Thermosetting adhesive compositions, thermosetting adhesive sheets, and printed circuit boards

Abstract

To provide a thermosetting adhesive composition that exhibits low dielectric constant and dielectric loss tangent even after thermal curing, and good processability before thermal curing. [Solution] This technology provides a thermosetting adhesive composition for joining substrates, comprising 30 to 60 parts by mass of a styrene-based elastomer, 20 to 40 parts by mass of a cyclic hydrocarbon resin, and as a crosslinking component, (A) a modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, and an epoxy resin. An epoxy resin curing agent may be further included, and the total content of the radical polymerization initiator, epoxy resin, and epoxy resin curing agent is 10 parts by mass or less.

Description

Technical Field

[0001] This technology relates to a thermosetting adhesive composition, a thermosetting adhesive sheet, and a printed wiring board.

Background Art

[0002] Due to the high speed and large capacity of information communication, the trend of high frequency of signals flowing through printed wiring boards is accelerating. In order to cope with this, characteristics such as low dielectric constant and low dielectric tangent are required for the constituent materials (for example, adhesive compositions) of rigid boards and flexible printed wiring boards (FPCs).

[0003] In particular, for the dielectric tangent, taking the liquid crystal polymer (LCP), which is a resin material for high frequencies, as a reference, it is preferably less than 0.0030, and more preferably less than 0.0020.

[0004] The transmission loss of signals in a high-frequency circuit depends on the dielectric tangent (tanδ) as an index. Generally, the dielectric tangent deteriorates depending on the temperature. Therefore, a material that does not deteriorate the signal transmission loss, that is, a material whose dielectric tangent does not increase significantly, is required even in an environment where the periphery of the circuit becomes high temperature due to the signal processing load of the high-frequency circuit.

[0005] Also, in the manufacturing process of a flexible printed wiring board, when punching the adhesive composition with a mold or the like, it is desirable that the processability of the adhesive composition before thermosetting is good, for example, it is difficult for punching defects to occur even in a complex shape.

[0006] Thus, it is desirable that the adhesive composition has a low dielectric constant and a low dielectric tangent even after thermosetting, and good processability before thermosetting.

[0007] Patent Document 1 discloses an adhesive composition for flexible printed circuit boards, and Patent Document 2 discloses an elastomer composition that has good adhesive strength to polyimide and good high-frequency characteristics. However, Patent Documents 1 and 2 neither describe nor suggest an adhesive composition that has low dielectric constant and dielectric loss tangent even after heat curing and good processability before heat curing. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 7351912 [Patent Document 2] Japanese Patent Publication No. 2015-131866 [Overview of the project] [Problems that the invention aims to solve]

[0009] This technology was proposed in view of the conventional situation described above, and provides a thermosetting adhesive composition that has low dielectric constant and dielectric loss tangent even after thermal curing, and good processability before thermal curing. [Means for solving the problem]

[0010] This technology relates to a thermosetting adhesive composition for joining substrates, wherein, per 100 parts by mass of the total thermosetting adhesive composition, it contains 30 to 60 parts by mass of a styrene-based elastomer, 20 to 40 parts by mass of a hydrocarbon resin having a ring structure, and as a crosslinking component, (A) a modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, and an epoxy resin, and may further contain an epoxy resin curing agent, with the total content of the radical polymerization initiator, epoxy resin, and epoxy resin curing agent being 10 parts by mass or less.

[0011] This technology provides a thermosetting adhesive composition for joining substrates, comprising a styrene elastomer, a hydrocarbon resin having a ring structure, and as a crosslinking component, (A) a modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, and an epoxy resin. The dielectric loss tangent after curing is less than 0.0030 at both 23°C and 80°C, the rate of change represented by the following formula 1 is less than 50%, and the processability before thermosetting satisfies the following condition 1. Equation 1: Rate of change (%) = ((Dielectric loss tangent of the thermosetting adhesive composition at 80°C after curing) / (Dielectric loss tangent of the thermosetting adhesive composition at 23°C after curing) - 1) × 100 Condition 1: Using a press machine equipped with a punch and a die (model number: SBP305S, manufactured by Nippon Automatic Machine Co., Ltd.), a thermosetting adhesive sheet, in which an adhesive layer of thermosetting adhesive composition with a thickness of 5 to 50 μm is formed on a substrate with a thickness of 12 to 50 μm, can be processed to a size of diameter of 0.75 mm to 4.3 mm, with a processing speed of 99.9 mm / s, a punch depth of 0.4 mm, and a gap distance (clearance) between the punch and the die of 0.02 mm or less. [Effects of the Invention]

[0012] This technology makes it possible to provide a thermosetting adhesive composition that has low dielectric constant and dielectric loss tangent even after thermal curing, and good processability before thermal curing. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a cross-sectional view showing an example of a printed circuit board configuration. [Figure 2] Figure 2 is a cross-sectional view showing an example of a multilayer printed circuit board configuration. [Figure 3] Figure 3 is a plan view showing an example of the configuration of the TEG used in the bending resistance test. [Figure 4] Figure 4 is a perspective view showing the measuring device used in the bending resistance test. [Figure 5]FIG. 5 is a cross-sectional view for explaining the measurement method of the workability test. [Figure 6] FIG. 6 is a cross-sectional view for explaining the measurement method of the workability test. [Figure 7] FIG. 7 is a cross-sectional view for explaining the measurement method of the workability test. [Figure 8] FIG. 8 is a plan view showing an example of the test piece after processing obtained in the workability test. [Figure 9] FIG. 9 is an example of a photograph taken of the test piece after processing when the workability test is OK from the planar direction. [Figure 10] FIG. 10 is an example of a photograph taken of the test piece after processing when the workability test is NG from the planar direction.

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, embodiments of the present technology will be described. In this specification, normal temperature refers to the range of 20°C ± 15°C (5°C to 35°C) defined by Japanese Industrial Standard (JIS Z 8703).

[0015] Also, in this specification, the values of the weight average molecular weight (Mw) and the number average molecular weight (Mn) refer to the values calculated from the molecular weights in terms of standard polystyrene measured by gel permeation chromatography (GPC) method. The specific measurement conditions of the GPC method are as follows. Solvent: Tetrahydrofuran Column: KF-806M, KF-806M, KF-803, KF-801, KF-800D (manufactured by Showa Denko KK)<s Column temperature: 40°C Sample concentration: 0.25 mass% Detector: RI detector Flow rate (flow velocity): 1.0 ml / min Injection volume: 200 μL Calibration curve: Use the calibration curve with 10 samples from standard polystyrene Mw = 605 to 5,680,000

[0016] <Thermosetting adhesive composition> The thermosetting adhesive composition according to this technology contains, per 100 parts by mass of the total thermosetting adhesive composition, 30 to 60 parts by mass of styrene elastomer, 20 to 40 parts by mass of a hydrocarbon resin having a cyclic structure, and as a crosslinking component, a modified polyphenylene ether resin having radical polymerizable groups at the molecular ends (hereinafter also referred to as component (A)), polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000 (hereinafter also referred to as component (B)), a radical polymerization initiator, and an epoxy resin, and may further contain an epoxy resin curing agent. Furthermore, the thermosetting adhesive composition according to this technology has a total content of 10 parts by mass or less of radical polymerization initiator, epoxy resin, and epoxy resin curing agent.

[0017] The thermosetting adhesive composition according to this technology, having such a configuration, can maintain low dielectric constant and dielectric loss tangent even after thermal curing. Furthermore, the thermosetting adhesive composition according to this technology can also maintain a low rate of change in dielectric loss tangent at temperature. Thus, the thermosetting adhesive composition according to this technology exhibits good dielectric properties after curing.

[0018] The thermosetting adhesive composition according to this technology has a dielectric loss tangent of less than 0.0030 at both 23°C and 80°C after curing, and can exhibit a change rate of less than 50% as represented by the following formula 1. Equation 1: Rate of change (%) = ((Dielectric loss tangent of the thermosetting adhesive composition after curing at 80°C) / (Dielectric loss tangent of the thermosetting adhesive composition after curing at 23°C) - 1) × 100

[0019] The dielectric constant of the cured thermosetting adhesive composition is preferably less than 2.40, and more preferably less than 2.30. The dielectric constant of the cured thermosetting adhesive composition can be measured by the method described in the examples below.

