JP3608896B2 - Electron tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron tube using a field emission electron emission source, and more particularly to an electron tube having a light emitting display function.
[0002]
[Prior art]
In an electron tube having a light emitting display function such as a so-called flat panel display, a field emission type having a high electron emission density is used as an electron beam generating source instead of a hot cathode type.
[0003]
FIG. 7 is a sectional view of an electron tube using a field emitter as a field emission type electron emission source. However, in order to explain the configuration and basic operation, the electrical system and the relative arrangement of the components constituting the pixel are schematically shown. As shown in the figure, a bottomed substantially cylindrical airtight container 60 has a conductive base 64 attached to one end of an insulating side tube 62, and a glass face plate 66 and a metal holder 68 attached to the other end. It is comprised by attaching via. On the inner surface of the base 64, a needle-like field emitter 70 usually formed of a semiconductor such as Si or a refractory metal such as Mo or W is provided. Further, facing the field emitter 70, there is disposed a fluorescent screen 76 in which a conductive transparent film 70, a fluorescent layer 72, and a so-called metal back electrode 74 are sequentially formed on the inner surface of the glass face plate 66. In such an electron tube configuration, the field emitter 70 has a predetermined negative high potential with respect to the phosphor screen 76. For this reason, after electrons (e ⁻ ) are emitted from the tip of the needle of the field emitter 70, as indicated by an arrow in FIG. 7, it is accelerated and incident on the phosphor screen 76 to emit light.
[0004]
[Problems to be solved by the invention]
Incidentally, it is necessary to increase the emission current density of the field emitter 70 in order for the above-described electron tube to obtain sufficient luminance necessary for light-emitting display. However, since a large amount of Joule heat is generally generated as a result, the surface state of the field emitter 70 may change and the electron emission characteristics may change. Further, the electrons are accelerated and incident on the phosphor screen 76, whereby cations are emitted from the phosphor screen 76. This positive ion causes so-called ion feedback that collides with the field emitter 70 applied with a negative voltage with respect to the phosphor screen 76, which may change the electron emission characteristics. Such a change in the electron emission characteristics is an essential problem from the viewpoint of the stability of the operation of the electron tube.
[0005]
One method for solving such a problem is disclosed in Japanese Patent Laid-Open No. 8-241682. This publication discloses that a large number of secondary electrons obtained by multiplying electrons emitted from a field emitter by a microchannel plate (MCP) are accelerated and incident on a phosphor screen. . According to this configuration, even when the electron emission density of the field emission type electron emission source is reduced, electrons for converting into an optical image having practical luminance on the phosphor screen can be efficiently obtained by the MCP.
[0006]
However, even if the electron tube provided with the MCP has a light emitting display function, the size is determined by the size of the MCP. MCP has a complicated structure in which about 1 million glass capillaries having a diameter of about 10 μm are bundled, and is expensive. Further, even if the MCP is applied to an electron tube such as a flat panel display, the size of the MCP is currently limited to a rectangle of 10 cm × 10 cm at the maximum in manufacturing. Although it is possible to arrange MCPs having a small shape in a two-dimensional manner, the size of the MCP is determined by a glass thin tube, and secondary electrons sufficient for light emission may not be generated. Therefore, an electron tube using MCP has no practical significance.
[0007]
Accordingly, an object of the present invention is to provide an electron tube that can be put into practical use in which a field emission type electron emission source stably and efficiently emits electrons.
[0008]
[Means for Solving the Problems]
The electron tube according to the present invention is made to achieve the above object, and a field emission type electron emission source that emits electrons by applying a voltage, and a positive voltage is maintained with respect to the field emission type electron emission source, A positive voltage is maintained with respect to the transmissive secondary electron surface that multiplies electrons and emits secondary electrons from a surface different from the surface on which the electrons are incident, and the transmissive secondary electron surface. An anode including a phosphor screen for converting secondary electrons into an optical image upon incidence is provided inside the hermetic container, and the transmission type secondary electron surface is composed of diamond or diamond as a main component, and is zero or negative. It has an electron affinity.
