JP2021070727A - Resin composition, resin film and metal-clad laminate - Google Patents

Abstract

To provide a resin composition and a resin film which improve dielectric characteristics without impairing mechanical characteristics such as bending properties by addition of an inorganic filler.SOLUTION: A resin composition contains a polyamide acid or polyimide, and spherical silica particles. A frequency distribution curve of spherical silica particles obtained by particle size distribution measurement based on volume by a laser diffraction scattering method satisfies a) an average particle diameter D50 where the cumulative value is 50% of 9.0-12.0 μm, b) a particle diameter D90 where the cumulative value is 90% of 15-20 μm, and c) a particle diameter D100 where the cumulative value is 100% of 25 μm or less, and a content of the spherical silica particles is within a range of 20-65 vol.% with respect to the polyamide acid or the polyimide.SELECTED DRAWING: None

Description

The present invention relates to a resin composition containing spherical silica particles which are inorganic fillers, a resin film using the same, 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. As an example, a resin-attached copper foil having a resin mixture containing an epoxy resin, a polyimide resin and an aromatic polyamide resin, a resin layer containing an imidazole-based curing catalyst and an inorganic filler, and having dielectric properties corresponding to high-frequency transmission has been proposed. (For example, Patent Document 1).

International release WO2017 / 014079

Although Patent Document 1 describes that the dielectric loss tangent of the resin layer can be reduced by adding an inorganic filler such as silica, no detailed study has been made on the specific configuration of the inorganic filler suitable for the purpose. Further, the addition of the inorganic filler has a problem that the bending property of the resin film is lowered and the like has an effect.

An object of the present invention is to provide a resin composition and a resin film whose dielectric properties are improved without impairing mechanical properties such as bendability by adding an inorganic filler.

The resin composition of the present invention is a resin composition containing polyamic acid or polyimide and spherical silica particles. In the resin composition of the present invention, the frequency distribution curve of the spherical silica particles obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method satisfies the following conditions a to c, and the content of the spherical silica particles is high. It is in the range of 20 to 65% by volume with respect to the polyamic acid or the polyimide.
a) The average particle size D _{50 at} which the cumulative value is 50% is within the range of 9.0 to 12.0 μm.
b) The particle size D _{90 at} which the cumulative value is 90% is within the range of 15 to 20 μm.
c) The particle size D _{100 at} which the cumulative value is 100% is 25 μm or less.

In the resin composition of the present invention, the spherical silica particles may further satisfy the following condition d.
d) It has a frequency maximum value F1 and a frequency maximum value F2, and the F1 is in the region of 9.0 to 14.0 μm and the F2 is in the region of 0.5 to 3.0 μm.

In the resin composition of the present invention, the spherical silica particles may further satisfy the following condition e.
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1 / F2) is in the range of 3 to 28.

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 spherical silica-containing polyimide layer made of a cured product of the above resin composition. The thickness of the spherical silica-containing polyimide layer is in the range of 5 to 150 μm.

In the resin film of the present invention, the particle diameter D ₁₀₀ of the spherical silica particles may be in the range of 0.05 to 0.7 with respect to the thickness of the spherical silica-containing polyimide layer.

The resin film of the present invention has a thickness in the range of 5 to 150 μm, and the ratio of the thickness of the spherical 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.

By containing spherical silica particles having a specific particle size distribution represented by the conditions a to c, the resin composition of the present invention can improve the dielectric properties without deteriorating the mechanical properties such as bendability. It will be possible. 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.

[Resin composition]
The resin composition according to the embodiment of the present invention is a resin composition containing polyamic acid or polyimide and spherical 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), 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 substantially equimolar amounts in an organic solvent, stirring at a temperature in the range of 0 to 100 ° C. for 30 minutes to 24 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.

<Spherical silica particles>
Spherical silica particles are silica 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 frequency distribution curve of the spherical silica particles obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method satisfies the following conditions a to c.
a) The average particle size D _{50 at} which the cumulative value is 50% is within the range of 9.0 to 12.0 μm.
b) The particle size D _{90 at} which the cumulative value is 90% is within the range of 15 to 20 μm.
c) The particle size D _{100 at} which the cumulative value is 100% is 25 μm or less.

