JP7824044B2 - Dispersion composition, its manufacturing method, manufacturing method of fluororesin film, and manufacturing method of metal-clad laminate - Google Patents

Description

The present invention relates to a dispersion composition, a method for producing the same, a method for producing a fluororesin film, and a method for producing a metal-clad laminate.

In recent years, with the advancement of smaller, lighter, and more space-saving electronic devices, there has been growing demand for flexible printed circuits (FPCs), which are thin, lightweight, flexible, and highly durable even when repeatedly bent. Because FPCs allow for three-dimensional, high-density mounting even in limited spaces, their applications are expanding to include wiring for moving parts in electronic devices such as HDDs, DVDs, and smartphones, as well as components such as cables and connectors.

FPCs are manufactured by etching and wiring the metal layer of metal-clad laminates such as copper-clad laminates (CCL). Currently, metal-clad laminates that use a highly heat-resistant polyimide as the insulating resin layer in contact with the metal foil are commonly used.

With the recent increase in communication speeds, development of 5G and even 6G communications is progressing, and circuit board materials are being investigated for millimeter-wave radar substrates and antenna substrates that are compatible with high-speed communication standards. Among these materials, fluororesins have attracted attention due to their low dielectric dissipation factor. However, because fluororesins have a high thermal expansion coefficient, their use in combination with inorganic fillers has been considered to achieve the low thermal expansion required for insulating materials for circuit boards while taking advantage of their low dielectric dissipation factor. 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.

International Publication No. WO2019/131809 International Publication No. WO2021/132055

The object of the present invention is to provide a dispersion composition in which the particulate fluororesin and inorganic filler are uniformly dispersed with minimal agglomeration.

After extensive research, the inventors discovered that by kneading a powdered fluororesin, inorganic filler, and dispersant at a high solids concentration using a small amount of polar solvent, it is possible to obtain a dispersion composition with few agglomerated particles and a uniformly dispersed solid content, leading to the completion of the present invention.

That is, the dispersion composition of the present invention comprises the following components (A) to (C):
(A) a powdery fluorine-based resin;
(B) an inorganic filler;
(C) a dispersant,
and has a viscosity of 1000 cP or more measured at 25°C using an E-type viscometer.
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 whose viscosity cannot be measured (the same applies hereinafter).

The dispersion composition of the present invention may have a total weight ratio of component (A) and component (B) of 75% by weight 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.
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
It may have the following structure.

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.
Proportion of component (C): Within the range of 0.8 to 13.2% by weight of the total weight;
Proportion of polar solvent as component (D): 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 1,000 cP to 50,000 cP.

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

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:

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 ratio of the powdery fluororesin and the inorganic filler to the total weight of all components is within a range of 60 to 75 wt %, and the viscosity measured at 25°C using an E-type viscometer is within a range of 1,000 cP to 50,000 cP;
may also include:

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:

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:

The dispersion composition of the present invention has few agglomerated particles, and the granular fluororesin and inorganic filler are uniformly dispersed. Furthermore, in a solid state containing a low solvent content, it maintains dispersion stability over long periods of time. Furthermore, in a liquid state containing a specified solvent content, it can be adjusted to an appropriate viscosity for thick-film coating, providing excellent coatability and dispersion stability. Therefore, resin films obtained by applying the dispersion composition of the present invention and metal-clad laminates incorporating this composition as an insulating resin layer can be thickened to thick insulating layers, while achieving both the excellent dielectric properties of the fluororesin and the low thermal expansion properties of the added inorganic filler. Therefore, resin films and metal-clad laminates obtained using the dispersion composition of the present invention are useful as circuit board materials capable of complying with high-speed communication standards.

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) a powdery fluorine-based resin;
(B) an 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.

Component (A):
Component (A) is a granular fluororesin. Here, "granular" means, for example, an aggregate of particles having an average particle diameter (D ₅₀ ) in the range of 0.05 to 100 μm, preferably 0.5 to 50 μm, and more preferably 0.5 to 10 μm. The average particle diameter (D ₅₀ ) of the granular fluororesin can be determined, for example, by measuring the particle size distribution of the powder particles by laser diffraction/scattering, determining 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%.

The fluorine-based resin is a polymer containing fluorine atoms, and the type thereof is not particularly limited, but examples thereof 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), polyvinylidene fluoride (PVDF), etc. These may be used in combination of two or more types, or may contain a monomer unit based on a perfluoroolefin having a functional group in a portion of the fluorine-based resin. Preferred functional groups are carbonyl group-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 preferred as they exhibit low dielectric tangents.

