JP2006316232A - Adhesive film and its preparation process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive film having a thermoplastic polyimide layer formed on at least one surface of a high heat-resistance polyimide layer and having little stickiness, and to provide a process for suitably producing the adhesive film. <P>SOLUTION: The process of producing the adhesive film of the present invention comprises a step of immersing into a solvent an adhesive film wherein an adhesive layers comprising a thermoplastic polyimide layer is laminated on at least one surface of a high heat-resistance polyimide layer. Accordingly, only a low molecular weight component included in the adhesive layer of the adhesive film can be removed. According to the present invention, the adhesive film having little stickiness can be suitably produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive film and a method for producing the same, and more particularly to an adhesive film having a thermoplastic polyimide layer formed on at least one surface of a high heat resistant polyimide layer and a method for producing the same.

  In recent years, the demand for various printed circuit boards has increased with the reduction in weight, size and density of electronic products. Among these printed boards, the demand for flexible wiring boards is growing. The flexible wiring board has a structure in which a circuit made of a metal layer is formed on an insulating film. The flexible wiring board is also called a flexible printed wiring board (FPC).

  The above-mentioned flexible wiring board is generally formed by 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. In addition, as the adhesive material, epoxy-based, acrylic-based thermosetting adhesives are generally used. A flexible wiring board using such a thermosetting adhesive has a three-layer structure of substrate / adhesive material / metal foil, and is hereinafter referred to as “three-layer FPC” for convenience of explanation.

  The thermosetting adhesive used for the three-layer FPC has an advantage that it can be bonded at a relatively low temperature. On the other hand, as the demands for various properties such as heat resistance, flexibility, and electrical reliability become stricter for FPC in the future, it will be difficult to cope with three-layer FPC using a thermosetting adhesive. Yes.

  On the other hand, a flexible wiring board in which a metal layer is directly provided on an insulating film and a flexible wiring board using a thermoplastic polyimide as an adhesive layer have been proposed. Since these flexible wiring boards are in a state in which a metal layer is directly formed on an insulating substrate, they are hereinafter referred to as “two-layer FPC” for convenience of explanation. This two-layer FPC has characteristics superior to those of the three-layer FPC, and can sufficiently meet the demands for the various characteristics described above. Therefore, it is expected that demand will increase in the future.

  The two-layer FPC is manufactured using a flexible metal-clad laminate having a structure in which a metal foil is laminated on a substrate. Examples of the method for producing the flexible metal-clad laminate include a casting method, a metalizing method, and a laminating method. The casting method is a method in which polyamic acid, which is a polyimide precursor, is cast and applied onto a metal foil and then imidized. The metalizing method is a method in which a metal layer is directly provided on a polyimide film by sputtering or plating. The laminating method is a method in which an adhesive film in which a thermoplastic polyimide layer is provided on at least one surface of a high heat resistant polyimide layer is bonded to a metal foil.

  Among these, the lamination method is excellent 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 an apparatus for performing the laminating method, a hot roll laminating apparatus or a double belt press apparatus for continuously laminating a roll-shaped material is used. Among these apparatuses, a hot roll laminating apparatus can be particularly preferably used because of high productivity and low initial equipment investment.

  In the flexible metal-clad laminate produced by the laminating method, an adhesive film in which a thermoplastic polyimide layer is provided on at least one surface of a polyimide film is widely used as a substrate.

  As a method for producing the adhesive film, (1) a coating method in which a thermoplastic polyimide in a solution state or a precursor thereof is applied to one side or both sides of a polyimide film as a substrate and dried, (2 ) Thermal laminating method in which a thermoplastic polyimide film is heated and bonded to one or both sides of a polyimide film as a base material, or (3) A polyimide film layer and a thermoplastic polyimide layer as a base material are simultaneously cast and applied. And a coextrusion-casting coating method formed by the above method (see Patent Documents 1 and 2).

Further, Patent Document 3 discloses a method for producing an adhesive film that imparts stable adhesive strength to a polyimide-based adhesive film. In the method for producing an adhesive film described in Patent Document 3, first, a polyamic acid solution is heated to imidize to obtain a solvent-soluble polyimide solution, and then a poor solvent is dropped to precipitate only a high molecular weight component. Separate. Thereafter, a high molecular weight polyimide resin in which the weight fraction of a low molecular weight component of 10,000 or less obtained by dissolving only the components separated by filtration in a good solvent is 10% or less of the total polyimide component is used as the polyimide component.
Japanese Patent No. 2946416 (registered on July 2, 1999, published publication: JP-A-11-99554, published on April 13, 1999) Japanese Patent Laid-Open No. 7-214636 (published on August 15, 1995) Japanese Patent Laid-Open No. 10-237414 (published on September 8, 1998)

  The adhesive film manufactured by the above-described method is used as an insulating layer when applied to a two-layer FPC. Therefore, a circuit pattern is created on the metal foil after the metal foil is laminated, and the circuit pattern is incorporated into the apparatus through a soldering process or the like. However, the adhesive film manufactured by the above-mentioned method may not be soldered well because the soldering tool is in close contact with the adhesive film during the soldering process (this phenomenon is referred to as “stickiness”). .

