阅读说明：本技术 二氧化硅粒子、树脂组合物、树脂膜及覆金属层叠板 (Silica particles, resin composition, resin film, and metal-clad laminate ) 是由 王宏远 藤麻织人 平石克文 田中睦人 出合博之 于 2020-10-28 设计创作，主要内容包括：本发明提供一种能够在不损害弯折性等机械特性的情况下实现介电特性的改善的二氧化硅粒子以及通过添加所述二氧化硅粒子而介电特性得到改善的树脂组合物、树脂膜及覆金属层叠板。二氧化硅粒子用于3GHz～20GHz的频率范围中,通过利用激光衍射散射法的体积基准的粒度分布测定而获得的频度分布曲线中的累计值成为50％的平均粒径D-(50)为0.3μm～3μm的范围内,比表面积为超过5m～2/g且为20m～2/g以下的范围内,利用共振腔微扰法所测定的介电损耗角正切为0.004以下。树脂组合物含有所述二氧化硅粒子、与聚酰胺酸或聚酰亚胺,相对于聚酰胺酸或聚酰亚胺,二氧化硅粒子的含量为30体积％～70体积％的范围内。(The invention provides a silica particle capable of improving dielectric characteristics without damaging mechanical characteristics such as bending, and a resin composition, a resin film and a metal-clad laminate with improved dielectric characteristics by adding the silica particle. The silica particles are used in a frequency range of 3GHz to 20GHz, and the integrated value in a frequency distribution curve obtained by volume-based particle size distribution measurement by a laser diffraction/scattering method is 50% of the average particle diameter D 50 In the range of 0.3 to 3 μm, and a specific surface area of more than 5m 2 A ratio of/g to 20m 2 In the range of/g or less, the dielectric loss tangent measured by the resonance cavity perturbation method is 0.004 or less. The resin composition contains the silica particles and polyamic acid or polyimide, and the content of the silica particles is in the range of 30 to 70 vol% with respect to the polyamic acid or polyimide.)

1. A silica particle for use in a frequency range of 3GHz to 20GHz, the silica particle characterized by:

by using laser diffractionAn average particle diameter D of which the integrated value in a frequency distribution curve obtained by volume-based particle size distribution measurement by the scatterometry is 50%₅₀In the range of 0.3 to 3 μm, and a specific surface area of more than 5m²A ratio of/g to 20m²In the range of/g or less, the dielectric loss tangent measured by the resonance cavity perturbation method is 0.004 or less.

2. A resin composition comprising the silica particles according to claim 1 and a polyamic acid or polyimide, the resin composition being characterized in that:

the content of the silica particles is in the range of 30 to 70 vol% with respect to the polyamic acid or polyimide.

3. A resin film having a single layer or a plurality of polyimide layers, the resin film being characterized in that:

at least one layer of the polyimide layers is a silica-containing polyimide layer comprising a cured product of the resin composition according to claim 2, the silica-containing polyimide layer having a thickness in a range of 10 μm to 200 μm.

4. The resin film according to claim 3, wherein: the thickness of the whole resin film is in the range of 10-200 μm, and the proportion of the thickness of the silicon dioxide-containing polyimide layer is more than 50%.

5. A metal clad laminate comprising an insulating resin layer, and a metal layer laminated on at least one side of the insulating resin layer, characterized in that:

the insulating resin layer comprises the resin film according to claim 3 or 4.

Technical Field

The present invention relates to silica particles that can be preferably used for electric and/or electronic devices used in a high-frequency region, a resin composition containing the silica particles, a resin film using the resin composition, and a metal-clad laminate.

Background

In recent years, there has been an increasing demand for downsizing and weight reduction of electronic devices, as represented by mobile phones, Light Emitting Diode (LED) lighting fixtures, and related parts around automobile engines. Along with this, flexible circuit boards, which are advantageous for downsizing and weight reduction of devices, are widely used in the field of electronics. Among them, a flexible circuit board having an insulating layer made of polyimide is widely used because of its excellent heat resistance, chemical resistance, and the like.

On the other hand, with the improvement in performance and functionality of electric and/or electronic devices, the rapid transmission of information has been progressing. Therefore, parts or members for electric and/or electronic equipment are also required to cope with high-speed transmission. In order to provide resin materials used for such applications with electrical characteristics corresponding to high-speed transmission, attempts have been made to reduce the dielectric constant and the dielectric loss tangent. For example, a low dielectric resin composition has been proposed in which a filler such as silica having a particle size of 1 μm or less is blended with polyimide in an amount of 5 to 70 wt% of the total solid content (patent document 1). In order to achieve a low dielectric loss tangent, a thermosetting resin composition has also been proposed in which an inorganic filler such as silica is added in an amount of 60 mass% or more to a polyimide having a structural unit derived from a bismaleimide compound (patent document 2).