[0020] The dielectric loss tangent of the cured thermosetting adhesive composition is preferably less than 0.0030 at 23°C, and more preferably less than 0.0020. Furthermore, the dielectric loss tangent of the cured thermosetting adhesive composition is preferably less than 0.0030 at 80°C, and more preferably less than 0.0020. The dielectric loss tangent of the cured thermosetting adhesive composition can be measured by the method described in the examples below.

[0021] Furthermore, the cured thermosetting adhesive composition is preferable if the rate of change represented by Formula 1 is small, that is, the smaller the temperature dependence of the dielectric loss tangent. For example, the cured thermosetting adhesive composition is preferably less than 50%, more preferably less than 40%, and even more preferably less than 30%.

[0022] Furthermore, the thermosetting adhesive composition according to this technology can maintain good flexibility and heat resistance (e.g., solder heat resistance) even after heat curing. For example, because the thermosetting adhesive composition has good heat resistance after heat curing, component mounting and connection to other printed circuit boards can be performed using solder reflow or hot bar soldering processes, just as with conventional printed circuit boards, even in high-frequency printed circuit boards. Therefore, the thermosetting adhesive composition according to this technology can be suitably used for applications involving joining substrates, such as adhesives (interlayer adhesives) for flexible printed circuit boards.

[0023] The following describes an example of the composition of a thermosetting adhesive composition related to this technology. The thermosetting adhesive composition related to this technology contains a styrene-based elastomer, a hydrocarbon resin having a ring structure, component (A), component (B), a radical polymerization initiator, and an epoxy resin, and may further contain an epoxy resin curing agent.

[0024] [Styrene-based elastomer] Styrene elastomers are copolymers of styrene and olefins (e.g., conjugated dienes such as butadiene and isoprene), and / or hydrogenated thereof. Styrene elastomers are block copolymers in which styrene is the hard segment and the conjugated diene is the soft segment. Examples of styrene elastomers include styrene / butadiene / styrene block copolymers, styrene / isoprene / styrene block copolymers, styrene / ethylene / butylene / styrene block copolymers, styrene / ethylene / propylene / styrene block copolymers, and styrene / butadiene block copolymers. Alternatively, styrene / ethylene / butylene / styrene block copolymers, styrene / ethylene / propylene / styrene block copolymers, and styrene / butadiene block copolymers (also called hydrogenated styrene elastomers), in which the double bond of the conjugated diene component is eliminated by hydrogenation, may also be used.

[0025] The styrene-based elastomer may have functional groups that promote the curing reaction of the epoxy resin. If the styrene-based elastomer has functional groups that promote the curing reaction of the epoxy resin, it also has the function of an epoxy resin curing agent, so there is no need to use an epoxy resin curing agent separately. However, an epoxy resin curing agent may be used in combination separately, to the extent that it does not impair the effects of this technology.

[0026] Examples of functional groups that promote the curing reaction of epoxy resins include amines and acid anhydrides. When using a styrene-based elastomer having functional groups that promote the curing reaction of epoxy resins, forming the thermosetting adhesive composition according to this technology into a film restricts the movement of the polymer chains containing the functional groups that promote the curing reaction of epoxy resins, thereby imparting latent properties to the polymer side (e.g., the styrene-based elastomer). Examples of such styrene-based elastomers include amine-modified styrene-based elastomers and acid-modified styrene-based elastomers.

[0027] The styrene content in the styrene-based elastomer is not particularly limited and can be, for example, 67% or less, 60% or less, 50% or less, 42% or less, less than 42%, 30% or less, 20% or less, 15% or less, or between 12% and 67%.

[0028] Specific examples of styrene-based elastomers include ToughTec 1221 (styrene ratio 12%, manufactured by Asahi Kasei), ToughTec MP1911 (styrene ratio 30%, acid-modified styrene-based elastomer, manufactured by Asahi Kasei), ToughTec H1051 (styrene ratio 42%, manufactured by Asahi Kasei), and ToughTec H1043 (styrene ratio 67%, manufactured by Asahi Kasei).

[0029] The styrene elastomer content is 30 to 60 parts by mass per 100 parts by mass of the total thermosetting adhesive composition. A styrene elastomer content of 30 parts by mass or more tends to prevent the relative content of other components (e.g., radical polymerization initiator, epoxy resin, and epoxy resin curing agent) from becoming too high, thereby lowering the dielectric constant and dielectric loss tangent of the cured thermosetting adhesive composition, as well as the temperature change rate of the dielectric loss tangent. Furthermore, a styrene elastomer content of 60 parts by mass or less tends to prevent the relative content of other components (e.g., components (A) and (B)) from becoming too low, thereby lowering the temperature change rate of the dielectric loss tangent of the cured thermosetting adhesive composition, and also tends to improve the heat resistance of the cured thermosetting adhesive composition. Additionally, a styrene elastomer content of 60 parts by mass or less tends to provide sufficient hardness and improve the processability of the thermosetting adhesive composition before thermosetting.

[0030] The lower limit of the styrene-based elastomer content may be 35 parts by mass or more, 40 parts by mass or more, 46 parts by mass or more, 48 parts by mass or more, or 50 parts by mass or more, per 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0031] The upper limit for the styrene-based elastomer content may be 54 parts by mass or less, 48 ​​parts by mass or less, or 46 parts by mass or less, per 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0032] Styrene elastomers may be used individually or in combination of two or more types. When using two or more styrene elastomers in combination, it is preferable that their total amount satisfies the above-mentioned content range.

[0033] As an example of how styrene-based elastomers can be used, a styrene-based elastomer with a styrene ratio of 67% or less may be used in combination with a styrene-based elastomer with a styrene ratio exceeding 67%. In this case, the content of the styrene-based elastomer with a styrene ratio of 67% or less in the thermosetting adhesive composition is preferably 50% by mass or more, may be 55% by mass or more, may be 60% by mass or more, may be 65% by mass or more, may be 70% by mass or more, may be 75% by mass or more, may be 80% by mass or more, may be 85% by mass or more, may be 90% by mass or more, may be 95% by mass or more, or may be 99% by mass or more.

[0034] [Hydroxide resin with a ring structure] A hydrocarbon resin having a ring structure is, for example, compatible with a styrene-based elastomer in an adhesive composition and is a component that improves the processability of the adhesive composition before heat curing (for example, the processability of a thermosetting adhesive sheet, on which an adhesive layer made of a thermosetting adhesive composition is formed on a substrate, before heat curing).

[0035] A hydrocarbon resin having a ring structure is, for example, a hydrocarbon resin having a ring structure in its main chain or side chains. The ring structure is, for example, at least one of an aromatic ring structure and an alicyclic structure. The number of carbon atoms in the ring structure is, for example, 3 to 10, and may also be 6 to 9. The ring structure may be a monocyclic or polycyclic structure.

[0036] A hydrocarbon resin having a ring structure may be, for example, a hydrocarbon resin having at least one aromatic ring structure and an alicyclic structure in the main chain, a hydrocarbon resin having at least one aromatic ring structure and an alicyclic structure in the side chain, or a hydrocarbon resin having at least one aromatic ring structure and an alicyclic structure in both the main chain and the side chain. Furthermore, a hydrocarbon resin having a ring structure may be a hydrocarbon resin having an aromatic ring structure in the main chain, a hydrocarbon resin having an alicyclic structure in the main chain, a hydrocarbon resin having an aromatic ring structure in the side chain, or a hydrocarbon resin having an alicyclic structure in the side chain.

[0037] Examples of hydrocarbon resins having a ring structure include aromatic petroleum resins, homopolymers of monomers having an aromatic ring structure, and saturated aliphatic hydrocarbon resins.

[0038] Aromatic petroleum resins are copolymers of C5-C10 petroleum resins having a ring structure, and one example is a hydrocarbon resin having an aromatic ring structure in its side chain. Aromatic petroleum resins are copolymers using two or more elements selected from the group consisting of indene, styrene, vinyltoluene, methylindene, methylstyrene, and dicyclopentadiene. A commercially available aromatic petroleum resin is, for example, Petocol 140 manufactured by Tosoh Corporation (an aromatic hydrocarbon resin polymerized mainly from styrene, vinyltoluene, indene, etc.).

