Thermosetting resin composition, prepreg, resin film, metal-clad laminate, printed wiring board, antenna device, antenna module, and communication device

Abstract

Provided is a metal-clad laminate that enables board appearance inspection by an AOI device even for an antenna module. Also provided is a thermosetting resin composition that makes it possible to produce such a metal-clad laminate. Further provided are a prepreg, a resin film, a laminate, a printed wiring board, an antenna device, an antenna module, and a communication device, each of which is obtained using this thermosetting resin composition. The thermosetting resin composition contains (A) a thermosetting resin and (B) one or more high dielectric constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers, wherein, in a chart obtained by performing board appearance inspection by the method described in the specification, the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition are detected separately.

Description

Thermosetting resin composition, prepreg, resin film, metal-clad laminate, printed wiring board, antenna device, antenna module, and communication device

[0001] The present disclosure relates to a thermosetting resin composition, a prepreg, a resin film, a metal-clad laminate, a printed wiring board, an antenna device, an antenna module, and a communication device.

[0002] In recent years, the widespread use of mobile devices such as smartphones, coupled with technological innovations such as the Internet of Things (IoT), has led to an increase in the number of home appliances and electronic devices with wireless communication capabilities. This has led to concerns about increased communication traffic on wireless networks, resulting in a decline in communication speed and quality. To address this issue, fifth-generation mobile communication systems (hereinafter sometimes referred to as "5G") are being developed and are already being used. 5G uses multiple antenna elements to perform advanced beamforming and spatial multiplexing, and in addition to the conventional 6 GHz frequency signals, it also uses millimeter-wave signals with higher frequencies, such as tens of GHz. This is expected to increase communication speeds and improve communication quality. Hereinafter, frequencies above 10 GHz are referred to as high frequencies.

[0003] Thus, 5G requires antenna modules to be able to handle high-frequency signals. To achieve this, laminates are required to have low dielectric constants (Dk) and dielectric loss tangents (Df) in the high-frequency band, particularly low dielectric loss tangents (Df). Because high-frequency radio waves have high linearity, signals carried on high-frequency radio waves tend to be easily blocked by obstacles such as buildings. Therefore, to avoid this blocking, multiple antenna devices are mounted on an antenna module. Since increasing the dielectric constant (Dk) of the substrate material can reduce the size of the antenna device, increasing the dielectric constant (Dk) is effective for mounting multiple antenna devices and also leads to the miniaturization of the antenna module and ultimately the miniaturization of the communication device. Therefore, laminates used in antenna modules that can handle high-frequency signals are required to have a predetermined high dielectric constant (Dk) and a low dielectric loss tangent (Df).

[0004] One method for increasing the relative permittivity (Dk) of a substrate material is to use a high-permittivity material (see, for example, Patent Document 1). The small antenna described in Patent Document 1 is manufactured by laminating a first dielectric layer made of a low-permittivity material between second and third dielectric layers made of a high-permittivity material.

[0005] WO 2005 / 101574

[0006] An effective method for evaluating the quality of substrate materials is to perform visual inspection of substrates using an automated optical inspection (AOI) device. AOI devices perform visual inspections using optical equipment that utilizes light reflection, etc. Because optical equipment can check fine surface conditions that cannot be confirmed visually by the human eye, AOI devices are often used to evaluate the quality of substrate materials. However, the inventors' investigations have revealed that metal-clad laminates for antenna modules often cannot be visually inspected using an AOI device.

[0007] In view of the current situation, the present disclosure aims to provide a metal-clad laminate that enables substrate appearance inspection using an AOI device even for use in an antenna module, to provide a thermosetting resin composition that enables the production of such a metal-clad laminate, and to provide a prepreg, a resin film, a printed wiring board, an antenna device, an antenna module, and a communication device that are obtained using the thermosetting resin composition.

[0008] As a result of extensive research, the present inventors have found that the above-mentioned object can be achieved by using the thermosetting resin composition and metal-clad laminate of the present disclosure.

[0009] The present disclosure includes the following embodiments [1] to

[20] . [1] A thermosetting resin composition comprising: (A) a thermosetting resin; and (B) one or more high-dielectric-constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers, wherein a peak derived from a metal foil and a peak derived from a cured product of the thermosetting resin composition are detected separately in a chart obtained by performing a substrate visual inspection using the following method. (Substrate visual inspection method) A metal-clad laminate in which a cured product of the thermosetting resin composition and a metal foil are superimposed is prepared, and a test piece in which a portion of the surface of the cured product of the thermosetting resin composition is revealed is produced by etching away the metal foil while leaving a portion of the metal foil. The test piece is set in an automatic optical inspection device and inspected, whereby a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected in a graph in which the horizontal axis is gray level and the vertical axis is pixels. [2] The thermosetting resin composition according to [1] above, wherein the component (A) comprises one or more resins selected from the group consisting of epoxy resins, maleimide compounds, modified polyphenylene ether resins, phenolic resins, polyimide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. [3] The thermosetting resin composition according to [1] or [2] above, wherein the titanium-based inorganic filler is one or more resins selected from the group consisting of titanium dioxide and metal titanates. [4] The thermosetting resin composition according to [3] above, wherein the metal titanates are one or more resins selected from the group consisting of alkali metal titanates, alkaline earth metal titanates, and lead titanates. [5] The thermosetting resin composition according to any one of [1] to [4] above, wherein the zircon-based inorganic filler is an alkali metal zirconate. [6] The thermosetting resin composition according to any one of the above [1] to [5], further comprising (G) one or more selected from dyes and pigments.[7] The thermosetting resin composition according to any one of [1] to [6] above, wherein a peak derived from the metal foil appears at a gray level of 230 to 256, and a peak derived from the cured product of the thermosetting resin composition appears at a gray level of 220 or less. [8] A prepreg containing the thermosetting resin composition according to any one of [1] to [7] above or a semi-cured product of the thermosetting resin composition. [9] A resin film containing the thermosetting resin composition according to any one of [1] to [7] above or a semi-cured product of the thermosetting resin composition.

[10] A metal-clad laminate plate having a cured product of the thermosetting resin composition according to any one of [1] to [7] above and a metal foil.

[11] A metal-clad laminate having a cured product of a thermosetting resin composition and a metal foil, wherein the thermosetting resin composition contains: (A) a thermosetting resin; and (B) one or more high-dielectric-constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers. In a chart obtained by performing a substrate visual inspection using the following method, a peak attributable to the metal foil and a peak attributable to the cured product of the thermosetting resin composition are detected separately. (Substrate visual inspection method) A test piece is prepared by etching away the metal foil while leaving a portion of the metal foil of the metal-clad laminate, revealing a portion of the surface of the cured product of the thermosetting resin composition. The test piece is then set in an automatic optical inspection device and inspected, whereby a peak attributable to the metal foil and a peak attributable to the cured product of the thermosetting resin composition are detected in a graph with the horizontal axis representing gray level and the vertical axis representing pixels.

[12] The metal-clad laminate according to

[11] above, wherein the titanium-based inorganic filler is one or more selected from the group consisting of titanium dioxide and metal titanates.

[13] The metal-clad laminate according to

[12] above, wherein the metal titanate is at least one selected from the group consisting of alkali metal titanate, alkaline earth metal titanate, and lead titanate.

[14] The metal-clad laminate according to any one of

[11] to

[13] above, wherein the zircon-based inorganic filler is an alkali metal zirconate.

[15] The metal-clad laminate according to any one of

[11] to

[14] above, further comprising (G) at least one selected from dyes and pigments.

[16] The metal-clad laminate according to any one of

[11] to

[15] above, wherein a peak derived from the metal foil appears at a gray level of 230 to 256, and a peak derived from the cured product of the thermosetting resin composition appears at a gray level of 220 or less.

