Dispersion composition, its manufacturing method, manufacturing method of fluororesin film, and manufacturing method of metal-clad laminate

Abstract

To provide a dispersion composition in which a granular fluorine-based resin and an inorganic filler are uniformly dispersed.SOLUTION: A method for producing a dispersion composition includes a step of mixing a granular fluorine-based resin, an inorganic filler, a dispersion agent, and a polar solvent, wherein the total ratio of the granular fluorine-based resin and the inorganic filler is 75 wt.% or more when kneading is performed in the state in which the total ratio of the granular fluorine-based resin and the inorganic filler is 75 wt.% or more with respect to the total weight of the mixture, and a solid first dispersion composition is obtained. The total ratio of the granular fluorine-based resin and the inorganic filler with respect to the total weight of the total component is within a range of 60-75 wt.% when the first dispersion composition is diluted with a polar solvent, and a second dispersion composition having viscosity measured at 25°C using an E type viscometer of 1,000 cp to 50,000 cp is obtained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersion composition, a method for producing the same, a method for producing a fluorine-based resin film, and a method for producing a metal-clad laminate. [Background technology]

[0002] In recent years, with the progress in miniaturization, weight reduction, and space-saving of electronic devices, there has been an increasing demand for flexible printed circuits (FPCs), which are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Because FPCs allow for three-dimensional, high-density packaging even in limited spaces, their applications are expanding to include wiring for moving parts in electronic devices such as hard disk drives, DVDs, and smartphones, as well as components such as cables and connectors.

[0003] FPCs are manufactured by etching the metal layer of metal-clad laminates such as copper-clad laminates (CCL) to create wiring. Currently, metal-clad laminates that use highly heat-resistant polyimide for the insulating resin layer that comes into contact with the metal foil are widely used.

[0004] Recently, with the increasing speed of communication devices, development of 5G and even 6G communication is progressing. Circuit board materials are being investigated for millimeter-wave radar substrates and antenna substrates compatible with high-speed communication standards. Among these materials, fluororesins have attracted attention due to their low dielectric loss tangent. However, because fluororesins have a high thermal expansion coefficient, the use of inorganic fillers in combination with fluororesins has been investigated to achieve low thermal expansion, a required characteristic of insulating materials for circuit boards, while taking advantage of their low dielectric loss tangent. For example, a method has been proposed for producing fluororesin films using a dispersion in which fluororesin powder and inorganic filler are dispersed in water or an organic solvent (Patent Documents 1 and 2). However, the low viscosity of dispersions containing fluororesin powder and inorganic filler makes thick film coating difficult, leading to problems such as uneven thickness during coating and the need for redispersion after long-term storage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2019 / 131809 [Patent Document 2] International Publication No. WO2021 / 132055 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a dispersion composition in which a powdery fluororesin and an inorganic filler are uniformly dispersed with few agglomerated particles. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that a dispersion composition with few agglomerated particles and a uniformly dispersed state of solids can be obtained by kneading a particulate fluororesin, an inorganic filler, and a dispersant at a high solids concentration using a small amount of polar solvent, and have thus completed the present invention.

[0008] That is, the dispersion composition of the present invention comprises the following components (A) to (C): (A) granular fluororesin, (B) inorganic filler; (C) a dispersant, The viscosity measured at 25°C using an E-type viscometer is 1000 cP or more. However, the rotation speed set in viscosity measurement should be such that the viscosity obtained at the set rotation speed is within a viscosity range of 10% to 90% of the torque of the set rotation speed, and this includes materials that become solid and cannot have their viscosity measured (the same applies below).

[0009] The dispersion composition of the present invention may have a total weight ratio of component (A) and component (B) of 75% or more, and may be solid. In this case, the dispersion composition of the present invention has the following composition: The total ratio of component (A) and component (B) is within the range of 75 to 99% by weight of the total weight. The volume ratio of component (A) to component (B) (A:B) is within the range of 15:85 to 95:5. The proportion of component (C) is within the range of 1 to 15% by weight of the total weight. The proportion of polar solvent as component (D) is 0 to 24% by weight. It may have the following structure.

[0010] The dispersion composition of the present invention has the following composition: The total of component (A) and component (B) is 60 to 75% by weight of the total weight. The volume ratio of component (A) to component (B) (A:B) is within the range of 15:85 to 95:5. The proportion of component (C) is within the range of 0.8 to 13.2% by weight of the total weight. The proportion of polar solvent as component (D) is 11.8 to 39.2% by weight of the total weight. and the viscosity measured at 25°C using an E-type viscometer may be in the range of 1000 cP to 50000 cP.

[0011] In the dispersion composition of the present invention, the inorganic filler of component (B) may have a Mohs hardness of 2 or more.

[0012] The method for producing a dispersion composition of the present invention is a method for producing a dispersion composition by kneading a plurality of materials including a powdery fluororesin and an inorganic filler, a step of mixing the powdery fluorine-based resin, the inorganic filler, a dispersant, and a polar solvent; a step of obtaining a solid first dispersion composition by kneading the mixture in a state in which the total weight of the mixture contains the powdery fluororesin and the inorganic filler at 75% by weight or more; The present invention is characterized by comprising:

[0013] The method for producing a dispersion composition of the present invention further includes a step of diluting the first dispersion composition with a polar solvent to obtain a second dispersion composition, in which the total weight of the powdery fluororesin and the inorganic filler is in the range of 60 to 75% by weight based on the total weight of all components, and the viscosity measured at 25°C using an E-type viscometer is in the range of 1000 cP to 50000 cP; may also include:

[0014] The method for producing a fluorine-based resin film of the present invention includes the steps of: applying the second dispersion composition obtained by the above method to a substrate to form a coating film; a step of forming a fluorine-based resin layer by heat-treating the coating film; Contains:

[0015] The method for producing a metal-clad laminate of the present invention includes the steps of applying the second dispersion composition obtained by the above method to a metal foil to form a coating film; a step of heat-treating the coating film to obtain a metal-clad laminate in which a fluororesin layer and a metal layer are laminated; Contains: [Effects of the Invention]

[0016] The dispersion composition of the present invention has few agglomerated particles, and the particulate fluororesin and inorganic filler are uniformly dispersed. Moreover, in a solid state containing a low solvent content, the dispersion composition has long-term dispersion stability. Furthermore, in a liquid state containing a predetermined solvent content, the viscosity can be adjusted to an appropriate level for thick-film coating, resulting in excellent coatability and dispersion stability. Therefore, resin films obtained by applying the dispersion composition of the present invention and metal-clad laminates having the same as an insulating resin layer can be thickened, and both the excellent dielectric properties of the fluororesin and the low thermal expansion properties of the inorganic filler are achieved. Therefore, resin films and metal-clad laminates obtained using the dispersion composition of the present invention are useful as circuit board materials that can comply with high-speed communication standards. DETAILED DESCRIPTION OF THE INVENTION

[0017] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. The dispersion composition according to the embodiment of the present invention comprises the following components (A) to (C); (A) granular fluororesin, (B) inorganic filler; (C) a dispersant, and has a viscosity of 1000 cP or more. Here, a viscosity of 1000 cP or more includes a solid form. This dispersion composition can take two forms: a solid first dispersion composition, and a liquid second dispersion composition obtained by diluting the first dispersion composition with a solvent.

[0018] Component (A): Component (A) is a powdery fluororesin. Here, "powdery" refers to, for example, an average particle diameter (D 50 ) in the range of 0.05 to 100 μm, preferably in the range of 0.5 to 50 μm, and more preferably in the range of 0.5 to 10 μm. 50 ) can be calculated by, for example, measuring the particle size distribution of powder particles using laser diffraction / scattering, calculating a cumulative curve with the total volume of the powder particles as 100%, and measuring the particle diameter at the point on the cumulative curve where the cumulative volume is 50%.

[0019] Fluorine-based resins are polymers containing fluorine atoms, and the type is not particularly limited, but examples include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-tetrafluoroethylene-hexafluoropropylene copolymer (EFEP), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF). These may be used in combination of two or more types, or the fluororesin may contain a monomer unit based on a perfluoroolefin having a functional group as part of the fluororesin. Preferred functional groups are carbonyl-containing groups, hydroxy groups, epoxy groups, amide groups, amino groups, and isocyanate groups. Among these fluorine-based resins, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are more preferable as they exhibit low dielectric tangent.

[0020] Ingredient (B): Component (B) is an inorganic filler, and the type thereof is not particularly limited. However, from the viewpoint of reducing the thermal expansion coefficient of the resin film, for example, silicon dioxide (silica), aluminum oxide (alumina), magnesium oxide (magnesia), beryllium oxide, niobium oxide, titanium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, magnesium fluoride, potassium silicofluoride, talc, glass, barium titanate, etc. are preferred. These may be used in combination of two or more. Among these, silicon dioxide (silica), aluminum oxide, boron nitride, glass, etc. are more preferred because they have a low thermal expansion coefficient.

[0021] Average particle size of component (B) (D 50) is not particularly limited, but is preferably in the range of 0.05 to 50 μm, and more preferably in the range of 0.1 to 20 μm, in consideration of the ratio to the thickness of the insulating resin layer when used in a circuit board and from the viewpoint of ensuring the drilling processability of the insulating resin layer. Furthermore, the specific surface area is not particularly limited, but is preferably in the range of 0.1 to 20 μm, in consideration of suppressing deterioration of the dielectric loss tangent. 2 / g, preferably 0.1 to 10 m 2 / g range is preferable. The average particle size of an inorganic filler can be determined by, for example, measuring the particle size distribution of the powder particles using a laser diffraction / scattering method, calculating a cumulative curve with the total volume of the powder particles set to 100%, and measuring the particle size at the point on the cumulative curve where the cumulative volume is 50%.The specific surface area can be measured using the BET method.

[0022] The shape of component (B) is not particularly limited, but from the viewpoint of reducing the difference in thermal expansion coefficient between the thickness direction and the plane direction, for example, a spherical shape, a crushed spherical shape, etc. Component (B) may also be hollow.

[0023] The hardness of component (B) is not particularly limited, but from the viewpoint of breaking down agglomerates due to shearing during kneading, the Mohs hardness is preferably 2 or more, and more preferably within the range of 2 to 9. If the Mohs hardness is less than 2, the material may be deformed by the shearing force during kneading, making it difficult to break down agglomerates.

[0024] Although not particularly limited, component (B) is preferably surface-treated with a coupling agent, etc. Examples of coupling agents used for the surface treatment include 3-aminopropylethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropylethoxysilane, 3-isocyanatopropylethoxysilane, and hexamethyldisilazane.

[0025] Ingredients (C): The dispersant for component (C) is not particularly limited as long as it has a dispersing effect on components (A) and (B), but from the viewpoint of dispersing the fluororesin, for example, a fluorosurfactant is preferred. As the fluorosurfactant, for example, a nonionic fluorosurfactant having a perfluoroalkenyl structure with a double bond in the molecule is more preferred.

