JP2017179148A - Polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide laminate film capable of suppressing generation of phenomenon, referred to as breakage, of a polyimide film serving as a substrate in an alkali environment, when a flexible laminate is manufactured by arranging a metal layer on a polyimide film and further a flexible printed wiring board is continuously manufactured by a roll-to-roll method.SOLUTION: There is provided a non-thermoplastic polyimide film in which an aggregate structure is controlled, and yield strength and difficulty in plastic deformation are thus improved by a primary structure of a resin and a manufacturing method. There is provided a polyimide film which is a non-thermoplastic polyimide film. There is provided a polyimide film having an inclination of a plastic deformation area in a stress-strain curve of 1.0 or more and less than 2.0 and stress at 10% strain of 180 MPa or more. There is provided a polyimide film having storage elastic modulus at 380°C in a dynamic viscoelasticity of 0.6 GPa to 2.0 GPa and a temperature explained by an inflection point of storage elastic modulus of 270°C to 340°C. There is provided a polyimide film where polyimide has a flexible block component and a stiffness block component.SELECTED DRAWING: None

Description

  The present invention relates to a polyimide film capable of suppressing the occurrence of film tearing in the production process of a flexible metal-clad laminate and a method for producing a polyimide film.

  In recent years, demand for various flexible printed circuit boards (hereinafter also referred to as FPCs) has been increasing with increasing demand for electronic products such as smartphones, tablet computers, notebook computers, and the like. Among these, a two-layer flexible printed wiring board (hereinafter also referred to as a two-layer FPC) using thermoplastic polyimide as an adhesive layer is expected to further increase demand because of its excellent heat resistance and flexibility. Recently, demands for lighter, smaller and thinner electronic devices are increasing, and in order to achieve this, the FPC to be mounted is also desired to be thinner. In addition, with the change in the production process of flexible copper clad laminates due to productivity improvement (cost reduction), demands on the load on materials such as polyimide film, particularly improvement in mechanical strength, are increasing.

  In the conventional manufacturing method of FPC, a manufacturing process including a developing process, an etching process, a resist stripping process, and the like is performed in a batch manner (non-continuous process). Conventionally, a polyimide (for example, Patent Document 1) whose resistance to an alkaline solution used in development, etching, and resist stripping processes is controlled has been reported. Moreover, the method of improving the intensity | strength of a polyimide film by high orientation is also disclosed (for example, patent document 2).

JP 2012-186377 A WO01 / 081456

  When processing into FPC, there is a step of contacting with an alkaline aqueous solution, and alkali resistance is also required. However, in the roll-to-roll type which is an example of a continuous type, unlike the conventional batch type, It will contact with alkaline aqueous solution in the state where tension was applied to the longitudinal direction. As a result, the present inventors have revealed that there arises a problem that a phenomenon such as tearing in the polyimide laminated film, which has not been recognized by the alkali treatment in the conventional batch method, occurs. Further, in the step of contacting with the alkaline aqueous solution, a state in which stress is repeatedly applied in the thickness direction of the base material by spraying the chemical solution. Furthermore, since a base material is conveyed along the roll which supports a base material at the time of conveyance of a base material, a bending stress will also generate | occur | produce in a state contacted with the chemical | medical solution. These stresses also apply a load to the film, which causes the film to tear.

  In order to solve these problems, a method for suppressing cracking by performing a heat treatment in the β relaxation temperature range as disclosed in Patent Document 1 has been reported. Bring about a decline.

  Furthermore, in the material disclosed in Patent Document 2, biaxial stretching of the gel film is performed in order to achieve toughness and high strength. As a result, the number of processes increases and productivity decreases. In addition, the stretched film tends to be relatively poor in toughness due to the strong in-plane orientation of molecular chains. Therefore, even if there is no problem in the conventional batch type FPC manufacturing process, the toughness is insufficient to withstand the process of continuously manufacturing the FPC by the roll-to-roll method as described above. No polyimide material has been provided so far that does not tear even after passing through.

  The present invention has been made in view of these problems, and its purpose is to manufacture a flexible metal laminate in accordance with a process change to a roll-to-roll system for thinning the material and improving productivity in recent years. An object of the present invention is to provide a polyimide film, a polyimide laminate film, and a metal-clad laminate that can suppress the tearing of the film that occurs in an alkaline environment without separately performing heat treatment or stretching.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have determined that non-thermoplastic polyimide has an agglomerated structure in order to suppress film tearing, and the agglomerated structure is produced by the primary structure and manufacturing method of the resin. By controlling the above, it becomes possible to improve the toughness by suppressing the tearing of the film in an alkaline environment without greatly changing the film manufacturing process.

  In the present invention, in suppressing cracking, it is important to improve yield strength and resistance to plastic deformation, and the primary structure of the polyimide, the polymerization method, and the polyimide film using the polyimide are further studied. Thus, the present invention has been completed.

