Information
-
Patent Grant
-
6624566
-
Patent Number
6,624,566
-
Date Filed
Tuesday, August 28, 200123 years ago
-
Date Issued
Tuesday, September 23, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Blakely, Sokoloff, Taylor & Zafman
-
CPC
-
US Classifications
Field of Search
US
- 313 495
- 313 496
- 313 497
- 313 309
- 313 310
- 313 311
- 313 422
-
International Classifications
- H01J162
- H01J6304
- H01J105
- H01J102
- H01J2970
-
Abstract
A vacuum fluorescent display includes a front glass member, substrate, control electrode, plate-like field emission type electron-emitting source, mesh-like electron extracting electrode, and phosphor film. The front glass member has light transmission properties at least partly, and the substrate opposes the front glass member through a vacuum space. The control electrode is formed on an inner surface of the substrate. The plate-like field emission type electron-emitting source with a plurality of through holes is arranged in the vacuum space to be spaced apart from the control electrode. The mesh-like electron extracting electrode is formed between the field emission type electron-emitting source and the front glass member to be spaced apart from the field emission type electron-emitting source. The phosphor film is formed inside the front glass member.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum fluorescent display which emits light by bombarding electrons emitted from a field emission type electron-emitting source against a phosphor.
Conventionally, as a display component for an audio apparatus or automobile dashboard, a vacuum fluorescent display is one type of electronic display device frequently used. In the vacuum fluorescent display, an anode attached with a phosphor and a cathode are arranged in a vacuum vessel to oppose each other, and electrons emitted from the cathode are bombarded against the phosphor to emit light. As a general vacuum fluorescent display, a triode structure is used most often, in which a grid for controlling the electron flow is provided between the cathode and anode, so the phosphor selectively emits light.
Recently, to greatly increase the luminance of the vacuum fluorescent display, a vacuum fluorescent display in which a field emission type electron-emitting source using carbon nanotubes is used as a cathode is proposed.
FIG. 7
shows a conventional vacuum fluorescent display. Referring to
FIG. 7
, the conventional vacuum fluorescent display has an envelope
300
constituted by a front glass member
301
which has light transmission properties at least partly, a substrate
302
opposing the front glass member
301
, and a frame-like spacer
303
for hermetically connecting the edges of the front glass member
301
and substrate
302
. The interior of the envelope
300
is vacuum-evacuated.
In the envelope
300
, a plurality of front surface support members
304
vertically stand on the inner surface of the front glass member
301
to be parallel to each other at a predetermined interval. Each light-emitting portion
310
constituting a display pixel is formed on a corresponding region on the inner surface of the front glass member
301
which is sandwiched by the front surface support members
304
. The light-emitting portion
310
is constituted by a band-like phosphor film
311
formed on the inner surface of the front glass member
301
and a metal back film
312
formed on the surface of the phosphor film
311
and used as an anode.
A plurality of substrate support members
305
vertically stand on the substrate
302
to oppose the front surface support members
304
. A plurality of band-like wiring electrodes
320
are formed in regions on the inner surface of the substrate
302
each of which is sandwiched by the substrate support members
305
to oppose the respective light-emitting portions
310
. Field emission type electron-emitting sources
330
made of carbon nanotubes are formed on the wiring electrodes
320
, respectively. Further, a plurality of mesh-like electron extracting electrodes
340
are arranged to be spaced apart from the field emission type electron-emitting sources
330
by a predetermined distance. The electron extracting electrodes
340
are formed in the direction perpendicular to the field emission type electron-emitting sources
330
to have a band-like shape, and arranged to be parallel to each other at a predetermined interval. The electron extracting electrodes
340
are sandwiched and fixed between the substrate support members
305
and front surface support members
304
.
The operation of the vacuum fluorescent display will be described next with reference to FIG.
8
. Note that the support members
304
, and the support members
305
, arranged between the electrodes are not shown in FIG.
8
. Referring to
FIG. 8
, the field emission type electron-emitting sources
330
are arranged to be parallel to each other at a predetermined interval, and the electron extracting electrodes
340
are arranged above the field emission type electron-emitting sources
330
. The electron extracting electrodes
340
are formed in the direction perpendicular to the field emission type electron-emitting sources
330
and arranged to be parallel to each other at a predetermined interval. The plurality of light-emitting portions
310
are arranged above the electron extracting electrodes
340
at positions opposing the respective field emission type electron-emitting sources
330
.
