Thermoplastic polyimide, crosslinked polyimide, adhesive film, laminate, coverlay film, resin-coated copper foil, metal-clad laminate, circuit board and multilayer circuit board

Abstract

To provide polyimide which uses dimer diamine as a raw material, and can suppress transfer loss of a high-frequency signal when applied to a circuit board by a low dielectric loss tangent.SOLUTION: A thermoplastic polyimide contains 40 mol% or more of a diamine residue derived from a dimer diamine composition with respect to the total diamine residue, and 2-40 mol% of the total of a diamine residue derived from a diamine compound represented by the general formula (1). In the general formula (1), a connection group A represents a single bond and -COO- or -CONH-, a substituent E represents a hydrogen atom, a monovalent alkyl group which may be substituted with a halogen atom and has 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a vinyl group, an acrylic group, a methacrylic group or an allyl group, m represents 1 to 2, and p and q represent integers of 0 to 4.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic polyimide useful as a material for electronic components, and to a crosslinked polyimide, adhesive film, laminate, coverlay film, resin-coated copper foil, metal-clad laminate, circuit board, and multilayer circuit board using the same. [Background technology]

[0002] In recent years, the performance of electronic devices has been improving, making it necessary to accommodate higher-frequency transmission signals. When transmitting high-frequency signals, if there is large transmission loss in the transmission path, inconveniences such as loss of electrical signals and long signal delay times will occur. Therefore, in the future, it will be important to reduce transmission loss in circuit boards such as flexible printed circuit boards (FPCs; Flexible Printed Circuits).

[0003] In order to efficiently transmit high-frequency signals in circuit boards, it is important to reduce the dielectric loss tangent of the insulating resin layer, including the adhesive layer. Generally, this can be achieved by reducing the polar structure in the resin composition to reduce polarity, or by using a crystalline structure like a liquid crystalline polymer.

[0004] Polyimide is commonly used as the material for the insulating resin layer of FPCs, but polyimide for adhesive layers must be able to be thermocompressed, so a crystalline structure that easily hardens irreversibly cannot be used.

[0005] In Patent Documents 1 and 2, a low dielectric loss tangent is achieved by using dimer diamine, an aliphatic diamine, as a raw material for polyimide.

[0006] However, Patent Document 1 attempts to lower the dielectric loss tangent by copolymerizing dimer diamine with phenylenediamine. In the specific examples disclosed, aromatic phenylenediamine is used in an amount of 33 to 58 mol% of the total diamine compounds. This raises concerns that the adhesiveness and thermocompression processability required for the polyimide used in the adhesive layer may be reduced, and that reduced solubility may shorten the varnish life.

[0007] Furthermore, in Patent Document 2, a polyimide obtained by copolymerizing dimer diamine with a flexible diamine compound achieves a low dielectric loss tangent while maintaining adhesiveness. However, the polyimide film described in Patent Document 2 has a dielectric loss tangent of 0.002 or more, and further improvement is required in view of the fact that transmission signals will continue to increase in frequency. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-117631 [Patent Document 2] Japanese Patent Application Publication No. 2018-140544 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a polyimide made from dimer diamine as a raw material, which has a low dielectric loss tangent and is capable of suppressing transmission loss of high-frequency signals when applied to a circuit board. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that a polyimide obtained by copolymerizing a dimer diamine with a rigid diamine compound having a biphenyl skeleton or a terphenyl skeleton, or a -COO- group or a -CONH- group in the molecule has suppressed molecular mobility and exhibits a low dielectric loss tangent, thereby completing the present invention.

[0011] That is, the thermoplastic polyimide of the present invention is a thermoplastic polyimide containing an acid dianhydride residue derived from the acid dianhydride component and a diamine residue derived from the diamine component. The thermoplastic polyimide of the present invention is characterized by containing, relative to the total diamine residues, 40 mol % or more of diamine residues derived from a dimer diamine composition containing, as a main component, a dimer diamine obtained by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups, and containing, relative to the total diamine residues, 2 to 40 mol % of diamine residues derived from a diamine compound represented by the following general formula (1):

[0012] [ka]

[0013] In general formula (1), the linking group A represents a single bond or a divalent group selected from -COO- and -CONH-; the substituents E independently represent a hydrogen atom, a monovalent alkyl group having 1 to 3 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, a vinyl group, an acrylic group, a methacrylic group, or an allyl group; m represents an integer of 1 or 2; and p and q independently represent integers of 0 to 4.

[0014] The thermoplastic polyimide of the present invention may have a weight average molecular weight (Mw) in the range of 5,000 or more and 200,000 or less.

[0015] The thermoplastic polyimide of the present invention may contain 10 mol % or more of acid dianhydride residues derived from benzophenonetetracarboxylic dianhydride based on the total acid dianhydride residues.

[0016] In the thermoplastic polyimide of the present invention, the diamine residue may contain a diamine residue derived from a diamine compound having a substituent with a carbon-carbon double bond.

[0017] The thermoplastic polyimide of the present invention may have a crosslinked structure formed by a C=N bond between a ketone group contained in the thermoplastic polyimide and an amino group of an amino compound having at least two primary amino groups as functional groups.

[0018] The thermoplastic polyimide of the present invention may have a crosslinked structure formed by the carbon-carbon double bonds contained therein.

[0019] The adhesive film of the present invention is characterized by containing the above-mentioned thermoplastic polyimide or crosslinked polyimide.

[0020] The adhesive film of the present invention may have a dielectric loss tangent (Tanδ) of less than 0.002 at 10 GHz measured using a split post dielectric resonator (SPDR) after being conditioned for 24 hours under constant temperature and humidity conditions (normal state) of 23°C and 50% RH.

[0021] The laminate of the present invention is a laminate having a substrate and an adhesive layer laminated on at least one surface of the substrate, and the adhesive layer is made of the adhesive film described above.

[0022] The coverlay film of the present invention is a coverlay film having a coverlay film material layer and an adhesive layer laminated on the coverlay film material layer, and the adhesive layer is made of the adhesive film described above.

[0023] The resin-coated copper foil of the present invention is a resin-coated copper foil obtained by laminating an adhesive layer and a copper foil, and the adhesive layer is made of the above-mentioned adhesive film.

[0024] The metal-clad laminate of the present invention is a metal-clad laminate having an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and at least one layer of the insulating resin layer is made of the above-mentioned adhesive film.

[0025] The metal-clad laminate of the present invention is a metal-clad laminate having an insulating resin layer, an adhesive layer laminated on at least one side of the insulating resin layer, and a metal layer laminated on the insulating resin layer via the adhesive layer, wherein the adhesive layer is made of the above-mentioned adhesive film.

[0026] The metal-clad laminate of the present invention comprises a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface of the first metal layer; a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one surface of the second metal layer; a metal-clad laminate comprising: an adhesive layer disposed so as to abut on the first insulating resin layer and the second insulating resin layer, and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; The adhesive layer is made of the adhesive film.

[0027] The metal-clad laminate of the present invention comprises a single-sided metal-clad laminate having an insulating resin layer and a metal layer laminated on one side of the insulating resin layer, and an adhesive layer laminated on the other side of the insulating resin layer, wherein the adhesive layer is made of the above-mentioned adhesive film.

[0028] The circuit board of the present invention is obtained by wiring the metal layer of the metal-clad laminate.

[0029] The circuit board of the present invention comprises a first base material, a wiring layer laminated on at least one surface of the first base material, and an adhesive layer laminated on the surface of the first base material facing the wiring layer so as to cover the wiring layer, wherein the adhesive layer is made of the above-mentioned adhesive film.

[0030] The circuit board of the present invention comprises a first substrate, a wiring layer laminated on at least one surface of the first substrate, an adhesive layer laminated on the surface of the first substrate facing the wiring layer so as to cover the wiring layer, and a second substrate laminated on the surface of the adhesive layer opposite the first substrate, wherein the adhesive layer is made of the adhesive film described above.

[0031] The circuit board of the present invention comprises a first substrate, an adhesive layer laminated on at least one side of the first substrate, a second substrate laminated on the side of the adhesive layer opposite the first substrate, and wiring layers laminated on the sides of the first substrate and the second substrate opposite the adhesive layer, respectively, wherein the adhesive layer is made of the above-mentioned adhesive film.

[0032] The multilayer circuit board of the present invention is a multilayer circuit board including a laminate including a plurality of laminated insulating resin layers, and at least one wiring layer embedded inside the laminate, At least one of the plurality of insulating resin layers is formed of an adhesive layer that has adhesiveness and covers the wiring layer, and the adhesive layer is made of the adhesive film. [Effects of the Invention]

[0033] The thermoplastic polyimide of the present invention is obtained by copolymerizing dimer diamine with a diamine compound represented by general formula (1), and therefore can form a polyimide film having good solubility, a low dielectric loss tangent, and excellent adhesiveness and thermocompression processability. Therefore, when the polyimide film obtained from the thermoplastic polyimide of the present invention is applied to a circuit board or the like that transmits high-frequency signals in the GHz frequency range (e.g., 1 to 40 GHz), the polyimide film can effectively reduce transmission loss in high-frequency signal transmission. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic diagram showing a cross-sectional configuration of a laminate according to an embodiment of the present invention. [Figure 2]1 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to an embodiment of the present invention. [Figure 3] FIG. 4 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to another embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to yet another embodiment of the present invention. [Figure 5] 1 is a schematic diagram showing a cross-sectional configuration of a circuit board according to an embodiment of the present invention; [Figure 6] FIG. 10 is a schematic diagram showing a cross-sectional configuration of a circuit board according to another embodiment of the present invention. [Figure 7] FIG. 10 is a schematic diagram showing a cross-sectional configuration of a circuit board according to yet another embodiment of the present invention. [Figure 8] 1 is a schematic diagram showing a cross-sectional configuration of a multilayer circuit board according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0035] An embodiment of the present invention will be described with reference to the drawings as appropriate. A thermoplastic polyimide according to one embodiment of the present invention has high adhesiveness and thermocompression processability due to its thermoplasticity, making it possible to use it as an adhesive. Hereinafter, the polyimide of this embodiment may be referred to as an "adhesive polyimide." Note that "thermoplastic polyimide" generally refers to a polyimide that can be softened by heating and solidified by cooling, repeating this process, and has a clearly identifiable glass transition temperature. However, in the present invention, it refers to a polyimide whose glass transition temperature is clearly identifiable in a temperature range below 150°C. Furthermore, from the viewpoint of thermocompression bondability at low temperatures, the thermoplastic polyimide is preferably a polyimide whose glass transition temperature is clearly identifiable in a temperature range below 100°C, and has a storage modulus of 1.0 x 10 at 30°C measured using a dynamic viscoelasticity measuring device (DMA). 8 Pa or more, and the storage modulus at the glass transition temperature + 30°C is 1.0 x 10 7On the other hand, the term "non-thermoplastic polyimide" refers to a polyimide that does not soften or exhibit adhesiveness even when heated, and in the present invention, the term "non-thermoplastic polyimide" refers to a polyimide that does not exhibit a storage modulus of 1.0 × 10 at 30°C measured using a dynamic viscoelasticity measuring device (DMA). 9 Pa or more, and the storage modulus at 300°C is 1.0 x 10 8 This means that it indicates Pa or higher.

