JPH09283007A - Field emission element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a field emission element which can be driven by a low anode voltage. SOLUTION: A field emission cathode is made up as follows: on a cathode electrode 2 is formed on a cathode substrate 1 composed of glass, etc., emitters 5 are formed into a shape of cone. The area where the emitters 5 are not formed on the cathode electrode 2, are formed insulating layers 3 on which first gate electrodes 4 are formed, and the field emission cathode thus constituted. Second gate electrodes 11 are arranged, and above the second gate electrodes is arranged an anode electrode 9. To the second gate electrodes 11 is applied a voltage equal to that of the first gate electrode 4. In the space between the second gate electrodes 11 and the field emission cathode, a spatial electric charge saturation area is produced. In this state, by the application to the anode electrode 9 of only such a low voltage as several tens volts, electron can be attracted from the said spatial electric charge saturation area to the anode electrode 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission device utilizing field emission.

[0002]

2. Description of the Related Art An electric field applied to a metal or semiconductor surface is 10
^At about ⁹ [V / m 2], electrons pass through the barrier due to the tunnel effect and are emitted in a vacuum even at room temperature. This is called field emission, and a cathode that emits electrons based on such a principle is called a field emission cathode (F).
EC). In recent years, it has become possible to manufacture a surface emission type FEC in which micron-sized field emission cathodes are integrated in an array by making full use of semiconductor processing technology.

FIG. 7 (a) shows an example of the Spindt (Sp
ind) type is shown. In this figure, a cathode 102 made of metal such as aluminum is provided on a cathode substrate 101 such as glass, and a cone-shaped emitter 105 made of metal such as molybdenum is formed on the cathode 102. An insulating layer 103 made of silicon dioxide (SiO ₂ ) or the like is formed on a portion of the cathode 102 where the emitter 105 is not formed, and a gate electrode 104 is further formed thereon. An opening 106 is provided in the gate electrode 104 and the insulating layer 103, and the cone-shaped emitter 105 is located in the opening 106. That is, the tip of the cone-shaped emitter 105 faces the opening 106.

The pitch between the cone-shaped emitters 105 can be set to 10 μm or less, and tens of thousands to hundreds of thousands of emitters 105 can be provided on one substrate. Further, since the distance between the gate electrode 104 and the tip of the cone of the emitter 105 can be set in submicron units, a gate-emitter voltage Vg of only several tens of volts is applied between the gate electrode 104 and the emitter 105. As a result, electrons can be field-emitted from the emitter 105. If the anode electrode 109 to which the positive voltage Va is applied is provided opposite to the gate electrode 104, electrons emitted from the emitter 105 by field emission can be collected by the anode electrode 109. In this case, if a phosphor is provided on the anode electrode 109, a portion of the phosphor of the anode electrode 109 where electrons emitted from the emitter 105 are collected can be emitted. By using such a principle, a display element using FEC can be manufactured. This display element is called a field emission display (FED).

Further, in such an FED, there is also proposed an FED in which spread of electrons emitted from the emitter 105 is prevented and leakage light emission does not occur even when high-definition display is performed. An example of the structure of such an FED is shown in FIG. In this figure, FIG.
The same numbers are given to the same components as in (a), and duplicate explanations will be omitted. As shown, this FED
In addition, the insulating layer 103 is also formed on the gate electrode 104.
And a second gate electrode 107 is provided thereon. The second gate electrode 107 has a cathode 10
2, that is, the negative voltage Vg2 is applied to the emitter 105, which is different from the above-mentioned FED.

In this way, the second electrode is formed above the gate electrode 104.
By providing a gate electrode 107 for the second gate electrode and applying a negative voltage Vg2 to the second gate electrode, the orbits of the electrons emitted from the emitter 105 are converged by the second gate electrode 107 and the anode electrode 109 is formed. Will be reached. As a result, the area of the display device where electrons are projected onto the anode electrode can be narrowed, and leakage light emission can be prevented.

