JP5069846B2 - Novel polyimide film, adhesive film obtained using the same, and flexible metal-clad laminate - Google Patents

Description

  The present invention is a polyimide film that can suppress the dimensional change that occurs in the manufacturing process of a flexible metal-clad laminate, and in particular, has excellent dimensional stability when an adhesive layer is provided and a metal foil is bonded by a thermal laminating method. The present invention relates to a polyimide film from which a flexible metal-clad laminate is obtained, an adhesive film obtained by using the polyimide film, and a flexible metal-clad laminate.

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

  The flexible metal-clad laminate that is the basis of the flexible wiring board is generally formed of various insulating materials, and a flexible insulating film is used as a substrate, and a metal foil is attached to the surface of the substrate via various adhesive materials. Manufactured by a method of bonding by heating and pressure bonding. 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, an FPC (hereinafter also referred to as a two-layer FPC) in which a metal layer is directly provided on an insulating film or a thermoplastic polyimide is used for an adhesive layer has been proposed. This two-layer FPC has characteristics superior to those of the three-layer FPC, and demand is expected to increase in the future.

  As a method for producing a flexible metal-clad laminate for use in a two-layer FPC, a polyamic acid, which is a polyimide precursor, is cast on a metal foil, applied, and then casted directly onto a polyimide film by sputtering or plating. Examples thereof include a metallizing method for providing a metal layer and a laminating method for bonding a polyimide film and a metal foil through a thermoplastic polyimide. 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. Of these, the hot roll laminating method can be used more preferably from the viewpoint of productivity.

  When a conventional three-layer FPC was produced by a laminating method, a thermosetting resin was used for the adhesive layer, so that the laminating temperature could be less than 200 ° C. (see Patent Document 1). On the other hand, since the two-layer FPC uses thermoplastic polyimide as an adhesive layer, it is necessary to apply a high temperature of 200 ° C. or higher, and in some cases, close to 400 ° C., in order to develop heat-fusibility. Therefore, residual distortion occurs in the flexible metal-clad laminate obtained by laminating, and it appears as a dimensional change when wiring is formed by etching and when solder reflow is performed to mount components.

  In particular, in the laminating method, when an adhesive layer containing a thermoplastic polyimide is provided on a polyimide film, the polyamic acid which is a precursor of the thermoplastic polyimide is cast and applied, and then continuously heated to imidize, Since the heating and pressurization is continuously performed when the metal foil is bonded, the material is often placed in a heating environment under tension. Therefore, different thermal stresses are generated in the MD direction and the TD direction. Specifically, a pulling force acts in the MD direction where tension is applied, and conversely, a shrinking force acts in the TD direction. As a result, when the metal foil is etched from the flexible laminate and when heated through solder reflow, this strain is released, the MD direction contracts, and conversely, the TD direction expands.

  In recent years, in order to achieve miniaturization and weight reduction of electronic devices, wiring provided on a substrate has been miniaturized, and components to be mounted are mounted with miniaturization and high density. For this reason, if the dimensional change after forming the fine wiring is increased, there is a problem that the component and the board are not well connected due to deviation from the component mounting position in the design stage.

  Therefore, attempts have been made to suppress dimensional changes by controlling the laminating pressure or controlling the tension of the adhesive film (see Patent Document 2 or 3). However, although the dimensional change is improved by these means, it is not sufficient yet, and further improvement of the dimensional change is demanded.

  Particularly in recent years, the use of lead-free solder tends to increase the required level of moisture-absorbing solder resistance. To meet this trend, the adhesive layer has a higher Tg (glass transition temperature). Necessary temperature is inevitably high. Therefore, the thermal stress applied to the material is further increased, and a dimensional change is likely to occur. Therefore, there is a need for a material design that more efficiently relieves thermal stress.

In addition, the thickness of the insulating layer used in the current two-layer FPC is mainly 25 μm (1 mil). However, the thickness of the insulating layer is reduced to 15 μm or less due to further reduction of the board mounting space and problems such as springback. The so-called “half-mill” demand has begun to appear. However, since the thickness of the adhesive film is thinner in the half-mill product, it is more susceptible to thermal stress during lamination, and the hurdle for improving the dimensional change is considerably higher than that of the 1-mil product.
JP-A-9-199830 JP 2002-326308 A JP 2002-326280 A

  The present invention has been made in view of the above-described problems, and its purpose is to provide a polyimide film capable of suppressing dimensional changes that occur in the manufacturing process of a flexible copper-clad laminate, particularly heat applied to a material by a laminating method. A polyimide film having a function of suppressing distortion, an adhesive film provided with an adhesive layer on at least one side of the polyimide film, and a dimensional change generated by bonding a metal foil to the adhesive film by a heat laminating method. An object of the present invention is to provide a flexible metal-clad laminate that can be suppressed, particularly a flexible metal-clad laminate that can suppress the occurrence of dimensional changes even when the thickness of an adhesive film is thin.

As a result of intensive studies in view of the above-mentioned problems, the present inventors have found that a polyimide film whose storage elastic modulus value is controlled within a specific range is a dimension that can occur in a manufacturing process of a flexible copper-clad laminate using the polyimide film. The ability to suppress changes, in particular, it can be used as the core layer of an adhesive film with an adhesive layer on at least one side of the film, thereby reducing thermal distortion during thermal lamination and effectively suppressing the occurrence of dimensional changes. The present invention has been completed. That is, the above object can be achieved by the following novel polyimide film, an adhesive film using the same, and a flexible metal-clad laminate.
1) A polyimide film obtained by imidizing a polyamic acid obtained by reacting an aromatic diamine and an aromatic acid dianhydride, the following conditions (1) to (4) (1) 280 ° C. to 320 Has an inflection point of storage elastic modulus in the range of ℃,
(2) The peak top of tan δ, which is a value obtained by dividing the loss elastic modulus by the storage elastic modulus, is in the range of 320 ° C. to 380 ° C.,
(3) The storage elastic modulus at 380 ° C. is 0.4 GPa to 2.0 GPa,
(4) and the storage modulus alpha ₁ (GPa) at the inflection point, storage at 380 ° C. modulus alpha ₂ (GPa) is within the range of the following formula (1) (Equation 1); 85 ≧ {(α 1 - α ₂ ) / α ₁ } × 100 ≧ 65
A polyimide film characterized by satisfying all of the above.
2) The polyimide film has the following steps (a) to (c).
(A) An aromatic acid dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends (b) (C) Further, the aromatic dianhydride is added and polymerized so that the aromatic dianhydride and the aromatic diamine are substantially equimolar in all steps. The polyimide film as described in 1), which is obtained by imidizing a polyamic acid solution obtained by passing.
3) The polyimide film according to 2), wherein the aromatic diamine in the step (a) is a flexible diamine, and the aromatic diamine in the step (b) is a rigid diamine.
4) The polyimide film as described in 3), wherein 4,4′-diaminodiphenyl ether is used as the flexible diamine.
5) The polyimide film as described in 3) or 4), wherein p-phenylenediamine is used as the rigid diamine.
6) The polyimide film according to 2) to 5), wherein benzophenone tetracarboxylic dianhydride and pyromellitic dianhydride are used in the step (a).
7) The polyimide film according to 1) to 6), wherein the polyimide film has a tensile modulus of 7.0 GPa or more.
8) The polyimide film according to 1) to 7), wherein the polyimide film has a linear expansion coefficient at 100 ° C. to 200 ° C. of 13 ppm / ° C. or less.
9) An adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one side of the polyimide film described in 1) to 8).
10) The adhesive film according to 9), wherein the thermoplastic polyimide has a glass transition temperature (Tg) of 230 ° C. or higher.
11) The adhesive film according to 9) or 10), wherein the film thickness is 15 μm or less.
12) A flexible metal-clad laminate obtained by bonding a metal foil to an adhesive film according to any one of claims 9 to 11 using a hot roll laminator having a pair of metal rolls.
13) Non-thermoplastic polyimide or glass transition temperature (Tg) is 50 ° C. or more higher than the laminating temperature when a metal foil is bonded to an adhesive film using a hot roll laminating apparatus having the pair of metal rolls. A flexible metal-clad laminate according to 12), which is obtained by laminating a protective film made of thermoplastic polyimide between a metal foil and a roll, and then peeling off the protective film when cooled after lamination. Laminated board.
14) After the lamination, before peeling off the protective film, the laminate in which the protective film and the flexible metal-clad laminate are in close contact with each other is brought into contact with the heating roll in the range of 0.1 to 5 seconds, and then cooled. The flexible metal-clad laminate according to 13), wherein the protective material is peeled from the laminate.
15) The dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil is in the range of −0.04 to + 0.04% in both the MD direction and the TD direction. 14) The flexible metal-clad laminate described in 14).
16) The thickness of the adhesive film is 15 μm, and the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil is in the range of −0.05 to + 0.05% in both the MD direction and the TD direction. The flexible metal-clad laminate according to any one of 12) to 14), wherein the flexible metal-clad laminate is provided.

