Cathode ray tube for multimedia

Details Cathode ray tube for multimedia Cathode ray tube for multimedia

2000-10-17

2002-01-29

Day, Michael H. (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

Reexamination Certificate

active

06342757

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a cathode ray tube (CRT) for multimedia and a method of making the same and, more particularly, to a method of making a multimedia CRT which simultaneously produces high resolution and high brightness for use in both computers requiring high-resolution and televisions or videos requiring high-brightness.
(b) Description of the Related Art
Generally, in the CRT, the electron beam emitted from the electron gun passes through the beam-guide apertures of the shadow mask having a color selection function while it is deflected by the deflection yoke. Then it excites the phosphors coated on the panel screen to produce the picture image.
A plurality of dot, slit or stripe-shaped apertures for guiding the electron beam are formed on the shadow mask, the shadow mask having a curvature ratio identical with that of the inside of the panel.
The stripe matrix type shadow mask, having a high beam-permeability, is used in the CRT for televisions or videos requiring high-brightness (collectively referred to hereinafter as “public CRT”) while the dot matrix type shadow mask, having a fine-pitch, is used in the CRT for computers or data processors requiring high-resolution (collectively referred to hereinafter as “industrial CRT”). That is to say, the public CRT requires high-brightness to display clear pictures on the screen which are capable of being viewed from a long distance. On the other hand, the industrial CRT requires high-resolution to display distinct letters or symbols on the screen.
The CRT using a stripe matrix type shadow mask has a beam-permeability higher than that using a dot matrix type shadow mask. Conversely, the CRT using a dot matrix type shadow mask with a fine pitch (the distance between neighboring beam-guide apertures) has a resolution higher than that using the stripe matrix type shadow mask.
The permeability R of the electron beam is mathematically given by the following formula:
R=((area of beam-guide aperture×number of beam-guide aperture)/whole area of shadow mask)×100%,  (1)
where the permeability of the electron beam may be calculated by the permeability per unit area or the area of the beam-guide aperture per pitch area (horizontal pitch×vertical pitch).
Therefore, Eq. 1 may be rewritten by
R=(area of beam-guide aperture/(horizontal pitch×vertical pitch))×100%.  (2)
Using Eqs. 1 or 2, it can be shown that the permeability R of the CRT using the dot matrix type shadow mask is about 17 to 19% while the permeability of the CRT using the stripe matrix type shadow mask is about 20 to 22%.
For example, the permeability of a 15-inch industrial CRT using a dot matrix type shadow mask can be given by
R=((2×&pgr;×0.06
2
)/(0.27×0.4677))×100=17.9%.  (3)
The permeability R of a 17-inch industrial CRT using a dot matrix type shadow mask is given by
R=((2×&pgr;×0.06
2
)/(0.26×0.4677))×100=18.6%.  (4)
The permeability R of a 25-inch public CRT using a stripe matrix type shadow mask is given by
R=((0.65×0.18)/(0.76×0.73))×100=21.08%.  (5)
The permeability of a 24-inch wide public CRT using a stripe matrix type shadow mask is given by
R=((0.6×0.175)/(0.76×0.73))×100=21.17%.  (6)
As described above, in the prior art, the CRT using a stripe matrix type shadow mask has a resolution unsuitable for industrial usage while the CRT using a dot matrix shadow mask has a brightness unsuitable for public usage. Therefore, one CRT cannot be used for both industrial and public purposes.
However, as multimedia computer systems, incorporating televisions, videos and computers to display combinations of moving and still pictures, and words, or television systems having an Internet connection function, became more developed and come into wide use, the need for a CRT having both high-brightness and high-resolution increases.
SUMMARY OF THE INVENTION
Accordingly, an embodiment of the present invention is directed to a CRT for multimedia which substantially obviates one or more of the problems due to the limitations and disadvantages of the related art.
An object of an embodiment of the present invention is to provide a method of making a multimedia CRT for simultaneously producing high brightness and high resolution.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To accomplish these and other advantages, the multimedia CRT includes a shadow mask having a plurality of beam-guide apertures. Each of the beam-guide apertures has a stripe shape, and the ratio of the horizontal length of the effective screen to the horizontal pitch of the beam-guide apertures in the center of the shadow mask is in the range of 1:8.81×10
−4
to 1:1.23×10
−3
.
Furthermore, the ratio of the horizontal pitch of the beam-guide apertures in the center of the shadow mask to the thickness of the shadow mask is in the range of 1:0.25 to 1:0.56.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 4859901 (1989-08-01), Thompson-Russell
patent: 5928047 (1999-07-01), Ishibashi et al.

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