U.S. patent application number 11/353902 was filed with the patent office on 2006-06-22 for image displaying device.
Invention is credited to Hisao Tanabe.
Application Number | 20060132009 11/353902 |
Document ID | / |
Family ID | 28457571 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060132009 |
Kind Code |
A1 |
Tanabe; Hisao |
June 22, 2006 |
Image displaying device
Abstract
A main object of the present invention is to make it possible to
supply current to electric field light emitting elements without
decreasing the aperture ratio of pixels. In order to achieve the
object, the present invention provides an image displaying device
wherein: current driven typed light emitting elements and
transistors for current driving are formed on a same substrate;
comprising a plurality of display cells having such a structure
that the current driven typed light emitting elements and
transistors for current driving are connected in between a power
supply line and a ground line; the transistors for current driving
are selectively driven to conduct display; and a power supply
electrode column for supplying currents to each display cell is
formed on a power supply common electrode that is formed on a
surface of a facing substrate parallel to the substrate.
Inventors: |
Tanabe; Hisao; (Tokyo,
JP) |
Correspondence
Address: |
SEYFARTH SHAW LLP
55 E. MONROE STREET
SUITE 4200
CHICAGO
IL
60603-5803
US
|
Family ID: |
28457571 |
Appl. No.: |
11/353902 |
Filed: |
February 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10476340 |
Oct 29, 2003 |
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PCT/JP03/03351 |
Mar 19, 2003 |
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11353902 |
Feb 14, 2006 |
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Current U.S.
Class: |
313/1 |
Current CPC
Class: |
H01L 51/525 20130101;
H01L 27/322 20130101; H01L 27/3276 20130101; H01L 27/3251
20130101 |
Class at
Publication: |
313/001 |
International
Class: |
H01J 61/94 20060101
H01J061/94 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2002 |
JP |
2002-080542 |
Mar 22, 2002 |
JP |
2002-080540 |
Mar 22, 2002 |
JP |
2002-080541 |
Claims
1-2. (canceled)
3. An image displaying device, wherein a substrate having
transistors for current driving formed thereon and a substrate
having current driven typed light emitting elements formed thereon
are faced to each other, and an image is displayed by driving the
transistors for current driving and supplying currents individually
to each pixel of the current driven typed light emitting elements
through a power supply electrode column extending between both
substrates.
4. The image displaying device according to claim 3: wherein an
anode; a light emitting layer, a cathode are formed, in this order,
on the substrate having current driven typed light emitting
elements formed thereon; also a notch is formed in the light
emitting layer and in the cathode per every anode; and the power
supply electrode column, extending from the substrate having the
transistors for current driving formed thereon, is connected to the
notch.
5. The image displaying device according to claim 3, wherein the
current driven typed light emitting elements are provided with a
color conversion layer.
6. The image displaying device according to claim 5: wherein a
color conversion layer, an anode, a light emitting layer, and a
cathode are formed, in this order, on the substrate having current
driven typed light emitting elements formed thereon; also a notch
is formed in the light emitting layer and in the cathode per every
anode; and the power supply electrode column, extending from the
substrate having transistors for current driving formed thereon, is
connected to the notch.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image displaying device
using current driven typed light emitting elements such as organic
light emitting elements.
BACKGROUND ART
[0002] FIG. 4 is a diagram showing an example of an image
displaying device using organic light emitting elements. FIG. 4A is
a sectional view, and FIG. 4B is a top view.
[0003] Insulating layers 2 and 3 are laminated on a glass substrate
1, and an anode 4 made of a transparent conductive film which
prescribes each light emitting area, is formed thereon. And
further, on the entire surface thereof, an organic light emitting
layer 5 and a cathode 6 are formed. Moreover on the glass substrate
1, a transistor for current driving 8 which current is supplied via
a power supply line 7, a transistor 9 for ON/OFF control of the
transistor for current driving 8, and a vertical electrode 10 and a
horizontal electrode 11, for selecting display cells to emit light,
are formed. The vertical electrode 10 and the horizontal electrode
11 are insulated by the insulating layer 2. Each transistor is
protected by the insulating layer 3, and also a surface on the
transistor is smoothed. In addition, the transistor for current
driving 8 is connected to the anode 4 via a through hole of the
insulating layer 3. Moreover, a facing seal plate 12 is provided so
as to cover the entire cathode 6 for hermetically sealing the image
displaying device.
