Metal-clad laminates, printed wiring boards and their manufacturing methods

Abstract

The objective of this invention is to provide a metal-clad laminate with excellent adhesion between the insulating layer and the metal foil, and excellent dielectric properties, and the application technology thereof. The metal-clad laminate comprises: an insulating layer comprising a resin composition and a fibrous substrate, and a metal foil bonded to the insulating layer; wherein the resin composition contains a specific resin (A) and specific polymer particles (B), and the surface ten-point average roughness (Rz) of the metal foil is 2.0 μm or less.

Description

Technical Field

[0001] This invention relates to metal-clad laminates, printed wiring boards using the metal-clad laminates, and methods for manufacturing the same. Background Technology

[0002] Metal-clad laminates are used in the manufacture of printed wiring boards and semiconductor substrates for electronic devices. Epoxy resin is typically used as the insulating layer in metal-clad laminates. For example, Patent Document 1 discloses a metal-clad laminate made from a resin composition in which polymer particles are dispersed in a thermosetting resin such as epoxy resin.

[0003] In recent years, with the increase in signal capacity of electronic devices, metal-clad laminates are required to have dielectric properties such as low dielectric constant and low dielectric loss tangent, which are necessary for high-speed communication. However, the dielectric properties of metal-clad laminates using epoxy resin are insufficient.

[0004] Polyphenylene oxide (PPE) and other specific resins are known to possess excellent dielectric properties, such as dielectric constant and dielectric loss tangent, exhibiting superior dielectric characteristics even in the high-frequency band (high-frequency region) from MHz to GHz. Therefore, there is ongoing research into using resins with excellent dielectric properties, such as PPE, as substrate materials for printed wiring boards in electronic devices utilizing high-frequency bands.

[0005] For example, Patent Document 2 discloses a metal-clad laminate comprising an insulating layer containing a resin composition and a metal foil, wherein the resin composition comprises a resin with a dielectric loss tangent within a specific range and core-shell polymer particles with a specific volume average particle size.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication Publisher No. WO2020 / 196922

[0009] Patent Document 2: International Publication Publisher No. WO2020 / 027189 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the existing technology described above is insufficient from the viewpoint of balancing the adhesion between the insulating layer and the metal foil and the dielectric properties of the metal-clad laminate, and there is room for further improvement.

[0012] One embodiment of the present invention addresses the above-mentioned problems and aims to provide a metal-clad laminate with excellent adhesion between the insulating layer and the metal foil and excellent dielectric properties, a printed wiring board using the metal-clad laminate, and a method for manufacturing the metal-clad laminate.

[0013] Problem Solving Methods

[0014] The inventors conducted in-depth research to solve the above-mentioned problems, and as a result, completed this invention. Specifically, one embodiment of the metal-clad laminate of this invention comprises: an insulating layer containing a resin composition and a fibrous substrate, and a metal foil bonded to the insulating layer.

[0015] The above resin composition contains a resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and polymer particles (B).

[0016] The polymer particles (B) described above satisfy the following conditions (i) and (ii):

[0017] (i) The volume average particle size is 10 nm to 400 nm;

[0018] (ii) A core-shell copolymer comprising a core polymer and grafts bonded to the core polymer.

[0019] The above-mentioned nuclear polymer contains the following structural units as structural units:

[0020] Structural units from aromatic vinyl compounds having one vinyl group, and

[0021] Structural units derived from aromatic vinyl compounds having two or more vinyl groups,

[0022] The grafting portion described above includes the following structural units:

[0023] Structural units from aromatic vinyl compounds having one vinyl group, and

[0024] Structural units derived from (meth)acrylates with epoxy groups,

[0025] The surface roughness (Rz) of the above-mentioned metal foil at ten points is less than 2.0 μm.

[0026] Another embodiment of the present invention provides a method for manufacturing a metal-clad laminate, comprising:

[0027] The process of preparing a masterbatch by dispersing polymer particles (B) in a solvent containing methyl ethyl ketone;

[0028] The process of preparing resin varnish by mixing the above-mentioned masterbatch, resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and solvent;

[0029] The process of preparing a prepreg by impregnating the above-mentioned resin varnish with glass cloth; and

[0030] The process of laminating metal foil onto the prepreg described above

[0031] The polymer particles (B) described above satisfy the following conditions (i) and (ii):

[0032] (i) The volume average particle size is 10 nm to 400 nm;

[0033] (ii) A core-shell copolymer comprising a core polymer and grafts bonded to the core polymer.

[0034] The above-mentioned nuclear polymer contains the following structural units as structural units:

[0035] Structural units from aromatic vinyl compounds having one vinyl group, and

[0036] Structural units derived from aromatic vinyl compounds having two or more vinyl groups,

[0037] The grafting portion described above includes the following structural units:

[0038] Structural units from aromatic vinyl compounds having one vinyl group, and

[0039] Structural units derived from (meth)acrylates with epoxy groups,

[0040] The ten-point average roughness (Rz) of the interface between the metal foil and the prepreg is less than 2.0 μm.

[0041] The effects of the invention

[0042] According to one embodiment of the present invention, a metal-clad laminate with excellent adhesion between the insulating layer and the metal foil and excellent dielectric properties can be provided. Detailed Implementation

[0043] The following describes one embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to the solutions described below, and various modifications can be made within the scope shown in the specification. Furthermore, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included within the technical scope of the present invention. Moreover, the technical means disclosed in each embodiment can be combined to form new technical features. It should be noted that all academic and patent documents recorded in this specification are cited as references in this specification. Additionally, unless otherwise specified, "A~B" in this specification refers to "A or more (inclusive of A and greater than A) and B or less (inclusive of B and less than B)".

[0044] [1. Technical concept of one embodiment of the present invention]

[0045] With the rapid development of high-speed signal transmission technologies such as 5G in recent years, the electrical signals transmitted in electronic circuits such as printed circuit boards (PCBs) have become increasingly higher frequency. Therefore, there is a growing demand for lower dielectric constants (lower dielectric constant and lower dielectric loss tangent) in the metal-clad laminates used in the manufacture of PCBs. If the dielectric constant (ε) of the insulating layer of the metal-clad laminate increases, the propagation speed of electrical signals in the electronic circuits decreases. Furthermore, as shown in the following equation, if both the dielectric constant (ε) and the dielectric loss tangent (Df: tanδ) increase, the signal transmission loss also increases, with the dielectric loss tangent having a particularly significant impact.

[0046]

[0047] (In the formula, f is the frequency, C is the speed of light, ε is the dielectric constant, and tanδ is the dielectric loss tangent.)

[0048] Therefore, reducing the dielectric constant and the dielectric loss tangent of the insulating layer of metal-clad laminates is indispensable for the high performance of electronic devices.

[0049] Patent Document 1 discloses a metal-clad laminate comprising a resin composition obtained by mixing a powder containing polymer particles with a thermosetting resin (e.g., a multifunctional epoxy resin) as an insulating layer. By dispersing the polymer particles in the multifunctional epoxy resin constituting the insulating layer, the brittleness and other weaknesses of the multifunctional epoxy resin can be improved. Therefore, the metal-clad laminate disclosed in Patent Document 1 can be suitably applied to semiconductor substrates used in consumer electronics such as home appliances and automotive electronics. However, the dielectric constant and dielectric loss tangent of the insulating layer using multifunctional epoxy resin are relatively high, therefore, from the viewpoint of semiconductor substrates used in high-speed communication technologies such as 5G, there is room for further improvement in dielectric properties.

[0050] To achieve the excellent dielectric properties required for high-speed communication technology, materials with low dielectric loss tangents, such as (X) polyphenylene ether (PPE), were investigated for use as the insulating layer. In addition, efforts were made to minimize the surface roughness (Rz) of the metal foil stacked on the (Y) insulating layer, specifically to reduce the average roughness (Rz) of the surface at ten points to below 2 μm, thereby reducing the transmission loss of the metal-clad laminate.

[0051] However, the following problems exist: (a) insulating layers made with resins having a low dielectric loss tangent have poorer adhesion to the metal foil compared to insulating layers made with resins having a high dielectric loss tangent, such as epoxy resin; and (b) the smaller the surface roughness (Rz) of the metal foil, the worse the adhesion between it and the insulating layer. Therefore, the metal-clad laminate with improved dielectric properties through the above (X) and (Y) suffers from poor adhesion between the insulating layer and the metal foil.

[0052] To address this issue, the aforementioned Patent Document 2 improves the adhesion between the insulating layer and the metal foil by adding core-shell polymer particles with a specific volume average particle size to a resin with a low dielectric loss tangent.

[0053] However, from the viewpoint of adhesion and dielectric loss tangent, the core-shell polymer particles disclosed in Patent Document 2 have room for further improvement. That is, from the viewpoint of balancing the adhesion between the insulating layer and the metal foil and the dielectric properties of the metal-clad laminate, the metal-clad laminate in Patent Document 2 has room for further improvement.

[0054] One embodiment of the present invention was made in view of the above-mentioned problems, and its object is to provide a metal-clad laminate with excellent adhesion between the insulating layer and the metal foil and excellent dielectric properties. The inventors conducted in-depth research to solve the above problems, and as a result, successfully developed a masterbatch obtained by dispersing polymer particles having a specific volume average particle size and containing specific structural units in a solvent. It was found that the insulating layer containing a resin composition made using this masterbatch exhibits high adhesion to the metal foil and a low dielectric loss tangent, thus completing the present invention.

[0055] [2. Metal-clad laminate]

[0056] One embodiment of the metal-clad laminate of the present invention comprises: an insulating layer comprising a resin composition and a fibrous substrate, and a metal foil bonded to the insulating layer.

[0057] The above resin composition contains a resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and polymer particles (B).

[0058] The polymer particles (B) described above satisfy the following conditions (i) and (ii):

[0059] (i) The volume average particle size is 10 nm to 400 nm;

[0060] (ii) A core-shell copolymer comprising a core polymer and grafts bonded to the core polymer.

[0061] The above-mentioned nuclear polymer contains the following structural units as structural units:

[0062] Structural units from aromatic vinyl compounds having one vinyl group, and

[0063] Structural units derived from aromatic vinyl compounds having two or more vinyl groups,

[0064] The grafting portion described above includes the following structural units:

[0065] Structural units from aromatic vinyl compounds having one vinyl group, and

[0066] Structural units derived from (meth)acrylates with epoxy groups,

[0067] The surface roughness (Rz) of the above-mentioned metal foil at ten points is less than 2.0 μm.

[0068] The metal-clad laminate of one embodiment of the present invention, having the above-described configuration, exhibits excellent adhesion between the insulating layer and the metal foil, as well as excellent dielectric properties. It should be noted that, in this specification, excellent dielectric properties refer to a low dielectric loss tangent. Furthermore, for the metal-clad laminate, the lower the dielectric loss tangent of the resin composition constituting the insulating layer, and the lower the dielectric loss tangent of the resin (A) and polymer particles (B) in the resin composition, the better the dielectric properties.

[0069] In this specification, the term "metal-clad laminate of one embodiment of the present invention" is sometimes simply referred to as "this metal-clad laminate". That is, the term "this metal-clad laminate" refers to one embodiment of the metal-clad laminate of the present invention. In this specification, "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0070] (2-1. Insulation layer)

[0071] (2-1-1. Resin Composition)

[0072] The insulating layer comprises a resin composition and a fibrous substrate. The components that may be included in the resin composition contained in the insulating layer are described below.

[0073] (Resin(A))

[0074] There are no particular limitations on resin (A) as long as its dielectric loss tangent (Df) at 10 GHz is below 0.0100. Examples of resin (A) include benzo[a] Azides, cyanate ester resins, polyimide (PI), bismaleimide (BMI), divinylbenzene and other multifunctional styrene compounds, silicone resins, polyester resins, liquid crystal polymers (LCP), hydrocarbon resins, polyphenylene ether, modified polyphenylene oxide (PPO), cyclic olefin copolymers (COC), poly(p-phenylene sulfide) (PPS), poly(ether sulfone) (PES), poly(ether ether ketone) (PEEK), polytetrafluoroethylene (PTFE), etc.

[0075] Because of its exceptionally low dielectric loss tangent and thermosetting properties, resin (A) is preferably a cyanate ester resin, BMI, a polyfunctional styrene compound, a hydrocarbon resin, polyphenylene ether, or modified polyphenylene ether, more preferably polyphenylene ether or modified polyphenylene ether, and even more preferably modified polyphenylene ether. It is known that the dielectric loss tangent of polyphenylene ether is approximately 0.002.

[0076] As resin (A), one of the resins and copolymers selected above may be used alone, or two or more may be used in combination. Examples of resin (A) suitable for use include (a) a mixture of polyphenylene ether and hydrocarbon resin, and (b) a mixture of cyanate resin and bismaleimide.

[0077] Hydrocarbon resins have high weight loss temperatures, making them a preferred choice. They are also less prone to decomposition at high temperatures, further enhancing their appeal. Hydrocarbon resins can also be considered resins with excellent thermal stability.

[0078] Even when a large amount of silica is incorporated into the mixture of cyanate ester resin and bismaleimide, the resulting resin composition exhibits low viscosity and is easy to handle. Since silica has a low dielectric loss tangent, insulating layers containing resin compositions with a large amount of silica have the advantage of a low dielectric loss tangent. That is, when using a mixture of cyanate ester resin and bismaleimide as resin (A), by including a larger amount of silica in the resin composition, an insulating layer with a low dielectric loss tangent is obtained.

[0079] In this metal-clad laminate, the resin (A) preferably comprises polyphenylene ether having crosslinkable functional groups. The resin (A) is more preferably polyphenylene ether having crosslinkable functional groups. Based on the above configuration, the resulting metal-clad laminate exhibits superior dielectric properties.

[0080] The resin and / or copolymer (component other than the crosslinking agent) in resin (A) preferably contains polyphenylene ether having crosslinkable functional groups. Of 100% by weight of the resin and / or copolymer (component other than the crosslinking agent), the resin and / or copolymer (component other than the crosslinking agent) in resin (A) preferably contains 40% by weight or more, more preferably 50% by weight or more, more preferably 60% by weight or more, more preferably 65% ​​by weight or more, more preferably 70% by weight or more, more preferably 75% by weight or more, more preferably 80% by weight or more, more preferably 85% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, and particularly preferably 100% by weight. The resin and / or copolymer (component other than the crosslinking agent) in resin (A) is more preferably formed solely of polyphenylene ether having crosslinkable functional groups.

[0081] Examples of polyphenylene ethers having crosslinkable functional groups include (a) polyaryl ether copolymers formed from at least one of difunctional and trifunctional phenols and 2,6-dimethylphenol, and polyphenylene ethers with (b) poly(2,6-dimethyl-1,4-phenylene ether) as the main component. More specifically, examples of polyphenylene ethers having crosslinkable functional groups include polyphenylene ethers having the structure shown in Formula 1.

[0082] [Chemical Formula 1]

[0083]

[0084] In Formula 1, s and t are each independently an integer greater than or equal to 0. For example, the sum of s and t is preferably 1 to 30. Alternatively, s is preferably 0 to 20, and t is preferably 0 to 20. That is, it is preferable that s represents 0 to 20, t represents 0 to 20, and the sum of s and t represents 1 to 30.

[0085] In one embodiment of the present invention, the resin (A) is preferably a modified polyphenylene ether (hereinafter also simply referred to as "modified polyphenylene ether") that has been terminally modified by substituents having carbon-carbon unsaturated double bonds. According to the above configuration, the dielectric properties of the resulting metal-clad laminate are improved.

[0086] In one embodiment of the present invention, the resin (A) comprises a polyphenylene ether having crosslinkable functional groups, more preferably a modified polyphenylene ether whose ends have been modified by substituents having carbon-carbon unsaturated double bonds. According to the above configuration, the resulting metal-clad laminate exhibits superior dielectric properties.

[0087] There are no particular limitations on the substituents having carbon-carbon unsaturated double bonds; examples include acrylate groups, methacrylate groups, and substituents shown in Formula 2 below.

