JP7621161B2 - Resin films, laminates, coverlay films, resin-coated copper foils, metal-clad laminates, circuit boards and multilayer circuit boards - Google Patents

Description

The present invention relates to resin films, laminates, coverlay films, resin-coated copper foils, metal-clad laminates, circuit boards, and multilayer circuit boards that are useful as materials for electronic components.

In recent years, with the progress of miniaturization, weight saving, and space saving of electronic devices, there is an increasing demand for flexible printed circuits (FPCs) that are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Because FPCs allow three-dimensional and high-density mounting even in a limited space, their applications are expanding to include wiring for moving parts of electronic devices such as HDDs, DVDs, and smartphones, as well as components such as cables and connectors.

One embodiment of FPC is a structure in which a circuit pattern is formed on a polyimide film having excellent heat resistance and flexibility, and a coverlay film having an adhesive layer is laminated to the surface of the polyimide film. Polyimide is also used as the material for the adhesive layer of the coverlay film having such a structure. For example, Patent Document 1 proposes applying a crosslinked polyimide obtained by reacting a polyimide made from a dimer diamine derived from a dimer acid with an amino compound having at least two primary amino groups as functional groups to the adhesive layer of the coverlay film. Here, the dimer acid is a dimerized fatty acid obtained by Diels-Alder reaction using natural fatty acids such as soybean oil fatty acid, tall oil fatty acid, rapeseed oil fatty acid, and the like, and oleic acid, linoleic acid, linolenic acid, erucic acid, and the like, which are refined from these, as raw materials, and it is known that a polybasic acid compound derived from a dimer acid is obtained as a composition of raw fatty acids and fatty acids that are trimerized or higher (for example, Patent Document 2).

JP 2013-1730 A JP 2017-137375 A

Nowadays, with the advancement of high performance devices, it is necessary to deal with the high frequency of transmission signals. When transmitting high frequency signals, if the transmission loss in the transmission path is large, inconveniences such as loss of electrical signals and long signal delay times occur. For FPCs, it is important to effectively reduce the transmission loss in both frequency bands of Sub6 (e.g., 3.6 GHz to less than 6 GHz) and millimeter waves (e.g., 28 GHz to 300 GHz) in order to support 5G (fifth generation mobile communication system). Therefore, further improvement of the dielectric properties of resin films as constituent materials of FPCs is also required, and it is considered preferable that the dielectric tangent, which is closely related to transmission loss, shows a low value below a certain level in the entire frequency range of the GHz band (e.g., 1 to 50 GHz), especially the 10 GHz to 40 GHz frequency band. However, since the dielectric tangent of conventional resin films using polyimide shows a tendency to increase with increasing frequency (frequency dependency), improvement in this respect was strongly demanded.

Therefore, the object of the present invention is to provide a resin film that exhibits a low dielectric tangent over the entire frequency band from 10 GHz to 40 GHz and can more effectively reduce the transmission loss of high-frequency signals.

As a result of extensive research, the inventors have found that a resin film using a polyimide made from dimer diamine has no frequency dependence of dielectric tangent or shows a tendency for the dielectric tangent to decrease inversely with increasing frequency, and have completed the present invention.
That is, the resin film of the present invention is a resin film containing a polyimide as a resin component, the polyimide containing a tetracarboxylic acid residue derived from a tetracarboxylic anhydride component and a diamine residue derived from a diamine component, and containing 30 mol % or more of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine in which two terminal carboxylic acid residues of a dimer acid are substituted with a primary aminomethyl group or an amino group, relative to the total diamine residues. The resin film of the present invention has a dielectric loss tangent (Tan δ 1 ) at 10 GHz and a dielectric loss tangent (Tan δ ₂ ) at 28 GHz, both of which are less than 0.0025, as measured by a split cylinder resonator (SCDR) after 24 hours of humidity control under constant temperature and humidity conditions ( _normal state) of 23° C. and 50% RH, and a ratio (Tan δ ₂ /Tan δ ₁ ) of Tan δ ₂ to Tan δ ₁ is 0.5 or more and 1.0 or less.

In the resin film of the present invention, the absolute value of the difference between Tan δ ₁ and Tan δ ₂ may be 0.0010 or less.

The resin film of the present invention may have a dielectric loss tangent (Tan δ ₃ ) of less than 0.0025 at 40 GHz measured with a split cylinder resonator (SCDR) after being conditioned for 24 hours under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH.

In the resin film of the present invention, a ratio of Tan δ ₃ to Tan δ ₁ (Tan δ ₃ /Tan δ ₁ ) may be 0.5 or more and 1.0 or less.

In the resin film of the present invention, the absolute value of the difference between Tan δ ₁ and Tan δ ₃ may be less than 0.0011.

The resin film of the present invention may contain a crosslinked polyimide obtained by crosslinking the polyimide through an imine bond.

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 any of the resin films described above.

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 any of the resin films described above.

The resin-coated copper foil of the present invention is a resin-coated copper foil formed by laminating an adhesive layer and a copper foil, and the adhesive layer is made of any of the resin films described above.

The metal-clad laminate of the first aspect 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 any of the resin films described above.

The metal-clad laminate of the second aspect of the present invention is 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, and the adhesive layer is made of any of the resin films described above.

A third aspect of the present invention provides a metal-clad laminate comprising: 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 is disposed so as to abut against the first insulating resin layer and the second insulating resin layer, and is laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate,
The adhesive layer is made of any one of the resin films described above.

The metal-clad laminate of the fourth aspect 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, the adhesive layer being made of any of the resin films described above.

The circuit board according to the first aspect of the present invention is formed by wiring the metal layer of the metal-clad laminate.

The circuit board according to the second aspect of the present invention is 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 the surface of the first base material facing the wiring layer so as to cover the wiring layer, the adhesive layer being made of any of the resin films described above.

The circuit board according to the third aspect of the present invention is a circuit board including 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, the adhesive layer being made of any of the resin films described above.

The circuit board according to the fourth aspect of the present invention is a circuit board including a first substrate, an adhesive layer laminated on at least one surface of the first substrate, a second substrate laminated on the surface of the adhesive layer opposite the first substrate, and wiring layers laminated on the surfaces of the first substrate and the second substrate opposite the adhesive layer, respectively, and the adhesive layer is made of any of the resin films described above.

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 in the laminate,
At least one of the insulating resin layers is formed of an adhesive layer having adhesiveness and covering the wiring layer, and the adhesive layer is made of any of the resin films described above.

By using a polyimide made from dimer diamine as a raw material, the resin film of the present invention not only exhibits a low dielectric tangent over the entire frequency band from 10 GHz to 40 GHz, but also shows that the dielectric tangent remains constant or even tends to decrease as the frequency increases. Therefore, when the resin film of the present invention is applied to a circuit board or the like that transmits high-frequency signals in frequency bands including both Sub6 and millimeter waves, it is possible to effectively reduce transmission loss, making it highly advantageous for application to 5G-compatible communication devices.

1 is a schematic diagram showing a cross-sectional configuration of a laminate according to an embodiment of the present invention. 1 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to another embodiment of the present invention. FIG. 4 is a schematic diagram showing a cross-sectional configuration of a metal-clad laminate according to yet another embodiment of the present invention. 1 is a schematic diagram showing a cross-sectional configuration of a circuit board according to an embodiment of the present invention; FIG. 13 is a schematic diagram showing a cross-sectional configuration of a circuit board according to another embodiment of the present invention. FIG. 13 is a schematic diagram showing a cross-sectional configuration of a circuit board according to still another embodiment of the present invention. 1 is a schematic diagram showing a cross-sectional configuration of a multilayer circuit board according to an embodiment of the present invention;

An embodiment of the present invention will be described with reference to the drawings as appropriate. A resin film according to one embodiment of the present invention is a resin film containing polyimide as a resin component. The polyimide used in this embodiment is a polyimide having adhesive properties (hereinafter, may be referred to as "adhesive polyimide"). In the following, adhesive polyimide will be described first, and then the resin film will be described.

[Adhesive polyimide]
The adhesive polyimide contains a tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride component and a diamine residue derived from a diamine component. In the present invention, the "tetracarboxylic acid residue" refers to a tetravalent group derived from a tetracarboxylic acid dianhydride, and the "diamine residue" refers to a divalent group derived from a diamine compound. When the raw materials, tetracarboxylic acid dianhydride and diamine compound, are reacted in approximately equal molar amounts, the types and molar ratios of the tetracarboxylic acid residue and diamine residue 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, polybenzimidazoleimide, etc.

(Acid anhydride)
The adhesive polyimide may be made of any tetracarboxylic dianhydride generally used in thermoplastic polyimides as a raw material, without any particular restrictions. However, it is preferable to use a raw material containing 90 mol % or more of tetracarboxylic dianhydrides represented by the following general formula (1) and/or (2) in total relative to the total tetracarboxylic dianhydride components. In other words, it is preferable for the adhesive polyimide to contain 90 mol % or more of tetracarboxylic dianhydrides derived from the following general formula (1) and/or (2) in total relative to the total tetracarboxylic dianhydride residues. By containing 90 mol % or more of tetracarboxylic dianhydrides derived from the following general formula (1) and/or (2) in total relative to the total tetracarboxylic dianhydride residues, it is preferable that the adhesive polyimide is easily compatible with flexibility and heat resistance. If the total amount of tetracarboxylic dianhydrides derived from the following general formula (1) and/or (2) is less than 90 mol %, the adhesive polyimide tends to have a low solvent solubility.

