阅读说明：本技术 含有聚四氟乙烯及填充剂的板状的复合材料 (Plate-like composite material containing polytetrafluoroethylene and filler ) 是由 八锹晋平 植村高 今村骏二 笠置智之 顾涛 于 2018-05-30 设计创作，主要内容包括：目的在于,提供表现出低的相对介电常数、且在暴露于电子电路基板的制造所使用的处理液等时不易产生外观不良和特性变化的复合材料。包含聚四氟乙烯及规定的填充剂、且满足规定条件的板状的复合材料成为表现出低的相对介电常数、且在暴露于电子电路基板的制造所使用的处理液等时也不易产生外观不良和特性变化的复合材料。(The purpose is to provide a composite material which exhibits a low relative permittivity and is less likely to cause appearance defects and characteristic changes when exposed to a processing liquid or the like used for the production of an electronic circuit board. A plate-like composite material containing polytetrafluoroethylene and a predetermined filler and satisfying predetermined conditions is a composite material that exhibits a low relative permittivity and is less likely to cause appearance defects and characteristic changes when exposed to a processing liquid or the like used for manufacturing an electronic circuit board.)

1. A composite material characterized by being a plate-like composite material containing polytetrafluoroethylene and a filler,

the filler comprises a porous inorganic fine particle aggregate formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200nm,

the porosity of the composite material is 35% or more, and,

the critical liquid-repellent tension determined by the following wetting tension test is 34.0mN/m or less,

[ wetting tension test ]

In compliance with japanese industrial standard JISK 6768: 1999, a test mixture having a wetting tension at 23 ℃ of 22.6mN/m, 25.4mN/m, 27.3mN/m, 30.0mN/m, 31.0mN/m, 32.0mN/m, 33.0mN/m, 34.0mN/m, 35.0mN/m, 36.0mN/m, 37.0mN/m, 38.0mN/m, 39.0mN/m, 40.0mN/m, 41.0mN/m, 42.0mN/m, 43.0mN/m, 44.0mN/m, 45.0mN/m, 46.0mN/m, 48.0mN/m, and 50.0mN/m, immersing the test object at 25 ℃ for 1 minute, confirming whether or not the test mixture has permeated into the test object, the value of the wetting tension that is the smallest of the wetting tensions in the test mixture that has not permeated the subject is determined as the critical liquid-repellent tension of the subject.

2. The composite of claim 1, whereinThe BET specific surface area of the filler is 30-240 m²/g。

3. The composite material according to claim 1 or 2, wherein the content of the filler is 40 parts by mass or more, assuming that the total amount of the polytetrafluoroethylene and the filler is 100 parts by mass.

4. The composite material according to any one of claims 1 to 3, wherein the filler has an apparent specific gravity of 100g/L or less.

5. A composite material according to any one of claims 1 to 4 for use in an electronic circuit substrate.

Technical Field

The present invention relates to a plate-like composite material suitable for an electronic circuit board and the like.

Background

Due to the development of electronic technology, the use of electronic devices such as computers, mobile communication devices, and the like in high frequency bands is increasing. A high-frequency wiring board or a multilayer wiring board used in such electronic devices is generally required to have a low relative dielectric constant, and a nonpolar resin material such as polyethylene, polypropylene, polystyrene, or polytetrafluoroethylene is used.

For example, as a wiring board material excellent in mechanical properties, thermal properties, and electrical properties, a composite material in which hydrophobic-coated hollow inorganic microspheres are blended in a fluoropolymer matrix has been proposed (see patent document 1). Further, as a material for a printed wiring board in which the content of the filler is small and drilling work is easy, a composite material in which boron nitride or the like is blended with a fluoropolymer has been proposed (see patent document 2).

Disclosure of Invention

Problems to be solved by the invention

In the case where various chemicals are used in the process of manufacturing an electronic circuit board, for example, when the board or a material thereof is exposed to a highly permeable treatment liquid, the treatment liquid may penetrate into the inside, and the board may have poor appearance or changed characteristics. In particular, a substrate having a large amount of a filler (filler) blended therein for the purpose of improving dimensional stability and strength or having a porosity for the purpose of lowering a dielectric constant is likely to be penetrated with a treatment liquid, and thus, attention is required.

That is, the present invention provides a composite material which exhibits a low relative permittivity and is less likely to cause appearance defects and characteristic changes when exposed to a processing liquid or the like used for manufacturing an electronic circuit board.

Means for solving the problems

To achieve the above object, the gist of the present invention is [1] to [5] below.

[1] A composite material in the form of a sheet comprising polytetrafluoroethylene and a filler, wherein the filler comprises a porous inorganic fine particle aggregate formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200nm, the porosity of the composite material is 35% or more, and the critical liquid repellent tension determined by the following wetting tension test is 34.0mN/m or less.

