Metal layer laminate

Abstract

To provide a film for a metal layer laminate and a metal layer laminate excellent in stiffness while suppressing variation in dielectric constant before and after pressing.SOLUTION: A film 1 for a metal layer laminate includes a porous resin layer 2 having a tensile modulus at 25°C of 800 MPa or more and 2000 MPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film for a metal layer laminate and a metal layer laminate. [Background technology]

[0002] A film for a metal layer laminate having a porous resin layer is known (see, for example, Patent Document 1 below). The film for a metal layer laminate in the examples of Patent Document 1 contains, as a porous resin layer, a porous polyimide film that is a reaction product of a diamine component containing p-phenylenediamine and oxydianiline with an acid dianhydride component. A metal layer laminate is produced from the film for a metal layer laminate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2018 / 186486 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a metal layer laminate, the film for a metal layer laminate may be pressed in the thickness direction (specifically, heat pressed). Furthermore, when processing a metal layer laminate, the film for a metal layer laminate may also be pressed in the thickness direction (specifically, heat pressed). In such cases, the substrate for metal layer lamination of Patent Document 1 has an excessively large reduction in thickness after pressing. This causes a problem of a large increase in dielectric constant after pressing.

[0005] Furthermore, metal layer laminates may be bent and placed in narrow spaces. However, the metal layer laminate of Patent Document 1 has excessive stiffness. This causes a problem in that it is difficult to bend the metal layer laminate by applying a load. Stiffness is the stress of a metal layer laminate bent under a load, and a low stiffness value indicates excellent stiffness.

[0006] The present invention provides a film for metal layer laminates and a metal layer laminate that are excellent in stiffness while being able to suppress the rate of thickness reduction after pressing. [Means for solving the problem]

[0007] The present invention (1) includes a film for metal layer laminates, which includes a porous resin layer having a tensile modulus at 25°C of 800 MPa or more and 2000 MPa or less.

[0008] The present invention (2) includes the film for metal layer laminates according to (1), further comprising an adhesive layer disposed on one surface in the thickness direction of the porous resin layer.

[0009] The present invention (3) includes a metal layer laminate comprising the film for metal layer laminate described in (1) or (2) and a metal layer disposed on one surface in the thickness direction of the film for metal layer laminate. [Effects of the Invention]

[0010] The film for metal layer laminate and the metal layer laminate of the present invention are excellent in stiffness while being able to suppress fluctuations in dielectric constant before and after pressing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of the film for metal layer laminate of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a modified example of the metal layer laminate. [Figure 3] FIG. 3 is a cross-sectional view of a modified example of the film for metal layer laminate. [Figure 4] FIG. 4 is a cross-sectional view of a modified example of the film for metal layer laminate. [Figure 5] FIG. 5 is a cross-sectional view illustrating the evaluation of stiffness in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Film for metal layer laminates> One embodiment of the film for metal layer laminate of the present invention will be described with reference to Figure 1. The film for metal layer laminate 1 has a thickness. The film for metal layer laminate 1 has one side 11 and another side 12 that face each other in the thickness direction. The one side 11 faces one side in the thickness direction. The other side 12 faces the other side in the thickness direction. The thickness of the film for metal layer laminate 1 is not particularly limited. The film for metal layer laminate 1 extends in a plane direction perpendicular to the thickness direction.

[0013] The film 1 for metal layer laminates includes a porous resin layer 2. In this embodiment, the film 1 for metal layer laminates includes only the porous resin layer 2. One side 11 and the other side 12 of the porous resin layer 2 are the same as the one side 11 and the other side 12 of the film 1 for metal layer laminates, respectively.

[0014] <Tensile Modulus of Porous Resin Layer 2> The tensile modulus of elasticity of the porous resin layer 2 at 25° C. is 800 MPa or more and 2000 MPa or less.

[0015] If the tensile modulus of elasticity of the porous resin layer 2 at 25° C. is less than the lower limit, the reduction rate of the thickness of the film for metal layer laminate 1 after pressing increases, and the dielectric constant after pressing increases significantly.

[0016] If the tensile modulus of elasticity of the porous resin layer 2 at 25° C. exceeds the upper limit described above, the stiffness of the film for metal layer laminates 1 will decrease.

[0017] The tensile modulus of the porous resin layer 2 at 25° C. is preferably 900 MPa or more, more preferably 950 MPa or more. The tensile modulus of the porous resin layer 2 at 25° C. is preferably 1600 MPa or less, more preferably 1500 MPa or less, even more preferably 1300 MPa or less, and particularly preferably 1100 MPa or less.