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent No. 3660501 publication

[ patent document 2] Japanese patent laid-open publication No. 2018-012747

Disclosure of Invention

[ problems to be solved by the invention ]

The larger the particle diameter of the silica particles, the lower the dielectric loss tangent tends to be, and even when the silica particles are blended with a resin such as polyimide, the effect of lowering the dielectric loss tangent of the resin film is large. On the other hand, when silica particles having a large particle size are added, there is a problem that the bendability of the resin film is lowered.

The present invention aims to provide silica particles capable of improving dielectric characteristics without impairing mechanical characteristics such as bendability, and further to provide a resin composition and a resin film having improved dielectric characteristics by adding the silica particles.

[ means for solving problems ]

The silica particles of the present invention are silica particles used in a frequency range of 3GHz to 20GHz, and have an average particle diameter D in which an integrated value in a frequency distribution curve obtained by volume-based particle size distribution measurement by a laser diffraction/scattering method is 50%₅₀In the range of 0.3 to 3 μm, and a specific surface area of more than 5m²Per g andis 20m²In the range of/g or less, the dielectric loss tangent measured by the resonance cavity perturbation method is 0.004 or less.

The resin composition of the present invention is a resin composition containing the silica particles and a polyamic acid or polyimide, and the content of the silica particles is in the range of 30 to 70 vol% with respect to the polyamic acid or polyimide.

The resin film of the present invention is a resin film having a single layer or a plurality of polyimide layers, at least one of the polyimide layers being a silica-containing polyimide layer containing a cured product of the resin composition, the silica-containing polyimide layer having a thickness in a range of 10 to 200 μm.

The thickness of the entire resin film in the resin film of the present invention may be in the range of 10 to 200 μm, and the ratio of the thickness of the silica-containing polyimide layer may be 50% or more.

The metal-clad laminate of the present invention is a metal-clad laminate comprising an insulating resin layer containing the resin film, and a metal layer laminated on at least one surface of the insulating resin layer.

[ Effect of the invention ]

The silica particles of the present invention have an average particle diameter D₅₀As small as 0.3 to 3 μm, but the specific surface area is controlled, the dielectric loss tangent is low, and thus the dielectric ceramic composition can be effectively used as an insulating material for high frequencies. In addition, the resin composition of the present invention can improve dielectric characteristics without reducing mechanical characteristics such as flexibility by containing the silica particles. Therefore, in the electric and/or electronic device or electronic part using the resin composition of the present invention, high-speed transmission can be coped with, and reliability can be ensured.

Detailed Description

The resin composition according to one embodiment of the present invention is a resin composition containing polyamic acid or polyimide and the silica particles as an inorganic filler. The resin composition may be a varnish (resin solution) containing a polyamic acid, or a polyimide solution containing a solvent-soluble polyimide.

< Polyamic acid or polyimide >

The polyimide is generally represented by the following general formula (1). Such a polyimide can be produced by a known method of polymerizing a diamine component and an acid dianhydride component in a substantially equimolar amount in an organic polar solvent. In this case, the molar ratio of the acid dianhydride component to the diamine component can be adjusted to a desired range of viscosity, and is preferably set to a range of, for example, 0.980 to 1.03.

[ solution 1]

Here, Ar₁Is a tetravalent organic radical having more than one aromatic ring, Ar₂Is a divalent organic group having one or more aromatic rings. And, Ar₁It can be said to be a residue of acid dianhydride, Ar₂It can be said to be the residue of a diamine. N represents the number of repetitions of the structural unit of the general formula (1), and is 200 or more, preferably 300 to 1000.

The acid dianhydride is preferably, for example, a dianhydride consisting of O (OC)₂-Ar₁-(CO)₂Examples of the aromatic tetracarboxylic dianhydride represented by O include those in which the following aromatic acid anhydride residue is provided as Ar₁Acid dianhydride of (1).

[ solution 2]

The acid dianhydride may be used alone or in combination of two or more. Among these, it is preferable to use one selected from pyromellitic dianhydride (PMDA), 3',4,4' -biphenyltetracarboxylic dianhydride (BPDA), 3',4,4' -benzophenonetetracarboxylic dianhydride (BTDA), 3',4,4' -benzophenonetetracarboxylic dianhydride (3,3',4,4' -benzophenonetetracarboxylic dianhydride), 3',4,4' -diphenylsulfonetetracarboxylic dianhydride (DSDA), and 4,4' -Oxydiphthalic Dianhydride (ODPA).

