TWI895381B - Polyimide, cross-linked polyimide, adhesive film and their applications - Google Patents

Abstract

The present invention provides a polyimide, a cross-linked polyimide, an adhesive film, and their applications. The invention aims to further improve the dielectric properties of an adhesive layer made of a polyimide derived from a dimer diamine and more effectively reduce the transmission loss of high-frequency signals. A polyimide comprising: a) 60 mol% or more of diamine residues derived from a dimer diamine composition containing a dimer diamine as a main component, relative to all diamine residues; b1) a content of carbon atoms derived from a six-membered aromatic ring within a range of 12 wt% to 40 wt% relative to the total content of all atoms in the polyimide; and b2) 5 mol% to 40 mol% of diamine residues derived from a diamine compound represented by general formula (A1), relative to all diamine residues. c) The weight average molecular weight is in the range of 5,000 to 200,000.

Description

Polyimide, cross-linked polyimide, adhesive film and its application

The present invention relates to a polyimide that is effectively used as a material for electronic components, a crosslinked polyimide using the same, an adhesive film, a laminate, a coverlay film, a resin-coated copper foil, a metal-clad laminate, a circuit board, and a multi-layer circuit board.

In recent years, with the advancement of miniaturization, lightweighting, and space-saving electronic devices, there has been a growing demand for flexible printed circuits (FPCs) that are thin, lightweight, flexible, and highly durable even with repeated bending. FPCs enable three-dimensional, high-density mounting even in limited spaces, and are therefore finding increasing use in components such as wiring, cables, and connectors for movable parts in electronic devices such as hard disk drives (HDDs), digital video disks (DVDs), and smart phones.

One type of FPC includes a structure in which a circuit pattern is formed on a polyimide film with excellent heat resistance and flexibility, and a cover film having an adhesive layer is laminated to the surface. Polyimide is used as the adhesive layer material for the cover film in this structure. For example, a crosslinked polyimide obtained by reacting a polyimide derived from a diamine compound derived from a dimer acid with an amino compound having at least two primary amino groups as functional groups has been proposed for use in the cover film adhesive layer (e.g., Patent Document 1).

In addition, it has been proposed that a three-layer metal-clad laminate, which is a material for a circuit board such as an FPC, be formed by bonding a metal layer processed with wiring to an insulating resin layer via an adhesive layer, wherein the adhesive layer contains a polyimide containing a predetermined amount or more of a diamine residue derived from a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups (for example, Patent Document 2).

Furthermore, in addition to the aforementioned increase in density, device performance is also being driven by the need to cope with the increase in the frequency of transmitted signals. When transmitting high-frequency signals, if transmission loss in the transmission path is high, this can lead to problems such as electrical signal loss and increased signal delay. Therefore, reducing transmission loss will become increasingly important in FPCs going forward. Therefore, it has been proposed to consider the relationship between the thickness, dielectric constant, and dielectric loss tangent of the polyimide insulating layer and the cover film in a circuit substrate comprising a polyimide insulating layer, a circuit wiring layer laminated on at least one surface of the polyimide insulating layer, and a cover film laminated on the circuit wiring layer (for example, Patent Document 3).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2013-1730

[Patent Document 2] Japanese Patent Publication No. 2018-140544

[Patent Document 3] Japanese Patent Publication No. 2016-192531

As described in Patent Documents 1 and 2, adhesive layers using polyimide made from dimer diamine exhibit excellent adhesion, low dielectric constant, and dielectric loss tangent. However, further improvement in dielectric properties is required to cope with the increasing frequency of transmission signals.

Therefore, the purpose of the present invention is to further improve the dielectric properties of adhesive layers using polyimide made from dimer diamine and to more effectively reduce the transmission loss of high-frequency signals.

The present inventors conducted intensive research and discovered that by controlling the amount of aromatic rings contained in polyimide made from dimer diamine, or by using a copolymer composition of dimer diamine and a diamine having a specific structure, the dielectric properties of the polyimide can be improved. This led to the completion of the present invention.

The polyimide of the present invention is a polyimide containing tetracarboxylic acid residues derived from a tetracarboxylic anhydride component and diamine residues derived from a diamine component. The polyimide of the present invention is characterized by satisfying the following conditions a, b1, and c, or a, b2, and c.

a) Containing 60 mol% or more of diamine residues based on the total diamine residues, derived from a dimer diamine composition having as its main component a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups.

b1) The content of carbon atoms derived from a six-membered aromatic ring (excluding carbon atoms derived from a six-membered aromatic ring of the dimer diamine composition) relative to the total content of all atoms in the polyimide is within a range of 12% by weight to 40% by weight.

b2) Containing diamine residues derived from a diamine compound represented by the following general formula (A1) in an amount of 5 mol% to 40 mol% relative to all diamine residues.

In general formula (A1), Y and Z each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an alkenyl group, or an alkynyl group having 1 to 6 carbon atoms; the linking group X represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -CH ₂ -O-, -C(CH ₃ ) ₂ -, -NH-, or -CONH-; and m represents an integer from 1 to 4. When a plurality of linking groups X are present in the molecule, they may be the same or different.

c) The weight average molecular weight is within the range of 5,000~200,000.

The polyimide of the present invention may satisfy the following condition d while satisfying the aforementioned conditions a, b1, and c.

d) The CM value, which is an indicator of the amount of 6-membered aromatic rings contained in the polyimide calculated based on the following formula (i), is within the range of 3 to 38.

CM value = (C/Mw) × 10 ⁴ ...(i)

[Wherein, C refers to the weight content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms derived from a 6-membered aromatic ring of the dimer diamine composition) relative to the total content of all atoms in the polyimide, and Mw refers to the weight average molecular weight of the polyimide]

The polyimide of the present invention may satisfy the following condition e while satisfying the aforementioned conditions a, b1, and c.

e) The content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms derived from a 6-membered aromatic ring in the dimer diamine composition) relative to the total content of all atoms in all diamine components of the raw material is within the range of more than 0 and not more than 32% by weight.

The polyimide of the present invention may satisfy the following condition f while satisfying the aforementioned conditions a, b1, and c.

f) The DM value, which is an indicator of the amount of the six-membered aromatic ring derived from the diamine component contained in the polyimide and is calculated based on the following formula (ii), is within the range of more than 0 and 32 or less.

DM value = (D/Mw) × 10 ⁴ ...(ii)

[Wherein, D refers to the weight content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms derived from a 6-membered aromatic ring in the dimer diamine composition) relative to the total content of all atoms in all diamine residues, and Mw refers to the weight average molecular weight of the polyimide]

When the polyimide of the present invention satisfies conditions a, b1, and c, it may contain diamine residues derived from the dimer diamine composition in an amount ranging from 60 mol% to 99 mol% of the total amount of the diamine residues. In this case, it may contain diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formulae (B1) to (B7) in an amount ranging from 1 mol% to 40 mol%.

In formulas (B1) to (B7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, _-SO- , -SO2-, -COO-, _-CH2- , -C( _CH3 ) _2- , -NH-, or -CONH-, and _n1 independently represents an integer from 0 to 4. The portion of formula (B3) that is repeated with formula (B2) is removed, and the portion of formula (B5) that is repeated with formula (B4) is removed.

The polyimide of the present invention may contain a total of 90 mol% or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (2) and/or general formula (3) relative to the total amount of the acid anhydride residues.

In the general formula (2), _X1 represents a single bond or a divalent group selected from the following formulae. In the general formula (3), the cyclic moiety represented by _Y1 represents a cyclic saturated alkyl group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, or an 8-membered ring.

[Chemistry 4]

In the above formula, _Z1 represents _-C6H4- , -( _CH2 ) _m1- , or _{-CH2- CH} (-OC(=O) _-CH3 ) _-CH2- , and m1 represents an integer of 1 to 20.

When the polyimide of the present invention satisfies the above-mentioned conditions a, b2, and c, it may contain, in a range of 10 mol% to 90 mol% relative to all tetracarboxylic acid residues, tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride wherein the group _X1 in the general formula (2) is -CO-, and may contain 10 mol% or more of at least one tetracarboxylic acid residue derived from tetracarboxylic anhydride represented by the general formula (2) and/or the general formula (3) (except the above-mentioned benzophenonetetracarboxylic dianhydride).

The crosslinked polyimide of the present invention contains ketone groups in its molecule. The ketone groups form a crosslinked structure with the amino groups of an amino compound having at least two primary amino groups as functional groups via C=N bonds.

The adhesive film of the present invention contains the polyimide or the cross-linked polyimide.

When the polyimide film of the present invention satisfies conditions a, b1, and c, and is conditioned at constant temperature and humidity (23°C, 50% RH) for 24 hours, the dielectric loss tangent (Tanδ1) at 10 GHz measured by a Split Post Dielectric Resonator (SPDR) can be less than 0.005, and _the relative dielectric constant ( _E1 ) can be less than 3.0.

When the polyimide film of the present invention satisfies conditions a, b1, and c, and is conditioned at constant temperature and humidity (23°C, 50% RH) for 24 hours, the dielectric loss tangent ( _Tanδ2 ) at 20 GHz measured by a separated dielectric resonator (SPDR) can be less than 0.005, and the relative dielectric constant ( _E2 ) can be less than 3.0.

When the polyimide film of the present invention satisfies conditions a, b1, and c, the difference (Tanδ 2 -Tanδ 1 ) between the dielectric loss tangent (Tanδ ₁ ) at 10 GHz and the dielectric loss tangent (Tanδ ₂ ) at 20 GHz, as measured by a separated dielectric resonator (SPDR), can be equal to or less than 0 after humidification at constant temperature and humidity conditions of ₂₃ °C and 50% _RH for 24 hours.

When the polyimide film of the present invention satisfies conditions a, b2, and c, and is humidified at constant temperature and humidity (23°C, 50% RH) for 24 hours, the dielectric loss tangent ( _Tanδ1 ) at 10 GHz measured by a separated dielectric resonator (SPDR) can be less than 0.002, and the relative dielectric constant ( _E1 ) can be less than 3.0.

When the polyimide film of the present invention satisfies conditions a, b2, and c, and is humidified at constant temperature and humidity (23°C, 50% RH) for 24 hours, the dielectric loss tangent ( _Tanδ2 ) at 20 GHz measured by a separated dielectric resonator (SPDR) can be less than 0.002, and the relative dielectric constant ( _E2 ) can be less than 3.0.

The laminate of the present invention comprises a substrate and an adhesive layer laminated on at least one surface of the substrate, and in the laminate, the adhesive layer comprises any of the adhesive films described above.

The covering film of the present invention comprises a covering film material layer and an adhesive layer laminated on the covering film material layer, and in the covering film, the adhesive layer includes any of the above-mentioned adhesive films.

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

The metal-clad laminate of the present invention comprises an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer. In the metal-clad laminate, at least one layer of the insulating resin layer includes any of the aforementioned adhesive films.

Another aspect of the present invention provides a metal-clad laminate comprising: an insulating resin layer; an adhesive layer laminated on at least one side of the insulating resin layer; and a metal layer laminated on the insulating resin layer via the adhesive layer. In the metal-clad laminate, the adhesive layer includes any of the adhesive films described above.

According to another aspect of the present invention, a metal-clad laminate comprises: a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side 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 side of the second metal layer; and an adhesive layer disposed so as to abut the first insulating resin layer and the second insulating resin layer and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate. Furthermore, in the metal-clad laminate of the present invention, the adhesive layer includes any of the adhesive films described above.

Another aspect of the present invention provides a metal-clad laminate comprising: a single-sided metal-clad laminate having an insulating resin layer and a metal layer laminated on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer, wherein the adhesive layer includes any of the adhesive films described above.

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

Another aspect of the present invention provides a circuit board comprising: a first substrate; a wiring layer laminated on at least one surface of the first substrate; and an adhesive layer laminated on a surface of the first substrate facing the wiring layer so as to cover the wiring layer. In the circuit board, the adhesive layer includes any of the adhesive films described above.

According to another aspect of the present invention, a circuit board includes: a first substrate; a wiring layer laminated on at least one surface of the first substrate; an adhesive layer laminated on a surface of the first substrate facing the wiring layer so as to cover the wiring layer; and a second substrate laminated on a surface of the adhesive layer opposite to the first substrate. In the circuit board, the adhesive layer includes any of the adhesive films.

According to another aspect of the present invention, a circuit board comprises: a first substrate; an adhesive layer deposited on at least one surface of the first substrate; a second substrate deposited on a surface of the adhesive layer opposite to the first substrate; and wiring layers deposited on surfaces of the first and second substrates opposite to the adhesive layer, respectively. In the circuit board, the adhesive layer includes any of the adhesive films.

The multilayer circuit board of the present invention comprises: a laminate including a plurality of laminated insulating resin layers; and at least one or more wiring layers embedded within the laminate. In the multilayer circuit board, at least one or more of the plurality of insulating resin layers is formed from an adhesive layer having adhesive properties and covering the wiring layer, and the adhesive layer includes any of the adhesive films.

The polyimide of the present invention achieves excellent adhesion, a low dielectric constant and a low dielectric loss tangent, by controlling the amount of aromatic rings contained in the polyimide derived from dimer diamine, or by adopting a copolymer composition of dimer diamine and a diamine with a specific structure. Furthermore, it effectively suppresses transmission loss in high-frequency signal transmission. Therefore, the polyimide of the present invention can effectively reduce transmission loss when used in circuit boards that transmit high-frequency signals in the GHz band (e.g., 1 GHz to 20 GHz).

10: Base material

11: First substrate

12: Second substrate

20: Next, the agent layer

30, 33, 34: Insulating resin layer

31: First insulating resin layer

32: Second insulating resin layer

41: First single-sided metal laminate

42: Second single-sided metal laminate

50: Wiring layer

M: Metal layer

M1: First metal layer

M2: Second metal layer

100: Layered 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: Multi-layer circuit board

Figure 1 is a schematic diagram showing the cross-sectional structure of a laminate according to an embodiment of the present invention.

Figure 2 is a schematic diagram showing the cross-sectional structure of a metal-clad laminate according to an embodiment of the present invention.

FIG3 is a schematic diagram showing the cross-sectional structure of a metal-clad laminate according to another embodiment of the present invention.