[0036] The adhesive polyimide contains an acid dianhydride residue derived from the acid dianhydride component and a diamine residue derived from the diamine component. When the raw materials, an acid dianhydride and a diamine compound, are reacted in approximately equimolar amounts, the types and molar ratios of the acid dianhydride residues and diamine residues contained in the polyimide can be made to correspond approximately to the types and molar ratios of the raw materials. In the present invention, the term "polyimide" refers to a resin made of a polymer having an imide group in the molecular structure, such as polyimide, polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, or polybenzimidazoleimide.

[0037] The acid dianhydride residues and diamine residues constituting the adhesive polyimide will be described below together with their raw materials.

[0038] (acid dianhydride) For the adhesive polyimide, any acid dianhydride generally used as a raw material for thermoplastic polyimides can be used without any particular limitation. Examples of such acid dianhydrides include 3,3',4,4'-, 2,3',3,4'-, 2,2',3,3'-, or 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride ( 6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylenebis(trimellitic acid monoester anhydride) (TAHQ), ethylene glycol bisanhydrotrimellitate (TMEG), pyromellitic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3''-p-terphenyl tetraanhydride tetracarboxylic acid dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic acid dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 2,2-bis(3,4- dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylenetetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl Examples of suitable tetracarboxylic acid dianhydrides include aromatic tetracarboxylic acid dianhydrides such as 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride, 1,2,3,4-cyclopentane tetracarboxylic acid dianhydride, 1,2,4,5-cyclohexane tetracarboxylic acid dianhydride, 1,2,4,5-cycloheptane tetracarboxylic acid dianhydride, and 1,2,5,6-cyclooctane tetracarboxylic acid dianhydride.

[0039] Here, when crosslinking is performed using ketone groups (carbonyl groups) contained in the adhesive polyimide as described below, it is preferable to use a raw material containing benzophenone tetracarboxylic dianhydride in an amount of preferably 10 mol% or more, more preferably 50 mol% or more, based on the total acid dianhydride components. In other words, the adhesive polyimide preferably contains acid dianhydride residues derived from benzophenone tetracarboxylic dianhydride in an amount of preferably 10 mol% or more, more preferably 50 mol% or more, based on the total acid dianhydride residues. By containing a total of 10 mol% or more of acid dianhydride residues derived from benzophenone tetracarboxylic dianhydride based on the total acid dianhydride residues, it is easy to achieve both flexibility and heat resistance of the adhesive polyimide, and the carbonyl groups (ketone groups) contribute to adhesion, thereby improving the adhesion of the adhesive polyimide. Here, if the content of acid dianhydride residues derived from benzophenone tetracarboxylic dianhydride is less than 10 mol% in total with respect to all acid dianhydride residues, the number of ketone groups (carbonyl groups) that serve as crosslinking points in the crosslinking formation described below will be reduced, which is disadvantageous from the viewpoint of improving solder heat resistance. Note that any of 3,3',4,4'-, 2,3',3,4'-, 2,2',3,3'-, or 2,3,3',4'-benzophenone tetracarboxylic dianhydride can be used as the benzophenone tetracarboxylic dianhydride.

[0040] (diamine) The adhesive polyimide can be made using any diamine compound commonly used in thermoplastic polyimides as a raw material, without particular limitation. However, the diamine residues derived from a dimer diamine composition, primarily composed of a dimer diamine in which two terminal carboxylic acid residues of a dimer acid are substituted with primary aminomethyl groups or amino groups, are preferably present in an amount of 40 mol% or more, preferably 40 mol% to 98 mol%, and more preferably 60 mol% to 95 mol%, relative to the total diamine residues. By including the diamine residues derived from the dimer diamine composition in the above range, the solubility of the polyimide can be improved and the dielectric constant and dielectric loss tangent can be reduced. If the content of the diamine residues derived from the dimer diamine composition is less than 40 mol% relative to the total diamine residues, the relative dielectric constant and dielectric loss tangent tend to increase due to the relatively increased polar groups contained in the polyimide. Furthermore, including the diamine residues derived from the dimer diamine composition in the above amount can improve thermocompression bonding properties by lowering the glass transition temperature (Tg) of the polyimide and alleviate internal stress by lowering the elastic modulus. On the other hand, if the content of diamine residues derived from the dimer diamine composition exceeds 98 mol % with respect to all diamine residues, the mobility of the molecular chains of the polyimide may increase excessively, resulting in an increase in the dielectric loss tangent.

[0041] The dimer diamine composition is a purified product containing the following component (a) as a main component, with the amounts of components (b) and (c) controlled:

[0042] (a) dimer diamine; The dimer diamine of component (a) refers to a diamine in which the two terminal carboxylic acid groups (—COOH) of a dimer acid are replaced with primary aminomethyl groups (—CH—NH) or amino groups (—NH). Dimer acids are known dibasic acids obtained by the intermolecular polymerization of unsaturated fatty acids. Their industrial production process is largely standardized in the industry, and they are obtained by dimerizing unsaturated fatty acids with 11 to 22 carbon atoms using a clay catalyst or the like. Industrially obtained dimer acids are primarily composed of a 36-carbon dibasic acid obtained by dimerizing 18-carbon unsaturated fatty acids such as oleic acid, linoleic acid, and linolenic acid. However, depending on the degree of purification, they may contain arbitrary amounts of monomer acid (18 carbon atoms), trimer acid (54 carbon atoms), and other polymerized fatty acids with 20 to 54 carbon atoms. Although double bonds remain after the dimerization reaction, in the present invention, dimer acids that have been further hydrogenated to reduce the degree of unsaturation are also included in the definition of dimer acids. The dimer diamine of component (a) can be defined as a diamine compound obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with a primary aminomethyl group or an amino group.

[0043] Dimer diamines are characterized by their ability to impart properties derived from the dimer acid skeleton. Dimer diamines are aliphatic macromolecules with molecular weights of approximately 560 to 620, which increases the molecular molar volume and reduces the relative polarity of polyimides. These characteristics of dimer acid diamines are believed to contribute to improving the dielectric properties of polyimides by reducing their dielectric constant and dielectric loss tangent while suppressing a decrease in their heat resistance. Furthermore, the presence of two freely movable hydrophobic chains with 7 to 9 carbon atoms and two linear aliphatic amino groups with a length approaching 18 carbon atoms not only imparts flexibility to polyimides but also allows them to have asymmetric or nonplanar chemical structures, thereby potentially lowering the dielectric constant of polyimides.

[0044] The dimer diamine composition used should be one in which the dimer diamine content of component (a) has been increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more, by a purification method such as molecular distillation. By increasing the dimer diamine content of component (a) to 96% by weight or more, the broadening of the molecular weight distribution of the polyimide can be suppressed. If technically possible, it is best for the entire dimer diamine composition (100% by weight) to be composed of component (a) dimer diamine.

[0045] (b) a monoamine compound obtained by substituting the terminal carboxylic acid group of a monobasic acid compound having 10 to 40 carbon atoms with a primary aminomethyl group or an amino group; The monobasic acid compound having 10 to 40 carbon atoms is a mixture of a monobasic unsaturated fatty acid having 10 to 20 carbon atoms derived from the raw material of dimer acid, and a monobasic acid compound having 21 to 40 carbon atoms that is a by-product during the production of dimer acid. The monoamine compound is obtained by substituting the terminal carboxylic acid group of these monobasic acid compounds with a primary aminomethyl group or an amino group.

[0046] The monoamine compound (b) is a component that suppresses an increase in the molecular weight of the polyimide. During polymerization of the polyamic acid or polyimide, the monofunctional amino group of the monoamine compound reacts with the terminal acid anhydride groups of the polyamic acid or polyimide, thereby capping the terminal acid anhydride groups and suppressing an increase in the molecular weight of the polyamic acid or polyimide.

[0047] (c) Amine compounds obtained by substituting the terminal carboxylic acid group of a polybasic acid compound having a hydrocarbon group having 41 to 80 carbon atoms with a primary aminomethyl group or an amino group (excluding the dimer diamine); The polybasic acid compound having a hydrocarbon group having 41 to 80 carbon atoms is a polybasic acid compound whose main component is a tribasic acid compound having 41 to 80 carbon atoms, which is a by-product during the production of dimer acid. It may also contain a polymerized fatty acid other than dimer acid having 41 to 80 carbon atoms. The amine compound is obtained by substituting the terminal carboxylic acid group of these polybasic acid compounds with a primary aminomethyl group or an amino group.

[0048] The amine compound (c) is a component that promotes an increase in the molecular weight of the polyimide. The tri- or higher functional amino group, primarily composed of a triamine derived from a trimer acid, reacts with the terminal acid anhydride group of the polyamic acid or polyimide, rapidly increasing the molecular weight of the polyimide. Furthermore, amine compounds derived from polymerized fatty acids other than dimer acids having 41 to 80 carbon atoms also increase the molecular weight of the polyimide, causing gelation of the polyamic acid or polyimide.

[0049] When quantifying each component by gel permeation chromatography (GPC), a sample of the dimer diamine composition treated with acetic anhydride and pyridine is used, and cyclohexanone is used as an internal standard to facilitate confirmation of the peak start, peak top, and peak end of each component of the dimer diamine composition. Using the sample thus prepared, each component is quantified by area percent in the GPC chromatogram. The peak start and peak end of each component are the minimum values ​​of each peak curve, and the area percent of the chromatogram can be calculated based on these values.

[0050] Furthermore, the dimer diamine composition has a total area percentage of components (b) and (c) of 4% or less, preferably less than 4%, in a chromatogram obtained by GPC measurement. By keeping the total area percentage of components (b) and (c) at 4% or less, broadening of the molecular weight distribution of the polyimide can be suppressed.

