Prepreg, metal-coated laminate and printed wiring board

Abstract

The present invention discloses a prepreg that combines excellent heat resistance of the cured material with excellent small-diameter openings for solder resist formation on a printed circuit board. The prepreg (1) comprises at least one of a resin composition and a semi-cured form of the resin composition; and a fibrous substrate (11). The resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C). The thermosetting resin (A) comprises an epoxy resin (A1). The cured form of the prepreg (1) has a glass transition temperature of 200°C or higher, and a reflectance of light with a wavelength of 365 nm or higher and 405 nm or lower of 20% or less.

Description

[Technical Field]

[0001] This disclosure generally relates to prepregs, metal-coated laminates and printed wiring boards, and more specifically to prepregs containing epoxy resin, metal-coated laminates and printed wiring boards. [Previous Technology]

[0002] Printed wiring boards are widely used in various fields such as electronic machines, communication machines, and computers. In recent years, in particular, the multi-functionality, high performance, thinness, and miniaturization of small machines such as recording media, portable communication terminals, and notebook PCs have progressed rapidly. Consequently, printed wiring boards used in these products are also pursuing high performance in terms of conductor wiring miniaturization, high density, multi-layer conductor wiring, thinness, and mechanical properties.

[0003] As a material for the printed wiring board, Patent Document 1 discloses a prepreg. The prepreg comprises a substrate and a resin layer. The resin layer is formed from a semi-cured resin composition impregnated into the substrate. The resin composition contains an epoxy compound, a maleimide compound having an N-phenylmaleimide structure, a phenolic compound, a core and outer shell rubber, and an inorganic filler. Furthermore, relative to a total of 100 parts by mass of the epoxy compound, maleimide compound, and phenolic compound, the content of the maleimide compound is in the range of 10 parts by mass or more and less than 40 parts by mass.

[0004] However, although the hardened prepreg described in Patent Document 1 has a high glass transfer temperature, it easily reflects light in the main wavelength region of 365nm to 405nm used by metal halide lamps or UV LED light sources for curing general ultraviolet-cured resins. That is, light in this wavelength region is reflected and scattered on the surface of the hardened material. Therefore, for solder resist formed on a printed circuit board having an insulating layer containing the aforementioned hardened material, undesirable reactions may occur due to the reflection and scattering of light in this wavelength region on the surface of the insulating layer. In other words, the solder resist reaction caused by exposure to light in this wavelength region cannot be controlled. Accordingly, when forming solder resist on a printed circuit board produced using the aforementioned prepreg, and forming an opening by exposing and developing the solder resist with light in this wavelength region, the smaller the inner diameter of the opening, the worse its shape may be. That is, there may be a problem with poor small-diameter opening performance. Previous Art Documents

[0005] Patent Document Patent Document 1: International Publication No. 2020 / 121734 [Summary of the Invention]

[0006] The purpose of this disclosure is to provide a prepreg, a metal-clad laminate, and a printed wiring board that can take into account both the excellent heat resistance of the hardened material and the excellent small-diameter opening of the solder resist formed on the printed wiring board.

[0007] The present invention discloses a prepreg comprising: at least one of a resin composition and a semi-cured form of the aforementioned resin composition; and a fibrous substrate. The aforementioned resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C). The aforementioned thermosetting resin (A) comprises an epoxy resin (Al). The cured form of the aforementioned prepreg has a glass transition temperature of 200°C or higher, and a reflectance of light with a wavelength of 365 nm or higher and 405 nm or lower of 20% or less.

[0008] The present invention discloses a metal-clad laminate comprising: an insulating layer comprising a hardened prepreg; and a metal layer.

[0009] The present invention discloses a printed wiring board comprising: an insulating layer comprising a hardened prepreg; and conductor wiring.

Implementation Method

[0016] 1. Summary The prepreg 1 of this embodiment comprises at least one of a resin composition and a semi-cured form of the resin composition; and a fibrous substrate 11. The resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C). The thermosetting resin (A) includes an epoxy resin (A1). The glass transition temperature (Tg) of the cured form of the prepreg 1 is 200°C or higher, and the reflectance of light with a wavelength of 365 nm or higher and 405 nm or lower is 20% or lower.

[0017] As described above, the prepreg 1 comprises a resin layer 10 containing the aforementioned resin composition or a semi-cured form of the resin composition, and the aforementioned resin composition contains the aforementioned components and thus possesses the aforementioned characteristics. Therefore, the printed circuit board 3 manufactured using the prepreg 1 can have good small-diameter opening properties of the solder resist layer (SR) 6 formed on its surface (see Figure 4). Specifically, firstly, solder resist 6 is formed on the printed circuit board 3 manufactured using the prepreg 1. The formed solder resist 6 is exposed to irradiation light in the wavelength range of 365 nm and above and 405 nm and below through a photomask, causing the desired portion of the solder resist 6 to react. Here, the insulating layer 30 of the printed circuit board 3 manufactured using the prepreg 1 can suppress the reflection and scattering of irradiation light in the wavelength range reaching its surface. Therefore, the reaction of the undesired portion of the solder resist 6 formed on the printed circuit board 3 can be suppressed or prevented. Afterward, the solder resist 6 can be formed into the desired shape using a developing solution. That is, the excellent small-diameter opening properties of the solder mask 6 mean that the removal of the solder mask 6 can be carried out more precisely and accurately. In other words, by using the prepreg 1 to manufacture the printed wiring board 3, it is possible to help to miniaturize and increase the density of the conductor wiring 31 on the printed wiring board 3.

[0018] Furthermore, the solder resist 6 may use materials with known compositions, such as epoxy resin, polyimide resin, polyphenylene ether resin, aromatic polyene resin, etc. In addition, a negative solder resist is one that reacts in the light-irradiated part but does not dissolve in the developer; a positive solder resist is one that reacts in the light-irradiated part but dissolves in the developer.

[0019] Furthermore, in this disclosure, small-diameter aperture quality means that the aperture portion 5 formed on the solder mask 6 by exposure and development using irradiation light in that wavelength region has a good shape. Also, small diameter refers to a roughly circular shape with a diameter of 100µm or less.

[0020] Furthermore, since the glass transition temperature of the hardened prepreg 1 is above 200°C, the hardened prepreg 1 can also have excellent heat resistance.

[0021] That is, according to this embodiment, a prepreg 1, a metal-clad laminate 2, and a printed wiring board 3 can be obtained that can simultaneously achieve excellent heat resistance of the hardened material and excellent small-diameter opening properties of the solder resist 6 formed on the printed wiring board 3. We believe that by using at least one of the prepreg 1 and the metal-clad laminate 2 to manufacture the printed wiring board 3, the printed wiring board 3 can be endowed with excellent heat resistance, and it is beneficial to the miniaturization and high density of the conductor wiring 31 on the surface of the printed wiring board 3. 2. Detailed contents (1) Prepreg

[0022] The prepreg 1 of this embodiment can be used, for example, as a material for metal-clad laminate 2, a material for printed wiring board 3, and for multilayering (addition layering) of printed wiring board 3.

