JP7630226B2 - Resin film, coverlay film, circuit board, resin-coated copper foil, metal-clad laminate, multi-layer circuit board, polyimide and adhesive resin composition - Google Patents

Description

The present invention relates to polyimides that are useful as adhesives for circuit boards such as printed wiring boards, and their uses.

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 mobile phones, as well as components such as cables and connectors.

In addition to the increased density mentioned above, the increasing performance of devices has also necessitated the need to accommodate higher frequencies for transmission signals. In the fields of information processing and communications, efforts are being made to increase transmission frequencies in order to transmit and process large volumes of information, and printed circuit board materials are being required to reduce transmission loss by making insulating layers thinner and improving the dielectric properties of the insulating layers. In the future, FPCs and adhesives that can handle higher frequencies will be required, and reducing transmission loss will be important.

As a technique for an adhesive layer mainly composed of polyimide, it has been proposed to apply a crosslinked polyimide resin obtained by reacting a polyimide made from a diamine compound derived from an aliphatic diamine such as dimer acid (dimer fatty acid) with an amino compound having at least two primary amino groups as functional groups to the adhesive layer of a coverlay film (for example, Patent Document 1). It has also been proposed to apply a resin composition using such a polyimide in combination with a thermosetting resin such as an epoxy resin and a crosslinking agent to a copper-clad laminate (for example, Patent Document 2). However, Patent Documents 1 and 2 do not take into consideration the influence of by-products other than the dimer diamine derived from the dimer acid contained in the raw material.

Dimer acids are dimerized fatty acids obtained by the Diels-Alder reaction using natural fatty acids such as soybean oil fatty acids, tall oil fatty acids, rapeseed oil fatty acids, and the like, as well as oleic acid, linoleic acid, linolenic acid, erucic acid, and the like, which are refined from these, as raw materials. It is known that polybasic acid compounds derived from dimer acids are obtained as compositions of the raw fatty acids and trimerized or higher fatty acids (for example, Patent Document 3).

JP 2013-1730 A JP 2017-119361 A JP 2017-137375 A

As a means of controlling the physical properties of resins whose main component is polyimide, it is important to control the molecular weight of the polyimide precursor, polyamic acid, or polyimide. However, when dimer diamine is used as a raw material, it is used in a state that contains by-products other than dimer diamine derived from dimer acid. Such by-products not only make it difficult to control the molecular weight of the polyimide, but also affect its dielectric properties over a wide frequency range and its humidity dependency.

The object of the present invention is to provide a resin film and polyimide having dielectric properties that are suppressed in dependence on humidity while improving the dielectric properties to enable electronic devices to handle higher frequencies.

The resin film of the present invention is a resin film containing a polyimide as a resin component, the polyimide being obtained by reacting a tetracarboxylic anhydride component with a diamine component, and the diamine component contains 40 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 component.
The resin film of the present invention satisfies the following configurations I and II.

I) Formula (i) below:
E ₁ =√ε ₁ ×Tanδ ₁ ...(i)
[wherein ε ₁ denotes the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR) after 24 hours of conditioning under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH, and Tan δ ₁ denotes the dielectric loss tangent at 10 GHz measured by a SPDR after 24 hours of conditioning under constant temperature and humidity conditions of 23° C. and 50% RH]
The _E1 value, which is an index of dielectric properties at 10 GHz after 24 hours of conditioning under constant temperature and humidity conditions of 23°C and 50% RH, calculated based on the above formula, is 0.010 or less.

II) Formula (ii) below:
E ₂ =√ε ₂ ×Tan δ ₂ ...(ii)
[where _ε2 represents the dielectric constant at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours, and Tan _δ2 represents the dielectric tangent at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours]
The _E2 value is an index of dielectric properties at 10 GHz after absorbing water at 23°C for 24 hours, calculated based on the following:
The ratio of the _E2 value to the _E1 value ( _E2 / _E1 ) is within the range of 3.0 to 1.0.

In addition, in the formulas (i) and (ii), "√ε ₁ " and "√ε ₂ " respectively mean the square roots of "ε ₁ " and "ε ₂ ".

The coverlay film of the present invention is a coverlay film in which an adhesive layer and a coverlay film material layer are laminated, and the adhesive layer is made of the above-mentioned resin film.

The circuit board of the present invention comprises a substrate, a wiring layer formed on the substrate, and the above-mentioned coverlay film that covers the wiring layer.

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 the above-mentioned resin film.

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

The multilayer circuit board of the present invention is a multilayer circuit board comprising a laminate including a plurality of laminated insulating resin layers, and one or more conductor circuit layers embedded inside the laminate. In the multilayer circuit board of the present invention, at least one of the plurality of insulating resin layers is formed of an adhesive layer that has adhesive properties and covers the conductor circuit layer, and the adhesive layer is made of the above-mentioned resin film.

The polyimide of the present invention is obtained by reacting a tetracarboxylic anhydride component with a diamine component, and the diamine component contains 40 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 component.
The polyimide of the present invention has the following components (a) to (c), in terms of area percentage of a chromatogram measured by gel permeation chromatography for the dimer diamine composition:
(a) dimer diamine;
(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 content of the component (c) in the composition is 2% or less.

The polyimide of the present invention may contain 50 mol % or more of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) based on the total amount of the tetracarboxylic anhydride component.

The adhesive resin composition of the present invention comprises the following components (A) and (B):
(A) the polyimide; and (B) an amino compound having at least two primary amino groups as functional groups.
Including,
The component (B) is contained so that the primary amino groups are contained in a total amount within a range of 0.004 mol to 1.5 mol per 1 mol of the ketone group of the BTDA residue derived from BTDA in the component (A).