[17] A printed wiring board having a cured product of the thermosetting resin composition according to any one of [1] to [7] above.

[18] An antenna device having the metal-clad laminate according to any one of

[10] to

[16] above.

[19] An antenna module having a feed circuit and the antenna device according to

[18] above.

[20] A communication device having a baseband signal processing circuit and the antenna module according to

[19] above.

[0010] The present disclosure makes it possible to provide a metal-clad laminate that enables substrate appearance inspection using an AOI device, even for use in an antenna module, a thermosetting resin composition that enables the production of such a metal-clad laminate, and prepregs, resin films, printed wiring boards, antenna devices, antenna modules, and communication devices that are obtained using the thermosetting resin composition.

[0011] 1 is a schematic top view of an example of a test piece used in substrate visual inspection in the present embodiment; FIG. 2 is a graph obtained by calibration of substrate visual inspection in Example 1; FIG. 3 is a graph obtained by calibration of substrate visual inspection in Example 2; FIG. 4 is a graph obtained by calibration of substrate visual inspection in Comparative Example 1; and FIG. 5 is a graph obtained by calibration of substrate visual inspection in Comparative Example 2.

[0012] In the numerical ranges described in this disclosure, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples. Furthermore, the lower and upper limits of a numerical range can be arbitrarily combined with the lower or upper limit of another numerical range. In the expression "AA to BB," the two extreme values ​​AA and BB are included as the lower and upper limits, respectively, of the numerical range. In this disclosure, for example, the expression "10 or more" means 10 and a value greater than 10, and this also applies when the numerical values ​​differ. Furthermore, for example, the expression "10 or less" means 10 and a value less than 10, and this also applies when the numerical values ​​differ. Furthermore, unless otherwise specified, each component and material exemplified in this disclosure may be used alone or in combination of two or more types. In this disclosure, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0013] In the present disclosure, "resin component" refers to all components of the solid content constituting the resin composition, excluding inorganic compounds such as inorganic fillers, which will be described later. In the present disclosure, "solid content" refers to components other than the solvent, and components that are liquid at 25°C are also considered to be solid content. The expression "containing XX" described in the present disclosure naturally means simply containing XX, but also includes containing XX in a reacted state. Any combination of the items described in the present disclosure is also included in the present disclosure and the present embodiment.

[0014] [Thermosetting Resin Composition] The thermosetting resin composition of this embodiment is as follows: A thermosetting resin composition containing: (A) a thermosetting resin (hereinafter, sometimes referred to as component (A)); and (B) one or more high-dielectric-constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers (hereinafter, sometimes referred to as component (B)), wherein a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected separately in a chart obtained by performing a substrate visual inspection by the following method. (Substrate Visual Inspection Method) A metal-clad laminate in which the cured product of the thermosetting resin composition and metal foil are superimposed is prepared, and the metal foil is etched away while leaving a portion of the metal foil, thereby producing a test piece in which a portion of the surface of the cured product of the thermosetting resin composition is exposed. The test piece is set in an automated optical inspection (AOI) device and inspected, and a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected in a graph with the horizontal axis being gray level and the vertical axis being pixels.

[0015] Because the thermosetting resin composition of this embodiment contains the component (B), it has a high dielectric constant (Dk), enabling the miniaturization of antenna devices. Therefore, the metal-clad laminate of this embodiment, manufactured using this thermosetting resin composition, is useful for antenna modules. As mentioned above, metal-clad laminates for antenna modules often cannot be inspected for their substrate appearance using an AOI device. However, the metal-clad laminate of this embodiment allows the surface appearance of the cured thermosetting resin composition beneath the metal foil to be inspected using an AOI device. This is achieved by detecting peaks originating from the metal foil and peaks originating from the cured thermosetting resin composition at separate locations in the chart obtained by substrate appearance inspection. On the other hand, if the peaks originating from the metal foil and peaks originating from the cured thermosetting resin composition overlap, an error occurs in the AOI device, making inspection impossible. The AOI device is not particularly limited, but the "Discovery (registered trademark)" series of AOI devices manufactured by Orbotech can be used. Examples of the "Discovery (registered trademark)" series include the Discovery-8000.

[0016] In a chart obtained by performing a visual inspection of a substrate, it is preferable that the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition are completely separated. It is more preferable that the peak derived from the metal foil appears at a gray level of 230 to 256 and the peak derived from the cured product of the thermosetting resin composition appears at a gray level of 220 or less. It is even more preferable that the peak derived from the metal foil appears at a gray level of 235 to 256 and the peak derived from the cured product of the thermosetting resin composition appears at a gray level of 215 or less. Here, for example, when a peak appears at a gray level of 230 to 256, it means that the start point of the peak is 230 or higher. Note that the gray level of 256 is the maximum value on the horizontal axis. Also, for example, when a peak appears at a gray level of 220 or lower, it means that the end point of the peak is 220 or lower. These concepts also apply when the gray level values ​​are different.

[0017] There are no particular limitations on the size of the peaks in the chart obtained by performing a substrate visual inspection. In metal-clad laminates for antenna modules, the peaks derived from the cured thermosetting resin usually tend to be larger than the peaks derived from the metal foil. For example, the peak top value (number of pixels) derived from the cured thermosetting resin may be three or more times, or even four or more times, the peak top value (number of pixels) derived from the metal foil. Note that the peak top value (number of pixels) derived from the cured thermosetting resin may usually be 20 or less times, or 15 or less times, the peak top value (number of pixels) derived from the metal foil.

[0018] There are no particular limitations on the method for detecting the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition so that they are separated from each other in the chart obtained by performing a substrate visual inspection. For example, a method of incorporating one or more components selected from the group consisting of dyes and pigments (G) described below into the thermosetting resin composition is effective. By incorporating the component (G) into the thermosetting resin composition, it is possible to separate the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition.

[0019] Next, the details of the substrate visual inspection method will be described. (0) Preparation of a test piece. First, a metal-clad laminate is prepared in which a cured product of the thermosetting resin composition and a metal foil are superimposed. Specifically, a metal-clad laminate can be manufactured according to the method for manufacturing a metal-clad laminate described below. A test piece (see Figure 1) is prepared in which a portion of the surface of the cured product of the thermosetting resin composition is exposed by etching away the metal foil of the metal-clad laminate while leaving a portion of the metal foil. Figure 1 shows a state in which copper foil 1 remains on a portion of the surface of a cured product 2 of the thermosetting resin composition.

[0020] (1) The test piece is set in an automated optical inspection (AOI) device. (2) Calibration is first performed. The entire test piece is photographed from above with a camera (a camera installed in the AOI device). Next, the image obtained by the camera is converted into a grayscale image. Grayscale conversion is a process of re-expressing color shading and brightness in black and white shading (256 gradations), and known methods can be used. The following formula is usually used for grayscale conversion: (Gray is the pixel value of a grayscale image, and Red, Green, and Blue are the pixel values ​​of an RGB color image.)

[0021] After grayscaling is complete, each pixel (0.02-0.04 mm x 0.02-0.04 mm), the smallest unit of the image, is assigned 256 gradations and graphed. For example, if there are 25,000 pixels corresponding to 220 gradations, the gray level 220 on the horizontal axis will be plotted at the 25,000 pixel position on the vertical axis. Specifically, graphs like those shown in FIGS. 2 and 3 are obtained. In FIGS. 2 and 3, the small peak on the right is the peak derived from the metal foil, and the large peak on the left is the peak derived from the cured product of the thermosetting resin composition. In this way, in this embodiment, the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition can be separated, which enables the next step (3).

