JP2021070592A - Silica particle, resin composition, resin film, and metal-clad laminate - Google Patents

Abstract

To provide silica particles which can improve dielectric characteristics without impairing mechanical characteristics such as bending properties, and a resin composition and a resin film which improve dielectric characteristics by addition of the silica particles.SOLUTION: Silica particles are used in a frequency region of 3-20 GHz, and have an average particle diameter D50 here the cumulative value in a frequency distribution curve obtained by particle size distribution measurement based on volume by a laser diffraction scattering method is 50% of 0.3-3 μm, have a specific surface area of more than 5 m2/g and 20 m2/g or less, and have a dielectric loss tangent measured by a cavity resonator perturbation method of 0.004 or less. The resin composition contains the above silica particles, a polyamide acid or polyimide, and a content of the silica particles is within a range of 30-70 vol.% with respect to the polyamide acid or the polyimide.SELECTED DRAWING: None

Description

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

In recent years, there has been an increasing demand for miniaturization and weight reduction of electronic devices as represented by mobile phones, LED lighting fixtures, and related parts around automobile engines. Along with this, flexible circuit boards, which are advantageous for miniaturization and weight reduction of equipment, have come to be widely used in the field of electronic technology. Among them, a flexible circuit board having polyimide as an insulating layer is widely used because of its good heat resistance and chemical resistance.

On the other hand, high-speed transmission of information is progressing along with higher performance and higher functionality of electric and electronic devices. Therefore, parts and components used in electrical and electronic devices are also required to support high-speed transmission. Attempts have been made to reduce the dielectric constant and the low dielectric loss tangent so that the resin material used for such applications has electrical characteristics corresponding to high-speed transmission. For example, a low-dielectric resin composition 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% by weight of the total solid content has been proposed (Patent Document 1). Further, in order to achieve low dielectric loss tangent, a thermosetting resin composition in which 60% by mass or more of an inorganic filler such as silica is blended in polyimide having a structural unit derived from a bismaleimide compound has also been proposed (Patent Document 2). ).

Japanese Patent No. 3660501 Japanese Unexamined Patent Publication No. 2018-012747

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

An object of the present invention is to provide silica particles capable of improving the dielectric properties without impairing mechanical properties such as bendability, and further, by adding the silica particles, the dielectric properties can be improved. It is an object of the present invention to provide an improved resin composition and a resin film.

The silica particles of the present invention are silica particles used in the frequency range of 3 to 20 GHz, and the average particle diameter at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method is 50%. D ₅₀ is in the range of 0.3 to 3 μm, the specific surface area is in the range ^{of more than 5 m 2} / g and 20 m ² / g or less, and the dielectric tangent measured by the cavity resonator perturbation method is 0.004 or less. ..

The resin composition of the present invention is a resin composition containing the above silica particles and the polyamic acid or polyimide, and the content of the silica particles is 30 to 70% by volume with respect to the polyamic acid or the polyimide. Is within the range of.

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

In the resin film of the present invention, the total thickness of the resin film is 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 and a metal layer laminated on at least one surface of the insulating resin layer, and the insulating resin layer is the resin film. It consists of.

Although the silica particles of the present invention have an average particle diameter D ₅₀ as small as 0.3 to 3 μm, they have a low dielectric loss tangent due to the controlled specific surface area, and are therefore useful as an insulating material for high frequencies. Is. Further, by containing the silica particles, the resin composition of the present invention can improve the dielectric properties without deteriorating the mechanical properties such as bendability. Therefore, in electric / electronic devices and electronic parts using the resin composition of the present invention, it is possible to support high-speed transmission and ensure reliability.

Hereinafter, embodiments of the present invention will be described.

[Silica particles]
The silica particles of one embodiment of the present invention are used in the frequency range of 3 to 20 GHz. More specifically, it is silica particles used as a material for parts and members in electrical and electronic equipment used in the frequency range of 3 to 20 GHz. The shape of the silica particles of the present embodiment is preferably spherical. The term "spherical" means particles having a shape close to a true sphere, and the ratio of the average major axis to the average minor axis is close to 1 or 1.