[0018] The tensile modulus of elasticity of the porous resin layer 2 is determined as the initial slope of a stress-strain curve obtained when the porous resin layer 2 is subjected to a tensile test at 25° C. and a speed of 5 mm / min.

[0019] The porous resin layer 2 is porous. The porous resin layer 2 has a closed-cell structure and / or an open-cell structure. The porosity of the porous resin layer 2 is, for example, 50% or more, preferably 60% or more, and more preferably 70% or more. The porosity of the porous resin layer 2 is, for example, less than 100%, or even 99% or less. When the porous resin layer 2 is made of a polyimide resin, the porosity can be calculated by the following formula.

[0020] Dielectric constant of porous resin layer 2=Dielectric constant of air×Porosity+Dielectric constant of polyimide resin×(1−Porosity)

[0021] The porous resin layer 2 has a thickness of, for example, 2 μm or more, or preferably 5 μm or more, and for example, 1,000 μm or less, or preferably 500 μm or less.

[0022] <Material of Porous Resin Layer 2> The material of the porous resin layer 2 is a resin. The resin is not limited. Specific examples of the resin include polycarbonate resin, polyimide resin, fluorinated polyimide resin, epoxy resin, phenol resin, urea resin, melamine resin, diallyl phthalate resin, silicone resin, thermosetting urethane resin, fluororesin (fluorine-containing olefin polymer (specifically, polytetrafluoroethylene (PTFE))), and liquid crystal polymer (LCP). These can be used alone or in combination of two or more. Of the above-mentioned resins, polyimide resin is preferable from the viewpoint of mechanical strength. Details of polyimide resin, including its physical properties and manufacturing method, are described, for example, in WO2018 / 186486 and JP2020-172667A. Note that polyimide resin may also be simply referred to as polyimide.

[0023] <Physical properties of film 1 for metal layer laminates>

[0024] The dielectric constant of the film for metal layer laminate 1 at a frequency of 10 GHz is, for example, 2.5 or less, preferably 2.0 or less, more preferably 1.9 or less, even more preferably 1.8 or less, particularly preferably 1.7 or less, and most preferably 1.6 or less, and is, for example, greater than 1.0. The dielectric constant of the film for metal layer laminate 1 is measured by a resonator method. Furthermore, when the film for metal layer laminate 1 includes a layer other than the porous resin layer 2, as in the modified example described below, the dielectric constant of the film for metal layer laminate 1 may be different from the dielectric constant of the porous resin layer 2.

[0025] In this embodiment, the tensile modulus of the film for metal layer laminate 1 at 25°C is the same as the tensile modulus of the porous resin layer 2 at 25°C. Furthermore, when the film for metal layer laminate 1 includes a layer other than the porous resin layer 2, as in the modified example described below, the tensile modulus of the film for metal layer laminate 1 may be different from the tensile modulus of the porous resin layer 2. In that case, the tensile modulus of the film for metal layer laminate 1 at 25°C is, for example, 500 MPa or more, preferably 600 MPa or more, more preferably 700 MPa or more, even more preferably 700 MPa or more, particularly preferably 840 MPa or more, and 2000 MPa or less. The method for measuring the tensile modulus of the film for metal layer laminate 1 is the same as that for the porous resin layer 2.

[0026] <Method of manufacturing film 1 for metal layer laminate> Next, a method for producing the film for metal layer laminate 1 will be described.

[0027] Specifically, first, a metal layer 3 (virtual line) is prepared. The metal layer 3 is a metal film extending in the planar direction. Examples of metals include copper, iron, silver, gold, aluminum, nickel, and alloys thereof (stainless steel, bronze). A preferred example of the metal is copper. The thickness of the metal layer 3 is, for example, 0.1 μm or more, preferably 1 μm or more, and for example, 100 μm or less, preferably 50 μm or less.

[0028] Next, a varnish containing the above-mentioned resin precursor, a porosifying agent, a nucleating agent, and a solvent is prepared, and then the varnish is applied to one surface in the thickness direction of the metal layer 3 to form a coating film. The types and blending ratios of the porosifying agent, nucleating agent, and solvent in the varnish are described, for example, in WO2018 / 186486.

[0029] The case where the resin is a polyimide resin will be described. The precursor of the polyimide resin is, for example, a reaction product of a diamine component and an acid dianhydride component. Examples of the diamine component include aromatic diamines and aliphatic diamines. As the diamine component, an aromatic diamine is preferably used from the viewpoint of obtaining a tensile modulus of elasticity equal to or less than the above-mentioned upper limit.