A positive voltage (accelerating voltage) is applied to the metal back films
312
of the light-emitting portions
310
. In this state, in the vacuum fluorescent display, voltages applied to each field emission type electron-emitting source
330
and each electron extracting electrode
340
switch the ON/OFF states of a corresponding one of the light-emitting portions
310
which opposes the intersecting region of the field emission type electron-emitting source
330
and electron extracting electrode
340
. In this vacuum fluorescent display, when 0 V is applied to the electron extracting electrode
340
, an electric field required for emitting electrons is not generated in the field emission type electron-emitting sources
330
. Accordingly, the light-emitting portion
310
becomes an OFF state
310
a
independently of a voltage applied to the field emission type electron-emitting source
330
.
When a predetermined positive voltage is applied to the electron extracting electrode
340
, a voltage applied to each field emission type electron-emitting source
330
through a corresponding one of the wiring electrodes
320
can switch the ON/OFF states of a corresponding one of the light-emitting portions
310
which opposes the intersecting region of the field emission type electron-emitting source
330
and electron extracting electrode
340
. In this case, when a voltage applied to the field emission type electron-emitting source
330
is 0 V, the light-emitting portion
310
becomes an ON state
310
b
, and when a predetermined positive voltage is applied to the field emission type electron-emitting source
330
, the light-emitting portion
310
becomes the OFF state
310
a
. Accordingly, in this vacuum fluorescent display, scanning is performed such that the positive voltage is sequentially applied to the respective electron extracting electrodes
340
, and in synchronism with this scanning, voltages applied to the respective field emission type electron-emitting sources
330
are switched in correspondence with the respective pixels to be displayed, thereby performing matrix display.
In the conventional vacuum fluorescent display, however, the electron-emitting sources are formed on the substrate. Therefore, when faults such as a luminance nonuniformity and the like have been found in the electron-emitting source, the substrate itself must be discarded, thereby causing a decrease in manufacturing yield.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a vacuum fluorescent display using a field emission type electron-emitting source which increases the manufacturing yield.
In order to achieve the above object, according to the present invention, there is provided a vacuum fluorescent display comprising a front glass member which has light transmission properties at least partly, a substrate opposing the front glass member through a vacuum space, a control electrode formed on an inner surface of the substrate, a plate-like field emission type electron-emitting source with a plurality of through holes which is arranged in the vacuum space to be spaced apart from the control electrode, a mesh-like electron extracting electrode formed between the field emission type electron-emitting source and the front glass member to be spaced apart from the field emission type electron-emitting source, and a phosphor film formed inside the front glass member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a sectional view showing the main part of a vacuum fluorescent display according to the first embodiment of the present invention;
FIG. 2
is an enlarged sectional view showing a field emission type electron-emitting source shown in
FIG. 1
;
FIG. 3
is a view for explaining the relationship between voltages applied to electrodes and light emission states of light-emitting portions of the vacuum fluorescent display shown in
FIG. 1
;
FIG. 4
is a graph showing the relationship between a voltage applied to an electron extracting electrode and an emission current generated by electrons emitted from the field emission type electron-emitting source;
FIG. 5
is a sectional view showing the main part of a vacuum fluorescent display according to the second embodiment of the present invention;
FIG. 6
is a view for explaining the relationship between voltages applied to electrodes and light emission states of light-emitting portions of the vacuum fluorescent display shown in
FIG. 5
;
FIG. 7
is a sectional view showing the main part of a conventional vacuum fluorescent display; and
FIG. 8
is a view for explaining the relationship between voltages applied to electrodes and light emission states of light-emitting portions of the conventional vacuum fluorescent display shown in FIG.
7
.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1
shows a vacuum fluorescent display according to the first embodiment of the present invention. Referring to
FIG. 1
, the vacuum fluorescent display of this embodiment has an envelope
100
constituted by a front glass member
101
which has light transmission properties at least partly, a substrate
102
opposing the front glass member
101
, and a frame-like spacer
103
for hermetically connecting the edges of the front glass member
101
and substrate
102
. The interior of the envelope
100
is vacuum-evacuated.
