Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1998-11-23
2001-11-20
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S496000, C313S497000, C445S023000, C445S024000
Reexamination Certificate
active
06320309
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an anode substrate for a display device which includes a glass plate provided on an inner surface thereof with color filters and a method for manufacturing the same, and more particularly to a color filter-equipped anode substrate for a display device such as, for example, a fluorescent display device, a field emission display (FED) utilizing field emission cathodes (FECs) as an electron source, a plasma display (PDP) or the like and a method for manufacturing the same.
There has been known in the art a color fluorescent display device including a combination of a phosphor ZnO:Zn emitting light of a bluish green luminous color and color filters. Manufacturing of the color fluorescent display device includes a heat treatment step carried out at a temperature of 500° C., thus, a material for the color filters is required to be heat resistant. For example, color filters made of an organic material and used for an LCD or the like fail to be used for the color fluorescent display device. Thus, it is required to make the color filters of an inorganic material. Inorganic materials conventionally used for this purpose include a metal colloid, an inorganic pigment and the like.
Now, arrangement of color filters in an FED will be described with reference to FIG.
6
. First of all, an anode substrate
100
made of a light-permeable material such as glass or the like is formed thereon with color filters
101
,
102
and
103
, on which a smoothing layer
104
is commonly arranged. Then, transparent conductive films
105
made of indium tin oxide (ITO) or the like are arranged on the smoothing layer
104
. The smoothing layer
104
may be constituted of a SiO
2
film or the like made by sputtering, vapor deposition, CVD, sol-gel techniques or the like. Then, a phosphor is deposited on each of the transparent conductive films
105
, to thereby form a phosphor layer, resulting in the anode substrate
100
being finished. Then, a cathode substrate on which FECs are formed is arranged in such a manner that the FECs face the phosphors of the anode substrate
100
while being spaced at a microdistance from the phosphors. Finally, both substrates are sealedly joined to each other by means of a spacer member arranged in a gap defined therebetween while being positioned at an outer periphery of the substrates, to thereby provide an envelope, which is then evacuated to a high vacuum.
In operation of the thus-formed FED, electrons emitted from the FECs are impinged on the phosphor layers of the anode substrate
100
, leading to luminescence of the phosphor layers. Luminescence of the phosphor layers is observed through the transparent conductive films
105
, color filters
101
,
102
and
103
, and anode substrate
100
from an outside of the anode substrate
100
. The ZnO:Zn phosphor has a wide spectrum. Thus, when the color filters
101
,
102
and
103
are colored red (R), green (G) and blue (B) and the phosphor layers are selectively driven so as to emit light in a dot-like manner, the FED is permitted to carry out full-color graphic display.
A color filter made of an inorganic material is disclosed in Japanese Patent Application Laid-Open Publication No. 310061/1994 and Japanese Patent Application Laid-Open Publication No. 73827/1995. Unlike an organic color filter, the inorganic color filter is reduced in tinting strength. Thus, in order to ensure that the inorganic color filter satisfactorily exhibits a color reproduction range, it is required that the color filter is formed into an increased thickness as large as several microns to tens of microns. Unfortunately, such an increase in thickness of the color filter causes a difference in level to occur between the color filter and the anode substrate. This requires to laminatedly arrange the smoothing layer on the color filters to smooth an upper surface of the color filters as described above. However, there has been found no inorganic material which permits the smoothing layer increased in thickness in conformity to the color filters to be provided at a reduced cost. Thus, formation of the smoothing layer sufficiently increased in thickness in conformity to a thickness of the color filters so as to prevent formation of the difference in level causes the smoothing layer
104
to be readily broken or cracked. In view of such a problem, it would be considered that the transparent conductive films
105
each are formed directly on each of the color filters
101
,
102
and
103
as shown in FIG.
7
. Unfortunately, this causes disconnection of the transparent conductive film
105
at a level difference between each of the color filters
101
,
102
and
103
and the anode substrate
100
. Also, such formation of the smoothing layer
104
on the color filters using SiO
2
or the like as described above with reference to
FIG. 6
actually renders smoothing of the level difference between the color filters
101
,
102
and
103
and the anode substrate
100
highly difficult as shown in
FIG. 8
, so that the level difference leads to disconnection of the transparent conductive film
105
of ITO or the like formed on each of the color filters
101
,
102
and
103
. Further, this, even when such disconnection of the transparent conductive films
105
does not occur, gives rise to another problem when the phosphor layers are formed on the transparent conductive films
105
by rotary coating in the subsequent step. More particularly, the rotary coating includes a step of rotating the substrate to spread a liquid for forming each of the phosphor layers on the substrate by centrifugal force, leading to formation of a film of the phosphor forming liquid. However, this substantially fails to permit the phosphor forming liquid which run onto the level difference on the substrate by centrifugal force to be uniformly coated all over each of the transparent conductive films
105
, to thereby render the coating non-uniform.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide an anode substrate for a display device which is made of a glass plate and of which an inner surface formed thereon with color filters is smoothed with a smoothing layer.
It is another object of the present invention to provide a method for manufacturing an anode substrate for a display device which is made of a glass plate and of which an inner surface formed thereon with color filters is smoothed with a smoothing layer.
In accordance with one aspect of the present invention, an anode substrate for a display device which is constituted by a glass plate formed on an inner surface thereof with color filters and is subject to a heating treatment during manufacturing thereof is provided. The anode substrate includes at least one smoothing layer made of low-melting glass and formed on the inner surface of the glass plate. The low-melting glass has a softening point lower than a distortion point of the glass plate and a distortion point equal to or higher than a heating temperature in the subsequent step.
In a preferred embodiment of the present invention, the glass plate is made of borosilicate glass.
In a preferred embodiment of the present invention, the color filters each are made of an inorganic pigment.
In a preferred embodiment of the present invention, the low-melting glass is ZnO glass free of Pb.
In a preferred embodiment of the present invention, the ZnO glass free of Pb is selected from the group consisting of low-melting ZnO—B
2
O
3
—SiO
2
glass and low-melting Bi
2
O
3
—ZnO—SiO
2
glass.
In a preferred embodiment of the present invention, the anode substrate further includes an acid-resistant protective film formed on the smoothing layer.
In a preferred embodiment of the present invention, the anode substrate further includes a conductive film formed on the acid-resistant protective film by etching.
In accordance with another aspect of the present invention, a method for manufacturing an anode subs
Naito Yasuyuki
Namikawa Mamoru
Nomura Yuji
Futaba Denki Kogyo Kabushiki Kaisha
Haynes Mack
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Nimeshkumar D.
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