[0026] The dispersion composition of this embodiment has few agglomerated particles, and the particulate fluororesin and inorganic filler are uniformly and stably dispersed. Furthermore, as will be described below, the first dispersion composition in a solid state containing a small amount of solvent has long-term dispersion stability, while the second dispersion composition in a liquid state containing a predetermined amount of solvent has excellent thick-film coatability and dispersion stability.

[0027] <First Dispersion Composition> The first dispersion composition is solid, and the total weight of the first dispersion composition is 75 wt % or more of the components (A) and (B). Here, "solid" refers to a state in which there is almost no viscous deformation, making it impossible to measure using an E-type viscometer. Because the first dispersion composition is produced by kneading in a "solid state," i.e., by hard kneading, the total weight of the first dispersion composition is preferably within the range of 75 to 99 wt %, more preferably within the range of 75 to 90 wt %. If the total weight of the components (A) and (B) is less than 75 wt %, it becomes difficult to produce the first dispersion composition by hard kneading, and if it exceeds 99 wt %, the first dispersion composition becomes powdery.

[0028] Furthermore, since the first dispersion composition is produced by dispersion through stiff kneading, the volume ratio (A:B) of component (A) to component (B) is preferably within the range of 15:85 to 95:5, more preferably within the range of 20:80 to 80:20. If the volume ratio of component (A) to component (B) is less than 15, the resin becomes brittle and film formation becomes difficult, whereas if it exceeds 95, the viscosity during kneading increases, making it difficult to produce by dispersion through stiff kneading.

[0029] Furthermore, in order to improve the dispersibility of the solid content in the first dispersion composition, the content of component (C) is preferably in the range of 1 to 15 wt %, more preferably in the range of 1 to 10 wt %, based on the total weight of the first dispersion composition. If the content of component (C) is less than 1 wt %, the solid content cannot be sufficiently dispersed, and if it exceeds 15 wt %, the dielectric loss tangent may deteriorate.

[0030] Furthermore, from the viewpoints of producing the first dispersion composition by kneading and of long-term storage in a solid state, the content of the polar solvent as component (D) is preferably 0 to 24 wt %, more preferably in the range of 9 to 24 wt %, relative to the total weight. Here, component (D) is an optional component in the first dispersion composition and may not be contained. If the content of component (D) exceeds 24 wt %, the fluidity becomes too high, making it impossible to produce the dispersion by kneading, resulting in a deterioration in the dispersion state, and causing sedimentation and aggregation of solids during long-term storage, which tends to reduce dispersion stability over time.

[0031] The type of polar solvent for component (D) is not particularly limited, but from the viewpoint of exerting its solvent function during kneading and in the dispersion composition, it is preferably liquid at 25° C. From this viewpoint, for example, water, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol, methanol, ethanol, isopropanol, methyl ethyl ketone, cyclohexanone, γ-butyrolactone, and the like are preferred. Among these, from the viewpoint of suppressing the amount of solvent evaporation due to heat generation during kneading, high boiling point solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, and N-methyl-2-pyrrolidone (NMP) are more preferred.

[0032] <Second Dispersion Composition> The second dispersion composition is a dispersion containing a polar solvent, and from the viewpoint of achieving a viscosity that allows for coating in a thick film, the total proportion of components (A) and (B) is preferably in the range of 60 to 75 wt%, more preferably 60 to 70 wt%, based on the total weight. If the total proportion of components (A) and (B) is less than 60 wt%, the solids concentration will be too low and the film-forming ability in the case of a thick film may be reduced, while if it exceeds 75 wt%, the solids concentration will be too high and film formation by casting may be difficult.

[0033] In addition, the volume ratio (A:B) of component (A) to component (B) of the second dispersion composition is preferably within a range of 15:85 to 95:5, more preferably within a range of 20:80 to 80:20. The reason for setting the volume ratio (A:B) within the above range is the same as that for the first dispersion composition.

[0034] Furthermore, from the viewpoint of ensuring dispersibility and suppressing deterioration of the dielectric loss tangent, the content of component (C) in the second dispersion composition is preferably in the range of 0.8 to 13.2 wt%, more preferably in the range of 1 to 10 wt%, based on the total weight of the dispersion composition. If the content of component (C) is less than 0.8 wt%, poor dispersion is likely to occur, and if it exceeds 13.2 wt%, the dielectric loss tangent of the resin film obtained from the dispersion composition will be deteriorated.

[0035] Furthermore, from the viewpoint of preparing a dispersion composition with a viscosity that allows for thick film coating, the content of the polar solvent as component (D) is preferably in the range of 11.8 to 39.2 wt %, more preferably in the range of 20 to 39 wt %, relative to the total weight of the second dispersion composition. Here, component (D) is an essential component in the second dispersion composition. If component (D) is less than 11.8 wt %, the viscosity will be too high, making it difficult to form a coating film by casting. If it exceeds 39.2 wt %, the fluidity will be too high, making it difficult to form a thick coating film and making it prone to sedimentation and aggregation of solids.

[0036] The polar solvent in the second dispersion composition can be any of those exemplified for the first dispersion composition, although the type of polar solvent may differ between the first dispersion composition and the second dispersion composition.