That is, this invention relates to the following polyimide films.
1) A polyimide film, wherein a slope of a plastic deformation region in a stress-strain curve is 1.0 or more and less than 2.0.
2) The polyimide film according to 1), wherein the polyimide film is a non-thermoplastic polyimide film.
3) The polyimide film according to 1) or 2), wherein a stress at 10% strain in a stress-strain curve is 180 MPa or more.
4) The storage elastic modulus at 380 ° C. in the dynamic viscoelasticity measurement is 0.6 GPa to 2.0 GPa, and the temperature indicated by the inflection point of the storage elastic modulus is 270 ° C. to 340 ° C. The polyimide film according to any one of 1) to 3).
5) wherein the density of the polyimide film is ^{1.40g / cm 3 ~1.55g / cm 3} , a polyimide film according to any one of 1) to 4).
6) The polyimide film according to any one of 1) to 5), wherein the polyimide contains a flexible block component and a rigid block component.

  The polyimide film obtained by the present invention can provide a flexible metal-clad laminate without any special change in the film production process.

It is a schematic diagram which shows the testing method of the shaking test which concerns on the Example of this invention. It is a figure which shows the inclination of the plastic deformation area | region which concerns on the Example of this invention.

  Embodiments of the present invention will be described below. First, although the case of the polyimide film which concerns on this invention is demonstrated based on the example of the embodiment, this invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications can be made within the scope shown in 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. In addition, all the academic literatures and patent literatures described in this specification are incorporated by reference in this specification. Unless otherwise specified in this specification, “A to B” indicating a numerical range means “A or more (including A and greater than A) and B or less (including B and less than B)”, respectively.

  As described above, when processing FPC by roll-to-roll method, in addition to tension in the longitudinal direction in the presence of an aqueous alkali solution, the batch type such as repetitive stress and bending stress in the thickness direction is used. Also, the substrate is in a state of being loaded. When a solvent is present, the strength of the polymer is generally lower than when no solvent is present. Therefore, it is preferable that the yield strength is high in order to suppress plastic deformation. Also, under repeated stress, the polymer fatigues and gradually begins plastic deformation. Therefore, after plastic deformation started, we thought that the resistance value against the stress (hardness to plastic deformation) would be more effective in suppressing cracking.

  The present inventors diligently studied the molecular design of polyimide in order to improve the toughness of the polyimide laminated film in an alkaline environment. As a result, the aggregate structure of the non-thermoplastic polyimide layer contained in the polyimide laminate film contributes to the toughening of the polyimide film in an alkaline environment, and the aggregate structure is controlled by the primary structure of the polyimide and the polyimide production method. Thus, it was found that tearing of the film in an alkaline environment can be suppressed without greatly changing the film manufacturing process. In other words, the present inventors have found for the first time the knowledge that the polymer can easily form an agglomerated structure to perform molecular design that can express these characteristics and the toughness in an alkaline environment is improved. Is.

  The aggregated structure in the present invention means packing of molecular chains having local order. Polyimides are composed of rigid structural units such as aromatic rings or aromatic heterocycles, so there is little entanglement, and it is difficult to form a folded chain like ordinary polymers. On the other hand, molecular chain packing unique to a molecular chain having an imide ring occurs, and molecular chain packing with the local ordering occurs. It has been found in the present invention that the aggregation structure of the polyimide is related to the toughness in an alkaline environment. The aggregation structure can be controlled by the film forming conditions and the primary structure of the polyimide film.

  The thermoplastic polyimide in the present invention refers to a polyimide that is softened when it is fixed to a metal fixed frame in the state of a film and heated at 450 ° C. for 2 minutes so that the original shape is not retained.

  The non-thermoplastic polyimide in the present invention retains its shape without being wrinkled or stretched when it is fixed to a metal fixed frame in the state of a film and heated at 450 ° C. for 2 minutes. Refers to polyimide.

(Slope of plastic deformation region in stress-strain curve)
The polyimide film of the present invention is characterized in that the slope of the plastic deformation region in the stress-strain curve is 1.0 or more and less than 2.0. As a result of earnestly examining the durability against the tear of the polyimide film in an alkaline environment, the present inventors have satisfied the two conditions that the polyimide film is difficult to plastically deform and has a high yield strength. The present inventors have found a new finding that it exhibits high durability against tearing in an alkaline environment. In the present invention, in a polyimide laminated film containing thermoplastic polyimide and non-thermoplastic polyimide, particularly for non-thermoplastic polyimide, increasing the slope of the plastic deformation region in the stress-strain curve and increasing the yield strength. It is easier to obtain the effect by giving these two characteristics.

  The plastic deformation region and its inclination in the present invention will be described. The plastic deformation region refers to a strain region after the yield point in a stress-strain curve in a tensile test using a polyimide film. The property of “not easily plastically deformed” is intended to increase the stress greatly in the plastic deformation region, or to increase the stress required at the time of plastic deformation. The characteristic of “not easily plastically deformed” can be rephrased as the inclination in the plastic deformation region. For example, the result of measuring the tensile properties according to ASTM D882 is expressed as “slope (ie, s) −s curve slope) ”. In the present invention, the slope is between “10% strain stress” and “breaking stress” in the s-s curve. The calculation formula is shown below.

