Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
1998-07-09
2001-04-10
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S112000
Reexamination Certificate
active
06215240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode-ray tube and a method of manufacturing the same and, more particularly, to a color cathode-ray tube in which filter films are disposed between the inner surface of a face panel and phosphor films, and a method of manufacturing the same.
2. Description of the Prior Art
FIG. 1
is a sectional view of the main part of a color cathode-ray tube. As shown in
FIG. 1
, the outer shape of a color cathode-ray tube
1
consists of a face panel
2
and a funnel
15
. A black matrix film
3
and filter films
7
are formed on the inner surface of the face panel
2
. The filter films
7
are formed at positions where light-transmitting windows
4
are located. Red, blue, and green phosphor films
8
are formed on the inner surfaces of the filter films
7
. The color cathode-ray tube
1
also comprises a shadow mask
9
, an electron gun
16
, and a deflection coil
17
. The shadow mask
9
is arranged at a position slightly remote from the phosphor films
8
to oppose them. The electron gun
16
emits electrons. The deflection coil
17
controls the paths of the electrons.
In recent years, as personal computers spread widely, market requirements for high resolution, high luminance, and the like become more and more intense. In particular, since the graphic display function has become substantial, a further increase in color purity is demanded. As a means for increasing the color purity, a technique for arranging color filter films corresponding to the emission colors of phosphors between the face panel and phosphor films is introduced, as described in Journal of Electrochemical Society, Vol. 28, No. 11 (1981).
FIGS. 2A
to
2
I are views for explaining the conventional process in the manufacture of filter films and phosphor films. The steps of forming a blue filter film and blue phosphor film will be described as an example.
FIG. 2A
is a sectional view showing a state wherein a black matrix film
3
(to be referred to as a BM film hereinafter) and light-transmitting windows
4
are formed on the inner surface of a face panel
2
in advance.
As shown in
FIG. 2B
, a blue filter solution is applied to cover the BM film
3
and light-transmitting windows
4
, to such a degree that the BM film
3
and the face panel
2
sink slightly, and is dried, to form a blue filter layer
7
b
on the entire surface of the face panel
2
.
As shown in
FIG. 2C
, only a required portion, i.e., a desired light-transmitting window
4
, of the blue filter layer
7
b
is exposed with ultraviolet light
10
through a shadow mask
9
.
As shown in
FIG. 2D
, since only the exposed portion is water-insoluble, when development is performed with water, other portions that are not exposed are removed, and a desired blue filter film
7
B is formed in only the exposed light-transmitting window
4
.
Similarly, a green filter film
7
G and a red filter film
7
R are sequentially formed, as shown in FIG.
2
E. In this manner, the desired filter films
7
G,
7
B, and
7
R are formed at predetermined positions on the inner surface of the face panel
2
, i.e., in the light-transmitting windows
4
.
Phosphor films are formed by coating on the corresponding filter films
7
G,
7
B, and
7
R that are formed with the above method. How to form a blue phosphor film
8
B will be described.
As shown in
FIG. 2F
, a blue phosphor slurry is applied to the upper surfaces of the filter films
7
G,
7
B, and
7
R formed on the inner surface of the face panel
2
, and is dried to form a blue phosphor layer
8
b.
As shown in
FIG. 2G
, only a required portion of the blue filter layer
8
b,
i.e., the upper surface portion of the blue filter film
7
B formed in the above step, is exposed with ultraviolet light
10
through the shadow mask
9
.
As shown in
FIG. 2H
, since only the exposed portion is water-insoluble, when development is performed with water, other portions that are not exposed are removed, and only a desired blue phosphor film
8
B that is exposed is formed as it is stacked on the blue filter film
7
B.
Similarly, a green phosphor film
8
G and a red phosphor film
8
R are sequentially formed, as shown in FIG.
2
I. In this manner, the phosphor films
8
B,
8
G, and
8
R are formed at predetermined positions on the inner surface of the face panel
2
, i.e., such that they are stacked on the filter films
7
B,
7
G, and
7
R, respectively.
As described above, the color cathode-ray tube manufacturing method requires two exposing steps, i.e., one in the filter film forming step of forming the filter films
7
B (
7
G,
7
R) and one in the phosphor film forming step of forming the phosphor films
8
B (
8
G,
8
R) by stacking them on the filter films
7
B (
7
G,
7
R). Due to misalignment between the face panel
2
and the shadow mask
9
and the like, a displacement sometimes occurs between the filter films
7
B (
7
G,
7
R) and the phosphor films
8
B (
8
G,
8
R). For example, if the green phosphor films
8
G are exposed to extend onto the adjacent blue filter films
7
B, color mixture occurs to degrade the color purity. Despite that the step of forming the respective filter films and the step of forming the phosphor films are basically identical, these similar steps must be provided as two steps, leading to a very high manufacturing cost.
As a means for solving these problems, for example, Japanese Unexamined Patent Publication No. 6-295683 discloses the following technique. Water-soluble polymers having different cloudy points are used as the base polymers of the filter slurry and the phosphor slurry. A filter layer is formed of the filter slurry having the first cloudy point, and the phosphor layer is formed on it using the phosphor slurry having the second cloudy point. Thereafter, exposure is performed once to eliminate misalignment between filter films and phosphor films.
With this technique, although the entire process is shortened when compared to the conventional manufacturing method, additional steps may be required in accordance with the cloudy point, temperature control must be performed in the process, and factors that largely influence the fraction nondefective may be present.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation of the prior art, and has as its object to provide a color cathode-ray tube in which filter films and phosphor films are stacked at high precision, and a color cathode-ray tube manufacturing method that can shorten the manufacturing process and can improve the fraction nondefective.
In order to achieve the above objects, according to the first aspect of the present invention, there is provided a color cathode-ray tube having a black matrix film having a plurality of light-transmitting windows that are formed on an inner surface of a face panel to have a predetermined positional relationship with each other, filter films formed in the light-transmitting windows to correspond to green, blue, and red, and phosphor films formed by stacking green, blue, and red phosphors on inner surfaces of the filter films, the filter films being made of a photo-tacky resin containing a filter dispersion.
The color cathode-ray tube according to the first aspect described above has auxiliary aspects as follows.
The green, blue, and red phosphors are fixed and stacked due to tackiness of the photo-tacky resin that forms the filter films.
The photo-tacky resin containing the filter dispersion consists of a fine-particle material having wavelength selectivity, and the fine-particle material is a pigment.
The tackiness of the photo-tacky resin that forms the filter films is exhibited upon exposure.
In order to achieve the above objects, according to the second aspect of the present invention, there is provided a method of manufacturing a color cathode-ray tube having a black matrix film having a plurality of light-transmitting windows that are formed on an inner surface of a face panel to have a predetermined positional relationship with each other, filter films formed in th
McGuireWoods LLP
NEC Corporation
Patel Ashok
LandOfFree
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