FIG4 is a schematic diagram showing the cross-sectional structure of a metal-clad laminate according to another embodiment of the present invention.

FIG5 is a schematic diagram showing the cross-sectional structure of a circuit board according to an embodiment of the present invention.

FIG6 is a schematic diagram showing a cross-sectional structure of a circuit board according to another embodiment of the present invention.

FIG7 is a schematic diagram showing a cross-sectional structure of a circuit board according to another embodiment of the present invention.

FIG8 is a schematic diagram showing the cross-sectional structure of a multi-layer circuit board according to an embodiment of the present invention.

Figure 9 is a graph schematically showing the relationship between the aromatic ring concentration and the dielectric loss tangent of the adhesive polyimide.

The embodiments of the present invention will be described with reference to the drawings.

The polyimide of one embodiment of the present invention is an adhesive polyimide. Hereinafter, the polyimide of this embodiment may be referred to as an "adhesive polyimide." The adhesive polyimide contains tetracarboxylic acid residues derived from a tetracarboxylic anhydride component and diamine residues derived from a diamine component. In the present invention, "tetracarboxylic acid residues" refer to tetravalent groups derived from tetracarboxylic dianhydride, and "diamine residues" refer to divalent groups derived from a diamine compound. When the tetracarboxylic anhydride and diamine compound as raw materials are reacted in approximately equimolar amounts, the types and molar ratios of the tetracarboxylic acid residues and diamine residues contained in the polyimide can be adjusted to approximately correspond to the types and molar ratios of the raw materials.

Furthermore, when referred to in the present invention as "polyimide," it refers to resins containing polymers having imide groups in their molecular structures, such as polyamide imide, polyether imide, polyester imide, polysiloxane imide, and polybenzimidazole imide, in addition to polyimide.

The adhesive polyimide of this embodiment satisfies the following conditions a, b1, and c, or conditions a, b2, and c. The details of the raw monomers, tetracarboxylic acid residues, and diamine residues of the adhesive polyimide are described below.

Condition a)

A dimer diamine composition containing at least 60 mol% of diamine residues derived from a dimer diamine primarily composed of a dimer acid having both terminal carboxylic acid groups substituted with primary aminomethyl or amino groups, relative to the total diamine residues: By setting the content of diamine residues derived from the dimer diamine composition to at least 60 mol%, preferably within the range of 60 mol% to 99 mol%, more preferably within the range of 60 mol% to 95 mol%, further preferably within the range of 65 mol% to 95 mol%, and most preferably within the range of 70 mol% to 90 mol%, the relative dielectric constant and dielectric loss tangent of the polyimide can be reduced. If the content of diamine residues derived from the dimer diamine composition is less than 60 mol%, the relative dielectric constant and dielectric loss tangent tend to increase due to the relative increase in polar groups in the polyimide. Furthermore, if the content of diamine residues derived from the dimer diamine composition exceeds 99 mol% relative to the total diamine residues, the mobility of the polyimide molecular chain is excessively enhanced, potentially increasing the dielectric loss tangent. Furthermore, by incorporating dimer diamine in this amount, the dielectric properties of the polyimide can be improved. Furthermore, the lowering of the polyimide's glass transition temperature (Tg) improves heat-pressing properties, and the lowering of the elastic modulus can alleviate internal stress.

Condition b1)

The content of carbon atoms derived from six-membered aromatic rings (excluding carbon atoms derived from six-membered aromatic rings in the dimer diamine composition) relative to the total content of all atoms in the polyimide is within a range of 12% to 40% by weight. The content of carbon atoms derived from six-membered aromatic rings refers to the content of aromatic rings (aromatic ring concentration) contained in the adhesive polyimide. By setting the content of carbon atoms derived from six-membered aromatic rings within a range of 12% to 40% by weight, the molecular motion of the polyimide is restricted due to interactions between the aromatic rings, resulting in a lower dielectric loss tangent. If the content of carbon atoms derived from six-membered aromatic rings is less than 12% by weight, the molecular chain motion of the polyimide is not suppressed, resulting in a higher dielectric loss tangent. If the content of carbon atoms derived from the six-membered aromatic ring exceeds 40% by weight, the molecular polarity increases, and the dielectric loss tangent increases. The content of carbon atoms derived from the six-membered aromatic ring is preferably in the range of 17% to 38% by weight, and more preferably in the range of 20% to 30% by weight.

Condition b2)

The content of diamine residues derived from the diamine compound represented by general formula (A1) is within the range of 5 mol% to 40 mol% relative to the total diamine residues: By setting the content of diamine residues derived from the diamine compound represented by general formula (A1) to within the range of 5 mol% to 40 mol%, preferably within the range of 10 mol% to 30 mol%, relative to the total diamine residues, the relative dielectric constant and dielectric loss tangent of the polyimide can be reduced. If the content of diamine residues derived from the diamine compound represented by general formula (A1) is less than 5 mol%, the mobility of the molecular chain of the polyimide may be excessively increased, resulting in an increase in the dielectric loss tangent. Furthermore, when the content of diamine residues derived from the diamine compound represented by general formula (A1) exceeds 40 mol% relative to all diamine residues, the polarity of the polyimide molecular chain increases excessively, and the dielectric loss tangent may increase.

Condition c)

Weight-average molecular weight range of 5,000-200,000: If the weight-average molecular weight of the adhesive polyimide is less than 5,000, it may become brittle during film formation. On the other hand, if the weight-average molecular weight exceeds 200,000, the varnish will have a high viscosity, which may cause uneven thickness during application.

The weight-average molecular weight of the adhesive polyimide is preferably in the range of 10,000-100,000, more preferably 10,000-60,000, and even more preferably 20,000-55,000. A weight-average molecular weight of less than 10,000 increases the number of highly polar ends in the polyimide molecular chain, which may tend to increase the relative dielectric constant and dielectric loss tangent. A weight-average molecular weight exceeding 100,000 increases the molecular chain length, making it difficult to achieve an ordered structure, which may tend to increase the relative dielectric constant and dielectric loss tangent.

The polyimide of this embodiment preferably satisfies conditions a, b1, and c, and also satisfies at least one of the following conditions d, e, and f.

Condition d)

The CM value, which is an indicator of the amount of 6-membered aromatic rings contained in the polyimide, is calculated based on the following formula (i): CM value = (C/Mw) × 10 ⁴ ...(i)

[Wherein, C refers to the weight content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms derived from a 6-membered aromatic ring of the dimer diamine composition) relative to the total content of all atoms in the polyimide, and Mw refers to the weight average molecular weight of the polyimide]

Keeping the CM value within an appropriate range is effective in lowering the dielectric loss tangent of polyimide. When the CM value is less than 3, the aromatic ring concentration decreases, resulting in increased molecular mobility and a higher dielectric loss tangent. On the other hand, when the CM value exceeds 38, the aromatic ring concentration becomes excessive, resulting in increased polarity and a higher dielectric loss tangent.

Condition e)

The weight content of carbon atoms derived from six-membered aromatic rings (excluding carbon atoms derived from six-membered aromatic rings in the dimer diamine composition) relative to the total content of all atoms in the diamine components of the starting materials is within a range exceeding 0 and not exceeding 32% by weight. By controlling the aromatic ring content within an appropriate range, the molecular motion of the polyimide is restricted due to the interaction between the aromatic rings, thereby exhibiting a low dielectric loss tangent. To achieve this objective, it is effective to also control the content of carbon atoms derived from six-membered aromatic rings relative to the total content of carbon atoms in the diamine components of the starting materials within the above range. If the content of carbon atoms derived from six-membered aromatic rings in the total diamine components of the starting materials exceeds 32% by weight, the resulting polyimide molecules will have increased polarity and a higher dielectric loss tangent.

Condition f)

The DM value, which is an indicator of the amount of the 6-membered aromatic ring derived from the diamine component contained in the polyimide, is within the range of more than 0 and 32, calculated based on the following formula (ii): DM value = (D/Mw) × 10 ⁴ ... (ii)

[Wherein, D refers to the weight content of carbon atoms derived from a 6-membered aromatic ring (excluding carbon atoms derived from a 6-membered aromatic ring in the dimer diamine composition) relative to the total content of all atoms in all diamine residues, and Mw refers to the weight average molecular weight of the polyimide]

For the same reason as condition e, it is effective to set the content of carbon atoms derived from the six-membered aromatic ring in the diamine residue relative to the total content of all atoms in the polyimide within the above range.

(anhydride)

The adhesive polyimide can be made of a tetracarboxylic anhydride commonly used in thermoplastic polyimide without particular limitation. However, it is preferred to use a raw material containing 90 mol% or more of tetracarboxylic anhydride represented by the following general formula (2) and/or general formula (3) relative to the total tetracarboxylic anhydride components. In other words, the adhesive polyimide preferably contains 90 mol% or more of tetracarboxylic acid residues derived from the tetracarboxylic anhydride represented by the following general formula (2) and/or general formula (3) relative to the total tetracarboxylic acid residues. By containing 90 mol% or more of tetracarboxylic acid residues derived from the tetracarboxylic anhydride represented by the following general formula (2) and/or general formula (3) relative to the total tetracarboxylic acid residues, it is easier to achieve both softness and heat resistance in the adhesive polyimide. If the total amount of tetracarboxylic acid residues derived from tetracarboxylic anhydrides represented by the following general formula (2) and/or general formula (3) is less than 90 mol%, the solvent solubility of the adhesive polyimide tends to decrease.

In the general formula (2), _X1 represents a single bond or a divalent group selected from the following formulae. In the general formula (3), the cyclic moiety represented by _Y1 represents a cyclic saturated alkyl 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, _Z1 represents _-C6H4- , -( _CH2 ) _m1- , or _{-CH2 -} CH(-OC(=O) _-CH3 ) _-CH2- , and m1 represents an integer of 1 to 20.

Examples of the tetracarboxylic anhydride represented by the general formula (2) include 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 2,3',3,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride, and 4,4'-dibenzophenone tetracarboxylic dianhydride. Anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylene bis(trimellitic acid monoester) anhydride (TAHQ), and ethylene glycol bisanhydro trimellitate (TMEG) are particularly preferred. Among these, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) is particularly preferred. When using BTDA, the carbonyl (ketone) groups in its molecular backbone contribute to adhesion, thereby improving the adhesion of the resulting polyimide. Furthermore, the ketone groups in BTDA's molecular backbone react with the amino groups of the amino compound used for crosslinking (described later) to form C=N bonds, which can enhance heat resistance. From this perspective, the content of tetracarboxylic acid residues derived from BTDA is preferably 50 mol% or more, more preferably 60 mol% or more, relative to the total tetracarboxylic acid residues.

In addition, examples of the tetracarboxylic anhydride represented by the general formula (3) include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cycloheptanetetracarboxylic dianhydride, and 1,2,5,6-cyclooctanetetracarboxylic dianhydride.

Here, the adhesive polyimide preferably satisfies conditions a, b2, and c, and also satisfies the following condition g related to the acid anhydride.

Condition g)

The present invention further comprises tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride in which the group _X1 in the general formula (2) is -CO-, in an amount of 10 mol% or more and 90 mol% or less of all tetracarboxylic acid residues, and at least 10 mol% or more of at least one tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride represented by the general formula (2) and/or the general formula (3) (excluding the benzophenonetetracarboxylic dianhydride). By containing tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride in an amount of 10 mol% or more and 90 mol% or less of all tetracarboxylic acid residues, it is easy to achieve both flexibility and heat resistance of the adhesive polyimide. The ketone group contributes to the adhesiveness, thereby improving the adhesiveness of the adhesive polyimide. If the content of tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride is less than 10 mol% relative to the total tetracarboxylic acid residues, the number of keto groups serving as crosslinking points decreases, and solder heat resistance may not be exhibited. Furthermore, if the content of tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride exceeds 90 mol% relative to the total tetracarboxylic acid residues, diamine residues derived from the diamine compound react with the keto groups derived from the benzophenonetetracarboxylic dianhydride, significantly reducing solubility. Specifically, since the keto groups present in the molecular skeleton of benzophenonetetracarboxylic dianhydride react with the amine groups derived from the diamine compound to form C=N bonds, resulting in a higher molecular weight and gelation, the upper limit is set to 90 mol% or less. Furthermore, as the benzophenonetetracarboxylic dianhydride, any one of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,3′,3,4′-benzophenonetetracarboxylic dianhydride, 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, and 2,3,3′,4′-benzophenonetetracarboxylic dianhydride can be used.

On the other hand, tetracarboxylic anhydrides represented by general formula (2) and/or general formula (3) (excluding benzophenonetetracarboxylic dianhydride) do not have a functional group that reacts with a diamine residue derived from a diamine compound. Therefore, when used in combination with benzophenonetetracarboxylic dianhydride, the decrease in solvent solubility can be suppressed and the solder heat resistance can be improved.

Therefore, when conditions a, b2, and c are satisfied, the storage stability can be improved by setting the content of tetracarboxylic acid residues derived from benzophenonetetracarboxylic dianhydride to a range of 10 mol% to 90 mol%, preferably 10 mol% to 50 mol%, relative to all tetracarboxylic acid residues, and setting the content of at least one type of tetracarboxylic acid residue derived from tetracarboxylic anhydride represented by general formula (2) and/or general formula (3) (excluding benzophenonetetracarboxylic dianhydride) to a range of 10 mol% to 50 mol%.

The adhesive polyimide may contain tetracarboxylic acid residues derived from an acid anhydride other than the tetracarboxylic acid anhydride represented by the general formula (2) and the general formula (3) as long as the effects of the invention are not impaired. Such tetracarboxylic acid residues are not particularly limited, and examples thereof include tetracarboxylic acid residues derived from pyromellitic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3",4,4"-p-terphenyltetracarboxylic dianhydride, 2,3,3",4"-p-terphenyltetracarboxylic dianhydride or 2,2",3,3"-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride. bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfonium dianhydride or bis(3,4-dicarboxyphenyl)sulfonium dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic 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-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride 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 tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as 2,3,6,7-tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, and 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride.

(Diamine)

The adhesive polyimide can be made from diamine compounds commonly used in thermoplastic polyimides without particular limitation. However, the adhesive polyimide should be a diamine composition containing, as a main component, 60 mol% or more of a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups, based on the total diamine components. In other words, as described in condition a, the adhesive polyimide contains, relative to the total diamine residues, 60 mol% or more of diamine residues derived from a dimer diamine composition in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups.