[0009]
According to this configuration, although the transmission type secondary electron surface has a very simple structure, secondary electrons for converting into an optical image having a practical luminance on the phosphor screen are efficiently converted. Can be generated. For this reason, the voltage applied to the field emission electron emission source can be lowered, and the field emission current can also be reduced. Therefore, the defined operation of the field emission type electron emission source is realized. Further, since the transmission type secondary electron surface is made of polycrystalline diamond or polycrystalline diamond as a main component, it is advantageous in terms of mass production and production cost. Furthermore, since the secondary electrons spread in the transmissive secondary electron plane is only a few μm at the maximum, a position detection function is also provided.
[0010]
Further, the field emission electron emission source may be made of diamond or a material mainly composed of diamond, and may have zero or negative electron affinity.
[0011]
As a result, the potential barrier becomes thin and a tunnel effect is likely to occur, and the electron emission characteristics are improved.
[0012]
In addition, the field emission electron emission sources may be arranged one-dimensionally or two-dimensionally so that the electron tube of the present invention has a one-dimensional or two-dimensional display function. Alternatively, the field emission type electron emission source and the transmission type secondary electron surface may be arranged one-dimensionally or two-dimensionally.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.
[0014]
FIGS. 1 to 3 are cross-sectional views schematically showing an electrical system and a relative arrangement of components constituting a pixel in order to explain the configuration and basic operation of an embodiment of an electron tube according to the present invention. FIG.
[0015]
FIG. 1 is a cross-sectional view of a first embodiment of the electron tube of the present invention. As shown in FIG. 1, the bottomed substantially cylindrical airtight container 10 has a conductive base 14 attached to one end of an insulating side tube 12 and a glass face plate 16 made of metal at the other end. It is comprised by attaching via the holder 20. A needle-like field emitter 20 is provided on the inner surface of the base 13 as a field emission electron source. The field emitter 20 is made of polycrystalline diamond. This is because diamond not only has thermal resistance, but also has zero or negative electron affinity depending on the surface state. In particular, in this embodiment, hydrogen (not shown) terminates on the diamond surface, and its electron affinity is zero or negative. As a result, the potential barrier of diamond is reduced to such an extent that the tunnel effect is likely to occur, and the electron emission characteristics of the field emitter 20 are improved.
[0016]
However, such field emitters are not limited to those made of polycrystalline diamond terminated with hydrogen. For example, in a material mainly composed of a carbon-based material, that is, amorphous diamond-like carbon having sp ³ hybrid orbital and sp ² hybrid orbital, glassy carbon having a one-dimensional chain structure of carbon atoms, etc. Of course, the same effect can be obtained. However, it is difficult to produce diamond-like carbon or glassy carbon having a certain quality. Therefore, polycrystalline diamond having a low quality and stable quality is suitable at present.
[0017]
A fluorescent screen 22 is formed on the inner surface of the glass face plate 16. That is, a conductive transparent film 24 made of ITO or the like is formed on the inner surface of the glass face plate 16, a highly insulating fluorescent layer 26 is deposited on the conductive transparent film 24, and further on the fluorescent layer 26. Is attached so that a so-called metal back electrode 28 made of Al or the like is electrically connected to the conductive transparent film 24.
[0018]
Between the field emitter 20 and the phosphor screen 22, a transmission type secondary electron surface 32 having an annular reinforcing frame 30 made of Si attached to the lower peripheral edge portion is provided through the wall of the side tube 12. The stem pin 34 is supported. The transmission secondary electron surface 32 is made of a thin film of polycrystalline diamond. Therefore, since the electron affinity becomes zero or negative depending on the state of the thin film surface, the secondary electron generation efficiency is high. Further, since the secondary electrons spread only within the maximum several μm in such a transmissive secondary electron surface 32, a position detection function superior to MCP is also provided.
[0019]
Here, the reason why the polycrystalline diamond is used is that it is advantageous in terms of mass production and production cost. Similar to the diamond of the field emitter 20, the diamond surface constituting the transmission type secondary electron surface 32 is terminated with hydrogen (not shown) so as to have a negative electron affinity. The diamond thin film is preferably doped with boron (B) and has p-type conductivity. This is because, according to the experimental results, such a diamond thin film has a higher secondary electron generation efficiency.