[0022] (3) Next, a threshold value is set between the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition. The threshold value can be changed depending on the defect detection level. For example, the end point (right end) of the peak derived from the cured product of the thermosetting resin composition can be set as the minimum value, and the start point (left end) of the peak derived from the metal foil can be set as the maximum value, and the difference between the minimum and maximum values ​​can be set as the threshold. This is usually the default setting. In (2) above, if the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition overlap (see Figures 4 and 5), (3) cannot be performed, resulting in an error and preventing visual inspection. This completes the calibration process.

[0023] (4) After step (3) above, an appearance inspection is performed by photographing the entire test piece from above with a camera (a camera installed in the AOI device). While not particularly limited, the image size may be approximately 3 mm x approximately 4 mm per image. (5) Based on the image obtained in step (4) above, the presence or absence of defects is confirmed. In this manner, a substrate appearance inspection can be performed using an AOI device.

[0024] Next, the components contained in the thermosetting resin composition of this embodiment will be described in detail. ((A) Thermosetting Resin) Examples of the component (A) include epoxy resins, maleimide compounds, modified polyphenylene ether resins, phenolic resins, polyimide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. Among these, the component (A) is preferably an epoxy resin, a maleimide compound, or a polyphenylene ether resin. From the viewpoints of low thermal expansion and heat resistance, the epoxy resin and the maleimide compound are more preferred. From the viewpoints of low thermal expansion and dielectric loss tangent (Df), the maleimide compound and the polyphenylene ether resin are more preferred. As the component (A), one type may be used alone, or two or more types may be used in combination.

[0025] The epoxy resin is preferably an epoxy resin having two or more epoxy groups in one molecule. Here, epoxy resins are classified into glycidyl ether type epoxy resins, glycidyl amine type epoxy resins, glycidyl ester type epoxy resins, etc. Among these, glycidyl ether type epoxy resins are preferred.

[0004] Epoxy resins are classified into various epoxy resins depending on the difference in their main skeletons, and each of the above types of epoxy resins can be further classified into bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; alicyclic epoxy resins such as dicyclopentadiene-type epoxy resins; aliphatic chain epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, bisphenol A novolac-type epoxy resins, bisphenol F novolac-type epoxy resins, phenol aralkyl novolac-type epoxy resins, and biphenyl aralkyl novolac-type epoxy resins; stilbene-type epoxy resins; naphthalene-skeleton-containing epoxy resins such as naphthol novolac-type epoxy resins and naphthol aralkyl-type epoxy resins; biphenyl aralkyl-type epoxy resins; xylylene-type epoxy resins; and dihydroanthracene-type epoxy resins.

[0026] The maleimide compound preferably includes one or more selected from the group consisting of maleimide compounds having one or more (preferably two or more) N-substituted maleimide groups and derivatives thereof. The maleimide compound having one or more N-substituted maleimide groups is not particularly limited, and examples thereof include aromatic maleimide compounds preferably having one N-substituted maleimide group bonded to an aromatic ring, such as N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, and N-benzylmaleimide; bis(4-maleimidophenyl)methane, bis(4-maleimidophenyl)ether, bis(4-maleimidophenyl)sulfone, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl- Examples of suitable bismaleimide compounds include aromatic bismaleimide compounds having two N-substituted maleimide groups bonded to an aromatic ring, such as 1,3-phenylene bismaleimide, m-phenylene bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, and indane ring-containing bismaleimides; aromatic polymaleimide compounds having three or more N-substituted maleimide groups bonded to an aromatic ring, such as polyphenylmethane maleimide and biphenylaralkyl maleimide; and aliphatic maleimide compounds such as N-dodecylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, 1,6-bismaleimide-(2,2,4-trimethyl)hexane, and pyrrolonic acid binder-type long-chain alkylbismaleimides. Among these, from the viewpoints of compatibility with other resins, peel strength, heat resistance, low thermal expansion, and mechanical properties, aromatic bismaleimide compounds preferably having two N-substituted maleimide groups bonded to an aromatic ring are more preferred, and 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane is even more preferred.

[0027] Examples of the derivatives of maleimide compounds include addition reaction products of maleimide compounds having one or more (preferably two or more) N-substituted maleimide groups with amine compounds such as monoamine compounds and diamine compounds (hereinafter, these may be referred to as "modified maleimide compounds"). Examples of the monoamine compounds include monoamine compounds having an acidic substituent, such as o-aminophenol, m-aminophenol, p-aminophenol, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, 3,5-dihydroxyaniline, and 3,5-dicarboxyaniline. Examples of the diamine compound include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylpropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4,4'-diaminodiphenyl)propane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylethane, 3,3'-diethyl-4,4'-diaminodiphenylethane, 4,4' Examples of the monoamine compound include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl thioether, 3,3'-dihydroxy-4,4'-diaminodiphenylmethane, 2,2',6,6'-tetramethyl-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 3,3'-dibromo-4,4'-diaminodiphenylmethane, 2,2',6,6'-tetrachloro-4,4'-diaminodiphenylmethane, 2,2',6,6'-tetrabromo-4,4'-diaminodiphenylmethane, and siloxane diamine. Among these, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and siloxane diamine are preferred. The monoamine compound and the diamine compound may each be used alone or in combination of two or more.The maleimide compound preferably includes an addition reaction product between a maleimide compound having two or more N-substituted maleimide groups and an amine compound, more preferably includes an addition reaction product between a maleimide compound having two or more N-substituted maleimide groups and a diamine compound, and even more preferably includes an addition reaction product between a maleimide compound having two or more N-substituted maleimide groups and a diamine compound including a siloxane diamine.

[0028] The weight-average molecular weight of the maleimide compound is not particularly limited, but from the viewpoint of handleability and moldability, it is preferably 400 to 10,000, more preferably 1,000 to 5,000, even more preferably 1,500 to 4,000, and particularly preferably 2,000 to 3,000. In the present disclosure, the weight-average molecular weight (Mw) means a value measured in terms of polystyrene by gel permeation chromatography (GPC).

[0029] The modified polyphenylene ether resin is preferably a polyphenylene ether resin having an ethylenically unsaturated bond-containing group at its terminal, and more preferably a polyphenylene ether resin having ethylenically unsaturated bond-containing groups at both terminals. Here, the term "ethylenically unsaturated bond-containing group" refers to a substituent containing a carbon-carbon double bond capable of addition reaction, and does not include a double bond in an aromatic ring. Examples of the ethylenically unsaturated bond-containing group include unsaturated aliphatic hydrocarbon groups such as vinyl, allyl, 1-methylallyl, isopropenyl, 2-butenyl, 3-butenyl, and styryl; and groups containing a heteroatom and an ethylenically unsaturated bond, such as a maleimide group and a (meth)acryloyl group. The ethylenically unsaturated bond-containing group is preferably a group containing a heteroatom and an ethylenically unsaturated bond, more preferably a (meth)acryloyl group, and even more preferably a methacryloyl group. In the present disclosure, the term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group.

[0030] The weight average molecular weight of the modified polyphenylene ether resin is not particularly limited, but from the viewpoint of handleability and moldability, it is preferably 400 to 10,000, more preferably 500 to 5,000, even more preferably 500 to 3,500, and particularly preferably 1,000 to 3,000.

[0031] (Content of Component (A)) The content of the thermosetting resin (A) in the thermosetting resin composition of the present embodiment is not particularly limited, but from the viewpoints of the dielectric loss tangent (Df), heat resistance, and moldability, the content is preferably 5 to 95 parts by mass, more preferably 10 to 80 parts by mass, even more preferably 10 to 60 parts by mass, and particularly preferably 15 to 40 parts by mass, relative to 100 parts by mass of the solid content in the thermosetting resin composition.

