Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
1999-03-01
2002-03-19
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S47700R, C313S478000
Reexamination Certificate
active
06359380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode ray tube, in particular, to that having anti-reflective and antistatic properties and capable of realizing high-contrast image display.
2. Description of the Related Art
Color cathode ray tubes to be used as color TV picture tubes or monitor tubes for information appliances and others have a vacuum vessel that comprises a panel, a neck for housing an electron gun therein, and a funnel for connecting the panel and the neck, in which the inner surface of the panel is coated with a phosphor layer in different colors to give a display screen, and plural (generally, three) electron beams as emitted by the electron gun housed in the neck are modulated according to image signals and impinge on the individual phosphors of different colors (generally, three colors) that constitute the phosphor layer to reproduce images.
FIG. 6
is a schematic sectional view showing an outline of the structure of a shadow mask-type color cathode ray tube, which is one example of color cathode ray tubes of that type. In
FIG. 6
, the reference numeral
1
indicates a panel,
2
indicates a neck,
3
indicates a funnel,
4
indicates a phosphor layer,
5
indicates a shadow mask,
6
indicates a mask frame,
7
indicates a shadow mask support mechanism,
8
indicates a support pin,
9
indicates a magnetic shield,
10
indicates an anode button,
11
indicates an internal electric conductive coating,
12
indicates a deflector,
13
indicates an electron gun, and
14
indicates three electron beams (red, green, blue).
In the color cathode ray tube of
FIG. 6
, the panel
1
to form a screen, the neck
2
for housing an electron gun therein, and the funnel
3
to connect the panel and the neck constitute a vacuum vessel. The inner surface of the vacuum vessel is coated with the internal electric conductive coating
11
via which the high cathode voltage as applied to the anode button
5
is transmitted to the inner surface of the screen and to the electron gun. The shadow mask
5
is welded to the mask frame
6
, and is suspended between the support pins
8
that are embedded in the inner wall of the skirt portion of the panel
1
, via the shadow mask support mechanism
7
therebetween. This is kept opposed to the phosphor layer
4
as formed on the inner surface of the panel
1
, while being spaced from the phosphor layer
4
at a predetermined interval therebetween. The magnetic shield
9
is to shield the electron beams
14
from the external magnetic field of, for example, terrestrial magnetism, and this is kept welded to the mask frame
6
.
The deflector
12
is mounted on the funnel in the position adjacent to the neck, by which are formed a horizontal magnetic field and a vertical magnetic field around the flow of the electron beams being emitted by the electron gun. In that condition, three electron beams as emitted by the electron gun
13
are deflected in two directions of a horizontal direction and a vertical direction, thereby to scan the phosphor layer
4
in the two-dimensional direction.
The cathode ray tube of that type is provided with an anti-reflective and antistatic film (film for surface treatment, hereinafter referred to as “surface film”) which is for preventing the ambient light that enters the screen of the panel from reflecting to lower the contrast of the display image formed, and for preventing the panel from being electrostatically charged by the static electricity to be caused by the electron beam scanning.
FIG. 7
is to show one example of the anti-reflective structure for ambient light in the color cathode ray tube illustrated above.
FIG. 7
is a schematic sectional view showing the portion A of
FIG. 6
on an enlarged scale. In
FIG. 7
, the reference numeral
42
indicates a black matrix for partitioning the phosphor layer into plural color phosphors
43
, thereby preventing color mixing so as to improve the contrast of the display image formed;
43
indicates three phosphors of red, green and blue;
44
indicates a metal back for generating a screen potential;
51
indicates an electron beam passing opening; R, G and B indicate electron beams of red, green and blue, respectively;
20
indicates an anti-reflective and antistatic film;
23
indicates the light emitted by the phosphor;
24
indicates ambient light; and
25
and
26
indicate reflected light from the ambient light
24
. The other reference numerals that are the same as those in
FIG. 6
correspond to those in FIG.
6
.
As in
FIG. 7
, three electron beams R, G and B emitted by the electron gun are selected in color, while passing through the electron beam passing openings
51
of the shadow mask
5
, and impinge on the individual phosphors
43
. With the electron beams impinging thereon, the phosphors
43
are excited and emit light, and the emitted light runs outside through the panel
1
(toward the viewer looking at the display image). On the outer surface of the panel
1
, formed is the anti-reflective and antistatic film
20
. The anti-reflective and antistatic film
20
is composed of two layers, of which the first layer
20
a
is of a thin electric conductive film with high refractivity (having a refractive index of about 2), and the second layer
20
b
is of a thin, irregular reflective film having a lower refractive index (1.47) than the layer
20
a.
Of the ambient light
24
to enter the panel
1
, the light
25
having penetrated into the anti-reflective and antistatic film
20
is absorbed by or interfered with the film
20
, whereby its energy is attenuated, resulting in that the intensity of harmful reflected light that may degrade the display image formed could be lowered. In addition, the ambient light
24
reflects irregularly on the outer surface of the panel to give irregularly-reflected light
26
, whereby the harmful reflection that may degrade the display image is retarded. The first layer
20
a
of an electric conductive film is connected with the earth outside the effective display region. The static electricity generated on the outer surface of the panel
1
flows to the earth via the first layer
20
a
, whereby the screen is prevented from being electrostatically charged.
In general, the anti-reflective and antistatic film
20
of that type is formed on the outer surface of the panel according to a so-called sol-gel method.
Concretely, the film
20
may be formed according to any of the following methods:
(1) A mixture composition capable of forming a layer with high refractivity, which is prepared by dispersing fine grains (having a grain size of at most tens nm) of an electric conductive oxide (e.g., ATO (antimony-doped tin oxide) or ITO (tin-doped indium oxide)) in an alcoholic solution, is applied onto glass for the panel
1
through so-called spin-coating to form a lower layer of an even film having a uniform thickness of from about 60 to about 100 nm, and a hydrolytic solution of a silicon alkoxide compound is applied thereover through spin-coating or spray-coating to form an upper layer of an even film having a uniform thickness of from about 80 nm to about 130 nm, thereby completing the formation of a two-layered, anti-reflective and antistatic film of those lower and upper layers on the glass.
(2) An antimony-doped, organic or inorganic tin compound is applied onto glass for the panel
1
through CVD (chemical vapor deposition) or LVD (liquid vapor deposition) to form an ATO film on the glass, and thereafter a hydrolytic solution of a silicon alkoxide compound is uniformly applied thereover to form a two-layered film having a uniform thickness of from about 80 nm to about 100 nm. In addition, for the purpose of reducing the reflected color density of the two-layered, anti-reflective and antistatic film and for reducing the reflectance thereof for visible rays falling within a wavelength range of from 380 nm to 780 nm, a hydrolytic solution of a silicon alkoxide compound is further sprayed over the two-layered film to form a third layer of a light-scattering film having a
Ito Maki
Kamoto Daigoro
Matsukiyo Hidetsugu
Miura Kiyoshi
Nishizawa Masahiro
Guharay Karabi
Patel Ashok
LandOfFree
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