The resin film and polyimide of the present invention have low humidity dependency of dielectric properties and excellent stability because the content of amine compounds other than dimer diamine in the dimer diamine composition is controlled. Therefore, the resin film and polyimide of the present invention can be particularly suitably used for circuit boards such as FPCs in electronic devices that require high-speed signal transmission.

The following describes an embodiment of the present invention.

<Resin film>
The resin film of the present embodiment is formed by forming a film with a resin component as a main component. In order to impart excellent high frequency characteristics and stability against humidity, the resin film of the present embodiment contains, as a resin component, a polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component containing 40 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 a primary aminomethyl group or an amino group, based on the total diamine component. The resin film of the present embodiment may contain, for example, a filler as an optional component other than the resin component.

(Dielectric Properties)
The resin film of the present embodiment is represented by the following formula (i):
E ₁ =√ε ₁ ×Tanδ ₁ ...(i)
[wherein ε ₁ denotes the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR) after 24 hours of conditioning under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH, and Tan δ ₁ denotes the dielectric loss tangent at 10 GHz measured by a SPDR after 24 hours of conditioning under constant temperature and humidity conditions of 23° C. and 50% RH]
The _E1 value, which is an index showing the dielectric properties at 10 GHz after 24 hours of humidity conditioning under constant temperature and humidity conditions of 23° C. and 50% RH, calculated based on the above, is 0.010 or less, preferably 0.009 or less, and more preferably 0.008 or less. If the _E1 value exceeds the above upper limit, for example, when used in a circuit board such as an FPC, problems such as loss of electrical signals are likely to occur in the transmission path of high-frequency signals.

(Dielectric constant)
In order to ensure impedance matching when used in a circuit board such as an FPC and to reduce loss of an electric signal, the resin film of the present embodiment has a dielectric constant (ε ₁ ) at 10 GHz after 24 hours of humidity conditioning under constant temperature and humidity conditions of 23° C. and 50% RH of preferably 3.2 or less, more preferably 3.0 or less. If the dielectric constant exceeds 3.2, problems such as loss of an electric signal are likely to occur on the transmission path of a high-frequency signal when used in a circuit board such as an FPC.

(Dielectric tangent)
In addition, in order to reduce loss of an electric signal when the resin film of the present embodiment is used in a circuit board such as an FPC, the dielectric loss tangent (Tan δ ₁ ) at 10 GHz after 24 hours of humidity conditioning under constant temperature and humidity conditions of 23° C. and 50% RH is preferably less than 0.005, more preferably 0.004 or less. If the dielectric loss tangent is 0.005 or more, problems such as loss of an electric signal are likely to occur on the transmission path of a high-frequency signal when the resin film is used in a circuit board such as an FPC.

(Moisture absorption dependency)
In order to reduce loss of electrical signals and ensure impedance matching in both dry and wet conditions when used in a circuit board such as an FPC, the resin film of the present embodiment satisfies the following formula (ii):
E ₂ =√ε ₂ ×Tan δ ₂ ...(ii)
[where _ε2 represents the dielectric constant at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours, and Tan _δ2 represents the dielectric tangent at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours]
In the _E2 value, which is an index showing the dielectric properties at 10 GHz after absorbing water at 23°C for 24 hours and is calculated based on the above, the ratio of the _E2 value to the _E1 value calculated based on the above formula (i) ( _E2 / _E1 ) is in the range of 3.0 to 1.0, preferably in the range of 2.5 to 1.0, and more preferably in the range of 2.2 to 1.0. If _E2 / _E1 exceeds the above upper limit, when used in a circuit board such as an FPC, the dielectric constant and dielectric loss tangent will increase when wet, and problems such as loss of electrical signals will easily occur on the transmission path of high-frequency signals.

(Moisture absorption rate)
In addition, in order to reduce the influence of humidity when the resin film of the present embodiment is used for a circuit board such as an FPC, the moisture absorption rate of the resin film is preferably 0.5% by mass or less, more preferably less than 0.3% by mass. Here, the "moisture absorption rate" means the moisture absorption rate after 24 hours or more have passed under constant temperature and humidity conditions of 23°C and 50% RH (the same meaning is used in this specification). If the moisture absorption rate of the resin film exceeds 0.5% by mass, it becomes susceptible to the influence of humidity when used for a circuit board such as an FPC, and inconveniences such as fluctuations in the transmission speed of high-frequency signals are likely to occur. In other words, if the moisture absorption rate of the resin film exceeds the above range, it becomes easy to absorb water with a high dielectric constant, which leads to an increase in the dielectric constant and dielectric loss tangent, and inconveniences such as loss of electrical signals on the transmission path of high-frequency signals are likely to occur.

(Storage Modulus)
The resin film of the present embodiment may have a temperature range in the range of 40 to 250°C in which the storage modulus decreases steeply with increasing temperature. It is considered that such a characteristic of the resin film is a factor in, for example, alleviating internal stress during thermocompression bonding and maintaining dimensional stability after circuit processing. The resin film preferably has a storage modulus of 5 x 10 ⁷ [Pa] or less at the upper limit temperature of the temperature range. By setting the storage modulus at such a range, even if it is the upper limit of the above temperature range, thermocompression bonding at 250°C or less is possible, and adhesion is ensured and dimensional change after circuit processing can be suppressed.
In addition, since the resin film of the present embodiment has high thermal expansion but low elasticity, even if the CTE exceeds 30 ppm/K, the internal stress generated during lamination can be alleviated.

(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.

(Thickness)
The thickness of the resin film of the present embodiment is preferably, for example, 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.

<Polyimide>
The polyimide of the present embodiment is obtained by imidizing a precursor polyamic acid obtained by reacting a tetracarboxylic anhydride component with a diamine component containing 40 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 component.