  The polyimide film of this invention can suppress the dimensional change which generate | occur | produces in the manufacturing process of a flexible copper clad laminated board. In particular, in order to relieve thermal stress during lamination, an inflection point of the storage elastic modulus is given and the value is controlled. As a result, in a flexible metal-clad laminate in which a metal foil is bonded to an adhesive film using the polyimide film as a core by a laminating method, the occurrence of dimensional change is effectively suppressed. Specifically, the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil can be set to a range of −0.04 to + 0.04% in both the MD direction and the TD direction. Therefore, it can be suitably used for an FPC or the like in which fine wiring is formed, and problems such as misalignment can be improved.

  Embodiments of the present invention will be described below. First, the case of the polyimide film according to the present invention will be described based on an example of the embodiment.

(Polyimide film of the present invention)
In the present invention, if the polyimide film satisfies all of the following physical properties (1) to (4), dimensional changes that occur when a flexible metal-clad laminate is produced using the polyimide film can be effectively suppressed. It is.
(1) having an inflection point of storage elastic modulus in the range of 280 ° C to 320 ° C;
(2) The peak top of tan δ, which is a value obtained by dividing the loss elastic modulus by the storage elastic modulus, is in the range of 320 ° C. to 380 ° C.,
(3) The storage elastic modulus at 380 ° C. is 0.4 GPa to 2.0 GPa,
(4) and the storage modulus alpha ₁ (GPa) at the inflection point, storage at 380 ° C. modulus alpha ₂ (GPa) is within the range of the following formula (1) (Equation 1); 85 ≧ {(α 1 - α ₂ ) / α ₁ } × 100 ≧ 65
The inflection point of the storage elastic modulus will be described. The inflection point of the storage elastic modulus needs to be in the range of 280 to 320 ° C., preferably 290 to 310 ° C., from the viewpoint of relaxation of thermal stress when the metal foil is bonded by the laminating method. Here, when the inflection point of the storage elastic modulus is lower than the above range, the temperature at which the dimensional change after heating of the flexible metal-clad laminate is evaluated (in the field of two-layer FPC, it is often evaluated at 250 ° C. ), Since the softening of the core layer starts, the dimensional change becomes worse. On the other hand, when the temperature is higher than the above range, the temperature at which the softening of the core layer starts is high, so that the thermal stress is not sufficiently relaxed at the time of thermal lamination, and the dimensional change is deteriorated.

  Further, the peak top of tan δ, which is a value obtained by dividing the loss elastic modulus by the storage elastic modulus, needs to be in the range of 320 ° C. to 380 ° C. or more, preferably 330 ° C. to 360 ° C. When the peak top of tan δ is lower than the above range, the temperature at which tan δ begins to increase is around 250 ° C or lower, and the core layer may begin to soften during dimensional change measurement, so the dimensional change rate may deteriorate. There is sex. Conversely, when the peak top of tan δ is higher than the above range, the temperature required to soften the core layer to a level sufficient to alleviate strain becomes too high, and the existing laminating equipment sufficiently relaxes the thermal stress. The dimensional change may get worse. When it is out of the above range, the dimensional change becomes worse as well as the inflection point of the storage elastic modulus.

  Further, the storage elastic modulus at 380 ° C. needs to be in the range of 0.4 to 2.0 GPa, preferably 0.6 to 1.8 GPa, more preferably 0.7 to 1.6 GPa. As a result of intensive studies, the present inventors have found that the glass transition temperature of the adhesive layer needs to be 240 ° C. to 280 ° C. when solder heat resistance is also achieved. In that case, a lamination temperature of about 380 ° C. is necessary in order to perform lamination with high productivity. Therefore, storage elastic modulus control at 380 ° C. is very important. When the storage elastic modulus at 380 ° C. is lower than the above range, the film cannot maintain the self-supporting property at the time of imidization or thermal lamination of the film, and the productivity of the film is deteriorated, or the obtained flexible metal-clad laminate Causes the appearance of the product to deteriorate. On the other hand, when the temperature is higher than the above range, the core layer is not sufficiently softened, so that the thermal stress relaxation effect at the time of thermal lamination is not sufficiently exhibited, and the dimensional change is deteriorated.

Further, the present inventors have made study for the relationship between the value of the storage modulus modulus alpha ₂ (GPa) at a 380 ° C. storage modulus alpha ₁ (GPa) at the inflection point, the range of the following formula (1) It has been found that it is important to suppress dimensional changes that occur in the process of manufacturing a flexible metal-clad laminate.
85 ≧ {(α ₁ −α ₂ ) / α ₁ } × 100 ≧ 65 (Formula 1)
When it falls below the above range, the degree of decrease in the storage elastic modulus is small, so that the thermal stress relaxation effect at the time of thermal lamination is not sufficiently exhibited, and the dimensional change of the resulting flexible metal-clad laminate is deteriorated. On the other hand, when the temperature is higher than the above range, the film cannot maintain the self-supporting property, thereby deteriorating the productivity of the film or deteriorating the appearance of the obtained flexible metal-clad laminate.

  In order to obtain a flexible metal-clad laminate excellent in dimensional stability, a polyimide film that satisfies all the above three conditions is required.

So far, no polyimide film satisfying all of the above properties has been known. The method for obtaining such a polyimide film is not particularly limited, but will be described with an example.
The polyimide film of the present invention is obtained from a solution of polyamic acid which is a polyimide precursor. The polyamic acid is usually controlled by dissolving the polyamic acid organic solvent solution obtained by dissolving the aromatic diamine and the aromatic dianhydride in an organic solvent so as to have a substantially equimolar amount. 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.

The polyimide film of the present invention can control various physical properties by controlling not only the structure of diamine and acid dianhydride as raw material monomers but also the order of monomer addition. Therefore, in order to obtain the polyimide film of the present invention, it is preferable to imidize the polyamic acid solution obtained through the following steps (a) to (c).
(A) An aromatic acid dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends (b) (C) Furthermore, the aromatic dianhydride is added and polymerized so that the aromatic dianhydride and the aromatic diamine are substantially equimolar in all steps. The aromatic diamine that can be used as a raw material monomer for the polyimide film of the invention includes 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, and 3,3′-dimethyl. Benzidine, 2,2′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 2,2′-dimethoxybenzidine, 4,4′-diaminodiphenyl sulfide, 3 3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4 '-Diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (3-amino Phenoxy) phenyl} sulfone, 4,4′-bis (4-amino) Phenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, bis {4- (4-aminophenoxy) phenyl} propane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone and Those analogs are mentioned.