[0020]
In the configuration as described above, as shown in FIG. 1, the transmissive secondary electron surface 32 is set to a predetermined positive potential with respect to the field emitter 20. Further, the phosphor screen 22 is set to a predetermined positive potential with respect to the transmissive secondary electron surface 32, and the phosphor screen 22 also functions as an anode. As a result, the electrons (e ⁻ ) of the field emitter 20 do not directly enter the phosphor screen 22 but are once incident on one surface of the transmission-type secondary electron surface 32 to be multiplied by the secondary electrons and then emitted from the other surface. Will come to be. This means that even if the negative potential of the field emitter 20 relative to the transmissive secondary electron surface 32 is relatively small, that is, the electron emission density of the field emitter 20 is reduced, the kinetic energy is lost in the phosphor screen 22. This means that a large number of secondary electrons for causing the phosphor screen 22 to emit light are generated by the transmissive secondary electron surface.
[0021]
For this reason, an essential phenomenon hardly occurs for an electron tube using field emission. For example, the generation of Joule heat is suppressed. Moreover, the ions on the phosphor screen 22 are hardly adsorbed on the surface of the field emitter 20 by so-called ion feedback. For this reason, in the case of the field emitter 20 made of diamond, the hydrogen that has terminated the diamond surface hardly occurs. Further, residues other than hydrogen in the hermetic container 10 are hardly adsorbed on the surface of the field emitter 20. As a result, the change in work function on the surface of the field emitter 20 can be ignored, and the electron emission characteristics of the field emitter 20 are maintained almost constant.
[0022]
Although the above-described field emitter 20 is not illustrated, it is manufactured as follows, for example. First, a silicon substrate is prepared, and a polycrystalline diamond thin film having a thickness of about 20 μm is formed on this (100) surface by microwave CVD. Then, when a spot-like photoresist film having a diameter of about 10 μm is formed, and this is used as a mask and processed with ECR plasma, a field emitter having a pointed shape is obtained.
[0023]
In addition, the transmission type secondary electron surface 32 is produced by a microwave plasma chemical vapor deposition (hereinafter referred to as “microwave plasma CVD”) method according to FIGS.
[0024]
First, a Si substrate 36 having a diameter of 2 inches is prepared and placed in a deposition chamber of a microwave plasma CVD apparatus. The reason why this Si substrate 36 is used is that it is advantageous in producing a diamond thin film because the quality is stable. Next, when hydrogen as an excitation gas is introduced into the deposition chamber, it is brought into a plasma state by microwaves. In this state, methane (CH ₄ ), which is a raw material for the diamond thin film, is introduced into the deposition chamber. At this time, CH ₄ is dissociated by hydrogen ions in the vicinity of the deposition chamber inlet, and polycrystalline diamond 38 is deposited with a uniform thickness of about 5 μm on the Si substrate 36 (FIG. 4A). )reference). Note that diborane (B ₂ H ₆ ) as a dopant gas may be introduced into the deposition chamber together with CH ₄ in order to deposit polycrystalline diamond having a p-type conductivity.
[0025]
Next, a photoresist 40 is applied to the lower surface of the Si substrate 36 (see FIG. 4B), and a 40 mm × 40 mm rectangular mask (not shown) is disposed in the central portion of the photoresist 40. Photolithography is performed in this state, and thereafter, the photoresist 40a that has not been exposed by the mask is removed (see FIG. 4C).
[0026]
Next, the Si substrate 36 is removed by etching with a hydrofluoric acid + nitric acid (HF + HNO ₃ ) mixed solution (see FIG. 4D). Thereafter, when the photoresist 40b at the lower periphery of the Si substrate 36 is removed, a 40 mm × 40 mm rectangular transmissive secondary electron surface 32 is obtained with the Si substrate 36 attached as a reinforcing frame 30 at the lower periphery. become.