(Tetracarboxylic acid anhydride component)
The tetracarboxylic anhydride used in the polyimide of the present embodiment may include any tetracarboxylic anhydride generally used in thermoplastic polyimides without any particular limitations, but preferably contains tetracarboxylic anhydrides represented by the following general formula (1) in a total amount of 90 mol % or more based on the total tetracarboxylic anhydride components. By containing tetracarboxylic anhydrides represented by the following general formula (1) in a total amount of 90 mol % or more based on the total tetracarboxylic anhydride components, it is preferable that the polyimide is easily compatible in terms of flexibility and heat resistance. If the total amount of tetracarboxylic anhydrides represented by the following general formula (1) is less than 90 mol %, the solvent solubility of the polyimide tends to decrease.

In general formula (1), X represents a single bond or a divalent group selected from the following formulas:

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.

Incidentally, the term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed, but in the present invention, it refers to a polyimide whose storage modulus at 30° C. is 1.0×10 ⁸ Pa or more and whose storage modulus at 300° C. is less than 3.0×10 ⁷ Pa, as measured using a dynamic viscoelasticity measuring apparatus (DMA). Furthermore, the term "non-thermoplastic polyimide" generally refers to a polyimide that does not soften or exhibit adhesiveness even when heated, but in the present invention, it refers to a polyimide whose storage modulus at 30° C. is 1.0×10 ⁹ Pa or more and whose storage modulus at 300° C. is 3.0×10 ⁸ Pa or more, as measured using a dynamic viscoelasticity measuring apparatus (DMA).

Examples of tetracarboxylic acid anhydrides 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, when 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) is used, the adhesion of the polyimide can be improved, and the ketone group present in the molecular skeleton may react with the amino group of the (B) component described below to form a C=N bond, which is likely to produce the effect of improving heat resistance. From this perspective, it is preferable to contain BTDA in an amount of preferably 50 mol % or more, more preferably 60 mol % or more, of the total tetracarboxylic anhydride components.

The polyimide of the present embodiment may contain tetracarboxylic acid residues derived from acid anhydrides other than the tetracarboxylic acid anhydride represented by the above general formula (1) 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, 2,2-biphenyltetracarboxylic dianhydride, 2,3',3,4''- ...3',3,4''-, 2,3',3,4''-, 2,3',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,4''-, 2,3',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3',3,4''-, 2,3',3,4''-, 2,3',3, 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, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic 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 Examples of the tetracarboxylic acid residues include those derived from aromatic tetracarboxylic acid dianhydrides such as 2,3,6,7-(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, cyclopentane-1,2,3,4-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 ethylene glycol bisanhydrotrimellitate.

(Diamine component)
The polyimide of the present embodiment contains 40 mol % or more, more preferably 60 mol % or more, of the dimer diamine composition based on the total diamine components. By containing the dimer diamine composition in the above amount, the dielectric properties of the polyimide can be improved, and the thermocompression bonding properties can be improved by lowering the glass transition temperature (lowering Tg) of the polyimide, and the internal stress can be alleviated by lowering the elastic modulus.

(Dimer diamine composition)
The dimer diamine composition contains the following component (a) with the amounts of components (b) and (c) being 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.

It is advisable to use a dimer diamine composition in which the dimer diamine content of component (a) has been increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more, by a purification method such as molecular distillation. By increasing the dimer diamine content of component (a) to 96% by weight or more, it is possible to suppress the broadening of the molecular weight distribution of the polyimide. If technically possible, it is best that all of the dimer diamine composition (100% by weight) is composed of component (a) dimer diamine.

(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.

The above dimer diamine composition is quantified for 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 is calculated based on this.

In addition, the dimer diamine composition used in the present invention 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, it is possible to suppress the broadening of the molecular weight distribution of the polyimide.

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 weight-average molecular weight of the polyimide is preferably within the range of 10,000 to 200,000, for example. If the weight-average molecular weight of the polyimide is within this range, it is easy to control the weight-average molecular weight of the polyimide. For example, when applied as an adhesive for FPC, the weight-average molecular weight of the polyimide is more preferably within the range of 20,000 to 150,000, and even more preferably within the range of 40,000 to 150,000. If the weight-average molecular weight of the polyimide is less than 20,000, the flow resistance tends to deteriorate. On the other hand, if the weight-average molecular weight of the polyimide exceeds 150,000, the viscosity increases excessively and the polyimide becomes insoluble in a solvent, and defects such as uneven thickness of the adhesive layer and streaks tend to occur during the coating process.

The dimer diamine composition used in the present invention is preferably purified in order to reduce components other than dimer diamine. The purification method is not particularly limited, but known methods such as distillation and precipitation purification are suitable. The dimer diamine composition before purification is commercially available, for example, PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan.

Diamine compounds other than dimer diamine used in polyimides include aromatic diamine compounds and aliphatic diamine compounds. Specific examples of these include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3 -aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3 ,3'-Dimethoxybenzidine, 3,3''-Diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t -butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, 1,3-bis(3-aminophenoxy)benzene and other diamine compounds.

Polyimide can be produced by reacting the above tetracarboxylic anhydride component and diamine component in a solvent to produce polyamic acid, which is then heated to close the ring. For example, the tetracarboxylic 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, preferably 10 to 40% by weight, in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, 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 cps to 100,000 cps. 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 the polyimide of this embodiment, the dielectric properties, thermal expansion coefficient, tensile modulus, glass transition temperature, etc. can be controlled by selecting the type of the tetracarboxylic anhydride component and diamine component, and the molar ratio of each when two or more types of tetracarboxylic anhydride components or diamine components are used. In addition, in the polyimide of this embodiment, when the polyimide has multiple structural units of polyimide, they may exist as blocks or randomly, but it is preferable that they exist randomly.

The imide group concentration of the polyimide of this embodiment is preferably 22% by weight or less, and 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 polyimide of the present embodiment 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).

