Antistatic/antireflective coating for video display screen with improved refractivity

• US 6,521,346 B1
• Filed: 09/27/2001
• Issued: 02/18/2003
• Est. Priority Date: 09/27/2001
• Status: Active Grant

• Current Assignee: CPT Technology (Group) Co., Ltd.
• Original Assignee: Chunghwa Picture Tubes Limited
• Inventors: Wang, Kuo-Chu, Hu, Chun-Min
• Primary Examiner(s): Jones, Deborah
• Assistant Examiner(s): BLACKWELL, GWENDOLYN
• Application Number:
  US09/965,309
• Time in Patent Office: 509 Days
• Field of Search: 428/432, 313/479, 313/478, 313/467, 313/473, 348/834
• US Class Current: 428/432
• CPC Class Codes: C03C 17/3411 with at least two coatings of inorganic materials C03C17/36, C03C17/42 take precedence
• CPC Class Codes: C03C 2217/475 Inorganic materials
• CPC Class Codes: C03C 2218/365 Coating different sides of a glass substrate
• CPC Class Codes: H01J 2229/8635 Antistatic shielding
• CPC Class Codes: H01J 2229/882 having particular electrical resistive or conductive properties
• CPC Class Codes: H01J 2229/8913 Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices
• 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: H01J 29/896 Anti-reflection means, e.g. eliminating glare due to ambient light

Abstract

A two-layer coating for the outer surface of a glass display screen of a video display device such as a cathode ray tube (CRT) includes an inner antistatic layer and an outer antireflective layer. The outer antireflective layer contains silica and has a refractive index in the range of 1.4-1.5. The inner layer contains carbon black powder particles which provide high electrical conductivity to dissipate electrostatic charge on the glass display screen. The inner layer further includes a surface activation agent, such as glycol, for dispersing the carbon black particles in the antistatic solution. To increase the refractive index of the inner layer to a value greater than its typical value, which is in the range of 1.5-2.0, for the purpose of reducing light reflection from the glass display screen while maintaining high conductivity, ZrO₂, ZnO, ZnS or TiO₂, or a combination thereof, is added to the inner antistatic layer to provide a stable solution with optically and electrically desirable characteristics.

Claims

1. A multi-layer coating for the outer surface of a display screen of a self-emitting display device, wherein said display screen further includes a phosphor coating on an inner surface thereof, and wherein said phosphor coating is responsive to energetic electrons incident thereon for providing a video image, said coating comprising:

an inner antistatic layer disposed on the outer surface of the display screen and having a first refractive index n₁, wherein said inner antistatic layer includes electrically conductive particles having a high specific surface area and a surface activation agent to disperse said conductive particles in said inner antistatic layer;

an outer antireflective layer disposed on said inner antistatic layer and having a second refractive index n₂, where n₁≧

n₂, and wherein said outer antireflective layer includes silica; and

a high light refractive material added to said inner antistatic layer to increase the refractive index n₁ of said inner antistatic layer and reduce light reflection from the display screen, wherein said high light refractive material is from the group comprising ZrO₂, ZnO and ZnS.

2. The coating of claim 1 wherein said high light refractive material further includes TiO₂.

3. The coating of claim 2 wherein said surface activation agent is glycol.

4. The coating of claim 3 wherein said electrically conductive particles are comprised of carbon black.

5. The coating of claim 4 wherein n₁ is in the range of 1.5-2.0, n₂ is in the range of 1.4-1.5, and ZrO₂, ZnO, ZnS, and TiO₂ each have a respective index of refraction of 1.98, 2.02, 2.37 and 2.7.

6. The coating of claim 1 for covering the display screen of a self-emitting display device such as a field emission display, a plasma discharge panel, a vacuum flourescent screen, a gas discharge screen, or a cathode ray tube.