[0030] The diamine component and the acid dianhydride component can be used alone or in combination. Specifically, as the diamine component, preferably, an aromatic diamine is used alone, and preferably, an aromatic diamine and an aliphatic diamine are used in combination.

[0031] <Single use of aromatic diamine> An embodiment in which the aromatic diamine is used alone will be described.

[0032] Aromatic diamines include primary, secondary, and tertiary diamines.

[0033] The first diamine contains a single aromatic ring. Examples of the first diamine include phenylenediamine, dimethylbenzenediamine, and ethylmethylbenzenediamine. From the viewpoint of mechanical strength, phenylenediamine is preferred. Examples of the phenylenediamine include o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine. Examples of the phenylenediamine include p-phenylenediamine. p-Phenylenediamine is sometimes abbreviated as PDA.

[0034] The second diamine contains a plurality of aromatic rings and ether bonds disposed between them. Examples of the second diamine include oxydianiline. Examples of the oxydianiline include 3,4'-oxydianiline and 4,4'-oxydianiline. From the viewpoint of mechanical strength, 4,4'-oxydianiline (also known as 4,4-diaminodiphenyl ether) is preferred. 4,4'-oxydianiline is sometimes abbreviated as ODA.

[0035] The tertiary diamine contains a plurality of aromatic rings and ester bonds between them. Examples of the tertiary diamine include aminophenylaminobenzoate, and preferably 4-aminophenyl-4-aminobenzoate, from the viewpoint of obtaining a tensile modulus equal to or greater than the above-mentioned lower limit. 4-aminophenyl-4-aminobenzoate is sometimes abbreviated as APAB.

[0036] In addition to the primary to tertiary diamines, examples of the aromatic diamine include 4,4'-methylenedianiline, 4,4'-dimethylenedianiline, 4,4'-trimethylenedianiline, and bis(4-aminophenyl)sulfone.

[0037] The diamine components described above can be used alone or in combination. A preferred diamine component is a combination of a primary diamine, a secondary diamine, and a tertiary diamine. A more preferred diamine is a combination of p-phenylenediamine (PDA), 4,4'-oxydianiline (ODA), and 4-aminophenyl-4-aminobenzoate (APAB).

[0038] The molar fraction of the first diamine in the diamine component is, for example, 10 mol% or more, preferably 20 mol% or more, and for example, 70 mol% or less, preferably 65 mol% or less. The molar fraction of the second diamine in the diamine component is, for example, 5 mol% or more, preferably 10 mol% or more, and for example, 40 mol% or less, preferably 30 mol% or less. The molar fraction of the tertiary diamine in the diamine component is, for example, 5 mol% or more, for example, 10 mol% or more, and for example, 40 mol% or less, preferably 30 mol% or less.

[0039] Furthermore, the molar amount of the tertiary diamine relative to 100 molar parts in total of the first diamine and the second diamine is, for example, 5 molar parts or more, preferably 10 molar parts or more, more preferably 20 molar parts or more, and for example, 100 molar parts or less, preferably 50 molar parts or less, more preferably 30 molar parts or less.

[0040] <Combined use of aromatic diamine and aliphatic diamine> The combined use of an aromatic diamine and an aliphatic diamine will now be described. The aromatic diamine may be any of the aromatic diamines described above, preferably a primary diamine, and more preferably p-phenylenediamine (PDA).

[0041] Aliphatic diamines contain a long-chain alkyl group, but may also contain a cyclic moiety within the molecule. Examples of aliphatic diamines include hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, and dimer diamine. A preferred example of an aliphatic diamine is dimer diamine. Dimer diamine is, for example, an amine compound in which two carboxyl groups of a dimer acid are substituted with primary amino groups. Dimer acid is a dimer of an unsaturated fatty acid. An example of an unsaturated fatty acid is oleic acid. Dimer diamines are described, for example, in JP 2020-172667 A and JP 2018-168369 A. Commercially available dimer diamines can be used, specifically, the PRIAMINE series (manufactured by Croda).

[0042] In an embodiment in which an aromatic diamine and an aliphatic diamine are used in combination, the molar fraction of the aromatic diamine in the diamine component is preferably 40 mol% or more, more preferably 55 mol% or more, more preferably 70 mol% or more, and for example, 98 mol% or less, preferably 90 mol% or less, more preferably 85 mol% or less. The molar fraction of the aliphatic diamine in the diamine component is preferably 2 mol% or more, more preferably 10 mol% or more, more preferably 15 mol% or more, and for example, 60 mol% or less, preferably 45 mol% or less, more preferably 30 mol% or less. The molar ratio of the aliphatic diamine to 100 mol parts of the aromatic diamine is, for example, 0.1 mol parts or more, preferably 1 mol parts or more, more preferably 5 mol parts or more, and for example, less than 50 mol parts, preferably 40 mol parts or less, more preferably 30 mol parts or less.

