U.S. patent number RE41,828 [Application Number 11/088,221] was granted by the patent office on 2010-10-19 for image display and a manufacturing method of the same.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Toshiaki Kusunoki, Masakazu Sagawa, Mutsumi Suzuki.
United States Patent |
RE41,828 |
Suzuki , et al. |
October 19, 2010 |
Image display and a manufacturing method of the same
Abstract
The present invention provides an image display capable of
enhancing a production yield. The image display comprises a display
device including a first plate which has a plurality of
electron-emitter elements each having a structure comprised of a
base electrode, an insulating layer and a top electrode stacked on
one another in this order, the electron-emitter element emitting
electrons from the surface of the top electrode when a voltage of
positive polarity is applied to the top electrode; a plurality of
first electrodes for respectively applying driving voltages to the
base electrodes of the electron-emitter elements lying in a row (or
column) direction; and a plurality of second electrodes for
respectively applying driving voltages to the top electrodes of the
electron-emitter elements lying in the column (or row) direction, a
frame component, and a second plate having phosphors, wherein a
space surrounded by the first plate, the frame component and the
second plate is brought into vacuum. In the display apparatus, the
at least one electron-emitter element includes the base electrode
and the top electrode, at least one of which is connected to the
first electrode or the second electrode through a resistor
element.
Inventors: |
Suzuki; Mutsumi (Kodaira,
JP), Sagawa; Masakazu (Inagi, JP),
Kusunoki; Toshiaki (Tokorozawa, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
17284717 |
Appl.
No.: |
11/088,221 |
Filed: |
September 4, 2000 |
PCT
Filed: |
September 04, 2000 |
PCT No.: |
PCT/JP00/05988 |
371(c)(1),(2),(4) Date: |
January 16, 2002 |
PCT
Pub. No.: |
WO01/20639 |
PCT
Pub. Date: |
March 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
10030982 |
Jan 16, 2002 |
06538391 |
Mar 25, 2003 |
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Current U.S.
Class: |
315/169.3;
315/169.4; 313/495 |
Current CPC
Class: |
H01J
31/127 (20130101); H01J 1/312 (20130101); B82Y
10/00 (20130101); H01J 2201/319 (20130101); H01J
2329/00 (20130101) |
Current International
Class: |
G09G
3/10 (20060101) |
Field of
Search: |
;315/169.1-169.4
;345/40,30 ;313/495,500 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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01-154426 |
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Nov 1988 |
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JP |
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02-247936 |
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Mar 1989 |
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JP |
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04-284324 |
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Mar 1991 |
|
JP |
|
06-251691 |
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Dec 1993 |
|
JP |
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07-326287 |
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May 1994 |
|
JP |
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08-329826 |
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May 1995 |
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JP |
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9-320456 |
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Nov 1996 |
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JP |
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10-308164 |
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May 1997 |
|
JP |
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11-120898 |
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Oct 1997 |
|
JP |
|
2001-035423 |
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Jul 1999 |
|
JP |
|
Other References
Office Action from the Japanese Patent Office for Japanese Patent
Application 11-255869 dated Feb. 6, 2006 (English translation).
cited by other .
Office Action from the Japanese Patent Office for Japanese Patent
Application 2005-110920 dated Feb. 6, 2006 (English translation).
cited by other.
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Primary Examiner: Owens; Douglas W
Assistant Examiner: Alemu; Ephrem
Attorney, Agent or Firm: Stites & Harbison, PLLC
Marquez, Esq; Juan Carlos A.
Claims
What is claimed is:
1. An image display comprising: a display device including, a first
plate having, a plurality of electron-emitter elements each having
a structure comprised of a base electrode, an insulating layer and
a top electrode stacked on one another in this order, said
electron-emitter element emitting electrons from the surface of the
top electrode when a voltage of positive polarity is applied to the
top electrode; a plurality of first electrodes for respectively
applying driving voltages to the base electrodes of the
electron-emitter elements lying in a row (or column) direction, of
said plurality of electron-emitter elements; and a plurality of
second electrodes for respectively applying driving voltages to the
top electrodes of the electron-emitter elements lying in the column
(or row) direction, of said plurality of electron-emitter elements;
a frame component; and a second plate having phosphors; wherein a
space surrounded by said first plate, said frame component and said
second plate is brought into vacuum; wherein at least on said
electron-emitter element includes its corresponding base electrode
and top electrode, at least one of which is connected to the first
electrode or second electrode through a resistor element.
2. An image display comprising: a display device including, a first
plate having, a plurality of electron-emitter elements each having
a structure comprised of a base electrode, an insulating layer and
a top electrode stacked on one another in this order, said
electron-emitter element emitting electrons from the surface of the
top electrode when a voltage of positive polarity is applied to the
top electrode; a plurality of first electrodes for respectively
applying driving voltages to the base electrodes of the
electron-emitter elements lying in a row (or column) direction, of
said plurality of electron-emitter element; and a plurality of
second electrodes for respectively applying driving voltages to the
top electrodes of the electron-emitter elements lying in the column
(or row) direction, of said plurality of electron-emitter elements;
a frame component; and a second plate having phosphors; wherein a
space surrounded by said first plate, said frame component and said
second plate is brought into vacuum; wherein said plurality of
electron-emitter elements respectively include the base electrodes
and top electrodes, at least one of which are respectively
connected to the first electrodes or the second electrodes through
resistor elements.
3. An image display according to claim 1, further including first
driving means for supplying driving voltages to said respective
first electrode, and second driving means for supplying driving
voltages to aid respective second electrodes, and the resistance
value of said each resistor element is larger than a value obtained
by multiplying a larger value of output impedance of said first
driving means and an output impedance of said second driving mean
by ten times.
4. An image display according to claim 1, wherein when the
resistance value of the resistor element is defined as R, and the
electrostatic capacitance of the electron-emitter element is
defined as C, the product (RC) of the resistance value of the
resistor element and the electrostatic capacitance of the
electron-emitter element is smaller than a horizontal scanning
period 1H of a displayed video signal.
5. An image display according to claim 1, wherein the resistance
value of the resistor element is smaller than a differential
resistance of the electron-emitter element in an operation region
thereof.
6. An image display according to claim 1, wherein each of said
resistor elements includes at least some portion thereof that does
not intersect either the first electrodes or the second
electrodes.
7. An image display according to claim 1, wherein the resistor
element has at least one bend.
8. An image display according to claim 1, wherein the resistor
element has a portion narrower than other portions in line width or
a portion thinner than other portions in thickness.
9. An image display according to claim 1, wherein said each first
electrode shares the base electrode of said each electron-emitter
element, and the electron-emitter element connected with the
resistor element includes the top electrode connected to the second
electrode through the resistor element.
10. An image display according to claim 9, wherein the
electron-emitter element connected with the resistor element has a
top electrode busline under-layer film electrically connected to
the top electrode, and the resistor element is formed of the same
material as the top electrode busline under-layer film.
11. An image display according to claim 10, further including top
electrode buslines, each of which is provided so as to cover an
edge of the base electrode, and is on the top electrode busline
under-layer film.
12. An image display according to claim 9, wherein the resistor
element is formed of the same material as the top electrode of the
electron-emitter element connected with the resistor element.
13. An image display according to claim 12, further including top
electrode busline each electrically connected to the top electrode
and provided so as to cover an edge of the base electrode.