[ wetting tension test ]

In compliance with japanese industrial standard JISK 6768: 1999, a wetting tension at 23 ℃ of each of the test mixtures of 22.6mN/m, 25.4mN/m, 27.3mN/m, 30.0mN/m, 31.0mN/m, 32.0mN/m, 33.0mN/m, 34.0mN/m, 35.0mN/m, 36.0mN/m, 37.0mN/m, 38.0mN/m, 39.0mN/m, 40.0mN/m, 41.0mN/m, 42.0mN/m, 43.0mN/m, 44.0mN/m, 45.0mN/m, 46.0mN/m, 48.0mN/m and 50.0mN/m, immersing the specimen at 25 ℃ for 1 minute, and confirming whether or not each of the test mixture permeates into the specimen, the value of the wetting tension which is the smallest of the wetting tensions in the test liquid mixture which has not permeated into the subject is determined as the critical liquid-repellent tension of the subject.

[2]According to [1]The composite material is characterized in that the BET specific surface area of the filler is 30-240 m²/g。

[3] The composite material according to item [1] or [2], wherein the content of the filler is 40 parts by mass or more, based on 100 parts by mass of the total amount of the polytetrafluoroethylene and the filler.

[4] The composite material according to any one of [1] to [3], wherein the apparent specific gravity of the filler is 100g/L or less.

[5] The composite material according to any one of [1] to [4], which is used for an electronic circuit substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a composite material which exhibits a low relative permittivity and is less likely to cause appearance defects and characteristic changes when exposed to a processing liquid or the like used for manufacturing an electronic circuit substrate.

Drawings

Fig. 1 is an image (a photograph in place of the drawing) of a composite material containing polytetrafluoroethylene and hollow inorganic fine particles (filler) taken by a Scanning Electron Microscope (SEM).

Fig. 2 is an image taken by a Scanning Electron Microscope (SEM) (an image in which a three-dimensional fine network structure is formed by porous inorganic fine particle aggregates formed by aggregating polytetrafluoroethylene and inorganic fine particles having an average primary particle diameter of 5 to 200 nm) (a) a sectional image in a thickness direction (magnification of 50000 times) and (b) a sectional image in a plane direction (magnification of 50000 times)) of a composite material according to an embodiment of the present invention (a substitute photograph for the drawing).

FIG. 3 is an image (a photograph in place of the drawing) of a Scanning Electron Microscope (SEM) image of a porous inorganic fine particle aggregate formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200 nm.

Detailed Description

Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

< composite Material >

A composite material according to one embodiment of the present invention (hereinafter, may be abbreviated as "composite material") is a plate-like composite material containing polytetrafluoroethylene and a filler, the filler containing porous inorganic fine particle aggregates (hereinafter, may be abbreviated as "inorganic fine particle aggregates") formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200nm, and the composite material having a porosity of 35% or more and a critical liquid-repellent tension (hereinafter, may be abbreviated as "critical liquid-repellent tension") determined by the following wetting tension test of 34.0mN/m or less.

[ wetting tension test ]

In compliance with japanese industrial standard JISK 6768: 1999, a wetting tension at 23 ℃ of each of the test mixtures of 22.6mN/m, 25.4mN/m, 27.3mN/m, 30.0mN/m, 31.0mN/m, 32.0mN/m, 33.0mN/m, 34.0mN/m, 35.0mN/m, 36.0mN/m, 37.0mN/m, 38.0mN/m, 39.0mN/m, 40.0mN/m, 41.0mN/m, 42.0mN/m, 43.0mN/m, 44.0mN/m, 45.0mN/m, 46.0mN/m, 48.0mN/m and 50.0mN/m, immersing the specimen at 25 ℃ for 1 minute, and confirming whether or not each of the test mixture permeates into the specimen, the value of the wetting tension which is the smallest of the wetting tensions in the test liquid mixture which has not permeated into the subject is determined as the critical liquid-repellent tension of the subject.

The present inventors have repeatedly studied plate-like materials suitable for electronic circuit boards and the like, particularly dispersion strengthened composites (dispersed strained composites) in which a polymer compound is used as a base material (matrix) and particles are mixed, and have confirmed that when hollow inorganic fine particles are used as a filler as in the composite material described in patent document 1, the hollow inorganic fine particles are broken in the production process of the composite material (see Scanning Electron Microscope (SEM) image of fig. 1), and thus the functions thereof cannot be sufficiently exhibited. Further, the present inventors have found that when an inorganic fine particle aggregate is used as a filler, the inorganic fine particle aggregate is not destroyed even by mixing, molding, rolling, or other treatments, and can ensure good characteristics such as a relative dielectric constant and an expansion ratio.