[0043] <Acid dianhydride component> The acid dianhydride component is not limited. The acid dianhydride component may contain, for example, an acid dianhydride containing an aromatic ring. Examples of the acid dianhydride containing an aromatic ring include aromatic tetracarboxylic dianhydrides. Examples of the aromatic tetracarboxylic dianhydride include benzene tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, biphenyl sulfone tetracarboxylic dianhydride, and naphthalene tetracarboxylic dianhydride.

[0044] Examples of benzenetetracarboxylic dianhydrides include benzene-1,2,4,5-tetracarboxylic dianhydride (also known as pyromelotic dianhydride). Examples of benzophenonetetracarboxylic dianhydrides include 3,3'-4,4'-benzophenonetetracarboxylic dianhydride. Examples of biphenyltetracarboxylic dianhydrides include 3,3'-4,4'-biphenyltetracarboxylic dianhydride, 2,2'-3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-diphenylethertetracarboxylic dianhydride. Examples of biphenylsulfonetetracarboxylic dianhydrides include 3,3',4,4'-biphenylsulfonetetracarboxylic dianhydride. Examples of naphthalenetetracarboxylic dianhydrides include 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,4,5-naphthalenetetracarboxylic dianhydride, and 1,4,5,8-naphthalenetetracarboxylic dianhydride. These can be used alone or in combination. From the viewpoint of mechanical strength, the dianhydride component is preferably biphenyltetracarboxylic dianhydride, and more preferably 3,3'-4,4'-biphenyltetracarboxylic dianhydride. 3,3'-4,4'-biphenyltetracarboxylic dianhydride is sometimes abbreviated as BPDA.

[0045] The ratio of the diamine component to the acid dianhydride component is adjusted so that the molar amount of the amino group (-NH2) of the diamine component and the molar amount of the acid anhydride group (-CO-O-CO-) of the acid dianhydride component are, for example, equal.

[0046] To prepare a polyimide resin precursor, the diamine component, the acid dianhydride component, and a solvent are mixed to prepare a varnish, and the varnish is heated to prepare a precursor solution. Subsequently, a nucleating agent and a porosifying agent are mixed with the precursor solution to prepare a porous precursor solution.

[0047] Thereafter, the porous precursor solution is applied to the other surface of the metal layer 3 in the thickness direction to form a coating film.

[0048] The coating is then dried by heating to form a precursor film. As the solvent is removed by the heating, a precursor film having a phase-separated structure of the polyimide resin precursor and the porosifying agent, with the nucleating agent as the core, is prepared.

[0049] Thereafter, the porosifying agent is extracted (pulled out or removed) from the precursor film by, for example, supercritical extraction using supercritical carbon dioxide as a solvent.

[0050] Thereafter, the precursor film is cured by heating to form a porous resin layer 2 made of polyimide resin.

[0051] Thereafter, if necessary, the metal layer 3 is removed as indicated by the solid line in FIG. 1 . For example, the metal layer 3 is dissolved using a stripping solution. Examples of the stripping solution include FeCl3. In this way, a film 1 for a metal layer laminate including a porous resin layer 2 is obtained. Note that when a metal layer laminate 10, which will be described later, is produced, the metal layer 3 is not removed but remains as the metal layer 3.

[0052] <Application> Next, a metal layer laminate 10 including a film for metal layer laminate 1 will be described as shown by the imaginary line in Fig. 1. This metal layer laminate 10 includes a film for metal layer laminate 1 including a porous resin layer 2, and a metal layer 3 shown by the imaginary line.

[0053] The film 1 for a metal layer laminate is provided on a metal layer laminate 10. That is, the film 1 for a metal layer laminate is used to laminate the metal layer 3.

[0054] The metal layer 3 is disposed on one surface 11 in the thickness direction of the porous resin layer 2. Specifically, the metal layer 3 is in contact with one surface 11 in the thickness direction of the porous resin layer 2. Therefore, the metal layer laminate 10 includes the porous resin layer 2 and the metal layer 3 in this order toward one side in the thickness direction. Examples of materials for the metal layer 3 include the metals exemplified for the metal layer 3. Preferably, copper is used. The thickness of the metal layer 3 is, for example, 0.1 μm or more, preferably 1 μm or more, and for example, 100 μm or less, preferably 50 μm or less.

