Coating processes – Electrical product produced – Fluorescent or phosphorescent base coating
Patent
1997-10-02
2000-05-16
Parker, Fred J.
Coating processes
Electrical product produced
Fluorescent or phosphorescent base coating
427282, 427356, 10628719, B05D 132, C09K 300
Patent
active
060634340
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a paste composition for screen printing a cathode ray tube (CRT) shadow mask and a screen printing method using the same, and more particularly, to a paste composition for screen printing a CRT shadow mask, which coats the surface of the shadow mask to suppress a doming phenomenon, and a screen printing method using the same.
BACKGROUND OF THE INVENTION
Generally, as shown in FIG. 1, a CRT includes a panel 10 having a fluorescent layer 2 on the inner side thereof, a shadow mask frame assembly 4 fixed to the inner side of the panel 10, being separated from the fluorescent layer 2 by a predetermined distance, an electron gun 7 and a deflection yoke 5, installed at a neck portion 6 and a cone portion 8, respectively. Here, the shadow mask frame assembly 4 installed in the panel 10, as shown in FIG. 2, includes a shadow mask 3 having a hole portion 3a with a plurality of electron beam passing holes H and a concave skirt portion 3b extending from the edge of the hole portion 3a, and a frame 9 coupled with the skirt portion 3b for supporting the shadow mask 3. Also, the shadow mask frame assembly 4 is coupled with a spring (not shown) fixed on the side of the frame 9 and a stud pin (not shown) fixed on the inner side of the panel, thereby separating the shadow mask 3 from the fluorescent layer 2 by a predetermined distance.
According to the CRT having the above structure, after the electron beam emitted from the electron gun 7 is selectively deflected by the deflection yoke 5 according to the scanning position of the electron beam on the fluorescent layer 2, the electron beam passes through the electron beam passing holes H of the shadow mask 3 supported by the frame 9 and reaches the fluorescent layer, thereby forming an image. Here, only 15.about.30% of the electrons pass through the electron beam passing holes H of the shadow mask. The remaining electrons which could not pass through the electron beam passing holes H collide with the hole portion 3a of the shadow mask 3, so that the shadow mask 3 and the frame 9 supporting the shadow mask 3 are heated, which causes a doming phenomenon of the shadow mask 3.
Due to the doming phenomenon of the shadow mask 3, the location of the electron beam passing holes H in the hole portion 3a of the shadow mask 3 is changed, so that the electron beam emitted from the electron gun 7 is not correctly incident on a fluorescent point of the florescent layer 2.
To solve this problem, according to a conventional method, the interval between the fluorescent layer 2 and the shadow mask 3 is controlled by moving the shadow mask 3.
However, by such a method, the doming phenomenon is suppressed only when the shadow mask 3 is completely domed through a thermal expansion thereof. Thus, decreased resolution due to an initial doming phenomenon cannot be prevented.
In order to prevent the doming phenomenon, a shadow mask made of invar (invariable steel) is disclosed in U.S. Pat. Nos. 4,665,338 and 4,420,366. The conventional shadow mask made of invar can resist the thermal expansion. However, the use of invar has disadvantages in cost and processing.
As another method for reducing the thermal expansion ratio of the shadow mask, depositing a material having a low thermal expansion ratio, such as lead borate, on the surface of the shadow mask is known.
As still another method for preventing the doming phenomenon, depositing an insulating material on the surface of the shadow mask is widely known. This method prevents the transfer of heat generated by the electron beam to the shadow mask, wherein ceramic is mainly used as the insulating material.
As still yet another method, a material having a high thermal radiating coefficient is applied to the surface of the shadow mask or the shadow mask is darkened, to increase the thermal radiating ratio. Also, depositing an aqueous suspension including an electron reflection material on the surface of the shadow mask has been disclosed by Phillips.
Generally, the thermal insulating material, thermal
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Han Dong-hee
Kim Jae-Myung
Rho Hwan-Chul
Parker Fred J.
Samsung Display Devices Co. Ltd.
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