  In the step (a), it is preferable to obtain a prepolymer that forms a block component derived from thermoplastic polyimide. In order to obtain a prepolymer that forms a block component derived from thermoplastic polyimide, it is preferable to react a flexible diamine with an acid dianhydride. In the present invention, the block component derived from thermoplastic polyimide refers to a component that melts when the high molecular weight film is heated to 400 ° C. and does not retain the shape of the film. Specifically, it is confirmed whether the polyimide obtained by equimolar reaction of the aromatic diamine compound and aromatic acid anhydride component used in step (a) melts at the above temperature or does not maintain the shape of the film. By doing so, an aromatic diamine compound and an aromatic dianhydride component can be selected. By using the prepolymer and proceeding the reactions in the steps (b) and (c), a polyamic acid having thermoplastic sites scattered in the molecular chain can be obtained. Here, if the aromatic diamine compound and the aromatic dianhydride component used in the steps (b) and (c) are selected and the polyamic acid is polymerized so that the finally obtained polyimide becomes non-thermoplastic. The polyimide film obtained by imidizing this has a thermoplastic portion, and thus exhibits an inflection point of the storage elastic modulus in a high temperature region. On the other hand, most of the molecular chain has a non-thermoplastic structure, so controlling the ratio of thermoplastic and non-thermoplastic parts prevents the storage elastic modulus from drastically decreasing at high temperatures. It becomes possible.

Here, in the step (a), a prepolymer for forming a block component derived from non-thermoplastic polyimide is obtained by reacting a rigid diamine component and an acid dianhydride component, and (b), (c) It is also possible to obtain a polyamic acid in which thermoplastic sites are scattered in the molecular chain by connecting the prepolymer with a block component derived from thermoplastic polyimide in the reaction of the process. However, this method makes the block length of the thermoplastic part non-uniform and makes it difficult to balance the storage elastic modulus. Specifically, the storage elastic modulus at 380 ° C. does not decrease so much even though the E ′ inflection occurs at a low temperature.
Accordingly, in the present invention, it is necessary to first form a block component derived from a thermoplastic polyimide and then form a block derived from a non-thermoplastic polyimide component.
The diamine having flexibility in the present invention is a diamine having a diamine flexible structure having a flexible structure such as an ether group, a sulfone group, a ketone group, or a sulfide group, and preferably represented by the following general formula (1) It is.

（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、Ｈ−，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。）
上記工程を経ることによって得られたポリイミドフィルムが、何故無処理でも高接着性を発現するのか、詳しいことはまだ明らかになっていない。分子鎖中に点在する屈曲部位が表面脆弱層の形成を阻害するか、接着層との接着に何らかの関与をしていると考えられる。

R _{5 in} the formula is the same or different and is H—, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —, or a group selected from the group consisting of divalent organic groups represented by One group selected from the group consisting of COOH, —CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—. )
It has not yet been clarified why the polyimide film obtained through the above process exhibits high adhesion even without treatment. It is considered that the bent sites scattered in the molecular chain inhibit the formation of the surface fragile layer or have some involvement in the adhesion with the adhesive layer.

    Furthermore, the diamine component used in the step (b) is preferably a rigid diamine from the viewpoint that the film finally obtained can be made non-thermoplastic. 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Ｈ−，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。

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

  Here, the use ratio of the diamine of the rigid structure and the flexible structure (flexible diamine) is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and particularly 60:40 to 40:40. It is preferable to be in the range of 40:60. When the use ratio of the rigid structure diamine exceeds the above range, the glass transition temperature of the resulting film becomes too high, the storage elastic modulus in the high temperature region hardly decreases, or the linear expansion coefficient becomes too small. There is. On the other hand, if it falls below this range, the opposite adverse effects may occur.

The above-mentioned flexible structure and rigid structure diamines may be used in combination of two or more, and preferred examples of the flexible structure diamine include diaminodiphenyl ether and bis {4- (4-aminophenoxy) phenyl} propane. Preferable examples of the rigid diamine include phenylenediamine and diaminonaphthalene.
However, if the types of raw materials used are increased, the number of times the raw materials are added during polymerization increases, leading to a decrease in production cycle. In addition, polyimides using bis {4- (4-aminophenoxy) phenyl} propane tend to change in physical properties depending on the film firing conditions, so a process window is required to balance physical properties such as elastic modulus and linear expansion coefficient. It may become narrower.
Accordingly, in the polyimide film of the present invention, it is preferable to use one kind each of the flexible structure and the rigid structure diamine, the 4,4′-diaminodiphenyl ether as the flexible structure diamine, and p-phenylene as the rigid structure diamine. Particular preference is given to using diamines.

    Since 4,4'-diaminodiphenyl ether has only one ether bond which is a bending site, it exhibits an intermediate property between the two kinds of flexible diamines. That is, it has the effect of lowering the storage elastic modulus, but does not increase the linear expansion coefficient so much. Therefore, it becomes easy to balance the physical properties of the obtained polyimide film.

  The amount of 4,4'-diaminodiphenyl ether used is preferably 10 mol% or more, more preferably 15 mol% or more of the total diamine component. If it is less than this, the above-mentioned effects may not be sufficiently exhibited. On the other hand, about an upper limit, 50 mol% or less is preferable and 40 mol% or less is more preferable. If it is more than this, the linear expansion coefficient of the resulting polyimide film may become too small due to a synergistic effect with the rigid structure diamine.

  Examples of the acid dianhydride that can be used as a raw material monomer for the polyimide film of the present invention include 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, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,4′-oxyphthalic dianhydride 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) Methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimellitic acid mono Ester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and the like. These may be used alone or in any desired mixture.

As in the case of diamine, acid dianhydrides are also classified into a flexible structure and a rigid structure, and the former is used in step (a) and the latter is used in step (c). Preferred examples of the acid dianhydride used in the step (a) include benzophenone tetracarboxylic dianhydrides, oxyphthalic dianhydrides, and biphenyl tetracarboxylic dianhydrides. Among these, benzophenone tetracarboxylic acid is a preferred example. A preferred example of the acid dianhydride used in the step (c) is pyromellitic dianhydride. Moreover, the preferable usage-amount of benzophenone tetracarboxylic dianhydrides, oxyphthalic dianhydrides, and biphenyl tetracarboxylic dianhydrides is 10-50 mol% with respect to all the acid dianhydrides, More preferably, 15 It is -45 mol%, Most preferably, it is 20-40 mol%. When the amount is less than the above range, the glass transition temperature of the resulting polyimide film may be too high or the storage elastic modulus in the high temperature region may not be sufficiently lowered with the flexible diamine alone. On the other hand, when the amount is larger than the above range, the glass transition temperature may be too low, or the storage elastic modulus in the high temperature region may be too low to make film formation difficult.
Moreover, when using pyromellitic dianhydride, the preferable usage-amount is 40-100 mol%, More preferably, it is 50-90 mol%, Most preferably, it is 60-80 mol%. By using pyromellitic dianhydride in this range, it becomes easy to keep the glass transition temperature and the storage elastic modulus in the high temperature region of the resulting polyimide film in a range suitable for use or film formation.