[0088] [Chemical Formula 2]

[0089]

[0090] In Equation 2, n represents an integer from 0 to 10. In Equation 2, Z represents an arylene when n is any value from 1 to 10 (a), and an arylene or carbonyl group when n = 0 (b). In Equation 2, R... 1 ~R 3 Independently represents a hydrogen atom or an alkyl group.

[0091] Here, in Equation 2 above, when n = 0, it means that Z is directly bonded to the end of the polyphenylene ether.

[0092] Examples of arylethematous and carbonyl groups representing Z include (a) monocyclic aromatic groups such as phenylene and (b) polycyclic aromatic groups such as naphthyl rings. It should be noted that this also includes derivatives of monocyclic and polycyclic aromatic groups in which the hydrogen atom bonded to the aromatic ring is replaced by functional groups such as alkenyl, alkynyl, formyl, alkyl carbonyl, alkenyl carbonyl, or alkynyl carbonyl.

[0093] As a preferred example of the functional group shown in Formula 2 above, a functional group containing a vinyl benzyl group can be cited, specifically, at least one substituent selected from Formula 3 or Formula 4 below.

[0094] [Chemical Formula 3]

[0095]

[0096] [Chemical Formula 4]

[0097]

[0098] Other specific examples of substituents having carbon-carbon unsaturated double bonds include, for example, the (meth)acrylate group shown in Formula 5 below.

[0099] [Chemical Formula 5]

[0100]

[0101] In Equation 5, R 4 It represents a hydrogen atom or an alkyl group.

[0102] The case where resin (A) is a modified polyphenylene ether will be described. The method for synthesizing the modified polyphenylene ether is not particularly limited as long as it is possible to synthesize a modified polyphenylene ether whose end has been modified by substituents having carbon-carbon unsaturated double bonds. Specifically, for example, methods using compounds as shown in Formula 6 below can be cited.

[0103] [Chemical Formula 6]

[0104]

[0105] In Equation 6, n, Z and R 1 ~R 3 Similar to Equation 2 above. That is, n represents an integer from 0 to 10. Z represents an arylene when n is any value from 1 to 10, and an arylene or carbonyl when n = 0. R 1 ~R 3 Independently representing a hydrogen atom or an alkyl group. Additionally, in Formula 6, X represents a halogen atom, specifically including chlorine, bromine, iodine, and fluorine atoms. Preferably, X is a chlorine atom.

[0106] The compounds represented by Formula 6 above are not particularly limited, but are preferably p-chloromethylstyrene and m-chloromethylstyrene.

[0107] The compound represented by Formula 6 above can be used alone or in combination of two or more of the compounds listed above.

[0108] The method for synthesizing the modified polyphenylene ether using the compound of Formula 6 above will be specifically described. The polyphenylene ether (a) in which the hydrogen atoms of the terminal phenolic hydroxyl groups of the polyphenylene ether have been substituted with alkali metal atoms such as sodium and / or potassium, and (b) the compound represented by Formula 6 above, are dissolved in a solvent and stirred. Thus, the polyphenylene ether substituted with alkali metal atoms reacts with the compound represented by Formula 6 above (hereinafter, this reaction is also referred to as reaction A) to obtain the modified polyphenylene ether with terminal modification by substituents having carbon-carbon unsaturated double bonds.

[0109] The above reaction A is preferably carried out in the presence of an alkali metal hydroxide. Therefore, the reaction is considered to proceed suitably.

[0110] There are no particular limitations on the alkali metal hydroxides mentioned above, as long as they can function as dehalogenating agents; examples include sodium hydroxide. Furthermore, alkali metal hydroxides are typically used in aqueous solutions; for instance, sodium hydroxide is used as an aqueous solution.

[0111] The reaction time and temperature of reaction A may vary depending on the compound represented by Formula 6 above, but there are no particular limitations as long as the conditions are suitable for reaction A. Specifically, the reaction temperature of reaction A is preferably between room temperature and 100°C, more preferably between 30°C and 100°C. The reaction time of reaction A is preferably between 0.5 and 20 hours, more preferably between 0.5 and 10 hours.

[0112] The solvent used for reaction A is not particularly limited as long as it can dissolve the polyphenylene ether and the compound represented by Formula 6 above, and does not hinder reaction A. Toluene is an example.

[0113] Reaction A is preferably carried out in the presence of a phase transfer catalyst in addition to an alkali metal hydroxide. That is, reaction A is preferably carried out in the presence of both an alkali metal hydroxide and a phase transfer catalyst. This is considered more suitable for reaction A.

[0114] The aforementioned phase transfer catalysts are not particularly limited; for example, quaternary ammonium salts such as tetra-n-butylammonium bromide can be cited.

[0115] In one embodiment of the present invention, the resin composition preferably comprises the modified polyphenylene ether obtained as described above as resin (A), thereby providing a metal-clad laminate with excellent low dielectric properties and heat resistance. In another embodiment of the present invention, the resin composition further preferably comprises methacrylic acid-modified polyphenylene ether and / or vinyl benzyl-modified polyphenylene ether as resin (A). According to this configuration, a metal-clad laminate with even better low dielectric properties and heat resistance can be provided.

[0116] Resin (A) preferably further comprises a crosslinking agent having carbon-carbon unsaturated double bonds. In other words, resin (A) is preferably crosslinked by a crosslinking agent having carbon-carbon unsaturated double bonds. According to the above configuration, the crosslinked structure of resin (A) becomes robust, and the resulting metal-coated laminate exhibits excellent heat resistance.

[0117] The crosslinking agent is preferably a compound that (a) has two or more carbon-carbon unsaturated double bonds in one molecule and (b) functions as a crosslinking agent for the resin and / or copolymer contained in the resin (A). As a specific example of such a compound, a compound represented by the following formula 7 is preferred.

[0118] [Chemical Formula 7]

[0119]

[0120] In Equation 7, R 1 ~R 3 Similar to Formula 2 above, it independently represents a hydrogen atom or an alkyl group. In Formula 7, m represents an integer from 1 to 3, p represents 0 or 1, U represents any group among arylene, tricyclodecane skeleton, or isocyanurate group. Y represents

[0121] [Chemical Formula 8]

[0122]

[0123] [Chemical Formula 9]

[0124]

[0125] [In the formula, L represents an integer greater than 1].

[0126] More specifically, examples of crosslinking agents include (a) isocyanuric acid tripenyl ester compounds such as triallyl isocyanurate (TAIC), (b) polyfunctional methacrylate compounds having two or more methacrylate groups in their molecules, (c) polyfunctional acrylate compounds having two or more acrylate groups in their molecules, (d) polyfunctional styrene compounds such as styrene and divinylbenzene having vinyl benzyl groups in their molecules and polymers derived from such polyfunctional styrene compounds, (e) butadiene-styrene liquid polymers, and (f) butadiene liquid polymers. When using the above-mentioned compounds, it is considered that crosslinking is more suitably formed through a curing reaction with resins and / or copolymers, which can improve the heat resistance of metal-clad laminates.

[0127] The crosslinking agent can be one of the compounds listed above used alone, or two or more compounds can be used in combination. Alternatively, compounds having two or more carbon-carbon unsaturated double bonds in one molecule and compounds having one carbon-carbon unsaturated double bond in one molecule can be used in combination. Examples of compounds having one carbon-carbon unsaturated double bond in one molecule include compounds having one vinyl group in one molecule (monovinyl compounds).

[0128] When resin (A) contains a crosslinking agent, the content of resin and / or copolymer (components other than the crosslinking agent) in resin (A) is preferably 30 to 99 parts by weight, more preferably 40 to 85 parts by weight, even more preferably 50 to 80 parts by weight, further preferably 60 to 75 parts by weight, and particularly preferably 65 to 70 parts by weight, relative to a total of 100 parts by weight of resin (A) and / or copolymer and crosslinking agent (b). Furthermore, the content of crosslinking agent in resin (A) is preferably 1 to 70 parts by weight, more preferably 15 to 60 parts by weight, even more preferably 20 to 50 parts by weight, further preferably 25 to 40 parts by weight, and particularly preferably 30 to 35 parts by weight, relative to a total of 100 parts by weight of resin (A) and / or copolymer and crosslinking agent (b). That is, the weight ratio of (a) resin and / or copolymer to (b) crosslinking agent in resin (A) (resin and / or copolymer: crosslinking agent) is preferably 99:1 to 30:70, more preferably 85:15 to 40:60, even more preferably 80:20 to 50:50, further preferably 75:25 to 60:40, and particularly preferably 70:30 to 65:35. If the contents of (a) resin and / or copolymer and (b) crosslinking agent are such that they satisfy the above weight ratio, the resulting metal-clad laminate has excellent heat resistance and excellent adhesion between the insulation layer and the metal foil. This is believed to be because the curing reaction of the resin and / or copolymer with the crosslinking agent proceeds appropriately.

[0129] It should be noted that, for example, Japanese Patent Application Publication No. 2017-128718 can be used as the polyphenylene ether mentioned above.

[0130] In 100% by weight of the resin composition, the content of resin (A) in the resin composition is preferably 40% by weight or more, more preferably 45% by weight or more, more preferably 50% by weight or more, more preferably 55% by weight or more, and even more preferably 60% by weight or more. According to this configuration, the resulting metal-clad laminate has a low dielectric loss tangent and therefore exhibits excellent dielectric properties.

[0131] The less resin in the resin composition that has a dielectric loss tangent (Df) greater than 0.0100 at 10 GHz, i.e., resin other than resin (A), the better. In 100% by weight of the resin composition, the content of resin other than resin (A) in the resin composition is preferably 5% by weight or less, more preferably 3% by weight or less, further preferably 1% by weight or less, and particularly preferably 0.1% by weight or less.

[0132] (Polymer microparticles (B))

[0133] The polymer particles (B) are (i) particles with a volume average particle size of 10 nm to 400 nm and (ii) particles comprising a core-shell copolymer having a core polymer and grafted portions bonded to the core polymer, wherein the core polymer and the grafted portions comprise structural units derived from a specific compound (monomer). By dispersing the polymer particles (B) having the above-described structure in the resin (A), when used as a material for the insulating layer of a metal-clad laminate, the adhesion between the insulating layer and the metal foil can be improved while maintaining a low dielectric loss tangent of the insulating layer.

[0134] (Volume average particle size)

[0135] The volume average particle size of the polymer microparticles (B) is 10 nm to 400 nm, preferably 30 nm to 350 nm, more preferably 40 nm to 300 nm, even more preferably 60 nm to 250 nm, and particularly preferably 80 nm to 200 nm. Based on the above configuration, excellent adhesion between the insulating layer and the metal foil can be obtained. The volume average particle size of the polymer microparticles (B) in the resin composition can be measured, for example, using a Microtrac (manufactured by Nikkiso Corporation, Microtrac UPA). For the volume average particle size of the polymer microparticles (B) in the metal-clad laminate, for example, the metal-clad laminate can be cut, the cut surface photographed, and the obtained photographic data (image) used for measurement.

[0136] The polymer particles (B) are preferably dispersed in the resin composition as primary particles. The dispersion of the polymer particles (B) as primary particles can be confirmed, for example, by a volume average particle size (Mv) / number average particle size (Mn) value of 3 or less. The volume average particle size (Mv) / number average particle size (Mn) value is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less. When the volume average particle size (Mv) / number average particle size (Mn) value exceeds 3, it indicates that the polymer particles (B) have formed secondary aggregates. It should be noted that the number average particle size (Mn) can also be determined using the same method as the volume average particle size. The volume average particle size (Mv) / number average particle size (Mn) value can be obtained by dividing the volume average particle size (Mv) by the number average particle size (Mn).

[0137] From the viewpoint of easily ensuring the dispersion diameter in the resin composition, the primary particle size of the polymer microparticles (B) is preferably 10 nm to 400 nm, more preferably 30 nm to 350 nm, even more preferably 50 nm to 300 nm, further preferably 80 nm to 250 nm, and particularly preferably 100 nm to 200 nm. If the value of the above-mentioned volume average particle size (Mv) / number average particle size (Mn) is 3 or less, the average primary particle size can be directly used as the value of the volume average particle size.

[0138] (Core-shell copolymer)

[0139] Polymer microparticles (B) are particles comprising a core polymer and a graft copolymer grafted to the core polymer. By including the graft copolymer in polymer microparticles (B), it is advantageous that polymer microparticles (B) can be dispersed in a primary particle state.

[0140] In polymer microparticles (B), graft copolymers having a core polymer and grafted portions bonded to the core polymer can form a layered structure. For example, the core polymer forms the innermost layer (also called the core layer), and a layer of grafted portions can form on the outside of the core polymer as the outermost layer (also called the shell layer). Therefore, the graft copolymer contained in polymer microparticles (B) is called a core-shell copolymer. In other words, polymer microparticles (B) are particles containing a core-shell polymer having a core polymer and grafted portions bonded to the core polymer.

[0141] It should be noted that in the core-shell copolymer constituting the polymer particles (B), the core polymer and the graft may not form a complete layered structure. That is, in this specification, "core-shell copolymer" refers to a core-shell particle shape in which the core polymer (core layer or innermost layer) and the graft (shell layer or outermost layer) form a layered structure, without limitation, and also includes a case where the core polymer and the graft do not form a layered structure.

[0142] The graft portion may cover at least a portion of the core polymer, or it may cover the entire core polymer. A portion of the graft portion may also extend into the inner side of the core polymer. Preferably, at least a portion of the graft portion covers at least a portion of the core polymer. In other words, at least a portion of the graft portion is preferably located on the outermost side of the polymer particle (B).

[0143] (a) From the perspectives of reducing the viscosity of the resin composition, ease of handling, and (b) ensuring stable dispersion of the polymer particles (B) in the resin composition, the weight ratio of the core polymer to the grafted portion, expressed as the weight of the core polymer / weight of the grafted portion (the weight ratio of the structural units of the polymer forming each layer), is preferably in the range of 50 / 50 to 99 / 1, more preferably 60 / 40 to 95 / 5, and even more preferably 70 / 30 to 90 / 10. It should be noted that if the polymerization conversion rate and grafting rate are 100%, then the "weight ratio of the structural units of the polymer forming each layer" is consistent with the "weight ratio of the monomers used to form the polymers in each layer." By including polymer particles (B) in the resin composition, the insulating layer of this metal-clad laminate exhibits excellent adhesion to the metal foil.

[0144] (Nuclear polymer)

[0145] The nuclear polymer comprises a crosslinker, the crosslinker comprising structural units from an aromatic vinyl compound having one vinyl group and structural units from an aromatic vinyl compound having two or more vinyl groups as structural units.

[0146] An aromatic vinyl compound having one vinyl group is also called a monomer having an aromatic ring and one vinyl group within the same molecule. In this specification, "an aromatic vinyl compound having one vinyl group" is also referred to as "monomer a".

[0147] Additionally, aromatic vinyl compounds having two or more vinyl groups (monomer b) are also referred to as monomers having an aromatic ring and two or more vinyl groups within the same molecule. In this specification, "aromatic vinyl compounds having two or more vinyl groups" are also referred to as "monomer b".

[0148] Aromatic vinyl compounds having one vinyl group (monomer a) and aromatic vinyl compounds having two or more vinyl groups (monomer b) are also collectively referred to as "aromatic vinyl compounds". Aromatic vinyl compounds have low polarity due to the presence of aromatic rings within their molecules.

[0149] By including structural units from monomer a and monomer b in the core polymer, the polarity of the structural units constituting the core polymer is reduced. As a result, the dielectric loss tangent of the core polymer is reduced. The higher the content of aromatic vinyl compounds (e.g., monomer a and monomer b) in the core polymer, the lower the dielectric loss tangent of the core polymer. The lower the dielectric loss tangent of the core polymer, the lower the dielectric loss tangent of the polymer particles (B) containing the core polymer. The lower the dielectric loss tangent of the polymer particles (B), the lower the dielectric loss tangent of the insulating layer containing the polymer particles (B). The lower the dielectric loss tangent of the insulating layer, the more the dielectric loss tangent of the metal-clad laminate can be reduced. In other words, by including structural units from monomer a and monomer b in the core polymer, the dielectric loss tangent of the final metal-clad laminate can be reduced. Furthermore, the higher the content of aromatic vinyl compounds (e.g., monomer a and monomer b) in the core polymer, the more the dielectric loss tangent of the final metal-clad laminate can be reduced.