In general formula (1), X represents a single bond or a divalent group selected from the following formulas, and in general formula (2), the cyclic portion represented by Y represents a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, or an 8-membered ring.

In the above formula, Z represents —C ₆ H ₄ —, —(CH ₂ )n— or —CH ₂ —CH(—O—C(═O)—CH ₃ )—CH ₂ —, where n represents an integer of 1 to 20.

Examples of tetracarboxylic dianhydrides represented by the above general formula (1) include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 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), and ethylene glycol bisanhydrotrimellitate (TMEG). Among these, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) is particularly preferred. When BTDA is used, the carbonyl group (ketone group) contributes to adhesion, so the adhesion of the adhesive polyimide can be improved. In addition, the ketone group present in the molecular skeleton of BTDA may react with the amino group of an amino compound for crosslinking, which will be described later, to form a C=N bond, which is likely to produce an effect of improving heat resistance. From this perspective, it is preferable that the tetracarboxylic acid residues derived from BTDA are contained in an amount of preferably 50 mol% or more, more preferably 60 mol% or more, of the total tetracarboxylic acid residues.

Examples of tetracarboxylic dianhydrides represented by general formula (2) include 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 1,2,4,5-cycloheptane tetracarboxylic dianhydride, and 1,2,5,6-cyclooctane tetracarboxylic dianhydride.

The adhesive polyimide may contain tetracarboxylic acid residues derived from acid anhydrides other than the tetracarboxylic acid dianhydrides represented by the above general formula (1) and general formula (2) within the scope of the invention. There are no particular limitations on such tetracarboxylic acid residues, and examples thereof include pyromellitic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'- or 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3',3,4''- ...4''-, 2,3',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3', ,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 dianhydride, 2,3,6,7-anthracene tetracarboxylic 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 acid dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic acid dianhydride, thiophene-2,3,4,5-tetracarboxylic acid dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and other aromatic tetracarboxylic acid dianhydrides are included.

(Diamine)
The adhesive polyimide may use, as a raw material, any diamine compound generally used for thermoplastic polyimides without any particular restrictions, but a raw material containing 30 mol % or more of a dimer diamine composition mainly composed of a dimer diamine in which two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups, relative to the total diamine components, is used. In other words, the adhesive polyimide contains 30 mol % or more of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine in which two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups, relative to the total diamine residues.
The dielectric constant and dielectric loss tangent of the polyimide can be reduced by making the content of the diamine residue derived from the dimer diamine composition 30 mol% or more, preferably 40 mol% or more, more preferably in the range of 70 to 99 mol%, and even more preferably in the range of 80 to 95 mol% relative to the total diamine residues. If the content of the diamine residue derived from the dimer diamine composition is less than 30 mol%, the dielectric constant and dielectric loss tangent tend to increase due to the relatively increased polar groups contained in the polyimide. In addition, by containing the diamine residue derived from the dimer diamine composition in the above amount, the glass transition temperature of the polyimide can be lowered (reduced Tg), thereby improving the thermocompression bonding properties, and the internal stress can be alleviated due to the reduced elastic modulus.

The dimer diamine composition is a refined product that contains the following component (a) as the main component, with the amounts of components (b) and (c) controlled.

(a) dimer diamine;
The dimer diamine of the component (a) means a diamine in which two terminal carboxylic acid groups (-COOH) of a dimer acid are replaced by primary aminomethyl groups (-CH ₂ -NH ₂ ) or amino groups (-NH ₂ ). Dimer acid is a known dibasic acid obtained by intermolecular polymerization of unsaturated fatty acids, and its industrial production process is almost standardized in the industry, and is obtained by dimerizing unsaturated fatty acids having 11 to 22 carbon atoms using a clay catalyst or the like. Industrially obtained dimer acid is mainly composed of a dibasic acid having 36 carbon atoms obtained by dimerizing unsaturated fatty acids having 18 carbon atoms, such as oleic acid, linoleic acid, and linolenic acid, but contains any amount of monomer acid (having 18 carbon atoms), trimer acid (having 54 carbon atoms), and other polymerized fatty acids having 20 to 54 carbon atoms depending on the degree of purification. In addition, although double bonds remain after the dimerization reaction, in the present invention, those which have been further subjected to a hydrogenation reaction to reduce the degree of unsaturation are also included in the dimer acid. The dimer diamine of the component (a) can be defined as a diamine compound obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having a carbon number of 18 to 54, preferably 22 to 44, with a primary aminomethyl group or an amino group.

Dimer diamine has the characteristic of being able to impart properties derived from the dimer acid skeleton. In other words, since dimer diamine is an aliphatic macromolecule with a molecular weight of approximately 560 to 620, it is possible to increase the molecular molar volume and relatively reduce the polar groups of the polyimide. It is believed that such characteristics of dimer acid type diamine contribute to improving the dielectric properties by reducing the dielectric constant and dielectric tangent while suppressing the deterioration of the heat resistance of the polyimide. In addition, since it has two freely moving hydrophobic chains with 7 to 9 carbon atoms and two chain-like aliphatic amino groups with a length close to 18 carbon atoms, it is not only possible to impart flexibility to the polyimide, but also to give the polyimide an asymmetric chemical structure or a non-planar chemical structure, which is believed to be able to reduce the dielectric constant of the polyimide.

The dimer diamine composition is preferably one in which the dimer diamine content of component (a) is increased to 96% by weight or more, preferably 97% by weight or more, more preferably 98% by weight or more by a purification method such as molecular distillation. By making the dimer diamine content of component (a) 96% by weight or more, the spread of the molecular weight distribution of the polyimide can be suppressed. If technically possible, it is best that all (100% by weight) of the dimer diamine composition is composed of component (a) dimer diamine. The dimer diamine composition may contain a dimer diamine having a 6-membered aromatic ring as the molecular skeleton. In the adhesive polyimide, the ratio of aromatic monomers directly bonded to the imide bond site is the subject of control, but in the dimer diamine having a 6-membered aromatic ring, the 6-membered aromatic ring is an imide bond via an aliphatic chain having a length of 7 carbon atoms or more, so the 6-membered aromatic ring in the adhesive polyimide is not the subject of control. Therefore, the 6-membered aromatic ring derived from the dimer diamine is excluded from the content of carbon atoms derived from the 6-membered aromatic ring in the adhesive polyimide. In addition, the ratio of aromatic rings derived from dimer diamine is preferably 20 moles or less per mole of amino groups, as quantified by 1H-NMR.

(b) a monoamine compound obtained by substituting a 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 which 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.

The monoamine compound of component (b) is a component that suppresses the increase in 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 group of the polyamic acid or polyimide, thereby blocking the terminal acid anhydride group and suppressing the increase in molecular weight of the polyamic acid or polyimide.

(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 above-mentioned dimer diamine);
The polybasic acid compound having a hydrocarbon group having 41 to 80 carbon atoms is a polybasic acid compound mainly composed of 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.

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, the main component of which is a triamine derived from trimer acid, reacts with the terminal acid anhydride group of the polyamic acid or polyimide, rapidly increasing the molecular weight of the polyimide. In addition, 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 the polyamic acid or polyimide to gel.

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

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

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 it in this range, it is possible to suppress a decrease in the molecular weight of the polyimide, and further to widen the range of the molar ratio of the tetracarboxylic anhydride component and the diamine component. Note that component (b) does not have to be included in the dimer diamine composition.

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 it in this range, a sudden increase in the molecular weight of the polyimide can be suppressed, and further, an increase in the dielectric tangent of the resin film over a wide frequency range can be suppressed. Note that component (c) does not have to be included in the dimer diamine composition.

In addition, when the ratio (b/c) of the area percentages of the chromatograms of components (b) and (c) is 1 or more, the molar ratio of the tetracarboxylic anhydride component and the diamine component (tetracarboxylic anhydride 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.

In addition, 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 anhydride component and the diamine component (tetracarboxylic anhydride 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.

The dimer diamine composition is available as a commercially available product, and is preferably purified to reduce the amount of components other than the dimer diamine in component (a), for example to make the amount of component (a) 96 area % or more. There are no particular limitations on the purification method, but known methods such as distillation and precipitation purification are suitable. Examples of commercially available dimer diamine compositions include PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan.

The adhesive polyimide may contain diamine residues derived from diamine components other than those mentioned above. Examples of such diamine residues include diamine residues derived from diamine compounds having a fluorene skeleton, such as bisanilinefluorene (BAFL), 9,9-bis(3-methyl-4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, and 9,9-bis[4-(aminophenoxy)phenyl]fluorene, and diamine residues derived from diamine compounds represented by the following general formulas (B1) to (B7). In particular, diamine residues derived from diamine compounds having a fluorene skeleton, such as BAFL, contain four aromatic rings, and can therefore be advantageously used for the purpose of adjusting the aromatic ring concentration.