[0032] (B) One or more high-dielectric-constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers) From the viewpoint of the dielectric constant (Dk), the titanium-based inorganic filler is preferably one or more selected from the group consisting of titanium dioxide and metal titanates. From the viewpoint of the dielectric constant (Dk), examples of the metal titanates include alkali metal titanates such as potassium titanate; alkaline earth metal titanates such as barium titanate, calcium titanate, and strontium titanate; and lead titanate. The metal titanate is preferably one or more selected from these examples, and from the viewpoint of the dielectric constant (Dk), alkaline earth metal titanates are more preferred, and calcium titanate and strontium titanate are even more preferred. From the viewpoint of the dielectric constant (Dk), the zircon-based inorganic filler is preferably an alkali metal zirconate. From the viewpoint of the dielectric constant (Dk), the alkali metal zirconate is preferably one or more selected from the group consisting of calcium zirconate and strontium zirconate. As the component (B), from the viewpoint of the dielectric loss tangent (Df) and specific gravity, titanium-based inorganic fillers are preferred, and more preferred ones are as described above.

[0033] The average particle diameter of component (B) is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.4 μm or more. From the viewpoint of heat resistance, it is even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. The upper limit of the average particle diameter of component (B) is preferably 4.5 μm or less, more preferably 4.0 μm or less, even more preferably 3.5 μm or less, particularly preferably 3.0 μm or less, and most preferably 2.5 μm or less, from the viewpoint of eliminating coarse particles that may cause insulation failure. For these reasons, the average particle diameter of component (B) is preferably 0.1 to 4.5 μm, and the lower and upper limits within this numerical range can be changed based on the above-mentioned description. Here, in the present disclosure, the average particle diameter refers to the average primary particle diameter. In the present disclosure, the average particle diameter is the d50 value (median diameter of the volume distribution) obtained by analyzing the particle size distribution using a particle size distribution analyzer. The method and conditions for analyzing the particle size distribution may be, in detail, those described in the Examples. The shape of component (B) is not particularly limited, but since industrially available high dielectric constant inorganic fillers generally have irregular shapes, the component (B) may have an irregular shape, or may have another shape such as a spherical shape.

[0034] (Content of Component (B)) The content of component (B) in the thermosetting resin composition of this embodiment is not particularly limited, but from the viewpoint of the dielectric constant (Dk), it is preferably 1 to 60 vol%, more preferably 2 to 30 vol%, 3 to 20 vol%, 7 to 30 vol%, or even 12 to 25 vol%, relative to the solid content in the thermosetting resin composition. When the content of component (B) is expressed in parts by mass, it is preferably 5 to 95 parts by mass, more preferably 15 to 90 parts by mass, even more preferably 20 to 70 parts by mass, particularly preferably 20 to 55 parts by mass, and most preferably 25 to 50 parts by mass, relative to 100 parts by mass of the solid content in the thermosetting resin composition. When the content of component (B) in the thermosetting resin composition of this embodiment is equal to or greater than the lower limit, the dielectric constant (Dk) tends to be sufficiently increased, and when it is equal to or less than the upper limit, the dielectric loss tangent (Df) tends to be prevented from becoming too high.

[0035] ((C) Elastomer) The thermosetting resin composition of this embodiment is not particularly limited, but preferably further contains (C) an elastomer. Examples of the (C) elastomer include styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic elastomers, and silicone-based elastomers. These elastomers are composed of a hard segment component and a soft segment component, and generally, the hard segment component contributes to heat resistance and strength, while the soft segment component contributes to flexibility and toughness. One type of (C) elastomer may be used alone, or two or more types may be used in combination.

[0036] From the viewpoint of high-frequency characteristics, the elastomer (C) is preferably a styrene-based elastomer, and more preferably a styrene-based thermoplastic elastomer. The styrene-based elastomer may have a structural unit derived from a styrene-based compound. From the viewpoints of high-frequency characteristics, adhesion to a conductor, heat resistance, and low thermal expansion, one or more types selected from the group consisting of hydrogenated styrene-butadiene-styrene block copolymers (SEBS and SBBS), hydrogenated styrene-isoprene-styrene block copolymers (SEPS), and styrene-maleic anhydride copolymers (SMA) are preferred, one or more types selected from the group consisting of hydrogenated styrene-butadiene-styrene block copolymers (SEBS) and hydrogenated styrene-isoprene-styrene block copolymers (SEPS) are more preferred, and hydrogenated styrene-butadiene-styrene block copolymers (SEBS) are even more preferred. The styrene-based elastomer (excluding the SMA) may be modified with an acid anhydride such as maleic anhydride, and examples thereof include SEBS modified with an acid anhydride such as maleic anhydride, and SEPS modified with an acid anhydride such as maleic anhydride. The acid value of the acid-modified styrene-based elastomer (excluding the SMA) is not particularly limited, but is preferably 2 to 20 mg CH ３ ONa / g is preferred, 5 to 15 mg CH ３ ONa / g is more preferred, 7 to 13 mg CH ３ ONa / g is more preferred.

[0037] In the styrene-based elastomer, the content of styrene-derived structural units [hereinafter sometimes referred to as "styrene content"] is not particularly limited, but from the viewpoints of high-frequency characteristics, adhesion to conductors, heat resistance, and low thermal expansion, it is preferably 5 to 80 mass%, more preferably 10 to 75 mass%, even more preferably 15 to 60 mass%, and particularly preferably 20 to 45 mass%. The weight-average molecular weight (Mw) of the styrene-based elastomer is not particularly limited, but is preferably 12,000 to 1,000,000, more preferably 30,000 to 500,000, even more preferably 50,000 to 120,000, and particularly preferably 70,000 to 100,000. The melt flow rate (MFR) of the styrene-based elastomer is not particularly limited, but is preferably 0.1 to 20 g / 10 min, more preferably 1 to 15 g / 10 min, still more preferably 2 to 10 g / 10 min, and particularly preferably 3 to 7 g / 10 min, measured under the conditions of 230°C and a load of 2.16 kgf (21.2 N).

[0038] (Content of Component (C)) When the thermosetting resin composition of this embodiment contains the elastomer (C), the content thereof is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, per 100 parts by mass of the solid content in the thermosetting resin composition. When the content of the elastomer (C) is equal to or greater than the lower limit, better high-frequency characteristics tend to be obtained, and when it is equal to or less than the upper limit, good heat resistance, moldability, processability, and flame retardancy tend to be obtained.

[0039] The thermosetting resin composition of this embodiment may further contain other components. The other components are not particularly limited, but preferably include at least one selected from the group consisting of (D) an inorganic filler (excluding component (B)), a coupling agent, (E) a curing accelerator, (F) a flame retardant, and (G) a dye and pigment, as well as at least one selected from the group consisting of an antioxidant, a flame retardant aid, an adhesion improver, a heat stabilizer, an antistatic agent, an ultraviolet absorber, and a lubricant.

[0040] (D) Inorganic Filler The thermosetting resin composition of the present embodiment is not particularly limited, but preferably further contains an inorganic filler (E). By containing the inorganic filler (D), the thermosetting resin composition of the present embodiment tends to have better low thermal expansion, high elastic modulus, heat resistance, and flame retardancy. However, the inorganic filler (D) does not contain the component (B). One type of inorganic filler (D) may be used alone, or two or more types may be used in combination.

[0041] (D) As inorganic fillers, silica, alumina, mica, beryllia, aluminum carbonate, magnesium hydroxide, aluminum hydroxide, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, silicon nitride, boron nitride, clay such as calcined clay, molybdate compounds such as zinc molybdate, talc, aluminum borate, silicon carbide, etc. can be mentioned. Among these, from the viewpoint of low thermal expansion, elastic modulus, heat resistance and flame retardancy, silica, alumina, mica, and talc are preferred, silica and alumina are more preferred, and silica is even more preferred. As silica, crushed silica, fumed silica, fused silica, etc. can be mentioned. Among these, fused silica is preferred, and fused spherical silica is more preferred.