  Therefore, the development of an adhesive film with less stickiness is considered to be very important industrially. However, neither the development of technology for reducing stickiness in adhesive films, nor the investigation of the cause of stickiness has been made at all.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an adhesive film with less stickiness and a method for suitably producing such an adhesive film.

  As a result of intensive studies in view of the above problems, the present inventors have uniquely found that the main factor of stickiness is a low molecular weight component contained in the thermoplastic polyimide on the outermost surface of the adhesive film. Furthermore, the present inventors have found that even if the thermoplastic polyimide is insoluble in the solvent, the low molecular weight component contained therein is eluted in the solvent, and the present invention has been completed.

  That is, the method for producing an adhesive film according to the present invention includes at least a step of immersing an adhesive film in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface of a high heat-resistant polyimide layer in a solvent. It is said.

  The solvent preferably contains an organic polar solvent.

  Further, the solvent is selected from N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide, tetrahydrofuran, methanol, and ethanol. It is preferably a seed or a mixture of two or more.

  Moreover, it is preferable that the temperature of the said solvent is 10 to 100 degreeC.

  In addition, the method for producing an adhesive film described above is characterized in that only the low molecular weight component contained in the adhesive layer is removed.

  The adhesive film concerning this invention is manufactured by said manufacturing method of an adhesive film, It is characterized by the above-mentioned.

  The adhesive film according to the present invention is an adhesive film in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface of a high heat-resistant polyimide layer, and only a low molecular weight component contained in the adhesive layer is removed. It is characterized by having.

  The manufacturing method of the adhesive film concerning this invention includes the process of immersing the adhesive film by which the adhesive layer containing a thermoplastic polyimide was laminated | stacked on the at least single side | surface of the high heat resistant polyimide layer in a solvent. Therefore, only the low molecular weight component contained in the adhesive layer can be removed. Therefore, there is an effect that an adhesive film with less stickiness can be produced.

  Moreover, the adhesive film concerning this invention does not contain a low molecular weight component in the contact bonding layer. Therefore, when the adhesive film is fixed to an apparatus or the like by soldering, the soldering tool can be satisfactorily soldered without being in close contact with the adhesive film.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this.

  The method for producing an adhesive film according to the present invention uses, as a solvent, an adhesive film in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface of a high heat-resistant polyimide layer (hereinafter also referred to as “pre-treatment adhesive film”). What is necessary is just to include the process to immerse at least, and it does not specifically limit about another specific structure.

  Hereinafter, the “adhesive film before treatment”, “the method for producing an adhesive film according to the present invention”, and “the adhesive film according to the present invention obtained by the method” will be described in detail.

<I. Pre-treatment adhesive film>
The pre-treatment adhesive film is an adhesive film in which an adhesive layer containing thermoplastic polyimide is laminated on at least one surface of the high heat-resistant polyimide layer, and is an adhesive film before being immersed in the solvent.

  The “high heat resistant polyimide layer” and “adhesive layer” contained in the pre-treatment adhesive film will be described in detail below.

(I-1. High heat resistant polyimide layer)
The molecular structure and thickness of the high heat-resistant polyimide layer are not particularly limited, and it is sufficient that the non-thermoplastic polyimide resin is contained by 90% by weight or more. The non-thermoplastic polyimide can be produced by producing polyamic acid as a precursor and imidizing it.

  The polyamic acid can be produced using any known method. For example, a substantially equimolar amount of an aromatic tetracarboxylic dianhydride and an aromatic diamine are dissolved in an organic solvent, and the acid dianhydride and the diamine are polymerized under controlled temperature conditions. It can be produced by stirring until complete. The polyamic acid obtained by this production method is an organic solvent solution (hereinafter also referred to as “polyamic acid solution”), and the concentration of the polyamic acid is usually within the range of 5 wt% to 35 wt%, preferably 10 wt%. It is in the range of ˜30% by weight. A concentration within this range has a molecular weight and solution viscosity suitable for the present invention.

  As a method for polymerizing the polyamic acid, any known method and a combination thereof can be used. The characteristic of the polyamic acid polymerization method is the order of addition of the monomer components. Therefore, various physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomer components. Therefore, in the present invention, the addition order of the monomer components may be appropriately determined according to various physical properties required for the non-thermoplastic polyimide to be finally obtained. A monomer component may be added.

  Thus, the polymerization method of polyamic acid is not particularly limited, and any polymerization method may be used. Examples of typical polymerization methods include the following methods.

  (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 using 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 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 additional addition of the aromatic diamine compound, the aromatic tetracarboxylic dianhydride is added so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. Method of polymerization using.

  (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 mixture of substantially equimolar aromatic tetracarboxylic dianhydride and aromatic diamine is reacted in an organic polar solvent for polymerization.

  In addition, these methods may be used alone or in combination.

  The organic polar solvent used for polymerizing the polyamic acid is not particularly limited as long as it dissolves the polyamic acid, and any solvent can be used. Specific examples include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N, N-dimethylformamide, and N, N-dimethyl. Acetamide can be particularly preferably used.