The dimer diamine composition is a purified product containing the following component (a) as the main component, and the amounts of components (b) and (c) are controlled.

(a) Dimer diamine; The so-called dimer diamine as component (a) refers to a diamine in which the two terminal carboxylic acid groups (-COOH) of the dimer acid are replaced by primary aminomethyl groups ( _-CH2 - _NH2 ) or amino groups ( _-NH2 ). Dimer acid is a known dibasic acid obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Its industrial production process is largely standardized in the industry and can be obtained by dimerizing unsaturated fatty acids with 11 to 22 carbon atoms using clay catalysts, etc. Industrially available dimer acids are primarily composed of a 36-carbon dibasic acid obtained by dimerizing unsaturated fatty acids with 18 carbon atoms, such as oleic acid, linoleic acid, or linolenic acid. Depending on the degree of purification, they may contain any amount of monomeric acid (with 18 carbon atoms), trimer acid (with 54 carbon atoms), and other polymerized fatty acids with 20-54 carbon atoms. Although double bonds remain after the dimerization reaction, the present invention also includes compounds whose unsaturation has been reduced by further hydrogenation. The dimer diamine, component (a), can be defined as a diamine compound obtained by substituting the terminal carboxylic acid group of a dibasic acid compound with 18-54 carbon atoms, preferably 22-44 carbon atoms, with a primary aminomethyl group or amino group.

Dimer diamines are characterized by the ability to impart properties derived from the dimer acid backbone. Specifically, dimer diamines are large, aliphatic molecules with a molecular weight of approximately 560-620, which increases the molecular molar volume and relatively reduces the number of polar groups in the polyimide. These characteristics of dimer acid-based diamines are believed to help suppress the degradation of the polyimide's heat resistance and improve dielectric properties by reducing the dielectric constant and dielectric loss tangent. Furthermore, since it contains two freely mobile hydrophobic chains with 7 to 9 carbon atoms and two chain-like aliphatic amine groups with a length close to 18 carbon atoms, it not only imparts flexibility to the polyimide but also allows it to have an asymmetric or non-planar chemical structure, thus potentially lowering the dielectric constant of the polyimide.

The dimer diamine composition preferably contains a dimer diamine component (a) whose content is increased to 96% by weight or greater, preferably 97% by weight or greater, and even more preferably 98% by weight or greater, by purification methods such as molecular distillation. By increasing the dimer diamine content of component (a) to 96% by weight or greater, the broadening of the molecular weight distribution of the polyimide can be suppressed. Furthermore, if technically feasible, it is optimal for the dimer diamine composition to consist entirely (100% by weight) of the dimer diamine component (a). Furthermore, the dimer diamine composition may also contain a dimer diamine having a six-membered aromatic ring as its molecular backbone. In the polyimide of this embodiment, the focus is on the proportion of aromatic monomers directly bonded to the imide bond site. While this is a target for control, in the dimer diamine having a six-membered aromatic ring, the six-membered aromatic ring is an imide bond mediated by an aliphatic chain having seven or more carbon atoms, and therefore is not a target for control of the six-membered aromatic ring in the polyimide of this embodiment. Therefore, for the contact polyimide, conditions b1, d, e, and f exclude the six-membered aromatic ring derived from the dimer diamine. Furthermore, quantification using 1H nuclear magnetic resonance (NMR) indicates that the proportion of aromatic rings derived from the dimer diamine is preferably 20 mol or less per 1 mol of amino groups.

(b) Monoamine compounds obtained by substituting the terminal carboxylic acid group of a monoacid compound having 10 to 40 carbon atoms with a primary aminomethyl group or an amino group. The monoacid compound having 10 to 40 carbon atoms is a mixture of a monounsaturated fatty acid having 10 to 20 carbon atoms, which is a raw material for dimer acid, and a monoacid compound having 21 to 40 carbon atoms, which is a by-product during the production of dimer acid. Monoamine compounds are compounds obtained by substituting the terminal carboxylic acid group of these monoacid compounds with a primary aminomethyl group or an amino group.

The monoamine compound (b) suppresses the increase in molecular weight of the polyimide. During polymerization of the polyamic acid or polyimide, the monofunctional amine group of the monoamine compound reacts with the terminal anhydride groups of the polyamic acid or polyimide, thereby capping the terminal anhydride groups 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 polyacid compound having an alkyl group in the range of 41 to 80 carbon atoms with a primary aminomethyl group or an amino group (excluding the dimer diamine). Polyacid compounds having an alkyl group in the range of 41 to 80 carbon atoms are polyacid compounds primarily composed of tribasic acid compounds having 41 to 80 carbon atoms, which are by-products during the production of dimer acid. Polymerized fatty acids other than dimer acids having 41 to 80 carbon atoms may also be included. Amine compounds are compounds obtained by substituting the terminal carboxylic acid group of these polyacid compounds with a primary aminomethyl group or an amino group.

The amine compound, component (c), promotes the increase in the molecular weight of the polyimide. Triamines derived from trimer acid react with the terminal anhydride groups of the polyamic acid or polyimide to rapidly increase the molecular weight of the polyimide. Amine compounds derived from polymerized fatty acids other than dimer acids with 41 to 80 carbon atoms also increase the molecular weight of the polyimide and contribute to its gelation.

When quantifying each component by gel permeation chromatography (GPC), a sample of the dimer diamine composition treated with acetic anhydride and pyridine was used to facilitate identification of the peak start, peak top, and peak end of each component, with cyclohexanone used as an internal standard. Using the sample prepared as described above, each component was quantified using the area percentage of the GPC chromatogram. The peak start and peak end of each component were set to the minimum value of each peak curve, and the area percentage of the chromatogram was calculated based on this minimum value.

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

The area percentage of component (b) in the chromatogram is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. By setting this range, the decrease in the molecular weight of the polyimide can be suppressed, thereby expanding the range of the molar ratio of the tetracarboxylic anhydride component and the diamine component. Furthermore, component (b) does not necessarily have to be included in the dimer diamine composition.

Furthermore, the area percentage of the chromatogram of component (c) is preferably 2% or less, preferably 1.8% or less, and more preferably 1.5% or less. By setting this range, a rapid increase in the molecular weight of the polyimide can be suppressed, thereby suppressing an increase in the dielectric loss tangent of the resin film over a wide frequency range. Furthermore, component (c) may not be included in the dimer diamine composition.

When the area percentage ratio (b/c) of component (b) to component (c) in the chromatogram is 1 or greater, the molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is preferably set to 0.97 or greater and less than 1.0. By setting this molar ratio, the molecular weight of the polyimide can be more easily controlled.

When the area percentage ratio (b/c) of component (b) and component (c) in the chromatogram is less than 1, the molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is preferably set to 0.97 or greater and 1.1 or less. By setting this molar ratio, the molecular weight of the polyimide can be more easily controlled.

A commercially available dimer diamine composition can be used. It is preferably purified to reduce components other than the dimer diamine (component (a)). For example, the content of component (a) is preferably adjusted to 96% by weight or greater. The purification method is not particularly limited, but known methods such as distillation and precipitation purification are suitable. Examples of commercially available dimer diamine compositions include PRIAMINE 1073 (trade name) manufactured by Croda Japan Co., Ltd., PRIAMINE 1074 (trade name) manufactured by Croda Japan Co., Ltd., and PRIAMINE 1075 (trade name) manufactured by Croda Japan Co., Ltd.

As described as condition b2, the adhesive polyimide may contain diamine residues derived from a diamine compound represented by general formula (A1). In diamines represented by general formula (A1), since the aromatic rings are bonded at the para position relative to the amine groups, molecular chain alignment is facilitated, making them advantageous for achieving low dielectric loss tangent.

In formula (A1), Y and Z each independently represent a hydrogen atom, a monovalent alkyl group, an alkoxy group, an alkenyl group, or an alkynyl group having 1 to 6 carbon atoms; the linking group X represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -CH ₂ -O-, -C(CH ₃ ) ₂ -, -NH-, or -CONH-; and m independently represents an integer from 1 to 4. When a molecule contains multiple linking groups X, they may be the same or different. Furthermore, in formula (A1), the hydrogen atoms in the two terminal amino groups may be substituted, for example, they may be -NR ₂ R ₃ (wherein R ₂ and R ₃ independently represent any substituent such as an alkyl group).

The diamine represented by formula (A1) [hereinafter sometimes referred to as "diamine (A1)"] is an aromatic diamine having two or more benzene rings. Diamine (A1) is believed to contribute to improved orientation of the polyimide molecular chain due to the amino group directly bonded to at least one benzene ring being in the para position relative to the divalent linking group X. Therefore, the use of diamine (A1) improves the low dielectric properties of the polyimide. Preferred linking groups X are -O-, -S-, -CO-, -SO-, _-SO2- , -COO-, -CH2- _, -CH2 _- O-, -C( _CH3 ) _2- , -NH-, and -CONH-.

Examples of the diamine (A1) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,4,4'-triaminodiphenyl ether, 4,4'-bis(4-aminophenyl sulfide), 4,4'-diaminodiphenylsulfone, 2,2'-bis(4-aminobenzyloxyphenyl)propane, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4'-diaminobenzanilide, 4,4'-methylenedianiline, and 4,4'-diaminobenzophenone. Among these, 2,2-bis[4-(4-aminophenoxy)phenyl]propane is particularly preferred.

The adhesive polyimide preferably contains diamine residues derived from at least one diamine compound selected from diamine (A1) in an amount within a range of 5 mol% to 40 mol%, preferably 10 mol% to 30 mol%, relative to the total diamine residues. Diamine (A1) has a highly linear structure, so using at least one diamine compound selected from diamine (A1) in an amount within the above range improves the orientation of the polyimide molecular chain and imparts low dielectric properties. If the diamine residues derived from at least one diamine compound selected from diamine (A1) exceed 40 mol%, the molecular polarity of the polyimide increases, leading to an increase in the dielectric loss tangent. Furthermore, the solubility of the polyimide decreases, causing gelation. On the other hand, if the concentration is less than 5 mol%, the molecular chain motion cannot be suppressed, and the dielectric loss tangent increases.

Furthermore, when the adhesive polyimide satisfies conditions a, b1, and c, it may contain the following diamine residues. Preferred examples of such diamine residues include diamine residues derived from bisaniline fluorene (BAFL), 9,9-bis(3-methyl-4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, 9,9-bis[4-(aminophenoxy)phenyl]fluorene, or diamine compounds represented by General Formulas (B1) to (B7). In particular, diamines having a fluorene skeleton, such as BAFL, contain four aromatic rings and are therefore advantageously used for adjusting the aromatic ring concentration.

[Chemistry 8]

In formulas (B1) to (B7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, linking group A independently represents a divalent group selected from -O-, -S-, -CO-, _-SO- , -SO2-, -COO-, _-CH2- , -C( _CH3 ) _2- , -NH-, or -CONH-, and _n1 independently represents an integer from 0 to 4. In formula (B3), the portion repeating with formula (B2) is removed, and in formula (B5), the portion repeating with formula (B4) is removed. Here, the term "independently" means that multiple linking groups A, multiple _R1s , or multiple _n1s in one or more of formulas (B1) to (B7) may be the same or different. Furthermore, in the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, they may be -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. Diamine (B1), by virtue of the amino group directly bonded to at least one of the benzene rings and the divalent linking group A being at the meta position, is believed to increase the degree of freedom and flexibility of the polyimide molecular chain, contributing to improved flexibility. Therefore, the use of diamine (B1) enhances the thermoplasticity of the polyimide. Preferred linking group A is -O-, _-CH2- , -C( _CH3 ) _2- , -CO-, _-SO2- , or -S-.

Examples of the diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-diamino)diphenylamine.

The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. Diamine (B2) is believed to increase the degree of freedom and flexibility of the polyimide molecular chain due to the amino group directly bonded to at least one of the benzene rings and the divalent linking group A being at the meta position, thereby contributing to improved flexibility of the polyimide molecular chain. Therefore, the use of diamine (B2) improves the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-.

Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]aniline, and 3-[3-(4-aminophenoxy)phenoxy]aniline.

The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. It is believed that the two divalent linking groups A directly bonded to a single benzene ring in diamine (B3) are located at the meta position relative to each other, increasing the degree of freedom and flexibility of the polyimide molecular chain, thereby contributing to improved flexibility. Therefore, the use of diamine (B3) improves the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-.

Examples of diamine (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. Diamine (B4) is believed to possess high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being located at the meta position, thereby contributing to improved flexibility of the polyimide molecular chain. Therefore, the use of diamine (B4) enhances the thermoplasticity of the polyimide. Preferred linking group A is -O-, _-CH2- , -C( _CH3 ) _2- , _-SO2- , -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]sulfonium, 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. It is believed that the two divalent linking groups A directly bonded to at least one benzene ring in diamine (B5) are located at the meta position relative to each other, increasing the degree of freedom and flexibility of the polyimide molecular chain, thereby contributing to improved flexibility. Therefore, the use of diamine (B5) improves the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-.

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

The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. Diamine (B6) is believed to possess high flexibility due to the presence of at least two ether bonds, contributing to improved flexibility of the polyimide molecular chain. Therefore, the use of diamine (B6) enhances the thermoplasticity of the polyimide. Preferred linking group A is -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. Diamine (B7) has highly flexible divalent linking groups A on either side of the diphenyl backbone, which is believed to contribute to improved flexibility of the polyimide molecular chain. Therefore, the use of diamine (B7) enhances the thermoplasticity of the polyimide. The linking group A is preferably -O-.

Examples of diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl and bis[4-(4-aminophenoxy)]biphenyl.

The adhesive polyimide preferably contains diamine residues derived from at least one diamine compound selected from diamines (B1) to (B7) in an amount preferably within a range of 1 mol% to 40 mol%, more preferably within a range of 5 mol% to 35 mol%, relative to the total diamine residues. Diamines (B1) to (B7) have flexible molecular structures. Therefore, using at least one diamine compound selected from these compounds in an amount within the above range can enhance the flexibility of the polyimide molecular chain and impart thermoplastic properties.

