Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
2001-07-17
2003-10-07
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S466000, C445S045000, C445S047000, C427S068000
Reexamination Certificate
active
06630778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a color cathode ray tube having a luminescent surface with color filters and a manufacturing method thereof.
2. Background Art
In general, as shown in
FIG. 6
, on an interior surface of a panel
13
(face panel) of a color cathode ray tube
60
, a phosphor screen
61
with phosphor layers of each color of blue (B), green (G) and red (R) are formed arranged in dots or in stripes. On each of these phosphor layers, an electron beam
62
output from an electron gun
63
, and deflected by a deflector
64
, is impinged to emit each corresponding color, thereby resulting in the display of images. Here, a panel
13
of a color cathode ray tube
60
is constituted of a faceplate with an exterior surface formed flat and a skirt portion (sidewall portion) connected thereto.
In such a color cathode ray tube, in order to absorb light from other than phosphors to improve contrast, between adjacent phosphor dots or phosphor stripes that are pixels, a light absorption layer (black layer) is disposed as black matrix.
The light absorption layer (the black layer) is formed, for instance, in the following way. First, on an interior surface of a glass panel, photo-resist is coated, followed by exposure through a shadow mask and development, to form a resist pattern arranged in dots or stripes. Thereafter, on a resulting structure a dispersion liquid of light absorbing material (black material) such as graphite is coated to be fixed on the resulting structure. Next, the surplus black layer adhered to the interior surface of the sidewall of the panel is scraped to be removed (generally referred to as trimming), followed by decomposition of the resist layer due to a resist decomposition agent such as an aqueous solution of hydrogen peroxide. Thereby, the resist layer is dissolved and peeled off as a whole including the black material adhered thereon.
Here, scraping of the surplus black layer adhered on the interior surface of the sidewall of the panel, that is trimming, is implemented in the following two ways. In one way, as shown in
FIG. 2
, by use of a rotary brush
11
, the black layer is scraped or rubbed mechanically, followed by water washing. In the other way, as shown in
FIG. 3
, the black layer is dipped in a solution of decomposition agent
12
of the black material such as an aqueous solution of ammonium fluoride to chemically decompose the black layer. Thereby, the black layer is peeled off, followed by water washing. In these figures, reference numeral
13
denotes a panel, reference numeral
13
f
denotes a faceplate thereof, and reference numeral
13
s
denotes a sidewall, respectively. In addition, reference numeral
14
denotes the black layer (black matrix) formed in a prescribed pattern on the interior surface of the faceplate
13
f
of the panel and
14
s
denotes the surplus black layer adhered on the interior surface of the sidewall
13
s.
Recently, in a color cathode ray tube, with an object to improve brightness and contrast of the luminescent surface, between the panel and phosphor layers, corresponding to each emission color of the respective phosphors, color filters (an optical filter layer) transmitting only the light of desired wavelength are disposed.
In order to form such an optical filter layer, for instance, on an interior surface of a panel thereon a black layer (black matrix) is formed and a dispersion liquid of pigment is coated to form a pigment layer, followed by coating photo-resist thereon, exposing and development. By repeating this process, pigment layers of the respective colors are patterned in dots or in stripes. In the course of formation of such an optical filter layer, surplus pigment layers (filter layers) adhered on the interior surface of the sidewall of the panel, in the identical way as the black layer, are scraped to be removed (trimming). Reference numeral
15
s
denotes the surplus filter layer adhered on the interior surface of the sidewall
13
s
of the panel.
The reason why the trimming of the surplus black layer and surplus filter layer both adhered on the interior surface of the sidewall of the panel is necessary is as follows. After the phosphor layers are formed, a funnel
65
(
FIG. 6
) is joined airtightly by use of frit glass or the like to the sidewall portion of a panel
13
. When the black layer or filter layer remains adhered in the neighborhood of an edge surface of the panel being joined to the funnel
65
, in sealing, there is an inconvenience that cracks may occur at the portion connecting with the funnel
65
.
Further, in detaching the mask in the step of later patterning, the surplus black layer or the filter layer may be rubbed by a mask-frame or a frame-holder to result in peeling off in certain cases. Thereby, peeled fragments tend to clog holes of the shadow mask. In order to prevent such an inconvenience from occurring, trimming is implemented onto the surplus layer of the interior surface of the sidewall of the panel.
However, in trimming such a black layer or optical filter layer, so far no particular attention has been paid to the lengths from an edge of the panel being joined to the funnel
65
to the peeling edges of the respective surplus layers (hereinafter refers as trimming dimension). It has thereby frequently occurred that, as shown in
FIG. 4
, the trimming dimension (a) of the black layer
14
s
is shorter than the trimming dimension (b) of the filter layer
15
s.
In such cases, in trimming the filter layer
15
s
, the circumference portion of the surplus black layer
14
s
is likely to be scraped off again. Fragments of the black layer that are pulverized due to scraping by the rotary brush or fragments dissolved and peeled off due to immersion into an aqueous solution of ammonium fluoride enter into the interior surface of the faceplate
13
f
of the panel washing with water, and remain there without being completely removed. As a result of this, as shown in
FIG. 5
, a small fragment
16
of the black layer may result in a display defect. In
FIG. 5
, reference numeral
17
denotes an interior surface of the faceplate
13
f
and
18
denotes a black layer formed in a stripe as the black matrix.
Thus, the fragment
16
of the black layer entered into the interior surface
17
of the faceplate, in washing with water during trimming of the filter layer, for instance, can be removed by increasing an amount of washing water up to 20 to 30 l/min. In such a case, while the display defect due to the residual fragments of the black layer can be reduced, the filter layer is likely to be peeled off due to the water washing. Thereby, increasing the amount of washing water is difficult to put to practical use.
In trimming the black layer, the small fragments of the black layer peeled and pulverized by the rotary brush or dissolved and peeled in an aqueous solution of ammonium fluoride may come into the interior surface of the panel in washing with water. In such cases, since the small fragments of the black layer do not remain, no problem occurs. This is because the fragments of the black layer that intrude into the interior surface during the step of trimming of the black layer can be completely removed in the course of following steps of dissolving and peeling of the resist layer or the like.
SUMMARY OF THE INVENTION
The objects of the present invention are to provide a color cathode ray tube that can prevent fragments of black layer, which occur in trimming an optical filter layer, from adhering and remaining on an interior surface of a panel to give a defect-less display, and to provide a method for manufacturing such color cathode ray tubes with high yield.
A first aspect of the present invention is a color cathode ray tube, the color cathode ray tube comprising a transparent panel, a funnel joined airtightly to a circumference portion of a sidewall of the panel, a light absorption layer and an optical filter layer disposed on an interior surface of the panel, and a phosphor layer formed on the optical filter layer. Here, a len
Iida Keisuke
Inamura Masaaki
Washiyama Koji
Kabushiki Kaisha Toshiba
Macchiarolo Peter
O'Shea Sandra
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