Inclination of plastic deformation region = (stress2-stress1) / (strain2-strain1)
here,
stress1: Stress at 10% strain stress2: Breaking stress strain1: 10% strain strain2: Breaking strain.

  The “material which is not easily plastically deformed” in the present invention is characterized in that “the inclination of the plastic deformation region is 1.0 or more and less than 2.0”.

  “Yield strength” can be evaluated by “stress at 10% strain” when tensile properties are measured in accordance with ASTM D882. For example, “a material having a high yield strength” is intended herein to mean “a stress at 10% strain of 180 MPa or more”.

(Shaking test)
In order to confirm whether or not the material is not torn even after the process of continuously manufacturing FPC in a roll-to-roll method, a wide and long material is obtained by providing a metal foil with a continuous method on a wide and long material. Using a flexible metal-clad laminate, a circuit is required to be formed by an FPC manufacturing process including a development process, an etching process, and a resist stripping process in a roll-to-roll manner. However, this method is not practical because it is costly and time consuming. As a long film or a long flexible metal-clad laminate as a material, the present inventors cut out test pieces from both ends and the center and measured ST in a shaking test, which is 700 seconds or longer. It has been found that no tearing occurs when such a material is used. The shaking test can be performed easily and at low cost, and a flexible metal-clad laminate that does not cause tearing can be obtained very easily by using a material having an ST of 700 seconds or longer.

  When the ST of the polyimide film when the shaking test is performed at both ends and the center of the film is 700 seconds or more, it is used as a flexible metal-clad laminate, and a roll-to-roll continuous FPC manufacturing process. Even when a flexible wiring board is manufactured, the occurrence of tearing is suppressed, but it is preferably 1500 seconds or longer, and more preferably 2000 seconds or longer.

  Since the polyimide film of the present invention is a material used for continuous FPC production as described above, it is a wide and long polyimide film. And it is a film in which ST is 700 seconds or more when the shaking test is performed at three points at both ends and the center of the film. If such a film is used, the FPC obtained through the continuous FPC process does not tear, so that the FPC can be produced efficiently.

(Polyimide)
The polyimide film of this invention is comprised from the polyimide containing a flexible block component and a rigid block component, It is characterized by the above-mentioned.

  As a result of intensive studies, the present inventors have found that a flexible block component is particularly important for suppressing film tearing in an alkaline environment.

  The flexible block component is preferably thermoplastic. Furthermore, it is more preferable that the side chain of the block component does not contain a bulky substituent, and is composed of a highly planar skeleton and a skeleton having a high molecular mobility of molecular chains such as an ether bond. As a result, the packing of the molecular chains becomes dense, the growth of the aggregate structure is promoted, and the final film can be provided with toughness.

  The rigid block component is preferably non-thermoplastic. Furthermore, it is more preferable that the monomer constituting the block component contains a bent chain such as an ether bond. The molecular mobility of the polymer molecular chain may be insufficient with only a highly planar skeleton composed of only a benzene ring such as pyromellitic dianhydride or 4,4'-diaminobenzene. Introducing a bent chain can increase molecular mobility and promote formation of an aggregated structure. The monomer having a bent chain is not limited as long as it does not contain a bulky substituent in the side chain and has a structure such as an ether bond. Among 100% of the diamine monomer component constituting the rigid block component, the monomer component having a bent chain is effective in promoting the formation of an aggregated structure when it is in the range of 10 mol% to 30 mol%, which is preferable.

  In the non-thermoplastic polyimide of the present invention, the composition of the flexible block and the rigid block is preferably in the range of 40 mol%: 60 mol% to 60 mol%: 40 mol%.

  The polyimide which comprises the polyimide film of this invention is obtained by imidating the polyamic acid used as a precursor. The monomer that forms the polyamic acid will be described below.

  The diamine used as the main component in the polyimide of the present invention is not particularly limited, but an aromatic diamine is preferable from the viewpoint of heat resistance and the like. For example, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 3,3 '-Diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenyldiethyl Silane, 4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4- Diaminobenzene (p-phenylenediamine), bis {4- (4-aminophenoxy) pheny } Sulfone, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 2,2-bis (4-aminophenoxyphenyl) propane 2,2′-dimethylbenzidine and the like, and these can be used alone or in combination. Aromatic diamines particularly preferably used for the polyimide of the present invention include 4,4′-diaminodiphenyl ether, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-bis (4 -Aminophenoxy) biphenyl, p-phenylenediamine, 1,3-bis (4-aminophenoxy) benzene and the like.

