Organic light-emitting elements, which have recently been being studied and developed, are light-emitters making use of an electric-field light-emitting phenomenon occurring in organic material and have a structure in which a light-emitting layer is interposed between an anode and a cathode.
Commonly, a light-emitting layer is partitioned for each organic light-emitting element by banks composed of insulating material, and a shape of the light-emitting layer is defined by such banks. In addition, between an anode and a light-emitting layer, a combination of a hole injection layer and a hole transport layer or a hole injection/transport layer is interposed as necessary, and between a cathode and a light-emitting layer, a combination of an electron injection layer and an electron transport layer or an electron injection/transport layer is interposed as necessary. Since the light-emitting layer, the hole injection layer, the hole transport layer, the hole injection/transport layer, the electron injection layer, the electron transport layer, and the electron injection/transport layer each achieve a corresponding function among functions such as the emission of light, the injection of electric charge, and the transportation of electric charge, such layers are collectively referred to as the “functional layer”.
In an organic display device having a full-color display capability, such an organic light-emitting element corresponds to one sub-pixel, and further, a combination of three adjacent sub-pixels corresponding to the colors R, G, and B form one pixel. A plurality of such pixels are arranged in a matrix to form an image display region of an organic display device.
So as to enable such an organic display device to display high definition images, there is a demand for forming each pixel of an organic display device to have a microscopic size. In specific, it is demanded that each pixel be formed to have a length shorter than approximately 500 μm at each side thereof. In order to realize pixels having such a microscopic size, it is required that a functional layer in each organic light-emitting element be formed so as to have a small film thickness of tens to hundreds of nanometers.
The manufacture of an organic display device includes a step of forming a functional layer on a substrate. In the step of forming a functional layer, a wet process is often used in which an ink (an application solution) prepared by dissolving a functional material for forming the functional layer in a solvent is filled to between banks by an inkjet method (a droplet ejection method) or the like and then the filled ink is dried though a method of forming a film of low molecular material by the application of a vacuum process is also used. When the wet process is applied, a functional layer can be formed relatively easily even in a large panel.