In formulae (B1) to (B7), R ₁ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and n ₁ independently represents an integer of 0 to 4. However, formula (B3) excluding those which overlap with formula (B2), and formula (B5) excluding those which overlap with formula (B4). Here, "independently" means that in one or two or more of formulae (B1) to (B7), multiple linking groups A, multiple R _1s or multiple n _1s may be the same or different. In the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR ₂ R ₃ (wherein R ₂ and R ₃ independently represent any substituent such as an alkyl group).

The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. In this diamine (B1), since an amino group directly bonded to at least one benzene ring and a divalent linking group A are at meta positions, the degree of freedom of the polyimide molecular chain is increased and the polyimide has high flexibility, which is considered to contribute to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (B1), the thermoplasticity of the polyimide is increased. Here, as the linking group A, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, and -S- are preferable.

Examples of diamines (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-bisamino)diphenylamine.

The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. In this diamine (B2), the amino group directly bonded to at least one benzene ring and the divalent linking group A are in the meta position, which increases the degree of freedom of the polyimide molecular chain and gives it high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B2) increases the thermoplasticity of the polyimide. Here, -O- is preferable as the linking group A.

Examples of diamines (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzeneamine, and 3-[3-(4-aminophenoxy)phenoxy]benzeneamine.

The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. In this diamine (B3), two divalent linking groups A directly bonded to one benzene ring are in the meta position relative to each other, which increases the degree of freedom of the polyimide molecular chain and gives it high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B3) increases the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

Examples of diamines (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, and 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline.

The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. This diamine (B4) has high flexibility due to the fact that the amino group directly bonded to at least one benzene ring and the divalent linking group A are at the meta position, and is considered to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B4) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO-, or -CONH-.

Examples of diamines (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, and bis[4,4'-(3-aminophenoxy)]benzanilide.

The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. In this diamine (B5), two divalent linking groups A directly bonded to at least one benzene ring are mutually in meta positions, which increases the degree of freedom of the polyimide molecular chain and gives it high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B5) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

Examples of diamines (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, etc.

The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. This diamine (B6) has high flexibility due to having at least two ether bonds, and is considered to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B6) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -C( _CH3 ) _2- , -O-, _-SO2- , or -CO-.

Examples of diamines (B6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), and bis[4-(4-aminophenoxy)phenyl]ketone (BAPK).

The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. This diamine (B7) has a highly flexible divalent linking group A on both sides of the diphenyl skeleton, and is therefore thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B7) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

Examples of diamines (B7) include bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl, etc.

The adhesive polyimide may contain a total of 70 mol % or less, preferably 60 mol % or less, more preferably 1 to 30 mol %, and even more preferably 5 to 20 mol % of diamine residues derived from a diamine compound having a fluorene skeleton and at least one diamine compound selected from diamines (B1) to (B7) relative to the total diamine residues. The diamine compound having a fluorene skeleton is effective in adjusting the aromatic ring concentration, and diamines (B1) to (B7) have a flexible molecular structure, so that by using at least one diamine compound selected from these in an amount within the above range, the flexibility of the polyimide molecular chain can be improved and thermoplasticity can be imparted.

The adhesive polyimide may further contain diamine residues derived from diamine compounds other than those mentioned above, as long as the effects of the invention are not impaired.

Adhesive polyimide can be produced by reacting the above-mentioned acid anhydride component and diamine component in a solvent to produce polyamic acid, which is then heated to close the ring. For example, the acid anhydride component and diamine component 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 obtaining polyamic acid, which is a precursor of polyimide. In the reaction, the reaction components are dissolved so that the resulting precursor is in the range of 5 to 50% by weight in the organic solvent, preferably in the range of 10 to 40% by weight. 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, dimethylsulfoxide (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 in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such organic solvents used 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 about 5 to 50% by weight.

The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, 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 it is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating operations using a coater, etc.

There are no particular limitations on the method for imidizing polyamic acid to form polyimide, 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 it may be changed during the process.

In adhesive polyimides, the physical properties such as dielectric properties, thermal expansion coefficient, tensile modulus, glass transition temperature, etc. can be controlled by selecting the types of the acid anhydride components and diamine components, and the respective molar ratios when two or more types of acid anhydride components or diamine components are used. In addition, when the adhesive polyimide has multiple structural units, they may be present as blocks or randomly, but it is preferable that they are present randomly.

The imide group concentration of the adhesive polyimide is preferably 22% by weight or less, more preferably 20% by weight or less. Here, "imide group concentration" means 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 decreases, and the low moisture absorption property deteriorates due to an increase in polar groups, and Tg and elastic modulus increase.

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

(Crosslinking of adhesive polyimide)
When the adhesive polyimide has a ketone group, the ketone group and the amino group of an amino compound having at least two primary amino groups as functional groups (hereinafter, sometimes referred to as "amino compound for crosslinking") are reacted to form a C=N bond, thereby forming a crosslinked structure. A polyimide having such a crosslinked structure (hereinafter, sometimes referred to as "crosslinked polyimide") is an application example of an adhesive polyimide and is a preferred embodiment. Since the weight average molecular weight varies greatly due to crosslinking, it is sufficient that the adhesive polyimide before crosslinking satisfies the weight average molecular weight described below, and the crosslinked polyimide does not have to satisfy the weight average molecular weight described below. In addition, a polyimide composition in which a crosslinking agent is blended with an adhesive polyimide having a ketone group is another application example of an adhesive polyimide and is a preferred embodiment. The heat resistance of the adhesive polyimide can be improved by forming a crosslinked structure. A preferred example of a tetracarboxylic dianhydride for forming an adhesive polyimide having a ketone group is 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and a preferred example of a diamine compound is an aromatic diamine such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) or 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

For the purpose of forming a crosslinked structure, it is particularly preferable to react a crosslinking amino compound with the above adhesive polyimide, which contains BTDA residues derived from BTDA in an amount of preferably 50 mol % or more, more preferably 60 mol % or more, based on the total tetracarboxylic acid residues. In the present invention, the term "BTDA residue" refers to a tetravalent group derived from BTDA.

Examples of amino compounds for forming crosslinks include (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds are prone to form crosslinked structures even at room temperature, which raises concerns about the storage stability of the varnish, while aromatic diamines require high temperatures to form crosslinked structures. In this way, 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, diglyceryl ester dihydrazide, ... Dihydrazide compounds such as 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-bisbenzene dihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridine diacid dihydrazide, and itaconic acid dihydrazide are preferred. The above dihydrazide compounds may be used alone or in combination of two or more.

The above 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 beyond the scope of the category, such as a combination of (I) and (II), a combination of (I) and (III), or a combination of (I), (II), and (III).

In order to make the mesh-like structure formed by the 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 three-dimensionally bulky, making it difficult for the remaining amino groups to form C=N bonds.

When crosslinking the ketone group in the adhesive polyimide with the crosslinking amino compound, the crosslinking amino compound is added to a resin solution containing the 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 become a hardened product. In this case, the amount of the crosslinking amino compound added can be 0.004 to 1.5 moles, preferably 0.005 to 1.2 moles, more preferably 0.03 to 0.9 moles, and most preferably 0.04 to 0.6 moles of primary amino groups per mole 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 is insufficient, and heat resistance after curing tends to be difficult to achieve. If the amount of crosslinking amino compound added exceeds 1.5 moles, the unreacted crosslinking amino compound acts as a thermoplasticizer, tending to reduce the heat resistance of the adhesive layer.

The conditions of the condensation reaction for forming crosslinks are not particularly limited as long as the ketone group in the adhesive polyimide reacts with the primary amino group of the amino compound for forming crosslinks to form an imine bond (C=N bond). The temperature of the heat condensation is preferably within the range of, for example, 120 to 220°C, more preferably within the range of 140 to 200°C, for the purpose of releasing water generated by condensation out of the system, or for the purpose of simplifying the condensation step when the heat condensation reaction is carried out subsequently after 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 confirmed by, for example, a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO) by measuring the infrared absorption spectrum, and by the decrease or disappearance of the absorption peak derived from the ketone group in the polyimide resin at around 1670 cm ^-1 and the appearance of the absorption peak derived from the imine group at around 1635 cm ^-1 .

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, following synthesis (imidization) of an adhesive polyimide, an amino compound for crosslinking is added and heated;
(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 an amino compound for crosslinking and heated together with the adhesive polyimide;
Or,
(3) A method in which the adhesive polyimide composition containing the above-mentioned crosslinking 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.

In order to impart heat resistance to adhesive polyimide, an example of crosslinked polyimide with a crosslinked structure formed by the formation of imine bonds has been given, but the present invention is not limited to this. As a method for curing polyimide, it is also possible to mix and cure it with compounds having unsaturated bonds, such as epoxy resins, epoxy resin curing agents, maleimides, activated ester resins, and resins having a styrene skeleton.

