26.3: Multicolor Pixel Patterning of Light‐Emitting Polymers by Ink‐Jet Printing

Abstract

In order to realize a multicolor display, we tried to pattern three different colors to make pixels by using ink‐jet technology. Light emitting polymer, poly(p‐phenylene vinylene) (PPV), was successfully formulated into inks for ink‐jet printing. Those inks showed a good ink‐jetting behavior and became a good light emitting film. By combining the ink‐jet printing with the self‐patterning ability of the substrate, in which the hydrophilic and hydrophobic region is alternately constructed, an ink droplet can be patterned into the narrow pixel gap of 10 μm with precision of 1 μm order. We developed stacked structures combining PPV with Polyfluorene. It was confirmed that energy conversion from the wider gap layer to the smaller one occurred. As a result, we demonstrated the three color electroluminescence from the small pixels. This is the first demonstration of the fine pixel patterning of the multicolor light emitting polymers by ink‐jet technology.

Droplet Behaviors on Substrates in Thin-Film Formation Using Ink-Jet Printing

“…Many 50-to 100-µm pixels for each of the three primary RGB colors (red, green, and blue) are printed on the substrate by an ink-jet nozzle head less than 1 mm away. Because the flight accuracy of an ink-jet printer is about ±25 µm (3) , it is important to predict spreading of the droplets on the bank and on the ITO surface surrounded with the bank. Figure 2 (b) shows how a continuous film is deposited by using an ink-jet.…”

“…Droplets of a solution with a viscosity less than 0.01 Pa·s can be easily ejected by conventional ink-jet nozzles, and the diameter of the droplets produced by a commercial ink-jet printer is between 10 and 100 µm. In this paper, the specifications and properties of droplets from a commercial ink-jet printer are set typically as follows: droplet volume V 0 = 40 fm 3 …”

“…This paper uses the term ink-jet deposition for the technology depositing a thin-film on substrate by ink-jet printing. Ink-jet deposition has recently been used in semiconductor packaging to make solder bumps (1) and has also been used to produce organic electro-luminescence (EL) displays (2), (3) , organic transistors (4) , and other devices. The organic EL device, in which the organic luminescence layer glows when a voltage is applied to it, is the next-generation display.…”

A new approach to molecular devices using SAMs, LSMCD and Cat-CVD

“…Particularly, the photochemical reaction of SAMs under vacuum ultraviolet (VUV) light irradiation has markedly attracted researchers attention as a promising nanotechnology for the photographic area-selection of various surfaces such as silicon, ITO glass, metals, and oxides [3], to a level beyond the scope of the current photolithography used in the semiconductor industry. Also, the direct printing of transistors and other electronic circuits, including electro-luminescence devices, has been achieved by the inkjet method to a resolution of tens of microns [6,7]. In this method, the hydrophobic and hydrophilic properties of the inks are utilized in the formation of thin films of polymers.…”

Fabrication of Multi Color Polymer EL Devices using the Photo-bleaching Method.

“…Also the pixel size in micrometer scale is technically difficult to achieve. On the other hand, arrays of RGB pixels fabricate by inkjet printing in the polymer EL devices have been reported [ 7 ] . Thus, the device fabrication process of the polymer devices is easier than that of small molecules.…”