In the envelope
100
, a plurality of front surface support members
104
vertically stand on the inner surface of the front glass member
101
to be parallel to each other at a predetermined interval. Each light-emitting portion
110
constituting a display pixel is formed on a corresponding region on the inner surface of the front glass member
101
which is sandwiched by the front surface support members
104
. The light-emitting portion
110
is constituted by a band-like phosphor film
111
formed on the inner surface of the front glass member
101
and a metal back film
112
formed on the surface of the phosphor film
111
and used as an anode.
A plurality of substrate support members
105
vertically stand on the substrate
102
to oppose the front surface support members
104
, and a plurality of band-like control electrodes
120
are formed in regions sandwiched by the substrate support members
105
to oppose the respective light-emitting portions
110
. A plate-like field emission type electron-emitting source
130
with a large number of through holes is arranged to be spaced apart from the control electrodes
120
by a predetermined distance in the direction toward the front glass member
101
. The field emission type electron-emitting source
130
is supported by the substrate support members
105
and arranged to correspond to all the control electrodes
120
.
A plurality of mesh-like electron extracting electrodes
140
are arranged to be spaced apart from the field emission type electron-emitting source
130
by a predetermined distance in the direction to the front glass member
101
. The band-like electron extracting electrodes
140
are formed in the direction perpendicular to the control electrodes
120
and arranged to be parallel to each other at a predetermined interval. The electron extracting electrodes
140
are sandwiched and fixed between the front surface support members
104
and an intermediate support member
106
which is formed through the field emission type electron-emitting source
130
so as to correspond to the substrate support members
105
.
The front glass member
101
, substrate
102
, and spacer
103
constituting the envelope
100
are made of soda-lime glass. As the front glass member
101
and substrate
102
, flat glass with a thickness of 1 mm to 2 mm is used. The front surface support member
104
is made of an insulator formed by screen-printing an insulating paste containing low-melting frit glass repeatedly to a predetermined height at a predetermined position on the inner surface of the front glass member
101
, and calcining the printed insulating paste. In this embodiment, the front surface support member
104
has a width of 50 μm, and a height of 2 mm to 4 mm, and each light-emitting portion
110
arranged on a region sandwiched by the front surface support members
104
has a width of 0.3 mm.
The phosphor film
111
is made of a phosphor with a predetermined light emission color and is formed by screen-printing a phosphor paste in a stripe on the inner surface of the front glass member
101
, and calcining the printed stripe to have a thickness of 10 μm to 100 μm and a width of 0.3 mm. In this case, as the phosphor film
111
, three types of phosphor films may be used for emitting three primary colors of red (R), green (G), and blue (B) in color display, and a single type of phosphor film may be used for emitting a white color in monochrome display. As the phosphor film
111
, known oxide phosphors or sulfide phosphors which are generally used in a cathode-ray tube or the like and emit light upon being bombarded with electrons accelerated by a high voltage of 4 kV to 10 kV can be used. The metal back film
112
is formed of an aluminum thin film with a thickness of about 0.1 μm, and is formed on the surface of the phosphor film
111
by using a known vapor deposition method.
The substrate support members
105
are made of an insulator formed by screen-printing an insulating paste containing low-melting frit glass repeatedly to a predetermined height so as to sandwich the control electrodes
120
on the substrate
102
, and calcining the printed insulating paste. The substrate support member
105
has, e.g., a width of 50 μm, a height of 0.3 mm to 0.6 mm. The control electrode
120
sandwiched by the substrate support members
105
has a width of 0.3 mm.
The control electrode
120
is formed on the substrate
102
in a predetermined pattern by screen-printing a conductive paste containing silver or carbon as a conductive material, and calcining the printed conductive paste to have a thickness of about 10 μm. A method of forming the control electrode
120
is not limited to screen printing, and the control electrode
120
may be formed from, e.g., an aluminum thin film with a thickness of about 1 μm formed by using known sputtering and etching.
As shown in
FIG. 2
, the field emission type electron-emitting source
130
is comprised of a plate-like metal member
131
with a large number of through holes
131
a
and serving as a growth nucleus for nanotube fibers, and a coating film
132
made of a large number of nanotube fibers that cover the surface of the plate-like metal member
131
and the inner walls of the through holes
131
a
. The plate-like metal member
131
is a metal plate made of iron or an iron-containing alloy. The through holes
131
a
are formed in a matrix in the plate-like metal member
131
so the plate-like metal member
131
has a grid-like shape.