Regarding the condition a, if the average particle size D ₅₀ of the spherical silica particles is less than 9.0, the effect of improving the dielectric properties becomes small. On the other hand, if the average particle size D ₅₀ exceeds 12.0 μm, it becomes difficult to fill the particles, and it becomes difficult to maintain mechanical properties such as a decrease in bendability when a resin film is formed.
Regarding conditions b and c, the abundance ratio of spherical silica particles having a particle size of 15 to 25 μm is suppressed, and coarse particles are eliminated by having a maximum particle size of 25 μm or less. The foldability can be made good.

Further, it is preferable that the spherical silica particles further satisfy the following conditions d and e.
d) It has a maximum frequency value F1 and a maximum frequency value F2, F1 is in the region of 9.0 to 14.0 μm, and F2 is in the region of 0.5 to 3.0 μm.
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1 / F2) is in the range of 3 to 28.
Regarding condition d and condition e, by containing a certain amount of small spherical silica having a particle size in the range of 0.5 to 3.0 μm in the spherical silica particles, deterioration of bendability at the time of film formation is suppressed. At the same time, the dielectric properties can be further improved.

As the spherical silica particles, a commercially available product can be appropriately selected and used. For example, spherical cristobalite silica powder (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name; CR10-20), spherical amorphous silica powder (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name; SC70-2) and the like can be preferably used. .. These can be used in combination of two or more.

<Mixed composition>
The content of the spherical silica particles in the resin composition is in the range of 20 to 65% 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 spherical silica particles is less than 20% by volume, the effect of lowering the dielectric loss tangent cannot be sufficiently obtained. Further, when the content ratio of the spherical silica particles exceeds 65% by volume, the resin film becomes brittle when formed, the bendability decreases, and the viscosity of the resin composition increases when the resin film is to be formed. , 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, if necessary, the resin composition of the present embodiment may contain an inorganic filler other than the spherical silica particles satisfying the above conditions a to c and an organic filler as long as the effects of the invention are not impaired. Good. Specifically, for example, silica particles that do not satisfy the above conditions a to c, inorganic fillers such as aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride, and fluorine. Examples thereof include organic fillers such as based polymer particles and 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, 5000 cps to 100,000 cps, and is preferably in the range of 10000 cps to 10000 cps, for example, as the viscosity range in which the handleability when coating the resin composition grains 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, spherical silica particles may be directly blended with a resin solution of polyamic acid. Alternatively, in consideration of the dispersibility of the filler, spherical 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 stirred. May be charged to allow the polymerization to proceed. In either method, the entire amount of spherical 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 if at least one of the polyimide layers is a spherical silica-containing polyimide layer made of a cured product of the above resin composition. Good.

In the resin film, the thickness of the spherical silica-containing polyimide layer formed by the resin composition is preferably in the range of, for example, 5 to 150 μm, and more preferably in the range of 45 to 100 μm. Further, it is preferable that the particle size D ₁₀₀ of the spherical silica particles is in the range of 0.05 to 0.7 with respect to the thickness of the spherical silica-containing polyimide layer. If the particle size D ₁₀₀ of the spherical silica particles is less than 0.05 with respect to the thickness of the spherical silica-containing polyimide layer, the effect of improving the dielectric properties may be insufficient, and if it exceeds 0.7, the spherical silica particles are spherical. The smoothness of the surface of the silica-containing polyimide layer may be impaired, and the bendability may decrease when a resin film is formed.

The thickness of the entire resin film is preferably in the range of, for example, 5 to 150 μm, and more preferably in the range of 45 to 80 μm. If the thickness of the resin film is less than 5 μm, problems such as wrinkles in the metal foil 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 100 μm, the bendability of the resin film is lowered, which tends to be disadvantageous.

The ratio of the thickness of the spherical 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 spherical 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 spherical 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 spherical 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 spherical 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 spherical 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 supporting 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 only of a polyimide layer containing an inorganic filler such as spherical silica particles (including the above-mentioned spherical 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, 5 × 10 -6} to 40 × 10 ^-6 / K (5 to 40 ppm / K), and is preferably 10 × 10 ^−. More preferably, it is in the range of ^{6 to 35 × 10-6} / K (10 to 35 ppm / K). If the coefficient of thermal expansion of the resin film is ^{smaller than 5 × 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 40 × 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 10 GHz is preferably 0.005 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 10 GHz exceeds 0.005, when the resin film is applied as the insulating resin layer of the circuit board, inconveniences such as a large loss of electric signals on the transmission path of high frequency signals are likely to occur. The lower limit of the dielectric loss tangent at 10 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 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.

