Coating composition and laminate

Abstract

This invention provides an aqueous coating composition capable of forming a fluoropolymer coating layer with excellent electrical and surface properties and good adhesion. The coating composition contains two or more fluoropolymers, characterized in that at least one fluoropolymer has a functional group number relative to the number of functional groups per 10... 6 The coating composition contains a fluoropolymer (I) with a main chain of 30 to 1000 carbon atoms, and also contains inorganic fillers, surfactants and liquid media.

Description

Technical Field

[0001] This invention relates to coating compositions and laminates. Background Technology

[0002] One application of fluoropolymer-containing coating compositions is known in the field of electronic materials. In particular, printed circuit board materials corresponding to high-frequency bands have also been studied (Patent Documents 1-3).

[0003] Patent document 4 discloses a fluororesin composition having carbonyl functional groups and silica in a specific ratio as a fluororesin in order to improve adhesion and coefficient of linear expansion.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-183005

[0007] Patent Document 2: International Publication 2018 / 016644

[0008] Patent Document 3: International Publication 2019 / 031071

[0009] Patent Document 4: International Publication 2020 / 145133 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The purpose of this invention is to provide a coating composition and laminate that are particularly suitable for use in the field of electronic materials.

[0012] Methods for solving problems

[0013] This invention relates to a coating composition containing two or more fluoropolymers, characterized in that...

[0014] At least one fluoropolymer is a fluoropolymer with a functional group number relative to 10 6 Fluoropolymers (I) with a main chain carbon number of 30 to 1000 atoms.

[0015] The coating composition also contains inorganic fillers, surfactants, and liquid media.

[0016] The functional groups contained in the above-mentioned fluororesin (I) are preferably carbonyl groups.

[0017] The carbonyl-containing group mentioned above is preferably at least one group selected from the group consisting of carbonyl amide, carboxyl, acyl fluorine and methoxy carbonyl.

[0018] The fluoropolymer (I) mentioned above is preferably a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

[0019] The functional groups contained in the above-mentioned fluoropolymer (I) are preferably located at the ends of the polymer backbone.

[0020] As other fluoropolymers, it is preferred that they also contain a number of functional groups relative to the number of 10 6 Fluoropolymer (II) with fewer than 30 carbon atoms in its main chain.

[0021] The average particle size of the above-mentioned fluoropolymer is preferably less than 0.3 μm.

[0022] At least one of the above-mentioned fluoropolymers is preferably PTFE.

[0023] The inorganic filler is preferably silica particles.

[0024] The specific surface area of ​​the aforementioned silica particles is preferably less than 6.5 m². 2 / g.

[0025] The surfactants mentioned above are preferably non-fluorinated surfactants.

[0026] The liquid medium mentioned above preferably contains water.

[0027] The present invention also relates to a laminate characterized in that it has a coating layer formed by applying the above-described coating composition onto a substrate.

[0028] The aforementioned substrate is preferably a metallic raw material.

[0029] The aforementioned laminate is preferably a printed circuit board, a dielectric material for a substrate, or a laminated circuit board.

[0030] The effects of the invention

[0031] According to the present invention, a coating composition is obtained that can form a fluoropolymer coating layer with excellent electrical and surface properties and good adhesion. Detailed Implementation

[0032] Fluoropolymers are known to have various applications and forms of use, such as powders and films, due to their excellent heat resistance, weather resistance, oil resistance, solvent resistance, chemical resistance, and non-adhesive properties.

[0033] In addition, considering dielectric properties and hygroscopicity, printed circuit boards used in applications at high frequencies in the tens of gigahertz range mainly utilize laminates with insulating layers formed of fluoropolymer resin.

[0034] However, due to the high non-adhesiveness exhibited by fluoropolymers, the adhesion between fluoropolymer-based coatings and substrates is sometimes insufficient. In particular, to achieve adequate adhesion to metal substrates such as copper foil, there is a need to develop fluoropolymer coating compositions with improved adhesion. In recent years, to improve performance, the use of smooth copper foil with low surface roughness has been investigated, thus requiring further improvements in adhesion.

[0035] Furthermore, printed circuit boards require high-temperature heating during the soldering process. Therefore, the resin needs excellent heat resistance. Consequently, it needs to possess all the necessary properties, including heat resistance, film-forming properties, and adhesion.

[0036] In view of the above, the present invention has discovered that by blending two or more fluoropolymers in a coating composition, and by making the number of functional groups of at least one fluoropolymer relative to each 10 6 With a main chain containing 30 to 1000 carbon atoms, it can impart good adhesion and also achieve good heat resistance.

[0037] The present invention will now be described in detail.

[0038] The coating composition of the present invention comprises two or more fluoropolymers, at least one of which has a functional group. Furthermore, in the fluoropolymers having the aforementioned functional group, each 10 6 The number of functional groups per carbon atom in the main chain must be between 30 and 1000 (hereinafter referred to as fluororesin (I)). It should be noted that the functional groups here refer to those that interact with the surface of the adherend and contribute to improved adhesion. Specifically, the functional groups shown in Table 1 below are preferred.

[0039] The coating composition of the present invention uses a mixture containing the above-mentioned fluororesin (I) and other fluororesins (hereinafter referred to as fluororesin (II)).

[0040] As for the aforementioned fluoropolymer (II), there are no particular limitations, the number of functional groups relative to 10 6 The number of carbon atoms in the main chain is preferably less than 30. That is, it is preferable to differ from the above-mentioned fluoropolymer (I) in terms of the number of functional groups.

[0041] The lower limit of the number of functional groups is more preferably 50, and even more preferably 100. In addition, the upper limit of the number of functional groups is more preferably 700, and even more preferably 500.

[0042] The identification of the types of functional groups and the determination of the number of functional groups mentioned above can be achieved using infrared spectroscopy.

[0043] The number of functional groups mentioned above can be analyzed by analyzing the aqueous dispersion of the fluororesin alone, or by separating the target fluororesin from the coating.

