SCHOTT Challenges Corning’s Dominance of Cover Glass with Launch of “Nearly Unbreakable” Xensation α

Published October 18, 2021

In a direct challenge to Corning’s dominant position in smartphone cover glass, German glassmaker SCHOTT launched a new cover glass last week, Xensation Alpha (α), that they call “nearly unbreakable”. Xensation α is a chemically strengthened lithium alumino borosilicate (LABS) glass and the company believes it is the best of breed. According to SCHOTT’s, Xensation Alpha outperforms current aluminosilicate (AS) or lithium aluminosilicate (LAS) cover glass by up to 100% when it comes to drop performance and is less susceptible to scratches than commercially available AS and LAS glass substrates. SCHOTT also claimed that the new material offers significantly better drop performance from double the height compared to other LAS-based premium cover glasses. SCHOTT also claimed the new glass offers better scratch resistance than commercially available AS and LAS glass types and achieves the same performance whether its bent or flat.

Glass Composition

SCHOTT’s cover glass competitors include Asahi Glass, Corning and NEG. Market leader Corning has offered a series of advanced cover glasses after launch of their original Gorilla Glass in 2007. While years ago, Corning described Gorilla Glass as aluminosilicate, with more recent versions Corning has been less specific about glass composition. A query to Corning about Gorilla Glass composition was unanswered at the time of our deadline, but a SCHOTT representative replied that while not commenting on competitors’ products “when looking at the present high-performance cover glass market, we recognize LAS glass as the “quasi standard” in the high-end segment.” Unless we get contradictory information from Corning, we believe that Gorilla Glass Victus has an LAS composition, and is the right comparison for Xensation α.

The advantage of LAS over AS is that it enables a two-stage ion exchange process. Ion exchange is the mechanism to strengthen this type of glass, as smaller ions in the glass structure are displaced by larger ions, creating a layer of compressive stress. With AS, sodium ions are displaced by potassium ions, and with LAS this process goes further with lithium ions displaced.

Source: SCHOTT AG
Source: SCHOTT AG

Where does SCHOTT stand and how did they improve their material? By adding the “semimetal” boron. SCHOTT has a long history of experience with borosilicate glass for specialty applications and says that the addition of boron improves the scratch performance of the glass. SCHOTT refers to Xensation α as a lithium alumino-borosilicate or LABS glass.

Drop Test Performance

In SCHOTT’s launch video accompanying the announcement, the highlight was a demonstration of drop test performance. Corning has frequently cited consumer surveys saying that drop test is the most important performance item for a cover glass, and the successive advancements of Gorilla Glass since 2014 have all included enhanced drop performance. SCHOTT’s video included a drop test that appeared to be from about two meters, which matches the claim made by Corning for Gorilla Glass Victus. Corning claimed that Victus survived drops onto hard, rough surfaces from up to two meters while other materials fail when dropped from 0.8 meters. Similarly, SCHOTT claimed that Xensation α offered drop resistance from double the height compared to other LAS-based premium cover glasses.

Source: SCHOTT AG
Source: SCHOTT AG

Because it appears that both SCHOTT and Corning claim two meters for their best glass, I asked SCHOTT which version of Gorilla Glass they were comparing to. The response from SCHOTT:

“With our new Xensation® α cover glass, we do not fear any comparison with any product on the market. We do not comment on its competitors or their products. However, our new product Xensation® α (Alpha) made a large stride toward unbreakable glass. Xensation® α outperforms current market leading lithium aluminosilicate (LAS) cover glasses by up to 100% in drop performance, especially on rough grounds. This means, that it can survive drops up to twice the height and shows significantly improved scratch performance. This is of immense importance to the end-user, who wants a glass that can survive day-to-day activities and accidental drops and scratches. We are addressing a broad market and have seen big interest from several major brands in the industry.”

Our conclusion based on the claims from the two companies is that Victus and Xensation α have comparable drop performance, and that both glasses have drop performance substantially better than earlier iterations.

