JP2006199871A - Adhesive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive film which can be resisted to a soft soldering and reflow under strict conditions of moisture and can be well used as a flexible printed circuit (FPC) board while keeping an adhesion with the adhesive film and a metal foil. <P>SOLUTION: The adhesive film comprises a highly heat resistant polyimide layer, an adhesive layer containing a thermoplastic polyimide formed in at least one surface of the highly heat resistant polyimide layer, in which the adhesive film includes 0.5-30 wt% of a non-thermoplastic polyimide composed of the highly heat resistant polyimide layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one surface of a high heat resistant polyimide layer.

  In recent years, the demand for various printed circuit boards has increased along with the reduction in weight, size and density of electronic products. In particular, the demand for flexible laminates (also referred to as flexible printed circuit boards (FPCs), etc.) has increased. ing. The flexible laminate has a structure in which a circuit made of a metal foil is formed on an insulating film.

  The flexible laminate is generally formed of various insulating materials, a flexible insulating film is used as a substrate, and a metal foil is bonded to the surface of the substrate by heating and pressure bonding via various adhesive materials. Manufactured by. A polyimide film or the like is preferably used as the insulating film. As the adhesive material, a thermosetting adhesive such as epoxy or acrylic is generally used (FPC using these thermosetting adhesives is hereinafter also referred to as three-layer FPC).

  Thermosetting adhesives have the advantage that they can be bonded at relatively low temperatures. However, in the future, as required characteristics such as heat resistance, flexibility, and electrical reliability become stricter, it is considered that it is difficult to cope with a three-layer FPC using a thermosetting adhesive. On the other hand, a material in which a metal layer is directly laminated on an insulating film and an FPC using a thermoplastic polyimide compound for an adhesive layer (hereinafter also referred to as a two-layer FPC) have been proposed. This two-layer FPC has characteristics superior to those of the three-layer FPC, and is expected to be an industrially useful product.

  As a method for producing a flexible metal-clad laminate for use in a two-layer FPC, a polyamic acid, which is a precursor of a polyimide compound, is cast on a metal foil, applied and then imidized, and then on a polyimide film by sputtering or plating. Examples thereof include a metalizing method in which a metal layer is directly provided on the substrate, and a laminating method in which a polyimide film and a metal foil are bonded via a thermoplastic polyimide compound. Among these, the lamination method is superior in that the thickness range of the metal foil that can be handled is wider than that of the casting method, and the apparatus cost is lower than that of the metalizing method. As a device for laminating, a hot roll laminating device or a double belt press device for continuously laminating a roll-shaped material is used.

  Here, as a substrate material used for the laminating method, an adhesive film in which an adhesive layer having a thermoplastic polyimide compound is provided on at least one surface of a polyimide film is widely used.

  Properties required for the adhesive film include strength when the metal foil is peeled off from the adhesive film, that is, peel strength, and heat resistance that can withstand soldering and reflow in an environment with severe moisture absorption conditions. However, the above two characteristics are generally contradictory, and there is a problem that heat resistance under hygroscopic conditions decreases when adhesion increases.

Patent Document 1 discloses a specific thermoplastic polyimide resin using a diamine having a hydroxyl group or a carboxyl group, and a bond ply obtained by applying this polyimide resin to one side or both sides of a non-thermoplastic polyimide film, It describes that it has excellent adhesion and solder heat resistance. However, what is described in Patent Document 1 is to improve the adhesion and solder heat resistance by devising the structure of the thermoplastic polyimide resin, and to include a non-thermoplastic polyimide resin in the adhesive layer. Is not described.
JP 2002-363284 A

  This invention is made | formed in view of said subject, Comprising: It is providing the adhesive film which can be used favorably as a FPC board | substrate.