Examples will be shown below, and the features of the present invention will be described in more detail. However, the scope of the present invention is not limited to the examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[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 one minute after the start of the measurement, the value when the viscosity became stable was read.

[Measurement of relative permittivity and dielectric loss tangent]
<Silica particles>
Using a permittivity measuring device manufactured by Kanto Denshi Applied Development Co., Ltd. by the cavity resonator permittivity method, set the permittivity measurement mode to TM101 and measure the relative permittivity (ε1) and dielectric loss tangent (Tanδ1) of silica particles at a frequency of 10 GHz. did. The inner diameter of the sample tube is 1.68 mm, the outer diameter is 2.8 mm, and the height is 8 cm.
<Resin film>
The relative permittivity and dielectric loss tangent are determined by using a vector network analyzer (manufactured by Agilent, trade name; vector network analyzer E8633C) and an SPDR resonator, and the relative permittivity (ε1) of the resin film (resin film after curing) at a frequency of 10 GHz. ) And the dielectric loss tangent (Tanδ1) were 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 method of coefficient of linear thermal expansion (CTE)]
A resin film having a size of 3 mm × 20 mm was heated from 30 ° C. to 265 ° C. at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, trade name; 4000SA). Further, after holding at that temperature for 10 minutes, the film was cooled at a rate of 5 ° C./min to obtain an average coefficient of thermal expansion (coefficient of thermal expansion) from 200 ° C. to 100 ° C.

[Measurement method of particle size]
The particle size was measured by a laser diffraction / scattering type measurement method using a laser diffraction type particle size distribution measuring device (manufactured by Malvern Co., Ltd., trade name; Master Sizer 3000).

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

[Evaluation of 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".

The abbreviations used in Synthesis Examples, Comparative Examples, and Examples indicate the following compounds.
PMDA: pyromellitic dianhydride BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane m-TB: 2,2'-dimethyl-4,4'-diaminobiphenylDMAc: N, N-dimethylacetamide
Filler 1: Nittetsu Chemical & Materials Co., Ltd., trade name; CR10-20 (spherical cristobalite silica powder, spherical, silica content; 99.4% by weight, cristobalite phase; 98% by weight, true specific surface area; 2.33 Specific surface area; 0.63 m ² / g, D ₅₀ ; 10.8 μm, D ₉₀ ; 16.4 μm, D ₁₀₀ ; 24.1 μm, particle size of maximum frequency F1; 11.2 μm, maximum frequency F1; 10. 6%, particle size of maximum frequency F2; 1.0 μm, maximum frequency F2; 1.4%, F1 / F2; 11.2, relative permittivity at 10 GHz; 3.16, dielectric loss tangent at 10 GHz; 0. 0008)
Filler 2: Manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name; SC70-2 (spherical amorphous silica powder, true sphere, silica content; 99.9% by weight, true specific gravity; 2.33, specific surface area; 1. 1 m ² / g, D ₅₀ ; 11.7 μm, D ₉₀ ; 16.4 μm, D ₁₀₀ ; 24.1 μm, particle size of maximum frequency F1; 11.2 μm, maximum frequency F1; 10.8%, maximum frequency Particle size of value F2; 1.5 μm, maximum frequency F2; 1.2%, F1 / F2; 7.5, relative permittivity at 10 GHz; 3.08, dielectric loss tangent at 10 GHz; 0.0015)
Filler 3: Manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name; SP40-10 (spherical amorphous silica powder, true sphere, silica content; 99.9% by weight, true specific gravity; 2.21, specific surface area; 8. 6m ² / g, D ₅₀ ; 2.5 μm, D ₉₀ ; 3.6 μm, D ₁₀₀ ; 7.0 μm, particle size of maximum frequency F1; 2.2 μm, maximum frequency F1; 9.0%, maximum frequency Particle size of value F2; 0.9 μm, maximum frequency F2; 4.3%, F1 / F2; 2.4, relative permittivity at 10 GHz; 2.78, dielectric loss tangent at 10 GHz; 0.0030)

(Synthesis Example 1)
21.65 g of m-TB (101.66 mmol) and 255 g of DMAc were placed in a 300 ml separable flask, and the mixture was stirred at room temperature under a nitrogen stream. After complete dissolution, 17.46 g of PMDA (80.03 mmol) and 5.90 g of BPDA (20.01 mmol) were added and stirred at room temperature for 18 hours to polyamic acid solution A (solid content concentration; 15%). Got The viscosity of the obtained polyamic acid solution A was 22,400 cps.