[0042] The average particle size of the inorganic filler (D) is not particularly limited, but is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, even more preferably 0.2 to 3 μm, and particularly preferably 0.3 to 1.0 μm.

[0043] (Content of Component (D)) When the thermosetting resin composition of this embodiment contains an inorganic filler (D), its content is not particularly limited, but from the viewpoints of thermal expansion coefficient, elastic modulus, heat resistance, and flame retardancy, it is preferably 3 to 70 vol%, more preferably 5 to 65 vol%, even more preferably 5 to 60 vol%, even more preferably 10 to 50 vol%, particularly preferably 10 to 40 vol%, and most preferably 10 to 30 vol% relative to the solid content in the thermosetting resin composition. When the content of component (D) is expressed in parts by mass, it is preferably 1 to 60 parts by mass, more preferably 5 to 50 parts by mass, even more preferably 10 to 45 parts by mass, particularly preferably 15 to 45 parts by mass, and most preferably 20 to 40 parts by mass relative to 100 parts by mass of the solid content in the thermosetting resin composition.

[0044] When an inorganic filler is used, a coupling agent may be used in combination as needed to improve the dispersibility of the inorganic filler and the adhesion between the inorganic filler and the organic components in the resin composition. Examples of coupling agents include silane coupling agents and titanate coupling agents. Coupling agents may be used alone or in combination of two or more. When a coupling agent is used, the treatment method may be a so-called integral blend treatment method in which the inorganic filler is blended into the resin composition and then the coupling agent is added. However, a method in which an inorganic filler that has been previously surface-treated with a coupling agent by a dry or wet method is preferred. By adopting this method, the characteristics of the inorganic filler can be more effectively expressed. Furthermore, the inorganic filler may be used as a slurry in which it is previously dispersed in an organic solvent, as needed.

[0045] (E) Curing Accelerator The thermosetting resin composition of the present embodiment is not particularly limited, but preferably further contains (E) a curing accelerator. Examples of the (E) curing accelerator include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, organometallic salts, acidic catalysts, and organic peroxides. In the present embodiment, imidazole-based curing accelerators are not classified as amine-based curing accelerators. One type of curing accelerator may be used alone, or two or more types may be used in combination. Preferred curing accelerators are amine-based curing accelerators, imidazole-based curing accelerators, and phosphorus-based curing accelerators. Examples of the amine-based curing accelerators include amine compounds having primary to tertiary amino groups, such as triethylamine, 4-aminopyridine, tributylamine, and dicyandiamide; and quaternary ammonium compounds. Examples of the imidazole-based curing accelerator include imidazole compounds such as methylimidazole, phenylimidazole, 2-undecylimidazole, and isocyanate-masked imidazole (for example, an addition reaction product of hexamethylene diisocyanate resin and 2-ethyl-4-methylimidazole). Examples of the phosphorus-based curing accelerator include tertiary phosphines such as triphenylphosphine; and quaternary phosphonium compounds such as an addition reaction product of p-benzoquinone and tri-n-butylphosphine.

[0046] (Content of Component (E)) When the thermosetting resin composition of this embodiment contains the curing accelerator (E), the content thereof is not particularly limited, but is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2.5 parts by mass, still more preferably 0.1 to 2.5 parts by mass, and particularly preferably 0.5 to 2.3 parts by mass, relative to 100 parts by mass of the resin components in the thermosetting resin composition. When the content of the curing accelerator (E) is within the above range, better dielectric loss tangent (Df), heat resistance, storage stability, and moldability tend to be obtained.

[0047] (F) Flame Retardant The thermosetting resin composition of the present embodiment is not particularly limited, but preferably further contains a (F) flame retardant. Examples of the (F) flame retardant include inorganic phosphorus-based flame retardants; organic phosphorus-based flame retardants; and metal hydrates such as aluminum hydroxide hydrate and magnesium hydroxide hydrate. Note that metal hydroxides may also fall under the category of inorganic fillers, but metal hydroxides that can impart flame retardancy are classified as flame retardants. Among these, organic phosphorus-based flame retardants are preferred as the (F) flame retardant. Examples of organic phosphorus-based flame retardants include aromatic phosphate esters, phosphonic acid diesters, and phosphinic acid esters; metal salts of phosphinic acid, organic nitrogen-containing phosphorus compounds, and cyclic organic phosphorus compounds. Here, examples of the "metal salt" include lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, aluminum salts, titanium salts, and zinc salts. Among these, aromatic phosphate esters are preferred as the organic phosphorus-based flame retardants.

[0048] (Content of Component (F)) When the thermosetting resin composition of the present embodiment contains the flame retardant (F), the content thereof is not particularly limited, but is preferably 0.1 to 30 parts by mass, alternatively 1 to 25 parts by mass, alternatively 3 to 20 parts by mass, or alternatively 5 to 15 parts by mass, relative to 100 parts by mass of the solid content in the thermosetting resin composition. When the content of the flame retardant (F) is equal to or greater than the lower limit, better flame retardancy tends to be obtained. When the content is equal to or less than the upper limit, better moldability, peel strength, and heat resistance tend to be obtained.

[0049] (G) One or more selected from dyes and pigments) The thermosetting resin composition of this embodiment preferably further contains one or more selected from dyes and pigments (G). When the thermosetting resin composition of this embodiment contains the component (G), it is possible to easily separate the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition. This is presumably due to the effect of the component (G) suppressing light reflection in the cured product of the thermosetting resin composition. Although not particularly limited, it is preferable to use both a dye and a pigment as the component (G) from the viewpoint of easily separating the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition.

[0050] As the dye, known dyes can be used. Examples of the dye include coumarin dyes, anthraquinone dyes, pyrazolone dyes, perinone dyes, methine dyes, and quinophthalone dyes. The dye is not particularly limited, but from the viewpoint of easily separating the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition, a yellow dye is preferred, and a pyrazolone dye is more preferred.

[0051] As the pigment, for example, known pigments can be used. Examples of pigments include inorganic pigments and organic pigments. Examples of inorganic pigments include metal compounds such as metal oxides and metal complex salts; natural mineral pigments such as graphite; and synthetic inorganic pigments such as iron blue, zinc oxide, and cobalt blue. Examples of the metal oxides include oxides or composite oxides of metals such as iron, cobalt, aluminum, cadmium, lead, copper, titanium, magnesium, chromium, zinc, and antimony. Examples of the metal complex salts include metal complex salts containing ions of metals such as Cr, Cu, Ni, and Co. Examples of organic pigments include coumarin pigments, yellow pigments such as various C.I. Pigment Yellows, orange pigments such as various C.I. Pigment Oranges, red pigments such as various C.I. Pigment Reds, blue-purple pigments such as various C.I. Pigment Violets, blue pigments such as various C.I. Pigment Blues, and black pigments such as various C.I. Pigment Blacks. Here, C.I. The organic pigment is not particularly limited, but from the viewpoint of easily separating the peak derived from the metal foil from the peak derived from the cured product of the thermosetting resin composition, a yellow pigment is preferred, and a coumarin-based pigment is more preferred.

[0052] (Content of Component (G)) When the thermosetting resin composition of this embodiment contains the component (G), its content is not particularly limited, but is preferably 0.01 to 10 parts by mass, alternatively 0.1 to 5 parts by mass, alternatively 0.1 to 3 parts by mass, or alternatively 0.3 to 2 parts by mass, relative to 100 parts by mass of the solid content in the thermosetting resin composition. When the content of the component (G) is equal to or greater than the lower limit, it tends to be easier to separate the peak derived from the metal foil from the peak derived from the cured product of the thermosetting resin composition. When the content is equal to or less than the upper limit, it tends to be easier to maintain good heat resistance and insulation reliability.

