finally obtained three-layer polyimide film was remarkably changed in appearance and was not worthy of various evaluations.

(Comparative Example 6)
Evaluation was carried out in the same manner as in Example 2 without performing additional heating.

1. Metal foil Polyimide film

Claims (3)

  A polyimide precursor or a polyimide-containing solution is simultaneously cast on a support to form a multilayer liquid film, and the multilayer liquid film is heat treated to form a multilayer self-supporting film. A method for producing a multilayer polyimide film, comprising a step of heat-treating a multilayer self-supporting film in a superheated steam atmosphere.   At least one of the multilayer self-supporting film having a residual solvent amount of 31% by weight to 150% by weight and the multilayer polyimide film having a residual solvent amount of 0.01% by weight to 30% by weight is subjected to heat treatment in a superheated steam atmosphere. The method for producing a multilayer polyimide film according to claim 1, comprising a step.   The multilayer polyimide film is a multilayer polyimide film in which a thermoplastic polyimide layer containing at least a thermoplastic polyimide is laminated on at least one surface of a non-thermoplastic polyimide layer containing at least a non-thermoplastic polyimide. The manufacturing method of the multilayer polyimide film in any one of 2.