TW202045565A - Liquid composition, ferroelectric insulation sheet, and method for producing same - Google Patents

Abstract

Provided are: a liquid composition from which a ferroelectric insulation sheet can be produced that has excellent flexibility, dielectric properties including a high dielectric constant and a low dielectric loss tangent, and bondability or adhesiveness; a method for producing a ferroelectric insulation sheet using said liquid composition; and a ferroelectric insulation sheet having excellent flexibility, the above-mentioned dielectric properties, and adhesiveness or bondability. A liquid composition according to the present invention comprises: powder including a tetrafluoroethylene-based polymer having a melt viscosity of 1*102-1*106 Pa·s at 380 DEG C, and having an average particle diameter of 30 [mu]m or less; an inorganic filler having a dielectric constant of 10 or more at 25 DEG C; and a liquid dispersion medium, wherein the liquid composition has a viscosity of 50-10,000 mPa·s at 25 DEG C.

Description

Liquid composition, strong dielectric insulating sheet and manufacturing method thereof

The present invention relates to a liquid composition and a ferroelectric insulating sheet comprising a tetrafluoroethylene polymer with high melt processability and a ferroelectric inorganic filler, and a method of manufacturing the same.

With the miniaturization and high-functionality of electronic devices such as mobile phones, research on embedding electronic parts mounted on printed wiring boards in substrates has been popular. If a ferroelectric insulating sheet is inserted between a pair of electrodes as a dielectric layer, a small and thin capacitor can be constructed. Previously, the use of ceramic sintered bodies as ferroelectric insulating sheets in capacitors used for embedding in printed wiring boards was the mainstream. However, ceramic sintered bodies have low flexibility and become brittle when thinned. In order to solve this problem, it has been proposed to use a ferroelectric insulating sheet containing a fluorine-containing polymer and a ferroelectric inorganic filler (see Patent Documents 1 to 3). Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2010-180070 Patent Document 2: Japanese Patent Laid-Open No. 2013-008724 Patent Document 3: Japanese Patent Laid-Open No. 2002-076547

[The problem to be solved by the invention]

However, according to research conducted by the inventors of the present invention, the ferroelectric insulating sheets of Patent Documents 1 to 3 are not sufficient in terms of flexibility or dielectric properties. In addition, when the ferroelectric insulating sheet is mounted on an electronic device, adhesion or adhesion to other substrates (members) is also required. However, the ferroelectric insulating sheets of Patent Documents 1 to 3 are also insufficient in this respect. The object of the present invention is to provide a liquid composition capable of manufacturing a flexible, dielectric properties including high dielectric constant and low dielectric loss tangent, and excellent bonding or adhesion properties. And its purpose is to provide a method for manufacturing a ferroelectric insulating sheet using the liquid composition, and a ferroelectric insulating sheet excellent in flexibility, the above-mentioned dielectric properties, and adhesion or adhesion. [Technical means to solve the problem]

The present invention has the following aspects. [1] A liquid composition having a viscosity of 50 to 10000 mPa·s at 25°C and containing: tetrafluoroethylene with a melt viscosity of 1×10 ² ～1×10 ⁶ Pa·s at 380°C Ethylene polymer powder with an average particle size of 30 μm or less, an inorganic filler with a dielectric constant of 10 or more at 25°C, and a liquid dispersion medium. [2] The liquid composition as described in [1], wherein the above-mentioned tetrafluoroethylene-based polymer system further has tetrafluoroethylene-based polymerization of perfluoro(alkyl vinyl ether)-based units or hexafluoropropylene-based units Things. [3] The liquid composition according to [1] or [2], wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) and having polar functional groups A polymer or a tetrafluoroethylene-based polymer that contains 2.0 to 5.0 mol% of perfluoro(alkyl vinyl ether)-based units with respect to all units and does not have a polar functional group. [4] The liquid composition according to any one of [1] to [3], wherein the average particle size of the powder is 0.05 to 6 μm. [5] The liquid composition according to any one of [1] to [4], wherein the content of the inorganic filler is 10% by mass or more.

[6] The liquid composition according to any one of [1] to [5], wherein the inorganic filler is a perovskite-type ferroelectric filler or a bismuth layered perovskite-type ferroelectric filler. [7] The liquid composition according to any one of [1] to [6], wherein the inorganic filler is a spherical inorganic filler having an average particle diameter of 2 μm or less, or an average length of 30 μm or less and an average diameter of 2 μm The following fibrous inorganic fillers. [8] The liquid composition according to any one of [1] to [7], wherein the liquid dispersion medium is an aprotic polar solvent. [9] The liquid composition according to any one of [1] to [8], which further includes an inorganic filler having a linear expansion coefficient of 10 ppm/°C or less and a dielectric constant of less than 10 at 25°C. [10] The liquid composition according to any one of [1] to [9], which further contains a dispersant.

[11] A method for manufacturing a ferroelectric insulating sheet, which comprises applying the liquid composition as described in any one of [1] to [10] above to the surface of a support, and heating the liquid composition The crystalline dispersion medium is removed, and the tetrafluoroethylene-based polymer is fired to obtain a ferroelectric insulating sheet having a layer containing the tetrafluoroethylene-based polymer and the inorganic filler. [12] A ferroelectric insulating sheet comprising a tetrafluoroethylene polymer with a melt viscosity of 1×10 ² ～1×10 ⁶ Pa·s at 380°C and a dielectric constant of 10 at 25°C The above inorganic fillers. [13] The ferroelectric insulating sheet according to [12], wherein the inorganic filler is a perovskite-type ferroelectric filler or a bismuth-layered perovskite-type ferroelectric filler. [14] The ferroelectric insulating sheet as described in [12] or [13], which has a thickness of 1-100 μm. [15] The ferroelectric insulating sheet described in any one of [12] to [14] has a dielectric constant of 10 or more, and a dielectric loss tangent of 0.1 or less. [Effects of Invention]

According to the present invention, there is provided a ferroelectric insulating sheet, which has high flexibility and uniform dielectric properties due to the use of tetrafluoroethylene polymer powder with high thermal melting property.

The following terms have the following meanings. "Viscosity of the liquid composition" is the viscosity of the liquid composition measured at 25°C with a rotation speed of 30 rpm using a type B viscometer. Repeat the measurement 3 times and take the average of the 3 measurements. "The thixotropy ratio of the liquid composition" is the value calculated by dividing the viscosity η1 measured at a speed of 30 rpm by the viscosity η2 measured at a speed of 60 rpm. Repeat the measurement of each viscosity 3 times and take the average of the 3 measurements. The "average particle size of the powder" is to disperse the powder in water and analyze it by the laser diffraction-scattering method using a laser diffraction-scattering particle size distribution measuring device (manufactured by Horiba, Ltd., LA-920 measuring device) And find out. That is, the particle size distribution of the powder is measured by the laser diffraction-scattering method, and the total volume of the cluster of particles is set to 100% to obtain the cumulative curve. The point on the cumulative curve where the cumulative volume becomes 50% is the average particle size . The same applies to the average particle size of the inorganic filler. The "average length and average diameter of the fibrous inorganic filler" is the average of the values measured by each of the fibrous inorganic fillers by taking a 200-fold image of the scanning electron microscope to take 10 field of view photography. The "melting temperature of polymer" is the temperature corresponding to the maximum value of the melting peak of the polymer measured by differential scanning calorimetry (DSC).