[0039] A homopolymer of monomers having an aromatic ring structure is, for example, a hydrocarbon resin having an aromatic ring structure in its side chain. An example of a homopolymer of monomers having an aromatic ring structure is a homopolymer of styrene. An example of a commercially available homopolymer of monomers having an aromatic ring structure is SX100 (styrene resin) manufactured by Yasuhara Chemical Co., Ltd.

[0040] Saturated aliphatic hydrocarbon resins are, for example, hydrogenated aromatic petroleum resins. Saturated aliphatic hydrocarbon resins are, for example, hydrocarbon resins having alicyclic structures in their side chains. A commercially available example of a saturated aliphatic hydrocarbon resin is P125 manufactured by Alcon.

[0041] A hydrocarbon resin having a cyclic structure may have a functional group that promotes the curing reaction of epoxy resin. Examples of functional groups that promote the curing reaction of epoxy resin include amines and acid anhydrides. When a hydrocarbon resin having a cyclic structure has a functional group that promotes the curing reaction of epoxy resin, it also possesses the function of an epoxy resin curing agent, so there is no need to use an epoxy resin curing agent. However, an epoxy resin curing agent may be used separately to the extent that it does not impair the effects of this technology.

[0042] The weight-average molecular weight (Mw) of the cyclic hydrocarbon resin is not particularly limited, but is preferably 1,000 to 10,000, for example, from the viewpoint of improving adhesive strength (peel strength of the thermosetting adhesive composition after heat curing).

[0043] The content of the ring-structured hydrocarbon resin is 20 to 40 parts by mass per 100 parts by mass of the total thermosetting adhesive composition. By using this content, the thermosetting adhesive composition can maintain low dielectric constant, dielectric loss tangent, and rate of change of dielectric loss tangent at temperature even after thermosetting, while also having good flexibility resistance after thermosetting, processability before thermosetting, and peel strength after thermosetting. If the content of the ring-structured hydrocarbon resin is less than 20 parts by mass per 100 parts by mass of the total thermosetting adhesive composition, depending on the blending ratio of other components, for example, the processability of the thermosetting adhesive composition before thermosetting and the peel strength of the thermosetting adhesive composition after thermosetting may deteriorate. Furthermore, if the content of the ring-structured hydrocarbon resin is more than 40 parts by mass per 100 parts by mass of the total thermosetting adhesive composition, depending on the blending ratio of other components, for example, the dielectric loss tangent of the thermosetting adhesive composition after thermosetting and the heat resistance of the thermosetting adhesive composition after thermosetting may deteriorate.

[0044] The content of the hydrocarbon resin having a ring structure may be 38 parts by mass or less, 36 parts by mass or less, 34 parts by mass or less, 32 parts by mass or less, 30 parts by mass or less, or 28 parts by mass or less, per 100 parts by mass of the total thermosetting adhesive composition. Furthermore, the content of the hydrocarbon resin having a ring structure may be 22 parts by mass or more, 24 parts by mass or more, 26 parts by mass or more, or 28 parts by mass or more, per 100 parts by mass of the total thermosetting adhesive composition. For example, the content of the hydrocarbon resin having a ring structure can be 20 to 36 parts by mass, or 26 to 36 parts by mass, per 100 parts by mass of the total thermosetting adhesive composition.

[0045] A hydrocarbon resin having a ring structure may be used alone or in combination of two or more types. For example, the hydrocarbon resin having a ring structure may be a combination of an aromatic petroleum resin, a homopolymer of a monomer having an aromatic ring structure, and a saturated aliphatic hydrocarbon resin, or a combination of a homopolymer of a monomer having an aromatic ring structure and a saturated aliphatic hydrocarbon resin. Using two or more hydrocarbon resins having a ring structure in combination tends to improve, for example, the peel strength of the thermosetting adhesive composition after heat curing, or the processability of the thermosetting adhesive composition before heat curing. When using two or more hydrocarbon resins having a ring structure in combination, it is preferable that their total amount satisfies the above-mentioned content range.

[0046] [(A) component] Component (A), i.e., the modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, is a crosslinking component, having polyphenylene ether chains in its molecule and radical polymerizable groups at its molecular ends. As described above, the radical polymerizable groups at the molecular ends of component (A) are crosslinked by the radical polymerization initiator in the thermosetting adhesive composition, thereby improving flexural resistance and heat resistance even after thermosetting. Component (A) preferably has, for example, two or more ethylenically unsaturated bonds as radical polymerizable groups in one molecule. In particular, from the viewpoint of compatibility with the styrene-based elastomer described above and the dielectric properties of the thermosetting adhesive composition after curing, it is preferable that component (A) has at least one type of ethylenically unsaturated bond (e.g., (meth)acryloyl group, vinylbenzyl group) at both molecular ends. Here, the (meth)acryloyl group includes both acryloyl group and methacryloyl group.

[0047] Furthermore, modified polyphenylene ether resins other than component (A), such as modified polyphenylene ether resins having hydroxyl groups at the molecular ends, are undesirable because they are too polar, resulting in poor compatibility with the styrene-based elastomers mentioned above, which may prevent the thermosetting adhesive composition from being formed into a film.

[0048] (A) An example of a modified polyphenylene ether resin having vinyl benzyl groups at both ends of the molecule is obtained, for example, by vinyl benzyl etherification of the terminal phenolic hydroxyl groups of a difunctional phenylene ether oligomer obtained by oxidative coupling of a difunctional phenol compound and a monofunctional phenol compound.

[0049] The weight-average molecular weight (or number-average molecular weight) of component (A) is preferably 1,000 to 3,000, from the viewpoint of compatibility with the styrene-based elastomer described above and the ability to follow steps when heat-curing (pressing) the wiring pattern side and coverlay of a wired resin substrate, which comprises a substrate and a wiring pattern, via the cured product of the thermosetting adhesive composition.

[0050] (A)Specific examples of component include OPE-2St (modified polyphenylene ether resin having vinyl benzyl groups at both ends of the molecule, manufactured by Mitsubishi Gas Chemical Co., Ltd.), OPE-2EA (modified polyphenylene ether resin having acryloyl groups at both ends of the molecule, manufactured by Mitsubishi Gas Chemical Co., Ltd.), and Noryl SA9000 (modified polyphenylene ether resin having methacryloyl groups at both ends, manufactured by SABIC Corporation).

[0051] The content of component (A) is preferably 4 to 20 parts by mass per 100 parts by mass of the total thermosetting adhesive composition. By having a content of 20 parts by mass or less of component (A), the flexibility after thermosetting can be improved. Furthermore, by having a content of 4 parts by mass or more of component (A), the dielectric loss tangent of the thermosetting adhesive composition after curing can be lowered.

[0052] The content of component (A) may be 18 parts by mass or less, 15 parts by mass or less, 13 parts by mass or less, 10 parts by mass or less, or 8 parts by mass or less, per 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0053] The content of component (A) may be 6 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more, based on 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0054] Component (A) may be used alone or in combination of two or more. When using two or more components (A) in combination, it is preferable that their total amount satisfies the numerical range of the above content.

[0055] [(B) Component] Component (B) is a crosslinking component, which is polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000. Component (B) is at least one of the following: a polybutadiene resin (a resin having only a polybutadiene structure) having a weight-average molecular weight of 10,000 to 50,000; a polyisoprene resin (a resin having only a polyisoprene structure) having a weight-average molecular weight of 10,000 to 50,000; or a resin having a weight-average molecular weight of 10,000 to 50,000 and possessing both a polybutadiene structure and a polyisoprene structure; or a combination thereof. Furthermore, as long as component (B) mainly contains a butadiene structure or a polyisoprene structure, it may also contain other structures other than the butadiene structure and polyisoprene structure, to the extent that it does not impair the effects of this technology. However, from the viewpoint of improving the effects of this technology, compatibility with other components, dispersibility, etc., it is preferable that it substantially does not contain other structures (e.g., a styrene structure). (B) Component is preferably liquid at room temperature from the standpoint of ease of handling.