[0150] Furthermore, monomers a and b are monomers that provide homopolymers with a glass transition temperature (Tg) above room temperature (23°C) by homopolymerizing each monomer. Therefore, the core polymer containing structural units from these monomers can exist as a rigid polymer in a glassy state at room temperature.

[0151] The number of aromatic rings in one molecule of an aromatic vinyl compound is not limited; it can be one or more (e.g., 2 to 10, 2 to 5, 2 to 3, or 2). Furthermore, the type of aromatic ring in an aromatic vinyl compound is not limited; for example, it can be at least one selected from benzene rings, non-benzene aromatic rings, heteroaromatic rings, and fused aromatic rings.

[0152] Examples of monomer 'a' include: unsubstituted monovinyl aromatic compounds such as styrene and 2-vinylnaphthalene; substituted monovinyl aromatic compounds such as α-methylstyrene; cycloalkylated monovinyl aromatic compounds such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, 2,4,6-trimethylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene; cycloalkoxylated monovinyl aromatic compounds such as 4-methoxystyrene and 4-ethoxystyrene; cyclohalogenated monovinyl aromatic compounds such as 2-chlorostyrene and 3-chlorostyrene; cycloesterified monovinyl aromatic compounds such as 4-ethoxystyrene; and cyclohydroxylated monovinyl aromatic compounds such as 4-hydroxystyrene. These compounds can be used individually or in combination of two or more.

[0153] Due to its superior economic efficiency and ease of application to free radical polymerization such as emulsion polymerization, monomer a preferably comprises one or more selected from unsubstituted monovinyl aromatic compounds, substituted monovinyl aromatic compounds, and cycloalkylated monovinyl aromatic compounds, more preferably comprising only one or more selected from unsubstituted monovinyl aromatic compounds, substituted monovinyl aromatic compounds, and cycloalkylated monovinyl aromatic compounds. Due to its even superior economic efficiency and easier application to free radical polymerization such as emulsion polymerization, monomer a preferably comprises one or more selected from styrene, α-methylstyrene, and cycloalkylated monovinyl aromatic compounds, more preferably comprising only one or more selected from styrene, α-methylstyrene, and cycloalkylated monovinyl aromatic compounds.

[0154] The number of vinyl groups in one molecule of monomer b can be, for example, 2 to 6, 2 to 5, 2 to 4, 2 to 3, or 2.

[0155] Examples of monomers b include divinylbenzene, divinylbiphenyl, divinylnaphthalene, and N,N-divinylaniline. These compounds can be used individually or in combination of two or more.

[0156] Due to its excellent economic efficiency and ease of application to free radical polymerization such as emulsion polymerization, monomer b is preferably divinylbenzene.

[0157] When isomers are present in monomer b, any isomer can be used in the same way, or a mixture thereof. Furthermore, for example, when monomer b is divinylbenzene, commercially available divinylbenzene is typically a mixture of isomers with different vinyl substitution positions, ethylvinylbenzene, and its isomers. In commercially available divinylbenzene, the higher the content (percentage) of divinylbenzene and its isomers, in other words, the lower the content (percentage) of ethylvinylbenzene and its isomers, the higher the purity of the commercially available divinylbenzene. In one embodiment of the present invention, both high-purity and low-purity commercially available divinylbenzene can be used.

[0158] When the weight of the core polymer is set to 100% by weight, the core polymer preferably contains 30% by weight or more of structural units from monomer a, more preferably 40% by weight or more, even more preferably 50% by weight or more, and particularly preferably 75% by weight or more. When the core polymer contains 30% by weight or more of structural units from monomer a (especially 50% by weight or more), it has the advantage of further reducing the dielectric loss tangent of the core polymer. The preferred range for the upper limit of the content of structural units from monomer a is not particularly limited and can be appropriately adjusted accordingly to the content of structural units from monomer b, etc. For example, the upper limit of the content of structural units from monomer a in 100% by weight of the core polymer is 99.9% by weight.

[0159] When the weight of the core polymer is set to 100 wt%, the core polymer preferably contains 0.1 wt% to 30.0 wt% of structural units from monomer b, more preferably 0.5 wt% to 20.0 wt%, even more preferably 1.0 wt% to 15.0 wt%, and particularly preferably 2.0 wt% to 10.0 wt%. When the core polymer contains more than 0.1 wt% of structural units from monomer b, monomer b functions as a crosslinking agent, introducing a crosslinked structure into the core polymer without increasing the dielectric loss tangent of the core polymer. By introducing a crosslinked structure into the core polymer, it has the advantage of maintaining the dispersion stability of the polymer particles (B). When the core polymer contains less than 30.0 wt% of structural units from monomer b, the polymer particles exhibit excellent economy, a lower dielectric loss tangent, and excellent adhesion between the insulating layer and the metal foil.

[0160] In addition to structural units from monomer a and monomer b, the nucleopolymer may also include structural units from compounds other than monomer a and monomer b (other compounds (monomers)) as structural units. Examples of such other compounds include one or more compounds selected from diene monomers such as butadiene, isoprene, and chloroprene, and (meth)acrylate monomers such as butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and butyl methacrylate.

[0161] When the weight of the core polymer is set to 100% by weight, the sum of the content of structural units from monomer a and structural units from monomer b in the core polymer is preferably 50.0% by weight or more, more preferably 70.0% by weight or more, further preferably 90.0% by weight or more, and particularly preferably 100.0% by weight. The core polymer is particularly preferably composed only of structural units from monomer a and structural units from monomer b. The higher the content of structural units from monomer a and monomer b in the core polymer, in other words, the lower the content of structural units from the other compounds mentioned above, in addition to the advantage of (a) the easy reduction of the dielectric loss tangent of the core polymer, it also has the surprising advantage of (b) being able to achieve a high level of balance between the adhesion between the insulating layer and the metal foil and the dielectric properties of the metal-clad laminate in the resulting metal-clad laminate.

[0162] (Cross-linked structure of nuclear polymers)

[0163] The core polymer is preferably cross-linked. This configuration has the following advantages: (a) it can maintain the dispersion stability of polymer particles (B) in resin (A), (b) it prevents the impregnation of polymer particles (B) by solvents and compounding agents, thereby reducing the viscosity of the resin composition.

[0164] As a method for introducing a crosslinked structure into a core polymer, a generally used method can be employed, for example, the following method. Specifically, a method can be described as follows: in the manufacture of a core polymer, a method in which multifunctional monomers and / or crosslinking monomers such as thiol-containing compounds are mixed in monomers capable of constituting the core polymer, and then polymerization is carried out. In this specification, the manufacture of polymers such as core polymers is also referred to as polymerizing polymers.

[0165] In one embodiment of the invention, monomer b can be used as a crosslinking monomer (crosslinking agent). In other words, monomer b can function as a crosslinking agent in the polymerization of the core polymer. By using monomer b as a crosslinking agent for introducing crosslinked structures into the core polymer, the content of structural units from aromatic vinyl compounds in the core polymer can be increased. Therefore, it has the advantage of further reducing the dielectric loss tangent of the core polymer.

[0166] In the polymerization of the core polymer, monomer b can be used in combination with other polyfunctional monomers and / or thiol-containing compounds as crosslinking agents. The amount of the other polyfunctional monomers and / or thiol-containing compounds is preferably within the range described above, where "the total content of monomer a and monomer b in the core polymer" is the amount within the preferred range.

[0167] Other multifunctional monomers include (meth)acrylates such as allyl alkyl methacrylates and allyloxyalkyl methacrylates, which have olefinically unsaturated double bonds. Monomers having two (meth)acrylate groups include ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, cyclohexanediethanol di(meth)acrylate, and polyethylene glycol di(meth)acrylates. Examples of the aforementioned polyethylene glycol di(meth)acrylates include triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol (600) di(meth)acrylate. In addition, examples of monomers having three (meth)acrylate groups include alkoxylated trimethylolpropane tri(meth)acrylates, glyceryl tri(meth)acrylate propoxylate, pentaerythritol tri(meth)acrylate, and tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate. Examples of alkoxylated trimethylolpropane tri(meth)acrylates include trimethylolpropane tri(meth)acrylate and trimethylolpropane triethoxylate. Furthermore, examples of monomers having four (meth)acrylate groups include pentaerythritol tetra(meth)acrylate and bis(trimethylolpropane tetra(meth)acrylate. Furthermore, examples of monomers having five (meth)acrylate groups include dipentaerythritol penta(meth)acrylate. Furthermore, examples of monomers having six (meth)acrylate groups include bis(trimethylolpropane hexa(meth)acrylate. In addition, as multifunctional monomers, examples include allyl methacrylate, diallyl phthalate, triallyl cyanurate, and triallyl isocyanurate (TAIC) and other isocyanuric acid trialkylene ester compounds.

[0168] Examples of mercapto-containing compounds include alkyl-substituted thiols, allyl-substituted thiols, aryl-substituted thiols, hydroxy-substituted thiols, alkoxy-substituted thiols, cyano-substituted thiols, amino-substituted thiols, silyl-substituted thiols, acid-substituted thiols, halogen-substituted thiols, and acyl-substituted thiols. As alkyl-substituted thiols, alkyl-substituted thiols with 1 to 20 carbon atoms are preferred, and alkyl-substituted thiols with 1 to 10 carbon atoms are more preferred. As aryl-substituted thiols, phenyl-substituted thiols are preferred. As alkoxy-substituted thiols, alkoxy-substituted thiols with 1 to 20 carbon atoms are preferred, and alkoxy-substituted thiols with 1 to 10 carbon atoms are more preferred. As acid-substituted thiols, alkyl-substituted thiols with 1 to 10 carbon atoms having a carboxyl group or aryl-substituted thiols with 1 to 12 carbon atoms having a carboxyl group are preferred.

[0169] These multifunctional monomers and / or thiol-containing compounds can be used alone or in combination of two or more.

[0170] The following situation is explained: Crosslinking of the core polymer occurs when multifunctional monomers and / or mercapto-containing compounds other than monomer b are not used, or even if used, they are used in small amounts, with monomer b being the primary component. In this case, the following advantages are also present: (i) through crosslinking of the core polymer, (a) the dispersion stability of polymer particles (B) in the resin (A) can be maintained, and (b) the impregnation of polymer particles (B) such as solvents and compounding agents can be prevented, thereby reducing the viscosity of the resin composition; and (ii) by increasing the content of structural units from aromatic vinyl compounds in the core polymer, the dielectric loss tangent of the core polymer can be further reduced.

[0171] In the structural units constituting the core polymer, of the 100% by weight of structural units derived from crosslinking monomers (monomer b, multifunctional monomers other than monomer b, and thiol-containing compounds other than monomer b), the content of structural units derived from monomer b is preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 100% by weight. In the structural units constituting the core polymer, the structural units derived from crosslinking monomers are particularly preferably composed only of structural units derived from monomer b.

[0172] (Gel content of nuclear polymer)

[0173] The core polymer is preferably a core polymer that can swell in a suitable solvent but is substantially insoluble. The core polymer is preferably insoluble in resin (A).

[0174] The gel content of the core polymer is preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the gel content of the core polymer is within the above range, the viscosity of the masterbatch obtained by dispersing polymer particles (B) in a solvent and the resulting resin composition can be reduced, and the heat resistance of the cured product (insulating layer) obtained by curing the resin composition can be maintained at a high level.

[0175] In this specification, the method for calculating the gel content is as follows. First, an aqueous latex containing polymer microparticles (B) is obtained. Next, granules of polymer microparticles (B) are obtained from the aqueous latex. The method for obtaining granules of polymer microparticles (B) from the aqueous latex is not particularly limited; for example, the following method can be used: (a) agglomerating the polymer microparticles (B) in the aqueous latex, (b) dehydrating the obtained agglomerate, and (c) further drying the agglomerate to obtain granules of polymer microparticles (B). Next, 2.0 g of the granules of polymer microparticles (B) are dissolved in 50 mL of methyl ethyl ketone (MEK). Then, the obtained MEK solution is separated into a component soluble in MEK (MEK soluble component) and a component insoluble in MEK (MEK insoluble component). Specifically, a centrifuge (Hitachi Koki Co., Ltd., CP60E) was used to centrifuge the obtained MEK solution at 30,000 rpm for 1 hour, separating the solution into MEK soluble and MEK insoluble components. A total of 3 centrifugation operations were performed. The weights of the obtained MEK soluble and MEK insoluble components were measured, and the gel content was calculated using the following formula.

[0176] Gel content (%) = (weight of methyl ethyl ketone insoluble component) / {(weight of methyl ethyl ketone insoluble component) + (weight of methyl ethyl ketone soluble component)} × 100.

[0177] (Glass transition temperature of nucleopolymers)

[0178] The glass transition temperature of a nucleopolymer is not particularly limited, but can be, for example, above -30°C, above 0°C, above 50°C, or above 90°C. The glass transition temperature can be calculated based on the monomer composition used in the polymerization of the nucleopolymer using the Fox formula shown below, expressed in Kelvin and converted to Celsius.

[0179] 1 / Tg = w1 / Tg1 + w2 / Tg2 + ... + w n / Tg n

[0180] Here, Tg1, Tg2, ..., Tg n Let Tg(K), w1, w2, ..., wn be the homopolymers of the components (i.e., monomers used in the manufacture of the core polymer) 1, 2, ..., n, respectively. n These are the weight fractions of the components constituting the core polymer (i.e., the monomers used in the manufacture of the core polymer), 1, 2, ..., n. Additionally, the Tg of the homopolymer can be, for example, the value described in the Polymer Handbook Fourth Edition (edited by J. Brandup et al., J. Phon Wiley & Sons, Inc.).

[0181] The glass transition temperature of a core polymer varies depending on the structural units that make up the core polymer. For example, the higher the content of structural units from the aromatic vinyl compounds (e.g., monomers a and b) that make up the core polymer, the higher the glass transition temperature of the core polymer, and the core polymer becomes a rigid polymer.

[0182] (A variation of a nuclear polymer)

[0183] In one embodiment of the invention, the "core polymer" of the polymer microparticle (B) may be formed from only one type of core polymer with the same composition of structural units. Alternatively, in another embodiment of the invention, the "core polymer" of the polymer microparticle (B) may be formed from multiple types of core polymers with different compositions of structural units.

[0184] In one embodiment of the present invention, the case where the "core polymer" of the polymer microparticle (B) is formed by multiple core polymers with different compositions of structural units will be described. In this case, the multiple core polymers are respectively designated as core polymer 1, core polymer 2, ..., and core polymer n. Here, n is an integer of 2 or more. The "core polymer" of the polymer microparticle (B) may also include a composite of core polymer 1, core polymer 2, ..., and core polymer n, which are polymerized separately. The "core polymer" of the polymer microparticle (B) may include a single core polymer obtained by sequentially polymerizing core polymer 1, core polymer 2, ..., and core polymer n. So far, the sequential polymerization of multiple core polymers (polymers) is also called multi-stage polymerization. A single core polymer obtained by multi-stage polymerization of multiple core polymers is also called a multi-stage polymerized core polymer. The method for manufacturing the multi-stage polymerized core polymer will be described in detail below.

[0185] A multi-segment polymeric core polymer formed from core polymer 1, core polymer 2, ..., and core polymer n is described. In this multi-segment polymeric core polymer, core polymer n may encapsulate at least a portion of core polymer n-1, or may encapsulate the entire core polymer n-1. In this multi-segment polymeric core polymer, a portion of core polymer n may sometimes penetrate into the interior of core polymer n-1.