[0023] The prepreg 1 comprises at least one of a resin composition and a semi-cured form of the resin composition; and a fibrous substrate 11. The resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C). The thermosetting resin (A) includes an epoxy resin (A1).

[0024] The glass transition temperature of the cured prepreg 1 is 200°C or higher, preferably 205°C or higher, and more preferably 210°C or higher. This allows the cured prepreg 1 to possess excellent heat resistance. Furthermore, the upper limit of the aforementioned glass transition temperature is, for example, 400°C, but there is no particular limitation.

[0025] The reflectance of light with wavelengths of 365 nm or higher and 405 nm or lower in the hardened prepreg 1 is 20% or less. Therefore, the printed circuit board 3 manufactured using the prepreg 1 can have excellent small-diameter opening properties of the solder resist layer 6 formed on its surface. Specifically, firstly, solder resist 6 is formed on the printed circuit board 3 manufactured using the prepreg 1. The formed solder resist 6 is exposed to irradiation light in the aforementioned wavelength range through a photomask, causing the desired portion of the solder resist 6 to react. Here, the insulating layer 30 of the printed circuit board 3 manufactured using the prepreg 1 can suppress the reflection and scattering of irradiation light in the aforementioned wavelength range reaching its surface. Therefore, the reaction of the undesirable portion of the solder resist 6 formed on the printed circuit board 3 can be suppressed or prevented. Afterwards, the solder resist 6 can be formed into the desired shape using a developing solution. That is, by using the prepreg 1 to manufacture the printed wiring board 3, it is possible to help to miniaturize and increase the density of the conductor wiring 31 on the printed wiring board 3.

[0026] Furthermore, as long as the prepreg 1 is manufactured using a conventional manufacturing method, the surface roughness of its cured form will not affect the reflectivity. That is, the reflectivity of the cured form of the prepreg 1 is not affected by the surface roughness, but depends solely on the composition of the resin composition. Therefore, the cured form of the prepreg 1 manufactured using the aforementioned resin composition is not affected by the surface roughness, and the reflectivity of light with wavelengths of 365 nm and above and 405 nm and below can reach 20% or less. The surface roughness of the cured form of the prepreg 1 is, for example, expressed as an arithmetic mean roughness Sa. This arithmetic mean height Sa is not particularly limited, and is, for example, 0.01 µm or more and 2 µm or less.

[0027] The prepreg 1 is one type of resin-impregnated substrate. The resin-impregnated substrate is a fibrous substrate impregnated with a resin composition or a semi-cured resin composition. Examples of resin-impregnated substrates other than the prepreg 1 include resin cloth.

[0028] The following describes the composition and manufacturing method of the prepreg 1. (1.1) Composition of the prepreg <resin composition>

[0029] The resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C). Therefore, the resin composition may be thermosetting. The thermosetting resin (A) includes an epoxy resin (A1).

[0030] The resin composition is adjusted, for example, in the following manner: a thermosetting resin (A) containing epoxy resin (A1), a coumarin compound (B) and an inorganic filler (C) are blended, diluted with a suitable solvent, and then stirred and mixed to homogenize it.

[0031] The following describes the composition of the resin composition. Furthermore, in this disclosure, parts by mass and percentage by mass refer only to the mass of each component, excluding the mass of the solvent. ≪Thermosetting Resin (A)≫

[0032] The resin composition as described above contains a thermosetting resin (A). The thermosetting resin (A) contains a thermosetting compound. When heated, the thermosetting compound undergoes a polymerization reaction, causing the molecular chains to cross-link and form a three-dimensional polymer network structure, thus hardening.

[0033] The thermosetting resin (A) includes epoxy resin (A1) as described above. Furthermore, the thermosetting resin (A) may also include thermosetting compounds other than epoxy resin (A1). Specifically, phenolic resin (A2) may be an example of such a thermosetting compound. Moreover, the thermosetting resin (A) may further include thermosetting compounds other than epoxy resin (A1) and phenolic resin (A2). Examples of such thermosetting compounds include, for example, benzo[a]pyrene resin, polyphenylene ether resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polysiloxane resin, polyurethane resin, polyimide resin, acrylic resin, methacrylic resin, etc., but there are no particular limitations. The thermosetting resin (A) contained in the resin composition may be only one type or may be two or more types.

[0034] The thermosetting resin (A) should preferably not contain maleimide resin as a thermosetting compound. If the thermosetting resin (A) contains maleimide resin, the crosslinking density of the cured resin composition will increase, which may lead to brittleness and reduced toughness. Furthermore, maleimide resin is a compound having one or more maleimide groups within a single molecule. [Epoxy resin (A1)]

[0035] The thermosetting resin (A) includes epoxy resin (A1) as described above. Epoxy resin (A1) is a component that can improve the glass transition temperature, adhesion to metals and glass, heat resistance, electrical insulation, flame retardancy, etc. of the cured prepreg 1.

[0036] Epoxy resin (A1) is a compound having one or more epoxy groups in a molecule. Epoxy resin (A1) can be solid or liquid at 25°C.

[0037] Examples of epoxy resin (A1) include: bisphenol type epoxy resin, phenolic varnish type epoxy resin, biphenyl type epoxy resin, alkylene type epoxy resin, arylalkylene type epoxy resin, naphthalene type epoxy resin, naphthalene skeleton modified epoxy resin, triphenylmethane type epoxy resin, anthracene type epoxy resin, dicyclopentadiene type epoxy resin, norphenene type epoxy resin, stilbene type epoxy resin, phosphorus-containing epoxy resin with phosphorus atoms introduced into the above epoxy resins, etc., but there is no particular limitation. The thermosetting resin (A) may contain only one type of epoxy resin (A1) or two or more types.

[0038] Examples of bisphenol type epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, etc., but there are no particular limitations.

[0039] Examples of phenolic varnish-type epoxy resins include: phenolic varnish-type epoxy resins, cresol varnish-type epoxy resins, etc., but there are no particular limitations.

[0040] Examples of arylalkyl epoxy resins include: phenol arylalkyl epoxy resin, biphenyl arylalkyl epoxy resin, biphenyl phenolic varnish epoxy resin, biphenyl dimethyl epoxy resin, triphenol phenolic varnish epoxy resin, tetramethyl biphenyl epoxy resin, etc., but there are no particular limitations.

