A Guide to the Transflective LCD and Transmissive LCD Modes

Posted by ANNA WILSON on August 5th, 2021

The phrases "trans missive" and "transflective" are frequently used when discussing liquid crystal display (LCD) technology. They cover the many methods for illuminating LCD modules. The sun, artificial room light, or an integrated backlight, which is frequently inspired by LED (light-emitting diode) semiconductors, are all necessary for LCDs, in contrast to emissive display technologies such as OLED displays (organic light-emitting diode) and VFDs.

Transmissive Type

Transmissive refers to the method of operation in which light from a backlight flows through the LCD glass. Light from the backlight travels through the LCD cell depending on the orientation of liquid crystal molecules, and the LCD glass or LCD panel serves as an "optical switch." An electrical field can “switch” the direction on or off. Backlights emit a lot of light, which makes the display appear brighter. The disadvantage of employing backlights is that they consume a lot of energy in an LCD module, unlike the transflective LCD, mainly because the backlight must be turned on all the time, even if there is no content on the screen. If the sunshine overpowers the brightness of the backlight, a transmissive LCD panel might become "washed out."

Backlights that are powerful enough to retain appropriate contrast in direct sunshine – such as those used in aviation displays – are incompatible with the needs of portable devices.

Transflective Type

Both transmissive and reflecting properties are present in transflective LCDs. They have an integrated lighting device as well as a semi-transparent or hole-filled reflector for each pixel. The reflector can be located either behind the rear polarizer or within the LCD cell, behind the liquid crystal layer.

The semi-transparent reflector allows light from the backlight to flow through, allowing the display to function in the transmissive mode. Simultaneously, ambient light can be reflected, making the display viewable even in direct sunlight. It's important to remember that light only goes through the liquid crystal layer in the transmissive mode of operation once.

In contrast, reflectively, light passes through the liquid crystal layer twice. Transflective display have a compromise appearance. It is the most adaptable solution since it allows for decreased power usage in bright areas while maintaining readability in any lighting situation. This comes at the cost of high performance in pure lighting modes and, in some cases, a significant increase in production costs.

To summarize, LCDs require a light source from outside. The mode of operation determines how the light source is given to the LCD cell and can be reflecting, transmissive, or transflective. Because of their energy economy, a reflective or transflective LCD is preferred for outdoor applications. An LCD transmissive or transflective screen is the finest choice for viewing in dark lighting conditions.