[0055] To manufacture the metal layer laminate 10, a laminate 21 that is in the middle of manufacturing the film 1 for a metal layer laminate and that includes the metal layer 3 and the film 1 for a metal layer laminate is provided as is as the metal layer laminate 10. In this way, the metal layer laminate 10 is manufactured that includes the film 1 for a metal layer laminate and the metal layer 3 disposed on one surface 11 in the thickness direction of the film 1. Thereafter, the metal layer 3 is formed into a pattern by, for example, etching.

[0056] Depending on the application and purpose, the metal layer laminate 10 is pressed before, during, and / or after the formation of the above-mentioned pattern. Specifically, the metal layer laminate 10 is hot-pressed. In this way, the metal layer laminate 10 is manufactured.

[0057] This metal layer laminate 10 is used, for example, in fifth-generation (5G) standard wireless communications and high-speed flexible printed circuit boards (FPCs).

[0058] (Effects of one embodiment) In the film 1 for metal layer laminates, the tensile modulus of the porous resin layer 2 is 800 MPa or more, so that the reduction rate of the thickness of the film 1 for metal layer laminates after pressing can be suppressed.

[0059] Furthermore, in the film 1 for metal layer laminates, the tensile modulus of the porous resin layer 2 is 2000 MPa or less, so that the stiffness of the film 1 for metal layer laminates can be improved.

[0060] Furthermore, since the metal layer laminate 10 includes the film 1 for metal layer laminates described above, it has excellent stiffness while allowing for a small reduction in thickness after pressing.

[0061] <Modification> In the following modifications, the same components and steps as those in the above-described embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, the modifications can achieve the same effects as those in the above-described embodiment, unless otherwise specified. Furthermore, the embodiment and its modifications can be combined as appropriate.

[0062] 2, the metal layer laminate 10 can further include a second metal layer 4. This metal layer laminate 10 includes, in order toward one side in the thickness direction, a metal layer 4, a porous resin layer 2, and a metal layer 3. The configuration of the second metal layer 4 is the same as that of the metal layer 3.

[0063] As shown in FIG. 3, the film 1 for metal layer laminate and the metal layer laminate 10 can each further include an adhesive layer 7. The film 1 for metal layer laminate, shown by a solid line in FIG. 3, includes an adhesive layer 7 and a porous resin layer 2, in that order, toward one side in the thickness direction. The metal layer laminate 10, shown by a solid line and a virtual line in FIG. 3, includes a second metal layer 4 (virtual line), an adhesive layer 7, a porous resin layer 2, and a metal layer 3, in that order, toward one side in the thickness direction. The adhesive layer 7 is disposed between the two layers, the porous resin layer 2 and the second metal layer 4, and is therefore sometimes referred to as an "interlayer adhesive layer."

[0064] The adhesive layer 7 is disposed on the other surface in the thickness direction of the porous resin layer 2. Specifically, the adhesive layer 7 is in contact with the other surface in the thickness direction of the porous resin layer 2. The adhesive layer 7 forms the other surface 12 of the film for metal layer laminate 1. The adhesive layer 7 may be either a single layer or multiple layers (specifically, two layers). The thickness of the adhesive layer 7 is not limited. The thickness of the adhesive layer 7 is, for example, 1 μm or more, preferably 5 μm or more, and for example, 50 μm or less, preferably 30 μm or less. The material of the adhesive layer 7 is not limited. Examples of materials for the adhesive layer 7 include adhesive compositions, preferably curable adhesive compositions, more preferably thermosetting adhesive compositions, and even more preferably epoxy-based thermosetting adhesive compositions.

[0065] To manufacture the metal layer laminate 10 and film 1 for metal layer laminate shown in FIG. 3, the laminate 21 (metal layer laminate 10) and adhesive laminate 20 shown in FIG. 1 are prepared. The adhesive laminate 20 has a second metal layer 4 and an adhesive layer 7, in that order, toward one side in the thickness direction. Next, the adhesive layer 7 of the adhesive laminate 20 is bonded to the porous resin layer 2 of the laminate 21 shown in FIG. 1. If the material of the adhesive layer 7 is a thermosetting adhesive composition, the adhesive layer 7 is then heated to completely cure. This results in a metal layer laminate 10, which has a second metal layer 4, adhesive layer 7, porous resin layer 2, and metal layer 3, in that order, toward one side in the thickness direction.

[0066] Next, the second metal layer 4 and the metal layer 3 are removed, thereby obtaining a film 1 for metal layer laminates, which is provided with the adhesive layer 7 and the porous resin layer 2 in that order towards one side in the thickness direction.

