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Evolving Foldable OLED Smartphone Displays

9/25/2019

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Samsung Electronics re-launched its Galaxy Fold smartphone at IFA 2019 in September. Other brands have also joined in to introduce many different design concepts of foldable smartphones with OLED display in different sizes and formats.

Foldable smartphones and 5G-technology received strong attention at IFA as high transmission speed and low latency are expected to drive innovative products and boost demand in a slow smartphone market. There are still many issues that need to be resolved before consumer acceptance – extremely high prices, no standardization in design, robustness and durability. Innovations in the display materials and processes will continue to bring better products and reduce costs.

Many designs, sizes and prices

Royole’s FlexPai has the distinction of being the first foldable smartphone to be introduced at the end of 2018 at around $1,300 price. Samsung introduced the Galaxy Fold in early 2019, but delayed shipments due to some hinge and film issues; then the firm reintroduced it again with a new version at IFA this month. Samsung’s Galaxy fold is a 5G foldable (AMOLED) product with a front cover 4.6” display and 7.3”main display and expected to be priced around $2000 (I was told €2,100 at IFA - Editor).

The Huawei Mate X is a 5G foldable OLED smartphone that has an 8” main display that can fold to 6.6” on the front side and 6.38” display on the back with an expected price of $2600. Other smartphone suppliers such as TCL, Oppo, Vivo, Xiaomi, and Lenovo are expected to introduce their products in the future. Apple has not announced any plan for foldable iPhones, but is expected to make an introduction in 2020. With very high prices, a lack of standardization, and concerns about durability, foldable smartphone products will have very limited shipments in 2019.

​Higher requirements for displays

Commercialization of foldable smartphones up to now has been based on foldable AMOLED (active matrix organic light emitting diode) display technology. For a foldable display, all the layers within the panel should be foldable, durable, and transparent with a total bending radius of less than 1.5 mm. That is why new components are needed for foldable OLEDs. Foldable requirements are as follows:
  • Cover windows need to have hybrid organic/inorganic coating on transparent polyimide (PI)
  • Polarizer needs to be thin and bendable
  • Flexible touchscreen needs non ITO materials such as silver nanowire or metal mesh
  • Need for Flexible Adhesive OCA/OCR
  • Reliability (to withstand more than 200K times bending/folding).
Bendability has a trade off with durability and robustness. Bending of a very thin film after a certain point can generate a crease or lead to deformation. The display industry has developed numerous materials and processing challenges to balance bendability with durability. However significant challenges still remain.

Complexity in In-fold and Out-fold Design

New designs for foldable smartphones still have many issues with foldable hinges, flexible covers, increased thickness and bulkier designs. Samsung’s Galaxy Fold is in-fold design while Royole’s FlexPai and Huawei’s Mate X are out-fold. Xiaomi’s future product is expected to be be based on a double-fold concept. Lenovo’s future product is expected to fold vertically in the middle. Samsung is apparently working on out-folding and vertically mid-folding designs to introduce in the near future.

The in-fold design has the advantage of better protection of the inner display, but there are disadvantages from having two displays, including a need for higher battery capacity, higher thickness and may be even higher costs.

Out-fold designs have the advantage of single display for both a phone cover and tablet display, but the disadvantage of the display screen being exposed to the outside, so it is easy to scratch or damage. Therefore a foldable cover window has to be integrated with a scratch or abrasion resistant function.

Balance of bendability with durability for cover window

The biggest challenge for a foldable smartphone is replacing the glass cover with plastic film. Glass is strong, durable and hard to scratch. The cover plastic film needs to be mechanically durable to withstand more than 200K times folding/bending as well as be scratch resistant. In an out-folding design, the cover film must provide protection as well as endure the highest level of tensile strain during the out-folding condition. It needs more than a 9H pencil hardness for the flexible cover film. Samsung is using transparent polyimide (PI) for the cover film instead of glass for the Galaxy Fold.

Corning is currently working on developing an ultrathin and durable glass solution for foldable displays that can bend at a tight radius - hundreds of thousands of times without significant damage at the fold. The product is still in development and company is working with customers to optimize the product for design requirements. Ultra thin glass that can get to a very thin tight radius also has to be able to survive drop and resist damage.

Asahi Glass (AGC) is also working on flexible glass for folding smartphones. Suppliers are expecting ultra thin glass for foldable products in one to two years. If a glass solution can balance bendability with robustness for foldable display, it could resolve many durability challenges.