14. An image display according to claim 1, wherein said each
electron-emitter element has a top electrode busline which is
electrically connected to the top electrode and shares the second
electrode, and the electron-emitter element connected with the
resistor element includes the base electrode connected to the first
electrode through the resistor element.
15. An image display according to claim 1, wherein electron-emitter
elements from which the resistor elements are respectively cut off
and which are respectively electrically disconnected from the first
electrodes or the second electrodes.
16. An image display .[.display.]. comprising: a display device
including, a first plate having, a plurality of electron-emitter
elements each having a structure comprised of a base electrode, an
insulating layer and a top electrode stacked on one another in this
order, said electron-emitter element emitting electrons from the
surface of the top electrode when a voltage of positive polarity is
applied to the top electrode; a plurality of first electrodes for
respectively applying driving voltages to the base electrodes of
the electron-emitter elements lying in a row (or column) direction,
of said plurality of electron-emitter element; and a plurality of
second electrodes for respectively applying driving voltages to the
top electrodes of the electron-emitter elements lying in the column
(or row) direction, of said plurality of electron-emitter elements;
a frame component; and a second plate having phosphors; wherein a
space surrounded by said first plate, said frame component and said
second plate is brought into vacuum, and wherein a plurality of
said electron-emitter elements respectively include the base
electrodes and the top electrodes, at least one of which are
respectively connected to the first electrodes or the second
electrodes through connection wires.
17. An image display a according to claim 16, wherein each of said
connection wires includes at least some portion thereof that does
not intersect either the first electrodes or the second
electrodes.
18. An image display according to claim 16, wherein the connection
wire has at least one bend.
19. An image display according to claim 16, wherein the connection
wire has a portion narrower than other portions in line width or a
portion thinner than other portions in thickness.
20. An image display according to claim 16, further including
electron-emitter elements from which the connection wires are cut
and which are electrically disconnected from the first electrodes
or the second electrodes.
21. A method of manufacturing an image display comprising: a
display device including, a first plate having, a plurality of
electron-emitter elements each having a structure comprised of a
base electrode, an insulating layer and a top electrode stacked on
one another in this order, said electron-emitter element emitting
electrons from the surface of the top electrode when a voltage of
positive polarity is applied to the top electrode; a plurality of
first electrodes for respectively applying driving voltages to the
base electrodes of the electron-emitter elements lying in a row (or
column) direction, of said plurality of electron-emitter elements;
and a plurality of second electrodes for respectively applying
driving voltages to the top electrodes of the electron-emitter
elements lying in the column (or row) direction, of said plurality
of electron-emitter elements; a frame component; and a second plate
having phosphors; wherein a space surrounded by said first plate,
said frame component and said second plate is brought into vacuum,
and wherein said respective electron-emitter elements have the base
electrodes and the top electrodes, at least one of which are
respectively connected to the first electrodes or the second
electrodes through resistor elements, said method comprising the
step of: cutting the resistor elements corresponding to arbitrary
electron-emitter elements of said plurality of electron-emitter
elements and electrically disconnecting the arbitrary
electron-emitter elements from the first electrodes or the second
electrodes.
22. A method of manufacturing an image display comprising: a
display device including, a first plate having, a plurality of
electron-emitter elements each having a structure comprised of a
base electrode, an insulating layer and a top electrode stacked on
one another in this order, said electron-emitter element emitting
electrons from the surface of the top electrode when a voltage of
positive polarity is applied to the top electrode; a plurality of
first electrodes for respectively applying driving voltages to the
base electrodes of the electron-emitter elements lying in a row (or
column) direction, of said plurality of electron-emitter element;
and a plurality of second electrodes for respectively applying
driving voltages to the top electrodes of the electron-emitter
elements lying in the column (or row) direction, of said plurality
of electron-emitter elements; a frame component; and a second plate
having phosphors; wherein a space surrounded by said first plate,
said frame component and said second plate is brought into vacuum,
and wherein said respective electron-emitter elements have the base
electrodes and the .[.to.]. .Iadd.top .Iaddend.electrodes, at least
one of which are respectively connected to the first electrodes or
the second electrodes through connection wires, said method
comprising the step of: cutting the connection wires corresponding
to arbitrary electron-emitter elements of said plurality of
electron-emitter elements and electrically disconnecting the
arbitrary electron-emitter elements from the first electrodes or
the second electrodes.
.Iadd.23. An image display, comprising: a plurality of
electron-emitter elements arranged in a matrix form; a plurality of
column wires arranged in a first direction, and applying a first
driving voltage to the electron-emitter elements; a plurality of
row wires arranged in a second direction crossing the first
direction, and applying a second driving voltage to the
electron-emitter element; a first plate comprising the row wires
and column wires; and a second plate having phosphors, wherein a
space enclosed by the first plate and the second plate is a vacuum,
the plurality of electron-emitter elements are provided in an area
where the column wires are formed and outside the area where the
row wires are formed, the plurality of electron-emitter elements
comprise a first electrode and a second electrode, the first
electrode is coupled to the column wire, the second electrode is
coupled to the row wire, a connecting wire is placed between the
second electrode and the row wire, and the line width of the row
wire is thicker than the line width of the connecting
wire..Iaddend.
.Iadd.24. The image display according to claim 23, wherein the
connecting wire is resistor element..Iaddend.
.Iadd.25. The image display according to claim 23, wherein the
connecting wires placed between the row wires and the second
electrodes have connecting wires cut..Iaddend.
.Iadd.26. The image display according to claim 23, wherein the
connecting wire is coupled to the row wire in a portion where the
connecting wire traverses the row wire..Iaddend.
.Iadd.27. The image display according to claim 26, further
comprising: a first driving circuit applying the first driving
voltage to the column wire, wherein the resistance of the
connecting wire is larger than an output impedance of the first
driving circuit multiplied by 10..Iaddend.
.Iadd.28. The image display according to claim 26, wherein the
resistance value of the connecting wire multiplied by the
electrostatic capacitance of the electron-emitter element is
smaller than the horizontal scanning period of a displayed video
signal..Iaddend.
.Iadd.29. The image display according to claim 26, wherein the
resistance value of the connecting wire is smaller than the
differential resistance of the operation region of the
electron-emitter element..Iaddend.
.Iadd.30. The image display according claim 1, wherein the phosphor
comprises a first phosphor layer, a second phosphor layer, and a
third phosphor layer; the plurality of electron-emitter elements
include a first electron-emitter element emitting electrons to the
first phosphor layer, a second electron-emitter element emitting
electrons to the second phosphor layer, and a third
electron-emitter element emitting electrons to the third phosphor
layer; and a pixel displaying color images which is comprised of
the first, second, and third electron-emitter
elements..Iaddend.
.Iadd.31. The image display according to claim 30, wherein the
first, second, third electron-emitters are coupled to the same row
wire..Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an image display and a method of
manufacturing the same, and particularly to a technology effective
for application to a display apparatus which has thin-film electron
emitters having an electrode-insulator-electrode structure to emit
electrons into vacuum.
The thin-film electron emitters are electron-emitter elements each
using hot electrons produced by applying a high electric field to
an insulator.
As a typical example, an MIM (Metal-Insulator-Metal) electron
emitter comprising a thin film having a three-layer structure of a
top electrode-insulating layer-base electrode will be
explained.