"Polymer melt viscosity" is based on ASTM D 1238, using a flow tester and a 2ϕ-8L die, the polymer sample (2 g) heated at the measurement temperature for 5 minutes in advance is maintained under a load of 0.7 MPa Measure the measured value of the temperature. "Storage modulus of polymer" is based on the value measured in ISO 6721-4: 1994 (JIS K7244-4: 1999). The "melt viscosity of polymer" is based on ASTM D 1238, using a flow tester and a 2ϕ-8L die, a sample (2 g) of the polymer heated in advance at the measurement temperature for 5 minutes is maintained under a load of 0.7 MPa It is the value measured by measuring the temperature. "Ten point average roughness (Rzjis)" is the value specified in JIS B 0601:2013 Annex JA. "Peel strength" is to fix the position of the laminate cut into a rectangular shape (length 100 mm, width 10 mm) at a position 50 mm from one end of the long side direction, with a stretching speed of 50 mm/min from one end of the long side direction The maximum load (N/cm) applied when the metal foil and the polymer layer are peeled off at an angle of 90° with respect to the laminate. "Filling crystallinity" is the value measured by the X-ray diffraction device, which separates the X-ray diffraction pattern of the filler into the crystalline peak intensity generated from the crystalline component and the value generated from the amorphous component The intensity of the amorphous halo is calculated by the integral intensity of each, and the value calculated by the following formula (1). Crystallinity (%)=Sc/(Sc＋Sa)×100・・・(1) Furthermore, Sc represents the integrated intensity of the crystalline peak, and Sa represents the integrated intensity of the amorphous halo. The "unit" in the polymer can be an atomic group directly formed from a molecule of monomer by polymerization reaction, or it can be the structure of the aforementioned atomic group by processing the polymer obtained by polymerization reaction by a specific method Part of the atom group after transformation.

The liquid composition of the present invention contains: containing average particles of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") with a melt viscosity of 1×10 ² to 1×10 ⁶ Pa·s at 380°C Powder with a diameter of 30 μm or less (hereinafter also referred to as "F powder"), an inorganic filler with a dielectric constant of 10 or more at 25°C, and a liquid dispersion medium. The viscosity of the liquid composition of the present invention is 50 to 10,000 mPa·s. The manufacturing method of the present invention is a method of applying the liquid composition on the surface of a support, heating to remove the liquid dispersion medium, and firing the F polymer to obtain the F polymer and the above Ferroelectric insulating sheet of inorganic filler (also referred to as "FE sheet" below). The liquid composition of the present invention is a liquid composition containing F powder and the above-mentioned inorganic filler, each of which has high dispersion uniformity and excellent stability. As the reason, the aspect that the F powder contains a specific hot-melt F polymer and the aspect that the powder has a specific particle size can be cited. It is believed that by dispersing the F powder in a liquid dispersion medium, not only the viscosity of the liquid composition is concentrated in a specific range, but also the dispersion state of the above-mentioned inorganic filler, which has a high specific gravity and is easy to precipitate or agglomerate, is substantially improved. The improvement of the dispersibility is more remarkable when the content of the above-mentioned inorganic filler contained in the liquid composition is higher. In addition, it is also considered that if an FE sheet is produced from a liquid composition in this state, the powder particles are densely packed with each other in the film of the liquid composition formed on the surface of the support (hereinafter also referred to as "wet film") Therefore, the above-mentioned inorganic fillers are not easy to deposit and are uniformly dispersed in the FE sheet. In addition, it is also considered that due to the meltability of the F polymer, the above-mentioned inorganic filler is uniformly dispersed in the dense matrix of the F polymer in the FE sheet, forming a sheet with adhesiveness or adhesion. It is inferred that due to these synergistic effects, the flexibility of the FE sheet becomes higher, and an FE sheet with excellent dielectric properties and adhesion or adhesion is obtained.

In contrast, when a liquid composition containing a solvent-soluble fluoropolymer such as polyvinylidene fluoride and the above-mentioned inorganic filler is used to produce an FE sheet, the above-mentioned inorganic filler is easily deposited on the liquid film and cannot be The FE sheet in which the above-mentioned inorganic filler is uniformly dispersed is obtained, and the characteristics of the FE sheet tend to become uneven. In addition, when extruding a kneaded product of the non-melting fibrous tetrafluoroethylene polymer and the above-mentioned inorganic filler to produce an FE sheet, the kneaded product has low processability and cannot be obtained with high flexibility. FE film. In addition, it is difficult to uniformly knead the tetrafluoroethylene-based polymer and the inorganic filler due to the poor specific gravity or low compatibility. Therefore, the inorganic fillers are concentrated in the FE sheet, and the characteristics of the FE sheet tend to become uneven. Furthermore, during kneading, the above-mentioned tetrafluoroethylene-based polymer is easily fibrillated, and the porosity of the FE sheet increases. Therefore, it is difficult to improve the dielectric properties of the FE sheet due to the presence of an air layer.

The F polymer in the present invention is a polymer having units based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The F polymer can be a homopolymer of TFE or a copolymer of TFE and a comonomer that can be copolymerized with TFE. The F polymer preferably has 90-100 mol% of TFE units with respect to all units constituting the polymer. The fluorine content of the F polymer is preferably 70 to 76% by mass, more preferably 72 to 76% by mass. If the F polymer with the fluorine content in the above range is used, the dielectric properties of the FE sheet can be improved (especially low dielectric loss tangent). Examples of F polymers include: polytetrafluoroethylene (PTFE), copolymers of TFE and ethylene (ETFE), copolymers of TFE and propylene, TFE and perfluoro (alkyl vinyl ether) (hereinafter also referred to as " PAVE”) copolymer (PFA), TFE and hexafluoropropylene (hereinafter also referred to as “HFP”) copolymer (FEP), TFE and fluoroalkyl ethylene (hereinafter also referred to as “FAE”) copolymer, Copolymer of TFE and chlorotrifluoroethylene (CTFE). Furthermore, the copolymer may further have units based on other comonomers.

The polymer melt viscosity at 380 F deg.] C of ^{1 × 10 2 ~ 1 × 10} 6 Pa · s, more preferably at 300 deg.] C of ^{1 × 10 2 ~ 1 × 10} 6 Pa · s. The FE sheet formed by the F polymer of the melt viscosity has higher flexibility and is easy to process. Therefore, the FE sheet is advantageous for use in the field of substrates with built-in electronic components. The F polymer is preferably a hot-melt F polymer, more preferably an F polymer having a melting temperature of 140-320°C, and still more preferably an F polymer having a melting temperature of 260-320°C. In this case, it is easy to form an FE sheet with a uniform thickness. In addition, it is easy to form an FE sheet that is more excellent in adhesion or adhesion. Preferred specific examples of the F polymer include FEP, PFA, and PTFE with a number average molecular weight of 200,000 or less. Furthermore, the above-mentioned PTFE also contains a copolymer of TFE and a very small amount of comonomers (HFP, PAVE, FAE, etc.). The number average molecular weight of the aforementioned PTFE is preferably 10 or less, more preferably 50,000 or less. The number average molecular weight of the aforementioned PTFE is preferably 10,000 or more. In addition, the number average molecular weight is a value calculated based on the following formula (2). Mn=2.1×10 ¹⁰ ×ΔHc ^-5.16・・・(2) In formula (2), Mn represents the number average molecular weight of the PTFE, and ΔHc represents the heat of crystallization of the PTFE measured by differential scanning calorimetry ( cal/g).