The present inventors have also revealed that when a substrate or a material thereof is exposed to a treatment liquid having high permeability as described above, the treatment liquid penetrates into the substrate, and a new problem occurs in that the substrate has poor appearance and changed properties. The present inventors have also found that a composite material exhibiting a low relative permittivity and being less likely to cause appearance defects and characteristic changes when exposed to a processing liquid or the like used for the production of an electronic circuit board can be obtained by controlling the critical liquid-repellent tension of the composite material to 34.0mN/m or less by adjusting the inorganic fine particle aggregates, the surface composition, the surface structure, and the like of the composite material.

Hereinafter, the physical properties and characteristics of "polytetrafluoroethylene", "filler" and "composite material", the form and structure of "composite material", the use of "composite material", the method for producing "composite material", and the like will be described in detail.

(Polytetrafluoroethylene (PTFE))

The composite material is a plate-like material containing polytetrafluoroethylene and a filler, and the polytetrafluoroethylene in the composite material is preferably "fibrillated (fiber-like structured)". The fibrillated fibers are more preferably oriented not only in one direction but in a plurality of directions, and particularly preferably, as shown in the SEM-photographed image of fig. 2, fibrils are connected to inorganic fine particle aggregates described later to form a "three-dimensional fine network structure". When polytetrafluoroethylene is fibrillated in a composite material, particularly when a three-dimensional fine network structure is formed, excellent mechanical strength and dimensional stability can be ensured as a composite material. Fibrillation of polytetrafluoroethylene or the like can be confirmed by surface observation using SEM or the like. Further, the fibrillation of polytetrafluoroethylene can be promoted by applying a shear force, more specifically, by multistage calendering described later. The three-dimensional fine network structure is obtained by anisotropic multistage rolling, which will be described later.

(Filler)

One of the characteristics of the composite material is that the composite material is a plate-shaped material containing polytetrafluoroethylene and a filler, wherein the filler comprises a porous inorganic fine particle aggregate formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200nm, specifically, the porous inorganic fine particle aggregate means: as shown in the SEM image of fig. 3, the plurality of inorganic fine particles are fused to form an aggregate, and the inorganic fine particles are formed to be porous with voids therebetween. Here, the "porous" of the porous inorganic fine particle aggregate means a void between the inorganic fine particles constituting the aggregate.

Examples of the material of the inorganic fine particles include oxides (including composite oxides) of typical elements such as silicon oxide (silicon monoxide, silicon dioxide (silica), and the like), aluminum oxide (alumina), and the like; transition metal oxides (including composite oxides) such as titanium oxide (titanium dioxide (artificial rutile), etc.), iron oxide, zirconium oxide (zirconium dioxide (zirconia)), etc.; and nitrides of typical elements such as boron nitride and silicon nitride, and these may be used alone or in combination of 2 or more. Among them, oxides of typical elements are preferable, and silicon dioxide (silica) is particularly preferable. The oxide of the typical element can suppress the relative permittivity of the composite material to be extremely low, and can produce the composite material at a lower cost. The crystallinity of the inorganic fine particles is not particularly limited, and silica is generally amorphous.

The inorganic fine particles have an average primary particle diameter of 5 to 200nm, preferably 10nm or more, more preferably 15nm or more, further preferably 20nm or more, preferably 150nm or less, more preferably 120nm or less, further preferably 100nm or less, particularly preferably 80nm or less, and most preferably 70nm or less. When the amount is within the above range, the inorganic fine particle aggregates are not easily broken even by mixing, molding, rolling, or other treatment, and a good gap can be secured between the inorganic fine particles, and a smooth surface can be easily secured as a plate-shaped composite material. The average primary particle size of the inorganic fine particles is a value obtained by measuring the particle size by SEM observation and averaging the measured values. Specifically, the method comprises the following steps: the number of the inorganic fine particles (100) was randomly selected, the particle diameters (lengths of long sides of the particles) were measured, and the obtained particle diameters were averaged.

The average particle diameter of the primary aggregate of inorganic fine particles is usually 100nm or more, preferably 120nm or more, more preferably 150nm or more, and usually 400nm or less, preferably 380nm or less, more preferably 350nm or less.

The average particle diameter of the secondary aggregates (aggregates of the primary aggregates) of the inorganic fine particles is usually 0.1 μm or more, preferably 1 μm or more, more preferably 2 μm or more, and usually 100 μm or less, preferably 90 μm or less, more preferably 80 μm or less.

The inorganic fine particle aggregate in the composite material is preferably in the state of a secondary aggregate. In the state of secondary aggregates, the three-dimensional fine network structure is easily formed.

The average particle size of the primary aggregates of the inorganic fine particles and the average particle size of the secondary aggregates of the inorganic fine particles can be calculated by the same method as the average primary particle size of the inorganic fine particles.