[0056] Polybutadiene can be any resin having a polybutadiene structure, and the polybutadiene structure may be included in the main chain or in the side chains. The butadiene structure may or may not be partially hydrogenated.

[0057] Polyisoprene can be any resin having a polyisoprene structure, and the polyisoprene structure may be included in the main chain or in the side chains. The polyisoprene structure may be partially hydrogenated or not.

[0058] Component (B) may have a functional group that promotes the curing reaction of the epoxy resin. If component (B) has a functional group that promotes the curing reaction of the epoxy resin, it also functions as an epoxy resin curing agent, so there is no need to use an epoxy resin curing agent. However, an epoxy resin curing agent may be used separately, to the extent that it does not impair the effects of this technology. Examples of functional groups that promote the curing reaction of the epoxy resin include acid anhydrides. Examples of such components (B) include acid-modified polybutadiene and acid-modified polyisoprene.

[0059] Regarding the weight-average molecular weight of component (B), having a weight-average molecular weight of 10,000 or more suppresses excessive crosslinking density, thereby improving the peel strength and flexural resistance of the cured thermosetting adhesive composition. The weight-average molecular weight of component (B) may be 15,000 or more, 20,000 or more, 25,000 or more, 30,000 or more, or 35,000 or more.

[0060] Furthermore, by having a weight-average molecular weight of component (B) of 50,000 or less, it is possible to suppress the crosslinking density from becoming too low, reduce the temperature change rate of the dielectric loss tangent of the thermosetting adhesive composition after curing, and improve compatibility with component (A). The weight-average molecular weight of component (B) may be 45,000 or less, 40,000 or less, 35,000 or less, or 30,000 or less.

[0061] The content of component (B) is preferably 4 to 10 parts by mass per 100 parts by mass of the total thermosetting adhesive composition. By having a content of 10 parts by mass or less of component (B), the peel strength and flexural resistance of the thermosetting adhesive composition after curing can be improved. Furthermore, by having a content of 4 parts by mass or more of component (B), the temperature change rate of the dielectric loss tangent of the thermosetting adhesive composition after curing can be lowered.

[0062] The content of component (B) may be 9 parts by mass or less, 8 parts by mass or less, 7 parts by mass or less, 6 parts by mass or less, or 5 parts by mass or less, per 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0063] The content of component (B) may be 5 parts by mass or more, 6 parts by mass or more, 7 parts by mass or more, or 8 parts by mass or more, based on 100 parts by mass of the total amount of the thermosetting adhesive composition.

[0064] Furthermore, the total amount of component (A) and component (B) is preferably 25 parts by mass or less, but may be 24 parts by mass or less, 23 parts by mass or less, 22 parts by mass or less, 21 parts by mass or less, 20 parts by mass or less, 19 parts by mass or less, 18 parts by mass or less, 17 parts by mass or less, 16 parts by mass or less, 15 parts by mass or less, 14 parts by mass or less, or 13 parts by mass or less.

[0065] The lower limit of the sum of the content of component (A) and the content of component (B) is not particularly limited as long as it satisfies the above-mentioned content of component (A) and the content of component (B). For example, it may be 8 parts by mass or more, 10 parts by mass or more, 12 parts by mass or more, 13 parts by mass or more, 14 parts by mass or more, 15 parts by mass or more, 16 parts by mass or more, 17 parts by mass or more, 18 parts by mass or more, 19 parts by mass or more, or 20 parts by mass or more.

[0066] Furthermore, it is preferable that the content of component (A) and the content of component (B) satisfy the following formula 2. Equation 2: (Content of component (A) in the thermosetting adhesive composition) > (Content of component (B) in the thermosetting adhesive composition)

[0067] By ensuring that the content of component (A) and component (B) in the thermosetting adhesive composition satisfies Equation 2, the dielectric constant and dielectric loss tangent of the cured thermosetting adhesive composition can be more effectively reduced, the temperature change rate of the dielectric loss tangent can also be more effectively reduced, and the flexural resistance and heat resistance of the cured thermosetting adhesive composition can be more effectively improved.

[0068] Component (B) may be used alone or in combination of two or more. When using two or more components (B) in combination, it is preferable that their total amount satisfies the numerical range of the above content.

[0069] [Radical polymerization initiator] A radical polymerization initiator is a catalyst that promotes the radical curing reaction of unsaturated bonds. For example, a radical polymerization initiator crosslinks the radical polymerizable groups at the molecular ends of component (A) or the radical polymerizable groups in component (B) by thermal curing. By including a radical polymerization initiator in a thermosetting adhesive composition, the heat resistance of the thermosetting adhesive composition after curing can be improved. From the viewpoint of the shelf life of the thermosetting adhesive composition at room temperature, a peroxide with a high reaction initiation temperature is preferred as the radical polymerization initiator. For example, an organic peroxide with a decomposition temperature of 170°C or higher for a half-life of 1 minute is preferred. Examples of such organic peroxides include dicumyl peroxide (decomposition temperature of 175°C for a half-life of 1 minute), t-butylcumyl peroxide (decomposition temperature of 173°C for a half-life of 1 minute), and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (decomposition temperature of 194°C for a half-life of 1 minute).

[0070] The amount of radical polymerization initiator is not particularly limited as long as the total amount of radical polymerization initiator, epoxy resin, and epoxy resin curing agent is 10 parts by mass or less per 100 parts by mass of the total thermosetting adhesive composition. For example, it can be 0.5 parts by mass or more, 1 part by mass or more, 1 to 5 parts by mass, 1 to 4 parts by mass, or 1 to 3 parts by mass.

[0071] Radical polymerization initiators may be used individually or in combination of two or more. When two or more radical polymerization initiators are used in combination, it is preferable that their total amount satisfies the numerical range of the above-mentioned content.

[0072] [Epoxy resin] Examples of epoxy resins include epoxy resins having a naphthalene skeleton, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins, siloxane type epoxy resins, biphenyl type epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, and hydantoin type epoxy resins. In particular, from the viewpoint of film moldability, epoxy resins having a naphthalene skeleton, bisphenol A type epoxy resins, or bisphenol F type epoxy resins that are liquid at room temperature are preferred.

[0073] The epoxy resin content is not particularly limited as long as the total content of radical polymerization initiator, epoxy resin, and epoxy resin curing agent is 10 parts by mass or less per 100 parts by mass of the total thermosetting adhesive composition. For example, it may be less than 5 parts by mass, 0.5 parts by mass or more, 1 part by mass or more, 1 to 7 parts by mass, 1 to 6 parts by mass, 1 to 5 parts by mass, 1 to 4 parts by mass, 1 to 3 parts by mass, or 1 to 2 parts by mass.

[0074] Epoxy resins may be used individually or in combination of two or more types. When using two or more epoxy resins in combination, it is preferable that their total amount satisfies the numerical range of the above-mentioned content.

[0075] [Epoxy resin hardener] The epoxy resin curing agent is a catalyst that promotes the curing reaction of the epoxy resin described above. Examples of epoxy resin curing agents include imidazole-based, phenol-based, amine-based, acid anhydride-based, and organic peroxide-based curing agents. In particular, from the viewpoint of the shelf life (storage at room temperature) of the thermosetting adhesive composition, it is preferable that the epoxy resin curing agent be a latent curing agent, and it is more preferable that it be an imidazole-based curing agent that is encapsulated and latent. Good storage at room temperature makes it easier to manage the supply and use of the thermosetting adhesive composition. Specifically, as an epoxy resin curing agent, for example, a microcapsule-type latent curing agent can be used, which has a latent imidazole modified material as a core and its surface coated with polyurethane. Alternatively, as an epoxy resin curing agent, for example, a hydrazide-based latent curing agent can be used. Examples of commercially available epoxy resin curing agents include Novacure 3941 (manufactured by Asahi Kasei E-Materials Co., Ltd.) and Amicure UDH-J (manufactured by Ajinomoto Fine Techno Co., Ltd.).

[0076] If the thermosetting adhesive composition contains an epoxy resin curing agent, the amount of epoxy resin curing agent is not particularly limited as long as the total amount of radical polymerization initiator, epoxy resin, and epoxy resin curing agent per 100 parts by mass of the total thermosetting adhesive composition is 10 parts by mass or less. For example, it may be 0.1 parts by mass or more, 0.5 parts by mass or more, 0.8 parts by mass or more, 1 part by mass or more, 0.1 to 3 parts by mass, 0.5 to 3 parts by mass, or 1 to 2 parts by mass.