Note that the openings of the through holes
131
a
may be of any shape as far as the coating film
132
is uniformly distributed on the plate-like metal member
131
, and the sizes of the openings need not be the same. For example, the openings may be polygons such as triangles, quadrangles, or hexagons, those formed by rounding the corners of such polygons, or circles or ellipses. The sectional shape of the plate-like metal member
131
between the through holes
131
a
is not limited to a square, but may be any shape such as a circle or ellipse constituted by curves, a polygon such as a triangle, quadrangle, or hexagon, or those formed by rounding the corners of such polygons.
The plate-like metal member
131
is fabricated in the following manner. First, a photosensitive resist film is formed on a flat metal plate made of iron or an iron-containing alloy. Then, a mask with a pattern of a large number of through holes is placed on the resist film, exposed with light or ultraviolet rays, and developed, thereby forming a resist film with a desired pattern. Subsequently, the metal plate is dipped in an etching solution to remove an unnecessary portion of it. After that, the resist film is removed and the resultant structure is washed, thus obtaining the plate-like metal substrate
131
having the through holes
131
a.
In this case, the opening portions of through holes
131
a
may be formed into an arbitrary shape by the mask pattern. If a pattern is formed on the resist film on one surface of the metal plate while leaving the resist film on the other surface intact, the sectional shape of the metal portion between the adjacent through holes
131
a
and constituting the grid becomes trapezoidal or triangular. If patterns are formed on the resist films on the two surfaces, the sectional shape becomes hexagonal or rhombic. The sectional shape can be changed in this manner in accordance with the manufacturing methods and manufacturing conditions. After etching, if electropolishing is performed, a curved sectional shape can be obtained.
Iron or an iron-containing alloy is used as the plate-like metal member
131
because iron serves as a growth nucleus for carbon nanotube fibers. When iron is selected to form the plate-like metal member
131
, industrial pure iron (Fe with a purity of 99.96%) is used. This purity is not specifically defined, and can be, e.g., 97% or 99.9%. As the iron-containing alloy, for example, a 42 alloy (42% of Ni) or a 42-6 alloy (42% of Ni and 6% of Cr) can be used. However, the present invention is not limited to them. In this embodiment, a 42-6 alloy thin plate with a thickness of 0.05 mm to 0.20 mm was used considering the manufacturing cost and availability.
The nanotube fibers of the coating film
132
have thicknesses of about 10 nm or more and less than 1 μm, and lengths of about 1 μm or more and less than 100 μm, and are made of carbon. The nanotube fibers may be single-layered carbon nanotubes in each of which a graphite single layer is cylindrically closed and a 5-membered ring is formed at the tip of the cylinder. Alternatively, the nanotube fibers may be coaxial multilayered carbon nanotubes in each of which a plurality of graphite layers are multilayered to form a telescopic structure and are respectively cylindrically closed, hollow graphite tubes each with a disordered structure to produce a defect, or graphite tubes filled with carbon. Alternatively, the nanotubes may mixedly have these structures.
Such a nanotube fiber has one end connected to the surface of the plate-like metal member
131
or the inner wall of a through hole
131
a
and is curled or entangled with other nanotube fibers to cover the surface of the metal portion constituting the grid, thereby forming the cotton-like coating film
222
. In this case, the coating film
132
covers the plate-like metal member
131
made of a 42-6 alloy with the thickness of 0.05 mm to 0.20 mm by a thickness of 10 μm to 30 μm to form a smooth curved surface.
The coating film
132
can be formed by using the following thermal CVD (Chemical Vapor Deposition). First, the plate-like metal member
131
is set in the reaction chamber, and the interior of the reaction chamber is evacuated to vacuum. Then, methane gas and hydrogen gas, or carbon monoxide gas and hydrogen gas are introduced into the reaction chamber at a predetermined ratio, and the interior of the reaction chamber is held at 1 atm. In this atmosphere, the plate-like metal member
131
is heated for a predetermined period of time by an infrared lamp, so that the carbon nanotube fiber is grown on the surface of the plate-like metal member
131
and the inner walls of the through holes
131
a
constituting the grid, thus forming the coating film
132
. With thermal CVD, carbon nanotube fibers constituting the coating film
132
can be formed in a curled state.
Since the field emission type electron-emitting source
130
need not be printed on the substrate
102
, operation check can be performed to only the field emission type electron-emitting source
130
to check whether nonuniform electron emission which causes luminance nonuniformity is present. Therefore, the field emission type electron-emitting source
130
is incorporated in the vacuum fluorescent display after the end of the operation check.