The F polymer is preferably an F polymer having a TFE unit and a functional group. As the functional group, a carbonyl group-containing group, a hydroxyl group, an epoxy group, an amino group, and an isocyanate group are preferable. The functional group may be contained in the unit in the F polymer, or may be contained in the terminal group of the main chain of the polymer. As the latter polymer, a polymer having a functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc. can be mentioned. In addition, F polymers with functional groups obtained by plasma treatment or radiation treatment of F polymers can also be cited. The F polymer having a functional group is preferably an F polymer having a TFE unit and a unit having a functional group. The unit having a functional group is preferably a unit based on a monomer having a functional group, and more preferably a unit based on a monomer having a carbonyl group-containing group, a hydroxyl group, an epoxy group, an amine group, and an isocyanate group.

The monomer having a carbonyl group-containing group is preferably a cyclic monomer having an acid anhydride residue, a monomer having a carboxyl group, vinyl ester and (meth)acrylate, and more preferably a cyclic monomer having an acid anhydride residue The body is particularly preferably itaconic anhydride, citraconic anhydride, 5-norene-2,3-dicarboxylic anhydride (alias: bicycloheptene dicarboxylic anhydride; hereinafter also referred to as "NAH") and maleic anhydride. As a preferable specific example of the F polymer having a functional group, an F polymer having a TFE unit, an HFP-based unit, a PAVE-based unit or a FAE-based unit, and a functional group-based unit can be cited. Examples of PAVE include: CF ₂ =CFOCF ₃ , CF ₂ =CFOCF ₂ CF ₃ , CF ₂ =CFOCF ₂ CF ₂ CF ₃ (PPVE), CF ₂ =CFOCF ₂ CF ₂ CF ₂ CF ₃ , CF ₂ =CFO( CF ₂ ) ₈ F. Examples of FAE include: CH ₂ =CH(CF ₂ ) ₂ F, CH ₂ =CH(CF ₂ ) ₃ F, CH ₂ =CH(CF ₂ ) ₄ F, CH ₂ =CF(CF ₂ ) ₃ H, CH ₂ =CF(CF ₂ ) ₄ H. The F polymer preferably has 90 to 99 mol% of TFE units, 0.5 to 9.97 mol% of HFP-based units, PAVE-based units or FAE-based units, and 0.01 mol% of all units constituting the polymer. ~3 mol% of units with functional groups. As a specific example of the F polymer, the polymer described in International Publication No. 2018/16644 can be cited.

When the F polymer has a functional group (especially a carbonyl group-containing group), the FE sheet is more excellent in adhesion or adhesion when it is attached to other members (substrate, sheet, film, etc.). In addition, when the FE sheet is used as an interlayer insulating layer for embedding electronic parts with a printed wiring board, it exhibits higher adhesion to the electronic parts, and the fixing force of the electronic parts to the printed wiring board becomes higher.

Preferable specific examples of the F polymer include: a polymer containing a TFE unit and a PAVE unit with a polar functional group (hereinafter also referred to as "polymer (p1)"), and a TFE unit and a PAVE unit and relatively A polymer without a polar functional group containing 2.0-5.0 mol% of PAVE units in all units (hereinafter also referred to as "polymer (p2)"). In the case of using these polymers, the dispersibility of the liquid composition is easier to improve. In addition, fine crystals are easily formed when the sheet is formed, and the FE sheet is easily excellent in adhesion or adhesion.

As the polymer (p1), a polymer containing a TFE unit, a PAVE unit, and a unit based on a monomer having a polar functional group is preferred. The polymer preferably contains 90 to 99 mol% of TFE units, 0.5 to 9.97 mol% of PAVE units, and 0.01 to 3 mol% of units based on monomers with polar functional groups, respectively, relative to all units. . Furthermore, as the monomer having a polar functional group, itaconic anhydride, citraconic anhydride, and NAH are preferred. As a specific example of the polymer (p1), the polymer described in International Publication No. 2018/16644 can be cited.

The polymer (p2) is preferably composed of only TFE units and PAVE units, and contains 95.0-98.0 mol% of TFE units and 2.0-5.0 mol% of PAVE units with respect to all units. The content of the PAVE unit in the polymer (p2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more with respect to all units. Furthermore, that the polymer (p2) does not have polar functional groups means that the number of polar functional groups in the polymer is less than 500 per 1×10 ⁶ carbon atoms constituting the main chain of the polymer. The number of the aforementioned polar functional groups is preferably 100 or less, more preferably less than 50. The lower limit of the number of the aforementioned polar functional groups is usually zero.

The polymer (p2) can be produced using a polymerization initiator or chain transfer agent that does not generate polar functional groups as the end groups of the polymer chain, or it can be used for F polymers with polar functional groups (in the main chain of the polymer). The terminal group has a polar functional group derived from the polymerization initiator, etc.) by fluorination treatment. As a method of fluorination treatment, a method using fluorine gas (refer to Japanese Patent Laid-Open No. 2019-194314, etc.) can be cited.

The average particle size of the F powder is preferably 0.05-6 μm, more preferably 0.2-3 μm. Within this range, the fluidity and dispersibility of the powder become better, the accumulation effect of the powder particles is higher, and the dielectric properties of the FE sheet are further improved. The bulk density of the F powder is preferably 0.05 g/mL or more, more preferably 0.08 to 0.5 g/mL. The dense packed bulk density of the powder is preferably 0.05 g/mL or more, more preferably 0.1 to 0.8 g/mL. When the loose packing bulk density or the close packing bulk density is within the above range, the powder has excellent handling properties.

The F powder in the present invention may also contain polymer components (aromatic polymers, etc.) other than the F polymer, but it is preferable to have the F polymer as the main component. The content of the F polymer in the F powder is preferably 80% by mass or more, more preferably 100% by mass. In addition, the surface of the F powder can also be coated with silicon dioxide.

The dielectric constant of the inorganic filler in the present invention at 25°C is 10 or more, preferably 25 or more, and more preferably 50 or more. The upper limit of the dielectric constant is preferably 10,000. If an inorganic filler having a dielectric constant in the above-mentioned range is used, excellent dielectric properties (high dielectric constant and low dielectric loss tangent) can be easily imparted to the FE sheet. Furthermore, the dielectric constant in the present invention is the dielectric constant measured at 28 GHz. The inorganic filler is preferably an inorganic filler containing barium titanate, lead zirconate titanate, lead titanate, zirconium oxide, titanium oxide, strontium bismuth tantalate, strontium bismuth niobate, or bismuth titanate. As the inorganic filler, in terms of higher dielectric constant and resistivity, perovskite-type ferroelectric filler and bismuth-layered perovskite-type ferroelectric filler are preferred. Examples of perovskite-type ferroelectric fillers include barium titanate fillers, lead zirconate titanate fillers, lead titanate fillers, zirconium oxide fillers, and titanium oxide fillers. Examples of the bismuth layered perovskite type ferroelectric filler include bismuth strontium tantalate filler, bismuth strontium niobate filler, and bismuth titanate filler.