In the adhesive polyimide, the content of carbon atoms derived from six-membered aromatic rings (excluding carbon atoms of six-membered aromatic rings derived from the dimer diamine composition) relative to the total content of all atoms in the polyimide is preferably within the range of 12 to 40% by weight, more preferably within the range of 17 to 38% by weight, and even more preferably within the range of 20 to 30% by weight. The content of carbon atoms derived from six-membered aromatic rings means the content of aromatic rings contained in the adhesive polyimide (aromatic ring concentration). By setting the content of carbon atoms derived from six-membered aromatic rings within the range of 12 to 40% by weight, the molecular motion is restricted by the interaction between the aromatic rings in the polyimide, and the effect of reducing the dielectric tangent is realized. If the content of carbon atoms derived from six-membered aromatic rings is less than 12% by weight, the motion of the molecular chain of the polyimide cannot be suppressed, and the dielectric tangent becomes high. If the content of carbon atoms derived from six-membered aromatic rings exceeds 40% by weight, the polarity of the molecule becomes large, and the dielectric tangent becomes high.

Aromatic rings such as benzene rings vibrate at high frequencies, increasing heat loss. Therefore, as a general trend, the dielectric loss tangent increases as the aromatic ring concentration in polyimide increases. However, in adhesive polyimides, if the aromatic ring concentration is within the range of 12 to 40% by weight, the dielectric loss tangent does not increase even if the aromatic ring concentration increases, and instead, the dielectric loss tangent tends to decrease up to a certain aromatic ring concentration. The reason for this behavior is not yet clear, but since adhesive polyimides are made from a dimer diamine composition, they have a relatively low aromatic ring concentration compared to polyimides made from aromatic diamines alone. It is presumed that if the aromatic ring concentration is gradually increased from a state where the aromatic ring concentration is low, the molecular movement is restricted by the interaction between the aromatic rings, and the dielectric loss tangent is kept low. It is considered that a sufficiently low dielectric loss tangent can be maintained regardless of the increase in frequency until the aromatic ring concentration reaches 40% by weight.

The adhesive polyimide preferably has a weight average molecular weight (Mw) in the range of 10,000 to 200,000, more preferably in the range of 10,000 to 60,000. If the Mw of the adhesive polyimide is less than 10,000, the dielectric constant and dielectric dissipation factor tend to increase due to an increase in highly polar end groups in the polyimide molecular chain, but if the Mw is 10,000 or more, the increase in highly polar end groups is suppressed, and the increase in the dielectric constant and dielectric dissipation factor can be suppressed. On the other hand, if the Mw exceeds 200,000, the viscosity becomes high when made into a varnish, which reduces the handling properties and makes it easy for thickness unevenness to occur during coating. A more preferable range for the Mw of the adhesive polyimide is in the range of 15,000 to 60,000, and most preferably in the range of 18,000 to 50,000. If Mw is less than 15,000, the dielectric constant and dielectric loss tangent may tend to increase due to an increase in highly polar acid ends in the polyimide molecular chain. If Mw is more than 60,000, the molecular chain length becomes longer, making it difficult to achieve the effect of introducing an alicyclic diamine or aromatic diamine, and the dielectric constant and dielectric loss tangent may tend to increase.

The adhesive polyimide preferably has a ratio (Mw/Mn) of Mw to number average molecular weight (Mn) in the range of 1.5 to 2.5, more preferably 1.8 to 2.0.
The ratio Mw/Mn represents the degree of polydispersity, and it is preferable that the adhesive polyimide has a ratio Mw/Mn of 1.5 or more. Even if Mn is about the same, the higher the degree of dispersion, the higher the frequency of high molecular weight bodies, so that the suppression of movement due to molecular entanglement is enhanced, and the dielectric loss tangent and tear strength are improved. In addition, since Mn represents the number of terminals of the polyimide chain more directly than Mw, the ratio Mw/Mn is set to 2.5 or less, and by ensuring a certain degree of dispersion and balancing with Mn, the increase of highly polar terminals in the polyimide molecular chain can be suppressed, and the increase of the relative dielectric constant and dielectric loss tangent can be suppressed. The control of Mn is possible by increasing the content of dimer diamine in the dimer diamine composition (i.e., reducing the trimer component and monomer component), which is thought to suppress the spread of the molecular weight of the adhesive polyimide and also contribute to the improvement of the frequency dependency.

The adhesive polyimide can be used in the form of a resin composition. For example, the adhesive polyimide can be used in the form of a resin composition comprising the following components (A) and (B):
(A) an adhesive polyimide having a ketone group;
and (B) a crosslinking agent having a functional group that undergoes a nucleophilic addition reaction with the ketone group.
In this case, as the crosslinking agent of the component (B), the above-mentioned amino compound for crosslinking can be used.

The polyimide composition preferably contains adhesive polyimide as the main component of the resin component, more preferably 70% by weight or more of the resin component, even more preferably 90% by weight or more of the resin component, and most preferably as the entire resin component. The main component of the resin component means a component that is contained in an amount of more than 50% by weight of the total resin component. The polyimide composition can also contain component (B) so that the functional groups are in the range of 0.04 to 0.50 moles in total, preferably 0.04 to 0.40 moles, more preferably 0.06 to 0.30 moles, per mole of ketone group in component (A). If the functional groups of the crosslinking agent are less than 0.04 moles in total per mole of ketone group, crosslinking does not proceed sufficiently, and heat resistance after curing tends to be difficult to develop. On the other hand, if it exceeds 0.5 moles, the dielectric tangent tends to increase. This is presumably because the mobility of the polyimide molecular chain is restricted by the excess crosslinking agent, inhibiting the formation of an ordered structure of the molecular chain that is effective in suppressing the dielectric tangent during curing. Furthermore, if the amount of crosslinking agent is too large, the unreacted crosslinking agent will act as a thermoplasticizer, tending to reduce the heat resistance of the adhesive layer.

The polyimide composition forms crosslinks by a nucleophilic addition reaction between the ketone groups in the ketone group-containing polyimide and the functional groups of the crosslinking agent, resulting in a crosslinked polyimide, which is a cured product. The conditions for the nucleophilic addition reaction for forming crosslinks are not particularly limited and can be selected according to the type of crosslinking agent. For example, when reacting the primary amino groups of the crosslinking amino compound with the ketone groups in the ketone group-containing polyimide, an imine bond (C=N bond) is generated by a condensation reaction caused by heating, and a crosslinked structure is formed.

In addition, since the adhesive polyimide is soluble in a solvent, the polyimide composition can be used in a form containing a solvent. 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, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diglyme, triglyme, methanol, ethanol, benzyl alcohol, cresol, and acetone. 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.

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

The polyimide 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, and flame retardants, as long as the effects of the invention are not impaired.

[Resin film]
The resin film according to the present embodiment is a film obtained by processing the adhesive polyimide or crosslinked polyimide into a film. The resin film is not particularly limited as long as it contains the adhesive polyimide or crosslinked polyimide as the main component of the resin component, preferably 60% by weight or more of the resin component, more preferably 90% by weight or more of the resin component, and most preferably the entire resin component. The main component of the resin component means a component contained in an amount of more than 50% by weight of the total resin component. The resin film may be a film (sheet) made of adhesive polyimide or crosslinked polyimide, or may be laminated on a resin substrate such as a copper foil or a glass plate, or a polyimide film, a polyamide film, or a polyester film. The resin film may contain, as an optional component, a plasticizer, another curable resin component such as an epoxy resin, a curing agent, a curing accelerator, an organic filler, an inorganic filler, a coupling agent, a flame retardant, or the like.

(Dielectric tangent)
The resin film of the present embodiment has a dielectric loss tangent (Tan δ ₁ ) at 10 GHz and a dielectric loss tangent (Tan δ 2 ) at 28 GHz, both of which are less than 0.0025 when measured by a split cylinder resonator (SCDR) after 24 hours of humidity conditioning under constant temperature and humidity conditions ( _normal state) of 23° C. and 50% RH. If the dielectric loss tangent (Tan δ ₁ and Tan δ ₂ ) exceeds the above values, it leads to an increase in dielectric loss when applied to a circuit board, and inconveniences such as loss of electrical signals on the transmission path of high-frequency signals are likely to occur. By making the dielectric loss tangent (Tan δ ₁ and Tan δ ₂ ) less than 0.0025, the dielectric loss during high-frequency signal transmission can be effectively reduced. Here, a dielectric loss tangent (Tan δ ₁ ) of less than 0.0025 at 10 GHz means that the transmission loss in the frequency band for Sub6 applications can be effectively reduced. Furthermore, a dielectric loss tangent (Tan δ ₂ ) of less than 0.0025 at 28 GHz means that the transmission loss can be effectively reduced in the frequency band from Sub6 to over 10 GHz, including millimeter waves.

In addition, the resin film of the present embodiment has a ratio of Tan δ ₂ to Tan δ ₁ (Tan δ ₂ /Tan δ ₁ ) of 0.5 to 1.0, preferably 0.6 to 1.0, more preferably 0.7 to 1.0. The ratio (Tan δ ₂ /Tan δ ₁ ) is an index of frequency dependency, and being 0.5 to 1.0 means that even if the frequency increases in the frequency band of 10 to 28 GHz, the dielectric tangent does not increase, but remains the same, or even decreases. Therefore, the loss during signal transmission of 10 GHz or more can be effectively reduced, and this is a suitable property for application to a transmission circuit of high-frequency signals from Sub6 to millimeter waves. If the ratio (Tan δ ₂ /Tan δ ₁ ) is less than 0.5, the variation with frequency becomes large, making it difficult to use it as a material compatible with a wide frequency band, and if it exceeds 1.0, the transmission loss increases with increasing frequency, which is not preferable.