An FED capable of color display using such an FEC has been proposed (Japanese Patent Application No. 6-24891).
issue). An example of the structure of this FED is shown in FIG. In this figure, reference numeral 108 denotes a phosphor provided on the lower surface of a transparent anode electrode 109 formed on one surface of an anode substrate 110. As shown, the phosphors 108 corresponding to the three primary colors RGB are striped. It is formed into a shape. Further, on the cathode substrate 101, stripe-shaped cathode electrodes 102 are formed in a direction orthogonal to each stripe of the phosphor 108, and a plurality of cathode electrodes 102 are formed on the cathode electrodes 102 at positions facing the phosphors 108. A cone-shaped emitter 105 is provided.

Further, a first electrode is formed on the cathode electrode 102.
Gate electrodes 104 are provided in a stripe shape so as to be orthogonal to the cathode electrode 102, and G1-1, G2
-1 indicates a stripe of the first gate electrode.
In addition, each stripe G1- of the first gate electrode 104
1, the emitter 10 in the opening opened in G1-2
5 is located. And each of the first
Each of the stripes G1-1 and G1-2 of the gate electrode 104 of
The second gate electrode 107, which serves as a focusing electrode, is provided on the G2-R so as to correspond to the RGB phosphors 108.
1, G2-G1 and G2-B1 are provided respectively, and openings are also formed in these second gate electrodes corresponding to the positions where the emitter 105 is formed.

In the color FED configured as described above, any one of the cathode electrode, the first gate electrode and the second gate electrode is supplied with a line scanning electrode and image data for supplying a voltage corresponding to the image data. Color display can be performed by using an electrode and a color pixel selection electrode for selecting RGB color pixels. For example, the cathode electrode is a line scanning electrode, the first gate electrode is an image data electrode, The second gate electrode can be a color pixel selection electrode.

Further, the FED shown in FIG.
, The second corresponding to each emitter 105
The second gate electrode (converging electrode) can be formed for each array (emitter array) of a plurality of emitters corresponding to each pixel. FEDs have been proposed (Japanese Patent Laid-Open No. 7-104679).

FIG. 8B is a diagram showing the structure of this FED. As shown in this figure, the second gate electrode 107
Are formed in a lattice shape so as to surround the array of the plurality of emitters 105. Further, in this example, the anode electrode 109 and the first gate electrode 104 have the same positive potential, and the second gate electrode 107 has a negative potential. 1 for the cathode electrode 102 as shown
A plurality of emitters 105 forming a pixel is a unit region arranged thereon, and 120 is a cathode electrode 1.
02 for matrix driving (Thin Film Tr
ansister: thin film transistor) part. Electrons emitted from the selected unit area are focused on the focusing electrode 10
The anode 109 is converged by 7 and does not diffuse.
It will impinge on the phosphor 108 formed in the above.

[0012]

[Problems to be Solved by the Invention]
In the ED, it was necessary to apply a considerably high voltage of about 200 [V] or more to the anode electrode. Therefore, if the anode electrode is divided into stripes or the like in order to select the light-emitting portion and then sequentially selected for light-emission display, switching at high voltage becomes difficult and the configuration of the drive circuit becomes difficult. Inconvenience such as dielectric breakdown occurs due to switching. Therefore, also in the example shown in FIG. 8A, the light emitting region is not selected by the anode electrode. Further, as shown in FIG. 8B, when the light emitting region is selected by the TFT portion, there is a drawback that the substrate structure becomes complicated and the cost becomes high.

Therefore, an object of the present invention is to provide a field emission device that can be driven with a low anode voltage. Lowering the anode voltage facilitates switching at the anode. Since the emission brightness of the phosphor in the display element is determined by the product of the anode voltage and the anode current, a predetermined brightness can be obtained by increasing the anode current by the amount that the anode voltage is lowered.

[0014]

In order to achieve the above object, the field emission device of the present invention comprises a cathode electrode formed on a substrate, an emitter formed on the cathode electrode, and an emitter formed on the cathode electrode. An extraction gate electrode for extracting electrons, a cutoff electrode arranged above the emitter for controlling whether or not the extraction gate electrode allows the electrons extracted from the emitter to pass, and an anode electrode. I have. The emitter is composed of an array of cone-shaped emitters.

Further, the cutoff electrode is a thin film or a metal plate formed on the extraction gate electrode via an insulating layer, and an opening is formed immediately above the array of the cone-shaped emitters. It is configured by. Furthermore, the cut-off electrode is formed in an XY matrix on the extraction gate electrode so that the electric field just above a specific region in the array of the cone-shaped emitters can be changed. There is something.