[0004] In the image displaying device having such a configuration,
when the transistor 9, of a display cell selected by the vertical
electrode 10 and the horizontal electrode 11, turns on, the
transistor for current driving 8 turns on, and a current flows from
the power supply line 7 through the anode 4, the organic light
emitting layer 5 and the cathode 6, thus the selected cell emits
light. This light emitting state is continued until a signal for
turning off is applied to the transistor 9. By thus selecting and
driving each light emitting cell arranged in a matrix form by
transistors, image display is conducted.
[0005] The current driven typed light emitting element such as the
organic light emitting element emits light by applying current
through it, so that, for maintaining the light emitting state, it
is necessary to continue applying the current flow. Therefore, for
active matrix driving of a current driven typed light emitting
element, at least two active elements are needed, one is an element
to keep applying the current flow and another is an element to
control the former element. Furthermore, to keep applying the
current flow, a dedicated current supply line is needed.
[0006] As shown in FIG. 4, the current driven typed light emitting
element is connected to the transistor for current driving 8, and
connected in between the common power supply line 7 and a common
installed line (cathode). At least two transistors are required for
one current driven typed light emitting element. As for the wiring,
four electrodes of a data line for selecting a current driven typed
light emitting element, a scanning line (the vertical electrode and
the horizontal electrode), the power supply line, and a ground line
are needed, resulting in a complicated structure. Especially, as
the number of display pixels increases, the power supply line is
required to have low resistance because higher current supply
capability is required. There is a problem that the aperture ratio
of pixels is decreased if the line width is increased in order to
lower the resistance.
[0007] Furthermore, since the yield of the transistor circuit part
and the current driven typed light emitting elements are different,
there is also a problem that it is difficult to ensure a high yield
and a high quality as the whole.
[0008] In some cases, a color conversion method is used in the
current driven typed light emitting elements. In the color
conversion method, light of a light emitting layer of a specific
color is converted to light of another color by using a fluorescent
dye. For example, apart of light of the blue color light emitting
later is converted to green or red. In this case, the color
conversion layer is formed so as to be connected to the light
emitting layer. For active matrix driving of organic light emitting
elements of such a color conversion method, the following two
methods are conceivable.
[0009] (1) Thin film transistors are formed on a color conversion
layer, and further, an organic electric field light emission layer
is formed thereon.
[0010] (2) An organic electric field light emission layer is formed
on thin film transistors, and further, a color conversion layer is
formed thereon.
[0011] In the method of (1), the color conversion layer is formed,
and thereafter the transistors are formed thereon. Therefore, the
color conversion layer is required to have heat resistance of at
least the process temperature 400.degree. C. at the time of
transistor fabrication, and it is extremely difficult. On the other
hand, in the method of (2), the color conversion layer is formed on
the light emitting layer. However, since the light emitting layer
is extremely vulnerable to moisture, it is extremely difficult to
form the color conversion layer directly on the light emitting
layer.
[0012] As a countermeasure against them, application of, not the
bottom emission method in which light is taken out from the glass
substrate side as shown in FIG. 4, but the top emission method in
which light is taken out from the cathode side is conceivable. This
aims to implement active matrix driving of the color conversion
method by individually fabricating a substrate having a light
emitting layer using a transparent cathode formed thereon and a
substrate having a color conversion layer formed thereon, and then
putting the substrates together. In addition to a problem in
reliability of the transparent cathode, there is a problem that the
image quality is degraded because the light emitting layer and the
color conversion layer are optically separated so that the
occurrence of optical crosstalk is inevitable.
DISCLOSURE OF THE INVENTION
[0013] The present invention aims to solve the above mentioned
problems. An object of the present invention is to make it possible
to supply a current to light emitting elements without decreasing
the aperture ratio of pixels and maintain light emitting elements
having high quality with a high yield.
[0014] Moreover, in the case where the color conversion method is
used for current driven typed light emitting elements, an object is
to make it possible to conduct active matrix driving of the current
driven typed light emitting elements without optical crosstalk and
without using a transparent cathode.
[0015] Therefore, the present invention provides an image
displaying device wherein: current driven typed light emitting
elements and transistors for current driving are formed on a same
substrate; comprising a plurality of display cells having such a
structure that the current driven typed light emitting elements and
transistors for current driving are connected in between a power
supply line and a ground line; the transistors for current driving
are selectively driven to conduct display; and a power supply
electrode column for supplying currents to each display cell is
formed on a power supply common electrode that is formed on a
surface of a facing substrate parallel to the substrate.
