Display module ghosting and optimization solutions
When the LCD screen of the display module displays a single image for an extended period of time, an electric charge accumulates inside, causing a ghost image to appear due to the internal electric field.
Afterimages clustered together:
Differences in LCD liquid crystal materials, pixel leakage, larger Cst design and smaller Feedthrough design in TFT circuits, moisture absorption of LCD PI, panel’s optimal VCOM drifting over time or temperature leading to severe image retention, image retention caused by special UI, and prolonged display of the same fixed image during manufacturing processes:
Afterimage Verification:
The afterimage will disappear after baking at 80℃ for 4 hours. You can use a 5*5 checkerboard pattern to light up the image for the test time and then switch to 127 gray, or use the image of the customer where the afterimage appeared to light up the image for a long time and then switch to 127 gray to reproduce the image.
| Chessboard grid lighting time | Switch L127 time | Judge | Determination |
| 30min | 1min | It is not allowed | PASS |
| 1hr | 1min | It is not allowed | PASS |
| 2hr | 5min | It is not allowed | PASS |
Image retention optimization:
| Serial Number | Improvement | Effective measures to improve image retention |
| 1 | Screen manufacturers | Optimize driver code and change the toggling method. |
| 2 | Screen manufacturers | Optimize driver code and change scanning method |
| 3 | Screen manufacturers | Optimize driver code and reduce VGL voltage. |
| 4 | Screen manufacturers | Optimize driver code and adjust asymmetric GAMMA voltage to Black (+0.2V, -0.6V). |
| 5 | Screen manufacturers | The forward and reverse VCOM values in the overall machine driver code are masked, and a probe is used to perform single-chip OTP VCOM for each product. |
| 6 | Client | For high-contrast interfaces, lower the contrast as much as possible. For example, change pure gray RGB=0*FFFFFF fonts or pure white RGB=0*FFFFFF icons to white RGB=0*F0F0F0 fonts and grayish-white RGB=0*F0F0F0 icons. |
| 7 | Client | The grayscale level of the UI should be at least 127 pixels to avoid the previous screen leaving a residue on the grayscale. |
| 8 | Client | The display refresh rate should ideally be ≥50Hz to minimize LCD pixel leakage time. |
| 9 | Client | To avoid prolonged viewing on a single screen, based on our project experience, viewing at 50°C for more than 1 hour will result in ghosting. Therefore, the screen should be set to automatically hide or refresh if viewed for extended periods. |
| 10 | Screen manufacturers | Drive LCD glass manufacturers to optimize liquid crystal material properties and TFT driving circuits |