​Different requirements for Foldable Touch Screen

Smartphone touch screens generally use glass cover lens and touch sensors made from Indium Tin Oxide (ITO). Touch sensitivity depends on proximity of the sensor to the finger and materials in the display module.

According to inputs from the Fieldscale company, glass has a significantly higher relative permittivity (ε=5-8) than plastic and adhesives (ε=3-4)). That means that a touch sensor can tolerate relatively thick glass cover up to and exceeding 4mm, but plastic covers above 2mm can experience inferior touch performance. ITO for flexible displays can create some issues - processing beyond 200 degrees temperature, ITO can display poor electrical conductivity and transmittance.

To reduce problems from this issue, touch suppliers have turned into ITO alternatives such as Metal Mesh and Silver Nanowires (AgNw). Metal Mesh has a typical bend radius of 4mm, but it can face challenges such as production imperfections (in printed metal mesh) and poor optical performance. Silver Nanowires are solution-coated on films and left to dry. After the drying process is complete, a random pattern of silver electrodes emerges. High performance silver nanowire-based devices need to optimize this pattern and that can create challenges. Silver Nanowires can provide high flexibility. Fieldscale has simulation software that can create a virtual prototype of the whole design to provide answers relating to touch sensor questions.

Foldable OLED display supply In general, foldable AMOLED display yield rates are significantly lower than general flexible OLED smartphone displays due to complex requirements. Samsung Display, BOE, Royole and LG Display are all working towards developing dedicated capacity for foldable displays in the future. As the foldable market gains momentum, other flexible OLED suppliers such as Visionox, China Star, Tianma may also join in with dedicated foldable display capacity in 2020. AUO is also expected to focus on foldable display in future. Supply will increase in the next two to three years. Improvements in yield rates and material costs can reduce costs and increase production volume in the future. High costs and complex manufacturing issues will limit unit shipments for foldable OLED displays in the near future.

The potential future of next generation foldable displays is promising, but there are many challenges including extremely high price, higher costs, design issues, durability issues, design acceptance by consumers and consumer’s willingness to pay higher prices for new designs. Innovations in materials and processes will help foldable smartphones evolve in the next few years in design, production, and shipments. - (SD)

Sweta Dash is the founding president of Dash-Insights, a market research and consulting company specializing in the display industry. For more information, contact sweta@dash-insights.com or visit www.dash-insight.com
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Opportunities for Flexible OLED Smartphone Displays

9/3/2019

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Flexible OLED display is considered to be the best solution for next generation smartphone market. New smartphone products with flexible OLED displays generally get rave reviews for their superior display performance. This display technology is gaining shares even in a slow demand market. New capacity is coming, production is increasing, and new products are being launched bringing in new opportunities for flexible OLED displays.

Higher costs, lower yield rates, high prices, and lack of product differentiation, seasonal demand patterns and uncertain economic outlook are creating challenges for stronger growth in demand. More focus on cost reductions, new features, increased product differentiations, new form factors and need for 5G-based models can bring more opportunities for flexible OLED in 2020.

Flexible OLED - Best solutions for next gen smartphones

Flexible OLED display provides the best solution for superior image quality with very high contrast ratio, wider color gamut; faster refresh rates and wide viewing angles. It also enables thin, light, curved, flexible, foldable form factors and design differentiation. In a mature slow demand growth market, smartphone brands are looking for differentiation to drive replacement demand. Samsung’s Galaxy smartphones and Apple’s iPhones flagship products have popularized flexible OLED displays. This technology is poised to dominate the next generation smartphone market with thinner, lighter, bezel less, immersive screens and differentiating form factors. But high costs will limit adoption rates in the near term, especially when most of the growth is coming from lower priced mass-market products.


Rigid OLED and LTPS LCD - Solutions for mass-market products

Samsung, LGE and top Chinese brands are focusing on mass-market products with enhanced features and lower prices (<$500) to capture Asia Pacific and emerging market demand. Samsung Electronics reported in its Q2 2019 result that even when overall market demand for smartphones declined due to the negative macroeconomic environment and seasonal weakness, Samsung’s shipments increased QoQ led by strong sales of new Galaxy A series (mass market models). However, sales of flagship models fell QoQ on weak sales momentum for the Galaxy S10 (flagship product) and stagnant demand for premium products. In the second half of 2019, market demand is expected to stay weak due to growing uncertainties of global economy and trade. Samsung plans to continue to strengthen its flagship lineups and increase sales of new mass-market models. Flagship products are usually served by flexible OLED while rigid OLED or even LTPS LCD enables lower priced mass-market products for most brands.