[0051] The area percentage of the chromatogram of component (b) is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. By setting the area percentage within this range, it is possible to suppress a decrease in the molecular weight of the polyimide and to widen the range of the molar ratio of the tetracarboxylic dianhydride component and the diamine component. Note that component (b) does not necessarily have to be contained in the dimer diamine composition.

[0052] The area percentage of the chromatogram of component (c) is 2% or less, preferably 1.8% or less, and more preferably 1.5% or less. By setting the area percentage within this range, a rapid increase in the molecular weight of the polyimide can be suppressed, and an increase in the dielectric loss tangent of the resin film over a wide frequency range can be suppressed. Note that component (c) does not necessarily have to be contained in the dimer diamine composition.

[0053] Furthermore, when the ratio (b / c) of the area percentages of the chromatograms of the components (b) and (c) is 1 or more, the molar ratio of the tetracarboxylic dianhydride component to the diamine component (tetracarboxylic dianhydride component / diamine component) is preferably 0.97 or more and less than 1.0, and such a molar ratio makes it easier to control the molecular weight of the polyimide.

[0054] Furthermore, when the ratio (b / c) of the area percentages of the components (b) and (c) in the chromatogram is less than 1, the molar ratio of the tetracarboxylic dianhydride component to the diamine component (tetracarboxylic dianhydride component / diamine component) is preferably 0.97 or more and 1.1 or less, and by setting such a molar ratio, it becomes easier to control the molecular weight of the polyimide.

[0055] Commercially available dimer diamine compositions are preferably purified to reduce the amount of components other than the dimer diamine in component (a), for example, to 96 area percent or more of component (a). The purification method is not particularly limited, but known methods such as distillation and precipitation purification are suitable. Commercially available dimer diamine compositions include PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan.

[0056] The adhesive polyimide preferably contains, relative to the total diamine residues, a total of 2 to 40 mol %, preferably 5 to 40 mol %, more preferably 5 to 30 mol %, and even more preferably 10 to 30 mol % of diamine residues derived from at least one diamine compound represented by the following general formula (1): If the total content of diamine residues derived from diamine compounds represented by general formula (1) is less than 2 mol %, the effect of lowering the dielectric tangent is not fully exhibited. On the other hand, if the total content of diamine residues derived from diamine compounds represented by general formula (1) is more than 40 mol %, the adhesiveness and thermocompression processability may be reduced.

[0057] [ka]

[0058] In general formula (1), the linking group A represents a single bond or a divalent group selected from -COO- and -CONH-; the substituents E independently represent a hydrogen atom, a monovalent alkyl group having 1 to 3 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, a vinyl group, an acrylic group, a methacrylic group, or an allyl group; m represents an integer of 1 or 2; and p and q independently represent integers of 0 to 4.

[0059] By using a diamine compound represented by general formula (1) in combination with a dimer diamine composition as a raw material monomer, the molecular motion of the polyimide molecular chain can be suppressed, resulting in a low dielectric loss tangent. Specifically, the diamine compound represented by general formula (1) has a highly rigid biphenyl or terphenyl skeleton within the molecule, or a highly rigid -COO- or -CONH- group as the linking group A of adjacent aromatic rings, and the two amino groups and the linking group A are in the para position, resulting in a highly linear molecular structure. Therefore, compared with a case where all of the diamine residues are derived from the dimer diamine composition, replacing a portion of them with diamine residues derived from the diamine compound represented by general formula (1) is thought to suppress the overall motion of the polyimide molecular chain and enable a low dielectric loss tangent.

[0060] Furthermore, since the diamine residues derived from the dimer diamine composition have the function of imparting excellent solvent solubility to the adhesive polyimide, reducing the amount of diamine residues derived from the dimer diamine composition tends to reduce the solvent solubility accordingly. However, since the diamine compound represented by general formula (1) has a significant effect of lowering the dielectric tangent even in small amounts, it is possible to achieve a low dielectric tangent in an amount used that does not impair the solvent solubility of the adhesive polyimide.

[0061] As described above, the diamine compound represented by general formula (1) has a great effect in suppressing molecular motion, and a small amount is sufficient to sufficiently reduce the dielectric tangent. Therefore, unlike the phenylenediamine described in Patent Document 1, there is little concern that the compound will reduce the adhesiveness and thermocompression processability required for adhesive applications, and there is also no concern that the compound will reduce solvent solubility and shorten the varnish life.

[0062] Specific examples of the diamine compound represented by general formula (1) include: 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4,4'-diaminobiphenyl, 2,2'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, 3,3'-diethoxy-4,4'-diaminobiphenyl, 3,3'-dipropoxy-4,4'- Examples of such compounds include diaminobiphenyl, 3,3'-n-propyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3',5,5'-tetramethylbenzidine, 2,2'-ditrifluoromethylbenzidine (TFMB), 4,4'-diamino-2,2',5,5'-tetrachlorobiphenyl, 4,4'-diaminooctafluorobiphenyl, 4-aminophenyl-4'-aminobenzoate (APAB), 4,4'-diaminobenzanilide, 2'-methoxy-4,4'-diaminobenzanilide, 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), and 4,4'-diamino-p-terphenyl. Among these, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) and 2,2'-ditrifluoromethylbenzidine (TFMB) are preferred from the viewpoint of enhancing the orientation of molecular chains and efficiently suppressing molecular motion due to the side chain length and bonding position, and 2,2'-divinyl-4,4'-diaminobiphenyl (VAB) is preferred from the viewpoint of efficiently suppressing molecular chain mobility due to the electronic interaction also caused by the conjugated structure of the side chain.

[0063] In addition to the above, the adhesive polyimide may contain diamine residues derived from diamine compounds generally used in thermoplastic polyimides, provided that the effects of the invention are not impaired.

[0064] Adhesive polyimides can be produced by reacting the acid anhydride and diamine components in a solvent to form polyamic acid, followed by heating and ring closure. For example, the acid anhydride and diamine components are dissolved in approximately equimolar amounts in an organic solvent, and the mixture is stirred at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to cause a polymerization reaction, thereby producing polyamic acid, a precursor to polyimide. During the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is in the range of 5 to 50 wt %, preferably 10 to 40 wt %, of the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diglyme, triglyme, methanol, ethanol, benzyl alcohol, and cresol. Two or more of these solvents can be used together, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such organic solvents is not particularly limited, but it is preferable to adjust the amount so that the concentration of the polyamic acid solution obtained by the polymerization reaction is approximately 5 to 50% by weight.

[0065] The synthesized polyamic acid is usually advantageously used as a solution in a reaction solvent, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Polyamic acid is also advantageously used because it generally has excellent solvent solubility. The viscosity of the polyamic acid solution is preferably within the range of 500 mPa·s to 100,000 mPa·s. If the viscosity is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating using a coater or the like.

[0066] The method for imidizing polyamic acid to form polyimide is not particularly limited, and a suitable method is, for example, heat treatment in the solvent at a temperature in the range of 80 to 400° C. for 1 to 24 hours. The temperature may be constant, or the temperature may be changed during the process.

[0067] In the adhesive polyimide, by selecting the types of the acid anhydride component and diamine component, or by selecting the molar ratio of each when two or more types of acid anhydride component or diamine component are used, it is possible to control physical properties such as dielectric characteristics, thermal expansion coefficient, tensile modulus, glass transition temperature, etc. Furthermore, when the adhesive polyimide has a plurality of structural units, they may be present as blocks or randomly, but random presence is preferred.

[0068] The adhesive polyimide obtained as described above contains a certain amount or more of residues derived from dimer diamine, and is therefore a solvent-soluble polyimide that is soluble in organic solvents such as N-methyl-2-pyrrolidone (NMP), and is suitable for use in an application in which it is applied to a substrate such as a metal foil.

[0069] The adhesive polyimide preferably has a weight average molecular weight (Mw) in the range of 5,000 to 200,000. If the Mw of the adhesive polyimide is less than 5,000, the film tends to be brittle. On the other hand, if the Mw exceeds 200,000, the varnish tends to have high viscosity, which can easily cause thickness unevenness during coating. The Mw of the adhesive polyimide is more preferably in the range of 10,000 to 60,000, and even more preferably in the range of 20,000 to 60,000. If the Mw is less than 10,000, the polyimide molecular chain may have an increased number of highly polar acid terminals, which may increase the relative dielectric constant and dielectric loss tangent. If the Mw is more than 60,000, the molecular chain length may be increased, which may make it difficult to achieve the effect of copolymerizing the dimer diamine and the diamine compound represented by general formula (1), which may increase the relative dielectric constant and dielectric loss tangent.

[0070] The adhesive polyimide preferably has a ratio (Mw / Mn) of Mw to number average molecular weight (Mn) in the range of 1.5 to 2.8, more preferably 1.8 to 2.8. The Mw / Mn ratio represents the polydispersity, and in the adhesive polyimide of this embodiment, the Mw / Mn ratio is preferably 1.5 or greater. Even if the Mn is approximately the same, the higher the polydispersity, the greater the frequency of high molecular weight molecules. This increases the suppression of motion due to molecular entanglement, resulting in a lower dielectric loss tangent and improved tear strength. Furthermore, since Mn more directly represents the number of polyimide chain terminals than Mw, by setting the Mw / Mn ratio to 2.8 or less and achieving a balance with Mn while ensuring a certain degree of polydispersity, it is possible to suppress the increase in highly polar terminals in the polyimide molecular chain and thus suppress increases in the dielectric constant and dielectric loss tangent. Mn can be controlled by increasing the content of dimer diamine in the dimer diamine composition (i.e., by reducing the trimer component and monomer component), thereby suppressing the spread of the molecular weight of the adhesive polyimide.

[0071] The imide group concentration of the adhesive polyimide is preferably 22% by weight or less, more preferably in the range of 15 to 22% by weight, and even more preferably in the range of 18 to 22% by weight. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO)2-N-) in the polyimide by the molecular weight of the entire polyimide structure. If the imide group concentration exceeds 22% by weight, the molecular weight of the resin itself will decrease, and the increase in polar groups will deteriorate the low moisture absorption properties, resulting in an increase in Tg and elastic modulus.

[0072] The adhesive polyimide is most preferably a completely imidized structure. However, a portion of the polyimide may be an amic acid. The imidization rate can be determined by measuring the infrared absorption spectrum of the polyimide thin film by the single-reflection ATR method using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) at 1015 cm -1 Based on the benzene ring absorber near 1780cm -1 It can be calculated from the absorbance of the C=O stretching derived from the imide group.

[0073] The adhesive polyimide can be made into an adhesive composition by appropriately blending optional components such as a plasticizer, other curable resin components such as epoxy resin, a curing agent, a curing accelerator, an organic filler, an inorganic filler, a coupling agent, and a flame retardant.

