OLED colorization technology

- Feb 21, 2019 -

Full color display is an important indicator to verify whether the display is competitive in the market. Therefore, many full-colorization technologies are also applied to OLED displays. There are usually three types of panel types: RGB pixel independent illumination, color conversion (Color) Conversion) and color filter (Color Filter).

 

First, RGB pixels are independently illuminated

Independent illumination with luminescent materials is currently the most widely used color mode. It uses a precise metal shadow mask and CCD pixel alignment technology. First, it prepares the red, green and blue primary color illuminating centers, then adjusts the color mixing ratio of the three color combinations to produce true color, so that the three-color Oled components are independently illuminated. One pixel. The key to this technology is to improve the color purity and luminous efficiency of the luminescent material, while the metal shadow mask etching technology is also crucial.


At present, the organic small molecule luminescent material AlQ3 is a good green light luminescence small fraction of the material, its green color purity, luminous efficiency and stability are very good. However, the best red light-emitting small molecule material of OLED has a luminous efficiency of only 31 mW and a lifetime of 10,000 hours. The development of blue light-emitting small molecule materials is also very slow and difficult. The biggest bottleneck faced by organic small molecule luminescent materials is the purity, efficiency and longevity of red and blue materials. However, by doping the host luminescent material, blue light and red light with good color purity, luminous efficiency and stability have been obtained.

The advantage of the polymer luminescent material is that it can be adjusted by chemical modification. It has been obtained from blue to green to red in various colors covering the entire visible range, but its lifetime is only one tenth of that of small molecule luminescent materials. Therefore, for high molecular polymers, the luminous efficiency and lifetime of the luminescent materials need to be improved. Continuous development of luminescent materials with excellent performance should be an arduous and long-term issue for material developers.

With the colorization, high resolution and large area of the OLED display, the metal shadow mask etching technology directly affects the quality of the display panel image, so more stringent requirements are placed on the dimensional accuracy and positioning accuracy of the metal shadow mask.

 Second, light color conversion

  

The light color conversion is a combination of a blue OLED and a light color conversion film array. First, a device for emitting a blue light OLED is prepared, and then a blue light excitation color conversion material is used to obtain red light and green light to obtain full color. The key to this technology is to improve the color purity and efficiency of the light color conversion material. This technology does not require a metal shadow mask alignment technology, and only needs to evaporate blue OLED components, which is one of the potential full colorization technologies for large-size full-color OLED displays in the future. However, its disadvantage is that the light-color conversion material easily absorbs blue light in the environment, resulting in a decrease in image contrast, and the light guide also causes a problem of reduced picture quality. Japan's Idemitsu Kosan Co., Ltd., which currently controls this technology, has produced 10-inch OLED displays.

Third, color filter film

This technology utilizes a white light OLED combined with a color filter film to first prepare a device for emitting a white light OLED, and then obtains three primary colors through a color filter film, and then combines three primary colors to realize color display. The key to this technology is to obtain high efficiency and high purity white light. The manufacturing process does not require a metal shadow mask alignment technology, and the color filter film fabrication technology of the mature liquid crystal display LCD can be used. Therefore, it is one of the potential full-colorization technologies for large-size full-color OLED displays in the future, but this technology can cause up to two-thirds of the light loss caused by the color filter film. At present, TDK Corporation of Japan and Kodak Corporation of the United States use this method to fabricate OLED displays.


RGB pixel independent illumination, light color conversion and color filter film three manufacturing OLED display full color technology, each has advantages and disadvantages. Can be determined according to the process structure and organic materials.