Polymeric antistatic coating for cathode ray tubes

• US 5,773,150 A
• Filed: 11/17/1995
• Issued: 06/30/1998
• Est. Priority Date: 11/17/1995
• Status: Expired due to Fees

• Current Assignee: Chunghwa Picture Tubes Limited
• Original Assignee: Chunghwa Picture Tubes Limited
• Inventors: Hu, Chun-Min, Tong, Hua-Sou
• Primary Examiner(s): Thibodeau, Paul J.
• Assistant Examiner(s): TARAZANO, DONALD LAWRENCE
• Application Number:
  US08/560,478
• Time in Patent Office: 956 Days
• Field of Search: 427/372.2, 427/407.2, 427/387, 427/389.7, 427/314, 427/240, 427/441, 427/64, 427/68, 427/72, 427/165, 427/167, 313/479, 313/478, 313/466, 313/474, 428/429, 428/446, 428/447, 428/332, 428/411.1, 428/922, 428/522
• US Class Current: 428/429
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: H01B 1/127 comprising five-membered aromatic rings in the main chain, e.g. polypyrroles, polythiophenes
• CPC Class Codes: H01B 1/128 comprising six-membered aromatic rings in the main chain, e.g. polyanilines, polyphenylenes
• CPC Class Codes: H01J 29/868 Screens covering the input or output face of the vessel, e.g. transparent anti-static coatings, X-ray absorbing layers
• CPC Class Codes: Y10T 428/31612 As silicone, silane or siloxane
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

A high molecular weight, i.e., molecular weight of 90,000-750,000, conductive polymer soluble in both water and alcohol is mixed with a solution of water, alcohol, tetraethoxysilane (TES), and nitric acid (HNO₃) to provide an antistatic coating for a glass display panel of a cathode ray tube (CRT) for grounding static charge on the panel. Conductive polymers such as of polyaniline mixed with either polystyrene sulfonic acid or polyacrylic acid in a molecular ratio of 1:1 or 3,4 polyethylenedioxythiophene added to polystyrenesulphonate in a molecular ratio of 1:1 form a conductive complex which when mixed with a solution of water, alcohol, TES and HNO₃ provides a coating solution with a resistivity in the range of 10^7-109 ohm/cm² on the outer surface of the CRT display panel.

Claims

1. A video display apparatus comprising:

a display panel having an outer and an inner surface, wherein said outer surface is in facing relation to a viewer of the video display apparatus; and

an antistatic coating layer applied to the outer surface of said display panel by either spin or spray coating, said coating layer comprised of a solution of water, alcohol, tetraethoxysilane, nitric acid and an electrically conductive polymer soluble in water and alcohol dissolved in the solution, wherein said conductive polymer and comprises a mixture of polyaniline with either polvstvrene sulfonic acid or polyacrylic acid in a molecular ratio of 1;

1.

2. The video display apparatus of claim 1 wherein said conductive polymer forms 0.2-6 wt. % of said antistatic coating layer.

3. The video display apparatus of claim 2 wherein said solution is comprised of water, alcohol, 2-12 wt. % tetraethoxysilane, and 1.0 wt. % HNO₃.

4. The video display apparatus of claim 1 wherein said conductive polymer is comprised of a mixture of 3,4 polyethylenedioxythiophene and polystyrenesulphonate in a molecular ratio of 1:

1.

5. An antistatic coating applied to an outer surface of a glass display panel of a video display device by either spin or spray coating, wherein said outer surface is in facing relation to a viewer of the video display device, said antistatic coating comprising:

a solution of water, alcohol, tetraethoxysilane and nitric acid; and

an electrically conductive polymer soluble in water and alcohol dissolved in said solution, said conductive polymer comprises a mixture of polyaniline with either polystyrene sulfonic acid or polyacrylic acid in a molecular ratio of 1;

1.

6. The antistatic coating of claim 5 wherein said solution is comprised of water, alcohol, 2-12 wt. % tetraethoxysilane and 1.0 wt. % HNO₃.

7. The antistatic coating of claim 6 wherein said conductive polymer is 0.2-6 wt. % of said solution.

8. The antistatic coating of claim 5 wherein said conductive polymer is comprised of a mixture of 3,4 polyethylenedioxythiophene and polystyrenesulphonate in a molecular ratio of 1:

1.

9. A method for providing an antistatic coating on an outer surface of a glass video display panel, wherein said outer surface is in facing relation to a viewer of the video display panel, said method comprising the steps of:

mixing polystyrene sulfonic acid or polyacrylic acid with polyaniline to form an electrically conductive complex, wherein said polystyrene sulfonic acid or said polyacrylic acid is mixed with said polyaniline in a molecular ratio of 1;

1;

adding said conductive complex to a mixture of water, alcohol, tetraethoxysilane and HNO₃ to form an antistatic coating; and

applying the antistatic coating to the outer surface of the glass video display panel in the form of a layer by either spin or spray coating.

10. The method of claim 9 further comprising the step of preheating the video display panel to a temperature on the order of 45°

C. prior to the step of applying the antistatic coating to the video display panel.

11. The method of claim 10 further comprising the step of baking the video display panel with said antistatic coating on the outer surface thereof at a temperature in the range of 110°

-180°

C. for 15-45 minutes.

12. The method of claim 9 wherein said conductive complex is added to said mixture so as to form 0.2-6 wt. % of said mixture.

13. The method of claim 12 wherein said mixture is comprised of water, alcohol, 2-12 wt. % tetraethoxysilane, and 1.0 wt. % HNO₃.

14. The method of claim 9 wherein the step of applying the antistatic coating includes either spin or spray coating the antistatic coating on the outer surface of the glass display panel.