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Not since the launch of Apple’s iPhone in 2007 has there been a game-changing disruptive technology that will again transform mobile technology and how it is used. Based on advances in colorless polyimides (CPI), a foldable smartphone display is expected to hit the market shortly, with major manufacturers in a race to be first.

Before discussing why this technology is a game changer, let’s get educated with the basics of polyimide films and the importance of achieving colorlessness.

1. What is a Polyimide?

A polyimide is a class of polymer used in a variety of applications including thin films for flexible printed circuitry and cable insulation; fibers for fire protective clothing; and rigid foams for insulation of naval vessels and commercial aircraft. Polyimides have such beneficial characteristics as good dielectric properties, chemical resistance and retention of mechanical properties, all under extended high-temperature conditions.

Polyimides are orange-brown in color. This is most easily seen when they are used to produce flexible and rigid printed circuitry, such as those found in TVs, radios, cell phones and other small electronics. In fact, it is this dark color that has prevented polyimides from being used in a wealth of additional applications, such as displays, until now.

2. What are the Building Blocks of Polyimides?

Polyimides are based on two essential building blocks: diamines and dianhydrides. Diamines are organic compounds containing two amino groups. Dianhydrides contain two double carboxylic acid anhydride groups. Diamines and dianhydrides tend to be aromatic, with a strong absorbance in the UV region that tails into the visible portion of the spectrum. It is this tail from the UV absorbance that gives aromatic polyimides their characteristic orange-brown color.

Research into the combination of these two building blocks to capture their respective advantages for colorless polyimides has been going on for years, and new combinations have been developed that finally achieve this goal.

3. What Does Colorless Mean?

For some, colorless can mean clear as glass, while for others, it can mean hazy, or all possibilities in between the two. There really are two distinguishing factors that explain colorlessness.

Color can be defined by the Yellowness Index (YI). On this scale, a drinking glass would have a YI of zero, a typical polycarbonate film would measure 0.5 and a typical polyimide film would weigh in at approximately 90. To get some perspective on where colorless polyimides are going, the new target is approximately 2!

The second factor is transparency, the physical property that characterizes how much light can pass through a material without the light being scattered. Transparency is defined by transmittance, or how much light can pass through a material at a certain wavelength; and haze, referring to the amount of light scatter within the material. For example, a piece of Scotch® tape is colorless but has haze, and a traditional piece of polyimide film is orange in color, but is transparent since it can be seen through. A drinking glass is both colorless and transparent.

4. Where Will Colorless Polyimides be Used?

Polyimides are already widely used in aerospace, automobile, electronics and other high-technology areas based on their excellent mix of properties.

Expectations are that colorless polyimides will rapidly take hold and that their use will encompass what we now consider to be futuristic applications. The trick is to come up with the right combination of building blocks, creating a recipe where the formulations are not only developed, but are balanced and optimized.

With the advent of colorless polyimides, indications are prevalent that there will be a major surge in applications. Three mainstream areas include:

Smartphones

Smartphones are ubiquitous, and most users would admit to cracking the glass of their display at some point. The glass used by all of the manufacturers is certainly durable, but has two downsides: it is prone to cracking and breakage and it weighs a substantial amount given the size of the device.

A smartphone that is lighter, with the glass display replaced with a piece of film, would be a major advantage. The display would be high quality, colorless, have the appropriate tactile feel and, when it is dropped, have zero chance of screen shatter. The technology could replace virtually any type of portable display.

Photovoltaic Cells

Photovoltaic cells use glass cover plates to protect the fragile circuitry within. While an ideal solution for the application, the glass is extremely heavy and subject to breakage. Replacing the weighty, damage-prone photovoltaic shielding material with one that is light, durable and colorless is possible with the new polyimide technology.

Medical Applications

There are many potential applications in the medical field that would match the attributes of colorless polyimides. Tubing used for drug delivery, for example, requires high optical quality, thermal stability, light weight and stringent hygiene conformity.

5. They’re Available Now

Today, a special handful of companies are offering colorless polyimides commercially and expectations are that their number will grow rapidly. Manufacturers have successfully formulated products that feature very low YI and that are transparent and haze-free.

Colorless polyimides feature a combination of attributes that the marketplace has attempted to achieve, but could not until now: high quality, true colorlessness, temperature stability, good surface hardness, light weight, smooth texture and chemical and moisture resistance.

As with all technology, expectations are that initial costs will be high, so adoption will take place with high-end products first and then trickle down.

6. How Big is This?

There is substantial evidence that colorless polyimides are a disruptive technology. Just recently, the following products have been discussed, all of which are based on colorless polyimide technology.

• Huawei, the third largest phone maker globally, is expected to launch a foldable handset in late 2018.
• Apple is supposedly secretly working on a folding iPhone for launch in 2020; this rumor is unconfirmed by Apple but reported by industry analysts.
• Samsung is openly discussing plans to build a foldable smartphone to launch later this year.
• LG is also rumored to be in the folding phone market.
• A recent article claimed that a leading supplier of foldable display technology confirmed that five tech companies were testing foldable smartphones.

Why is this such a big deal? Displays enabled by colorless polyimides will roll up, fold up, be carried easily in a pocket or be integrated into clothing, are light and thin, and feature tactile response. The flexible film serves as a substrate for the necessary circuitry onboard.

While creating colorless polyimides may have been a possibility in the past, it would have taken an astronomical price tag to do so. Today, colorless polyimides are the only polymer solution that is commercialized and offer truly transformational possibilities in a wide range of applications.

Summary

As more companies jump on the bandwagon of colorless, polyimide-based, commercialized displays, there are still many considerations. As with most exciting innovations, development is quickly followed by establishing a secure supply chain, mastering the scale-up of production and ensuring sustainability.

As a dianhydride supplier, Jayhawk Fine Chemicals Corporation is in a unique position. It provides a wide range of dianhydrides, including ultrapure grades designed for sophisticated polyimide synthesis. Jayhawk is also committed to bringing its custom manufacturing experience to the table, providing a platform for developing new products that will continue to serve this exciting marketplace via partnerships and collaborative efforts with customers.

For more information on Jayhawk’s role in supplying polyimide building blocks, visit the Jayhawk website.

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