The electron extracting electrode
140
is formed of a 50 μm thick stainless steel plate or 42-6 alloy and has a mesh structure in which a large number of electron passing holes are formed by etching. Each electron passing hole has a diameter of 20 μm to 100 μm. The intermediate support member
106
is formed of an insulating substrate with a plurality of slits corresponding to the respective light-emitting portions
110
, and stacked on the field emission type electron-emitting source
130
. The slit has the same length and width as those of the light-emitting portion
110
. A 0.3 mm thick alumina substrate is used as the insulating substrate, and the slits are formed by using laser beam.
The intermediate support member
106
is not limited to the alumina substrate, and the insulating substrate such as a glass substrate may be used. A distance between the field emission type electron-emitting source
130
and electron extracting electrodes
140
is set by the thickness of the intermediate support member
106
. In this case, the thickness of the intermediate support member
106
must be set considering the height of the substrate support member
105
which serves as a distance between the field emission type electron-emitting source
130
and control electrode
120
because the strength of the electric field applied to the field emission type electron-emitting source
130
is affected.
The operation of the vacuum fluorescent display with the above arrangement will be described with reference to FIG.
3
. The support members
104
,
105
, and
106
arranged between the electrodes are not shown in FIG.
3
. Referring to
FIG. 3
, the single field emission type electron-emitting source
130
is arranged above the control electrodes
120
which are arranged to be parallel to each other at a predetermined interval. The plurality of electron extracting electrodes
140
are arranged above the field emission type electron-emitting source
130
to be parallel to each other at a predetermined interval, which are formed in the direction perpendicular to the control electrodes
120
. The plurality of light-emitting portions
110
are arranged above the electron extracting electrodes
140
at positions opposing the respective control electrodes
120
.
The field emission type electron-emitting source
130
is connected to ground (GND), and a positive voltage (accelerating voltage) is applied to the metal back films
112
of the light-emitting portions
110
. In this state, voltages applied to each control electrode
120
and each electron extracting electrode
140
switch the ON/OFF states of a corresponding one of the light-emitting portions
110
which opposes the intersecting region of these electrodes. When 0 V is applied to the electron extracting electrode
140
, an electric field required for emitting electrons is not generated in the field emission type electron-emitting source
130
. Accordingly, the light-emitting portion
110
becomes an OFF state
110
a
independently of a voltage applied to the control electrode
120
.
When a predetermined positive voltage is applied to the electron extracting electrode
140
, a voltage applied to each control electrode
120
can switch the ON/OFF states of a corresponding one of the light-emitting portions
110
which opposes the intersecting region of the control electrode
120
and electron extracting electrode
140
. In this case, when a voltage applied to the control electrode
120
is 0 V, the light-emitting portion
110
becomes an ON state
110
b
, and when a predetermined negative voltage is applied to the control electrode
120
, the light-emitting portion
110
becomes the OFF state
110
a
. A reason why a voltage applied to each control electrode
120
switches the ON/OFF states of a corresponding one of the light-emitting portions
110
, as described above, will be described next.
When a high electric field is applied to a solid surface, a potential barrier on the surface which confines electrons in a solid becomes low and thin. Thus, electrons confined in the solid are emitted outside by the tunneling effect. This phenomenon is called field emission, and the field emission type electron-emitting source is an electron-emitting source utilizing the field emission phenomenon. To observe the field emission, a high electric field of 10
9
V/cm must be applied to the solid surface. As a method of implementing field emission, an electric field is applied to a conductor with a sharp tip. According to this method, the electric field is concentrated to the sharp tip of the conductor, so that a required high electric field can be obtained to emit electrons from the tip of the conductor.
In this embodiment, a high electric field acts on the nanotube fibers of the coating film
132
constituting the field emission type electron-emitting source
130
, so that electrons are field-emitted from the nanotube fibers. The field emission type electron-emitting source
130
has the plurality of through holes
131
a
, is arranged between the control electrodes
120
and electron extracting electrodes
140
, and is connected to ground (GND). At this time, 0 V is applied to the control electrodes
120
, and a positive voltage of, e.g., 2 kV is applied to the electron extracting electrodes
140
, thereby making a high electric field act on the nanotube fibers. This can field-emit electrons from the nanotube fibers, and an emission current can be obtained.
