Lcd Box Reflection Spectrum For The Study Of Cell Thickness Measurement

In the productive procedure of LCD, in order to make LC layer satisfy the requirement of design and guarantee the complement of LCD special display mode, the thickness and size of LCD is usually seriously controlled. Those modes, for example, include Twisted Nematic LC display mode(TN working mode), Super Twist Nematic mode(STN working mode), Electronic Controlled Bi-refraction mode(ECB working mode) and so on. For the detail, the main effect of the thickness of LCD for the LCD's performance includes the following two aspects: First, for the higher contrast ratio, response speed, luminous, LCD gap's precision must be controlled under 0.1μm. Especially, the precision requirement of Colorful STN-LCD is more serious, and it must be under±0.05μm. Second, the LC cell's thickness regularity is vital important for the displaying regularity. If the LC cell is not regular, it could cause change of LCD's color and make the cell into fake. Especially in the process of STN-LCD manufacturing, the key technology is controlling the thickness of LCD gap.In this dissertation a new thickness measurement technology of LCD gap has been researched. This technology is based on the max value of reflective light intense and use the optimal fitting method to get the final measurement value. This method use the white light as the light resource, through relationship between wavelengths and the reflective light intense to obtain measured LCD gap's relative data information. The measurement data will be stored in PC through USB interface. After data process, LCD's thickness could be received directly. The benefit of this measurement method is that the procedure of measument data is fully programmable, and operator could get the result without understanding LC physic feature,complex formulations of Jones Matrix and optic principle.The measurement objective is 6μm LCD gap which is widely used. Through comparing the methods of spectral interference and max value fitting, the advantage and disadvantage between two measurement methods is self-proof. The result has shown that this difference could be controlled under 0.1μm by using the max value fitting method , the measurement scope is between 5μm and 30μm, and measurement exhausting time is under 1 second. This measurement technology could be well used in the process of LCD manufacturing.