In addition, the resin film of the present embodiment preferably has an absolute value of the difference between Tan δ ₁ and Tan δ ₂ of 0.0010 or less. If this absolute value exceeds 0.0010, the variation due to frequency becomes large, making it difficult to use as a material compatible with a wide frequency band from Sub6 to millimeter waves. Therefore, the absolute value of the difference between Tan δ ₁ and Tan δ ₂ is more preferably 0.00060 or less, and most preferably 0.00040 or less. The absolute value of the difference between Tan δ ₁ and Tan δ ₂ means both |Tan δ ₁ -Tan δ ₂ | and |Tan δ ₂ -Tan δ ₁ |.

In addition, the resin film of the present embodiment preferably has a dielectric loss tangent (Tan δ 3 ) at 40 GHz measured by a split cylinder resonator (SCDR) of less than 0.0025 after 24 hours of humidity conditioning under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH. If the dielectric loss tangent (Tan δ ₃ ) exceeds the above value, it leads to an increase in dielectric loss when applied to a circuit board, and is likely to cause _{inconveniences} such as loss of electrical signals on the transmission path of high-frequency signals. By making the dielectric loss tangent (Tan δ ₃ ) less than 0.0025, the dielectric loss during high-frequency signal transmission can be effectively reduced. In particular, a dielectric loss tangent (Tan δ ₃ ) of less than 0.0025 at 40 GHz means that the transmission loss in a frequency band including millimeter waves can be effectively reduced.

In addition, the resin film of the present embodiment has a ratio of Tan δ ₃ to Tan δ ₁ (Tan δ ₃ /Tan δ ₁ ) of 0.5 to 1.0, preferably 0.6 to 1.0, more preferably 0.7 to 1.0. The ratio (Tan δ ₃ /Tan δ ₁ ) is an index of frequency dependency, and being 0.5 to 1.0 means that even if the frequency increases in the frequency band of 10 to 40 GHz, the dielectric loss tangent does not increase, but remains the same, or even decreases. Therefore, the loss during signal transmission of 10 GHz or more can be effectively reduced, and this is a suitable property for application to a transmission circuit of high-frequency signals from Sub6 to millimeter waves. Note that if the ratio (Tan δ ₃ /Tan δ ₁ ) is less than 0.5, the variation with frequency becomes large, making it difficult to use it as a material compatible with a wide frequency band, and if it exceeds 1.0, the transmission loss increases with increasing frequency, which is not preferable.

In addition, the resin film of the present embodiment preferably has an absolute value of the difference between Tan δ ₁ and Tan δ ₃ of less than 0.0011. If this absolute value is 0.0011 or more, the variation due to frequency becomes large, making it difficult to use as a material compatible with a wide frequency band from Sub6 to millimeter waves. Therefore, the absolute value of the difference between Tan δ ₁ and Tan δ ₃ is more preferably 0.00070 or less, and most preferably 0.00045 or less. The absolute value of the difference between Tan δ ₁ and Tan δ ₃ means both |Tan δ ₁ -Tan _{δ 3} | and |Tan δ ₃ -Tan δ ₁ |.

(Dielectric constant)
The resin film of the present embodiment has a dielectric constant (ε) of 3.0 or less, preferably 2.7 or less, in the frequency band of 10 GHz to 40 GHz measured by a split cylinder resonator (SCDR) after 24 hours of humidity conditioning under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH. If the dielectric constant (ε) exceeds the above value, it leads to an increase in dielectric loss when applied to a circuit board, and is likely to cause inconveniences such as loss of electrical signals on the transmission path of high-frequency signals in the GHz band (e.g., 1 to 50 GHz).

(Glass Transition Temperature)
The resin film of the present embodiment preferably has a glass transition temperature (Tg) of 250° C. or less, more preferably in the range of 40° C. or more and 200° C. or less. By making the Tg of the resin film 250° C. or less, thermocompression bonding at a low temperature is possible, so that the internal stress generated during lamination can be alleviated and dimensional change after circuit processing can be suppressed. If the Tg of the resin film exceeds 250° C., the bonding temperature becomes high, and there is a risk of impairing dimensional stability after circuit processing.

(Tensile Modulus)
The tensile modulus of the resin film is preferably 3000 MPa or less, preferably 100 MPa or more and 2500 MPa or less, more preferably 200 MPa or more and 2000 MPa or less. If the tensile modulus is less than 100 MPa, the film is likely to wrinkle, and handling properties such as air entrapment during lamination may be poor. If the tensile modulus exceeds 3000 MPa, warping may occur or dimensional stability may decrease when the substrate and the resin film are laminated. By setting the tensile modulus to the above range, a laminate having good handling properties, suppressing warping and excellent dimensional stability can be obtained.

(Thickness)
Although there is no particular limit to the thickness of the resin film of the present embodiment, for example, in the case of making it a self-supporting film, the thickness is preferably in the range of 5 μm to 125 μm, and more preferably in the range of 8 μm to 100 μm. If the thickness of the resin film is less than 5 μm, there is a risk of problems such as wrinkles occurring during transportation in the production of the resin film, while if the thickness of the resin film exceeds 125 μm, there is a risk of a decrease in productivity of the resin film.
On the other hand, when the resin film of the present embodiment is used in a state of being laminated with a substrate or an arbitrary resin layer, the lower limit of the thickness may be, for example, 0.1 μm or more.

The use of the resin film of the present embodiment is not particularly limited, but is preferably a high-frequency transmission board in the GHz band (for example, 1 to 50 GHz), and examples include a transmission circuit board used in 5G and a millimeter-wave transmission board used in sensors in automobiles, etc. Liquid crystal polymers (LCPs) are sometimes used for high-frequency transmission FPCs, but LCPs have a tendency for the dielectric tangent to increase with an increase in the frequency of the signal (frequency dependence), and aromatic polyimides also show frequency dependence in which the dielectric tangent increases with an increase in frequency. Some conventional materials have a dielectric tangent that decreases with an increase in frequency, but in such cases, the dielectric tangent in the GHz band is 0.003 or more, and is not suitable for transmitting high-frequency signals. In contrast, as described above, the resin film of the present embodiment has a very low dielectric loss tangent (Tan δ ₁ , Tan δ ₂ and Tan δ ₃ ) of less than 0.0025, but has the excellent feature that the dielectric loss tangent remains constant or decreases in the opposite direction as the frequency increases (frequency independence), making it particularly suitable for use in the GHz band.

A preferred form of the resin film in this embodiment is an adhesive film.

The method for producing the resin 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 in a solution state (for example, in a polyimide composition state) to an arbitrary substrate 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 necessary.
[2] A method in which a solution of a polyamic acid, which is a precursor of an adhesive polyimide, is applied to any substrate, dried, and then imidized to form a film, which is then peeled off from the substrate as necessary.
[3] A method in which a solution of polyamic acid, which is 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 a resin film.
The method for applying the adhesive polyimide solution (or polyamic acid solution) onto the substrate is not particularly limited, and it is possible to apply it using, for example, a coater such as a comma, die, knife or lip coater.

Next, we will explain the preferred embodiments of the laminate, metal-clad laminate, circuit board, and multilayer circuit board that use the resin film by giving specific examples.

[Laminate]
The laminate 100 according to one embodiment of the present invention has a substrate 10 and an adhesive layer 20 laminated on at least one surface of the substrate 10, as shown in FIG. 1, and the adhesive layer 20 is made of the resin film. The laminate 100 may include any layer other than the above. The substrate 10 in the laminate 100 may be, for example, a substrate made of an inorganic material such as copper foil or a glass plate, or a substrate made of a resin material such as a polyimide film, a polyamide film, or a polyester film. The laminate 100 can be manufactured according to any one of the above-mentioned methods [1] to [3] for manufacturing the resin film, except that the laminate 10 is not peeled off from the substrate 10. The laminate 100 may also be manufactured by preparing the substrate 10 and the resin film separately and laminating them together.
Preferred embodiments of the laminate 100 include a coverlay film, a copper foil with resin, and the like.

(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 above-mentioned resin film. The coverlay film may include any layer other than those described above.

The material of the coverlay film material layer is not particularly limited, but may be, for example, a polyimide-based film such as polyimide resin, polyetherimide resin, or polyamideimide resin, a polyamide-based film, or a polyester-based film. Of these, it is preferable to use a polyimide-based film having excellent heat resistance. In addition, the coverlay film material layer may contain a black pigment to effectively exhibit light-shielding properties, concealing properties, design properties, etc., and may also contain optional components such as a matte pigment that suppresses surface gloss, as long as the effect of improving the dielectric properties is not impaired.

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.

The coverlay film of the present embodiment can be produced by the method exemplified below.
First, as a first method, polyimide that will become the adhesive layer 20 is applied in a solution state (for example, a varnish state containing a solvent is preferable, and a polyimide composition is preferable) to one side of a film material layer for the coverlay, 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 film material layer for the coverlay and the adhesive layer 20.

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

(Copper foil with resin)
Although not shown, the 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 resin film. The resin-coated copper foil of this embodiment may include any layer other than those described above.

