Figure 1: The make-up of an e-paper display
By Alchin Wang, General Manager
Once you’ve read a document on electronic paper (e-paper), you’ll never want to go back to traditional liquid crystal (LCD), light-emitting diode (LED) or organic light-emitting diode (OLED) displays.
The only problem is that e-paper has still not reached the level of market maturity that makes it capable of being sufficiently commoditized. This is because most manufacturers cannot create e-paper displays (EPDs) that operate under the toughest environmental conditions. Achieving the highest possible levels of reliability and performance remains a significant challenge.
The demands of e-paper
Users of e-paper justifiably put significant demands on the technology. They expect it to perform exactly like paper — including the absence of compromises when it comes to operating conditions.
Like paper, e-paper reflects light rather than emitting it. It is also expected to be easier on the eyes and offer wider viewing angles than LCD, LED, or OLED displays. E-paper manufacturers must therefore deliver scalable solutions capable of operating under the same environmental conditions as paper.
Traditional displays are designed to mimic paper, but they do not truly behave like it. There is a growing demand from customers for a technology that bridges this gap.
Traditional displays typically operate between 0°C and +70°C. Industrial-grade variants handle -40°C to +85°C, but at much higher cost. Even then, customization is extremely limited. Users may need enclosures or other measures for environmental protection. By contrast, EPDs come in customized formats capable of operating over a far wider temperature range.
How to manufacture an e-paper display
Figure 1 shows the make-up of an EPD which incorporates such unique features as edge glue, an e-ink film and a protective sheet. These combine to make up the front plane laminate (FPL), shown in Figure 2.
Figure 2: The front plane laminate (FPL) of an EPD
When manufacturing an e-paper display, a roller attaches the FPL to the TFT substrate and compresses the layers with silver glue. This ensures conductivity between the e-ink and the substrate. Any cavities from suboptimal glue contact can cause surface defects and poor image quality. It is also essential that a protective sheet used on EPDs offers not just excellent environmental protection but also high levels of light transmission.
Figure 3: Surface defects can be created in EPDs during the rolling process
The Pervasive Displays solution
With many years of experience backed by extensive R&D, Pervasive Displays has put itself at the forefront of e-paper display design and manufacturing.
For example, we created a proprietary silver glue that eliminates defects by suspending silver particles in a paste with a double-dot design. Likewise, the adhesive used to attach the protective film achieves 4.5 times the moisture resistance of similar glues. It also minimizes shrinkage during curing. This makes the product far more reliable and durable under demanding conditions.
Our protective sheet material is at least 10 times more resistant to moisture than competing materials. Special surface treatments, including 3H hardness, make our EPDs highly resistant to acetone, detergents, alcohol, perfumes, and many other chemicals. The result is superior optical performance across a wide range of conditions. The contrast ratio for 2- and 3-color products is increased by 15%, and the chromaticity index for 3-color products is boosted by 5%.
Market maturity
As the market matures, Pervasive Displays has ramped up production and now sells more than 20 million displays per year. With unrivalled expertise and experience, we continue to push technological boundaries — ensuring e-paper finally takes its place as a genuine replacement for paper.