_{The silica particles of the present embodiment have an average particle diameter D 50} of 0.3 to 3 μm, which is a cumulative value of 50% in the frequency distribution curve obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method. , It is preferably in the range of 0.5 to 2.5 μm. Within this range, for example, it is possible to improve the dielectric properties while suppressing a decrease in bendability when blended in a resin film. If the average particle size D ₅₀ of the silica particles is less than 0.3, the effect of lowering the dielectric loss tangent cannot be sufficiently obtained. On the other hand, if the average particle size D ₅₀ exceeds 3 μm, it becomes difficult to maintain mechanical properties such as a decrease in bendability when blended in a resin film.

Further, the silica particles of the present embodiment is in the range the specific surface area is less than ^{5 m} 2 / g, greater ^{20 m} 2 / g, preferably in the range of 6~15m ² / g. By setting the specific surface area of the silica particles within the above range, it is possible to improve the bulk density of the silica particles. Therefore, the average particle diameter D ₅₀ is as low as 0.3 to 3 μm, even if it is small. A dielectric loss tangent is obtained. Specifically, the dielectric loss tangent of the silica particles measured by the cavity resonator perturbation method can be 0.004 or less. When the specific surface area is 5 m ² / g or less, or ^{when it exceeds 20 m 2} / g, the dielectric loss tangent of the silica particles is not sufficiently low, and the effect of blending cannot be obtained. The specific surface area of the silica particles can be determined by the BET specific surface area measurement method.

As the silica particles, commercially available products can be appropriately selected and used. For example, spherical amorphous silica powder (manufactured by Nittetsu Chemical & Materials, trade name; SP40-10), spherical amorphous silica powder (manufactured by Nittetsu Chemical & Materials, trade name; SPH507), spherical amorphous Silica powder (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name; SPH516M) or the like can be preferably used. These can be used in combination of two or more.

[Resin composition]
The resin composition according to the embodiment of the present invention is a resin composition containing a polyamic acid or polyimide and the silica particles which are inorganic fillers. 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>
Polyimide is generally represented by the following general formula (1). Such a polyimide can be produced by a known method in which a diamine component and an acid dianhydride component are substantially equimolarized and polymerized in an organic polar solvent. In this case, the molar ratio of the acid dianhydride component to the diamine component may be adjusted in order to keep the viscosity in a desired range, and the range is, for example, within the range of the molar ratio of 0.980 to 1.03. It is preferable to do so.

Here, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is a divalent organic group having one or more aromatic rings. And Ar ₁ can be said to be a residue of acid dianhydride, and Ar ₂ can be said to be a residue of diamine. Further, n represents the number of repetitions of the structural unit of the general formula (1), and is a number of 200 or more, preferably 300 to 1000.

As the acid dianhydride, for example, _{an aromatic tetracarboxylic dianhydride represented by O (OC) 2-} Ar _1- (CO) ₂ O is preferable, and the following aromatic acid anhydride residue is designated as _{Ar 1.} What is given is exemplified.

The acid dianhydride can be used alone or in combination of two or more. Among these, pyromellitic dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4'-benzophenonetetracarboxylic dianhydride Use one selected from anhydrides (BTDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydrides (DSDA), and 4,4'-oxydiphthalic acid dianhydrides (ODPA). Is preferable.

As the diamine, for example, an aromatic diamine represented by _{H 2} N-Ar _2- NH ₂ is preferable, and an aromatic diamine that gives the following aromatic _{diamine residue as Ar 2 is exemplified.}

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

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 and ring-closing (imidizing). For example, a polyamic acid can be obtained by dissolving an acid dianhydride and a diamine compound in an organic solvent in approximately equimolar amounts, stirring at a temperature in the range of 0 to 100 ° C. for 30 minutes to 72 hours, and carrying out a polymerization reaction. In the reaction, the reaction components are dissolved in an organic solvent so that the precursor produced is in the range of 5 to 30% by weight, preferably in the range of 10 to 20% by weight. Examples of the organic solvent used in the polymerization reaction include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -Butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethylsulfate, cyclohexanone, dioxane, tetrahydrofuran, diglime, triglime, cresol and the like can be mentioned. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can be used in combination. The amount of such an organic solvent used is not particularly limited, but it should be adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. Is preferable.

The synthesized polyamic acid is usually advantageous to be used as a reaction solvent solution, but if necessary, it can be concentrated, diluted or replaced with another organic solvent to form a resin composition. The method for imidizing the polyamic acid is not particularly limited, and for example, a heat treatment such as heating in the solvent under a temperature condition in the range of 80 to 400 ° C. for 1 to 24 hours is preferably adopted.