[0077] Furthermore, if the thermosetting adhesive composition contains, for example, a styrene-based elastomer having a functional group that promotes the curing reaction of epoxy resin, this styrene-based elastomer having a functional group that promotes the curing reaction of epoxy resin shall be included in the content of the styrene-based elastomer as described above, and shall not be included in the content of the epoxy resin curing agent. Similarly, if the thermosetting adhesive composition contains, for example, a component (B) having a functional group that promotes the curing reaction of epoxy resin as component (B), this component (B) having a functional group that promotes the curing reaction of epoxy resin shall be included in the content of component (B) as described above, and shall not be included in the content of the epoxy resin curing agent. Furthermore, if the thermosetting adhesive composition contains, for example, a styrene-based elastomer having a functional group that promotes the curing reaction of epoxy resin as styrene-based elastomer, or if the thermosetting adhesive composition contains, for example, a component (B) having a functional group that promotes the curing reaction of epoxy resin as component (B), the thermosetting adhesive composition may or may not contain a separate epoxy resin curing agent.

[0078] The epoxy resin curing agent may be used alone or in combination of two or more types. When using two or more epoxy resin curing agents in combination, it is preferable that their total amount satisfies the numerical range of the above-mentioned content.

[0079] In the thermosetting adhesive composition according to this technology, the total content of the radical polymerization initiator, epoxy resin, and epoxy resin curing agent is 10 parts by mass or less, per 100 parts by mass of the total amount of the thermosetting adhesive composition (styrene elastomer, hydrocarbon resin having a ring structure, component (A), component (B), radical polymerization initiator, epoxy resin, and epoxy resin curing agent), and may be 9 parts by mass or less, 6 parts by mass or less, 5 parts by mass or less, 4 parts by mass or less, or 4 to 6 parts by mass. By having a total content of 10 parts by mass or less of the radical polymerization initiator, epoxy resin, and epoxy resin curing agent, the dielectric properties of the thermosetting adhesive composition after curing can be improved.

[0080] Furthermore, the lower limit of the total content of radical polymerization initiator, epoxy resin, and epoxy resin curing agent in the thermosetting adhesive composition is not particularly limited. For example, it may be 0.1 parts by mass or more, 0.5 parts by mass or more, or 1 part by mass or more, per 100 parts by mass of the total thermosetting adhesive composition.

[0081] As described above, in the first embodiment, the thermosetting adhesive composition relating to this technology includes an epoxy resin curing agent when the styrene elastomer does not have a functional group that promotes the curing reaction of the epoxy resin. That is, the thermosetting adhesive composition in the first embodiment contains 30 to 60 parts by mass of a styrene elastomer, 20 to 40 parts by mass of a hydrocarbon resin having a ring structure, and as a crosslinking component, (A) a modified polyphenylene ether resin having radical polymerizable groups at the molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, an epoxy resin, and an epoxy resin curing agent, wherein the total content of the radical polymerization initiator, epoxy resin, and epoxy resin curing agent is 10 parts by mass or less.

[0082] Furthermore, in a second embodiment, the thermosetting adhesive composition relating to this technology may or may not contain an epoxy resin curing agent if, for example, the styrene elastomer and / or hydrocarbon resin having a ring structure has a functional group that promotes the curing reaction of the epoxy resin. That is, the thermosetting adhesive composition in the second embodiment contains 30 to 60 parts by mass of a styrene elastomer, 20 to 40 parts by mass of a hydrocarbon resin having a ring structure, and at least the following crosslinking components: (A) a modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, and an epoxy resin, with the total content of the radical polymerization initiator and epoxy resin being 10 parts by mass or less.

[0083] A third aspect of the thermosetting adhesive composition relating to this technology is a thermosetting adhesive composition for joining substrates, comprising a styrene elastomer, a hydrocarbon resin having a ring structure, and as a crosslinking component, (A) a modified polyphenylene ether resin having radical polymerizable groups at its molecular ends, (B) polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, a radical polymerization initiator, and an epoxy resin, and may further contain an epoxy resin curing agent, wherein the dielectric loss tangent after curing is less than 0.0030 at both 23°C and 80°C, the rate of change represented by the above formula 1 is less than 50%, and the processability before thermosetting satisfies the following condition 1.

[0084] <Condition 1> Using a press machine equipped with a punch and die (model number: SBP305S, manufactured by Nippon Automatic Machine Co., Ltd.), a thermosetting adhesive sheet, in which an adhesive layer of thermosetting adhesive composition with a thickness of 5 to 50 μm is formed on a substrate with a thickness of 12 to 50 μm, can be processed to a size of 0.75 mm to 4.3 mm in diameter, at a processing speed of 99.9 mm / s, a punch depth of 0.4 mm, and a clearance distance between the punch and die of 0.02 mm or less. Here, "successfully processed" of the thermosetting adhesive sheet means, as detailed in the section on the evaluation method of processability in the examples, that the processed thermosetting adhesive sheet is completely separated from the pre-processed thermosetting adhesive sheet, and that the burr area on the processed thermosetting adhesive sheet is 0.1 mm². 2 This refers to being less than a certain value.

[0085] [Other ingredients] The thermosetting adhesive composition may further contain other components besides those described above, as long as they do not impair the effects of this technology. Other components include organic solvents, adhesion promoters other than hydrocarbon resins having a cyclic structure, and fillers for adjusting fluidity or providing flame retardancy. The organic solvent is not particularly limited, but examples include alcohol-based solvents, ketone-based solvents, ether-based solvents, aromatic solvents, and ester-based solvents. Among these, aromatic solvents and ester-based solvents are preferred from the viewpoint of solubility. The organic solvent may be used alone or in combination of two or more.

[0086] <Thermosetting adhesive sheet> The thermosetting adhesive sheet according to this technology has a thermosetting adhesive layer formed on a substrate using the thermosetting adhesive composition described above, and is in the form of a film. The thermosetting adhesive sheet can be obtained, for example, by diluting the thermosetting adhesive composition described above with a solvent, applying it to at least one side of a substrate using a bar coater, roll coater, etc., so that the thickness after drying is 10 to 60 μm, and drying it at a temperature of about 50 to 130°C. The substrate can be, for example, a release substrate that has been treated with silicone or the like, if necessary, can be a substrate such as polyethylene terephthalate film or polyimide film.

[0087] The thickness of the thermosetting adhesive layer constituting the thermosetting adhesive sheet can be set appropriately depending on the purpose. For example, it can be 1 to 100 μm, 5 to 50 μm, or 1 to 30 μm.

[0088] As described above, the thermosetting adhesive layer constituting the thermosetting adhesive sheet has a low dielectric constant and dielectric loss tangent even after heat curing, a low rate of change in dielectric loss tangent at temperature, and good flexibility and heat resistance even after heat curing. Therefore, it can be applied, for example, as an interlayer adhesive for flexible printed circuit boards, or for bonding and fixing the terminal portion of a flexible printed circuit board to a connecting substrate for backing it. Furthermore, the thermosetting adhesive sheet also has good peel strength, heat resistance, and storage properties at room temperature after curing.

[0089] The thermosetting adhesive layer constituting the thermosetting adhesive sheet exhibits good processability before heat curing by using the thermosetting adhesive composition described above.

[0090] <Printed wiring board> The printed circuit board according to this technology, for example, has a wiring pattern side of a wiring substrate, which includes a substrate and a wiring pattern, and a coverlay laminated together via a cured product (thermosetting adhesive layer) of the thermosetting adhesive composition described above. The printed circuit board is obtained, for example, by integrating the wiring substrate and the coverlay by placing the thermosetting adhesive layer of a thermosetting adhesive sheet between the wiring pattern side of the wiring substrate and the coverlay and then heat-pressing them together. The coverlay is an insulating layer for protecting the wiring pattern of the wiring substrate.