The adhesive polyimide may further contain diamine residues other than those mentioned above within a range that does not impair the effects of the invention.

Adhesive polyimide can be produced by reacting the acid anhydride component and the diamine component in a solvent to generate polyamide, followed by heating for ring closure. For example, the acid anhydride component and the diamine component are dissolved in an organic solvent at approximately equimolar amounts and stirred at a temperature between 0°C and 100°C for 30 minutes to 24 hours to carry out a polymerization reaction. This yields the polyamide, which serves as a precursor for the polyimide. During the reaction, the reaction components are dissolved so that the resulting precursor reaches a concentration 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, dimethyl sulfoxide (DMSO), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), methanol, ethanol, benzyl alcohol, and cresol. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. The amount of the organic solvent used is not particularly limited, but it is preferably adjusted so that the concentration of the polyamide solution obtained by the polymerization reaction is approximately 5% to 50% by weight.

The synthesized polyamine is advantageously used as a reaction solvent solution, which can be concentrated, diluted, or replaced with other organic solvents as needed. Polyamine is also generally highly soluble in solvents, making it advantageous for use. The viscosity of the polyamine solution is preferably within the range of 500 mPa·s to 100,000 mPa·s. Exceeding this range can easily lead to defects such as uneven thickness and streaking in the film during coating using a coating machine.

The method for imidizing polyamic acid to form polyimide is not particularly limited. For example, a heat treatment such as heating in the aforementioned solvent at a temperature range of 80°C to 400°C for 1 to 24 hours can be suitably employed. Furthermore, the temperature can be maintained constant or varied during the process.

By selecting the types of anhydride and diamine components in the adhesive polyimide, or by adjusting the molar ratio of two or more anhydride or diamine components, physical properties such as dielectric properties, thermal expansion coefficient, tensile modulus, and glass transition temperature can be controlled. Furthermore, when the adhesive polyimide has multiple structural units, they may exist in a block or random pattern, but a random pattern is preferred.

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" refers to the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide divided by the molecular weight of the polyimide structure as a whole. If the imide group concentration exceeds 22% by weight, the molecular weight of the resin itself decreases, and the increase in polar groups deteriorates its low hygroscopicity, resulting in an increase in Tg and elastic modulus.

The adhesive polyimide is preferably a completely imidized structure. However, a portion of the polyimide may also be amide. The imidization rate can be determined by measuring the infrared absorption spectrum of the polyimide film using a Fourier transform infrared spectrophotometer (commercially available: JASCO Corporation FT/IR620) using the attenuated total reflection (ATR) method. The absorbance at 1780 cm-1, derived from the C=O stretching of the imide group, is calculated based on the benzene ring absorber near 1015 cm ^{-1 .}

Adhesive polyimide compositions can be prepared by appropriately blending optional ingredients such as plasticizers, epoxy resins and other curing resin components, hardeners, curing accelerators, organic fillers, inorganic fillers, coupling agents, solvents, and flame retardants.

(Cross-linking formation of adhesive polyimide)

When the adhesive polyimide has ketone groups, these ketone groups can be reacted with amine groups of an amino compound having at least two primary amino groups as functional groups (hereinafter sometimes referred to as a "crosslinking amino compound") to form C=N bonds, thereby forming a crosslinked structure. This polyimide with a crosslinked structure (hereinafter sometimes referred to as a "crosslinked polyimide") is an application example of an adhesive polyimide and is a preferred form. Furthermore, since crosslinking significantly changes the weight-average molecular weight, the adhesive polyimide before crosslinking can satisfy condition c. The crosslinked polyimide does not need to satisfy condition c. Another preferred application of adhesive polyimide is an adhesive resin composition made by mixing a crosslinking agent with an adhesive polyimide containing ketone groups. The crosslinked structure improves the heat resistance of the adhesive polyimide. Examples of preferred tetracarboxylic anhydrides for forming adhesive polyimides having keto groups include 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). Examples of diamine compounds include aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

To form a crosslinked structure, it is particularly preferred that a crosslink-forming amino compound be allowed to act on the adhesive polyimide, wherein the adhesive polyimide contains BTDA residues derived from BTDA in an amount of preferably 50 mol% or more, more preferably 60 mol% or more, relative to all tetracarboxylic acid residues. In the present invention, "BTDA residues" refer to tetravalent groups derived from BTDA.

Examples of crosslink-forming amino compounds include (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds readily form crosslinks even at room temperature, which can affect the storage stability of the varnish. Meanwhile, aromatic diamines require high temperatures to form crosslinks. As described above, the use of dihydrazide compounds can achieve both improved storage stability and a shortened curing time for the varnish. Preferred dihydrazide compounds include oxalic acid dihydrazide, malonate dihydrazide, succinate dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and diethylene glycol. Dihydrazide compounds such as dihydrazide of tartrate, dihydrazide of apple acid, dihydrazide of phthalate, dihydrazide of isophthalate, dihydrazide of terephthalate, dihydrazide of 2,6-naphthoic acid, dihydrazide of 4,4-diphenyldihydrazide, dihydrazide of 1,4-naphthoic acid, dihydrazide of 2,6-pyridinediacid, and dihydrazide of itaconic acid. The above dihydrazide compounds may be used alone or in combination of two or more.

Furthermore, the amino compounds (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines may be used in combination of two or more, for example, a combination of (I) and (II), a combination of (I) and (III), or a combination of (I) with (II) and (III).

Furthermore, from the perspective of making the network structure formed by crosslinking with the crosslink-forming amino compound denser, the molecular weight (weight average molecular weight when the crosslink-forming amino compound is an oligomer) of the crosslink-forming amino compound used in the present invention is preferably 5,000 or less, more preferably 90 to 2,000, and even more preferably 100 to 1,500. A crosslink-forming amino compound having a molecular weight of 100 to 1,000 is particularly preferred. If the molecular weight of the crosslink-forming amino compound is less than 90, one amino group of the crosslink-forming amino compound is limited to forming a C=N bond with a ketone group of the adhesive polyimide, and the surrounding area of the remaining amino groups becomes larger sterically, making it less likely for the remaining amino groups to form C=N bonds.

To crosslink the ketone groups in the adhesive polyimide with the crosslinking amino compound, the crosslinking amino compound is added to a resin solution containing the adhesive polyimide, causing a condensation reaction between the ketone groups in the adhesive polyimide and the primary amine groups of the crosslinking amino compound. The condensation reaction causes the resin solution to cure into a cured product. In this case, the amount of the crosslinking amino compound added is preferably 0.004 to 1.5 mol, preferably 0.005 to 1.2 mol, more preferably 0.03 to 0.9 mol, and most preferably 0.04 to 0.6 mol, of primary amine groups per 1 mol of ketone groups. If the amount of the crosslinking amino compound added is less than 0.004 mol of primary amino groups per 1 mol of ketone groups, crosslinking by the crosslinking amino compound is insufficient, and heat resistance after curing tends to be poorly developed. If the amount of the crosslinking amino compound added exceeds 1.5 mol, unreacted crosslinking amino compound acts as a thermoplastic, tending to reduce the heat resistance of the adhesive layer.

The conditions for the crosslink-forming condensation reaction are not particularly limited, as long as the ketone groups in the adhesive polyimide react with the primary amine groups of the crosslink-forming amino compound to form imine bonds (C=N bonds). The temperature for the heat-condensation reaction is preferably in the range of 120°C to 220°C, more preferably 140°C to 200°C, for reasons such as releasing water generated by the condensation out of the system and simplifying the condensation process when the heat-condensation reaction is performed after the synthesis of the adhesive polyimide. The reaction time is preferably approximately 30 minutes to 24 hours. The endpoint of the reaction can be confirmed, for example, by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercially available: FT/IR620, manufactured by JASCO Corporation) and observing the decrease or disappearance of the absorption peak at around 1670 cm ^-1 originating from the ketone groups in the polyimide resin and the appearance of the absorption peak at around 1635 cm ^-1 originating from the imine groups.

The thermal condensation of the ketone group of the adhesive polyimide and the primary amino group of the crosslink-forming amino compound can be carried out, for example, by the following methods: (1) a method in which the crosslink-forming amino compound is added immediately after the synthesis (imidization) of the adhesive polyimide and the heating is carried out; (2) a method in which an excess amino compound is added as a diamine component immediately after the synthesis (imidization) of the adhesive polyimide, and the remaining amino compound that does not participate in the imidization or amidation is used as the crosslink-forming amino compound and heated together with the adhesive polyimide; or (3) a method in which the adhesive polyimide composition to which the crosslink-forming amino compound is added is processed into a predetermined shape (for example, after coating on an arbitrary substrate or forming into a film) and the heating is carried out.

To impart heat resistance to adhesive polyimides, this description uses crosslinked polyimides that form a crosslinked structure through imide bonds as an example. However, this is not limiting. Polyimides can also be cured by mixing compounds containing unsaturated bonds, such as epoxy resins, epoxy resin hardeners, maleimides, activated ester resins, and resins with styrene skeletons.

[Adhesive resin composition]

Since the adhesive polyimide is solvent-soluble, it can be used in the form of a composition containing a solvent. Specifically, the adhesive resin composition contains the adhesive polyimide and a solvent capable of dissolving the adhesive polyimide. Furthermore, the adhesive resin composition may contain a crosslinking amino compound as an optional component. The adhesive resin composition contains the adhesive polyimide as the main component of the resin, preferably at least 70% by weight of the resin, more preferably at least 90% by weight of the resin, and most preferably, the entire resin. The term "main component" of the resin refers to a component that is present in an amount exceeding 50% by weight of the total resin.

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

The ratio of adhesive polyimide to solvent in the adhesive resin composition is not particularly limited as long as it maintains a viscosity sufficient for coating. The viscosity of the adhesive resin composition is preferably within a range of 500 mPa.s to 100,000 mPa.s. Exceeding this range can easily lead to defects such as uneven thickness and streaks in the resin film during coating.

The adhesive resin composition may contain, as appropriate, other curing resin components such as plasticizers, epoxy resins, curing agents, curing accelerators, organic fillers, inorganic fillers, coupling agents, flame retardants, etc. as optional ingredients, within the scope that does not impair the effects of the invention.

[Adhesive film]

The adhesive film of one embodiment of the present invention is formed by processing the adhesive polyimide or crosslinked polyimide into a film. The adhesive film is not particularly limited as long as it contains the adhesive polyimide or crosslinked polyimide as the main component of the resin, preferably comprising at least 70% by weight of the resin, more preferably at least 90% by weight of the resin, and most preferably comprising the entire resin. The term "main component" in the resin refers to a component comprising more than 50% by weight of the total resin. The adhesive film can be a film (sheet) comprising an adhesive polyimide or cross-linked polyimide. For example, it can be laminated onto an inorganic substrate such as copper foil or glass plate, or onto a resin substrate such as a polyimide film, polyamide film, or polyester film. The adhesive film can be appropriately formulated with optional ingredients such as plasticizers, other curing resin components such as epoxy resins, hardeners, curing accelerators, organic fillers, inorganic fillers, coupling agents, and flame retardants.

Adhesive films formed from adhesive polyimide meeting conditions a, b1, and c preferably have a dielectric loss tangent (Tanδ1) of 0.005 or less and _a relative dielectric constant ( _E1 ) of 3.0 or less at 10 GHz, as measured by a separate dielectric resonator (SPDR) after 24 hours of humidification at constant temperature and humidity (23°C, 50% RH). If the dielectric loss tangent ( _Tanδ1 ) and relative dielectric constant ( _E1 ) exceed these values, the film may increase dielectric loss when used in circuit boards, potentially causing problems such as signal loss in high-frequency signal transmission paths.

Furthermore, adhesive films formed from adhesive polyimide meeting conditions a, b1, and c preferably have a dielectric loss tangent ( _Tanδ2 ) of 0.005 or less and a relative dielectric constant ( _E2 ) of 3.0 or less at 20 GHz, as measured by a separate dielectric resonator (SPDR) after humidification for 24 hours at constant temperature and humidity (23°C, 50% RH). If the dielectric loss tangent ( _Tanδ2 ) and relative dielectric constant ( _E2 ) exceed these values, the film may increase dielectric loss when used in circuit boards, potentially causing problems such as signal loss in high-frequency signal transmission paths.

Furthermore, for an adhesive film formed from an adhesive polyimide meeting conditions a, b1, and c, after humidification for 24 hours at constant temperature and humidity of 23°C and 50% RH (normal state), the difference (Tanδ 2 - Tanδ 1 ) between the dielectric loss tangent at 10 GHz (Tanδ ₁ ) and the dielectric loss tangent at 20 GHz (Tanδ ₂ ) as measured by a separated dielectric resonator (SPDR) is preferably zero or less. A difference (Tanδ ₂ - Tanδ _{1 )} of _zero or less means that even when the frequency is increased from 10 GHz to 20 GHz, the transmission loss does not increase but remains the same or decreases.

On the other hand, adhesive films formed from adhesive polyimide meeting conditions a, b2, and c preferably have a dielectric loss tangent ( _Tanδ1 ) of less than 0.002 and a relative dielectric constant ( _E1 ) of 3.0 or less at 10 GHz, as measured by a separate dielectric resonator (SPDR) at constant temperature and humidity (23°C, 50% RH) for 24 hours. If the dielectric loss tangent ( _Tanδ1 ) and relative dielectric constant ( _E1 ) exceed these values, the film will increase dielectric loss when used in circuit boards, potentially causing problems such as signal loss in high-frequency signal transmission paths.

Furthermore, adhesive films formed from adhesive polyimide meeting conditions a, b2, and c preferably have a dielectric loss tangent ( _Tanδ2 ) of less than 0.002 and a relative dielectric constant ( _E2 ) of 3.0 or less at 20 GHz, as measured by a separate dielectric resonator (SPDR) after 24 hours of humidification at constant temperature and humidity (23°C, 50% RH). If the dielectric loss tangent ( _Tanδ2 ) and relative dielectric constant ( _E2 ) exceed these values, the film may increase dielectric loss when used in circuit boards, potentially causing problems such as signal loss in high-frequency signal transmission paths.