<Mixed composition>
The content of silica particles in the resin composition is in the range of 30 to 70% by volume, preferably in the range of 30 to 60% by volume, based on the polyamic acid or polyimide. If the content ratio of the silica particles is less than 30% by volume, the effect of lowering the dielectric loss tangent cannot be sufficiently obtained. Further, when the content ratio of the silica particles exceeds 70% by volume, the resin film becomes brittle when formed, the bendability decreases, and when the resin film is to be formed, the viscosity of the resin composition increases. Workability is also reduced.

The resin composition of the present embodiment can contain an organic solvent. Examples of the organic solvent include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, and dimethyl. Examples thereof include sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethylformamide, cyclohexanone, dioxane, tetrahydrofuran, diglime, triglime, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can be used in combination. The content of the organic solvent is not particularly limited, but it is preferable to adjust the content so that the concentration of polyamic acid or polyimide is about 5 to 30% by weight.

Further, the resin composition of the present embodiment may contain an inorganic filler other than the silica particles or an organic filler, if necessary, as long as the effects of the invention are not impaired. Specifically, for example, silica particles that do not meet the above conditions, inorganic fillers such as aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride, and fluorine-based polymer particles. And organic fillers such as liquid crystal polymer particles. These can be used alone or in admixture of two or more. Further, if necessary, a plasticizer, a curing accelerator, a coupling agent, a filler, a pigment, a flame retardant and the like can be appropriately blended as other optional components.

<Viscosity>
The viscosity of the resin composition is preferably in the range of, for example, 3000 cps to 100,000 cps, and is preferably in the range of 5000 cps to 100,000 cps as the viscosity range in which the handleability when coating the resin composition granules is enhanced and a coating film having a uniform thickness is easily formed. It is more preferably within the range of 50,000 cps. If it is out of the above viscosity range, defects such as thickness unevenness and streaks are likely to occur in the film during coating work by a coater or the like.

<Preparation of resin composition>
When preparing the resin composition, for example, silica particles may be directly blended with a resin solution of polyamic acid. Alternatively, in consideration of the dispersibility of the filler, silica particles are previously mixed in a reaction solvent containing either one of the acid dianhydride component and the diamine component, which are the raw materials of the polyamic acid, and then the other raw material is added under stirring. It may be charged to allow the polymerization to proceed. In either method, the entire amount of silica particles may be added at one time, or may be added little by little in several portions. In addition, the raw materials may be added all at once, or may be divided into several times and mixed little by little.

[Resin film]
The resin film of the present embodiment is 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 made of a cured product of the above resin composition. ..

In the resin film, the thickness of the silica-containing polyimide layer formed by the resin composition is preferably in the range of, for example, 10 to 200 μm, and more preferably in the range of 25 to 100 μm. If the thickness of the silica-containing polyimide layer is less than 10 μm, the resin film becomes brittle and the effect of improving the dielectric properties of the resin film cannot be sufficiently obtained. On the contrary, if the thickness of the silica-containing polyimide layer exceeds 200 μm, the bendability of the resin film is lowered, which tends to be disadvantageous.

The thickness of the entire resin film is preferably in the range of, for example, 10 to 200 μm, and more preferably in the range of 25 to 100 μm μm. If the thickness of the resin film is less than 10 μm, problems such as wrinkles in the metal foil and tearing of the resin film are likely to occur in the transport process during the production of the metal-clad laminate. On the contrary, if the thickness of the resin film exceeds 200 μm, the bendability of the resin film is lowered, which tends to be disadvantageous.

The ratio of the thickness of the silica-containing polyimide layer to the total thickness of the resin film is preferably 50% or more. If the ratio of the thickness of the silica-containing polyimide layer to the total thickness of the resin film is less than 50%, the effect of improving the dielectric properties cannot be sufficiently obtained.