(Synthesis Example 2)
29.21 g of BAPP (71.15 mmol) and 255 g of DMAc were placed in a 300 ml separable flask, and the mixture was stirred at room temperature under a nitrogen stream. After complete dissolution, 14.74 g of PMDA (67.60 mmol) and 1.05 g of BPDA (3.56 mmol) were added, and the mixture was stirred at room temperature for 18 hours to obtain a polyamic acid solution B. The viscosity of the obtained polyamic acid solution B (solid content concentration; 15%) was 21,074 cps.

[Example 1]
70.0 g of polyamic acid solution A and 7.8 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 1 (viscosity; 24,800 cps, filler content with respect to polyamic acid) 32.6% 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 resin film 1 (thickness; 46.1 μm) had a relative permittivity of 2.78, a dielectric loss tangent of 0.0037, and a CTE of 34 ppm / K, and had good bendability. The evaluation results of the resin film 1 are shown in Table 1.

[Example 2]
60.0 g of polyamic acid solution A and 20.0 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) 59.2% 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 resin film 2 (thickness; 78.1 μm) had a relative permittivity of 2.71, a dielectric loss tangent of 0.0028, and a CTE of 34 ppm / K, and had good bendability. The evaluation results of the resin film 2 are shown in Table 1.

[Example 3]
58.7 g of polyamic acid solution B and 6.1 g of filler 1 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 3 (viscosity; 23,000 cps, filler content with respect to polyamic acid) 30.0% 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 resin film 3 (thickness; 51.6 μm) had a dielectric constant of 3.04 and a dielectric loss tangent of 0.0044, and had good bendability. The evaluation results of the resin film 3 are shown in Table 1.

[Example 4]
70.0 g of polyamic acid solution A and 7.8 g of filler 2 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 4 (viscosity; 23,600 cps, filler content with respect to polyamic acid) 33.8% 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 resin film 4 (thickness; 50.4 μm) had a relative permittivity of 2.84, a dielectric loss tangent of 0.0038, and a CTE of 28.2 ppm / K, and had good bendability. The evaluation results of the resin film 4 are shown in Table 1.

[Example 5]
60.0 g of polyamic acid solution A and 20.0 g of filler 2 are mixed, and the mixture is visually stirred until a uniform solution is obtained. Polyamic acid solution 5 (viscosity; 30,100 cps, filler content with respect to polyamic acid) 60.5% 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 resin film 5 (thickness; 79.3 μm) had a relative permittivity of 2.75, a dielectric loss tangent of 0.0028, and a CTE of 20.4 ppm / K, and had good bendability. The evaluation results of the resin film 5 are shown in Table 1.

[Example 6]
56.2 g of polyamic acid solution B and 5.5 g of filler 2 were mixed, and the mixture was visually stirred until a uniform solution was obtained. Polyamic acid solution 6 (viscosity; 23,600 cps, filler content with respect to polyamic acid). 30.0% 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 resin film 6 (thickness; 50.7 μm) had a relative permittivity of 3.04 and a dielectric loss tangent of 0.0047, and had good bendability. The evaluation results of the resin film 6 are shown in Table 1.

(Comparative Example 1)
70.0 g of 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 7.
In the same manner as in Example 1, the copper foil of the metal-clad laminate 7 was removed by etching to prepare a resin film 7. The resin film 7 (thickness; 26.7 μm) had a dielectric constant of 3.13, a dielectric loss tangent of 0.0056, and a CTE of 21.3 ppm / K, and had good bendability. The evaluation results of the resin film 7 are shown in Table 2.

(Comparative Example 2)
60.0 g of the polyamic acid solution B was applied onto the copper foil 1 and dried at 90 ° C. for 1 minute and at 130 ° C. for 5 minutes. Then, a stepwise heat treatment was performed from 155 ° C. to 360 ° C. to imidize the metal-clad laminate 8.
In the same manner as in Example 1, the copper foil of the metal-clad laminate 8 was removed by etching to prepare a resin film 8. The resin film 8 (thickness; 41.4 μm) had a dielectric constant of 3.16, a dielectric loss tangent of 0.0062, and a CTE of 51.3 ppm / K, and had good bendability. The evaluation results of the resin film 8 are shown in Table 2.