FIG. 14 is a diagram for describing the principle of operation of
an MIM electron emitter illustrated as a typical example of a
thin-film electron emitter.
A driving voltage is applied between a top electrode 11 and a base
electrode 13 to set an electric field within a tunneling insulator
12 to 1 MV/cm to 10 MV/cm and over. Thus, electrons placed in the
neighborhood of the Fermi level in the base electrode 13 are
transmitted through a barrier by tunneling phenomena. Thereafter,
they are injected into the conduction bands of the tunneling
insulator 12 and top electrode 11, thereby resulting in hot
electrons.
Some of these hot electrons are subjected to scattering under
interaction with a solid in the tunneling insulator 12 and the top
electrode 11, thus leading to the loss of energy.
As a result, hot electrons having various energies exist when they
have reached an interface between the top electrode 11 and vacuum
10.
Of these hot electrons, ones having energy larger than the work
function .phi. of the top electrode 11 are emitted into the vacuum
10, and ones other than the above ones flow into the top electrode
11.
Assuming that a current based on the electrons flowing from the
base electrode 13 to the top electrode 11, is called a diode
current (Id), and a current based on the electrons emitted into the
vacuum 10 is called an emission current (Ie), an electron emission
efficiency (Ie/Id) ranges from about 1/10.sup.3 to about
1/10.sup.5.
Incidentally, the MIM thin-film electron emitter has been described
in, for example, Japanese Patent Application Laid-Open No. Hei
9-320456.
Now, the top electrode 11 and the base electrode 13 are provided in
plural form and these plural top electrodes 11 and base electrodes
13 are formed orthogonal to one another to thereby form thin-film
electron emitters in matrix form. Consequently, electron beams can
be produced from arbitrary locations and hence they can be used as
electron emitters for a display apparatus.
Namely, a display apparatus can be constructed wherein thin-film
electron-emitter elements are placed at every pixel, and electrons
emitted therefrom are accelerated in vacuo and thereafter applied
to each of phosphors to thereby allow the applied phosphor to emit
light, whereby a desired image is displayed thereon.
The thin-film electron emitters have excellent features as
electron-emitter elements for the display apparatus in that they
are capable of implementing a high-resolution display apparatus
because the emitted electron beams are excellent in directionality,
and they are easy to handle because they are insusceptible to the
influence of their surface contamination, for example.
In the display apparatus using the conventional thin-film electron
emitters, when one of a large number of thin-film electron-emitter
elements (electron emission regions) placed in matrix form was
short-circuited due to a failure in manufacture thereof or other
reasons, no electrons were emitted from all the thin-film
electron-emitter elements on a row or/and a column to which such a
thin-film electron-emitter element was connected, thus causing no
light emission. Namely, a "point defect" of one thin-film
electron-emitter element has caused a "line defect".
The above-described point will be explained below.
FIG. 15 is a diagram showing a schematic configuration of a
conventional thin-film electron-emitter matrix.
Thin-film electron-emitter elements 301 are respectively formed at
points where row electrodes (base electrodes) 310 and column
electrodes (top electrodes) 311 intersect respectively.
Incidentally, while the thin-film electron-emitter matrix is
illustrated with 3 rows and 3 columns in FIG. 15, the thin-film
electron-emitter elements 301 are actually placed by the number of
pixels constituting a display apparatus, or the number of
sub-pixels in the case of a color display apparatus.
Now, the respective thin-film electron-emitter elements 301 are
directly connected to the row electrodes 310 and the column
electrodes 311 respectively.
Therefore, when, for example, a thin-film electron-emitter element
301 placed at an intersection (R2, C2) of a row electrode 310 of R2
and a column electrode 311 of C2 is short-circuited due to a
failure in manufacture thereof or the like, the row electrode 310
of R2 and the column electrode 311 of C2 are short-circuited. Hence
even if an attempt were made to apply a suitable voltage to both
electrodes from a row electrode driving circuit 41 or a column
electrode driving circuit 42, the voltage would not be applied
thereto.
Therefore, all the thin-film electron-emitter elements 301 on the
row electrode of R2, or/and all the thin-film electron-emitter
elements 301 on the column electrode 311 of C2 are not operated,
thus causing a "line defect".
Even if elements equivalent to about 1/10000 of the total number of
pixels have "point defects" in a matrix-type display apparatus such
as a liquid-crystal display apparatus or the like, no problem
occurs from a practical standpoint and they can be used in most
cases.
Namely, about 100 "point defects" can be allowed in the case of a
display apparatus configured in 480.times.640.times.3 dots, for
example.
However, one having a "line defect" such as non-light emission of
all elements on one line cannot be used as a display apparatus.
Thus, the display apparatus using the conventional thin-film
electron emitters was accompanied by a problem that the "point
defects" produced the "line defect", thereby reducing production
yields.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problem of the
prior art. An object of the present invention is to provide a
technology capable of enhancing production yields in an image
display.
The above, other objects and novel features of the present
invention will become apparent from the description of the present
specification and the accompanying drawings.
Summaries of typical one of the inventions disclosed in the present
application will be described in brief as follows:
There is provided an image display which comprises a display device
including a first plate which has a plurality of electron-emitter
elements each having a structure comprised of a base electrode, an
insulating layer and a top electrode stacked on one another in this
order, the electron-emitter element emitting electrons from the
surface of the top electrode when a voltage of positive polarity is
applied to the top electrode; a plurality of first electrodes for
respectively applying driving voltages to the base electrodes of
the electron-emitter elements lying in a row (or column) direction,
of the plurality of electron-emitter elements; and a plurality of
second electrodes for respectively applying driving voltages to the
top electrodes of the electron-emitter elements lying in the column
(or row) direction, of the plurality of electron-emitter elements,
a frame component, and a second plate having phosphors, whereby a
space surrounded by the first plate, the frame component and the
second plate is brought to vacuum, wherein at least one the
electron-emitter element includes its corresponding base electrode
and top electrode at least one of which is connected to the first
electrode or second electrode through a resistor element.
Namely, the present invention is characterized in that a resistor
is inserted between a column electrode and a thin-film
electron-emitter element or between a row electrode and a thin-film
electron-emitter element, or resistors are respectively inserted
between a column electrode and a thin-film electron-emitter element
and between a row electrode and a thin-film electron-emitter
element.
FIG. 1 is a diagram showing a schematic configuration of one
example of a thin-film electron-emitter matrix of an image display
of the present invention.
The image display shown in FIG. 1 is equipped with a thin-film
electron-emitter matrix in which resistors 305 are respectively
inserted between column electrodes 311 and thin-film
electron-emitter elements 301.
Incidentally, the resistors 305 will be called pixel resistors in
the following description.
While one pixel is formed of a combination of respective sub-pixels
of red, blue and green in the case of a color image display, the
"pixels" defined herein are equivalent to the sub-pixels in the
case of the color image display. In the present specification,
pixels in the case of a monochrome image display, and sub-pixels in
the case of a color image display are also called "dots".
Consider where the resistance value of the resistor 305 is set to
10 times or more the output impedance of each column electrode
driving circuit 42. Since the resistance between a row electrode
310 of R2 and a column electrode of C2 is sufficiently larger than
the output impedance of the corresponding driving circuit even if a
thin-film electron-emitter element 301 at (R2, C2) is
short-circuited, a sufficient voltage is applied to both electrodes
and hence other thin-film electron-emitter elements 301 on both
electrodes normally operate. Of course, the thin-film
electron-emitter element 301 at (R2, C2) does not operate.