  The tetracarboxylic dianhydride that can be used as the acid dianhydride component of the polyamic acid composition in the present invention 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'-benzophenone tetracarboxylic dianhydride, 4,4'- Oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ) Propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3- Dicarboxyphenyl) Tan dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimellitic acid mono Ester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), and bisphenol A bis (trimellitic acid monoester acid anhydride), and the like. These compounds may be used singly or as a mixture in combination at an arbitrary ratio.

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

  Among the above four acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4, When using at least one selected from 4′-biphenyltetracarboxylic dianhydride, the glass transition temperature of the polyimide film becomes too low, or the storage elastic modulus during heating becomes too low. It is preferable that the film formation itself is within a range that does not become difficult. Specifically, it is preferably 60 mol% or less, more preferably 55 mol% or less, and further preferably 50 mol% or less with respect to the total acid dianhydride component.

  In addition, when pyromellitic dianhydride is used among the above four types of acid dianhydrides, the amount used is preferably in the range of 40 to 100 mol%, and in the range of 45 to 100 mol%. It is more preferable that it is within the range of 50 to 100 mol%, and further preferable. By using pyromellitic dianhydride in this range, it becomes easy to keep the glass transition temperature and the storage elastic modulus at the time of heat within the ranges suitable for use or film formation.

  The diamine that can be used as the diamine component of the polyamic acid composition that is a precursor of the non-thermoplastic polyimide according to the present invention is not particularly limited. For example, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'- Dimethoxybenzidine, 2,2′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfide, 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'-diaminodiphenylethylphosphine Oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′- Aminodiphenyl 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-amino Phenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3 -Aminophenoxy) benzene, 3,3'-diaminobenzophenone, and 4,4'-diaminobenzophenone, side by side And the like analogs of these compounds. In addition, these compounds may be used independently and may be used as a mixture combined at an arbitrary ratio.

  As the diamine component, a diamine having a rigid structure (hereinafter also referred to as “rigid dian”) and a diamine having a flexible structure (hereinafter also referred to as “flexible diamine”) may be used in combination. In this case, if the use ratio of the rigid diamine is too high, the tensile elongation of the film tends to be small. On the other hand, if the ratio of rigid diamine used is too low, the glass transition temperature may become too low, or the storage modulus during heat may become too low, making film formation difficult. Therefore, it is preferable that the ratio of the rigid diamine used is in a range where the above-described adverse effects do not occur. Specifically, the molar ratio of rigid diamine to flexible diamine, that is, rigid diamine: flexible diamine is preferably in the range of 80:20 to 20:80, and in the range of 70:30 to 30:70. It is more preferable that it is in the range of 60:40 to 30:70.

In the present invention, rigid diamine refers to the following general formula (1)
NH ₂ -R ₂ -NH ₂ ··· formula (1)
(Wherein R ₂ represents the following general formula group (2)

(In the formula, R ₃ may be the same or different, but H—, 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-).
Is a group selected from the group consisting of divalent aromatic groups represented by the formula: )
The one represented by

  The flexible diamine is a diamine having a flexible structure such as an ether group, a sulfone group, a ketone group, or a sulfide group, and preferably the following general formula (3)

(Wherein R ₄ represents the following general formula group (4)

And R ₅ may be the same or different, but H—, CH ₃ —, —OH, —CF. ₃ , —SO ₄ , —COOH, —CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—. )
Can be mentioned.

  When the polyamic acid is polymerized using the rigid diamine, a polymerization method for obtaining a prepolymer (for example, the method (2) or (3) described above) is selected from the polyamic acid polymerization methods described above. Is preferred. By using these polymerization methods, a polyimide film having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained.

  The molar ratio of the rigid diamine to the acid dianhydride when obtaining the prepolymer is not particularly limited. However, if the proportion of rigid diamine is high, the linear expansion coefficient tends to be too small or the tensile elongation tends to be reduced. On the other hand, if the proportion of rigid diamine is low, the effect of improving the elastic modulus and hygroscopic expansion coefficient tends to be difficult to obtain. Therefore, it is preferable to use rigid diamine and acid dianhydride as long as such problems do not occur. Specifically, the rigid diamine: acid dianhydride component in a molar ratio is preferably in the range of 100: 70 to 100: 99 or in the range of 70: 100 to 99: 100, and more preferably 100: 75 to More preferably, it is in the range of 100: 90 or in the range of 75: 100 to 90: 100.

  The polyimide film used in the present invention is determined by appropriately determining the type and blending ratio of the aromatic dianhydride and the aromatic diamine so as to be a film having desired characteristics in the above range, Obtainable.

  Other components that can be included in the high heat-resistant polyimide layer include various resins that can be blended with the high heat-resistant polyimide and that do not impair the physical properties of the heat-resistant layer, and various properties of the heat-resistant layer. Various additives can be mentioned. Among these, in the present invention, it is preferable to add a filler. By adding the filler, it is possible to improve various properties such as slidability, slidability, thermal conductivity, conductivity, corona resistance and loop stiffness of the resulting adhesive film.

