Branched vapor-grown carbon fiber, electrically conductive transparent composition and use thereof

• US 20040036060A1
• Filed: 06/19/2003
• Published: 02/26/2004
• Est. Priority Date: 12/20/2000
• Status: Active Grant

• Current Assignee: Showa Denko KK (Resonac Holdings Corp.)
• Original Assignee: Showa Denko KK (Resonac Holdings Corp.)
• Inventors: Morita, Toshio, Yamamoto, Ryuji, Inoue, Hitoshi
• Granted Patent: US 7,122,132 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C08K 2201/016 Additives defined by their aspect ratio
• CPC Class Codes: C08K 7/24 inorganic
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: D01F 9/127 by thermal decomposition of hydrocarbon gases or vapours or other carbon-containing compounds in the form of gas or vapour, e.g. carbon monoxide, alcohols
• CPC Class Codes: H01B 1/04 mainly consisting of carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: Y10T 428/2918 including free carbon or carbide or therewith [not as steel]

Abstract

A branched vapor-grown carbon fiber having an outer diameter of 0.5 μm or less and an aspect ratio of at least 10, the carbon fiber having a compressed specific resistance of 0.02 Ω·cm or less, each fiber filament having a hollow cylindrical structure, preferably the carbon fiber containing boron and having a compressed specific resistance of 0.018 Ω·cm or less. An electrically conductive transparent composition comprising a resin binder and carbon fiber incorporated into the binder, having transparency and comprising vapor grown carbon fiber having an outer diameter of 0.01-0.1 μm, an aspect ratio of 10-15,000, and a compressed specific resistance of 0.02 Ω·cm or less, and surface resistivity of 10,000 Ω/□ or less. An electrically conductive transparent material formed from the aforementioned electrically conductive transparent composition.

Claims

1. Branched vapor-grown carbon fiber having an outer diameter of 0.5 μ

m or less and an aspect ratio of at least 10, each fiber filament having a hollow cylindrical structure, characterized by having a compressed specific resistance of 0.02 Ω

·

cm or less.

2. Branched vapor-grown carbon fiber as claimed in claim 1, which has an outer diameter of 0.05-0.5 μ

m, a length of 1-100 μ

m, and an aspect ratio of 10-2,000.

3. Branched vapor-grown carbon fiber as claimed in claim 1, which has an outer diameter of 0.002-0.05 μ

m, a length of 0.5-50 μ

m, and an aspect ratio of 10-25,000.

4. Branched vapor-grown carbon fiber as claimed in claim 2 or 3, which has a compressed specific resistance of 0.018 Ω

·

cm or less, each fiber filament having a structure such that a central hollow portion extends throughout the filament including a branched portion thereof.

5. Branched vapor-grown carbon fiber as claimed in claim 4, which comprises, in an amount of at least 10 mass %, branched carbon fiber, each fiber filament having a structure such that a central hollow portion extends throughout the filament including a branched portion thereof.

6. Branched vapor-grown carbon fiber as claimed in claim 1, which further comprises boron.

7. Branched vapor-grown carbon fiber as claimed in claim 6, which comprises boron in an amount of 0.01-5 mass %.

8. Branched vapor-grown carbon fiber as claimed in any one of claims 1 to 7, which has a heat conductivity of at least 100 kcal (mh°

C.)<sup>−

1</sup>.

9. Branched vapor-grown carbon fiber as claimed in claim 8, which has a heat conductivity of at least 100 kcal (mh°

C.)<sup>−

1</sup> when the fiber is compressed so as to attain a bulk density of 0.8 g/cm³.

10. A process for producing branched vapor grown carbon fiber as claimed in claim 1, by thermal decomposition of an organic compound with a transition metal catalyst, characterized by spraying droplets of organic compound containing 5-10 mass % of a transition metal element or its compound on a heating furnace wall to allow reaction to form carbon fiber filaments on the furnace wall, burning the recovered filaments at 800-1,500°

C. in a non-oxidative atmosphere, and heating them at 2,000-3,00°

C. to perform graphitization treatment in a non-oxidative atmosphere.

11. The process as claimed in claim 10, wherein the heating for graphitization treatment is performed after doping with boron or at least one boron compound selected from the group consisting of boron oxide, boron carbide, boric ester, boric acid or its salt, and organic boron compounds as a crystallization promotion compound in an amount of 0.1-5 mass % in terms of boron.

12. An electrically conductive transparent composition comprising a resin binder and carbon fiber incorporated into the binder, characterized by having transparency and comprising vapor grown carbon fiber having an outer diameter of 0.01-0.1 μ

m, an aspect ratio of 10-15,000, and a compressed specific resistance of 0.02 Ω

·

cm or less.

13. The electrically conductive transparent composition as claimed in claim 12, wherein the carbon fiber is vapor grown carbon fiber having an outer diameter of 0.05-0.1 μ

m or less, a length of 1-100 μ

m, and an aspect ratio of 10-2,000, each fiber filament having a hollow cylindrical structure.

14. The electrically conductive transparent composition as claimed in claim 12, wherein the blending amount of vapor grown carbon fiber is 5-40 mass % of the total composition.

15. The electrically conductive transparent composition as claimed in claim 12, which has a surface resistivity of 10,000 Ω

/□

or less.

16. The electrically conductive transparent composition as claimed in claim 12, which has a surface resistivity of 5-10,000 Ω

/□

, and a transmittance of at least 60% when the composition is formed to have a thickness of 0.5 μ

m.

17. The electrically conductive transparent composition as claimed in claim 12 or 13, wherein the carbon fiber is vapor grown carbon fiber having an interlayer distance (d₀₀₂) of carbon crystal layers of 0.339 nm or less and a compressed specific resistance of 0.018 Ω

·

cm or less.

18. The electrically conductive transparent composition as claimed in claim 13, wherein the branched vapor grown carbon fiber has a compressed specific resistance of 0.018 Ω

·

cm or less, each fiber filament thereof having a structure such that a central hollow portion extends throughout the filament including a branched portion thereof.

19. The electrically conductive transparent composition as claimed in claim 18, wherein the carbon fiber comprises, in an amount of at least 10 mass %, branched vapor-grown carbon fiber, each fiber filament having a structure in which a central hollow portion extends throughout the filament including a branched portion thereof.

20. The electrically conductive transparent composition as claimed in claim 12 or 13, wherein the vapor grown carbon fiber comprises boron or a combination of boron and nitrogen in an amount of 0.01-3 mass %.

21. The electrically conductive transparent composition as claimed in claim 12 or 13, wherein the vapor grown carbon fiber comprises fluorine in an amount of 0.001-0.05 mass %.

22. The electrically conductive transparent composition as claimed in claim 12 or 13, wherein the vapor grown carbon fiber is coated with 20-70 mass % aluminum oxide.

23. The electrically conductive transparent composition as claimed in claim 12 or 13, which comprises carbon black together with the vapor grown carbon fiber.

24. An electrically conductive transparent material formed from an electrically conductive transparent composition according to claim 12 or 13.

25. The electrically conductive transparent material as claimed in claim 24, which assumes a form of coating, film produced through spraying, film, or sheet.