  The polyimide film according to the present invention has a desired glass transition temperature and a storage elastic modulus in a high temperature region by determining and using the types and blending ratios of the aromatic dianhydride and aromatic diamine within the above range. Although it can be expressed, considering the processing method of the adhesive film that is the intended use, that is, processing by the thermal laminating method, the tensile elastic modulus is preferably 7.0 GPa or more, and 7.5 GPa or more. Is more preferable. When the tensile elastic modulus is smaller than the above value, it is easily affected by the tension, and residual stress is generated in the flexible metal-clad laminate, causing a dimensional change. Further, when the film thickness is reduced, the stiffness of the film is weak, which may cause problems in transportability and handleability. As an upper limit of a tensile elasticity modulus, 10 GPa or less is preferable and 9.0 GPa or less is more preferable. If the value is larger than the above value, the stiffness may be too strong, which may cause a problem in handling. The tensile modulus increases as the proportion of the rigid diamine or dianhydride, or 4,4'-diaminodiphenyl ether increases, and decreases as the proportion decreases.

Moreover, when the influence on a dimensional change is considered, it is preferable that the linear expansion coefficient in 100 to 200 degreeC of the said polyimide film is 13 ppm / degrees C or less, and it is more preferable that it is 11 ppm / degrees C or less. When the linear expansion coefficient is larger than the above value, the linear expansion coefficient when the adhesive film is formed becomes too large, and the difference from the linear expansion coefficient of the metal foil becomes large, which causes a dimensional change. On the other hand, if the linear expansion coefficient of the polyimide film is too small, the difference in the linear expansion coefficient of the metal foil is also increased. Therefore, the lower limit of the linear expansion coefficient is preferably 5 ppm / ° C, and more preferably 6 ppm / ° C. When the linear expansion coefficient of the polyimide film is in the range of 5 to 13 ppm / ° C., preferably 6 to 11 ppm / ° C., it becomes easy to bring the linear expansion coefficient of the adhesive film closer to that of the metal foil. As described above, the linear expansion coefficient of the polyimide film can be adjusted by the mixing ratio of the flexible structural component and the rigid structural component.
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 addition, a filler can be added for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

The particle size of the filler is not particularly limited because it is determined by the film characteristics to be modified and the kind of filler to be added, but generally the average particle size is 0.05 to 100 μm, preferably 0.1. It is -75 micrometers, More preferably, it is 0.1-50 micrometers, Most preferably, it is 0.1-25 micrometers. If the particle diameter is below this range, the modification effect is difficult to appear. If the particle diameter is above this range, the surface properties may be greatly impaired or the mechanical properties may be greatly deteriorated. Further, the number of added parts of the filler is not particularly limited because it is determined by the film properties to be modified, the filler particle diameter, and the like. Generally, the addition amount of the filler is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight with respect to 100 parts by weight of the polyimide. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired. Addition of filler
1. 1. A method of adding to a polymerization reaction solution before or during polymerization 2. A method of kneading fillers using three rolls after 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.
A conventionally well-known method can be used about the method of manufacturing a polyimide film from these polyamic-acid solutions. This method includes a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which an imidization reaction proceeds only by heating without causing a dehydrating ring-closing agent or the like to act. The chemical imidization method acts by applying a chemical conversion agent and / or a catalyst to a polyamic acid solution. This is a method for promoting imidization.

Here, the chemical conversion agent means a dehydrating ring-closing agent for polyamic acid, for example, aliphatic acid anhydride, aromatic acid anhydride, N, N′-dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower Examples include fatty acid anhydrides, arylphosphonic acid dihalides, thionyl halides, or mixtures of two or more thereof. Among these, from the viewpoint of easy availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic acid anhydride, or a mixture of two or more thereof can be preferably used.
The catalyst means a component having an effect of promoting the dehydration ring-closing action on the polyamic acid. For example, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine or the like is used. Among them, those selected from heterocyclic tertiary amines are particularly preferably used from the viewpoint of reactivity as a catalyst. Specifically, quinoline, isoquinoline, β-picoline, pyridine and the like are preferably used.
Either method may be used to produce the film, but the imidization by the chemical imidization method tends to easily obtain a polyimide film having various characteristics suitably used in the present invention.
In addition, the production process of the polyimide film particularly preferable in the present invention is as follows.
a) reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution;
b) casting a film-forming dope containing the polyamic acid solution on a support;
c) a step of peeling the gel film from the support after heating on the support;
d) further heating to imidize and dry the remaining amic acid,
It is preferable to contain.
In the above step, a curing agent containing a dehydrating agent typified by an acid anhydride such as acetic anhydride and an imidation catalyst typified by a tertiary amine such as isoquinoline, β-picoline or pyridine may be used. .
In the following, a preferred embodiment of the present invention, a chemical imidization method, is taken as an example to describe the process for producing a polyimide film. However, the present invention is not limited to the following examples. The film forming conditions and heating conditions can vary depending on the type of polyamic acid, the thickness of the film, and the like.
A film forming dope is obtained by mixing a dehydrating agent and an imidization catalyst in a polyamic acid solution at a low temperature. Subsequently, this film-forming dope is cast into a film on a support such as a glass plate, an aluminum foil, an endless stainless steel belt or a stainless drum, and the temperature on the support is 80 ° C. to 200 ° C., preferably 100 ° C. to 180 ° C. By heating in the region, the dehydrating agent and imidization catalyst are activated to partially cure and / or dry and then peel from the support to obtain a polyamic acid film (hereinafter referred to as a gel film).
The gel film is in the intermediate stage of curing from polyamic acid to polyimide and has self-supporting properties (Formula 2)
(AB) × 100 / B (Equation 2)
In (Formula 2), A and B represent the following.
A: Weight of gel film B: The volatile content calculated from the weight after heating the gel film at 450 ° C. for 20 minutes is in the range of 5 to 500% by weight, preferably 5 to 200% by weight, more preferably 5 to 5%. It is in the range of 150% by weight. It is preferable to use a film in this range, and problems such as film breakage, uneven film color due to drying unevenness, and characteristic variations may occur during the baking process.
The preferable amount of the dehydrating agent is 0.5 to 5 mol, preferably 1.0 to 4 mol, relative to 1 mol of the amic acid unit in the polyamic acid.
Moreover, the preferable quantity of an imidation catalyst is 0.05-3 mol with respect to 1 mol of amic acid units in a polyamic acid, Preferably it is 0.2-2 mol.
If the dehydrating agent and the imidization catalyst are below the above ranges, chemical imidization may be insufficient, and may break during firing or mechanical strength may decrease. Moreover, when these amounts exceed the above range, the progress of imidization becomes too fast, and it may be difficult to cast into a film, which is not preferable.

The end of the gel film is fixed to avoid shrinkage during curing, water, residual solvent, residual conversion agent and catalyst are removed, and the remaining amic acid is completely imidized to obtain the present invention. A polyimide film is obtained.
At this time, it is preferable to finally heat at a temperature of 400 to 650 ° C. for 5 to 400 seconds. Above this temperature and / or for a long time, the film may suffer from thermal degradation and may cause problems. Conversely, if the temperature is lower than this temperature and / or the time is shorter, the predetermined effect may not be exhibited.
Moreover, in order to relieve the internal stress remaining in the film, heat treatment can be performed under the minimum tension necessary for transporting the film. This heat treatment may be performed in the film manufacturing process, or may be provided separately. The heating conditions vary depending on the characteristics of the film and the apparatus used, and therefore cannot be determined in general. However, it is generally 200 ° C. or higher and 500 ° C. or lower, preferably 250 ° C. or higher and 500 ° C. or lower, particularly preferably 300 ° C. or higher. The internal stress can be relaxed by heat treatment at a temperature of 450 ° C. or lower for 1 to 300 seconds, preferably 2 to 250 seconds, particularly preferably 5 to 200 seconds.
Moreover, in order to cancel the influence of the tension | tensile_strength and the extending | stretching by lamination at the time of finally processing by a thermal laminating method, a polyimide film can be formed so that a molecular orientation may be carried out in a conveyance direction (MD direction). As means for orienting the polyimide film in the MD direction,
1) Stretching the gel film in the MD direction 2) Introducing a step of fixing and transporting the gel film so that the TD direction tension is substantially tensionless is introduced into a part of the film baking step. Here, the fact that the tension in the TD direction is substantially tensionless means that the tensile tension due to mechanical handling is not applied in the TD direction other than the tension due to the weight of the film.