  The filler in this invention is not specifically limited, For example, the inorganic filler which consists of various inorganic compounds can be mentioned. Specifically, silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium carbonate, calcium hydrogen phosphate, calcium phosphate, mica, and the like can be preferably used.

  Further, the amount of filler added is not particularly limited because it is determined by the film properties to be modified, the particle size of the filler, and the like. That is, it is sufficient that the modification effect by the filler appears and the mechanical properties of the film are not impaired. Specifically, it is preferably 0.01 to 100 parts by weight, more preferably 0.01 to 90 parts by weight, and 0.02 to 80 parts by weight with respect to 100 parts by weight of the high heat resistant polyimide. It is particularly preferred that

  The method for adding the filler is not particularly limited, and specific examples include the following methods.

  (A) A method of adding to a polymerization reaction solution before or during polymerization.

  (B) A method in which the filler is kneaded using three rolls after completion of the polymerization.

  (C) A method of preparing a dispersion containing a filler and mixing it with a polyamic acid organic solvent solution.

  Among these methods, (C) a method of mixing a dispersion containing a filler with a polyamic acid solution is preferable, and a method of mixing a dispersion containing a filler with a polyamic acid solution immediately before film formation is particularly preferable. If this method is adopted, the filler can be mixed immediately before forming the gel film, so that the possibility of filler remaining in the production line of the adhesive film and the possibility of filler contamination accompanying it are reduced most. Can do.

  The method for preparing the dispersion containing the filler is not particularly limited, and the dispersion may be prepared by adding the filler to be used to an appropriate solvent. It is preferable to use the same solvent as the polyamic acid polymerization solvent as the solvent. Further, in order to disperse the filler satisfactorily and stabilize the dispersion state, additives such as a dispersant and a thickener may be used within a range that does not affect the film physical properties.

(I-2. Adhesive layer)
The adhesive layer included in the pre-treatment adhesive film according to the present invention contains thermoplastic polyimide, and if it is a layer that can exhibit adhesiveness under predetermined conditions, the content, molecular structure, and thickness of the thermoplastic polyimide resin. Other configurations such as are not particularly limited. The adhesive layer preferably exhibits a significant adhesive force particularly when the adhesive film and the object are adhered by a laminating method. However, in order to develop a significant adhesive force, it is preferable that the thermoplastic polyimide resin is substantially contained by 50% by weight or more.

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

  The physical properties of the thermoplastic polyimide used in the present invention are not particularly limited, and the adhesive film and the metal foil can be laminated using an existing apparatus, and the heat resistance of the resulting metal-clad laminate is reduced. It is preferable that it is not damaged. Specifically, the thermoplastic polyimide in the present invention preferably has a glass transition temperature (hereinafter also referred to as “Tg”) in the range of 150 to 300 ° C. Tg can be obtained from the value of the inflection point of the storage elastic modulus measured by a dynamic viscoelasticity measuring apparatus (hereinafter also referred to as “DMA”).

  The thermoplastic polyimide contained in the adhesive layer is obtained by a conversion reaction from the precursor polyamic acid (hereinafter also referred to as “imidization reaction”). The method for producing the polyamic acid is not particularly limited, and any known method can be used. Specifically, in the same manner as the precursor of the high heat resistant polyimide described in the section (I-1. High heat resistant polyimide layer), the polyamic acid can be produced by selecting the monomer raw material and the production conditions.

  In addition, the thermoplastic polyimide used in this invention can adjust various characteristics by combining various monomer raw materials to be used similarly to the high heat-resistant polyimide. However, generally, when the use ratio of the rigid diamine is increased, the Tg is increased and / or the storage modulus during heat is increased. As a result, the adhesiveness and workability of the adhesive layer are reduced. Therefore, in the case of producing the thermoplastic polyimide used in the present invention, when the rigid diamine is used in combination with the diamine component used for polymerizing the precursor polyamic acid, the rigid diamine in the total diamine component is used. Is preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 20 mol% or less.

  Specific examples of preferable thermoplastic polyimide resins include those obtained by polymerizing an acid dianhydride including biphenyltetracarboxylic dianhydrides and a diamine having an aminophenoxy group.

  Further, the adhesive layer may contain a resin other than polyimide and various additives, like the high heat resistant polyimide layer. For example, a filler may be added as necessary, like the high heat resistant polyimide layer. Examples of the filler in this case include inorganic or organic fillers, but are not particularly limited, and specific types, amounts used, and the like may be appropriately selected according to physical properties required for the adhesive layer. . Thereby, the characteristic of an adhesive film is controllable.

<II. Manufacturing method of adhesive film according to the present invention>
The method for producing an adhesive film according to the present invention only needs to include at least a “step of immersing the pre-treatment adhesive film in a solvent” (hereinafter, also referred to as “immersion step”). Is not particularly limited. In other words, the pre-treatment adhesive film may be produced by any method. For example, “a method of forming an adhesive layer on a high heat resistant polyimide layer”, “a method of forming an adhesive layer into a sheet and bonding it to a high heat resistant polyimide layer”, or a coextrusion-casting coating method, etc. It can be used suitably. The above-mentioned “coextrusion-casting method” means “a solution containing a precursor of a high heat-resistant polyimide and a solution containing a thermoplastic polyimide or a solution containing a precursor of a thermoplastic polyimide in two or more layers. A film manufacturing method including a step of simultaneously supplying to an extruder having a die and extruding both solutions from a discharge port of the multilayer die onto a support as at least two layers of thin film.