The diamine is preferably, for example, H₂N-Ar₂-NH₂As the aromatic diamine, the following aromatic diamine residue can be exemplified as Ar₂The aromatic diamine of (4).

[ solution 3]

Among these diamines, diaminodiphenyl ether (DAPE), 2'-dimethyl-4,4' -diaminobiphenyl (2,2'-dimethyl-4,4' -diaminodiphenyl, m-TB), p-phenylenediamine (p-PDA), 1,3-bis (4-aminophenoxy) benzene (1,3-bis (4-aminophenoxy) benzene, TPE-R), 1,3-bis (3-aminophenoxy) benzene (1,3-bis (3-aminophenoxy) benzene, APB), 1,4-bis (4-aminophenoxy) benzene (1,4-bis (4-aminophenoxy) benzene, TPE-Q), and 2,2-bis [4- (4-aminophenoxy) phenyl ] propane (2), 2-bis [4- (4-amino phenyl) phenyl ] propane, BAPP), and 2,2-bis (trifluoromethyl) benzidine (2,2-bis (trifluoromethyl) benzidine, TFMB) are preferred.

Polyimide can be produced by reacting an acid dianhydride with a diamine compound in a solvent to produce a polyamic acid as a precursor, and then heating the polyamic acid for ring closure (imidization). For example, the polyamic acid is obtained by dissolving an acid dianhydride and a diamine compound in an organic solvent in approximately equimolar amounts, and stirring the solution at a temperature in the range of 0 to 100 ℃ for 30 minutes to 72 hours to effect polymerization. During the reaction, the reaction components are dissolved in the organic solvent so that the produced precursor is present in an amount of 5 to 30 wt%, preferably 10 to 20 wt%. Examples of the organic solvent used in the polymerization reaction include: n, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, Dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, cresol, and the like. Two or more of these solvents may be used in combination, and an aromatic hydrocarbon such as xylene or toluene may be used in combination. The amount of the organic solvent used is not particularly limited, but is preferably adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30 wt%.

The polyamic acid synthesized is generally advantageously used as a reaction vehicle solution, which can be concentrated, diluted, or replaced with other organic vehicles as needed to form a resin composition. The method for imidizing the polyamic acid is not particularly limited, and for example, a heat treatment in which heating is performed in the solvent at a temperature in the range of 80 to 400 ℃ for 1 to 24 hours is preferably employed.

< composition of blending >

The content of the silica particles in the resin composition is in the range of 30 to 70 vol%, preferably 30 to 60 vol%, with respect to the polyamic acid or polyimide. If the content of the silica particles is less than 30% by volume, the effect of lowering the dielectric loss tangent cannot be sufficiently obtained. When the content of the silica particles exceeds 70 vol%, the resin film becomes brittle and the bending property is reduced, and when the resin film is to be formed, the viscosity of the resin composition is increased and the workability is also reduced.

The resin composition of the present embodiment may contain an organic solvent. Examples of the organic solvent include: n, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, cresol, and the like. Two or more of these solvents may be used in combination, and an aromatic hydrocarbon such as xylene or toluene may be used in combination. The content of the organic solvent is not particularly limited, and is preferably adjusted to a use amount of about 5 to 30 wt% of the concentration of the polyamic acid or polyimide.

Further, the resin composition of the present embodiment may contain an inorganic filler or an organic filler other than the silica particles as necessary within a range not impairing the effects of the present invention. Specific examples thereof include: silica particles, inorganic fillers such as alumina, magnesia, beryllia, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride, and organic fillers such as fluorine-based polymer particles and liquid crystal polymer particles, which do not satisfy the above conditions. These may be used alone or in combination of two or more. Further, as other optional components, plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants and the like may be suitably blended as required.

< viscosity >

The viscosity of the resin composition is preferably in the range of, for example, 3000cps to 100000cps, more preferably 5000cps to 50000cps, as a viscosity range in which handling properties in coating the resin composition are improved and a coating film having a uniform thickness can be easily formed. If the viscosity is out of the range, defects such as uneven thickness and streaks are likely to occur in the film during coating work using a coater or the like.

< preparation of resin composition >

In the preparation of the resin composition, for example, silica particles may be directly prepared in a resin solution of polyamic acid. Alternatively, in consideration of the dispersibility of the filler, silica particles may be prepared in advance in a reaction solvent in which either an acid dianhydride component or a diamine component, which is a raw material of the polyamic acid, is charged, and then the other raw material may be charged under stirring to carry out polymerization. In either method, the silica particles may be charged all at once, or may be added in portions. In addition, the raw materials may be put together or may be mixed little by little.