[0053] (Content of Components Other Than the Above-mentioned Components) When the thermosetting resin composition of the present embodiment contains components other than the above-mentioned components (for example, a flame retardant aid, an adhesion improver, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a lubricant, and other components), the content of each of these components is not particularly limited, and may be, for example, 0.01 parts by mass or more, 10 parts by mass or less, 5 parts by mass or less, 1 part by mass or less, or none at all, relative to 100 parts by mass of the resin component of the thermosetting resin composition.

[0054] In the thermosetting resin composition of the present embodiment, the total amount of the components (A) to (G) may be 50 to 100 mass%, 70 to 100 mass%, 80 to 100 mass%, 90 to 100 mass%, or 95 to 100 mass%, based on the solid content of the thermosetting resin composition.

[0055] (Organic Solvent) The thermosetting resin composition of this embodiment may be a so-called "varnish" containing an organic solvent from the viewpoint of ease of handling and ease of production of the prepreg described below. The organic solvent is not particularly limited, but examples thereof include alcohol-based solvents such as ethanol, propanol, butanol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether-based solvents such as tetrahydrofuran; aromatic solvents such as toluene, xylene, and mesitylene; nitrogen-containing solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; sulfur-containing solvents such as dimethyl sulfoxide; and ester-based solvents such as γ-butyrolactone. From the viewpoint of solubility, ketone-based solvents are preferred, and methyl isobutyl ketone is more preferred. The organic solvent may be used alone or in combination of two or more.

[0056] When the thermosetting resin composition of this embodiment is used as a varnish, the solids concentration is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 55 to 70% by mass. When the solids concentration of the thermosetting resin composition is within this range, the thermosetting resin composition is easy to handle, the impregnation into a substrate and the appearance of the produced prepreg are good, and the coatability when made into a resin film is also good.

[0057] The thermosetting resin composition of this embodiment can be produced by mixing components (A) and (B) and the other optional components using a known method. In this process, each component may be dissolved or dispersed in the organic solvent while stirring. The mixing order, temperature, time, and other conditions are not particularly limited and can be set as desired. Because the thermosetting resin composition of this embodiment can exhibit a high relative dielectric constant (Dk) and a low dielectric loss tangent (Df), it is useful for antenna modules, particularly miniaturized antenna modules compatible with fifth-generation mobile communication systems (5G).

[0058] [Prepreg] The prepreg of this embodiment is a prepreg containing the thermosetting resin composition of this embodiment or a semi-cured product of the thermosetting resin composition. The prepreg of this embodiment contains, for example, the thermosetting resin composition of this embodiment or a semi-cured product of the thermosetting resin composition and a sheet-like fiber substrate. The prepreg is formed using the thermosetting resin composition of this embodiment and a sheet-like fiber substrate. For example, the prepreg can be obtained by impregnating or coating the sheet-like fiber substrate with the thermosetting resin composition of this embodiment, drying it, and semi-curing (B-staging) it as needed. More specifically, the prepreg of this embodiment can be produced by, for example, semi-curing (B-staging) it by heating and drying it in a drying oven, typically at a temperature of 80 to 200°C for 1 to 30 minutes. Here, B-staging in this disclosure refers to achieving a B-stage state as defined in JIS K6900 (1994). The amount of the thermosetting resin composition used can be appropriately determined so that the solid content concentration of the thermosetting resin composition in the dried prepreg is 30 to 90 mass %. By setting the solid content concentration within this range, better moldability tends to be obtained when the prepreg is made into a laminate.

[0059] As the sheet-like fiber substrate for the prepreg, known materials used in various laminates for electrical insulating materials are used. Materials for the sheet-like fiber substrate include inorganic fibers such as E-glass, D-glass, S-glass, and Q-glass; organic fibers such as polyimide, polyester, and tetrafluoroethylene; and mixtures thereof. These sheet-like fiber substrates have shapes such as woven fabric, nonwoven fabric, roving, chopped strand mat, and surfacing mat.

[0060] The thickness of the prepreg is not particularly limited, and may be 10 to 170 μm, 10 to 120 μm, or 10 to 70 μm.

[0061] The prepreg of the present embodiment can exhibit a high relative dielectric constant (Dk) and a low dielectric loss tangent (Df), and is therefore useful for antenna modules, particularly for miniaturized antenna modules compatible with 5G.

[0062] [Resin Film] The resin film of this embodiment is a resin film containing the thermosetting resin composition of this embodiment or a semi-cured product of the thermosetting resin composition. The resin film of this embodiment can be produced, for example, by applying a thermosetting resin composition containing an organic solvent, i.e., a varnish, to a support, and then heating and drying to semi-cure (B-stage) as necessary. Examples of the support include plastic film, metal foil, and release paper. The drying temperature and drying time can be determined appropriately depending on the amount of organic solvent used, the boiling point of the organic solvent used, and the like, but the resin film can be suitably formed by drying at 50 to 200°C for about 1 to 10 minutes.

[0063] The resin film of the present embodiment can exhibit a high relative dielectric constant (Dk) and a low dielectric loss tangent (Df), and is therefore useful for antenna modules, particularly for miniaturized antenna modules compatible with 5G.

[0064] [Metal-Clad Laminate] The metal-clad laminate of this embodiment is a metal-clad laminate having a cured product of the thermosetting resin composition of this embodiment and a metal foil. The metal-clad laminate of this embodiment can be produced, for example, by placing a metal foil on one or both sides of a prepreg obtained by stacking two or more prepregs of this embodiment, or by placing a metal foil on one or both sides of a prepreg obtained by stacking a total of two or more prepregs of this embodiment and prepregs other than this embodiment, and then hot-pressing and molding. In the metal-clad laminate obtained by this production method, the prepreg of this embodiment is C-staged. In this disclosure, C-staging refers to bringing the prepreg into a C-stage state as defined in JIS K6900 (1994). Another metal-clad laminate of this embodiment can be produced, for example, by placing a metal foil on one or both sides of a resin film of this embodiment, or by placing a metal foil on one or both sides of a laminate obtained by stacking two or more resin films of this embodiment, and then hot-pressing and molding. In the laminate obtained by this manufacturing method, the resin film of this embodiment is C-staged. The metal of the metal foil is not particularly limited, but from the viewpoint of electrical conductivity, it may be copper, gold, silver, nickel, platinum, molybdenum, ruthenium, aluminum, tungsten, iron, titanium, chromium, or an alloy containing one or more of these metal elements, with copper and aluminum being preferred, and copper being more preferred. The conditions for the hot-press molding are not particularly limited, but can be, for example, a temperature of 100 to 300°C, a pressure of 0.2 to 10 MPa, and a time of 0.1 to 5 hours. Furthermore, the hot-press molding can be performed using a vacuum press or the like to maintain a vacuum state for 0.5 to 5 hours.

[0065] The metal-clad laminate of this embodiment can also be described as a metal-clad laminate having a cured product of a thermosetting resin composition and a metal foil, wherein the thermosetting resin composition contains (A) a thermosetting resin, and (B) one or more high-dielectric-constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers, and wherein a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected separately in a chart obtained by performing a substrate visual inspection using the method described below. Details of the thermosetting resin composition and the substrate visual inspection method described below are as described above. (Substrate visual inspection method) A test piece is prepared in which a portion of the surface of the cured product of the thermosetting resin composition is revealed by etching away the metal foil from the metal-clad laminate while leaving a portion of the metal foil. The test piece is set in an automatic optical inspection device and inspected, and a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected in a graph with the horizontal axis being gray level and the vertical axis being pixels.

[0066] The metal-clad laminate of this embodiment has a high relative dielectric constant (Dk) and a low dielectric loss tangent (Df), and is therefore useful for antenna modules, particularly for miniaturized antenna modules compatible with 5G.