<Adhesive resin composition>
The adhesive resin composition of the present embodiment contains, as component (A), the above-mentioned polyimide containing BTDA residues derived from BTDA in an amount of preferably 50 mol % or more, more preferably 60 mol % or more, based on all tetracarboxylic acid residues, and, as component (B), an amino compound having at least two primary amino groups as functional groups. In the present invention, the "BTDA residue" means a tetravalent group derived from BTDA.

(Amino Compounds)
In the adhesive resin composition of the present embodiment, the amino compound having at least two primary amino groups as functional groups of the above component (B) can be exemplified by dihydrazide compounds, aromatic diamines, aliphatic amines, etc. 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 the shortening of the curing time. Examples of the 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 dihydrazide, and the like. Preferred are dihydrazide compounds such as cholic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoedioic acid dihydrazide, 4,4-bisbenzene dihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridine diacid dihydrazide, itaconic acid dihydrazide, etc. 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).

From the viewpoint of making the mesh-like structure formed by the crosslinking with the amino compound of component (B) denser, the amino compound of component (B) used in the present invention preferably has a molecular weight (weight average molecular weight when the 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, amino compounds having a molecular weight of 100 to 1,000 are particularly preferred. If the molecular weight of the amino compound is less than 90, only one amino group of the amino compound will form a C=N bond with a ketone group of the polyimide resin, 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 of the BTDA residue with the amino compound, the amino compound is added to a resin solution containing component (A) to cause a condensation reaction between the ketone group in the polyimide and the primary amino group of the amino compound. This condensation reaction hardens the resin solution to become a cured product. In this case, the amount of the amino compound added is such that the total number of primary amino groups per mole of ketone group is 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. If the amount of the amino compound added is less than 0.004 moles of primary amino groups per mole of ketone group, crosslinking by the amino compound is insufficient, and heat resistance after curing tends to be difficult to develop, and if the amount of the amino compound added exceeds 1.5 moles, the unreacted amino compound acts as a thermoplasticizer, tending to reduce the heat resistance of the adhesive layer.

The conditions of the condensation reaction for forming the crosslinks are not particularly limited as long as the ketone group in the polyimide of component (A) and the primary amino group in the amino compound of component (B) react to form an imine bond (C=N bond). The temperature of the heat condensation is preferably in the range of, for example, 120 to 220°C, more preferably in the range of 140 to 200°C, for the purpose of releasing water generated by the 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 polyimide of component (A). 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 Corporation) 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 about 1670 cm ^-1 and the appearance of the absorption peak derived from the imine group at about 1635 cm ^-1 .

The thermal condensation of the ketone group of the polyimide (A) and the primary amino group of the amino compound (B) can be carried out, for example, as follows:
(1) A method in which, following synthesis (imidization) of a polyimide (A), an amino compound (B) 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 synthesis (imidization) of a polyimide of component (A), the remaining amino compound that is not involved in imidization or amidation is heated together with the polyimide as component (B), or
(3) This can be achieved by a method in which the polyimide composition of component (A) to which the amino compound of component (B) has been added is processed into a predetermined shape (for example, after being applied to a substrate or formed into a film), and then heated.

The formation of imine bonds has been described as a method for forming a crosslinked structure to impart heat resistance to the polyimide of component (A), but this is not limiting. As a method for curing the polyimide of component (A), it is also possible to blend and cure it with, for example, epoxy resins, epoxy resin curing agents, active ester compounds, benzoxazine resins, cyanate ester resins, maleimides, activated ester resins, resins having a phenyl ether skeleton or a styrene skeleton with an unsaturated bond, etc. Here, the active ester compound functions as a curing agent for the epoxy resin and has an active ester.

In addition to the polyimide (A) and amino compound (B), the adhesive resin composition of the present embodiment preferably contains an inorganic filler (C) as an optional component. If necessary, other optional components such as plasticizers, other resin components such as epoxy resins, fluororesins, and olefin resins, curing accelerators, coupling agents, fillers, pigments, solvents, and flame retardants can be appropriately blended. However, some plasticizers contain a large number of polar groups, which may promote the diffusion of copper from the copper wiring, so it is preferable to avoid using plasticizers as much as possible.

When an adhesive layer is formed using the adhesive resin composition of this embodiment, it has excellent flexibility and thermoplasticity, and has favorable properties as an adhesive for coverlay films that protect wiring parts of FPCs, rigid-flex circuit boards, etc.

<Coverlay film>
The coverlay film of the present embodiment is composed of an adhesive layer made of the above-mentioned resin film or the above-mentioned adhesive resin composition, and a coverlay film material layer. The coverlay film material is not particularly limited, but for example, polyimide resin films such as polyimide resins, polyetherimide resins, polyamideimide resins, polyamide resin films, polyester resin films, etc. can be used. Among these, it is preferable to use a polyimide resin film having excellent heat resistance. The thickness of the coverlay film material layer is not particularly limited, but is preferably, for example, 5 μm or more and 100 μm or less. The thickness of the adhesive layer is not particularly limited, but is preferably, for example, 10 μm or more and 50 μm or less.

The coverlay film material may also contain black pigments to effectively exhibit light-blocking properties, concealment properties, design properties, etc., and may also contain optional components such as matte pigments to suppress surface gloss, as long as the effect of improving the dielectric properties is not impaired.

The coverlay film of the present embodiment can be produced, for example, by the method exemplified below.
As a first method, an adhesive resin composition that will become the adhesive layer is applied in a solution state (e.g., a varnish-like state containing a solvent) to one side of a film material for a coverlay, and then the resulting film is thermocompressed at a temperature of, for example, 60 to 220°C to form a coverlay film having a film material layer for a coverlay and an adhesive layer.

