3M’s APF (Advanced Polarizing Film) is not a traditional “absorptive polarizer.” Instead, it is an on‑glass reflective polarizer applied directly to the LCD glass. Its primary functions are to improve backlight efficiency, increase brightness, reduce module thickness, and enhance display performance from wide viewing angles.

As shown in the picture below, APF allows the polarization direction required by the LCD to pass through, while reflecting the orthogonal polarization back into the backlight system. The reflected light undergoes multiple scatterings inside the backlight cavity, and part of it returns with a rotated polarization state that can be reused. In other words, APF recycles light that would otherwise be wasted, thereby improving brightness and energy efficiency.

Reference: https://www.3m.com/3M/en_US/p/d/b5005047084/

Advantages of APF

• Brightness Enhancement (by around 30%)

Reduces optical loss and improves both on‑axis and wide‑angle brightness.

• Power Savings

By increasing backlight efficiency, APF reduces backlight power consumption, helping achieve lower energy usage and longer battery life.

• Thinner Module

Since APF is laminated directly on glass, it can replace part of the BEF/DBEF stack, simplifying the optical structure.

• Better Viewing‑Angle Performance

The reflective polarizer structure improves brightness uniformity and wide‑angle brightness.

• Higher Environmental Robustness

More stable than “free‑standing reflective films,” with lower thermal load and better durability.

Comparison Between APF and DBEF

Based on the comparison above, we will recommend APF when you need thinness, efficiency, and wide‑angle performance, and DBEF when you need maximum brightness at lower cost.

Should you have any questions, please consult our engineering.

E-ink or E-paper displays are widely used in e-readers, digital signage and digital art frames.  They offer ultra-low power consumption, and are easily readable in direct sunlight.

Its key features and benefits include:

• Low Power Consumption
• Paper-Like Appearance and Eye-Friendly Reading
• Flexibility and Versatility

However, one of the main primary weaknesses of e-ink displays is its slow refresh rate. Compared to LCD or OLED, e-ink displays normally cannot display videos.

Why does E-ink refresh so slowly? Because E‑ink displays form images by physically moving real micro‑particles suspended in liquid, rather than lighting up pixels with electric current like LCD or OLED panels.

Table 1. Refresh Speed of Different Display Types

Take the simplest black‑and‑white e‑ink display as an example. Its working principle is as follows:

Each pixel contains many microcapsules filled with:

• Positively charged white particles
• Negatively charged black particles

https://www.eink.com/

By applying an electric field, white particles are pulled to the top → the pixel appears white; black particles are pulled to the top → the pixel appears black.

The key point is that this is mechanical displacement, not electronic transition. These particles are microns in size and move within a high‑viscosity fluid, so their speed is far slower than electrons moving through a conductor. If the particles move too quickly, they may not settle accurately, causing artifacts or ghosting.

Refreshing an e‑ink display is not a simple on/off action. It involves multiple steps:

• Clearing the screen
• Reverse driving
• Multiple pull‑backs and fine adjustments

Each step requires waiting for the particles to stabilize. This is why you see the screen flash and gradually become clear during a refresh.

E‑ink is designed to be bi‑stable, meaning it can retain an image for long periods without power, with a paper‑like stable appearance. Achieving this requires sacrificing some refresh speed in exchange for ultra‑low power consumption and reduced eye strain.

With ongoing improvements, modern e‑ink displays can increase refresh speed through several optimizations:

1. Black‑and‑white 1‑bit Mode

Fast‑refresh modes often support only pure black and white, removing the complexity of 16‑level grayscale calculations. The image is simplified to 1‑bit data, enabling extremely fast processing.

2. Partial Refresh / A2 Mode

A full refresh cycles through black‑white‑black transitions to eliminate ghosting. Fast modes update only the pixels that change, without forcing a full‑screen wipe, greatly reducing update time.

3. Dithering Algorithms

Techniques like Floyd–Steinberg dithering simulate gray levels using patterns of black and white pixels. This preserves acceptable image quality while maximizing refresh speed.

These techniques improve speed, but image quality decreases and ghosting accumulate more quickly.

Why Is Color E‑Ink Even Slower?

Because color e‑ink adds additional layers of complexity on top of an already slow black‑and‑white system. Each color technology introduces extra steps that slow down refresh.

Current mainstream color e‑ink technologies (Kaleido, Gallery) do not emit RGB light directly. Instead, they rely on layered structures or multi‑particle systems.

