In comparison with liquid crystal display, organic light-emitting diode (OLED) display has the advantages of self-luminescence, fast response, wide viewing angle, high brightness, bright color and small thickness, and is considered as next-generation display technology.
A thin film of an organic light-emitting device is prepared mainly by means of vacuum evaporation or with a solution method. Vacuum evaporation is suitable for small organic molecules, the film prepared by means of vacuum evaporation has good uniformity, and vacuum evaporation technology is relatively mature. However, in the vacuum evaporation technology, it is high in equipment cost, and is low in utilization ratio of materials and alignment accuracy of masks used in large-dimension products. The solution method is suitable for polymer materials and soluble small molecules, is low in equipment cost, and has prominent advantages in large-dimension mass production. A process of the solution method includes spin coating, inkjet printing, nozzle coating method, and so on.
A process of manufacturing an OLED display device by means of inkjet printing comprises: ejecting, by an inkjet printer, a soluble material of OLED functional layer with a certain volume to a corresponding sub-pixel region; and then forming an organic light-emitting layer by means of drying. Due to the factors such as a few types of inkjet heads of an inkjet printer, different requirements of ink viscosity and surface tension for the inkjet heads, different ink characteristics and requirements of ink film formation process, and different sizes of sub-pixels determined according to a design of display panel, it often occurs that, in a process of inkjet printing, a thickness of an organic thin film is less than a thickness required by the device after n droplets of ink have been ejected, and is greater than the thickness required by the device after (n+1) droplets of ink have been ejected, so that an ink volume cannot be matched with a thickness required by a display device structure.
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