The BET specific surface area of the inorganic fine particle aggregate is usually 10m²A ratio of 20m or more, preferably²A value of 30m or more, more preferably 30m²A total of 40m or more, preferably 40m²A ratio of the total amount of the components to the total amount of the components in the composition of 250m or more²A ratio of 240m or less, preferably 240m²(ii) less than g, more preferably 210m²A ratio of not more than 150 m/g, preferably²A ratio of 80m or less in particular²The ratio of the carbon atoms to the carbon atoms is less than g. When the amount is within the above range, a high porosity can be ensured as the composite material, and an increase in the dielectric loss tangent can be suppressed. In particular, when the BET specific surface area is too high, the dielectric loss tangent of the composite material tends to be high. The BET specific surface area of the inorganic fine particle aggregate is calculated from the BET formula by substituting the gas adsorption amount measured by a gas adsorption method (particularly, nitrogen adsorption isotherm) and the like into the BET formulaNumerical values.

The apparent specific gravity of the inorganic fine particle aggregate is usually 10g/L or more, preferably 20g/L or more, more preferably 30g/L or more, and still more preferably 40g/L or more, and usually 100g/L or less, preferably 90g/L or less, more preferably 80g/L or less, still more preferably 70g/L or less, and particularly preferably 60g/L or less. When the content is within the above range, a high porosity can be secured as the composite material, and the inorganic fine particle aggregate is not easily broken. The apparent specific gravity of the inorganic fine particle aggregate is as follows: the inorganic fine particle aggregate is filled in a container capable of measuring volume such as a 250mL graduated cylinder, the filling mass (Xg) and the filling volume (YmL) of the inorganic fine particle aggregate are measured, and the filling mass is divided by the filling volume ([ apparent specific gravity (g/L) ] -X/Y × 1000).

Examples of the inorganic fine particle aggregate include Mizukasil series (manufactured by Mizukasil Chemical Co., Ltd.), SYLYSIA series (manufactured by Fuji Silysia Chemical Ltd.), hydrophobic AEROSIL series (manufactured by Nippon AEROSIL Co., Ltd.), NIPSIL series (manufactured by Tosoh silicon Corporation), and the like, and hydrophobic fumed Silica of hydrophobic AEROSIL series (manufactured by Nippon AEROSIL Co., Ltd.) is particularly preferable.

The filler may contain a filler other than the inorganic fine particle aggregate, and the content of the inorganic fine particle aggregate in the entire filler is usually 60 mass% or more, preferably 70 mass% or more, more preferably 80 mass% or more, further preferably 90 mass% or more, and particularly preferably 100 mass%. When the content is within the above range, a high porosity can be secured as the composite material, and the inorganic fine particle aggregate is not easily broken.

Examples of the filler other than the inorganic fine particle aggregate include a particulate filler and a fibrous filler, and examples of the particulate filler include solid carbon such as carbon black; silicon dioxide (silica) such as fused silica and silica gel; transition metal oxides (including composite oxides) such as titanium oxide (titanium dioxide (artificial rutile), etc.), iron oxide, zirconium oxide (zirconium dioxide (zirconia)), etc.; the nitride of a typical element such as boron nitride or silicon nitride includes, as a fibrous filler, glass fiber, carbon fiber, and the like. These may be used alone or in combination of 2 or more.

The hydrophobicity of the filler (including the inorganic fine particle aggregate) can be confirmed by a wettability test of the powder with a methanol aqueous solution. The method for testing the wettability of the powder comprises the following steps: the powder was dispersed in an aqueous methanol solution at 25 ℃ to determine the methanol concentration in the aqueous methanol solution at which the amount of the powder suspended was 0 mass%. The more hydrophobic the filler is, the more difficult it is to settle in water, and the higher the methanol concentration is, the more likely it is to settle. Therefore, the lower the methanol concentration at which the suspended amount of the powder becomes 0 mass%, the more hydrophobic the filler is.

The hydrophobicity (methanol concentration in the wettability test of the powder) of the filler (including the inorganic fine particle aggregate) is usually 70 mass% or less, preferably 65 mass% or less, more preferably 60 mass% or less, further preferably 55 mass% or less, particularly preferably 50 mass% or less, and usually 30 mass% or more.

The content of the filler in the composite material is usually 30 parts by mass or more, preferably 40 parts by mass or more, more preferably 45 parts by mass or more, further preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more, and is usually 85 parts by mass or less, preferably 80 parts by mass or less, more preferably 75 parts by mass or less, further preferably 70 parts by mass or less, and particularly preferably 65 parts by mass or less, when the total amount of the polytetrafluoroethylene and the filler is taken as 100 parts by mass. When the amount is within the above range, good characteristics such as a relative dielectric constant and an expansion ratio can be secured as the composite material. The composite material having a high content of the filler, particularly the inorganic fine particle aggregate can be more effectively used because the treatment liquid easily permeates.

The composite material may contain substances other than the polytetrafluoroethylene and the filler described above, and the total content of the polytetrafluoroethylene and the filler in the entire composite material is usually 60 mass% or more, preferably 70 mass% or more, more preferably 80 mass% or more, further preferably 90 mass% or more, and particularly preferably 100 mass%.

