Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Heterojunction
Reexamination Certificate
2003-06-20
2004-04-27
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Heterojunction
Reexamination Certificate
active
06727513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method of manufacturing an organic EL (electroluminescent) element, and an organic EL element manufactured by the method.
2. Description of Related Art
In recent years, development of an organic EL element (a luminous element having a structure including an anode and a cathode, and a light emitting layer formed of an organic matter sandwiched between the anode and the cathode) has increasingly proceeded to provide a self-luminescent type display as an alternative to a liquid crystal display. Materials for the light emitting layer of such an organic EL element include, for example, a low molecular weight organic material, such as quinolinolatoaluminum complex (Alq3), and a high molecular weight organic material, such as poly(para-phenylene-vinylene) (PPV).
A film of a light emitting layer formed of a low molecular weight organic material is provided by a vapor deposition process, as is described in, for example, “Appl. Phys. Lett. 51(12), 21 Sep. 1987 pp. 913”. A film of a light emitting layer formed of a high molecular weight organic material is provided by a coating process, as is described in, for example, “Appl. Phys. Lett. 71(1), 7 Jul. 1997 pp. 34+”.
In many cases, a hole transporting layer is provided between the light emitting layer and the anode of the organic EL element. A hole is injected from the anode to the hole transporting layer, and the hole transporting layer transports the hole to the light emitting layer. When the light emitting layer has a capability of transporting a hole, the hole transporting layer is not always provided. In some cases, a hole injecting layer is provided as a layer other than the hole transporting layer. When the light emitting layer is formed of a high molecular weight material, such as PPV, a conductive polymer, such as a polythiophene derivative or a polyaniline derivative, is used as the hole transporting layer in many cases. When the light emitting layer is formed of a low molecular weight material, such as Alq3, a phenylamine derivative or the like is used as the hole transporting layer in many cases.
For example, in an organic EL element for display, anodes are formed in individual pixels on a substrate, and a light emitting layer and a hole transporting layer must be placed on each anode. Accordingly, if the light emitting layer and the hole transporting layer can be placed by ink jet process, coating (application) and patterning can be performed concurrently to thereby yield a patterning with a high precision for a short time. Additionally, this process is also effective to cut wastes in material and to reduce manufacturing cost, since a minimum of material is all that needs to be used.
To place the light emitting layer and hole transporting layer by ink jet process, liquid materials must be used. When a high molecular weight material such as PPV is used as the material for light emitting layer, the use of, for example, a solution of its precursor can place the light emitting layer by ink jet process. The placement of a light emitting layer that is formed of PPV high molecular weight material is described in, for example, Japanese Unexamined Patent Application Publication No. 11-40358, Japanese Unexamined Patent Application Publication No. 11-54270, and Japanese Unexamined Patent Application Publication No. 11-339957.
In the ink jet process, a region on which the light emitting layer and hole transporting layer are formed is surrounded with a barrier, and a liquid material is discharged toward the region surrounded with the barrier to thereby place the liquid material in the region. As the barrier, a two-layer structure barrier including a lower layer (substrate side) formed of an inorganic insulator, such as silicon oxide, and an upper layer formed of an organic polymer, such as polyimide is described in, for example, PCT International Publication No. WO99/48229.
FIG. 21
is a sectional view showing the aforementioned structure. Each of anodes
2
is formed in each pixel position on substrate
1
, and lower barrier
31
formed of silicon oxide is formed so as to surround the periphery of each anode
2
. Additionally, upper barrier
32
formed of polyimide is formed on lower barrier
31
. Lower barrier
31
and upper barrier
32
are formed, for example, to a thickness (total thickness) of 1 to 3 &mgr;m by thin-film formation and patterning operations.
However, in the barrier of two-layer structure in which the upper barrier is formed of polyimide, the thickness of the light emitting layer might become uneven in the vicinity of the barrier and at the center, with regard to the height of the barrier, and of the affinity for polyimide of a liquid (a liquid containing a material for the formation of light emitting layer) discharged by ink jet process. When the thickness of the light emitting layer becomes uneven, the light emission color or the amount of light emission becomes uneven or unstable in the pixel to thereby deteriorate luminous efficacy.
In a color display in which red, green and blue three color pixels are placed adjacent to one another, it is necessary to ensure that different liquids are placed separately in adjacent pixels and to avoid the liquid in each pixel from being contaminated by another liquid for the adjacent pixel. The barrier having the aforementioned structure is also susceptible to being enhanced in this regard. In a contaminated pixel, purity of emitted light color is deteriorated.
In this connection, these problems can be enhanced also by the method described in PCT International Publication No. WO99/48229, but this method requires plasma treatment and is also susceptible to enhancement in, for example, cost.
The present invention has been accomplished focusing attention on these problems of the conventional technologies, and an object of the present invention is to ensure that a liquid is placed in a predetermined region (without placing the same in the adjacent region) to a uniform thickness in the region, when a light emitting layer or hole transporting layer constituting an organic EL element is placed by a liquid placing step such as ink jet process.
SUMMARY OF THE INVENTION
In order to solve the above problems, the present invention provides a method of manufacturing an organic EL element including a cathode, an anode, and one or more constitutive layers sandwiched between the cathode and anode, which constitutive layer includes at least a light emitting layer. The method includes the step of selectively placing a liquid containing a material for the formation of constitutive layer in a region for the formation of constitutive layer, using a pattern having an opening corresponding to the region for the formation of constitutive layer, in at least one constitutive layer, and, in the liquid placing step, an ultrathin organic film pattern having a surface being repellent to the liquid is formed as the pattern, using a compound having a functional group being bondable to the constitutive atom of a face, on which the film is formed, and a functional group being repellent to the liquid.
The liquid-repellency of the surface of the ultrathin organic film pattern preferably has such liquid-repellency that the contact angle of the liquid is 50° or more.
In the method according to the present invention, it is preferred that at least one constitutive layer is further subjected to the step of forming an ultrathin organic film on a face on which the constitutive layer is formed, which ultrathin organic film has a surface having affinity for the liquid, using a compound having a functional group being bondable to the constitutive atom of a face on which the film is formed, and a functional group having affinity for the liquid, and this step is between the ultrathin organic film pattern forming step and the liquid placing step.
The term “ultrathin film” as used in the present invention means a thin film having a thickness of about several nanometers (e.g., 3 nm or less). Such an ultrathin organic films includes, for examp
Fujimori Natsuo
Ishida Masaya
Le Thao P.
Nelms David
Oliff & Berridg,e PLC
Seiko Epson Corporation
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