[0067] As shown by solid lines in FIG. 4, the film 1 for metal layer laminates can include two porous resin layers 2. The film 1 for metal layer laminates includes two porous resin layers 2 and an adhesive layer 7 sandwiched between the two porous resin layers 2 in the thickness direction. Specifically, the film 1 for metal layer laminates includes a porous resin layer 2, an adhesive layer 7, and a porous resin layer 2, in that order toward one side in the thickness direction. A metal layer laminate 10, shown by solid lines and imaginary lines in FIG. 4, includes the film 1 for metal layer laminates, a metal layer 3, and a second metal layer 4. Specifically, the metal layer laminate 10 includes a second metal layer 4, a porous resin layer 2, an adhesive layer 7, a porous resin layer 2, and a metal layer 3, in that order toward one side in the thickness direction. To manufacture the metal layer laminate 10 shown in Figure 4, the porous resin layer 2 of a first laminate 21A having a metal layer 3 and a porous resin layer 2 and the porous resin layer 2 of a second laminate 21B having a second metal layer 4 and a porous resin layer 2 are bonded together via an adhesive layer 7. [Example]

[0068] The present invention will be described in more detail below with reference to examples and comparative examples. It should be noted that the present invention is not limited to these examples and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be substituted with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Description of the Invention" above.

[0069] < reference Example 1> < Corresponding to Figure 1 reference Example> A diamine component solution was prepared by dissolving 64.88 g (0.60 mol) of p-phenylenediamine (PDA) (primary diamine), 40.05 g (0.20 mol) of 4,4'-oxydianiline (ODA) (secondary diamine), and 45.65 g (0.20 mol) of 4-aminophenyl-4-aminobenzoate (APAB) (tertiary diamine) in 2300 g of N-methyl-2-pyrrolidone (NMP). Subsequently, 294.2 g (1.00 mol) of 3,3'-4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added to the diamine component solution and stirred at 80°C. The stirring was stopped and the mixture was allowed to cool, yielding a polyimide precursor solution.

[0070] To 100 parts by mass of the polyimide precursor solution, 150 parts by mass of polyoxyethylene dimethyl ether (NOF Corp., Grade: MM400) with a weight-average molecular weight of 400 was added as a porosifying agent, and 3 parts by mass of PTFE powder with a particle size of 1 μm or less was added as a nucleating agent. The mixture was stirred to obtain a transparent, homogeneous solution. To the resulting solution, 4 parts by mass of 2-methylimidazole was added as an imidization catalyst to prepare a varnish. The prepared varnish was applied to a metal layer 3 consisting of copper foil (Fukuda Metal Foil & Powder Co., Ltd., CF-T49A-DS-HD2), heated and dried to remove the NMP. This produced a polyimide precursor film approximately 50 μm thick on one side of the metal layer 3 in the thickness direction.

[0071] The polyimide precursor film and the metal layer 3 were then immersed in supercritical carbon dioxide pressurized to 30 MPa at 60°C, and the supercritical carbon dioxide was passed through for 5 hours to promote extraction and removal of the porosifying agent, phase separation of the remaining NMP, and pore formation. The supercritical carbon dioxide was then reduced in pressure to obtain a polyimide precursor porous film with the metal layer 3.

[0072] Furthermore, the obtained polyimide precursor porous film with the metal layer 3 was heated under vacuum at 390°C for 185 minutes to remove residual components and promote imidization, thereby producing a metal layer laminate 10 (single-sided copper clad laminate) (CCL) having a second metal layer 4 and a porous resin layer 2.

[0073] Thereafter, the metal layer laminate 10 was immersed in an FeCl3 solution to dissolve and remove the metal layer 3. In this way, a film 1 for metal layer laminates having a porous resin layer 2 was produced.

[0074] <Example 2> <Example corresponding to FIG. 3> reference The first laminate 21A including the metal layer 3 and porous resin layer 2 in Example 1, an adhesive layer 7 made of an epoxy adhesive composition (uncured) having a thickness of 10 μm, and a metal layer 4 were pressed in a vacuum at 60°C and 1 MPa for 10 seconds using a press. The adhesive layer 7 was sandwiched between the porous resin layer 2 and the metal layer 4. The laminate was then further heated and pressed in a vacuum at 160°C and 3 MPa for 30 minutes to completely cure the adhesive layer 7. As a result, the porous resin layer 2 and the metal layer 4 were bonded by the adhesive layer 7, as shown in FIG. 3 . This produced a metal layer laminate 10 including the second metal layer 4, adhesive layer 7, porous resin layer 2, and metal layer 3, arranged in this order toward one side in the thickness direction.