[0091] The substrate with wiring, like the adhesive composition described above, preferably has excellent electrical properties in the high-frequency range, for example, low dielectric constant and dielectric loss tangent in the frequency range of 1 to 10 GHz. Specific examples of substrates include those mainly composed of liquid crystal polymer (LCP), polytetrafluoroethylene, polyimide, and polyethylene naphthalate. Among these substrates, a substrate mainly composed of liquid crystal polymer (liquid crystal polymer film) is preferred. Liquid crystal polymer has a very low moisture absorption rate compared to polyimide and is less affected by the operating environment.

[0092] An example of the configuration of a printed circuit board using the thermosetting adhesive composition related to this technology will be described. In the printed circuit board 1 shown in Figure 1, the copper foil 3 side of a wiring substrate (copper-clad laminate: CCL) comprising a liquid crystal polymer film 2 and copper foil (rolled copper foil) 3, and the liquid crystal polymer film 4 are laminated together via a cured layer 5 made of the thermosetting adhesive composition (thermosetting adhesive layer) described above.

[0093] Furthermore, the printed circuit board may have a multilayer structure, for example, as shown in Figure 2. The printed circuit board 6 shown in Figure 2, for example, has a copper-plated layer 9 side of a wiring substrate comprising a polyimide layer 7 (thickness 25 μm), copper foil 8 (thickness 18 μm), and a copper-plated layer 9 (thickness 10 μm), and a coverlay 10 (thickness 25 μm) are laminated together via a cured product layer 5 (thickness 35 μm) made of the thermosetting adhesive composition (thermosetting adhesive layer) described above (total thickness 201 μm). [Examples]

[0094] The following describes some embodiments of this technology. However, this technology is not limited to these embodiments.

[0095] <Styrene-based elastomer> ToughTec H1221: Hydrogenated styrene-based thermoplastic elastomer (styrene ratio 12%), manufactured by Asahi Kasei Corporation. • ToughTec M1911: Hydrogenated styrene-based thermoplastic elastomer (styrene ratio 30%), manufactured by Asahi Kasei Corporation. ToughTec H1051: Hydrogenated styrene-based thermoplastic elastomer (styrene ratio 42%), manufactured by Asahi Kasei Corporation. ToughTec H1043: Hydrogenated styrene-based thermoplastic elastomer (styrene ratio 67%), manufactured by Asahi Kasei Corporation.

[0096] P125: Aliphatic saturated hydrocarbon resin, manufactured by Alcon Corporation. Petocol 140: An aromatic hydrocarbon resin polymerized primarily from styrene, vinyltoluene, indene, etc., manufactured by Tosoh Corporation. SX100: Styrene resin (100% styrene tackifier, product name YS Resin SX100), manufactured by Yasuhara Chemical Co., Ltd.

[0097] <(A) Modified polyphenylene ether resin having radical polymerizable groups at the molecular ends> OPE-2St2200: Modified polyphenylene ether resin (Mn=2,200) with vinylbenzyl groups at both ends of the molecule, manufactured by Mitsubishi Gas Chemical Company. SA9000: Modified polyphenylene ether resin with methacryloyl groups at both ends of the molecule (Mw=1,700), manufactured by SABIC Corporation.

[0098] <(B) Polybutadiene and / or polyisoprene with a weight-average molecular weight of 10,000 to 50,000> Ricon154: Liquid polybutadiene (Mw=15,000, Mn=5,200), manufactured by Clay Valley Corporation. LIR-30: Liquid polyisoprene (Mw=28,000), manufactured by Kuraray Co., Ltd.

[0099] <Radical polymerization initiator> Dicumyl peroxide: (Decomposition temperature of 175°C is required for a half-life of 1 minute) Dilauroyl peroxide: (The decomposition temperature for which the half-life is 1 minute is 116°C)

[0100] <Epoxy resin> JER828: Epoxy resin, manufactured by Mitsubishi Chemical Corporation. 4032D: Naphthalene-type epoxy resin, manufactured by DIC Corporation.

[0101] <Epoxy resin hardener> Novacure 3941: A microencapsulated latent curing agent consisting of an imidazole-modified core coated with polyurethane, manufactured by Asahi Kasei E-Materials Corporation. Amicure UDH-J: Hydrazide-based latent curing agent, manufactured by Ajinomoto Fine Techno Co., Ltd. 2E4MZ: 2-Ethyl-4-methylimidazole (Imidazole without latent properties)

[0102] <Preparation of thermosetting adhesive composition> Each component shown in Table 1 was weighed to the mass shown in Table 1 and uniformly mixed in an organic solvent containing toluene and ethyl acetate to prepare a thermosetting adhesive composition (a coating for forming a thermosetting adhesive layer). In Table 1, the column for "(B) included" states, for example, "satisfying" in Example 1, which means that component (B) is included. Also, in Table 1, the column for "(A) and (B) relationship" states, for example, "satisfying" in Example 1, which means that the content of component (A) is greater than the content of component (B) ((A)>(B)).

[0103] <Preparation of thermosetting sheets> The obtained thermosetting adhesive composition was applied to a release-treated polyethylene terephthalate film and dried in a drying oven at 40-130°C to produce a thermosetting adhesive sheet having a polyethylene terephthalate film with a thickness of 12-50 μm and a thermosetting adhesive layer with a thickness of 5-50 μm.

[0104] <Rating> <Evaluation of the applicability (film state) of paints for forming thermosetting adhesive layers> During the preparation of the thermosetting adhesive sheet described above, the applicability of the thermosetting adhesive composition was evaluated according to the following criteria. The results are shown in Table 1. In practical terms, a rating of "○" is preferable.

[0105] ○(OK): The thermosetting adhesive composition has good compatibility, and the evaluation described later can be performed in film form. ×(NG): The thermosetting adhesive composition has poor compatibility, making it impossible to perform the evaluation described later in film form.

[0106] <Dielectric constant (Dk)> Thermosetting adhesive sheets prepared in the examples and comparative examples were laminated together to create 1 mm thick test specimens. These specimens were then heat-cured at 180°C and 1.0 MPa for 1 hour to prepare evaluation specimens. For these evaluation specimens, the dielectric constant was determined using a dielectric constant measuring device (manufactured by AET) by the cavity resonance perturbation method at measurement temperatures of 23°C and 80°C and a measurement frequency of 10 GHz. The dielectric constant was evaluated according to the following criteria. The results are shown in Table 1.

[0107] A: Dielectric constant is less than 2.30 B: Dielectric constant is 2.30 or higher and less than 2.40 C: Dielectric constant is 2.40 or higher and less than 2.60 D: Dielectric constant of 2.60 or higher

[0108] In practical terms, the dielectric constant is preferably A or B, and more preferably A.

[0109] <Dielectric Loss Tangent (Df)> The dielectric loss tangent was determined for the evaluation specimen using the same method as described above for measuring the dielectric constant. The dielectric loss tangent was evaluated according to the following criteria. The results are shown in Table 1.

[0110] A: Dielectric loss tangent is less than 0.0020 B: Dielectric loss tangent is 0.0020 or greater, and less than 0.0030. C: Dielectric loss tangent is 0.0030 or greater, and less than 0.0050. D: Dielectric loss tangent is 0.0050 or higher

[0111] In practical terms, the dielectric loss tangent is preferably A or B, and more preferably A. That is, the dielectric loss tangent of the thermosetting adhesive composition is preferably less than 0.0030 at both 23°C and 80°C, and more preferably less than 0.0020 at both temperatures.

[0112] <Rate of change in dielectric loss tangent> The percentage change (%) between the measurement at 80°C and the measurement at 23°C was calculated and evaluated according to the following criteria. The results are shown in Table 1. A: The rate of change between 23℃ and 80℃ is less than 30%. B: The rate of change between 23℃ and 80℃ is 30% or more, but less than 50%. C: Temperature change rate between 23℃ and 80℃ is 50% or more.

[0113] In practical terms, the evaluation of the rate of change in the dielectric loss tangent is preferably A or B, and more preferably A. That is, the thermosetting adhesive composition preferably exhibits a rate of change in the dielectric loss tangent after curing, represented by the above formula 1, of less than 50%, and more preferably less than 30%.