[0044] Regarding the number of functional groups, specifically, it was determined using the following method. First, tablets were prepared using the aforementioned fluororesin powder and KBr. The tablets were analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the aforementioned fluororesin, and a differential spectrum was obtained compared with the background spectrum of a fully fluorinated fluororesin without functional groups. The number of functional groups in the aforementioned fluororesin was calculated from the absorption peaks of specific functional groups shown in the differential spectrum according to the following formula (A), based on the number of functional groups per 1 × 10⁻⁶ KBr. 6 The number of functional groups N of each main-chain carbon atom.

[0045] N = I × K / t(A)

[0046] I: Absorbance

[0047] K: Correction coefficient

[0048] t: Membrane thickness (mm)

[0049] For reference, the absorption frequencies, molar absorptivity, and correction factors for the functional groups in this invention are shown in Table 1. Furthermore, the molar absorptivity was determined using FT-IR measurement data from low-molecular-weight model compounds.

[0050] [Table 1]

[0051]

[0052] It should be noted that the absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of Kaiser (cm) lower than those of -CF2H, -COF, free -COOH, and bonded -COOH, -COOCH3, and -CONH2, respectively, as shown in the table. -1 ).

[0053] Therefore, for example, the number of functional groups in -COF refers to the number of functional groups originating from the absorption frequency of -CF2COF, which is 1883 cm⁻¹. -1 The number of functional groups derived from the absorption peak at 1840 cm⁻¹ and the absorption frequency originating from -CH₂COF were also analyzed. -1 The total number of functional groups obtained from the absorption peak at the given location.

[0054] The aforementioned functional groups are functional groups present at the ends of the main chain or side chains of the fluoropolymer (I), and functional groups present in the main chain or side chains. In this invention, the aforementioned functional groups are preferably located at the ends of the polymer main chain. By having functional groups at the polymer ends, adhesion can be efficiently improved.

[0055] The number of functional groups mentioned above can be the total number of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2 and -CH2OH.

[0056] In this invention, the aforementioned functional group is preferably a carbonyl group, and more preferably at least one group selected from the group consisting of carbonyl amide, carboxyl, acyl fluorine, and methoxy carbonyl. From the viewpoint of imparting adhesiveness, carboxyl and carbonyl amide groups are particularly preferred.

[0057] The aforementioned functional groups can be introduced into fluoropolymers, for example, through chain transfer agents or polymerization initiators used in the manufacture of fluoropolymers. For instance, when using an alcohol as a chain transfer agent or a peroxide having a -CH2OH structure as a polymerization initiator, -CH2OH is introduced into the end of the fluoropolymer's main chain. Alternatively, the aforementioned functional groups can also be introduced into the fluoropolymer by polymerizing monomers having functional groups (e.g., anhydrides of unsaturated dicarboxylic acids such as itaconic anhydride, citraconic anhydride, nadic anhydride, and maleic anhydride).

[0058] The aforementioned functional groups are preferably introduced into the fluoropolymer terminus through chain transfer agents and polymerization initiators used in the manufacture of fluoropolymers. This structure is preferred from the perspective of improving adhesion.

[0059] The aforementioned functional groups can also be converted into other structures by further reacting the functional groups introduced into the ends of the fluororesin with chain transfer agents and polymerization initiators used in the manufacture of fluororesins. Additionally, there is a method for generating functional groups at the ends of the main chain by corona treatment of fluororesin powder.

[0060] The melting point of the aforementioned fluoropolymer (I) is preferably 190°C to 350°C. More preferably, it is 200°C or higher; even more preferably, 220°C or higher; particularly preferably, 280°C or higher; and even more preferably, 330°C or lower. The aforementioned melting point corresponds to the maximum value in the heat of fusion curve obtained by heating at a rate of 10°C / min using a differential scanning calorimeter (DSC).

[0061] As the aforementioned fluororesin (I), a fluororesin that exhibits fluidity upon melting and is capable of melt processing is preferred. Furthermore, due to its excellent electrical properties, at least one copolymer selected from the group consisting of copolymers containing tetrafluoroethylene units (TFE units) and fluoroalkyl allyl ethers or (per)fluoro(alkyl vinyl ether) units (PAVE units) (hereinafter referred to as TFE / fluoroalkyl allyl ether or PAVE copolymers (or PFA)) and copolymers containing TFE units and hexafluoropropylene units (HFP units) (hereinafter referred to as TFE / HFP copolymers (or FEP)) is particularly preferred, as it imparts superior adhesion.

[0062] As the above-mentioned fluororesin (I), two or more fluororesins may also be used together.

[0063] (Per)fluoro(alkyl vinyl ether) (PAVE) can be either fluoroalkyl vinyl ether or perfluoro(alkyl vinyl ether). In this invention, "perfluoro(alkyl vinyl ether)" refers to an alkyl vinyl ether that does not contain a CH bond.

[0064] As a PAVE that constitutes the above PAVE unit, the PAVE can be selected from the general formula (1):

[0065] CF2 = CFO(CF2CFY) 1 O) p -(CF2CF2CF2O) q -R f (1)

[0066] (where Y) 1 Indicates F or CF3, R f The monomers and general formula (2) are shown below, where p represents an integer from 0 to 5 and q represents an integer from 0 to 5.

[0067] CFX = CXOCF2OR 1 (2)

[0068] (In the formula, X being the same or different represents H, F, or CF3, R) 1 It refers to at least one of the monomers in the group consisting of a straight-chain or branched fluoroalkyl group having 1 to 6 carbon atoms and containing at least one atom selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms and containing at least one atom selected from the group consisting of H, Cl, Br and I.

[0069] Among them, the monomer represented by general formula (1) is preferred as the PAVE, more preferably selected from at least one of the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) (PPVE), and even more preferably PPVE.

