Computer graphics processing and selective visual display system – Display driving control circuitry
Reexamination Certificate
2000-09-08
2003-08-19
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display driving control circuitry
C345S074100, C345S055000, C345S084000, C345S074100, C345S087000, C345S088000, C345S100000, C345S075100, C345S075200, C313S309000, C313S310000, C315S169100, C315S169300
Reexamination Certificate
active
06608620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display apparatus, particularly relates to an effective technology applied to a display apparatus for displaying a picture, wherein light-emission elements are arranged to form a matrix and the picture is displayed by controlling light emissions of the light-emission elements.
2. Description of Prior Art
A matrix-type display apparatus has a plurality of rows and a plurality of columns arranged in directions orthogonal to each other. Each of the rows and the columns has a plurality of electrodes. Each intersection of any of the rows and any of the columns in the matrix-type display apparatus is referred to as a pixel. A matrix-type display apparatus displays a picture by adjusting a voltage applied to each pixel. Examples of a matrix-type display apparatus are a liquid-crystal display (LED) apparatus, a field-emission display (FED) apparatus, an electro-luminescence (EL) display apparatus and a light-emitting diode (LED) display apparatus.
As disclosed in Japanese publication of unexamined applications No.4-289644, electron emitter elements arranged in an FED apparatus each serve as a pixel. Electrons emitted from the electron emitter elements are accelerated in a vacuum before being radiated to phosphors to cause portions of the phosphors hit by the radiated electrons to emit lights.
As typical electron emitter elements used in an FED apparatus, a matrix of thin-film electron emitters is available. A thin-film electron emitter element is an electron emitter element that utilizes hot electrons generated by applying a strong electric field to an insulator.
An MIM (Metal-Insulator-Metal)-type electron emitter is a representative electron emitter. The following description explains the MIM-type electron emitter with a structure having 3 layers, namely, a top electrode, an insulator and a base electrode.
FIG. 21
is an explanatory diagram used for describing the principle of operation of an MIM-type electron emitter.
If a driving voltage is applied between a top electrode
11
and a base electrode
13
to set an electric field in a tunneling insulator
12
at a value in the range 1 to 10 MV/cm or greater, electrons in close proximity to the Fermi level in the base electrode
13
travel through the barrier by the tunneling phenomenon, becoming hot electrons injected into the conduction band of the top electrode
11
.
In the tunneling insulator
12
and the top electrode
11
, some of the hot electrons are scattered by interactions with a solid, losing energy.
As a result, at the time the hot electrons reach the boundary between the top electrode
11
and a vacuum
10
, the hot electrons have different amounts of energy.
Some of the hot electrons having energy of an amount not smaller than a work function (&PHgr;) of the top electrode
11
are emitted to the vacuum
10
while the remaining hot electrons flow into the top electrode
11
.
The MIM-type thin-film electron emitter is disclosed in, among other documents, Japanese publication of unexamined applications No.9-320456.
A plurality of top electrodes
11
are arranged to form typically a column of a matrix while a plurality of base electrodes
13
are arranged to form typically a row of the matrix. A plurality of such rows and a plurality of such columns are laid out in directions orthogonal to each other to form the matrix. An intersection of a row and a column has a top electrode
11
on the column and a base electrode
13
on the row. Such an intersection is referred to as a thin-film electron emitter. Since each MIM-type thin-film electron emitter in the matrix is capable of emitting an electron beam, the thin-film electron emitter serves as an electron emitter element of a matrix-type display apparatus.
Each of the MIM-type thin-film electron emitters in the matrix is a pixel of the display apparatus. In the display apparatus with such a configuration, electrons emitted by each of the MIM-type thin-film electron emitter in the matrix are accelerated in the vacuum
10
before being radiated to phosphors to cause portions of the phosphors hit by the radiated electrons to emit lights to display a desired picture.
The thin-film electron emitter displays excellent characteristics, which qualify the electron emitter to serve as an electron emitter element for FED. The excellent characteristics include the fact that the thin-film electron emitter satisfies a requirement for implementation of a high-resolution display apparatus due to its excellence in the directionality of its emitted electron beam. Another example of the excellent characteristics is easy handling attributed to the fact that the thin-film electron emitter is not severely affected by surface contamination.
SUMMARY OF THE INVENTION
Since the display apparatus using a matrix of thin-film electron emitters employs neither a shadow mask nor beam-deflection circuitry, unlike a cathode-ray tube (CRT), the power consumption of such a display apparatus is slightly smaller than or about equal to that of a CRT display apparatus.
The power consumption of a matrix of thin-film electron emitters driven by adopting the conventional driving technique in a display apparatus employing the matrix of thin-film electron emitters is estimated as follows.
FIG. 22
is a diagram showing the configuration of the conventional matrix of thin-film electron emitters in a simple and plain manner.
A row electrode
310
stretched in the row direction is connected to one of the electrodes, that is, the base electrode
13
, of each thin-film electron emitter element
301
associated with the row electrode
310
. On the other hand, a column electrode
311
stretched in the column direction is connected to the other electrode, that is, the top electrode
11
, of each thin-film electron emitter element
301
associated with the column electrode
311
.
It should be noted that, while
FIG. 22
shows the configuration of a typical matrix of 3 rows×3 columns, in actuality, the matrix has as many laid-out thin-film electron emitter elements
301
as pixels composing the display apparatus or sub-pixels composing a color display apparatus.
Assume that a negative voltage pulse (−V
1
) is applied to the row electrode
310
on the R
2
th row and a positive voltage pulse (+V
2
) is applied to the column electrode
311
on the C
2
th column. In this case, since a voltage of (V
1
+V
2
) is applied to the thin-film electron emitter element
301
at an intersection (R
2
, C
2
) of the row electrode
310
on the R
2
th row and the column electrode
311
on the C
2
th column, the thin-film electron emitter element
301
emits electrons.
The emitted electrons are accelerated and then radiated to phosphors, causing the phosphors to emit lights.
In a line-at-a-time operation, a pixel emits a light during a period in a unit time. The ratio of the period to the unit time is referred to as a duty ratio, which is inversely proportional to a scanning-line count N, that is, the number of row electrodes
310
. That is, the brightness of the screen is proportional to 1/N.
As indicated in the 1997 SID International Symposium Digest of Technical Papers, pages 123 to 126 (May 1997), however, the brightness of a light emitted during application of a voltage pulse in a display apparatus employing thin-film electron emitter elements
301
and phosphors is sufficiently high so that enough screen brightness is obtained even if a line-at-a-time operation is adopted.
In addition, a relation between the applied voltage and the brightness exhibits a steep threshold characteristic. Thus, even for N of about 1,000, passive-matrix addressing results in sufficient contrast.
That is, unlike a liquid-crystal display apparatus, in the case of a display apparatus employing thin-film electron emitters, it is not necessary to provide a switching element on each pixel in order to improve the threshold characteristic and to increase the duty ratio of the light emitting period.
Next, let us find a dissipation power of drivers in the configurat
Kaneko Yoshiyuki
Kusunoki Toshiaki
Sagawa Masakazu
Suzuki Mutsumi
Hitachi , Ltd.
Hjerpe Richard
Miles & Stockbridge P.C.
Zamani Ali
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