[0027]
However, the size of the transmissive secondary electron surface is not limited to the above. However, in order to obtain a larger area than the transmission type secondary electron surface, the rigidity of the transmission type secondary electron surface needs to be further supplemented. Therefore, in addition to attaching the Si substrate as the reinforcing means to the peripheral portion of the polycrystalline diamond thin film, it is necessary to attach a lattice-like or spiral reinforcing means to the polycrystalline diamond thin film. Furthermore, the film thickness of the polycrystalline diamond thin film is not limited to the above. In consideration of the potential between the field emitter 20 and the transmissive secondary electron surface 32, the film thickness should be determined so that as many secondary electrons as possible are incident on the phosphor screen 22. Moreover, although the Si substrate has been described as means for reinforcing the polycrystalline diamond thin film, a substrate made of a refractory metal such as molybdenum (Mo) or copper (Cu) may be used. This is because a high-quality polycrystalline diamond thin film can be deposited as with the Si substrate.
[0028]
Furthermore, although not shown, the electron tube of the present embodiment is assembled as follows.
[0029]
First, the field emitter 20 is disposed on the base 14. Further, a conductive transparent film 24 made of ITO or the like is formed on the inner surface of the glass face plate 16, a fluorescent layer 26 is deposited thereon, and a so-called metal back electrode 28 made of Al or the like is provided on the fluorescent layer 26 with a conductive transparent The film 24 is deposited so as to be electrically connected to the film 24. In addition, the side pipe | tube 12 with which the stem pin 34 was provided through the wall body is prepared.
[0030]
Next, the transmission type secondary electron surface 32 described above is attached to the stem pin 34 via the reinforcing frame 30. Thereafter, the base 22 is hermetically attached to one end of the side tube 12 so that the field emitter 20 is installed in the side tube 12, and the glass face plate 16 is mounted so that the phosphor screen 22 is installed in the side tube 12. Attached to the other end of the side tube 12 in an airtight manner. In this state, the inside of the hermetic container 18 is evacuated and then vacuum-sealed with an adhesive to obtain the above-described electron tube.
[0031]
FIG. 2 is a cross-sectional view of a second embodiment of the electron tube of the present invention. Unlike the electron tube of the first embodiment, this electron tube is provided with a ring-shaped gate electrode 44 around the field emitter 20 via a ring-shaped insulator 42. The gate electrode 44 is connected to one end of the stem pin 46 of the side tube 12, and the other end extends outside through the wall of the side tube 12. The gate electrode 44 is set to a positive potential with respect to the field emitter 20 by the stem pin 46. Therefore, the electron tube of the second embodiment can control the electrons from the field emitter 20 by the gate electrode 44.
[0032]
FIG. 3 is a cross-sectional view of a third embodiment of the electron tube of the present invention. In this electron tube, a ring-shaped converging electrode 50 is provided via a ring-shaped insulator 48 on the gate electrode 44 of the electron tube of the second embodiment. The converging electrode 50 is connected to the stem pin 52 and has a negative potential with respect to the gate electrode. In this electron tube, electrons from the field emitter 20 are controlled by the gate electrode 44 and then decelerated by the converging electrode 50, so that a lens effect is produced. Therefore, the electrons that have passed through the focusing electrode 50 are converged and the spatial resolution is improved.
[0033]
The electron tubes according to the first to third embodiments described above are for easily explaining the relative arrangement and basic operation of components constituting the electrical system and the pixel. Therefore, it goes without saying that the components constituting the pixel need to be arranged one-dimensionally or two-dimensionally in order to enable light-emitting display.
[0034]
FIG. 5 is a schematic perspective view of a so-called flat panel display in which the pixels of the electron tube of the first embodiment are two-dimensionally arranged and function as a display element. In this figure, a single phosphor screen 22 is disposed opposite to field emitters arranged in a two-dimensional manner with a pitch width of 100 μm. A transmissive secondary electron surface 32 having a film thickness of about 2 μm and a diameter of 10 to 150 μm is two-dimensionally arranged between each field emitter and the phosphor screen. In addition, these parts mentioned above shall be accommodated in the airtight container which is not illustrated. Each pixel is selectively driven by a so-called static drive system having a switch circuit (not shown) independently. However, a dynamic drive system that performs repetitive drive by time division may be used.