[0016] Moreover, in the above mentioned invention, it is preferable
that the power supply electrode column is connected to a power
supply pad provided at a notch that is formed in a part of a
cathode formed on the current driven typed light emitting element,
and is connected to the transistor for current driving via the
pad.
[0017] Further, the present invention provides an image displaying
device, wherein a substrate having transistors for current driving
formed thereon and a substrate having current driven typed light
emitting elements formed thereon are faced to each other, and an
image is displayed by driving the transistors for current driving
and supplying currents individually to each pixel of the current
driven typed light emitting elements through a power supply
electrode column extending between both substrates.
[0018] In the above mentioned invention, it is preferable that an
anode, a light emitting layer, and a cathode are formed, in this
order, on the substrate having current driven typed light emitting
elements formed thereon; also a notch is formed in the light
emitting layer and in the cathode per every anode; and the power
supply electrode column, extending from the substrate having the
transistors for current driving formed thereon, is connected to the
notch.
[0019] In the present invention, the current driven typed light
emitting elements may have a color conversion layer.
[0020] In the above mentioned invention, it is preferable that a
color conversion layer, an anode, a light emitting layer, and a
cathode are formed, in this order, on the substrate having current
driven typed light emitting elements formed thereon; also a notch
is formed in the light emitting layer and in the cathode per every
anode; and the power supply electrode column, extending from the
substrate having transistors for current driving formed thereon, is
connected to the notch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a diagram showing an example of an image
displaying device of the present invention;
[0022] FIG. 2 is a diagram showing another example of an image
displaying device of the present invention;
[0023] FIG. 3 is a diagram showing another example of an image
displaying device of the present invention; and
[0024] FIG. 4 is a diagram showing a conventional example of an
image displaying device using organic light emitting elements.
BEST MODE FOR CARRYING OUT THE INVENTION
[0025] The present invention relates to an image displaying device
using current driven typed light emitting elements, such as organic
light emitting elements. This image displaying device is
characterized in that a power supply electrode column for supplying
a current is provided between a substrate having current driven
typed light emitting elements formed thereon and another substrate
facing across the current driven typed light emitting elements. In
the present invention, it is possible to realize an image
displaying device in which a current can be supplied to electric
field light emitting elements without decreasing the aperture ratio
of the pixel part by providing the above mentioned power supply
electrode column.
[0026] There are three embodiments in the image displaying device
of the present invention. In a first embodiment, a power supply
common electrode is provided on a substrate facing a substrate
having current driven typed light emitting elements formed thereon,
and a current is supplied from the power supply common electrode
via a power supply electrode column formed in between the
substrates. In a second embodiment, transistors for current driving
and an organic light emitting layer are respectively formed on
different substrates, and those substrates are connected by a power
supply electrode column to supply a current. In a third embodiment,
transistors for current driving and an organic light emitting layer
having a color conversion layer are formed on different substrates,
and those substrates are connected by a power supply electrode
column to supply a current.
[0027] Hereafter, an image displaying device of each embodiment of
the present invention will be described.
1. FIRST EMBODIMENT
[0028] First, a first embodiment in an image displaying device of
the present invention will now be described. An image displaying
device of the present embodiment will be described with reference
to FIG. 1. FIG. 1 is a diagram showing an example of an image
displaying device of the present embodiment. FIG. 1A is a sectional
view, and FIG. 1B is a top view. The same numerals as those shown
in FIG. 4 denote the same contents, so that detailed description
thereof will be omitted.
[0029] In the present embodiment, insulating layers 2 and 3, an
anode 4 formed of a transparent conductive film, an organic light
emitting layer 5, and a cathode 6 are formed on a glass substrate
1. In addition, a current is supplied to the anode 4 via a
transistor for current driving 8 formed on the glass substrate
1.
[0030] In the present embodiment, a power supply common electrode
20 is formed on an entire surface of a facing substrate 13
(corresponding to the facing seal plate 12 in FIG. 4), which is
located so as to be faced to the glass substrate 1, facing to the
cathode 6. A power supply electrode column 21, for supplying a
current to the transistors for current driving 8 of each display
cell, is formed on the power supply common electrode 20. The power
supply electrode column is formed of metal or conductive resin. The
power supply electrode column also has a function as a spacer
between substrates. In a part of the cathode 6 and the organic
light emitting layer 5 which are formed on the entire surface of
the glass substrate 1, a notch is formed per every anode
prescribing each light emitting area of display cells. In this
part, a power supply pad 22 is formed, and is connected to each
power supply electrode column 21.
