Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2000-11-02
2003-05-20
Kim, Robert H. (Department: 2882)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S501000, C313S506000, C313S507000
Reexamination Certificate
active
06566806
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an (electro-)luminescence device utilized in copying machines, printers and display apparatus, e.g., as a backlight device for a display apparatus and a light source for illuminating an original in an image-reading apparatus.
Hitherto, as light-emission devices for converting applied electricity into light, there have been used, e.g., tubes and bulbs, such as incandescent lamps utilizing light emission caused by resistance heating and fluorescent tubes utilizing light emission caused by discharge in dilute gas, and semiconductor devices, such as light-emitting diodes (LED) utilizing light-emission caused by recombination of electrons and holes at pn-junctions formed in organic crystals. As indoor or outdoor illumination light sources, the tubes and bulbs have been most frequently used, but LEDs have been frequently used as indicators for various electronic appliances. Furthermore, recently, liquid crystal display apparatus equipped with fluorescent lamps as a backlight have been used as a display device for computers and portable display terminals. In addition to such usages directly exposed to human eyes, there have been frequently used functional devices, such as light sources for illuminating originals in image reading apparatus for facsimile apparatus and image scanners, and photo-writing heads in LED printers.
These light source devices have their own advantages and disadvantageous depending on their types. For example, the tubes and bulbs are suitable for emitting intense light by receiving a large electric power but are large in size and liable to be broken. Further, they are not suitable for usages requiring a high-speed responsiveness. On the other hand, LEDs can emit only relatively weak light but are advantageous in that they are small in size, have excellent reliability and have high-speed responsiveness.
While not being as popular as the above-mentioned light sources, there has been partially used an electroluminescence device wherein a thin film layer comprising a crystalline fluorescent substance is formed on a substrate by coating or vapor deposition and is supplied with an AC electric field via an insulating layer to cause luminescence. Such an electroluminescence device can be formed in a thin film on a substrate and is advantageous for usages for uniformly illuminating wide ranges or for providing a small-sized, particularly a thin, apparatus including a light source.
However, such an electroluminescence device has drawbacks that it can only emit weak light even lower than an LED and requires a difficult drive scheme requiring a relatively high AC voltage, so that it has not been a popular light source device.
On the other hand, in recent years, there has been developed an organic film luminescence device (also called an organic LED device), which is provided in a film on a substrate, provides high luminance and allows a DC drive.
FIG. 11
illustrates a representative organization (laminar structure) of such an organic LED device.
Referring to
FIG. 11
, an organic LED device includes a substrate
1100
, an anode
1201
comprising a transparent electrode of indium tin oxide (ITO), a hole-transporting layer
1202
comprising an organic hole-transporting material, such as an organic diamine (of, e.g., formula (1) below), an electron-transporting layer
1203
comprising an organic electron-transporting material, such as tris(8-quinolinolato)aluminum (of formula (2) below) and a cathode
1204
of a substance having a low work function such as Al and/or Hg—Ag alloy, laminated in this order.
When a voltage is applied between the anode
1201
and the cathode
1204
, holes injected from the anode
1202
to the hole-transporting layer
1202
and electrons injected from the cathode
1204
to the electron-transporting layer, are re-combined to cause luminescence.
FIG. 12
illustrates a state of luminescence occurring in the organic LED device of FIG.
11
.
Referring to
FIG. 12
, a portion denoted by
A
schematically represents the luminescence caused by recombination of holes injected to the hole-transporting layer
1202
from the anode
1201
and electrons injected to the electron-transporting layer
1203
from the cathode
1204
.
Such organic LED devices can emit various colors of luminescence, e.g., by using different organic materials for the hole-transporting layer
1202
or the electron-transporting layer
1203
, by admixing another organic material into these layers, or by inserting a luminescence layer comprising another organic material between these layers.
However, according to a conventional organic LED device, the luminescence color is determined by organic materials constituting a luminescence part, so that pixels of respectively different luminescence colors have to be formed in a usage, like a full-color display, requiring independent control of different luminescence colors.
FIG. 13
illustrates a typical organization of such an organic LED device.
Referring to
FIG. 13
, the organic LED device includes a substrate
1100
; a first pixel comprising an anode (portion)
1201
comprising ITO for the first pixel, a hole-transporting layer (portion)
1202
of an aromatic diamine (of formula (1)), an electron-transporting layer/luminescence layer
1203
of tris(8-quinolinolato)aluminum (of formula (2)) and a cathode
1204
of Al or Hg—Ag alloy, etc.; and also a second pixel comprising an anode (portion)
1401
comprising ITO, a hole-transporting layer (portion)
1202
of an aromatic diamine (of formula (1)), an electron-transporting layer/luminescence layer
1203
of a mixture of tris(8-quinolinolato)aluminum complex (of formula (2)) and a fluorescent substance (of formula (3) below), and a cathode
1404
of Al or Mg—Ag alloy.
In the above-mentioned device, the first pixel emits green luminescence, and the second pixel emits red luminescence.
In the device, the respective luminescence layers
1203
,
1403
and the respective cathodes
1204
,
1404
, have to be patterned into shapes of the respective pixels. Moreover, if the cathodes
1204
and
1404
of the adjacent pixels directly contact each other, or even in a single pixel, if the cathode
1204
(
1404
) directly contacts the anode
1202
(
1401
) or the hole-transporting layer
1202
(
1402
), phenomena, such as crosstalk and current leakage, undesirable for the device performances, are liable to occur, so that the mutually adjacent pixels have to be formed in sufficient separation from each other.
In this case, as different luminscence colors are emitted from different pixels, different color pixels are liable to be noticeable to human eyes by a careful observation, thus providing an unsatisfactory display quality.
When such an organic LED device is used as a light source for illuminating an original in an image reading apparatus, the directively of illumination light reaching a certain point on the original can be different for respective luminescence colors due to the fact that different luminescence colors are emitted from fairly separated different pixels, so that color irregularity is liable to occur depending on the surface gloss of the original.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the prior art, a principal object of the present invention is to provide a luminescence device, particularly an organic LED device, having a minimized difference in sites for emitting different luminescence colors.
According to the present invention, there is provided, a luminescence device, comprising a substrate, and a laminated layer structure formed on the substrate including a plurality of luminescence layers emitting different luminescence colors, and a plurality of electrodes forming at least one pair of electrodes each sandwiching an associated luminescence layer, wherein at least one of the plurality of electrodes is provided with apertures, through which a luminescence flux emitted from at least one of the luminescence layers is caused to pass.
Each of the plurality of luminescence layers may comprise
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