Bistable LCD Technology Introduction
Bistable LCD can retain an image without power (Zero Power). The crystals may exist in one of two stable orientations and power is only required to change the image. Bistable LCD can change colors, and keep that color even when power is cut off.
Bistable LCD Advantages
No flicking: eyes not get tied easily.
Low power: no power is needed to maintain the image. Made into e-book, 20,000 pages can be read with 2 AAA batteries of 3V.
Possible high resolution which can achieve 200 dpi. Can achieve 256 gray scale.
Possible low cost and a green display: no polarizer (for some bistable LCDs), color filter and backlight are needed.
High contrast and wide viewing angle: The monochromatic bistable LCD’s contrast ratio is as high as 25:1, viewing angle about 80 degree in all directions.
Bistable LCD Colors
|Reflective Color of Bi-stable LC||Color Absorbing Layer||Character Color||Background Color|
|Double Layer||Yellow Blue||Black||White, Yellow, Blue, Black|
|Triple Layer||Red Green Blue||Black||Full Color|
How Bi-stable LCD Works
For Cholesteric materials with positive dielectric anisotropy, the molecules in the planar structure will easily realign parallel to an applied electric field, generating the reflective layered structure. To break up the helical layered structure is to apply voltage around 6V to 30V. In order to switch from focal conic state back to planar state, even higher voltage is needed (35V). The exact voltage required for switching depends on cell gap as well as dielectric anisotropy of liquid crystals. The focal state is less stable than the planar state.
Bistable LCD limitations
Refresh rate is slow: 2-3 seconds
Between each screen refreshing, the screen has to be refreshed with a dark screen.
Bistable Liquid Crystal materials require protection from UV light. A UV blocking material with a minimum 98% cut of at 380nm and lower spectral components is required.
The finished product design should incorporate a transparent cover such as acrylic, polycarbonate etc. to protect the viewing area of the display. Place the protective cover as close to the display module as possible. The protective cover should be sufficient thickness to resist bending.
Adding an anti-glare and or anti-reflective surface film or finish to the viewing side of the protection cover may improve the optical performance.
The power used for screen refreshing is pretty high. So, it will not worthwhile for an application if the screen has to be refreshed more than 20 to 50 times depending on the battery used. Bistable technology has been used for shelf label and E-reader. Bi-stable LCDs requires the use of a voltage booster. Designing into some environments needs to be cautious, examples: explosive gas. Bistable LCDs are limited to one color of character and one color of background.
Bistable LCDs are reflective and do not require a backlight. This can be a disadvantage in areas with dark ambient light. If the lighting has to be used, it can only use front light instead of backlight. It can be expensive and lose its key advantage of low power.
Orient Display Standard Bistable LCDs
- Single Layer Bistable LCD (Background: Blue; Character: White) : JAZZ-W-B
Fig.1 White Blue Bistable LCD
- Single Layer Bistable LCD (Background: Black; Character: Green) : JAZZ-CG-D
Fig.2 Green Black Bistable LCD
- Single Layer Bistable LCD (Background: Black; Character: Yellow) : JAZZ-CY-D
Fig.3 Green Black Bistable LCD
- Double Layer Bistable LCD (Background: Pink/Blue; Character: Yellow) : JAZZ-CY-PB
Fig.4 Double Layer Bistable LCD
- Black White Bistable LCD
Fig.5 Black White Bistable LCD
Customer Made Bistable LCD
Any type of monochrome and multicolor LCDs including digit, character and graphic bi-stable LCDs can be custom made. Please contact Orient Display technical support team for details.
Competitive Technology: E-ink
Fig.6 HTN LCD
Compared with E-ink, bistable is flexible for custom made solution. The tooling cost and unit prices are lower than E-ink. Bistable is also flexible for MOQ. But there is a major disadvantage compared with E-ink: the backlight of E-ink is closer to paper which makes E-ink widely used in e-book (Kindle for Amazon) which is the biggest market for zero power display.
For more information for E-ink technology, please refer to https://www.eink.com/electronic-ink.html
Orient Display also works with e-paper company to provide total solution for the technology, feel free to Contact Us and we are willing to help!