Scratch Test Performance

Improving drop performance and scratch performance are usually at odds with each other. Several years ago, Motorola released a phone with an unbreakable screen, the Moto X Force, which employed a plastic cover, but the phone failed because the screen was prone to scratches. A few years earlier, Corning dismissed the threat of sapphire as a replacement for cover glass because while sapphire is nearly impervious to scratches, it is brittle and shatters upon impact.

“The glass chemistries that people have been using to improve the compressive stress profiles aren’t necessarily the best for scratch performance,” said John Mauro, a professor of materials science and engineering at Penn State University who had previously spent 18 years at Corning, quoted in a WIRED article last year.

Schott says that the addition of boron leads to improved scratch performance for Xensation α and claims that the new glass is less sensitive to scratches than conventional LAS glasses shown in the Knoop indenter scratch test. The SCHOTT video included a picture of a scratch test result that seemed very similar to the claim on the product information sheet for Victus. Corning claims that while competitor AS glasses fail at a load of four Newtons, the scratch threshold for Victus is typically at 7-10 Newtons.

Knoop Test Performance of Xensation α (L) and Gorilla Glass Victus (R) Against Competitor Glasses

Sources: Schott AG, Corning
Sources: Schott AG, Corning

Similar to drop test, our conclusion based on the claims from the two companies is that Victus and Xensation α have comparable scratch performance, and that both glasses have drop performance substantially better than earlier iterations.

Chemical Strengthening

SCHOTT said that its new composition allows for an improved ion exchange capability compared to LAS glass. In response to a question about what is “improved”, a SCHOTT representative replied that “We optimize our glasses in a way that the glass structure enables a deep and strong ion exchange layer with compressive stress. Xensation® α offers an improved ion exchange capability, enabling a deeper, more effective ion exchange process during chemical strengthening.”

A deeper layer of compressive stress generally means a stronger glass, but this might also require a longer time in the ion exchange salt bath, which would increase costs. If the ion exchange was “more effective”, though, they may be able to get a deeper layer without additional time.

Specifications

The product information sheet for Xensation α allows for a comparison of some items with the corresponding sheet for Victus, and a similar sheet for AGC’s Dragontrail provided by Abrisa Technologies.

What About Ceramic Shield?

In its release, SCHOTT made abundant comparisons to other AS and LAS glasses, but the cover window material launched last year on the iPhone 12, Ceramic Shield, is technically not a glass but a glass ceramic. Corning described it as a “new-to-the world material”. In response to a query about glass ceramics, the SCHOTT representative replied:

“We decided to focus on highly specialized glass, which is highly adapted to ion exchange process for maximum strength. We are convinced that properties of our Xensation® α match performance of glass-ceramics or is even better.

A key property for cover glass materials is its ability to enable effective chemical strengthening. However, excellent strengthening is not the only factor determining breakage resistance. Other factors such as brittleness, elasticity and cohesiveness also contribute to reduce breakage. A strong glass network is critical for both.”

We have reported that Ceramic Shield appeared to survive a drop test of three meters performed by CNET, but that while the cover glass was intact, the panel experienced damaged pixels and the camera stopped working. Corning has said that Ceramic Shield is exclusive to Apple because Apple helped pay for the development of the new cover.

Applications

SCHOTT’s previous Xensation Up glass was used in the Vivo X60 Pro and X70 Pro as well as the Oppo Watch and Honor Play 5. Xensation α glass is expected to be used on both the front and back of smartphones as well as smartwatches and tablets. It will appear in an upcoming Vivo flagship smartphone. SCHOTT said that “Xensation® α is designed for electronic devices that have a risk to drop on the ground. There is no relevant size or format limit that would apply for such applications.”

Conclusion

It appears that without question, SCHOTT has achieved a breakthrough in performance for its cover glass. While it is less clear whether Xensation α is better than Gorilla Glass Victus, the new glass seems to have many similar performance aspects. For several years, Corning has enjoyed a clear advantage over its competitors for drop test performance. Corning has translated that advantage into both a dominant position among premium smartphones and a price premium over competitive glasses. With the introduction of Xensation α, that era may be at an end.

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Written by

Bob O'Brien

bob.obrien@displaysupplychain.com