[0074] (Crosslinking of adhesive polyimide) Adhesive polyimides can be crosslinked by various methods. The formation of a crosslinked structure can significantly improve the heat resistance of adhesive polyimides. Adhesive polyimides with a crosslinked structure (hereinafter sometimes referred to as "crosslinked polyimides") are an application example of adhesive polyimides and are a preferred form. Note that, since crosslinking significantly changes the Mw, the Mw of crosslinked polyimides will be a different value from the Mw of adhesive polyimides before crosslinking. Below, we will explain crosslinking via imine bonds (C=N bonds) and crosslinking using carbon-carbon double bonds.

[0075] (A) Cross-linking via imine bond (C=N bond): When an adhesive polyimide has a ketone group, the ketone group can be reacted with the amino group of an amino compound having at least two primary amino groups as functional groups (hereinafter sometimes referred to as a "crosslinking amino compound") to form a C=N bond, thereby forming a crosslinked structure. Another application example and preferred embodiment is an adhesive composition in which a crosslinking agent is blended with an adhesive polyimide having a ketone group. Examples of preferred tetracarboxylic dianhydrides for forming adhesive polyimides having ketone groups include 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and examples of preferred diamine compounds include aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

[0076] For the purpose of forming a crosslinked structure, it is particularly preferred to react a crosslinking amino compound with an adhesive polyimide containing BTDA residues derived from BTDA in an amount of preferably 50 mol % to 100 mol %, more preferably 60 mol % to 100 mol %, based on the total acid dianhydride residues. In the present invention, the term "BTDA residue" refers to a tetravalent group derived from BTDA.

[0077] Examples of crosslinking amino compounds include (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds tend to form crosslinked structures even at room temperature, raising concerns about the storage stability of the varnish. On the other hand, aromatic diamines require high temperatures to form crosslinked structures. When a dihydrazide compound is used, it is possible to achieve both the storage stability of the varnish and a shortened curing time. Examples of dihydrazide compounds include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and diglycerides. Preferred dihydrazide compounds include cholic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridine dioic acid dihydrazide, itaconic acid dihydrazide, etc. The above dihydrazide compounds may be used alone or in combination of two or more.

[0078] Furthermore, the amino compounds such as (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines can also be used in combination of two or more types across categories, such as a combination of (I) and (II), a combination of (I) and (III), or a combination of (I), (II), and (III).

[0079] Furthermore, from the viewpoint of making the network structure formed by crosslinking with the crosslinking amino compound denser, the crosslinking amino compound used in the present invention preferably has a molecular weight (weight average molecular weight when the crosslinking amino compound is an oligomer) of 5,000 or less, more preferably 90 to 2,000, and even more preferably 100 to 1,500. Among these, crosslinking amino compounds having a molecular weight of 100 to 1,000 are particularly preferred. If the molecular weight of the crosslinking amino compound is less than 90, only one amino group of the crosslinking amino compound will form a C=N bond with a ketone group of the adhesive polyimide, and the surroundings of the remaining amino groups will be sterically bulky, making it difficult for the remaining amino groups to form C=N bonds.

[0080] When crosslinking a ketone group in an adhesive polyimide with a crosslinking amino compound, the crosslinking amino compound is added to a resin solution containing an adhesive polyimide to cause a condensation reaction between the ketone group in the adhesive polyimide and the primary amino group of the crosslinking amino compound. This condensation reaction hardens the resin solution to form a cured product. In this case, the amount of crosslinking amino compound added can be 0.004 to 1.5 mol, preferably 0.005 to 1.2 mol, more preferably 0.03 to 0.9 mol, and most preferably 0.04 to 0.6 mol of primary amino groups per 1 mol of ketone group. If the amount of crosslinking amino compound added is such that the total number of primary amino groups per mole of ketone groups is less than 0.004 moles, crosslinking by the crosslinking amino compound will be insufficient, and heat resistance after curing will tend to be difficult to achieve. If the amount of crosslinking amino compound added exceeds 1.5 moles, the unreacted crosslinking amino compound will act as a thermoplasticizer, tending to reduce the heat resistance of the adhesive layer.

[0081] The conditions for the condensation reaction for crosslinking are not particularly limited, as long as they are conditions under which the ketone group in the adhesive polyimide reacts with the primary amino group of the crosslinking amino compound to form an imine bond (C=N bond). The temperature for the thermal condensation is preferably within the range of, for example, 120 to 220°C, more preferably within the range of 140 to 200°C, for reasons such as discharging water produced by condensation outside the system or simplifying the condensation step when the thermal condensation reaction is carried out subsequently to the synthesis of the adhesive polyimide. The reaction time is preferably about 30 minutes to 24 hours. The end point of the reaction can be determined by measuring the infrared absorption spectrum using, for example, a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) at 1670 cm -1 The decrease or disappearance of the absorption peak due to the ketone group in the polyimide resin near 1635 cm -1 This can be confirmed by the appearance of an absorption peak derived from a nearby imine group.

[0082] The thermal condensation of the ketone group of the adhesive polyimide with the primary amino group of the crosslinking amino compound can be carried out, for example, by the following method: (1) A method in which an amino compound for crosslinking is added and heated after synthesis (imidization) of adhesive polyimide; (2) A method in which an excess amount of an amino compound is charged in advance as a diamine component, and following the synthesis (imidization) of an adhesive polyimide, the remaining amino compound that is not involved in imidization or amidation is used as a crosslinking amino compound and heated together with the adhesive polyimide; Or, (3) A method in which a solution of adhesive polyimide (adhesive composition) containing the above-mentioned crosslinking-forming amino compound is processed into a predetermined shape (for example, after being applied to a substrate or formed into a film), and then heated; This can be done by, etc.

[0083] (B) Cross-linking using carbon-carbon double bonds: The adhesive polyimide contains a highly reactive carbon-carbon double bond (reactive double bond), which allows for crosslinking and further improves solder heat resistance and flame retardancy. For this purpose, the adhesive polyimide preferably contains a diamine residue derived from a diamine compound having a substituent containing a reactive double bond (hereinafter, sometimes referred to as a "reactive double bond-containing diamine residue"). Examples of reactive double bonds include carbon-carbon double bonds contained in vinyl groups, acrylic groups (acrylate groups), methacrylic groups (methacrylate groups), and allyl groups. Therefore, examples of diamine compounds having a substituent containing a reactive double bond include compounds represented by the general formula (1) in which the substituent E is a vinyl group, acrylic group, methacrylic group, or allyl group, and p or q is 1 or greater.

[0084] When crosslinking is performed using reactive double bonds, the content of reactive double bond-containing diamine residues is preferably within the range of 5 mol % to 25 mol % and more preferably within the range of 10 mol % to 20 mol % relative to the total diamine residues in the adhesive polyimide. If the content of diamine residues derived from diamine compounds containing reactive double bonds is less than 5 mol %, crosslinking may be insufficient, while if it exceeds 25 mol %, polymerization reactions between reactive double bond-containing diamine residues are likely to occur, making crosslinking difficult.

[0085] To achieve crosslinking, it is preferable to react a crosslinking agent with an adhesive polyimide having a reactive double bond-containing diamine residue. The crosslinking agent may be any compound having a functional group in its molecule that can react with the reactive double bond in the adhesive polyimide to form a crosslink. Examples of such functional groups include vinyl groups, acrylic groups (acrylate groups), methacrylic groups (methacrylate groups), allyl groups, and acryloyl groups. Examples of compounds having such functional groups include 1,5-hexadiene, triallylamine, and dipentaerythritol hexaacrylate. Alternatively, a compound containing an atom such as phosphorus in its molecule may be used as the crosslinking agent. In this case, the flame retardancy of the resin film after crosslinking can be improved.

[0086] The crosslinking agent is preferably used in an amount of 5 to 30 parts by weight, more preferably 10 to 25 parts by weight, per 100 parts by weight of the adhesive polyimide having a reactive double bond-containing diamine residue. If the amount of crosslinking agent is less than 5 parts by weight, crosslinking does not proceed sufficiently, making it difficult to improve solder heat resistance and flame retardancy. If the amount of crosslinking agent is more than 30 parts by weight, unreacted crosslinking agent may cause bleed-out, reducing adhesion when a resin film is formed, and reactions between crosslinking agents may occur, reducing handleability.

[0087] Crosslinking between an adhesive polyimide having a reactive double bond-containing diamine residue and a crosslinking agent is carried out by reacting a substituent having a reactive double bond in the adhesive polyimide with a functional group contained in the crosslinking agent. For example, this can be achieved by (i) a method in which a crosslinking agent is added and heated following synthesis (imidization) of an adhesive polyimide having a reactive double bond-containing diamine residue, or (ii) a method in which a resin composition containing an adhesive polyimide having a reactive double bond-containing diamine residue and a crosslinking agent is processed into a predetermined shape (for example, after being applied to a substrate or formed into a film), and then heated. The reaction conditions for crosslinking are not particularly limited, but may be, for example, a method of heating to a temperature in the range of 100 to 220°C, preferably 120 to 200°C. The reaction time is preferably about 30 minutes to 24 hours. Here, a polymerization initiator may be used, if necessary, to hasten the start of the reaction.

[0088] The polymerization initiator can be any of those commonly used as radical polymerization initiators without any particular limitation, but preferred examples include dihalogen compounds, azo compounds, and organic peroxides. Among these, organic peroxides are preferred. As the polymerization initiator, commercially available products can be appropriately selected and used. Preferred examples of such commercially available polymerization initiators include Perbutyl (registered trademark) P (manufactured by NOF Corporation) and Perbutyl (registered trademark) C (manufactured by NOF Corporation). The polymerization initiator is preferably used in an amount of 0.5 to 2.0 parts by weight per 100 parts by weight of the adhesive polyimide having a reactive double bond-containing diamine residue. If the amount of polymerization initiator is less than 0.5 parts by weight per 100 parts by weight of the adhesive polyimide having a reactive double bond-containing diamine residue, the effect of adding the polymerization initiator may not be fully achieved. On the other hand, if the amount of polymerization initiator exceeds 2.0 parts by weight, the dielectric loss tangent may deteriorate and the storage stability and handling properties of the resin composition may be reduced.

[0089] The above describes examples of crosslinking by imine bonds (C=N bonds) and crosslinking using carbon-carbon double bonds to impart heat resistance to adhesive polyimides, but the present invention is not limited to these. Polyimide curing methods also include blending and curing compounds having unsaturated bonds, such as epoxy resins, epoxy resin curing agents, maleimides, activated ester resins, and resins having a styrene skeleton.