[0186] In a multi-segment polymeric core polymer, multiple core polymers can each form a layered structure. For example, in the case where the multi-segment polymeric core polymer is formed by core polymer 1, core polymer 2, and core polymer 3, the following is also an embodiment of the present invention: core polymer 1 forms the innermost layer, a layer of core polymer 2 is formed on the outside of core polymer 1, and then a layer of core polymer 3, which serves as the outermost layer of the core polymers, is formed on the outside of the layer of core polymer 2. Thus, a multi-segment polymeric core polymer in which multiple core polymers each form a layered structure is also called a multilayer core polymer. That is, in one embodiment of the present invention, the "core polymer" of the polymer particles (B) can include (a) a composite of multiple core polymers, (b) a multi-segment polymeric core polymer, and / or (c) a multilayer core polymer.

[0187] (Grafting point)

[0188] The grafted portion is a polymer comprising structural units from an aromatic vinyl compound (monomer a) having one vinyl group and structural units from an epoxy (meth)acrylate having an epoxy group. This configuration offers the following advantages: (a) by reducing the polarity of the structural units constituting the grafted portion, the dielectric loss tangent of the grafted portion is reduced; (b) the compatibility between the polymer particles (B) and the resin (A) is improved; (c) the dispersibility of the polymer particles (B) in the resin (A) is improved; (d) in the resin composition or insulating layer, the polymer particles (B) are easily dispersed in a primary particle state; and (e) the adhesion between the insulating layer and the metal foil is further improved. The lower the dielectric loss tangent of the grafted portion, the lower the dielectric loss tangent of the polymer particles (B) containing the grafted portion, and the lower the dielectric loss tangent of the insulating layer containing the polymer particles (B) can be maintained.

[0189] As an example of monomer a used in the manufacture of the graft, and as a preferred example of monomer a, the description of the above-mentioned (nuclear polymer) item is appropriately cited.

[0190] Examples of epoxy-containing (meth)acrylates (hereinafter also referred to as "monomer C") include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, allyl glycidyl ether, monoallyl diglycidyl isocyanurate, and diallyl monoglycidyl isocyanurate. These compounds may be used individually or in combination of two or more. It should be noted that in this specification, (meth)acrylate refers to acrylates and / or methacrylates.

[0191] Due to its excellent economic efficiency and stability, and its ease of application to free radical polymerization such as emulsion polymerization, monomer C is preferably glycidyl (meth)acrylate.

[0192] When the weight of the grafted portion is set to 100% by weight, the grafted portion preferably contains 20% or more of structural units from monomer a, more preferably 30% or more, more preferably 40% or more, more preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and particularly preferably 70% or more. When the grafted portion contains 40% or more of structural units from monomer a (especially 50% or more), it has the advantage of further reducing the dielectric loss tangent of the grafted portion. Furthermore, the inventors have independently discovered the following insight when the grafted portion contains 40% or more of structural units from monomer a (especially 50% or more): the affinity between the low-polarity resin (A) and the polymer particles (B) increases, thereby stabilizing the dispersion of the polymer particles (B) in the resin composition. Surprisingly, this results in a further improvement in the adhesion between the resulting insulating layer and the metal foil.

[0193] The upper limit of the content of structural units from monomer a in the graft portion is not particularly limited, and can be appropriately adjusted accordingly with the content of structural units from monomer c, etc. For example, the upper limit of the content of structural units from monomer a in 100% by weight of the graft portion is 99.9% by weight.

[0194] When the weight of the graft is set to 100% by weight, the graft preferably contains 5% to 80% by weight of structural units from monomer c, more preferably 5% to 70% by weight, more preferably 5% to 60% by weight, more preferably 10% to 50% by weight, more preferably 10% to 45% by weight, even more preferably 15% to 40% by weight, and particularly preferably 20% to 30% by weight. When the weight of the grafted portion is set to 100% by weight, the following advantages are achieved: (a) When the structural unit from monomer c is 5% or more by weight, the dispersion stability of the polymer particles (B) in the solvent can be improved, and functional groups with excellent affinity for the metal foil can be introduced into the polymer particles (B). As a result, the obtained insulating layer can be endowed with affinity for the metal foil. (b) When the structural unit from monomer c is 50% or less by weight, the dielectric loss tangent of the grafted portion is low, and good affinity between the polymer particles (B) and the low polarity resin (A) can be obtained, which can further improve the dispersibility of the polymer particles (B) in the resin (A).

[0195] When the weight of polymer particles (B) is set to 100 wt%, the polymer particles (B) preferably contain 0.5 wt% to 10.0 wt% of structural units from monomer c, more preferably 1.0 wt% to 7.0 wt%, and even more preferably 2.0 wt% to 5.0 wt%. For polymer particles (B), when the weight of polymer particles (B) is set to 100 wt%, the following advantages are available: (a) when the structural units from monomer c are contained at 0.5 wt% or more, the dispersion stability of polymer particles (B) in the solvent can be improved, and functional groups with excellent affinity for metal foil can be introduced into the polymer particles (B). As a result, the obtained insulating layer can be endowed with affinity for metal foil; (b) when the content is 10.0 wt% or less, the dielectric loss tangent of polymer particles (B) is low, and good affinity between polymer particles (B) and low-polarity resin (A) can be obtained, further improving the dispersibility of polymer particles (B) in resin (A).

[0196] From the viewpoint of achieving all three goals—low dielectric loss tangent at the grafting portion, improved dispersion of polymer microparticles (B), and improved adhesion between the insulating layer and the metal foil—when the total weight of structural units from monomer a and structural units from monomer c is set to 100% by weight, the content ratio of structural units from monomer a to structural units from monomer c in the grafting portion is preferably 40% to 95% by weight, more preferably 50% to 90% by weight, and even more preferably 60% to 85% by weight.

[0197] In one embodiment of the invention, in addition to monomers a and c, the graft portion may further include structural units from an aromatic vinyl compound (monomer b) having two or more vinyl groups as structural units. Monomer b has low polarity and functions as a crosslinking agent. Therefore, by further including structural units from monomer b in the graft portion, a crosslinked structure can be introduced into the graft portion without increasing the dielectric loss tangent of the graft portion.

[0198] In one embodiment, the grafted portion is preferably cross-linked. This provides the following advantages: (a) it prevents the swelling of polymer particles (B) in the resin composition; (b) it improves the dispersibility of polymer particles (B) in the resin (A); and (c) it tends to improve the processability of the masterbatch, resin composition, and resin varnish in order to suppress the increase in viscosity. Furthermore, if the masterbatch has a low viscosity, it has the advantage of reducing the amount of adhesive residue formed by the masterbatch adhering to the tank wall during masterbatch manufacturing. Additionally, if the masterbatch has a low viscosity, the resin composition manufactured using the masterbatch, and the resin varnish containing the resin composition, also have a low viscosity. Therefore, it also has the advantage of reducing the amount of adhesive residue on the tank wall during the manufacture of the resin composition or resin varnish. Moreover, the lower the viscosity of the resin varnish, the higher the impregnation of the resin varnish into the fibrous substrate (glass cloth), and the better the surface properties of the resulting prepreg.

[0199] In the polymerization of the graft, monomer b, and (other) polyfunctional monomers and / or thiol-containing compounds other than monomer b can be used as crosslinking agents. Preferably, the amounts of the other polyfunctional monomers and / or thiol-containing compounds used are within the preferred range described above, where the content of structural units from monomers a, b, and c in the graft is respectively within the preferred range.

[0200] As examples of monomer b, multifunctional monomers and mercapto-containing compounds used in the manufacture of grafts, and preferred examples of monomer b, multifunctional monomers and mercapto compounds, the description in the above-mentioned (nuclear polymer) item is appropriately cited.

[0201] When the grafted portion further includes structural units from monomer b, and the weight of the grafted portion is set to 100% by weight, the grafted portion preferably includes 0.5% to 20.0% by weight of structural units from monomer b, more preferably 1.0% to 10.0% by weight, even more preferably 1.5% to 7.0% by weight, and particularly preferably 2.0% to 5.0% by weight. With the above configuration, there is the advantage of being able to adjust the degree of crosslinking of the grafted portion to a suitable range.

[0202] In the structural units constituting the grafting portion, of the 100% by weight of structural units from the crosslinking monomer (monomer b, multifunctional monomers other than monomer b, and thiol-containing compounds other than monomer b), the content of structural units from monomer b is preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 100% by weight. In the structural units constituting the grafting portion, the structural units from the crosslinking monomer are particularly preferably composed only of structural units from monomer b.

[0203] In addition to structural units from monomers a, b, and c, the graft portion may include structural units from compounds other than monomers a, b, and c (other compounds (monomers)) as structural units. Examples of such other compounds include diene monomers such as (a) butadiene, isoprene, and chloroprene; (b) butyl acrylate, 2-ethylhexyl acrylate, 4-hydroxybutyl acrylate, methyl methacrylate, and butyl methacrylate; (c) acrylonitrile, methacrylonitrile, and other cyanide vinyl monomers; and one or more compounds selected from the polyfunctional monomers and mercapto-containing compounds described in the (nuclear polymer) section above.

[0204] When the weight of the grafted portion is set to 100% by weight, the combined content of structural units from monomer a and structural units from monomer b in the grafted portion is preferably 40.0% by weight or more, more preferably 50.0% by weight or more, further preferably 60.0% by weight or more, and particularly preferably 70.0% by weight or more. The higher the content of structural units from monomer a and monomer b in the grafted portion, in addition to the advantage that (a) the dielectric loss tangent of the grafted portion is more easily reduced, it also has the surprising advantage that (b) the resulting metal-clad laminate can achieve a high level of balance between the adhesion between the insulating layer and the metal foil and the dielectric properties of the metal-clad laminate.

[0205] When the weight of the grafted portion is set to 100% by weight, the total content of structural units from monomer a, monomer b, and monomer c in the grafted portion is preferably 70.0% by weight or more, more preferably 80.0% by weight or more, further preferably 90.0% by weight or more, even more preferably 95.0% by weight or more, and particularly preferably 100% by weight. The grafted portion is particularly preferably composed only of structural units from polymer a, monomer b, and monomer c. When the grafted portion is composed only of structural units from monomer a, monomer b, and monomer c, it has the advantages of (a) easier reduction of the dielectric loss tangent of the grafted portion, (b) a higher level of balance between the adhesion between the insulating layer and the metal foil and the dielectric properties of the metal-clad laminate in the resulting metal-clad laminate, and (c) a tendency to suppress the increase in the viscosity of the masterbatch. The reason for the inhibition of viscosity increase in the masterbatch described in (c) above has not yet been determined, but it is inferred that it is because it can reduce the polarity of the grafted portion, thereby inhibiting the impregnation of polar solvents into the polymer particles (B). It should be noted that the present invention is not limited to the above inference.

[0206] (Grafting rate at the grafting point)

[0207] In one embodiment of the invention, the polymer particles (B) may be polymers having the same structure as the graft portion and not grafted to the core polymer. In this specification, polymers having the same structure as the graft portion and not grafted to the core polymer are also referred to as ungrafted polymers. These ungrafted polymers are equivalent to free polymers (FPs) described later. The aforementioned ungrafted polymers are also referred to as polymers produced in the polymerization of the graft portion that are not grafted to the core polymer.

[0208] In this specification, the proportion of polymers not grafted to the core polymer in the polymer produced during the polymerization of the grafted portion, i.e., the grafted portion, is called the grafting ratio. The grafting ratio is also expressed as (weight of grafted portion) / {(weight of grafted portion)+(weight of ungrafted polymer)}×100.

[0209] The grafting rate of the grafted portion is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. When the grafting rate is 80% or more, it has the following advantages: (a) the viscosity of the resin composition does not become too high, and (b) the heat resistance of the cured product (insulating layer) obtained by curing the resin composition can be maintained at a high level.

[0210] In this specification, the method for calculating the grafting rate is as follows. First, an aqueous latex containing polymer particles (B) is obtained. Next, powder of polymer particles (B) is obtained from the aqueous latex. Specifically, a method for obtaining powder of polymer particles (B) from the aqueous latex includes: (i) coagulating the polymer particles (B) in the aforementioned aqueous latex; (ii) dehydrating the obtained coagulated material; and (iii) further drying the coagulated material to obtain powder of polymer particles (B). Next, 2 g of the powder of polymer particles (B) is dissolved in 50 mL of methyl ethyl ketone (MEK). Then, the obtained MEK solution is separated into a component soluble in MEK (MEK soluble component) and a component insoluble in MEK (MEK insoluble component). Specifically, using a centrifuge (Hitachi Koki Co., Ltd., CP60E), the obtained MEK solution was centrifuged at 30,000 rpm for 1 hour to separate the solution into MEK soluble and MEK insoluble components. Three centrifugation operations were performed in total. Next, 20 ml of the concentrated MEK soluble component was mixed with 200 ml of methanol, and an aqueous solution of calcium chloride (0.01 g dissolved in water) was added. The mixture was stirred for 1 hour. Then, the solution was separated into methanol-soluble and methanol-insoluble components, and the amount of methanol-insoluble component was taken as the amount of free polymer (FP).

[0211] The grafting rate is calculated using the following formula.

[0212] Grafting rate (%) = 100 - [(FP amount) / {(FP amount) + (MEK insoluble component)}] / (weight of polymer at the graft) × 10000

[0213] It should be noted that the weight of the polymer outside the grafted portion includes the amount of monomers constituting the polymer outside the grafted portion. The polymer outside the grafted portion is, for example, a core polymer. Furthermore, if the polymer particles (B) contain a surface-crosslinked polymer described later, the polymer outside the grafted portion includes both the core polymer and the surface-crosslinked polymer. The weight of the polymer at the grafted portion is the amount of monomers constituting the polymer at the grafted portion. Additionally, in calculating the grafting rate, the method for coagulating the polymer particles (B) is not particularly limited; methods using solvents, coagulants, or spraying water-based latex can be used, etc.

[0214] (Example of a modified grafting section)

[0215] In one embodiment of the invention, the graft portion may be formed by only one type of graft portion constituting structural units having the same composition. In another embodiment of the invention, the graft portion may also be formed by multiple types of graft portions having structural units having different compositions.

[0216] In one embodiment of the present invention, the case where the graft portion is formed by multiple graft portions will be described. In this case, the multiple graft portions are respectively designated as graft portion 1, graft portion 2, ..., graft portion n (n is an integer of 2 or more). The graft portion may also comprise a composite of graft portions 1, graft portion 2, ..., and graft portion n, which are polymerized separately. The graft portion may comprise a single polymer obtained by multi-stage polymerization of graft portions 1, graft portion 2, ..., and graft portion n. The polymer obtained by multi-stage polymerization of multiple graft portions is also referred to as a multi-stage polymerized graft portion. The method for manufacturing the multi-stage polymerized graft portion will be described in detail later.

[0217] When the grafted portion is formed by multiple grafted portions, not all of these grafted portions need to be grafted and bonded to the core polymer. At least a portion of at least one type of grafted portion needs to be grafted and bonded to the core polymer; other types (multiple other types) of grafted portions can also be grafted and bonded to the grafted portion grafted to the core polymer. Furthermore, when the grafted portion includes multiple grafted portions, multiple polymers (multiple non-grafted polymers) with the same structure as the multiple grafted portions but not grafted and bonded to the core polymer can also be included.

[0218] The multi-segmented aggregated grafting section formed by grafting portion 1, grafting portion 2, ..., and grafting portion n will be described. In this multi-segmented aggregated grafting section, grafting portion n may cover at least a portion of grafting portion n-1, or may cover the entire grafting portion n-1. In this multi-segmented aggregated grafting section, a portion of grafting portion n may also extend into the inner side of grafting portion n-1.

[0219] In a multi-segment polymer grafted section, each graft portion can have a layered structure. For example, in the case where the multi-segment polymer grafted section is formed by graft portion 1, graft portion 2, and graft portion 3, the following arrangement is also an embodiment of the present invention: graft portion 1 is the innermost layer of the grafted sections, a layer of graft portion 2 exists outside the layer of graft portion 1, and a layer of graft portion 3 exists outside the layer of graft portion 2 as the outermost layer. In this way, the multi-segment polymer grafted section in which each graft portion has a layered structure is also called a multi-layer grafted section. That is, in one embodiment of the present invention, the grafted section can include a mixture of various graft portions, a multi-segment polymer grafted section, and / or a multi-layer grafted section.