The crystallinity of the inorganic filler is preferably 80% or more, more preferably 90% or more. The crystallinity is below 100%. In this case, the inorganic filler is not only excellent in high dielectric properties, but also easily improves the liquid properties of the liquid composition.

The inorganic filler is preferably surface-treated. Examples of surface treatment agents include polyols (trimethylolethane, pentaerythritol, propylene glycol, etc.), saturated fatty acids (stearic acid, lauric acid, etc.), saturated fatty acid esters, alkanolamines, amines (trimethyl Amine, triethylamine, etc.), paraffin, silane coupling agent, silicone, polysiloxane. As the silane coupling agent, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxy Silane, 3-methacryloxypropyltriethoxysilane and 3-isocyanatopropyltriethoxysilane.

The specific gravity of the inorganic filler is preferably 4 or more, more preferably 6 or more. The shape of the inorganic filler can be any of granular, needle-shaped (fibrous), and plate-shaped. Specific shapes of inorganic fillers include: spherical, scaly, layered, leaf-shaped, almond-shaped, columnar, coronal, equiaxed, leaf-shaped, mica-shaped, massive, flat, and wedge-shaped , Rose flower-shaped, net-shaped, angular columnar. As described above, in the liquid composition of the present invention, the F powder is uniformly dispersed, so the inorganic filler is easily dispersed well. From the viewpoint of densely and uniformly dispersing the inorganic filler to obtain an FE sheet with more excellent dielectric properties, it is preferable to use an inorganic filler having a fine structure as the inorganic filler. Preferred specific examples of the inorganic filler having a fine structure include spherical inorganic fillers having an average particle diameter of 2 μm or less, and fibrous inorganic fillers having an average length of 30 μm or less and an average diameter of 2 μm or less. The average particle diameter of the former inorganic filler is preferably 0.05-5 μm, more preferably 0.1-3 μm. In this case, the inorganic filler is less likely to precipitate in the liquid composition and wet film. In the latter inorganic filler, the average length is the average length of the fiber, and the average diameter is the average diameter of the fiber. The average length is preferably 1-30 μm, more preferably 10-20 μm. The average diameter is preferably 0.1 to 1 μm, more preferably 0.3 to 0.6 μm.

As the liquid dispersion medium in the present invention, a polar solvent that is liquid at 25°C is preferred, and it may be protic or aprotic. In addition, the liquid dispersion medium may be an aqueous solvent or a non-aqueous solvent. As the liquid dispersion medium, an aprotic polar solvent is preferred in terms of easily improving the liquid properties of the liquid composition. Furthermore, a liquid dispersion medium can also use 2 or more types together. As the liquid dispersion medium, water, amide, alcohol, arylene, ester, ketone, and glycol ether are preferable, water, ketone, and amide are more preferable, and ketone and amide are still more preferable.

Specific examples of the liquid dispersion medium include: water, methanol, ethanol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2 -Pyrolidone, dimethyl sulfide, diethyl ether, dioxane, ethyl lactate, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone , Ethylene glycol monoisopropyl ether, cellosolve (methyl cellosolve, ethyl cellosolve, etc.). Preferable specific examples of aprotic polar solvents include methyl ethyl ketone, cyclohexanone, and N-methyl-2-pyrrolidone.

From the viewpoint of further improving the dispersibility of each component, the liquid composition of the present invention preferably further contains a dispersant. The dispersant is a compound having a hydrophilic group and a hydrophobic group. The dispersant is preferably a fluorine-based dispersant, a silicone-based dispersant, and an acetylene-based dispersant, and more preferably a fluorine-based dispersant. The dispersant is preferably nonionic. As the fluorine-based dispersant, fluorinated monohydric alcohols, fluorinated polyhydric alcohols, fluorosilicones, and fluoropolyethers are preferred. The fluorinated polyol is preferably a copolymer of fluorinated (meth)acrylate and (meth)acrylate having a hydroxyl group, more preferably (meth)acrylic acid having a polyfluoroalkyl group or a polyfluoroalkenyl group Esters, and (meth)acrylates having a polyoxyalkylene monool group. The fluorosilicone is preferably a polyorganosiloxane containing a C-F bond in a part of the side chain. The fluoropolyether is preferably a compound in which a part of hydrogen atoms of polyoxyalkylene alkyl ether is substituted with fluorine atoms.

The liquid composition of the present invention preferably further contains an inorganic filler having a linear expansion coefficient of 10 ppm/°C or less and a dielectric constant of less than 10 at 25°C (hereinafter also referred to as "second inorganic filler"). In addition, the above-mentioned inorganic filler having a dielectric constant of 10 or more at 25°C is also referred to as the "first inorganic filler" below. If the liquid composition of the present invention contains the second inorganic filler, the thermal expansion of the FE sheet formed therefrom is likely to be further reduced. The second inorganic filler may be included in the first inorganic filler, or may be included in the form of another filler different from the first inorganic filler. The liquid composition of the present invention contains an F polymer with excellent dispersibility and has excellent liquid properties. Therefore, even when the second inorganic filler is included, the liquid physical properties imparted by the interaction between the second inorganic filler and the first inorganic filler are not easily reduced. In addition, in the FE sheet formed by the two, the two are evenly distributed, so the physical properties of the two are easy to be highly expressed.

When the second inorganic filler is included, the ratio of the second inorganic filler in the liquid composition of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more. The ratio of the second inorganic filler is preferably 40% by mass or less, more preferably 30% by mass or less. Even when a large amount of the second inorganic filler is contained, the liquid properties of the liquid composition of the present invention are excellent. The second inorganic filler has a dielectric constant of less than 8 at 25°C. The dielectric constant of the second inorganic filler at 25°C is preferably 1 or more. The linear expansion coefficient of the second inorganic filler is more preferably 8 ppm/°C or less. The linear expansion coefficient of the second inorganic filler is preferably 0.01 ppm/°C or more.

As the second inorganic filler, boron nitride and silicon oxide (silicon dioxide) are preferred, and silicon oxide (silicon dioxide) is more preferred. These second inorganic fillers may be sintered bodies (ceramics). As the second inorganic filler, boron nitride filler and silicon dioxide filler are preferred. The average particle diameter of the second inorganic filler is preferably 0.1 μm or more, more preferably 0.3 μm or more. The average particle size is preferably 10 μm or less, more preferably 6 μm or less. If the average particle diameter is within this range, the interaction between the components is relatively high, and the dispersibility of the liquid composition is likely to be improved.