As a result of intensive studies in view of the above-mentioned problems, the present inventors have uniquely defined the constituent requirements of an adhesive film that can be used favorably as an FPC board even when a dense circuit pattern is created using the following new adhesive film. The headline and the present invention have been completed.
1) An adhesive film having a high heat resistant polyimide layer and an adhesive layer containing a thermoplastic polyimide formed on at least one surface of the high heat resistant polyimide layer, wherein the adhesive layer has a high heat resistance. An adhesive film comprising 0.5 to 30 wt% of a non-thermoplastic polyimide resin constituting the polyimide layer.
2) The adhesive film according to claim 1, wherein the non-thermoplastic polyimide resin contained in the adhesive layer is the same polyimide resin as the non-thermoplastic polyimide resin contained in the high heat-resistant polyimide layer.
3) The adhesive film according to 1) or 2), wherein the adhesive film is produced by laminating an adhesive layer containing a thermoplastic polyimide on at least one surface of the high heat-resistant polyimide layer by a coextrusion-casting method. .
4) At least one of the solutions used in the coextrusion-cast coating method contains a chemical dehydrating agent and a catalyst, and 1 mol of amic acid unit in the polyamic acid contained in the solution containing the chemical dehydrating agent and the catalyst. The adhesive film according to 3), wherein 0.5 to 4.0 moles of chemical dehydrating agent and 0.05 to 2.0 moles of catalyst are used.

  According to the present invention, there is provided an adhesive film that can be used satisfactorily as an FPC board, capable of withstanding soldering and reflow in an environment where moisture absorption conditions are severe, while ensuring adhesion between the adhesive film and the metal foil. it can.

  Embodiments of the present invention will be described below.

  The adhesive film of the present invention is an adhesive film having a high heat resistant polyimide layer and an adhesive layer containing a thermoplastic polyimide formed on at least one surface of the high heat resistant polyimide layer, the adhesive layer Further, it is characterized by containing 0.5-30 wt% of non-thermoplastic polyimide resin.

  The non-thermoplastic polyimide resin forming the high heat-resistant polyimide layer is superior in heat resistance under hygroscopic conditions than the thermoplastic polyimide. In the present invention, the heat resistance of the adhesive layer under the moisture absorption condition is improved by adding an appropriate amount of non-thermoplastic polyimide resin to the adhesive layer. Furthermore, by making the non-thermoplastic polyimide resin to be included in the adhesive layer the same resin as the non-thermoplastic polyimide resin constituting the high heat-resistant polyimide layer, the adhesion between both layers is also improved, and the peel strength with the metal foil Can also be increased.

  When the non-thermoplastic polyimide resin contained in the adhesive layer is less than 0.5 wt%, the effects of the present invention may not be sufficiently exerted. When the content exceeds 30 wt%, the adhesion between the adhesive layer and the metal foil is insufficient. May be.

  Hereinafter, it demonstrates in order of manufacture of a high heat resistant polyimide layer, an adhesive layer, and an adhesive film.

<High heat resistant polyimide layer>
The high heat resistant polyimide layer according to the present invention is not particularly limited in its molecular structure and thickness as long as it contains 90 wt% or more of a non-thermoplastic polyimide resin. The non-thermoplastic polyimide used for the high heat resistant polyimide layer is manufactured using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid, and usually, the aromatic tetracarboxylic dianhydride and the aromatic diamine are controlled by dissolving substantially equimolar amounts in an organic solvent. It is produced by stirring under temperature conditions until the polymerization of the acid dianhydride and diamine is completed. These polyamic acid solutions are usually obtained at a concentration of 5 to 35 wt%, preferably 10 to 30 wt%. When the concentration is in this range, an appropriate molecular weight and solution viscosity are obtained.

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 is reacted with an excess molar amount of an aromatic diamine compound 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 this invention, it is also preferable to use the polymerization method which obtains a prepolymer using the diamine component which has a rigid structure mentioned later. 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 tetracarboxylic dianhydrides that can be used in the present invention are pyromellitic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra. Carboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′- Benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic acid Dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxy) Phenyl) eta 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 can be used alone or in a mixture of any proportion.

  Among these acid dianhydrides, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′ It is preferable to use at least one selected from 4,4'-biphenyltetracarboxylic dianhydride.

  Among these acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetra The preferred amount of use in the case of using at least one selected from carboxylic dianhydrides is 60 mol% or less, preferably 55 mol% or less, more preferably 50 mol% or less, based on the total acid dianhydrides. 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride When using at least one kind, if the amount used exceeds this range, the glass transition temperature of the polyimide film may become too low, or the storage elastic modulus at the time of heating may become too low, making film formation itself difficult. Therefore, it 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 polyamic acid composition that is a precursor of the non-thermoplastic polyimide according to the present invention include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, and 3,3 ′. -Dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'- Diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-oxydianiline, 3,3′-oxydianiline, 3,4′-oxydianiline, 1,5-diaminonaphthalene, 4,4 '-Diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'- Aminodiphenylethylphosphine oxide, 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- (4-aminophenoxy) phenyl} propane, 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-amino) Phenoxy) benzene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone and the like.