[0114] <Peel strength> The obtained thermosetting adhesive sheet was cut into strips of a predetermined size (2 cm x 5 cm). The cut thermosetting adhesive layer was temporarily attached to a 2 cm x 7 cm x 50 μm thick liquid crystal polymer film using a laminator set to 100°C. The substrate (polyethylene terephthalate film) was then removed to expose the thermosetting adhesive layer. The rolled copper foil side (the side without roughening treatment) of a copper-clad laminate of the same size (CCL consisting of a 12 μm thick rolled copper foil and a 50 μm thick liquid crystal polymer film) was then placed on top of the exposed thermosetting adhesive layer and thermocured at 180°C and 1.0 MPa for 1 hour. A sample was then prepared.

[0115] The obtained samples were subjected to a 90-degree peel test at a peeling speed of 50 mm / min, and the force required to peel them off (initial peel strength and peel strength after reliability testing) was measured. The results are shown in Table 1.

[0116] [Initial stage (measured immediately after heat curing under the aforementioned conditions of 180°C and 1.0 MPa)] A: Peel strength of 8 N / cm or more B: Peel strength of 6 N / cm or more, and less than 8 N / cm C: Peel strength of 4 N / cm or more, and less than 6 N / cm D: Peel strength less than 4 N / cm

[0117] [After reliability testing (85°C, 85% relative humidity, 240 hours (i.e., after thermal curing under the aforementioned conditions of 180°C and 1.0 MPa, the sample was placed in an environment of 85°C and 85% relative humidity for 240 hours, and measured 3 hours after removal))] A: Peel strength of 7 N / cm or more B: Peel strength of 5 N / cm or more, and less than 7 N / cm C: Peel strength of 3 N / cm or more, and less than 5 N / cm D: Peel strength less than 3 N / cm

[0118] In practical terms, the evaluation of the initial peel strength and the peel strength after reliability testing is preferably A or B, and more preferably A.

[0119] <Heat resistance (solder heat resistance)> The aforementioned samples were subjected to a solder float test three times at a temperature of 288°C for 10 seconds. After each test, the appearance of the samples was visually inspected and evaluated according to the following criteria to determine whether delamination or blistering had occurred. The results are shown in Table 1.

[0120] A: No abnormalities were found after passing through three times. B: No abnormalities were found after the first two passes, but abnormalities such as peeling and swelling of 0.2 mm or more in diameter occurred on the third pass. C: No abnormalities were found after the first pass, but abnormalities such as peeling and swelling of 0.2 mm or more in diameter occurred on the second pass. D: Abnormalities such as peeling or swelling of 0.2 mm or more in diameter occurred during the first treatment.

[0121] In practical terms, the heat resistance rating is preferably A or B, and more preferably A.

[0122] <Bending resistance> The obtained thermosetting adhesive sheet was cut into strips of a predetermined size (1.5 cm × 12 cm), and the cut thermosetting adhesive layer was temporarily attached to a 1.5 cm × 12 cm × 50 μm thick liquid crystal polymer film using a laminator set to 100°C. Then the base material (polyethylene terephthalate film) was removed to expose the thermosetting adhesive layer. An FPC-TEG (Test Elementary Group) for the MIT flexural resistance test was placed on top of the exposed thermosetting adhesive layer and heat-cured at 180°C and 1.0 MPa for 1 hour to obtain a test specimen. The configuration of the TEG for the MIT flexural resistance test is shown in Figure 3. TEG11 is made by forming copper wiring from CCL consisting of a liquid crystal polymer film (thickness 50 μm) as the base material and rolled copper foil (thickness 12 μm). A coverlay (not shown) is bonded to the copper wiring of TEG11. In Figure 3, "130 mm" is the total length of TEG11, "120 mm" is the length of the coverlay (a combination of a thermosetting adhesive layer and a liquid crystal polymer film), "15 mm" is the total width of TEG11 and the width of the coverlay, "11 mm" is the distance between copper wires (outside), and "10 mm" is the distance between copper wires (inside), with a copper wire width of 1 mm. The MIT bending fatigue test was performed by setting the prepared test specimen 12 in an MIT bending fatigue testing machine 13 equipped with a plunger 14, an upper chuck 15, a rotary chuck 16, and a bending block 17, as shown in Figure 4. The test was performed under the conditions of a bending angle of 135°, a bending clamp angle R=0.38, and a test speed of 175 cpm. The number of bends until the copper wire broke was confirmed. The results are shown in Table 1.

[0123] A: More than 1200 folds before breaking. B: Number of folds before breaking: 600 or more, but less than 1200. C: Number of folds before breakage is 300 or more, but less than 600. D: Less than 300 folds before breaking.

[0124] In practical terms, the evaluation of flexural resistance is preferably A or B, and more preferably A.

[0125] <Workability> Figures 5-7 are cross-sectional views illustrating the measurement method for the processability test. Figure 8 is a plan view showing an example of a processed test piece 20A obtained in the processability test. First, a test piece 20 was prepared by cutting the fabricated thermosetting adhesive sheet to a predetermined size (80 mm x 80 mm). As shown in Figure 5, the test piece 20 was placed on the die 23 of the processing machine 21, and as shown in Figures 6 and 7, the test piece 20 was held down with the stripper plate 25 while the punch 22 was lowered to the die 23 to a specified depth, and the test piece 20 was processed to a predetermined processing size (φ) as shown in Figure 8, to obtain the processed test piece 20A.

[0126] <Processing conditions> Processing size (φ): 4.3mm, 1.8mm, 1.4mm, 0.75mm Processing machine: Press machine (model number: SBP305S, manufactured by Nippon Automatic Machine Co., Ltd.), outer dimensions of die 23 and stripper plate 25: 120mm x 140mm Machining speed: 99.9mm / s Punch depth (as shown in Figure 7, the distance from the surface of the die 23 on the test piece 20 side to the bottom surface of the punch 22 (the surface of the punch 22 on the test piece 20A side after processing): 0.4 mm

[0127] The test specimen 20 was machined for the clearances A to D described below. Clearance refers to the distance between the punch 22 and the die 23 (Y in Figure 7). After machining, the test specimen 20A was visually inspected to determine whether machining had been successful for each clearance.

[0128] <Clearance (mm)> A: 0.02 B:0.01 C:0.005 D:0~0.003

[0129] Figure 9 is an example of a photograph taken from the planar direction of the processed test piece 20A when the processability test is OK. Figure 10 is an example of a photograph taken from the planar direction of the processed test piece 20A when the processability test is NG.

[0130] If processing is successful (the processability test is OK), for example, as shown in Figure 7, the processed test piece 20A is completely separated from the test piece 20, and as shown in Figure 8, the area of ​​the burr 24 when the processed test piece 20A is viewed from above is 0.1 mm². 2 This means that the value is less than [a certain value]. The processed test piece 20A shown in Figure 9 is an example of a case where the processability test is OK. Here, burrs 24 refer to the portion of the polyethylene terephthalate film or thermosetting adhesive layer that makes up the processed test piece 20A that extends beyond the processing size (φ). If multiple burrs 24 occur in the processed test piece 20A, the judgment was made based on the area of ​​each individual burr 24, not the sum of the areas of the multiple burrs 24.

[0131] On the other hand, cases where processing is not possible (the processability test fails) include, for example, (i) when the processed test piece 20A is not completely separated from the test piece 20, or (ii) when the processed test piece 20A is completely separated from the test piece 20, but the area of ​​the burr 24 on the processed test piece 20A shown in Figure 8 is 0.1 mm². 2 The above is what is meant. If multiple burrs 24 occur in the processed test piece 20A, then of the multiple burrs 24, the area of ​​0.1 mm² is considered to be the same. 2 If even one of the above conditions was met, the processability test was judged to be a failure. The processed test piece 20A shown in Figure 10 is an example of a case where the processability test is a failure because the processed test piece 20A was not completely separated from the test piece 20.

[0132] In Table 1, a machinability rating of "A" means that machining was possible (OK) for all clearances of 0.02 mm, 0.01 mm, 0.05 mm, and 0-0.003 mm. A machinability rating of "B" means that machining was possible (OK) for clearances of 0.01 mm, 0.05 mm, and 0-0.003 mm. A machinability rating of "C" means that machining was possible (NG) for clearances of 0.05 mm and 0-0.003 mm. A machinability rating of "D" means that machining was possible only for clearances of 0-0.003 mm (NG). In other words, a machinability rating of "D" means that machining was not possible for clearances of 0.02 mm, 0.01 mm, and 0.05 mm. In practical terms, a machinability evaluation result of A or B is preferable, and A is more preferable. The results are shown in Table 1.