[ resin film ]

The resin film of the present embodiment may be a resin film having a single layer or a plurality of polyimide layers, and at least one of the polyimide layers may be a silica-containing polyimide layer containing a cured product of the resin composition.

In the resin film, the thickness of the silica-containing polyimide layer formed from the resin composition is, for example, preferably in the range of 10 to 200 μm, and more preferably in the range of 25 to 100 μm. If the thickness of the polyimide layer containing silicon dioxide is less than 10 μm, the resin film becomes brittle, and the effect of improving the dielectric characteristics of the resin film cannot be sufficiently obtained. Conversely, if the thickness of the polyimide layer containing silicon dioxide exceeds 200 μm, the polyimide layer tends to be disadvantageous in terms of, for example, the bendability of the resin film.

The thickness of the entire resin film is, for example, preferably in the range of 10 to 200. mu.m, and more preferably in the range of 25 to 100. mu.m. If the thickness of the resin film is less than 10 μm, defects such as wrinkles in the metal foil and cracks in the resin film are likely to occur in the conveying step in the production of the metal-clad laminated plate. Conversely, if the thickness of the resin film exceeds 200 μm, the resin film tends to have a disadvantage in terms of, for example, a decrease in the bendability of the resin film.

The ratio of the thickness of the polyimide layer containing silicon dioxide to the thickness of the entire resin film is preferably 50% or more. When the ratio of the thickness of the polyimide layer containing silicon dioxide to the thickness of the entire resin film is less than 50%, the effect of improving the dielectric characteristics cannot be sufficiently obtained.

A method for forming the silicon dioxide-containing polyimide layer may be a known method without particular limitation. The most representative example of which is shown here.

First, a resin composition is directly cast-coated onto an arbitrary supporting substrate to form a coating film. Then, the solvent is dried to some extent at a temperature of 150 ℃ or lower to remove the coating film. When the resin composition contains a polyamic acid, the coating film is then subjected to a heat treatment at a temperature of 100 to 400 ℃, preferably 130 to 360 ℃, for about 5 to 30 minutes in order to further imidize the film. This allows the formation of a silicon dioxide-containing polyimide layer on the support substrate. In the case of providing two or more polyimide layers, the resin solution of the first polyamic acid is applied and dried, and then the resin solution of the second polyamic acid is applied and dried. Thereafter, similarly, the resin solution of polyamic acid is applied and dried in order of a resin solution of third polyamic acid, a resin solution of second polyamic acid, and generally a desired number of times. Then, the imidization is preferably carried out by performing a heat treatment at a temperature of 100 to 400 ℃ for about 5 to 30 minutes. If the temperature of the heat treatment is lower than 100 ℃, the dehydration ring-closure reaction of the polyimide may not sufficiently proceed, whereas if it exceeds 400 ℃, the polyimide layer may deteriorate.

Another example of forming a polyimide layer containing silicon dioxide is described.

First, the resin composition is cast and applied to an arbitrary supporting base material to be formed into a film shape. The film-shaped product is dried by heating on a support base material to prepare a gel film having self-supporting properties. When the resin composition contains polyamic acid after the gel film is peeled from the supporting substrate, the resin composition is further subjected to heat treatment at a high temperature to imidize the resin composition, thereby producing a polyimide resin film.

The supporting substrate for forming the silicon dioxide-containing polyimide layer is not particularly limited, and any substrate can be used. In addition, when forming a resin film, it is not necessary to form a resin film in which imidization is completely completed on a substrate. For example, the resin film in the state of a polyimide precursor in a semi-cured state may be separated from the supporting substrate by a method such as peeling, and imidization may be completed after the separation to obtain the resin film.

The resin film may include only a polyimide layer containing an inorganic filler (including the silica-containing polyimide layer) or may have a polyimide layer containing no inorganic filler. When the resin film has a multilayer laminated structure, it is preferable that all layers contain an inorganic filler in view of improvement of dielectric characteristics. In particular, when the adjacent layer of the polyimide layer containing an inorganic filler is a layer containing no inorganic filler or a layer containing a low content of the inorganic filler, the inorganic filler can be prevented from slipping off during processing. When the polyimide layer does not contain an inorganic filler, the thickness of the polyimide layer is preferably in the range of 1/100 to 1/2, preferably 1/20 to 1/3, of the polyimide layer containing an inorganic filler. In the case of having a polyimide layer containing no inorganic filler, adhesion between the metal layer and the insulating resin layer is improved when the polyimide layer is in contact with the metal layer.