[0041] Examples of naphthalene skeleton modified epoxy resins include: naphthalene skeleton modified cresol phenolic varnish type epoxy resin, naphthalene glycol aralkyl type epoxy resin, naphthol aralkyl type epoxy resin, methoxynaphthalene modified cresol phenolic varnish type epoxy resin, methoxynaphthalene dimethylene type epoxy resin, etc., but there are no particular limitations.

[0042] Furthermore, epoxy resins (A1) are not necessarily classified into only one type. For example, biphenyl alkyl type epoxy resins can be classified not only as arylalkyl type epoxy resins, but also as biphenyl type epoxy resins.

[0043] The epoxy resin (A1) preferably includes at least one selected from the group consisting of biphenyl-type epoxy resins, naphthalene-type epoxy resins, and dicyclopentadiene-type epoxy resins. In this case, the glass transition temperature, heat resistance, and flame retardancy of the cured prepreg 1 can be improved. Furthermore, the biphenyl-type epoxy resin preferably includes at least one of biphenyl phenolic varnish-type epoxy resins and biphenyl aralkyl-type epoxy resins.

[0044] The content of epoxy resin (A1) relative to the total amount of thermosetting resin (A) should preferably be 20% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more. In this case, the glass transition temperature, adhesion to metals and glass, heat resistance, flame retardancy, and electrical insulation of the cured prepreg 1 can be improved. Furthermore, there is no particular upper limit to the content of epoxy resin (A1), and it can also be 100% by mass relative to the total amount of thermosetting resin (A). That is, only epoxy resin (A1) may be used for thermosetting resin (A).

[0045] The epoxy equivalent of the epoxy resin (A1) should preferably be 100 g / eq. or more, and more preferably 150 g / eq. or more. Furthermore, the epoxy equivalent of the epoxy resin (A1) should preferably be 350 g / eq. or less, and more preferably 300 g / eq. or less. [Phenolic resin (A2)]

[0046] The thermosetting resin (A) may also include phenolic resin (A2). Phenolic resin (A2) is a component that can improve the glass transition temperature, heat resistance, etc. of the cured prepreg 1.

[0047] Phenolic resin (A2) can react with epoxy resin (A1). Phenolic resin (A2) has phenolic hydroxyl groups in its molecule. Phenolic resin (A2) can be solid or liquid at 25°C.

[0048] Examples of phenolic resins (A2) include: biphenyl aryl phenolic resins, phenyl aryl phenolic resins, phenolic varnish-type phenolic resins, cresol phenolic varnish-type phenolic resins, bisphenol A phenolic varnish-type phenolic resins, naphthol-type phenolic resins, tetraphenol-type phenolic resins, and phosphorus-containing phenolic resins in which phosphorus atoms are introduced, etc., but there are no particular limitations. The thermosetting resin (A) may contain only one type of phenolic resin (A2) or two or more types.

[0049] The phenolic resin (A2) preferably includes at least one of a naphthyl phenolic resin and a biphenyl phenolic resin. In this case, the glass transition temperature and heat resistance of the cured prepreg 1 can be increased.

[0050] The content of phenolic resin (A2) relative to the total amount of thermosetting resin (A) should preferably be 10% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more. In this case, the glass transition temperature and heat resistance of the cured prepreg 1 can be increased. Furthermore, the content of phenolic resin (A2) relative to the total amount of thermosetting resin (A) should preferably be 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. In this case, the reduction of brittleness of the cured prepreg 1 can be suppressed.

[0051] The phenolic hydroxyl equivalent of the phenolic resin (A2) should preferably be 100 g / eq. or more, and more preferably 120 g / eq. or more. Furthermore, the phenolic hydroxyl equivalent of the phenolic resin (A2) should preferably be 650 g / eq. or less, and more preferably 600 g / eq. or less.

[0052] When the thermosetting resin (A) contains phenolic resin (A2), the mass ratio of epoxy resin (A1) to phenolic resin (A2) is preferably 5:1 to 1:2, and more preferably 5:2 to 2:3. In this case, the glass transition temperature and heat resistance of the cured prepreg 1 can be increased. ≪Coumarin compound (B)≫

[0053] The resin composition as described above contains coumarin compound (B). Coumarin compound (B) has a coumarin skeleton. The coumarin skeleton is an aromatic compound formed by the condensation of a lactone ring and an aromatic ring. Since coumarin compound (B) has good absorbance for irradiation light in the above-mentioned wavelength region, the reflectivity of the hardened prepreg 1 for light with wavelengths above 365 nm and below 405 nm can be reduced.

[0054] The coumarin compound (B) preferably comprises at least one of the following formulas (1) and (2): [Chemical Formula 1][Chemical Formula 2]

[0055] In formulas (1) and (2), R1 and R2 independently represent hydrogen atoms, alkyl groups, aryl groups, or hydroxyalkyl groups, respectively. R3, R4, and R5 independently represent hydrogen atoms, alkyl groups, or aryl groups, respectively. Furthermore, there is no particular limitation on the number of carbon atoms in alkyl and hydroxyalkyl groups. Also, alkyl and hydroxyalkyl groups can be straight-chain or branched, and the number of carbon atoms can be, for example, 8 or less, but there is no particular limitation. R1 to R5 can also be bonded to other substituents to form a ring structure.

[0056] Examples of coumarin compounds (B1) include coumarin, 4-methylcoumarin, 7-amino-4-methylcoumarin, etc., but there are no particular limitations. The resin composition may contain only one or more coumarin compounds (B1).

[0057] The absorbance and absorption wavelength of coumarin compound (B) can be changed by introducing substituents. For example, by introducing an electron-donating group into the 7-position of coumarin compound (B), the electron-donating group and the electron-withdrawing group will coexist in the molecule of coumarin compound (B) and generate charge transfer within the molecule, thus resulting in greater absorbance.

[0058] The absorbance of coumarin compound (B) depends on the number of molecules. The more molecules there are, that is, the larger the mole number of the molecules, the greater the absorbance.

[0059] The content of coumarin compound (B) is preferably 0.1% by mass or more, more preferably 1.5% by mass or more, and more preferably 2.0% by mass or more, relative to the total amount of thermosetting resin (A) and coumarin compound (B). In this case, the reflectivity of the cured prepreg 1 at wavelengths of 365 nm or more and 405 nm or less can be reduced. Furthermore, the content of coumarin compound (B) is preferably 10% by mass or less, more preferably 7% by mass or less, and more preferably 6% by mass or less, relative to the total amount of thermosetting resin (A) and coumarin compound (B). In this case, the decrease in glass transition temperature of the cured prepreg 1 can be suppressed. ≪Inorganic filler (C)≫

[0060] The resin composition as described above contains inorganic filler (C). Inorganic filler (C) can reduce the coefficient of thermal expansion of the cured prepreg 1.