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

The material of the copper foil in the resin-coated copper foil is preferably one whose main component is copper or a copper alloy. The thickness of the copper foil is preferably 35 μm or less, and more preferably in the range of 5 to 25 μm. From the viewpoint of production stability and handling, 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. In addition, commercially available copper foils can be used as the copper foil.

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

[Metal-clad laminate]
(First aspect)
The metal-clad laminate according to one embodiment of the present invention includes an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and at least one of the insulating resin layers is made of the resin film. Note that the metal-clad laminate according to this embodiment may include any layer other than those described above.

(Second Aspect)
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 surface of the insulating resin layer 30, and a metal layer M laminated on the insulating resin layer 30 via the adhesive layer 20, as shown in FIG. 2, and the adhesive layer 20 is made of the above-mentioned resin film. The three-layer metal-clad laminate 101 may include any layer other than the above. The three-layer metal-clad laminate 101 may have the adhesive layer 20 on one or both surfaces of the insulating resin layer 30, and the metal layer M may have the adhesive layer 20 on one or both surfaces of the insulating resin layer 30. In other words, the three-layer metal-clad laminate 101 may be a single-sided metal-clad laminate or a double-sided metal-clad laminate. A single-sided or double-sided FPC can be manufactured by etching the metal layer M of the three-layer metal-clad laminate 101 to perform wiring circuit processing.

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 constituting the insulating resin layer 30 may be a single layer or multiple layers, but preferably includes a non-thermoplastic polyimide layer.

The thickness of the insulating resin layer 30 in the three-layer metal-clad laminate 101 is preferably within the range of 1 to 125 μm, for example, and more preferably within the range of 5 to 100 μm. If the thickness of the insulating resin layer 30 is less than the above lower limit, problems such as inability to ensure sufficient electrical insulation may occur. On the other hand, if the thickness of the insulating resin layer 30 exceeds the above upper limit, problems such as the metal-clad laminate becoming more susceptible to warping may occur.

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 this embodiment, if the thickness of the adhesive layer 20 is less than the above-mentioned lower limit, problems such as inability to ensure sufficient 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. In addition, 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.

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 setting such a ratio, warping of the three-layer metal-clad laminate 101 can be suppressed. The insulating resin layer 30 may contain a filler as necessary. 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 a mixture of two or more types.

(Third Aspect)
A metal-clad laminate according to yet another embodiment of the present invention is, for example, as shown in Fig. 3, a laminated type metal-clad laminate 102 formed by laminating at least two single-sided metal-clad laminates via an adhesive layer 20. The laminated type metal-clad laminate 102 includes 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 above-mentioned resin film.
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 side 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 side of the second metal layer M2. The adhesive layer 20 is disposed so as to abut against the first insulating resin layer 31 and the second insulating resin layer 32. The laminated metal-clad laminate 102 may include any layer other than those described above.

The first insulating resin layer 31 and the second insulating resin layer 32 in the laminated type 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 placing a resin film between the first insulating resin layer 31 and the second insulating resin layer 32 and laminating them together.

(Fourth aspect)
4, a metal-clad laminate according to still another embodiment of the present invention is a metal-clad laminate 103 with an adhesive layer, which includes 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, the adhesive layer 20 being made of the above-mentioned resin film. Note that the metal-clad laminate 103 with an adhesive layer 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 a configuration similar to that of 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 manufactured by preparing a single-sided metal-clad laminate having an insulating resin layer 33 and a metal layer M, and laminating a resin film to the insulating resin layer 33 side.

In any of the first to fourth exemplary embodiments of the metal-clad laminates described 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 that of the metal layer M.

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 handling, it is preferable that the lower limit of the thickness of the metal foil is 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. In addition, commercially available copper foil may be used as the copper foil. In addition, the metal foil may be subjected to a surface treatment, for example, with siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc., for the purpose of, for example, rust prevention treatment and improvement of adhesive strength.

[Circuit board]
(First aspect)
The circuit board according to the 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 manufacturing a circuit board such as an FPC. The circuit board may include a coverlay film that covers the wiring layer.

(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 above-mentioned resin film. 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 a resin film to the wiring layer 50 side of a circuit board including the first base material 11 and the wiring layer 50 laminated on at least one surface of the first base material 11.

(Third Aspect)
As shown in FIG. 6, the circuit board 201 according to 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, and the adhesive layer 20 is made of the resin film. The circuit board 201 may include any layer other than those described above. The first substrate 11 and the second substrate 12 in the circuit board 201 may have the same configuration as 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 a resin film.

(Fourth aspect)
A circuit board 202 according to another embodiment of the present invention includes, as shown in FIG. 7, 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, and the adhesive layer 20 is made of the resin film. The circuit board 202 may include any layer other than the above. The first substrate 11 and the second substrate 12 in the circuit board 202 may have the same configuration as the insulating resin layer of the metal-clad laminate.
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 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 second substrate 12, and then placing a resin film between first substrate 11 of the first circuit board and second substrate 12 of the second circuit board and laminating them together.

[Multilayer circuit board]
A multilayer circuit board according to an embodiment of the present invention includes a laminate in which a plurality of insulating resin layers are laminated, and one or more wiring layers embedded inside the laminate, and at least one of the plurality of insulating resin layers is formed of an adhesive layer 20 that has adhesiveness and covers the wiring layer, and the adhesive layer 20 is made of the above-mentioned resin 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, the multilayer circuit board 203 of this embodiment has at least two insulating resin layers 34 and at least two wiring layers 50, and at least one of the wiring layers 50 is 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 a wiring layer 50 exposed on the surface of the multilayer circuit board 203. The multilayer circuit board 203 may also have an interlayer connection electrode (via electrode) in contact with the wiring layer 50. The wiring layer 50 is 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 in a damascene (embedded) manner. The insulating resin layer 34 in the multilayer circuit board 203 may have the same configuration as the insulating resin layer of the metal-clad laminate.

The circuit board and multilayer circuit board of each of the above embodiments have an adhesive layer 20 that contains adhesive polyimide, making it possible to reduce transmission loss even in high-frequency transmission.

The following examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to these examples. In the following examples, unless otherwise specified, the various measurements and evaluations were performed as follows.

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

[Measurement of weight average molecular weight (Mw) and number average molecular weight (Mn) of polyimide]
The weight average molecular weight and the number average molecular weight were 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.

[How to calculate Cp value]
The weight content of carbon atoms derived from 6-membered aromatic rings (excluding carbon atoms in 6-membered aromatic rings derived from the dimer diamine composition) relative to the total content of all atoms in the polyimide was defined as the Cp value.

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) was measured using a thermomechanical analyzer (TMA: manufactured by Netzsch, product name: TMA4000SA) for an adhesive film measuring 5 mm x 20 mm, at a heating rate of 5°C/min from 0°C to 300°C. The temperature at which the elongation during heating becomes inflection was taken as the glass transition temperature.
Here, the term "thermoplastic polyimide" generally refers to a polyimide that can be softened by heating and solidified by cooling, and this can be repeated, and the glass transition temperature can be clearly confirmed. In the present invention, however, it means a polyimide whose glass transition temperature can be clearly confirmed in a temperature range of 150° C. or less. From the viewpoint of thermocompression bonding at low temperatures, the thermoplastic polyimide is preferably a polyimide whose glass transition temperature can be clearly confirmed in a temperature range of 100° C. or less, and more preferably has a storage modulus of 1.0×10 ⁸ Pa or more at 30° C. measured using a dynamic viscoelasticity measuring device (DMA) and a storage modulus of less than 1.0×10 ⁷ Pa at the glass transition temperature +30° C. In contrast, the term "non-thermoplastic polyimide" refers to a polyimide that does not soften or exhibit adhesiveness even when heated, but in the present invention, it means a polyimide whose storage modulus of 1.0×10 ⁹ Pa or more at 30° C. measured using a dynamic viscoelasticity measuring device (DMA) and a storage modulus of 1.0×10 ⁸ Pa or more at 300° C.

[Tensile modulus]
The tensile modulus was measured by the following procedure. First, a test piece (width 12.7 mm x length 127 mm) was prepared from the adhesive film using a tension tester (manufactured by Orientec Co., Ltd., product name: Tensilon). A tensile test was performed at 50 mm/min using this test piece, and the tensile modulus at 25°C was obtained.

[Measurement of dielectric constant and dielectric tangent]
Using a network analyzer (Keysight Technologies, product name: Network Analyzer N5290A) and a split cylinder resonator (SCDR), a predetermined number of resin sheets were stacked at a temperature of 23°C and a humidity of 50% to obtain an evaluation sample with a total thickness of about 100 μm, and then heat-treated at a temperature of 180°C, a pressure of 2 MPa, and 1.0 hour using a small precision press machine manufactured by Kitagawa Seiki Co., Ltd., and after 24 hours or more of humidity control under the conditions of a temperature of 23°C and a humidity of 50%, the relative dielectric constant (ε ₁ ) and dielectric loss tangent (Tan δ ₁ ) at a frequency of 10 GHz, the relative dielectric constant (ε ₂ ) and dielectric loss tangent (Tan δ ₂ ) at a frequency of 28 GHz, and the relative dielectric constant (ε ₃ ) and dielectric loss tangent (Tan δ ₃ ) at a frequency of 40 GHz were measured. In addition, a value serving as an index of the frequency dependency of the dielectric loss tangent was calculated by the following formula.
_P12 value = Tan _δ2 / Tan _δ1
R12 value = Tan _{δ 1} - Tan δ _2
P13 value = Tan δ ₃ / Tan δ _1
R13 value = Tan _{δ 1} - Tan δ ₃

[Warpage evaluation method]
The evaluation of warpage was performed by the following method. A polyimide solution or an adhesive composition was applied 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 thickness after drying was 25 μm, and a test piece was prepared. In this state, the polyimide film or the copper foil was placed on the underside, and the average height of the warpage at the four corners of the test piece was measured, and a value of 5 mm or less was rated as "good", and a value of more than 5 mm was rated as "no good".