[0037] Furthermore, from the viewpoint of enabling thick film formation, the viscosity of the second dispersion composition, measured using an E-type viscometer at a temperature of 25°C, is preferably in the range of 1000 cP to 50,000 cP, more preferably in the range of 1000 to 30,000 cP. The rotation speed set in the viscosity measurement is set so that the viscosity obtained at the set rotation speed is within a viscosity range of 10% to 90% of the torque at the set rotation speed. If the viscosity is less than 1000 cP, the fluidity becomes too high when the second dispersion composition is cast onto a substrate, making it difficult to form a thick coating film. In particular, it becomes impossible to form a relatively thick coating film in the range of 30 to 150 μm for high-frequency transmission applications. If the viscosity is less than 1000 cP, sedimentation or aggregation of solids may occur. On the other hand, if the viscosity of the second dispersion composition exceeds 50,000 cP, the viscosity is too high, making it difficult to form a coating film by casting.

[0038] The first dispersion composition and the second dispersion composition may contain, as optional components, for example, an organic filler, a curing agent, a plasticizer, an elastomer, a coupling agent, a pigment, a flame retardant, and the like.

[0039] <Method for producing first dispersion composition> The first dispersion composition can be produced by carrying out the steps exemplified below and kneading a plurality of materials including a powdery fluorine-based resin and an inorganic filler.

[0040] (Mixing process) In this step, a powdery fluororesin as component (A), an inorganic filler as component (B), a dispersant as component (C), and a polar solvent as component (D) are mixed. The polar solvent of component (D) is used to wet the surfaces of the particulate fluororesin and inorganic filler to prevent aggregation during kneading, and is preferably used in an amount of 24% by weight or less based on the total weight. If the amount of polar solvent is too large, it will be difficult to apply sufficient shear force in the subsequent kneading step. Therefore, this step is preferably carried out with a mixture containing, relative to the total weight, component (A) in the range of 10 to 80 wt %, component (B) in the range of 3.5 to 73.5 wt %, component (C) in the range of 1 to 15 wt %, and component (D) in the range of 1.5 to 24 wt %.

[0041] The order in which the components are added is not particularly limited, but it is preferable to add and mix, for example, component (A), component (B), component (D), and component (C) in that order.

[0042] (Kneading process) In this step, a solid first dispersion composition is obtained by kneading the mixture obtained in the mixing step so that the total proportion of components (A) and (B) is 75 wt % or more relative to the total weight of the mixture. Here, "kneading" refers to applying a large shear force to a mixture in a solid, almost non-fluid state. Kneading eliminates agglomerations of the particulate fluororesin and inorganic filler particles, which are the solid components in the mixture, and uniformly disperses them in the form of primary particles. For this purpose, kneading is performed when the total proportion of the particulate fluororesin and inorganic filler is 75 wt % or more, preferably in the range of 75 to 99 wt %, and more preferably in the range of 75 to 83.5 wt %, relative to the total weight of the mixture. If the total proportion of the particulate fluororesin and inorganic filler is less than 75 wt %, sufficient shear force is not applied to the solid components, resulting in agglomerated particles remaining, making it difficult to obtain a uniform and stable dispersion.

[0043] The kneading is preferably carried out using, for example, a planetary kneader at a temperature of 40° C. or less for 30 minutes or more.

[0044] <Method for producing second dispersion composition> The second dispersion composition can be produced by diluting the first dispersion composition with the polar solvent of component (D). That is, the second dispersion composition can be obtained by carrying out a step of diluting the first dispersion composition with component (D) so that the sum of components (A) and (B) is in the range of 60 to 75% by weight, preferably 60 to 70% by weight, relative to the total weight, and the viscosity is in the range of 1000 cP to 50,000 cP, preferably 1000 to 30,000 cP.

[0045] Since the second dispersion composition is obtained via the first dispersion composition, the solid components, that is, the particulate fluororesin and inorganic filler particles, are uniformly dispersed in the form of almost primary particles, and therefore, unlike a dispersion obtained by mixing and dispersing each component in a polar solvent at a low solid concentration, sedimentation or aggregation of the solid components is unlikely to occur.

[0046] <Method of manufacturing resin film and metal-clad laminate> The method for producing a resin film using the second dispersion composition is not particularly limited, but the following method can be exemplified.

[0047] (Coating film formation process) In this step, the second dispersion composition is applied to an arbitrary substrate to form a coating film. That is, the second dispersion composition is applied to any substrate so as to have a desired thickness after the heat treatment step, and then dried to form a coating film on the substrate. The substrate to be used is not particularly limited, but it is preferable to use a heat-resistant material such as a metal foil such as copper foil, a copper foil with an adhesive layer, or a polyimide film. The method for applying the second dispersion composition to the substrate is not particularly limited, and it can be applied using a coater such as a comma, die, knife, or lip.

[0048] (Heat treatment process) In this step, the coating film obtained in the coating film forming step is heat-treated to form a fluorine-based resin layer. That is, the coating film and the substrate are heat-treated to melt the particulate fluororesin, and then cooled and solidified to form a film, thereby forming a fluororesin layer on the substrate. The heat treatment temperature for melting the particulate fluororesin may be equal to or higher than the melting point of the fluororesin, and the upper limit can be determined appropriately depending on the type of resin, but it is preferable to set the temperature to be, for example, 10°C to 80°C higher than the melting point.

[0049] When forming multiple fluororesin layers, the heat treatment may be performed each time the second dispersion composition is applied and dried, or the process of applying and drying the second dispersion composition may be repeated multiple times and then all the layers may be heat-treated at once.