[0061] Inorganic filler (C) may include, for example, fused silica or crystalline silica, talc, boehmite, magnesium hydroxide, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, clay, mica, etc., but is not particularly limited. The resin composition may contain only one type of inorganic filler (C) or two or more types.

[0062] The inorganic filler (C) preferably includes at least one filler selected from the group consisting of silica, talc, boehmite, magnesium hydroxide and aluminum hydroxide. In this case, the coefficient of thermal expansion of the hardened prepreg 1 can be reduced.

[0063] In order to improve the affinity with thermosetting resins (A) and prevent aggregation, the inorganic filler (C) may also be surface-treated. Examples of surface treatments include aminosilane treatment, mercaptosilane treatment, and alkoxysilane treatment, but there are no particular limitations.

[0064] The average particle size (D50) of the inorganic filler (C) should preferably be 0.1 µm or more. Furthermore, the average particle size of the inorganic filler (C) should preferably be 10 µm or less. Here, in this disclosure, "average particle size" means the particle size that accounts for 50% of the cumulative value in the particle size distribution of the volume reference obtained by laser diffraction scattering method.

[0065] The content of inorganic filler (C) should preferably be 50 parts by mass or more, and more preferably 75 parts by mass or more, relative to 100 parts by mass of the total thermosetting resin (A) and coumarin compound (B). In this case, the coefficient of thermal expansion of the cured prepreg 1 can be reduced. Furthermore, the content of inorganic filler (C) should preferably be 300 parts by mass or less, and more preferably 250 parts by mass or less, relative to 100 parts by mass of the total thermosetting resin (A) and coumarin compound (B). In this case, the reduction in adhesion and crack resistance of the cured prepreg 1 can be suppressed. ≪Amine compound (D)≫

[0066] The resin composition may also contain an amine compound (D) that does not have a coumarin skeleton. Thus, the amine compound (D) is a different compound from the coumarin compound (B1) shown in formula (2). The amine compound (D) has the following function: it acts as a hardener or hardening accelerator in the crosslinking (hardening) reaction of the thermosetting resin (A), thereby assisting the crosslinking reaction.

[0067] Amino compounds (D) can be exemplified by aromatic amine compounds, fatty acid amine compounds, etc.

[0068] Examples of aromatic amine compounds include imidazole compounds such as 2-methylimidazole and 2-ethyl-4-methylimidazole, but there are no particular limitations. Aromatic amine compounds preferably include imidazole compounds.

[0069] Examples of aliphatic amine compounds include alicyclic amine compounds such as dicyandiamide (DICY), diazabicycloundecene (DBU), and isophorone diamine (IPDA), and chain aliphatic amine compounds such as diethylenetriamine (DTA) and triethylenetriamine (TTA), but there are no particular limitations. Aliphatic amine compounds preferably include dicyandiamide.

[0070] The amine compound (D) contained in the resin composition may be only one type or may be two or more types.

[0071] Relative to 100 parts by mass of the thermosetting resin (A) and the coumarin compound (B), the content of the amine compound (D) should preferably be 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, and even more preferably 0.05 parts by mass or more. Furthermore, relative to 100 parts by mass of the thermosetting resin (A) and the coumarin compound (B), the content of the amine compound (D) should preferably be 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less. ≪Additives≫

[0072] As long as the additives do not impair the effect of this embodiment, there are no particular limitations on their composition and content.

[0073] Additives may include, for example: hardeners and hardening accelerators other than amine compounds (D), core and shell rubbers, thermoplastic resins, flame retardants, colorants, coupling agents, heat stabilizers, antioxidants, reaction initiators, defoamers, antistatic agents, dyes, pigments, polymerization inhibitors, lubricants, etc., but there are no particular limitations.

[0074] Curing agents and curing accelerators other than amine compounds (D) include, for example, acid anhydrides, cyanate ester compounds, triphenylphosphine, thiols, and metal soaps, as well as organic acid-metal salts. ≪Preparation Method of Resin Composition≫

[0075] Methods for preparing the resin composition may include, for example, mixing epoxy resin (A1) as a thermosetting resin (A), coumarin compound (B), and inorganic filler (C) in a predetermined amount, but there are no particular limitations. In addition, phenolic resin (A2), amine compound (D), and additives may be added as needed and mixed.

[0076] Furthermore, the resin composition may also contain organic solvents. That is, the resin composition should preferably be used in the form of a varnish-like resin composition containing organic solvents. In addition, a varnish-like resin composition refers to one in which organic solvents are further added in addition to the components contained in the above-mentioned resin composition.

[0077] The resin composition in the varnish state described above is prepared in the following manner. First, the components of the resin composition that are soluble in organic solvents are added to an organic solvent and stirred to mix them, thereby preparing a mixture. Alternatively, the mixture can be prepared by stirring while heating. Next, the components that are insoluble in organic solvents are added to the mixture and dispersed using a ball mill, bead mill, or planetary mixer until the desired dispersion state is achieved, thereby preparing the resin composition in the varnish state. Furthermore, the organic solvent used here is not particularly limited, but it is preferable to be one that can dissolve thermosetting resins (A), coumarin compounds (B), etc., and does not hinder the curing reaction of the resin composition. Examples of organic solvents include toluene and methyl ethyl ketone (MEK), but there are no particular limitations. (1.2) Method for manufacturing prepreg

[0078] Figure 1 shows an example of the prepreg 1 of this embodiment. The prepreg 1 is integrally in the form of a film or sheet. The prepreg 1 can be used to manufacture metal-clad laminates 2 and printed wiring boards 3. Specifically, the prepreg 1 can be used as a material for metal-clad laminates 2, a material for printed wiring boards 3, and for multilayering (additional layering) of printed wiring boards 3.

[0079] The prepreg 1 comprises at least one of a resin composition and a semi-cured resin composition as described above. Furthermore, as shown in FIG. 1, the prepreg 1 may also include a resin layer 10. That is, the resin layer 10 comprises at least one of a resin composition and a semi-cured resin composition. The resin layer 10 further comprises a fibrous substrate 11. That is, the prepreg 1 may also include a resin layer 10, which comprises at least one of a resin composition and a semi-cured resin composition within the fibrous substrate 11.

[0080] Furthermore, the prepreg 1 obtained using the resin composition, as described above, may be a semi-cured material containing the resin composition, or it may be a material containing an uncured resin composition, i.e., an uncured material containing the resin composition.

[0081] Furthermore, in this embodiment, the resin composition is an uncured material, which is soluble and fusible in a certain liquid in its initial stage. That is, the uncured resin composition is in stage A.

