Common LCD Display Problems: Lines, Ghosting, Dark Spots, Leaks And Fading
Quick answer: most LCD problems in products come from a short list of causes. Lines usually point to the connection between the glass and the electronics: a damaged FPC, a poor zebra or connector contact, or broken driver bonding. Ghosting on segment LCDs means the drive voltage or bias is wrong for the temperature; on TFTs it is usually image retention. Dark spots and spreading stains come from pressure damage, polarizer defects or cracked glass leaking liquid crystal. Fading comes from temperature, voltage drift or ageing polarizers and backlights.
The table below links each symptom to its likely causes and to a detailed SuccessLCD engineering article. Many of these failures are prevented in design and sample validation rather than fixed in the field.
Symptom Finder
| Symptom | Display type | Common causes | Read more |
|---|---|---|---|
| Horizontal or vertical lines | TFT | Damaged FPC or COF, poor connector seating, cracked driver bonding, timing or power problems | Timing and power debugging, FPC connector mismatch |
| Missing segments or a whole row off | Segment | Zebra connector contact, cold pin solder joint, wrong COM mapping | LCD connection types |
| Off segments faintly visible (ghosting) | Segment | VLCD too high, wrong duty or bias, high temperature | Duty and bias explained |
| Previous image remains (image retention) | TFT | Static image held for long periods, DC imbalance, VCOM setting | TFT LCD image retention |
| White screen after power-on | TFT | Missing initialisation, reset timing, supply sequencing, interface mismatch | White screen after power-on |
| Flicker | TFT and segment | Frame rate too low, VCOM, PWM backlight dimming | Flicker debugging; camera bands are often not real flicker: camera banding |
| Uneven brightness, clouds or color patches (mura) | TFT | Panel or backlight non-uniformity, mechanical stress, bonding pressure | Red and blue mura case study |
| Dim or dying backlight | TFT and backlit segment | LED ageing, drive current too high, heat | Backlight failure and brightness decay |
| Dark spot or spreading stain | All | Point pressure, cracked glass leaking liquid crystal, polarizer bubbles or delamination | See dark spots and leaks below |
| Slow or smeared update in the cold | All | Liquid crystal viscosity rises at low temperature | LCD response at low temperature |
| Display goes black with sunglasses | All | Polarizer axis crossed with polarized sunglasses | LCDs and polarized sunglasses |
| Resets or glitches when touched | TFT | Electrostatic discharge entering through the bezel or cable | ESD reset and enclosure review |
Lines On An LCD
A line that runs the full width or height of a TFT means a whole row or column is not being driven correctly. Because rows and columns are driven from the panel edge, the cause is almost always at the edge: the flexible circuit, the bonding of the driver IC to the glass, or the board connector. Pressing gently near the edge and seeing the line change is a typical sign of a contact or bonding problem. Lines that appear only with certain images or at certain temperatures can also be timing or power issues.
On segment LCDs the equivalent symptom is a group of segments that never turns on. Check the zebra connector compression, the pin solder joints and the COM/SEG mapping in firmware before suspecting the glass.
Ghosting And Image Retention
On a segment LCD, ghosting means off segments are faintly visible. It is an electrical setting problem: the LCD operating voltage is too high for the duty and bias, or the temperature has risen and lowered the threshold voltage. Lower the voltage, check the bias setting and use temperature compensation in wide-temperature products.
On a TFT LCD, a faint copy of a previous image is usually image retention. Unlike OLED burn-in, LCD image retention is normally temporary and fades when the image changes, but long static images, DC imbalance and an incorrect VCOM voltage make it worse. Details are in the TFT LCD image retention guide.
Dark Spots, Stains And Leaking Liquid Crystal
- Pressure spots: pressing on an unsupported LCD changes the cell gap and shows a dark or rainbow-colored spot that may recover. Repeated pressure can damage the alignment permanently. Support the glass and keep the touch panel or cover lens from pressing on it.
- Cracked glass: when the glass cracks, the liquid crystal can spread between the plates or escape as an oily, sticky liquid, and a dark stain grows from the crack. The display cannot be repaired and must be replaced. Avoid skin contact with the liquid, wash hands with soap and water, and follow the module’s safety information.
- Polarizer defects: bubbles, delamination or yellowing of the polarizer film after heat, humidity or UV exposure look like patches or a general loss of contrast.
Fading And Low Contrast
A display that slowly loses contrast is usually affected by temperature, drive voltage or materials:
- Contrast changes with temperature unless the drive voltage is compensated; see LCD operating voltage and temperature.
- A DC component on a segment LCD degrades the liquid crystal over time; the drive must be AC.
- Backlight LEDs lose brightness with operating time and heat.
- Polarizers age faster under UV and high humidity; outdoor products need suitable materials and protection.
How To Prevent LCD Problems In A Product
- Design the mechanics: support the glass evenly, relieve strain on the FPC, avoid sharp bends and keep the bezel off the active area.
- Design for ESD: provide a discharge path in the enclosure and protect the interface lines; see LCD ESD protection.
- Set the drive correctly: duty, bias, voltage, frame frequency and TFT initialisation exactly as on the drawing.
- Validate samples: test at temperature extremes, with vibration and humidity where relevant, and inspect against agreed criteria; see the sample validation checklist.
- Control changes: when replacing a discontinued display, run a compatibility test first; see LCD replacement compatibility testing.
SuccessLCD reviews the drawing, drive conditions, connection and mechanical stack with OEM customers before samples, so that these failure modes are designed out rather than found in the field.
LCD Problem FAQs
What causes horizontal lines on an LCD screen?
Usually a connection problem at the panel edge: a damaged flexible circuit, broken driver bonding or a poorly seated connector. Timing and power problems can also cause lines that change with the image or temperature.
Can an LCD screen burn in?
LCDs do not burn in the way OLED and plasma screens can. They can show temporary image retention after a static image is held for a long time, which normally fades. Severe DC imbalance or a wrong VCOM setting can make retention persist.
What is the liquid leaking from a broken LCD?
It is liquid crystal, an oily material held between the glass plates. It escapes when the glass cracks. Avoid skin contact, wash with soap and water, and replace the display; a cracked LCD cannot be repaired.
Why do faint segments appear on my segment LCD?
This is ghosting. The LCD drive voltage is too high for the duty and bias, or the temperature has risen. Check the duty, bias and voltage settings against the drawing and add temperature compensation if the product runs hot.
Why does my LCD fade over time?
Common causes are drive voltage drift or missing temperature compensation, a DC component on the glass, ageing backlight LEDs and polarizer degradation from heat, humidity or UV.
Investigating a display problem or replacing a failing LCD? Send photos of the symptom, the part number or drawing, and how the display is mounted and driven. Send the details for an engineering review, read the discontinued LCD replacement guide, or browse TFT LCD modules and monochrome LCD modules. For a replacement design, see custom LCD module options.