(Properties and Properties of composite Material)

One of the characteristics of the composite material is that the porosity is 35% or more, and the porosity of the composite material is preferably 40% or more, more preferably 45% or more, further preferably 50% or more, particularly preferably 55% or more, and usually 80% or less, preferably 70% or less. When the amount is within the above range, good characteristics such as a relative dielectric constant and an expansion ratio can be secured as the composite material. In particular, in the case of a composite material having a high porosity, the treatment liquid is easily permeated, and therefore the present invention can be more effectively utilized. The porosity of the composite material is a value calculated by measuring the volume of the composite material, the specific gravity and mass (compounding mass) of Polytetrafluoroethylene (PTFE), and the specific gravity and mass (compounding mass) of the inorganic fine particle aggregate, and substituting them into the following formula.

[ porosity (%) ] ═ ([ volume of composite ] - [ mass of PTFE/specific gravity of PTFE ] - [ mass of inorganic fine particle aggregate/specific gravity of inorganic fine particle aggregate ])/[ volume of composite ] × 100

One of the characteristics of the composite is that the critical liquid-repellent tension is 34.0mN/m or less, the critical liquid-repellent tension of the composite is preferably 33.0mN/m or less, more preferably 32.0mN/m or less, further preferably 31.0mN/m or less, and particularly preferably 30.0mN/m or less, and the lower limit value is usually 22.6 mN/m. Within the above range, the electronic circuit board is particularly less likely to have poor appearance or change in characteristics due to a processing liquid or the like used for manufacturing the electronic circuit board. The following wet tension test is described in detail below.

[ wetting tension test ]

In compliance with japanese industrial standard JISK 6768: 1999, a wetting tension at 23 ℃ of each of the test mixtures of 22.6mN/m, 25.4mN/m, 27.3mN/m, 30.0mN/m, 31.0mN/m, 32.0mN/m, 33.0mN/m, 34.0mN/m, 35.0mN/m, 36.0mN/m, 37.0mN/m, 38.0mN/m, 39.0mN/m, 40.0mN/m, 41.0mN/m, 42.0mN/m, 43.0mN/m, 44.0mN/m, 45.0mN/m, 46.0mN/m, 48.0mN/m and 50.0mN/m, immersing the specimen at 25 ℃ for 1 minute, and confirming whether or not each of the test mixture permeates into the specimen, the value of the wetting tension which is the smallest of the wetting tensions in the test liquid mixture which has not permeated into the subject is determined as the critical liquid-repellent tension of the subject.

As a product conforming to japanese industrial standard JISK 6768: the test mixture described in 1999 is "mixture for wet tensile test" manufactured by Wako pure chemical industries, Ltd. Note that, JISK 6768: 1999 is a modified standard based on the international organization for standardization ISO 8296. The mixed solution for wetting tension test contains 36 kinds (in the range of 22.6 to 73.0 mN/m) of mixed solutions having different wetting tensions (23 ℃), and each of the mixed solutions contains a colorant, and thus whether or not the mixed solution has penetrated into the specimen can be easily confirmed by visual inspection. The test mixture may be judged not to permeate into the subject by the change rate of mass after immersion being less than 1% (it should be noted that the judgment based on the change rate of mass is considered to be preferable). When a method of determining the critical liquid repellent tension is described by taking specific examples, when a mixed liquid for a wetting tension test of 33.0mN/m or less permeates into a specimen and a mixed liquid for a wetting tension test of 34.0mN/m or more does not permeate into the specimen, the value of the wetting tension of the test mixed liquid having the smallest non-permeated wetting tension is 34.0mN/m, and the critical liquid repellent tension of the specimen is 34.0 mN/m. The immersion of the sample into the mixture for wet tensile test that apparently does not permeate or the mixture for wet tensile test that apparently permeates may be omitted as appropriate.

The method for controlling the critical liquid repellent tension of the composite material to 34.0mN/m or less is not particularly limited, and known techniques can be suitably employed, and specifically, the following methods (i) and (ii) can be mentioned.

(i) A method of modifying the surface of a filler (including inorganic fine particle aggregates) with a surface modifier having a hydrophobic group (hereinafter sometimes abbreviated as "surface modifier").

(ii) A method for forming a fine structure on the surface of a filler.

Hereinafter, the methods of (i) and (ii) will be described in detail.

Examples of the hydrophobic group of the surface modifier in the method (i) include a fluoro group (-F) and a hydrocarbon group (-C)_nH_2n+1(n is 1 to 30)), and the like, a fluorine group which exhibits liquid repellency not only to water but also to an oil agent is particularly preferable.

