New technique for large OLED-TVs from SONY


The panel has the top emission structure in which light is emitted to the opposite direction from the TFT formed on the glass substrate. With this structure, it is possible to exclude a sealed glass while assuring a high aperture ratio. In addition, colors can be adjusted by controlling the width of a luminescence material. Sony calls the structure Super Top Emission.

The luminescence material used in the prototype panel is described as the low-molecular type. Sony decided to employ this type of material because it can be applied in a vacuum atmosphere, thereby avoiding water or hydrogen that can cause degradation from being mixed in the material. In general, a low-molecular OLED panel is obtained by defining the film deposition area with a shadow mask, followed by vacuum deposition pattering. This time, the company has employed a laser transfer technology called Laser Induced Pattern wise Sublimation (LIPS) to deposit the luminescence material. A donor substrate is prepared by applying the luminescence material on the entire surface of the glass substrate. Then, the substrate is selectively irradiated with a laser beam so as to form the film deposition areas respectively corresponding to red, green, and blue lights by patterning without using a mask. With the adoption of this method, degradation in patterning precision resulting from the deformation of the shadow mask, which has been the bottleneck in the production of large size panels, can be prevented. Organic materials such as hole and electron transport materials, which need to be applied on the entire surface of the substrate without patterning, are subjected to deposition as usual. Meanwhile, Sony has also prototyped an 11-inch OLED panel and presented a TV set using it at 2007 International CES. All organic materials used in this panel are applied by deposition.

There is a laser transfer technology known as LITI which is developed by 3M Co. as with the LIPS. Since a luminescence material is transferred in the atmosphere during the LITI process, this technology involves a problem of possible degradation factors being mixed in. In contrast, during the LIPS process, the donor substrate and a substrate formed with TFT are bonded together in a vacuum. Then, a portion called PDL surrounded by exterior walls on the TFT substrate is brought into a vacuum state. In this way, the laser transfer process itself is carried out in the atmosphere while placing the portion with which the material is applied in a vacuum
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