[0070] The content of PAVE units in the above-mentioned TFE / PAVE copolymer is preferably 1.0% to 10% by mass, more preferably 2.0% or more by mass, further preferably 3.5% or more by mass, particularly preferably 4.0% or more by mass, most preferably 5.0% or more by mass, more preferably 8.0% or less by mass, further preferably 7.0% or less by mass, particularly preferably 6.5% or less by mass, and most preferably 6.0% or less by mass, relative to all monomer units. It should be noted that the amount of PAVE units described above is determined by… 19 The determination was performed using F-NMR. The aforementioned TFE / PAVE copolymer can be a copolymer composed solely of TFE and PAVE units.

[0071] When the fluoropolymer (I) is a TFE / PAVE copolymer, the melting point is preferably 280°C to 322°C, more preferably 290°C or higher, and more preferably 315°C or lower.

[0072] When the fluoropolymer (I) is a TFE / PAVE copolymer, the glass transition temperature (Tg) is preferably 70°C to 110°C, more preferably 80°C or higher, and even more preferably 100°C or lower. The glass transition temperature is a value obtained by dynamic viscoelasticity measurement.

[0073] The above-mentioned TFE / HFP copolymer contains TFE units and HFP units. The content of TFE units in the above-mentioned TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, more preferably 99.8% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less, relative to all monomer units.

[0074] The preferred mass ratio (TFE / HFP) of the above-mentioned TFE / HFP copolymer is 70–99 / 1–30 (mass%). More preferably, the mass ratio (TFE / HFP) is 85–95 / 5–15 (mass%).

[0075] The aforementioned TFE / HFP copolymer may further contain (per)fluoro(alkyl vinyl ether) (PAVE) units. Examples of PAVE units included in the aforementioned TFE / HFP copolymer include units identical to the aforementioned PAVE units. The aforementioned TFE / PAVE copolymer does not contain HFP units, and therefore differs from the TFE / HFP / PAVE copolymer in this respect.

[0076] When the aforementioned TFE / HFP copolymer is a copolymer comprising TFE units, HFP units, and PAVE units (hereinafter also referred to as "TFE / HFP / PAVE copolymer"), the mass ratio (TFE / HFP / PAVE) is preferably 70–99.8 / 0.1–25 / 0.1–25 (mass%). More preferably, the mass ratio (TFE / HFP / PAVE) is 75–98 / 1.0–15 / 1.0–10 (mass%). The aforementioned TFE / HFP / PAVE copolymer preferably comprises a total of 1% or more of HFP units and PAVE units relative to all monomer units.

[0077] In the aforementioned TFE / HFP / PAVE copolymer, the HFP unit preferably comprises 25% by mass or less of all monomer units. More preferably, the HFP unit content is 20% by mass or less, further preferably 18% by mass or less, and particularly preferably 15% by mass or less. Furthermore, the HFP unit content is preferably 0.1% by mass or more, more preferably 1% by mass or more, and particularly preferably 2% by mass or more. It should be noted that the HFP unit content can be determined by… 19 The determination was performed using F-NMR.

[0078] The content of PAVE units is more preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 3% by mass or less. Furthermore, the content of PAVE units is preferably 0.1% by mass or more, more preferably 1% by mass or more. It should be noted that the content of PAVE units can be determined by… 19 The determination was performed using F-NMR.

[0079] The aforementioned TFE / PAVE copolymer and TFE / HFP copolymer may also contain other olefinic monomer (α) units. There are no particular limitations on the other olefinic monomer (α) units, as long as they are monomer units capable of copolymerizing with TFE, HFP, and PAVE. Examples include fluorinated olefinic monomers such as vinyl fluoride (VF), vinylidene fluoride (VdF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE), or non-fluorinated olefinic monomers such as ethylene, propylene, and alkyl vinyl ethers. The content of other olefinic monomer (α) units is preferably 0 to 25% by mass, more preferably 0.1% to 25% by mass.

[0080] When the above copolymer is a TFE / HFP / PAVE / other olefinic monomer (α) copolymer, the mass ratio (TFE / HFP / PAVE / other olefinic monomer (α)) is preferably 70-98 / 0.1-25 / 0.1-25 / 0.1-25 (mass%). The above TFE / HFP / PAVE / other olefinic monomer (α) copolymer preferably contains monomer units other than TFE units totaling 1% or more by mass.

[0081] The melting point of the above-mentioned TFE / HFP copolymer is preferably 200°C to 322°C, more preferably above 200°C, even more preferably above 220°C, more preferably below 300°C, and even more preferably below 280°C.

[0082] The glass transition temperature (Tg) of the above-mentioned TFE / HFP copolymer is preferably 60°C to 110°C, more preferably 65°C or higher, and even more preferably 100°C or lower. The above-mentioned glass transition temperature is a value obtained by dynamic viscoelasticity measurement.

[0083] The aforementioned fluoropolymer (I) can be manufactured, for example, by appropriately mixing monomers, polymerization initiators, and other additives that will become its structural units and performing emulsion polymerization, suspension polymerization, or other known methods. Among these, emulsion polymerization is more preferred.

[0084] The MFR value of the aforementioned fluoropolymer (I) is preferably in the range of 0.5 to 100, measured at 372°C and a 5 kg load. This range is preferred from the perspective that the aforementioned amount of functional groups can be easily obtained through the terminal functional groups.

[0085] The coating composition of the present invention uses a mixture containing the above-mentioned fluororesin (I) and other fluororesins (II).

[0086] As the aforementioned fluoropolymer (II) is not particularly limited, the number of functional groups is preferably relative to the number of 10 6 The number of carbon atoms in the main chain is less than 30. That is, it is preferable to differ from the above-mentioned fluoropolymer (I) in terms of the number of functional groups.

[0087] Fluoropolymers with a high number of functional groups exhibit excellent adhesion properties, but on the other hand, their electrical properties and heat resistance tend to become insufficient. Therefore, as fluoropolymers (II), it is preferable to use fluoropolymers with excellent electrical properties and heat resistance in combination. This allows the formation of a coating layer with excellent electrical properties, heat resistance, and other coating properties.

