Carbon nanotube assembly and electrically conductive film

1. An aggregate of carbon nanotubes, wherein, at least 50 of 100 carbon nanotubes randomly selected from the aggregate of carbon nanotubes are double-walled carbon nanotubes when observed by a transmission microscope, a height ratio (G/D ratio) of G band to D band b Raman spectroscopic analysis of wavelength 532 nm of the aggregate of carbon nanotubes is 30 or more, and when a mixture of 10 mg of the aggregate of carbon nanotubes, 30 mg of sodium polystyrene sulfonate and 10 mL of water is subjected to ultrasonic homogenizer treatment, subsequently subjected to centrifugal treatment at 20000 G, and then 9 mL of supernatant is sampled, the content of the aggregate of carbon nanotubes in the supernatant is 0.6 mg/mL or more.

2. The aggregate of carbon nanotubes of claim 1 , wherein the aggregate of carbon nanotubes is used as a dispersion liquid, light transmittance of a film obtained by coating the dispersion liquid on a substrate is 85% or more, and surface resistance of the film is less than 1×10 5 Ω/□.

3. The aggregate of carbon nanotubes of claim 1 , wherein at least 70 of 100 carbon nanotubes randomly selected from the aggregate of carbon nanotubes are double-walled carbon nanotubes when observed by a transmission microscope.

4. A dispersion wherein the aggregate of carbon nanotubes of claim 1 is dispersed in a dispersion media.

5. The dispersion of an aggregate of carbon nanotubes of claim 4 , further containing a surfactant or a polymer.

6. The dispersion of an aggregate of carbon nanotubes of claim 4 , wherein the concentration of aggregate of carbon nanotubes is from 0.01 weight % to 20 weight %.

7. A conductive film wherein an aggregate of carbon nanotubes of claim 1 is coated on a substrate, and the light transmittance is 85% or more and the surface resistance is less than 1×10 5 Ω/□.

8. The conductive film of claim 7 , wherein transmittance of the conductive film/light transmittance of a transparent substrate is >0.85.

9. The conductive film of claim 7 , wherein the surface resistance is less than 1×10 4 Ω/□.

10. A method for producing the aggregate of carbon nanotubes of claim 1 , wherein a powdery catalyst supporting iron on magnesia is disposed in a vertical reactor over the whole area in a horizontal cross section direction of the reactor, methane is flowed in a vertical direction inside the vertical reactor, methane and said catalyst are contacted at 500 to 1200° C. to synthesize an aggregate of carbon nanotubes, thereafter, oxidation treatment is conducted.

11. The method for producing the aggregate of carbon nanotubes of claim 10 , wherein said oxidation treatment is to conduct burning treatment in a range of the combustion peak temperature of aggregate of carbon nanotubes±50° C.

12. The method for producing the aggregate of carbon nanotubes of claim 10 , wherein said oxidation treatment is to conduct burning treatment under atmosphere in a range of the combustion peak temperature of aggregate of carbon nanotubes±15° C.

13. The method for producing the aggregate of carbon nanotubes of claim 10 , wherein said oxidation treatment is to contact with oxygen intermittently.

14. The method for producing the aggregate of carbon nanotubes of claim 10 , wherein said oxidation treatment is to treat the aggregate of carbon nanotubes produced with hydrogen peroxide.

15. The method for producing the aggregate of carbon nanotubes of claim 10 , wherein said oxidation treatment is to treat the aggregate of carbon nanotubes produced with a mixed acid.

16. The method for producing the aggregate of carbon nanotubes of claim 15 , further treating with a basic compound after treating with a mixed acid.

17. The method for producing the aggregate of carbon nanotubes of claim 16 , wherein said basic compound is an organic amine.

18. A field emission material using the aggregate of carbon nanotubes of claim 1 .