Thus, the present invention is capable of preventing the "point
defects" from leading to the "line defect".
The following restrictions are imposed on the resistance value (Rr)
of the pixel resistor 305.
Assuming that capacitance obtained by adding together parasitic
capacitance of each thin-film electron-emitter element per se and
parasitic capacitance within one pixel is defined as Ce, CeRr
results in time constant of a change in signal voltage applied to
the corresponding thin-film electron-emitter element 301.
Thus, (CeRr<1H) must be taken when used as the display
apparatus.
Here, 1H indicates a horizontal scanning period. Assuming that a
field frequency is defined as f and the effective number of scan
lines is defined as Neff (when two lines are simultaneously driven:
(the number of scan lines+2)), the horizontal scanning period (1H)
is given by the following equation (1): 1H=1/(fNeff) (1) When f=60
Hz and Neff=256, for example, 1H=64 .mu.s is obtained.
A second effect of the present invention resides in that the
influence of deviations in characteristics of wire resistance and a
driving circuit can be reduced.
Such a functional relation as expressed by the following equation
(2) is established between a diode voltage (Vd) applied between
both electrodes (top electrode 11 and base electrode 13) of the
thin-film electron emitter 301 and a diode current (Id) flowing
therebetween: Id=f(Vd) (2)
On the other hand, the total wire resistance of the row electrodes
310 and column electrodes 311 is defined as R(line) the output
impedance of each row electrode driving circuit 41 is defined as
Zout(row), and the output impedance of each column electrode
driving circuit 42 is defined as Zout(column).
Assuming that the difference between a voltage outputted from the
row electrode driving circuit 41 and a voltage outputted from the
column electrode driving circuit 42, i.e., an externally applied
voltage is defined as V0, the diode voltage (Vd) applied across the
thin-film electron-emitter element 301 is expressed in the
following equation (3): Vd=V0-Id(R(line)+Zout(row)+Zout(column))
(3)
Thus, the diode current (Id) that flows through the thin-film
electron-emitter element 301, is expressed in the following
equation (4): Id=f[V0-id(R(line)+Zout(row)+Zout(column))] (4)
Therefore, when deviations .DELTA.R(line), .DELTA.Zout(row) and
.DELTA.Zout(column) exist in R(line), .DELTA.Zout(row) and
.DELTA.Zout (column), respectively, the diode current (Id) also
varies in its current value.
A current (emission current) (Ie) emitted into vacuum from the
thin-film electron-emitter element 301 varies according to the
current value of the diode current (Id).
Accordingly, brightness non-uniformity occurs in the display
apparatus.
In the present invention, the resistors 305 are inserted every
thin-film electron-emitter elements. Assuming that the resistance
value of the resistor 305 is defined as Rr, a diode voltage (Vd)
applied across the thin-film electron-emitter element 301 is
expressed in the following equation (5):
Vd=V0-Id(Rr+R(line)+Zout(row)+Zout(column)) (5)
Then, Rr is set so as to become larger than the deviations
{R(line), .DELTA.Zout(row) and .DELTA.Zout(column). Consequently,
these deviations will not cause a deviation in the current value of
the diode current (Id) and hence no brightness non-uniformity
occurs.
Next consider the influence of a deviation in the resistance value
of the pixel resistor 305 on a deviation in the amount of the
emission current.
Let's assume that the externally applied voltage V0 is applied over
all. The influence of the deviation in the resistance value R of
the pixel resistor 305 on the current that flows through the
thin-film electron-emitter element 301 is estimated.
Assuming that the diode current-voltage characteristics of the
thin-film electron-emitter element 301 are represented as Id=f(V),
and currents that flow when the resistance value of the pixel
resistor 305 is given as R and R+.DELTA.R, are respectively defined
as I and I+.DELTA.I, the relation expressed in the following
equation (6) is established:
.DELTA..DELTA..DELTA..alpha..alpha..DELTA. dd ##EQU00001##
Thus, if the resistance value R+.DELTA.R of the pixel resistor 305
is set smaller than a differential resistance re of the thin-film
electron-emitter element 301 (in an operation region).
If .alpha..gtoreq.1 is established, then the above equation (6) can
be transformed as the following equation (7):
.DELTA..ltoreq..times..DELTA..DELTA. ##EQU00002##
Thus, the influence of the deviation .alpha.R in the resistance
value of the pixel resistor 305 on uniformity of a displayed image
is lessened.
In other words, the allowance of the deviation in the resistance
value of the pixel resistor 305 becomes large and hence the display
apparatus is easy to be manufactured.
The present invention provides a display apparatus which comprises
a display device including a first plate which has a plurality of
electron-emitter elements each having a structure comprised of a
base electrode, an insulating layer and a top electrode stacked on
one another in this order, the electron-emitter element emitting
electrons from the surface of the top electrode when a voltage of
positive polarity is applied to the top electrode; a plurality of
first electrodes for respectively applying driving voltages to the
base electrodes of the electron-emitter elements lying in a row (or
column) direction, of the plurality of electron-emitter elements;
and a plurality of second electrodes for respectively applying
driving voltages to the top electrodes of the electron-emitter
elements lying in the column (or row) direction, of the plurality
of electron-emitter elements, a frame component, and a second plate
having phosphors, whereby a space surrounded by the first plate,
the frame component and the second plate is brought into vacuum,
wherein the at least one electron-emitter element includes its
corresponding base electrode and top electrode at least one of
which is connected to the first electrode or second electrode
through a resistor element or a connection wire.
In the present invention, when a defect due to a short circuit of
the thin-film electron-emitter element 301 is found at a production
stage, the corresponding element is cut off to thereby enable
prevention of the occurrence of the "line defect".
FIG. 16 is a plan view showing a thin-film electron-emitter element
structure of a conventional thin-film electron-emitter matrix.
In the conventional thin-film electron-emitter matrix as shown in
FIG. 16, thin-film electron-emitter elements 301 are respectively
formed at regions where row electrodes 310 and column electrodes
311 spatially overlap in fact. It was therefore difficult to
separate only the thin-film electron-emitter elements 301 from the
row electrodes 310 or column electrodes 311.
In the present invention, as will be described in detail in the
following embodiments, electron-emitter structures of respective
pixels are devised to thereby easily separate thin-film
electron-emitter elements 301 at specific pixels through the use of
a laser repair technology or breakage by current-heating, whereby
the occurrence of "line defects" can be lessened.
Incidentally, a prior-art search has been carried out based on the
result of the present invention from the viewpoint that the
resistors are formed in every pixels.
As a result, the corresponding art has not been found in the
display apparatus using the thin-film electron emitters, which is
intended for the present invention.
As a result of a further investigation of objects to be researched,
which is extended up too other-types electron emitters, an example
in which a resistive sheet is inserted into individual pixels in
field-emission electron emitters, has been found out in
EURODISPLAY'90, 10th International Display Research Conference
Proceedings (vde-verlag, Berlin, 1990), pp. 374-377.
This reference describes a field-emitter array comprising
multiplicity of electron-emitting tips(emitter tips) for each
pixel. By introducing a resister sheet which functions as
resistance independently for each emitter tip, a negative feedback
resulting from the voltage drop in the resistor at each emitter tip
averages the current deviation among the every emitter tips in each
pixel, and thereby alleviating the deviation.