[0088] The aforementioned fluororesin (II) is not particularly limited as long as it is a fluororesin, and examples include polytetrafluoroethylene resin (PTFE), PFA, and FEP. Among these, PTFE is particularly preferred. Furthermore, since the homopolymer particles of TFE are soft and easily adhere, they are less prone to cracking, making PTFE preferred. The softness index is not particularly limited, but the Shore hardness (D grade) is preferably D65 or less, more preferably D60 or less, and particularly preferably D55 or less. Regarding PFA and FEP, it is preferable to use resins with the same resin composition as the aforementioned fluororesin (I) but with a different number of functional groups.

[0089] There are no particular limitations on the polymerization method for the aforementioned fluoropolymer (II), and examples include bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization. In the above polymerization, the various conditions such as temperature and pressure, the polymerization initiator, and other additives can be appropriately set according to the desired composition and amount of the fluoropolymer.

[0090] The above-mentioned fluororesin (II) can be prepared by fluorination to have the number of functional groups within the above-mentioned range.

[0091] The above-mentioned fluorination treatment can be carried out by contacting an unfluorinated fluororesin with a fluorinated compound.

[0092] There are no particular limitations on the fluorinated compounds mentioned above; any fluorine radical source that generates fluorine radicals under fluorination conditions can be cited. Examples of such fluorine radical sources include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and fluorinated halogens (e.g., IF5, ClF3).

[0093] The aforementioned fluorine radical source, such as F2 gas, can be 100% concentrated, but from a processability perspective, it is preferable to mix it with an inert gas and dilute it to 5% to 50% by mass before use, more preferably to dilute it to 15% to 30% by mass. Examples of the aforementioned inert gas include nitrogen, helium, and argon; from an economic perspective, nitrogen is preferred.

[0094] The conditions for the above-mentioned fluorination treatment are not particularly limited. Molten fluororesin can be brought into contact with a fluorinated compound. This treatment can typically be carried out below the melting point of the fluororesin, preferably at 20°C to 220°C, and more preferably at 100°C to 200°C. The fluorination treatment generally lasts from 1 hour to 30 hours, preferably from 5 hours to 25 hours. Preferably, the fluorination treatment involves contacting the unfluorinated fluororesin with fluorine gas (F2 gas).

[0095] The preferred mixing ratio (mass ratio) of the fluororesin (I) and the fluororesin (II) is fluororesin (I): fluororesin (II) = 90:10 to 10:90. More preferably, it is 80:20 to 20:80, and even more preferably, it is 70:30 to 30:70. If the amount of fluororesin (I) is small, the adhesion may become insufficient. In addition, if the amount of fluororesin (II) is small, the electrical properties and heat resistance may decrease, which is not preferred.

[0096] The fluororesin in the coating composition of the present invention is preferably present in the coating composition in particulate form. In this case, the average particle size of the fluororesin particles is preferably less than 0.3 μm. Here, the average particle size is not limited to fluororesin (I) or fluororesin (II), but is a value calculated by measuring randomly selected particles from the fluororesin particles contained in the coating composition.

[0097] Specifically, the coating composition is diluted 1000 times with water, one drop of the diluted liquid is placed on aluminum foil, allowed to dry naturally, and an SEM (scanning electron microscope) image is taken. The particle size is measured from the image data of 50 randomly selected particles using SEM image analysis software, and the average value is calculated.

[0098] The lower limit of the above-mentioned average particle size is preferably 0.05 μm, more preferably 0.07 μm, and even more preferably 0.1 μm.

[0099] To improve electrical properties, strength, and heat resistance, the coating composition of the present invention also contains inorganic fillers. There are no particular limitations on the inorganic fillers, and examples include, for instance, silicon dioxide (more specifically, crystalline silicon dioxide, fused silicon dioxide, spherical fused silicon dioxide, etc.), titanium dioxide, zirconium oxide, zinc oxide, tin oxide, silicon nitride, silicon carbide, boron nitride, calcium carbonate, calcium silicate, potassium titanate, aluminum nitride, indium oxide, aluminum oxide, antimony oxide, cerium oxide, magnesium oxide, iron oxide, and tin-doped indium oxide (ITO). Additionally, minerals such as montmorillonite, talc, mica, boehmite, kaolin, montmorillonite, gold vermiculite, vermiculite, and sericite can be included. Other fillers include carbon compounds such as carbon black, acetylene black, Ketjen black, and carbon nanotubes; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; and various types of glass such as glass beads, glass sheets, and glass spheres.

[0100] One or more inorganic fillers can be used as the aforementioned inorganic fillers.

[0101] In addition, inorganic fillers can be used directly as powders or dispersed in resins.

[0102] As the aforementioned inorganic filler, silica, alumina, titanium dioxide, boron nitride, talc, etc., are preferred, with silica having a low dielectric constant and a specific gravity close to that of fluoropolymers being particularly preferred. By containing silica, the coefficient of thermal expansion of the coating film can be kept low. Furthermore, this effect helps to suppress substrate warping, and is therefore preferred. Moreover, it also improves the peel strength of the coating layer.

[0103] The specific surface area of ​​the aforementioned inorganic filler, such as that based on the BET method, is preferably less than 6.5 m². 2 / g, more preferably less than 6.3m 2 / g. Additionally, a concentration greater than 1m is preferred. 2 / g. With a specific surface area within the above range, the inorganic filler in the membrane exhibits less aggregation, resulting in a smooth coating surface; therefore, it is preferred.

[0104] The average particle size of the aforementioned inorganic filler is preferably 0.1 μm to 20 μm. If the average particle size is within this range, there is less agglomeration, resulting in good surface roughness. The lower limit of the aforementioned average particle size is more preferably 0.3 μm. The upper limit of the aforementioned average particle size is more preferably 5 μm, and even more preferably 2 μm. The aforementioned average particle size is a value determined by laser diffraction scattering.

