Osaka Gas Company scientists have created new carbon nanotube resins for computer circuit boards and electronic components operating in the gigahertz range. The resin compositions have a low dielectric constant, a low dielectric loss tangent, high heat resistance and high mechanical strength.
With the recent rapid increase in the amount of information communicated, reductions in size and weight and increases in the speed of information communication devices, such as PHS and cellular phones, are strongly demanded, and electrical insulating materials with low dielectric constants that can cope with such demands are required.
In particular, portable mobile communications such as automobile phones and digital cellular phones, mobile communication devices such as satellite communications, and like devices use radio waves at high frequencies in the MHz to GHz bands. Further, due to the decrease of usable wavelength bands, high-frequency bands such as microwave and milliwave bands are increasingly used. Furthermore, the CPU clock time of computers has reached a GHz band, and higher and higher frequencies are used. To reduce the size and weight of communication devices operating at such high-frequency bands, it is necessary to develop an electric insulating material that has both excellent RF transmission characteristics and low dielectric properties
Osaka Gas Co., Ltd (Osaka-Shi, JP) earned U.S. Patent 7,652,098 for a resin composition for GHz-band electronic components. The composition includes nanoscale carbon tubes and at least one member selected from the group consisting of thermoplastic resins, curable resins, and composite resins of thermoplastic resins and curable resins. The nanoscale carbon tubes are present in an amount of 0.0001 to 0.4 wt. % based on the resin; and an electronic component obtainable from the resin composition.
The main object of the present invention is to develop an additive that, even when added in a small amount, can reduce dielectric loss (or tan .delta.) in the GHz band, thereby providing a resin composition for electronic components that flexibly meet various demands, say inventors Kouichi Yamaguchi, Hidekazu Hayama, Ren-De Sun, Masahiro Yamada and Yasunori Yokomichi.
Another object is to provide a resin composition that is extremely advantageous for producing circuit board materials for electrical and electronic devices, in particular circuit board materials for the GHz band, and other electronic components.
The inventors conducted extensive research to achieve the GHz resin, and found that the addition of nanoscale carbon tubes in a small amount within a specific range to a synthetic resin suppresses an increase of the dielectric loss tangent in high-frequency bands. The resin is intended in particular for use the GHz band, and allows the synthetic resin to retain its properties, such as thermal conductivity, heat resistance, mechanical strength, dielectric constant, etc. A resin composition containing a specific small amount of nanoscale carbon tubes can be used extremely advantageously as a circuit board material, and in particular a circuit board material for the GHz band, say the inventors.
When nanoscale carbon tubes, which are inherently electrically conductive, are added to a resin composition in an amount of 5 wt. % or more, (as in Japanese Unexamined Patent Publication 1996-134263), electronic components molded from the resulting resin composition are also conductive. Therefore, nanoscale carbon tubes cannot be added to a resin for high-frequency electronic components in a large amount and no attempt has been heretofore made to reduce the dielectric loss tangent in high-frequency bands using nanoscale carbon tubes.
Another object is to provide a resin composition that is extremely advantageous for producing circuit board materials for electrical and electronic devices, in particular circuit board materials for the GHz band, and other electronic components.
The inventors conducted extensive research to achieve the GHz resin, and found that the addition of nanoscale carbon tubes in a small amount within a specific range to a synthetic resin suppresses an increase of the dielectric loss tangent in high-frequency bands. The resin is intended in particular for use the GHz band, and allows the synthetic resin to retain its properties, such as thermal conductivity, heat resistance, mechanical strength, dielectric constant, etc. A resin composition containing a specific small amount of nanoscale carbon tubes can be used extremely advantageously as a circuit board material, and in particular a circuit board material for the GHz band, say the inventors.
When nanoscale carbon tubes, which are inherently electrically conductive, are added to a resin composition in an amount of 5 wt. % or more, (as in Japanese Unexamined Patent Publication 1996-134263), electronic components molded from the resulting resin composition are also conductive. Therefore, nanoscale carbon tubes cannot be added to a resin for high-frequency electronic components in a large amount and no attempt has been heretofore made to reduce the dielectric loss tangent in high-frequency bands using nanoscale carbon tubes.
However, the present inventors' research unexpectedly revealed that when carbon nanotubes are added to a resin composition in a minute amount that is much smaller than the 5 wt. %, the dielectric loss tangent in the GHz band is reduced or its increase is suppressed.