  The acid dianhydride used as the acid dianhydride of the polyimide of the present invention is not particularly limited, but an aromatic acid dianhydride is preferable from the viewpoint of heat resistance. For example, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6 -Naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2 ', 3,3′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,4′-oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane Acid dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propanoic dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ) Ethanoic acid dianhydride 1,1-bis (3,4-dicarboxyphenyl) ethanoic dianhydride, bis (2,3-dicarboxyphenyl) methanoic dianhydride, bis (3,4-dicarboxyphenyl) ethanoic acid Anhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, p-phenylenebis (trimellitic acid monoester anhydride), ethylene bis (trimellitic acid monoester anhydride) Product), bisphenol A bis (trimellitic acid monoester anhydride), and the like. Acid dianhydrides particularly preferably used for the polyimide of the present invention are pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, 4 , 4′-oxyphthalic dianhydride and the like.

As the flexible block component diamine, 4,4′-diaminodiphenyl ether, 4,4′-bis (4-aminophenoxy) biphenyl, p-phenylenediamine, and 1,3-bis (4-aminophenoxy) benzene are preferable. Used for. As the acid dianhydride, 4,4′-biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, and 4,4′-oxyphthalic dianhydride are preferably used. Furthermore, a combination including 4,4′-diaminodiphenyl ether, 4,4′-biphenyltetracarboxylic dianhydride, and benzophenone tetracarboxylic dianhydride is particularly preferable.
As the rigid block component diamine, 4,4′-diaminodiphenyl ether, 4,4′-bis (4-aminophenoxy) biphenyl, p-phenylenediamine, and 1,3-bis (4-aminophenoxy) benzene are preferable. Used for. As the acid dianhydride, 4,4′-biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, and pyromellitic dianhydride are preferably used. Furthermore, a combination containing 4,4′-diaminodiphenyl ether, p-phenylenediamine, and pyromellitic dianhydride is particularly preferable.

(Solvent for polyamic acid production)
As the preferred solvent for producing the polyamic acid, any solvent that dissolves the polyamic acid can be used. For example, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like can be exemplified. Among these, N, N-dimethylformamide and N, N-dimethylacetamide are particularly preferable.

(Production of polyamic acid)
As the method for producing the polyamic acid in the present invention, any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of the polyamic acid is the order of addition of the monomers, and various physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any method of adding monomers may be used for the polymerization of polyamic acid. Examples of typical polymerization methods include the following methods.

For example, the following steps (Aa) to (Ac):
(Aa) a step of reacting an aromatic diamine and an aromatic dianhydride in an organic polar solvent in an excess of aromatic diamine to obtain a prepolymer having amino groups at both ends;
(Ab) a step of additionally adding an aromatic diamine having a structure different from that used in the step (Aa),
(Ac) Further, the aromatic dianhydride having a structure different from that used in the step (Aa) is substantially equal to the aromatic diamine and aromatic dianhydride in all steps. Adding and polymerizing so that
Can be manufactured by.

Alternatively, the following steps (Ba) to (Bc):
(Ba) An aromatic diamine and an aromatic acid dianhydride are reacted in an organic polar solvent in an excess of aromatic acid dianhydride, and a prepolymer having acid anhydride groups at both ends is obtained. Obtaining step,
(Bb) a step of additionally adding an aromatic dianhydride having a structure different from that used in the step (Ba),
(Bc) Furthermore, the aromatic diamine having a different structure from that used in the step (Ba) is used so that the aromatic diamine and the aromatic dianhydride are substantially equimolar in all steps. Adding and polymerizing,
It is also possible to obtain polyamic acid by going through.
Synthetic methods (for example, steps (Aa) to (Ac), and (A)) in which the order of addition is set so that a specific diamine or acid dianhydride selectively binds to any diamine or acid dianhydride, and ( Ba) to (Bc)) are referred to as sequence polymerization in the present invention. On the other hand, a synthesis method in which the diamine and acid dianhydride to be bonded are not selected in the charging order is referred to as random polymerization in the present invention.

  In the present invention, as a preferable polymerization method for obtaining a polyimide resin effective for suppressing film tearing, the remaining diamine and / or acid are formed after forming a flexible block component ideally for the purpose of forming a block component. It is particularly preferred to use a method in which a dianhydride is used to form a rigid block component to form a non-thermoplastic polyimide precursor.

(Solid content concentration of polyamic acid)
The solid content concentration of the non-thermoplastic polyamic acid of the present invention is not particularly limited, and it is usually 5% to 35% by weight, preferably 10% to 30% by weight. When the concentration is in this range, it is possible to obtain an appropriate molecular weight and solution viscosity.

(Polyamide acid composition)
A filler may be added to the non-thermoplastic polyamic acid of the present invention 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.

  Other thermosetting resins and thermoplastic resins may be mixed with the polyimide of the present invention as long as the properties of the obtained polyimide film are not impaired. Various known techniques can be applied to the method of adding these thermosetting resins and thermoplastic resins. For example, if it is soluble in a solvent, a method of adding it to the state of polyamic acid which is a precursor of polyimide can be mentioned.