[0220] (Surface cross-linked polymer)

[0221] The core-shell copolymer preferably has a surface-crosslinked polymer in addition to the core polymer and the graft portion grafted to the core polymer. In other words, the polymer particles (B) preferably have a surface-crosslinked polymer in addition to the core polymer and the graft portion grafted to the core polymer. Hereinafter, an embodiment of the present invention will be described by way of example in which the polymer particles (B) (core-shell copolymer) further have a surface-crosslinked polymer. In this case, (a) when the polymer particles (B) are manufactured in powder form, the anti-blocking property can be improved, and (b) the dispersibility of the polymer particles (B) in the resin (A) is good. As a reason, without particular limitation, it can be presumed that by coating at least a portion of the core polymer with the surface-crosslinked polymer, the exposure of the core polymer portion of the polymer particles (B) is reduced, and as a result, the core polymers are less likely to stick together, and the dispersibility of the polymer particles (B) is improved.

[0222] When the polymer particles (B) have surface-crosslinked polymers, the following effects can be further achieved: (a) reducing the viscosity of the resin composition; (b) increasing the crosslinking density in the core polymer; (c) improving the grafting efficiency of the grafted portion; and (d) preventing solvent wetting of the core polymer and maintaining the particle shape of the core polymer when the core polymer is dispersed in the solvent during the manufacture of the polymer particles (B). The crosslinking density in the core polymer refers to the degree of crosslinking of the overall core polymer structure.

[0223] The polymer microparticles (B) may comprise a surface-crosslinked polymer polymer polymerized independently of the core-shell copolymer, or may comprise a surface-crosslinked polymer polymerized together with the core-shell copolymer. The polymer microparticles (B) may be a multi-segmented polymer obtained by sequentially polymerizing the core polymer, the surface-crosslinked polymer, and the graft portion in multiple segments. In any of the above embodiments, the surface-crosslinked polymer may coat at least a portion of the core polymer.

[0224] The surface-crosslinked polymer can also be considered as part of the core polymer. In other words, the surface-crosslinked polymer can also be considered as part of a core-shell copolymer, and can also be called the surface-crosslinked polymeric part. When the polymer particles (B) contain the surface-crosslinked polymer, the graft portion (a) can be grafted onto the core polymer other than the surface-crosslinked polymer, (b) can be grafted onto the surface-crosslinked polymer, and (c) can be grafted onto both the core polymer other than the surface-crosslinked polymer and the surface-crosslinked polymer. When the polymer particles (B) contain the surface-crosslinked polymer, the volume average particle size of the core polymer mentioned above refers to the volume average particle size of the core polymer containing the surface-crosslinked polymer.

[0225] The following describes a case (Case A) in which the polymer particles (B) are multi-segment polymers obtained by sequentially polymerizing a core polymer, a surface crosslinked polymer, and a graft portion. In Case A, the surface crosslinked polymer may coat a portion of the core polymer or the entire core polymer. In Case A, a portion of the surface crosslinked polymer may sometimes extend into the inner side of the core polymer. In Case A, the graft portion may coat a portion of the surface crosslinked polymer or the entire surface crosslinked polymer. In Case A, a portion of the graft portion may sometimes extend into the inner side of the surface crosslinked polymer. In Case A, the core polymer, the surface crosslinked polymer, and the graft portion may have a layered structure. For example, one embodiment of the present invention may have the core polymer as the innermost layer (core layer), the surface crosslinked polymer layer as an intermediate layer outside the core polymer, and the graft portion layer as the outermost layer (shell layer) outside the surface crosslinked polymer.

[0226] In the presence of a surface-crosslinked polymer, the proportion of the surface-crosslinked polymer relative to the polymer particles (B) is preferably 0.50 to 5.00% by weight, more preferably 0.75 to 4.00% by weight, and even more preferably 0.75 to 3.00% by weight. In particular, the formation of an intermediate layer by coating the core polymer with the surface-crosslinked polymer has the following effects: suppressing the swelling of the polymer particles (B) caused by the resin (A) and solvent, and suppressing the increase in the viscosity of the resin varnish and the melt viscosity of the resin composition. Furthermore, it is also effective in suppressing the adhesion between the polymer particles (B) and each other; therefore, it is suitable for suppressing the adhesion of the polymer particles (B) to the walls of the mixing tank, etc., during the manufacture of the resin composition.

[0227] Examples of crosslinking monomers that can be used for the polymerization of surface crosslinking polymers include monomers identical to those described in the section on (crosslinking structure of core polymers), such as monomer b, other multifunctional monomers, and mercapto-containing compounds. Among these crosslinking monomers, examples of preferred crosslinking monomers for the polymerization of surface crosslinking polymers include isocyanuric acid triacrylate compounds such as triallyl isocyanurate (TAIC), butanediol di(meth)acrylate, allyl (meth)acrylate, diallyl itaconic acid, diallyl phthalate, etc. These crosslinking monomers can be used individually or in combination of two or more. From the viewpoint of crosslinking efficiency and grafting efficiency, isocyanuric acid triacrylate compounds such as triallyl isocyanurate (TAIC) are particularly preferred.

[0228] (The content of structural units derived from aromatic vinyl compounds in polymer particles (B))

[0229] In 100% by weight of polymer microparticles (B), the total content of structural units from monomer a and structural units from monomer b (which is the total content of structural units contained in polymer microparticles (B), whether core polymers or grafted portions) is preferably 75% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. Based on the above configuration, the dielectric loss tangent of the polymer microparticles (B) can be reduced, and a metal-clad laminate with excellent electrical properties can be obtained.

[0230] (Method for manufacturing polymer microparticles (B))

[0231] There are no particular limitations on the manufacturing method of polymer microparticles (B), and they can be manufactured by known methods, such as emulsion polymerization, suspension polymerization, and micro-suspension polymerization. Among these, the manufacturing method using multi-stage emulsion polymerization is particularly preferred. Specific examples of emulsifiers (dispersants) used in emulsion polymerization include: alkyl or aryl sulfonic acids such as dioctyl sulfosuccinic acid and dodecylbenzene sulfonic acid, alkyl or aryl ether sulfonic acids, alkyl or aryl sulfuric acids such as dodecyl sulfuric acid, alkyl or aryl ether sulfuric acid, alkyl or aryl substituted phosphoric acid, alkyl or aryl ether substituted phosphoric acid, N-alkyl or aryl sarcosine such as dodecyl sarcosine, alkyl or aryl carboxylic acids such as oleic acid and stearic acid, alkyl or aryl ether carboxylic acids, and various alkali metal salts or ammonium salts of acids; nonionic emulsifiers or dispersants such as alkyl or aryl substituted polyethylene glycol; and dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives. One of these can be used alone, or two or more can be used in combination.

[0232] From the viewpoint of polymerization stability, the emulsifier is preferably an anionic emulsifier, more preferably an anionic emulsifier of alkali metal salt, and even more preferably an anionic emulsifier of sodium salt and / or potassium salt.

[0233] From the perspective of a preferred embodiment of the invention, these emulsifiers (dispersants) are used in the smallest possible amount, within a range that does not impede the dispersion stability during the preparation of the aqueous solvent dispersion containing polymer particles (B). Alternatively, during the preparation of the resin composition, a residual amount can be extracted and removed to a level that does not affect the physical properties of the resin composition for use. For this purpose, the emulsifier (dispersant) is more preferably water-soluble.

[0234] (Resin Composition)

[0235] Relative to 100.0 parts by weight of resin (A), the content of polymer particles (B) in the resin composition is preferably 0.5 parts by weight to 30.0 parts by weight, more preferably 1.0 parts by weight to 20.0 parts by weight, even more preferably 1.5 parts by weight to 15.0 parts by weight, and particularly preferably 2.0 parts by weight to 12.0 parts by weight. According to the above configuration, the resulting metal-clad laminate has the advantages of (a) excellent adhesion between the insulating layer and the metal foil and (b) excellent dielectric properties resulting from a low dielectric loss tangent.

[0236] The dielectric loss tangent (Df) of the polymer microparticles (B) at 10 GHz is not particularly limited, but is preferably 0.0060 or less, more preferably 0.0058 or less, even more preferably 0.0056 or less, and particularly preferably 0.0054 or less. According to the above configuration, the resulting metal-clad laminate has a lower dielectric loss tangent and superior dielectric properties (electrical properties). The dielectric loss tangent of the polymer microparticles (B) can be measured using a cavity resonator device or the like, and specific measurement methods are described in the examples described later. It should be noted that when the content of resin other than resin (A) in the resin composition is low (e.g., 5% or less in 100% by weight of the resin composition), the dielectric loss tangent of the insulating layer will largely depend on the dielectric loss tangent of the polymer microparticles (B). In other words, it can be considered that when the dielectric loss tangent (Df) of the polymer microparticles (B) at 10 GHz is within the above range, there is a high probability that the dielectric loss tangent of the insulating layer will be 0.0100 or less at 10 GHz. Furthermore, the dielectric loss tangent of the metal-clad laminate largely depends on the dielectric loss tangent of the insulating layer. In other words, when the dielectric loss tangent (Df) of the polymer particles (B) at 10 GHz is within the aforementioned range, the metal-clad laminate exhibits a low dielectric loss tangent and can therefore be considered to possess excellent dielectric properties.

[0237] (Other ingredients)

[0238] The resin composition can be formed from a resin (A) without a crosslinking agent and polymer particles (B), or from a resin (A) containing a crosslinking agent and polymer particles (B). In addition to the resin (A) and polymer particles (B), the resin composition may further contain other components. Examples of other components include, for instance, inorganic fillers, flame retardants, and additives.

[0239] The resin composition preferably further contains an inorganic filler (D).

[0240] The inorganic filler (D) that can be used in one embodiment of the present invention is not particularly limited. Examples of inorganic filler (D) include silica such as spherical silica and crushed silica, barium sulfate, silica powder, calcined talc, barium titanate, titanium dioxide, clay, alumina, mica, boehmite, zinc borate, zinc stannate, other metal oxides, and metal hydrates. When the resin composition contains inorganic filler (D), thermal expansion can be suppressed and dimensional stability can be improved in the resulting metal-coated laminate.

[0241] As an inorganic filler (D), silica is preferred because it enables the obtained metal-clad laminate to exhibit excellent heat resistance and dielectric loss tangent. Silica has a low dielectric loss tangent.

[0242] Silica may or may not have undergone surface treatment (it may be untreated). Examples of surface treatment agents for silica include vinylsilanes.

[0243] As an inorganic filler (D), silica that has been surface-treated with vinyl silane (vinyl silane-treated silica) is preferred because it can achieve excellent dispersion stability and maintain a high level of mechanical properties and toughness of the cured product (insulating layer) obtained by curing the resin composition.

[0244] When the resin composition contains an inorganic filler (D), the total content of resin (A) and polymer particles (B) is set to 100 parts by weight, and the content of inorganic filler (D) in the resin composition is preferably 40 to 200 parts by weight. When the content of inorganic filler (D) is 200 parts by weight or less as described above, there is no concern about a decrease in the penetration of the resin varnish into the fibrous substrate or a decrease in the adhesion between the insulation layer and the metal foil during the fabrication of the insulation layer.

[0245] In addition to resin (A) and polymer microparticles (B), the resin composition may also contain the aforementioned inorganic filler (D), and may further contain other additives. Examples of other additives include: silicone-based defoamers, acrylate-based defoamers, flame retardants, heat stabilizers, antistatic agents, synergists, ultraviolet absorbers, dyes and pigments, lubricants, and dispersants such as wetting and dispersing agents.

[0246] (2-1-2. Fibrous substrate)

[0247] Examples of fibrous substrates include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. Glass cloth is preferred as a fibrous substrate because it allows for the production of metal-clad laminates with excellent mechanical strength; glass cloth that has undergone a flattening process is more preferred. Specifically, the flattening process of the glass cloth can be achieved by continuously applying appropriate pressure to the glass cloth using pressure rollers, thereby flattening the glass cloth. It should be noted that the thickness of the fibrous substrate is typically, for example, 0.04 to 0.3 mm.

[0248] (2-1-3. The dielectric loss tangent of the insulating layer)

[0249] The dielectric loss tangent of the insulating layer is not particularly limited, but is preferably 0.0100 or less, more preferably 0.0080 or less, even more preferably 0.0060 or less, and particularly preferably 0.0040 or less under 10 GHz conditions. The lower limit of the dielectric loss tangent of the insulating layer is not particularly limited, but is, for example, greater than 0.0000. When the dielectric loss tangent of the insulating layer is within the above range, the electrical characteristics of the metal-clad laminate become excellent. The dielectric loss tangent of the insulating layer can be measured using the same method as that for the dielectric loss tangent of the polymer particles (B). Furthermore, for the insulating layer laminated on the metal-clad laminate, after removing the metal foil from the metal-clad laminate, the dielectric loss tangent of the insulating layer can be measured using the obtained insulating layer using the same method as that for the dielectric loss tangent of the polymer particles (B). The method for removing the metal foil from the metal-clad laminate is not particularly limited; for example, methods such as dissolving the metal of the metal-clad laminate using an etching solution can be cited.

[0250] (2-2. Metal foil)

[0251] The metal foil used in this metal-clad laminate is not particularly limited, and examples include copper foil, silver foil, and gold foil. However, from the viewpoint of cost and conductivity, copper foil is preferred.

[0252] The surface ten-point average roughness (Rz) of the metal foil is 2.0 μm or less, preferably 1.5 μm or less, and more preferably 1.0 μm or less. Based on the above configuration, the resulting metal-clad laminate exhibits excellent dielectric properties. The surface ten-point average roughness of the metal foil can be measured, for example, by a method based on JIS B 0601 or by observation using a scanning electron microscope. Furthermore, for the metal foil laminated on the metal-clad laminate, the surface ten-point average roughness can be measured using the peeled metal foil after peeling it from the metal-clad laminate, using the method described above.

[0253] (2-3. Physical properties of metal-clad laminates)

[0254] (90° metal foil peel strength)

[0255] The adhesion between the insulating layer and the metal foil in a metal-clad laminate can be evaluated by the 90° metal foil peel strength (N / mm). A higher 90° metal foil peel strength indicates better adhesion between the insulating layer and the metal foil. The 90° metal foil peel strength of the metal-clad laminate is not particularly limited, but preferably exceeds 0.42 N / mm, more preferably 0.43 N / mm or more, even more preferably 0.45 N / mm or more, further preferably 0.50 N / mm or more, and particularly preferably 0.55 N / mm or more. The upper limit of the 90° metal foil peel strength of the metal-clad laminate is not particularly limited, for example, it is 2 N / mm or less. When the 90° metal foil peel strength of the metal-clad laminate is within the above range, the adhesion between the insulating layer and the metal foil of the metal-clad laminate is excellent. In this specification, the 90° peel strength of the metal-clad laminate is defined as a value obtained by measurement based on the method of JIS C6481. The specific measurement method is described in the examples described later.

[0256] (glass transition temperature (Tg))

[0257] The heat resistance of metal-clad laminates can be evaluated by their glass transition temperature (Tg). A higher glass transition temperature (Tg) indicates better heat resistance. The glass transition temperature (Tg) of a metal-clad laminate is not particularly limited, but is preferably 170°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, and particularly preferably 200°C or higher. The upper limit of the glass transition temperature (Tg) of a metal-clad laminate is not particularly limited, for example, it is 400°C or lower. When the glass transition temperature (Tg) of a metal-clad laminate is within the above range, the heat resistance of the metal-clad laminate is excellent. The glass transition temperature (Tg) of a metal-clad laminate can be measured using a thermomechanical analysis apparatus (TMA) or similar device according to the apparatus's instruction manual.