As a second method, the adhesive resin composition for the adhesive layer can be applied in a solution state (for example, in a varnish state containing a solvent) 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, and this resin film can be thermocompressed to a film material for the coverlay at a temperature of, for example, 60 to 220°C to form the coverlay film of this embodiment. Note that the adhesive layer can also be formed by applying the adhesive resin composition in a solution state onto any substrate, for example, by screen printing to form a coating film, and drying this at a temperature of, for example, 80 to 180°C to form a film for use.

<Circuit board>
The circuit board of the present embodiment includes a base material, a wiring layer formed on the base material, and a coverlay film that covers the wiring layer. The base material of the circuit board is not particularly limited, but in the case of an FPC, it is preferable to use a material similar to the above-mentioned coverlay film material, and it is preferable to use a base material made of a polyimide resin.

<Resin-coated copper foil>
The resin-coated copper foil of the present embodiment comprises an adhesive layer made of the above-mentioned resin film or the above-mentioned adhesive resin composition, and a copper foil.

The thickness of the adhesive layer is preferably, for example, in the range of 0.1 to 125 μm, and more preferably in the range of 0.3 to 100 μm. If the thickness of the adhesive layer 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 exceeds the above upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the viewpoint of achieving a low dielectric constant and a low dielectric loss tangent, the thickness of the adhesive layer is preferably 3 μm or more.

In the resin-coated copper foil of this embodiment, the material of the 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 of this embodiment may be prepared, for example, by preparing a resin film, sputtering a metal to form a seed layer, and then forming a copper layer, for example, by copper plating, or by laminating it with copper foil by a method such as thermocompression bonding.

Furthermore, the resin-coated copper foil of this embodiment may be prepared by casting a coating liquid for forming a resin layer on the copper foil, drying it to form a coating film, and then heat treating it.

<Metal-clad laminate>
The metal-clad laminate of the present embodiment includes an insulating resin layer, an adhesive layer made of the resin film or the adhesive resin composition laminated on at least one side of the insulating resin layer, and a metal layer laminated on the insulating resin layer via the adhesive layer, and is a so-called three-layer metal-clad laminate. The three-layer metal-clad laminate may have an adhesive layer on one or both sides of the insulating resin layer, and a metal layer on one or both sides of the insulating resin layer via the adhesive layer. In other words, the metal-clad laminate of the present embodiment 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 processing the wiring circuit by etching the metal layer of the metal-clad laminate of the present embodiment.

The insulating resin layer 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 it is preferable that it is made of polyimide. The polyimide layer constituting the insulating resin layer may be a single layer or multiple layers, but it is preferable that it includes a non-thermoplastic polyimide layer.

The thickness of the insulating resin layer is preferably in the range of 1 to 125 μm, and more preferably in the range of 5 to 100 μm. If the thickness of the insulating resin layer is less than the lower limit, problems such as insufficient electrical insulation may occur. On the other hand, if the thickness of the insulating resin layer exceeds the upper limit, problems such as the metal-clad laminate being more likely to warp may occur. In addition, the ratio of the thickness of the insulating resin layer to the thickness of the adhesive layer (thickness of the insulating resin layer/thickness of the adhesive layer) is preferably in the range of 0.5 to 2.0. By setting such a ratio, the warping of the metal-clad laminate can be suppressed.

The insulating resin layer 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 may be used alone or in combination of two or more.

The thickness of the adhesive layer 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 of this embodiment, if the thickness of the adhesive layer 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 exceeds the above-mentioned upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the viewpoint of reducing the dielectric constant and dielectric loss tangent of the entire insulating layer, which is a laminate of an insulating resin layer and an adhesive layer, the thickness of the adhesive layer is preferably 3 μm or more.

The material of the metal layer in the metal-clad laminate of this embodiment 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 thickness of the metal layer is not particularly limited, but for example, when copper foil is used as the metal layer, 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 copper 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.

When copper foil is used as the metal layer, it is preferable that the copper foil comprises a base copper foil and an anti-rust treatment layer formed on the surface of the base copper foil on the side on which the adhesive layer (or insulating resin layer) is formed. In addition to the above-mentioned anti-rust treatment, the surface of the copper foil may be subjected to a surface treatment, for example, with siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc., in order to improve adhesive strength.

<Multilayer circuit board>
The multilayer circuit board of the present embodiment comprises a laminate including a plurality of stacked insulating resin layers, and one or more conductor circuit layers embedded inside the laminate, at least one of the plurality of insulating resin layers being formed of an adhesive layer having adhesive properties and covering the conductor circuit layer, the adhesive layer being made of the above-mentioned resin film or the above-mentioned adhesive resin composition.

The multilayer circuit board of this embodiment has at least two insulating resin layers and at least two conductor circuit layers, and at least one of the conductor circuit layers is a conductor circuit layer covered with an adhesive layer. The adhesive layer covering the conductor circuit layer may partially cover the surface of the conductor circuit layer, or may cover the entire surface of the conductor circuit layer. In addition, the multilayer circuit board of this embodiment may optionally have a conductor circuit layer exposed on the surface of the multilayer circuit board. It may also have an interlayer connection electrode (via electrode) in contact with the conductor circuit layer.

The conductor circuit layer is formed by forming a conductor circuit in a predetermined pattern on one or both sides of an insulating resin layer. The conductor circuit may be formed by patterning the surface of the insulating resin layer, or by damascene (embedded) patterning.

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

[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.

[Dielectric property evaluation]
Using a vector network analyzer (manufactured by Agilent, product name: Vector Network Analyzer E8363C) and an SPDR resonator, the resin sheet (resin sheet after curing) was left for 24 hours under conditions of temperature: 23°C and humidity: 50%, and then the dielectric constant (ε ₁ ) and dielectric loss tangent (Tan δ ₁ ) at a frequency of 10 GHz were measured. E ₁ , which is an index showing the dielectric properties of the resin laminate, was calculated based on the above formula (i). In addition, after absorbing water at 23°C for 24 hours, the dielectric constant (ε ₂ ) and dielectric loss tangent (Tan δ ₂ ) at a frequency of 10 GHz of the resin sheet (resin sheet after curing) were measured. E ₂ , which is an index showing the dielectric properties of the resin laminate, was calculated based on the above formula (ii).