(Production method of polyimide film)
The method for obtaining the polyimide film in the present invention is not particularly limited, and various known methods can be applied. For example, the following step i) a step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a non-thermoplastic polyamic acid solution,
ii) casting a film-forming dope containing the non-thermoplastic polyamic acid solution from a die onto a support to form a resin layer (sometimes referred to as a liquid film);
iii) a step of peeling the gel film from the support after the resin layer is heated on the support to obtain a self-supporting gel film,
iv) further heating, imidizing the remaining amic acid and drying to obtain a non-thermoplastic polyimide film;
It is preferable to contain.

  ii) Subsequent steps are roughly divided into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is cast as a film-forming dope without using a dehydrating ring-closing agent or the like, and imidation is advanced only by heating. One chemical imidization method is a method of promoting imidization by using, as a film-forming dope, a polyamic acid solution to which at least one of a dehydrating cyclization agent and a catalyst is added as an imidization accelerator. Either method may be used, but the chemical imidation method is superior in productivity.

  As the dehydrating ring-closing agent, acid anhydrides typified by acetic anhydride can be suitably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be suitably used.

  As the support for casting the film-forming dope, a glass plate, aluminum foil, endless stainless steel belt, stainless steel drum or the like can be suitably used. The heating conditions are set according to the thickness of the finally obtained film and the production rate, and after at least one of imidization or drying is partially performed, the film is peeled off from the support and is called a polyamic acid film (hereinafter referred to as a gel film). )

  Fix the end of the gel film and heat treatment to avoid shrinkage during curing, remove water, residual solvent, imidization accelerator, dehydrating ring closure agent, etc. from the gel film, and remove the remaining amic acid. Fully imidized to obtain a film containing polyimide. About a heating condition, what is necessary is just to set suitably according to the thickness and production rate of the film finally obtained.

(Manufacture of polyimide laminated film)
Using the polyimide film of the present invention, it is also possible to produce a polyimide laminated film in which another polyimide layer or an adhesive layer is laminated on at least one surface thereof. The method for producing the polyimide laminated film is not particularly limited, and various known methods can be applied. For example, a co-extrusion die may be used to simultaneously form a multilayer resin layer containing a non-thermoplastic polyamic acid that is a precursor of the polyimide of the present invention and a thermoplastic polyamic acid that can be an adhesive layer. In addition, a polyamide acid which is a precursor of the polyimide of the present invention is synthesized, and a polyimide film obtained by using the polyamide acid is collected once, and then a resin containing a thermoplastic polyamide acid newly by coating or the like thereon A layer may be formed. Since a very high temperature is required for imidization, when the resin layer other than polyimide is provided, it is preferable to adopt the latter means in order to suppress thermal decomposition. When a thermoplastic polyimide layer is provided by coating, a thermoplastic polyamic acid may be applied and then imidized, or a thermoplastic polyimide solution capable of forming a thermoplastic polyimide layer may be applied and dried. May be. Moreover, it is also possible to manufacture a polyimide laminated film by applying an acrylic adhesive or an epoxy adhesive to a polyimide film. Various surface treatments such as corona treatment and plasma treatment can be performed on the outermost surface of the polyimide laminated film.

  The total thickness of the polyimide laminated film of the present invention is preferably 6 μm to 60 μm. Even within this range, a thinner thickness is preferable because it contributes to weight reduction as an FPC and improves bendability. For example, the thickness is preferably 7 μm to 20 μm, and more preferably 7 μm to 15 μm.

(Flexible metal-clad laminate)
A flexible metal-clad laminate can be produced by attaching a metal foil to at least one surface of a polyimide laminate film. The method for producing the flexible metal-clad laminate is not particularly limited, and various known methods can be applied. For example, a continuous process by a hot roll laminating apparatus having a pair of metal rolls or a double belt press (DBP) can be used.

  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 also preferable.

  A means of casting a multilayer organic solvent solution containing at least one of a thermoplastic polyamic acid solution and a non-thermoplastic polyamic acid solution on the metal foil can also be used. The means for casting the organic solvent solution containing the polyamic acid on the metal foil is not particularly limited, and conventionally known means such as a die coater, comma coater (registered trademark), reverse coater, knife coater and the like can be used. When the polyimide resin layer and the non-thermoplastic polyimide film in the present invention are included, or when the polyimide resin layer is provided in multiple layers, or when a resin layer other than the polyimide is provided, the above casting and heating processes are repeated a plurality of times or co-extruded. Alternatively, a means of forming a cast layer by continuous casting and heating it at a time can be suitably used. By this means, a flexible metal-clad laminate is obtained at the same time as imidization is completed. When providing metal foil on both surfaces of the resin layer, the metal foil may be bonded to the opposite resin layer surface by heat and pressure.

