Electric lamp and discharge devices – Discharge devices having a multipointed or serrated edge...
Reexamination Certificate
1999-08-25
2004-09-21
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Discharge devices having a multipointed or serrated edge...
C313S310000, C313S311000
Reexamination Certificate
active
06794805
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission electron source that emits an electron beam through strong electric field emission using a semiconductor material, and its production and use, and is an improvement of U.S. patent application Ser. No. 09/140,647 (Field emission electron source array, and its production and use), now U.S. Pat. No. 6,249,080, issued Jun. 19, 2001, of which the contents are incorporated in their entirety herein by reference.
2. Description of the Related Art
The present inventors proposed a planar field emission electron source produced by forming a porous polycrystal silicon layer that is processed by thermal oxidation on an electrically conductive substrate, and forming surface electrodes made of thin metal films on the thermally oxidized porous polycrystal silicon layer (Japanese Patent Application No. 65592/1998). The field emission electron source emits electrons through the surface of the surface electrode by applying a direct current voltage across the surface electrode and the conductive substrate, with the surface electrode serving as the positive electrode, and applying a direct current voltage across the surface electrode and a collector electrode that is disposed to oppose the surface electrode, with the surface electrode serving as the negative electrode.
A display apparatus that utilizes the field emission electron source of this type comprises a glass substrate
33
disposed to oppose the surface electrodes
7
of the field emission electron source
10
′ as shown in
FIG. 22
, while collector electrodes
31
formed in the form of stripes on a surface of the glass substrate
33
that opposes the field emission electron source
10
′, and a phosphor layer
32
formed to cover the collector electrode
31
for emitting visible light when irradiated with electron beams emitted by the surface electrodes
7
. The field emission electron source
10
′ has a thermally oxidized porous polycrystal silicon layer
6
formed on an n-type silicon substrate
1
′ that is an electrically conductive substrate, and surface electrodes
7
formed in stripes on the porous polycrystal silicon layer
6
. The n-type silicon substrate
1
′ has an ohmic electrode
2
formed on the back surface thereof.
In the display apparatus described above, it is necessary to apply a voltage selectively to regions from which it is desired to emit electrons in order to emit electrons from predetermined regions of the planar field emission electron source
10
′.
Thus in the display apparatus of this type, the surface electrodes
7
are formed in the configuration of stripes and the collector electrodes
31
are formed in the configuration of stripes that cross the surface electrodes
7
at right angles, so that electrons are emitted only from those of the surface electrode
7
to which a voltage is applied, by selecting some of the collector electrodes
31
and some of the surface electrodes
7
and applying the voltage (strong electric field) therebetween. Of the electrons emitted, only those electrons emitted from the region of the surface electrodes
7
opposing the collector electrode
31
to which the voltage is applied are accelerated, thereby to cause the phosphor covering the collector electrode
31
to emit light. To sum up, in the display apparatus of the configuration shown in
FIG. 22
, light is emitted from the phosphor layer
32
only at a portion thereof corresponding to that where the electrodes
7
,
31
to which the voltage is applied intersect each other, by applying the voltage to the particular surface electrode
7
and the particular collector electrode
31
. By switching the surface electrode
7
and the collector electrode
31
to which the voltage is applied, images or characters can be displayed. In the display apparatus described above, however, it is necessary to accelerate the electrons by applying a high voltage to the collector electrode
31
in order to cause the phosphor layer
32
to emit light with the electrons emitted by the field emission electron source
10
′, and a high voltage of several hundreds to several thousands of volts is usually applied to the collector electrode
31
in the case of the display apparatus using the field emission electron source.
However, it is necessary to switch a high voltage of several hundreds to several thousands of volts applied to the collector electrode
31
in the case of the display apparatus using the field emission electron source
10
′ of the configuration shown in
FIG. 22
, thus giving rise to such a problem that a surge voltage generated when switching the high voltage requires it to use a switching element that has a high withstanding voltage that leads to a higher cost. Furthermore, assuming a collector current of 1 mA flowing in the collector electrode
31
and a collector voltage of 1 kV applied, for example, a switching element having a capability of 1 W is required for each of the collector electrodes
31
, mere switching elements provided for the number of collector electrodes
31
become very bulky.
Under the above circumstances, the present invention has been made, and a first object thereof is to provide a field emission electron source that is capable of emitting electrons selectively from a desired region of surface electrodes without switching the collector electrodes to which a high voltage is applied, and a method of producing the same.
SUMMARY OF THE INVENTION
In order to achieve the first object described above, the present invention provides a field emission electron source comprising an electrically conductive substrate having a lower electrode which may be formed from a conductive layer located on at least one of principal surfaces; a strong electric field drift layer formed on the conductive layer of the electrically conductive substrate; and surface electrodes consisting of a thin conductive film formed on the strong electric field drift layer, wherein electrons are injected from the electrically conductive substrate into the strong electric field drift layer and are drifted and emitted through the thin conductive film by applying a voltage across the thin conductive film and the conductive layer of the electrically conductive substrate with the thin conductive film serving as a positive electrode, wherein the conductive layer provided on the conductive substrate is formed from a plurality of stripes extending in parallel to each other at predetermined intervals and the thin conductive film is formed from a plurality of stripes extending in parallel to each other at predetermined intervals to oppose and cross the stripes of the conductive layer via the strong electric field drift layer; and wherein the strong electric field drift layer is a porous polycrystal semiconductor layer that is oxidized or nitrized, with the conductive layer and the thin conductive film hold the strong electric field drift layer therebetween at each position where the strips of the conductive layer and the stripes of the thin conductive film that oppose each other intersect, thereby forming a plurality of electron sources arranged at predetermined intervals on the conductive substrate.
By selecting the lower electrode and the surface electrode and applying a voltage to them, electrons can be emitted only from a selected region of the surface electrode to which the lower electrodes cross. Therefore, firstly it is made possible to emit electrons only from a desired region of the surface electrodes. Also secondly it is made possible to eliminate a circuit that switches a high voltage of several hundreds to several thousands of volts applied to the collector electrode in case of a display apparatus having such a configuration as the collector electrodes is disposed to oppose the surface electrode. Thus the present invention has an advantage to reduce the size and cost of the field emission electron source array that is capable of selectively emitting electrons from a desired region of the surface electr
Aizawa Koichi
Hatai Takashi
Honda Yoshiaki
Ichihara Tsutomu
Komoda Takuya
Greenblum & Bernstein P.L.C.
Matsushita Electric & Works Ltd.
Patel Ashok
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