  As the thermoplastic polyimide contained in the adhesive layer of the adhesive film according to the present invention, 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.

  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. Further, taking into account the hygroscopic solder resistance, Tg is preferably 230 ° C. or higher, and more preferably 240 ° C. or higher. 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 is not particularly limited, and any known polyamic acid can be used. Also for the production, known raw materials, reaction conditions, and the like can be used (for example, see Examples described later). Moreover, you may add an inorganic or organic filler as needed.

  The adhesive film according to the present invention is obtained by providing an adhesive layer containing thermoplastic polyimide on at least one surface of the polyimide film. As a method for producing an adhesive film, a method of forming an adhesive layer on a polyimide film to be a base film, or a method of forming an adhesive layer into a sheet and bonding it to the base film can be suitably exemplified. . Among these, when taking the former method, if the polyamic acid that is the precursor of the thermoplastic polyimide contained in the adhesive layer is completely imidized, the solubility in an organic solvent may decrease, It may be difficult to provide the adhesive layer on the base film. Therefore, from the above viewpoint, it is more preferable to prepare a solution containing polyamic acid which is a precursor of thermoplastic polyimide, apply this to a base film, and then imidize. As the imidization method at this time, either a thermal cure method or a chemical cure method can be used.

  In any of the imidization procedures, the temperature at that time is in the range of (glass transition temperature of thermoplastic polyimide−100 ° C.) to (glass transition temperature + 200 ° C.) from the viewpoint that imidization can be efficiently advanced. It is preferable to set within the range of (Glass transition temperature of thermoplastic polyimide−50 ° C.) to (Glass transition temperature + 150 ° C.). The higher the temperature of the heat curing, the easier the imidization occurs, so the curing speed can be increased, which is preferable in terms of productivity. However, if it is too high, the thermoplastic polyimide may thermally decompose. On the other hand, if the temperature of the heat curing is too low, imidization is difficult to proceed even with chemical curing, and the time required for the curing process becomes long.

  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. Moreover, in order to improve the melt fluidity of the adhesive layer, it is possible to intentionally lower the imidization rate and / or leave the solvent.

  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. When the tension is smaller than the above range, sagging may occur when the film is conveyed, and problems such as inability to wind up uniformly may occur. On the other hand, if it is larger than the above range, the adhesive film is heated to a high temperature with a strong tension applied, so even if a core film with a high tensile elastic modulus or a core film of MD oriented core film is used. Thermal stress is generated on the film, which may affect dimensional changes.

  The method for casting and applying the polyamic acid solution to the base film is not particularly limited, and existing methods such as a die coater, a reverse coater, and a blade coater can be used. In addition, the polyamic acid solution may contain other materials such as a filler, depending on the application.

  What is necessary is just to adjust suitably about the thickness structure of each layer of an adhesive film so that it may become the total thickness according to a use. However, it is preferable to set the thermal expansion coefficient of the adhesive film at 200 to 300 ° C. to be close to that of the metal foil from the viewpoint of suppressing the occurrence of thermal strain during thermal lamination. Specifically, it is preferably within ± 10 ppm, more preferably within ± 5 ppm of the thermal expansion coefficient of the metal foil.

  Further, if necessary, various surface treatments such as corona treatment, plasma treatment, and coupling treatment may be performed on the core film surface before or after providing the adhesive layer.

  The flexible metal-clad laminate according to the present invention can be obtained by bonding a metal foil to the adhesive film. The metal foil to be used is not particularly limited, but when the flexible metal-clad laminate of the present invention is used for electronic equipment / electric equipment, for example, copper or copper alloy, stainless steel or its alloy, nickel Alternatively, a foil made of a nickel alloy (including 42 alloy), aluminum, or an aluminum alloy can be used. In general flexible metal-clad laminates, copper foil such as rolled copper foil and electrolytic copper foil is frequently used, but it can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil.

  In the present invention, the thickness of the metal foil is not particularly limited, and may be any thickness as long as a sufficient function can be exhibited depending on the application. As a method for bonding the adhesive film and the metal foil, for example, a heat roll laminating apparatus having a pair of metal rolls or a continuous process using a double belt press (DBP) can be used. Among these, it is preferable to use a hot roll laminating apparatus having a pair of metal rolls because the apparatus configuration is simple and advantageous in terms of maintenance cost. In addition, since the dimensional change is particularly likely to occur when bonded to a metal foil with a hot roll laminating apparatus having a pair of metal rolls, the polyimide film and adhesive film of the present invention are bonded with a hot roll laminating apparatus. Has a remarkable effect. The “heat roll laminating apparatus having a pair of metal rolls” herein may be an apparatus having a metal roll for heating and pressurizing a material, and the specific apparatus configuration is particularly limited. It is not a thing.

The specific configuration of the means for carrying out the thermal lamination is not particularly limited, but a protective material is disposed between the pressing surface and the metal foil in order to improve the appearance of the resulting laminate. It is preferable to do. Examples of the protective material include materials that can withstand the heating temperature in the heat laminating process, that is, heat-resistant plastics such as non-thermoplastic polyimide films, copper foils, aluminum foils, metal foils such as SUS foils, and the like. Among these, a non-thermoplastic polyimide film or a film made of thermoplastic polyimide that is 50 ° C. higher than the laminating temperature is preferably used from the viewpoint of excellent balance between heat resistance and reusability. In addition, if the thickness is small, the buffering and protecting functions are not sufficiently fulfilled during lamination, so the thickness of the non-thermoplastic polyimide film is preferably 75 μm or more.
Further, the protective material does not necessarily have to be a single layer, and may have a multilayer structure of two or more layers having different characteristics.

  Further, when the laminate temperature is high, if the protective material is used as it is for the laminate, the appearance and dimensional stability of the resulting flexible metal-clad laminate may not be sufficient due to rapid thermal expansion. Therefore, it is preferable to preheat the protective material before lamination. Examples of the preheating means include a method of bringing a protective material into contact with a heating roll. The contact time is preferably 1 second or longer, more preferably 3 seconds or longer. By preheating the protective material, since the thermal expansion of the protective material is completed when laminating, the appearance and dimensional characteristics of the flexible metal-clad laminate are suppressed. When the contact time is shorter than the above, since the lamination is performed without the thermal expansion of the protective material, the thermal expansion of the protective material occurs during the lamination, and the appearance and dimensional characteristics of the resulting flexible metal-clad laminate are deteriorated. There are things to do. The distance at which the protective material is held on the heating roll is not particularly limited, and may be appropriately adjusted from the diameter of the heating roll and the contact time.

  The heating method of the material to be laminated in the heat laminating means is not particularly limited. For example, heating using a conventionally known method capable of heating at a predetermined temperature, such as a heat circulation method, a hot air heating method, an induction heating method, or the like. Means can be used. Similarly, the pressurization method of the material to be laminated in the heat laminating means is not particularly limited, and a conventionally known method capable of applying a predetermined pressure such as a hydraulic method, a pneumatic method, a gap pressure method, etc. The pressurizing means adopting can be used.