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

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

(Film density)
The density of the polyimide film of the present invention is preferably in the range of ^{1.40g / cm 3 ~1.55g / cm 3} , to be within the scope of 1.40g / cm ³ ~1.50g / cm 3 More preferred. When polyimide has an agglomerated structure, the density of the polyimide film falls within this range, and even when a solvent such as an alkaline aqueous solution is present, it is difficult for the solvent to enter between the molecular chains and the molecular chains are difficult to slip, resulting in tearing of the film. It becomes difficult to do. In addition, since the rigidity of the molecular chain is appropriate, it is possible to prevent the film from becoming hard and brittle. The density can be appropriately set even under the film forming conditions of the polyimide film, and can be adjusted to this range by post-treatment of the polyimide film. Further, the density can be adjusted by stretching the polyimide film.

(Temperature indicated by inflection point of storage modulus)
The temperature indicated by the inflection point of the storage elastic modulus by dynamic viscoelasticity measurement of the polyimide film of the present invention (also referred to as E ′ inflection point temperature) is a viewpoint of relaxation of thermal stress when the metal foil is bonded by the laminating method. To 270 ° C. to 340 ° C., more preferably 280 ° C. to 330 ° C. If the temperature indicated by the inflection point of the storage elastic modulus is within this 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. ) Is small and good. Furthermore, since the temperature at which the softening of the core layer starts is lower than the temperature at the time of thermal lamination, it is sufficiently relaxed at that temperature, and the dimensional change is small and good.

(Storage elastic modulus at 380 ° C.)
The storage elastic modulus at 380 ° C. by dynamic viscoelasticity measurement of the polyimide film of the present invention is preferably in the range of 0.6 GPa to 2.0 GPa, more preferably in the range of 0.8 GPa to 1.8 GPa, and 0.9 GPa. More preferably, it is in the range of -1.6 GPa.

  When the storage elastic modulus at 380 ° C. is in the range of 0.6 GPa to 2.0 GPa, the film can maintain the self-supporting property at the time of imidization or thermal lamination of the film, and the productivity of the film can be improved. A flexible metal-clad laminate with good appearance can be obtained. Furthermore, the stress relaxation effect at the time of thermal lamination is fully exhibited.

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

  In addition, the evaluation method of how to obtain ST, which is an index of dynamic viscoelasticity, thermal linear expansion coefficient, tensile characteristics, 10% strain stress, density, and toughness of non-thermoplastic polyimide in the synthesis examples, examples and comparative examples, It is as follows.

(Dynamic viscoelasticity)
The storage elastic modulus was obtained by measuring dynamic viscoelasticity in an air atmosphere using DM6100 manufactured by SII Nanotechnology, and plotting the correlation with the measurement temperature to read the inflection point temperature and the storage elastic modulus at 380 ° C.
Sample measurement range: width 9 mm, distance between grippers: 20 mm
Measurement temperature range: 0 ° C to 440 ° C
Temperature increase rate: 3 ° C / min
Strain amplitude: 10 μm
Measurement frequency: 1Hz, 5Hz, 10Hz
Minimum tension / compression force: 100mN
Tension / compression gain; 1.5
Initial value of force amplitude: 100mN

(Thermal expansion coefficient)
The thermal linear expansion coefficient was measured by using TMA / SS6100 manufactured by SII Nano Technology, Inc., once heated from −10 ° C. to + 400 ° C. in a nitrogen atmosphere, cooled to −10 ° C., and then raised again to + 400 ° C. The average value was calculated from the linear thermal expansion coefficient from + 100 ° C. to + 200 ° C. during the second temperature increase.
Sample shape: Width 3mm
Length 10mm
Load; 3g (29.4mN)
Temperature increase rate: 10 ° C / min

(Tensile properties, 10% strain stress, slope of plastic deformation region)
The stress at 10% strain can be obtained from the measurement data of the tensile modulus. The tensile elastic modulus was measured according to ASTM D882. For the measurement, AUTOGRAPH AGS-J manufactured by Shimadzu Corporation was used, and measurement was performed in an environment of 23 ° C. and 55% RH.
Sample measurement range: 15 mm
Distance between grips: 100mm
Tensile speed: 200 mm / min

(density)
The density was measured at a test temperature of 23 ° C. according to JIS K7112, using a density gradient tube method. After the 5 mm square sample was gently placed in the density gradient tube, when the sample reached an equilibrium position in the liquid and stopped, the position was read from the scale of the density gradient tube. The final density was calculated from a correction curve for density and scale.

