JPH11167886A - Fluorescent character display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron emission part easy to handle and difficult to deteriorate to enhance reliability by constituting an emitter with a carbon nanotube comprising cylindrical graphite layers, and applying potential between the emitter and an electron extraction electrode to form a field emission type cold cathode electron source. SOLUTION: Pillar-shaped graphite 121 having a length of several μm to several mm comprising carbon nanotube aggregate fixed with a conductive adhesive 122 to the about 3 mmϕ region of an electrode 106b arranged on a ceramic substrate 106a of a cathode structure 106 so that the length direction faces a fluorescent screen 104. When voltage is supplied from the outside to produce an electric field between the electrode 106b and a housing 106d, high electric field is concentrated on the tip of the carbon nanotube of the pillar 1 shaped graphite 121, electrons are extracted, and emitted from a mesh part 106e. High voltage is applied to an anode structure 105 from the outside, emitted electrons are accelerated with a cylindrical anode 105b and bombarded against the fluorescent screen 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display device utilizing light emission of a phosphor by the impact of an electron beam.

[0002]

2. Description of the Related Art In a fluorescent display device, electrons emitted from an electron emission portion are contained in a vacuum vessel at least one of which is transparent.
This is an electron tube that emits light by colliding with a phosphor to emit light, and uses the emitted light. Usually, the fluorescent display device having a triode structure provided with a grid for controlling the function of electrons is most often used. Conventionally, a cathode called a filament is used for the electron emission portion, and thermions emitted from the cathode collide with the phosphor to emit light. Among such fluorescent display devices, there is an image tube that constitutes a pixel of a large screen display device.

Hereinafter, the picture tube will be described with reference to FIG. First, a face glass 202 having translucency is placed in a cylindrical glass bulb 201 with a low melting point frit glass 20.
3 to form a vacuum container (envelope). Further, a fluorescent screen 204, an anode electrode structure 205, and a cathode structure 206 constituting an electron emission portion are arranged therein. The face glass 202 has a convex lens-shaped spherical portion 202a on the front side.
Is formed, and a step portion 202b is formed in a peripheral portion in a flange shape. The main surface of the inner surface 202c has a fluorescent surface 2
04 and an Al metal back film 207 are sequentially laminated.

Further, an inner surface 202 of the face glass 202
c, a contact piece 2 having an elastic force formed by processing a thin plate of, for example, stainless steel by a press molding method.
07a is inserted at one end. In addition, the contact piece 2
07a is brought into contact with the Al metal back film 207 by a conductive adhesive made of a mixture of carbon or silver and frit glass, for example.
2c is adhesively fixed to a predetermined portion. The other end of the contact piece 207a extends toward the inner wall surface of the glass bulb 201.

On the other hand, the stem glass 208 forming the bottom of the glass bulb 201 has lead pins 209 a to 209.
e, and the exhaust pipe 208a is integrally formed. On the stem glass 208, an anode lead 210 is fixed to the tip of the lead pin 209a by welding, and a cylindrical anode electrode assembly 205 is fixed to the tip of the anode lead 210 by welding and mounted. Structure. This anode electrode assembly 205
Is a ring-shaped anode 205a formed by rolling a stainless steel metal wire into a ring shape, and the ring-shaped anode 2
A cylindrical anode 205b formed by winding a rectangular stainless steel thin plate around the outer peripheral surface of 05a and fixing the overlapped portion at two points by welding or the like.

The anode electrode assembly 205 is welded to a tip of the anode lead 210 at a predetermined position with a ring-shaped anode 205a. The structure is such that it is welded and fixed at the contact portion. Further, a part of the ring-shaped anode 205a includes a Ba getter 20.
5c is attached and fixed by welding or the like.

[0007] Further, cathode leads 211b to 211e are fixed to the tips of the lead pins 209b to 209e by welding.
The cathode structure 206 is fixedly arranged by welding and mounted at the tip of the. The cathode structure 206 is configured as follows. First, the back electrode 206b is arranged at the center on the ceramic substrate 206a. Further, a filament cathode 206c is fixed at a predetermined interval above the filament cathode 206c. An elliptical grid housing 206d having a mesh portion 206e is mounted on the ceramic substrate 206a so as to cover them. Also, the mesh part 20
6e has a shape protruding spherically in the direction of the fluorescent screen 204.