Examples of the shape of the second inorganic filler include spherical, scaly, plate, and fibrous shapes. When the second inorganic filler is spherical, the ratio of the short diameter to the long diameter is preferably 0.8 or more and less than 1. In this case, the interaction between the components is likely to increase. When the second inorganic filler is scaly, the aspect ratio is preferably 5 or more, more preferably 10 or more. The aspect ratio is preferably 1000 or less. In this case, the average long diameter (the average value of the diameter in the length direction) is preferably 1 μm or more, more preferably 3 μm or more. The average long diameter is preferably 20 μm or less, more preferably 10 μm or less. The average short diameter is preferably 0.01 μm or more, more preferably 0.1 μm or more. The average short diameter is preferably 1 μm or less, more preferably 0.5 μm or less. In this case, the interaction between the components is likely to increase. As a preferable specific example of the second inorganic filler, spherical silica fillers ("Admafine" series manufactured by Admatechs, etc.) having an average particle diameter of more than 0.10 μm and less than 1 μm can be cited.

Furthermore, the liquid composition may contain other materials within the range which does not impair the effect of this invention. Other materials can be dissolved in the liquid composition or insoluble. The other material may be a non-curable resin or a curable resin. Examples of non-curable resins include hot-melt resins and non-melt resins. As the hot-melt resin, thermoplastic polyimide can be cited. Examples of the non-meltable resin include a cured product of a curable resin.

Examples of curable resins include polymers having reactive groups, oligomers having reactive groups, low-molecular compounds, and low-molecular compounds having reactive groups. Examples of the reactive group include a carbonyl group-containing group, a hydroxyl group, an amino group, and an epoxy group. Examples of curable resins include epoxy resins, thermosetting polyimides, polyimides, acrylic resins, phenol resins, polyester resins, polyolefin resins, and modified polyimides. Polyphenylene ether resin, polyfunctional cyanate resin, polyfunctional maleimide-cyanate resin, polyfunctional maleimide resin, vinyl ester resin, urea resin, diallyl phthalate Resin, melanin resin, guanamine resin, melamine-urea co-condensation resin.

Specific examples of epoxy resins include naphthalene type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, Alicyclic epoxy resin, aliphatic chain epoxy resin, cresol novolac epoxy resin, phenol novolac epoxy resin, alkylphenol novolac epoxy resin, aralkyl epoxy Resin, biphenol type epoxy resin. Examples of the bismaleimide resin include the resin composition (BT Resin) described in JP 7-70315 A, and the resin described in International Publication No. 2013/008667. Polyamide acid usually has a reactive group capable of reacting with the oxygen-containing polar group possessed by the F polymer. Examples of the diamines and polycarboxylic dianhydrides that form polyamide acids include paragraph [0020] of Japanese Patent No. 5766125, paragraph [0019] of Japanese Patent No. 5766125, and Japanese Patent Laid-Open No. 2012- The compound described in paragraph [0055] and paragraph [0057] of Bulletin No. 145676.

Examples of the hot-melt resin include thermoplastic resins such as thermoplastic polyimide, and hot-melt cured products of curable resins. Examples of thermoplastic resins include polyester resins, polyolefin resins, styrene resins, polycarbonates, thermoplastic polyimides, polyarylates, polyarylenes, polyarylenes, aromatic polyamides, and aromatic polyethers. Amide, polyphenylene sulfide, polyaryl ether ketone, polyamide imide, liquid crystal polyester, polyphenylene ether, preferably thermoplastic polyimide, liquid crystal polyester, and polyphenylene ether. Moreover, as the other materials, thixotropy imparting agents, defoamers, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, brighteners, and coloring agents may also be cited , Conductive agent, release agent, surface treatment agent, viscosity regulator, flame retardant.

The viscosity of the liquid composition of the present invention is preferably 75-5000 mPa·s, more preferably 100-2000 mPa·s. In this case, it is possible to more reliably prevent the precipitation of the inorganic filler in the liquid composition and the wet film. Moreover, its coating properties are also more excellent. In addition, the thixotropic ratio of the liquid composition is preferably 1.0 to 2.2, more preferably 1.4 to 2.2, and even more preferably 1.5 to 2.0. In this case, not only is the dispersibility of the liquid composition excellent, but the homogeneity of the FE sheet is also easier to improve.

The ratio of the F polymer in the liquid composition of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more. The ratio is preferably 60% by mass or less, and more preferably 50% by mass or less. The ratio of the inorganic filler in the liquid composition of the present invention is preferably 1% by mass or more, more preferably 10% by mass or more. The ratio is preferably 50% by mass or less, more preferably 40% by mass or less. The liquid composition of the present invention is highly stable in the dispersed state by the F powder, and therefore, even if it contains a large amount of inorganic filler, the dispersibility is excellent. The ratio of the liquid dispersion medium in the liquid composition of the present invention is preferably 10% by mass or more. The ratio is preferably 50% by mass or less, more preferably 40% by mass or less. When the liquid composition of the present invention contains a dispersant, the ratio is preferably 10% by mass or less, and more preferably 5% by mass or less. When the liquid composition of the present invention contains the above-mentioned second inorganic filler, the liquid composition of the present invention preferably contains 10-60% by mass of F polymer and 10-50% by mass of the first inorganic filler in this order. Filler and 10-50% by mass of the second inorganic filler. Even in this aspect including a large amount of the first inorganic filler and the second inorganic filler, the liquid composition of the present invention has excellent dispersibility.

In the manufacturing method of the ferroelectric insulating sheet of the present invention, first, the liquid composition of the present invention is applied to the surface of the support to form a wet film on the surface of the support. Then, the wet film is heated to remove the liquid dispersion medium from the wet film, and the F polymer is fired to obtain an FE sheet laminated on the support. Thereafter, if necessary, the support is separated from the FE sheet to obtain a separate FE sheet. The manufacturing target of the manufacturing method of the present invention may be a laminate of a support and an FE sheet, or a separate FE sheet separated from the support.

The support may be a releasable support that can remove the FE sheet from the laminate of the support and the FE sheet, or it may be a non-peelable support. Examples of the support having a releasable surface include: a sheet or film containing a material that the F polymer is not easily fused during firing of the F polymer, and a sheet or film that has been subjected to a releasable surface treatment. Optionally, it may also be a support containing a material that can be removed from the laminate with a solvent or an etchant. As the non-peelable support, a sheet or film containing a material that the F polymer easily fuses during firing of the F polymer can be cited. Examples of the material of the support include inorganic materials such as metals and glass, heat-resistant resins such as heat-resistant resins or cured products of curable resins. The support in the production method of the present invention is preferably a film or sheet containing a metal material (hereinafter also referred to as "metal foil"), and as the production target, it is preferably an FE sheet present on a metal foil. In addition, the FE sheet existing on the metal foil can also be made into a separate FE sheet by removing the metal foil with an etchant.

If metal foil is used for the support, a metal foil with an FE sheet (metal foil with a resin layer) is obtained as a laminate. Hereinafter, the FE sheet layer in this laminate is also referred to as "resin layer". If the metal foil is processed into a circuit pattern by etching or the like in this laminate, a printed wiring board is obtained. In this case, the thickness of the resin layer is preferably 1-50 μm, more preferably 2-15 μm. Within this range, it is easy to balance electrical characteristics and warpage suppression when the laminate is processed into a printed wiring board. Moreover, if another metal foil is joined to the surface of the resin layer on the opposite side to the metal foil, a thin capacitor can be produced. The capacitor can also be used to form a non-volatile memory (FeRAM). In this case, the thickness of the resin layer is preferably 0.01-50 μm, more preferably 0.1-15 μm.

