Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1998-08-14
2001-03-27
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S422000
Reexamination Certificate
active
06208072
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image display apparatus, and more particularly relates to a thin image display apparatus used for a video camera and the like.
BACKGROUND OF THE INVENTION
Conventionally, a cathode ray tube has been used mainly as an image display apparatus for color television, personal computer and the like. However, in recent years, an image display apparatus has been required to be miniaturized, lightened and thinner. In order to satisfy these demands, various types of thin image display apparatus have been developed and commercialized.
Under these circumstances, various types of thin image display apparatus have been researched and developed recently. In particular, a liquid crystal display and a plasma display have been developed actively. The liquid crystal display has been applied to various types of products such as a portable computer, a portable television, a video camera, a car-navigation system and the like. In addition to that, the plasma display has been applied to a product such as a large-scale display, for example, 20 inch-display or 40-inch display.
However, there are the following problems for the liquid crystal display and the plasma display. The liquid crystal display has a narrow visual angle and a slow response. Regarding the plasma display, high brightness can't be obtained and the consumed electricity is large.
Then, an image display apparatus (hereinafter referred to as “a field emission display”, or “a display”) to which field emission, that is, a phenomenon in which electrons are emitted in a vacuum at room temperature, is applied, has attracted considerable attention. The field emission display is a spontaneous luminescent type, therefore it is possible to obtain a wide visual angle and high brightness. Further, its basic principle (to illuminate a fluorescent substance with electron beams) is same as that of a conventional cathode ray tube, and therefore a picture with natural color and high reproduction can be displayed.
The above-mentioned type of field emission display is disclosed in Japanese Laid Open Patent No. (Tokkai-Sho) 61-221783, Japanese Laid Open Patent No. (Tokkai-Hei) 1-100842, and Japanese Laid Open Patent No. (Tokkai-Hei) 2-61946.
FIG. 7
is a cross-sectional view showing schematic structure of a first conventional field emission display (refer to Japanese Laid Open Patent No. (Tokkai-Sho) 61-221783). As shown in
FIG. 7
, the conventional field emission display comprises an electron emission source
21
, a transparent flat substrate
24
, a fluorescent layer
23
and a conductive thin film
25
. The fluorescent layer
23
and the conductive thin film
25
are layered sequentially on the inner surface of the transparent flat substrate
24
and face the electron emission source
21
. The cathode (electron emission source)
21
comprises a plurality of conductive micro-points
21
a
formed on the surface of a conductive coating material
21
b
and the conductive coating material
21
b
is layered on the surface of an insulating substrate
21
c
. Each conductive micro-point
21
a
is separated by an insulating coating material
21
d
. A grid
21
e
, in which a hole is provided at the position corresponding to each conductive micro-point
21
a
, is provided on the insulating coating material
21
d.
According to the above-mentioned field emission display, conductive micro-points
21
a
emit electrons to excite the fluorescent layer
23
. The excited fluorescent layer
23
emits a light and the light is observed through a transparent flat substrate
24
. According to the conventional technique, it is required to form 20,000 to 30,000 pieces of conductive micro-points
21
a
per square-millimeter and electrons (electron beams) are emitted from a plurality of conductive micro-points
21
a
to illuminate one pixel.
FIG. 8
is a cross-sectional view showing schematic structure of a second conventional field emission display (refer to Japanese Laid Open Patent No. (Tokkai-Hei) 2-61946). As shown in
FIG. 8
, the conventional field emission display comprises an electron emission source
31
, a fluorescent layer
33
a
,
33
b
and
33
c
, a transparent flat substrate
34
, and a conductive thin film
35
a
,
35
b
and
35
c
. The fluorescent layers,
33
a
,
33
b
and
33
c
, and the conductive thin films
35
a
,
35
b
and
35
c
are layered sequentially on the inner surface of the transparent flat substrate
34
and face the electron emission source
31
. The electron emission source
31
comprises a plurality of conductive micro-points
31
a
formed on a conductive coating material
31
b
, and the conductive coating material
31
b
is layered on the surface of an insulating substrate
31
c
. Each conductive micro-point
31
a
is separated by an insulating coating material
31
d
. A grid
31
e
is provided on the insulating coating material
31
d.
According to the above-mentioned field emission display, electrons which are emitted from a plurality of conductive micro-points
31
a
can be landed at intended components of the fluorescent layer (in
FIG. 8
, a fluorescent layer
33
a
) by controlling a potential which is applied to the conductive thin films
35
.
FIG. 9
is a cross-sectional view showing schematic structure of a third conventional field emission display (refer to Japanese Laid Open Patent No. (Tokkai-Hei) 1-100842). As shown in
FIG. 9
, the conventional field emission display comprises an electron emission source
41
, a fluorescent layer
43
a
and
43
b
, a faceplate
44
and a transparent electrode
45
. The fluorescent layers
43
a
and
43
b
are provided on the faceplate
44
via the transparent electrode
45
. The electron emission source
41
faces the fluorescent layers
43
a
and
43
b
. The electron emission source
41
comprises a substrate
41
e
, a thin film
41
c
formed on the substrate
41
e
and electrodes
41
a
and
41
b
which are provided for applying a voltage to the thin film
41
c
. An electron emission part
41
d
is provided by processing the thin film
41
c.
According to the above-mentioned field emission display, the deflection of electron beams emitted from the electron emission part
41
d
is controlled by controlling a voltage applied to electrodes
41
a
and
41
b
, and the deflected electron beam excites a fluorescent layer
43
a
or
43
b
, and the fluorescent layer
43
a
or
43
b
is illuminated. Further, in the conventional field emission display, a technology such that electron beams are focused on the surface of the fluorescent layer by providing a flat electrode (not shown in
FIG. 9
) between the electron emission source
41
and the fluorescent layer
43
and applying a voltage lower than that of a transparent electrode
45
to the flat electrode, is used, that is, the technology such that the electron beams are focused on the surface of the fluorescent layer by utilizing the lens effect, is used.
However, the conventional field emission display shown in
FIG. 7
has following problems. Electrons which are emitted from a conductive micro-point
21
a
are very weak, therefore a fluorescent layer
23
and an electron emission source
21
are required to face each other very closely. Further, it is required that one pixel of fluorescent substance is illuminated by electrons which are emitted from a plurality of conductive micro-points
21
a
, and therefore electron beams can't be deflected and focused. As a result, electrons which land on the fluorescent layer
23
extend, and therefore it is difficult to increase the density of the fluorescent layer
23
. Consequently, a display having high resolution can't be provided.
In the conventional field emission display shown in
FIG. 8
, electron beams are deflected by controlling (switching) a potential which is applied to a conductive thin film
35
. In order to switch the conducive thin film
35
, it is required that a switching scan be performed under a high voltage. However, it is very difficult to realize a circuit element in which a high voltage of kilo volt order applied to
Fujishiro Kenji
Imai Kanji
Kawachi Makoto
Watanabe Michiaki
Yokomakura Mitsunori
Day Michael H.
Matsushita Electronics Corporation
Merchant & Gould P.C.
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