The Coefficient of Thermal Expansion (CTE) of the resin film is not particularly limited, and is preferably 10X 10^-6/K～60×10^-6In the range of/K (10ppm/K to 60ppm/K), more preferably 20X 10^-6/K～50×10^-6A value of/K (20ppm/K to 50 ppm/K). If the coefficient of thermal expansion of the resin film is less than 10X 10^-6and/K, curling is likely to occur after the metal-clad laminate is produced, and handling properties are poor. On the other hand, if the coefficient of thermal expansion of the resin film exceeds 60X 10^-6The material/K tends to have poor dimensional stability as an electronic material such as a flexible substrate and to have low heat resistance.

< dielectric loss tangent >

When the resin film is used as an insulating resin layer of a circuit board, for example, in order to reduce dielectric loss during high-frequency signal transmission, the dielectric loss tangent (Tan δ) at 3GHz to 20GHz as measured by a Split Post Dielectric Resonator (SPDR) is preferably 0.006 or less, more preferably 0.004 or less, as the entire film. In order to improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer, and the effect of reducing the transmission loss is increased by setting the dielectric loss tangent within the above range. Therefore, when the resin film is applied to, for example, an insulating resin layer of a high-frequency circuit board, transmission loss can be reduced efficiently. When the dielectric loss tangent at 3GHz to 20GHz exceeds 0.006, a problem such as an increase in loss of an electrical signal on a transmission path of a high-frequency signal is likely to occur when the resin film is applied to an insulating resin layer of a circuit board. The lower limit of the dielectric loss tangent at 3GHz to 20GHz is not particularly limited, but physical properties of the resin film when applied to an insulating resin layer of a circuit board need to be controlled.

< relative dielectric constant >

When the resin film is applied to, for example, an insulating resin layer of a circuit board, the relative dielectric constant of the entire film at 3GHz to 20GHz is preferably 4.0 or less in order to ensure impedance matching. If the relative dielectric constant at 3GHz to 20GHz exceeds 4.0, the dielectric loss is deteriorated when the resin film is applied to an insulating resin layer of a circuit board, and a problem such as an increase in loss of an electric signal on a transmission path of a high-frequency signal is likely to occur.

< Metal-clad laminate >

The metal-clad laminate of the present embodiment is a metal-clad laminate including an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, at least one layer of the insulating resin layer including the resin film. The metal-clad laminate may be a single-sided metal-clad laminate having a metal layer only on one side of the insulating resin layer, or may be a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer.

The metal-clad laminate of the present embodiment does not exclude the use of an adhesive for bonding a polyimide layer containing an inorganic filler and a metal foil. In the case where the adhesive layer is interposed between the metal-clad laminates having the metal layers on both surfaces of the insulating resin layer, the thickness of the adhesive layer is preferably less than 30%, more preferably less than 20% of the thickness of the entire insulating resin layer so as not to impair the dielectric characteristics. In the case where the adhesive layer is interposed between the single-sided metal-clad laminate having the metal layer only on one side of the insulating resin layer, the thickness of the adhesive layer is preferably less than 15%, more preferably less than 10% of the thickness of the entire insulating resin layer so as not to impair the dielectric characteristics. The adhesive layer is preferably a polyimide layer because it constitutes a part of the insulating resin layer. From the viewpoint of imparting heat resistance, the glass transition temperature of the silica-containing polyimide, which is a main material of the insulating resin layer, is preferably 300 ℃. The acid dianhydride or diamine component constituting the polyimide can be appropriately selected when the glass transition temperature is 300 ℃ or higher.

Examples of the method for producing a metal-clad laminate in which a resin film is used as an insulating resin layer include a method in which a metal foil is heat-pressed onto a resin film directly or via an optional adhesive, and a method in which a metal layer is formed on a resin film by a method such as metal vapor deposition. The double-sided metal-clad laminate can be obtained, for example, by a method of forming a single-sided metal-clad laminate, then pressing and bonding polyimide layers to each other by hot pressing, a method of pressing and bonding a metal foil to a polyimide layer of a single-sided metal-clad laminate, or the like.

< Metal layer >

The material of the metal layer is not particularly limited, and examples thereof include: copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, alloys of these, and the like. Among them, copper or a copper alloy is particularly preferable. The metal layer may be one containing a metal foil or one formed by vapor deposition of a metal on a film. In addition, in terms of the ability to directly apply the resin composition, a metal foil or a metal plate can be used, and a copper foil or a copper plate is preferred.

The thickness of the metal layer is not particularly limited, and is preferably in the range of 5 μm to 3mm, and more preferably in the range of 12 μm to 1mm, for example, because it is appropriately set according to the purpose of use of the metal-clad laminate. If the thickness of the metal layer is less than 5 μm, defects such as wrinkles may occur during transportation, for example, in the production of the metal-clad laminate. On the other hand, if the thickness of the metal layer exceeds 3mm, the metal layer becomes hard and the workability is deteriorated. The thickness of the metal layer is generally a thick metal layer suitable for applications such as a circuit board for a vehicle, and a thin metal layer suitable for applications such as a circuit board for an LED.