The surface modifier may be a low-molecular compound or a high-molecular compound, and may chemically adsorb (react) or physically adsorb to the surface of the filler. The surface modifier that chemically adsorbs (reacts) the surface of the filler generally has a reactive functional group that reacts with a surface functional group (hydroxyl group (-OH), etc.) of the filler, and examples of the reactive functional group include an alkoxysilyl group (-SiOR (the carbon number of R is 1 to 6)), a chlorosilyl group (-SiCl), a bromosilyl group (-SiBr), and a hydrosilyl group (-SiH). In addition, a known method can be suitably used for modifying the surface of the filler with the surface modifier, and the filler is brought into contact with the surface modifier.

The surface modifier is not limited to 1 type, and 2 or more types may be used in combination. For example, the surface of the filler may be reacted with a surface modifier of a low molecular weight compound having a reactive functional group, and then a surface modifier of a high molecular weight compound having a hydrophobic group may be physically adsorbed thereon. The filler may be dissolved (decomposed) when exposed to an alkaline aqueous solution, for example, silicon dioxide (silica) as a material, and thus, when modified, the resistance to an alkaline aqueous solution can be improved.

The thermal decomposition temperature of the surface modifier is usually 250 ℃ or higher, preferably 300 ℃ or higher, more preferably 350 ℃ or higher, still more preferably 360 ℃ or higher, and particularly preferably 370 ℃ or higher. Within the above range, decomposition can be suppressed even when a treatment such as high-temperature heating is performed. The thermal decomposition temperature of the surface modifier was 5% weight loss at 20 ℃ per minute by thermogravimetric analysis (TG-DTA).

Examples of the surface modifier for a low-molecular-weight compound having a fluorine group and a reactive functional group include compounds represented by the following formulae. The compounds represented by the following formula are commercially available and can be suitably obtained and used as a surface modifier.

Examples of the surface modifier for a polymer compound having a fluorine group include those represented by the following formulae. In the following formula, n and m represent positive numbers of 1 or more.

As the surface modifier, a commercially available solution can be used, and a suitable commercially available product includes Novec (registered trademark) 2202 manufactured by 3M. Novec (registered trademark) 2202 discloses a polymer compound containing a fluorine group and compounded with a "fluoroalkyl silane polymer". When Novec (registered trademark) 2202 is used as the surface modifier, there is an advantage that the critical liquid repellent tension of the composite material can be easily suppressed to be low by a relatively simple operation.

The content of the surface modifier (organic matter content) in the filler is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, and particularly preferably 4% by mass or more, and is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, further preferably 25% by mass or less, and particularly preferably 20% by mass or less. When the amount is within the above range, the critical liquid repellent tension of the composite material can be easily reduced, and the thermal expansion coefficient and the dielectric loss tangent can be easily reduced.

Examples of the fine structure in the method (ii) include a "glass surface fine structure" described in japanese patent laid-open No. 2008-239429 and a "candy-like protrusion" described in japanese patent laid-open No. 2012-219004. The surface of the filler is formed with a fine structure to exhibit super water-and oil-repellency, and the critical liquid-repellent tension of the composite material can be controlled to 34.0mN/m or less. As a method for forming a fine structure, the methods described in these documents can be cited.

Other physical properties, characteristics, and the like of the composite material are not particularly limited as long as the porosity is 35% or more and the critical liquid repellent tension is 34.0mN/m or less, and preferred numerical ranges of the relative permittivity, dielectric loss tangent, thermal expansion coefficient, and the like of the composite material are described below.

The relative dielectric constant (frequency: 10GHz) of the composite material is usually 2.0 or less, preferably 1.90 or less, more preferably 1.8 or less, still more preferably 1.75 or less, particularly preferably 1.70 or less, and usually 1.55 or more. The relative permittivity of the composite material is a value of a real part (. epsilon.r') calculated by measuring a complex permittivity by a cavity resonator perturbation method (measurement frequency: 10 GHz).

The dielectric loss tangent (frequency: 10GHz) of the composite material is usually 0.01 or less, preferably 0.008 or less, more preferably 0.006 or less, further preferably 0.004 or less, particularly preferably 0.002 or less, and usually 0.0005 or more. The dielectric loss tangent of the composite material is a ratio (ε r "/ε r ') of an imaginary part (ε r") to a real part (ε r') calculated by measuring a complex dielectric constant by a cavity resonator perturbation method (measurement frequency: 10 GHz).

The composite material has a thermal expansion coefficient of usually 70ppm/K or less, preferably 60ppm/K or less, more preferably 55ppm/K or less, still more preferably 50ppm/K or less, particularly preferably 45ppm/K or less, and usually 10ppm/K or more. The Thermal linear expansion coefficient of the composite material is a value of an average Thermal linear expansion coefficient of-50 to 200 ℃ obtained by a TMA (Thermal mechanical analysis) method. Specifically, a composite material having a width of 4mm and a length of 20mm was fixed in the longitudinal direction, and a load of 2g was applied to the composite material, and the composite material was heated from room temperature (23 ℃) to 200 ℃ at a heating rate of 10 ℃/min and held for 30 minutes, thereby removing the residual stress of the material. Then, the mixture was cooled to-50 ℃ at 10 ℃ per minute, held for 15 minutes, and then heated to 200 ℃ at 2 ℃ per minute. And taking the average thermal expansion coefficient of-50-200 ℃ in the 2 nd heating process as the thermal expansion coefficient.