  The heating temperature in the thermal laminating step, that is, the laminating temperature, is preferably a glass transition temperature (Tg) of the adhesive film + 50 ° C. or higher, and more preferably Tg + 100 ° C. or higher of the adhesive film. If it is Tg + 50 degreeC or more temperature, an adhesive film and metal foil can be heat-laminated favorably. Moreover, if it is Tg + 100 degreeC or more, the lamination speed | rate can be raised and the productivity can be improved more. In particular, the polyimide film used as the core of the adhesive film of the present invention is designed to effectively relax thermal stress when laminated at Tg + 100 ° C. or higher. An excellent flexible metal-clad laminate can be obtained with high productivity.

  Here, the thermal stress relaxation mechanism during thermal lamination will be described. When thermoplastic polyimide is contained in the adhesive layer of the adhesive film, the laminating temperature is inevitably high, so the flexible metal-clad laminate immediately after laminating is also very hot. Here, when the storage elastic modulus of the core layer of the adhesive film is lowered to a certain value or more, the entire adhesive film is softened together with the adhesive layer (however, the self-supporting property is maintained). At that time, the thermal stress accumulated in the laminated plate is relieved by the tension and pressure at the time of thermal lamination.

  In order to relieve the thermal stress more efficiently, it is preferable to keep the tension applied to the laminated plate to a minimum. For this reason, the flexible metal-clad laminate immediately after lamination is brought into contact with the heating roll while the protective material is still placed, and the residual strain generated during thermal lamination in a state where it is not affected by tension. It is preferable to relax and then separate from the heating roll. The contact time with the heating roll is preferably 0.1 seconds or more, more preferably 0.2 seconds or more, and particularly preferably 0.5 seconds or more. When the contact time is shorter than the above range, the relaxation effect may not be sufficiently generated. The upper limit of the contact time is preferably 5 seconds or less. Even if the contact is made for 5 seconds or more, the relaxation effect does not appear more and it is not preferable because the lowering of the laminating speed and the restriction of the line handling occur.

  Moreover, even if it is brought into contact with a heating roll after lamination and subjected to slow cooling, the difference between the flexible metal-clad laminate and room temperature is still large, and the residual strain may not be alleviated. Therefore, the flexible metal-clad laminate after being brought into contact with a heating roll and gradually cooled is preferably passed through a post-heating step with the protective material still disposed. The tension at this time is preferably in the range of 1 to 10 N / cm. Moreover, it is preferable to make the atmospheric temperature of post-heating into the range of (lamination temperature -200 degreeC)-(lamination temperature +100 degreeC). The “atmosphere temperature” here refers to the outer surface temperature of the protective material in close contact with both surfaces of the flexible metal-clad laminate. The actual temperature of the flexible metal-clad laminate varies somewhat depending on the thickness of the protective material, but if the temperature of the surface of the protective material is within the above range, the effect of post-heating can be exhibited. The outer surface temperature of the protective material can be measured using a thermocouple or a thermometer.

  The laminating speed in the thermal laminating step is preferably 0.5 m / min or more, and more preferably 1.0 m / min or more. If it is 0.5 m / min or more, sufficient thermal lamination is possible, and if it is 1.0 m / min or more, productivity can be further improved.

  The higher the pressure in the thermal laminating process, that is, the laminating pressure, is advantageous in that the laminating temperature can be lowered and the laminating speed can be increased. There is a tendency to get worse. Conversely, if the laminating pressure is too low, the adhesive strength of the metal foil of the laminate obtained is lowered. Therefore, the laminating pressure is preferably in the range of 49 to 490 N / cm (5 to 50 kgf / cm), and more preferably in the range of 98 to 294 N / cm (10 to 30 kgf / cm). Within this range, the three conditions of the lamination temperature, the lamination speed and the lamination pressure can be made favorable, and the productivity can be further improved.

  The adhesive film tension in the laminating step is preferably 0.01 to 4 N / cm, more preferably 0.02 to 2.5 N / cm, and particularly preferably 0.05 to 1.5 N / cm. When the tension is below the above range, sagging or meandering occurs during the conveyance of the laminate, and it is difficult to obtain a flexible metal-clad laminate having a good appearance because it is not uniformly fed to the heating roll. On the other hand, if it exceeds the above range, the influence of tension becomes so strong that it cannot be relaxed by controlling the Tg and storage modulus of the adhesive layer, and the dimensional stability may be inferior.

  In order to obtain the flexible metal-clad laminate according to the present invention, it is preferable to use a thermal laminating apparatus that continuously press-bonds the material to be laminated while heating, but in this thermal laminating apparatus, before the thermal laminating means, A laminated material feeding means for feeding the laminated material may be provided, or a laminated material winding means for winding the laminated material may be provided after the thermal laminating means. By providing these means, the productivity of the thermal laminating apparatus can be further improved. The specific configuration of the laminated material feeding means and the laminated material winding means is not particularly limited. For example, a known roll shape capable of winding an adhesive film, a metal foil, or a laminated sheet to be obtained. A winder etc. can be mentioned.

  Furthermore, it is more preferable to provide a protective material winding means and a protective material feeding means for winding and feeding the protective material. If these protective material take-up means and protective material feeding means are provided, the protective material can be reused by winding the protective material once used in the thermal laminating step and installing it again on the pay-out side. . Further, when winding up the protective material, end position detecting means and winding position correcting means may be provided in order to align both ends of the protective material. As a result, the end portions of the protective material can be aligned and wound with high accuracy, so that the efficiency of reuse can be increased. The specific configurations of the protective material winding means, the protective material feeding means, the end position detecting means, and the winding position correcting means are not particularly limited, and various conventionally known devices can be used.

  In the flexible metal-clad laminate obtained by the manufacturing method according to the present invention, the total value of the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil is −0.04 in both the MD direction and the TD direction. Very preferably in the range of ~ + 0.04. The dimensional change rate before and after heating is represented by a ratio between a difference between a predetermined dimension in the flexible metal-clad laminate after the etching process and a predetermined dimension after the heating process and a predetermined dimension before the heating process.

  When the dimensional change rate is out of this range, in the flexible metal-clad laminate, the dimensional change at the time of component mounting becomes large, and the dimensional change rate deviates from the component mounting position at the design stage. As a result, there is a possibility that the component to be mounted and the board are not connected well. In other words, if the rate of dimensional change is within the above range, it can be considered that there is no problem in component mounting.

  The method for measuring the dimensional change rate is not particularly limited, and any method known in the art can be used as long as it can measure the increase or decrease in dimensions that occurs before and after the etching or heating process in the flexible metal-clad laminate. Can be used.

  Here, it is essential to measure the dimensional change rate in both the MD direction and the TD direction. In the case of continuous imidization and laminating, the tension is different in the MD direction and the TD direction, so a difference appears in the degree of thermal expansion / contraction and the dimensional change rate is also different.

                                          Therefore, a material having a small dimensional change rate is required to have a low change rate in both the MD direction and the TD direction. In the present invention, the total value of the dimensional change rate before and after heating of the flexible metal-clad laminate after removing the metal foil at 250 ° C. for 30 minutes is −0.04 to +0.04 in both the MD direction and the TD direction. It is highly preferred that it is in the range.

  Furthermore, as described above, the polyimide film of the core layer used in the adhesive film of the present invention has a characteristic of effectively relieving thermal stress, so that it has a thickness of 15 μm or less that is more susceptible to thermal stress. Even when this adhesive film is used, the dimensional change rate of the obtained flexible metal-clad laminate can be reduced. Specifically, the total value of the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil is in the range of −0.05 to +0.05 in both the MD direction and the TD direction.

  In addition, in the heating process at the time of measuring the dimensional change rate, it is sufficient that heating is performed at 250 ° C. for 30 minutes, and specific conditions are not particularly limited.

  As described above, the flexible metal-clad laminate obtained by the manufacturing method according to the present invention can be mounted with various miniaturized and high-density components by forming a desired pattern wiring by etching the metal foil. It can be used as a flexible wiring board. Of course, the application of the present invention is not limited to this, and it goes without saying that it can be used for various applications as long as it is a laminate including a metal foil.