[GPC and Chromatogram Area Percentage Calculation]
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 1000 ppm of cyclohexanone). The prepared sample was measured using a Tosoh Corporation product name: HLC-8220GPC under the following conditions: column: TSK-gel G2000HXL, G1000HXL, flow rate: 1 mL/min, column (oven) temperature: 40° C., injection amount: 50 μL. Cyclohexanone was treated as a standard substance for the correction of the elution time.

In this case, the retention times were adjusted so that the peak top of the cyclohexanone main peak was at 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 2 minutes, and the peak top of the main peak excluding the cyclohexanone peak was at a retention time of 18 to 19 minutes, and the period from the peak start to the peak end of the main peak excluding the cyclohexanone peak was at a retention time of 2 minutes to 4 minutes 30 seconds,
(a) Component represented by the main peak;
(b) A component represented by a GPC peak detected at a time later than the minimum retention time of the main peak;
(c) a component represented by a GPC peak detected at a time earlier than the minimum retention time of the main peak;
was detected.

The abbreviations used in the examples represent the following compounds.
BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride DDA: aliphatic diamine having 36 carbon atoms (manufactured by Croda Japan Co., Ltd., product name: refined PRIAMINE 1074, component a: 97.9%, component b: 0.3%, component c: 1.8%, amine value: 210 mg KOH/g, mixture of dimer diamines having a cyclic structure and a chain structure)
BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane BAFL: bisanilinefluorene 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)
SR-3000: Phosphate ester (manufactured by Daihachi Chemical Industry Co., Ltd., product name: SR-3000, non-halogen aromatic condensed phosphate ester, phosphorus content: 7.0%)
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 by the following formula.
Molecular weight = 56.1 x 2 x 1000 / amine value

[Example 1]
A polyamic acid solution was prepared by charging 21.35g of BTDA (0.0663 mol), 29.44g of 6FDA (0.0663 mol), 63.72g of DDA (0.1193 mol), 5.44g of BAPP (0.0133 mol), 168.0g of NMP and 112.0g of xylene into a 1000ml separable flask and thoroughly mixing for 1 hour at 40°C. The polyamic acid solution was heated to 190°C, heated and stirred for 5 hours, and xylene was added so that the solid content was 30% by weight to complete imidization, thereby preparing a polyimide solution 1 (weight average molecular weight: 41,428, number average molecular weight: 21,924, C _p : 19.90%).

[Examples 2 to 4]
Polyimide solutions 2 to 4 were prepared in the same manner as in Example 1, except that the raw material compositions shown in Table 1 were used.

[Example 5]
Polyimide solution 1 was applied to one side of a 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 the release PET film 1 to prepare an adhesive film 1 having a thickness of 25 μm. The various evaluation results of adhesive film 1 are as follows.
ε ₁ ; 2.5, Tan δ ₁ ; 0.00141
ε ₂ ; 2.5, Tan δ ₂ ; 0.00132
ε ₃ ; 2.5, Tan δ ₃ ; 0.00128
_P12 value = Tan _δ2 /Tan _δ1 = 0.94
_R12 value = Tan δ ₁ - Tan δ ₂ = 0.00009
_P13 value = Tan δ ₃ / Tan δ ₁ = 0.91
_R13 value = Tan δ ₁ - Tan δ ₃ = 0.00013
Tg: 46°C (thermoplastic), tensile modulus: 590MPa

[Examples 6 to 8]
Adhesive films 2 to 4 were prepared in the same manner as in Example 5, except that polyimide solutions 2 to 4 were used. The results of the evaluation of various properties are shown in Table 2.

[Example 9]
1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution 4 (30 g as solid content), and 7.5 g of OP935 and 14.0 g of xylene were added to dilute the mixture, and the mixture was further stirred for 1 hour to prepare adhesive composition 9.

The adhesive composition 9 was applied to one side of the release PET film 1 and dried at 120°C for 10 minutes to obtain a resin laminate with an adhesive layer thickness of 25 μm. The adhesive layer was then peeled off from the release PET film 1 to prepare an adhesive film 9 with a thickness of 25 μm.

The adhesive film 9 was heat-treated at a temperature of 180° C. and a pressure of 2 MPa for 1.0 hour using a small precision press manufactured by Kitagawa Seiki Co., Ltd. to prepare a resin sheet 9. Spectral measurement of the resin sheet 9 using a laser Raman spectrophotometer (manufactured by JASCO Corporation, product name: NRS-3100) confirmed a peak due to crosslinking formation near 1575 cm ⁻¹ .
The results of various evaluations of the resin sheet 9 are as follows.
ε ₁ ; 2.7, Tan δ ₁ ; 0.00182
ε ₂ ; 2.7, Tan δ ₂ ; 0.00156
ε ₃ ; 2.7, Tan δ ₃ ; 0.00146
_P12 value = Tan δ ₂ / Tan δ ₁ = 0.86
_R12 value = Tan δ ₁ - Tan δ ₂ = 0.00026
_P13 value = Tan δ ₃ / Tan δ ₁ = 0.80
_R13 value = Tan δ ₁ - Tan δ ₃ = 0.00036
Tg: 51°C (thermoplastic), tensile modulus: 1,500 MPa

[Example 10]
1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution 4 (30 g as solid content), and diluted with 6.0 g of SR-3000 and 14.0 g of xylene, and further stirred for 1 hour to prepare adhesive composition 10.

An adhesive film 10 was obtained and a resin sheet 10 was prepared in the same manner as in Example 9, except that adhesive composition 10 was used.
The results of various evaluations of the resin sheet 10 are as follows.
ε ₁ ; 2.7, Tan δ ₁ ; 0.00170
ε ₂ ; 2.6, Tan δ ₂ ; 0.00164
ε ₃ ; 2.6, Tan δ ₃ ; 0.00158
_P12 value = Tan _δ2 /Tan _δ1 = 0.96
_R12 value = Tan δ ₁ - Tan δ ₂ = 0.00006
_P13 value = Tan δ ₃ / Tan δ ₁ = 0.93
_R13 value = Tan δ ₁ - Tan δ ₃ = 0.00012
Tg: 48°C (thermoplastic), tensile modulus: 1,100 MPa

Comparative Example 1
The dielectric properties of the LCP film (liquid crystal polymer film, manufactured by Kuraray Co., Ltd., trade name: Vecstar CT-Z, thickness: 100 μm) are as follows:
ε ₁ ; 3.5, Tan δ ₁ ; 0.00210
ε ₃ ; 3.5, Tan δ ₃ ; 0.00240
_P13 value = Tan δ ₃ / Tan δ ₁ = 1.14
_R13 value = Tan δ ₁ - Tan δ ₃ = -0.00030

The results of the evaluation of various characteristics for Examples 9 and 10 and Comparative Example 1 are summarized in Table 3.

[Example 11]
The adhesive composition 9 was applied to one side of an electrolytic copper foil having a thickness of 12 μm and dried at 120° C. for 30 minutes to prepare a resin-coated copper foil 11 having an adhesive layer thickness of 50 μm. The warpage state of the resin-coated copper foil 11 was “good”.

[Example 12]
The adhesive composition 9 was further applied to the surface of the adhesive layer of the resin-coated copper foil 11, and dried at 120° C. for 30 minutes to prepare a resin-coated copper foil 12 having an adhesive layer with a total thickness of 100 μm. The warpage state of the resin-coated copper foil 12 was “good”.

[Example 13]
The adhesive composition 9 was applied to one side of a polyimide film 1 (manufactured by DuPont-Toray Co., Ltd., product name: Kapton 50EN, ε ₁ = 3.6, tan δ ₁ = 0.0084, length × width × thickness = 200 mm × 300 mm × 12 μm) and dried at 120° C. for 10 minutes to prepare a coverlay film 13 with an adhesive layer thickness of 25 μm. The warpage state of the coverlay film 13 was "good".

[Example 14]
The release PET film 1 was laminated so as to be in contact with the adhesive layer side of the coverlay film 13, and pressure-bonded for 2 minutes at a temperature of 160° C. and a pressure of 0.8 MPa using a vacuum laminator. Thereafter, the adhesive composition 9 was applied to the polyimide film 1 side of the coverlay film 13 with the release PET film 1 pressure-bonded to the adhesive layer side so as to have a thickness of 25 μm after drying, and dried at 120° C. for 10 minutes. The release PET film 1 was laminated so as to be in contact with the surface on which the adhesive composition 9 was applied and dried, and pressure-bonded for 2 minutes at a temperature of 160° C. and a pressure of 0.8 MPa using a vacuum laminator to prepare a polyimide adhesive laminate 14 having adhesive on both sides of the polyimide film.

