TFT LCM simple use and troubleshooting

I. Use of TFT LCM

Due to the special principle and structure of TFT LCM devices, the use of installation must pay attention to.

(1) to prevent over-pressurization.

LCD device is made of two pieces of glass made of liquid crystal box, only 5 ~ 10um between them, and the inner surface of the glass is also coated with a layer of orientation layer, it is easy to destroy, so the assembly, use should pay attention to.

LCD surface can not be pressurized too much, so as not to destroy the orientation layer, in case the pressure is too large, or pressed by hand in the middle of the LCD, need to be placed at least 1 hour before powering up. Assembly remembers to pressure evenly, only the edge of the device, not the middle of the pressure, and not uneven force.

(2) Prevent glass breakage.

Because the LCD is made of glass, if lost, the impact will certainly cause rupture, so the design of the whole machine must be considered when the assembly method, assembly of vibration and impact resistance performance.

(3) Prevent the application of direct current.

The smaller the DC component of the drive voltage, the better, preferably not more than 50mV, the long time to apply too much DC component will cause an electrochemical reaction of the electrode and aging. In the segment display, often introduced in the oscillation circuit dichotomous circuit to ensure the symmetry of the square wave.

(4) device moisture:

As the LCD is low-voltage, micro-power, liquid crystal material resistivity is very high (up to 1010Ω.cm or more), so the glass surface conductivity due to moisture is enough to affect the display. Between segments will produce a “crosstalk” display. Therefore, the entire machine design should be considered moisture-proof, the chassis is well sealed, and even the use of laminated conductive rubber strip.

(5) Protection pin:

If the pin is TFT LCM, the LCD should be installed 2mm or more away from the line board, and can not be too much force, heat too high, so as not to destroy the connection. The maximum temperature resistance of the connection shall not exceed 80℃. No detergent shall be used at the tube foot because the detergent will decompose Cl2 in daylight and form hydrochloric acid after absorbing water thus corroding the electrode.

(6) Use and storage within the specified temperature range:

Since the liquid crystal state will disappear beyond a certain temperature range, it must be used and stored within the specified temperature range. If the temperature is too high, the liquid crystal state will disappear and become an isotropic liquid state, the display surface will be black and cannot work. At this time, do not energize, wait for the temperature to return to normal display surface will also return to normal. If the temperature is too low, the liquid crystal state will also disappear and turn into a crystal. At this point, there is a possibility that the formation of crystals in the process of breaking the orientation layer and causes permanent damage.

(7) UV protection:

Liquid crystal and polarizer are organic, the photochemical reaction will be produced under UV light irradiation, so it should be considered according to the LCD use conditions and the environment whether the device needs to prevent UV light filter.

(8) To prevent scratches, pollution:

Because the surface of the LCD device is a plastic polarizer, so the assembly, use should absolutely avoid hard object scratches, staining, TFT LCM on the surface of the polarizer have a layer of protective film, so as not to cause scratches, staining. When assembling, the protective film should be removed at the end of the assembly. Even so, it is best to wear cotton gloves during installation and operation to avoid staining by hand sweat, oil, cosmetics, etc. If it has been stained, it should be promptly treated with a fine cloth, cotton ball wipe; if the stain is too heavy and must be cleaned with solvents, only with isopropyl alcohol (glycerin), alcohol, Freon wipe, and quickly dry, but never with acetone, aromatic solvents (such as toluene and water scrubbing), otherwise it will damage the LCD surface polarizer.

(9) electrostatic interference:

Because the LCD working voltage is very low, the internal resistance is very large, so when using a multimeter (× 10K file) check, sometimes there will be a “string” phenomenon, which is due to electrode overhang, which is a normal phenomenon.

II. the use of troubleshooting

A qualified display device with, sometimes due to unreasonable use, unsuitable conditions and accessories unqualified or improper installation method failure. The causes and troubleshooting methods are as follows.

(1) the exclusion of the handwriting:

After a few hours or days of use, the electrode discoloration appears black, brown “handwriting”, liquid crystal box bubbles, resulting in the inability to display. This is due to the drive voltage DC component being too large, thus causing the electrochemical reaction caused. Check the circuit to exclude excessive DC components, and then replace the LCD with a new one. When the “word” just appeared, the LCD can be heated to above the temperature, that is, when the display surface of the display device all changes color, stop heating, natural cooling, generally can be removed from the “word”.

(2) vague TFT LCM display:

After assembly also should not show the pen also be vaguely displayed, so that can not be read out, the reasons may be.

① conductive rubber stripes are not correct, not parallel, insulation performance is poor, replace the conductive rubber stripes can be.

② AC square wave up and down amplitude is not symmetrical, resulting in the cut-off when the extinguished, adjust the square wave amplitude can be solved.

③ Common electrode or segment electrode overhang, reassemble reliable, can be eliminated.

④ The weather is too damp, the glass surface conductive, indoor drying can be restored.

⑤ lead between not clean, with dry fine cloth wipe cloth can be.

(3) poor contrast exclusion:

Poor contrast, or negative image, or display confusion, or all display, generally due to the back electrode overhang caused by the exclusion can be.

(4) the exclusion of the lack of scratch display, the lack of scratch display may be caused by.

① electrode leads staining, resulting in poor assembly contact.

② Conductive rubber staining, resulting in poor assembly contact.

The above two only need to be cleaned and processed after assembly, assembly can not touch the cleaned and processed parts by hand.

③ The glass edge is broken and scratches the outer lead conductive layer.

④ assembly pressure frame is not qualified.

(5) intermittent display of the exclusion:

functional disorder, can not be adjusted, the reason is that the power supply voltage is not normal, battery depletion, then need to replace the battery.

(6) all show the exclusion:

The decoder is normal, but all show generally is not connected to the back electrode, or back electrode DC.

(7) chaotic TFT LCM display of the exclusion:

External interference may also cause confusion, exclusion.

(8) the exclusion of chaotic display:

The causes of the chaotic TFT LCM display may be: back electrode overhang, drive for DC, power fluctuations, poor contact, battery depletion, etc. can be excluded according to different reasons.

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