[0031] In such a configuration, a voltage from the power supply
common electrode 20 on the facing substrate is always applied to
the transistors for current driving 8 through the power supply
electrode column 21 and the power supply pad 22. Therefore, if the
transistor 9 in the display cell selected by the vertical electrode
10 and the horizontal electrode 11 turns on, then the corresponding
transistor for current driving 8 turns on, and a current flows
through the anode 4, the organic light emitting layer 5 and the
cathode 6 so that the selected cell emits light.
[0032] In this way, the power supply lines are not formed on the
glass substrate 1 and a current is supplied from the power supply
electrode column 21, which extends from the facing substrate
perpendicularly, unlike the conventional technique. Therefore, the
light emitting area is not restricted by the power supply line, and
a high aperture ratio can be ensured. As for the facing substrate
12, it is provided as the seal plate in the conventional technique
as well, and the seal plate is also used to form the power supply
common electrode. Therefore, while maintaining the conventional
structure, the aperture ratio can be increased.
[0033] In the conventional technique, when conducting active matrix
driving of current driven typed light emitting elements, such as
organic light emitting elements, wiring for supplying power to each
pixel is needed on the same plane as the light emitting elements,
being a factor of decreasing the aperture ratio of the pixels. In
the present embodiment, however, the power supply common electrode
is formed on the facing seal substrate, and a current is supplied
from the power supply common electrode to each pixel through the
power supply electrode column. Therefore, the power supply lines on
the substrate of the light emitting element side are no longer
necessary, and it becomes possible to realize a high aperture
ratio.
2. SECOND EMBODIMENT
[0034] A second embodiment in an image displaying device of the
present invention will now be described. The image displaying
device of the present embodiment will be described with reference
to FIG. 2. In the present embodiment, a substrate having
transistors for current driving formed thereon and a substrate
having an organic light emitting layer formed thereon are
separated. And facing both substrates to each other, a current is
supplied per every display cell through a power supply electrode
column that extends in between the substrates. A current is
supplied without decreasing the aperture ratio, and both substrates
which differ in yield can be produces separately.
[0035] A transistor for current driving 8, a transistor for ON/OFF
control of the transistor for current driving 8, and a vertical
electrode and a horizontal electrode for selecting a display cell
that should emit light are formed on a glass substrate 1. From a
power supply pad 22 which is connected to the transistor for
current driving 8, a power supply electrode column 21 penetrates to
the surface through an insulating layer 3 and extends to the facing
substrate. The vertical electrode and the horizontal electrode are
insulated by an insulating layer 2. Each transistor is protected by
the insulating layer 3, and the surfaces on the transistors are
smoothed. Since electrodes are not formed on the insulating layer 3
in the present embodiment, it is also possible to omit this.
[0036] On the other hand, on a glass substrate 13 facing to the
glass substrate 1, an anode 23 formed of a transparent electrode is
formed per each division, which prescribe light emitting areas. An
organic light emitting layer 24 and a cathode 25 are laminated on
the anode over the entire surface of the substrate. A notch is
formed in a part of the organic light emitting layer 24 and the
cathode 25 per every anodes and the power supply electrode column
21 is connected to the anode 23 through this part. The power supply
electrode column 21 is formed of metal or conductive resin, and
also has a function as a spacer between the both substrates.
[0037] In such a configuration, when a transistor, selected by the
vertical electrode and the horizontal electrode formed on the glass
substrate 1 side, turns on, the pertinent transistor for current
driving 8 turns on, and a current flows through the power supply
electrode column 21 which is connected to the transistor for
current driving 8, the anode 23 which is formed of the
corresponding transparent conductive film, the organic light
emitting layer 24 and the cathode 25 to make the selected cell emit
light. An optical output is obtained from the glass substrate 13
side through the transparent conductive film.
[0038] In this way, in the present embodiment, the glass substrate
1 side is used as the circuit substrate for selecting and driving
the current driven typed light emitting elements, and the current
driven typed light emitting elements are formed on the side of the
glass substrate 13, which is facing to the glass substrate 1.
Current supply to the current driven typed light emitting elements
is conducted by the power supply electrode column 21 which extends
vertically from the glass substrate 1 side. Therefore on the
substrate of the current driven typed light emitting elements side,
the transistors for current driving and wiring for them are no
longer necessary so that the light emitting area is not restricted
by the power supply line and the like, and a high aperture ratio
can be ensured. In addition, quality control of the substrate for
the transistor circuit for current driving and the quality control
of the substrate for the current driven typed light emitting
elements can be done separately.