[Example 15]
An adhesive film 9, a polyimide film 2 (manufactured by DuPont, product name: Kapton 100-EN, thickness 25 μm, ε ₁ = 3.6, tan δ ₁ = 0.0084), and another adhesive film 9 and an electrolytic copper foil of 12 μm were laminated in this order on an electrolytic copper foil of 12 μm, 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. The temperature was then raised from room temperature to 160° C., and the laminate was heat-treated at 160° C. for 4 hours to prepare a copper-clad laminate 15.

[Example 16]
The coverlay film 13 was laminated on a 12 μm thick electrolytic copper foil so that the adhesive layer side was in contact with the copper foil, and then pressed using a vacuum laminator at a temperature of 160° C. and a pressure of 0.8 MPa for 2 minutes. The temperature was then increased from room temperature to 160° C., and the film was heat-treated at 160° C. for 2 hours to prepare a copper-clad laminate 16.

[Example 17]
An adhesive film 9 was laminated on a 12 μm thick rolled copper foil, and the polyimide film 1 side of the coverlay film 13 was laminated so that it was in contact with the adhesive film 9. Further, a 12 μm thick rolled copper foil was sequentially laminated on the adhesive layer side of the coverlay film 13, and the resultant was pressed using a vacuum laminator at a temperature of 160° C. and a pressure of 0.8 MPa for 2 minutes. The temperature was then raised from room temperature to 160° C., and the resultant was heat-treated at 160° C. for 2 hours to prepare a copper-clad laminate 17.

[Example 18]
Two sheets of resin-coated copper foil 11 were prepared, and laminated so that the adhesive layer sides of the two resin-coated copper foils 11 were in contact with each other with a polyimide film 3 (manufactured by DuPont, product name: Kapton 200-EN, thickness 50 μm, ε ₁ = 3.6, tan δ ₁ = 0.0084). The laminate was then pressed using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 5 minutes, and then heated from room temperature to 160°C and heat-treated at 160°C for 4 hours to prepare a copper-clad laminate 18.

[Example 19]
The adhesive composition 9 was applied to the polyimide side of a single-sided copper-clad laminate 1 (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX MC12-25-00UEM, length x width x thickness = 200 mm x 300 mm x 25 μm) and dried at 120°C for 30 minutes to prepare an adhesive-coated copper-clad laminate 19 having an adhesive layer thickness of 50 μm. The single-sided copper-clad laminate 1 was laminated so that the polyimide side surface of the single-sided copper-clad laminate 1 was in contact with the adhesive layer side of the adhesive-coated copper-clad laminate 19, and the laminate was pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes using a small precision press to prepare a copper-clad laminate 19.

[Example 20]
Two adhesive-coated copper-clad laminates 19 were laminated together with the adhesive layer sides in contact, and pressed together using a small precision press at a temperature of 160° C. and a pressure of 4.0 MPa for 120 minutes to prepare a copper-clad laminate 20 .

[Example 21]
An adhesive film 9 was laminated on the resin layer side of the single-sided copper-clad laminate 1, and then another adhesive film 9 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 9. The laminate was then pressed using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to prepare a copper-clad laminate 21.

[Example 22]
The adhesive composition 9 was applied to one side of a release PET film 1, dried at 120° C. for 15 minutes, and the adhesive layer was peeled off from the release PET film 1 to obtain an adhesive film 22 having a thickness of 15 μm.

An adhesive film 22 was laminated on the resin layer side of the single-sided copper-clad laminate 1, and then another adhesive film 22 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 22. The laminate was then pressed using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to prepare the copper-clad laminate 22.

[Example 23]
A double-sided copper-clad laminate 2 (product name: ESPANEX MB12-25-00UEG, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was prepared, and the copper foil on one side was subjected to circuit processing by etching to form a conductor circuit layer, thereby preparing a wiring board 2A.

The copper foil on one side of double-sided copper-clad laminate 2 was etched away to prepare copper-clad laminate 2B.

An adhesive film 22 was sandwiched between the conductive circuit layer side of the wiring board 2A and the resin layer side of the copper-clad laminate 2B, and in this laminated state, they were thermocompressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to prepare a multilayer circuit board 23.

[Example 24]
A double-sided copper-clad laminate 24 was prepared using an insulating substrate made of 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 ₁ = 3.40, tan δ ₁ = 0.0022) with 18 μm-thick electrolytic copper foil provided on both sides thereof. The copper foil on one side was subjected to circuit processing by etching to form a conductor circuit layer, thereby preparing a wiring board 24A.

The copper foil on one side of the double-sided copper-clad laminate 24 was etched away to prepare copper-clad laminate 24B.

The adhesive film 22 was sandwiched between the conductive circuit layer side of the wiring board 24A and the insulating base layer side of the copper-clad laminate 24B, and in this laminated state, they were thermocompressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to prepare the multilayer circuit board 24.

The above describes in detail the embodiment of the present invention for illustrative purposes, but the present invention is not limited to the above embodiment and various modifications are possible.

REFERENCE SIGNS LIST 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 (18)

A resin film containing polyimide as a resin component,
The polyimide contains a tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride component and a diamine residue derived from a diamine component, and contains 30 mol % or more of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine obtained by substituting two terminal carboxylic acid residues of a dimer acid with a primary aminomethyl group or an amino group , relative to the total diamine residues, and the dimer diamine composition contains the following components (a) to (c):
(a) a dimer diamine in which the two terminal carboxylic acid groups of a dimer acid are substituted with a primary aminomethyl group or an amino group;
(b) a monoamine compound obtained by substituting a 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 above-mentioned dimer diamine);
The component (a) is contained in an amount of 96% by area or more,
the weight average molecular weight (Mw) of the polyimide is within a range of 18,000 to 50,000, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is within a range of 1.5 to 2.5;
A resin film characterized in that, after being conditioned for 24 hours under constant temperature and humidity conditions (normal state) of 23°C and 50% RH, the dielectric loss tangent (Tan δ ₁ ) at 10 GHz and the dielectric loss tangent (Tan δ ₂ ) at 28 GHz, as measured by a split cylinder resonator (SCDR), are both less than 0.0025, and the ratio of Tan δ ₂ to Tan δ ₁ (Tan δ ₂ /Tan δ ₁ ) is 0.5 or more and 1.0 or less. 2. The resin film according to claim 1, wherein an absolute value of a difference between the Tan δ ₁ and the Tan δ ₂ is 0.0010 or less. The resin film according to claim 1 or 2, which has a dielectric loss tangent (Tan _δ3 ) at 40 GHz measured by a split cylinder resonator (SCDR) after being conditioned for 24 hours under constant temperature and humidity conditions (normal state) of 23°C and 50% RH, of less than 0.0025, and a ratio of Tan _δ3 to Tan _δ1 (Tan _δ3 /Tan _δ1 ) of 0.5 to 1.0 . The resin film according to claim 3, wherein an absolute value of a difference between the Tan δ ₁ and the Tan δ ₃ is less than 0.0011. 2. The resin film according to claim 1, wherein the content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms of the 6-membered aromatic ring derived from the dimer diamine composition) relative to the total content of all atoms in the polyimide is within a range of 20 to 30% by weight. The resin film according to any one of claims 1 to 5, which contains a crosslinked polyimide in which the polyimide is crosslinked by an imine bond. A laminate having a substrate and an adhesive layer laminated on at least one surface of the substrate,
A laminate comprising the resin film according to claim 1 , wherein the adhesive layer is made of the resin film according to claim 1 . 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 is made of the resin film according to claim 1 . A resin-coated copper foil in which an adhesive layer and a copper foil are laminated,
A resin-coated copper foil, characterized in that the adhesive layer is made of the resin film according to any one of claims 1 to 6. A metal-clad laminate having an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer,
7. A metal-clad laminate, wherein at least one of the insulating resin layers is made of the resin film according to claim 1. 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,
A metal-clad laminate, wherein the adhesive layer is made of the resin film according to claim 1 . 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 is disposed so as to abut against the first insulating resin layer and the second insulating resin layer, and is laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate,
A metal-clad laminate, wherein the adhesive layer is made of the resin film according to claim 1 . 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, the adhesive layer being made of a resin film according to any one of claims 1 to 6. A circuit board obtained by wiring the metal layer of the metal-clad laminate according to any one of claims 10 to 13. 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,
A circuit board, wherein the adhesive layer is made of the resin film according to claim 1 . 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,
A circuit board, wherein the adhesive layer is made of the resin film according to claim 1 . 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 each of the first base material and the second base material opposite to the adhesive layer,
A circuit board, wherein the adhesive layer is made of the resin film according to claim 1 . A multilayer circuit board comprising a laminate including a plurality of laminated insulating resin layers, and at least one wiring layer embedded in the laminate,
At least one of the plurality of insulating resin layers is formed of an adhesive layer having adhesiveness and covering the wiring layer,
7. A multilayer circuit board, comprising the adhesive layer comprising the resin film according to claim 1.

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