Display Glass: The Ultimate Contest Between Strength And Flexibility

Editor's Note: Though often overlooked, the humble glass becomes an indispensable component when integrated into electronic devices. Within the specialized field of electronic glass, two types stand out as particularly critical: substrate glass, which forms the foundation beneath the screen, and cover glass, which shields the display from the outside world. From HD to ultra-high definition, from flat to curved surfaces, and from traditional bar phones to multi-foldable devices, glass has been a silent yet essential partner behind every leap in display technology. These two thin sheets of glass have quite literally supported the rapid ascent of the display panel industry. Today, display glass is venturing beyond its traditional boundaries, extending its reach into the semiconductor sector through glass-core packaging technology.

 

Ultra-Thin Foldable Glass: The Delicate Dance Between Rigidity and Flexibility

 

Ever since Apple's iPhone revolutionized smartphones with touchscreen technology, cover glass has emerged as a key driver of product evolution. As consumers increasingly demand both aesthetic appeal and rock-solid durability, cover glass design and manufacturing have been on a fast track of continuous innovation: scratch resistance, drop protection, high transparency. Then came the rise of foldable phones, pushing the inherent strength and flexibility of glass to their absolute limits-and forcing manufacturers to reconcile these seemingly contradictory qualities.

 

In this industry-wide pursuit of materials that are both strong and flexible, domestically produced cover glass has gradually carved out its own competitive edge, steadily winning recognition in the global market.

 

The Four Generations of Cover Glass Evolution

 

Rewind to 2007. At the invitation of Steve Jobs, Corning developed a specialized protective glass exclusively for the first iPhone. This innovation did more than just enhance the durability and aesthetics of smartphone screens-it marked the beginning of a new era for protective glass worldwide. Over the following two decades, cover glass underwent four distinct phases of transformation.

 

During the Basic Protection Era (2007-2011) , phone covers had one simple job: provide basic physical shielding. Corning's first-generation Gorilla Glass became the defining product of this period.

 

As touchscreen technology matured, particularly with full-lamination techniques like In-cell, On-cell, and OGS becoming mainstream, the role of cover glass expanded beyond protection. It now needed to meet the demands of processes like graphic circuit fabrication, requiring higher light transmittance and specific dielectric properties. This ushered in the Advanced Protection Era (2012-2016) .

 

The bar kept rising. Cover glass now needed enhanced drop and scratch resistance while adapting to complex manufacturing processes like cold bending, hot bending, or laser cutting. This led to the Comprehensive Protection Era (2017-2021) . During this phase, glass-ceramics emerged, pushing cover glass hardness to unprecedented levels.

 

Drop resistance has always been a top priority for phone cover glass, and market expectations continue to climb. In the premium segment, glass-ceramics have become the go-to choice. Apple's iPhone 16 continues the trend that began with the iPhone 12, featuring glass-ceramics. Beyond Apple, brands like Huawei, Xiaomi, OPPO, and Meizu have forged deep partnerships with domestic manufacturers like Xinjing and Jiahe, incorporating glass-ceramics in select flagship models.

 

However, as competition intensifies, manufacturers are increasingly focused on optimizing the cost-performance equation. The relatively high cost of glass-ceramics currently limits its mass-market adoption.

 

Zhou Xiaodong, China General Manager of Corning Gorilla Glass, noted in an interview with China Electronics News that even in the mid-to-low-end phone market, consumer expectations for screen durability are rising. This pushes the glass industry to balance performance improvements with cost reduction strategies. Currently, secondary strengthened glass-particularly deeply strengthened variants-has emerged as the sweet spot for most phones. In response, Corning launched its deeply strengthened Gorilla Glass 7i in 2024, representing a strategic balance between performance and affordability.

 

Industry insiders note that while deeply strengthened glass doesn't quite match glass-ceramics in protective properties, it significantly outperforms standard secondary strengthened glass. With compressive stress layer depths reaching 140-150 micrometers and a substantially lower price point than glass-ceramics, it's an ideal fit for mid-to-high-end devices.

 

Then came the foldable revolution. Overnight, the marketing focus shifted from drop and scratch resistance to uncompromising flexibility. All performance metrics and manufacturing processes for cover glass pivoted toward flexibility, ushering in the New Flexible Era. Ultra-Thin Flexible Glass emerged as the new crown jewel of electronic glass.