The method for forming the silica-containing polyimide layer is not particularly limited, and a known method can be adopted. Here, the most typical example is shown.
First, the resin composition is cast and applied directly onto an arbitrary supporting base material to form a coating film. Next, the solvent is dried and removed from the coating film at a temperature of 150 ° C. or lower to some extent. When the resin composition contains a polyamic acid, the coating film is then further heat-treated for imidization in a temperature range of 100 to 400 ° C., preferably 130 to 360 ° C. for about 5 to 30 minutes. In this way, the silica-containing polyimide layer can be formed on the supporting base material. When forming two or more polyimide layers, a resin solution of the first polyamic acid is applied and dried, and then a resin solution of the second polyamic acid is applied and dried. After that, in the same manner, the resin solution of the third polyamic acid, then the resin solution of the fourth polyamic acid, and so on, the resin solution of the polyamic acid is sequentially applied as many times as necessary. ,dry. After that, it is preferable to carry out heat treatment for about 5 to 30 minutes in a temperature range of 100 to 400 ° C. for imidization. If the heat treatment temperature is lower than 100 ° C., the dehydration ring closure reaction of the polyimide does not proceed sufficiently, and conversely, if it exceeds 400 ° C., the polyimide layer may be deteriorated.

Another example of forming a silica-containing polyimide layer will be given.
First, the resin composition is cast-coated on an arbitrary supporting base material and molded into a film. This film-like molded product is heat-dried on a supporting base material to obtain a gel film having self-supporting properties. After the gel film is peeled off from the supporting base material, if the resin composition contains a polyamic acid, it is further heat-treated at a high temperature and imidized to obtain a polyimide resin film.

The supporting base material used for forming the silica-containing polyimide layer is not particularly limited, and a base material of any material can be used. Further, in forming the resin film, it is not necessary to form the resin film that has been completely imidized on the base material. For example, the resin film in the semi-cured polyimide precursor state can be separated from the supporting base material by means such as peeling, and imidization is completed after the separation to obtain a resin film.

The resin film may consist of only a polyimide layer containing an inorganic filler (including the silica-containing polyimide layer), or may have a polyimide layer not containing an inorganic filler. When the resin film has a laminated structure of a plurality of layers, it is preferable that all the layers contain an inorganic filler in consideration of improvement in dielectric properties. However, by setting the adjacent layer of the polyimide layer containing the inorganic filler to a layer not containing the inorganic filler or a layer having a low content thereof, it is advantageous that the inorganic filler can be prevented from slipping off during processing or the like. It can be effective. When the polyimide layer containing no inorganic filler is provided, the thickness thereof is, for example, within the range of 1/100 to 1/2, preferably 1/20 to 1/3 of the polyimide layer containing the inorganic filler. That is good. When the polyimide layer containing no inorganic filler is provided, if the polyimide layer is brought into contact with the metal layer, the adhesiveness between the metal layer and the insulating resin layer is improved.

The coefficient of thermal expansion (CTE) of the resin film is not particularly limited ^{, but is preferably in the range of, for example, 10 × 10 -6 to} 60 × 10 ^-6 / K (10 to 60 ppm / K), and is preferably 20 × 10 ^−. More preferably, it is in the range of ⁶ to 50 × ^{10-6 / K (20 to 50 ppm / K).} If the coefficient of thermal expansion of the resin film is ^{smaller than 10 × 10 -6} / K, curling is likely to occur after the metal-clad laminate is formed, and the handleability is poor. On the other hand, when the coefficient of thermal expansion of the resin film ^{exceeds 60 × 10-6} / K, the dimensional stability as an electronic material such as a flexible substrate is inferior, and the heat resistance tends to be lowered.

<Dissipation factor>
When the resin film is applied as an insulating resin layer of a circuit board, for example, when the film as a whole is measured by a split post dielectric resonator (SPDR) in order to reduce the dielectric loss during transmission of a high frequency signal. The dielectric loss tangent (Tanδ) at 3 to 20 GHz is preferably 0.006 or less, and more preferably 0.004 or less. 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 by setting the dielectric loss tangent within the above range, the effect of reducing the transmission loss is increased. Therefore, when the resin film is applied as, for example, an insulating resin layer of a high-frequency circuit board, the transmission loss can be efficiently reduced. If the dielectric loss tangent at 3 to 20 GHz exceeds 0.006, inconveniences such as a large loss of electrical signals on the high-frequency signal transmission path are likely to occur when the resin film is applied as the insulating resin layer of the circuit board. .. The lower limit of the dielectric loss tangent at 3 to 20 GHz is not particularly limited, but it is necessary to consider the physical property control when the resin film is applied as the insulating resin layer of the circuit board.