[0067] Considering that the metal-clad laminate of this embodiment is used for an antenna module, it is preferable that the metal-clad laminate has conductor patterns such as a power supply conductor pattern, a ground conductor pattern, and a short-circuit conductor. The short-circuit conductor is a conductor that shorts the power supply conductor pattern and the ground conductor pattern and is provided in the via hole portion described below. The conductor patterns are preferably formed of a metal whose main component is copper, aluminum, gold, silver, or an alloy thereof.

[0068] The metal-clad laminate of this embodiment preferably has via holes. The via holes enable the formation of the short-circuiting conductors, enabling electrical continuity between the power supply conductor pattern and the grounding conductor pattern. The method for forming the via holes is not particularly limited, and methods such as laser, plasma, or a combination thereof can be used. Examples of lasers that can be used include carbon dioxide lasers, YAG lasers, UV lasers, and excimer lasers. Furthermore, after the via holes are formed, a desmear treatment may be performed using an oxidizing agent. Examples of oxidizing agents include permanganates such as potassium permanganate and sodium permanganate; dichromates; ozone; hydrogen peroxide-sulfuric acid; and nitric acid. Permanganates are more preferred, and an aqueous solution of sodium hydroxide in a permanganate, i.e., an aqueous solution of alkaline permanganate, is even more preferred. The metal-clad laminate of this embodiment may have short-circuiting conductors formed in the via holes after the via holes are formed. The conductor used here is preferably formed from the same metal as the metal forming the conductor pattern.

[0069] [Printed Wiring Board] The printed wiring board of this embodiment comprises one or more materials selected from the group consisting of a cured product of the thermosetting resin composition of this embodiment and a cured product of the prepreg of this embodiment. It can also be said that the printed wiring board of this embodiment comprises one or more materials selected from the group consisting of a cured product of the thermosetting resin composition of this embodiment, a cured product of the prepreg of this embodiment, and a metal-clad laminate of this embodiment. The printed wiring board of this embodiment can be manufactured, for example, by performing circuit formation processing such as drilling, metal plating, and metal foil etching using one or more materials selected from the group consisting of the prepreg of this embodiment, the resin film of this embodiment, and the metal-clad laminate of this embodiment, using a known method. Furthermore, a multilayer printed wiring board can also be manufactured by further performing multilayer adhesive processing as necessary. In the printed wiring board of this embodiment, the prepreg of this embodiment or the resin film of this embodiment is C-staged to form a cured product.

[0070] [Antenna Device] The present disclosure also provides an antenna device having the metal-clad laminate or printed wiring board of the present embodiment. The antenna device may have one or more of the metal-clad laminate or printed wiring board. There are no particular limitations on how the multiple antenna elements are arranged, but it is preferable that they be arranged in a two-dimensional array, for example. The configuration of the antenna device is not particularly limited, but reference can be made to, for example, Japanese Patent No. 6777273.

[0071] [Antenna Module] The present disclosure also provides an antenna module having a power supply circuit and the antenna device of this embodiment. The power supply circuit is not particularly limited, but an RFIC (Radio Frequency Integrated Circuit) or the like can be used. The RFIC includes a switch, a power amplifier, a low-noise amplifier, an attenuator, a phase shifter, a signal combiner-demultiplexer, a mixer, an amplifier circuit, and the like. A high-frequency signal supplied from the RFIC is transmitted to the feed point of the power supply conductor via a short-circuiting conductor formed in a via of a metal-clad laminate for an antenna module. The configuration of the antenna module is not particularly limited, but reference can be made to, for example, Japanese Patent No. 6777273.

[0072] [Communication Device] The present disclosure also provides a communication device including a baseband signal processing circuit and the antenna module of the present embodiment. The communication device of the present embodiment can upconvert a signal transmitted from the baseband signal processing circuit to the antenna module into a high-frequency signal and radiate it from the antenna device, and can downconvert a high-frequency signal received by the antenna device and process the signal in the baseband signal processing circuit.

[0073] Although preferred embodiments have been described above, these are merely examples for the purpose of explaining the present disclosure, and the scope of the present disclosure is not intended to be limited to these embodiments. The present disclosure also includes various aspects that differ from the above-described embodiments without departing from the gist of the present disclosure.

[0074] The present embodiment will be specifically described below with reference to examples, but the present embodiment is not limited to the following examples.

[0075] In each example, the weight average molecular weight (Mw) was measured by the following method. (Method for measuring weight average molecular weight (Mw)) The weight average molecular weight was calculated by gel permeation chromatography (GPC) from a calibration curve using standard polystyrene. The calibration curve was approximated by a cubic equation using standard polystyrene: TSKstandard POLYSTYRENE (Types: A-2500, A-5000, F-1, F-2, F-4, F-10, F-20, F-40) [manufactured by Tosoh Corporation, trade name]. The GPC measurement conditions are shown below. Apparatus: Pump: L-6200 type [manufactured by Hitachi High-Technologies Corporation] Detector: L-3300 type RI [manufactured by Hitachi High-Technologies Corporation] Column oven: L-655A-52 [manufactured by Hitachi High-Technologies Corporation] Column: Guard column; TSK Guard column HHR-L + column; TSKgel G4000HHR + TSKgel G2000HHR (all manufactured by Tosoh Corporation, trade names) Column size: 6.0 x 40 mm (guard column), 7.8 x 300 mm (column) Eluent: tetrahydrofuran Sample concentration: 30 mg / 5 mL Injection volume: 20 μL Flow rate: 1.00 mL / min Measurement temperature: 40°C

[0076] The average particle diameters of the components (B) and (D) used in each example were measured by the following method. (Method for measuring average particle diameter) The particle size distribution was measured using a particle size distribution measuring device "Microtrac MT3300EXII" (manufactured by Microtrac Bell Co., Ltd.) to determine the average particle diameter (d50). The measurement solvent was water (containing 0.1% by mass of sodium hexametaphosphate), and the measurement mode was transmission, with the measurement time being 30 seconds.

[0077] [Production Example 1: Production of Modified Maleimide Compound] 100 parts by mass of 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 5.6 parts by mass of a siloxane compound (functional group equivalent: 750 g / mol) having amino groups at both ends, 7.9 parts by mass of 3,3'-diethyl-4,4'-diaminodiphenylmethane, and 171 parts by mass of propylene glycol monomethyl ether were added to a 5 L reactor equipped with a thermometer, a stirrer, and a reflux condenser and moisture content monitor, and the mixture was allowed to react under reflux for 2 hours. The mixture was concentrated at reflux temperature for 3 hours to produce a modified maleimide compound solution with a solids concentration of 65% by mass. The weight-average molecular weight (Mw) of the resulting modified maleimide compound was approximately 2,700.

[0078] [Examples 1 and 2, Comparative Examples 1 and 2] A thermosetting resin composition (varnish) having a solids concentration of 60 to 65% by mass was prepared by stirring and mixing at room temperature the components shown in Table 1 together with 58 parts by mass of toluene and 10 parts by mass of methyl isobutyl ketone according to the formulation shown in Table 1. The varnish obtained above was applied to a glass cloth (E-glass, manufactured by Nitto Boseki Co., Ltd.) having a thickness of 0.08 mm, and then heated and dried at 150°C for 5 minutes to produce a prepreg having a solids content derived from the thermosetting resin composition of approximately 47% by mass. A low-profile copper foil (BF-ANP18, M-side Rz: 1.5 μm, manufactured by CIRCUIT FOIL) with a thickness of 18 μm was placed on the top and bottom of this prepreg so that the M-side (matte side) was in contact with the prepreg. Then, a double-sided copper-clad laminate (thickness: 0.10 mm) was produced by hot-press molding at a temperature of 230 °C, a pressure of 3.0 MPa, and a time of 90 minutes. One side of the obtained double-sided copper-clad laminate was etched away, leaving a portion of the copper foil, to produce a test specimen (see FIG. 1) in which a portion of the surface of the cured product of the thermosetting resin composition was exposed. The test specimen measured 540 mm long x 530 mm wide, with the copper foil remaining on the test specimen measuring 10 mm long x 530 mm wide. Using the test specimens obtained in each example, a board appearance inspection was performed according to the following method.

