Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1999-12-22
2001-11-20
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100, C345S046000
Reexamination Certificate
active
06320322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light emitting appliance, and more particularly to a light emitting appliance having unit light emitting devices each with at least three light emitting elements with substantially different emitting colors.
2. Description of the Related Art
As an example of an image display, a full-color image display using an organic EL (electroluminescence) has been proposed.
FIG. 16A
schematically shows the configuration of a display panel DP used in such a full color image display.
The display panel DP is provided with a glass substrate GL. On the glass substrate, a large number of anodes ANO's are arranged in stripes. On the anodes ANO's, a red light emitting layer R, a green light emitting layer G and a blue light emitting layer B are cyclically arranged in stripes in this order in stripes in a direction orthogonal to the anodes ANO's. Cathodes CR, CG and CB are arranged on and along the red light emitting layer R, green light emitting layer G and blue light emitting layer B, respectively.
A set of red light emitting layer R, green light emitting layer G and blue light emitting layer, which are sandwiched between a single anode ANO and a set of cathodes CR, CG and CB, constitute a unit light emitting device UL. Namely, the display panel DP is composed of a larger number of unit light emitting devices UL's arranged in a matrix form.
By adjusting the luminance of the red light emitting layer R, green light emitting layer G, blue light emitting layer B, the unit light emitting device UL can be caused to emit light at any color. By causing a large number of the unit light emitting devices UL's arranged in a matrix form to emit light, a full color image with any desired full color image can be displayed.
However, the above conventional full color image display using the organic EL presents the following problem.
FIG. 16B
is an equivalent circuit diagram of the unit light emitting device UL constituting the display panel DP shown in FIG.
16
A. As seen from
FIG. 16B
, in order to cause the unit light emitting device UL to emit light at any color in the display panel DP, four terminals (one anode ANO and a set of cathodes CR, CG and CB) are required.
This makes the appliance structure inclusive of its wiring complicate, thus making it difficult to realize the display at a high density. Particularly, where a large number of display panels DP's shown in
FIG. 16A
are used in order to constitute a full color image display having a large number of pixels, the structure inclusive of the wiring becomes more complicate, thus making it further difficult to realize the display at a high density.
Further, in the display panel DP, three light emitting layers arranged at intervals on a plane, i.e. a red light emitting layer R, green light emitting layer G and blue light emitting layer B constitute a unit light emitting device UL. Therefore, there was a limitation to realize the high density of the display.
Further, generally, the luminance of each of the red light emitting layer R, green light emitting layer G and blue light emitting layer B are not equal on the same condition. In order to approximate the luminance of each light emitting layer to one another, the light emitting are, i.e. width of each light emitting layer, is made different. If the luminance of the red light emitting layer
1
is the lowest, that of the blue light emitting layer
2
is intermediate and that of the green light emitting layer
3
is the highest, as seen in
FIG. 17
, the width of the red light emitting layer
1
is made the largest W
1
, that of the blue light emitting layer
2
is made intermediate W
2
, and that of the green light emitting layer
3
is made the smallest W
3
. However, in such a technique, the green light emitting layer
3
having the smallest width W
3
is a bottleneck in fabrication, and the presence of the red light emitting layer
1
further accelerates the difficulty of the display at a high density.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems to provide a light emitting appliance which can be realize the display at a high density.
In order to attain the above objects, the present invention is realized in various aspects defined in claims.
In accordance with a first aspect of the present invention, there is provided a light emitting appliance comprising unit light emitting devices each composed of at least three light emitting elements which are caused to emit light by application of a voltage between their anode and cathode and have substantially different emitted light colors, wherein a first light emitting element and a second light emitting element are coupled in series with each other to constitute a ring and coupling points of these elements are used to a first connecting point and a second connecting point, and the one electrode of a third light emitting element is connected to the first input terminal and the other electrode thereof is used as a third input terminal.
In this configuration, an input voltage to be applied to each of the first to third input terminals is adjustable so that a light emitting state of each of the first to third light emitting elements is adjusted. It is only required that the three input terminals are wired so that the wiring structure can be simplified, thereby realizing a high density display.
In the second to sixth aspects of the present invention, the first input terminal is grounded; the second input terminal is connected so as to be selectable from three connecting states of being connected to a positive potential, a negative potential and neither potential; and third input terminal is connected so as to be selectable from two connecting states of being connected to the positive or negative potential and neither potential.
In this configuration, the light emitting states of the three light emitting elements can be adjusted in a simple manner that the input state of the first input terminal is fixed and only the input states of the second input terminal and third input terminal are altered. This further simplifies the structure of the appliance inclusive of its wiring, thereby realizing the higher density display.
In the seventh aspect of the light emitting appliance according to the present invention, the three kinds of light emitting elements are stacked as three layers, and adjacent electrodes in a direction of stacking the light emitting elements are commonized(formed in common).
In such a configuration, since the three kinds of light emitting elements are stacked in three layers, the projected area of a unit light emitting device can be made approximately equal to that of a single light emitting element. Therefore, the projected area of the unit light emitting device can be reduced while the area of each of the light emitting elements is assured. This realizes a higher density display.
Since the adjacent electrodes are commonized in a direction of stacking the light emitting elements, the number of the electrodes can be reduced, the appliance structure inclusive of its wiring can be further simplified.
In an eighth aspect of the light emitting appliance according to the present invention, each of the three kinds of light emitting elements is a light emitting element having a light emitting layer sandwiched between its anode and cathode; and the first electrode serving as the first input terminal, light emitting layer of the first light emitting element, second electrode serving as the second input terminal, light emitting layer of the second light emitting element, intermediate electrode formed to be connected to the first electrode, light emitting layer of the third light emitting element, third electrode serving as the third input terminal are stacked in this order.
Therefore, with the three light emitting elements each having a light emitting layer between the anode and cathode, the electrodes and the light emitting layers have only to be alternately stacked, thereby a high density d
Morgan & Lewis & Bockius, LLP
Rohm & Co., Ltd.
Tran Thuy Vinh
Wong Don
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