[0075] Thereafter, the metal layer laminate 10 was immersed in an FeCl3 solution to dissolve and remove the metal layer 3 and the second metal layer 4. In this way, a film 1 for a metal layer laminate including the adhesive layer 7 and the porous resin layer 2 was produced.

[0076] Example 3 <Example corresponding to FIG. 4> reference An adhesive layer 7 made of an epoxy adhesive composition (uncured) having a thickness of 10 μm was sandwiched between two laminates 21 (first laminate 21A and second laminate 21B) in Example 1, and these were pressed using a press under vacuum at 60°C and 1 MPa for 10 seconds. At this time, the adhesive layer 7 was sandwiched between two porous resin layers 2. Thereafter, the adhesive layer 7 was completely cured by further heating and pressing under vacuum at 160°C and 3 MPa for 30 minutes. As a result, a metal layer laminate 10 was produced, which includes, in order toward one side in the thickness direction, a second metal layer 4, a porous resin layer 2, an adhesive layer 7, a porous resin layer 2, and a metal layer 3, as shown in FIG. 4 .

[0077] Thereafter, the metal layer laminate 10 was immersed in an FeCl3 solution to dissolve and remove the metal layer 3 and the second metal layer 4. In this way, a film 1 for a metal layer laminate including the porous resin layer 2, the adhesive layer 7, and the porous resin layer 2 was produced.

[0078] Example 4 <Example corresponding to FIG. 3> A film 1 for metal layer laminates was produced in the same manner as in Example 2, except that two adhesive layers 7 were used in a superposed manner.

[0079] < reference Example 5> < Corresponding to FIG. 1, the diamine component contains an aromatic diamine and an aliphatic diamine. reference Example> A diamine component solution was prepared by dissolving 99.49 g (0.92 mol) of p-phenylenediamine (PDA) (aromatic diamine: primary diamine) and 42.8 g (0.08 mol) of PRIAMINE 1075 (manufactured by Croda) (aliphatic diamine: dimer diamine) in 2258 g of N-methyl-2-pyrrolidone (NMP). 294.22 g (1.00 mol) of 3,3'-4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added to the diamine component solution and stirred at 80°C. The stirring was stopped and the mixture was allowed to cool to prepare a polyimide precursor solution.

[0080] To 100 parts by mass of the polyimide precursor solution, 200 parts by mass of polyoxyethylene dimethyl ether (NOF Corp., Grade: MM400) with a weight-average molecular weight of 400 was added as a porosifying agent, and 3 parts by mass of PTFE powder with a particle size of 1 μm or less was added as a nucleating agent. The mixture was stirred to obtain a transparent, homogeneous solution. 4 parts by mass of 2-methylimidazole was added to the resulting solution as an imidization catalyst to prepare a varnish. The prepared varnish was applied to a metal layer 3 consisting of copper foil (Fukuda Metal Foil & Powder Co., Ltd., CF-T49A-DS-HD2), and then heated and dried to remove the NMP. This produced a polyimide precursor film approximately 25 μm thick on one side of the metal layer 3 in the thickness direction.

[0081] The polyimide precursor film and the metal layer 3 were then immersed in supercritical carbon dioxide pressurized to 30 MPa at 60°C, and the supercritical carbon dioxide was passed through for 5 hours to promote extraction and removal of the porosifying agent, phase separation of the remaining NMP, and pore formation. The supercritical carbon dioxide was then decompressed to obtain a polyimide precursor porous film with the metal layer 3.

[0082] Furthermore, the obtained polyimide precursor porous film with the metal layer 3 was heated under vacuum at 350°C for 185 minutes to remove residual components and promote imidization, thereby producing a metal layer laminate 10 (single-sided copper clad laminate) (CCL) having a second metal layer 4 and a porous resin layer 2.

[0083] Thereafter, the metal layer laminate 10 was immersed in an FeCl3 solution to dissolve and remove the metal layer 3. In this way, a film 1 for metal layer laminates having a porous resin layer 2 was produced.

[0084] <Comparative Example 1> reference A film 1 for metal layer laminates was produced in the same manner as in Example 1. However, the polyimide precursor varnish used was a varnish prepared in accordance with Example 1 of WO2018 / 186486. Specifically, a diamine component containing PDA and ODA was used.

[0085] <Comparative Example 2> A film 1 for metal layer laminates was produced in the same manner as in Example 3. However, the polyimide precursor varnish used was a varnish prepared in accordance with Example 1 of WO2018 / 186486. Specifically, a diamine component containing PDA and ODA was used.