The reference above mentioned aims to solve the problem that only
specific emitter tips inside a pixel emit a large current, thus
generating "bright spots" INSIDE the pixel which causes degradation
in image quality.
Further, the technology described in the known art encounters
difficulties in cutting off a defect pixel with laser beam
irradiation or the like for defect repairing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a schematic configuration of one
example of a thin-film electron-emitter matrix of an image display
of the present invention;
FIG. 2 is a plan view illustrating a configuration of part of a
thin-film electron-emitter matrix of a cathode plate employed in an
embodiment 1 of the present invention;
FIG. 3 is a plan view showing the relationship in position between
the cathode plate and a phosphor plate employed in the embodiment 1
of the present invention;
FIGS. 4(a) and 4(b) are respectively fragmentary cross-sectional
views depicting a configuration of an image display according to
the embodiment 1 of the present invention;
FIGS. 5(a) through 5(g) are respectively diagrams for describing a
method of manufacturing the cathode plate employed in the
embodiment 1 of the present invention;
FIG. 6 is a diagram showing other shapes of pixel resistors
employed in the embodiment 1 of the present invention;
FIG. 7 is a connection diagram illustrating a state in which
driving circuits are connected to a display panel employed in the
embodiment 1 of the present invention;
FIG. 8 is a timing chart showing one example illustrative of
waveforms of driving voltages outputted from the respective driving
circuits shown in FIG. 7;
FIG. 9 is a diagram showing a configuration of one thin-film
electron-emitter matrix of a cathode plate employed in an
embodiment 2 of the present invention;
FIGS. 10(a) through 10(g) are respectively diagrams for describing
a method of manufacturing the thin-film electron-emitter matrix of
the cathode plate employed in the embodiment 2 of the present
invention;
FIG. 11 is a diagram showing a schematic configuration of a
thin-film electron-emitter matrix according to an embodiment 3 of
the present invention;
FIG. 12 is a plan view of the thin-film electron-emitter matrix
according to the embodiment 3 of the present invention;
FIG. 13 is a cross-sectional view illustrating a fragmentary
section structure of one thin-film electron-emitter element
employed in the embodiment 3 of the present invention;
FIG. 14 is a diagram for describing the principle of operation of a
thin-film electron emitter;
FIG. 15 is a diagram showing a schematic configuration of a
conventional thin-film electron-emitter matrix; and
FIG. 16 is a plan view showing a pixel structure of a conventional
display apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will hereinafter be
described in detail with reference to the accompanying
drawings.
Incidentally, elements of structure each having the same function
in all drawings for describing the embodiments are respectively
identified by the same reference numerals and their repetitive
description will therefore be omitted.
Embodiment 1
An image display according to an embodiment 1 of the present
invention has a configuration wherein a display panel (display
device of the present invention) in which brightness-modulation
elements for respective dots are formed by combining a thin-film
electron-emitter matrix functioning as electron emitters used for
emitting electrons and phosphors, is used to connect driving
circuits to row electrodes and column electrodes of the display
panel respectively.
Now the display panel comprises a cathode plate formed with a
thin-film electron-emitter matrix, and a phosphor plate formed with
phosphor patterns.
FIG. 2 is a plan view showing a configuration of part of a
thin-film electron-emitter matrix of a cathode plate according to
the present embodiment, and FIG. 3 is a plan view showing the
relationship in position between the cathode plate and phosphor
plate according to the present embodiment, respectively.
FIG. 4 is a fragmentary cross-sectional view showing a
configuration of the image display according to the present
embodiment, wherein FIG. 4(a) is cross-sectional views taken along
cut lines A-B shown in FIGS. 2 and 3, and FIG. 4(b) is
cross-sectional views taken along cut lines C-D shown in FIGS. 2
and 3.
However, the illustration of a plate 14 is omitted from FIGS. 2 and
3.
Further, a reduction scale as viewed in a vertical height direction
is arbitrary in FIG. 4. Namely, while base electrodes 13, top
electrode buslines 32, and the like are respectively less than or
equal to a few .mu.m in thickness, the distance between the plate
14 and a plate 110 is equivalent to a length of from about 1 mm to
about 3 mm.
While the following description is made using an electron-emitter
matrix with 3 rows and 3 columns, it is needless to say that the
numbers of rows and columns in an actual display panel respectively
result in several hundreds rows to a few thousand rows, and a few
thousand columns.
In FIG. 2, regions 35 surrounded by dot lines indicate
electron-emission regions (electron-emitter elements in the present
invention) respectively.
Each of the electron-emission regions 35 emits electrons into
vacuum from within its area or region at a location defined by a
tunneling insulator 12.
Since the electron-emission region 35 is not represented on a plan
view because it is covered with a top electrode 11, it is
illustrated by a dotted line.
FIG. 5 is a diagram for describing a method of manufacturing a
cathode plate employed in the present embodiment.
A method of fabricating a thin-film electron-emitter matrix of the
cathode plate employed in the present embodiment will be explained
below with reference to FIG. 5.
Incidentally, while only one thin-film electron-emitter element 301
formed at a point where one of row electrodes 310 and one of column
electrodes 311 both shown in FIGS. 2 and 3 intersect, is extracted
and plotted in FIG. 5, a plurality of thin-film electron-emitter
elements 301 are actually arranged in matrix form as illustrated in
FIGS. 2 and 3.
Further, the right columns shown in FIG. 5 are respectively plan
views, whereas the left columns are respectively cross-sectional
views taken along lines A-B in the views on the right side.
An electrically conductive film for a base electrode 13 is formed
with a thickness of 300 nm, for example, on an insulating substrate
14 such as glass or the like.
As a material for the base electrode 13, may be used, for example,
an aluminum (Al: hereinafter called "Al") alloy.
In the present method, an Al-neodymium (Nd: hereinafter called
"Nd") alloy was used.
For example, a sputtering method, resistive-heating evaporation or
the like may be used to form such an Al alloy film.
Next, the Al alloy film is processed into strip form by resist
formation using photo lithography and etching following it to
thereby form a base electrode 13 as shown in FIG. 5(a).
A resist used herein may be one suitable for etching, and either of
wet etching and dry etching may be used as the etching.
Next, a resist is applied and patterned by exposing it with an
ultraviolet-ray, followed by patterning, thereby forming a resist
pattern 501 as shown in FIG. 5(b).
As the resist, may be used, for example, a quinonediazide positive
resist.
Next, anodic oxidation is done while the resist pattern 501 remains
attached to the base electrode 13 to thereby form a protection
layer 15 as shown in FIG. 5(c).
In the present embodiment, an anodization voltage was set to about
100V upon such anodic oxidation, and the thickness of the
protection layer 15 was set to about 140 nm.
The resist pattern 501 is removed with an organic solvent such as
acetone or the like and thereafter the surface of the base
electrode 13 which had been covered with the resist is anodically
oxidized again to thereby form a tunneling insulator 12 as shown in
FIG. 5(d).
In the present embodiment, an anodization voltage was set to 6 V
upon such re-anodization, and the thickness of the tunneling
insulator was set to 8 nm.
Next, an electrically conductive film for a top electrode busline
under-layer film is formed and the resist is patterned and
subjected to etching to thereby form the top electrode busline
under-layer film 33 as shown in FIG. 5(e).