 

Here's the fundamental challenge: in glass, hardness and flexibility exist in inherent tension-higher hardness typically means lower flexibility, and vice versa. For manufacturers, the ultimate engineering challenge lies in achieving the perfect balance between strength and flexibility.

 

After years of exploration, we've discovered several effective approaches to strike this balance, explained Yang Guohong, General Manager of Rainbow Group, in an interview with China Electronics News. To ensure ultra-thin glass delivers both drop and scratch resistance, manufacturers can apply ion exchange treatment to enhance surface rigidity. Alternatively, special surface treatments-such as laminating thin polymer layers-can enable greater bending angles while preventing breakage during folding.

Yang further revealed that some companies have developed an upgraded UTG variant called UFG, designed to deliver flexibility, scratch resistance, and durability simultaneously-enabling multiple folds without visible creases. The key difference between UFG and UTG lies in its non-uniform thickness. The bending area is thinner, improving bending toughness and minimizing creases, while the surrounding areas are slightly thicker to enhance overall screen durability, Yang explained.

 

The Rise of Domestic Cover Glass

 

In recent years, guided by the industry's pursuit of strength and flexibility, domestically produced cover glass has steadily built its competitive position and gained market acceptance.

 

Based on shipment area as of August 2024, China's Xuhong Optoelectronics has surpassed Japan's Asahi Glass-the world's second-largest manufacturer-and is challenging for 20% global market share. Rainbow Group now rivals Asahi Glass for the third position, while another domestic float glass company, CSG Holding, ranks fifth.

 

With the ascent of domestic manufacturers, Chinese cover glass continues expanding its advantages, demonstrating significant progress and development potential across multiple dimensions. These strengths extend beyond technological breakthroughs and quality improvements to include cost control, supply chain responsiveness, and market adaptability.

 

Currently, China's innovation capabilities in the cover glass industry are notably robust.

 

"From a technological perspective, China has achieved significant breakthroughs in high-end materials including high-alumina glass, glass-ceramics, and UTG/UFG," Academician Ouyang Zhongcan from the Chinese Academy of Sciences told China Electronics News. He cited examples like Sichuan Hongke's Panda King high-alumina glass, whose performance metrics for bending, scratch, and impact resistance have reached internationally advanced levels. The Vickers hardness of materials like Chongqing Xinjing Teboli's Kunlun Glass and Xiaomi's Dragon Crystal Glass has even surpassed the glass-ceramics used in Apple's iPhone 15 series. Companies like Rainbow Group and Triumph Group have achieved mass production capabilities for UTG at thicknesses of 100μm, 50μm, and even 30μm. Additionally, some domestic manufacturers can now supply deeply strengthened glass.

 

A representative from Triumph Group's glass subsidiary stated in an interview with China Electronics News that China's 30μm UTG technology has fully caught up with international advanced levels, and its next-generation UFG technology may be pulling ahead. Triumph continues upgrading its technology and has successfully developed UTG below 15μm, now moving toward industrial mass production.

Industry experts suggest that successful mass production of sub-15μm UTG could enable China's ultra-thin glass industry to transition from following and competing to leading globally.

 

Moreover, Chinese cover glass holds advantages in both production costs and market responsiveness.

 

Professor Tian Yingliang from the Faculty of Materials and Manufacturing at Beijing University of Technology, who also serves at the National Engineering Laboratory for Flat Panel Display Glass Technology and Equipment, explained the cost dynamics to China Electronics News: "Thanks to China's float process, single-line production capacity exceeds the overseas-dominated fusion process by several times, while investment costs remain significantly lower. Consequently, domestic phone glass costs approximately 50% less than foreign products, giving Chinese cover glass a strong price-performance advantage.

 

Rapid responsiveness to changing market demands represents another key strength. The Triumph representative noted that as smartphones undergo faster upgrade cycles, brands need greater flexibility in adjusting production and design strategies to meet diverse consumer needs. Domestic manufacturers, leveraging their comprehensive supply chains, can provide quicker and more efficient customized services, better supporting the demands of the end-user market.

 

"In the mid-to-low-end cover glass segments-including soda-lime glass, aluminosilicate glass, and standard secondary strengthened glass-China is largely on par with overseas competitors. In fact, our domestic products often lead in cost-performance ratio due to manufacturing cost advantages. This explains why overseas companies have gradually scaled back their production capacity in these segments over the past year or two. Yang Guohong stated. Looking ahead, as more phone brands choose domestic cover glass, the market share of Chinese glass enterprises is poised for continued growth.