In the picture tube configured as described above, first, a voltage (heating power source) is supplied to the lead pins 209c and 209d from an external circuit, so that the cathode lead 211 is supplied.
A predetermined potential is applied to the filament cathode 206c via the lines c and 211d so that the thermoelectrons are emitted.
In addition, by supplying a voltage to the lead pin 209b from an external circuit, the back electrode 2 is connected via the cathode lead 211b.
At 06b, a negative potential is applied to the filament cathode 206c. In addition, a lead pin 209 is connected from an external circuit.
By applying a voltage to e, a positive potential is applied to the filament cathode 206c to the grid housing 206d via the cathode lead 211e, so that an electron beam is emitted from the mesh portion 206e of the grid housing 206d.

Then, the lead pin 209a is supplied from an external circuit.
To the anode lead 210 → the anode electrode assembly 2
05 (cylindrical anode 205b) → Electric electrons are accelerated by the cylindrical anode 205b by conducting the respective paths of the contact pieces 207a and applying a high voltage to the Al metal back film 207, Al metal back film 2
07 and penetrates the fluorescent screen 204. As a result, the fluorescent screen 204 is excited by the electron impact, and the fluorescent screen 20 is excited.
The emission color corresponding to the phosphor constituting the face glass 2
02, light is displayed on the front side.

[0010]

By the way, the filament (filament cathode) as an electron emitting portion used in the conventional fluorescent display device has a diameter of 7 to 20 μm.
An electron-emitting material is applied to a thin tungsten wire of m. The electron-emitting material is generally made of a so-called ternary oxide of barium oxide / calcium oxide / strontium oxide. Here, these oxides are extremely unstable in air.
For this reason, in the production of the filament, in the form of a so-called carbonate of barium carbonate, calcium carbonate, and strontium carbonate, a tungsten thin wire is applied so as to have an outer shape of 22 to 35 μm. After assembling together with each part, the inside of the envelope is evacuated and oxidized at the stage of aging.

Therefore, in the conventional fluorescent display device, since the above-described filament is used as the electron emitting portion, there are the following problems. First, it is inconvenient to handle because a very thin and fragile filament must be attached and assembled. Further, as described above, the number of steps for producing the filament cathode was very large. Next, the electron flow emitted from the filament cathode depends greatly on the temperature of the filament cathode. For this reason, if the heat radiation from both ends of the filament cathode is large, the electron flow varies depending on the position of the filament. This depends on the fluorescent display device used.
This may cause unevenness in light emission from the phosphor screen. As described above, the surface of the filament cathode is coated with the electron-emitting substance, which is weak against the gas released in the vacuum vessel of the fluorescent display device, and in some cases, deteriorates in a short time. There was something.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to stably and reliably emit electrons from an electron emission portion of a fluorescent display device for a long time. The purpose is to do.

[0013]

According to a fluorescent display device of the present invention, an electron emitting portion is formed of a carbon nanotube formed of a cylindrical graphite layer, and its tip is disposed toward a fluorescent screen side. An emitter from which electrons are emitted from the tip and an electron extraction electrode for extracting electrons from the emitter arranged on the electron emission side of the emitter are provided. With this configuration, in the electron emission portion, when a potential is applied between the emitter and the electron extraction electrode, a high electric field is concentrated on the tip of the carbon nanotube, and electrons are extracted.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a configuration of an image tube which is a fluorescent display device according to an embodiment of the present invention. The structure of the picture tube according to this embodiment will be described below together with the manufacturing method. First, a face glass 102 is bonded and fixed to a cylindrical glass bulb 101 with a low-melting frit glass 103, and a vacuum vessel (envelope) Is configured. And the fluorescent screen 1
04, an anode electrode structure 105, and a cathode structure 106 constituting an electron emission portion. In addition,
Naturally, the fluorescent screen 104 and the anode electrode structure 10
5, and after disposing the cathode structure 106 constituting the electron-emitting portion, the face glass 102 is bonded and fixed to the glass bulb 101.

The face glass 102 has a convex lens-shaped spherical portion 102a formed on the front side, and a flange-shaped step portion 102b formed at the peripheral edge. Although not shown on the inner surface 102c of the face glass 102,
A recess is formed in a part of the periphery.
A fluorescent screen 104 is formed on the main surface of the inner surface 102c, and an Al metal back film 107 is formed on the surface of the fluorescent screen 104. In addition, the fluorescent screen 1 is provided in the recess.
04 is not formed, and only the Al metal back film 107 is formed. One end of a contact piece 107a having an elastic force and formed by processing a thin plate of, for example, stainless steel by press molding is inserted into the recess. The contact piece 107a is formed by, for example, bonding and fixing to a concave portion thereof with a conductive adhesive made of a mixture of carbon or silver and frit glass. The other end of the contact piece 107a extends toward the inner wall surface of the glass bulb 101, and is in contact with a cylindrical anode 105b described below.