FIG. 4
shows the relationship between a voltage applied to the electron extracting electrode
140
and an emission current generated by electrons emitted from the field emission type electron-emitting source
130
. As shown in
FIG. 4
, to generate field emission from the field emission type electron-emitting source
130
, a voltage equal to or higher than a predetermined threshold voltage must be applied to the electron extracting electrode
140
to set the strength of an electric field acting on the nanotube fibers to a predetermined threshold value or more. For example, if a voltage applied to the electron extracting electrode
140
is 1 kV or more, an emission current can be obtained.
On the other hand, if a negative voltage of, e.g., −1 kV is applied to the control electrode
120
, the strength of the electric field acting on the nanotube fibers becomes lower than the predetermined threshold value because a negative electric field acts through the through holes
131
a
of the field emission type electron-emitting source
130
. As a result, field emission is interfered, so an emission current cannot be obtained.
If, therefore, a positive voltage of, e.g., 2 kV is applied to the electron extracting electrodes
140
, electrons are emitted from the first region of the field emission type electron-emitting source
130
, i.e., a region sandwiched by the electron extracting electrode
140
and the corresponding control electrode
120
to which a voltage of 0 V is applied. Most of the emitted electrons pass through the mesh structure of the electron extracting electrode
140
and are accelerated toward the metal back film
112
. The accelerated electrons are transmitted through the metal back film
112
and bombard against the phosphor film
111
, causing it to emit light. Thus, the light-emitting portion
110
corresponding to the first region becomes the ON state
110
b.
On the other hand, in the second region of the field emission type electron-emitting source
130
, i.e., a region sandwiched by the electron extracting electrode
140
and the control electrode
120
to which a negative voltage of, e.g., −1 kV is applied, electron emission is inhibited. Accordingly, the light-emitting portion
110
corresponding to the second region becomes the OFF state
110
a.
According to this embodiment, since the electron-emitting source is formed of a single plate-like member, operation check can be performed to only the electron-emitting source. This allows to find defective products before assembly, thus decreasing faults due to the electron-emitting source and increasing the manufacturing yield. Since the source is formed of a single member, assembly can be facilitated, and the number of assembling steps can be decreased. In addition, the electron-emitting source is comprised of the plate-like metal member with the through holes and serving as a growth nucleus for the nanotube fibers and the coating film formed of the nanotube fibers that cover the surface of the metal member and the walls of the through holes. Consequently, ON/OFF control by the control electrodes can be done, and uniform electron emission can be obtained at a high density.
The second embodiment of the present invention will be described below with reference to
FIGS. 5 and 6
.
This embodiment is different from the first embodiment in that each light-emitting portion
210
comprising of a display segment is constituted by a band-like transparent electrode
212
formed on the inner surface of a front grass member
201
and used as an anode, and a phosphor film
211
formed on the surface of the transparent electrode
212
. In addition, an electron extracting electrode
240
is formed of a single plate-like member with a size almost equal to that of a field emission type electron-emitting source
230
.
The front grass member
201
, a substrate
202
, and a spacer
203
, all of which constitute an envelope
200
, front support members
204
, substrate support members
205
, an intermediate support member
206
, control electrodes
220
, and the field emission type electron-emitting source
230
are the same as those in the first embodiment, and a description thereof will be omitted.
The transparent electrode
212
is formed of an ITO (Indium Tin Oxide) film as a transparent conductive film, and is formed on the inner surface of the front glass member
201
to have a predetermined pattern by using known sputtering and lift-off. The transparent electrode
212
is not limited to the ITO film, and another transparent conductive film such as an indium oxide film may be used. In place of a transparent conductive film, an aluminum thin film with an opening may be formed by using known sputtering and etching, to serve as the transparent electrode
212
.
The phosphor film
211
is made of a phosphor that can be excited by a low-speed electron beam and with a predetermined light emission color. The phosphor film
211
is formed by screen-printing a phosphor paste on the transparent electrode
111
to have a predetermined display pattern, and calcining it. As the phosphor that can be excited by a low-speed electron beam, an oxide phosphor or sulfide phosphor generally used in a vacuum fluorescent display can be used. The types of phosphors may be changed for each display pattern so different light emission colors can be obtained, as a matter of course.