In the present embodiment, titanium (Ti) was used as a material for
the top electrode busline under-layer film, and the thickness
thereof was set to about 20 nm.
Next, an electrically conductive film for a top electrode busline
is formed and a resist is patterned and subjected to etching to
thereby form the top electrode busline 32 and a column electrode
311 as shown in FIG. 5(f).
In the present embodiment, an Al alloy was used as a material for
the top electrode busline 32 and the column electrode 311, and the
thickness thereof was set to about 300 nm.
Incidentally, Au or the like may be used as the material for the
top electrode busline 32 and the column electrode 311.
Next, an iridium (Ir) having a thickness of 1 nm, a platinum (Pt)
having a thickness of 2 nm, and a gold (Au) having a thickness of 3
nm are formed by sputtering in that order.
According to a resist and patterning by etching, a multi-layer film
of Ir--Pt--Au is patterned as the top electrode 11 as shown in FIG.
5(g).
Incidentally, a region 35 surrounded by a dotted line indicates an
electron emission region in FIG. 5(g).
The electron-emission region 35, from which electrons emit into
vacuum, is defined by the tunneling insulator 12.
The thin-film electron-emitter matrix is completed on the plate 14
according to the above-described process.
In the thin-film electron n-emitter matrix according to the present
embodiment, electrons are emitted from the region
(electron-emission region 35) defined by the tunneling insulator
12, i.e., the region define by the resist pattern 501.
Since the protection layer 15, which is of a thick insulating film,
is for ed on the periphery of the electron-emission region 35, an
electric field applied between the top electrode and the base
electrode does not concentrate at sides or edges of the base
electrode 13 and hence an electron emission characteristic stable
over a long time is obtained.
The top electrode busline under-layer film 33 has three roles.
The first role resides in that a busline under-layer film 33, being
thin in thickness is provided to make certain of an electrical
contact between a top electrode 11, whose thickness is about 10 nm
or less, and a top electrode busline 32, thereby improving
reliability.
When the top electrode 11 is directly formed on the top electrode
busline 32 except for the top electrode busline under-layer film
33, the top electrode 11 is easy to break at steps of the top
electrode busline 32 (100 nm thick) and the reliability of a
electrical connection between the top electrode busline 32 and the
top electrode 11 is reduced.
The second role resides in the formation of a pixel resistor
305.
As shown in FIG. 5(g), the pixel resistor 305 is shaped in a bent
form, and the resistance value of the pixel resistor 305 is defined
as the value of resistance between the top electrode busline 32 and
the column electrode 311.
The resistance value is determined according to a material for the
pixel resistor 305, the thickness thereof, and the geometrical form
of the pixel resistor 305.
When, for example, titanium (Ti) is used as the material for the
top electrode busline under-layer film, the thickness thereof is
set to 20 nm, and a length/width ratio is set to about 40, the
resistance value Rr of the pixel resistor 305 results in about 1
k.OMEGA..
When a titanium nitride (TiN) film having a thickness of 20 nm is
used, its length/with ratio may be set to about 10 and the pixel
resistor 305 may be set to about 1 k.OMEGA..
Since a differential resistance (re) in an operation region, of
each thin-film electron-emitter element 301 is a few 10 k.OMEGA., a
condition of (re/Rr>1) is sufficiently satisfied.
Thus, the influence a deviation in the resistance value of each
pixel resistor 305 on a displayed image is lessened for the above
reason.
Since the electrostatic capacitance Ce of the thin-film
electron-emitter element 301 is about 0.1 nF, CeRr=0.1 .mu.s and a
condition of CeRr>1H is also sufficiently satisfied.
Here, 1H indicates a period, during which a signal corresponding to
one row is applied, and varies according to the number of scan
lines, a refresh rate (field period) and the like of the display
apparatus. 1H=10 .mu.s to 64 .mu.s in typical cases.
The third role resides in serving itself as a "cut point" for
separating a thin-film electron-emitter element 301 having caused a
defect due to a short circuit at production from its corresponding
column electrode 311.
Applying a voltage between a row electrode and a column electrode
associated with the defect thin-film electron-emitter element 301
to thereby burn out the corresponding pixel resistor 305 may cut it
off.
Alternatively, a laser beam may be applied to a portion of the
pixel resistor 305 to cut off it.
Since this portion is formed of the thin top-electrode busline
under-layer film 33, it is easy to cut.
Since other component are not placed underneath the pixel resistor
305, other region are not affected by the application of the laser
beam.
Namely, it is of importance that at least part of the pixel
resistor 305 exists in a location where it does not intersect both
of the row electrode 311 and the column electrode 311.
Incidentally, when the thin-film electron-emitter element 301
having caused the defect due to the short circuit at production is
separated from the corresponding column electrode 311, a connection
wire for connecting the column electrode 311 and the thin-film
electron-emitter element 301 may be used as an alternative to the
pixel resistor 305.
FIG. 6 is a diagram showing another shape of the pixel resistor 305
employed in the present embodiment.
FIG. 6 corresponds to FIG. 5(g). As shown in FIG. 6(a), a thin or
slight portion is provided at part of the pixel resistor 305, or a
portion thin in thickness may be partly provided as shown in FIG.
6(b).
The pixel resistor 30 can thus be cut easier upon the cutting
thereof by the application of the laser beam.
As described above, the advantage of the present embodiment resides
in that each pixel resistor 305 is formed through the use of the
process of forming the top electrode busline under-layer film 33,
which is used to enhance the reliability of the electrical
connectivity between the top electrode busline 32 and the top
electrode 11.
This is made possible since the pixel resistor 305 is formed of the
same material as the busline under-layer film 33.
Namely, as is understood from the manufacturing or fabricating
process shown in FIG. 5, the pixel resistors are introduced
according to the number of execution of lithography, which is
identical to the conventional one.
Thus, an increase in the production cost due to the introduction of
each pixel resistor 305 does not occur.
However, the present invention is not limited to it. The pixel
resistor 305 may of course be formed of a material different from
that for the busline under-layer film 33.
While a geometrical factor that will produce a deviation in the
resistance value of each pixel resistor 305 at its production,
results from the width and length of the pixel resistor 305, the
former (width) is defined by a photo-mask at the formation of the
pixel resistor 305. Therefore, the deviation in the width geometry
is small.
The latter (length) side fined by a photo-mask at the formation of
the column electrode 311 and the top electrode busline 32.
Therefore, the deviation in the length geometry is small. Namely,
the pixel resistor 305 can be formed with a small deviation.
There are steps each corresponding to the thickness (about 30 nm)
of the base electrode 13 are provided between the base electrode 13
and the plate 14.
In the present embodiment, as shown in FIGS. 2 and 4, the top
electrode busline 32 (about 300 nm in thickness) is designed to
extend across the steps to thereby avoid wire breaking at the
steps.
The phosphor plate according to the present embodiment comprises
black matrixes 120 formed on a plate 110 such as soda lime glass or
the like, phosphors (114A through 114C) of red (R), green (G) and
blue (B), which are formed within trenches or grooves of the black
matrixes 120, and a metal back film 122 formed over these.
A method of manufacturing the phosphor plate according to the
present embodiment will be explained below.
The black matrixes 120 are formed on the plate 110 with the object
of increasing the contrast ratio of the display apparatus (see FIG.