The tensile modulus of the adhesive film is preferably 3000 MPa or less, more preferably 100 MPa to 2500 MPa, and even more preferably 200 MPa to 2000 MPa. A tensile modulus of less than 100 MPa can easily cause wrinkling in the film and lead to poor handling properties, such as air intrusion during lamination. A tensile modulus exceeding 3000 MPa can cause warping and reduced dimensional stability during lamination of the substrate and adhesive film. By maintaining this tensile modulus, a laminate with good handling properties, suppressed warping, and excellent dimensional stability can be obtained.

There is no particular limitation on the method for producing the adhesive film of this embodiment, but the following methods [1] to [3] can be used as examples.

[1] A method in which an adhesive polyimide is applied in a solution state (e.g., in the state of an adhesive resin composition) on an arbitrary substrate to form a coating film, which is then dried at a temperature of, for example, 80°C to 180°C to form a film, and then peeled off from the substrate as needed.

[2] A method in which a solution of polyamide, which is a precursor of adhesive polyimide, is applied to an arbitrary substrate and dried, followed by imidization and film formation, and then peeled off from the substrate as needed.

[3] A method of coating a solution of polyamide, which is a precursor of adhesive polyimide, on an arbitrary substrate and drying it, then peeling the polyamide gel film from the substrate and performing imidization to prepare an adhesive film.

There are no particular limitations on the method for applying the adhesive polyimide solution (or polyamide solution) to the substrate. For example, coating can be performed using a coating machine such as a notched wheel, a die, a knife, or a die lip.

Next, specific examples are given to explain preferred embodiments of laminates, metal-clad laminates, circuit boards, and multilayer circuit boards to which adhesive films are applied.

[Collision]

For example, as shown in FIG1 , a laminate 100 according to an embodiment of the present invention comprises a substrate 10 and an adhesive layer 20 laminated on at least one surface of the substrate 10, wherein the adhesive layer 20 comprises the adhesive film. Furthermore, the laminate 100 may also comprise any layer other than the above-mentioned layers. Examples of the substrate 10 in the laminate 100 include: substrates of inorganic materials such as copper foil and glass plates, or substrates of resin materials such as polyimide films, polyamide films, and polyester films. The laminate 100 may be manufactured according to any one of the adhesive film manufacturing methods [1] to [3], except that it does not peel off from the substrate 10. Alternatively, the laminate 100 can be manufactured by separately preparing the substrate 10 and the adhesive film and laminating them together.

Preferred forms of the laminate 100 include a cover film, copper foil with resin, and the like.

(Coating film)

Although not shown, the covering film, which is one form of the laminate 100, comprises a covering film material layer serving as a base material 10 and an adhesive layer 20 laminated on one side of the covering film material layer. The adhesive layer 20 comprises the adhesive film. Furthermore, the covering film may include any other layers besides those described above.

The material of the covering film layer is not particularly limited. For example, polyimide films such as polyimide resins, polyetherimide resins, and polyamideimide resins, as well as polyamide films and polyester films, can be used. Among these, polyimide films with excellent heat resistance are preferred. Furthermore, the covering film layer may contain a black pigment to effectively enhance light-shielding properties, concealment, and design. Furthermore, optional components such as matte pigments to reduce surface gloss may be included as long as the dielectric properties are improved.

The thickness of the covering film layer is not particularly limited, but is preferably within the range of 5 μm to 100 μm.

In addition, the thickness of the adhesive layer 20 is not particularly limited, but is preferably within the range of 10 μm to 75 μm.

The covering film of this embodiment can be manufactured using the following exemplary method.

First, as a first method, polyimide, which will become the adhesive layer 20, is applied in a solution state (e.g., preferably in the form of a varnish containing a solvent, more preferably an adhesive resin composition) onto one side of the covering film material layer. This is then dried at a temperature of, for example, 80°C to 180°C to form the adhesive layer 20. This results in a covering film comprising the covering film material layer and the adhesive layer 20.

Alternatively, as a second method, the polyimide for the adhesive layer 20 is applied to an arbitrary substrate in a solution state (e.g., preferably in the form of a varnish containing a solvent, more preferably an adhesive resin composition), dried at a temperature of, for example, 80°C to 180°C, and then peeled off to form an adhesive film for the adhesive layer 20. This adhesive film is then heat-pressed to a covering film material layer at a temperature of, for example, 60°C to 220°C to form a covering film.

(Copper foil with resin)

Regarding the resin-coated copper foil, another form of the laminate 100, although not shown, an adhesive layer 20 is laminated on at least one side of the copper foil serving as the base 10. The adhesive layer 20 includes the aforementioned adhesive film. Furthermore, the resin-coated copper foil of this embodiment may include any other layers besides those described above.

The thickness of the adhesive layer 20 in the resin-coated copper foil is preferably within a range of 0.1 μm to 125 μm, more preferably 0.3 μm to 100 μm. If the thickness of the adhesive layer 20 is less than the lower limit, problems such as insufficient adhesion may arise. On the other hand, if the thickness of the adhesive layer 20 exceeds the upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the perspective of lowering the dielectric constant and dielectric loss tangent, the thickness of the adhesive layer 20 is preferably set to 3 μm or greater.

The copper foil in the resin-coated copper foil is preferably made primarily of copper or a copper alloy. The thickness of the copper foil is preferably 35 μm or less, more preferably within the range of 5 μm to 25 μm. From the perspectives of production stability and handling, the lower limit of the copper foil thickness is preferably 5 μm. The copper foil may be either rolled copper foil or electrolytic copper foil. Commercially available copper foil may be used.

Resin-coated copper foil can be produced, for example, by sputtering a metal onto an adhesive film to form a seed layer, then forming a copper layer, such as by copper plating. Alternatively, the adhesive film and copper foil can be laminated together using methods such as hot pressing. Furthermore, to form the adhesive layer 20 on the copper foil, the resin-coated copper foil can be produced by casting a coating of an adhesive polyimide or its precursor, drying the resulting coating, and then performing the required heat treatment.

[Metal-clad laminate]

(First Form)

A 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, wherein at least one layer of the insulating resin layer includes the adhesive film. Furthermore, the metal-clad laminate according to this embodiment may also include any other layers other than those described above.

(Second Form)

For example, as shown in FIG2 , another embodiment of the present invention includes a metal-clad laminate 101 comprising an insulating resin layer 30, an adhesive layer 20 laminated on at least one side of the insulating resin layer 30, and a metal layer M laminated on the insulating resin layer 30 via the adhesive layer 20. The adhesive layer 20 comprises the adhesive film. Furthermore, the three-layer metal-clad laminate 101 may include any other layers besides those described above. In a three-layer metal-clad laminate 101, the adhesive layer 20 can be provided on one or both sides of the insulating resin layer 30, and the metal layer M can be provided on one or both sides of the insulating resin layer 30, with the adhesive layer 20 interposed therebetween. In other words, the three-layer metal-clad laminate 101 can be a single-sided or double-sided metal-clad laminate. By etching the metal layer M of the three-layer metal-clad laminate 101 and then performing wiring circuit processing, a single-sided or double-sided FPC can be manufactured.

The insulating resin layer 30 in the three-layer metal-clad laminate 101 is not particularly limited as long as it comprises an electrically insulating resin. Examples include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, and ethylene tetrafluoroethylene (ETFE). Polyimide is preferred. The polyimide layer comprising the insulating resin layer 30 may be a single layer or multiple layers, but preferably comprises a non-thermoplastic polyimide layer.

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

The thickness of the adhesive layer 20 in the three-layer metal-clad laminate 101 is preferably within a range of 0.1 μm to 125 μm, and more preferably within a range of 0.3 μm 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 lower limit, problems such as insufficient adhesion may arise. On the other hand, if the thickness of the adhesive layer 20 exceeds the upper limit, problems such as reduced dimensional stability may occur. Furthermore, from the perspective of lowering the dielectric constant and dielectric loss tangent of the entire insulating layer as a laminate of the insulating resin layer 30 and the adhesive layer 20, the thickness of the adhesive layer 20 is preferably set to 3 μm or greater.

The ratio of the thickness of the insulating resin layer 30 to the thickness of the adhesive layer 20 (insulating resin layer 30 thickness/adhesive layer 20 thickness) is preferably within a range of 0.1 to 3.0, more preferably within a range of 0.15 to 2.0. By setting this ratio, warping of the three-layer metal-clad laminate 101 can be suppressed. Furthermore, the insulating resin layer 30 may contain a filler, if necessary. Examples of such fillers include silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and metal salts of organic phosphinic acids. These fillers may be used alone or in combination of two or more.

(Third Form)

For example, as shown in Figure 3, another embodiment of the present invention comprises a laminated metal-clad laminate 102 formed by laminating at least two single-sided metal-clad laminates with an adhesive layer 20 interposed therebetween. The laminated 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. The adhesive layer 20 comprises the adhesive film.

Here, the first single-sided metal-clad laminate 41 includes 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 includes 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. Furthermore, the bonded metal-clad laminate 102 may include any layers other than those described above.

The first insulating resin layer 31 and the second insulating resin layer 32 in the laminated metal-clad laminate 102 can have the same structure as the insulating resin layer 30 in the second type of three-layer metal-clad laminate 101.

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, respectively, placing an adhesive film between the first insulating resin layer 31 and the second insulating resin layer 32, and bonding them together.

(Fourth Form)

For example, as shown in FIG4 , another embodiment of the present invention includes a metal-clad laminate 103 with an adhesive layer, comprising an insulating resin layer 33, 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 includes the adhesive film. Furthermore, the metal-clad laminate 103 with an adhesive layer may include any other layers besides those described above.

The insulating resin layer 33 in the metal-clad laminate with adhesive layer 103 can have the same structure as the insulating resin layer 30 of the three-layer metal-clad laminate 101 of the second embodiment.

The metal-clad laminate 103 with an adhesive layer can be manufactured as follows: a single-sided metal-clad laminate having an insulating resin layer 33 and a metal layer M is prepared, and an adhesive film is applied to the insulating resin layer 33.

In any of the first to fourth exemplary metal-clad laminates, the material of the metal layer M (including the first metal layer M1 and the second metal layer M2; the same shall apply hereinafter) is not particularly limited. Examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among them, copper or a copper alloy is particularly preferred. The material of the wiring layer in the circuit board described below is also the same as that of the metal layer M1.

The thickness of the metal layer M is not particularly limited. For example, when using a metal foil such as copper foil, it is preferably 35 μm or less, and more preferably within the range of 5 μm to 25 μm. From the perspective of production stability and handling, the lower limit of the metal foil thickness is preferably 5 μm. Furthermore, when using copper foil, it can be either rolled copper foil or electrolytic copper foil. Commercially available copper foil can be used. Furthermore, the metal foil may be surface treated with, for example, siding, aluminum alkoxide, aluminum chelate, or silane coupling agent for rust protection or improved adhesion.

[Circuit board]

(First Form)

The circuit board of an embodiment of the present invention is formed by processing the metal layer of the metal-clad laminate of any of the aforementioned embodiments into wiring. By processing one or more metal layers of the metal-clad laminate into a pattern using conventional methods to form a wiring layer (conductive circuit layer), a circuit board such as an FPC can be manufactured. Furthermore, the circuit board may include a cover film covering the wiring layer.

(Second Form)

For example, as shown in Figure 5, a circuit board 200 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; and 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. The adhesive layer 20 includes the aforementioned adhesive film. Furthermore, the circuit board 200 may include any other layers besides those described above.

The first substrate 11 in the circuit board 200 can have the same structure as the insulating resin layer of the metal-clad laminate. The circuit board 200 can be manufactured by laminating an adhesive film to the wiring layer 50 side of the circuit board, which includes the first substrate 11 and the wiring layer 50 laminated on at least one side of the first substrate 11.

(Third Form)

For example, as shown in Figure 6, a 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, wherein the adhesive layer 20 includes the aforementioned adhesive film. Furthermore, the circuit board 201 may include any layers other than those described above. The first substrate 11 and the second substrate 12 in the circuit board 201 may have the same structure as the insulating resin layer of the metal-clad laminate.

The circuit board 201 can be manufactured by laminating the second substrate 12 to the wiring layer 50 side of the circuit board, which includes a first substrate 11 and a wiring layer 50 laminated on at least one surface of the first substrate 11, via a spacer film.

(Fourth Form)

For example, as shown in Figure 7, a circuit board 202 according to another embodiment of the present invention includes: a first substrate 11; an adhesive layer 20 laminated on at least one surface of the first substrate 11; a second substrate 12 laminated on the surface of the adhesive layer 20 opposite the first substrate 11; and wiring layers 50, 50 laminated on the surfaces of the first substrate 11 and the second substrate 12, respectively, opposite the adhesive layer 20. The adhesive layer 20 comprises the adhesive film. Furthermore, the circuit board 202 may include any layers other than those described above. The first substrate 11 and the second substrate 12 in the circuit board 202 may have the same structure as the insulating resin layer of the metal-clad laminate.

Circuit board 202 can be manufactured by preparing a first circuit board including a first substrate 11 and a wiring layer 50 laminated on at least one surface of the first substrate 11, and a second circuit board including a second substrate 12 and a wiring layer 50 laminated on at least one surface of the second substrate 12. An adhesive film is then placed between first substrate 11 of the first circuit board and second substrate 12 of the second circuit board, and the two substrates are bonded together.

[Multi-layer circuit board]

A multilayer circuit board according to one embodiment of the present invention includes a laminate formed by laminating a plurality of insulating resin layers and one or more wiring layers embedded within the laminate. At least one of the plurality of insulating resin layers is formed from an adhesive layer 20 having adhesive properties and covering the wiring layers. The adhesive layer 20 includes the adhesive film. Furthermore, the multilayer circuit board according to this embodiment may include any other layers than those described above.

For example, as shown in Figure 8 , the multilayer circuit board 203 of this embodiment includes at least two insulating resin layers 34 and at least two wiring layers 50. At least one layer of the wiring layers 50 is covered with an adhesive layer 20. The adhesive layer 20 covering the wiring layers 50 may cover a portion of the surface of the wiring layers 50 or the entire surface of the wiring layers 50. Furthermore, the multilayer circuit board 203 may optionally include wiring layers 50 exposed on the surface of the multilayer circuit board 203. Furthermore, the multilayer circuit board 203 may include interlayer connection electrodes (via electrodes) connected to the wiring layers 50. The wiring layer 50 is a layer formed with a conductive circuit in a predetermined pattern on one or both sides of the insulating resin layer 34. The conductive circuit can be patterned on the surface of the insulating resin layer 34 or embedded in the insulating resin layer. The insulating resin layer 34 in the multi-layer circuit board 203 can have the same structure as the insulating resin layer of the metal-clad laminate described above.