Flexible OLED- Facing challenges and opportunities

IDC reported on July 31st that worldwide smartphone shipments declined 2.3% YoY in the second quarter of 2019, but it was also the strongest quarterly performance since 2Q18. According to IDC, performance in Q2 indicates demand is starting to pick up as the market begins to stabilize again. A key driver in the second quarter was the availability of vastly improved mid-tier devices that offer premium designs and features while significantly undercutting ultra-high-end price.

Samsung, Huawei, and Apple all lost share while Xiaomi, OPPO, Vivo gained. Samsung, and Apple are top customers for flexible OLED displays. The adoption rate of flexible OLEDs by other Chinese brands depend on competitive panel prices. But most of the brands will focus more on lower priced mass -market products that can be enabled by rigid OLED display or even LTPS LCDs. Slower demand for high end products and higher demand for mid range mass-market consumer product will create challenges for the flexible OLED display in 2019.

IDC's forecast in May, 2019 showed that the smartphone market is facing another challenging year in 2019 with return to growth on the horizon. IDC expects slow recovery starting from 2020. The company expects smartphone shipments growth in the second half of 2019 driven by 5G acceleration, a growing selection of lower-priced premium handsets, and on-going uplifts from markets like India. It also reported that pricing remains a critical decision factor when purchasing a new handset and this is creating new opportunities for mid-range price points. The focus on mid-range price points will be a challenge but 5G acceleration and new high end product introductions will create new opportunities for flexible OLED.

Flexible OLED - Higher costs, complex manufacturing and lower yield

Flexible OLED displays currently face complex manufacturing challenges and yield management issues resulting in higher production costs. Mass production of thin film encapsulation (TFE) technology from companies such as Kateeva has enabled the elimination of rigid glass to create flexible displays. According to Kateeva’s presentation at DisplayWeek 2019, next generation TFE printing allows for narrower bezels to maximize screen-to-body ratio and supports complex fine pattern printing. The OLED industry is still searching for higher efficiency and longer lifetime materials. R and D in OLED materials and equipment are progressing.

Universal Display Corp (UDC) has been commercially producing phosphorescent OLED materials successfully for many years. PHOLED materials have enabled good power efficiency; increased lifetime and performance improvements in OLED. The industry is still facing challenges due to inefficient blue emitters. OLEDs use red, green and blue emitters. There is a race to provide the most efficient dark blue with long lifetime, which can reduce power consumption and increase lifetime. While the industry is working on better blue phosphorescence, Kyulux is working on a Hyperfluorescence solution while Cynora is working on TADF for emitter technology. Future growth is expected to come from flexible by providing thinner, lighter, unbreakable, flexible lower power and high performance products.

Higher costs, lower yield and long manufacturing times has created a surplus in the market but prices are not coming down aggressively due to custom manufacturing requirements, a low number of suppliers, and higher manufacturing costs. This results in flexible OLED meeting mostly high-end product requirements, but not mass-market consumer needs. Samsung Display dominates the flexible market but LGD and BOE are increasing production and supply. More capacity will also come from companies such as Tianma, Visionox, China Star and others in 2020. This can help to reduce costs and improve adoption rates in 2020.

Flexible OLED - Integration, innovation, and differentiation can help adoptionIn a slower smartphone market flexible OLED growth was delayed due to high pricea. Market demand for flexible OLED display-based products from Samsung and Apple are slowing down. This has resulted in lower utilization rates for flexible display and surplus. More shift into foldable display will reduce surplus plus increase demand even though there are still many challenges for foldable smartphone market. Major brands including Samsung and Apple are planning new product launches, which will increase demand.
The introduction of 5G-based products needing slimmer displays to accommodate 5G enabling components will increase flexible OLED demand. Integration of new technology such as fingerprints under display, in cell touch display, hole on display, camera under panel, sound on display, haptics on display, chip on film (COF)/chip on plastic (COP) to reduce border & increase screen to body ratio and foldable display can open up new opportunities for flexible OLED driving growth in demand and increasing adoption rates.
Flexible OLED display will be the best solution for next generation smartphone market with superior image quality, design differentiation, and integration of new features. Manufacturing complexity, lower yield, higher production costs may limit its adoption in the near future especially in slow market in 2019, but 2020 can bring lower cost, higher productions and increased opportunities for flexible OLED display. (SD)
Sweta Dash, President, Dash-Insights
Sweta Dash is the founding president of Dash-Insights, a market research and consulting company specializing in the display industry. For more information, contact sweta@dash-insights.com or visit www.dash-insight.com

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    Sweta Dash, Founder/President, Dash-Insights

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