[0082] Furthermore, in this embodiment, a semi-cured material refers to a resin composition that has been partially cured to a degree that allows for further curing. For example, when the resin composition of this embodiment is heated, its viscosity decreases slowly at the beginning of heating, but increases slowly as the resin composition begins to harden. Thus, a semi-cured material is a resin composition in a semi-cured state, that is, a resin composition that has undergone stage B curing.

[0083] As described above, the prepreg 1 may also include a resin layer 10, which is at least one of a resin composition and a semi-cured form of the resin composition impregnated in the fibrous substrate 11. When impregnating at least one of the resin composition and the semi-cured form of the resin composition into the fibrous substrate 11, a varnish made of the resin composition is preferably used.

[0084] As shown in Figure 1, the prepreg 1 has one fibrous substrate 11, but may also have two or more fibrous substrates 11.

[0085] The fibrous substrate 11 is a reinforcing material, and examples include: glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, lint paper, etc., but there are no particular limitations. In particular, by using glass cloth, laminates with excellent mechanical strength can be obtained. There are no particular limitations on the type of glass used in the glass cloth, and examples include E glass, S glass, Q glass, T glass, TS glass, NE glass, and L glass. Furthermore, when the prepreg 1 uses glass cloth as the fibrous substrate 11, the prepreg 1 can achieve the effect of this invention without being affected by the type of glass used in the glass cloth. The glass cloth should preferably undergo a flattening process. The flattening process can specifically be a method of continuously pressing the glass cloth with a pressure roller under appropriate pressure to compress the yarn into a flat shape. In addition, the thickness of the fibrous substrate 11 generally used is, for example, 10µm or more and 180µm or less, but there are no particular limitations. Glass cloth contains glass fibers, but may also contain reinforcing fibers other than glass fibers. The glass cloth may also undergo surface treatment with a coupling agent or the like before being impregnated with the resin composition in a varnish state. Surface treatment improves the adhesion between the glass cloth and the resin composition. Surface treatments may include, for example, treatment of the aforementioned inorganic filler (C), but are not particularly limited.

[0086] The thickness of the prepreg 1 is, for example, in the range of 10µm or more and 200µm or less, but there is no particular limitation.

[0087] Furthermore, to obtain the resin layer 10, the varnish is impregnated into the fibrous substrate 11 by immersing it in varnish or by coating the fibrous substrate 11 with varnish. However, the impregnation can be repeated several times as needed. Also, at this time, the resin layer 10 containing the desired composition and impregnation amount of resin composition or a semi-cured resin composition can be obtained by repeatedly impregnating with several varnishes of different compositions and concentrations.

[0088] Furthermore, regarding the method of producing the prepreg 1, for example, the resin layer 10 may be heated to reduce or remove the organic solvent from the resin layer 10, wherein the resin layer 10 is produced by impregnating the fibrous substrate 11 with a varnish containing resin components and organic solvent. The conditions for heating the resin layer 10 to reduce or remove the organic solvent from the resin layer 10 are, for example, a temperature of 80°C or higher and 180°C or lower, and a time of 1 minute or higher and 10 minutes or lower.

[0089] Furthermore, the method for manufacturing a prepreg 1 comprising at least one of a resin composition and a semi-cured form of the resin composition and a fibrous substrate 11 is not limited to the method described above. That is, the prepreg 1 of this embodiment, manufactured using the aforementioned resin composition, can be manufactured by an appropriate method.

[0090] Since the prepreg 1 of this embodiment is manufactured using the above-mentioned resin composition, the glass transition temperature of the cured prepreg 1 is 200°C or higher, and the reflectivity of light with wavelengths of 365nm or higher and 405nm or lower is 20% or lower. Therefore, the cured prepreg 1 has excellent heat resistance and can have excellent small-diameter opening properties for solder resist 6 formed on the printed wiring board 3 manufactured using the prepreg 1. Furthermore, the prepreg 1 of this embodiment is not limited to manufacturing printed wiring board 3, but can be applied to various applications. (2) Metal-clad laminate

[0091] FIG. 2 shows an example of a metal-clad laminate 2 according to this embodiment. The metal-clad laminate 2 includes: an insulating layer 20, which contains a hardened prepreg 1 according to this embodiment; and a metal layer 21, which is laminated with the insulating layer 20. The metal-clad laminate 2 can be used as a material for printed wiring boards 3, etc.

[0092] A method for manufacturing the metal-clad laminate 2 may include, for example, stacking a prepreg 1 and a metal layer 21, and heating and pressurizing the prepreg 1 to harden it into an insulating layer 20, thereby manufacturing the metal-clad laminate 2. More specifically, a metal layer 21 such as copper foil may be stacked on one or both sides of the prepreg 1, and the prepreg 1 and the metal layer 21 may be heated and pressurized to harden the prepreg 1 to form an insulating layer 20. Then, the insulating layer 20 containing the hardened prepreg 1 and the metal layer 21 may be laminated together to form a metal-clad laminate 2 in which a metal layer 21 is densely attached to one or both sides of the insulating layer 20 containing the hardened prepreg 1. Since the metal-clad laminate 2 is manufactured using the prepreg 1, a fibrous substrate 22 is present within the insulating layer 20 as shown in Figure 2. The fibrous substrate 22 may be a single sheet or two or more sheets.

[0093] The heating and pressurizing conditions during the manufacture of the metal-clad laminate 2 can be appropriately set according to the thickness of the metal-clad laminate 2 to be manufactured and the type and composition of the resin composition forming the insulating layer 20.

[0094] The heating temperature during the manufacture of the metal-clad laminate 2 is, for example, 200°C or higher and 250°C or lower. Furthermore, the pressure during the manufacture of the metal-clad laminate 2 is, for example, 1 MPa or higher and 5 MPa or lower. And, the heating and pressurizing time during the manufacture of the metal-clad laminate 2 is, for example, 30 minutes or higher and 120 minutes or lower.

[0095] When manufacturing the metal-clad laminate 2, the thickness of the metal layer 21 can be appropriately set according to the desired purpose. The thickness of the metal layer 21 is, for example, 5µm or more and 35µm or less, but there is no particular limitation. When using an extremely thin metal foil as the metal layer 21, in order to improve processability, a carrier-supported metal foil having a release layer and a carrier can also be used.

[0096] Furthermore, the method for manufacturing a metal-clad laminate 2 having an insulating layer 20 comprising a hardened prepreg 1 of this embodiment and a metal layer 21 adhered to the insulating layer 20 is not limited to the method described above. That is, the metal-clad laminate 2 manufactured using the prepreg 1 of this embodiment can be manufactured by any appropriate method.