  As the diamine component, a diamine having a rigid structure and a diamine having a flexible structure can be used in combination, and the preferred use ratio in that case is 80/20 to 20/80, more preferably 70/30 to 30/70, Particularly, it is 60/40 to 30/70. 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. In some cases, the film formation is difficult, and it may be harmful.

    In the present invention, the diamine having a rigid structure is

式中のＲ２は

R2 in the formula is

で表される２価の芳香族基からなる群から選択される基であり、式中のＲ₃は同一または異なって，ＣＨ₃−、−ＯＨ、−ＣＦ₃、−ＳＯ₄、−ＣＯＯＨ、−ＣＯ-ＮＨ₂、Ｃｌ−、Ｂｒ−、Ｆ−、及びＣＨ₃Ｏ−からなる群より選択される何れかの１つの基である）
で表されるものをいう。

A group selected from the group consisting of divalent aromatic groups represented by: R _{3 in} the formula is the same or different, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —COOH, _{-CO-NH 2, Cl-, Br-} , F-, and CH ₃ is any one group selected from the group consisting of O-)
The one represented by

  The diamine having a flexible structure is a diamine having a flexible structure such as an ether group, a sulfone group, a ketone group, or a sulfide group, and is preferably represented by the following general formula (2).

（式中のＲ₄は、

(R ₄ in the formula is

で表される２価の有機基からなる群から選択される基であり、式中のＲ₅は同一または異なって、ＣＨ₃−、−ＯＨ、−ＣＦ₃、−ＳＯ₄、−ＣＯＯＨ、−ＣＯ-ＮＨ₂、Ｃｌ−、Ｂｒ−、Ｆ−、及びＣＨ₃Ｏ−からなる群より選択される１つの基である。）
本発明において用いられるポリイミドフィルムは、上記の範囲の中で所望の特性を有するフィルムとなるように適宜芳香族酸二無水物および芳香族ジアミンの種類、配合比を決定して用いることにより得ることができる。

R _{5 in} the formula is the same or different and is CH ₃ —, —OH, —CF ₃ , —SO ₄ , —COOH, — One group selected from the group consisting of CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—. )
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.

  In the present invention, it is essential to add a filler for the purpose of imparting slipperiness. The filler according to the present invention may be any filler as long as it is generally called an inorganic filler. Preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium carbonate, and hydrogen phosphate. Examples include calcium, calcium phosphate, and mica. Various fillers may be added for the purpose of controlling other characteristics such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness.

Moreover, the addition amount of a filler is 0.01-100 weight part with respect to 100 weight part of high heat resistant polyimides, Preferably it is 0.01-90 weight part, More preferably, it is 0.02-80 weight part. 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 the 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, but a method of mixing a dispersion containing filler with a polyamic acid solution, particularly 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.

  In the present invention, the non-thermoplastic polyimide resin is a polyimide resin that does not melt or deform even when heat is applied. Specifically, whether or not it is a non-thermoplastic polyimide is determined from the polyimide resin. After the film is prepared and fixed with a metal frame and heat-treated at 450 ° C. for 1 minute, it can be determined by its appearance, and it can be confirmed by maintaining the appearance without melting or wrinkling.

<Adhesive layer>
In the adhesive layer according to the present invention, the content, molecular structure, and thickness of the thermoplastic polyimide resin contained in the layer are not particularly limited as long as a significant adhesive force is expressed by a laminating method. However, in order to develop a significant adhesive force, it is preferable that the thermoplastic polyimide resin is substantially contained in an amount of 50 wt% or more.

  Further, as described above, it is essential that the adhesive layer according to the present invention contains 0.5 to 30 wt% of a non-thermoplastic polyimide resin.

  In the present invention, it is important that both the non-thermoplastic polyimide resin and the thermoplastic polyimide resin are contained in the adhesive layer because both the adhesion to the metal foil and the heat resistance under moisture absorption can be achieved. The thermoplastic polyimide resin contained in the adhesive layer is a resin that melts when heat is applied. Specifically, the resin is melted when heated to about 225 to 500 ° C. Refers to something that does not hold

  The non-thermoplastic polyimide resin contained in the adhesive layer is the same as the non-thermoplastic polyimide resin described in the high heat-resistant polyimide layer. As the non-thermoplastic polyimide resin contained in the adhesive layer is closer to the composition and molecular weight of the non-thermoplastic polyimide resin contained in the high heat-resistant polyimide layer, the effect of the invention is more easily exhibited. More preferably, the mol% or more is the same, and most preferably the same as the non-thermoplastic polyimide resin contained in the high heat-resistant polyimide layer.