Examples of metals constituting the metal foil include copper, copper alloys, stainless steel, nickel, nickel alloys (including 42 alloys), aluminum, and aluminum alloys. As the metal foil, copper foil is preferred, and rolled copper foil without distinction between front and back or electrolytic copper foil with distinction between front and back is preferred. Furthermore, the metal foil may also be a metal foil with a carrier laminated on a carrier via an intermediate layer. In addition, the metal foil may have a laminated structure having a base material layer (for example, copper foil) containing the above-mentioned metal and a roughening treatment layer containing metal particles (roughened particles). In this case, the surface of the roughened layer constitutes the surface of the metal foil. The metal particles are preferably formed of metal or metal alloy, and more preferably formed of copper, nickel, cobalt, or an alloy containing one or more of these. In this laminated metal foil, it is easy to form minute irregularities reflecting the shape of the metal particles on the surface of the roughened layer. Therefore, the adhesion between the FE sheet and the metal foil can be improved. The ten-point average roughness of the surface of the metal foil is preferably 0.1 to 2.5 μm, more preferably 0.3 to 2 μm. In this case, even when the laminate is processed into a printed wiring board, the transmission loss can be suppressed. The roughening treatment layer can be formed by electroplating, or dry etching or wet etching on the surface of the metal foil.

In addition, from the viewpoint of improving various characteristics, the metal foil may include at least one of a heat-resistant treatment layer, a rust-proof treatment layer, and a chromate treatment layer. When the metal foil has a laminated structure, the layers are provided on the surface of the roughening treatment layer on the opposite side to the base layer, or between the roughening treatment layer and the metal foil. When the heat-resistant treatment layer, the anti-rust treatment layer or the chromate treatment layer constitutes the outermost layer of the metal foil, the surface constitutes the surface of the metal foil. The thickness of the metal foil is appropriately determined according to the purpose of the laminate, and when the laminate is processed into a printed wiring board for use, it is preferably 1-50 μm. In addition, when using a laminated metal foil formed by laminating an extremely thin metal foil and a supporting metal foil, the thickness of the extremely thin metal foil is preferably 2 to 5 μm.

As a method for applying the liquid composition to the surface of the support, it is sufficient to form a stable wet film containing the liquid composition on the surface of the support. Examples include coating method, droplet ejection method, and dipping The method is preferably a coating method. If the coating method is used, simple equipment can be used to efficiently form a wet film on the surface of the metal foil. Examples of coating methods include: spray coating, roll coating, spin coating, gravure coating, microgravure coating, gravure offset, knife coating, contact coating, bar coating, Die nozzle coating method, jet Meyer rod method, slit die nozzle coating method.

After the wet film is formed, it is preferable to heat the wet film and maintain it at a temperature at which the liquid dispersion medium in the liquid composition is volatilized, and the wet film is dried, and then the dried film is The powder is fired while maintaining the temperature higher than the temperature at which the liquid dispersion medium is volatilized. Specifically, it is preferable to calcinate the powder after maintaining at a temperature higher than the boiling point of the liquid dispersion medium. Drying can be carried out in one stage at a certain temperature, or in two or more stages at different temperatures. Examples of the drying method include: the method of using an oven, the method of using a ventilated drying furnace, and the method of irradiating heat such as infrared rays. Drying can be carried out under either normal pressure or reduced pressure. In addition, the dry atmosphere may be any of an oxidizing gas atmosphere (oxygen, etc.), a reducing gas atmosphere (hydrogen, etc.), and an inert gas atmosphere (helium, neon, argon, nitrogen, etc.).

Examples of the firing method include the method of using an oven, the method of using a ventilated drying furnace, and the method of irradiating thermal light such as infrared rays. These methods can also be combined. Furthermore, in order to improve the smoothness of the surface of the laminated body obtained, it is also possible to pressurize the dried material with a heating plate, a heating roller, etc. The roasting can be carried out under either normal pressure or reduced pressure. In addition, from the viewpoint of suppressing oxidative degradation of each of the metal foil and the formed FE sheet, the firing atmosphere is preferably a reducing gas atmosphere or an inert gas atmosphere. The firing temperature is set according to the type of F polymer, and is preferably 180°C to 400°C, more preferably 260 to 380°C. The firing temperature means the temperature of the firing atmosphere. The baking time is preferably 1 to 15 minutes.

In the case of removing the metal foil, the removal of the metal foil is preferably performed by wet etching. By wet etching, the metal foil can be removed accurately and fully. Moreover, in this case, wet etching is preferably performed using an acid solution. In the case where the F polymer has a hydrolyzable acid anhydride group as the above functional group, the functional group is activated by an acid solution, and therefore, the adhesiveness of the FE sheet is further improved. Here, as an example of activation of a functional group, conversion of an acid anhydride group into a 1,2-dicarboxylic acid group can be cited. For the acid solution, at least one of hydrochloric acid (hydrogen chloride aqueous solution), nitric acid aqueous solution, and hydrofluoric acid (hydrogen fluoride aqueous solution) can be used. The obtained single FE sheet can be used to connect two substrates to the adhesive layer, interlayer insulation film, solder resist layer, cover film, etc.

According to the present invention, there is provided an FE sheet containing an F polymer and an inorganic filler with a dielectric constant of 10 or more at 25°C. The FE sheet of the present invention may be a laminated body additionally having a support, or a single sheet. The F polymer in the FE sheet and the aforementioned inorganic filler are the same as the liquid composition of the present invention, including preferred aspects. The FE sheet of the present invention is a sheet made of a ferroelectric inorganic filler highly dispersed in a dense film formed by F polymer. It is flexible, has a high dielectric constant and a low dielectric loss tangent. A sheet with excellent dielectric properties and bonding or adhesion properties. The thickness of the FE sheet of the present invention is preferably 1-100 μm, more preferably 3-80 μm. The dielectric constant of the FE sheet of the present invention is preferably 10 or more. The dielectric loss tangent of the FE sheet of the present invention is preferably 0.1 or less, more preferably 0.05 or less, and still more preferably 0.01 or less. The peel strength of the FE sheet to other substrates (members) such as metal foil is preferably 10 N/cm or more, more preferably 15 N/cm or more. Furthermore, the upper limit of the peel strength is usually 20 N/cm. The warpage rate of the FE sheet is preferably 25% or less, particularly preferably 7% or less. In this case, it is easy to process the laminate into a printed wiring board or the like. The dimensional change rate of the FE sheet is preferably ±1% or less, and more preferably ±0.2% or less. In this case, it is easy to multi-layer the FE sheet.

Since the FE sheet of the present invention has excellent surface adhesion, it can be easily and firmly bonded to other substrates. As a method of layering other substrates on the surface area of the FE sheet, a method of hot pressing the FE sheet and other substrates can be cited. For example, when the other substrates are prepregs, the pressing temperature is preferably below the melting temperature of the F polymer, more preferably 120 to 300°C. From the viewpoint of suppressing the mixing of air bubbles and suppressing the degradation caused by oxidation, the hot pressing is preferably performed under a vacuum degree of 20 kPa or less. In addition, during hot pressing, it is preferable to raise the temperature after reaching the aforementioned degree of vacuum. With this, the FE sheet can be crimped in the state before it is softened, that is, in the state before it exhibits a certain degree of fluidity, thereby preventing the generation of bubbles. From the viewpoint of suppressing breakage of the substrate and firmly adhering the FE sheet to the substrate, the pressure in the hot pressing is preferably 0.2 to 10 MPa.