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.

The average particle size (D ₅₀ ) of component (B) is not particularly limited, but is preferably in the range of 0.05 to 50 μm, and more preferably 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. The specific surface area is also not particularly limited, but is preferably in the range of 0.1 to 20 m ² /g, and more preferably 0.1 to 10 m ² /g, in consideration of suppressing deterioration of the dielectric loss tangent.
The average particle diameter of the inorganic filler can be determined by, for example, measuring the particle size distribution of the powder particles by a laser diffraction/scattering method, determining a cumulative curve with the total volume of the powder particles set to 100%, and measuring the particle diameter at the point on the cumulative curve where the cumulative volume is 50%. The specific surface area can be measured by the BET method.

The shape of component (B) is not particularly limited, but from the perspective of reducing the difference in thermal expansion coefficient between the thickness direction and the plane direction, for example, spherical or crushed spherical shapes are preferred. Component (B) may also be hollow.

The hardness of component (B) is not particularly limited, but from the perspective of breaking down agglomerates due to shearing during kneading, it is preferable for the Mohs hardness to be 2 or higher, and more preferably within the range of 2 to 9. If the Mohs hardness is less than 2, the material may deform due to shearing forces during kneading, making it difficult to break down agglomerates.

Although component (B) is not particularly limited, it is preferable to surface treat it with a coupling agent or the like. Examples of coupling agents used for surface treatment include 3-aminopropylethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropylethoxysilane, 3-isocyanatopropylethoxysilane, and hexamethyldisilazane.

Component (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 having a double bond in the molecule is more preferred.

The dispersion composition of this embodiment has few agglomerated particles, and the powdered fluororesin and inorganic filler are uniformly and stably dispersed. Furthermore, as explained below, the first dispersion composition, which is a solid with a low solvent content, has long-term dispersion stability, while the second dispersion composition, which is a liquid with a specified solvent content, has excellent thick-film coating properties and dispersion stability.

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

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 in the range of 15:85 to 95:5, and more preferably in 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, while if it exceeds 95, the viscosity increases during kneading, making it difficult to produce by dispersion through stiff kneading.

In addition, to improve the dispersibility of the solids in the first dispersion composition, the content of component (C) is preferably in the range of 1 to 15 wt %, and more preferably in the range of 1 to 10 wt %, relative to the total weight. If the content of component (C) is less than 1 wt %, the solids cannot be sufficiently dispersed, and if it exceeds 15 wt %, the dielectric loss tangent may deteriorate.

Furthermore, from the viewpoint of producing the first dispersion composition by kneading and 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 included. If the content of component (D) exceeds 24 wt %, the fluidity becomes too high, making it impossible to produce the composition 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.

The type of polar solvent for component (D) is not particularly limited, but it is preferably liquid at 25°C from the perspective of exerting its solvent function during kneading and in the dispersion composition. From this perspective, 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, and γ-butyrolactone 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.

<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 thick film coating, 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 may be too low, which may reduce the film-forming ability in the case of thick films, and if it exceeds 75 wt%, the solids concentration may be too high, which may make it difficult to form a film by casting.

Furthermore, the volume ratio (A:B) of component (A) to component (B) of the second dispersion composition is preferably within the range of 15:85 to 95:5, and more preferably within the range of 20:80 to 80:20. The reasons for setting the volume ratio (A:B) within the above range are the same as those for the first dispersion composition.

In addition, from the viewpoint of ensuring dispersibility and preventing 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 %, and more preferably in the range of 1 to 10 wt %, based on the total weight. 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 deteriorate.

Furthermore, from the viewpoint of preparing a dispersion composition with a viscosity that allows for thick film application, the content of the polar solvent as component (D) is preferably in the range of 11.8 to 39.2 wt %, and 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 of 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 more susceptible to sedimentation and aggregation of solids.

The polar solvent in the second dispersion composition can be any of the solvents exemplified for the first dispersion composition. However, the types of polar solvents used in the first dispersion composition and the second dispersion composition may be different.

In addition, from the viewpoint of enabling thick film formation, the viscosity of the second dispersion composition, measured using an E-type viscometer at 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.

The first dispersion composition and the second dispersion composition may contain optional components such as organic fillers, curing agents, plasticizers, elastomers, coupling agents, pigments, and flame retardants.

<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.