  As the thermoplastic polyimide contained in the thermoplastic polyimide layer, thermoplastic polyimide, thermoplastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide and the like can be suitably used. Among these, thermoplastic polyesterimide is particularly preferably used from the viewpoint of low moisture absorption characteristics.

  The thermoplastic polyimide contained in the thermoplastic polyimide layer according to the present invention is obtained by a conversion reaction from the precursor polyamic acid. As the method for producing the polyamic acid, any known method can be used as in the precursor of the high heat resistant polyimide layer.

  In view of the fact that lamination with an existing apparatus is possible and the heat resistance of the resulting metal-clad laminate is not impaired, the thermoplastic polyimide in the present invention has a glass transition temperature (150 to 300 ° C.). Tg) is preferred. In addition, Tg can be calculated | required from the value of the inflexion point of the storage elastic modulus measured with the dynamic viscoelasticity measuring apparatus (DMA).

  The polyamic acid that is a precursor of the thermoplastic polyimide used in the present invention is not particularly limited, and any known polyamic acid can be used. Regarding the production of the polyamic acid solution, the raw materials and the production conditions can be used in exactly the same manner.

  The properties of thermoplastic polyimide can be adjusted by combining various raw materials to be used, but generally the glass transition temperature becomes higher and / or the storage elasticity when heated when the proportion of rigid diamine used is increased. This is not preferable because the rate increases and the adhesiveness and workability decrease. The diamine ratio of the rigid structure is preferably 40 mol% or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

  Specific examples of preferable thermoplastic polyimide resins include those obtained by polymerization reaction of acid dianhydrides including biphenyltetracarboxylic dianhydrides and diamines having aminophenoxy groups.

  In the adhesive film according to the present invention, it is essential that no inorganic filler is present on the surface of the adhesive layer. However, fine particles that do not interfere with the circuit formability may be contained in the surface layer. In the present invention, the surface layer of the adhesive layer specifies that there is no inorganic filler having a median average diameter of 1 μm or more. Yes. Various organic fillers and other resins may be added for the purpose of controlling the properties of the adhesive layer.

  As a method of causing the adhesive layer to contain a thermoplastic polyimide resin and a non-thermoplastic polyimide resin, a process of blending a solution containing a precursor of a thermoplastic polyimide resin and a solution containing a precursor of a non-thermoplastic polyimide resin is performed. Examples thereof include a method for producing an adhesive layer, a method for producing an adhesive layer through a step of blending a solution of a thermoplastic polyimide resin and a solution containing a precursor of a non-thermoplastic polyimide resin.

<Manufacture of adhesive film>
A method for obtaining the adhesive film according to the present invention will be described below.

  The method for obtaining the adhesive film of the present invention is not particularly limited, but a multi-layer liquid film is formed on a support using a solution containing a polyimide resin and / or two or more kinds of solutions containing a precursor thereof. Then, it is preferably produced by a production method including a step of allowing drying and imidization to proceed thereafter. The method of forming multiple layers of liquid film on the support is a method using a multilayer die, a method using a slide die, a method of arranging a plurality of single layer dies, a method of combining a single layer die and spray coating or gravure coating, etc. Conventionally known methods can be used. However, in consideration of productivity, maintainability, etc., a coextrusion-cast coating method using a multilayer die is particularly preferred. Hereinafter, a multilayer die will be described as an example.

  First, a solution containing a precursor of a high heat resistant polyimide and a solution containing a component for forming an adhesive layer or a solution containing a precursor of a thermoplastic polyimide are supplied to a multilayer die having two or more layers, Both solutions are extruded from the discharge port as a liquid film having a plurality of layers. Next, a plurality of liquid films extruded from the multilayer die are cast on a smooth support, and at least a part of the solvent of the plurality of liquid films on the support is volatilized, thereby providing a self-supporting property. A multilayer film having is obtained. Further, the multilayer film is peeled off from the support, and finally the multilayer film is sufficiently heated at a high temperature (250-600 ° C.) to substantially remove the solvent and advance imidization. Thereby, the target adhesive film is obtained. Further, for the purpose of improving the melt fluidity of the adhesive layer, the imidization rate may be intentionally lowered and / or the solvent may be left.