The liquid composition and the FE sheet of the present invention, and the manufacturing method thereof have been described above, but the present invention is not limited to the configuration of the above-mentioned embodiment. For example, the liquid composition and the FE sheet of the present invention may be added with other arbitrary configurations to the configuration of the above-mentioned embodiment, and may be replaced with arbitrary configurations that exert the same function. Moreover, the manufacturing method of the FE sheet of this invention can add other arbitrary steps to the structure of the said embodiment, and can also replace with arbitrary steps which perform the same function. [Example]

The present invention will be specifically described below by enumerating examples, but the present invention is not limited to these. 1. Preparation of each component and each component [Polymer] F Polymer 1: Contains 98.0 mol% of TFE-based units, 0.1 mol% of NAH-based units, and 1.9 mol% of PPVE-based units in sequence Unit copolymer (melting temperature: 300°C, melt viscosity at 380°C: 3×10 ⁵ Pa·s) F polymer 2: Contains 97.5 mol% of TFE-based units, and 2.5 mol% in sequence A copolymer based on PPVE units and without functional groups (melting temperature: 305℃, melt viscosity at 380℃: 3×10 ⁵ Pa·s) PTFE1: TFE homopolymer (melting temperature: 327℃, 380 Melt viscosity at ℃: 2×10 ⁹ Pa·s or more) PVDF (polyvinylidene fluoride, polyvinylidene fluoride) 1: Solvent-soluble polyvinylidene fluoride

[powder] F powder 1: powder containing F polymer 1 with an average particle size of 2.6 μm F powder 2: powder containing F polymer 2 with an average particle size of 18.8 μm F powder 3: powder containing PTFE1 with an average particle size of 7.2 μm

[First inorganic filler] Inorganic filler 1: Spherical ferroelectric filler of barium titanate with an average particle size of 0.4 μm, a dielectric constant of 91, and an fQ value of 5000 (manufactured by Kyoritsu Materials Co., Ltd., "HF-90D"). Furthermore, f is the frequency (GHz), and Q is the reciprocal of the dielectric loss tangent (1/tanδ). Inorganic filler 2: A fibrous ferroelectric filler of barium titanate with an average length of 15 μm, an average diameter of 0.5 μm, and a dielectric constant of 90 [Second Inorganic Filler] Inorganic filler 3: Silica filler with an average particle size of 5.2 μm, a dielectric constant of 4, and a linear expansion coefficient of 0.5 ppm/℃ [Metal Foil] Metal foil 1: Electrolytic copper foil with thickness of 18 μm and ten-point average roughness of 1.0 μm

2. Preparation of dispersion and manufacture of laminate (example 1) Put 38.5 parts by mass of N-methyl-2-pyrrolidone (NMP), 1.5 parts by mass of non-ionic fluorinated polyol, 30 parts by mass of F powder 1, and 30 parts by mass of inorganic filler 1 into the tank After the middle, put the zirconia ball into the tank. Thereafter, the tank was rotated at 150 rpm for 1 hour to disperse the F powder 1 and the inorganic filler 1 in NMP to prepare a dispersion liquid 1. Then, the dispersion liquid 1 is applied to the surface of the metal foil 1 by a die nozzle coating method in a roll-to-roll method to form a wet film. Then, the metal foil 1 on which the wet film was formed was passed through a drying oven at 140° C. for 5 minutes, and dried by heating. Thereafter, the dried film was heated and baked in a nitrogen oven at 380°C for 10 minutes. In this way, a laminate 1 with an FE sheet formed on the surface of the metal foil 1 is manufactured. Furthermore, the thickness of the FE sheet is 50 μm.

(Example 2) Except for changing the inorganic filler 1 to the inorganic filler 2, the dispersion liquid 2 was prepared in the same manner as in Example 1, and the layered body 2 was produced. (Example 3) Except for changing the F powder 1 to the F powder 2, the dispersion 3 was prepared in the same manner as in Example 1, and the layered body 3 was manufactured. (Example 4 (comparative example)) Except for changing the F powder 1 to the F powder 3, a dispersion liquid 4 was prepared in the same manner as in Example 1, and a layered body 4 was manufactured. (Example 5 (comparative example)). Except changing the F powder 1 to PVDF1, the dispersion 5 was prepared in the same manner as in Example 1, and the layered body 5 was manufactured. Furthermore, in the dispersion liquid 5, PVDF1 is dissolved in NMP, and the inorganic filler 1 is dispersed in NMP.

3. Evaluation and measurement 3-1. Determination of viscosity The viscosity of each dispersion is the viscosity measured using a B-type viscometer at 25°C and a rotation speed of 30 rpm. Repeat the measurement 3 times and take the average of the 3 measurements.

3-2. Evaluation of dispersion With respect to each dispersion, the degree of dispersion was evaluated based on K 5600-2-5: 1999 (ISO 1524: 1983) with a particle size meter 0-50 (manufactured by Allgood) in accordance with the following evaluation criteria. [Evaluation criteria] ○ (good): No aggregates were confirmed. △ (pass): agglomerates are confirmed in the range of at least 15 μm. × (unacceptable): agglomerates are confirmed in a range of at least 40 μm.

3-3. Measurement of dielectric constant and dielectric loss tangent The metal foil 1 of each laminate was etched with an aqueous ferric chloride solution to obtain individual FE sheets. After washing the FE sheet, it was dried in an oven at 100°C for 2 hours. After placing the dried FE sheet in an environment of 24°C and 50%RH for 24 hours, use SPDR (Separation Column Dielectric Resonator) and a network analyzer to measure the dielectric constant and dielectric loss tangent at 28 GHz.

3-4. Measurement of peel strength For the metal foil 1 of each laminate, the unnecessary parts are etched with ferric chloride aqueous solution so that a band-shaped part with a width of 2 mm remains. Thereafter, the peel strength when the band-shaped portion was peeled from the FE sheet at an angle of 90° and a speed of 50 mm/min was measured, and it was taken as the peel strength.

3-5. Evaluation of embeddedness Place 10 0402 chip resistors (0.4 mm×0.2 mm×height 0.13 mm) on the polyimide film as the base material. Overlay 4 FE sheets on the polyimide film so as to cover the entire chip resistance, and then overlay the metal foil 1 thereon, and vacuum-press in this state. In addition, the pressing conditions were set to 360° C.×10 minutes, and the pressure was set to 2 MPa. After that, the cross-section of the part where each chip resistor was embedded was checked for the presence or absence of voids, and evaluated according to the following evaluation criteria. [Evaluation criteria] ○ (good): No voids were confirmed. △ (Pass): Porosity was confirmed only at the interface between the end of the chip resistor and the polyimide film. × (unacceptable): Porosity was widely confirmed at the interface between the chip resistance and the polyimide film. The above results are shown in Table 1.