[ examples ]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the scope of these examples. In the following examples, unless otherwise specified, various measurements and evaluations were performed as follows.

[ measurement of particle diameter ]

The particle size was measured by a laser diffraction scattering measurement method using a laser particle size analyzer (trade name: laser Sizer)3000 manufactured by Malvern (Malvern) and water as a dispersion medium under a condition that the refractive index of the particles was 1.54.

[ method of measuring true specific gravity ]

The TRUE specific gravity was measured by a pycnometer method (liquid phase displacement method) using a continuous automatic powder TRUE density measuring apparatus (manufactured by Seishin corporation, trade name: AUTO TRUE Denser Mat-7000).

[ measurement of specific surface area ]

According to Japanese Industrial Standard (JIS) Z8830: 2013, the specific surface area was measured by BET specific surface area measurement method using a specific surface area measuring apparatus (trade name: Maccusou (Macsorb)210, manufactured by Maottech (Mountech) Inc.).

[ measurement of relative dielectric constant and dielectric loss tangent ]

< silica particles >

The relative dielectric constant (. epsilon.) of the silica particles at a predetermined frequency was measured using a dielectric constant measuring apparatus manufactured by KANTO ELECTRONIC APPLICATION AND DEVELOPMENT CO., LTD, by resonance-Cavity perturbation method₁) And dielectric loss tangent (Tan. delta.)₁). The sample tube had an inner diameter of 1.68mm, an outer diameter of 2.28mm and a height of 8 cm.

< resin film >

The relative dielectric constant (. epsilon.) of the resin film (cured resin film) at a predetermined frequency was measured using a vector network analyzer (vector network analyzer, trade name: vector network analyzer E8363C, manufactured by Agilent) and an SPDR resonator₁) And dielectric loss tangent (Tan. delta.)₁). The resin film used for the measurement was measured at a temperature: 24 ℃ to 26 ℃ and humidity: standing for 24 hours under the condition of 45-55 percent.

[ measurement of viscosity ]

The viscosity of the resin solution was measured at 25 ℃ using an E-type viscometer (product name: DV-II + Pro, manufactured by Brookfield corporation). The rotational speed was set so that the torque was 10% to 90%, and the value at which the viscosity was stable was read after 2 minutes had elapsed from the start of the measurement.

[ measurement of Coefficient of Thermal Expansion (CTE) ]

A polyimide film having a size of 3mm × 20mm was heated from 30 ℃ to 250 ℃ at a heating rate of 10 ℃/min while applying a load of 5.0g using a thermomechanical analyzer (product name: 4000SA manufactured by Bruker Co., Ltd.), and was held at the above temperature for 10 minutes, and then cooled at a rate of 5 ℃/min, to obtain an average thermal expansion coefficient (coefficient of thermal expansion, CTE) from 250 ℃ to 100 ℃.

[ evaluation of bendability ]

1)180 DEG bendability:

according to JISK5600-1, the center of the long side of a resin film having a size of 5cm × 10cm is uniformly bent so as to be wound around a metal rod having a diameter of 5mm Φ in 1 to 2 seconds, and the resin film is "good" when it is not broken or cracked even if it is bent 180 °, and "failed" when it is broken or cracked.

2) Folding property:

the resin film having a size of 5cm × 5cm was folded diagonally into a triangle, and then the resin film was recovered, and the resin film having no fracture or crack was defined as "ok", and the resin film having fracture or crack was defined as "not ok".

The abbreviations used in the examples and the like represent the following compounds.

m-TB: 2,2'-dimethyl-4,4' -diaminobiphenyl

TPE-R: 1,3-bis (4-aminophenoxy) benzene

BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl ] propane

TFMB: 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl

And (3) PMDA: pyromellitic dianhydride

BPDA: 3,3',4,4' -biphenyltetracarboxylic dianhydride

6 FDA: 2,2-bis (3, 4-dicarboxyphenyl) -hexafluoropropane dianhydride

DMAc: n, N-dimethyl acetamide

Packing 1: chemical of ferric chloride&Manufactured by materials corporation, trade name: SP40-10 (spherical amorphous silica powder, spherical, silica content: 99.9 wt%, true specific gravity: 2.21, specific surface area: 8.6 m)²/g、D₅₀：2.5μm、D₁₀₀：30μm)