  In general, polyimide is obtained by a dehydration conversion reaction from a polyimide precursor, that is, a polyamic acid. As a method for performing the conversion reaction, a thermal curing method performed only by heat and a chemical curing method using a chemical curing agent are used. The two methods are most widely known. However, considering the production efficiency, the chemical curing method is more preferable.

  As the multi-layer die, a multi-manifold system, a feed block system, a mixture of both, and the like are known, but any of them may be adopted.

  The support is preferably as smooth as possible in consideration of the application of the finally obtained adhesive film, and is preferably in the form of an endless belt or drum in consideration of productivity.

  Here, the chemical curing agent includes a dehydrating agent and a catalyst. The dehydrating agent here is a dehydrating ring-closing agent for polyamic acid, and as its main component, aliphatic acid anhydride, aromatic acid anhydride, N, N'-dialkylcarbodiimide, lower aliphatic halide, halogenated Lower aliphatic acid anhydrides, aryl sulfonic acid dihalides, thionyl halides or mixtures of two or more thereof can be preferably used. Of these, aliphatic acid anhydrides and aromatic acid anhydrides work particularly well. The catalyst is a component having an effect of accelerating 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 can be used. . Of these, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, or β-picoline are preferred. Furthermore, introduction of an organic polar solvent into a solution composed of a dehydrating agent and a catalyst can be appropriately selected.

  When the coextrusion-cast coating method is employed, it is preferable that at least one solution used in the method contains a chemical dehydrating agent and a catalyst, and the solution used for forming the high heat resistant polyimide layer is chemically More preferably, it contains a dehydrating agent and a catalyst.

  The amount of the chemical dehydrating agent and the catalyst is 0.5 to 4.0 mol of the chemical dehydrating agent and 0.05 to 4.0 mol per 1 mol of the amic acid unit in the polyamic acid contained in the solution containing the chemical dehydrating agent and the catalyst. It is preferred to use 2.0 moles of catalyst. If the chemical dehydrating agent is less than 0.5 moles per mole of amic acid units in the polyamic acid, or if the catalyst is less than 0.05 moles per mole of amic acid units in the polyamic acid, sufficient It may be difficult to obtain manufacturing efficiency. When the chemical dehydrating agent exceeds 4.0 moles with respect to 1 mole of amic acid units in the polyamic acid, or when the catalyst exceeds 2.0 moles with respect to 1 mole of amic acid units in the polyamic acid, high heat resistance The adhesive polyimide layer and the adhesive layer are peeled off, and an adhesive film having a good appearance may not be obtained.

  There is no particular limitation on the method of volatilization of the solvent in the precursor solution of the high heat resistant polyimide and the solution containing the component forming the adhesive layer (solution containing the thermoplastic polyimide or solution containing the precursor of the thermoplastic polyimide). However, the method by heating and / or blowing is the simplest method. When the temperature at the time of heating is too high, the solvent is volatilized rapidly, and the trace of the volatilization causes a micro defect to be formed in the finally obtained adhesive film. Preferably there is.

  As for the imidization time, it suffices to take a sufficient time for the imidization and drying to be substantially completed, and although it is not uniquely limited, generally it is appropriately set within a range of about 1 to 600 seconds. Is done.

  The tension applied during imidization is preferably in the range of 1 kg / m to 15 kg / m, and particularly preferably in the range of 5 kg / m to 10 kg / m. If the tension is smaller than the above range, sagging or meandering may occur during film conveyance, which may cause problems such as wrinkling during winding or inability to uniformly wind. On the other hand, when it is larger than the above range, since it is heated at a high temperature in a state where a strong tension is applied, the dimensional characteristics of the obtained flexible metal-clad laminate may be deteriorated.