Table 1 shows the results of the above-mentioned measurements. [Table 1] example 1 Example 2 Example 3 Example 4 Example 5 polymer F polymer 1 F polymer 1 F polymer 2 PTFE1 PVDF1 No. 1 inorganic filler Inorganic filler 1 Inorganic filler 2 Inorganic filler 1 Inorganic filler 1 Inorganic filler 1 Viscosity at 25℃[mPa・s] 300 1200 600 ＞10000 400 Dispersion ○ ○ △ × △ Dielectric constant (28 GHz) 11 10 11 7 15 Dielectric loss tangent (28 GHz) 0.01 0.01 0.01 0.01 ＞0.10 Peel strength [N/cm] 8 7 4 ＜1 2 Embeddedness ○ ○ △ × ×

(Example 6) The amount of NMP is set to 43.5 parts by mass, the amount of F powder 1 is set to 25 parts by mass, the amount of inorganic filler 1 is set to 15 parts by mass, and 15 parts by mass of inorganic filler 3 are prepared. A dispersion liquid 6 was prepared in the same manner as in Example 1, and a layered body 6 was produced. (Example 7) Except that the amount of NMP was changed to 48.5 parts by mass, the amount of F powder 1 was changed to 25 parts by mass, and the amount of inorganic filler 1 was changed to 25 parts by mass, dispersion 7 was prepared in the same manner as in Example 1. And manufacture the laminated body 7. (Example 8) Change F powder 1 to F powder 3, set the amount of NMP to 43.5 parts by mass, and set the amount of inorganic filler 1 to 15 parts by mass, and then mix 15 parts by mass of inorganic filler 3. In addition, follow Example 1 The dispersion liquid 8 is prepared in the same manner, and the layered body 8 is manufactured.

In the same manner as in Examples 1 to 5, dispersions 6 to 8 were subjected to measurement of viscosity at 25°C, evaluation of dispersion degree, and measurement of dielectric constant and dielectric loss tangent. Furthermore, a separate FE sheet was obtained from each of the laminated body 6 and the laminated body 7 in the same manner as in the case of the above-mentioned measurement of the dielectric constant and the dielectric loss tangent. The FE sheet was cleaned and cut into 180 mm squares, and the coefficient of linear expansion in the range of 25°C to 260°C was measured in accordance with the measurement method specified in JIS C 6471:1995. Table 2 shows the results of the above measurement.

[Table 2] Example 6 Example 7 Example 8 polymer F polymer 1 F polymer 1 PTFE1 No. 1 inorganic filler Inorganic filler 1 Inorganic filler 1 Inorganic filler 1 Viscosity at 25℃[mPa・s] 400 400 ＞10000 Dispersion ○ ○ × Dielectric constant (28 GHz) 9 11 - Dielectric loss tangent (28 GHz) 0.01 0.01 - Coefficient of linear expansion [ppm/℃] ≦20 ＞20 -

The FE sheets of Examples 1 and 2 have a high dielectric constant and are excellent in embedding (flexibility). It was also confirmed that the effect does not depend on the shape of the ferroelectric inorganic filler. On the other hand, in Example 4, since PTFE with higher melt viscosity was used, the liquid composition significantly increased the viscosity, and only FE sheets with significantly reduced peel strength and embedding properties were obtained. In addition, in Example 5, since solvent-soluble PVDF was used, only FE sheets with high dielectric loss tangent and reduced peel strength and embedding properties were obtained.

In addition, the dispersion liquid 6 each containing the first inorganic filler and the second inorganic filler at a high concentration has excellent dispersibility, and an FE sheet having excellent electrical characteristics and not easy to thermally expand is obtained from this. On the other hand, in Example 8, since PTFE with a higher melt viscosity was used, the dispersion state of the liquid composition was poor, and it was difficult to form an FE sheet from it. [Industrial availability]

The ferroelectric insulating sheet of the present invention has a high dielectric constant, low dielectric loss tangent, and excellent flexibility and bonding properties. Therefore, it is preferable as a dielectric layer of a capacitor built in a flexible multilayer printed wiring board. Furthermore, all the contents of the specification, scope of patent application, and abstract of Japanese Patent Application No. 2019-044626 filed on March 12, 2019 are cited in this article, and incorporated in the form of the disclosure of the specification of the present invention .

Claims (15)

A liquid composition with a viscosity of 50 to 10,000 mPa·s at 25°C and containing: tetrafluoroethylene polymer with a melt viscosity of 1×10 ² to 1×10 ⁶ Pa·s at 380°C Powder with an average particle size of 30 μm or less, an inorganic filler with a dielectric constant of 10 or more at 25°C, and a liquid dispersion medium. The liquid composition according to claim 1, wherein the above-mentioned tetrafluoroethylene-based polymer system further has a tetrafluoroethylene-based polymer based on a unit based on perfluoro(alkyl vinyl ether) or a unit based on hexafluoropropylene. The liquid composition of claim 1 or 2, wherein the above-mentioned tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing a unit based on perfluoro(alkyl vinyl ether) and having a polar functional group, or is relatively A tetrafluoroethylene-based polymer containing 2.0-5.0 mol% of perfluoro(alkyl vinyl ether)-based units in all units and without polar functional groups. The liquid composition according to any one of claims 1 to 3, wherein the average particle size of the above-mentioned powder is 0.05-6 μm. The liquid composition according to any one of claims 1 to 4, wherein the content of the above-mentioned inorganic filler is 10% by mass or more. The liquid composition according to any one of claims 1 to 5, wherein the above-mentioned inorganic filler is a perovskite-type ferroelectric filler or a bismuth layered perovskite-type ferroelectric filler. The liquid composition according to any one of claims 1 to 6, wherein the above-mentioned inorganic filler is a spherical inorganic filler having an average particle diameter of 2 μm or less, or a fibrous inorganic filler having an average length of 30 μm or less and an average diameter of 2 μm or less . The liquid composition according to any one of claims 1 to 7, wherein the liquid dispersion medium is an aprotic polar solvent. The liquid composition according to any one of claims 1 to 8, which further comprises an inorganic filler having a linear expansion coefficient of 10 ppm/°C or less and a dielectric constant of less than 10 at 25°C. The liquid composition according to any one of claims 1 to 9, which further contains a dispersant. A method for manufacturing a ferroelectric insulating sheet, which is to apply the liquid composition of any one of claims 1 to 10 on the surface of a support, heat to remove the liquid dispersion medium, and The tetrafluoroethylene-based polymer is calcined to obtain a ferroelectric insulating sheet having a layer containing the tetrafluoroethylene-based polymer and the inorganic filler. A ferroelectric insulating sheet comprising a tetrafluoroethylene polymer with a melt viscosity of 1×10 ² ～1×10 ⁶ Pa·s at 380°C and an inorganic with a dielectric constant of 10 or more at 25°C filler. Such as the ferroelectric insulating sheet of claim 12, wherein the above-mentioned inorganic filler is a perovskite-type ferroelectric filler or a bismuth layered perovskite-type ferroelectric filler. For example, the ferroelectric insulating sheet of claim 12 or 13 has a thickness of 1-100 μm. For example, the ferroelectric insulating sheet according to any one of claims 12 to 14 has a dielectric constant of 10 or more, and a dielectric loss tangent of 0.1 or less.