[0258] [3. Manufacturing method of metal-clad laminate]

[0259] A method for manufacturing a metal-clad laminate according to one embodiment of the present invention includes: a step of preparing a masterbatch by dispersing polymer particles (B) in a solvent containing methyl ethyl ketone; a step of preparing a resin varnish by mixing the masterbatch, a resin (A) having a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and a solvent; a step of preparing a prepreg by impregnating the resin varnish with glass cloth; and a step of laminating a metal foil onto the prepreg, wherein the polymer particles (B) satisfy the following conditions (i) and (ii): (i) the volume average particle size is 10 nm to 400 nm; (ii) the polymer particles contain... The core polymer and the core-shell copolymer grafted onto the graft portion of the core polymer, wherein the core polymer comprises structural units as structural units: structural units from an aromatic vinyl compound having one vinyl group and structural units from an aromatic vinyl compound having two or more vinyl groups, and the graft portion comprises structural units as structural units: structural units from an aromatic vinyl compound having one vinyl group and structural units from an epoxy group (meth)acrylate, wherein the ten-point average roughness (Rz) of the interface between the metal foil and the prepreg is 2.0 μm or less.

[0260] The manufacturing method of the metal-clad laminate according to one embodiment of the present invention has the above-described configuration, and therefore, it is possible to provide a metal-clad laminate with excellent adhesion between the insulating layer and the metal foil and excellent dielectric properties.

[0261] The method for manufacturing a metal-clad laminate according to one embodiment of the present invention can be suitably used to manufacture the metal-clad laminate described in [2. Metal-clad Laminate]. Therefore, the description of the resin (A), polymer particles (B), fibrous substrate and metal foil, inorganic filler (D) and flame retardant, etc., in the method for manufacturing a metal-clad laminate according to one embodiment of the present invention can be appropriately referenced from the description described in [2. Metal-clad Laminate].

[0262] (The process of preparing masterbatch)

[0263] Polymer microparticles (B) are manufactured as described above using known methods, ultimately obtained as a dispersion in an aqueous solvent, i.e., an aqueous solvent dispersion containing polymer microparticles (B) (also known as an aqueous latex). Therefore, the process of preparing the masterbatch is also referred to as the process of replacing the solvent of the dispersion containing polymer microparticles (B) from an aqueous solvent with a solvent containing methyl ethyl ketone (MEK). Polymer microparticles (B) are manufactured by multi-stage emulsion polymerization, preferably in the form of an aqueous latex.

[0264] Solvents containing methyl ethyl ketone (hereinafter also simply referred to as solvents) may also include solvents other than methyl ethyl ketone. Examples of solvents other than methyl ethyl ketone that may be included in a solvent include (a) water, (b) aromatic hydrocarbons such as toluene and xylene, (c) esters such as ethyl acetate and propylene glycol monomethyl ether acetate, (d) ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, and (e) solvents such as butanol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone.

[0265] One embodiment of the process for preparing masterbatch will be specifically described. The process for preparing masterbatch may sequentially include: a first step of obtaining a loose aggregate (re-aggregate) of polymer particles from an aqueous solvent dispersion containing polymer particles (B) (preferably an aqueous latex obtained by emulsion polymerization); a second step of obtaining a particle dispersion containing the polymer particles (B) and a solvent from the loose aggregate of the polymer particles; and a third step of evaporating the solvent and / or water from the particle dispersion.

[0266] The first, second, and third processes will be described in more detail.

[0267] The first step is as follows: after mixing the aqueous solvent dispersion containing the above-mentioned polymer particles (B) with a solvent, it is further mixed with water to obtain a slurry containing loose aggregates of floating polymer particles.

[0268] The second step is as follows: The liquid phase is removed from the slurry to obtain loose aggregates of polymer particles; then, the loose aggregates of polymer particles are mixed with a solvent to obtain a particle dispersion containing the aforementioned polymer particles (B) and solvent. The particle dispersion obtained in the second step contains water; therefore, it can be considered an aqueous particle dispersion.

[0269] As for the mixing device used in the first and second steps, known devices can be used. For example, a general device such as a mixing tank with stirring blades can be used, or a static mixer (stationary mixer) and a flow line mixer (a method of introducing the mixing device into a part of the piping) can be used.

[0270] The third step is to evaporate the solvent and / or water from the particle dispersion.

[0271] In the third step, there are no particular limitations on the method for evaporating the solvent and / or water from the particle dispersion, and known methods can be used. Examples include: (a) adding the particle dispersion to a tank and removing it by distillation under heating and reduced pressure; (b) convectively contacting the mixture with dry gas in a tank; (c) using a continuous method such as a thin-film evaporator; and (d) using an extruder equipped with a devolatilization mechanism or a continuous stirred tank. The temperature and time required for distilling away the water can be appropriately selected within a range that does not impair the quality of the obtained masterbatch.

[0272] By sequentially performing the first to third steps described above, a masterbatch in which polymer particles (B) are dispersed at a high concentration and stably can be easily obtained. The first to third steps described above have excellent processability; therefore, the process for preparing the masterbatch preferably includes the first to third steps described above.

[0273] In 100% by weight of masterbatch, the water content in the masterbatch obtained through the masterbatch preparation process is preferably 1.00% by weight or less, more preferably 0.50% by weight or less, more preferably 0.30% by weight or less, more preferably 0.20% by weight or less, more preferably 0.15% by weight or less, more preferably 0.14% by weight or less, more preferably 0.13% by weight or less, even more preferably 0.12% by weight or less, and particularly preferably 0.11% by weight or less. When the water content is within 1.00% by weight, the resulting insulating layer has excellent surface aesthetics and the advantage of eliminating the risk of foaming in the insulating layer.

[0274] The content of polymer particles (B) in the masterbatch obtained by the masterbatch preparation process is preferably 20 to 40% by weight, more preferably 22 to 38% by weight, and even more preferably 24 to 36% by weight, relative to the total weight of the masterbatch (100% by weight). When the content of polymer particles (B) in the masterbatch is (a) 20% by weight or more, excessive solvent is not introduced into the resin varnish used in the manufacture of the insulating layer, and therefore, the processability is good; (b) when it is 40% by weight or less, the viscosity of the masterbatch does not become too high, and it has an appropriate viscosity, and therefore, the handleability is good.

[0275] The lower the viscosity of the masterbatch, the more uniform the flow of the mixture (intermediate product or masterbatch) in the tank during the masterbatch preparation process. As a result, the amount of intermediate product or the obtained masterbatch adhering to the tank wall as a solid residue can be reduced.

[0276] For the same reason as the content of polymer particles (B), the total content of solvent in the masterbatch obtained by the process of preparing the masterbatch is preferably 60 to 80% by weight, more preferably 62 to 78% by weight, and even more preferably 64 to 76% by weight, relative to the total weight of the masterbatch (100% by weight).

[0277] (The process of preparing resin varnish)

[0278] The process for preparing a resin varnish involves mixing a masterbatch, a resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and a solvent. Alternatively, the process can involve adding the masterbatch and resin (A) to a solvent and mixing the resulting mixture. In other words, the resin varnish can also be considered a mixture of resin (A), polymer particles (B), and a solvent. Through the process of preparing the resin varnish, the resin (A) can be dissolved in the solvent, and the polymer particles (B) in the masterbatch can be dispersed in both the solvent and the resin (A).

[0279] Examples of solvents that can be used to mix with the masterbatch and resin (A) include: (a) solvents containing methyl ethyl ketone as described in the above-mentioned (step of preparing masterbatch), (b) water, (c) aromatic hydrocarbons such as toluene and xylene, (d) esters such as ethyl acetate and propylene glycol monomethyl ether acetate, (e) ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, and (f) solvents such as butanol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. One of these solvents may be used alone, or two or more may be used in combination.

[0280] Resin varnishes may further include inorganic fillers (D), flame retardants, and additives.

[0281] Furthermore, the resin varnish preferably further comprises a reaction initiator. When the resin varnish comprises a reaction initiator, the Tg and heat resistance of the obtained metal-clad laminate can be improved. Additionally, when the resin (A) comprises a crosslinking agent and the resin varnish comprises a reaction initiator, the reactivity of the resin and / or copolymer in the resin (A) with the crosslinking agent can be improved. As a result, the Tg and heat resistance of the obtained metal-clad laminate can be further improved.

[0282] The reaction initiator is not particularly limited as long as it can promote the curing reaction of (a) resin (A) and / or the curing reaction of the resin and / or copolymer in (b) resin (A) with the crosslinking agent. Specifically, examples include oxidants such as α,α'-bis(tert-butylperoxym-isopropyl)benzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-biphenylquinone, tetrachlorobenzoquinone, 2,4,6-tritert-butylphenoxy, tert-butylperoxyisopropyl carbonate, and azobisisobutyronitrile. Furthermore, carboxylic acid metal salts can be used in combination with the reaction initiator as needed. This further promotes the curing reaction of (a) resin (A) and / or the curing reaction of the resin and / or copolymer in (b) resin (A) with the crosslinking agent. Among these reaction initiators, α,α'-bis(tert-butylperoxym-isopropyl)benzene is preferred. The reaction initiation temperature of α,α'-bis(tert-butylperoxym-isopropyl)benzene is relatively high. Therefore, it can suppress the promotion of curing reactions during prepreg drying and other times when curing is not required, and can inhibit the reduction of the shelf life of resin varnishes. Furthermore, α,α'-bis(tert-butylperoxym-isopropyl)benzene has low volatility, so it does not volatilize during prepreg drying and during the storage of resin varnishes, exhibiting good stability. In addition, a single reaction initiator can be used, or two or more in combination.

[0283] When the resin varnish contains a reaction initiator, its content is preferably 0.01 to 3 parts by weight relative to a total of 100 parts by weight of resin (A) + polymer particles (B).

[0284] An example of the process for preparing a resin varnish is described. First, (a) a masterbatch containing resin (A) and polymer particles (B), and (b) any component soluble in the solvent, such as a compatible flame retardant, are added to the solvent, and the resulting mixture is mixed. At this time, the mixture may be heated if necessary. Through the above operation, the resin (A) and the solvent-soluble component dissolve in the solvent, and the polymer particles (B) are dispersed in the solvent. Then, any component insoluble in the solvent, such as an inorganic filler (D) and an incompatible flame retardant, is added to the mixture. The resulting mixture is then stirred until the dispersion state of each component in the solvent reaches a given dispersion state, thereby obtaining the resin varnish. The mixing of the components and the stirring of the resulting mixture can be performed using a ball mill, bead mill, planetary mixer, roller mill, or similar equipment.

[0285] It should be noted that when resin (A) contains a crosslinking agent, the crosslinking agent may volatilize during the manufacture of the prepreg using resin varnish. Therefore, in order to ensure that the content of crosslinking agent in the final metal-clad laminate is as described in the above section (resin (A)), the amount of crosslinking agent in resin (A) must be set taking into account the amount of crosslinking agent volatilization during the manufacture of the prepreg.

[0286] (Process for preparing prepreg)

[0287] The process for preparing the prepreg is described in detail. The prepreg is prepared by impregnating a fibrous substrate with a resin varnish and then drying the resulting fibrous substrate.

[0288] The impregnation of resin varnishes into fibrous substrates is achieved through impregnation and coating. This impregnation process can be repeated multiple times as needed. Furthermore, it is possible to repeatedly impregnate with various resin varnishes of different compositions and / or concentrations to ultimately adjust to the desired composition (content ratio) and resin amount.

[0289] By heating a fibrous substrate impregnated with resin varnish under desired heating conditions, such as 80–170°C, for 1–10 minutes, the solvent is removed, thereby obtaining a prepreg made of resin semi-cured.

[0290] (The process of laminating metal foil)

[0291] The process of laminating metal foil is described in detail below. One or more sheets of prepreg are overlapped, and then metal foil is overlapped on both sides or either side of the resulting prepreg laminate. The laminate is then heated and pressurized to form a single unit. This produces a metal-clad laminate with metal foil on both sides or on one side. The heating and pressurizing conditions can be appropriately set according to the thickness of the metal-clad laminate being manufactured and the composition of the resin varnish in the prepreg. For example, the temperature can be set to 170–220°C, the pressure to 1.5–5.0 MPa, and the time to 60–150 minutes.

[0292] It should be noted that the resin contained in the prepreg is in a semi-cured state, but it is fully cured during the lamination process of the metal foil. Furthermore, during the lamination process of the metal foil, the metal foil and the prepreg bond simultaneously as the resin in the prepreg cures. In other words, the metal-clad laminate comprises a cured prepreg and a metal foil. Additionally, the portion of the metal-clad laminate other than the metal foil is an insulating layer; in other words, the cured prepreg can be considered an insulating layer. Furthermore, the portion of the cured prepreg other than the fibrous substrate (e.g., glass cloth) (which may contain a cured resin (A), polymer particles (B), and inorganic fillers, etc.) is considered a resin composition.

[0293] [4. Printed wiring board]

[0294] One embodiment of the printed wiring board of the present invention includes the metal-clad laminate described in item [2. Metal-clad laminate]. The printed wiring board of one embodiment of the present invention has the above-described configuration, therefore, excellent adhesion between the insulating layer and the metal foil, and excellent dielectric properties.

[0295] As a method for manufacturing a printed wiring board according to one embodiment of the present invention, an example can be given: forming a circuit by etching a metal foil on the surface of a metal-clad laminate as described in item [2. Metal-clad laminate], thereby manufacturing a printed wiring board in which a conductor pattern as a circuit is provided on the surface of the laminate. That is, it can be considered that the printed wiring board according to one embodiment of the present invention is manufactured using the metal-clad laminate described in item [2. Metal-clad laminate].

[0296] [1] A metal-clad laminate comprising: an insulating layer comprising a resin composition and a fibrous substrate, and a metal foil bonded to the insulating layer.

[0297] The above resin composition contains a resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz and polymer particles (B).

[0298] The polymer particles (B) described above satisfy the following conditions (i) and (ii):

[0299] (i) The volume average particle size is 10 nm to 400 nm;

[0300] (ii) A core-shell copolymer comprising a core polymer and grafts bonded to the core polymer.

[0301] The above-mentioned nuclear polymer contains the following structural units as structural units:

[0302] Structural units from aromatic vinyl compounds having one vinyl group, and

[0303] Structural units derived from aromatic vinyl compounds having two or more vinyl groups,

[0304] The grafting portion described above includes the following structural units:

[0305] Structural units from aromatic vinyl compounds having one vinyl group, and

[0306] Structural units derived from (meth)acrylates with epoxy groups,

[0307] The surface roughness (Rz) of the above-mentioned metal foil at ten points is less than 2.0 μm.

[0308] [2] According to the metal-clad laminate described in [1], wherein,

[0309] The grafted portion further includes structural units from aromatic vinyl compounds having two or more vinyl groups as structural units.

[0310] [3] The metal-clad laminate according to [1] or [2], wherein,

[0311] The aforementioned nuclear polymer was cross-linked.

[0312] [4] The metal-clad laminate according to any one of [1] to [3], wherein,

[0313] The grafted portion was cross-linked.

[0314] [5] The metal-clad laminate according to any one of [1] to [4], wherein,

[0315] In the aforementioned nuclear polymer, when the weight of the aforementioned nuclear polymer is set to 100% by weight, the content of the structural unit from the aromatic vinyl compound having one vinyl group is 50% by weight or more.

[0316] [6] The metal-clad laminate according to any one of [1] to [4], wherein,

[0317] In the aforementioned core polymer, when the weight of the aforementioned core polymer is set to 100% by weight, the total content of the structural unit from the aromatic vinyl compound having one vinyl group and the total content of the structural unit from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more.

[0318] [7] The metal-clad laminate according to [2], wherein,

[0319] In the grafted portion, when the weight of the grafted portion is set to 100% by weight, the total content of the structural unit from the aromatic vinyl compound having one vinyl group and the total content of the structural unit from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more.

[0320] [8] The metal-clad laminate according to any one of [1] to [7], wherein,

[0321] In the grafted portion, when the weight of the grafted portion is set to 100% by weight, the content of the structural unit from the aromatic vinyl compound having one vinyl group is 50% by weight or more.

[0322] [9] The metal-clad laminate according to any one of [1] to [8], wherein,

[0323] The dielectric loss tangent (Df) of the aforementioned polymer particles (B) at 10 GHz is below 0.0060°.

