Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
1998-10-06
2001-05-22
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S404000, C313S407000
Reexamination Certificate
active
06236150
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on application No. 97-51630 filed in Korean Industrial Property Office on Oct. 8, 1997, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a mask assembly for a cathode ray tube (CRT), and more particularly, to a mask assembly for a CRT for reducing the amount of electron beam impinging on a shadow mask and thereby preventing doming phenomenon of the shadow mask.
(b) Description of the Related Art
Generally, a color CRT displays images by exciting phosphors with electron beams, and includes a screen on which red, green and blue color emitting phosphors are coated, an electron gun for forming three electron beams, a deflection yoke for directing the electron beams to the screen, and a shadow mask to permit each electron beam to strike only the phosphor elements associated with the beam.
The shadow mask is a thin sheet of metal, and includes a large central apertured portion through which the electron beams pass, a solid border portion surrounding the apertured portion, and a peripheral skirt portion angled from the border portions of the mask and directed to the electron gun, that is directed to opposite direction of a panel of the CRT. The apertures of the shadow mask are formed so as to correspond to the red, green and blue phosphors.
In the conventional shadow mask, approximately 20% of electron beam passes through the apertures formed on the shadow mask, and the remaining 80% of electron beam strikes the shadow mask to generate heat and raise the temperature of the shadow mask. Since the skirt portion of the shadow mask is firmly fixed to a frame of the CRT, the shadow mask is domed when it is heat-expanded. When the shadow mask is domed, the positions of apertures on the shadow mask are moved, and each electron beam can not strike the phosphor elements associated with the beam, but strikes the shadow mask or the phosphor of undesired colors. This results in the deterioration of the color purity of the CRT. The deterioration of the color purity due to the doming of the shadow mask and mis-landing of electron on the screen is generally called as “doming phenomenon”.
To prevent or reduce the “doming phenomenon”, a shadow mask made of Invar (an iron-nickel alloy) or a shadow mask on which powders of Invar are coated are developed. Since the Invar has very low heat expansion coefficient, the doming phenomenon is more or less reduced by using the Invar as the material of the shadow mask.
However, even though a material of low heat expansion coefficient is used to form shadow mask, the doming phenomenon is not fully reduced. Furthermore, there are disadvantages that the Invar is expensive and separate processing steps and various chemical compounds are required to coat the powder of the Invar on the shadow mask.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a mask assembly for a CRT which substantially obviates one or more of the problems due to the limitations and disadvantages of the related art. An object of the present invention is to provide a mask assembly for a CRT which can dramatically reduce the “doming phenomenon” and can be manufactured with low cost.
To accomplish these and other advantages, it is provided a mask assembly for a CRT which includes a shadow mask for permitting electron beam to strike the phosphor elements associated with the beam, and a frame for supporting the shadow mask. The mask assembly also includes an electron beam interceptor which selectively passes electron beam and is mounted on the frame at the opposite side of the shadow mask.
The electron beam interceptor is mounted between the shadow mask and an electron gun, and preferably includes a blocking mask on which a plurality of apertures are formed at the positions which correspond to the apertures of the shadow mask, and one or more supporters whose ends are adhered at the frame and the blocking mask, respectively, to support the mask in a funnel of the CRT.
REFERENCES:
patent: 4626737 (1986-12-01), Takenaka et al.
patent: 4652792 (1987-03-01), Tokita et al.
patent: 5180322 (1993-01-01), Yamamoto et al.
patent: 5200025 (1993-04-01), Toei et al.
patent: 5814928 (1998-09-01), Matsudate et al.
Christie Parker & Hale LLP
Guharay Karabi
Patel Nimeshkumar D.
Samsung Display Devices Co., Ltd
LandOfFree
Mask assembly for cathode ray tube having an electron beam... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mask assembly for cathode ray tube having an electron beam..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mask assembly for cathode ray tube having an electron beam... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452025