[0050] If necessary, the substrate can be peeled off to obtain a resin film of a fluorine-based resin. Furthermore, this manufacturing method can produce a metal-clad laminate having a fluororesin layer and a metal layer by using a metal foil as the substrate. For example, when a metal foil is used as the substrate, a single-sided metal-clad laminate having a fluororesin layer on one side of the metal layer is produced. Furthermore, a double-sided metal-clad laminate can be produced by using a metal foil as the substrate and forming another metal layer on the side of the resin film opposite the substrate, or by bonding two single-sided metal-clad laminates together.

[0051] <Resin film> The resin film obtained in the above manner contains a fluorine-based resin layer. The thickness of the resin film is not particularly limited, but when used as a resin layer of a circuit board, taking into consideration application to high-frequency signal transmission, the thickness is preferably within the range of 30 to 150 μm, more preferably within the range of 75 to 150 μm.

[0052] The resin film preferably has a dielectric loss tangent (Df) of 0.003 or less, more preferably 0.0025 or less, and even more preferably 0.0020 or less at frequencies up to 60 GHz, as measured using a split post dielectric resonator (SPDR) or split cylinder resonator after 72 hours of conditioning at a temperature of 24 to 26°C and a humidity of 45 to 55%. The dielectric constant (Dk) measured under the same conditions is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. If the dielectric loss tangent (Df) and the dielectric constant (Dk) exceed the above values, when the resin film is applied to a circuit board, this leads to increased dielectric loss, which can easily cause problems such as electrical signal loss in the transmission path of high-frequency signals in the GHz frequency range (e.g., 1 to 80 GHz).

[0053] Furthermore, in order to ensure dimensional stability, the coefficient of thermal expansion (CTE) of the resin film is preferably within a range of 10 to 30 ppm / K, and more preferably within a range of 15 to 25 ppm / K.

[0054] The resin film of the present embodiment may include any resin layer other than the fluorine-based resin layer.

[0055] <Metal-clad laminate> The metal-clad laminate obtained as described above comprises a fluororesin layer and a metal layer laminated on one or both sides of the fluororesin layer. That is, the metal-clad laminate of this embodiment may be a single-sided metal-clad laminate or a double-sided metal-clad laminate.

[0056] The material of the metal layer is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or copper alloys are particularly preferred.

[0057] The thickness of the metal layer is not particularly limited, but when a metal foil such as copper foil is used, it is preferably 35 μm or less, more preferably in the range of 5 to 25 μm. From the viewpoints of production stability and handleability, the lower limit of the metal foil thickness is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil, and may be, for example, a peelable copper foil in which a release layer is formed between a thin copper foil of 5 μm or less and a carrier foil. Furthermore, commercially available copper foils can be used as the copper foil. The surface roughness of the metal layer is not particularly limited, but from the viewpoint of ensuring adhesion to the fluororesin layer while reducing conductor loss, it is preferable that the ten-point average roughness (Rzjis) be in the range of 0.3 to 2.0.

[0058] Furthermore, the metal foil may be subjected to a surface treatment using, for example, siding, aluminum alcoholate, aluminum chelate, or a silane coupling agent, for the purpose of, for example, rust prevention or improving adhesive strength.

[0059] The configuration and thickness of the fluororesin layer in the metal-clad laminate are the same as those of the resin film. Note that the metal-clad laminate of the present embodiment may include any resin layer other than the fluororesin layer.

[0060] The metal-clad laminate of this embodiment is preferably used as a circuit board material. That is, by processing the metal layers on one or both sides of the metal-clad laminate into wiring circuits by etching or the like, circuit boards such as single-sided FPCs or double-sided FPCs can be produced. [Example]

[0061] The features of the present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[0062] [Viscosity measurement] The viscosity was measured at 25°C using an E-type viscometer (Brookfield, product name: DV-II+Pro). The rotation speed was set so that the viscosity could be measured in the torque range of 10% to 90%, and the viscosity was read when the viscosity stabilized 2 minutes after the start of measurement.

[0063] [Measurement of coefficient of thermal expansion (CTE)] A 3 mm x 20 mm polyimide film was heated from 30°C to 260°C at a constant heating rate while applying a 5.0 g load using a thermomechanical analyzer (trade name: TMA / SS6100, manufactured by Hitachi High-Technologies Corporation (formerly Seiko Instruments Inc.)). After holding at that temperature for 10 minutes, the film was cooled at a rate of 5°C / min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

[0064] [Measurement of relative permittivity and dielectric loss tangent] The relative permittivity (Dk) and dielectric loss tangent (Df) of the film at a frequency of 10 GHz were measured using a vector network analyzer (manufactured by Agilent, product name: E8363C) and a split post dielectric resonator (SPDR resonator). Furthermore, the dielectric constant (Dk) and dielectric loss tangent (Df) of the film at 60 GHz were measured using a split cylinder resonator (SCR resonator) in the same manner as above. The Dk and Df in the conditioned state were measured after the film used for the measurement was left to stand for 72 hours under conditions of a temperature of 24 to 26°C and a humidity of 45 to 55%.

[0065] [Measurement of copper foil surface roughness] The surface roughness of the copper foil was measured in tapping mode over an area of ​​80 μm × 80 μm on the copper foil surface using an AFM (manufactured by Bruker AXS, product name: Dimension Icon type SPM) and a probe (manufactured by Bruker AXS, product name: TESPA (NCHV), tip curvature radius 10 nm, spring constant 42 N / m), and the ten-point average roughness (Rzjis) was calculated.