(Mixing process)
In this step, a particulate fluororesin as component (A), an inorganic filler as component (B), a dispersant as component (C), and a polar solvent as component (D) are mixed together.
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 impossible to apply sufficient shear force in the subsequent kneading step.
Therefore, this step is preferably carried out with a composition in which, relative to the total weight of the mixture, component (A) is in the range of 10 to 80 wt %, component (B) is in the range of 3.5 to 73.5 wt %, component (C) is in the range of 1 to 15 wt %, and component (D) is in the range of 1.5 to 24 wt %.

There are no particular restrictions on the order in which the components are added, but it is preferable to add and mix them in the following order: component (A), component (B), component (D), and component (C).

(hardening 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 component (A) and component (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 approximately primary particles. For this purpose, kneading is preferably 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. 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 impossible to obtain a uniform and stable dispersion.

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

<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 wt %, preferably in the range of 60 to 70 wt %, relative to the total weight, and the viscosity is in the range of 1000 cP to 50,000 cP, preferably in the range of 1000 to 30,000 cP.

Because the second dispersion composition is obtained via the first dispersion composition, the solid components, the particulate fluororesin and inorganic filler particles, are uniformly dispersed in the form of almost primary particles. Therefore, unlike a dispersion obtained by mixing and dispersing each component in a polar solvent at a low solids concentration, sedimentation and aggregation of the solids are less likely to occur.

<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.

(Coating film forming 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 an arbitrary 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, for example, a coater such as a comma, die, knife, or lip.

(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.

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 layers may be heat-treated at once.

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.

<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 in the range of 30 to 150 μm, more preferably in the range of 75 to 150 μm.

After conditioning the resin film for 72 hours at a temperature of 24-26°C and a humidity of 45-55%, the dielectric loss tangent (Df) at frequencies below 60 GHz, as measured using a split post dielectric resonator (SPDR) or split cylinder resonator, is preferably 0.003 or less, more preferably 0.0025 or less, and even more preferably 0.0020 or less. Furthermore, the relative 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 relative dielectric constant (Dk) exceed the above values, this will lead to increased dielectric loss when the film is applied to a circuit board, making it more likely to experience problems such as electrical signal loss in the transmission path of high-frequency signals in the GHz range (e.g., 1-80 GHz).

In addition, to ensure dimensional stability, the coefficient of thermal expansion (CTE) of the resin film is preferably in the range of 10 to 30 ppm/K, and more preferably in the range of 15 to 25 ppm/K.

The resin film of this embodiment may include any resin layer other than the fluorine-based resin layer.

<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.

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

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, and more preferably in the range of 5 to 25 μm. From the perspective 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, or it 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. Commercially available copper foil can also be used as the copper foil. The surface roughness of the metal layer is not particularly limited, but from the perspective of ensuring adhesion to the fluororesin layer while also reducing conductor loss, it is preferable that the ten-point average roughness (Rzjis) be in the range of 0.3 to 2.0.

The metal foil may also be surface treated with, for example, siding, aluminum alcoholate, aluminum chelate, or silane coupling agent for the purposes of rust prevention or improving adhesive strength.

The configuration and thickness of the fluororesin layer in the metal-clad laminate are the same as those of the resin film described above. Note that the metal-clad laminate of this embodiment may also include any resin layer other than the fluororesin layer.

The metal-clad laminate of this embodiment is preferably used as a circuit board material. That is, by processing the metal layer 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 manufactured.

The following examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to these examples. In the following examples, various measurements and evaluations were performed as follows, unless otherwise noted.

[Viscosity measurement]
The viscosity was measured at 25°C using an E-type viscometer (manufactured by Brookfield, trade 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.

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

[Measurement of relative permittivity and dielectric loss tangent]
The relative dielectric constant (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, trade 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 values 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%.

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

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

Example 1
In a container of T.K.HIVIS 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, 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.

Next, in order 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 confirmed. 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 portions were observed inside the kneaded mixture. From the lumpy state, kneading at 30 rpm was started, stopped at 15-minute intervals, and the kneaded mixture was scraped off 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 1-1.
Dispersion Composition 1-1 was determined to be a "solid" because it had no fluidity and its viscosity could not be measured.

Dispersion composition 1-1 was then gradually diluted with DMAc and stirred so that the combined proportion of fluororesin powder (1) and silica filler surface-treated with hexamethyldisilazane (1) was 70% by weight of the total amount, yielding dispersion composition 1-2 with a viscosity of 1750 cP when measured at 50 rpm and 1420 cP when measured at 100 rpm.

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. The coating was then heat-treated in 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 agglomerates or other particles were observed in the resulting single-sided metal-clad laminate 1.