The circuit substrate and multi-layer circuit substrate of each of the above embodiments include an adhesive layer 20 comprising an adhesive polyimide with a controlled aromatic ring concentration, thereby reducing transmission loss during high-frequency transmission.

[Function]

Figure 9 is a diagram schematically showing the relationship between the aromatic ring concentration and the dielectric loss tangent when the adhesive polyimide of the present invention satisfies conditions a, b1, and c. The vertical axis of Figure 9 represents the dielectric loss tangent at 10 GHz, measured using the same method as in the examples described below, while the horizontal axis represents the weight content (aromatic ring concentration) of carbon atoms derived from six-membered aromatic rings relative to the total content of all atoms in the polyimide. Aromatic rings such as benzene rings vibrate at high frequencies, increasing thermal loss. Therefore, as a general rule, the dielectric loss tangent increases as the aromatic ring concentration in the polyimide increases. However, they discovered that when the aromatic ring concentration of the adhesive polyimide is within the range of 12% to 40% by weight, the dielectric loss tangent does not increase even with increasing aromatic ring concentration. Instead, it shows a tendency to decrease until a certain aromatic ring concentration is reached. While the reason for this behavior is not yet clear, the following considerations provide a plausible explanation.

Adhesive polyimides, made from a dimer diamine composition, have a relatively low aromatic ring concentration compared to polyimides made from aromatic diamines. It is speculated that as the aromatic ring concentration is gradually increased from a low state, the molecular motion is restricted due to interactions between the aromatic rings, further suppressing the dielectric loss tangent. Furthermore, it is believed that a sufficiently low dielectric loss tangent is achieved before the aromatic ring concentration reaches 40% by weight.

[Example]

The following examples illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited to the examples. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations are based on the following contents.

[Determination of amine value]

Weigh approximately 2g of the dimer diamine composition into a 200mL-250mL Erlenmeyer flask. Using phenolphthalein as an indicator, add 0.1mol/L ethanolic potassium hydroxide solution dropwise until the solution turns light pink. Dissolve the mixture in approximately 100mL of neutralized butanol. Add 3-7 drops of phenolphthalein solution and titrate with 0.1mol/L ethanolic potassium hydroxide solution while stirring until the sample solution turns light pink. Add 5 drops of bromophenol blue solution and titrate with 0.2mol/L hydrochloric acid/isopropanol solution while stirring until the sample solution turns yellow.

The amine value is calculated using the following formula (1).

Amine valence = {(V ₂ ×C ₂ )-(V ₁ ×C ₁ )}×M _KOH /m...(1)

Here, the amine value is expressed in mg-KOH/g, and M _KOH is the molecular weight of potassium hydroxide, 56.1. V and C represent the volume and concentration of the solution used in the titration, respectively. 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. Furthermore, m represents the sample weight in grams.

[Determination of the weight average molecular weight (Mw) of polyimide]

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

[Calculation Method of CM Value]

The CM value is calculated based on the following formula from the relationship between the weight average molecular weight (Mw) of the polyimide and the weight content ( _Cp ) of carbon atoms derived from six-membered aromatic rings (excluding carbon atoms derived from six-membered aromatic rings of the dimer diamine composition) relative to the total content of all atoms in the polyimide.

CM=(C _p /Mw)×10 ⁴ ...(i)

[DM value calculation method]

The DM value is calculated based on the following formula from the relationship between the weight average molecular weight (Mw) of the polyimide and the content ( _Cd ) of carbon atoms derived from six-membered aromatic rings (excluding carbon atoms derived from six-membered aromatic rings in the dimer diamine composition) relative to the total content of all atoms in all diamine components.

DM=(C _d /Mw)×10 ⁴ ...(ii)

[Calculation of the aromatic ring ratio of the dimer diamine composition]

The aromatic ring ratio of the dimer diamine composition is calculated according to the following process. First, a sample is prepared by dissolving approximately 50 μl of the dimer diamine composition in 550 μl of THF-d8. The prepared sample is subjected to liquid 1H-NMR measurement at room temperature using an FT-NMR apparatus (JNM-ECA400 manufactured by JEOL). The aromatic ring ratio is calculated as follows based on the ratio of the integrated value of the 1H peak derived from aromatic rings observed at 6.6 ppm to 7.2 ppm relative to the integrated value of the _1H peak derived from _CH2 groups directly bonded to NH2 groups observed at 2.6 ppm to 2.9 ppm.

Aromatic ring ratio [mol%] = (Z/Y) × 100

[Here, Y refers to the integrated value of the 1H peak at 2.6ppm to 2.9ppm, and Z refers to the integrated value of the 1H peak (derived from the aromatic ring) at 6.6ppm to 7.2ppm.

[Calculation of area percentage from GPC and chromatograms]

(a) Dimer diamine

(b) Monoamine compounds obtained by replacing the terminal carboxylic acid group of a monobasic acid compound having a carbon number in the range of 10 to 40 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 carbon number in the range of 41 to 80 and having an alkyl group with a primary aminomethyl group or an amino group (excluding the aforementioned dimer diamine).

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. The resulting solution was diluted with 10 mL of THF (containing 1000 ppm of cyclohexanone) to prepare the sample. The prepared sample was measured using a TOSOH HLC-8220 GPC analyzer (trade name: TSK-gel G2000HXL or G1000HXL) using TSK-gel columns, a flow rate of 1 mL/min, a column (oven) temperature of 40°C, and an injection volume of 50 μL. Cyclohexanone was used as a standard to correct the elution time.

At this time, the retention time of the peak top of the main peak of cyclohexanone was changed from 27 minutes to 31 minutes, and the peak-to-peak time of the main peak of cyclohexanone was adjusted to 2 minutes. The peak top of the main peak excluding the peak of cyclohexanone was changed from 18 minutes to 19 minutes, and the peak-to-peak time of the main peak excluding the peak of cyclohexanone was changed from 2 minutes to 4 minutes 30 seconds. Components (a) to (c) were detected: (a) the component represented by the main peak; (b) the component represented by the GPC peak detected at a later time, relative to the minimum value on the later retention time side of the main peak; (c) the component represented by the GPC peak detected at an earlier time, relative to the minimum value on the earlier retention time side of the main peak.

[Viscosity measurement]

The viscosity (cP) of the polyimide solution immediately after polymerization was measured using an E-type viscometer (DV-II+ProCP) at a temperature of 25°C, a rotation speed of 100 RPM, and a measurement time of 2 minutes.

[Determination of relative dielectric constant and dielectric loss tangent]

Using a Vector Network Analyzer (Agilent Technologies, trade name: Vector Network Analyzer E8363C) and SPDR, the resin sheets were left at 23°C and 50% humidity for 24 hours. The relative dielectric constant (ε ₁ ) and dielectric loss tangent (Tan δ ₁ ) at a frequency of 10 GHz, and the relative dielectric constant (ε ₂ ) and dielectric loss tangent (Tan δ ₂ ) at a frequency of 20 GHz were measured. The R value, an indicator of the frequency dependence of the dielectric loss tangent, was calculated using the following formula.

R value = Tanδ ₂ - Tanδ ₁

[Glass transition temperature (Tg)]

The glass transition temperature (Tg) was measured on a 5 mm x 20 mm resin sheet using a thermomechanical analyzer (TMA (Thermal Mechanical Analyzer): manufactured by NETZSCH, trade name: TMA4000SA) at a heating rate of 5°C/minute from 0°C to 300°C. The temperature at which the elongation during heating inflected was defined as the glass transition temperature.

[Tensile elastic modulus]

The tensile modulus was measured according to the following procedure. First, a test piece (12.7 mm wide x 127 mm long) was prepared from a resin sheet using a tension tester (manufactured by ORIENTEC, trade name: Tensilon). Using this test piece, a tensile test was performed at 50 mm/min to determine the tensile modulus at 25°C.

[Evaluation Methods of Cursive]

Warp evaluation is performed using the following method. A polyimide solution is applied to a 25μm-thick polyimide film (Toray Dupont, trade name: Kapton 100EN) or a 12μm-thick copper foil to a dried thickness of 25μm to prepare a test piece. The test piece is then placed with the polyimide film or copper foil facing downward. The average height of the warp at the four corners of the test piece is measured. A value of 5mm or less is considered "good," while a value exceeding 5mm is considered "unacceptable."

The abbreviations used in this example represent the following compounds.

BTDA: 3,3',4,4'-Benzophenonetetracarboxylic dianhydride

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

ODPA: 4,4'-oxydiphthalic anhydride

BPADA: 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride

DDA: C36 dimer diamine (a compound obtained by distillation purification of Priamine 1074 (trade name, Croda Japan Co., Ltd.); amine value: 210 mgKOH/g; a mixture of cyclic and chain dimer diamines; component (a): 97.9% by volume; component (b): 0.3% by volume; component (c): 1.8% by volume; aromatic ring ratio: 8.2 mol%).

BAFL: Bisaniline Fluorene

APB: 1,3-bis(3-aminophenoxy)benzene

BAPP: 2,2-Bis[4-(4-aminophenoxy)phenyl]propane

N-12: Dodecanedioic acid dihydrazine

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 _D50 : 2μm)

SR-3000: Phosphate ester (manufactured by Dahachi Chemical Industry Co., Ltd., trade name: SR-3000, non-halogenated aromatic condensed phosphate ester, phosphorus content: 7.0%)

Furthermore, the molecular weight of DDA is calculated using the following formula.

Molecular weight = 56.1 × 2 × 1000 / amine value

[Example A1]

A 1000 ml separable flask was charged with 46.43 g of BTDA (0.1441 mol), 68.60 g of DDA (0.1284 mol), 4.97 g of BAFL (0.0143 mol), 168 g of NMP, and 112 g of xylene. The mixture was thoroughly mixed at 40°C for 1 hour to prepare a polyamide solution. The polyamide solution was heated to 190°C and stirred for 5 hours. 98 g of xylene was then added to prepare imidized polyimide solution A1 (solid content: 30 wt%, weight-average molecular weight: 28,850, 6-membered aromatic ring content _Cd : 5.59%, _Cp : 21.57%, DM value: 1.9, CM value: 7.5).

[Example A2~Example A18]

Polyimide solutions A2 to A18 were prepared in the same manner as in Example A1, except that the raw material compositions were set as shown in Tables 1 and 2.

[Example A19]

Polyimide solution A1 was applied to one side of a release polyethylene terephthalate (PET) film 1 (manufactured by Dongshan Film Co., Ltd., trade name: HY-S05, length × width × thickness = 200 mm × 300 mm × 25 μm). The film was dried at 120°C for 10 minutes, and the adhesive layer was peeled off the release PET film 1 to obtain a 25 μm thick adhesive film A19. The evaluation results of adhesive film A19 are described below.

ε ₁ : 2.6, Tanδ ₁ : 0.0017, ε ₂ : 2.6, Tanδ ₂ : 0.0014, R value: -0.0003, Tg: 45°C, tensile modulus: 630 MPa

[Example A20~Example A36]

Adhesive films A20 to A36 were obtained in the same manner as in Example A19, except that polyimide solutions A2 to A18 were used. The results of various property evaluations are shown in Table 3.

[Example A37]

1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution A1 (30 g solid content). 7.5 g of OP935, 2.0 g of NMP, and 12.0 g of xylene were added for dilution, and the mixture was stirred for 1 hour to prepare adhesive composition A37.

[Example A38~Example A54]

Adhesive compositions A38 to A54 were prepared in the same manner as in Example A37, except that polyimide solutions A2 to A18 were used.

[Example A55]

0.6 g of N-12 (0.002 mol) was added to 100 g of polyimide solution A17 (30 g solid content). 7.5 g of OP935, 1.5 g of NMP, and 11.4 g of xylene were added for dilution, and the mixture was stirred for 1 hour to prepare adhesive composition A55.

[Example A56]

1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution A11 (30 g solid content). The mixture was diluted with 6.0 g of SR-3000, 0.3 g of NMP, and 10.3 g of xylene, and stirred for 1 hour to prepare adhesive composition A56.

[Example A57]

Adhesive composition A37 was applied to one side of a release PET film 1 and dried at 80°C for 15 minutes to obtain a resin sheet A57 with an adhesive layer thickness of 25 μm. The adhesive layer was then peeled off the release PET film 1 to obtain an adhesive film A57 with a thickness of 25 μm.

[Example A58~Example A76]

Except for using adhesive compositions A38 to A56, resin sheets A58 to A76 were obtained in the same manner as in Example A57, and then adhesive films A58 to A76 were obtained.

[Example A77]

Adhesive composition A37 was applied to one side of a polyimide film 1 (manufactured by Toray Dupont Co., Ltd., trade name: Kapton 50EN, ε ₁ = 3.6, tan δ ₁ = 0.0084, length × width × thickness = 200 mm × 300 mm × 12 μm). The film was dried at 80°C for 15 minutes to obtain a cover film A77 with a 25 μm thick adhesive layer. The warp quality of the obtained cover film A77 was rated "good."

[Example A78~Example A81]

Coating films A78 through A81 were obtained in the same manner as in Example A77, except that adhesive compositions A40, A54, A55, and A56 were used. The warping conditions of the obtained coating films A78 through A81 were all rated "good."

[Example A82]

The release PET film 1 and the adhesive-coated side of the cover film A77 were laminated together and pressed using a vacuum laminating press at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes.

Next, adhesive composition A37 was applied to a 25μm thickness after drying onto the polyimide film 1 side of the cover film A77, which was press-bonded with a release PET film 1 on the adhesive layer side. The film was then dried at 80°C for 15 minutes. The release PET film 1 and the surfaces coated and dried with adhesive composition A37 were then laminated, with the two surfaces facing each other. The laminate was then pressed using a vacuum laminating press at 160°C and a pressure of 0.8 MPa for 2 minutes, yielding a laminate A82 with adhesive layers on both sides of the polyimide film.