  Here, for the convenience of explanation, the method for producing an adhesive film according to the present invention will be described below by taking, as an example, a method including a step of “manufacturing an adhesive film before treatment by a coextrusion-casting method” and a dipping step. Detailed description.

  The above-mentioned “coextrusion-casting method” means “both solutions extruded from a multilayer die having two or more layers (a solution containing a precursor of a high heat-resistant polyimide and a solution containing a thermoplastic polyimide or a thermoplastic polyimide). And a solution containing the precursor of the above-mentioned solution are continuously extruded onto a smooth support ”(hereinafter also referred to as“ liquid film formation process ”), By removing at least a part, a process of obtaining a multilayer film having self-supporting property (hereinafter also referred to as “self-supporting process”), “peeling the multilayer film from the support, and finally, The multilayer film is sufficiently heat-treated at a high temperature (250-600 ° C.) to substantially remove the solvent and advance imidization ”(hereinafter also referred to as“ baking step ”). HaveThe above steps will be described in detail below.

(II-1. Liquid film forming step)
In the liquid film forming step, at least a solution containing a precursor of a high heat resistant polyimide and a solution containing a thermoplastic polyimide or a solution containing a precursor of a thermoplastic polyimide are used on the surface of the support. In this step, a liquid film made of a solution is stacked. “Liquid film” as used herein refers to a layer of a film-like resin solution formed using a resin solution containing polyimide or a precursor thereof, and is formed by applying the resin solution to the support surface. can do. In addition, the liquid film in the obtained laminated state is referred to as a multilayer liquid film for convenience.

  The above-mentioned support is for casting a multilayer liquid film extruded from a multilayer die, and heating and / or drying the multilayer liquid film on the support to give self-supporting property. The shape of the support is not particularly limited, but in consideration of the productivity of the adhesive film, a drum shape or a belt shape is preferable.

  Further, the material of the support is not particularly limited, and metal, plastic, glass, porcelain, etc. may be used. Among them, metals are preferable, and SUS materials having excellent corrosion resistance are more preferable. Moreover, you may give metal plating, such as Cr, Ni, or Sn.

(II-2. Self-supporting process)
In the self-supporting step, a gel multilayer film having self-supporting properties is formed by drying and / or heating the liquid film in a laminated state. “Having self-supporting” as used herein means that the liquid film becomes a gel-like film by drying and / or heating to partially imidize the polyamic acid or evaporate the solvent. Say. In other words, “a gel-like film having self-supporting property” means that a polyimide film is formed by heating and / or drying a polyamic acid solution or a polyimide solution, or a solution to which additives are added as necessary. In this case, a part of the organic solvent or reaction product is left in the polyimide film.

  The specific self-supporting step is not particularly limited, and the multilayer liquid film extruded from the multilayer die and formed on the smooth support is dried and / or heated to obtain a multilayer liquid film. At least a part of the solvent may be volatilized (evaporated) or partially imidized. Here, the heating and / or drying conditions (drying method, drying temperature, drying time, etc.) are not particularly limited, and the solvent can be evaporated to such an extent that self-supporting properties can be exhibited. The conditions or conditions that allow partial imidization may be used.

(II-3. Firing step)
In the firing step, the gel multilayer film is peeled from the surface of the support, and the gel multilayer film is sufficiently heated at a high temperature to substantially remove the solvent and advance imidization. Thereby, the multilayer film as an adhesive film can be obtained. 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 (hereinafter, also referred to as “imidation reaction”) from a polyimide precursor, that is, polyamic acid. As the method for carrying out the imidization reaction, two methods are most widely known: a thermal curing method performed only by heat and a chemical curing method using a chemical curing agent. Any method may be used, but in view of production efficiency, it is particularly preferable to employ a chemical curing method. If it is a chemical curing method, it becomes possible to realize higher productivity.

  The chemical curing agent includes a chemical dehydrating agent and a catalyst. The “chemical 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, arylsulfonic acid dihalides, thionyl halides or mixtures of two or more thereof can be preferably used. Among these compounds, aliphatic acid anhydrides and aromatic acid anhydrides can be particularly preferably used.

  The “catalyst” is a component having an effect of promoting the dehydration ring-closing action of the chemical dehydrating agent on the polyamic acid of the chemical curing agent. For example, an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine can be used. Among these compounds, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, and β-picoline can be particularly preferably used. Furthermore, you may introduce | transduce suitably an organic polar solvent in the solution which consists of a dehydrating agent and a catalyst.