On the inner surface 102c of the phosphor screen 104, as a white phosphor, for example, a material obtained by dissolving a mixed phosphor of Y ₂ O ₂ S: Tb + Y ₂ O ₃ : Eu in a solvent is applied to a thickness of about 20 μm. It is formed by applying and drying this. Note that the fluorescent screen 104 is not coated in the recess. An Al metal back film 107 is formed on the surface of the fluorescent screen 104 by depositing an aluminum film to a thickness of about 150 nm by vapor deposition. Here, since the fluorescent screen 104 is not applied in the above-described recess, only the Al metal back film 107 is formed.

If the thickness of the Al metal back film 107 is too small, the number of pinholes increases and the reflection of the phosphor screen 104 decreases. On the other hand, if the thickness is too large, the penetration of the electrons of the electron beam into the phosphor screen 104 is inhibited, and the light emission decreases. Therefore, the Al metal back film 10
Control of the thickness of 7 is important. Therefore, as described above, the Al metal back film 107 has a thickness of about 15
It is better to be about 0 nm. The fluorescent screen 104
After the formation of the Al metal back film 107, the face glass 102 is heated at 560.degree.
Baking in air for about 0 minutes to remove the solvents in the coating film.

The face glass 102 has, for example, a flange-like shape formed on the periphery of the face glass 102 at one open end of the glass bulb 101 having both ends cut at a diameter of about 20 mm and a length of about 50 mm. Step portion 102b
The part is bonded and fixed by the low melting point frit glass 103. On the other hand, the stem glass 108 constituting the bottom of the glass bulb 101 has a lead pin 109 inserted therethrough and an exhaust pipe 108a formed integrally therewith. On the stem glass 108, an anode lead 110 is fixed to the tip of the lead pin 109 by welding, and a cylindrical anode electrode assembly (electron acceleration electrode) 105 is fixed to the tip of the anode lead 110 by welding. The structure is arranged and mounted.

The anode electrode assembly 105 is composed of the following parts. First, a ring-shaped anode 105a is formed by rolling a metal wire (wire diameter of about 0.5 mm) of, for example, stainless steel into a ring shape. A thin stainless steel plate (having a thickness of 0.01 to
0.02 mm), and a cylindrical anode 105b formed into a cylindrical shape by fixing the overlapped portion at two points by welding or the like. The anode electrode assembly 105 is welded to the tip of the anode lead 110 at a predetermined position with the ring-shaped anode 105a. It is a structure that is fixed by welding and arranged. Further, a Ba getter 1 is provided on a part of the ring-shaped anode 105a.
05c is attached and fixed by welding or the like. In FIG. 1A, the cross section of the anode electrode structure 105 and the lead pins 109 is not shown. The above is almost the same as the conventional picture tube.

The stem glass 108 also has lead pins 109a and 109b inserted therethrough.
a, 109b are connected to the cathode leads 111a,
111b is fixed by welding.
A cathode structure 106 is fixedly arranged by welding and mounted on the distal ends of 11a and 111b. The cathode structure 106 is configured as follows. First, an electrode (conductive plate) 106b is arranged at the center on the ceramic substrate 106a. On the upper surface, as shown in an enlarged view in FIG.
In the region of φ, a needle-shaped columnar graphite (emitter) 121 having a length of several μm to several mm, which is made of an aggregate of carbon nanotubes, is fixedly arranged with its longitudinal direction substantially directed toward the fluorescent screen 104. The columnar graphite 121 is fixedly arranged by a conductive adhesive 122. A housing 106d having a mesh portion (electron extraction electrode) 106e is arranged so as to cover them.