<Relative permittivity>
When the resin film is applied as an insulating resin layer of a circuit board, for example, the relative permittivity of the film as a whole at 3 to 20 GHz is preferably 4.0 or less in order to ensure impedance matching. If the relative permittivity at 3 to 20 GHz exceeds 4.0, when the resin film is applied as the insulating resin layer of the circuit board, the dielectric loss is deteriorated, and the loss of the electric signal is large on the transmission path of the high frequency signal. Inconveniences such as

<Metal-clad laminate>
The metal-clad laminate of the present embodiment is a metal-clad laminate comprising an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and is at least one layer of the insulating resin layer. Is made of the above 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 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 adhering the polyimide layer containing the inorganic filler and the metal foil. However, when the adhesive layer is interposed in the double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer, the thickness of the adhesive layer is 30% of the thickness of the total insulating resin layer so as not to impair the dielectric properties. It is preferably less than, more preferably less than 20%. Further, when the adhesive layer is interposed in the single-sided metal-clad laminate having the metal layer on only one side of the insulating resin layer, the thickness of the adhesive layer is 15 of the thickness of the total insulating resin layer so as not to impair the dielectric properties. It is preferably less than%, and more preferably less than 10%. Further, since the adhesive layer constitutes a part of the insulating resin layer, it is preferably a polyimide layer. The glass transition temperature of the silica-containing polyimide, which is the main material of the insulating resin layer, is preferably 300 ° C. or higher from the viewpoint of imparting heat resistance. The glass transition temperature can be set to 300 ° C. or higher by appropriately selecting the above-mentioned acid dianhydride and diamine components constituting the polyimide.

As a method for producing a metal-clad laminate having a resin film as an insulating resin layer, for example, a method of heat-bonding a metal foil directly to a resin film or via an arbitrary adhesive, a method of heat-pressing a metal foil, or a method such as metal deposition of a resin is used. Examples thereof include a method of forming a metal layer on a film. The double-sided metal-clad laminate can be formed, for example, by forming a single-sided metal-clad laminate and then pressing the polyimide layers facing each other by heat pressing, or by applying a metal foil to the polyimide layer of the single-sided metal-clad laminate. It can be obtained by a method of crimping and forming.

<Metal layer>
The material of the metal layer is not particularly limited, but for example, copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese and these. Alloys and the like. Of these, copper or copper alloys are particularly preferable. The metal layer may be made of metal foil or may be metal-deposited on a film. Further, since the resin composition can be directly applied, either a metal foil or a metal plate can be used, and a copper foil or a copper plate is preferable.

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

Hereinafter, the contents of the present invention will be specifically described based on Examples, but the present invention is not limited to the scope of these Examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of particle size]
Measurement of particle size by laser diffraction / scattering type measurement method using a laser diffraction type particle size distribution measuring device (manufactured by Malvern, trade name; Master Sizer 3000) under the condition of a particle refractive index of 1.54 using water as a dispersion medium. Was done.

[Measurement method of true specific gravity]
The true specific gravity was measured by the pycnometer method (liquid phase substitution method) using a continuous automatic powder truth density measuring device (manufactured by Seishin Enterprise Co., Ltd., trade name; AUTO TRUE DENSERMAT-7000).

[Measurement of specific surface area]
In accordance with JIS Z 8830: 2013, the specific surface area was measured by a BET specific surface area measuring method using a specific surface area measuring device (manufactured by Mountech, trade name; Macsorb210).

[Measurement of relative permittivity and dielectric loss tangent]
<Silica particles>
The relative permittivity (ε1) and dielectric loss tangent (Tanδ1) of silica particles at a predetermined frequency were measured using a permittivity measuring device manufactured by Kanto Electronics Applied Development Co., Ltd. by the cavity resonator perturbation method. The inner diameter of the sample tube is 1.68 mm, the outer diameter is 2.28 mm, and the height is 8 cm.
<Resin film>
Relative permittivity (ε1) and dielectric loss tangent (Tanδ1) of a resin film (resin film after curing) at a predetermined frequency using a vector network analyzer (manufactured by Agilent, trade name; vector network analyzer E8633C) and an SPDR resonator. Was measured. The resin film used for the measurement was left to stand for 24 hours under the conditions of temperature: 24-26 ° C. and humidity: 45-55%.