[0324]

[10] A printed wiring board comprising any one of [1] to [9] a metal-clad laminate.

[0325]

[11] A method for manufacturing a metal-clad laminate, comprising:

[0326] The process of preparing a masterbatch by dispersing polymer particles (B) in a solvent containing methyl ethyl ketone;

[0327] The process of preparing resin varnish by mixing the above-mentioned masterbatch, resin (A) with a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and solvent;

[0328] The process of preparing a prepreg by impregnating the above-mentioned resin varnish with glass cloth; and

[0329] The process of laminating metal foil onto the prepreg described above

[0330] The polymer particles (B) described above satisfy the following conditions (i) and (ii):

[0331] (i) The volume average particle size is 10 nm to 400 nm;

[0332] (ii) A core-shell copolymer comprising a core polymer and grafts bonded to the core polymer.

[0333] The above-mentioned nuclear polymer contains the following structural units as structural units:

[0334] Structural units from aromatic vinyl compounds having one vinyl group, and

[0335] Structural units derived from aromatic vinyl compounds having two or more vinyl groups,

[0336] The grafting portion described above includes the following structural units:

[0337] Structural units from aromatic vinyl compounds having one vinyl group, and

[0338] Structural units derived from (meth)acrylates with epoxy groups,

[0339] The ten-point average roughness (Rz) of the interface between the metal foil and the prepreg is less than 2.0 μm.

[0340]

[12] The manufacturing method of the metal-clad laminate according to

[11] , wherein,

[0341] The grafted portion further includes structural units from aromatic vinyl compounds having two or more vinyl groups as structural units.

[0342]

[13] The method for manufacturing the metal-clad laminate according to

[11] or

[12] , wherein,

[0343] The aforementioned nuclear polymer was cross-linked.

[0344]

[14] A method for manufacturing a metal-clad laminate according to any one of

[11] to

[13] , wherein,

[0345] The grafted portion was cross-linked.

[0346]

[15] A method for manufacturing a metal-clad laminate according to any one of

[11] to

[14] , wherein,

[0347] In the aforementioned nuclear polymer, when the weight of the aforementioned nuclear polymer is set to 100% by weight, the content of the structural unit from the aromatic vinyl compound having one vinyl group is 50% by weight or more.

[0348]

[16] A method for manufacturing a metal-clad laminate according to any one of

[11] to

[14] , wherein,

[0349] In the aforementioned core polymer, when the weight of the aforementioned core polymer is set to 100% by weight, the total content of the structural unit from the aromatic vinyl compound having one vinyl group and the total content of the structural unit from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more.

[0350]

[17] The manufacturing method of the metal-clad laminate according to

[12] , wherein,

[0351] In the grafted portion, when the weight of the grafted portion is set to 100% by weight, the total content of the structural unit from the aromatic vinyl compound having one vinyl group and the total content of the structural unit from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more.

[0352]

[18] A method for manufacturing a metal-clad laminate according to any one of

[11] to

[17] , wherein,

[0353] In the grafted portion, when the weight of the grafted portion is set to 100% by weight, the content of the structural unit from the aromatic vinyl compound having one vinyl group is 50% by weight or more.

[0354]

[19] A method for manufacturing a metal-clad laminate according to any one of

[11] to

[18] , wherein,

[0355] The dielectric loss tangent (Df) of the aforementioned polymer particles (B) at 10 GHz is below 0.0060°.

[0356] Example

[0357] The following examples illustrate one embodiment of the present invention, but the embodiments of the present invention are not limited to these examples.

[0358] The methods for measuring the properties in the examples and comparative examples are described below.

[0359] [Volume Average Particle Size]

[0360] The volume average particle size of polymer particles was measured using a particle size measuring device (Made by Nikkiso Corporation, Microtrac UPA).

[0361] [Dielectric loss tangent of polymer particles (B)]

[0362] Asaflex 810 (a styrene-butadiene copolymer manufactured by Asahi Kasei) was dissolved in methyl ethyl ketone (MEK) to prepare an Asaflex 810 solution. Meanwhile, polymer particles (B) were dispersed in MEK to prepare a masterbatch (polymer particle dispersion). By adding the masterbatch to the Asaflex 810 solution, mixtures were prepared with polymer particles (B) and Asaflex 810 in ratios of 0 / 100, 30 / 100, and 60 / 100. The resulting mixtures were dried under reduced pressure at 120°C to obtain a dried residue. The dried residue was hot-pressed to produce evaluation pieces measuring 100 mm × 2 mm × 1 mm. The dielectric loss tangent at a frequency of 10 GHz was measured using a cavity resonator device (manufactured by Kanto Electronics Application Development). A curve was plotted showing the measured value versus the polymer particle (B) content, thus obtaining a linear approximation. Based on the obtained linear approximation, the dielectric loss tangent of the polymer particles (B) was determined. It should be noted that the masterbatch containing polymer particles (B) dispersed in MEK used in the determination of the dielectric loss tangent is equivalent to the masterbatch described in the manufacturing examples of the polymer particles (B) described later.

[0363] [Viscosity of masterbatch]

[0364] The viscosity of the masterbatch containing polymer particles (B) dispersed in MEK was measured at 25°C using a Type B viscometer (Anton Paar). If the viscosity was too high and the resistance (torque) exceeded the allowable range of the apparatus, it was set to "to" (torque too high). It should be noted that the masterbatch containing polymer particles (B) dispersed in MEK used in the viscosity measurement is equivalent to the masterbatch described in the various manufacturing examples of the polymer particles (B) described later.

[0365] [90° metal foil peel strength]

[0366] The 90° peel strength of the metal-clad laminate was measured based on JIS C6481:1996. The specific details are as follows: First, metal foil was laminated onto the prepreg obtained in each embodiment and comparative example to form a metal foil pattern with a width of 10 mm and a length of 100 mm. Next, the resulting laminate was heated and pressurized to form and integrally assembled, resulting in a metal-clad laminate. The metal foil was then peeled from the obtained metal-clad laminate using a tensile testing machine at a speed of 50 mm / min, and the peel strength was measured. The obtained value was taken as the 90° peel strength of the metal foil.

[0367] [Glass transition temperature (Tg)]

[0368] The thermomechanical analysis (TMA) apparatus was used to determine the Tg of the metal-clad laminate. The determination method followed the apparatus's instruction manual.

[0369] The main components and materials used in the examples and comparative examples are described below.

[0370] (Resin(A))

[0371] Resin (A) is a mixture of 70 parts by weight of the resin shown below and 30 parts by weight of the crosslinking agent shown below.

[0372] <Resin>

[0373] Methacrylic acid modified polyphenylene ether: SA9000 (manufactured by Sabic, number average molecular weight Mn: 1,000-3,000, dielectric loss tangent at 10 GHz: 0.005)

[0374] <Cross-linking agent>

[0375] Triallyl isocyanurate: TAIC (Japan Chemicals)

[0376] Butadiene-styrene liquid polymer: Ricon100 (manufactured by CrayValley)

[0377] In Examples 1-7 and Comparative Examples 1-12, TAIC was used as a crosslinking agent. In Examples 8-9 and Comparative Examples 13-15, Ricon100 was used as a crosslinking agent.

[0378] (Polymer microparticles (B))

[0379] Polymer microparticles manufactured by the methods described in Examples 1 to 17 below.

[0380] (Inorganic filler (D))

[0381] Vinylsilane surface-treated silica: ADMAFINE (manufactured by Admatech Co., Ltd., 70% by weight dispersion (dispersion medium: MEK), average particle size 0.5 μm)

[0382] (other)

[0383] <Reaction Initiator>

[0384] 2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexane: Perhexa25B (Nippon Oil Production)

[0385] (Fibrous substrate)

[0386] Fiberglass cloth: Fiberglass cloth (7628, E-glass) (manufactured by Nittobo Co., Ltd.)

[0387] (metal foil)

[0388] Copper foil: HS2-VSP (Made by Mitsui Metals Corporation, Rz = 1μm)

[0389] Copper foil: SI-VSP (Made by Mitsui Metals Corporation, Rz = 0.5μm).

[0390] The method for manufacturing polymer microparticles (B) is described below.

[0391] (Manufacturing Example 1)

[0392] In a 100L pressure polymerizer, 200 parts by weight of water, 0.03 parts by weight of tripotassium phosphate, 0.25 parts by weight of potassium dihydrogen phosphate, 0.002 parts by weight of disodium ethylenediaminetetraacetate (EDTA), 0.001 parts by weight of ferrous sulfate hexahydrate, and 1.5 parts by weight of sodium dodecylbenzenesulfonate (SDBS) were added. While stirring the added raw materials, oxygen was thoroughly removed from the pressure polymerizer by nitrogen purging. Then, 97 parts by weight of styrene (St) and 3 parts by weight of divinylbenzene (DVB) were added to the system, and the temperature inside the pressure polymerizer was raised to 45°C. Next, 0.015 parts by weight of p-menthane hydrogen peroxide (PHP) were added to the system, followed by 0.04 parts by weight of sodium formaldehyde sulfoxylate (SFS), and polymerization began. Four hours after the start of polymerization, 0.01 parts by weight of PHP, 0.0015 parts by weight of EDTA, and 0.001 parts by weight of ferrous sulfate 7-hydrate were added to the system. Ten hours after the start of polymerization, devolatilization was performed under reduced pressure to remove the residual monomers in the system, thereby ending the polymerization. The system was then cooled to obtain the nucleopolymer latex (C-1).

[0393] 241 parts by weight of the aforementioned nucleopolymer latex (C-1) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of triallyl isocyanurate (TAIC) and 0.07 parts by weight of cumene hydroperoxide (CHP), and the mixture was stirred for 60 minutes. Then, over a period of 110 minutes, a mixture of 12 parts by weight of St, 4 parts by weight of acrylonitrile (AN), 4 parts by weight of glycidyl methacrylate (GMA), and 0.08 parts by weight of tert-butyl hydroperoxide (TBP) was continuously added to the system. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-1) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 88 nm.

[0394] 126 parts by weight of MEK were added to a 1L mixing tank at 30°C. While stirring the MEK, 126 parts by weight of an aqueous latex (L-1) containing polymer microparticles (B) were added to the system. After the added raw materials were uniformly mixed, 200 parts by weight of water were added to the system at a feed rate of 80 parts by weight / min. After the water supply was completed, stirring was stopped immediately, resulting in a slurry containing loose aggregates of floating polymer microparticles.

[0395] Next, with the polymer microparticles remaining in the tank as loose aggregates, 350 parts by weight of the liquid phase were discharged from the outlet at the bottom of the tank, thus obtaining loose polymer microparticle aggregates. 150 parts by weight of MEK were added to the obtained loose polymer microparticle aggregates, and they were mixed to obtain an aqueous polymer microparticle dispersion containing polymer microparticles (B).

[0396] The resulting aqueous polymer particle dispersion was transferred to a 1L tank (a 100mm inner diameter agitator equipped with 90mm blade-type anchoring blades). This tank has a jacket, an inner diameter of 100mm, and is equipped with an agitator featuring 90mm blade-type anchoring blades. The jacket temperature was then set to 70°C, and the pressure was set to 200 torr to remove MEK and water by distillation until the polymer particle (B) concentration in the contents reached 20% by weight.

[0397] In the aforementioned tank, the polymer microparticles (B) of the contents were added to a MEK concentration of 10% by weight, and the contents were uniformly mixed. Then, the jacket temperature was set to 70°C and the pressure was set to 200 torr, and the MEK and water were removed by distillation until the polymer microparticle (B) concentration of the contents reached 25% by weight. Nitrogen gas was then introduced into the tank to restore the internal pressure to atmospheric pressure, resulting in a masterbatch (M-1) in which polymer microparticles (B) were dispersed in MEK. The dielectric loss tangent of the obtained polymer microparticles (B) at a frequency of 10 GHz and the viscosity of the masterbatch (M-1) at 25°C were measured. The results are shown in Table 2.

[0398] In addition, in Manufacturing Example 1, the adhesion rate of the adhesive material to the tank wall during the preparation of masterbatch (M-1) was calculated. Specifically, after the prepared masterbatch (M-1) was removed from the tank, the adhesive material adhering to the tank wall was cleaned with MEK and scraped off with a metal scraper, then recycled into the cleaning solution. Next, the recycled cleaning solution was dried at 120°C for 60 minutes, and the weight of the dried residue (i.e., the weight of the adhesive material) was measured. Then, the weight of the dried residue was divided by the weight of the polymer particles added to the tank during the preparation of masterbatch (M-1), and the resulting value was multiplied by 100 to calculate the adhesion rate of the adhesive material to the tank wall during the preparation of masterbatch (M-1). The result was 4.50% by weight.

[0399] (Manufacturing Example 2)

[0400] 256 parts by weight of the aforementioned nucleopolymer latex (C-1) (containing 85 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 11 parts by weight of St, 4 parts by weight of GMA, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Finally, 0.04 parts by weight of TBP was added to the system, and stirring continued for 1 hour to complete the polymerization, yielding an aqueous latex (L-2) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex is 86 nm.

[0401] Next, aqueous latex (L-2) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-2) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz was measured. The results are shown in Table 2.

[0402] (Manufacturing Example 3)

[0403] 256 parts by weight of the aforementioned nucleopolymer latex (C-1) (containing 85 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 14.55 parts by weight of St, 4 parts by weight of GMA, 0.45 parts by weight of DVB, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-3) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 86 nm.

[0404] Next, aqueous latex (L-3) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-3) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-3) at 25°C were measured. The results are shown in Table 2. In addition, the adhesion rate of the adhesive to the tank wall when preparing masterbatch (M-3) was calculated in the same manner as in Manufacturing Example 1, and the result was 0.28% by weight. The reason for the significant decrease in the adhesion rate of the adhesive to the tank wall when preparing masterbatch (M-3) compared with that when preparing masterbatch (M-1) is speculated to be that a cross-linking structure was introduced into the grafting part of polymer particles (B) during the preparation of masterbatch (M-3), resulting in a decrease in the viscosity of the obtained masterbatch (M-3). It should be noted that the present invention is not limited to the above speculation in any way.

[0405] (Manufacturing Example 4)

[0406] 256 parts by weight of the aforementioned nucleopolymer latex (C-1) (containing 85 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 9.55 parts by weight of St, 4 parts by weight of GMA, 1 part by weight of methyl methacrylate (MMA), 0.45 parts by weight of DVB, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-4) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 91 nm.

[0407] Next, aqueous latex (L-4) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-4) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-4) at 25 °C were measured. The results are shown in Table 2.

[0408] (Manufacturing Example 5)

[0409] 256 parts by weight of the aforementioned nucleopolymer latex (C-1) (containing 85 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 7.55 parts by weight of St, 4 parts by weight of GMA, 3 parts by weight of MMA, 0.45 parts by weight of DVB, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-5) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 87 nm.

[0410] Next, aqueous latex (L-5) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-5) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-5) at 25 °C were measured. The results are shown in Table 2.

[0411] (Manufacturing Example 6)

[0412] In a 100L pressure polymerizer, 200 parts by weight of water, 0.03 parts by weight of tripotassium phosphate, 0.25 parts by weight of potassium dihydrogen phosphate, 0.002 parts by weight of disodium ethylenediaminetetraacetate (EDTA), 0.001 parts by weight of ferrous sulfate hexahydrate, and 1.5 parts by weight of sodium dodecylbenzenesulfonate (SDBS) were added. While stirring the added raw materials, oxygen was thoroughly removed from the pressure polymerizer by nitrogen purging. Then, 75 parts by weight of butadiene (Bd) and 25 parts by weight of St were added to the system, and the temperature inside the pressure polymerizer was raised to 45°C. Next, 0.015 parts by weight of p-menthane hydrogen peroxide (PHP) were added to the system, followed by 0.04 parts by weight of sodium formaldehyde sulfoxylate (SFS), and polymerization began. Four hours after the start of polymerization, 0.01 parts by weight of PHP, 0.0015 parts by weight of EDTA, and 0.001 parts by weight of ferrous sulfate 7-hydrate were added to the system. Ten hours after the start of polymerization, devolatilization was carried out under reduced pressure to remove the residual monomers in the system, thereby ending the polymerization. The system was then cooled to obtain the nucleopolymer latex (C-2).