[0097] Furthermore, as long as the metal-clad laminate 2 is manufactured using a conventional manufacturing method, the surface roughness of the insulating layer 20 will not affect the reflectivity. That is, the reflectivity of the insulating layer 20 is not affected by the surface roughness, but depends solely on the composition of the resin composition. Therefore, the insulating layer 20 manufactured using the aforementioned resin composition is not affected by the surface roughness, and the reflectivity of light with wavelengths of 365 nm and above and 405 nm and below can reach 20% or less. The surface roughness of the insulating layer 20 is, for example, expressed as an arithmetic mean roughness Sa. This arithmetic mean height Sa is not particularly limited, for example, being 0.01 µm or more and 2 µm or less.

[0098] In this way, since the insulating layer 20 of the metal-clad laminate 2 of this embodiment is manufactured using the prepreg 1 of this embodiment, the glass transition temperature of the insulating layer 20 is 200°C or higher, and the reflectivity of light with wavelengths of 365nm or higher and 405nm or lower is 20% or lower. Therefore, the metal-clad laminate 2 has excellent heat resistance and can have excellent small-diameter opening properties for the solder mask 6 formed on the printed wiring board 3 manufactured using the metal-clad laminate 2. Furthermore, the metal-clad laminate 2 of this embodiment is not limited to manufacturing printed wiring board 3, but can be applied to various applications. (3) Printed wiring board

[0099] FIG3 shows an example of a printed wiring board 3 according to this embodiment. The printed wiring board 3 includes: an insulating layer 30, which includes a hardened prepreg 1; and conductor wiring 31, which is laminated with the insulating layer 30. The conductor wiring 31 may be formed on only one side of the insulating layer 30 or on both sides.

[0100] Since the printed wiring board 3 is manufactured using the prepreg 1, it has a fibrous substrate 32 as shown in Figure 3. The fibrous substrate 32 may be a single piece or two or more pieces.

[0101] Furthermore, the printed wiring board 3 can also be manufactured using the aforementioned metal-clad laminate 2. More specifically, the conductor wiring 31 can be formed by etching or other processes on the metal layer 21 of the surface of the metal-clad laminate 2. That is, the printed wiring board 3 can be formed by partially removing the metal layer 21 on the surface of the metal-clad laminate 2. By performing the above-described method, a printed wiring board 3 having an insulating layer 30 and conductor wiring 31 serving as a circuit on one or both sides of the insulating layer 30 can be manufactured.

[0102] In addition to the methods mentioned above, other methods for forming circuits include, for example, forming circuits by the Semi Additive Process (SAP) or the Modified Semi Additive Process (MSAP), but there are no particular limitations.

[0103] Furthermore, as long as the printed wiring board 3 is manufactured using a conventional manufacturing method, the surface roughness of the insulating layer 30 will not affect the reflectivity. That is, the reflectivity of the insulating layer 30 is not affected by the surface roughness, but depends solely on the composition of the resin composition. Therefore, the insulating layer 30 manufactured using the aforementioned resin composition is not affected by the surface roughness, and the reflectivity of light with wavelengths of 365 nm and above and 405 nm and below can reach 20% or less. The surface roughness of the insulating layer 30 is, for example, expressed as an arithmetic mean roughness Sa. This arithmetic mean height Sa is not particularly limited, for example, being 0.01 µm or more and 2 µm or less.

[0104] As a result, since the insulating layer 30 of the printed wiring board 3 of this embodiment is manufactured using the prepreg 1 of this embodiment, the glass transition temperature of the insulating layer 30 is 200°C or higher, and the reflectivity of light with wavelengths of 365nm or higher and 405nm or lower is 20% or lower. Therefore, the printed wiring board 3 has excellent heat resistance and can have excellent small-diameter openings for the solder resist 6 formed on the printed wiring board 3. 3. Appearance

[0105] As can be clearly seen from the above embodiments, this disclosure includes the following forms. Hereinafter, the symbols are enclosed in parentheses only to indicate the correspondence with the embodiments.

[0106] The first state sample of the prepreg (1) comprises: at least one of a resin composition and a semi-cured form of the resin composition, and a fibrous substrate (11); the resin composition contains a thermosetting resin (A), a coumarin compound (B) and an inorganic filler (C); the thermosetting resin (A) includes an epoxy resin (A1); and the glass transition temperature of the cured form of the prepreg (1) is 200°C or higher, and the reflectivity of light with a wavelength of 365nm or higher and 405nm or lower is 20% or lower.

[0107] According to this state, the excellent heat resistance of the hardened prepreg (1) and the excellent small-diameter opening of the solder resist (6) formed on the printed wiring board (3) made using the prepreg (1) can be taken into account.

[0108] The second state sample is based on the prepreg (1) of the first state sample. In the second state sample, the coumarin compound (B) includes at least one of the coumarin compounds (B1) shown in formula (1) and formula (2); [Chemical Formula 3][Chemical Formula 4]

[0109] (In formulas (1) and (2), R1 and R2 independently represent hydrogen atoms, alkyl, aryl or hydroxyalkyl, respectively; R3, R4 and R5 independently represent hydrogen atoms, alkyl or aryl, respectively).

[0110] The third state sample is based on the prepreg (1) of the first or second state sample. In the third state sample, the content of coumarin compound (B) is 0.4% by mass or more and 7% by mass or less relative to the total amount of thermosetting resin (A) and coumarin compound (B).

[0111] The fourth state sample is a prepreg (1) based on any one of the first to third state samples. In the fourth state sample, the content of epoxy resin (A1) is 20% by mass or more relative to the total amount of thermosetting resin (A).

[0112] The fifth state sample is a prepreg (1) based on any one of the first to fourth state samples. In the fifth state sample, the content of inorganic filler (C) is 50 parts by mass or more and 300 parts by mass relative to a total of 100 parts by mass of thermosetting resin (A) and the aforementioned coumarin compound (B).

[0113] The sixth state sample is a prepreg (1) based on any one of the first to fifth state samples. In the sixth state sample, the epoxy resin (A1) includes at least one selected from the group consisting of biphenyl type epoxy resin, naphthalene type epoxy resin and dicyclopentadiene type epoxy resin.

[0114] The seventh sample is a prepreg (1) based on any one of the first to sixth samples. In the seventh sample, the thermosetting resin (A) further comprises a phenolic resin (A2).

[0115] The eighth sample is based on the prepreg (1) of the seventh sample. In the eighth sample, the mass ratio of epoxy resin (A1) to the aforementioned phenolic resin (A2) is 5:1 to 1:2.

[0116] The 9th state sample is a prepreg (1) based on any one of the 1st to 8th state samples. In the 9th state sample, the resin composition further contains an amine compound (D) that does not have a coumarin skeleton.

