LCD Viewing Angle

The bias angle is the angle from the perpendicular from which the liquid crystal display (LCD) glass is best viewed. The LCD viewing angle is the angle formed on either side of the bias angle, where the contrast of the display is still considered acceptable (see figure 1). The orientation of the bias angle of LCD displays is often stated with reference to a clock. If the offset is above the display, it is referred to as a 12:00 or top view. In contrast, it is referred to as a 6:00 or bottom view.

Fig. 1 Definition of viewing angle

Relationship of Light Direction and Liquid Crystal Direction

The molecules of liquid crystals are usually much longer than they are wide. You can think of them like pencils. Depending on the specific liquid crystal, one direction will be faster than the other. When the light wave emerges from the liquid crystal, the direction of polarization may have been changed due to the difference in light speed along different directions. With a polarizer our eyes can detect the direction of light polarization.

With the light emission characteristic and control of the light brightness of LCD, the grayscale can be formed. Based on the relationship of the light direction and the liquid crystal direction, it shows different situations if you look from a different direction (see figure 2). When the light is parallel to liquid crystal long axis, the phase delay and transmission rate are small and it is dark. When the light is vertical to LC long axis, the phase delay and transmission rate are large and it is bright if look from above. It is clear that there is a different gray scale from a different direction.

Fig. 2 Situations in different directions

Measuring Method

The viewing angle is measured from the display’s normal axis to each of the four directions. Theoretically, the maximum angle is 90° and it might vary for each measuring direction.

Luminance, chromaticity, and luminance contrast are the three parameters used to evaluate a display viewing angle performance. A probe or a spot luminance meter/spectroradiometer is positioned at different angles with respect to the display and then the viewing angle can be measured by evaluating these parameters. While the test patterns and data analysis depend on the metric required, the number of measured viewing directions could range from a few to many, along the horizontal, vertical, and oblique directions or in the whole angular viewing space.

Our Advantages

Alfa Chemistry will be in touch with you throughout the liquid crystal and LCD analysis process to make sure your project objectives are accomplished. You will be able to decide whether your needs have been fulfilled and whether additional testing is required to meet your needs throughout the project. The final outcome will be a high-quality analysis. Please contact us or get a quote to discuss your testing needs for a complete list of our testing services.