(form and Structure of composite Material)

The composite material has a plate-like shape, and the thickness of the composite material is usually 0.01mm or more, preferably 0.02mm or more, more preferably 0.05mm or more, further preferably 0.07mm or more, and particularly preferably 0.08mm or more, and usually 2.0mm or less, preferably 1.0mm or less, more preferably 0.5mm or less, further preferably 0.2mm or less, and particularly preferably 0.15mm or less.

The composite material may comprise further layers on one or both sides. Examples of the other layer include a metal layer and a resin layer. The metal layer is used for wiring or the like when the composite material is used as an electronic circuit board, for example, and the resin layer can be used for various purposes, for example, for an adhesive layer when the composite material, the resin layer, and the metal layer are laminated in this order.

Examples of the metal species used as the metal layer in the case of wiring include gold (Au), silver (Ag), platinum (Pt), copper (Cu), aluminum (Al), and alloys containing these metal species.

The thickness of the metal layer when used as a wiring is usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and usually 50 μm or less, preferably 45 μm or less, more preferably 40 μm or less.

The resin layer used as the adhesive layer is usually a thermoplastic resin, preferably a fluorine-based resin, more preferably a perfluoroalkoxyalkane (PFA, melting point: 310 ℃ C.) having a lower melting point than polytetrafluoroethylene (PTFE, melting point: 327 ℃ C.), a tetrafluoroethylene/hexafluoropropylene copolymer (FEP, melting point: 260 ℃ C.), polychlorotrifluoroethylene (PCTEF, melting point: 220 ℃ C.), a tetrafluoroethylene/ethylene copolymer (ETFE, melting point: 270 ℃ C.), a chlorotrifluoroethylene/ethylene copolymer (ECTFE, melting point: 270 ℃ C.), or polyvinylidene fluoride (PVDF, melting point: 151 to 178 ℃ C.), particularly preferably PFA.

(use of composite Material)

The application of the composite material is not particularly limited, and an electronic circuit board, a wiring board of a module such as a mobile phone, a computer, and an antenna, and a wiring board of a millimeter wave antenna (a high-frequency wiring board) are preferably used. When the wiring board of the millimeter wave antenna is used for a purpose, the characteristics such as the relative dielectric constant of the composite material can be effectively utilized.

(method for producing composite Material)

The composite material is a plate-like material containing polytetrafluoroethylene and a filler, and the method for producing the composite material is not particularly limited, and can be suitably produced by using known knowledge. In particular, a method for producing a composite material including the following filler preparation step, mixing step, molding step, and rolling step (hereinafter, may be abbreviated as "method for producing a composite material").

Filler preparation step: a filler comprising porous inorganic fine particle aggregates formed by aggregating inorganic fine particles having an average primary particle diameter of 5 to 200nm is prepared (hereinafter, this may be abbreviated as "filler preparation step").

Mixing step: the precursor composition is obtained by mixing polytetrafluoroethylene and the filler (hereinafter, sometimes abbreviated as "mixing step").

A molding step: the precursor composition is molded to obtain a calenderable material to be calendered (hereinafter, sometimes abbreviated as "molding step").

Rolling step: the material to be rolled is rolled to obtain a rolled material (hereinafter, it may be abbreviated as "rolling step").

The "filler preparation step", "mixing step", "molding step", "rolling step", and the like will be described in detail below.

The filler preparation step is a step of preparing a filler containing an inorganic fine particle aggregate, and the filler (containing an inorganic fine particle aggregate) may be commercially available or may be produced by itself. In order to control the critical liquid repellent tension of the composite material to 34.0mN/m or less, the filler preparation step preferably includes performing at least one of the methods (i) and (ii) on the filler.

The mixing step is a step of mixing polytetrafluoroethylene and a filler to obtain a precursor composition, and the polytetrafluoroethylene is preferably a fine powder or a granulated product.

The average particle diameter of the polytetrafluoroethylene fine powder or granulated product is preferably 5 to 200nm larger than the average primary particle diameter of the inorganic fine particle aggregate, and particularly preferably more than 0.2 μm and 650 μm or less. The average particle diameter of the fine powder or granulated product can be determined in accordance with JIS K6891-5.4.

In the mixing step, it is preferable to add a solvent and a volatile additive to polytetrafluoroethylene and a filler and mix them. The solvent has the effect of making the precursor composition paste-like and uniformly dispersed, and the volatile additive has the effect of increasing the porosity of the composite material by eventually volatilizing it.