(Reference example 1)
A polyamic acid solution 9 was prepared in the same manner as in Example 1 except that 55.0 g of the polyamic acid solution A and 36.3 g of the filler 1 were mixed.
A polyamic acid solution 9 was applied onto the copper foil 1, a metal-clad laminate 9 was prepared in the same manner as in Example 1, and then a resin film 9 was prepared. The resin film 9 (thickness; 117.8 μm) had a relative permittivity of 2.56, a dielectric loss tangent of 0.0015, and a CTE of 31 ppm / K, and was not bendable. The evaluation results of the resin film 9 are shown in Table 3.

(Reference example 2)
A polyamic acid solution 10 was prepared in the same manner as in Example 1 except that 55.6 g of the polyamic acid solution A and 36.3 g of the filler 2 were mixed.
The polyamic acid solution 10 was applied onto the copper foil 1, and the metal-clad laminate 10 was prepared in the same manner as in Example 1, and then the resin film 10 was prepared. The resin film 10 (thickness; 116.7 μm) had a relative permittivity of 2.75, a dielectric loss tangent of 0.0018, and a CTE of 13 ppm / K, and was not bendable. The evaluation results of the resin film 10 are shown in Table 3.

(Reference example 3)
A polyamic acid solution 11 was prepared in the same manner as in Example 1 except that 56.2 g of the polyamic acid solution B and 5.5 g of the filler 3 were mixed.
The polyamic acid solution 11 was applied onto the copper foil 1, and the metal-clad laminate 11 was prepared in the same manner as in Example 1, and then the resin film 11 was prepared. The resin film 11 (thickness; 45.6 μm) had a relative permittivity of 3.25, a dielectric loss tangent of 0.0052, and a CTE of 40.9, and had good bendability. The evaluation results of the resin film 11 are shown in Table 3.

The polyimide film containing spherical silica particles having an average particle diameter D ₅₀ of 10 μm or more in Examples 1 to 6 has lower dielectric constants and dielectric loss tangents than the silica-free polyimide films of Comparative Examples 1 and 2. ing.
Further, the polyimide films of Reference Examples 1 and 2 containing 70 vol% or more of spherical silica particles had deteriorated bendability as compared with Examples.
Further, the polyimide film of Reference Example 3 in which spherical silica particles having an average particle diameter D ₅₀ as small as 2.5 μm were blended had a higher dielectric constant and dielectric loss tangent than the examples, and the effect of improving the dielectric properties was small.

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 (7)

A resin composition containing polyamic acid or polyimide and spherical silica particles.
The frequency distribution curve of the spherical silica particles obtained by volume-based particle size distribution measurement by the laser diffraction / scattering method has the following conditions a to c;
a) The average particle size D _{50 at} which the cumulative value is 50% is within the range of 9.0 to 12.0 μm;
b) The particle size D _{90 at} which the cumulative value is 90% is within the range of 15 to 20 μm;
c) The particle size D _{100 at} which the cumulative value is 100% is 25 μm or less;
The resin composition is characterized in that the content of the spherical silica particles is in the range of 20 to 65% by volume with respect to the polyamic acid or the polyimide. The spherical silica particles are further subjected to the following condition d;
d) It has a frequency maximum value F1 and a frequency maximum value F2, and the F1 is in the region of 9.0 to 14.0 μm and the F2 is in the region of 0.5 to 3.0 μm;
The resin composition according to claim 1, wherein the resin composition satisfies the above. The spherical silica particles are further subjected to the following condition e;
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1 / F2) is in the range of 3 to 28;
The resin composition according to claim 1 or 2, wherein the resin composition satisfies the above. A resin film having a single layer or a plurality of polyimide layers.
At least one layer of the polyimide layer is a spherical silica-containing polyimide layer made of a cured product of the resin composition according to any one of claims 1 to 3, and the thickness of the spherical silica-containing polyimide layer is 5 to 150 μm. A resin film characterized by being within the range of. _{The resin film according to claim 4, wherein the particle diameter D 100} of the spherical silica particles is in the range of 0.05 to 0.7 with respect to the thickness of the spherical silica-containing polyimide layer. The resin film according to claim 4 or 5, wherein the thickness is in the range of 5 to 150 μm, and the ratio of the thickness of the spherical 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 any one of claims 4 to 6.