[Example A83~Example A86]

Laminates A83 to A86 with a polyimide adhesive layer were obtained in the same manner as in Example A82, except that cover film A78, cover film A79, cover film A80, or cover film A81 was used and adhesive composition A40, adhesive composition A54, adhesive composition A55, or adhesive composition A56 was applied.

[Example A87]

Adhesive composition A37 was applied to one side of a 12μm-thick electrolytic copper foil and dried at 80°C for 15 minutes to obtain a 25μm-thick resin-coated copper foil A87. The curling quality of the resulting resin-coated copper foil A87 was rated "good."

[Example A88~Example A91]

Resin-coated copper foils A88 through A91 were obtained in the same manner as in Example A87, except that adhesive composition A40, A54, A55, or A56 was used. The curling properties of the obtained resin-coated copper foils A88 through A91 were all rated "good."

[Example A92]

Adhesive composition A37 was applied to one side of a 12μm-thick electrolytic copper foil and dried at 80°C for 30 minutes to obtain a 50μm-thick resin-coated copper foil A92. The curling condition of the resulting resin-coated copper foil A92 was rated "good."

[Example A93]

Adhesive composition A37 was further applied to the adhesive layer of resin-coated copper foil A92 and dried at 80°C for 30 minutes to obtain resin-coated copper foil A93, with a total adhesive layer thickness of 100 μm. The curling condition of the obtained resin-coated copper foil A93 was "good."

[Example A94]

Adhesive composition A37 was applied to one side of release PET film 1 and dried at 80°C for 30 minutes. The adhesive layer was then peeled off the release PET film 1 to obtain adhesive film A94 with a thickness of 50 μm.

On a 12μm thick electrolytic copper foil, adhesive film A94, polyimide film 2 (manufactured by Dupont, trade name: Kapton 100-EN, thickness: 25μm, ε ₁ =3.6, tan δ ₁ =0.0084), adhesive film A94, and 12μm thick electrolytic copper foil were sequentially laminated. The laminates were pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for 2 minutes. The laminates were then heated from room temperature to 160°C and heat treated at 160°C for 4 hours to obtain a copper-clad laminate A94.

[Example A95~Example A98]

Copper-clad laminates A95 to A98 were obtained in the same manner as in Example A94, except that adhesive composition A40, adhesive composition A54, adhesive composition A55, and adhesive composition A56 were used.

[Example A99]

A 12μm-thick electrolytic copper foil was laminated with the adhesive layer of the coating film A77 in contact with the copper foil. The laminate was pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for two minutes. The laminate was then heated from room temperature to 160°C and heat treated at 160°C for two hours to produce the copper-clad laminate A99.

[Example A100~Example A103]

Copper-clad laminates A100 to A103 were obtained in the same manner as in Example A99, except that cover films A78, A79, A80, and A81 were used.

[Example A104]

Adhesive film A57 was laminated onto a 12μm-thick rolled copper foil. The polyimide film side of the covering film A77 was then bonded to the adhesive film A57. Furthermore, another 12μm-thick rolled copper foil was laminated onto the adhesive layer side of the covering film A77. The laminate was then pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for two minutes. The laminate was then heated from room temperature to 160°C and heat treated at 160°C for two hours to produce the copper-clad laminate A104.

[Example A105~Example A108]

Copper-clad laminates A105 to A108 were fabricated in the same manner as in Example A104, except that adhesive films A60, A74, A75, and A76 were used instead of adhesive film A57, and cover films A78, A79, A80, and A81 were used instead of cover film A77.

[Example A109]

Two sheets of resin-coated copper foil A93 were prepared and laminated with a polyimide film 3 (manufactured by Dupont, trade name: Kapton 200-EN, thickness 50 μm, ε ₁ = 3.6, tan δ ₁ = 0.0084) so that the adhesive-coated sides of the two sheets of resin-coated copper foil A93 were in contact. The sheets were then pressed using a vacuum laminating press at a temperature of 160°C and a pressure of 0.8 MPa for 5 minutes. The sheets were then heated from room temperature to 160°C and heat treated at 160°C for 4 hours to obtain a copper-clad laminate A109.

[Example A110]

Adhesive composition A55 was applied to the resin layer (polyimide layer) side of a single-sided copper-clad laminate 1 (manufactured by Nippon Steel Chemical & Material Co., Ltd., trade name: Espanex MC12-25-00UEM, length × width × thickness = 200 mm × 300 mm × 25 μm). The adhesive composition was dried at 80°C for 30 minutes to obtain a copper-clad laminate A110 with a 50 μm adhesive layer. The single-sided copper-clad laminate 1 was laminated with the resin layer side contacting the adhesive layer side of the copper-clad laminate A110. 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 obtain the copper-clad laminate A110.

[Example A111]

The adhesive-coated side of the laminate was bonded to two copper-clad laminates A110 with adhesive layers. The laminates were then pressed together using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to produce copper-clad laminate A111.

[Example A112]

Adhesive film A73 was deposited on the resin layer side of the single-sided copper-clad laminate 1. Furthermore, another layer was laminated thereon so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with adhesive film A73. This 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 obtain copper-clad laminate A112.

[Example A113]

Adhesive composition A37 was applied to one side of release PET film 1 and dried at 80°C for 15 minutes. The adhesive layer was then peeled off the release PET film 1 to obtain adhesive film A113 with a thickness of 15 μm.

Adhesive film A113 was deposited on the resin layer side of the single-sided copper-clad laminate 1. Furthermore, another layer was laminated thereon so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with the adhesive film A113. This 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 obtain the copper-clad laminate A113.

[Example A114]

A double-sided copper-clad laminate 2 (Espanex MB12-25-00UEG, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was prepared. The copper foil on one side was etched to form a circuit, resulting in wiring board A114A with a conductive circuit layer.

The copper foil on one side of the double-sided copper-clad laminate 2 is etched away to obtain copper-clad laminate A114B.

An adhesive film A73 is sandwiched between the conductive circuit layer surface of wiring board A114A and the resin layer surface of copper-clad laminate A114B. In the laminated state, they are heat-pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to produce a multilayer circuit board A114.

[Example A115]

A copper-clad laminate A115 was prepared using a liquid crystal polymer film (Kuraray, trade name: CT-Z, thickness: 50μm, coefficient of thermal expansion (CTE): 18ppm/K, heat distortion temperature: 300°C, _ε1 = 3.40, _tanδ1 = 0.0022) as an insulating substrate. 18μm-thick electrolytic copper foil was placed on both sides of the film. Circuit processing was performed on one side of the copper foil by etching to obtain a wiring board A115A with a conductive circuit layer.

The copper foil on one side of the copper-clad laminate A115 is etched away to obtain copper-clad laminate A115B.

An adhesive film A73 is sandwiched between the conductive circuit layer surface of the wiring board A115A and the insulating base layer surface of the copper-clad laminate A115B. In the laminated state, they are heat-pressed for 120 minutes at a temperature of 160°C and a pressure of 4.0 MPa to obtain the multilayer circuit board A115.

[Example B1]

A 500 ml separable flask was charged with 27.90 g of BTDA (0.08642 mol), 6.702 g of ODPA (0.02161 mol), 46.50 g of DDA (0.08703 mol), 8.932 g of BAPP (0.02176 mol), 126 g of NMP, and 84 g of xylene. The mixture was thoroughly mixed at 40°C for 1 hour to prepare a polyamide solution. The polyamide solution was heated to 190°C and stirred for 5 hours. 60 g of xylene was then added to prepare imidized polyimide solution B1 (solid content: 30 wt%, weight average molecular weight: 35,332, viscosity: 2,627 cP).

[Example B2~Example B11]

Polyimide solutions B2 to B11 were prepared in the same manner as in Example B1, except that the raw material compositions were set as shown in Table 4.

[Example B12]

Polyimide solution B1 was applied to one side of a release PET film 1 (manufactured by Dongshan Film Co., Ltd., trade name: HY-S05, length × width × thickness = 200 mm × 300 mm × 25 μm). The film was dried at 100°C for 5 minutes and then at 120°C for 5 minutes. The adhesive layer was peeled from the release PET film 1 to obtain a 25 μm thick resin sheet B12. The evaluation results of resin sheet B12 are described below.

ε ₁ : 2.6, Tanδ ₁ : 0.0017, ε ₂ : 2.6, Tanδ ₂ : 0.0015, R value: -0.0002, Tg: 47°C, tensile modulus: 1230 MPa

[Example B13~Example B22]

Resin sheets B13 to B22 were obtained in the same manner as in Example B12, except that polyimide solutions B2 to B11 were used. The results of various property evaluations are shown in Table 5.

[Example B23]

1.1 g of N-12 (0.004 mol) was mixed with 100 g of polyimide solution B1 (30 g solid content). 7.5 g of OP935, 0.5 g of NMP, and 10.5 g of xylene were added for dilution, and the mixture was stirred for 1 hour to prepare adhesive composition B23.

[Example B24~Example B33]

Adhesive compositions B24 to B33 were prepared in the same manner as in Example B23, except that polyimide solutions B2 to B11 were used.

[Example B34]

0.6 g of N-12 (0.002 mol) was added to 100 g of polyimide solution B9 (30 g solid content). 7.4 g of OP935, 1.8 g of NMP, and 11.7 g of xylene were added for dilution, and the mixture was stirred for 1 hour to prepare adhesive composition B34.

[Example B35]

Adhesive composition B23 was applied to one side of a release PET film 1 and dried at 80°C for 15 minutes to obtain a resin sheet B35 with an adhesive layer thickness of 25 μm. The adhesive layer was then peeled off the release PET film 1 to obtain an adhesive film B35 with a thickness of 25 μm.

[Example B36~Example B46]

Adhesive films B36 to B46 were obtained in the same manner as in Example B35, except that adhesive compositions B24 to B34 were used.

[Example B47]

Adhesive composition B31 was applied to one side of a polyimide film 1 (manufactured by Toray Dupont Co., Ltd., trade name: Kapton 50EN, ε ₁ = 3.6, tan δ ₁ = 0.0084, length × width × thickness = 200 mm × 300 mm × 12 μm). The film was dried at 80°C for 15 minutes to obtain a cover film B47 with a 25 μm thick adhesive layer. The warp quality of the obtained cover film B47 was rated "good."

[Example B48, Example B49]

Coating films B48 and B49 were obtained in the same manner as in Example B47, except that adhesive compositions B24 and B25 were used. The warping conditions of both coating films B48 and B49 were rated "good."

[Example B50]

The release PET film 1 was laminated with the adhesive layer side of the cover film B47 in contact, and pressed using a vacuum laminating press at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes. Adhesive composition B31 was then applied to the polyimide film 1 side of the cover film B47, with the release PET film 1 pressed against the adhesive layer side, to a thickness of 25 μm after drying. The film was then dried at 80°C for 15 minutes. Next, the release PET film 1 was laminated with the surface coated with and dried with the adhesive composition B31. The two layers were pressed together using a vacuum laminating press at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes. This yielded a laminate B50 with adhesive layers on both sides of the polyimide film.

[Example B51, Example B52]

Laminates B51 and B52 with a polyimide adhesive layer were obtained in the same manner as in Example B50, except that cover films B48 and B49 were used and adhesive compositions B24 and B25 were applied.

[Example B53]

Adhesive composition B31 was applied to one side of a 12μm-thick electrolytic copper foil and dried at 80°C for 15 minutes to obtain a 25μm-thick resin-coated copper foil B53. The curling condition of the resulting resin-coated copper foil B53 was rated "good."

[Example B54~Example B56]

Resin-coated copper foils B54 through B56 were obtained in the same manner as in Example B53, except that adhesive compositions B24, B25, and B26 were used. The curling properties of the obtained resin-coated copper foils B54 through B56 were all rated "good."

[Example B57]

Adhesive composition B31 was applied to one side of a 12μm-thick electrolytic copper foil and dried at 80°C for 30 minutes to obtain a resin-coated copper foil B57 with a 50μm-thick adhesive layer. The curling condition of the resulting resin-coated copper foil B57 was rated "good."

[Example B58]

Adhesive composition B31 was further applied to the adhesive layer of resin-coated copper foil B57 and dried at 80°C for 30 minutes to obtain resin-coated copper foil B58, with a total adhesive layer thickness of 100 μm. The curling condition of the obtained resin-coated copper foil B58 was "good."

[Example B59]

Adhesive composition B31 was applied to one side of release PET film 1 and dried at 80°C for 30 minutes. The adhesive layer was then peeled off the release PET film 1 to obtain adhesive film B59 with a thickness of 50 μm.

[Example B60]

On a 12μm thick electrolytic copper foil, adhesive film B59, polyimide film 2 (manufactured by Dupont, trade name: Kapton 100-EN, thickness 25μm, ε ₁ =3.6, tan δ ₁ =0.0084), adhesive film B44, and a 12μm thick electrolytic copper foil were sequentially laminated. The laminates were pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for 2 minutes. The laminates were then heated from room temperature to 160°C and heat treated at 160°C for 4 hours to obtain a copper-clad laminate B60.

[Example B61~Example B63]

Copper-clad laminates B61 to B63 were obtained in the same manner as in Example B60, except that adhesive films B36, B37, and B38 were used.

[Example B64]

On a 12μm-thick electrolytic copper foil, a coating film B47 was laminated with the adhesive layer side of the coating film in contact with the copper foil. The laminate was pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for 2 minutes. The laminate was then heated from room temperature to 160°C and heat treated at 160°C for 2 hours to produce the copper-clad laminate B64.

[Example B65, Example B66]

Copper-clad laminates B65 and B66 were obtained in the same manner as in Example B64, except that cover films B48 and B49 were used.

[Example B67]

Adhesive film B44 was laminated onto a 12μm-thick rolled copper foil, with the polyimide film side of the covering film B47 in contact with the adhesive film B44. Furthermore, another 12μm-thick rolled copper foil was laminated onto the adhesive layer side of the covering film B47. The laminate was then pressed using a vacuum lamination press at 160°C and a pressure of 0.8 MPa for 2 minutes. The laminate was then heated from room temperature to 160°C and heat treated at 160°C for 2 hours to obtain the copper-clad laminate B67.

[Example B68, Example B69]

Copper-clad laminates B68 and B69 were produced in the same manner as in Example B67, except that adhesive films B35 and B36 were used instead of adhesive film B44, and cover films B48 and B49 were used instead of cover film B47.