Furthermore, the cut-off electrode is applied with a lower potential than at least the gate electrode when cutting off electrons, and when passing electrons, the cut-off electrode is more than the anode electrode. A high potential is applied.

Since the cutoff electrode is formed above the emitter, a space charge saturation region is formed between the cutoff electrode and the emitter, and electrons emitted from the emitter reach the anode electrode at a lower anode voltage than before. Will be able to.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration diagram of a field emission device of the present invention. In this figure, 1 is a cathode substrate made of glass or the like, 2 is a cathode electrode made of a metal such as aluminum on the cathode substrate, and 5 is a cone-shaped substrate made of a metal such as molybdenum on the cathode electrode 2. It is an emitter. 3 is an insulating layer formed in a region on the cathode 2 where the emitter 5 is not formed, 4 is the insulating layer 3
It is a first gate electrode (lead-out gate electrode) formed above. The above configuration is the same as the conventional FEC.

Further, 10 is an anode substrate made of glass or the like, and 9 is ITO (Indium Tin Oxi) on the anode substrate 10.
de) and the like are transparent anode electrodes. 1
Reference numeral 1 denotes a second gate electrode (cutoff electrode) newly provided according to the present invention, which is provided at an intermediate position between the first gate electrode 4 and the anode electrode 9.

It should be noted that the point shown in FIG.
The second gate electrode (converging electrode) shown in (b) or FIG. 8 is formed at a position close to the first gate electrode (extracting gate electrode), for example, at a distance of about 1 μm from the extracting gate electrode. On the other hand, the second gate electrode (cutoff electrode) in the present invention is arranged at a position with a larger distance (about 2 μm or more) from the extraction gate electrode. Further, as will be described later, in the conventional focusing electrode, a negative potential is applied in order to converge the trajectories of the electrons emitted from the emitter, but the cutoff electrode of the present invention is usually used as the extraction gate electrode. When the voltage is set to the same potential and the voltage is lower than that of the extraction gate electrode, the emitted electrons are prevented from passing through. That is, it can be said that the second gate electrode (cut-off electrode) of the present invention corresponds to, so to speak, a grid electrode in a vacuum tube or a fluorescent display tube.

The operation characteristics of the field emission device thus constructed will be described with reference to the simulation results shown in FIGS. 5 and 6. FIG. 5A is a diagram showing the dimensions of each part. As shown in the figure, in this example,
The diameter of the bottom of the emitter 5 is 1 μm, the distance between the emitter 5 and the first gate electrode 4 is 1 μm, the diameter of the opening of the first gate electrode is 1.2 μm, the first gate electrode 4 and the second gate electrode 4 are The thickness of the gate electrode is 0.4 μm, and the diameter of the opening of the second gate electrode is 100 μm. Under these conditions, the voltage Vg is applied between the cathode electrode 2 and the first gate electrode 4, the voltage Vc is applied between the cathode electrode 2 and the second gate electrode 11, and the cathode electrode 2 and the anode electrode 9 are applied. When a voltage Va is applied between and, the trajectory of the electrons emitted from the emitter 5 becomes, for example, as shown in (b) of FIG.

At this time, the second gate electrode 11 and the first gate electrode 11
Of the emitter current (Ie) and the anode current (Ia) when the distance L1 between the gate electrode 4 and the second gate electrode 11 and the distance L2 between the anode electrode 9 are changed. Is shown in FIGS. 6 (a) and 6 (b). At this time, each voltage is set as follows. Vg1 = Vg2 = 90 [V] Va = 30 [V] Further, the width of the anode electrode is 100 μm which is the same as the opening of the second gate electrode.

FIG. 6A shows the emitter current (Ie) and the anode current (Ie) with respect to the values of the distances L1 and L2.
FIG. 6B is a table showing the values of a), and FIG. 6B shows the anode current (Ia) and the emitter current (I) when the distance L2 is changed.
It is a graph which shows the ratio with e). Here, the emitter current (Ie) corresponds to the total amount of electrons emitted from the emitter 5, and the anode current (Ia) corresponds to the amount of electrons reaching the anode electrode 9.