The columnar graphite 121 is shown in FIG.
As shown in (c), the carbon nanotubes 121a
Are structures that are gathered in almost the same direction. FIG. 1C is a perspective view showing a cross section of the columnar graphite 121 cut in the middle. The carbon nanotubes 121a are completely graphitized to form a cylindrical shape, for example, as shown in FIG. 1D, and have a diameter of about 4 to 50 nm and a length on the order of 1 μm. Then, as shown in FIG. 1 (e), the tip is closed by the five-membered ring. Note that the tip may not be closed due to being on. This carbon nanotube has two carbon electrodes in helium gas of 1-2 mm.
When a direct current arc discharge occurs in a state of being separated to a certain extent, carbon on the anode side evaporates and is formed in a deposit aggregated at the tip of the carbon electrode on the cathode side.

That is, the gap between the carbon electrodes is 1 mm.
When a stable arc discharge is sustained in helium with the temperature maintained to a certain degree, a columnar deposit having a diameter substantially equal to the diameter of the carbon electrode of the anode is formed at the tip of the cathode. The columnar deposit is composed of two regions: a hard shell on the outside and a fragile black core on the inside. The inner core has a fibrous structure extending in the longitudinal direction of the sediment column. The fibrous structure is the above-described columnar graphite, and columnar graphite can be obtained by cutting out a sediment column or the like. The outer hard shell is a graphite polycrystal.

Then, in the columnar graphite,
A plurality of carbon nanotubes are aggregated together with carbon polyhedral fine particles (nanopolyhedoron). The carbon nanotube is shown in FIG.
In (e), as schematically shown, a single graphite layer is closed in a cylindrical shape, and a plurality of graphite layers are stacked in a nested structure so that each graphite layer is closed in a cylindrical shape. There are shapes that have a structure. And the center part of them is hollow.

As described above, in this embodiment, the columnar graphite 121 composed of the carbon nanotubes 120a is fixedly arranged on the electrode 106b, and the housing 106d is mounted on the ceramic substrate 106a so as to cover them. In this state, the cathode structure 106 was formed. Note that the mesh portion 106e has a shape slightly protruding in a spherical shape in the direction of the fluorescent screen 104. The mesh part 106e
May be in the form of a flat plate. Also, this housing 10
6d is formed by press forming a stainless steel plate having a thickness of about 100 μm. The mesh portion 106e is formed to have a vertical dimension of about 6 mm, a horizontal dimension of about 4 mm, and a height of about 1.25 mm. Then, the mesh portion 106e is set to be in a state of being separated from the tip of the columnar graphite 121 by about 0.5 to 1 mm. In addition, it is better to make these intervals as close as possible without contact.

The picture tube according to the present embodiment configured as described above firstly includes a lead pin 1 from an external circuit.
By supplying a voltage to the electrodes 09a and 109b, an electric field is applied between the electrode 106 and the housing 106d via the cathode leads 111a and 111b. As a result, a high electric field is concentrated on the end of the carbon nanotube of the columnar graphite 121 fixedly arranged on the electrode 106, and electrons are extracted and emitted from the mesh portion 106e. That is, in this embodiment, the cathode structure 10
No. 6 was configured as a field emission cold cathode electron source using the carbon nanotubes 121a of columnar graphite 121 as an emitter.

Then, a high voltage is supplied to the lead pin 109 from an external circuit, and the anode lead 110 → the anode electrode assembly 10
5 (cylindrical anode 105b) → Electric electrons are accelerated by the cylindrical anode 105b by conducting the respective paths of the contact pieces 107a and applying a high voltage to the Al metal back film 107, Al metal back film 10
7 and penetrates the fluorescent screen 104. As a result,
The phosphor constituting the phosphor screen 104 is excited by the electron impact, and emits a luminescent color corresponding to the phosphor.
02, and light is displayed on the front side (face glass 102 side).

As described above, according to this embodiment, the electron-emitting portion is made of carbon nanotubes, and this is used as a field emission cold cathode electron source.
Therefore, according to this embodiment, the electron-emitting portion
Since a fragile component such as a filament is not used, it is easy to handle, and there is no deterioration due to the released gas in the vacuum vessel. Also, since there is no need for a heating power supply for the filament, the number of lead pins can be reduced and power consumption can be suppressed.

In the above embodiment, the picture tube has been described, but the present invention is not limited to this. The present invention
It is needless to say that the present invention can be applied to other fluorescent display devices including a light emitting portion made of a phosphor in a vacuum vessel and an electron emission source for emitting the light. For example, the present invention can be similarly applied to a picture tube in which an optical filter is arranged between a face glass and a fluorescent screen to change the emission color. Also,
The present invention can be similarly applied to a multi-color picture tube provided with a plurality of fluorescent screens in the same vacuum vessel. Further, it is also possible to apply the present invention to a flat tube displaying a character having a desired shape by using a fluorescent screen having a desired shape.