[0133] <Life> The prepared thermosetting adhesive sheets were stored at room temperature for 4 months, and then evaluated in the same way as the peel strength evaluation described above. The rate of decrease compared to the peel strength evaluated immediately after the thermosetting adhesive sheet was prepared was checked. The results are shown in Table 1. In Table 1, a "-" in the life evaluation means that the film condition was not good and it was impossible to perform the evaluation. A: The decrease in peel strength is less than 10%. B: Decrease in peel strength is 10% or more, but less than 30%. C: Decrease in peel strength of 30% or more

[0134] [Table 1]

[0135] As shown in Examples 1 to 7, thermosetting adhesive compositions for joining substrates, comprising 30 to 60 parts by mass of styrene elastomer, 20 to 40 parts by mass of a cyclic hydrocarbon resin, 4 to 20 parts by mass of component (A) and 4 to 10 parts by mass of component (B) as crosslinking components, and a total of 10 parts by mass or less of radical polymerization initiator, epoxy resin, and epoxy resin curing agent, were found to have low dielectric constant and dielectric loss tangent after thermal curing, as well as a low rate of change of dielectric loss tangent at temperature. In addition, they were found to have good flexural resistance after thermal curing and good processability before thermal curing. Furthermore, the thermosetting adhesive compositions of Examples 1 to 7 were found to have good heat resistance and lifespan.

[0136] Regarding the dielectric constant and dielectric loss tangent after curing, it was found that the thermosetting adhesive compositions of Examples 1 to 7 exhibited a dielectric loss tangent of less than 0.003 at both 23°C and 80°C. Furthermore, regarding the rate of change of the dielectric loss tangent at temperature, it was found that the thermosetting adhesive compositions of Examples 1 to 7 showed a rate of change of less than 50%, as represented by Formula 1.

[0137] The thermosetting adhesive compositions of Comparative Examples 1 to 3 contained more than 60 parts by mass of styrene-based elastomer and either did not contain a hydrocarbon resin with a ring structure or contained less than 20 parts by mass of a hydrocarbon resin with a ring structure, and were found to have poor processability before thermosetting.

[0138] The thermosetting adhesive composition of Comparative Example 4 had a styrene-based elastomer content of more than 60 parts by mass, a cyclic hydrocarbon resin content of less than 20 parts by mass, and a total content of radical polymerization initiator, epoxy resin, and epoxy resin curing agent of more than 10 parts by mass. As a result, it was found that it had poor dielectric properties and poor processability before thermosetting.

[0139] The thermosetting adhesive composition of Comparative Example 5 contained more than 60 parts by mass of styrene-based elastomer and did not contain a hydrocarbon resin with a ring structure, so it was found to have poor processability before thermosetting. Furthermore, the thermosetting adhesive composition of Comparative Example 5 did not use an organic peroxide with a decomposition temperature of 170°C or higher, which results in a half-life of 1 minute, as a radical polymerization initiator, so it was found to have poor lifespan. [Explanation of symbols]

[0140] 1. Printed circuit board, 2. Liquid crystal polymer film, 3 copper foil, 4. Liquid crystal polymer film, 5. A cured layer made of an adhesive composition, 6. Printed circuit board, 7. Polyimide layer, 8 copper foil, 9. Copper plating layer, 10 coverlays, 11 TEG, 12 test specimens, 13. MIT Fracture Testing Machine 14 plungers, 15 Top zipper, 16 Rotary chucks, 17 Folding tops, 20 test specimens, 20A Test specimen after processing, 21 processing machines, 22 punches, 23 Die 24 Bali, 25 Stripper Plates

Claims

1. A thermosetting adhesive composition for joining substrates, For a total of 100 parts by mass of the thermosetting adhesive composition, 30 to 60 parts by mass of styrene-based elastomer, A hydrocarbon resin having a ring structure is provided in 20 to 40 parts by mass, As a cross-linking component, (A) A modified polyphenylene ether resin having radical polymerizable groups at the molecular ends, (B) Polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, Radical polymerization initiator and It contains epoxy resin, It may further contain an epoxy resin curing agent. A thermosetting adhesive composition in which the total content of the radical polymerization initiator, the epoxy resin, and the epoxy resin curing agent is 10 parts by mass or less.

2. The thermosetting adhesive composition according to claim 1, wherein the sum of the content of component (A) and the content of component (B) is 25 parts by mass or less per 100 parts by mass of the total thermosetting adhesive composition.

3. The thermosetting adhesive composition according to claim 1 or 2, wherein the composition contains 4 to 20 parts by mass of component (A) per 100 parts by mass of the total thermosetting adhesive composition.

4. The thermosetting adhesive composition according to claim 1 or 2, wherein the composition contains 4 to 10 parts by mass of component (B) per 100 parts by mass of the total thermosetting adhesive composition.

5. The dielectric loss tangent after curing is less than 0.0030 at both 23°C and 80°C. The thermosetting adhesive composition according to claim 1 or 2, wherein the rate of change represented by the following formula 1 is less than 50%. Formula 1: Rate of change (%) = ((dielectric loss tangent of the thermosetting adhesive composition at 80°C after curing) / (dielectric loss tangent of the thermosetting adhesive composition at 23°C after curing) - 1) × 100

6. The thermosetting adhesive composition according to claim 1 or 2, wherein the content of component (A) and the content of component (B) satisfy the following formula 2. Formula 2: (Content of component (A) in the thermosetting adhesive composition) > (Content of component (B) in the thermosetting adhesive composition)

7. The thermosetting adhesive composition according to claim 1 or 2, wherein the epoxy resin content is less than 5 parts by mass.

8. The thermosetting adhesive composition according to claim 5, wherein the rate of change represented by the above formula 1 is less than 30%.

9. The thermosetting adhesive composition according to claim 1 or 2, further comprising an epoxy resin curing agent.

10. The thermosetting adhesive composition according to claim 1 or 2, wherein the radical polymerization initiator is an organic peroxide having a decomposition temperature of 170°C or higher for which the half-life is 1 minute.

11. The thermosetting adhesive composition according to claim 1 or 2, wherein the styrene-based elastomer contains a styrene-based elastomer having a functional group that promotes the curing reaction of the epoxy resin.

12. A thermosetting adhesive composition for joining substrates, Styrene-based elastomer and A hydrocarbon resin having a ring structure, As a cross-linking component, (A) A modified polyphenylene ether resin having radical polymerizable groups at the molecular ends, (B) Polybutadiene and / or polyisoprene having a weight-average molecular weight of 10,000 to 50,000, Radical polymerization initiator and It contains epoxy resin, The dielectric loss tangent after curing is less than 0.0030 at both 23°C and 80°C. If the rate of change expressed in the following formula 1 is less than 50%, A thermosetting adhesive composition whose processability before heat curing satisfies the following condition 1. Formula 1: Rate of change (%) = ((dielectric loss tangent of the thermosetting adhesive composition at 80°C after curing) / (dielectric loss tangent of the thermosetting adhesive composition at 23°C after curing) - 1) × 100 Condition 1: Using a press machine equipped with a punch and a die (model number: SBP305S, manufactured by Nippon Automatic Machine Co., Ltd.), a thermosetting adhesive sheet, in which an adhesive layer of thermosetting adhesive composition with a thickness of 5 to 50 μm is formed on a substrate with a thickness of 12 to 50 μm, can be processed to a size of diameter of 0.75 mm to 4.3 mm, with a processing speed of 99.9 mm / s, a punch depth of 0.4 mm, and a gap distance (clearance) between the punch and the die of 0.02 mm or less.

13. A thermosetting adhesive sheet having an adhesive layer formed on a substrate, the adhesive layer being made of the thermosetting adhesive composition according to claim 1 or 12.

14. A printed circuit board in which a wiring pattern side of a wired resin substrate, which comprises a substrate and a wiring pattern, and a coverlay are laminated via a cured product of the thermosetting adhesive composition according to claim 1 or 12.

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