[Measurement of viscosity]
The viscosity of the resin solution was measured at 25 ° C. using an E-type viscometer (manufactured by Brookfield, trade name; DV-II + Pro). The rotation speed was set so that the torque was 10% to 90%, and 2 minutes after the start of the measurement, the value when the viscosity became stable was read.

[Measurement of coefficient of thermal expansion (CTE)]
A polyimide film having a size of 3 mm × 20 mm is raised from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, trade name; 4000SA). After warming and holding at that temperature for 10 minutes, the film was cooled at a rate of 5 ° C./min to determine the average coefficient of thermal expansion (coefficient of thermal expansion, CTE) from 250 ° C. to 100 ° C.

[Evaluation of bendability]
1) 180 ° bendability:
In accordance with JIS K5600-1, the center of the long side of a 5 cm x 10 cm size resin film is bent uniformly over 1 to 2 seconds so as to be wrapped around a 5 mmφ metal rod, and even if the resin film is bent at 180 ° C, it breaks. Alternatively, those without cracks were rated as "good", and those with breaks or cracks were rated as "impossible".
2) Foldability:
A 5 cm x 5 cm size resin film is folded diagonally into a triangle and then returned to its original position. If the resin film does not break or crack, it is considered "possible", and if it breaks or cracks occur, it is considered "impossible". did.

The abbreviations used in the examples and the like indicate the following compounds.
m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis (4-aminophenoxy) benzene BAPP: 2,2-bis (4-aminophenoxyphenyl) propaneTFMB : 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl PMDA: pyromellitic dianhydride BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride 6FDA: 2 , 2-Bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride DMAc: N, N-dimethylacetamide filler 1: Nittetsu Chemical & Materials Co., Ltd., trade name; SP40-10 (spherical amorphous) Silica powder, spherical, silica content; 99.9% by weight, true specific gravity; 2.21, specific surface area; 8.6 m ² / g, D ₅₀ ; 2.5 μm, D ₁₀₀ ; 30 μm)
Filler 2: Made by Nittetsu Chemical & Materials Co., Ltd. Product Name: SPH507 (Spherical Amorphous Silica Powder, Spherical Spherical, Silica Content: 99.99% by Weight, True Specific Weight: 2.21, Specific Surface Area: 6.4 m ² / g, D ₅₀ ; 0.83 μm, D ₁₀₀ ; 8.7 μm)
Filler 3: Made by Nittetsu Chemical & Materials Co., Ltd. Product name: SPH516M (spherical amorphous silica powder, true sphere, silica content; 99.98% by weight, true specific weight; 2.21, specific surface area; 12.7 m ² / g, D ₅₀ ; 0.64 μm, D ₁₀₀ ; 1.3 μm)
Filler 4: Made by Admatech, trade name: SE4050 (spherical amorphous silica powder, true sphere, silica content; 99.99% by weight, true specific weight; 2.2, specific surface area: 4.6 m ² / g, D ₅₀ ; 1.5 μm, D ₁₀₀ ; 6.0 μm)

The relative permittivity and dielectric loss tangent of fillers 1 to 4 were as follows.
<Filler 1>
1) Relative permittivity at 3 GHz ε ₁ ; 3.05, dielectric loss tangent Tan δ ₁ ; 0.0028
2) Relative permittivity at 5 GHz ε ₁ ; 2.97, dielectric loss tangent Tan δ ₁ ; 0.0028
3) Relative permittivity at 10 GHz ε ₁ ; 2.78, dielectric loss tangent Tan δ ₁ ; 0.003
<Filler 2>
1) Relative permittivity at 3 GHz ε ₁ ; 2.98, dielectric loss tangent Tan δ ₁ ; 0.0025
2) Relative permittivity at 5 GHz ε ₁ ; 2.99, dielectric loss tangent Tan δ ₁ ; 0.0026
3) Relative permittivity at 10 GHz ε ₁ ; 2.88, dielectric loss tangent Tan δ ₁ ; 0.0027
<Filler 3>
1) Relative permittivity at 3 GHz ε ₁ ; 2.88, dielectric loss tangent Tan δ ₁ ; 0.004
2) Relative permittivity at 5 GHz ε ₁ ; 2.82, dielectric loss tangent Tan δ ₁ ; 0.0039
3) Relative permittivity at 10 GHz ε ₁ ; 2.76, dielectric loss tangent Tan δ ₁ ; 0.004
<Filler 4>
1) Relative permittivity at 3 GHz ε ₁ ; 3.10, dielectric loss tangent Tan δ ₁ ; 0.0049
2) Relative permittivity at 5 GHz ε ₁ ; 3.06, dielectric loss tangent Tan δ ₁ ; 0.0049
3) Relative permittivity at 10 GHz ε ₁ ; 2.92, dielectric loss tangent Tan δ ₁ ; 0.0052