[0105] The maximum particle size of the aforementioned inorganic filler is preferably 10 μm or less. If the maximum particle size is 10 μm or less, there is less aggregation and better dispersion. Furthermore, the surface roughness of the resulting coating can be reduced. More preferably, the maximum particle size is 5 μm or less. SEM (Scanning Electron Microscopy) images are taken, and the maximum particle size is determined using SEM image analysis software from image data of 200 randomly selected particles.

[0106] The shape of the aforementioned inorganic filler is not particularly limited, and it can be spherical, columnar, conical, truncated conical, polyhedral, hollow, etc. Particularly preferred are spherical, cubic, basin-shaped, disc-shaped, octahedral, scale-shaped, rod-shaped, plate-shaped, rod-shaped, tetrahedral, hollow, and even more preferred are spherical, cubic, octahedral, plate-shaped, and hollow.

[0107] The aforementioned inorganic filler is preferably uniformly dispersed when mixed with 70% by mass of inorganic filler and 30% by mass of water. Uniform dispersion means that no precipitation occurs even when the dispersion is allowed to stand and the flow ceases. If the dispersibility is insufficient, the stability of the coating composition may be reduced.

[0108] The aforementioned inorganic filler can be a surface-treated inorganic filler, such as an inorganic filler surface-treated with an organosilicon compound. By surface-treating with the aforementioned organosilicon compound, the dielectric constant of the inorganic filler can be reduced.

[0109] There are no particular limitations on the organosilicon compounds mentioned above; any existing known organosilicon compounds may be used. For example, it is preferable to include at least one selected from the group consisting of silane coupling agents and organosilazanes.

[0110] Regarding the surface treatment amount of the aforementioned organosilicon compound, the reaction amount of the surface treatment agent on the surface of silica particles is preferably relative to the surface area per unit (nm). 2 The number of particles is 0.1 to 10, more preferably 0.3 to 7.

[0111] As the aforementioned inorganic filler, one or more inorganic fillers with different physical properties can be used.

[0112] In addition, inorganic fillers can be used directly as powders or dispersed in resins.

[0113] In the coating composition of the present invention, the preferred total amount of fluororesin to inorganic filler is 10:90 to 90:10 (mass ratio). By mixing fluororesin and inorganic filler in this ratio, effects such as preventing warping can be obtained. Regarding the above mixing amount, the lower limit of the mixing amount of fluororesin is more preferably 10, and even more preferably 20. Regarding the above mixing amount, the upper limit of the mixing amount of fluororesin is more preferably 90, and even more preferably 80. Regarding the above mixing amount, the upper limit of the mixing amount of inorganic filler is more preferably 60, and even more preferably 50.

[0114] The coating composition of the present invention also contains a surfactant. There are no particular limitations on the surfactant used; any known surfactant can be used, but a non-fluorinated surfactant is preferred. Non-fluorinated surfactants are more cost-effective than fluorinated surfactants. Furthermore, if a fluorinated surfactant is added, hydrofluoric acid will be generated during the firing of the fluoropolymer. This hydrofluoric acid promotes the deterioration of silica particles; therefore, it is preferable that the composition does not contain a fluorinated surfactant.

[0115] As for the aforementioned non-fluorinated surfactants, there are no particular limitations as long as they can stably disperse the fluororesin in the composition; any of the following can be used: anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Examples include: anionic surfactants such as sodium alkyl sulfate, sodium alkyl ether sulfate, triethanolamine alkyl sulfate, triethanolamine alkyl ether sulfate, ammonium alkyl sulfate, ammonium alkyl ether sulfate, sodium alkyl ether phosphate, and sodium fluoroalkylcarboxylate; cationic surfactants such as alkyl ammonium salts and alkyl benzyl ammonium salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, polyoxyethylene alkyl esters, propylene glycol-propylene oxide copolymers, perfluoroalkyl ethylene oxide adducts, and 2-ethylhexanol ethylene oxide adducts; and amphoteric surfactants such as alkylaminoacetic acid betaine, alkylamide acetic acid betaine, and imidazoline betaine. Among these, anionic and nonionic surfactants are preferred. Particularly preferred surfactants are nonionic surfactants with ethylene oxide chains that have low thermal decomposition residues.

[0116] Commercially available nonionic surfactants include, for example, Genapol X080 (manufactured by Clariant), the Noigen TDS series (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) with Noigen TDS-80 (trade name) and Noigen TDS-100 (trade name), the Leocol TD series (manufactured by LION) with Leocol TD-90 (trade name), the Lionol TD series (manufactured by LION), the T-Det A series (manufactured by Harcros Chemicals) with T-Det A138 (trade name), the Tergitol 15S series (manufactured by Dow), and Dispanol TOC (manufactured by Nippon Yushi Co., Ltd.).

[0117] As non-fluorinated surfactants mentioned above, hydrocarbon surfactants, organosilicon surfactants, alkynyl diols, and other alkynyl surfactants can also be used. Furthermore, one or more of these non-fluorinated surfactants can be used. It should be noted that nonylphenol surfactants are preferably not used.

[0118] The amount of the aforementioned non-fluorinated surfactant mixed with the fluoropolymer is preferably 0.01% to 50% by mass, more preferably 0.1% to 30% by mass, and even more preferably 0.2% to 20% by mass, relative to 100% of the total amount of the fluoropolymer. If the amount of surfactant added is too small, the dispersion of the fluoropolymer may become uneven, with some of it floating to the surface. On the other hand, if the amount of surfactant added is too large, there will be more surfactant decomposition residue caused by firing, resulting in coloring. Furthermore, the heat resistance and non-adhesiveness of the coating film will decrease.

[0119] Thickeners can also be added as needed. There are no particular limitations as long as the coating thickens without affecting the film properties. Nonionic emulsions of higher fatty acids form a three-dimensional network structure with fluoropolymer particles, increasing apparent viscosity and preventing film cracking, thus making them preferred. Oleic acid emulsions and octanoic acid emulsions are particularly preferred.