4(b)).
Next, the red phosphor 114A, green phosphor 114B and blue phosphor
114C are formed.
These phosphors were patterned by photo lithography in a manner
similar to being used in the phosphor screen of the ordinary
cathode-ray tube.
As the phosphors, for example, Y.sub.2O.sub.2S:Eu (P22-R), ZnS:Cu,
Al (P22-G), and ZnS:Ag (P22-B) were respectively used as red, green
and blue.
Next, filming is effected on the plate 110 with a film such as
nitrocellulose or the like and there after Al is evaporated onto
the entire plate 110 with a thickness of from about 50 nm to about
300 nm to thereby produce the metal back film 122.
Thereafter, the plate 110 is heated at about 400.degree. C. to
pyrolize organic substances such as a filming film, PVA, etc. The
phosphor plate is completed in this way.
The cathode plate and phosphor plate fabricated in this way are
sealed with frit glass with a spacer 60 interposed
therebetween.
A relationship of positions between the phosphors (114A through
114C) formed in the phosphor plate and the thin-film
electron-emitter matrix of the cathode plate is represented as
shown in FIG. 3.
Incidentally, the components on the plate 110 are illustrated by
oblique lines alone in FIG. 3 to show the relationship of positions
between the phosphors (114A through 114C), the black matrixes 120
and the components.
The relationship between the electron-emission region 35, i.e., the
portion where the tunneling insulator 12 is formed, and the width
of each of the phosphors (114A through 114C) is of importance.
In the present embodiment, the width of the electron-emission
region 35 is designed so as to be narrower than that of each of the
phosphors (114A through 114C) in consideration of an electron beam
emitted from the thin-film electron emitter 301 being slightly
broadened spatially.
Further, since FIG. 3 is a diagram for indicating the relationship
of positions between the electron-emission regions 35 and the
phosphors (114A through 114C), other components on the plate 14,
e.g., the top electrodes 11, the top electrode buslines 32, and the
pixel resistors 305 are omitted.
The distance between the plate 110 and the plate 14 is set so as to
range from about 1 mm to about 3 mm.
The spacer 60 is inserted to prevent breakage of the display panel
due to an external force of atmospheric pressure when the interior
of the display panel is vacuumized.
Thus, when a display apparatus having a display area represented by
less than or equal to a width of about 4 cm.times.a length of about
9 cm is fabricated by using glass having a thickness of 3 mm as for
the plates 14 and 110, it can endure the atmospheric pressure owing
to mechanical strengths of the plates 110 and 14 per se. It is
therefore unnecessary to insert the spacer 60.
The spacer 60 is shaped in the form of a rectangular parallelepiped
as shown in FIG. 3 by way of example.
While there are provided posts for the spacers 60 every three rows
in the present embodiment, the number of the posts (layout density)
may be reduced within an endurable range of mechanical
strength.
Sheet-shape or pillar-shape posts made up of glass or ceramic are
placed as the pacers 60.
Incidentally, while the spacer 60 seems like being not in contact
with the plate 14 in FIG. 4(a), it is actually in contact with the
column electrodes 311 on the plate 14.
In FIG. 4(a), a clearance can be defined by the thickness of the
column electrode 311.
The sealed display panel is sealed off by being pumped to a vacuum
of about 1.times.10.sup.-7 Torr.
In order to maintain the degree of vacuum in the display panel in a
high vacuum, a getter film is formed or a getter material is
activated at a predetermined position (not shown) lying within the
display panel immediately before or after its sealing.
In the case of a getter material with barium (Ba) as a principal
component, a getter film can be formed by inductive heating.
The display panel using the thin-film electron-emitter matrix is
completed in this way.
Since the distance between the plate 110 and the plate 14 extends
long so as to range from about 1 mm to about 3 mm in the present
embodiment, an acceleration voltage applied to the metal back film
122 can be set to a high voltage of 3 KV to 6 KV. Thus, the
phosphors for the cathode-ray tube (CRT) can be used for the
phosphors (114A through 114C) as described above.
FIG. 7 is a connection diagram showing a state in which driving
circuits are connected to the display panel according to the
present embodiment.
Row electrodes 310 (base electrodes 13) are respectively connected
to row electrode driving circuits 41, and column electrodes 311
(top electrode buslines 32) are respectively connected to column
electrode driving circuits 42.
Connections between the respective driving circuits (41 and 42) and
a cathode plate are made by, for example, one obtained by
subjecting a tape carrier package to connect-by-pressure by means
of an anisotropically conductive film, or chip-on-glass or the like
obtained by directly implementing a semiconductor chip constituting
each of the driving circuits (41 and 42) on the plate 14 of the
cathode plate.
An acceleration voltage, which ranges from about 3 KV to about 6
KV, is always applied to the metal back film 122 from an
acceleration voltage source 43.
FIG. 8 is a timing chart showing one example illustrative of
waveforms of driving voltages outputted from the respective driving
circuits shown in FIG. 7.
Let's now assume that an nth row electrode 310 is represented as
Rn, an mth column electrode 311 is represented as Cm, and a dot for
an intersection of the nth row electrode 310 and the mth column
electrode 311 is represented as (n, m) At a time t0, any electrode
carries a voltage of 0 and hence no electrons are emitted, whereby
the phosphors (114A through 114C) do not emit light.
At a time t1, the row electrode driving circuit 41 applies a
driving voltage of (V.sub.R1) to its corresponding row electrode
310 of R1, and the column electrode driving circuits 42 apply a
driving voltage of (V.sub.C1) to their corresponding column
electrodes 311 of (C1 and C2).
Since a voltage of (V.sub.C1-V.sub.R1) is applied between the top
electrode 11 and the base electrode 13 for dots (1, 1) and (1, 2)
through the pixel resistor 305, thin-film electron emitters for the
two dots emit electrons into vacuum if the voltage of
(V.sub.C1-V.sub.R1)) is set to greater than or equal to a threshold
voltage for electron emission.
In the present embodiment, V.sub.R1=-5V and V.sub.C1=4.5V.
The emitted electrons are accelerated by the voltage applied to the
metal back film 122 and thereafter collide with the phosphors (114A
through 114C) to thereby allow the phosphors (114A through 114C) to
emit light.
When the row electrode driving circuit 41 applies the driving
voltage of (V.sub.R1) to s corresponding row electrode 310 of R2,
and the column electrode driving circuit 42 applies the voltage of
(V.sub.C1) to its corresponding column electrode 311 of C1 at a
time t2, a dot (2, 1) lights up similarly.
When the driving voltages having such voltage waveforms as shown in
FIG. 8 are applied to their corresponding row and column electrodes
310 and 311, only dots diagonally shaded in FIG. 7 light up.
In this way, changing the signals applied to the column electrodes
311 allows the display of a desired image or information.
By suitably changing the magnitude of the driving voltage
(V.sub.C1) applied to each column electrode 311 in accordance with
an image signal, an image having a gray scale can be displayed.
Incidentally, in order t release the charges accumulated in the
tunneling insulator 12, the row electrode driving circuits 41 apply
a driving voltage of (V.sub.R2) to all of the row electrodes 310
and simultaneously the column electrode driving circuits 42 apply a
driving voltage of 0 V to all of the column electrodes at a time t4
in FIG. 8.
