Forming control method of inkjet printing OLED emitting layer pixel pit film

When the OLED emitting layers are produced by using the injet printing method, the film thickness of different pixel pits can cause Mura defects in the light-emitting devices. The main reason for the film thickness variation is the difference of ink volume in different pixel pits caused by the inconsistent droplet volume of different nozzles and the wrong deposition of droplets. To solve the problem of film thickness consistency, a film forming control method for OLED emitting layer based on droplet volume control and deposition position control is proposed. Firstly, the driving waveform is adjusted so that the droplets with appropriate volume can be generated from nozzles. Then, the droplet landing position of each nozzle is detected, and the deposition position of droplets is controlled by the offset compensation and abnormal nozzles screening. Finally, the ink volume in the pixel pit is controlled by droplets mixing method. In the experiment, the deviation of droplet landing position is controlled within +/- 10 mu m, and the volume difference of the ink is controlled within +/- 4% by droplets mixing method. The film thickness of the emitting layer after drying is measured. The experimental results show that the consistency of different pixel pit film thickness is more than 95%, and the OLED device with uniform light emission is obtained. The film thickness consistency control method can meet the manufacturing requirements of OLED functional layer.