[Measurement of moisture absorption rate]
Two test pieces (4 cm wide × 25 cm long) of the resin sheet (resin sheet after curing) were prepared and dried for 1 hour at 80° C. Immediately after drying, they were placed in a constant temperature and humidity chamber at 23° C./50% RH and left to stand for 24 hours or more, and the weight change before and after was calculated according to the following formula.
Moisture absorption rate (weight%) = [(weight after moisture absorption - weight after drying) / weight after drying] x 100

[Glass transition temperature (Tg) and storage modulus]
The glass transition temperature (Tg) and storage modulus were measured using a 5 mm x 20 mm resin sheet (cured resin sheet) at a heating rate of 4°C/min from 30°C to 400°C and a frequency of 11 Hz using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, product name: E4000F). The temperature at which the change in modulus (tan δ) was maximum was taken as the glass transition temperature.

[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 resin sheet (resin sheet after curing) using a tension tester (Tensilon manufactured by Orientec). A tensile test was performed at 50 mm/min using this test piece to determine the tensile modulus at 25°C.

[Warpage evaluation method]
The evaluation of warpage was carried out by the following method. A polyimide adhesive was applied to a 25 μm thick Kapton film or a 12 μm thick copper foil so that the thickness after drying was 25 μm. In this state, the Kapton film and the copper foil were placed on the bottom, and the average height of the warpage at the four corners of the film was measured. A value of 5 mm or less was rated as "good", and a value of more than 5 mm was rated as "no good".

The abbreviations used in the examples represent the following compounds.
BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride (manufactured by Evonik, trade name: BTDA Ultra Pure)
BisDA: 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (manufactured by SABIC Innovative Plastics Japan, LLC, product name: BisDA-1000)
BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride DDA1: product name: PRIAMINE 1075 manufactured by Croda Japan Co., Ltd., distilled and purified (component a: 98.2% by weight, component b: 0%, component c: 1.9%, amine value: 206 mg KOH/g)
DDA2: product name: PRIAMINE 1075 manufactured by Croda Japan Co., Ltd., distilled and purified (component a: 99.2% by weight, component b: 0%, component c: 0.8%, amine value: 210 mg KOH/g)
N-12: Dodecanedioic acid dihydrazide NMP: N-methyl-2-pyrrolidone APB: 1,3-bis(3-aminophenoxy)benzene BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane In the above DDA1 and DDA2, the "%" of component b and component c means the area percentage of the chromatogram in GPC measurement. The molecular weights of DDA1 and DDA2 were calculated by the following formula (1).
Molecular weight = 56.1 × 2 × 1000 / amine value (1)

[Example 1]
A polyamic acid solution was prepared by charging 55.51 g of BTDA (0.1721 mol), 94.49 g of DDA1 (0.1735 mol), 210 g of NMP, and 140 g of xylene into a 1000 ml separable flask and thoroughly mixing for 1 hour at 40° C. This polyamic acid solution was heated to 190° C. and heated and stirred for 10 hours, and 125 g of xylene was added to complete the imidization, preparing polyimide solution 1 (solid content: 30 wt %, weight average molecular weight: 82,900).

[Examples 2 to 12]
Polyimide solutions 2 to 12 were prepared in the same manner as in Example 1, except that the raw material compositions shown in Table 1 were used.

As shown in Table 1, in Examples 1 to 12, polyimides with weight average molecular weights in the range of 40,000 to 150,000 were obtained.

[Example 13]
2.7 g of N-12 (0.0105 mol; equivalent to 0.35 mol of primary amino groups per 1 mol of ketone groups of BTDA) was mixed with 169.49 g (50 g as solid content) of the polyimide solution 1 obtained in Example 1, and 6.0 g of NMP was added to dilute the mixture, followed by stirring for another 1 hour to obtain an adhesive resin composition 1.

The obtained adhesive resin composition 1 was applied to one side of a release PET film (Higashiyama Film Co., Ltd., product name: HY-S05, length x width x thickness = 200 mm x 300 mm x 25 μm), dried at 80°C for 15 minutes, and the adhesive layer was peeled off from the release PET film to prepare a resin film 1 with a thickness of 25 μm. This resin film 1 was heated in an oven at a temperature of 160°C for 2 hours to obtain an evaluation sample 1. The results of the evaluation of various characteristics are shown in Table 2.

[Examples 14 to 24]
Adhesive resin compositions 2 to 12 and resin films 2 to 12 were prepared in the same manner as in Example 13, except that polyimide solutions 2 to 12 were used instead of polyimide solution 1, and then evaluation samples 2 to 12 were obtained. The results of the evaluation of various characteristics are shown in Table 2.

[Example 25]
The adhesive resin composition 1 obtained in Example 13 was applied to one side of a polyimide film (manufactured by DuPont, product name: Kapton 100EN-S, ε1 = 3.5, tan δ1 = 0.012, length × width × thickness = 200 mm × 300 mm × 25 μm) and dried at 80° C. for 15 minutes to obtain a coverlay film 1 having an adhesive layer thickness of 25 μm. The warpage state of the obtained coverlay film was "good".

[Examples 26 to 36]
Coverlay films 2 to 12 were produced in the same manner as in Example 25, except that adhesive resin compositions 2 to 12 were used instead of adhesive resin composition 1. The warpage state of the obtained coverlay films 2 to 12 was all "good".

[Example 37]
The adhesive resin composition 1 obtained in Example 13 was applied to one side of an electrolytic copper foil having a thickness of 12 μm and dried at 80° C. for 15 minutes to obtain a resin-coated copper foil 1 having an adhesive layer thickness of 25 μm. The warpage state of the resin-coated copper foil 1 obtained was “good”.