[0090] [Adhesive composition] Since adhesive polyimides are solvent-soluble, they can be used in the form of a solvent-containing adhesive composition (polyimide solution). That is, the adhesive composition contains an adhesive polyimide and a solvent capable of dissolving the adhesive polyimide. The adhesive composition may also contain, as optional components, the above-mentioned crosslinking-forming amino compound, a crosslinking agent capable of reacting with the reactive double bond to form crosslinks, and a polymerization initiator. The adhesive composition contains adhesive polyimide as the main resin component, preferably at least 70 wt % of the resin component, more preferably at least 90 wt % of the resin component, and most preferably the entire resin component. The term "main resin component" refers to a component that accounts for more than 50 wt % of the total resin component.

[0091] The solvent is not particularly limited as long as it can dissolve the adhesive polyimide, and examples thereof include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diglyme, triglyme, methanol, ethanol, benzyl alcohol, cresol, acetone, etc. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination.

[0092] In the adhesive composition, the blending ratio of the adhesive polyimide and the solvent is not particularly limited as long as the viscosity of the composition can be maintained at a level that allows coating. The viscosity of the adhesive composition is preferably, for example, within the range of 500 mPa·s to 100,000 mPa·s. If the viscosity is outside this range, defects such as uneven thickness and streaks are likely to occur in the resin film during the coating process.

[0093] The adhesive composition may contain optional components such as plasticizers, other curable resin components such as epoxy resins, curing agents, curing accelerators, organic fillers, inorganic fillers, coupling agents, solvents, and flame retardants, as long as the effects of the invention are not impaired.

[0094] [Polyimide film / adhesive film] The polyimide film according to one embodiment of the present invention is obtained by processing the above-mentioned adhesive polyimide or crosslinked polyimide into a film shape. The polyimide constituting the polyimide film contains 40 mol % or more of diamine residues derived from a dimer diamine composition relative to the total diamine residues, and also contains a total of 2 to 40 mol % of diamine residues derived from at least one diamine compound selected from diamine compounds represented by general formula (1).

[0095] The polyimide film preferably has a dielectric loss tangent (Tanδ) of less than 0.002, more preferably 0.0018 or less, and a relative dielectric constant (ε) of 3.0 or less, preferably 2.7 or less, at 10 GHz, as measured by a split post dielectric resonator (SPDR) after 24 hours of conditioning at constant temperature and humidity (normal conditions) of 23°C and 50% RH. If the dielectric loss tangent (Tanδ) and relative dielectric constant (ε) exceed the above values, this leads to increased dielectric loss when applied to a circuit board, and is likely to cause problems such as electrical signal loss in the transmission path of high-frequency signals in the GHz frequency range (e.g., 1 to 40 GHz).

[0096] An example of a preferred form of polyimide film is an adhesive film. The adhesive film is not particularly limited as long as it contains the adhesive polyimide or crosslinked polyimide as the main resin component, preferably at least 70% by weight of the resin component, more preferably at least 90% by weight of the resin component, and most preferably the entire resin component. The term "main resin component" refers to a component that accounts for more than 50% by weight of the total resin component. The adhesive film may be a film (sheet) made of adhesive polyimide or crosslinked polyimide, or may be laminated on a resin substrate such as an inorganic material substrate (e.g., copper foil or glass plate), or a polyimide film, polyamide film, or polyester film. The adhesive film may contain optional components such as plasticizers, other curable resin components (e.g., epoxy resins), curing agents, curing accelerators, organic fillers, inorganic fillers, coupling agents, and flame retardants.

[0097] The method for producing the adhesive film of the present embodiment is not particularly limited, but the following methods [1] to [3] can be exemplified. [1] A method in which an adhesive polyimide is applied to a substrate in a solution state (for example, in the form of an adhesive composition) to form a coating film, which is then dried at a temperature of, for example, 80 to 180°C to form a film, and then peeled off from the substrate as needed. [2] A method in which a solution of polyamic acid, which is a precursor of adhesive polyimide, is applied to any substrate, dried, and then imidized to form a film, which is then peeled off from the substrate as needed. [3] A method in which a solution of polyamic acid, a precursor of adhesive polyimide, is applied to any substrate and dried, and then the gel film of polyamic acid is peeled off from the substrate and imidized to form an adhesive film. The method for applying the adhesive polyimide solution (or polyamic acid solution) onto the substrate is not particularly limited, and it can be applied using, for example, a coater such as a comma, die, knife, or lip coater.

[0098] Next, laminates, metal-clad laminates, circuit boards, and multilayer circuit boards, which are preferred embodiments to which the adhesive film is applied, will be described with specific examples.

[0099] [Laminate] As shown in FIG. 1, a laminate 100 according to one embodiment of the present invention includes a substrate 10 and an adhesive layer 20 laminated on at least one surface of the substrate 10, the adhesive layer 20 being made of the adhesive film described above. The laminate 100 may also include any other layer. Examples of the substrate 10 in the laminate 100 include substrates made of inorganic materials such as copper foil and glass plates, and substrates made of resin materials such as polyimide films, polyamide films, and polyester films. The laminate 100 can be manufactured according to any of the adhesive film manufacturing methods [1] to [3] described above, except that the laminate 100 is not peeled from the substrate 10. Alternatively, the laminate 100 may be manufactured by separately preparing the substrate 10 and the adhesive film and bonding them together. Preferred embodiments of the laminate 100 include a coverlay film, a resin-coated copper foil, and the like.

[0100] [Coverlay film] Although not shown, the coverlay film, which is one embodiment of the laminate 100, has a coverlay film material layer as a substrate 10 and an adhesive layer 20 laminated on one side of the coverlay film material layer, the adhesive layer 20 being made of the adhesive film. The coverlay film may also include any layer other than those described above.

[0101] The material of the coverlay film material layer is not particularly limited, but examples thereof include polyimide-based films such as polyimide resins, polyetherimide resins, and polyamideimide resins, as well as polyamide-based films and polyester-based films. Among these, it is preferable to use polyimide-based films, which have excellent heat resistance. Furthermore, the coverlay film material may contain a black pigment to effectively exhibit light-blocking properties, concealing properties, and design properties, and may also contain optional components such as matte pigments that suppress surface gloss, as long as the effect of improving the dielectric properties is not impaired.

[0102] The thickness of the coverlay film material layer is not particularly limited, but is preferably within the range of, for example, 5 μm or more and 100 μm or less. The thickness of the adhesive layer 20 is not particularly limited, but is preferably within the range of 10 μm to 75 μm, for example.

[0103] The coverlay film of the present embodiment can be produced by the following method. First, as a first method, polyimide that will become the adhesive layer 20 is applied to one side of the coverlay film material layer in a solution state (for example, a varnish containing a solvent is preferable, and an adhesive composition is preferable), and then the adhesive layer 20 is formed by drying at a temperature of, for example, 80 to 180°C, thereby forming a coverlay film having a coverlay film material layer and adhesive layer 20.

[0104] As a second method, polyimide for adhesive layer 20 is applied to any substrate in a solution state (for example, a varnish containing a solvent is preferable, and an adhesive composition is preferable), dried at a temperature of, for example, 80 to 180°C, and then peeled off to form a resin film for adhesive layer 20, and this resin film is then thermocompressed to a film material layer for coverlay at a temperature of, for example, 60 to 220°C to form a coverlay film.

[0105] [Resin-coated copper foil] Although not shown, a resin-coated copper foil, which is another embodiment of the laminate 100, is obtained by laminating an adhesive layer 20 on at least one side of a copper foil as a substrate 10, and the adhesive layer 20 is made of the above-mentioned adhesive film. Note that the resin-coated copper foil of this embodiment may include any layer other than those described above.

[0106] The thickness of the adhesive layer 20 in the resin-coated copper foil is preferably, for example, in the range of 0.1 to 125 μm, and more preferably in the range of 0.3 to 100 μm. If the thickness of the adhesive layer 20 is less than the above-mentioned lower limit, problems such as insufficient adhesion may occur. On the other hand, if the thickness of the adhesive layer 20 exceeds the above-mentioned upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the viewpoint of lowering the dielectric constant and the dielectric loss tangent, it is preferable that the thickness of the adhesive layer 20 be 3 μm or more.

[0107] The material of the copper foil in the resin-coated copper foil is preferably one containing copper or a copper alloy as a main component. The thickness of the copper foil is preferably 35 μm or less, more preferably in the range of 5 to 25 μm. From the viewpoint of production stability and handleability, the lower limit of the copper foil thickness is preferably 5 μm. The copper foil may be a rolled copper foil or an electrolytic copper foil. Furthermore, commercially available copper foils can be used as the copper foil.

[0108] The resin-coated copper foil may be prepared, for example, by sputtering a metal onto an adhesive film to form a seed layer, and then forming a copper layer by, for example, copper plating, or by laminating an adhesive film and a copper foil by a method such as thermocompression bonding. Furthermore, the resin-coated copper foil may be prepared by casting a coating solution of an adhesive polyimide or its precursor onto the copper foil, drying it to form a coating film, and then performing the necessary heat treatment to form the adhesive layer 20 on the copper foil.

[0109] [Metal-clad laminate] (First aspect) A metal-clad laminate according to one embodiment of the present invention comprises an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, at least one of the insulating resin layers being made of the adhesive film described above. Note that the metal-clad laminate of this embodiment may also include any other layer(s) besides those described above.

[0110] (Second aspect) As shown in FIG. 2 , a metal-clad laminate according to another embodiment of the present invention is a so-called three-layer metal-clad laminate 101 including an insulating resin layer 30, an adhesive layer 20 laminated on at least one side of the insulating resin layer 30, and a metal layer M laminated on the insulating resin layer 30 via the adhesive layer 20, where the adhesive layer 20 is made of the adhesive film described above. The three-layer metal-clad laminate 101 may also include any other layer. The three-layer metal-clad laminate 101 may include the adhesive layer 20 on one or both sides of the insulating resin layer 30, and the metal layer M may be provided on one or both sides of the insulating resin layer 30 via the adhesive layer 20. In other words, the three-layer metal-clad laminate 101 may be a single-sided or double-sided metal-clad laminate. A single-sided or double-sided FPC can be manufactured by etching or otherwise processing the metal layer M of the three-layer metal-clad laminate 101 into a wiring circuit.

[0111] The insulating resin layer 30 in the three-layer metal-clad laminate 101 is not particularly limited as long as it is made of a resin having electrical insulation properties, and examples thereof include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, etc., but is preferably made of polyimide. The polyimide layer that makes up the insulating resin layer 30 may be a single layer or multiple layers, but preferably includes a non-thermoplastic polyimide layer.