(Synthesis Examples 1 to 4)
In order to synthesize the polyamic acid solutions A to D, the solvent DMAc was added to a 3000 ml separable flask under a nitrogen stream so as to have the solid content concentration shown in Table 1, and the diamine shown in Table 1 was added. The components and the acid anhydride component were dissolved at room temperature with stirring for 10 minutes. Then, the solution was stirred at room temperature for 10 hours to carry out a polymerization reaction to prepare viscous solutions A to D of polyamic acid.

[Example 1]
100.24 g of polyamic acid solution A and 9.37 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 1 (viscosity; 27,500 cps, filler content with respect to polyamic acid) 30% by volume) was prepared.
The polyamic acid solution 1 was applied onto the copper foil 1 (electrolytic copper foil, thickness; 12 μm) and dried at 130 ° C. for 3 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 1.
The copper foil of the metal-clad laminate 1 was removed by etching to prepare a resin film 1. The CTE of the resin film 1 (thickness; 40 μm) was 33 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 1 was as follows.
1) Dissipation factor Tanδ _{1 at} 5 GHz; 0.0047
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0054}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0056}

[Example 2]
100.36 g of polyamic acid solution A and 21.88 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 2 (viscosity; 28,400 cps, filler content with respect to polyamic acid) (50% by volume) was prepared.
The metal-clad laminate 2 and the resin film 2 were prepared in the same manner as in Example 1. The CTE of the resin film 2 (thickness: 42 μm) was 31 ppm / K, and the 180 ° bendability was good and the foldability was not possible. The dielectric loss tangent of the resin film 2 was as follows.
1) Dissipation factor _{Tanδ 1 at 5 GHz; 0.0043}
2) Dissipation factor Tanδ _{1 at} 10 GHz; 0.0047
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0049}

[Example 3]
99.92 g of polyamic acid solution B and 9.33 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 3 (viscosity; 29,000 cps, filler content with respect to polyamic acid) 30% by volume) was prepared.
The metal-clad laminate 3 and the resin film 3 were prepared in the same manner as in Example 1. The CTE of the resin film 3 (thickness; 41 μm) was 35 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 3 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0029}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0033}
3) Dissipation factor Tanδ _{1 at} 20 GHz; 0.0035

[Example 4]
100.00 g of polyamic acid solution B and 21.81 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained, and the polyamic acid solution 4 (viscosity; 31,000 cps, content of filler with respect to polyamic acid) is obtained. (50% by volume) was prepared.
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 30 ppm / K, and the 180 ° bendability was possible and the foldability was not possible. The dielectric loss tangent of the resin film 4 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0028}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0030}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0031}

[Example 5]
80.00 g of polyamic acid solution C and 7.88 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 5 (viscosity; 24,000 cps, filler content with respect to polyamic acid) 30% by volume) was prepared.
A metal-clad laminate 5 and a resin film 5 were prepared in the same manner as in Example 1. The CTE of the resin film 5 (thickness; 46 μm) was 41 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 5 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0046}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0052}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0055}

[Example 6]
80.00 g of polyamic acid solution D and 7.92 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 6 (viscosity; 23,000 cps, filler content with respect to polyamic acid) 30% by volume) was prepared.
A metal-clad laminate 6 and a resin film 6 were prepared in the same manner as in Example 1. The CTE of the resin film 6 (thickness; 45 μm) was 46 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 6 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0046}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0052}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0055}

[Example 7]
80.00 g of polyamic acid solution D and 18.49 g of filler 1 were mixed, and the mixture was visually stirred until a uniform solution was obtained. Polyamic acid solution 7 (viscosity; 31,000 cps, filler content with respect to polyamic acid). (50% by volume) was prepared.
A metal-clad laminate 7 and a resin film 7 were prepared in the same manner as in Example 1. The CTE of the resin film 7 (thickness: 48 μm) was 28 ppm / K, and the 180 ° foldability was good and the foldability was possible. The dielectric loss tangent of the resin film 7 was as follows.
1) Dissipation factor _{Tanδ 1 at 5 GHz; 0.0051}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0054}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0055}