A. Color Filter Array (Kaleido)

This is the most common color e‑ink today.

https://www.eink.com/

Each color pixel is composed of multiple black‑and‑white sub‑pixels. A single-color pixel contains 3–4 monochrome sub‑pixels, and color depth is controlled by adjusting the black/white ratio. Changing a color cannot be achieved in a single drive cycle. To achieve fine grayscale control, multiple waveform adjustments are required, which increases refresh time.

Because this technology still relies on black‑and‑white particle movement, it can approach the speed of monochrome e‑ink, but color saturation is limited.

B. Multi‑Color Particles (Gallery / ACeP)

This is true full‑color e‑ink.

https://www.eink.com/

Each microcapsule contains four types of charged color particles (yellow, cyan, magenta, reflective white). Compared with controlling two particle types in monochrome e‑ink, this system must control four, greatly increasing complexity.

To display a specific color, each particle type must be positioned at the correct height. During refresh, the system must use extremely complex voltage waveforms to guide specific particles through a crowded mixture and bring them to the top. It’s like trying to push only the people wearing blue shirts to the front of a packed crowd—much harder than having everyone move together.

Particles collide and rub against each other during movement, and the internal electric field becomes more chaotic as particle types increase. To ensure accurate color without ghosting, the system must “shake” the particles repeatedly to settle them properly. This is why color e‑ink often flashes many times during refresh. A single refresh may require dozens or even hundreds of waveform cycles, taking several seconds or even more than ten seconds.

This technology produces vivid, saturated colors, but is too slow for interactive use.

Additionally, e‑ink is extremely temperature‑sensitive. At low temperatures, the liquid becomes more viscous, slowing particle movement further and requiring more complex compensation algorithms.

How Color E‑Ink Refresh Speed Can Be Improved

Current optimization efforts focus on hardware, software, and algorithmic improvements:

1. Hardware: Dedicated Display Memory and GPU

Traditional e‑readers rely on the CPU for image processing, but color e‑ink waveform control is too complex. Some manufacturers add a dedicated display processor to handle image conversion and waveform generation, reducing CPU load and improving refresh speed.

2. Software: Dynamic Refresh Modes

Manufacturers offer preset modes such as Fast or A2 Mode. These reduce color depth and resolution (using dithering) to increase speed. Page turns become very fast, and even cursor movement becomes visible, but noise and ghosting increase.

3. Algorithms: Waveform Optimization

Shortening voltage pulses allows particles to stop before reaching their “final” position, enabling quicker transitions.

Conclusion

Given current technology, e‑ink’s core strengths remain long‑term static display, low power consumption, and high readability. It cannot yet match TFT‑based displays in color vibrancy or interactive speed.

Should you have any questions, please consult our engineering.

Shop our E-Ink Display here: https://orientdisplay.com/e-paper/

Brightness Enhancement Film (BEF)

Brightness Enhancement Film (BEF), also known as a Prism Sheet, is a key component in the backlight module of TFT-LCDs. It is an optical film with precise microstructures that concentrates scattered light from the light source into a forward direction, narrowing the spread to approximately 70 degrees. This makes it an important energy-saving element in LCDs.

A single BEF can typically increase brightness by about 40–60%. When two BEF films are used together with their prism orientations placed at 90 degrees to each other, even higher brightness enhancement can be achieved.

The function of the BEF is to direct light, which would otherwise spread over a wide range of angles, into a narrower, forward-facing angle to increase the intensity of light seen from the front. Essentially, a basic brightness enhancement film is a prism sheet that refracts, reflects, and concentrates light to achieve enhanced brightness.

The drawback of BEF is that, at the same brightness level, the screen appears brighter when viewed directly from the front, but the image becomes dimmer when viewed from an angle.

DBEF (Dual Brightness Enhancement Film)

DBEF (Dual Brightness Enhancement Film) is a reflective polarizer that reflects S-polarized light before it is absorbed by the LCD panel. Through repeated reflections, it allows approximately 40% of the S-polarized light to be reused.

The light emitted from the backlight can be decomposed into P- and S-polarized light, which are orthogonal in polarization direction. DBEF can recycle and reuse the S-polarized light that would otherwise be absorbed by the polarizer, thereby improving the light utilization efficiency of the backlight system.

Compared to BEF, DBEF improves light utilization and increases brightness while overcoming the viewing angle limitations of BEF. Therefore, BEF is sometimes referred to as a “collimating film,” while DBEF is called a “brightness enhancement film.”

BEF and DBEF can be used together to maximize light emission efficiency and to optimize the cost.

Please also refer to the pictures below for the actual products Orient Display made. The right side is with BEF only, the right side is the combination of BEF and DBEF.

If you have any questions, please contact our technical support team.