[0112] The thickness of the insulating resin layer 30 in the three-layer metal-clad laminate 101 is preferably in the range of 1 to 125 μm, and more preferably in the range of 5 to 100 μm. If the thickness of the insulating resin layer 30 is less than the above-mentioned lower limit, problems such as insufficient electrical insulation may occur. On the other hand, if the thickness of the insulating resin layer 30 exceeds the above-mentioned upper limit, problems such as the metal-clad laminate becoming more prone to warping may occur.

[0113] The thickness of the adhesive layer 20 in the three-layer metal-clad laminate 101 is preferably, for example, in the range of 0.1 to 125 μm, and more preferably in the range of 0.3 to 100 μm. In the three-layer metal-clad laminate 101 of the present embodiment, if the thickness of the adhesive layer 20 is less than the above-mentioned lower limit, problems such as insufficient adhesion may occur. On the other hand, if the thickness of the adhesive layer 20 exceeds the above-mentioned upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the viewpoint of reducing the dielectric constant and dielectric loss tangent of the entire insulating layer, which is a laminate of the insulating resin layer 30 and the adhesive layer 20, the thickness of the adhesive layer 20 is preferably 3 μm or more.

[0114] The ratio of the thickness of the insulating resin layer 30 to the thickness of the adhesive layer 20 (thickness of the insulating resin layer 30 / thickness of the adhesive layer 20) is preferably in the range of 0.1 to 3.0, and more preferably in the range of 0.15 to 2.0. By adjusting the ratio in this manner, warping of the three-layer metal-clad laminate 101 can be suppressed. The insulating resin layer 30 may contain a filler as needed. Examples of fillers include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and metal salts of organic phosphinic acid. These can be used alone or in combination of two or more.

[0115] (Third aspect) 3, a metal-clad laminate according to yet another embodiment of the present invention is a laminated metal-clad laminate 102 formed by laminating at least two single-sided metal-clad laminates together via an adhesive layer 20. The laminated metal-clad laminate 102 comprises a first single-sided metal-clad laminate 41, a second single-sided metal-clad laminate 42, and an adhesive layer 20 laminated between the first single-sided metal-clad laminate 41 and the second single-sided metal-clad laminate 42, and the adhesive layer 20 is made of the adhesive film described above. Here, the first single-sided metal-clad laminate 41 has a first metal layer M1 and a first insulating resin layer 31 laminated on at least one surface of the first metal layer M1. The second single-sided metal-clad laminate 42 has a second metal layer M2 and a second insulating resin layer 32 laminated on at least one surface of the second metal layer M2. The adhesive layer 20 is disposed so as to abut the first insulating resin layer 31 and the second insulating resin layer 32. Note that the laminated metal-clad laminate 102 may include any layers other than those described above.

[0116] The first insulating resin layer 31 and the second insulating resin layer 32 in the laminated metal-clad laminate 102 may have the same configuration as the insulating resin layer 30 in the three-layer metal-clad laminate 101 of the second embodiment. The laminated metal-clad laminate 102 can be manufactured by preparing a first single-sided metal-clad laminate 41 and a second single-sided metal-clad laminate 42, and then placing an adhesive film between the first insulating resin layer 31 and the second insulating resin layer 32 and laminating them together.

[0117] (Fourth aspect) 4, a metal-clad laminate according to yet another embodiment of the present invention is an adhesive-layered single-sided metal-clad laminate 103 including a single-sided metal-clad laminate having an insulating resin layer 33 and a metal layer M laminated on one side of the insulating resin layer 33, and an adhesive layer 20 laminated on the other side of the insulating resin layer 33, wherein the adhesive layer 20 is made of the adhesive film described above. Note that the adhesive-layered metal-clad laminate 103 may include any layer other than those described above. The insulating resin layer 33 in the adhesive layer-attached metal-clad laminate 103 may have the same configuration as the insulating resin layer 30 in the three-layer metal-clad laminate 101 of the second embodiment. The adhesive layer-attached metal-clad laminate 103 can be produced by preparing a single-sided metal-clad laminate having an insulating resin layer 33 and a metal layer M, and then laminating an adhesive film to the insulating resin layer 33 side.

[0118] In the metal-clad laminate of any of the first to fourth embodiments exemplified above, the material of the metal layer M (including the first metal layer M1 and the second metal layer M2; the same applies below) is not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or copper alloys are particularly preferred. The material of the wiring layer in the circuit board described below is also the same as the metal layer M.

[0119] The thickness of the metal layer M is not particularly limited, but when a metal foil such as copper foil is used, it is preferably 35 μm or less, and more preferably in the range of 5 to 25 μm. From the viewpoint of production stability and handleability, the lower limit of the thickness of the metal foil is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Commercially available copper foil may be used as the copper foil. Furthermore, the metal foil may be surface-treated with, for example, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc., for the purpose of, for example, rust prevention or improving adhesive strength.

[0120] [Circuit board] (First aspect) A circuit board according to an embodiment of the present invention is formed by wiring the metal layer of the metal-clad laminate according to any of the above embodiments. One or more metal layers of the metal-clad laminate are patterned by a conventional method to form a wiring layer (conductor circuit layer), thereby producing a circuit board such as an FPC. The circuit board may also include a coverlay film that covers the wiring layer.

[0121] (Second aspect) 5, a circuit board 200 according to another embodiment of the present invention includes a first base material 11, a wiring layer 50 laminated on at least one surface of the first base material 11, and an adhesive layer 20 laminated on the surface of the first base material 11 facing the wiring layer 50 so as to cover the wiring layer 50, the adhesive layer 20 being made of the adhesive film described above. Note that the circuit board 200 may include any layer other than those described above. The first base material 11 in the circuit board 200 may have the same configuration as the insulating resin layer of the metal-clad laminate. The circuit board 200 can be manufactured by laminating an adhesive film to the side of the wiring layer 50 of a circuit board that includes the first base material 11 and the wiring layer 50 laminated on at least one surface of the first base material 11.

[0122] (Third aspect) 6, a circuit board 201 according to yet another embodiment of the present invention includes a first substrate 11, a wiring layer 50 laminated on at least one surface of the first substrate 11, an adhesive layer 20 laminated on the surface of the first substrate 11 facing the wiring layer 50 so as to cover the wiring layer 50, and a second substrate 12 laminated on the surface of the adhesive layer 20 opposite the first substrate 11, where the adhesive layer 20 is made of the adhesive film. The circuit board 201 may also include any other layers. The first substrate 11 and the second substrate 12 in the circuit board 201 may have a configuration similar to that of the insulating resin layer of the metal-clad laminate. The circuit board 201 can be manufactured by bonding a second substrate 12 to the wiring layer 50 side of a circuit board having a first substrate 11 and a wiring layer 50 laminated on at least one surface of the first substrate 11 via an adhesive film.

[0123] (Fourth aspect) 7, a circuit board 202 according to yet another embodiment of the present invention includes a first substrate 11, an adhesive layer 20 laminated on at least one surface of the first substrate 11, a second substrate 12 laminated on the surface of the adhesive layer 20 opposite the first substrate 11, and wiring layers 50, 50 laminated on the surfaces of the first substrate 11 and the second substrate 12 opposite the adhesive layer 20, respectively, where the adhesive layer 20 is made of the adhesive film. The circuit board 202 may also include any layer other than those described above. The first substrate 11 and the second substrate 12 in the circuit board 202 may have a configuration similar to that of the insulating resin layer of the metal-clad laminate. The circuit board 202 can be manufactured by preparing a first circuit board having a first substrate 11 and a wiring layer 50 laminated on at least one surface of the first substrate 11, and a second circuit board having a second substrate 12 and a wiring layer 50 laminated on at least one surface of the second substrate 12, and then placing an adhesive film between the first substrate 11 of the first circuit board and the second substrate 12 of the second circuit board and bonding them together.

[0124] [Multilayer circuit board] A multilayer circuit board according to one embodiment of the present invention comprises a laminate formed by stacking a plurality of insulating resin layers and one or more wiring layers embedded inside the laminate, wherein at least one of the plurality of insulating resin layers is formed by an adhesive layer 20 that has adhesive properties and covers the wiring layer, and the adhesive layer 20 is made of the adhesive film. Note that the multilayer circuit board of this embodiment may include any layer other than those described above. For example, as shown in FIG. 8 , a multilayer circuit board 203 of this embodiment has at least two insulating resin layers 34 and at least two wiring layers 50, with at least one of the wiring layers 50 being covered with an adhesive layer 20. The adhesive layer 20 covering the wiring layer 50 may partially cover the surface of the wiring layer 50 or may cover the entire surface of the wiring layer 50. The multilayer circuit board 203 may also have an optional wiring layer 50 exposed on the surface of the multilayer circuit board 203. The multilayer circuit board 203 may also have interlayer connection electrodes (via electrodes) in contact with the wiring layer 50. The wiring layer 50 has a conductor circuit formed in a predetermined pattern on one or both sides of the insulating resin layer 34. The conductor circuit may be patterned on the surface of the insulating resin layer 34 or may be patterned using a damascene (embedded) method. The insulating resin layer 34 in the multilayer circuit board 203 may have a configuration similar to that of the insulating resin layer of the metal-clad laminate.

[0125] The circuit board and multilayer circuit board of each of the above embodiments includes the adhesive layer 20 containing adhesive polyimide, and therefore, transmission loss can be reduced even in high frequency transmission. [Example]

[0126] The features of the present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[0127] [Method for measuring amine value] Approximately 2 g of dimer diamine composition is weighed into a 200-250 mL Erlenmeyer flask, and 0.1 mol / L ethanolic potassium hydroxide solution is added dropwise using phenolphthalein as an indicator until the solution turns light pink. The mixture is then dissolved in approximately 100 mL of neutralized butanol. 3-7 drops of phenolphthalein solution are added, and the sample solution is titrated with 0.1 mol / L ethanolic potassium hydroxide solution while stirring until the solution turns light pink. Five drops of bromophenol blue solution are added, and the sample solution is titrated with 0.2 mol / L hydrochloric acid / isopropanol solution while stirring until the solution turns yellow. The amine value is calculated by the following formula (1). Amine value = {(V2 × C2) - (V1 × C1)} × M KOH / m (1) Here, the amine value is a value expressed in mg-KOH / g, and M KOH is the molecular weight of potassium hydroxide, 56.1. V and C are the volume and concentration of the solution used in the titration, respectively, and the subscripts 1 and 2 represent a 0.1 mol / L ethanolic potassium hydroxide solution and a 0.2 mol / L hydrochloric acid / isopropanol solution, respectively. m is the sample weight in grams.