[0413] Using a nuclear polymer latex (C-2) instead of a nuclear polymer latex (C-1), an aqueous latex (L-6) containing polymer microparticles (B) was obtained in the same manner as in Manufacturing Example 1. The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex was 110 nm.

[0414] Next, aqueous latex (L-6) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-6) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-6) at 25 °C were measured. The results are shown in Table 3.

[0415] (Manufacturing Example 7)

[0416] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 15 parts by weight of St, 5 parts by weight of AN, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Finally, 0.04 parts by weight of TBP was added to the system, and stirring continued for 1 hour to complete the polymerization, yielding an aqueous latex (L-7) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex is 108 nm.

[0417] Next, aqueous latex (L-7) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-7) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-7) at 25 °C were measured. The results are shown in Table 3.

[0418] (Manufacturing Example 8)

[0419] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 7 parts by weight of St, 3 parts by weight of AN, 10 parts by weight of GMA, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-8) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 101 nm.

[0420] Next, aqueous latex (L-8) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-8) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-8) at 25 °C were measured. The results are shown in Table 3.

[0421] (Manufacturing Example 9)

[0422] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 20 parts by weight of GMA and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Finally, 0.04 parts by weight of TBP was added to the system, and stirring continued for 1 hour to complete the polymerization, yielding an aqueous latex (L-9) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex is 112 nm.

[0423] Next, aqueous latex (L-9) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-9) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-9) at 25 °C were measured. The results are shown in Table 3.

[0424] (Manufacturing Example 10)

[0425] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 12 parts by weight of St, 4 parts by weight of AN, 4 parts by weight of 4-hydroxybutyl acrylate, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-10) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 113 nm.

[0426] Next, water-based latex (L-10) was used instead of water-based latex (L-1), and otherwise, masterbatch (M-10) was obtained in the same manner as in Manufacturing Example 1. The viscosity of the obtained masterbatch (M-10) at 25°C was measured. The results are shown in Table 3.

[0427] (Manufacturing Example 11)

[0428] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 12 parts by weight of St, 4 parts by weight of AN, 4 parts by weight of methacrylic acid, and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-11) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 99 nm.

[0429] Next, water-based latex (L-11) was used instead of water-based latex (L-1), and otherwise, masterbatch (M-11) was obtained in the same manner as in Manufacturing Example 1. The viscosity of the obtained masterbatch (M-11) at 25°C was measured. The results are shown in Table 3.

[0430] (Manufacturing Example 12)

[0431] 241 parts by weight of the aforementioned nucleopolymer latex (C-2) (containing 80 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system, followed by 2 parts by weight of TAIC and 0.07 parts by weight of CHP. The mixture was stirred for 60 minutes. Then, a mixture of 12 parts by weight of St, 4 parts by weight of AN, 4 parts by weight of allyl methacrylate (ALMA), and 0.08 parts by weight of TBP was continuously added to the system over 110 minutes. Then, 0.04 parts by weight of TBP were added to the system, and the mixture was stirred for another hour to complete the polymerization, resulting in an aqueous latex (L-12) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) in the obtained aqueous latex was 104 nm.

[0432] Next, aqueous latex (L-12) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-12) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-12) at 25 °C were measured. The results are shown in Table 3.

[0433] (Manufacturing Example 13)

[0434] In a 100L pressure polymerizer, 200 parts by weight of water, 0.03 parts by weight of tripotassium phosphate, 0.25 parts by weight of potassium dihydrogen phosphate, 0.002 parts by weight of disodium ethylenediaminetetraacetate (EDTA), 0.001 parts by weight of ferrous sulfate hexahydrate, and 1.5 parts by weight of sodium dodecylbenzenesulfonate (SDBS) were added. While stirring the added raw materials, oxygen was thoroughly removed from the pressure polymerizer by nitrogen purging. Then, 60 parts by weight of Bd and 40 parts by weight of St were added to the system, and the temperature inside the pressure polymerizer was raised to 45°C. Next, 0.015 parts by weight of p-menthane hydrogen peroxide (PHP) was added to the system, followed by 0.04 parts by weight of sodium formaldehyde sulfoxylate (SFS), and polymerization began. Four hours after the start of polymerization, 0.01 parts by weight of PHP, 0.0015 parts by weight of EDTA, and 0.001 parts by weight of ferrous sulfate 7-hydrate were added to the system. Ten hours after the start of polymerization, devolatilization was carried out under reduced pressure to remove the residual monomers in the system, thereby ending the polymerization. The system was then cooled to obtain the nucleopolymer latex (C-3).

[0435] Using a core polymer latex (C-3) instead of a core polymer latex (C-1), an aqueous latex (L-13) containing polymer microparticles (B) was obtained in the same manner as in Manufacturing Example 1. The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex was 102 nm.

[0436] Next, aqueous latex (L-13) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-13) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz and the viscosity of masterbatch (M-13) at 25 °C were measured. The results are shown in Table 3.

[0437] (Manufacturing Example 14)

[0438] In a glass reactor, 238 parts by weight of deionized water, 0.008 parts by weight of EDTA, 0.002 parts by weight of ferrous sulfate 7-hydrate, 0.26 parts by weight of SFS, and 0.2 parts by weight of SDBS were added. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, a monomer addition device, and an emulsifier addition device. The gas in the glass reactor was purged with nitrogen while the added raw materials were stirred, and the temperature of the glass reactor was raised to 60°C. Next, a mixture of 98 parts by weight of St, 2 parts by weight of ALMA, and 0.03 parts by weight of CHP was continuously added dropwise to the system over 200 minutes. Stirring continued for 0.5 hours after the addition of the mixture to complete the polymerization, yielding a nucleopolymer latex (C-4).

[0439] 230 parts by weight of the aforementioned nucleopolymer latex (C-4) (containing 76.5 parts by weight of the nucleopolymer) and 65 parts by weight of water were added to a glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was purged with nitrogen, and the added raw materials were stirred at 60°C. Next, 0.004 parts by weight of EDTA, 0.001 parts by weight of ferrous sulfate 7-hydrate, and 0.2 parts by weight of SFS were added to the system. Then, a mixture of 20 parts by weight of MMA, 5 parts by weight of GMA, and 0.09 parts by weight of tert-butyl hydroperoxide (TBP) was continuously added to the system over 130 minutes. Finally, 0.04 parts by weight of TBP was added to the system, and stirring continued for 1 hour to complete the polymerization, yielding an aqueous latex (L-14) containing polymer microparticles (B). The volume average particle size of the polymer microparticles (B) contained in the obtained aqueous latex is 122 nm.

[0440] Next, aqueous latex (L-14) was used instead of aqueous latex (L-1), and otherwise, masterbatch (M-14) was obtained in the same manner as in Manufacturing Example 1. The dielectric loss tangent of the obtained polymer particles (B) at a frequency of 10 GHz was measured. The results are shown in Table 3.

[0441] The components and their amounts (by weight) of the nuclear polymer latex (C-1) to (C-4) are summarized in Table 1 below. Additionally, the components and their amounts (by weight) of the polymer microparticles (B) manufactured in Manufacturing Examples 1 to 14 (M-1 to M-14) are summarized in Tables 2 and 3 below.

[0442] [Table 1]

[0443] (Table 1)

[0444]

[0445]

[0446]

[0447] (Examples 1-9, Comparative Examples 1-15)

[0448] The components shown in Tables 4-6 were mixed with methyl ethyl ketone to achieve a solid content of 50% by weight. The resulting mixture was stirred at room temperature (25°C) to obtain a resin varnish.

[0449] The glass cloth was impregnated with the obtained resin varnish, thereby allowing the resin varnish to penetrate the glass cloth. Then, the glass cloth was dried at 120°C for 5 minutes to obtain a prepreg (resin content: 50% by mass).

[0450] Next, the eight prepreg sheets were reassembled and stacked to obtain the first laminate. Copper foil (HS2-VSP (Rz = 1 μm) or SI-VSP (Rz = 0.5 μm)) with a thickness of 35 μm was then stacked on both sides of the first laminate to obtain the second laminate. The second laminate was heated at 200 °C for 60 minutes under a pressure of 3 MPa to obtain a metal-clad laminate with a thickness of 1.6 mm.

[0451] The 90° peel strength of the obtained metal-clad laminate was measured. The results are shown in Tables 4-6.

[0452] Furthermore, the glass transition temperatures of the metal-clad laminates obtained in Examples 1 to 9 were measured, and all results were above 200°C. For example, the glass transition temperature of the metal-clad laminate in Example 3 was 241°C, the glass transition temperature of the metal-clad laminate in Example 4 was 239°C, and the glass transition temperature of the metal-clad laminate in Example 5 was 238°C. That is, the metal-clad laminates obtained in Examples 1 to 9 all exhibit good heat resistance.

[0453]

[0454]

[0455]

[0456] As shown in Table 4, the copper foil peel strength (copper foil: HS2-VSP) of the metal-clad laminates of Examples 1 to 7, which used TAIC as a crosslinking agent, all exceeded 0.50 N / mm, and the dielectric loss tangent of the polymer particles (B) was less than 0.0060°, thus taking into account both dielectric properties and the adhesion between the insulating layer and the metal foil.

[0457] In addition, as shown in Table 6, the copper foil peel strength (copper foil: HS2-VSP) of the metal-clad laminates of Examples 8 and 9, which used Ricon100 as a crosslinking agent, both exceeded 0.60 N / mm, and the copper foil peel strength (copper foil: SI-VSP) both exceeded 0.40 N / mm. Furthermore, the dielectric loss tangent of the polymer particles (B) was less than 0.0060°, thus taking into account both dielectric properties and the adhesion between the insulating layer and the metal foil.

[0458] Therefore, the copper foil peel strength of the metal-clad laminates in Examples 1-9 is high, and the dielectric loss tangent is low, thus balancing dielectric properties and the adhesion between the insulating layer and the metal foil. It should be noted that the dielectric properties (dielectric loss tangent) of the metal-clad laminate are related to the dielectric properties (dielectric loss tangent) of the polymer particles (B) contained in the metal-clad laminate.

[0459] Furthermore, by including structural units from divinylbenzene (monomer b) in addition to structural units from styrene (monomer a) and glycidyl methacrylate (monomer c) in the grafted portion of the polymer microparticles (B) of Manufacturing Examples 3-5, the viscosity of the masterbatch is reduced and the processability is excellent compared to the case without these structural units (Manufacturing Example 1). Because the masterbatch has low viscosity, the viscosity increase of the resin varnish can be suppressed. Therefore, the prepregs obtained in Examples 3-9 were manufactured using the masterbatch (M-3 to M-5) of Manufacturing Examples 3-5, resulting in excellent surface properties.

[0460] Furthermore, based on the comparison of Examples 5 to 7, the metal-clad laminate manufactured using masterbatch (M-3) without other compounds (monomers other than monomer a, monomer b, and monomer c) in the grafted portion (Example 5) compared to the metal-clad laminate manufactured using masterbatch (M-4 to M-5) containing other compounds (Examples 6 to 7) achieved a high level of balance between the adhesion between the insulation layer and the metal foil and the dielectric properties of the metal-clad laminate. In addition, due to the low viscosity of the masterbatch, the surface properties of the prepreg are excellent.

[0461] In contrast, compared with Examples 1 to 9 containing polymer particles (B), Comparative Examples 1 and 15, which do not contain polymer particles (B), show reduced copper foil peel strength and poor adhesion between the insulation layer and the metal foil.

[0462] Furthermore, compared to the polymer microparticles (B) of Manufacturing Examples 6-14, which do not satisfy the composition of the present invention in the composition of the core polymer and / or graft portion, and the metal-clad laminates of Comparative Examples 2-14, which are manufactured using the same polymer microparticles (B) and have the same amount of polymer microparticles (B), the dielectric properties and the adhesion between the insulating layer and the metal foil are inferior in either or both.

[0463] Industrial applicability

[0464] According to one embodiment of the present invention, a metal-clad laminate with excellent dielectric properties and excellent adhesion between the insulating layer and the metal foil can be provided. Therefore, one embodiment of the present invention can be suitably used in electronic components in electronic devices such as servers, millimeter-wave radars, and mobile devices.

Claims

1. A metal-clad laminate comprising: an insulating layer containing a resin composition and a fibrous base material, and a metal foil in contact with the insulating layer, wherein the resin composition contains a resin (A) having a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and polymer fine particles (B), the polymer fine particles (B) satisfy the following conditions (i) and (ii): (i) a volume average particle diameter of 10 nm to 400 nm; and (ii) containing a core-shell copolymer having a core polymer, and a grafted portion grafted to the core polymer, the core polymer contains, as a constitutional unit, a constitutional unit derived from an aromatic vinyl compound having one vinyl group, and a constitutional unit derived from an aromatic vinyl compound having two or more vinyl groups, the grafted portion contains, as a constitutional unit, a constitutional unit derived from an aromatic vinyl compound having one vinyl group, and a constitutional unit derived from a (meth)acrylate having an epoxy group, a surface ten-point average roughness (Rz) of the metal foil is 2.0 μm or less, and the grafted portion further contains, as a constitutional unit, a constitutional unit derived from an aromatic vinyl compound having two or more vinyl groups.

2. The metal-clad laminate according to claim 1, wherein the core polymer is crosslinked.

3. The metal-clad laminate according to claim 1 or 2, wherein the grafted portion is crosslinked.

4. The metal-clad laminate according to claim 1 or 2, wherein, in the core polymer, a content of the constitutional unit derived from the aromatic vinyl compound having one vinyl group is 50% by weight or more, based on 100% by weight of the core polymer.

5. The metal-clad laminate according to claim 1 or 2, wherein, in the core polymer, a total content of the constitutional unit derived from the aromatic vinyl compound having one vinyl group and the constitutional unit derived from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more, based on 100% by weight of the core polymer.

6. The metal-clad laminate according to claim 1 or 2, wherein, in the grafted portion, a total content of the constitutional unit derived from the aromatic vinyl compound having one vinyl group and the constitutional unit derived from the aromatic vinyl compound having two or more vinyl groups is 50.0% by weight or more, based on 100% by weight of the grafted portion.

7. The metal-clad laminate according to claim 1 or 2, wherein, in the grafted portion, a content of the constitutional unit derived from the aromatic vinyl compound having one vinyl group is 50% by weight or more, based on 100% by weight of the grafted portion.

8. The metal-clad laminate according to claim 1 or 2, wherein the polymer fine particles (B) have a dielectric loss tangent (Df) of 0.0060 or less at 10 GHz. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. A printed wiring board comprising the metal-clad laminate according to any one of claims 1 to 8.

10. A method for producing the metal-clad laminate according to any one of claims 1 to 8, the method comprising: a step of preparing a master batch in which polymer fine particles (B) are dispersed in a solvent comprising methyl ethyl ketone; a step of preparing a resin varnish by mixing the master batch, a resin (A) having a dielectric loss tangent (Df) of 0.0100 or less at 10 GHz, and a solvent; a step of preparing a prepreg by impregnating the resin varnish in a glass cloth; and a step of laminating a metal foil to the prepreg, wherein the polymer fine particles (B) satisfy the following conditions (i) and (ii): (i) a volume average particle diameter of 10 nm to 400 nm; and (ii) a core-shell copolymer having a core polymer and a graft portion grafted to the core polymer, the core polymer containing, as a constitutional unit, a constitutional unit derived from an aromatic vinyl compound having one vinyl group and a constitutional unit derived from an aromatic vinyl compound having two or more vinyl groups, the graft portion containing, as a constitutional unit, a constitutional unit derived from an aromatic vinyl compound having one vinyl group and a constitutional unit derived from a (meth)acrylate having an epoxy group, and the metal foil has a ten-point average roughness (Rz) of 2.0 μm or less at a boundary surface with the prepreg. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images