From FIG. 6B, under the above-mentioned conditions, the distance L between the second gate electrode 11 and the anode electrode 9 is L.
It can be seen that when 2 is smaller than 100 μm, 50% or more of the electrons emitted from the emitter 5 reach the anode electrode. Therefore, only 3
It can be seen that the anode current Va that is as low as 0 [V] provides a sufficient anode current for practical use.

In the field emission device of the present invention, a second gate electrode (cut-off electrode) is provided between the first gate electrode (lead-out gate electrode) and the anode electrode, and the second gate electrode is provided with the above-mentioned. By applying a gate voltage Vg2 that is substantially equal to the gate voltage Vg1 applied to the first gate electrode, a space charge saturation region is formed between the second gate electrode and the emitter, and the space is saturated at the anode, which is lower than before. Electrons are made to reach the anode by applying an anode voltage. With this configuration, the number 1
It is possible to have an anode voltage of 0 volts.

FIG. 3 shows a sectional view of an embodiment in which the field emission device of the present invention is applied to a display device. In this figure, 8 is a phosphor layer formed below the anode electrode. An insulating layer 3 is formed on the first gate electrode (lead-out gate electrode) 4 so as to surround an emitter array composed of a plurality of emitters corresponding to one pixel, and the second insulating layer 3 is formed on the insulating layer 3. A gate electrode (cutoff electrode) 11 is formed. The insulating layer 3 formed between the first gate electrode 4 and the second gate electrode 11 is larger than the insulating layer 3 formed between the cathode electrode 2 and the first gate electrode 4. It is formed thick and has the above-described gate-to-gate distance. in this way,
A second gate electrode 11 is formed so as to surround an emitter array including a plurality of emitters forming one pixel.

A gate voltage Vg of several tens of volts is applied to the first gate electrode (extract gate electrode) 4, and an anode voltage Va of several tens of volts is applied to the anode electrode 9. Further, as shown in the figure, a cutoff voltage Vc based on the potential of the first gate electrode 4 is applied to the second gate electrode (cutoff electrode), and this cutoff voltage Vc is set to 0 volt. When the voltage Vg is applied to the second gate electrode 11, the electrons emitted from the emitter reach the anode electrode 9 and the phosphor 8 emits light as described above. Further, when the cutoff voltage Vc is set to a predetermined potential other than 0 volt, the second gate electrode 11 becomes a voltage lower than the first gate electrode 4 by the cutoff voltage Vc and is emitted from the emitter 5. The electrons do not pass through the second gate electrode 11 to reach the anode, and the phosphor 8 does not emit light.

As described above, by switching the cutoff voltage Vc, it becomes possible to control light emission and non-light emission. For example, the anode electrode is formed solid and a constant voltage is applied to the anode electrode and the first gate electrode. Then, an XY matrix can be formed by the cathode electrode and the second gate electrode to form a matrix display device.

Further, as described above, according to the field emission device of the present invention, it is possible to operate at a low anode voltage of several tens of volts. Therefore, by forming the anode electrode in a predetermined pattern shape, the anode voltage is reduced. It becomes possible to select using. Therefore, when the field emission device of the present invention is used, it is possible to adopt the same driving method as in the following fluorescent display tube. (1) A solid anode electrode is formed, and a constant voltage is supplied to the anode electrode and the second gate electrode. And
A display position is selected by a matrix of the cathode electrode and the first gate electrode. (2) The anode electrode is formed in a predetermined pattern shape, the pattern is selected by the anode voltage, and the first gate voltage, the second gate voltage, and the cathode voltage are set to constant voltages. Then, the pattern for light emission is selected according to the anode voltage.

Next, another embodiment in which the field emission device of the present invention is applied to a display device will be described with reference to FIG. In this embodiment, two second anode electrodes are provided in a direction orthogonal to each other. 3A is a cross-sectional view of this embodiment, and FIG. 3B is a perspective view. In these drawings, 12 is a third gate electrode provided above the second gate electrode with the insulating layer 3 interposed therebetween in a direction orthogonal to the second gate electrode 11. As shown in FIG. 6B, the second gate electrodes 11 X1 and X
2 and the third gate electrodes 12 Y1 and Y2 surround the four sides of the emitter array.