[0086] <Evaluation> Example 2~4 and Comparative Examples 1 and 2 Reference Examples 1 and 5 The following physical properties were evaluated for the film 1 for metal layer laminates and the porous resin layer 2. The results are shown in Table 1.

[0087] <<Physical properties of porous resin layer 2>>

[0088] <Porosity> The porosity of the porous resin layer 2 was calculated based on the following formula.

[0089] Dielectric constant of porous resin layer 2 = dielectric constant of air × porosity + dielectric constant of non-porous polyimide × (1 - porosity) Here, the dielectric constant of air is 1 and the dielectric constant of non-porous polyimide is 3.5, so Dielectric constant of porous resin layer 2 = porosity + 3.5 (1 - porosity) Porosity=(3.5−dielectric constant of porous resin layer 2) / 2.5 Porosity (%)=[(3.5−dielectric constant of porous resin layer 2) / 2.5]×100 The dielectric constant of the porous resin layer 2 was measured by a dielectric resonator method at a frequency of 10 GHz.

[0090] <Tensile modulus> The porous resin layer 2 was processed to have a width of 5 mm and a size of 100 mm to prepare a sample. The prepared sample was subjected to a tensile test using a tensile tester (TG-1kN manufactured by MinebeaMitsumi) with a chuck distance of 40 mm and a speed of 5 mm / min. The tensile test was carried out at 25°C. A stress-strain curve was obtained from the tensile test. The tensile modulus was calculated as the initial slope of the stress-strain curve.

[0091] <<Physical properties of film 1 for metal layer laminates>> <Thickness> The thickness of the film 1 for metal layer laminates was measured using a thickness meter (manufactured by Fujiwork Co., Ltd.).

[0092] <Dielectric constant> The dielectric constant of the film 1 for metal layer laminates at 10 GHz was measured by a resonator method.

[0093] <Tensile modulus> The tensile modulus of the film 1 for metal layer laminates was measured at 25° C. The tensile modulus of the film 1 for metal layer laminates was measured in the same manner as the tensile modulus of the porous resin layer 2.

[0094] <Stiffness (bias force method)> A sample 30 was prepared by cutting the metal layer laminate film 1 into a shape measuring 30 mm in length and 10 mm in width. As shown in FIG. 5 , the sample 30 was folded so that both longitudinal ends 13 of the sample 30 approached each other, one thickness-direction surface 11 of each end 13 faced each other, and the distance between the other thickness-direction surface 12 of each end 13 was 2 mm. When the sample 30 was folded, each of the two plates 14 was brought into contact with both ends of the other thickness-direction surface 12. The two plates were parallel. The force in the opposing direction of the folded sample 30 was measured. The stiffness was calculated based on the following formula. The unit of stiffness is mN / mm. The above measurement method is called the bias force method.

[0095] (force at bending - initial mass) / 10mm width

[0096] <Thickness reduction rate after pressing> A sample measuring 40 mm x 40 mm was prepared from the film 1 for metal layer laminates. This sample was placed in an instantaneous vacuum laminating device VS008-1515 (manufactured by Mikado Technos Co., Ltd.) and pressed at 160°C and 5 MPa for 300 seconds. The reduction in thickness after pressing was calculated using the following formula.

[0097] Thickness reduction rate after pressing (%) = (thickness before pressing - thickness after pressing) / thickness before pressing x 100

[0098] The heat pressability was evaluated based on the reduction rate of thickness after pressing, based on the following criteria.

[0099] ×: The reduction rate of thickness after pressing was more than 5%. ◯: The reduction in thickness after pressing was 5% or less. [Table 1] [Explanation of symbols]

[0100] 1. Film for metal layer laminates 2 Porous resin layer 3 metal layer 4 Second metal layer 7 Adhesive layer 10 Metal layer laminate 11 One side

Claims

1. A laminate comprising a second metal layer, a film for a metal laminate plate, and a metal layer in that order toward one side in the thickness direction, The film for metal laminate plate includes an adhesive layer and a porous resin layer in this order toward one side in a thickness direction, The porous resin layer has a tensile modulus at 25° C. of 800 MPa or more and 2000 MPa or less, A metal layer laminate, wherein the thickness of the film for metal laminate is not 1.0 mm or more.

2. A laminate comprising a second metal layer, a film for a metal laminate plate, and a metal layer in that order toward one side in the thickness direction, The film for metal laminate plate includes two porous resin layers and an adhesive layer sandwiched between the two porous resin layers in a thickness direction, The porous resin layer has a tensile modulus at 25° C. of 800 MPa or more and 2000 MPa or less, A metal layer laminate, wherein the thickness of the film for metal laminate is not 1.0 mm or more.

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