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

  In addition, the glass transition temperature of the thermoplastic polyimide, the storage elastic modulus of the polyimide film, the tensile elastic modulus, the hygroscopic expansion coefficient, the molecular orientation axis angle and the linear expansion coefficient in the synthesis examples, examples and comparative examples, dimensions of the flexible metal-clad laminate The evaluation methods of the rate of change, the peel strength of the metal foil, and the moisture absorption solder resistance are as follows.

(Glass-transition temperature)
The glass transition temperature was measured with DMS6100 manufactured by SII Nanotechnology, and the inflection point of the storage elastic modulus was taken as the glass transition temperature.
Sample measurement range: width 9 mm, distance between grippers 20 mm
Measurement temperature range: 0 to 440 ° C
Temperature increase rate: 3 ° C./min Strain amplitude: 10 μm
Measurement frequency: 1, 5, 10 Hz
Minimum tension / compression force: 100mN
Tension / compression gain; 1.5
Initial value of force amplitude: 100mN
As shown in FIG. 1, the inflection point of the storage elastic modulus was drawn at each of the storage elastic modulus curves before and after the inflection, and the point (temperature) at which the two tangents intersected was defined as the inflection point.

(Storage elastic modulus of core film)
The storage elastic modulus was measured with the apparatus and conditions for measuring the glass transition temperature. In addition, the measurement was performed with respect to MD direction of a core film.

(Tensile modulus)
The tensile elastic modulus was measured according to ASTM D882. In addition, the measurement was performed with respect to MD direction of a core film.
Sample measurement range: width 15mm, distance between grips 100mm
Tensile speed: 200 mm / min
(Linear expansion coefficient)
The linear expansion coefficient of the polyimide film was measured by using a thermomechanical analyzer manufactured by SII Nanotechnology, Inc., trade name: TMA / SS6100, once raised to 0 ° C. to 460 ° C., cooled to 10 ° C., and further 10 ° C./min. The average value within the range of 100 to 200 ° C. at the time of the second temperature increase was determined. In addition, the measurement was performed with respect to MD direction and TD direction of the core film.
Sample shape: width 3mm, length 10mm
Load: 29.4 mN
Measurement temperature range: 0 to 460 ° C
Temperature increase rate: 10 ° C / min
(Dimensional change rate)
Based on JIS C6481, four holes were formed in the flexible laminate, and the distance of each hole was measured. Next, after carrying out an etching process to remove the metal foil from the flexible laminate, 20 ° C., 60% R.D. H. Left in a constant temperature room for 24 hours. Then, each distance was measured about the said four holes similarly to the etching process front. The measured value of the distance between the holes before removing the metal foil was set as D1, and the measured value of the distance between the holes after removing the metal foil was set as D2, and the dimensional change rate before and after etching was obtained by the following equation.
Dimensional change rate (%) = {(D2-D1) / D1} × 100
Subsequently, the measurement sample after etching was heated at 250 ° C. for 30 minutes, and then 20 ° C. and 60% R.D. H. Left in a constant temperature room for 24 hours. Then, each distance was measured about the said four holes. The measured value of the distance of each hole after heating was set to D3, and the dimensional change rate before and after heating was obtained by the following formula.
Dimensional change rate (%) = {(D3-D2) / D2} × 100
In addition, the said dimensional change rate was measured about both MD direction and TD direction.

(Stripping strength of metal foil: Adhesive strength)
A sample was prepared according to “6.5 Peel Strength” of JIS C6471, and a 5 mm wide metal foil part was peeled off at a peeling angle of 180 degrees and 50 mm / min, and the load was measured.

(Solder resistance of flexible metal-clad laminate)
After preparing a sample according to JIS C6471, the solder resistance of a sample prepared under two conditions of normal (20 ° C., 60% RH, after 24 hours adjustment) and moisture absorption (85 ° C., 85% RH, after 96 hours adjustment) is measured. Then, the presence or absence of abnormality of the whitening phenomenon and the peeling phenomenon on the appearance was judged. The normal solder was immersed in a solder bath at 300 ° C. for 1 minute, and the hygroscopic solder was immersed at 260 ° C. for 10 seconds. For the evaluation, ○ when the sample appearance does not change before and after immersion in the solder bath, × when the peeling of the metal foil layer from the sample, whitening of the adhesive film, or swelling of the sample is confirmed. did.

(Synthesis Example 1; Synthesis of thermoplastic polyimide precursor)
While adding 780 g of DMF and 115.6 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter also referred to as BAPP) to a glass flask having a capacity of 2000 ml, while stirring under a nitrogen atmosphere, 78.7 g of BPDA was gradually added. Subsequently, 3.8 g of TMEG was added and stirred for 30 minutes in an ice bath. A solution in which 2.0 g of TMEG was dissolved in 20 g of DMF was separately prepared, and this was gradually added to the reaction solution while being careful of the viscosity and stirred. When the viscosity reached 3000 poise, addition and stirring were stopped to obtain a polyamic acid solution.
The obtained polyamic acid solution was cast on a 25 μm PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.) so as to have a final thickness of 20 μm, and dried at 120 ° C. for 5 minutes. The dried self-supporting film was peeled off from PET, fixed to a metal pin frame, and dried at 150 ° C. for 5 minutes, 200 ° C. for 5 minutes, 250 ° C. for 5 minutes, and 350 ° C. for 5 minutes. . It was 240 degreeC when the glass transition temperature of the obtained single layer sheet was measured.

(Examples 1-4; synthesis of polyimide film)
With the reaction system maintained at 5 ° C., N, N-dimethylformamide (hereinafter also referred to as DMF) and 4,4′-diaminodiphenyl ether (hereinafter also referred to as 4,4′-ODA) are shown in Table 1. They were added at the indicated molar ratio and stirred. After visually confirming dissolution, benzophenone tetracarboxylic dianhydride (hereinafter also referred to as BTDA) was added at a molar ratio shown in Table 1 and stirred for 30 minutes.
Subsequently, pyromellitic dianhydride (hereinafter also referred to as PMDA) was added at a molar ratio shown in Table 1 and stirred for 30 minutes. Subsequently, p-phenylenediamine (hereinafter also referred to as p-PDA) was added at a molar ratio shown in Table 1, and the mixture was stirred for 50 minutes. Subsequently, PMDA was added again at a molar ratio shown in Table 1, and stirring was performed for 30 minutes.
Finally, a solution in which 3 mol% of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity. The polymerization was terminated when the viscosity of the polymer reached 4000 poise.
To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.3 / 4.0) was added at a weight ratio of 45% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless endless belt running 20 mm below the die. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt (volatile content 30% by weight) and fixed to the tenter clip, 300 ° C. × 30 seconds, 400 ° C. × 30 Second, and dried and imidized at 500 ° C. for 30 seconds to obtain a polyimide film having a thickness of 18 μm.

(Examples 5 to 8)
In the polyamic acid solution obtained in the same manner as in Examples 1 to 4, an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.3 / 4.0) was added to the polyamic acid solution. The mixture was added at a weight ratio of 45%, continuously stirred by a mixer, extruded from a T die, and cast on a stainless steel endless belt running 20 mm below the die. The resin film was heated at 130 ° C. for 100 seconds, and then the self-supporting gel film was peeled off from the endless belt (volatile content 30% by weight) and fixed to the tenter clip, 300 ° C. × 22 seconds, 400 ° C. × 22 Second, and dried and imidized at 500 ° C. for 22 seconds to obtain a polyimide film having a thickness of 10 μm.