[0066] The compounds used in the examples and comparative examples are as follows: Fluororesin powder (1): Fluon+ (Fluon is a registered trademark) EA-2000 PW 10: Fluororesin powder manufactured by AGC, average particle size 2 to 3 μm Silica filler (1): SPH507-05: Amorphous silica filler manufactured by Nippon Steel Chemical & Material, average particle diameter (D 50 )0.7μm, specific surface area 9.0m 2 / g Silica filler (2): SPH60-05: Amorphous silica filler manufactured by Nippon Steel Chemical & Material, average particle diameter (D 50 )1.7μm, specific surface area 9.2m 2 / g Dispersant (1): Futergent 710FL: Neos nonionic fluorine-containing dispersant (50% by weight of ingredients, 50% by weight of ethyl acetate)

[0067] Example 1 In a container of TKHIVIS MIX (model 2P-03) manufactured by PRIMIX Corporation (formerly Tokushu Kika Kogyo Co., Ltd.), 58.7 g of fluororesin powder (1) as a granular fluororesin, 141.3 g of silica filler (1) surface-treated with hexamethyldisilazane as an inorganic filler, 20 g of dispersant (1) and 21.1 g of DMAc as dispersants were added, and the mixture was stirred at 30 rpm for 5 minutes.

[0068] Next, to fine-tune the ratio of the fluororesin powder (1) and the silica filler (1) surface-treated with hexamethyldisilazane to the total amount, a small amount of DMAc was added to the kneaded mixture, and the mixture was stirred at 30 rpm for 5 minutes. The state of the kneaded mixture was then checked. This process was repeated until the mixture became lumpy. In this study, the mixture became lumpy when the total ratio of the fluororesin powder (1) and the silica filler (1) surface-treated with hexamethyldisilazane reached 79 wt% of the total amount, and no powdery parts were observed inside the kneaded mixture. Once the mixture became lumpy, kneading at 30 rpm was started, stopping every 15 minutes, and scraping the mixture off the stirring blades and the side walls of the container. This process was repeated four times for a total of 60 minutes, yielding Dispersion Composition 1-1. Dispersion Composition 1-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

[0069] Thereafter, dispersion composition 1-1 was gradually diluted and stirred with DMAc so that the total proportion of the fluororesin powder (1) and the silica filler (1) surface-treated with hexamethyldisilazane was 70% by weight, thereby obtaining dispersion composition 1-2 having a viscosity of 1750 cP when measured at 50 rpm and a viscosity of 1420 cP when measured at 100 rpm.

[0070] Dispersion composition 1-2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 50 μm, and then heat treatment was carried out using a hot air oven at 120°C for 3 minutes, 280°C for 3 minutes, and 340°C for 6 minutes to obtain single-sided metal-clad laminate 1. No aggregates or the like were observed in the obtained single-sided metal-clad laminate 1.

[0071] Next, the resin surfaces of the single-sided metal-clad laminates 1 were placed together and pressed at 320°C for 5 minutes under a pressure of 2 MPa to obtain a double-sided metal-clad laminate 1. The copper foil of the obtained double-sided metal-clad laminate 1 was etched away using an aqueous ferric chloride solution to prepare a fluororesin film 1. The CTE of Fluororesin Film 1 was 22.8 ppm / K, and when conditioned, Dk=2.52 and Df=0.0020 at 10 GHz, and when conditioned, Dk=2.61 and Df=0.0023 at 60 GHz.

[0072] <Example 2> In a container of TKHIVIS MIX (model 2P-03) manufactured by PRIMIX Corporation (formerly Tokushu Kika Kogyo Co., Ltd.), 58.7 g of fluororesin powder (1) as a granular fluororesin, 141.3 g of silica filler (2) surface-treated with hexamethyldisilazane as an inorganic filler, and 20 g of dispersant (1) and 21.1 g of DMAc as dispersants were added, and the mixture was stirred at 30 rpm for 5 minutes.

[0073] Next, to fine-tune the ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane to the total amount, a small amount of DMAc was added to the kneaded mixture, and the mixture was stirred at 30 rpm for 5 minutes. The state of the kneaded mixture was then checked. This process was repeated until the mixture became lumpy. In this study, the mixture became lumpy when the combined ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane reached 80.9 wt% of the total amount, and no powdery portions were observed within the kneaded mixture. Once the mixture became lumpy, kneading at 30 rpm was started, stopping at 15-minute intervals and scraping the mixture off the stirring blades and the side walls of the container. This process was repeated four times for a total of 60 minutes, yielding Dispersion Composition 2-1. Dispersion composition 2-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

[0074] Thereafter, dispersion composition 2-1 was gradually diluted and stirred with DMAc so that the total proportion of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane was 70% by weight of the total amount, thereby obtaining dispersion composition 2-2 having a viscosity of 1980 cP when measured at 50 rpm and a viscosity of 1450 cP when measured at 100 rpm.

[0075] Dispersion composition 2-2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 50 μm, and then heat treatment was carried out using a hot air oven at 120°C for 3 minutes, 280°C for 3 minutes, and 340°C for 6 minutes to obtain single-sided metal-clad laminate 2-1. No aggregates or the like were observed in the obtained single-sided metal-clad laminate 2-1.

[0076] Next, the resin surfaces of the single-sided metal-clad laminates 2-1 were placed together and pressed at 320°C for 5 minutes under a pressure of 2 MPa to obtain a double-sided metal-clad laminate 2-1. The copper foil of the obtained double-sided metal-clad laminate 2-1 was etched away using an aqueous ferric chloride solution to prepare a fluororesin film 2-1. The CTE of the fluororesin film 2-1 was 23.2 ppm / K, and when conditioned, Dk=2.67 and Df=0.0024 at 10 GHz, and when conditioned, Dk=2.78 and Df=0.0025 at 60 GHz.

