Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – Plural light emitting devices
Reexamination Certificate
2001-11-26
2004-08-31
Whitehead, Jr., Carl (Department: 2813)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
Plural light emitting devices
Reexamination Certificate
active
06784459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic electroluminescent (hereinafter abbreviated as “EL”) device and to a fabrication method therefor.
This application is based on Patent Application No. 2000-359885 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In recent years, development has accelerated with regard to luminous elements that use organic substances as a self-luminous display device. This type of self-luminous display device may supplant conventional liquid crystal display devices. EL elements that use an organic substance as a luminous material can mainly be manufactured by forming a membrane using vapor deposition of an organic EL material (a luminous material) with low molecular weight, as disclosed beginning on page 913 of Appl. Phys. Lett. 51 (12), Sep. 21, 1987, and by coating an organic EL material with high molecular weight, as disclosed beginning on page 37 of Appl. Phys. Lett. 71 (1), Jul. 7, 1997.
For colorization in the case of a low molecular weight material, respective membranes are formed with various luminous materials which are vapor-deposited on respective pixels through covering masks. On the other hand, in the case of a high molecular weight material, it has been notable to realize colorization by a fine patterning using an ink-jet method. Fabrication methods of EL elements using an ink-jet method are disclosed in JP-H7-235378A1, JP-H10-12377A1, JP-H10-153967A1, JP-H11-40358A1, JP-H11-54270A1, JP-H11-339957A1, and U.S. Pat. No. 6,087,196B1.
SUMMARY OF THE INVENTION
A super fine patterning of an EL material can be realized by an ink-jet method because it is possible to eject droplets having a diameter of a few micrometers in a high resolution manner and to form a coating therewith. On the other hand, the minute droplets coated on a substrate tend to dry in an extremely short period, and they dry even faster at edge portions (e.g., upper edge, lower edge, right edge, and left edge) of the coated area on the substrate where the partial pressure of the vapor from the minute droplets coated on a pixel area is relatively low. In addition, in the case in which the EL elements are to be actively driven by TFT (thin-film transistor) elements in use, pixels may not be allowed to be evenly disposed in both X and Y directions due to the TFT elements and the shape and disposition of electric wires, and the partial pressure of the vapor may vary locally around the droplet coated on each of the pixels. The time difference in the drying period for the liquid organic material coated on the pixels thus produced may cause uneven thickness of the organic membrane within a pixel or among a plurality of pixels. The uneven thickness of the membrane, in turn, may cause uneven displaying performance, such as uneven luminance, uneven chrominance, etc.
Based on the above description, an object of the present invention is to provide an enhanced fabrication method for an organic EL device that includes ejecting and coating an organic EL material on electrodes to form an organic EL layer, with which uniform physical conditions and drying period for the liquid EL material coated on a pixel area can be realized, and a uniform organic EL device without uneven luminance and uneven chrominance within a pixel or among a plurality of pixels in an effectively optical area can be obtained. It is also an object of the invention to provide such an organic EL device manufactured in accordance with the above method.
The present invention provides a method for manufacturing an organic EL device by coating a composition including an organic EL material above a plurality of electrodes to form an organic EL layer above each of the electrodes. The method includes: defining an effectively optical area in which the plurality of electrodes are formed; and defining a coating area being broader than the effectively optical area, in which the composition including an organic EL material is to be coated.
According to the above fabrication method, uniform physical conditions near the liquid EL material coated on the effectively optical area and uniform drying period for the EL material can be realized in the effectively optical area, and consequently a uniform thickness of the layer within a pixel or among a plurality of pixels can be obtained. An organic EL layer herein referred to includes a variety of layers contributing to a luminous effect, such as a hole-injection layer, a luminous layer, and an electron-injection layer. An effectively optical area herein refers to an area for the display pixels when the organic EL device is a display device, and refers to an area contributing to lighting when the organic EL device is a lighting equipment.
In a method for manufacturing an organic EL device according to the present invention, the coating area preferably includes the perimeter of the effectively optical area.
According to this method, the drying period for droplets on the pixels located near edges of the effectively optical area being much shorter than that for droplets on the pixels located inside the effectively optical area is avoided. Thus, a uniform thickness of the layer among a plurality of effectively optical pixels can be obtained.
In another method for manufacturing an organic EL device according to the present invention, the coating area located along the perimeter of the effectively optical area is preferably a dummy area in which the organic EL material solution is also coated to form an organic EL membrane layer.
Preferably, the method further includes: forming a layer that is made of the same material as that of the electrodes in the dummy area; and coating the composition including an organic EL material on the layer.
According to the above method, uniform physical conditions near the liquid EL material coated on the pixels can be realized even for the pixels located near the edges of the effectively optical area, and the drying period for droplets on the pixels located near the edges of the effectively optical area being much shorter than that for droplets on the pixels located inside the effectively optical area is avoided. Thus, a uniform thickness of the EL membrane layer among a plurality of pixels can be obtained.
Another method for manufacturing an organic EL device according to the present invention preferably includes: providing a group of effectively optical areas formed of a plurality of the effectively optical areas on a substrate; and defining dummy areas around the effectively optical areas, respectively, and another dummy area encompassing the group of effectively optical areas.
A dummy area herein refers to an area relating to neither display nor lighting. Therefore, the organic EL layer formed in a dummy area does not have to be illuminable, but may be slightly illuminable as long as this does not interfere with either display or lighting.
According to the above method, uniform physical conditions near the liquid EL material coated on the pixels located near the edges of the effectively optical area can be realized like for other pixels, and the drying period for droplets on the pixels located near the edges of the effectively optical area being much shorter than that for droplets on the pixels located inside the effectively optical area is avoided. Thus, a uniform thickness of the EL membrane layer among a plurality of pixels can be obtained, even when a plurality of the effectively optical areas are formed on a substrate, each of which is separated from others, in the final manufacturing process, to fabricate a plurality of EL devices. In this way, a plurality of EL devices without uneven luminance and uneven chrominance within a pixel or among a plurality of pixels can be manufactured from a substrate at one time.
In another method for manufacturing an organic EL device according to the present invention, a process of coating of the composition including an organic EL material is preferably started at the dummy area prior to coating on the effectivel
Morii Katsuyuki
Seki Shun-ichi
Dolan Jennifer M.
Jr. Carl Whitehead
Oliff & Berridg,e PLC
Seiko Epson Corporation
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