一, The core value of anti fog design: eliminating optical interference and ensuring real-time data
1. The direct impact of fog on LCD display performance
The display principle of LCD relies on the twisting of liquid crystal molecules under the action of an electric field to control the light flux. When the environmental humidity is too high or the temperature suddenly changes, water vapor in the air is prone to condense into mist on the surface of the LCD, leading to the following problems:
Light scattering effect: Mist droplets act as tiny lenses, scattering incident light and reducing transmittance. For example, during the rainy season, the LCD of a storage tank level gauge in a petrochemical enterprise fogged up, causing operators to misinterpret the level data and resulting in an overflow accident.
Contrast attenuation: Mist forms a diffuse reflection layer on the surface of the LCD, weakening the contrast of black background and white text. Experimental data shows that when the haze value increases from 0% to 5%, the LCD contrast can decrease by more than 30%.
Touch failure: In capacitive touch LCD, fog can change the dielectric constant of the medium, causing touch point displacement. A certain smart meter was tested in an environment with a humidity of 85%, and the touch error triggering rate increased by four times compared to a dry environment.
2. Fog Causes and Typical Cases in Industrial Scenarios
Severe changes in temperature and humidity: The LCD of the blast furnace monitoring system in a certain steel plant is located at the junction of the high-temperature production line and the air conditioning control room, with a temperature difference of 20 ℃ between day and night, resulting in the shell temperature being lower than the dew point, requiring manual wiping of the mist three times a day.
Process fogging: During the coating process of lithium batteries, solvent evaporates to form micrometer sized droplets, which adhere to the surface of the adjacent thickness detector LCD, expanding the measurement error to ± 5 μ m.
Oil mist condensation: The combination of cutting oil mist and water vapor in the machining workshop forms oily condensation on the surface of the LCD of the CNC machine tool, corroding the coating layer and causing a 15% decrease in transmittance within six months.
3. Systematic solution for anti fog technology
Physical isolation: Using positive pressure clean air curtain technology, continuously blowing dry air (dew point <= -40 ℃) in front of the LCD to form an airtight barrier. After a semiconductor equipment manufacturer applied this technology, the LCD failure rate decreased by 82%.
Material innovation: Using nano hydrophobic coating (contact angle>150 ℃) to form spherical rolling of water droplets on the surface. Experiments have shown that after coating treatment, the fogging time of LCD is extended to 5 times that of untreated samples in an environment of 85 ℃/85% RH.
Intelligent temperature control: Integrated PTC heating element and temperature sensor, using PID algorithm to control the LCD surface temperature to remain 2 ℃ above the dew point. After adopting this scheme, the problem of low-temperature fogging in winter was completely solved for a wind power variable pitch system.
2, The strategic significance of dust-proof design: blocking pollution pathways and extending equipment lifespan
1.Composite damage of dust to LCD
Mechanical wear: When the diameter of metal dust particles is greater than 5 μ m, scratches will form on the surface of the LCD. After one year of operation, the surface scratch density of a certain coal mine safety monitoring instrument LCD reached 12 scratches/cm ², resulting in a decrease in transmittance to 65% of the initial value.
Electrical short circuit: Conductive dust (such as carbon powder) entering the LCD driver circuit may cause local short circuits. A certain printing factory's spectrophotometer had its driver IC burned out due to dust, resulting in an increase of 230000 yuan in annual maintenance costs.
Optical pollution: Dust deposits on the surface of LCD to form a pollution layer, and for every 10 μ m increase in thickness, the transmittance decreases by about 1%. After using the LCD of a certain food packaging machine in a flour environment for 3 months, the display clarity score decreased from 92 points to 58 points.
2. Sources and characteristics of industrial dust
Process dust: Raw material dust (particle size 1-100 μ m) in cement production and metal dust (particle size 0.1-10 μ m) in welding workshops have strong adhesion.
Environmental dust: Suspended particles with an aerodynamic diameter of less than 10 μ m in desert areas that can penetrate ordinary protective structures. After a sandstorm, the LCD monitoring system of a certain photovoltaic power station had an internal dust deposition of 0.3g/m ².
Corrosive dust: Hydrogen chloride gas emitted by chemical enterprises combines with moisture to form hydrochloric acid mist, which causes electrochemical corrosion to LCD metal frames. The corrosion rate of the instrument LCD frame in a certain chemical plant reaches 0.02mm/year.
3. Multi level protection system for dust prevention technology
Structural sealing: Adopting an IP67 fully enclosed design, using silicone rubber sealing rings and ultrasonic welding technology to ensure that dust cannot enter. The LCD of a certain rail transit signal system has been tested and operated for 240 hours without any faults in a dust environment with a wind speed of 0.5m ³/h.
Airflow purification: Equipped with a built-in micro fan and HEPA filter, forming a positive pressure protection chamber. After adopting this solution, the internal particle concentration of a pharmaceutical company's cleanroom LCD is controlled within the ISO Class 5 standard.
<5 °) to make dust fall off under gravity or slight vibration. Experiments have shown that the cleaning cycle of coated LCDs in a flour environment has been extended from once a week to once a month.
