Method of manufacturing thin film, substrate having thin film, electron emission material, method of manufacturing electron emission material, and electron emission device

1. A substrate having a thin film obtained by:

mixing carbon nanofibers into an elastomer including an unsaturated bond or a group having affinity to the carbon nanofibers, and dispersing the carbon nanofibers by applying a shear force to obtain a carbon fiber composite material;

mixing the carbon fiber composite material and a solvent to obtain a coating liquid; and

applying the coating liquid to a substrate to form the thin film, the thin film in an uncrosslinked form having a first spin-spin relaxation time (T 2 n ) measured at 110° C. of 100 to 3,000 μsec, a second spin-spin relaxation time (T 2 nn ) measured at 110° C. of either 0 μsec or 1,000 to 10,000 μsec, a fraction (fn) of components having the first spin-spin relaxation time of 0.95 or more.

2. The substrate as defined in claim 1 , wherein the thin film has a g-value of a signal of an unpaired electron f carbon measured at 4,5° K by using an electron spin resonance spectrometer of 2.000 or more and less than 2.002.

3. The substrate as defined in claim 2 , wherein the thin film has a line width of a signal of an unpaired electron of carbon measured at 4.5° K by using an electron spin resonance spectrometer of 300 μT or more.

4. The substrate as defined in claim 1 , wherein the elastomer has a molecular weight of 5,000 to 5,000,000.

5. The substrate as defined in claim 1 , wherein at least one of a main chain, a side chain, and a terminal chain of the elastomer includes at least one of a double bond, a triple bond, an α-hydrogen, a carbonyl group, a carboxyl group, a hydroxyl group, an amino group, a nitrile group, a ketone group, an amide group, an epoxy group, an ester group, a vinyl group, a halogen group, a urethane group, a biuret group, an allophanate group, and a urea group.

6. The substrate as defined in claim 1 , wherein a network component of the elastomer in an uncrosslinked form has a spin-spin relaxation time (T 2 n ) measured at 30° C. by a Hahn-echo method using a pulsed nuclear magnetic resonance (NMR) technique of 100 to 3,000 μsec.

7. The substrate as defined in claim 1 , wherein a network component of the elastomer in an crosslinked form has a spin-spin relaxation time (T 2 n ) measured at 30° C. by a Hahn-echo method using a pulsed nuclear magnetic resonance (NMR) technique of 100 to 2,000 μsec.

8. The substrate as defined in claim 1 , wherein the carbon nanofibers have an average diameter of 0.5 to 500 nm.

9. The substrate as defined in claim 1 , wherein obtaining the carbon fiber composite material includes tight milling a mixture of the carbon nanofibers and the elastomer by using an open-roll method with a roll interval of 0.5 mm or less.

10. The substrate as defined in claim 9 , wherein two rolls used in the open-roll method have a surface velocity ratio of 1.05 to 3.00.

11. The substrate as defined in claim 1 , wherein obtaining the carbon fiber composite material is performed by an internal mixing method.

12. The substrate as defined in claim 1 , wherein obtaining the carbon fiber composite material is performed by a multi-screw extrusion kneading method.

13. The substrate as defined in claim 1 , wherein obtaining the carbon fiber composite material is performed at 0 to 50° C.

14. The substrate as defined in claim 1 , wherein forming the thin film is performed by a method selected from a spin coating method, a dipping method, a screen printing method, a spraying method, and an inkjet method.

15. An electron emission material comprising a thin film obtained by:

mixing carbon nanofibers into an elastomer including an unsaturated bond or a group having affinity to the carbon nanofibers, and dispersing the carbon nanofibers by applying a shear force to obtain a carbon fiber composite material;

mixing the carbon fiber composite material and a solvent to obtain a coating liquid; and

applying the coating liquid to a substrate to form the thin film, the thin film in an uncrosslinked form having a first spin-spin relaxation time (T 2 n ) measured at 110° C. of 100 to 3,000 μsec, a second spin-spin relaxation time (T 2 nn ) measured at 110° C. of either 0 μsec or 1,000 to 10,000 μsec, a fraction (fn) of components having the first spin-spin relaxation time of 0.95 or more.

16. An electron emission material comprising a carbon fiber composite material including an elastomer and carbon nanofibers dispersed in the elastomer, the carbon fiber composite material in an uncrosslinked form having a first spin-spin relaxation time (T 2 n ) measured at 110° C. of 100 to 3,0001 μsec, a second spin-spin relaxation time (T 2 nn ) measured at 110° C. of either 0 μsec or 1,000 to 10,000 μsec, a fraction (fn) of components having the first spin-spin relaxation time of 0.95 or more.

17. An electron emission device comprising:

a cathode including the electron emission material as defined in claim 15 ; and

an anode disposed at a specific interval from the cathode,

wherein the device is configured to emit electrons from the electron emission material when voltage is applied between the anode and the cathode.

18. An electron emission device comprising:

a cathode including the electron emission material as defined in claim 16 ; and

an anode disposed at a specific interval from the cathode,

wherein the device is configured to emit electrons from the electron emission material when voltage is applied between the anode and the cathode.