(Shaking test)
After diluting the polyimide precursor obtained in Synthesis Example 9 with DMF until the solid content concentration becomes 8% by weight, the final single-sided thickness of the thermoplastic polyimide layer (adhesive layer) is 3 μm on both sides of the polyimide film. A polyimide precursor was applied. Thereafter, heating was performed at 120 ° C. for 2 minutes. Subsequently, heating and imidization were performed at 350 ° C. for 15 seconds to obtain a polyimide laminated film. 12 μm electrolytic copper foil (3EC-M3S-HTE, made by Mitsui Metals) is arranged on both sides of the obtained polyimide laminated film, and further, protective films (Apical 125 NPI; Kaneka, thickness 125 μm) are used on both sides of the copper foil, Thermal lamination was performed under the conditions of a laminating temperature of 360 ° C., a laminating pressure of 265 N / cm (27 kgf / cm), and a laminating speed of 1.0 m / min to obtain a flexible metal-clad laminate. A flexible metal-clad laminate is cut to a size of 6.0 cm × 5.5 cm square, and a part of the metal foil is etched into a lattice shape (lattice size: 1.3 mm × 1.5 mm) as shown in FIG. A test piece was obtained. The test piece is placed in a container containing 800 mL of a 4% aqueous sodium hydroxide solution (23 ± 2 ° C.) and shaken at 23 ± 2 ° C. at a shaking speed of 230 rpm (ST) (Sec)). After etching, it was confirmed with an optical microscope that the radius of curvature inside each corner of the lattice was 50 μm or less, and a specimen having a radius of 50 μm or less was used. This test piece was put into a sodium hydroxide aqueous solution. Whether the film was torn or not was judged by stopping shaking every 100 seconds, applying light with a light box to each container in which the test piece was put, and judging that the film was torn when light passed through the test piece.

(Mock test in FPC manufacturing process)
A tension was applied to a long flexible metal-clad laminate on which a conductor pattern had been formed in advance, and the presence or absence of tearing when spraying a 5% aqueous sodium hydroxide solution at 45 ° C. with a spray was visually observed. Those in which no tearing occurred passed (◯), and those in which even one tearing occurred were regarded as unacceptable (x).

(Synthesis of non-thermoplastic polyimide precursor)
(Synthesis Example 1)
To a glass flask having a volume of 2000 ml, 655.69 g of N, N-dimethylformamide (hereinafter also referred to as DMF) and 28.86 g of diaminodiphenyl ether (hereinafter also referred to as ODA) were added, and while stirring under a nitrogen atmosphere, 25.44 g of 3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA) was gradually added. After visually confirming that BPDA was dissolved, 13.93 g of benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA) was added and stirred for 30 minutes. Thereafter, 3.46 g of ODA and 13.72 g of p-phenylenediamine (hereinafter also referred to as PDA) were added again and stirred for 5 minutes. Subsequently, 32.70 g of pyromellitic dianhydride (hereinafter also referred to as PMDA) was added and stirred for 30 minutes. Finally, a solution in which 1.89 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the above reaction solution while paying attention to an increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 2)
To a glass flask having a capacity of 2000 ml, 655.36 g of DMF and 29.25 g of ODA were added, and 25.79 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 14.12 g of BTDA was added and stirred for 30 minutes. Thereafter, 15.80 g of PDA was added and stirred for 5 minutes. Subsequently, 33.14 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.91 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 3)
To a glass flask having a capacity of 2000 ml, 656.91 g of DMF, 21.93 g of ODA, and 11.24 g of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter also referred to as BAPP) were added, and a nitrogen atmosphere was added. While stirring under, 16.11 g of BPDA was gradually added. After visually confirming that BPDA was dissolved, 22.06 g of BTDA was added and stirred for 30 minutes. Thereafter, 2.19 g of ODA and 13.62 g of PDA were added again and stirred for 5 minutes. Subsequently, 31.06 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.79 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to an increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 4)
To a glass flask having a capacity of 2000 ml, 657.90 g of DMF, 15.74 g of ODA, and 21.52 g of BAPP were added, and 19.28 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 16.89 g of BTDA was added and stirred for 30 minutes. Thereafter, 2.10 g of ODA and 13.04 g of PDA were added again and stirred for 5 minutes. Subsequently, 29.72 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.71 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to the increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 5)
To a glass flask having a capacity of 2000 ml, 656.86 g of DMF, 21.98 g of ODA, and 11.26 g of BAPP were added, and 24.22 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 13.26 g of BTDA was added and stirred for 30 minutes. Thereafter, 3.30 g of ODA and 13.06 g of PDA were added again and stirred for 5 minutes. Subsequently, 31.12 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.80 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to the increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 6)
To a glass flask having a capacity of 2000 ml, 657.92 g of DMF, 15.73 g of ODA, and 21.50 g of BAPP were added, and 23.11 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 12.65 g of BTDA was added and stirred for 30 minutes. Thereafter, 3.15 g of ODA and 12.46 g of PDA were added again and stirred for 5 minutes. Subsequently, 29.70 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.71 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to the increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 7)
To a glass flask having a capacity of 2000 ml, 655.69 g of DMF and 28.86 g of ODA were added, and 25.44 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 13.93 g of BTDA was added and stirred for 30 minutes. Thereafter, 3.46 g of ODA and 13.72 g of PDA were added again and stirred for 5 minutes. Subsequently, 32.70 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.89 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the above reaction solution while paying attention to an increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

(Synthesis Example 8)
To a glass flask having a capacity of 2000 ml, 657.82 g of DMF, 10.53 g of ODA, and 32.39 g of BAPP were added, and 16.95 g of BTDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BTDA was dissolved, 14.34 g of PMDA was added and stirred for 30 minutes. Thereafter, 14.22 g of PDA was added and stirred for 5 minutes. Subsequently, 29.83 g of PMDA was added and stirred for 30 minutes. Finally, a solution in which 1.72 g of PMDA was dissolved in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the above reaction solution while paying attention to an increase in viscosity. When the viscosity at 23 ° C. reached 2500 poise, addition and stirring were stopped to obtain a polyimide precursor.

