Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-12-16
2001-05-08
Nguyen, Kiet T. (Department: 2881)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S077000, C315S169300, C313S504000
Reexamination Certificate
active
06229505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an organic electroluminescent device having an organic layer including luminescent materials provided between a hole injection electrode and an electron injection electrode, and an organic electroluminescent apparatus using such an organic electroluminescent device. More particularly, it relates to an organic electroluminescent device capable of emitting light in various colors and an organic electroluminescent apparatus capable of simply changing the color of light emitted in the organic electroluminescent device and simply adjusting the luminance thereof.
2. Description of the Related Art
In recent years, the needs of flat panel display devices the consumed power and the size of which are smaller than those of a CRT (cathode-ray Tube) which has been conventionally generally employed have been increased as information equipments are diversified, for example. Therefore, an electroluminescent device has been paid attention to as one of the flat panel display devices.
The electroluminescent device is roughly divided into an inorganic electroluminescent device and an organic electroluminescent device depending on a used material.
The inorganic electroluminescent device is so adapted that a high electric field is generally exerted on a luminescent portion, and electrons are accelerated within the high electric field to collide with a luminescence center, so that the luminescence center is excited to emit light. On the other hand, the organic electroluminescent device is so adapted that electrons and holes are respectively injected into a luminescent portion from an electron injection electrode and a hole injection electrode, the electrons and the holes thus injected are recombined with each other to bring an organic molecule into its excited state, and the organic molecule emits fluorescence when it is returned from the excited state to its ground state.
In the case of the inorganic electroluminescent device, a high voltage of 100 to 200 volts is required as its driving voltage because a high electric field is exerted as described above. On the other hand, the organic electroluminescent device can be driven at a low voltage of approximately 5 to 20 volts.
Therefore, in recent years, various studies have been conducted on the organic electroluminescent device. A three-layer structure referred to as a DH structure obtained by laminating a hole transporting layer, a luminescent layer and an electron transporting layer between a hole injection electrode and an electron injection electrode, a two-layer structure referred to as an SH-A structure obtained by laminating a hole transporting layer and a luminescent layer abundant in electron transporting properties between a hole injection electrode and an electron injection electrode, and a two-layer structure referred to as an SH-B structure obtained by laminating a luminescent layer abundant in hole transporting properties and an electron transporting layer between a hole injection electrode and an electron injection electrode have been developed as the organic electroluminescent device.
The organic electroluminescent device can be caused to emit light in a suitable color by suitably selecting its luminescent material. Therefore, it is expected that the organic electroluminescent device can be also utilized as a multi-color display device, a full-color display device, and the like.
Conventionally when the organic electroluminescent device is caused to emit light, one organic electroluminescent device emits light in one type of color.
When multi-color or full-color display is performed using a conventional organic electroluminescent device, therefore, it is necessary to use a plurality of organic electroluminescent devices which differ in luminescent color in combination. When full-color display is performed, three types of organic electroluminescent devices emitting light in the three primary colors, that is, blue, green and red are used in combination.
In order to combine three types of organic electroluminescent devices to perform full-color display, however, three types of wiring for supplying a current to the organic electroluminescent devices must be provided, resulting in a complicated wiring method.
Since the three types of organic electroluminescent devices emitting light in blue, green and red are used as one unit to perform full-color display, the size of a pixel for performing full-color display is approximately three times a pixel in a single color. Therefore, it is difficult to display a highly precise full-color image particularly on a small-sized screen.
In recent years, in causing an organic electroluminescent device to emit light, a method of changing a voltage to be exerted on a portion between an electron injection electrode and a hole injection electrode in the organic electroluminescent device and a method of changing the duty ratio of a voltage to be applied have been proposed in order to adjust the luminance thereof.
In these methods, the luminance of light emitted from the organic electroluminescent device is merely adjusted, as described above. In one organic electroluminescent device, light in one type of color is only emitted. When multi-color or full-color display is performed, a plurality of organic electroluminescent devices which differ in luminescent color, as described above, must be used in combination, so that the above-mentioned problems still exist.
SUMMARY OF THE INVENTION
An object of the present invention is to make it possible to emit, when multi-color or full-color display is performed using an organic electroluminescent device having an organic layer including a luminescent material provided between a hole injection electrode and an electron injection electrode, light in various colors in one type of organic electroluminescent device.
Another object of the present invention is to make it possible to emit light in various colors in one type of organic electroluminescent device as well as to simply adjust the luminance thereof.
In a first organic electroluminescent device according to the present invention, in providing an organic layer including luminescent materials in which the emission spectrum varies depending on a voltage of an electric signal applied between a hole injection electrode and an electron injection electrode, used as said luminescent materials are luminescent materials comprising a luminescent material having carrier transporting properties and a luminescent material in which a peak on the longest wavelength side of the emission spectrum caused by excitation of ultraviolet lights exists on the longer wavelength side than that in the luminescent material having carrier transporting properties.
In a second organic electroluminescent device according to the present invention, in providing an organic layer including luminescent materials in which the emission spectrum varies depending on a voltage of an electric signal applied between a hole injection electrode and an electron injection electrode, used as said luminescent materials are luminescent materials comprising a luminescent material having electron transporting properties and a luminescent material in which the energy level of the lowest unoccupied molecular orbital (hereinafter referred to as LUMO) is lower than that in the luminescent material having electron transporting properties.
In each of the organic electroluminescent devices according to the present invention, when a voltage applied between the hole injection electrode and the electron injection electrode is changed, light is emitted in different colors from the organic electroluminescent devices depending on the value of the voltage.
Each of the organic electroluminescent devices may have any one of the DH structure, the SH-A structure, and the SH-B structure.
In each of the organic electroluminescent devices, it is preferable to use as the hole injection electrode an indium-tin oxide (hereinafter referred to as ITO), for example, having a large work function in order
Armstrong Westerman Hattori McLeland & Naughton LLP
Nguyen Kiet T.
Sanyo Electric Co,. Ltd.
LandOfFree
Organic electroluminescent device and organic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Organic electroluminescent device and organic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organic electroluminescent device and organic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2485998