With this structure, the second gate electrode 11 and the third gate electrode 12 can form a matrix. That is, the second gate electrode 1
A matrix display device can be configured by using one of the first and third gate electrodes 12 as a scanning electrode and supplying image data to the other. In this case, it suffices to apply a fixed voltage to all the other electrodes, which facilitates driving and simplifies the structure. Further, since it is not necessary to perform switching, a high voltage can be easily applied and the emission current can be increased. The configuration of this embodiment is suitable for a graphic display device.

FIG. 4 is a diagram showing another embodiment of the present invention. In this embodiment, the anode electrode is formed in a stripe shape, and the anode electrode and the second gate electrode form a matrix. In this case, the first gate electrode and the cathode electrode can be solidly formed, which simplifies the structure. This structure is suitable for a graphic display device.

In each of the above-mentioned embodiments,
The second gate electrode (cut-off electrode) 11 is provided corresponding to the array of the plurality of cone-shaped emitters 5, but the present invention is not limited to this, and the cut-off electrode 11 is provided for each cone-shaped emitter 5. It can also be formed.

Further, although the case where the field emission device of the present invention is applied to a display device has been described above as an example, the present invention is not limited to this, and the field emission device of the present invention can be applied to other devices such as a sensor. Can also be applied.

[0035]

As described above, according to the field emission device of the present invention, since the anode voltage can be lowered to several tens of volts, a low voltage operation close to that of a fluorescent display tube can be performed. Further, since the anode voltage is low, a high breakdown voltage drive circuit is not required when selecting the anode, so that it is possible to inexpensively produce a high-definition graphic display element. Furthermore, since it is not necessary to make a selection by using the extraction gate electrode, a drive circuit having a high breakdown voltage is unnecessary, a high voltage can be easily applied, and a sufficient discharge current can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a field emission device of the present invention.

FIG. 2 is a cross-sectional view for explaining an embodiment in which the field emission device of the present invention is applied to a display device.

FIG. 3 is a diagram for explaining another embodiment in which the field emission device of the present invention is applied to a display device.

FIG. 4 is a diagram for explaining an example of a driving method when the field emission device of the present invention is applied to a display device.

FIG. 5 is a diagram for explaining the operation of the field emission device of the present invention.

FIG. 6 is a diagram for explaining the operation of the field emission device of the present invention.

FIG. 7 is a diagram for explaining a conventional field emission device.

FIG. 8 is a diagram for explaining a conventional field emission display element.

[Explanation of symbols]

1, 101 cathode substrate 2, 102 cathode electrode 3, 103 insulating layer 4, 104 first gate electrode (extracting gate electrode) 5, 105 emitter 6, 106 opening 8, 108 phosphor layer 9, 109 anode electrode 10, 110 Anode Substrate 11 Second Gate Electrode (Cutoff Electrode) 12 Third Gate Electrode (Cutoff Electrode) 107 Second Gate Electrode (Converging Electrode) 120 in Conventional Technology 120 TFT Section

Claims (6)

[Claims] 1. A cathode electrode formed on a substrate, an emitter formed on the cathode electrode, an extraction gate electrode for extracting electrons from the emitter, and an extraction gate electrode disposed above the emitter. A field emission device having a cut-off electrode for controlling whether or not an electron extracted from the emitter is allowed to pass by a gate electrode, and an anode electrode. 2. The emitter according to claim 1, wherein the emitter comprises an array of cone-shaped emitters.
The field emission device described. 3. The cut-off electrode is a thin film or a metal plate formed on the extraction gate electrode via an insulating layer, and has an opening formed immediately above the array of the cone-shaped emitters. The field emission device according to claim 2, wherein the field emission device is configured by: 4. The cutoff electrode is formed in an XY matrix on the extraction gate electrode,
The field emission device according to claim 2, wherein the electric field immediately above a specific region in the array of the cone-shaped emitters can be changed. 5. The cutoff electrode according to claim 1, wherein at the time of cutting off electrons, a potential lower than that of the gate electrode is applied. Field emission device. 6. The field emission according to claim 1, wherein the cut-off electrode is applied with a higher potential than the anode electrode when passing electrons. element.