[Example 38]
The adhesive resin composition 4 obtained in Example 16 was applied to one side of an electrolytic copper foil having a thickness of 12 μm and dried at 80° C. for 30 minutes to obtain a resin-coated copper foil 2 having an adhesive layer thickness of 50 μm.

[Example 39]
An adhesive resin composition 4 was applied onto the resin surface of the resin-coated copper foil 2 obtained in Example 38, and dried at 80° C. for 30 minutes to obtain a resin-coated copper foil 3 having an adhesive layer thickness of 100 μm in total.

[Example 40]
The adhesive resin composition 1 obtained in Example 13 was applied to one side of a release PET film (Higashiyama Film Co., Ltd., product name: HY-S05, length x width x thickness = 200 mm x 300 mm x 25 μm), dried at 80 ° C. for 30 minutes, and the adhesive layer was peeled off from the release PET film to obtain a resin film 1' having a thickness of 50 μm. On an electrolytic copper foil having a thickness of 12 μm, a resin film 1', a polyimide film (manufactured by DuPont, product name: Kapton 100-EN, thickness 25 μm, ε1 = 3.6, tan δ1 = 0.084), a resin film 1', and an electrolytic copper foil having a thickness of 12 μm were sequentially laminated, and the laminate was pressed at a temperature of 160 ° C. and a pressure of 0.8 MPa for 2 minutes using a vacuum laminator, and then heat-treated at 160 ° C. for 4 hours to obtain a copper-clad laminate 1.

[Example 41]
The adhesive resin composition 1 obtained in Example 13 was applied to one side of a polyimide film (manufactured by DuPont, product name: Kapton 50EN, ε1 = 3.6, tan δ1 = 0.086, length x width x thickness = 200 mm x 300 mm x 12 μm), and dried at 80 ° C for 15 minutes to obtain a coverlay film 1' with an adhesive layer thickness of 25 μm. The coverlay film 1' was laminated on an electrolytic copper foil with a thickness of 12 μm so that the adhesive resin composition 1 side of the coverlay film 1' was in contact with the copper foil, and the film was pressed using a vacuum laminator at a temperature of 160 ° C and a pressure of 0.8 MPa for 2 minutes, and then heat-treated at 160 ° C for 2 hours to obtain a copper-clad laminate 2.

[Example 42]
On a rolled copper foil having a thickness of 12 μm, the resin film 1 (thickness: 25 μm) obtained in Example 13 and the coverlay film 1' obtained in Example 41 were laminated so that the polyimide film side was in contact with the resin film 1, and then the resin film 1 (thickness: 25 μm) and a rolled copper foil having a thickness of 12 μm were laminated in that order, 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, and then heat-treated at 160° C. for 2 hours to obtain a copper-clad laminate 3.

[Example 43]
Two sheets of the resin-coated copper foil 3 obtained in Example 39 were prepared, and a polyimide film (manufactured by DuPont, product name: Kapton 200-EN, thickness 50 μm, ε1 = 3.6, tan δ1 = 0.084) was laminated on the adhesive resin composition 4 side of one of the resin-coated copper foils 3, and another sheet of resin-coated copper foil 3 was laminated so that the adhesive resin composition 4 side was in contact with the polyimide film, and the laminate was pressed using a vacuum laminator at a temperature of 160°C and a pressure of 0.8 MPa for 5 minutes, and then heat-treated at 160°C for 4 hours to obtain a copper-clad laminate 4.

[Example 44]
The adhesive resin composition 1 obtained in Example 13 was applied to the polyimide side of a single-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ, length x width x thickness = 200 mm x 300 mm x 25 μm) and dried at 80 ° C. for 30 minutes to obtain an adhesive-coated copper-clad laminate 1 having an adhesive layer thickness of 50 μm. The single-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ) was laminated so that the polyimide of the single-sided copper-clad laminate was in contact with the adhesive resin composition 1 side of the adhesive-coated copper-clad laminate 1, 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 obtain a copper-clad laminate 5.

[Example 45]
The adhesive-coated copper-clad laminates 1 obtained in Example 44 were laminated together with the adhesive resin composition 1 sides in contact, and then pressed using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain copper-clad laminate 6.

[Example 46]
The resin film 4 (thickness 25 μm) obtained in Example 16 was laminated on the polyimide side of a single-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ), and further laminated so that the polyimide side of a single-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ) was in contact with the resin film 4, and the laminate was pressed using a small precision press at a temperature of 160° C. and a pressure of 4.0 MPa for 120 minutes to obtain a copper-clad laminate 7.

[Example 47]
The adhesive resin composition 1 obtained in Example 13 was applied to one side of a release PET film (Higashiyama Film Co., Ltd., product name: HY-S05, length x width x thickness = 200 mm x 300 mm x 25 μm), dried at 80 ° C. for 15 minutes, and the adhesive layer was peeled off from the release PET film to obtain a resin film 1 ″ having a thickness of 15 μm. The resin film 1 ″ was laminated on the polyimide side of a single-sided copper-clad laminate (Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ), and further laminated so that the polyimide side of the single-sided copper-clad laminate (Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FC12-25-00UEJ) was in contact with the resin film 1 ″, and pressed using a small precision press at a temperature of 160 ° C. and a pressure of 4.0 MPa for 120 minutes to obtain a copper-clad laminate 8.

[Example 48]
A double-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FB12-25-00UEY) was prepared, and the copper foil on one side of the laminate was subjected to circuit processing by etching to form a conductor circuit layer, thereby preparing a wiring board 1. In addition, the copper foil on one side of the double-sided copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ESPANEX FB12-25-00UEY) was removed by etching to prepare a copper-clad laminate 9. The resin film 1 obtained in Example 13 was sandwiched between the surface of the conductor circuit layer side of the wiring board 1 and the surface of the insulating base material layer side of the copper-clad laminate 9, and in the laminated state, the two were thermocompressed at a temperature and pressure of 4.0 MPa for 120 minutes to prepare a multilayer circuit board 1.