[0077] Example 3 In a container of TKHIVIS MIX (model 2P-03) manufactured by PRIMIX Corporation (formerly Tokushu Kika Kogyo Co., Ltd.), 78.5 g of fluororesin powder (1) as a granular fluororesin, 121.5 g of silica filler (2) surface-treated with hexamethyldisilazane as an inorganic filler, and 20 g of dispersant (1) and 21.1 g of DMAc as dispersants were added, and the mixture was stirred at 30 rpm for 5 minutes.

[0078] Next, to fine-tune the ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane to the total amount, a small amount of DMAc was added to the kneaded mixture, and the mixture was stirred at 30 rpm for 5 minutes. The state of the kneaded mixture was then checked. This process was repeated until the mixture became lumpy. In this study, the mixture became lumpy when the combined ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane reached 78.7 wt% of the total amount, and no powdery portions were observed within the kneaded mixture. Once the mixture became lumpy, kneading at 30 rpm was started, stopping at 15-minute intervals and scraping the mixture off the stirring blades and the side walls of the container. This process was repeated four times for a total of 60 minutes, yielding Dispersion Composition 3-1. Dispersion composition 3-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

[0079] Then, dispersion composition 3-1 was gradually diluted and stirred with DMAc so that the total proportion of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane was 70% by weight of the total amount, and dispersion composition 3-2 was obtained, having a viscosity of 2590 cP when measured at 50 rpm and a viscosity of 1700 cP when measured at 100 rpm.

[0080] Dispersion composition 3-2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 50 μm, and then heat treatment was carried out using a hot air oven at 120°C for 3 minutes, 280°C for 3 minutes, and 340°C for 6 minutes to obtain single-sided metal-clad laminate 3. No aggregates or the like were observed in the obtained single-sided metal-clad laminate 3.

[0081] Next, the resin surfaces of the single-sided metal-clad laminates 3 were placed together and pressed at 320°C for 5 minutes under a pressure of 2 MPa to obtain a double-sided metal-clad laminate 3. The copper foil of the obtained double-sided metal-clad laminate 3 was etched away using an aqueous ferric chloride solution to prepare a fluororesin film 3. The CTE of Fluororesin Film 3 was 58.1 ppm / K, and at 10 GHz after humidity conditioning, Dk=2.96, Df=0.0023, and at 60 GHz after humidity conditioning, Dk=3.03, Df=0.0027.

[0082] Example 4 In a container of TKHIVIS MIX (model 2P-03) manufactured by PRIMIX Corporation (formerly Tokushu Kika Kogyo Co., Ltd.), 98.4 g of fluororesin powder (1) as a granular fluororesin, 101.6 g of silica filler (2) surface-treated with hexamethyldisilazane as an inorganic filler, and 20 g of dispersant (1) and 21.1 g of DMAc as dispersants were added, and the mixture was stirred at 30 rpm for 5 minutes.

[0083] Next, to fine-tune the ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane to the total amount, a small amount of DMAc was added to the kneaded mixture, and the mixture was stirred at 30 rpm for 5 minutes. The state of the kneaded mixture was then confirmed. This process was repeated until the mixture became lumpy. In this study, the mixture became lumpy when the combined ratio of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane reached 78.3 wt% of the total amount, and no powdery portions were observed within the kneaded mixture. Once the mixture became lumpy, kneading at 30 rpm was started, stopping every 15 minutes, and scraping the mixture off the stirring blades and the side walls of the container. This process was repeated four times for a total of 60 minutes, yielding Dispersion Composition 4-1. Dispersion composition 4-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

[0084] Thereafter, dispersion composition 4-1 was gradually diluted and stirred with DMAc so that the total proportion of the fluororesin powder (1) and the silica filler (2) surface-treated with hexamethyldisilazane was 70% by weight of the total amount, thereby obtaining dispersion composition 4-2 having a viscosity of 2320 cP when measured at 50 rpm and a viscosity of 1720 cP when measured at 100 rpm.

[0085] Dispersion composition 4-2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 50 μm, and then heat treatment was carried out using a hot air oven at 120°C for 3 minutes, 280°C for 3 minutes, and 340°C for 6 minutes to obtain single-sided metal-clad laminate 4. No aggregates or the like were observed in the obtained single-sided metal-clad laminate 4.

[0086] Next, the resin surfaces of the single-sided metal-clad laminates 4 were placed together and pressed at 320°C for 5 minutes under a pressure of 2 MPa to obtain a double-sided metal-clad laminate 4. The copper foil of the obtained double-sided metal-clad laminate 4 was etched away using an aqueous ferric chloride solution to prepare a fluororesin film 4. The CTE of Fluororesin Film 4 was 117.5 ppm / K, and at 10 GHz after humidity conditioning, Dk=2.73, Df=0.0023, and at 60 GHz after humidity conditioning, Dk=2.78, Df=0.0027.

[0087] <Example 5> Dispersion Composition 2-1 obtained in Example 2 was diluted stepwise with DMAc and stirred so that the combined proportion of the fluororesin powder (1) and the silica filler surface-treated with hexamethyldisilazane (2) was 74 wt% or 72 wt% of the total amount. Dispersion Composition 2-3, which was 74 wt%, had a viscosity of 5160 cP when measured at 50 rpm and 3310 cP when measured at 100 rpm, while Dispersion Composition 2-4, which was 72 wt%, had a viscosity of 3320 cP when measured at 50 rpm and 2350 cP when measured at 100 rpm.

