Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2001-02-22
2004-11-16
Cariaso, Alan (Department: 2875)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C252S30140H, C252S30140R
Reexamination Certificate
active
06819041
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a luminescence crystal particle which emits light upon irradiation with an energy beam, a luminescence crystal particle composition, a display panel constituted of such luminescence crystal particles and a flat-panel display having such a display panel.
As an image display device that can be substituted for a currently mainstream cathode ray tube (CRT), flat-screen (flat-panel) displays are studied in various ways. Such fat-panel displays include a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display (PDP). There has been also proposed a cold cathode field emission display capable of emitting electrons into a vacuum from a solid without relying on thermal excitation, a so-called field emission display (FED), and it attracts attention from the viewpoint of the brightness of a display screen and low power consumption.
FIG. 1
shows a typical constitution of the cold cathode field emission display. In this display, a display panel
20
and a back panel
10
are placed so as to face each other, and these two panels
10
and
20
are bonded to each other through a frame (not shown) in their circumferential portions. A space closed with these two panels forms a vacuum space. The back panel
10
has cold cathode field emission devices (to be referred to as “field emission devices” hereinafter) as electron-emitting elements. One example shown in
FIG. 1
is a so-called Spindt-type field emission device having a conical electron-emitting portion
16
. The Spindt-type field emission device comprises a stripe-shaped cathode electrode
12
formed on a substrate
11
; an insulating layer
13
formed on the cathode electrode
12
and the substrate
11
; a stripe-shaped gate electrode
14
formed on the insulating layer
13
; and a conical electron-emitting portion
16
formed in an opening portion
15
formed in the gate electrode
14
and the insulating layer
13
. The electron-emitting portion
16
is formed on a portion of the cathode electrode
12
which portion is positioned in a bottom portion of the opening portion
15
. Generally, a number of such electron-emitting portions
16
are formed to correspond to one of phosphor layers
22
to be described later. A relatively negative voltage (video signal) is applied to the electron-emitting portion
16
from a cathode electrode driving circuit
31
through the cathode electrode
12
, and a negatively positive voltage (scanning signal) is applied to the gate electrode
14
from a gate electrode driving circuit
32
. An electric field is generated due to the application of these voltages, and due to the electric field, electrons are emitted from the top end of the electron-emitting portion
16
on the basis of a quantum tunnel effect. The electron-emitting element shall not be limited to the above Spindt-type field emission device, and field emission devices of other types such as edge-type, flat-type or crown-type field emission devices are used in some cases. Further, reversibly, the scanning signal may be inputted to the cathode electrode
12
, and the video signal may be inputted to the gate electrode
14
.
The display panel
20
has a plurality of phosphor layers
22
which are formed on a support member
21
made of glass or the like and have the form of dots or stripes, and an anode electrode
24
made of an electrically conductive reflection film formed on the phosphor layers
22
and the support member
21
. A positive voltage higher than the positive voltage applied to the gate electrode
14
is applied to the anode electrode
24
from an accelerating power source (anode electrode driving circuit)
33
, and it works to guide electrons emitted from the electron-emitting portion
16
to the vacuum space toward the phosphor layer
22
. Further, the anode electrode
24
functions to protect the phosphor particles constituting the phosphor layer
22
from sputtering by particles such as ions, functions to reflect light emitted from the phosphor layers
22
on the basis of electron excitation to the side of the support member
21
to improve the brightness of a display screen observed from an outside of the support member
21
, and functions to prevent excess charge to stabilize the potential of the display panel
20
. That is, the anode electrode
24
not only carries out its function as an anode electrode but also carries out the function of a member known as a metal back layer in the field of a cathode ray tube (CRT). The anode electrode
24
is generally constituted of a thin aluminum film. A black matrix
23
is formed between one phosphor layer
22
and another phosphor layer
22
.
FIG. 2A
shows a schematic plan view of the display panel having phosphor layers
22
R,
22
G and
22
B formed in the form of dots, and
FIG. 2B
shows a schematic partial cross-sectional view taken along a line X—X in
FIG. 2A. A
region where the phosphor layers
22
R,
22
G and
22
B are arranged is an effective field which carries out a practical function, and a region where the anode electrode is formed is nearly in agreement with the effective field. For clear showing in
FIG. 2A
, the region where the anode electrode is formed is provided with slanting lines. A circumferential region to the effective field is an ineffective field for supporting the function of the effective field, where peripheral circuits are formed and a display screen is mechanically supported.
In the cold cathode field emission display, the anode electrode is not necessarily required to be constituted of the anode electrode
24
made of an electrically conductive reflection film. It may be constituted of an anode electrode
25
made of a transparent electrically conductive film formed on the support member
21
, as is shown in
FIG. 2C
which is a schematic partial cross-sectional view similarly taken along a line X—X in FIG.
2
A. On the support member
21
, each of the anode electrodes
24
and
25
is formed nearly on the entire surface of the effective field.
FIG. 3A
shows a schematic plan view of the display panel having the phosphor layers
22
R,
22
G and
22
B formed in the form of stripes, and
FIGS. 3B and 3C
show schematic partial cross-sectional views taken along a line X—X in FIG.
3
A. In
FIGS. 3A
,
3
B and
3
C, the same portions as those in
FIGS. 2A
,
2
B and
2
C are shown by the same reference numerals, and detailed explanations of the same portions are omitted.
FIG. 3B
shows a constitution in which the anode electrode
24
is made of an electrically conductive reflection film, and
FIG. 3C
shows a constitution in which the anode electrode
25
is made of a transparent electrically conductive film. Each of the anode electrodes
24
and
25
is formed nearly on the entire surface of the effective field of the display panel.
In the cold cathode field emission display that is a flat-panel display, the flying distance of electrons is far smaller than the counterpart in a cathode ray tube, so that it is difficult to increase an electron-accelerating voltage to the level of an electron-accelerating voltage in the cathode ray tube. In the cold cathode field emission display, if the electron-accelerating voltage is too high, spark discharge is liable to take place between the electron-emitting portion in the back panel and the film which functions as an anode electrode in the display panel, and the display quality of the cold cathode field emission display may be impaired to a great extent. The accelerating voltage is therefore controlled to be approximately 10 kilovolts or lower.
In addition to the above problem, the cold cathode field emission display for which it is required to select the above low electron-accelerating voltage involves characteristic problems from which the cathode ray tube is free. In a cathode ray tube permitting the acceleration at a high voltage, electrons enter the phosphor layers deep, so that the electron energy is received in a relatively broad region inside the phosphor layers to excite a relatively large
Cariaso Alan
Dong Dalei
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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