The resin compositions were achieved by further research based on the Osaka researchers findings, and provides the following electronic component resin compositions:
Item 1. A resin composition for GHz-band electronic components, the composition comprising nanoscale carbon tubes and at least one resin selected from the group consisting of thermoplastic resins, curable resins, and composite resins of thermoplastic resins and curable resins, wherein the amount of the nanoscale carbon tubes is 0.0001 to 0.4 wt. % based on the resin.
Item 2. A resin composition for GHz-band electronic components according to item 1, wherein the nanoscale carbon tubes are: (i) single-walled carbon nanotubes or nested multi-walled carbon nanotubes; (ii) amorphous nanoscale carbon tubes; (iii) nanoflake carbon tubes; (iv) iron-carbon composites each composed of (a) a carbon tube selected from the group consisting of nanoflake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron, wherein the iron carbide or iron (b) fills 10 to 90% of the internal space of the carbon tube (a); or (v) a mixture of at least two of (i) to (iv).
Item 3. A resin composition for GHz-band electronic components according to item 1 or 2, wherein the nanoscale carbon tubes are amorphous nanoscale carbon tubes having an interlayer spacing between hexagonal carbon layers (002) of not less than 3.54 .ANG., an angle of diffraction (2.theta.) of not more than 25.1 degrees, and a 2.theta. band half-width of not less than 3.2 degrees, as determined by X-ray diffractometry (incident X-ray: CuK.alpha.). Further items are detailed in U.S. Patent 7,652,098
The resin compositions were achieved by further research based on the Osaka researchers findings, and provides the following electronic component resin compositions:
Item 1. A resin composition for GHz-band electronic components, the composition comprising nanoscale carbon tubes and at least one resin selected from the group consisting of thermoplastic resins, curable resins, and composite resins of thermoplastic resins and curable resins, wherein the amount of the nanoscale carbon tubes is 0.0001 to 0.4 wt. % based on the resin.
Item 2. A resin composition for GHz-band electronic components according to item 1, wherein the nanoscale carbon tubes are: (i) single-walled carbon nanotubes or nested multi-walled carbon nanotubes; (ii) amorphous nanoscale carbon tubes; (iii) nanoflake carbon tubes; (iv) iron-carbon composites each composed of (a) a carbon tube selected from the group consisting of nanoflake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron, wherein the iron carbide or iron (b) fills 10 to 90% of the internal space of the carbon tube (a); or (v) a mixture of at least two of (i) to (iv).
Item 3. A resin composition for GHz-band electronic components according to item 1 or 2, wherein the nanoscale carbon tubes are amorphous nanoscale carbon tubes having an interlayer spacing between hexagonal carbon layers (002) of not less than 3.54 .ANG., an angle of diffraction (2.theta.) of not more than 25.1 degrees, and a 2.theta. band half-width of not less than 3.2 degrees, as determined by X-ray diffractometry (incident X-ray: CuK.alpha.). Further items are detailed in U.S. Patent 7,652,098
FIG. 1 is a transmission electron microscope (TEM) photograph of one of the iron-carbon nanocomposites that make up the carbonaceous-material resin material.
FIG. 2 is a transmission electron microscope (TEM) photograph showing how the iron-carbon composites are present in the carbonaceous material.
FIG. 3 is a transmission electron microscope (TEM) photograph of one of the iron-carbon composites , which has been cut crosswise. The black triangles (.tangle-solidup.) shown in the photograph of FIG. 3 indicate EDX measurement points for elemental analysis.
Examples of such nanoscale carbon tubes include (i) single-walled carbon nanotubes or multi-walled carbon nanotubes; (ii) amorphous nanoscale carbon tubes developed byOsaka Gas ; (iii) nanoflake carbon tubes; (iv) iron-carbon composites each composed of (a) a carbon tube selected from the group consisting of nanoflake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron, wherein the iron carbide or iron (b) fills 10 to 90% of the internal space of the carbon tube (a); and (v) a mixture of two or more.
Among these, the amorphous nanoscale carbon tubes, nanoflake carbon tubes and iron-carbon composites have good dispersibility in solvents and binders, and thus are preferable. The reason why these tubes and composites have good dispersibility in solvents and binders has not been completely clarified yet, but is presumably due to the fact that the discontinuous outermost hexagonal carbon layers of the tubes and composites increase the compatibility with solvents, binders.
Among these, the amorphous nanoscale carbon tubes, nanoflake carbon tubes and iron-carbon composites have good dispersibility in solvents and binders, and thus are preferable. The reason why these tubes and composites have good dispersibility in solvents and binders has not been completely clarified yet, but is presumably due to the fact that the discontinuous outermost hexagonal carbon layers of the tubes and composites increase the compatibility with solvents, binders.
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