Since V.sub.R2=5 V now, a voltage of a -V.sub.R2=-5 V is applied to
each of the thin-film electron emitters 301.
Applying the voltage (reverse pulse) of polarity opposite to at
electron emission in this way allows an improvement in lifetime
characteristic of each thin-film electron emitter.
Incidentally, the use of a vertical blanking period of a video
signal as reverse pulse applying periods (see t4 to t5 and t8 to t9
in FIG. 18) yields satisfactory matching with the video signal.
Embodiment 2
FIG. 9 is a diagram showing a configuration of one thin-film
electron-emitter element 301 of a thin-film electron-emitter matrix
of a cathode plate employed in an embodiment 2 of the present
invention. The right side is a plan view and the left side is a
cross-sectional view taken along a cut line A-B.
In the present embodiment, a pixel resistor 305 is formed of the
same material as a top electrode 11.
A production process is simplified by forming the pixel editors 305
with the same material as the top electrode 11 in this way.
The resistance value of the pixel resistor 305 in this case is
defined as the value of resistance between a column electrode 311
and a top electrode busline 32 in a manner similar to the
embodiment 1.
Ones other than such a pixel structure are similar to the first
embodiment.
FIG. 10 is a diagram for describing a method of manufacturing the
thin-film electron-emitter matrix of the cathode plate according to
the present embodiment.
Incidentally, only one thin-film electron-emitter element 301
formed at the intersection of one of the row electrodes 310 and one
of the column electrodes 311 in FIG. 1 is extracted and plotted in
FIG. 10.
The right column in FIG. 10 shows plan views and the left column
shows cross-sectional views taken along cut lines A-B in the right
drawings.
Up to FIG. 10(d), the thin-film electron-emitter matrix is formed
according to th same method as up to FIG. 5(d).
Next, Sn-doped indium oxide (i.e., ITO (Indium Tin Oxide)) film is
formed by sputtering. Here, the thickness of the ITO film was set
to about 10 nm.
According to a resist and patterning by etching, the ITO film is
patterned to form a top electrode 11 as shown in FIG. 10(e).
Next, resists 502 are formed with a pattern shown in FIG. 10(f) and
thereafter subjected to electroplating to thereby form a top
electrode busline 32 and a column electrode 311.
In the present embodiment, an electroplating solution for
gold-plating is used to pass current of about 0.1A/dm.sup.2 through
the top electrode 11, whereby a gold film is selectively grown or
deposited on the top electrode 11.
The busline 32, which is about 400 nm in thickness, is formed in
this way.
While the gold electroplating is used in the present embodiment,
other electrode materials such as copper (Cu), Nickel (Ni), etc.
may of course be used.
After the busline 32 has been formed by plating, the resists 502
are peeled off to complete the thin-film electron-emitter matrix
according to the present embodiment as shown in FIG. 10(g).
The feature of the present embodiment resides in that the top
electrode 11, being thin in thickness is placed below the busline
32, being thick in thickness.
Therefore, the electrical connection between the top electrode
busline 32 and the top electrode 11 can be ensured with
satisfactory reliability even if its connection is not made via the
top electrode busline under-layer film.
The manufacturing method shown in FIG. 10 is illustrated as one
example. It is needless to say that the structure shown in FIG. 9
can be formed even if plating is not used for the growth or
deposition of the top electrode busline 32 and the column electrode
311.
A method of forming phosphors or the like on a plate 110, the
relationship of positions between thin-film electron-emitter
elements 301 and the phosphors (114A through 114C), a method of
connecting driving circuits, and a method of driving the same are
similar to those employed in the embodiment 1 mentioned
previously.
Embodiment 3
FIG. 11 is a diagram showing a schematic configuration of a
thin-film electron-emitter matrix according to an embodiment 3 of
the present invention
In the present embodiment as shown in FIG. 11, pixel resistors 305
are respectively inserted between row electrodes 310 and thin-film
electron emitter elements 301.
Described more specifically, the pixel resistors 305 are
respectively inserted between base electrodes 13 for thin-film
electron-emitter elements 301 and row electrodes 310.
As one example for implementing a pixel structure shown in FIG. 11,
a specific pixel structure is shown in FIGS. 12 and 13.
FIG. 12 is a plan view of the thin-film electron-emitter matrix
according to the present embodiment.
FIG. 13 is a cross-sectional view showing a fragmentary section
structure of one thin-film electron-emitter element 301 according
to the present embodiment, wherein FIG. 13(a) is a cross-sectional
view taken along cut line A-B of FIG. 12, and FIG. 13(b) is a
cross-sectional view taken along cut line C-D of FIG. 12.
As shown in FIG. 12, a pixel resistor 305 connects between a row
electrode 310 and a base electrode 13.
The pixel resistor 305 is covered with a pixel-resistor insulator
306, and the row electrode 310 is covered with a row-electrode
insulator 315.
The base electrode 13 is formed of an Al--Nd alloy or the like at a
portion corresponding to the thin-film electron-emitter element
(pixel) 301.
Subsequently, a thin-film electron emitter may be formed according
to a method substantially similar to the method described in the
embodiment 1.
As is understood from FIG. 12, the column electrode 311 and the top
electrode buslines 32 are identical in the present embodiment.
It is therefore easy to finely fabricate the pitch between the
columns adjacent to each other.
In a sub-pixel-configured color display apparatus of a vertical
RGB-stripe pattern, a sub-pixel pitch in a column direction, i.e.,
the pitch of an arrangement of the thin-film electron-emitter
elements 301 reaches 1/3 of a pitch in a row direction. It is
therefore of importance that the pitch in the column direction can
finely be set. This results in the advantage of this pixel
structure.
However, a drawback arises in that the production process becomes
slightly complex as compared with the embodiments 1 and 2.
A method of forming phosphors or the like on a plate 110, the
relationship of positions between thin-film electron-emitter
elements 301 and the phosphors (114A through 114C), a method of
connecting driving circuits, and a method of driving the same are
similar to those employed in the embodiment 1.
While the example (FIG. 1) of connecting the pixel resistors 305 to
their corresponding column electrodes 311 and the example (FIG. 11)
of connecting the same to their corresponding row electrodes 310
have been made in the above description, it is needless to say that
the effect of the present invention is obtained even if the pixel
resistors 305 are inserted between the column electrodes 311 and
electron-emitter element as well as between row electrodes 310 and
electron-emitter element.
While the embodiments in which the pixel resistors 305 have been
connected to all the electron-emitter elements 301, have been
described in the respective embodiments, the electron-emitter
elements 301 to which no pixel resistors 305 are connected, may be
provide in any number within a range in which a production yield is
not extremely reduced.
While the invention made by the present inventors has been
described specifically by the illustrated embodiments, the present
invention is not limited to the embodiments. It is needless to say
that various changes can be made thereto within the scope not
departing from the substance thereof.
Advantageous effects obtained by typical one of the inventions
disclosed in the present application will be explained in brief as
follows: (1) According to an image display of the present
invention, a production yield can be enhanced since it is possible
to prevent point defects from bringing about a "line defect". (2)
According to an image display of the present invention, since it is
possible to lessen the influence of a deviation in wire resistance
and a deviation in the characteristic of a driving circuit on the
non-uniformity across the display area in brightness and the amount
of a emission current, the fabrication thereof becomes easy, and
the production cost thereof can be reduced.
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