[0120] The coating composition of the present invention also contains a liquid medium. There are no particular limitations on the liquid medium, but water is preferred.

[0121] Furthermore, the coating composition of the present invention preferably contains a water-soluble solvent when used in conjunction with water. This water-soluble solvent wets the fluororesin, and the high-boiling-point solvent binds the resins together during drying after coating, acting as a drying delay agent to prevent cracking. Even high-boiling-point solvents evaporate at the firing temperature of the fluororesin, thus not adversely affecting the coating film.

[0122] Specific examples of the aforementioned water-soluble solvents include, as low-boiling-point organic solvents with boiling points up to 100°C, methanol, ethanol, isopropanol, sec-butanol, tert-butanol, acetone, and methyl ethyl ketone; as medium-boiling-point organic solvents with boiling points between 100°C and 150°C, methyl cellosolve and ethyl cellosolve; and as high-boiling-point organic solvents with boiling points above 150°C, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, 3-butoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N,N-dimethylformamide, ethylene glycol, propylene glycol, glycerol, dimethyl carbitol, butyl carbitol, butyl dicarbitol, butyl cellosolve, 1,4-butanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, and diethylene glycol monomethyl ether. Furthermore, one or more of these water-soluble solvents may be used. As the aforementioned water-soluble solvent, a high-boiling-point organic solvent is preferred, and from the perspective of dispersion stability, a diol-based solvent is more preferred.

[0123] As the above-mentioned diol solvent, it is preferred to include at least one selected from the group consisting of ethylene glycol, diethylene glycol monomethyl ether, glycerol and butyl carbitol.

[0124] The preferred mixing amount of the water-soluble solvent is 0.5% to 50% by mass of the total water content, more preferably 1% to 30% by mass. With low-boiling-point organic solvents, insufficient mixing can easily lead to bubble formation, while excessive mixing can make the composition flammable, compromising the advantages of an aqueous dispersion. With medium-boiling-point organic solvents, excessive mixing can sometimes leave residues in the coating after firing, causing adverse effects; insufficient mixing can cause the fluoropolymer to revert to powder during drying after coating, preventing firing. With high-boiling-point organic solvents, excessive mixing can sometimes leave residues in the coating after firing, causing adverse effects. The water-soluble solvent is preferably selected to be volatile or the mixing amount is adjusted to ensure that it does not remain in the coating after firing the fluoropolymer. It should be noted that the absence of glycol-based solvent residues after firing the fluoropolymer can be confirmed by removing the fired coating and observing a decrease in weight near the boiling point of the glycol-based solvent in TG / DTA measurements.

[0125] In the above coating composition, various additives commonly added to fluoropolymer compositions, such as stabilizers, thickeners, decomposition accelerators, rust inhibitors, corrosion inhibitors, and defoamers, can be mixed in.

[0126] One feature of this invention is that a laminate having a coating layer formed by applying the above-mentioned coating composition is also included.

[0127] The above-mentioned coating composition can be applied using conventional coating methods. Examples of such coating methods include spray coating, roller coating, coating using a doctor blade, dip coating, impregnation coating, swirl coating, curtain coating, coating using a bar coater, gravure coating, microgravure coating, and die coating.

[0128] After the above coating, the laminate of the present invention can be produced by drying and firing. As for the drying, there is no particular limitation as long as the liquid medium can be removed; examples include heating as needed at room temperature to 130°C for 5 to 30 minutes. The firing is performed above the melting temperature of the fluoropolymer, and is generally preferably performed at a temperature in the range of 200°C to 400°C for 10 to 60 minutes. To prevent oxidation of the coated metal foil, drying and firing under an inactive gas is preferred.

[0129] The coating film formed using the coating composition of the present invention preferably has a thickness of 2 μm to 40 μm after drying and firing. By forming a coating film within this range, it is possible to easily form a good coating film without causing problems with the film's condition, thereby fully utilizing the physical properties required for the coating film. The lower limit is more preferably 3 μm, and even more preferably 5 μm. The upper limit is more preferably 35 μm, and even more preferably 30 μm.

[0130] As the substrate in the laminate of the present invention, the following can be used: metals such as iron, stainless steel, copper, aluminum, and brass; glass products such as glass plates, woven and nonwoven fabrics of glass fibers; molded articles and coatings of general-purpose and heat-resistant resins such as polypropylene, polyoxymethylene, polyimide, modified polyimide, polyamide-imide, polysulfone, polyethersulfone, polyetheretherketone, and liquid crystal polymers; molded articles and coatings of general-purpose rubbers such as SBR, butyl rubber, NBR, and EPDM, and heat-resistant rubbers such as silicone rubber and fluororubber; woven and nonwoven fabrics of natural and synthetic fibers; or laminated substrates formed by combining these materials.

[0131] The aforementioned substrate may be a substrate that has undergone surface processing. Examples of such surface processing include surface processing that roughens the surface to a desired roughness using sandblasting, surface processing that roughens the surface by adhering particles, and surface processing that has undergone metal anti-oxidation treatment.

[0132] The coating composition of the present invention can improve adhesion to the substrate. Specifically, the adhesion strength between the coating film formed by applying the coating composition of the present invention and the substrate can be 5 N / cm or more.

[0133] The above-mentioned adhesive strength was measured as follows: A laminate consisting of a coating layer and a substrate was overlapped in a way that the coating layer and the copper foil were tightly bonded together. It was then pressed under vacuum at a heating temperature of 320°C and a pressure of 3MPa for 5 minutes to obtain a bond consisting of a laminate consisting of a coating layer and a substrate and a copper foil. The bond was then cut into strips with a width of 10mm × a length of 40mm × 3 sets to make test pieces. For these test pieces, an Autograph (Shimadzu Corporation AGS-J5kN) was used to perform a 90-degree peel test at 25°C and a tensile speed of 50mm / min according to JIS C 6481-1996. The peeling mode was observed and the value was measured.

