E-mode and O-mode polarizer
The principle of LCD display is to control the Angle of polarized light by controlling the rotation of liquid crystal molecules. Polarized light can pass in one direction and absorb polarized light in a direction perpendicular to it. This effect is called dichroism. In mass production, most sheet polarizers are submicroscopic dichroic crystals synthesized by uniaxial alignment of arrays. Polarizers based on crystal dichotomy are thus divided into two groups.
In an O-type polarizer, ordinary waves are transmitted, while abnormal waves are strongly affected and attenuated.
In an E-type polarizer, abnormal waves are transmitted, while ordinary waves are strongly affected and attenuated.
We will now discuss both types of polarizers.
The O-polarizer works by properly introducing iodine atoms into a stretched plastic material called polyvinyl chloride. Stretching results in a uniaxial arrangement of dichroic crystals or molecules (see Figure 2.1). As a result of stretching, the acicular molecules are arranged along a common axis in the film, resulting in uniaxial symmetry. Dichroic ratios greater than 10 are easy to find. Vector-amplitude polarized light parallel to the molecular axis can produce significant material absorption. Ordinary waves (o waves) can pass through the film without loss. For this reason, these wafer polarizers are called O-type polarizers.
E-mode polarization depends on the dichroism of the disk molecule, which is flat and similar in shape to a thin disk (see Figure 2.2). Uniform alignment of the disks is achieved through two steps in the deposition process. In the first step, the disk molecules pile up in the water into columnar structures due to the forces of the plane structure and the interactions between the molecules. In each column, all the molecules are facing the same direction. After drying, the crystallization process results in a more uniform arrangement of disc-like molecules in monoclinic crystals. The extraordinary wave (e wave) can pass through the polarizer without loss. For this reason, these wafer polarizers are called extraordinary (e type) polarizers.