[0117] The 10th state sample is a prepreg (1) based on any one of the 1st to 9th state samples. In the 10th state sample, the inorganic filler (C) comprises at least one filler selected from the group consisting of silica, talc, boehmite, magnesium hydroxide and aluminum hydroxide.

[0118] The metal-clad laminate (2) of the 11th state comprises: an insulating layer (20) which includes a hardened prepreg (1) according to any one of the 1st to 10th states; and a metal layer (21).

[0119] The printed wiring board (3) of the 12th state includes: an insulating layer (30) comprising a hardened prepreg (1) according to any one of the 1st to 10th states; and conductor wiring (31).

[0120] Examples Hereinafter, the present disclosure will be specifically described by way of examples. However, the present disclosure is not limited to the following examples. (1) Resin composition

[0121] The raw materials for the resin composition are those shown in Tables 1 and 2. Then, thermosetting resin (A), coumarin compound (B), inorganic filler (C), and amine compound (D) are blended in the amounts shown in Tables 1 and 2, diluted with a solvent (methyl ethyl ketone), and stirred and mixed to homogenize, thereby preparing the resin compositions in the varnish state of the Examples and Comparative Examples. Details of each component used are as follows. (1.1) Thermosetting Resins (A) <Epoxy Resins (A1)> - Epoxy Resin #1: Manufactured by Nippon Kayaku Co., Ltd., product name "NC-3500", biphenyl type epoxy resin, epoxy equivalent 209 g / eq. - Epoxy Resin #2: Manufactured by Nippon Kayaku Co., Ltd., product name "NC-3000H", biphenyl type epoxy resin, epoxy equivalent 280~300 g / eq. - Epoxy Resin #3: Manufactured by DIC Co., Ltd., product name "EPICLON 850S", bisphenol type epoxy resin, epoxy equivalent 184~194 g / eq. - Epoxy Resin #4: Manufactured by Printec Co., Ltd., product name "TECHMORE VG3101", aromatic trifunctional epoxy resin containing bisphenol backbone, epoxy equivalent 205~215 g / eq.

[0122] -Epoxy Resin #5: Manufactured by DIC Corporation, product name "EPICLON HP-4710", naphthalene-type epoxy resin, epoxy equivalent 160~180g / eq. <Phenolic Resin (A2)> -Phenolic Resin #1: Manufactured by Nippon Kayaku Co., Ltd., product name "KAYAHARD GPH-103", biphenyl-type phenolic resin, phenolic hydroxyl equivalent 231g / eq.

[0123] -Phenolic resin #2: Manufactured by Meiwa Chemical Co., Ltd., product name "MEHC-7403H", biphenyl type phenolic resin, phenolic hydroxyl equivalent 132 g / eq. (1.2) Coumarin compounds (B) -Coumarin compound #1: Manufactured by Tokyo Chemical Industry Co., Ltd., compound name "coumarin" -Coumarin compound #2: Manufactured by Tokyo Chemical Industry Co., Ltd., compound name "4-methylcoumarin"

[0124] -Coumarin compound #3: Manufactured by Tokyo Chemical Industry Co., Ltd., compound name "7-amino-4-methylcoumarin". (1.3) Inorganic filler (C)

[0125] -Inorganic filler #1: Manufactured by Admatechs, Inc., product name "SC2500-SXJ", aminosilane treated silica, average particle size (D50): 0.5µm. (1.4) Amine compound (D) -Amine compound #1: Manufactured by NIPPON CARBIDE INDUSTRIES CO., INC., compound name "Dicyandiamine (DICY)"

[0126] -Amine compound #2: Manufactured by Shikoku Chemical Industry Co., Ltd., product name "2E4MZ", compound name "2-ethyl-4-methylimidazole". (2) Prepreg

[0127] Prepare the glass cloth shown in Tables 1 and 2 as the fibrous substrate. The glass cloth is a fabric woven with approximately orthogonal warp and weft threads. The resin composition in a clear state is impregnated into the glass cloth such that the thickness of the cured prepreg is 100µm. Using a non-contact heating unit, the resin composition impregnated into the glass cloth is heated and dried at 130°C until it becomes a semi-cured product. The solvent in the resin composition is removed in this way, and a prepreg containing the glass cloth and the semi-cured product of the resin composition impregnated into the glass cloth is obtained. The total mass of the prepreg is 100%, and the content of the resin layer 10 in the prepreg is 46% by mass. The details of each glass cloth used are as follows. (2.1) Glass cloth - Glass cloth type E: Made by Nitto Boshoku Co., Ltd., #2118 type, product name "WEA2118T-107-S199", E glass

[0128] -Glass cloth type S: Nitto Boshoku Co., Ltd., #2118 type, product name "WTX2118T-107-S199", S glass. (3) Metal-clad laminate

[0129] Two prepregs obtained in the above manner were stacked together to obtain a laminate, and copper foil (Mitsui Metals & Minerals Co., Ltd., thickness: 12µm, 3EC-VLP-12) was stacked on both sides of the obtained laminate to form a metal layer to obtain a laminate with copper foil attached. The laminate with copper foil attached was heated and pressed to obtain a metal-clad laminate with metal layers on both sides and a thickness of 0.2mm. The heating and pressing conditions were 220°C, 2MPa, and 90 minutes. (4) Test (4.1) Glass transfer temperature

[0130] An unclad board is obtained by etching away the copper foil adhered to both sides of the metal-clad laminate. The unclad board is cut at a 45° angle (oblique) relative to the longitudinal or transverse lines of the glass cloth to obtain a test piece with dimensions of 50mm × 5mm × 0.2mm.

[0131] For this test piece, tanδ was measured using a dynamic viscoelasticity measuring device (manufactured by SII NanoTechnology Inc., "DMS6100") under a heating condition of 5℃ / min (DMA method), and its peak temperature was used as the glass transition temperature. (4.2) Reflectivity

[0132] An unclad board was obtained by etching away the copper foil adhered to both sides of the metal-clad laminate. A test piece of 50 mm × 50 mm × 0.2 mm was obtained from the unclad board.

[0133] For this test piece, an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, "UV-2500PC") was used to measure the reflectance of light with wavelengths of 365nm, 385nm, 395nm, and 405nm in the thickness direction of the test piece. The reflectance was measured using an integrating sphere (integrating sphere inner diameter: Φ60mm, barium sulfate coating type) accessory device, under the conditions of an incident angle of 5° and reflectance measurement mode, to perform relative total light reflectance measurement. (4.3) Surface roughness

[0134] For the test piece used in "(4.2) Reflectivity", the arithmetic mean height Sa was measured as the surface roughness using a shape-analyzing laser microscope (KEYENCE Corporation, "VK-X1000") in accordance with ISO25178. (4.4) Solder resist small diameter opening

[0135] First, an unclad board was obtained by etching away the copper foil attached to a 5cm × 5cm metal-clad laminate. A photosensitive dry film solder resist (manufactured by Taiyo Ink Mfg. Co., Ltd., PSR-800 AUS410, thickness: 20µm, negative) was applied to the entire surface of the unclad board using a vacuum laminator at a lamination temperature of 75°C, a vacuum holding time of 20 seconds, and a pressure time of 60 seconds to obtain a test piece.