In the vacuum fluorescent display having the aforementioned arrangement, the field emission type electron-emitting source
230
is connected to ground (GND), and positive voltages (accelerating voltages) are applied to the electron extracting electrode
240
and the transparent electrodes
212
of the light-emitting portions
210
. In this state, a voltage applied to each control electrode
220
switches the ON/OFF states of a corresponding one of the light-emitting portions
210
which opposes each control electrode
220
. That is, when a voltage applied to the control electrode
220
is 0 V, the corresponding light-emitting portion
210
becomes an ON state
210
b
, and when a predetermined negative voltage is applied to the control electrode
220
, the corresponding light-emitting portion
210
becomes an OFF state
210
a.
According to this embodiment, since not only the field emission type electron-emitting source
230
but also the electron extracting electrode
240
is formed of a single plate-like member, assembly is further facilitated in addition to the effects in the first embodiment.
In this embodiment, the light-emitting portions
210
used as display segments are formed to have a band-like shape. The present invention is not limited to this, and the light-emitting portion
210
may be of any shape. Obviously, each control electrode
220
is formed such that its shape matches that of the light-emitting portion
210
. In this case, the display patterns can be formed into the same shape as that of the thin-film transistors
210
and control electrodes
220
which are formed by printing, thus easily forming the display patterns even if they have a complicated shape.
As has been described above, according to the present invention, the field emission type electron-emitting source is not formed on the substrate directly. Since the electron-emitting source is formed independently of the substrate, operation check can be performed only the electron-emitting source. This can decrease substrate faults due to the electron-emitting source and increase the manufacturing yield. In addition, the electron-emitting source is formed of a single member, thereby reducing cost and facilitating assembly.
Claims
- 1. A vacuum fluorescent display comprising:a front glass member which has light transmission properties at least partly; a substrate opposing said front glass member through a vacuum space; a control electrode formed on an inner surface of said substrate; a plate-like field emission type electron-emitting source with a plurality of through holes which is arranged in the vacuum space to be spaced apart from said control electrode; a mesh-like electron extracting electrode formed between said electron-emitting source and said front glass member to be spaced apart from said electron-emitting source; and a phosphor film formed inside said front glass member, wherein said electron-emitting source includes: a plate-like metal member with a large number of through holes and serving as a growth nucleus for nanotube fibers; and a coating film made of a large number of nanotube fibers and formed on a surface of said metal member and inner walls of the through holes.
- 2. A display according to claim 1, whereinsaid phosphor film is formed into a shape corresponding to that of a pattern to be displayed, and said control electrode is formed into a shape corresponding to that of the pattern to be displayed and arranged to oppose said phosphor film.
- 3. A display according to claim 1, whereinsaid control electrode comprises a plurality of band-like control electrodes arranged parallel to each other, said electron extracting electrode comprises a plurality of band-like electron extracting electrodes formed to extend along a direction perpendicular to said bond-like control electrodes and arranged parallel to each other, and said phosphor film is arranged to oppose at least intersecting regions of said band-like control electrodes and said band-like electron extracting electrodes.
- 4. A display according to claim 1, whereinsaid control electrode comprises a plurality of band-like control electrodes arranged parallel to each other, said electron extracting electrode is formed of a single plate-like member with a size substantially equal to that of said electron-emitting source, and said phosphor film is arranged to oppose said band-like control electrodes.
- 5. A display according to claim 1, whereinsaid metal member is made of one of iron or iron-containing alloy, and said coating film is made of a large number of carbon nanotubes formed in a curled state.
- 6. A display according to claim 1, further comprising:first support members formed on said substrate so as to divide said control electrode into a plurality of band-like electrodes and having upper portions on which said electron-emitting source is supported; second support members formed on said electron-emitting source so as to correspond to said first support members and having upper portions on which said electron extracting electrode is supported; and third support members formed between said front glass member and said electron extracting electrode so as to correspond to said first and second support members.
- 7. A display according to claim 1, further comprising a light-emitting portion including said phosphor film formed on an inner surface of said front glass member and a metal back film formed on a surface of said phosphor film and used as an anode.
- 8. A display according to claim 1, further comprising a light-emitting portion including a transparent electrode formed on an inner surface of said front glass member and used as an anode and said phosphor film formed on a surface of said transparent electrode.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000/258622 |
Aug 2000 |
JP |
|
US Referenced Citations (6)