Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-07-10
2004-11-09
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169300, C345S074100, C345S080000, C345S090000
Reexamination Certificate
active
06815901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a display device (referred below to an FED (Field Emission Display)), which makes use of electron source elements (electron emitting elements). Also, the invention relates to a method of driving the FED. Further, the invention relates to an electronic equipment making use of the FED.
2. Description of the Related Art
An explanation will be given to an FED (Field Emission Display) making use of an electron source element. Here, an element emitting electrons owning to the electric field effect is referred to as an electron source element.
Electron source elements arranged on respective pixels of the FED emit electrons from electrodes due to the electric field effect. Electrons thus emitted are accelerated to be incident upon a fluorescent body. The fluorescent body in a region, upon which electrons are incident, emits light. A quantity of electrons emitted from the electron source elements on the respective pixels is controlled by a video signal input into the FED. The more electrons emitted, the higher emission luminance of the fluorescent body in the case where these electrons are incident upon the fluorescent body. Thus the FED represents gradation.
Electron source elements have various configurations. There are typically given an FE (Field Emission) type element for causing electrons to be emitted from a tip end of a convex electrode where an intense electric field is locally generated, a surface conduction type element for causing generation of electrons through flowing of an electric current in parallel to a thin film surface broken locally, an MIM (Metal-Insulator-Metal) type element composed of a first electrode, a second electrode and an insulating film interposed between the first electrode and the second electrode, and for emitting electrons upon application of voltage between the first electrode and the second electrode.
Here, what is regarded as important in electron source elements used in FEDs is whether elements can be made minute, or whether elements having a uniform performance can be fabricated, or whether elements can be driven with low voltage. Hereupon, MIM type electron source elements meeting these qualifications have been developed.
FIG. 6
shows an example of an MIM type electron source element. Its structure is described in SID 01 Digest page 193-195 “Novel Device Structure of MIM Cathode Array for Field Emission Displays”.
In
FIG. 6
, formed on a substrate
20
with an insulating surface are a lower electrode
21
, an upper electrode
23
, and an insulating film
22
interposed between the lower electrode
21
and the upper electrode
23
. Also, the reference numeral
24
denotes a protective insulating layer,
25
a
a contact electrode,
25
b
an upper electrode bus line, and
26
a protective electrode. In addition, a region where the upper electrode
23
overlaps an opening of the protective insulating layer
24
is referred to as an electron emission region and denoted by the reference numeral
27
in the figure.
Application of voltage between the upper electrode
23
and the lower electrode
21
causes injection of a hot carrier into the insulating film
22
. That hot carrier of the hot carrier thus injected, which has a greater energy than a work function of a material of the upper electrode
23
, passes through the upper electrode
23
to be emitted into the vacuum.
An MIM type electron source element having the structure shown in
FIG. 6
emits electrons when voltage of around 10 V is applied between the upper electrode
23
and the lower electrode
21
. In electron source elements, voltage applied between an upper electrode and a lower electrode when electrons are emitted is referred to as a drive voltage of an electron source element. An upper electrode of electron source elements is set to be high in electric potential as compared with a lower electrode thereof. In this manner, electrons are emitted from the upper electrode.
FIG. 7
shows an example of a display (FED) making use of the electron source element shown in FIG.
6
. In addition, the same parts as those in
FIG. 6
are denoted by the same reference numerals.
The FED shown in
FIG. 7
has on the first substrate
20
with an insulating surface x (natural number) signal lines S
1
to Sx arranged in a row direction, and y (natural number) scanning lines G
1
to Gy arranged in a column direction. Electron source elements are arranged on respective points of intersection of the x signal lines S
1
to Sx and the y scanning lines G
1
to Gy. One electron source element, and that part of the signal lines and the scanning lines, to which the electron source element is connected, constitute one pixel. In
FIG. 7
, the reference numeral
300
denotes one pixel. The lower electrode
21
of the electron source element is connected to one of the y scanning lines G
1
to Gy, and the upper electrode
23
is connected to one of the x signal lines S
1
to Sx.
In addition, the lower electrode
21
may be connected to one of the x signal lines S
1
to Sx and the upper electrode
23
may be connected to one of the y scanning lines G
1
to Gy.
A second substrate
19
is provided to face that surface of the first substrate
20
, on which the electron source element is provided. The second substrate
19
is light-transmissive. Arranged on the second substrate
19
is a fluorescent body
18
opposite to the electron source element. A black matrix
15
is arranged around the fluorescent body
18
. In addition, the fluorescent body
18
is formed on a surface thereof with a metal-backed layer
17
. Vacuum is kept between the first substrate and the second substrate.
A signal input into the scanning lines and a signal input into the signal lines cause emission of electrons from the upper electrode
23
in the electron source element of the pixel, in which voltage is applied between the upper electrode
23
and the lower electrode
21
. Electrons thus emitted are accelerated in the vacuum
16
by voltage applied between the metal-backed layer
17
and the upper electrode. Electrons thus accelerated are incident upon the fluorescent body
18
provided on the second substrate
19
through the metal-backed layer
17
. Thus the fluorescent body
18
in a region where electrons are incident emits light.
Here, a signal input into, for example, the scanning lines are kept constant in amplitude, and a signal input into the signal lines is varied in amplitude. A quantity of electrons emitted from the electron source element
28
is increased in accordance with voltage applied between the upper electrode
23
and the lower electrode
21
. The more electrons emitted, the higher emission luminance can be represented in the case where these electrons are accelerated to be incident upon the fluorescent body
18
on the second substrate
19
.
FIG. 8
shows a timing chart in the case where the display having the structure shown in
FIG. 7
is driven. In the timing chart, one frame period (F) is a period, in which one picture image is displayed.
First, a scanning line G
1
is selected. Here, other scanning lines G
2
to Gy are put in a state, in which they are not selected. In addition, selection of a scanning line in
FIGS. 7 and 8
means putting a scanning line connected to one of electrodes of an electron source element in a certain electric potential so that a quantity of electrons emitted from the electron source element is varied in accordance with an electric potential input into a signal line connected to the other of the electrodes of the electron source element.
For example, suppose that an electric potential of −8 V is input into a scanning line as selected in the case where a scanning line is connected to the lower electrode
21
of the electron source element and a signal line is connected to the upper electrode
23
. On the other hand, suppose that an electric potential of 8 V is input into scanning lines as not selected. Also, suppose that an electric potential of −8 to 8 V is input into a signal line. Here, suppose tha
Costellia Jeffrey L.
Philogene Haissa
Semiconductor Energy Laboratory Co,. Ltd.
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