Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-01-10
2003-11-25
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S495000, C313S310000
Reexamination Certificate
active
06653366
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron-emitting element emitting electrons utilizing the phenomenon of electric field electron emission, and to an image display device using such an electron-emitting element. More particularly, the present invention relates to a thin image display device used, for example, for audio-visual equipment.
2. Description of the Prior Art
Until now, mainly cathode ray tubes (CRTs) are used for displays (image display devices) such as color televisions or computer monitors. However recently, there is a need for ever smaller, lighter and thinner image display devices, and the development of new thinner image display devices is flourishing.
This situation has led to research and development activities for several types of thin image display devices, and of these, the development of liquid crystal displays and plasma displays is particularly thriving. Liquid crystal displays find application in many products, such as portable computers, portable televisions, video cameras, and car navigation systems. Plasma displays find application in products such as 20-inch or 40-inch large displays.
However, liquid crystal displays have the problem that their viewing angle is narrow, and their response times are slow, whereas plasma display devices have the problem that they can hardly attain high brilliance and their power consumption is large. As thin image display devices that solve these problems, image display devices utilizing the so-called “field emission” phenomenon, whereby electrons are emitted at regular temperatures in a vacuum, have had wide-spread attention (such devices are referred to as “FEDs” in the following). Such an FED is self-emitting, so that a broad viewing angle and a high brilliance can be attained. Moreover, its basic principle (using an electron beam to cause a phosphor to emit light) is the same as in conventional cathode ray tubes, so that an image with high color repeatability can be displayed naturally.
As the electron-emitting elements for the FED, Spindt-type microchip-type electron-emitting elements, surface-conducting elements formed on a metal thin film or an oxide thin film, and MIM-type (or similarly structured) electron-emitting elements have been proposed for example.
In recent years, carbon-based materials, such as diamond, graphite, DLC (diamond-like carbon), and carbon nanotubes have gained wide-spread attention as electron-emitting materials for making electron-emitting elements.
Such an electron-emitting element is disclosed, for example, in Japanese Patent Applications Tokkai Hei
10-149760
and Tokkai Hei
10-12124.
FIGS. 8 and 9
are schematic cross-sectional drawings of a first conventional electron-emitting element (see Tokkai Hei
10-149760
). The electron-emitting element in
FIG. 8
is made be applying purified carbon nanotubes
101
made by arc emission to a support substrate
102
made of a synthetic resin (FIG.
8
A), and then applying a resist and forming a pattern in accordance with the layout of the electron-emitting portions
103
by lithography, so that electron-emitting portions
103
made of carbon nanotubes
101
are formed on the support substrate
102
(FIG.
8
B). In this case, the carbon nanotubes
101
on the support substrate
102
lie one upon another like fallen trees, as shown in FIG.
9
.
When an electric field is applied to the carbon nanotubes
101
patterned into an electron-emitting portion
103
in such an electron-emitting element, electrons are emitted by the carbon nanotubes
101
.
FIG. 10
is a schematic cross-sectional drawing of a second conventional electron-emitting element (see same Tokkai Hei
10-149760
). The electron-emitting element in
FIG. 10
includes a support substrate
111
, a cathode wiring layer
112
disposed on the support substrate
111
, and an electron-emitting portion
116
disposed on the cathode wiring layer
112
. The electron-emitting portion
116
includes a conductive convex portion
114
formed in a portion of a conductive material layer
113
, and a plurality of carbon nanotubes
115
partially buried in the tip of the conductive convex portion
114
.
The following is an explanation of a method for manufacturing this second conventional electron-emitting element. First, a substrate of a silicon single-crystal is prepared, and a female mold substrate for the conductive convex portion
114
is formed by anisotropic etching. Carbon nanotubes
115
are disposed in this concave portion, a conductive material such as tungsten is deposited on top of it by sputtering, and a conductive material for wiring is sputtered on top of that. Then, the female mold substrate is removed, resulting in an electron-emitting element as shown in FIG.
10
.
In this electron-emitting element, the electron-emitting carbon nanotubes
115
are arranged at the tip of the conductive convex portion
114
, where an electric field tends to concentrate, so that a large electric field can be generated with a small driving voltage, and the electron-emitting carbon nanotubes
115
emit electrons efficiently.
FIG. 11
is a schematic cross-sectional drawing of a third conventional electron-emitting element (Tokkai Hei
10-12124
). The electron-emitting element shown in
FIG. 11
is formed as follows. First, an aluminum film
122
is formed by, for example, vapor deposition on a flat glass substrate
121
. Then, the aluminum film
122
is rinsed, and an insulating film
123
is formed by an anode oxidation process. After this process, the bottom portion of the pores
124
formed during the anode oxidation process are etched all the way to the aluminum film
122
by anisotropic RIE etching. In an electrocoloring process, a nickel metal catalyst
125
is buried in the pores
124
, and successively a heating process is performed at 1150° C. in a mixed atmosphere of methane gas and hydrogen to generate and grow carbon nanotubes
126
. With these steps, electron-emitting carbon nanotubes
126
can be orientationally aligned with high precision, and arranged to form an electron-emitting element with sharp tips.
With such an electron-emitting element, the carbon nanotubes
126
can be orientationally aligned into a shape with sharp tips, so that an electric field can be concentrated effectively at the electron-emitting material to attain an electron-emitting element with high efficiency.
However, the conventional electron-emitting element shown in
FIG. 8
has the following problems. First of all, if carbon nanotubes
101
are applied to the support substrate
102
by a method such as printing, since the carbon nanotubes
101
have a rod-like longish molecular shape, they lie one upon another like fallen trees, as shown in
FIG. 9
, when attached to the support substrate
102
. In this situation, the orientation of the electron-emitting carbon nanotubes
101
poses the problem that the tips, which are the most important for the electron emission, are partially buried. Thus, when a voltage is applied to the electron-emitting element, the electric field does not concentrate effectively, so that an efficient electron-emitting element is not attained. Moreover, forcing the carbon nanotubes
101
to assume an upright position with respect to the support substrate
102
, by press-inserting or burying it is extraordinarily difficult to let each and every molecule of the countless carbon nanotubes
101
stand upright on the support substrate
102
.
Moreover, in the conventional electron-emitting element shown in
FIG. 10
, with the manufacturing method described above, the carbon nanotubes
115
are arranged on a concave portion and a conductive material is sputtered on top of them, so that the carbon nanotubes
115
are buried inside the tip of the conductive convex portion
114
. Thus, even when the electric field concentrates in the conductive convex portion
114
, the electric field does not sufficiently concentrate on the carbon nanotubes
115
themselves, so that an effective electron-emitting element is not attained. Moreover, the step for f
Imai Kanji
Matsuo Kohji
Sekiguchi Tomohiro
Yokomakura Mitsunori
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Shosho Callie
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