  Table 1 shows polymerization prescriptions and polymerization methods of Synthesis Examples 1 to 8.

(Synthesis of thermoplastic polyimide precursor)
(Synthesis Example 9)
To a glass flask having a capacity of 2000 ml, 673.24 g of DMF and 71.83 g of BAPP were added, and 7.72 g of BPDA was gradually added while stirring in a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 31.30 g of PMDA was added and stirred for 30 minutes. Finally, a solution prepared by dissolving 1.15 g of PMDA in DMF to a solid content concentration of 7.2% was prepared, and this solution was gradually added to the reaction solution while paying attention to the increase in viscosity. When the viscosity at 23 ° C. reached 300 poise, addition and stirring were stopped to obtain a polyimide precursor.

  30.0 g of a curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 6.89 / 2.14 / 20.97) was added to this polyimide precursor (60 g), and stirring and defoaming were performed at a temperature of 0 ° C. or less. And it cast-coated on the aluminum foil using the comma coater. This resin film is heated at 120 ° C. for 3 minutes, then the self-supporting gel film is peeled off from the aluminum foil and fixed on a metal fixing frame, and dried at 250 ° C. for 1 minute, 300 ° C. for 200 seconds. -A polyimide film having a thickness of 20 μm was obtained by imidization. When this film was fixed to a metal fixed frame and heated at 450 ° C. for 2 minutes, it was confirmed that the film did not retain its shape and was thermoplastic.

Example 1
32.5 g of a curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 11.48 / 3.40 / 18.18) was added to the polyimide precursor (65 g) obtained in Synthesis Example 1, and 0 ° C. or less. The mixture was stirred and degassed at a temperature of 5 ° C and cast onto an aluminum foil using a comma coater. After heating this resin film at 115 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil and fixed to a metal fixing frame, and dried at 250 ° C. × 15 seconds, 350 ° C. × 79 seconds. A polyimide film having a thickness of 12.5 μm was obtained by imidization. When this film was fixed to a metal fixing frame and heated at 450 ° C. for 2 minutes, the form was maintained, and it was confirmed that the film was non-thermoplastic. Table 2 shows the film properties and ST of the obtained polyimide film.

(Example 2)
The same procedure as in Example 1 was performed except that the polyimide precursor obtained in Synthesis Example 1 was changed to Synthesis Example 6. When this film was fixed to a metal fixing frame and heated at 450 ° C. for 2 minutes, the form was maintained, and it was confirmed that the film was non-thermoplastic. Table 2 shows the film characteristics and ST.

(Comparative Examples 1 to 6)
The same procedure as in Example 1 was performed except that the polyimide precursor obtained in Synthesis Example 1 was changed to Synthesis Examples 2 to 5, 7, and 8. When this film was fixed to a metal fixing frame and heated at 450 ° C. for 2 minutes, the form was maintained, and it was confirmed that both were non-thermoplastic. Table 2 shows the film characteristics and ST.

(Discussion)
From the results in Table 2, in Examples 1 and 2 and Comparative Example 5 in which the flexible block component does not contain a bulky skeleton, the slope of the plastic deformation region was 1.0 or more, and the ST value was 700 seconds or more. Further, from the comparison between Examples 1 and 2, by introducing a bending chain into the rigid block component, the inclination of the plastic deformation region was increased, and accordingly ST was 900 seconds or more. From these results, it is shown that the resin layer is excellent in tear resistance due to difficulty in plastic deformation.

1. Metal foil Polyimide film Strain 1 (10% strain)
4). Strain 2 (breaking strain)
5). Stress1 (Stress at 10% strain)
6). Stress2 (breaking stress)
7). 7. s-s curve of Comparative Example 6 S-s curve of Example 1

Claims (6)

  A polyimide film, wherein a slope of a plastic deformation region in a stress-strain curve is 1.0 or more and less than 2.0.   The polyimide film according to claim 1, wherein the polyimide film is a non-thermoplastic polyimide film.   The polyimide film according to claim 1 or 2, wherein a stress at 10% strain in a stress-strain curve is 180 MPa or more.   The storage elastic modulus at 380 ° C in dynamic viscoelasticity measurement is 0.6 GPa to 2.0 GPa, and the temperature indicated by the inflection point of the storage elastic modulus is 270 ° C to 340 ° C. The polyimide film of any one of -3. Wherein the density of the polyimide film is ^{1.40g / cm 3 ~1.55g / cm 3} , a polyimide film according to any one of claims 1-4.   The polyimide film according to claim 1, wherein the polyimide includes a flexible block component and a rigid block component.