[0136] Next, the obtained test piece was exposed to the photomask with an aperture pattern of 100µm or 60µm in diameter using an exposure apparatus equipped with a metal halide lamp (manufactured by ORC Corporation, "HMW-680 GW20") at 20°C and a cumulative irradiation dose of 600mJ / cm2 to harden the dry film solder resist. In addition, the inner edge 4 of the unirradiated part in Figures 4 to 6 refers to the inner edge of the part that is not irradiated by irradiation light of 365nm or higher and 405nm or lower by the photomask.

[0137] After exposure, the test piece was developed by spray development. The development process involved spraying a 1% sodium bicarbonate aqueous solution at 30°C at a spray pressure of 0.2 MPa for 120 seconds. After development, a water wash was performed at 25°C and a spray pressure of 0.1 MPa for 45 seconds. After washing, a post-curing treatment was performed at 150°C for 60 minutes, followed by a post-UV treatment using a high-pressure mercury lamp at 1000 mJ / cm² to harden the dry film solder resist. Furthermore, the post-curing and post-UV treatments further hardened the exposed dry film solder resist. Through these treatments, solder resist 6 was formed on the test piece.

[0138] Then, the inner edge 4 of the un-illuminated portion of the above-mentioned test pieces was observed using a scanning electron microscope (SEM), and the observation results were classified according to the following evaluation criteria to evaluate the solder mask opening performance of each test piece. <Evaluation Criteria> S: Solder mask openings with spot diameters of Φ60µm and Φ100µm have good shape A: Solder mask openings with spot diameters of Φ100µm have good shape

[0139] B: Poor shape of solder resist opening with a diameter of Φ100µm.

[0140] A good solder mask opening shape, as defined by the evaluation criteria, refers to the following state: for each spot diameter, as shown in Figure 4, there is no residual solder mask 6 inside the inner edge of the unirradiated portion 4, and the opening portion 5 is approximately circular. On the other hand, a poor solder mask opening shape refers to the following state: for a spot diameter of Φ100µm, as shown in Figure 5, there is residual solder mask 6 inside the inner edge of the unirradiated portion 4, and the opening portion 5 is not circular, and only a portion of the inner edge of the unirradiated portion 4 is open; or, as shown in Figure 6, the opening portion 5 cannot be formed, and solder mask 6 remains entirely inside the inner edge of the unirradiated portion 4. Furthermore, evaluation A is the result of a good opening shape for a spot diameter of Φ100µm, but a poor opening shape for a spot diameter of Φ60µm.

[0141] If the evaluation is S or A, the small diameter opening performance of the solder mask is good. [Table 1][Table 2] [Simplified Explanation of the Diagram]

[0010] Figure 1 is a schematic cross-sectional view of a prepreg body according to an embodiment of the present disclosure.

[0011] Figure 2 is a schematic cross-sectional view showing a metal-clad laminate of one embodiment of the present disclosure.

[0012] Figure 3 is a schematic cross-sectional view showing a printed wiring board of one embodiment of the present disclosure.

[0013] Figure 4 is a schematic diagram showing the results of evaluating S or A in the small-diameter opening performance evaluation criteria of the present disclosure embodiment.

[0014] Figure 5 is a schematic diagram showing an example of the results of evaluation B in the small-diameter opening performance evaluation criterion of the present disclosure embodiment.

[0015] Figure 6 is a schematic diagram showing an example of the results of evaluation B in the small-diameter opening performance evaluation criterion of the present disclosure embodiment.

Claims

1. A prepreg comprising: at least one of a resin composition and a semi-cured form of the aforementioned resin composition; and a fibrous substrate; wherein the aforementioned resin composition contains a thermosetting resin (A), a coumarin compound (B), and an inorganic filler (C); wherein the aforementioned thermosetting resin (A) comprises an epoxy resin (Al); and wherein the cured form of the aforementioned prepreg has a glass transition temperature of 200°C or higher, and a reflectance of light with a wavelength of 365 nm or higher and 405 nm or lower of 20% or less.

2. The prepreg of claim 1, wherein the aforementioned coumarin compound (B) comprises at least one of formula (1) and formula (2) as shown in coumarin compound (B1); [Formula 1] [Formula 2] (in formula (1) and formula (2), R1 and R2 independently represent hydrogen atom, alkyl, aryl or hydroxyalkyl, respectively; R3, R4 and R5 independently represent hydrogen atom, alkyl or aryl, respectively).

3. The prepreg of claim 1, wherein the content of the coumarin compound (B) is 0.4% by mass or more and 7% by mass or less relative to the total amount of the aforementioned thermosetting resin (A) and the aforementioned coumarin compound (B).

4. The prepreg of claim 1, wherein the content of the epoxy resin (A1) is 20% by mass or more relative to the total amount of the aforementioned thermosetting resin (A).

5. The prepreg of claim 1, wherein the content of the inorganic filler (C) is 50 parts by mass or more and 300 parts by mass or less relative to a total of 100 parts by mass of the aforementioned thermosetting resin (A) and the aforementioned coumarin compound (B).

6. The prepreg of claim 1, wherein the aforementioned epoxy resin (A1) comprises at least one selected from the group consisting of biphenyl-type epoxy resins, naphthalene-type epoxy resins and dicyclopentadiene-type epoxy resins.

7. The prepreg of claim 1, wherein the aforementioned thermosetting resin (A) further comprises phenolic resin (A2).

8. The prepreg of claim 7, wherein the mass ratio of the aforementioned epoxy resin (A1) to the aforementioned phenolic resin (A2) is 5:1 to 1:

2.

9. The prepreg of claim 1, wherein the aforementioned resin composition further contains an amine compound (D) that does not have a coumarin skeleton.

10. The prepreg of claim 1, wherein the aforementioned inorganic filler (C) comprises at least one filler selected from the group consisting of silica, talc, boehmite, magnesium hydroxide and aluminum hydroxide.

11. A metal-clad laminate comprising: an insulating layer comprising a hardened prepreg as claimed in any one of claims 1 to 10; and a metal layer.

12. A printed wiring board comprising: an insulating layer comprising a hardened prepreg as claimed in any one of claims 1 to 10; and conductor wiring.

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