[0128] [Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polyimide] The weight-average molecular weight was measured by gel permeation chromatography (HLC-8220GPC manufactured by Tosoh Corporation). Polystyrene was used as a standard substance, and tetrahydrofuran (THF) was used as a developing solvent.

[0129] [Calculation of aromatic ring proportion in dimer diamine composition] The aromatic ring proportion of the dimer diamine composition was calculated using the following procedure. First, approximately 50 μl of the dimer diamine composition was dissolved in 550 μl of THF-d8 to prepare a sample. Liquid 1H-NMR measurement was performed on the prepared sample at room temperature using an FT-NMR device (JEOL, JNM-ECA400). The aromatic ring proportion was calculated using the ratio of the integral value of the 1H peak derived from the aromatic ring found at 6.6 to 7.2 ppm to the integral value of the 1H peak derived from the CH2 group directly bonded to the NH2 group found at 2.6 to 2.9 ppm, as shown in the following formula. Aromatic ring ratio [mol%] = (Z / Y) × 100 [Here, Y means the integral value of the 1H peak at 2.6 to 2.9 ppm, and Z means the integral value of the 1H peak (derived from the aromatic ring) at 6.6 to 7.2 ppm.]

[0130] [GPC and chromatogram area percentage calculation] (a) Dimer diamine (b) Monoamine compounds obtained by substituting the terminal carboxylic acid group of a monobasic acid compound having 10 to 40 carbon atoms with a primary aminomethyl group or an amino group. (c) Amine compounds obtained by substituting the terminal carboxylic acid group of a polybasic acid compound having a hydrocarbon group having 41 to 80 carbon atoms with a primary aminomethyl group or an amino group (excluding the dimer diamine).

[0131] For GPC, 20 mg of the dimer diamine composition was pretreated with 200 μL of acetic anhydride, 200 μL of pyridine, and 2 mL of THF to prepare a 100 mg solution, which was then diluted with 10 mL of THF (containing 1,000 ppm of cyclohexanone). The prepared sample was measured using a Tosoh Corporation HLC-8220GPC column (TSK-gel G2000HXL, G1000HXL), with a flow rate of 1 mL / min, a column (oven) temperature of 40°C, and an injection volume of 50 μL. Cyclohexanone was used as a standard substance to correct for elution time.

[0132] At this time, the peak top of the cyclohexanone main peak was adjusted to a retention time of 27 to 31 minutes, and the period from the peak start to the peak end of the cyclohexanone main peak was adjusted to 2 minutes, and the peak top of the main peak excluding the cyclohexanone peak was adjusted to 18 to 19 minutes, and the period from the peak start to the peak end of the main peak excluding the cyclohexanone peak was adjusted to 2 minutes to 4 minutes 30 seconds, under the conditions: (a) The component represented by the main peak; (b) Components represented by GPC peaks detected at times later than the minimum retention time of the main peak; (c) Components represented by GPC peaks detected at earlier retention times than the minimum value of the main peak; was detected.

[0133] [Measurement of relative permittivity and dielectric loss tangent] The resin sheet was left for 24 hours under conditions of a temperature of 23°C and a humidity of 50%, and then the relative permittivity (ε) and dielectric loss tangent (Tanδ) at a frequency of 10 GHz were measured using a vector network analyzer (manufactured by Agilent, product name: Vector Network Analyzer E8363C) and an SPDR resonator.

[0134] [Glass transition temperature (Tg)] The glass transition temperature (Tg) was measured using a 5 mm × 20 mm resin sheet at a temperature increase rate of 5°C / min from 0°C to 300°C using a thermomechanical analyzer (TMA: manufactured by Netsch GmbH, product name: TMA4000SA). The temperature at which the elongation changes during heating is defined as the glass transition temperature.

[0135] [Tensile modulus] The tensile modulus was measured by the following procedure. First, a test piece (12.7 mm wide x 127 mm long) was prepared from the resin sheet using a tension tester (trade name: Tensilon, manufactured by Orientec Co., Ltd.). A tensile test was performed at 50 mm / min using this test piece, and the tensile modulus at 25°C was determined.

[0136] [Warp evaluation method] Warpage was evaluated using the following method. Test specimens were prepared by applying a polyimide solution to a 25 μm thick polyimide film (manufactured by DuPont-Toray Co., Ltd., product name: Kapton 100EN) or a 12 μm thick copper foil, so that the dry thickness would be 25 μm. In this state, the test specimen was placed with the polyimide film or copper foil facing downwards, and the average height of the warpage at the four corners was measured. A value of 5 mm or less was rated "good," and a value of more than 5 mm was rated "unacceptable."

[0137] The abbreviations used in the examples represent the following compounds. BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride DDA: aliphatic diamine having 36 carbon atoms (manufactured by Croda Japan Co., Ltd., trade name: PRIAMINE 1075 purified product, amine value: 210 mg KOH / g, mixture of dimer diamines with cyclic and chain structures, component (a): 97.9%, component (b): 0.3%, component (c): 1.8%, aromatic ring ratio: 8.2 mol%) m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TFMB: 2,2'-ditrifluoromethylbenzidine VAB: 2,2'-divinyl-4,4'-diaminobiphenyl APB: 1,3-bis(3-aminophenoxy)benzene BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane N-12: Dodecanedioic acid dihydrazide NMP: N-methyl-2-pyrrolidone OP935: Aluminum salt of phosphinic acid (manufactured by Clariant, trade name: Exolit OP935, aluminum diethylphosphinate, phosphorus content 23%, average particle size 2 μm) In the above DDA, the "%" of component a, component b, and component c means the area percentage of the chromatogram in GPC measurement. The molecular weight of the above DDA was calculated using the following formula. Molecular weight = 56.1 x 2 x 1000 / amine value

[0138] [Example 1] A 1000 ml separable flask was charged with 46.59 g of BTDA (0.1446 mol), 68.83.95 g of DDA (0.1288 mol), 4.58 g of TFMB (0.0143 mol), 168 g of NMP, and 112 g of xylene, and the mixture was thoroughly mixed at 40° C. for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190° C. and stirred for 5 hours. 98 g of xylene was added to complete the imidization, preparing Polyimide Solution 1 (solids content: 30 wt %, weight average molecular weight: 39,552, number average molecular weight: 20,339).

[0139] [Examples 2 to 13] Polyimide solutions 2 to 13 were prepared in the same manner as in Example 1, except that the raw material compositions shown in Table 1 or Table 2 were used.

[0140] [Synthesis Examples 1 to 5] Polyimide solutions 14 to 18 were prepared in the same manner as in Example 1, except that the raw material compositions shown in Table 2 were used.

[0141] [Comparative Example 1] Polyimide solution 19 was prepared in the same manner as in Example 1 except for using the raw material composition shown in Table 2, and the solution was in a gel state with no fluidity.

[0142] [Table 1]

[0143] [Table 2]

[0144] [Example 14] Polyimide solution 1 was applied to one side of release PET film 1 (manufactured by Higashiyama Film Co., Ltd., product name: HY-S05, length x width x thickness = 200 mm x 300 mm x 25 μm), dried at 120°C for 10 minutes, and the adhesive layer was peeled off from release PET film 1 to obtain adhesive film 14 with a thickness of 25 μm. The various evaluation results of adhesive film 14 are as follows. ε: 2.7, Tanδ: 0.0016, Tg: 37°C, Tensile modulus: 0.8 GPa

[0145] [Examples 15 to 26] Except for using polyimide solutions 2 to 13, adhesive films 15 to 26 were obtained in the same manner as in Example 14. The results of evaluation of various properties are shown in Table 3.

[0146] [Comparative Examples 2 to 6] Adhesive films 27 to 31 were obtained in the same manner as in Example 14, except that polyimide solutions 14 to 18 were used. Table 3 shows the results of evaluation of various properties.

[0147] [Table 3]

[0148] [Example 27] 1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution 1 (30 g as solids), diluted with 7.5 g of OP935 and 14.0 g of xylene, and further stirred for 1 hour to prepare adhesive composition 27.

[0149] [Examples 28 to 37] Adhesive compositions 28 to 37 were prepared in the same manner as in Example 27, except that polyimide solutions 2 to 11 were used.

[0150] [Example 38] The adhesive composition 27 was applied to one side of a release PET film 1 and dried at 80°C for 15 minutes to obtain a resin sheet 38 having an adhesive layer thickness of 25 μm. The adhesive layer was then peeled off from the release PET film 1 to obtain an adhesive film 38 having a thickness of 25 μm.

[0151] [Examples 39 to 48] Resin sheets 39 to 48 were obtained in the same manner as in Example 38 except that adhesive compositions 28 to 37 were used, and then adhesive films 39 to 48 were obtained.

[0152] [Example 49] The adhesive composition 27 was applied to one side of a polyimide film 1 (manufactured by DuPont-Toray Co., Ltd., product name: Kapton 50EN, ε = 3.6, tanδ = 0.0084, length × width × thickness = 200 mm × 300 mm × 12 μm) and dried at 80°C for 15 minutes to obtain a coverlay film 49 with an adhesive layer thickness of 25 μm. The warpage state of the obtained coverlay film 49 was "good".

[0153] [Example 50] The release PET film 1 was laminated so that it was in contact with the adhesive layer side of the coverlay film 49, and the laminate was pressed using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes. Then, adhesive composition 27 was applied to the polyimide film 1 side of the coverlay film 49 with the release PET film 1 pressed onto the adhesive layer side so that the thickness after drying was 25 μm, and dried at 80°C for 15 minutes. The release PET film 1 was then laminated so that it was in contact with the surface onto which the adhesive composition 27 had been applied and dried, and the laminate was pressed using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes, yielding a polyimide adhesive laminate 50 having adhesive on both sides of the polyimide film.

[0154] [Example 51] The adhesive composition 27 was applied to one side of an electrolytic copper foil having a thickness of 12 μm and dried at 80° C. for 15 minutes to obtain a resin-coated copper foil 51 having an adhesive layer thickness of 25 μm. The warpage state of the obtained resin-coated copper foil 51 was “good”.

[0155] [Example 52] The adhesive composition 27 was applied to one side of an electrolytic copper foil having a thickness of 12 μm and dried at 80° C. for 30 minutes to obtain a resin-coated copper foil 52 having an adhesive layer thickness of 50 μm. The warpage state of the obtained resin-coated copper foil 52 was “good”.