Examples of the method of the present invention will be specifically described below, but the present invention is not limited to these examples. In addition, the measuring method of each physical-property value based on this invention is as follows.
[Peel strength]
In accordance with JIS C6471, “6.5 Peel Strength”, a sample was prepared, a 5 mm wide metal foil part was peeled off at 180 ° peeling angle and 200 mm / minute, and the load was measured to peel. Intensity was calculated. In the case where the peel strength was 13 N / cm or more, “◯”, and less than “X”.
[Solder heat resistance]
A sample was prepared according to JIS C6471, and the test was performed under conditions of 40 ° C., 90% RH, moisture absorption for 96 hours, and immersion at 280 ° C. for 10 seconds. After the test, the morphology of the copper layer of the test piece and the thermoplastic polyimide layer was observed, and the copper layer was etched to check whether the adhesive layer was cloudy. The case where the copper layer and the adhesive layer were not peeled off and there was no white turbidity was rated as “◯”, and the case where the copper layer was peeled off or white turbid was marked as “X”.
(Synthesis Example 1: Synthesis of a precursor of a non-thermoplastic polyimide resin)
239 kg of N, N-dimethylformamide (hereinafter also referred to as DMF) cooled to 10 ° C., 6.9 kg of 4,4′-oxydianiline (hereinafter also referred to as ODA), p-phenylenediamine (hereinafter also referred to as p-PDA) After dissolving 9.4 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter also referred to as BAPP) 6.2 kg, pyromellitic dianhydride (hereinafter also referred to as PMDA). ) 10.4 kg was added and dissolved by stirring for 1 hour. To this, 20.3 kg of benzophenone tetracarboxylic dianhydride (hereinafter also referred to as BTDA) was added and dissolved by stirring for 1 hour.

  A separately prepared DMF solution of PMDA (PMDA: DMF = 0.9 kg: 7.0 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 3500 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution of a precursor of a high heat resistant polyimide compound having a solid content concentration of 18% by weight and a rotational viscosity at 23 ° C. of 3500 poise.

The polyamic acid solution was uniformly coated on a glass plate using a coater so as to have a final thickness of 20 μm, and heated at 90 ° C. for 30 minutes. Next, the coating film was removed from the glass plate, fixed to a metal frame, and heated at 250 ° C. for 10 minutes and 450 ° C. for 10 minutes to produce a polyimide film. This film was fixed to a metal frame and further heat-treated at 450 ° C. for 1 minute, and was not melted or wrinkled. Therefore, it was judged as a non-thermoplastic polyimide.
(Synthesis Example 2: Synthesis of precursor of thermoplastic polyimide resin)
78 kg of DMF cooled to 10 ° C. and 11.56 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) were added, and while stirring under a nitrogen atmosphere, 3,3′4,4 7.87 kg of '-biphenyltetracarboxylic dianhydride (BPDA) was gradually added. Subsequently, 380 g of ethylene bis (trimellitic acid monoester acid anhydride) (TMEG) was added and stirred for 30 minutes. A solution in which 300 g of TMEG was dissolved in 3 kg of DMF was separately prepared, and this was gradually added to the above reaction solution while paying attention to the viscosity and stirred. When the viscosity reached 3000 poise, addition and stirring were stopped to obtain a polyamic acid solution of a precursor of a thermoplastic polyimide compound having a solid concentration of 18% by weight.

The polyamic acid solution was uniformly coated on a glass plate using a coater so as to have a final thickness of 20 μm, and heated at 90 ° C. for 30 minutes. Next, the coating film was removed from the glass plate, fixed to a metal frame, and heated at 250 ° C. for 10 minutes and 450 ° C. for 10 minutes to produce a polyimide film. This film was fixed to a metal frame and further heat-treated at 450 ° C. for 1 minute, and then melted and deformed. Therefore, it was judged as a thermoplastic polyimide.
Example 1
The following chemical dehydrating agent and catalyst were contained in the polyamic acid solution of the precursor of the high heat resistant polyimide obtained in Synthesis Example 1.
Chemical dehydrating agent: 2.0 mol per 1 mol of polyamic acid amic acid unit of acetic anhydride as precursor of high heat resistant polyimide Catalyst: 1 mol of amic acid unit of polyamic acid as precursor of high heat resistant polyimide 0.5 mol of the polyamic acid solution of the precursor of the thermoplastic polyimide obtained in Synthesis Example 2 and the polyamic acid solution of the precursor of the high heat-resistant polyimide obtained in Synthesis Example 1 are 5.1: Mixing at a ratio of 1.0, an adhesive layer polyamic acid solution containing 15 wt% of non-thermoplastic polyimide resin in the adhesive layer of the adhesive film finally obtained was obtained.

