Method of forming a uniform carbon nanotube electron-emission layer in a field emission display

• US 7,378,074 B2
• Filed: 01/31/2007
• Issued: 05/27/2008
• Est. Priority Date: 07/06/2004
• Status: Expired due to Fees

• Current Assignee: Teco Nanotech Co., Ltd. (TECO Electric & Machinery Pte Ltd.)
• Original Assignee: Teco Nanotech Co., Ltd. (TECO Electric & Machinery Pte Ltd.)
• Inventors: Cheng, Kuei-Wen, Li, Yu-An, Tsai, Jin-Lung, Hsaio, Chun-Yen
• Primary Examiner(s): Kopec; Mark
• Assistant Examiner(s): Nguyen; Tri V
• Application Number:
  US11/669,300
• Publication Number:
  US 20070295940A1
• Time in Patent Office: 482 Days
• Field of Search: 252/500, 252/502, 313/495, 423/447.1, 524/496, 427/81, 106/472, 977/742, 977/832, 977/835
• US Class Current: 423/447.1
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 31/123 Flat display tubes
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/832 having specified property, e.g. lattice-constant, thermal expansion coefficient
• CPC Class Codes: Y10S 977/835 Chemical or nuclear reactivity/stability of composition or compound forming nanomaterial

Abstract

A carbon nanotube suspension uses water as the basic solvent added with dispersant, stabilizer, coalescing aid, adhesion promoter, and a carbon nanotube. The basic solvent and the above solutes form a low viscosity solvent with carbon nanotube suspending therein. Therefore, the carbon nanotube suspension is formed to serve as a source material of the electron emission source of a field-emission display. That is, the carbon nanotube can be coated on a surface for forming the carbon nanotube electron-emission layer.

Claims

1. A method of forming a carbon nanotube electron-emission layer in a field emission display, comprising the sequence of steps as follows:

a) providing a carbon nanotube suspension by adding water as a solvent, uniformly adding 5% to 20% by weight of carbon nanotube which is shorter than 1 micron, 1% to 10% by weight of dispersant for motivating the carbon nanotube dispersing in the suspension, and 1% to 10% by weight of antifoam in the solvent for eliminating foams or bubbles caused by stirring;

b) vibrating and stirring the mixture of water, dispersant, antifoam and carbon nanotube for a predetermined period of time;

c) adding stabilizer in the mixture for prolonging storage life of the suspension and the carbon nanotube having sufficient time to disperse and stirring the mixture;

d) adding 5% to 20% by weight of coalescing aid for the suspension easily being attached to a glass substrate of a field-emission display, 1% to 5% by weight of adhesion promoter for increasing adhesion of the suspension so as to control a film thickness formed on the glass substrate and stirring the mixture;

e) sieving the mixture by a mesh to form a low-viscosity carbon nanotube suspension as low as 24 cps (centipoises), wherein a proportion of solid component is about 14% by weight, wherein the dispersant performs chemical dispersion such that the carbon nanotube in the suspension is not agglomerate, and the suspension is easily coated into a uniform form to be used for forming a uniform electron-emission layer in the field-emission display; and

f) performing a vacuum sintering process, in which the carbon nanotube of the suspension is directly attached to a cathode substrate to form the electron emission layer without requiring an adhesive additive of glass powder to prevent a deposit density of the carbon nanotube in the suspension from being diluted by addition of the adhesive additive.

2. The method of claim 1, wherein the dispersant includes ethyl hydroxide or organic methyl eikonogen.

3. The method of claim 1, wherein the antifoam includes polypropylene glycol (PPG).

4. The method of claim 1, wherein the coalescing aid includes one or more than one of aluminum sodium sulfate, silane coupling agent, alkyd resin and tetra-ethyl-ortho-silicate (TEOS).

5. The method of claim 1, wherein the adhesion promoter includes PVA (polyvinyl alcohol), PVP (polyvinyl pyrrolidone), methyl cellulose, ethyl cellulose, sodium polyacrylate or ammonium polyacrylate.

6. The method of claim 1, wherein the stabilizer includes sodium hydroxide, potassium hydroxide or ammonia.

7. The method of claim 1, wherein the vibration and stirring process includes an ultrasonic vibration and stirring process.

8. The method of claim 1, wherein a 500 mesh is used for sieving the mixture.