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>> Research on Low Temperature Heating of Large Size LCDs Based on Multizone ITO Films 15th,Nov,2017
In this paper, ITO film as a heating element, design and preparation of large-size LCD low temperature heating module. Five non-equally divided zonal heating structures were adopted to control the heating rate of the heating area and to adjust the temperature field distribution of the liquid crystal display by controlling the duty cycle of ITO film loading power in each area and introducing feedback regulation mechanism. In the 270V voltage, the first 12% of the power duty cycle quickly warming, and then 6% of the power duty cycle to maintain the temperature, can make the liquid crystal display in 300s to achieve rapid start requirements within 500s to reach a relatively stable temperature (-5 ℃). Meanwhile, the temperature difference between the centers in each area is kept within 2 ℃, which solves the problem of uneven heating of large-size liquid crystal displays at low temperature.
Liquid crystal displays (LCDs) have outstanding advantages such as small size, light weight, low power consumption and good electromagnetic compatibility and have become the mainstream display devices. Due to the increase of the viscosity coefficient of the liquid crystal molecules in the low temperature environment, the response time becomes longer, the image is severely tailing and can not be displayed normally, which results in the poor performance of the LCD at low temperature or even not working.
LCD in the low temperature environment can not work properly, the more way is to use ITO (Indium Tin Oxides) film glass as a heating element on the LCD low temperature heating compensation. When a current flows through the ITO film, the heat generated by the resistance of the ITO film itself is transferred to the LCD that is attached to it to achieve the required temperature for normal operation. At present, the uniformity of the temperature field in the area-based ITO heating method decreases as the size of the LCD increases. Overheating or underheating occurs in the local area, and in some cases, the LCD and ITO heating elements are even exploded.
In view of the above problems, this paper intends to use multi-area ITO film heating structure, the duty cycle control and the introduction of feedback adjustment mechanism to control the heating rate of heating elements to optimize the distribution of the temperature field, so that large-size LCD display can quickly start under low temperature and Stable work.
1 theory of optimal design
1.1 heating element design
In this paper, the size of 624mm × 240mm LCD display for the study, the use of sheet resistance of 50Ω / □ ITO glass to be heated. The ITO heater was divided into five regions at a ratio of 3: 2: 2: 2: 3 in length. From the formula (1) can be obtained by the value of each area.
Research on Low Temperature Heating of Large Size LCDs Based on Multizone ITO Films
Where ρ □ (Ω / □) is the sheet resistance of the ITO glass, and l1 is the length of each region after partitioning of the ITO heater, and l2 is the width.
1.2 software simulation
ANSYS software analysis of the load voltage is 135V, the power duty cycle is 30% of the heating field temperature field distribution and temperature rise of the center point, as shown in Figure 1.
Research on Low Temperature Heating of Large Size LCDs Based on Multizone ITO Films
Figure 1 Voltage 135V, power duty cycle 30% of the simulation of the heating temperature field and temperature rise curve
As can be seen from Figure 1, the temperature difference between the non-equally divided regions is within 4 ° C, which is more uniform than that of the single-region heating in the past.
2 heating sheet preparation
Wet etching was used to pattern the ITO substrate in proportion to obtain 5 non-uniform heating zones. Then nano-silver paste evenly coated on the edge of the five partitions, the lead wire leads the electrode, as shown in Figure 2. Test the resistance of each partition, see Table 1.
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