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 at 10 GHz after humidity conditioning, Dk was 2.52 and Df was 0.0020, and at 60 GHz after humidity conditioning, Dk was 2.61 and Df was 0.0023.

Example 2
In a container of T.K.HIVIS 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.

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 total 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 inside the kneaded mixture. From the lumpy state, kneading at 30 rpm was started, stopped at 15-minute intervals, and the kneaded mixture was scraped off 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 2-1.
Dispersion composition 2-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

Dispersion composition 2-1 was then gradually diluted with DMAc and stirred so that the combined weight of the fluororesin powder (1) and the silica filler surface-treated with hexamethyldisilazane (2) was 70% by weight, yielding dispersion composition 2-2 with a viscosity of 1980 cP when measured at 50 rpm and 1450 cP when measured at 100 rpm.

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. The coating was then heat-treated in 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 agglomerates or other particles were observed in the resulting single-sided metal-clad laminate 2-1.

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 the values of Dk=2.67 and Df=0.0024 at 10 GHz after humidity conditioning, and Dk=2.78 and Df=0.0025 at 60 GHz after humidity conditioning.

Example 3
In a container of T.K. HIVIS 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.

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 total 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 inside the kneaded mixture. From the lumpy state, kneading at 30 rpm was started, stopped at 15-minute intervals, and the kneaded mixture was scraped off 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 3-1.
Dispersion composition 3-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

Dispersion composition 3-1 was then gradually diluted with DMAc and stirred so that the combined weight of the fluororesin powder (1) and the silica filler surface-treated with hexamethyldisilazane (2) was 70% by weight, yielding dispersion composition 3-2 with a viscosity of 2590 cP when measured at 50 rpm and 1700 cP when measured at 100 rpm.

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. The coating was then heat-treated in 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 agglomerates or other particles were observed in the resulting single-sided metal-clad laminate 3.

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 the fluororesin film 3 was 58.1 ppm/K, and the values of Dk=2.96 and Df=0.0023 at 10 GHz after humidity conditioning, and Dk=3.03 and Df=0.0027 at 60 GHz after humidity conditioning.

Example 4
In a container of T.K.HIVIS 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.

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 total 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 inside the kneaded mixture. From the lumpy state, kneading at 30 rpm was started, stopped at 15-minute intervals, and the kneaded mixture was scraped off 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 4-1.
Dispersion composition 4-1 was determined to be "solid" because it had no fluidity and its viscosity could not be measured.

Dispersion composition 4-1 was then gradually diluted with DMAc and stirred so that the combined weight of the fluororesin powder (1) and the silica filler surface-treated with hexamethyldisilazane (2) was 70% by weight, yielding dispersion composition 4-2 with a viscosity of 2,320 cP when measured at 50 rpm and 1,720 cP when measured at 100 rpm.

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. The coating was then heat-treated in 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 agglomerates or other particles were observed in the resulting single-sided metal-clad laminate 4.

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 was 2.73 and Df was 0.0023, and at 60 GHz after humidity conditioning, Dk was 2.78 and Df was 0.0027.

Example 5
The dispersion composition 2-1 obtained in Example 2 was diluted stepwise with DMAc and stirred so that the total 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. The viscosity of the 74 wt % dispersion composition 2-3 was 5160 cP when measured at 50 rpm and 3310 cP when measured at 100 rpm, while the viscosity of the 72 wt % dispersion composition 2-4 was 3320 cP when measured at 50 rpm and 2350 cP when measured at 100 rpm.

Example 6
The dispersion composition 2-2 obtained in Example 2 was applied to a 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 treatment was carried out 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 a single-sided metal-clad laminate 2-2.
No agglomerates or the like were observed in the resulting single-sided metal-clad laminate 2-2.

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 fluororesin film 2-2 had a CTE of 23.4 ppm/K, 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.

<Comparative Example 1>
Into a container of a T.K. HIVIS 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 as dispersants were added, and the mixture was stirred at 30 rpm for 5 minutes. At this time, the total proportion of fluororesin powder (1) and silica filler (1) surface-treated with hexamethyldisilazane was 72.7 wt% of the total amount, 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, stopped at 15-minute intervals, and the kneaded mixture was scraped off the stirring blades and the side walls of the container. This operation was repeated four times for a total of 60 minutes of stirring, to obtain 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.

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

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. The coating was then heat-treated in 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 larger were observed over the entire surface of the obtained metal-clad laminate 5.

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 (7)

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