And (3) filler 2: chemical of ferric chloride&Manufactured by materials corporation, trade name: SPH507 (spherical amorphous silica powder, spherical, silica content: 99.99 wt%, true specific gravity: 2.21, specific surface area: 6.4 m)²/g、D₅₀：0.83μm、D₁₀₀：8.7μm)

And (3) filler: chemical of ferric chloride&Manufactured by materials corporation, trade name: SPH516M (spherical amorphous silica powder, spherical, silica content: 99.98 wt%, true specific gravity: 2.21, specific surface area: 12.7 m)²/g、D₅₀：0.64μm、D₁₀₀：1.3μm)

And (4) filler: manufactured by adama technologies (Admatech), trade name: SE4050 (spherical amorphous silica powder, spherical, silica content: 99.99 wt%, true specific gravity: 2.2, specific surface area: 4.6 m)²/g、D₅₀：1.5μm、D₁₀₀：6.0μm)

The relative dielectric constants and dielectric loss tangents of fillers 1 to 4 are as follows.

< Filler 1 >

1) Relative dielectric constant ε at 3GHz₁: 3.05, dielectric loss tangent Tan.delta₁：0.0028

2) Relative dielectric constant ε at 5GHz₁: 2.97, dielectric loss tangent Tan. delta₁：0.0028

3) Relative dielectric constant ε at 10GHz₁: 2.78, dielectric loss tangent Tan. delta₁：0.003

< Filler 2 >

1) Relative dielectric constant ε at 3GHz₁: 2.98 dielectric loss tangent Tan. delta₁：0.0025

2) Relative dielectric constant ε at 5GHz₁：2.99、Dielectric loss tangent Tan. delta₁：0.0026

3) Relative dielectric constant ε at 10GHz₁: 2.88 dielectric loss tangent Tan.delta₁：0.0027

< Filler 3 >

1) Relative dielectric constant ε at 3GHz₁: 2.88 dielectric loss tangent Tan.delta₁：0.004

2) Relative dielectric constant ε at 5GHz₁: 2.82 dielectric loss tangent Tan. delta₁：0.0039

3) Relative dielectric constant ε at 10GHz₁: 2.76 dielectric loss tangent Tan. delta₁：0.004

< Filler 4 >

1) Relative dielectric constant ε at 3GHz₁: 3.10 dielectric loss tangent Tan. delta₁：0.0049

2) Relative dielectric constant ε at 5GHz₁: 3.06, dielectric loss tangent Tan. delta₁：0.0049

3) Relative dielectric constant ε at 10GHz₁: 2.92, dielectric loss tangent Tan. delta₁：0.0052

(Synthesis examples 1 to 4)

To synthesize polyamic acid solutions a to D, DMAc as a solvent was added to a 3000ml separable flask under a nitrogen flow so as to have a solid content concentration shown in table 1, and a diamine component and an acid anhydride component shown in table 1 were dissolved at room temperature while stirring for 10 minutes. Thereafter, the solution was continuously stirred at room temperature for 10 hours and polymerization was performed, thereby preparing viscous solutions a to D of polyamic acid.

[ Table 1]

[ example 1]

100.24g of polyamic acid solution A and 9.37g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 1 (viscosity: 27,500cps, content of filler to polyamic acid: 30 vol%).

The polyamic acid solution 1 was coated on a copper foil 1 (electrolytic copper foil, thickness: 12 μm), and dried at 130 ℃ for 3 minutes. Thereafter, a stepwise heat treatment was performed from 155 ℃ to 360 ℃ and imidization was performed, thereby preparing a metal-clad laminate 1.

The copper foil of the metal-clad laminate 1 was removed by etching to prepare a resin film 1. The resin film 1 (thickness: 40 μm) had a CTE of 33ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 1 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0047

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0054

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0056

[ example 2]

100.36g of polyamic acid solution A and 21.88g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 2 (viscosity: 28,400cps, content of filler to polyamic acid: 50 vol%).

A metal-clad laminate 2 and a resin film 2 were prepared in the same manner as in example 1. The CTE of the resin film 2 (thickness: 42 μm) was 31ppm/K, and the 180 ℃ bendability was good and the foldability was not acceptable. The dielectric loss tangent of the resin film 2 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0043

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0047

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0049

[ example 3]

99.92g of polyamic acid solution B and 9.33g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 3 (viscosity: 29,000cps, content of filler to polyamic acid: 30 vol%).

A metal-clad laminate 3 and a resin film 3 were prepared in the same manner as in example 1. The resin film 3 (thickness: 41 μm) had a CTE of 35ppm/K, good 180 ℃ bendability and good foldability. The dielectric loss tangent of the resin film 3 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0029

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0033

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0035

[ example 4]

100.00g of polyamic acid solution B and 21.81g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 4 (viscosity: 31,000cps, content of filler to polyamic acid: 50 vol%).