  Next, a multi-manifold three-layer coextrusion multi-layer die having a lip width of 650 mm is formed in the order in which the outer layer is the above polyamic acid solution for the adhesive layer and the inner layer is the polyamic acid solution that is a precursor of the above high heat-resistant polyimide solution. The multilayer film thus formed was continuously extruded and cast on a stainless steel endless belt running 20 mm below the T die. Next, the multilayer film was heated at 130 ° C. for 100 seconds to be converted into a self-supporting gel film. Further, the self-supporting gel film was peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 300 ° C. × 30 seconds, 400 ° C. × 50 seconds, 450 ° C. × 10 seconds to obtain an adhesive film. .

  By using 18 μm rolled copper foil (BHY-22B-T, manufactured by Japan Energy Co., Ltd.) on both sides of the obtained adhesive film, and further using a protective material (Apical 125 NPI; manufactured by Kaneka Chemical Co., Ltd.) on both sides of the copper foil, A flexible metal-clad laminate is obtained by continuously laminating a polyimide film with a tension of 0.4 N / cm, a laminating temperature of 380 ° C., a laminating pressure of 196 N / cm (20 kgf / cm), and a laminating speed of 1.5 m / min. Fabricated, peel strength measurement and solder heat resistance evaluation.

As a result, the peel strength was 15 N / cm, so that the solder heat resistance was good.
(Example 2)
The polyamic acid solution of the precursor of the thermoplastic polyimide obtained in Synthesis Example 2 and the polyamic acid solution of the precursor of the high heat-resistant polyimide obtained in Synthesis Example 1 were mixed at a ratio of 3.6: 1.0. Then, the adhesive film and the flexible metal tension were the same as in Example 1, except that the polyamic acid solution for the adhesive layer containing 25 wt% of the non-thermoplastic polyimide resin was obtained in the adhesive layer of the adhesive film finally obtained. A laminate was prepared, and peel strength measurement and solder heat resistance evaluation were performed.
As a result, the peel strength was 13 N / cm, so that the solder heat resistance was good.
(Reference Example 1)
The adhesive film and flexible metal-clad as in Example 1 except that the polyamic acid solution of the precursor of thermoplastic polyimide obtained in Synthesis Example 2 is not mixed with the polyamic acid solution of the precursor of high heat-resistant polyimide. A laminate was prepared, and peel strength measurement and solder heat resistance evaluation were performed.

As a result, the peel strength was 16 N / cm, so that the solder heat resistance was x.
(Reference Example 2)
The polyamic acid solution of the precursor of the thermoplastic polyimide obtained in Synthesis Example 2 and the polyamic acid solution of the precursor of the high heat-resistant polyimide obtained in Synthesis Example 1 were mixed at a ratio of 1.67: 1.0. Then, the adhesive film and the flexible metal tension were the same as in Example 1 except that a polyamic acid solution for an adhesive layer containing 35 wt% non-thermoplastic polyimide resin was obtained in the adhesive layer of the adhesive film finally obtained. A laminate was prepared, and peel strength measurement and solder heat resistance evaluation were performed.
As a result, the peel strength was 7 N / cm, and the solder heat resistance was ◯.

Claims (4)

An adhesive film having a high heat resistant polyimide layer containing a non-thermoplastic polyimide resin and an adhesive layer containing a thermoplastic polyimide formed on at least one surface of the high heat resistant polyimide layer, wherein the adhesive layer In addition, the non-thermoplastic polyimide resin is contained in an amount of 0.5 to 30 wt% in all adhesive layer components. The adhesive film according to claim 1, wherein the non-thermoplastic polyimide resin contained in the adhesive layer is the same polyimide resin as the non-thermoplastic polyimide resin contained in the high heat-resistant polyimide layer. The adhesive film according to claim 1, wherein the adhesive film is produced by laminating an adhesive layer containing a thermoplastic polyimide on at least one surface of the high heat-resistant polyimide layer by a coextrusion-casting method. At least one solution of the solution used in the coextrusion-casting coating method contains a chemical dehydrating agent and a catalyst, with respect to 1 mol of amic acid unit in polyamic acid contained in the solution containing the chemical dehydrating agent and the catalyst. The adhesive film according to claim 3, wherein 0.5 to 4.0 moles of chemical dehydrating agent and 0.05 to 2.0 moles of catalyst are used.