[0039] In the conventional technique, when conducting active matrix
driving of current driven typed light emitting elements such as
organic light emitting elements, wiring for supplying power to each
pixel is needed on the same plane as the current driven typed light
emitting elements, resulting to be a factor of decreasing the
aperture ratio of the pixels. In the present embodiment, however,
the substrate for transistor circuit for current driving and the
substrate for the current driven typed light emitting elements are
separated, faced to each other, and a current is supplied from the
facing substrate for the transistor circuit for current driving to
each pixel. Therefore, the transistors for current driving and
wiring for them on the substrate for the current driven typed light
emitting elements are no longer necessary, and it becomes possible
to realize a high aperture ratio.
[0040] In addition, the substrate which forms the current driven
typed light emitting elements can be completely separated from the
substrate which forms the driven elements. Therefore, individual
quality control becomes possible, and an extremely high quality can
be ensured.
3. THIRD EMBODIMENT
[0041] A third embodiment in an image displaying device of the
present invention will now be described. The image displaying
device of the present embodiment will now be described with
reference to FIG. 3. In the present embodiment, a substrate having
transistors for current driving formed thereon and a substrate
having an organic light emitting layer with a color conversion
layer formed thereon are separated, faced to each other, and a
current is supplied per every display cell through an electrode
column that extends between the both substrates.
[0042] A transistor for current driving 8, a transistor for ON/OFF
control of the transistor for current driving 8, and a vertical
electrode and a horizontal electrode, for selecting a display cell
that should emit light, are formed on a glass substrate 1. From a
power supply pad 22 which is connected to the transistor for
current driving 8, a power supply electrode column 21 penetrates to
the surface through an insulating layer 3 and extends to the facing
substrate. The vertical electrode and the horizontal electrode are
insulated by an insulating layer 2. Each transistor is protected by
the insulating layer 3, and the surfaces on the transistors are
smoothed. Since electrodes are not formed on the insulating layer 3
in the present embodiment, it is also possible to omit this.
[0043] On the other hand, on a glass substrate 13 facing to the
glass substrate 1, a color conversion layer 26 is formed by
patterning in a photolithography process. On the color conversion
layer 26, an anode 23 formed of a transparent electrode is formed
per each division, which prescribes each light emitting area. An
organic light emitting layer 24 and a cathode 25 are laminated on
the anode over the entire surface of the substrate. A notch is
formed in a part of the organic light emitting layer 24 and the
cathode 25 per every anode, and the power supply electrode column
21 is connected to the anode 23 through this part. The power supply
electrode column 21 is formed of metal or conductive resin, and
also has a function as a spacer between the both substrates.
[0044] In such a configuration, a transistor for current driving 8,
selected by the vertical electrode and the horizontal electrode
formed on the glass substrate 1 side turns on, and a current flows
through the power supply electrode column 21 which is connected to
the transistor for current driving, the anode 22 formed of the
corresponding transparent conductive film, the organic light
emitting layer 23 and the cathode 24 to make the selected cell emit
light. Apart of light that has passed through the transparent
conductive film is converted by the color conversion layer 26. A
color optical output is obtained from the side if the glass
substrate 13.
[0045] In this way, in the present embodiment, the glass substrate
1 side is used as the circuit substrate for selecting and driving
the current driven typed light emitting elements, and the current
driven typed light emitting elements with color conversion layer
are formed on the glass substrate 13, which is faced to the glass
substrate 1. Therefore, it is possible to form current driven typed
light emitting elements with the color conversion layer with
extreme ease and conduct highly definite image display. In
addition, quality control of the transistor circuit substrate for
current driving and the quality control of the substrate for the
current driven typed light emitting elements can be done
separately.
[0046] In the conventional technique, when conducting active matrix
driving of current driven typed light emitting elements such as
organic light emitting elements, by using the color conversion
method, it is inevitable to use an extremely complicated layer
configuration, or use a transparent cathode with the top emission
structure, and occurrence of optical crosstalk is inevitable.
According to the present embodiment, it is possible to obtain a
highly definite image displaying device, conduct individual quality
control of the both substrates, and ensure an extremely high
quality, by forming the substrate having the transistors for
current driving formed thereon and the current driven typed light
emitting elements with the color conversion layer formed
thereon.
[0047] The present invention is not restricted by the above
mentioned embodiments. The above mentioned embodiments are nothing
but examples. Whatever having substantially the same configuration
and bringing about the same operation effects as the technical
thought described in claims of the present invention is
incorporated in the technical range of the present invention.
* * * * *