[Example B70]

Two sheets of resin-coated copper foil B57 were prepared and laminated with a polyimide film 3 (manufactured by Dupont, trade name: Kapton 200-EN, thickness 50 μm, ε ₁ = 3.6, tan δ ₁ = 0.0084) so that the adhesive-coated sides of the two sheets of resin-coated copper foil B57 were in contact. The sheets were then pressed using a vacuum lamination press at a temperature of 160°C and a pressure of 0.8 MPa for 5 minutes. The sheets were then heated from room temperature to 160°C and heat treated at 160°C for 4 hours to obtain a copper-clad laminate B70.

[Example B71]

Adhesive composition B31 was applied to the resin layer (polyimide layer) side of a single-sided copper-clad laminate 1 (manufactured by Nippon Steel Chemical & Material Co., Ltd., trade name: Espanex MC12-25-00UEM, length × width × thickness = 200 mm × 300 mm × 25 μm). The adhesive composition was dried at 80°C for 30 minutes to obtain a copper-clad laminate B71 with an adhesive layer having a thickness of 50 μm. The resin layer of the other single-sided copper-clad laminate 1 was laminated to the adhesive layer of the copper-clad laminate B71. The laminate was then pressed together using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain the copper-clad laminate B71.

[Example B72]

The adhesive-coated side of the laminate was bonded to two copper-clad laminates B71 with adhesive layers. The laminates were then pressed together using a small precision press at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to produce copper-clad laminate B72.

[Example B73]

Adhesive film B44 was deposited on the resin layer side of the single-sided copper-clad laminate 1. Furthermore, another layer was laminated thereon so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with adhesive film B44. This 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 obtain copper-clad laminate B73.

[Example B74]

Adhesive composition B31 was applied to one side of release PET film 1 and dried at 80°C for 15 minutes. The adhesive layer was then peeled off the release PET film 1 to obtain adhesive film B74 with a thickness of 15 μm.

[Example B75]

Adhesive film B74 was deposited on the resin layer side of single-sided copper-clad laminate 1. Furthermore, another layer was laminated thereon so that the resin layer side of the single-sided copper-clad laminate 1 was in contact with adhesive film B74. This 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 obtain copper-clad laminate B75.

[Example B76]

A double-sided copper-clad laminate 2 (Espanex MB12-25-00UEG, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was prepared. Circuitry was etched onto the copper foil on one side, resulting in a wiring board B76A with a conductive circuit layer.

The copper foil on one side of the double-sided copper-clad laminate 2 is etched away to obtain the copper-clad laminate B76B.

An adhesive film B44 is sandwiched between the conductive circuit layer surface of the wiring board B76A and the resin layer surface of the copper-clad laminate B76B. In the laminated state, they are hot-pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain the multi-layer circuit board B76.

[Example B77]

A copper-clad laminate B77 was prepared using a liquid crystal polymer film (manufactured by Kuraray, trade name: CT-Z, thickness: 50μm, CTE: 18ppm/K, heat deformation temperature: 300°C, _ε1 = 3.40, _tanδ1 = 0.0022) as an insulating substrate, with 18μm-thick electrolytic copper foil placed on both sides. Circuit processing was performed on one side of the copper foil by etching to obtain a wiring substrate B77A with a conductive circuit layer.

The copper foil on one side of copper-clad laminate B77 is etched away to obtain copper-clad laminate B77B.

An adhesive film B44 is sandwiched between the conductive circuit layer side of the wiring board B77A and the insulating base layer side of the copper-clad multilayer board B77B. In the laminated state, they are hot-pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain the multilayer circuit board B77.

While the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the embodiments described above and various modifications are possible.

This application claims priority based on Japanese Patent Application No. 2020-046163 filed in Japan on March 17, 2020, and Japanese Patent Application No. 2020-064081 filed in Japan on March 31, 2020, and the entire contents of those applications are incorporated herein by reference.

Claims (23)

A polyimide comprising tetracarboxylic acid residues derived from a tetracarboxylic anhydride component and diamine residues derived from a diamine component, wherein the polyimide satisfies the following conditions a, b1, and c, or conditions a, b2, and c: a) containing, relative to all diamine residues, 60 mol% or more and 99 mol% or less of a dimer diamine composition having as its main component a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups; b1) a content of carbon atoms derived from a 6-membered aromatic ring in the range of 21.57% by weight to 30% by weight relative to the total content of all atoms in the polyimide, wherein the carbon atoms derived from the 6-membered aromatic ring do not include carbon atoms derived from the 6-membered aromatic ring of the dimer diamine composition; b2) a diamine residue derived from a diamine compound represented by the following general formula (A1) in the range of 5 mol% to 40 mol% relative to all diamine residues; In the general formula (A1), Y and Z independently represent a hydrogen atom, an alkyl group, an alkoxy group, an alkenyl group or an alkynyl group having 1 to 6 carbon atoms, and the linking group X represents a group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -CH ₂ -O-, -C(CH ₃ ) ₂ -, -NH- or -CONH- wherein m represents a divalent group and an integer of 1 to 4; wherein, when a plurality of linking groups X are contained in the molecule, they may be the same or different; c) the weight average molecular weight is within the range of 10,000 to 60,000, and the dimer diamine composition contains the dimer diamine of component (a) as a main component and is a purified product in which the amounts of components (b) and (c) are controlled, wherein the dimer diamine content of component (a) is 96% by weight or more, wherein the dimer diamine of component (a) is a dimer acid in which both terminal carboxylic acid groups are substituted with primary aminomethyl or amino groups. wherein the component (b) is a monoamine compound obtained by substituting a terminal carboxylic acid group of a monobasic acid compound having a carbon number in the range of 10 to 40 with a primary aminomethyl group or an amino group, and the component (c) is an amine compound obtained by substituting a terminal carboxylic acid group of a polybasic acid compound having a carbon number in the range of 41 to 80 with a primary aminomethyl group or an amino group, wherein the dimer diamine, excluding the dimer diamine, contains a tetracarboxylic acid residue derived from a tetracarboxylic anhydride represented by the following general formula (2) and/or general formula (3) in an amount of 90 mol% or more relative to the total amount of the acid anhydride residues; In the general formula (2), _X1 represents a single bond or a divalent group selected from the following formulae; in the general formula (3), the cyclic moiety represented by _Y1 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; -CO-, _-SO2- , -O-, -C( _CF3 ) _2- , -COO- or -COO-Z ₁ -OCO- in the above formula, Z ₁ represents -C ₆ H ₄ -, -(CH ₂ ) _m1 - or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, m1 represents an integer from 1 to 20, and when the above conditions a, b2, and c are satisfied, the radical X in the above general formula (2) is contained in a range of 10 mol% or more and 90 mol% or less relative to the total tetracarboxylic acid residues. a tetracarboxylic acid residue derived from benzophenonetetracarboxylic dianhydride in which ₁ is -CO-, containing 10 mol% or more of at least one tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride represented by the general formula (2) and/or the general formula (3), wherein the tetracarboxylic acid anhydride represented by the general formula (2) and/or the general formula (3) does not include the benzophenonetetracarboxylic dianhydride; and a diamine residue derived from at least one diamine compound selected from the diamine compounds represented by the following general formulas (B1) to (B7) in an amount of 1 mol% to 40 mol% relative to the total amount of the diamine residues; In Formulas (B1) to (B7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, _-SO- , -SO2-, -COO-, _-CH2- , -C( _CH3 ) _2- , -NH-, or -CONH-, and _n1 independently represents an integer from 0 to 4. The portion of Formula (B3) that is repeated with Formula (B2) is removed, and the portion of Formula (B5) that is repeated with Formula (B4) is removed. The polyimide of claim 1, wherein, when conditions a, b1, and c are satisfied, the following condition d is also satisfied: d) the CM value, an indicator of the amount of six-membered aromatic rings contained in the polyimide, calculated based on the following formula (i): CM value = (C/Mw) × 10 ⁴ ... (i) In the formula, C refers to the weight content of carbon atoms derived from six-membered aromatic rings relative to the total content of all atoms in the polyimide, and Mw refers to the weight-average molecular weight of the polyimide, wherein the carbon atoms derived from six-membered aromatic rings do not include carbon atoms derived from six-membered aromatic rings of the dimer diamine composition. The polyimide according to claim 1, wherein, when conditions a, b1, and c are satisfied, the following condition e is also satisfied: e) the content of carbon atoms derived from six-membered aromatic rings relative to the total content of all atoms in all diamine components of the raw material is within the range of more than 0 and 32% by weight, wherein the carbon atoms derived from six-membered aromatic rings do not include carbon atoms derived from six-membered aromatic rings of the dimer diamine composition. The polyimide according to claim 1, wherein, when conditions a, b1, and c are satisfied, the following condition f is also satisfied: f) the DM value, which is an indicator of the amount of 6-membered aromatic rings derived from the diamine component contained in the polyimide and is calculated based on the following formula (ii), is within the range of greater than 0 and less than 32; DM value = (D/Mw) × 10 ⁴ ...(ii) wherein D is the weight content of carbon atoms derived from the 6-membered aromatic ring relative to the total content of all atoms in all diamine residues, and Mw is the weight-average molecular weight of the polyimide, wherein the carbon atoms derived from the 6-membered aromatic ring do not include carbon atoms derived from the 6-membered aromatic ring of the dimer diamine composition. A crosslinked polyimide, wherein the polyimide according to claim 1 contains a ketone group in the molecule, wherein the ketone group forms a crosslinked structure with an amino group of an amino compound having at least two primary amino groups as functional groups via a C=N bond. An adhesive film characterized by containing the polyimide described in claim 1 or the cross-linked polyimide described in claim 5. The adhesive film according to claim 6, wherein when the polyimide satisfies conditions a, b1, and c, after humidity adjustment at constant temperature and humidity of 23°C and 50% RH for 24 hours, the dielectric loss tangent ( _Tanδ1 ) at 10 GHz measured by a separate dielectric resonator is less than 0.005, and the relative dielectric constant ( _E1 ) is less than 3.0. The adhesive film according to claim 6, wherein when the polyimide satisfies conditions a, b1, and c, after humidity adjustment at constant temperature and humidity of 23°C and 50% RH for 24 hours, the dielectric loss tangent ( _Tanδ2 ) at 20 GHz measured by a separate dielectric resonator is less than 0.005, and the relative dielectric constant ( _E2 ) is less than 3.0. The adhesive film as described in claim 6, wherein when the polyimide satisfies the conditions a, b1, and c, after humidity adjustment at constant temperature and humidity conditions of 23°C and 50% RH for 24 hours, the difference (Tanδ 2 -Tanδ 1 ) between the dielectric loss tangent (Tanδ ₁ ) at 10 GHz and the dielectric loss tangent (Tanδ ₂ ) at 20 GHz measured by a separated dielectric _resonator is equal to _or less than 0. The adhesive film according to claim 6, wherein when the polyimide satisfies conditions a, b2, and c, after humidification at constant temperature and humidity of 23°C and 50% RH for 24 hours, the dielectric loss tangent ( _Tanδ1 ) at 10 GHz measured by a separate dielectric resonator is less than 0.002, and the relative dielectric constant ( _E1 ) is less than 3.0. The adhesive film according to claim 6, wherein when the polyimide satisfies conditions a, b2, and c, after humidification at constant temperature and humidity of 23°C and 50% RH for 24 hours, the dielectric loss tangent ( _Tanδ2 ) at 20 GHz measured by a separate dielectric resonator is less than 0.002, and the relative dielectric constant ( _E2 ) is less than 3.0. A laminate comprising a substrate and an adhesive layer laminated on at least one surface of the substrate, wherein the adhesive layer comprises the adhesive film according to claim 6. A covering film comprises a covering film material layer and an adhesive layer laminated on the covering film material layer, wherein the adhesive layer comprises the adhesive film according to claim 6. A resin-coated copper foil is formed by laminating an adhesive layer on a copper foil, wherein the adhesive layer comprises the adhesive film as described in claim 6. A metal-clad laminate comprises an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer. The metal-clad laminate is characterized in that at least one layer of the insulating resin layer comprises the adhesive film according to claim 6. A metal-clad laminate comprises: an insulating resin layer; an adhesive layer laminated on at least one side of the insulating resin layer; and a metal layer laminated on the insulating resin layer via the adhesive layer. The metal-clad laminate is characterized in that the adhesive layer comprises the adhesive film according to claim 6. A metal-clad laminate comprises: a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side 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 side of the second metal layer; and an adhesive layer disposed so as to abut the first insulating resin layer and the second insulating resin layer and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate. The metal-clad laminate is characterized in that the adhesive layer comprises the adhesive film according to claim 7. A metal-clad laminate characterized by comprising: a single-sided metal-clad laminate having an insulating resin layer and a metal layer laminated on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer, wherein the adhesive layer comprises the adhesive film according to claim 6. A circuit board is formed by performing wiring processing on the metal layer of the metal-clad laminate according to claim 15. A circuit board comprises: a first substrate; a wiring layer laminated on at least one surface of the first substrate; and an adhesive layer laminated on a surface of the first substrate facing the wiring layer so as to cover the wiring layer. The circuit board is characterized in that the adhesive layer comprises the adhesive film according to claim 6. A circuit board comprises: a first substrate; a wiring layer laminated on at least one surface of the first substrate; an adhesive layer laminated on a surface of the first substrate facing the wiring layer so as to cover the wiring layer; and a second substrate laminated on a surface of the adhesive layer opposite to the first substrate. The circuit board is characterized in that the adhesive layer comprises the adhesive film according to claim 6. A circuit board comprises: a first substrate; an adhesive layer deposited on at least one surface of the first substrate; a second substrate deposited on a surface of the adhesive layer opposite to the first substrate; and wiring layers deposited on surfaces of the first substrate and the second substrate opposite to the adhesive layer, respectively. The circuit board is characterized in that the adhesive layer comprises the adhesive film according to claim 6. A multilayer circuit board comprises: a laminate including a plurality of laminated insulating resin layers; and at least one or more wiring layers embedded within the laminate. The multilayer circuit board is characterized in that at least one of the plurality of insulating resin layers is formed of an adhesive layer having adhesive properties and covering the wiring layer, and the adhesive layer comprises the adhesive film according to claim 6.