[Example 49]
A copper-clad laminate 10 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., dielectric constant: 3.40, dielectric loss tangent: 0.0022) and copper foil (electrolytic copper foil, thickness: 9 μm, surface roughness Rz: 2.0 μm) on both sides thereof, and a circuit was formed on the copper foil on one side by etching to prepare a wiring board 2 having a conductor circuit layer. In addition, the copper foil on one side of the copper-clad laminate 10 was removed by etching to prepare a copper-clad laminate 10'. The resin film 1 obtained in Example 13 was sandwiched between the surface of the conductor circuit layer side of the wiring board 2 and the surface of the insulating substrate layer side of the copper-clad laminate 10', and in the laminated state, the surfaces were thermocompressed at a temperature and pressure of 4.0 MPa for 120 minutes to prepare a multilayer circuit board 2.

[Example 50]
A release PET film (manufactured by Higashiyama Film Co., Ltd., product name: HY-S05) was laminated on the adhesive composition 1 side of the coverlay film 1' obtained in Example 41 so as to be in contact with it, and a vacuum laminator was used to press the film at a temperature of 160 ° C. and a pressure of 0.8 MPa for 2 minutes. Thereafter, the adhesive resin composition 1 obtained in Example 13 was applied to the polyimide film side of the coverlay film 1' so as to have a thickness of 25 μm after drying, and dried at 80 ° C. for 15 minutes. Further, a release PET film (manufactured by Higashiyama Film Co., Ltd., product name: HY-S05) was laminated on the dried adhesive composition 1 side so as to be in contact with it, and a vacuum laminator was used to press the film at a temperature of 160 ° C. and a pressure of 0.8 MPa for 2 minutes, to prepare a polyimide adhesive laminate 1 having adhesive layers on both sides of the polyimide film.

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.

Claims (9)

A resin film containing polyimide as a resin component,
the polyimide is obtained by reacting a tetracarboxylic anhydride component with a diamine component, and the diamine component contains 40 mol % or more of a dimer diamine composition containing 98.2 wt % or more of a dimer diamine composition as a main component, the dimer diamine being obtained by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups, relative to the total diamine component;
The dimer diamine composition is measured by gel permeation chromatography, and the area percentage of the chromatogram is determined to be the following components (a) to (c):
(a) dimer diamine;
(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 content of the component (b) is 0% and the content of the component (c) is 2% or less,
the ratio (b/c) of the area percentages of the chromatograms of the component (b) and the component (c) is less than 1;
a molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is 0.97 or more and 1.008 or less,
Configurations I and II below:
I) Formula (i) below:
E ₁ =√ε ₁ ×Tanδ ₁ ...(i)
[wherein ε ₁ denotes the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR) after 24 hours of conditioning under constant temperature and humidity conditions (normal state) of 23° C. and 50% RH, and Tan δ ₁ denotes the dielectric loss tangent at 10 GHz measured by a SPDR after 24 hours of conditioning under constant temperature and humidity conditions of 23° C. and 50% RH]
The _E1 value, which is an index showing the dielectric properties at 10 GHz after 24 hours of conditioning under constant temperature and humidity conditions of 23° C. and 50% RH, calculated based on the above formula, is 0.010 or less;
II) Formula (ii) below:
E ₂ =√ε ₂ ×Tan δ ₂ ...(ii)
[where _ε2 represents the dielectric constant at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours, and Tan _δ2 represents the dielectric tangent at 10 GHz measured by SPDR after absorbing water at 23°C for 24 hours]
The _E2 value is an index of dielectric properties at 10 GHz after absorbing water at 23°C for 24 hours, calculated based on the following:
the ratio of the _E2 value to the _E1 value ( _E2 / _E1 ) is within the range of 3.0 to 1.0;
A resin film characterized by satisfying the above. A coverlay film having an adhesive layer and a coverlay film material layer laminated thereon,
A coverlay film, wherein the adhesive layer is made of the resin film according to claim 1. A circuit board comprising a substrate, a wiring layer formed on the substrate, and the coverlay film according to claim 2 that covers the wiring layer. A resin-coated copper foil having an adhesive layer and a copper foil laminated thereon,
2. A resin-coated copper foil, wherein the adhesive layer 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 multilayer circuit board comprising a laminate including a plurality of laminated insulating resin layers, and one or more conductor circuit layers 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 conductor circuit layer,
2. A multilayer circuit board, comprising the adhesive layer comprising the resin film according to claim 1. A polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component, the diamine component containing 40 mol % or more of a dimer diamine composition containing 98.2 wt % or more of a dimer diamine composition as a main component, the dimer diamine being obtained by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups, relative to the total diamine component;
The dimer diamine composition is measured by gel permeation chromatography, and the area percentage of the chromatogram is determined to be the following components (a) to (c):
(a) dimer diamine;
(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 content of the component (b) is 0% and the content of the component (c) is 2% or less,
the ratio (b/c) of the area percentages of the chromatograms of the component (b) and the component (c) is less than 1;
A polyimide characterized in that the molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is 0.97 or more and 1.008 or less. The polyimide according to claim 7, characterized in that it contains 50 mol % or more of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) based on the total amount of the tetracarboxylic anhydride component. The following components (A) and (B):
(A) the polyimide according to claim 8; and (B) an amino compound having at least two primary amino groups as functional groups.
Including,
An adhesive resin composition comprising the component (B) such that the total amount of the primary amino groups is within the range of 0.004 mol to 1.5 mol per 1 mol of ketone groups of the BTDA residue derived from BTDA in the component (A).