A metal-clad laminate 4 and a resin film 4 were prepared in the same manner as in example 1. The CTE of the resin film 4 (thickness: 44 μm) was 30ppm/K, the 180 ℃ bendability was good, and the foldability was not satisfactory. The dielectric loss tangent of the resin film 4 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0028

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0030

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0031

[ example 5]

80.00g of polyamic acid solution C and 7.88g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 5 (viscosity: 24,000cps, content of filler to polyamic acid: 30 vol%).

A metal-clad laminate 5 and a resin film 5 were prepared in the same manner as in example 1. The resin film 5 (thickness: 46 μm) had a CTE of 41ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 5 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0046

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0052

3) Dielectric loss at 20GHzAngle tangent Tan delta₁：0.0055

[ example 6]

80.00g of polyamic acid solution D and 7.92g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 6 (viscosity: 23,000cps, content of filler to polyamic acid: 30 vol%).

A metal-clad laminate 6 and a resin film 6 were prepared in the same manner as in example 1. The resin film 6 (thickness: 45 μm) had a CTE of 46ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 6 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0046

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0052

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0055

[ example 7]

80.00g of polyamic acid solution D and 18.49g of filler 1 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 7 (viscosity: 31,000cps, content of filler to polyamic acid: 50 vol%).

A metal-clad laminate 7 and a resin film 7 were prepared in the same manner as in example 1. The resin film 7 (thickness: 48 μm) had a CTE of 28ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 7 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0051

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0054

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0055

Comparative example 1

The copper foil 1 was coated with the polyamic acid solution a and dried at 130 ℃ for 3 minutes. Thereafter, the metal-clad laminate 8 is prepared by performing a stepwise heat treatment from 155 ℃ to 360 ℃ and imidizing.

A metal-clad laminate 8 and a resin film 8 were prepared in the same manner as in example 1. The resin film 8 (thickness: 42 μm) had a CTE of 17ppm/K, good 180 ℃ bendability and good foldability. The dielectric loss tangent of the resin film 8 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0052

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0062

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0065

Comparative example 2

The copper foil 1 was coated with the polyamic acid solution B and dried at 130 ℃ for 3 minutes. Thereafter, the metal-clad laminate 9 was prepared by performing a stepwise heat treatment from 155 ℃ to 360 ℃ and imidizing.

A metal-clad laminate 9 and a resin film 9 were prepared in the same manner as in example 1. The resin film 9 (thickness: 43 μm) had a CTE of 18ppm/K, good 180 ℃ bendability and good foldability. The dielectric loss tangent of the resin film 9 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0032

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0037

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0040

Comparative example 3

The copper foil 1 was coated with the polyamic acid solution C and dried at 130 ℃ for 3 minutes. Thereafter, the metal-clad laminate 10 is prepared by performing a stepwise heat treatment from 155 ℃ to 360 ℃ and imidizing.

A metal-clad laminate 10 and a resin film 10 were prepared in the same manner as in example 1. The resin film 10 (thickness: 41 μm) had a CTE of 51ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 10 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0055

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0062

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0068

Comparative example 4

The copper foil 1 was coated with the polyamic acid solution D and dried at 130 ℃ for 3 minutes. Thereafter, the metal-clad laminate 11 is prepared by performing a stepwise heat treatment from 155 ℃ to 360 ℃ and imidizing.

A metal-clad laminate 11 and a resin film 11 were prepared in the same manner as in example 1. The resin film 11 (thickness: 42 μm) had a CTE of 71ppm/K, good 180 DEG bendability and good foldability. The dielectric loss tangent of the resin film 11 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0069

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0077

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0079

Comparative example 5

100.24g of polyamic acid solution A and 9.37g of filler 4 were mixed and stirred until the same solution was visually observed to prepare polyamic acid solution 12 (viscosity: 28,000cps, content of filler to polyamic acid: 30 vol%).

A metal-clad laminate 12 and a resin film 12 were prepared in the same manner as in example 1. The CTE of the resin film 12 (thickness: 44 μm) was 34ppm/K, and both 180 ℃ bendability and foldability were not acceptable. The dielectric loss tangent of the resin film 12 is as follows.

1) Dielectric loss tangent Tan delta at 5GHz₁：0.0051

2) Dielectric loss tangent Tan delta at 10GHz₁：0.0054

3) Dielectric loss tangent Tan delta at 20GHz₁：0.0055

The embodiments of the present invention have been described in detail for the purpose of illustration, but the present invention is not limited to the embodiments and can be variously modified.