[0088] Example 6 Dispersion composition 2-2 obtained in Example 2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 75 μm, and then heat treated using a hot air oven at 120°C for 4 minutes 30 seconds, 280°C for 4 minutes 30 seconds, and 340°C for 9 minutes to obtain single-sided metal-clad laminate 2-2. No agglomerates or the like were observed in the obtained single-sided metal-clad laminate 2-2.

[0089] Next, the resin surfaces of the single-sided metal-clad laminates 2-2 were placed together and pressed at 320°C for 5 minutes under a pressure of 2 MPa to obtain a double-sided metal-clad laminate 2-2. The copper foil of the obtained double-sided metal-clad laminate 2-2 was etched away using an aqueous ferric chloride solution to prepare a fluororesin film 2-2. The CTE of the fluororesin film 2-2 was 23.4 ppm / K, and the values ​​of Dk=2.65 and Df=0.0024 at 10 GHz after humidity conditioning, and Dk=2.76 and Df=0.0025 at 60 GHz after humidity conditioning.

[0090] <Comparative Example 1> In a container of a TKHIVIS MIX (Model 2P-03) manufactured by PRIMIX Corporation (formerly Tokushu Kika Kogyo Co., Ltd.), 58.7 g of fluororesin powder (1) as a granular fluororesin, 141.3 g of silica filler (1) surface-treated with hexamethyldisilazane as an inorganic filler, 20 g of dispersant (1) and 55.1 g of DMAc were added and stirred at 30 rpm for 5 minutes. The total weight of the fluororesin powder (1) and the silica filler (1) surface-treated with hexamethyldisilazane was 72.7 wt % of the total weight, resulting in a highly viscous kneaded mixture that could not be kneaded into a solid state. The highly viscous kneaded mixture was stirred at 30 rpm, stopping every 15 minutes and scraping off the kneaded material from the stirring blades and the side walls of the container. This process was repeated four times for a total of 60 minutes, yielding Dispersion Composition 5-1. The viscosity of Dispersion Composition 5-1 was 89,300 cP when measured at 5 rpm and 52,300 cP when measured at 10 rpm.

[0091] Thereafter, dispersion composition 5-1 was gradually diluted and stirred with DMAc so that the total proportion of the fluororesin powder (1) and the silica filler (1) surface-treated with hexamethyldisilazane was 70% by weight of the total amount, thereby obtaining dispersion composition 5-2 having a viscosity of 1720 cP when measured at 50 rpm and a viscosity of 1410 cP when measured at 100 rpm.

[0092] Dispersion composition 5-2 was applied to copper foil (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) so that the thickness after heat treatment would be 50 μm, and then heat treatment was carried out using a hot air oven at 120°C for 3 minutes, 280°C for 3 minutes, and 340°C for 6 minutes to obtain metal-clad laminate 5. Visually observable aggregates of 100 μm or more were observed all over the obtained metal-clad laminate 5.

[0093] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible.

Claims

1. A dispersion composition for use in forming an insulating resin layer of a circuit board, comprising the following components (A) to (C): (A) a powdery fluorine-based resin; (B) an inorganic filler; (C) a dispersant, and having a viscosity of 1000 cP or more measured at 25°C using an E-type viscometer, A dispersion composition that is solid and contains component (A) and component (B) in a total amount of 75% by weight or more based on the total weight. (However, the rotation speed set in viscosity measurement should be such that the viscosity obtained at the set rotation speed is within a viscosity range of 10% to 90% of the torque at the set rotation speed, and this includes cases where the viscosity becomes solid and cannot be measured.)

2. The composition below: The total ratio of component (A) and component (B) is within the range of 75 to 99% by weight of the total weight. The volume ratio of component (A) to component (B) (A:B) is within the range of 15:85 to 95:

5. Proportion of component (C): in the range of 1 to 15% by weight of the total weight, Proportion of polar solvent as component (D): 0 to 24% by weight of the total weight; The dispersion composition of claim 1 having the formula:

3. 3. The dispersion composition according to claim 1, wherein the inorganic filler of component (B) has a Mohs hardness of 2 or more.

4. A method for producing the dispersion composition according to claim 1, A method for producing a dispersion composition by kneading a plurality of materials including a particulate fluorine-based resin and an inorganic filler, a step of mixing the powdery fluorine-based resin, the inorganic filler, a dispersant, and a polar solvent; a step of obtaining a solid first dispersion composition by kneading the mixture in a state in which the total weight of the mixture contains the powdery fluororesin and the inorganic filler at 75% by weight or more; A method for producing a dispersion composition, comprising:

5. A process of diluting the first dispersion composition obtained by the method according to claim 4 with a polar solvent to obtain a second dispersion composition in which the total weight of the particulate fluororesin and the inorganic filler is in the range of 60 to 75% by weight relative to the total weight of all components, and the viscosity measured at 25°C using an E-type viscometer is in the range of 1000 cP to 50000 cP; A method for producing a dispersion composition comprising: (However, the rotation speed set in viscosity measurement should be such that the viscosity obtained at the set rotation speed is within a viscosity range of 10% to 90% of the torque at the set rotation speed.)

6. A step of applying the second dispersion composition obtained by the method according to claim 5 to a substrate to form a coating film; a step of forming a fluorine-based resin layer by heat-treating the coating film; A method for producing a fluorine-based resin film, comprising:

7. A step of applying the second dispersion composition obtained by the method according to claim 5 to a metal foil to form a coating film; a step of heat-treating the coating film to obtain a metal-clad laminate in which a fluororesin layer and a metal layer are laminated; A method for producing a metal-clad laminate comprising: