About OLED colorization technology

Full color display is an important indicator to test whether the display is competitive in the market, so many full-color technology is also applied to the OLED display. There are usually the following three types according to the type of panel: RGB pixel independent light, light color conversion (Color Conversion) and Color Filter.

First, RGB pixel independent light emission Independent use of light-emitting materials is currently the most used color mode. It is the use of precision metal shadow mask and CCD pixel alignment technology, the first preparation of red, green, and blue primary color emission center, and then adjust the color mixing ratio of the three color combinations, resulting in true color, so that the three-color OLED components independent light One pixel. The key to this technology is to improve the color purity and luminous efficiency of luminescent materials, and metal shadow mask etching technology is also crucial.

At present, the organic small molecular light emitting material AlQ3 is a very good green light emitting sub-material, its green color purity, luminous efficiency and stability are very good. However, the best red light-emitting small molecule materials for OLEDs have a luminous efficiency of only 31 mW, a lifetime of 10,000 hours, and the development of blue light-emitting small molecule materials is also very slow and difficult. The biggest bottleneck for 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 having good color purity, luminous efficiency, and stability have been obtained.

The advantage of polymer luminescent materials is that they can be chemically modified to adjust their light emission wavelengths. Various colors covering the entire visible light range from blue to green to red have been obtained, but their lifetime is only one-tenth that of small molecule luminescent materials. Therefore, for the polymer, the luminous efficiency and life of the luminescent material need to be improved. The continuous development of excellent luminescent materials should be a difficult and long-term task for material development workers.

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. Therefore, more stringent requirements are imposed on the dimensional accuracy and positioning accuracy of the metal shadow mask.

Second, light color conversion Light color conversion is a combination of blue light OLED and light color conversion film array, first to prepare blue light emitting OLED devices, and then use its blue light excitation light color conversion material to obtain red and green light, so as 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 metal shadow mask alignment technology, just evaporated blue OLED components, is one of the potential full-color technology of large-size full-color OLED displays. However, its disadvantage is that the light color conversion material easily absorbs the blue light in the environment, causing the image contrast to decrease, and at the same time, the light guide also causes the problem of degradation of the picture quality. Currently, Idemitsu Kosan Co., Ltd., which masters this technology, has already produced 10-inch OLED displays.

Third, the color filter film This technology is the use of white OLED combined with a color filter film, first to prepare a device that emits white light OLED, and then through the color filter film to obtain three primary colors, and then combine the three primary colors to achieve color display. The key to this technology is to obtain high efficiency and high purity white light. Its production process does not require metal shadow mask alignment technology, and can use mature liquid crystal display LCD color filter film production technology. Therefore, it is one of the potential full-color technologies for large-size full-color OLED displays in the future. However, the use of this technology makes light loss through a color filter film as high as two-thirds. At present, Japan's TDK Corporation and the United States Kodak Corporation adopt this method to produce OLED displays.

The RGB pixels independently emit light, and the light color conversion and color filter films are used to manufacture full-color technology for OLED displays. Each has advantages and disadvantages. It can be decided according to the process structure and organic materials.

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