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A polarizer is a film that has been given a polarizing capability by impregnating with iodine molecules and dyeing mainly polyvinyl alcohol, stretching / orienting the material.
This polarizing capability only allows the passage of polarized light oscillating in a certain plane. In order to ensure the mechanical strength of the film, supporting structures and protective films are attached.
Three factors;transmission, degree of polarization, and hue are important optical properties of polarizers, and freely approaching the theoretical limits of 50% transmission and 100% polarization greatly influences advances in areas such as LCD brightness and contrast.
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A Retardation film is generally made of stretched polycarbonate that is used attached to a polarizer in order to compensate for the hue coloring that occurs mainly with STN liquid crystals.
This attached component is called an elliptical polarizer.
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The figure right shows the principles behind a typical twisted nematic LCD.
Because light is twisted in line with the twisted liquid crystals 90 degrees when twisted liquid crystals are sandwiched between two polarizers whose polarizing lines are oriented at right angles to each other, the light can pass through the polarizer below.(upper figure) Because the liquid crystal molecules line up straight and light is not twisted when voltage is applied, light cannot pass through the polarizer opposite(b).(lower figure) In other words, the LCD functions as a light shutter based on whether voltage is applied, or not.
Furthermore, the twisting angle of liquid crystal ranges from 180 to 270 degrees in STN LCDs that require optical compensation using retardation films.
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LCD patterns are classified by the relationship between the light source and viewer.
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| Transmissive LCDs (for PCs, car navigation, liquid crystal TVs, etc.) |
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| Reflective LCDs (for liquid crystal calculators, liquid crystal watches, etc.) |
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Transflective LCDs (for gauge indicators in vehicles, mobile phones, etc.).
Serves as both transmissive and reflective LCD.
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| Projection LCDs (for LCD projectors, rear projection TVs, etc.) |
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