(Comparative Example 1)
Polyamic acid solution A was applied onto the copper foil 1 and dried at 130 ° C. for 3 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 8.
A metal-clad laminate 8 and a resin film 8 were prepared in the same manner as in Example 1. The CTE of the resin film 8 (thickness; 42 μm) was 17 ppm / K, and the 180 ° foldability was good and the foldability was possible. The dielectric loss tangent of the resin film 8 was as follows.
1) Dissipation factor _{Tanδ 1 at 5 GHz; 0.0052}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0062}
3) Dissipation factor Tanδ _{1 at} 20 GHz; 0.0065

(Comparative Example 2)
Polyamic acid solution B was applied onto the copper foil 1 and dried at 130 ° C. for 3 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 9.
A metal-clad laminate 9 and a resin film 9 were prepared in the same manner as in Example 1. The CTE of the resin film 9 (thickness; 43 μm) was 18 ppm / K, and the 180 ° foldability was good and the foldability was possible. The dielectric loss tangent of the resin film 9 was as follows.
1) Dissipation factor Tanδ _{1 at} 5 GHz; 0.0032
2) Dissipation factor Tanδ _{1 at} 10 GHz; 0.0037
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0040}

(Comparative Example 3)
Polyamic acid solution C was applied onto the copper foil 1 and dried at 130 ° C. for 3 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 10.
A metal-clad laminate 10 and a resin film 10 were prepared in the same manner as in Example 1. The CTE of the resin film 10 (thickness; 41 μm) was 51 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 10 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0055}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0062}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0068}

(Comparative Example 4)
Polyamic acid solution D was applied onto the copper foil 1 and dried at 130 ° C. for 3 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 11.
A metal-clad laminate 11 and a resin film 11 were prepared in the same manner as in Example 1. The CTE of the resin film 11 (thickness; 42 μm) was 71 ppm / K, and the 180 ° bendability was good and the foldability was possible. The dielectric loss tangent of the resin film 11 was as follows.
1) Dissipation factor Tanδ _{1 at 5 GHz; 0.0069}
2) Dissipation factor Tanδ _{1 at 10 GHz; 0.0077}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0079}

[Comparative Example 5]
Mix 100.24 g of polyamic acid solution A and 9.37 g of filler 4 and stir until a visually uniform solution is obtained. Polyamic acid solution 12 (viscosity; 28,000 cps, filler content with respect to polyamic acid). 30% by volume) was prepared.
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 34 ppm / K, and neither 180 ° bendability nor foldability was possible. The dielectric loss tangent of the resin film 12 was as follows.
1) Dissipation factor _{Tanδ 1 at 5 GHz; 0.0051}
2) Dissipation factor _{Tanδ 1 at 10 GHz; 0.0054}
3) Dissipation factor Tanδ _{1 at 20 GHz; 0.0055}

Although the embodiments of the present invention have been described in detail for the purpose of exemplification, the present invention is not limited to the above embodiments and can be modified in various ways.

Claims (5)

Silica particles used in the frequency range of 3 to 20 GHz.
_{The average particle diameter D 50, which} has a cumulative value of 50% in the frequency distribution curve obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method, is within the range of 0.3 to 3 ^{μm, and the specific surface area exceeds 5 m 2} / g and is 20 m. ^{Silica particles in the range of 2} / g or less and having a dielectric tangent measured by the cavity resonator perturbation method of 0.004 or less. A resin composition containing the silica particles according to claim 1 and polyamic acid or polyimide.
A resin composition characterized in that the content of the silica particles is in the range of 30 to 70% by volume with respect to the polyamic acid or polyimide. A resin film having a single layer or a plurality of polyimide layers.
At least one layer of the polyimide layer is a silica-containing polyimide layer made of a cured product of the resin composition according to claim 2, and the thickness of the silica-containing polyimide layer is in the range of 10 to 200 μm. Resin film. The resin film according to claim 3, wherein the total thickness of the resin film is in the range of 10 to 200 μm, and the ratio of the thickness of the silica-containing polyimide layer is 50% or more. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer.
A metal-clad laminate characterized in that the insulating resin layer is made of the resin film according to claim 3 or 4.