  When the chemical curing method is adopted, if the content of the chemical dehydrating agent and the catalyst is too large, the chemical dehydrating agent and the catalyst are added when the multilayer film extruded from the extrusion die having two or more layers is dried. Solvent exudes from the layer. Therefore, the solvent accumulates between the high heat resistant polyimide layer and the thermoplastic polyimide layer. As a result, the adhesive strength between the respective layers may be reduced, and difficulty in peeling between the layers may be caused during the production of the adhesive film.

  Further, if the contents of the chemical dehydrating agent and the catalyst are too small, it becomes difficult to peel off the multilayer film from the support after the multilayer film extruded from the extrusion die is dried on a smooth support. Sometimes.

  Therefore, the contents of the chemical dehydrating agent and the catalyst are not particularly limited, but are preferably within a range in which the above problem does not occur. Specifically, the content of the chemical dehydrating agent is preferably 0.5 to 4.0 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the solution containing the chemical dehydrating agent and the catalyst. 1.0 to 3.0 mol is more preferable, and 1.2 to 2.5 mol is particularly preferable.

  The catalyst content is preferably 0.05 to 2.0 mol with respect to 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 more preferable that it is -1.0 mol, and it is especially preferable that it is 0.3-0.8 mol.

  Especially regarding the volatilization method of the solvent contained in the precursor solution of the high heat-resistant polyimide extruded from the multilayer die of two or more layers and the solution containing the thermoplastic polyimide or the solution containing the precursor of the thermoplastic polyimide Not. Specifically, the method by heating and / or blowing can be mentioned as the simplest method. Although the temperature at the time of the said heating is not specifically limited, It is preferable that it is less than the boiling point +50 degreeC of the solvent to be used. Thereby, it can prevent that a solvent volatilizes rapidly and a micro defect is formed in the adhesive film from which the said trace of volatilization is finally obtained.

  There is no particular limitation on the imidation time (heating time), and it is sufficient to take a sufficient time to complete the imidization and drying substantially. Specifically, it may be set as appropriate within a range of about 1 to 600 seconds.

  In the firing step, it is preferable to perform imidization while applying tension to the gel multilayer film. As a result, the production efficiency can be improved and the quality of the resulting multilayer film can be improved. The tension applied during imidization is not particularly limited. However, if the tension is too small, sagging or meandering may occur during film conveyance, which may cause problems such as wrinkling during winding or even winding. On the other hand, if the tension is too large, the film is heated at a high temperature in a state where a strong tension is applied, so that the dimensional characteristics of the obtained adhesive film may be deteriorated. Therefore, the tension is preferably in a range where the above problem does not occur. Specifically, it is preferably in the range of 1 kg / m to 15 kg / m, and more preferably in the range of 5 kg / m to 10 kg / m.

  The “multi-layer die having two or more layers” is not particularly limited, and various structures can be used. For example, a T-die for producing a multi-layer film can be used. In addition, examples of feed block T dies and multi-manifold T dies that can be used particularly preferably.

  Next, the “low molecular weight component removing step” will be described.

(II-4. Immersion process)
The method for producing an adhesive film according to the present invention includes at least a step of immersing the pre-treatment adhesive film in a solvent (immersion step).

  In the immersion step, only the low molecular weight component contained in the thermoplastic polyimide constituting the adhesive layer of the pre-treatment adhesive film is removed. That is, in the immersion step, the low molecular weight component is eluted in the solvent by immersing the adhesive film in a solvent, and only the low molecular weight component is eluted from the adhesive film.

  The “low molecular weight component” here is a component having a molecular weight of 30000 or less. The low molecular weight component can be detected, for example, by applying an organic polar solvent in which an adhesive film is immersed to GPC of a CCP & 8020 system manufactured by Tosoh.

  The amount of the low molecular weight component to be removed in the immersion step is not particularly limited, but the total amount of the low molecular weight component eluted from the adhesive film immersed in N, N-dimethylformamide at 100 ° C. for 7 days is 100%. When it is, it is preferable that it is 5% or more.

  In the method for producing an adhesive film according to the present invention, the stage of performing the dipping step is not particularly limited, but is after the imidization of the thermoplastic polyimide contained in the adhesive layer is substantially completed. Is preferred.

  The solvent is not particularly limited, but is preferably an organic polar solvent. Specifically, one selected from N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide, tetrahydrofuran, methanol, and ethanol, Or it is preferable that it is a mixture of two or more. In particular, N-methyl-2-pyrrolidone, N, N-dimethylformamide, and N, N-dimethylacetamide can be mentioned.

  The temperature of the solvent is not particularly limited, but is preferably 10 ° C. or higher in view of the elution rate of the low molecular weight component. In view of suppression of solvent volatilization from the viewpoint of safety, the temperature is preferably 100 ° C. or lower.

  Although the time which immerses the said adhesive film before a process in a solvent is not specifically limited, 10 second or more is preferable and 30 second or more is more preferable.

  After immersing the adhesive film in the solvent, it is preferable to remove the solvent adhering to the surface of the adhesive film. The method for removing the solvent is not particularly limited. For example, after removing most of the solvent by a method such as a roll, a scraper or air jet, a method of heating the adhesive film to a temperature near or above the boiling point of the solvent is exemplified.