Examples of the solvent include water, lower alcohols such as methanol, ethanol, isopropanol, and butanol.

The volatile additive is a compound having a boiling point of 30 to 300 ℃ and being liquid at room temperature, and the boiling point of the volatile additive is preferably 50 ℃ or higher, more preferably 100 ℃ or higher, further preferably 200 ℃ or higher, preferably 280 ℃ or lower, more preferably 260 ℃ or lower, and further preferably 240 ℃ or lower.

Examples of the volatile additive include hydrocarbons having low reactivity, ethers, esters, and alcohols, and aliphatic saturated hydrocarbons are preferable. Specific examples thereof include hexane (boiling point: 69 ℃ C.), heptane (boiling point: 98 ℃ C.), octane (boiling point: 126 ℃ C.), nonane (boiling point: 151 ℃ C.), decane (boiling point: 174 ℃ C.), undecane (boiling point: 196 ℃ C.), dodecane (boiling point: 215 ℃ C.), tridecane (boiling point: 234 ℃ C.), tetradecane (boiling point: 254 ℃ C.), etc., with dodecane being particularly preferred.

The amount of the volatile additive added is usually 1 part by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and usually 200 parts by mass or less, preferably 150 parts by mass or less, more preferably 130 parts by mass or less, further preferably 110 parts by mass or less, particularly preferably 100 parts by mass or less, when the total amount of the polytetrafluoroethylene and the filler is taken as 100 parts by mass. When the amount is within the above range, a good porosity can be secured as a composite material.

The molding step is a step of molding the precursor composition to obtain a rolled object capable of being rolled, and examples of a molding machine used in the molding step include an FT die, a press, an extrusion molding machine, and a calender roll. An FT mold is particularly preferred.

The rolling step is a step of rolling the material to be rolled to obtain a rolled material, and is preferably "multi-stage rolling" in which an operation of rolling the obtained rolled material as a rolled material by laminating the obtained rolled material is repeated a plurality of times, and particularly preferably "counter-directional multi-stage rolling" in which rolling of the material to be rolled is performed in a direction different from the previous rolling direction. As the anisotropic multistage rolling, for example, the following operations are repeated: and laminating the rolled objects in the same rolling direction to form the rolled objects, and rotating the rolling direction of the rolled objects by 90 degrees from the previous rolling direction to perform rolling.

The number of layers of the rolled product in the multistage rolling is usually 2 or more, preferably 3 or more, more preferably 4 or more, further preferably 10 or more, and particularly preferably 30 or more, and is usually 2000 or less, preferably 1000 or less, more preferably 500 or less, further preferably 200 or less, and particularly preferably 100 or less.

The rolling magnification in the rolling step is usually 10 or more, preferably 20 or more, more preferably 40 or more, further preferably 50 or more, and particularly preferably 100 or more, and usually 20000 or less, preferably 10000 or less, more preferably 5000 or less, further preferably 2000 or less, and particularly preferably 1000 or less.

The rolling magnification λ was determined from the formula of λ L2/L1 using the length of the web (L1) and the length after rolling (L2).

Examples of the apparatus used in the rolling step include a press, an extrusion molding machine, and a roll (for example, a calender roll).

The method for producing the composite material may include other steps, and specifically, the following steps may be mentioned.

An additive removal step: the volatile additive is removed from the rolled product (hereinafter, may be abbreviated as "additive removal step").

A heating and pressurizing step: the rolled product is heated and pressed (hereinafter, sometimes abbreviated as "heating and pressing step").

Other layer formation step: at least one of the metal layer and the resin layer is formed on one side or both sides of the rolled product (hereinafter, it may be abbreviated as "other layer forming step").

Patterning step: the metal layer is subjected to patterning treatment (hereinafter, sometimes abbreviated as "patterning process").

The following describes the "additive removing step", "heating and pressing step", "other layer forming step", "patterning step", and the like in detail.

The additive removing step is a step of removing the volatile additive from the rolled product, and a method of heating the rolled product in a heating furnace that can be used for drying is generally exemplified. The heating conditions may be appropriately selected depending on the boiling point of the volatile additive.

The heating and pressing step is a step of heating and pressing the rolled product, and generally includes a method of heating and pressing with a press or the like. The heating temperature is usually 300 to 500 ℃ and the pressurizing condition is usually 0.2 to 30MPa for 5 to 60 minutes.

The other layer forming step is a step of forming at least one of a resin layer and a metal layer on one side or both sides of the rolled product, and examples of a method for forming the metal layer include sputtering, plating, pressure bonding of a metal foil, and a laminating method. Examples of the method for forming the resin layer include: and a method of sandwiching a resin film between the composite material and the metal foil and pressure-bonding the resin film.

The patterning step is a step of patterning the metal layer, and examples of the patterning method include an Additive (Additive) method using a photoresist or the like, and a Subtractive (reactive) method using etching.