[0134] The aforementioned bonding strength is more preferably 7 N / cm or higher.

[0135] It should be noted that the adhesive strength described above can vary depending on the type of substrate, even when using the same coating composition. The coating composition of the present invention can achieve such excellent peel strength as described above even when using a substrate where peel strength is usually difficult to obtain, and is therefore particularly preferred.

[0136] More specifically, even when the substrate is a metal substrate with low surface roughness, the above-mentioned range of adhesive strength can be obtained. For example, when using copper foil with a surface roughness (Rz) of less than 1.0 μm as the substrate, conventional fluorinated coating compositions cannot achieve sufficient adhesion, but the coating layer formed by the coating composition of the present invention can exhibit an adhesive strength of 5 N / cm or more.

[0137] The surface roughness (Rz) mentioned above is the ten-point average roughness specified in JIS-B0601. In this specification, the Rz mentioned above is the value measured using a surface roughness meter (trade name: SURFCOM 470A, manufactured by Tokyo Seiki Co., Ltd.) with the measurement length set to 4 mm.

[0138] The laminates of the present invention can be used in fields requiring heat resistance, solvent resistance, lubricity, non-adhesion, etc., and can be used for films, fiber-reinforced films, prepregs, resin-coated metal foils, metal-clad laminates, printed circuit boards, dielectric materials for substrates, laminated circuit boards, etc.

[0139] The laminate of the present invention is particularly preferably formed on a copper foil by a coating layer of the coating composition of the present invention. In recent years, high-frequency communications have become increasingly prevalent in various fields. To reduce transmission losses when used in high-frequency regions, materials formed by laminating a dielectric layer containing a fluoropolymer to a copper foil are used. In such applications, the coating composition of the present invention is particularly suitable for use.

[0140] Example

[0141] The present invention will be described below through examples. In the examples, unless otherwise specified, % and parts in the mixing ratio refer to mass % and mass parts. The present invention is not limited to the examples described below.

[0142] (Preparation of FEP-1 aqueous dispersion)

[0143] An aqueous dispersion containing 30% FEP (TFE / HFP = 84 / 16 mass ratio) particles was obtained using the method described in Example 1 of Japanese Patent No. 4306072. The dried FEP had an MFR of 15 g / 10 min and a melting point of 228°C. The surfactant content was 5.5% relative to the weight of the FEP solids. The terminal groups of the FEP particles contained carboxylic acids from the initiator. The number of functional groups in the obtained FEP particles containing functional groups was determined by the above method. The results showed that, relative to 10... 6 The main chain has 207 carbon atoms.

[0144] (Preparation of FEP-2 aqueous dispersion)

[0145] For TFE and HFP, FEP (TFE / HFP = 85.7 / 14.3 mass ratio) was produced by suspension polymerization using a polymerization initiator (di(ω-hydroperfluorohexanoyl)peroxide). The resulting dry powder was directly pulverized using an air jet mill (manufactured by IMMATERIAL) to obtain micro-powder with an average particle size of 10 μm. For every 100 parts by mass of the obtained FEP micro-powder, 10 parts by mass of an acetylenol-based dispersant (Surfynol 440, manufactured by Air Products Japan), 10 parts by mass of an organosilicon surfactant (KP-106, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and 280 parts by mass of ion-exchanged water were thoroughly stirred and mixed with the FEP micro-powder to obtain an FEP dispersion. The number of functional groups in the obtained FEP particles was determined using the above method. The results showed that, relative to 10... 6 The main chain has 20 carbon atoms.

[0146] (PTFE aqueous dispersion)

[0147] The polymer solids concentration was 64% by mass, the nonionic surfactant concentration was 2.7% by mass relative to the polytetrafluoroethylene solids concentration, the average primary particle size was 312 nm, the standard specific gravity was 1.57, and the number of functional groups determined by the above method was relative to the number of 10 6 Aqueous dispersions of PTFE with fewer than 10 carbon atoms in the main chain.

[0148] (Preparation of PFA aqueous dispersion)

[0149] An aqueous dispersion containing 20% ​​PFA (TFE / PPVE = 96.6 / 3.4 mass ratio) particles was obtained using the method described in Example 4 of Japanese Patent No. 4306072. The dried PFA had an MFR of 22 g / 10 min and a melting point of 315°C. The surfactant content was 2.9% relative to the weight of the PFA solids. The number of functional groups in the obtained PFA particles was determined by the above method, and the results showed that, relative to 10 6 The main chain has 143 carbon atoms.

[0150] Example 1

[0151] (Coating)

[0152] The obtained FEP-1 aqueous dispersion and PTFE aqueous dispersion were mixed with a solid component ratio of FEP:PTFE of 20:80. Relative to the solid components of FEP and PTFE, 14 parts by mass of surfactant (Noigen TDS-80C), silica particles, and 20 parts by mass of ion-exchanged water were added for coating.

[0153] It should be noted that the silica particles used are as described below.

[0154] B-1: Admatechs-manufactured Admafine SC2500-SQ, average particle size 0.5 μm, specific surface area 6.1 m². 2 / g, spherical, specific gravity 2.2g / cm³ 3

[0155] B-2: Tokuyama-made Silfil, average particle size 125nm, specific surface area 30.0m² 2 / g, spherical, specific gravity 2.2g / cm³ 3

[0156] The average particle size of the fluoropolymer contained in the obtained coating composition was determined using the method described above. The results are shown in Table 2.

[0157] Examples 2-12

[0158] Except for the changes to each compounding component as shown in Tables 2 and 3, the coating process was carried out in the same manner as in Example 1.

[0159] Comparative Examples 1-5

[0160] Except for the changes to each compounding component as shown in Table 4, the coating process was carried out in the same manner as in Example 1.

[0161] The resin coating layer is obtained by the following method.

