Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2001-09-27
2003-02-18
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C313S473000, C313S479000
Reexamination Certificate
active
06521346
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to self-emitting color display devices such as cathode ray tubes (CRTs) and is particularly directed to a two-layer coating for the outer surface of the display screen of a self-emitting color display device including an inner antistatic layer and an outer antireflective layer having improved optical characteristics.
BACKGROUND OF THE INVENTION
Self-emitting display devices, such as of the CRT-type, produce a video image by bombardment of phosphor elements disposed on the inner surface of the device's display screen by high energy electrons. In a color display device, the phosphor elements are separated into three groups, with each group emitting one of the primary colors of red, green or blue when impinged upon by the energetic electrons.
Typically disposed on the outer surface of the device's display screen is a two-layer coating in the form of an inner antistatic layer and an outer antireflective layer, with the latter typically containing silica. The inner antistatic layer is electrically conductive for directing the accumulation of an electrostatic charge on the CRT's glass display screen to neutral ground. The build-up of electrostatic charge on the CRT's glass display screen attracts dust to the viewing surface, thus degrading a video image presented thereon. In addition, contact with the display screen by a viewer may cause a mild electric shock which is uncomfortable and may even be dangerous to the viewer. The dielectric nature of the glass display panel contributes to the possibility of the accumulation of a very high electrostatic charge thereon, particularly when the CRT is turned on or off, which charge may remain on the panel for an extended period.
The inner antistatic layer may be rendered electrically conductive by any number of components in its composition. For example, the inner antistatic layer may include a metallic compound to impart the desired antistatic characteristic, where the metallic compound includes at least one element selected from the group consisting of platinum, palladium, tin, and gold. Alternatively, a metal oxide such as tin oxide which is doped with another metal such as antimony may be included in the inner antistatic layer to provide the desired electrical conductivity. Another approach employs a hygroscopic layer such as of silane, water, sulfuric acid and an alcohol mixture for rendering the material conductive.
Another common approach is to provide the inner antistatic layer with electrically conductive carbon black particles to provide electrostatic shielding for the display device as well as grounding of the electrostatic charge. In order to provide a high level of conductivity, it is desirable to highly disperse the carbon black particles throughout the inner antistatic layer. Because the carbon black particles have a relatively high specific surface area, i.e., BET value, a large amount of surface activation agent is required to effectively disperse the carbon black particles throughout the inner antistatic layer. The addition of the surface activation agent, which is typically glycol, to the inner antistatic layer lowers the light refractive index of this solution. This lowering of the light refractive index of the inner antistatic layer relative to that of the outer antireflective layer increases the reflection of light from the display screen resulting in a degradation in the resolution and contrast of a video image presented on the display screen. Increased light reflection also causes eye fatigue in the viewer.
The light refractive index of the inner antistatic layer is typically in the range of 1.5-2.0. The outer antireflective layer containing silica typically has a light refractive index of 1.4-1.5. While it is highly desirable to raise the light refractive index of the inner antistatic layer to reduce light reflection, this is difficult to accomplish because of its lowered light refractive index caused by the addition of the aforementioned surface activation agent.
The present invention addresses the aforementioned limitations of the prior art by providing a two-layer coating for the outer surface of the glass display screen of a self-emitting video display device such as a CRT wherein light reflection from the display screen is reduced by increasing the refractive index of the inner antistatic layer relative to that of the outer antireflective layer.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a two-layer coating for the outer surface of the display screen: of a self-emitting color display device having high electrical conductivity and improved optical characteristics.
It is another object of the present invention to provide an inner antistatic layer in a two-layer coating deposited on the outer surface of the display screen of a CRT having a higher refractive index for reducing light reflection from the display screen.
A further object of the present invention is to provide for the adjustment of the light refractive index of a first inner antistatic layer in a two-layer coating which also includes a second outer antireflective layer applied to the outer surface of a CRT's display screen for improved video image viewing on the display screen.
A still further object of the present invention is to add one or more materials having a high light refractive index to the inner antistatic layer of a two-layer antistatic/antireflective coating on the surface of a video display screen to form a stable solution with the required light refractive index and electrical conductivity.
The present invention contemplates adding a material, or a combination of materials, with a high light refractive index to a solution which is to form the inner antistatic layer of a two-layer antistatic/antireflective coating on the surface of the screen of a video display device such as of the self-emitting type. The added material, or combination of materials, increases the light refractive index of the inner antistatic layer resulting in a reduction in the reflection of light from the display screen and improved presentation of a video image displayed thereon. The inner antistatic layer includes a conductive polymer and highly dispersed carbon black particles to provide the layer with the required electrical conductivity for directing an electrostatic charge on the display screen to neutral ground. To maintain the carbon black particles highly dispersed, a large quantity of a surface activation agent such as glycol is provided in the inner antistatic layer which reduces the light refractive index of the solution. To overcome this problem and provide the inner antistatic layer with the required light refractive index, materials having a high light refractive index such as ZrO
2
, ZnO, ZnS, or TiO
2
are added, either individually or in combination, to the inner antistatic layer to increase its light refractive index while maintaining high electrical conductivity in a stable solution. Increasing the light refractive index of the inner antistatic layer relative to that of the outer antireflective layer reduces light reflection from the video display screen for improved video image resolution and contrast and reduced viewer eye fatigue.
REFERENCES:
patent: 2522531 (1950-09-01), Mochel
patent: 2564677 (1951-08-01), Davis
patent: 2564707 (1951-08-01), Mochel
patent: 2564709 (1951-08-01), Mochel
patent: 2564710 (1951-08-01), Mochel
patent: 2612611 (1952-09-01), Szegho et al.
patent: 2680205 (1954-06-01), Burton
patent: 2734142 (1956-02-01), Barnes
patent: 2808351 (1957-10-01), Colbert et al.
patent: 2833902 (1958-05-01), Gaiser et al.
patent: 2852415 (1958-09-01), Colbert et al.
patent: 2919212 (1959-12-01), Gaiser
patent: 2977412 (1961-03-01), Rhodes et al.
patent: 3093598 (1963-06-01), McMillan et al.
patent: 3252829 (1966-05-01), Romstadt et al.
patent: 3689312 (1972-09-01), Long, III et al.
patent: 3738732 (1973-06-01), Ikenda
patent: 4263335 (1981-04-01), Wagner et al.
patent: 4393095 (1983-07-01), Greenberg
pa
Hu Chun-Min
Wang Kuo-Chu
Blackwell-Rudasill G. A.
Chunghwa Picture Tubes Ltd.
Emrich & -Dithmar
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