[0079] (Substrate Visual Inspection Method) (1) The test piece was placed in an automated optical inspection (AOI) device, Discovery-8000 (manufactured by Orbotech). (2) Next, calibration was performed. The entire test piece was photographed from above using a camera (a camera installed in the AOI device). The image obtained by the camera was then grayscaled. After grayscaling, each pixel (0.02-0.04 mm x 0.02-0.04 mm), the smallest unit of the image, was assigned 256 gradations and graphed. Graphs obtained in Examples 1 and 2 are shown in Figures 2 and 3, and graphs obtained in Comparative Examples 1 and 2 are shown in Figures 4 and 5. In Figures 2 and 3, the small peak on the right is the peak derived from the metal foil, and the large peak on the left is the peak derived from the cured product of the thermosetting resin composition. As such, in Examples 1 and 2, the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition were successfully separated. On the other hand, in Comparative Examples 1 and 2, an error occurred and it was not possible to proceed to the next operation. This result was caused by the fact that in Comparative Examples 1 and 2, the peaks derived from the metal foil and the peaks derived from the cured product of the thermosetting resin composition overlapped, as shown in Figures 4 and 5.

[0080] (3) In Examples 1 and 2, a threshold value was then set between the peak derived from the metal foil and the peak derived from the cured product of the thermosetting resin composition. The end point (right end) of the peak derived from the cured product of the thermosetting resin composition was set as the minimum value, and the start point (left end) of the peak derived from the metal foil was set as the maximum value, and the difference between the minimum and maximum values ​​was set as the threshold. This completed the calibration.

[0081] (4) After (3) above, an appearance inspection was again performed by photographing the entire test piece from above with a camera (a camera installed in the AOI device). In this photographing, the image size was set to approximately 3 mm x approximately 4 mm per image, although this was not particularly limited. (5) Based on the image obtained in (4) above, an inspection for the presence or absence of defects was performed. In this way, in Examples 1 and 2, substrate appearance inspection using the AOI device was possible.

[0082]

[0083] Each component shown in Tables 1 and 2 is explained below. [(A) Thermosetting Resin] A-1: ​​Modified maleimide compound obtained in Production Example 1 A-2: Polyphenylene ether having methacryloyl groups at both molecular terminals (weight average molecular weight 1,700)

[0084] [(B) High-dielectric-constant inorganic filler] B-1: strontium titanate, average particle size (d50): 1.6 μm [(C) Elastomer: styrene-based thermoplastic elastomer] C-1: maleic anhydride-modified hydrogenated styrene-based thermoplastic elastomer (maleic anhydride-modified SEBS), acid value 10 mg CH ３ ONa / g, styrene content 30%, MFR 5.0 g / 10 min (measurement conditions for the MFR: measured in accordance with ISO 1133 at 230° C. and a load of 2.16 kg).

[0085] [(D) Inorganic Filler] D-1: Spherical fused silica: average particle size 1.5 μm, 50 mass% slurry (solvent: toluene)

[0086] [(E) Curing accelerator] E-1: 2-undecylimidazole E-2: p-benzoquinone and tri-n-butylphosphine addition product E-3: dicyandiamide

[0087] [(F) Flame Retardant] F-1: Phosphate ester flame retardant having the following structural formula:

[0088] [(G) One or more selected from dyes and pigments] G-1: Yellow dye "HR-50" (pyrazolone dye, manufactured by Chuo Synthetic Chemical Co., Ltd.) G-2: Yellow pigment "HMT" (7-diethylamino-4-methylcoumarin, a coumarin pigment, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0089] 1 remaining metal foil 2 cured product of thermosetting resin composition

Claims

1. A thermosetting resin composition containing (A) a thermosetting resin, and (B) one or more high dielectric constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers, wherein a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected separately in a chart obtained by performing a substrate visual inspection by the following method. (Substrate visual inspection method) A metal-clad laminate in which the cured product of the thermosetting resin composition and the metal foil are superimposed is prepared, and a test piece in which a part of the surface of the cured product of the thermosetting resin composition is revealed is produced by etching and removing the metal foil while leaving a part of the metal foil. The test piece is set in an automatic optical inspection device and inspected, and a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected in a graph with the horizontal axis being gray level and the vertical axis being pixels.

2. The thermosetting resin composition according to claim 1, wherein the component (A) comprises one or more selected from the group consisting of epoxy resins, maleimide compounds, modified polyphenylene ether resins, phenolic resins, polyimide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins and melamine resins.

3. The thermosetting resin composition according to claim 1, wherein the titanium-based inorganic filler is at least one selected from the group consisting of titanium dioxide and metal titanates.

4. The thermosetting resin composition according to claim 3, wherein the metal titanate is at least one selected from the group consisting of alkali metal titanates, alkaline earth metal titanates, and lead titanate.

5. The thermosetting resin composition according to claim 1, wherein the zircon-based inorganic filler is an alkali metal zirconate.

6. The thermosetting resin composition according to claim 1, further comprising (G) one or more selected from dyes and pigments.

7. The thermosetting resin composition according to claim 1, wherein a peak derived from the metal foil appears at a gray level of 230 to 256, and a peak derived from the cured product of the thermosetting resin composition appears at a gray level of 220 or less.

8. A prepreg containing the thermosetting resin composition according to claim 1 or a semi-cured product of said thermosetting resin composition.

9. A resin film comprising the thermosetting resin composition according to claim 1 or a semi-cured product of said thermosetting resin composition.

10. A metal-clad laminate comprising a cured product of the thermosetting resin composition according to claim 1 and a metal foil.

11. A metal-clad laminate having a cured product of a thermosetting resin composition and a metal foil, the thermosetting resin composition containing (A) a thermosetting resin, and (B) one or more high dielectric constant inorganic fillers selected from the group consisting of titanium-based inorganic fillers and zircon-based inorganic fillers, wherein a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected separately in a chart obtained by performing a substrate visual inspection by the following method. (Substrate visual inspection method) A test piece is prepared in which a part of the surface of the cured product of the thermosetting resin composition is revealed by etching away the metal foil of the metal-clad laminate while leaving a part of the foil. The test piece is set in an automatic optical inspection device and inspected, and a peak derived from the metal foil and a peak derived from the cured product of the thermosetting resin composition are detected in a graph with the horizontal axis being gray level and the vertical axis being pixels.

12. The metal-clad laminate according to claim 11, wherein the titanium-based inorganic filler is at least one selected from the group consisting of titanium dioxide and metal titanates.

13. The metal-clad laminate according to claim 12, wherein the metal titanate is at least one selected from the group consisting of alkali metal titanates, alkaline earth metal titanates, and lead titanate.

14. The metal clad laminate of claim 11, wherein said zircon-based inorganic filler is an alkali metal zirconate.

15. The metal-clad laminate according to claim 11, further comprising (G) one or more selected from dyes and pigments.

16. The metal-clad laminate according to claim 11, in which a peak derived from the metal foil appears at a gray level of 230 to 256, and a peak derived from the cured product of the thermosetting resin composition appears at a gray level of 220 or less.

17. A printed wiring board having a cured product of the thermosetting resin composition according to claim 1.

18. An antenna device comprising the metal-clad laminate according to any one of claims 10 to 16.

19. An antenna module comprising a feeding circuit and an antenna device according to claim 18.

20. A communication device comprising a baseband signal processing circuit and an antenna module according to claim 19.

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