[0156] [Example 53] Adhesive composition 27 was further applied to the surface of the adhesive layer of resin-coated copper foil 52 and dried at 80°C for 30 minutes to obtain resin-coated copper foil 53 having a total adhesive layer thickness of 100 µm. The warpage state of the obtained resin-coated copper foil 53 was "good".

[0157] [Example 54] The adhesive composition 27 was applied to one side of a release PET film 1, dried at 80° C. for 30 minutes, and the adhesive layer was peeled off from the release PET film 1 to obtain an adhesive film 54 with a thickness of 50 μm.

[0158] [Example 55] An adhesive film 54, a polyimide film 2 (manufactured by DuPont, trade name: Kapton 100-EN, thickness 25 μm, ε=3.6, tanδ=0.0084), an adhesive film 54, and a 12 μm thick electrolytic copper foil were laminated in this order on a 12 μm thick electrolytic copper foil, and the laminate was pressure-bonded using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes.Then, the temperature was increased from room temperature to 160°C, and the laminate was heat-treated at 160°C for 4 hours, thereby obtaining a copper-clad laminate 55.

[0159] [Example 56] The coverlay film 49 was laminated onto a 12 μm thick electrolytic copper foil so that the adhesive layer side was in contact with the copper foil, and then pressure-bonded using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes.Then, the temperature was increased from room temperature to 160°C and heat-treated at 160°C for 2 hours to obtain a copper-clad laminate 56.

[0160] [Example 57] An adhesive film 38 was laminated onto a 12 μm thick rolled copper foil, then a coverlay film 49 was laminated so that the polyimide film 1 side was in contact with the adhesive film 38, and a 12 μm thick rolled copper foil was then laminated onto the adhesive layer side of the coverlay film 49 in sequence, and the laminate was pressed using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes.Then, the temperature was raised from room temperature to 160°C and the laminate was heat-treated at 160°C for 2 hours to obtain a copper-clad laminate 57.

[0161] [Example 58] Two sheets of resin-coated copper foil 53 were prepared, and the two sheets of resin-coated copper foil 53 were laminated so that the adhesive layer side of the two sheets of resin-coated copper foil 53 was in contact with a polyimide film 3 (manufactured by DuPont, product name: Kapton 200-EN, thickness 50 μm, ε=3.6, tanδ=0.0084). The laminate was then pressed together using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 5 minutes, after which the temperature was raised from room temperature to 160°C and the laminate was heat-treated at 160°C for 4 hours to obtain a copper-clad laminate 58.

[0162] [Example 59] Adhesive composition 27 was applied to the polyimide side of single-sided copper-clad laminate 1 (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX MC12-25-00UEM, length × width × thickness = 200 mm × 300 mm × 25 μm) and dried at 80°C for 30 minutes to obtain an adhesive-coated copper-clad laminate 59 with an adhesive layer thickness of 50 μm. The single-sided copper-clad laminate 1 was laminated so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with the adhesive layer side of adhesive-coated copper-clad laminate 59, and the laminate was pressed using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain copper-clad laminate 59.

[0163] [Example 60] Two adhesive-coated copper-clad laminates 59 were stacked with the adhesive layer sides facing each other, and then pressed together using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain copper-clad laminate 60.

[0164] [Example 61] An adhesive film 54 was laminated on the resin layer side of the single-sided copper-clad laminate 1, and then another single-sided copper-clad laminate 1 was laminated on top of that so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with the adhesive film 54.Then, using a small precision press, the laminate was pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain a copper-clad laminate 61.

[0165] [Example 62] The adhesive composition 27 was applied to one side of a release PET film 1, dried at 80° C. for 15 minutes, and the adhesive layer was peeled off from the release PET film 1 to obtain an adhesive film 62 with a thickness of 15 μm.

[0166] [Example 63] An adhesive film 62 was laminated on the resin layer side of the single-sided copper-clad laminate 1, and then another single-sided copper-clad laminate 1 was laminated on top of that so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with the adhesive film 62.Then, using a small precision press, the laminate was pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain a copper-clad laminate 62.

[0167] [Example 64] A double-sided copper-clad laminate 2 (manufactured by Nippon Steel Chemical & Material Co., Ltd., trade name: Espanex MB12-25-00UEG) was prepared, and the copper foil on one side was subjected to circuit processing by etching to form a conductor circuit layer, thereby obtaining a wiring board 64A.

[0168] The copper foil on one side of a double-sided copper-clad laminate 2 prepared separately was removed by etching to obtain a copper-clad laminate 64B.

[0169] An adhesive film 38 was sandwiched between the conductive circuit layer side of the wiring board 64A and the resin layer side of the copper-clad laminate 64B, and the laminated sheets were thermocompressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain a multilayer circuit board 64.

[0170] [Example 65] A copper-clad laminate 65 was prepared using a liquid crystal polymer film (manufactured by Kuraray Co., Ltd., product name: CT-Z, thickness: 50 μm, CTE: 18 ppm / K, heat distortion temperature: 300°C, ε=3.40, tanδ=0.0022) as an insulating substrate, with 18 μm-thick electrolytic copper foil provided on both sides. The copper foil on one side was subjected to circuit processing by etching, to obtain a wiring board 65A on which a conductor circuit layer was formed.

[0171] The copper foil on one side of a separately prepared copper-clad laminate 65 was removed by etching to obtain a copper-clad laminate 65B.

[0172] An adhesive film 54 was sandwiched between the conductive circuit layer side of the wiring board 65A and the insulating base material layer side of the copper-clad laminate 65B, and the laminated sheets were thermocompressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain a multilayer circuit board 65.

[0173] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible. [Explanation of symbols]

[0174] DESCRIPTION OF SYMBOLS 10...substrate, 11...first substrate, 12...second substrate, 20...adhesive layer, 30, 33, 34...insulating resin layer, 31...first insulating resin layer, 32...second insulating resin layer, 41...first single-sided metal-clad laminate, 42...second single-sided metal-clad laminate, 50...wiring layer, M...metal layer, M1...first metal layer, M2...second metal layer, 100...laminated body, 101...three-layer metal-clad laminate, 102...bonded metal-clad laminate, 103...metal-clad laminate with adhesive layer, 200, 201, 202...circuit board, 203...multilayer circuit board

Claims

1. A thermoplastic polyimide containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, A thermoplastic polyimide characterized by containing, relative to all diamine residues, 40 mol % or more of diamine residues derived from a dimer diamine composition containing, as a main component, 96 wt % or more of a dimer diamine obtained by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups, and containing, in total, 2 to 40 mol % of diamine residues derived from a diamine compound represented by the following general formula (1): 【Chemistry 1】 [In formula (1), the linking group A represents a single bond or a divalent group selected from -COO-; the substituents E independently represent a hydrogen atom, a monovalent alkyl group having 1 to 3 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, a vinyl group, an acrylic group, a methacrylic group, or an allyl group; m represents an integer of 1 or 2; and p and q independently represent integers of 0 to 4.]

2. 2. The thermoplastic polyimide according to claim 1, having a weight average molecular weight (Mw) in the range of 5,000 to 200,000.

3. 3. The thermoplastic polyimide according to claim 1, wherein the amount of acid dianhydride residues derived from benzophenonetetracarboxylic dianhydride is 10 mol % or more based on the total amount of acid dianhydride residues.

4. 3. The thermoplastic polyimide according to claim 1, wherein the diamine residue comprises a diamine residue derived from a diamine compound having a substituent with a carbon-carbon double bond.

5. A crosslinked polyimide in which a ketone group contained in the thermoplastic polyimide according to claim 3 and an amino group of an amino compound having at least two primary amino groups as functional groups form a crosslinked structure via a C=N bond.

6. A crosslinked polyimide having a crosslinked structure formed by the carbon-carbon double bonds contained in the thermoplastic polyimide according to claim 4.

7. An adhesive film comprising the thermoplastic polyimide according to any one of claims 1 to 4 or the crosslinked polyimide according to claim 5 or 6.

8. 8. The adhesive film according to claim 7, wherein the dielectric loss tangent (Tanδ) at 10 GHz measured using a split post dielectric resonator (SPDR) after 24 hours of conditioning under constant temperature and humidity conditions (normal conditions) of 23°C and 50% RH is less than 0.

002.

9. A laminate having a substrate and an adhesive layer laminated on at least one surface of the substrate, A laminate, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

10. A coverlay film having a coverlay film material layer and an adhesive layer laminated on the coverlay film material layer, A coverlay film, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

11. A resin-coated copper foil in which an adhesive layer and a copper foil are laminated, 9. A resin-coated copper foil, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

12. A metal-clad laminate having an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, 9. A metal-clad laminate, wherein at least one of the insulating resin layers is made of the adhesive film according to claim 7 or 8.

13. A metal-clad laminate having an insulating resin layer, an adhesive layer laminated on at least one surface of the insulating resin layer, and a metal layer laminated on the insulating resin layer via the adhesive layer, 9. A metal-clad laminate, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

14. a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface of the first metal layer; a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one surface of the second metal layer; an adhesive layer disposed so as to contact the first insulating resin layer and the second insulating resin layer and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate, 9. A metal-clad laminate, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

15. A metal-clad laminate comprising: a single-sided metal-clad laminate having an insulating resin layer and a metal layer laminated on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer, wherein the adhesive layer is made of the adhesive film of claim 7 or 8.

16. A circuit board obtained by wiring the metal layer of the metal-clad laminate according to any one of claims 12 to 15.

17. A circuit board comprising: a first base material; a wiring layer laminated on at least one surface of the first base material; and an adhesive layer laminated on a surface of the first base material facing the wiring layer so as to cover the wiring layer, 9. A circuit board, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

18. A circuit board comprising: a first base material; a wiring layer laminated on at least one surface of the first base material; an adhesive layer laminated on a surface of the first base material facing the wiring layer so as to cover the wiring layer; and a second base material laminated on a surface of the adhesive layer opposite to the first base material, 9. A circuit board, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

19. A circuit board comprising: a first base material; an adhesive layer laminated on at least one surface of the first base material; a second base material laminated on a surface of the adhesive layer opposite to the first base material; and wiring layers laminated on the surfaces of the first base material and the second base material opposite to the adhesive layer, 9. A circuit board, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

20. A multilayer circuit board comprising a laminate including a plurality of laminated insulating resin layers, and at least one wiring layer embedded inside the laminate, At least one of the plurality of insulating resin layers is formed of an adhesive layer that has adhesiveness and covers the wiring layer, 9. A multilayer circuit board, wherein the adhesive layer comprises the adhesive film of claim 7 or 8.

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