Shadow mask for color CRT and method for forming same
US5990607A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 14, 1998 |
| Grant date | Nov 23, 1999 |
| Priority date | — |
| Expiry date | Jul 14, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2229/0755
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A shadow mask, or color selection electrode, in a color cathode ray tube (CRT) is in the form of a thin metal foil and includes a large number of apertures through which electron beams are directed onto the phosphorescent coating on the CRT's display screen for forming a video image. The apertured shadow mask is also used with a light source during CRT manufacture to form a large number of spaced phosphor elements in the phosphorescent coating. Ideally, all of the beam passing apertures and phosphor elements are circular in cross-section, but the shadow mask is stretched and maintained under high tension when mounted in the CRT causing some of the apertures, particularly those adjacent its four corners, to also become stretched and assume an oval shape. This is avoided in the present shadow mask by providing the areas in the vicinity of four corners of the shadow mask with oval apertures which are elongated in a direction generally transverse to the mechanical forming direction, or the direction of greatest tension when the mask is stretched and mounted in a color CRT. After installation in a CRT, the oval apertures assume a circular shape because of the greater tension applied alo…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.