[0029]

As described above, according to the present invention, the electron-emitting portion is formed of a carbon nanotube formed of a cylindrical graphite layer, and the tip is disposed toward the fluorescent screen side. An emitter that emits more electrons and an electron extraction electrode that is arranged on the electron emission side of the emitter and that extracts electrons from the emitter are configured. With this configuration, the electron emission section becomes a field emission type cold cathode electron source in which when a potential is applied between the emitter and the electron extraction electrode, a high electric field is concentrated on the tip of the carbon nanotube to extract electrons. .
According to the present invention, the electron-emitting portion is configured without using a fragile component such as a filament or a chemically unstable electron-emitting substance. It is difficult to deteriorate.
As a result, according to the present invention, there is an effect that electrons can be stably emitted for a long time in a highly reliable state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a picture tube according to the present invention.

FIG. 2 is a configuration diagram showing a configuration of a conventional picture tube.

[Explanation of symbols]

101: glass bulb, 102: face glass, 10
3 ... low melting point frit glass, 104 ... phosphor screen, 105 ...
Anode electrode structure, 105a: ring-shaped anode, 105b: cylindrical anode, 105c: Ba getter, 106: cathode structure, 106a: ceramic substrate, 106b: electrode (conductive plate), 106d: housing, 106e: mesh part (electron drawer) Electrode), 107 ... Al metal back film,
107a: contact piece, 108: stem glass, 108a ...
Exhaust pipe, 109, 109a, 109b ... lead pin, 1
10: anode lead, 111a, 111b: cathode lead, 121: columnar graphite (emitter), 121a
... carbon nanotube, 122 ... conductive adhesive.

Claims (14)

[Claims] 1. An envelope having a light-transmitting display surface at least partially evacuated to the inside, a phosphor screen made of a phosphor formed inside the display surface, and An electron emission portion that is disposed inside the envelope and emits electrons to the phosphor screen, wherein the electron emission portion is made of a carbon nanotube formed of a cylindrical graphite layer, and a tip portion of the carbon nanotube is formed of the carbon nanotube. An emitter disposed toward the phosphor screen and emitting electrons from the tip, and an electron extraction electrode for extracting electrons from the emitter disposed on the electron emission side of the emitter. Fluorescent display device. 2. The fluorescent display device according to claim 1, wherein the emitter is fixed with a conductive adhesive on a plate-shaped conductive plate having a surface facing the fluorescent screen. A fluorescent display device. 3. The fluorescent display device according to claim 1, wherein the emitter is made of columnar graphite made of an aggregate of the carbon nanotubes. 4. The fluorescent display device according to claim 3, wherein the columnar graphite has a tip portion arranged toward the fluorescent screen. 5. The fluorescent display device according to claim 1, wherein a predetermined potential is applied to said fluorescent screen. 6. The fluorescent display device according to claim 1, wherein the extraction electrode is disposed between the fluorescent screen and the emitter. 7. The fluorescent display device according to claim 1, wherein the extraction electrode is disposed between the fluorescent screen and the display surface. 8. The fluorescent display device according to claim 1, wherein an optical filter is disposed between said fluorescent screen and said display surface. 9. The fluorescent display device according to claim 1, wherein a metal film formed on a surface of the phosphor screen, and a metal film formed between the phosphor screen and the electron extraction electrode,
A fluorescent display device, comprising: an electron acceleration electrode to which a higher potential is applied than the electron extraction electrode. 10. The fluorescent display device according to claim 9, wherein the metal film and the electron acceleration electrode are electrically connected. 11. The fluorescent display device according to claim 1, wherein the carbon nanotube has a single layer of graphite having a cylindrical shape and a closed end. . 12. The fluorescent display device according to claim 1, wherein the carbon nanotube has a single layer of graphite having a cylindrical shape and an open end. . 13. The fluorescent display device according to claim 1, wherein said carbon nanotube has a coaxial multilayer structure in which a plurality of graphite layers are cylindrical and their ends are closed. A fluorescent display device characterized by the above-mentioned. 14. The fluorescent display device according to claim 1, wherein the carbon nanotube has a coaxial multilayer structure in which a plurality of graphite layers are cylindrical and their ends are open. A fluorescent display device characterized by the above-mentioned.