[0035]
In such a display element, electrons can be emitted from a field emitter 20 of an arbitrary pixel, for example, a pixel whose address is X ₂ Y ₂ , and can be displayed on the phosphor screen 22. For this purpose, first, a switch circuit of a pixel whose address is X ₂ Y ₂ applies a predetermined potential to the field emitter 20, the phosphor screen 22 and the transmissive secondary electron surface 32 of the pixel via a control device (not shown). Then, electrons (e ⁻ ) are emitted from the field emitter 32. The electrons are multiplied by secondary electrons on the transmissive secondary electron surface 32 and are emitted from the transmissive secondary electron surface 32 as a secondary electron group. The secondary electron group collides with a specific position on the phosphor screen 22, and light is emitted.
[0036]
However, the flat panel display is not limited to that shown in FIG. FIG. 6 is a schematic perspective view of a flat panel display in which each pixel having the gate electrode 44 of the electron tube of the second embodiment is two-dimensionally arranged. Here, unlike the electron tube of FIG. 5, since it has the single transmissive | pervious secondary electron surface 32, a structure becomes simple and an assembly etc. become easy.
[0037]
In addition, a flat panel display is not limited to these, You may equip each pixel with the convergence electrode like the electron tube of 3rd Embodiment. Further, it can be applied not only to a flat panel display but also to a display having a one-dimensional line display function, and it goes without saying that the number of pixels is not limited. Furthermore, if the fluorescent screen emits light of each color of R, G, and B, a color display body can be obtained.
[0038]
【The invention's effect】
The electron tube of the present invention can efficiently generate secondary electrons for conversion into an optical image having a practical luminance on the fluorescent screen by a transmission type secondary electron surface having a very simple structure. Therefore, the field emission type electron emission source can operate stably without changing its state with a low electron emission density, so that the life of the electron tube can be extended.
[0039]
Moreover, it is easy to increase the area of such a transmissive secondary electron surface. Therefore, the electron tube of the present invention can perform light emission display with a large area as, for example, a flat panel display.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a first embodiment of an electron tube of the present invention.
FIG. 2 is a cross-sectional view schematically showing a second embodiment of the electron tube of the present invention.
FIG. 3 is a cross-sectional view schematically showing a third embodiment of the electron tube of the present invention.
4 is a cross-sectional view showing a part of a process for manufacturing the transmission type secondary electron surface of FIGS. 1 to 3; FIG.
FIG. 5 is a perspective view schematically showing a flat panel display in which the electron tubes of the first embodiment are two-dimensionally arranged.
FIG. 6 is a perspective view schematically showing a flat panel display in which the electron tubes of the second embodiment are two-dimensionally arranged.
FIG. 7 is a cross-sectional view schematically showing a conventional electron tube.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Airtight container, 20 ... Field emitter, 22 ... Phosphor screen, 30 ... Reinforcement frame, 32 ... Transmission-type secondary electron surface, 44 ... Gate electrode, 50 ... Focusing electrode.

Claims (4)

A field emission electron emission source that emits electrons when a voltage is applied;
A transmissive secondary electron surface that maintains a positive voltage with respect to the field emission electron emission source, and that multiplies the electrons to emit secondary electrons from a surface different from the surface on which the electrons are incident;
An anode including a phosphor screen that holds a positive voltage with respect to the transmissive secondary electron surface and converts the secondary electrons into an optical image by incidence of the secondary electrons;
With airtight container inside,
An electron tube characterized in that the transmission-type secondary electron surface is made of polycrystalline diamond or polycrystalline diamond as a main component and has zero or negative electron affinity. 2. The electron tube according to claim 1, wherein the field emission type electron emission source is made of diamond or one containing diamond as a main component and has zero or negative electron affinity. 3. The electron tube according to claim 1, wherein the field emission electron emission sources are arranged one-dimensionally or two-dimensionally. 3. The electron tube according to claim 1, wherein the field emission electron emission source and the transmission type secondary electron surface are arranged one-dimensionally or two-dimensionally.

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