  As mentioned above, in the manufacturing method of the adhesive film concerning this invention, the adhesive film is immersed in the solvent in the said immersion process. Therefore, only a low molecular weight component can be removed from the adhesive layer of the adhesive film. On the other hand, the conventional technique for removing low molecular weight components from the adhesive layer of the adhesive film as described in Patent Document 3 uses a polyimide resin that is soluble in a solvent. In addition, high molecular weight components are also extracted. That is, in the method for producing an adhesive film according to the present invention, a desired effect can be obtained by removing only the low molecular component without eluting the high molecular component.

<III. Adhesive Film According to the Present Invention>
The adhesive film according to the present invention is an adhesive film in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface of a high heat-resistant polyimide layer, and only a low molecular weight component contained in the adhesive layer is removed. It is an adhesive film.

  In addition, the adhesive film concerning this invention is <II. It is preferably manufactured by the method for manufacturing an adhesive film according to the present invention.

  Since only the low molecular weight component contained in the adhesive layer is removed from the adhesive film according to the present invention, the adhesive film is less sticky. Therefore, the adhesive film according to the present invention can be suitably used in applications such as a two-layer FPC. In other words, when the FPC is incorporated into the apparatus through a soldering process or the like, the soldering tool can be satisfactorily soldered without being in close contact with the adhesive film.

  That is, the adhesive layer of the adhesive film according to the present invention has a property that the adhesiveness to the metal foil is good, but the adhesiveness to a soldering tool (for example, a soldering iron) is low. . The adhesiveness between the adhesive film and the soldering tool can be easily determined by the “stickiness evaluation” method of an example described later.

  Thus, the adhesive film according to the present invention can be used for various resin molded products using polyimide. Further, it can be widely applied to electronic parts using such an adhesive film.

  The present invention is not limited to the configurations described above, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In addition, the stickiness of the adhesive film and the molecular weight of the low molecular weight component in the following examples and comparative examples were evaluated as follows.

[Sticky evaluation]
The tip of a soldering iron at 360 ° C. ± 0.5 ° C. was brought into contact with a 10 cm × 5 cm adhesive film placed on a smooth desk for 10 seconds. Thereafter, the soldering iron was gently lifted. The above-described operation was performed 10 times at random locations on the adhesive film. The case where the adhesive film was lifted by 3 cm or more was evaluated as “× (with stickiness)”, and the other cases were evaluated as “◯ (no stickiness)”.

[Evaluation of molecular weight of low molecular weight components]
After immersing the adhesive film in an organic polar solvent, the molecular weight was measured by applying the organic polar solvent to GPC of a CCP & 8020 system manufactured by Tosoh Corporation.

[Synthesis Example 1: Synthesis of Polyamic Acid as Precursor of High Heat-Resistant Polyimide Compound]
To 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”), 6.2 kg of p-Phenylenediamine (hereinafter also referred to as “p-PDA”) and 9.4 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter also referred to as “BAPP”) were dissolved. . Thereafter, 10.4 kg of pyromellitic dianhydride (hereinafter also referred to as “PMDA”) 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 stirred for 1 hour to dissolve.

  Next, a DMF solution of PMDA (PMDA: DMF = 0.9 kg: 7.0 kg) prepared separately is gradually added to the reaction solution, and added when the viscosity reaches about 3500 poise (350 Pa · s). Stopped. Thereafter, 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 (350 Pa · s).

[Synthesis Example 2: Synthesis of polyamic acid as precursor of thermoplastic polyimide compound]
78 kg of DMF and 11.56 kg of BAPP were added to a 300 L reactor, and 7.87 kg of 3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added while stirring under a nitrogen atmosphere. Slowly added. Subsequently, 0.38 kg of ethylene bis (trimellitic acid monoester anhydride) (hereinafter also referred to as “TMEG”) was added and stirred for 30 minutes in an ice bath. A solution prepared by dissolving 0.2 kg of TMEG in 4 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 800 poise (80 Pa · s), addition and stirring were stopped to obtain a polyamic acid solution as a precursor of a thermoplastic polyimide compound.

[Example 1: Adhesive film]
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 Next, from the multi-manifold type three-layer coextrusion multilayer die having a lip width of 650 mm, the outer layer is a polyamic acid solution of a precursor of the thermoplastic polyimide obtained in Synthesis Example 2, and the inner layer is highly heat resistant. The multilayer film formed in the order of the polyamic acid solution as the precursor of the polyimide solution was continuously extruded and cast on an endless belt made of SUS running 15 mm below the T die. Next, this 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 peeled off from the endless belt is fixed to a tenter clip, dried and imidized at 300 ° C. for 16 seconds, 400 ° C. for 29 seconds, 450 ° C. for 17 seconds, and heat resistant polyimide layer An adhesive film having a thickness of 18 μm and an adhesive layer of 3.5 μm was obtained.

  The obtained adhesive film was immersed in N, N-dimethylformamide at 80 ° C. for 1 minute, and the surface N, N-dimethylformamide was removed with a scraper, followed by drying at 140 ° C. for 1 minute. At this time, the molecular weight of the low molecular weight component extracted with N, N-dimethylformamide was 20000.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was O.