[0162] A coating was applied to copper foil (Fukuda Metal Foil Powder Industrial Co., Ltd. CF-V9S-SV-18, surface roughness 0.8μm (Rz)) using a rod coater (No. 30). The coated copper foil was then dried at 130°C for 15 minutes. Subsequently, it was fired at 350°C for 15 minutes under a nitrogen atmosphere to produce a coating film with a thickness of 10μm.

[0163] The resulting coating is then evaluated based on the following criteria.

[0164] (Adhesion to copper foil)

[0165] The adhesive strength was determined as follows: A laminate consisting of a coating layer and a substrate was overlapped with the copper foil in a tightly bonded manner. It was then pressed for 5 minutes at a heating temperature of 320°C and a pressure of 3 MPa to obtain a bond consisting of a laminate consisting of a coating layer and a substrate and a copper foil. The bond was then cut into strips with a width of 10 mm × a length of 40 mm × 3 sets to make test pieces. For these test pieces, a peel test was performed using an Autograph (Shimadzu Corporation AGS-J 5kN) at 25°C and a tensile speed of 50 mm / min according to JIS C6481-1996. The peel pattern was observed and the results were measured.

[0166] ×: Bond strength is less than 5 N / cm.

[0167] △: The bonding strength is above 5 N / cm.

[0168] 〇: The bonding strength is above 7N / cm.

[0169] (Heat resistance test)

[0170] A laminate consisting of a coating layer and a substrate is overlapped with a copper foil in a tightly bonded manner. It is then pressed under vacuum at a temperature of 320°C and a pressure of 3 MPa for 5 minutes to obtain a bond formed by the laminate of the coating layer and substrate and the copper foil. A pattern is then created by etching, and the bond is floated in a molten solder bath at 288°C for 10 seconds. After being lifted from the solder bath, the coating layer is visually inspected for peeling or swelling.

[0171] ×: There is peeling and swelling.

[0172] △: No peeling, slight expansion

[0173] 〇: No peeling, no expansion

[0174] (Condensation of silica)

[0175] Use SEM to examine the coated surface and confirm whether there is any aggregation of silica particles.

[0176] ×: There is cohesion

[0177] 〇: No coagulation

[0178] (Coating defects)

[0179] Visually inspect the coated surface to check for any defects in the coating.

[0180] ×: Yes

[0181] 〇: None

[0182] (Coefficient of linear expansion)

[0183] A laminate consisting of a coating layer and a substrate is overlapped with a copper foil in a way that the coating layer is tightly bonded together. It is then pressed under vacuum at a heating temperature of 320°C and a pressure of 3MPa for 5 minutes to obtain a bond consisting of a laminate consisting of a coating layer and a substrate and a copper foil. The substrate is then removed by etching, and the coefficient of linear expansion of the obtained coating is measured using a TMA (Technical Analysis Instrument) device manufactured by Hitachi Advanced Technology Co., Ltd. with a load of 5g.

[0184] ×: 160ppm or more

[0185] 〇: Less than 160ppm

[0186]

[0187]

[0188]

[0189] The examples demonstrate that the coating film obtained from the coating composition of the present invention exhibits excellent adhesion to the copper foil substrate and high heat resistance.

[0190] Industrial availability

[0191] According to the present invention, a coating composition capable of forming a coating layer having good adhesion to a metal substrate, excellent electrical properties, and superior surface properties can be obtained. The above-described coating composition is suitable for coating printed circuit boards, dielectric materials for substrates, laminated circuit boards, and the like.

Claims

1. A coating composition comprising two or more fluororesins, characterized in that, At least one fluoropolymer is a fluoropolymer with a functional group number relative to 10 6 Fluoropolymers (I) with a main chain carbon number of 30 to 1000 atoms. The fluororesin (I) is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). The coating composition also contains inorganic fillers, surfactants, and liquid media. The glass transition temperature (Tg) of the FEP is 60℃~110℃, and the glass transition temperature (Tg) of the PFA is 70℃~110℃. As with other fluoropolymers, it also contains functional groups relative to the number of 10 6 Fluoropolymer (II) with fewer than 30 carbon atoms in its main chain.

2. The coating composition according to claim 1, wherein, The functional groups contained in fluoropolymer (I) are carbonyl groups.

3. The coating composition according to claim 2, wherein, The carbonyl group is selected from at least one group chosen from the group consisting of carbonyl amide, carboxyl, acyl fluorine and methoxy carbonyl.

4. The coating composition according to any one of claims 1 to 3, characterized in that, The functional groups contained in fluoropolymer (I) are located at the ends of the polymer backbone.

5. The coating composition according to claim 1, wherein, The Shore hardness of fluoropolymer (II) is expressed as D grade, which is below D60.

6. The coating composition of claim 5, wherein, The ratio of the total amount of fluororesin to the total amount of inorganic filler, expressed by mass, is: total fluororesin: inorganic filler = 20:80 to 80:

20.

7. The coating composition of claim 6, wherein, The ratio of the total amount of fluororesin to the total amount of inorganic filler, expressed by mass, is: total amount of fluororesin: inorganic filler = 50:50 to 60:

40.

8. The coating composition according to any one of claims 1 to 3, wherein, The average particle size of the fluoropolymer is less than 0.3 μm.

9. The coating composition according to any one of claims 1 to 3, wherein, At least one of the fluoropolymers is PTFE.

10. The coating composition according to any one of claims 1 to 3, wherein, The inorganic filler is silica particles.

11. The coating composition of claim 10, wherein, The specific surface area of ​​the silica particles is less than 6.5 m². 2 / g.

12. The coating composition according to any one of claims 1 to 3, wherein, The surfactant is a non-fluorinated surfactant.

13. The coating composition according to any one of claims 1 to 3, wherein, The liquid medium contains water.

14. A laminate, characterized in that, It has a coating layer formed by applying the coating composition of any one of claims 1 to 3 onto a substrate.

15. The laminate as claimed in claim 14, wherein, The base material is a metallic raw material.

16. The laminate as claimed in claim 14, wherein it is a printed circuit board, a dielectric material for a substrate, or a laminated circuit board.

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