(Examples 9 to 16)
When the polyimide films of Examples 1 to 4 are used on both sides of the polyimide films obtained in Examples 1 to 8, the final one-side thickness of the thermoplastic polyimide layer (adhesive layer) is 3.5 μm. When using a polyimide film of 5 to 8, the thermoplastic polyimide precursor obtained in Synthesis Example 1 is applied with a gravure coater so that the final single-sided thickness of the thermoplastic polyimide layer (adhesive layer) is 2 μm, and is heated to 160 ° C. Heating was performed by passing through the set drying furnace 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 to obtain an adhesive film. Using the 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 protective films (Apical 125 NPI; manufactured by Kaneka Corporation) on both sides of the copper foil, The flexible metal-clad laminate according to the present invention is obtained by continuous thermal lamination under conditions of 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. Was made. The protective film was preheated by contacting the protective film for 3 seconds in advance and then laminated on the outside of the copper foil. Further, after lamination, the laminate was brought into contact with the heating roll for 0.2 seconds with the protective film still disposed, and then the protective film was peeled off after natural cooling was completed.

(Comparative Example 1)
After the polyamic acid solution obtained in Synthesis Example 1 is diluted with DMF until the solid content concentration becomes 10% by weight, the final single-sided thickness is 3. on both sides of an 18 μm-thick polyimide film (Apical 18HPP, manufactured by Kaneka Corporation). It apply | coated with the gravure coater so that it might be set to 5 micrometers, and it heated through the inside of the drying furnace set to 140 degreeC 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 to obtain an adhesive film. Using the 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 protective films (Apical 125 NPI; manufactured by Kaneka Corporation) on both sides of the copper foil, Thermally laminating was carried out under the conditions of 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 to produce a flexible metal-clad laminate.

(Comparative Example 2)
A flexible metal-clad laminate was prepared by using a 10 μm-thick polyimide film (Apical 10 HPP, manufactured by Kaneka Corporation) as the core film and performing the same operation as in Comparative Example 1 except that the coating thickness was 2 μm per side. .

(Comparative Example 3)
A flexible metal-clad laminate was prepared by using a 20 μm-thick polyimide film (Apical 20NPP, manufactured by Kaneka Corporation) as the core film and performing the same operation as in Comparative Example 1 except that the coating thickness was 2 μm per side. .

(Comparative Example 4)
As a core film, a polyimide film (Apical 12.5NPP, manufactured by Kaneka Corporation) with a thickness of 12.5 μm was used, and the same operation as in Comparative Example 1 was performed except that the coating thickness was 1.5 μm per side. A tension laminate was produced.

  The result of having evaluated the characteristic of the polyimide film obtained by each Example and the comparative example and a flexible metal-clad laminated board is shown to Tables 2-3.

比較例１〜４に示すように、コアフィルムの貯蔵弾性率、ｔａｎδピークが規定範囲外である場合は、熱ラミネート時に材料にかかる応力を効率良く緩和できず、寸法変化率が大きくなるという結果となった。特に、接着フィルム厚が薄くなると、更に寸法変化率が大きくなるという結果となっている。

As shown in Comparative Examples 1 to 4, when the storage elastic modulus of the core film and the tan δ peak are out of the specified range, the stress applied to the material at the time of thermal lamination cannot be efficiently relaxed, and the dimensional change rate is increased. It became. In particular, when the thickness of the adhesive film is reduced, the dimensional change rate is further increased.

  On the other hand, in Examples 9 to 16 using the core film in which all the characteristics are within the predetermined range, the generation of the dimensional change was suppressed even when the core film was produced by the thermal laminating method. In particular, in Examples 13 to 16 in which the adhesive film thickness is thin, the dimensional change rate is equivalent to that in Examples 9 to 12. Moreover, even if the storage elastic modulus is controlled, there is no influence on the adhesive strength and solder resistance, and there is no problem even in actual use.

It is a figure which shows how to obtain | require the inflexion point of storage elastic modulus.

Claims (16)

A polyimide film obtained by imidizing a polyamic acid obtained by reacting an aromatic diamine composed of 4,4′-diaminodiphenyl ether and p-phenylenediamine with an aromatic acid dianhydride, the following (1) to Condition (1) (4) Having an inflection point of storage elastic modulus in the range of 280 ° C to 320 ° C,
(2) The peak top of tan δ, which is a value obtained by dividing the loss elastic modulus by the storage elastic modulus, is in the range of 320 ° C. to 380 ° C.,
(3) The storage elastic modulus at 380 ° C. is 0.4 GPa to 2.0 GPa,
(4) and the storage modulus alpha ₁ (GPa) at the inflection point, storage at 380 ° C. modulus alpha ₂ (GPa) is within the range of the following formula (1) (Equation 1); 85 ≧ {(α 1 - α ₂ ) / α ₁ } × 100 ≧ 65
A polyimide film characterized by satisfying all of the above. The polyimide film has the following steps (a) to (c).
(A) An aromatic acid dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends (b) (C) Further, the aromatic dianhydride is added and polymerized so that the aromatic dianhydride and the aromatic diamine are substantially equimolar in all steps. The polyimide film according to claim 1, wherein the polyimide film is obtained by imidizing a polyamic acid solution obtained by passing.   The polyimide film according to claim 2, wherein the aromatic diamine in the step (a) is a flexible diamine, and the aromatic diamine in the step (b) is a rigid diamine.   The polyimide film according to claim 3, wherein 4,4'-diaminodiphenyl ether is used as the flexible diamine.   The polyimide film according to claim 3, wherein p-phenylenediamine is used as the rigid diamine. 6. The polyimide film according to claim 2, wherein benzophenone tetracarboxylic dianhydride and pyromellitic dianhydride are used in the step (a). The polyimide film according to any one of claims 1 to 6 , wherein the polyimide film has a tensile modulus of 7.0 GPa or more. The linear expansion coefficient at 100 ° C. to 200 DEG ° C. of polyimide film, and equal to or less than 13 ppm / ° C., the polyimide film according to any one of claims 1 to 7. The adhesive film which provided the adhesive layer containing a thermoplastic polyimide in the at least single side | surface of the polyimide film as described in any one of Claims 1 thru | or 8.   The adhesive film according to claim 9, wherein the thermoplastic polyimide has a glass transition temperature (Tg) of 230 ° C. or higher.   The adhesive film according to claim 9 or 10, wherein the film thickness is 15 µm or less. A flexible metal-clad laminate obtained by bonding a metal foil to the adhesive film according to any one of claims 9 to 11, using a hot roll laminator having a pair of metal rolls. .   Non-thermoplastic polyimide or thermoplastic having a glass transition temperature (Tg) of 50 ° C. or more higher than the laminating temperature when the metal foil is bonded to the adhesive film using the hot roll laminating apparatus having the pair of metal rolls. The flexible metal-clad laminate according to claim 12, wherein a protective film made of polyimide is placed between a metal foil and a roll to perform lamination, and the protective film is peeled off when cooled after lamination. Board.   After the lamination, before the protective film is peeled off, the laminate in which the protective film and the flexible metal-clad laminate are in close contact with each other is brought into contact with a heating roll in the range of 0.1 to 5 seconds, and then cooled and laminated. The flexible metal-clad laminate according to claim 13, wherein the protective material is peeled off. 15. The dimensional change rate before and after heating at 250 [deg.] C. for 30 minutes after removing the metal foil is in the range of -0.04 to + 0.04% in both the MD direction and the TD direction. The flexible metal-clad laminate according to any one of the above. The thickness of the adhesive film is 15 μm, and the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil is in the range of −0.05 to + 0.05% in both the MD direction and the TD direction. The flexible metal-clad laminate according to any one of claims 12 to 14, characterized in that:

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