[Example 2: Adhesive film]
The polyamic acid solution of the precursor of the high heat resistant polyimide obtained in Synthesis Example 1 was cooled to 0 ° C., and 2.1 mol of acetic anhydride and 1.1 mol of isoquinoline were added to 1 mol of the amic acid unit. After adding and stirring sufficiently, it was extruded from a single-layer T die maintained at 5 ° C. and cast on an endless belt. It was converted to a self-supporting gel film by heating at 130 ° C. for 100 seconds on an endless belt. Furthermore, the self-supporting gel film peeled off from the endless belt was fixed to a tenter clip, dried and imidized at 300 ° C. for 16 seconds, 400 ° C. for 29 seconds, 450 ° C. for 17 seconds, and a thickness of 18 μm. A heat resistant polyimide film was obtained.

  Subsequently, the polyamic acid solution of the precursor of the thermoplastic polyimide obtained in Synthesis Example 2 was diluted with N, N-dimethylformamide until the solid content concentration became 10% by weight. Thereafter, polyamic acid was applied to both surfaces of the heat-resistant polyimide film obtained by the above-described means so that the final single-sided thickness of the adhesive layer was 3.5 μm, and then heated at 140 ° C. for 1 minute. Then, it passed through the far-infrared heater furnace with an atmospheric temperature of 390 ° C. for 20 seconds to carry out heating imidization, thereby obtaining an adhesive film.

  The obtained adhesive film was immersed in N, N-dimethylformamide at 80 ° C. for 1 minute, and the surface N, N-dimethylformamide was removed with a scraper, followed by drying at 140 ° C. for 1 minute. At this time, the molecular weight of the low molecular weight component extracted with N, N-dimethylformamide was 20000.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was O.

[Example 3: Adhesive film]
Instead of “immersing the obtained adhesive film in N, N-dimethylformamide at 80 ° C. for 1 minute” in Example 2, “obtain the obtained adhesive film in N, N-dimethylformamide at 30 ° C. An adhesive film was produced in the same manner as in Example 2 except that the film was immersed for a minute. At this time, the molecular weight of the low molecular weight component extracted with N, N-dimethylformamide was 20000.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was O.

[Example 4: Adhesive film]
Instead of “immersing the obtained adhesive film in N, N-dimethylformamide at 80 ° C. for 1 minute” in Example 2, “obtaining the obtained adhesive film in N-methyl-2-pyrrolidone at 50 ° C. An adhesive film was produced in the same manner as in Example 2 except that the film was immersed for 3 minutes. At this time, the molecular weight of the low molecular weight component eluted with N-methyl-2-pyrrolidone was 20000.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was O.

[Comparative Example 1: Adhesive film]
Instead of “immersing the obtained adhesive film in N, N-dimethylformamide at 80 ° C. for 1 minute” in Example 1, “the obtained adhesive film was not immersed in N, N-dimethylformamide”. An adhesive film was produced in the same manner as in Example 1 except that.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was x.

[Comparative Example 2: Adhesive film]
Instead of “immersing the obtained adhesive film in N, N-dimethylformamide at 80 ° C. for 1 minute” in Example 2, “the obtained adhesive film was not immersed in N, N-dimethylformamide”. An adhesive film was produced in the same manner as in Example 2 except that.

  As a result of evaluating the stickiness of the adhesive film obtained by the above-mentioned means, it was x.

  Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention.

  As mentioned above, since the manufacturing method of the adhesive film concerning this invention includes the process of immersing the adhesive film in which the adhesive layer containing a thermoplastic polyimide was laminated | stacked in a solvent, it is contained in the adhesive layer of an adhesive film. Only low molecular weight components can be removed. Therefore, an adhesive film with little stickiness can be produced. Therefore, the present invention can be used not only in the field of producing various resin molded products represented by adhesive films and laminates using polyimide, but also using such adhesive films and laminates. It can be widely applied to fields related to the manufacture of electronic components.

Claims (7)

  The manufacturing method of the adhesive film characterized by including at least the process of immersing the adhesive film by which the adhesive layer containing a thermoplastic polyimide was laminated | stacked on the at least single side | surface of the high heat resistant polyimide layer in a solvent.   The method for producing an adhesive film according to claim 1, wherein the solvent contains an organic polar solvent.   The solvent is selected from N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide, tetrahydrofuran, methanol, and ethanol, It is a mixture of 2 or more types, The manufacturing method of the adhesive film of Claim 1 characterized by the above-mentioned. The temperature of the said solvent is 10 to 100 degreeC, The manufacturing method of the adhesive film of any one of Claims 1-3 characterized by the above-mentioned.   Only the low molecular weight component contained in the said adhesive layer is removed, The manufacturing method of the adhesive film of any one of Claims 1-4 characterized by the above-mentioned.   It manufactures with the manufacturing method of the adhesive film of any one of Claims 1-5, The adhesive film characterized by the above-mentioned.   An adhesive film in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface of a high heat-resistant polyimide layer, wherein only the low molecular weight component contained in the adhesive layer is removed.