Electric lamp and discharge devices – Discharge devices having a multipointed or serrated edge...
Reexamination Certificate
2000-04-18
2002-12-24
Kim, Robert H. (Department: 2882)
Electric lamp and discharge devices
Discharge devices having a multipointed or serrated edge...
C313S310000, C313S351000
Reexamination Certificate
active
06498424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission type cathode, an electron emission apparatus and an electron emission apparatus manufacturing method.
2. Description of the Related Art
There have been proposed various types of electron emission apparatuses having field emission type cathodes, such as a planar display apparatus, i.e., a panel type display apparatus. As for an apparatus for making a bright image display, a cathode ray-tube type structure for striking an electron beam on the fluorescent surface of an image formation plane to thereby emit light, is normally adopted.
As proposed in, for example, Japanese Patent Application Laid-Open (JP-A) No. 1-173555, a conventional planar display apparatus of a cathode ray-tube type structure is such that a plurality of thermoelectron emission cathodes, i.e., filaments are provided to face a fluorescent surface, thermoelectrons generated by these cathodes and secondary electrons resulting from the thermoelectrons are allowed to direct toward the fluorescent surface and that according to an image signal an electron beam excites the respective colors on the fluorescent surface to cause light emission. In this case, as the image plane becomes larger in size, the filaments are provided in common for many pixels, that is, many red, green and blue fluorescent substance trio forming the fluorescent surface.
Accordingly, as the image plane becomes, in particular, larger in size, the arrangement and assembly of the filaments become more complicated.
Furthermore, to make the planar display apparatus of the cathode ray-tube structure small in size, the length of the electron gun is decreased and the deflecting angle of electrons is widened to shorten the depth dimension of the apparatus. However, since the image plane of a planar display apparatus is becoming wider in recent years, the development of thinner planar display apparatuses is desired.
In the meantime, as for the conventional planar display apparatus, there is proposed an apparatus using field emission type cathodes or so-called cold cathodes. The structure of an example of such planar type display apparatus will be described hereinafter with reference to the drawings.
The planar display apparatus
100
shown in
FIG. 15
consists of a fluorescent surface
101
, a planar white light emission display apparatus main body
102
having field emission type cathodes K arranged to face the fluorescent surface
101
and a planar color shutter
103
arranged to contact or face the front surface of the apparatus at the side at which the fluorescent surface
101
is arranged.
In the display apparatus main body
102
, as shown in
FIG. 15
, a light transmitting front panel
104
and a back panel
105
face each other through a spacer (not shown) holding the panels
104
and
105
at predetermined intervals. The peripheral edges thereof are airtight sealed by glass frit or the like and a flat space is formed between the panels
104
and
105
.
An anode metal layer
160
and the fluorescent surface
101
entirely coated with, for example, white light emission fluorescent material in advance are formed on the inner surface of the front panel
104
. A metal back layer
106
such as an Al film as in the case of an ordinary cathode ray-tube is coated on the surface of the fluorescent surface
101
.
On the other hand, many cathode electrodes
107
extending in perpendicular direction in, for example, a band-like manner are arranged in parallel to one another and coated on the inner surface of the back panel
105
.
An insulating film
108
is coated on the cathode electrodes
107
and gate electrodes
109
extending to be almost orthogonal to the extension direction of the cathode electrodes
107
, for example, horizontally are arranged in parallel to one another on the insulating film
108
.
Holes
110
are formed at the crossings of the cathode electrodes
107
and the gate electrodes
109
, respectively. In these holes
110
, conical field emission type cathodes K are formed to be coated on the cathode electrodes
107
, respectively.
Each of the field emission type cathodes K is made of a material, such as Mo, W and Cr, which emits electrons by a tunnel effect when applied with a field of, for example, about 10
6
to 10
7
(V/cm).
To help understand the configuration of a cathode structure including the field emission type cathode K, the gate electrode and the like which constitute the planar display apparatus
100
of the above-stated conventional structure, one example of the configuration as well as its manufacturing method will be described with reference to manufacturing step views shown in
FIGS. 16
to
19
.
First, as already described with reference to
FIG. 15
, cathode electrodes
107
are formed on the inner surface of the back panel
105
along one direction, e.g., vertical scan direction.
Each of the cathode electrode
107
is configured such that a metal layer made of, for example, Cr is formed entirely by deposition, sputtering or the like and selectively etched by photolithography, to thereby form the cathode electrode
107
into a predetermined pattern.
Next, as shown in
FIG. 16
, on the patterned cathode electrode
107
, an insulating film
108
is coated on the entire surface thereof by sputtering or the like and a metal
111
such as high melting point metal of, for example, Mo or W, finally constituting a gate electrode
109
is formed on the insulating film
108
by deposition, sputtering or the like.
As shown in
FIG. 17
, a resist pattern made of, for example, a photoresist, though not shown therein, is formed. Using the resist pattern as a mask, anisotropic etching such as RIE (reactive ion etching) is conducted to the metal layer
111
to thereby form a band-shaped gate electrode
109
in a predetermined pattern, i.e., extending in the horizontal direction orthogonal to the extension direction of the cathode electrode
107
shown in FIG.
15
. Also, a plurality of small holes
111
h
, for example, are provided at crossings of the gate electrodes
109
and the cathode electrodes
107
, respectively.
Next, through these small holes
111
h
, chemical etching with which the gate electrode
109
, that is, the metal layer
111
is not etched but the insulating layer
108
is isotropically etched, is conducted, thereby forming holes
112
each having a width larger than the width of the small hole
111
h
and a depth corresponding to the entire thickness of the insulating layer
108
.
In this way, as shown in
FIG. 15
, holes
110
are formed out of the holes
112
and the small holes
111
h
at crossings of the cathode electrodes
107
and the gate electrodes
109
, respectively.
Thereafter, as shown in
FIG. 18
, a metal layer
113
made of, for example, Al or Ni is coated on the gate electrode
109
by oblique deposition. The oblique deposition is carried out while rotating the back panel
105
in the plane, so that round holes
114
each having a conical inner periphery are formed around the small holes
111
h
, respectively.
In that case, the deposition of the metal layer
113
is carried out with a selected angle with which the metal layer
113
is not coated in the holes
112
through the small holes
111
h.
Through the round holes
114
, a field emission type cathode material, that is, a metal, such as W or Mo, having a high melting point and a low work function is deposited on the cathode electrode
107
in the hole
112
perpendicularly to the cathode electrode surface by deposition, sputtering or the like. In that case, even if deposited perpendicularly, the cathode material is formed to have an inclined surface continuous to those of the metal layer
113
around the round holes
114
. Thus, if the cathode material reaches a certain thickness, the holes
114
become closed. As a result, in the respective holes
112
, conical, dot-like cathodes K each having a triangle cross section are formed on the cathode electrodes
107
, respectively.
Thereafter, as shown in
FIG. 19
, the metal layer
113
and the cathod
Inoue Kouji
Tachizono Shinichi
Yamagishi Takeshi
Kim Robert H.
Yun Jurie
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