Thermal expansion for color CRT

Details Thermal expansion for color CRT Thermal expansion for color CRT

1998-08-10

2000-11-07

Patel, Nimeshkumar D.

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

313402, 313406, H01J 2980

Patent

active

061441481

ABSTRACT:
A holder for maintaining an apertured shadow mask in fixed relation to the display screen of a color cathode ray tube (CRT) includes the combination of a mounting stud attached to an inner portion of the CRT's glass envelope and an apertured resilient metal holder attached to the shadow mask's peripheral frame and adapted to receive the mounting stud in a tight-fitting manner. A plurality of such mounting stud/metal holder combinations securely attach the top, bottom and lateral edges of the shadow mask frame to adjacent inner portions of the CRT's glass envelope adjacent its display screen. Heating of the shadow mask caused by the CRT's electron beams incident thereon gives rise to heating and thermal expansion of the shadow mask metal holders. Thermal expansion of the metal holders causes the shadow mask to rotate about the CRT's central axis resulting in a shift of the shadow mask apertures with respect to video image-producing phosphor deposits on the display screen's inner surface which degrades video image color purity. To prevent misalignment of the shadow mask apertures with the phosphor deposits caused by shadow mask holder thermal expansion, the shadow mask holders are formed from a material having a low coefficient of thermal expansion which maintains the shadow mask and its apertures in a fixed, predetermined location and orientation during CRT operation. The shadow mask holders are preferably comprised of a material having a coefficient of thermal expansion of less than 2.0.times.10.sup.-6 cm/cm/.degree. C. such as, for example, Invar, Neovar or Kovar.

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