Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-02-22
2001-11-20
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S414000
Reexamination Certificate
active
06320307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color display tube for high resolution and, more particularly, to a color cathode ray tube with an in-line electron gun.
2. Description of the Related Art
The description will be made first on a conventional color cathode ray tube with reference to FIG.
4
. In this drawing, three electron beams
11
R,
11
G, and
11
B generated by an in-line electron gun
11
are used for red, green and blue fluorescent materials, respectively, and pass through a hole
12
a
of a shadow mask
12
. On the other hand, there are provided stripe-shaped fluorescent materials
13
R,
13
G, and
13
B of red, green and blue on a display screen
13
of a glass bulb or tube (not shown). Accordingly, the central electron beam
11
G allows the green fluorescent material
13
G to shine, whereas outer electron beams
11
R and
11
B allow the red and blue fluorescent materials
13
R and
13
B to shine, respectively.
Referring to
FIG. 5
the electron gun
11
(
FIG. 4
) includes an electrode
14
in the main lens thereof. There are provided three apertures
14
R,
14
G, and
14
B in the main lens of the gun
11
. These apertures
14
R,
14
G and
14
B are designed to be the same in diameter as one another for such reasons as to prevent imbalance of the strengths of electrostatic lenses produced at each electrode and to hold the strength of the inner electrode
14
.
In order to enhance the focus property of the color cathode ray tube, it is required to improve the spherical aberration of the electrostatic lens formed among the electrodes. In general, in order to provide an electrostatic lens small in the spherical aberration, it is effective to enlarge the aperture diameter of the main lens unit.
However, it is impossible for the circular aperture-type electron gun
11
shown in
FIG. 5
to enlarge the diameter of each aperture
14
due to the strength of the inner electrode
14
.
Moreover, although it is required to correct the convergence for focus the three electron beams
11
R,
11
G and
11
B on the screen surface, such correction can be done with the help of the ferrite and/or the magnet or other related materials with respect to the red electron beam
11
R and the blue electron beam
11
B. However, it is impossible to correct the green electron beam
11
G with such means.
Furthermore, in the circular aperture-type electron gun
11
, the central electron gun is inferior, in the electron gun's characteristics, to the outer electron guns. This emanates from the experimental comparison, made at the center of the screen, in terms of their focus property.
In addition to that, the central electron beam corresponds to green, and its electric current is more than those of the outer electron guns, in operation. This leads to further degradation of the focus property.
Furthermore, the brightness characteristic is the one to influence the outward appearance on the screen of the cathode ray tube.
The easiest method to enhance the brightness is to enlarge the areas of the fluorescent materials. However, simply enlarging the areas easily causes occurrence of problems such as a mixture with the color of the adjacent fluorescent material.
Alternatively, enlarging the area of the fluorescent material corresponding to green, which greatly contributes to the brightness, causes an increase of the electric current for red, which violently changes more than usual, based upon the color temperature. In addition, the focus property may degrade in a low color temperature.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an improved color display tube.
It is another object of the present invention to provide a color cathode ray tube with solving the above problems to present a visually attractive-looking screen.
According to an aspect of the present invention, such a color cathode ray tube is provided that among three electron beams generated from an in-line electron gun, a center one is used for a blue color. That is, the center beam is used to irradiate a blue fluorescent material. The both ends of the three beams are used to irradiate respectively red and green fluorescent materials, accordingly.
It is convenient to make the area of the blue fluorescent material smaller than the red and green fluorescent materials.
In the preferred embodiment, the in-line gun has an electrode into which three apertures are provide for the three electron beams, and the center aperture is made smaller in diameter than the remaining apertures.
With the above construction in which a central electron beam tends to degrade in its focus property more than those of the electron beams on both sides, the blue fluorescent material which is lower in sensibility from the view point of the human engineering than a red and a green fluorescent material, corresponds to the central electron beam. Therefore, even though the focus properties of the fluorescent materials on both sides are inferior, this fact does not influence the display on the screen of the color cathode ray tube very much.
Moreover, for the blue fluorescent material, the electric current is lower than those of other color fluorescent materials. Even though the blue fluorescent material corresponds to the central electron beam, the focus property does not degrade very much.
In addition to the aforementioned configuration, the main lens unit aperture hole of the electron beam side gun is larger in diameter than the central gun. Thereby, the spherical aberration is improved, and the focus property is improved accordingly.
Wherein, from the necessity for maintaining the strength of the inner electrode, the diameter of the aperture of the central gun becomes small, conversely. Accordingly, the spherical aberration of the electrostatic lens degrades more than that of the side gun. However, as described above, since the blue is low in sensibility and the electric current ratio is low, the display on the screen of the color cathode ray tube can be maintained against something such as a blur.
Moreover, in addition to the configuration where the arrangement of the array of fluorescent materials are changed in such a manner that the fluorescent material corresponding to the central electron beam is blue, whereas the other fluorescent materials corresponding to the electron beams on both sides are red and green, the areas of fluorescent materials corresponding to the electron beams on both sides are enlarged. Therefore, lower electric current than ever is necessary, and the focus property on both sides is improved.
Furthermore, the green corresponding to the electron beams on both sides influences the intensity. This leads to an improvement of the intensity.
REFERENCES:
patent: 5013963 (1991-05-01), Ikegami et al.
patent: 5424604 (1995-06-01), Hyun
patent: 5682079 (1997-10-01), Kang
patent: 5898260 (1999-04-01), Misono
patent: 93-1483 (1993-01-01), None
patent: 98-28111 (1998-07-01), None
Korean Office Action, dated Dec. 13, 2000, with English language translation of Korean Examiner's comments.
Hopper Todd Reed
McGuireWoods LLP
NEC Corporation
Patel Nimeshkumar D.
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