High-Performance OCA Optical Adhesive: Key to Foldable Screens

In 2024, China’s foldable smartphone market continues to explode. According to market research data, the sales of foldable smartphones in China reached 2.62 million units in the second quarter, a year-on-year increase of 125% and a quarter-on-quarter increase of 11%, achieving three-digit year-on-year growth for four consecutive quarters.

In daily use, foldable smartphones need to endure hundreds of folds a day. OCA adhesive films not only need to enhance the display effect of the screen but, more importantly, provide necessary mechanical support for the fragile functional layers of the screen, ensuring the structural stability of each functional film layer.

OCA stands for Optical Clear Adhesive, primarily used for bonding optical components, such as cover glass, lenses, 3C consumer electronics, and in-car displays.

The OCA industry chain includes the steps from “raw materials → coating & die-cutting → touch display modules → end devices”. OCA optical adhesives mainly consist of adhesive and film materials. Film materials include PET polyester films, PO polyester films, etc., while adhesive materials include acrylic pressure-sensitive adhesives, polyurethane pressure-sensitive adhesives, etc. Midstream manufacturers first coat the adhesive material onto the film material, followed by die-cutting and other processing procedures, ultimately providing the finished product to downstream touch display module manufacturers.

Foldable OCA is a specially designed adhesive material for foldable screens, characterized by flexibility and fold resistance, capable of maintaining stable adhesion during repeated folding and unfolding, protecting the display and ensuring that images remain continuous and stable when folded. It is applied between the cover layer, polarizer layer, touch film layer, and OLED layer of the foldable smartphone screen.

The basic functions of OCA include bonding and enhancing optical display effects. When light passes through different materials, if there is a large difference in refractive index between the materials, a significant amount of reflection occurs. Without OCA, the air layer between screen materials causes a lot of reflection due to the low refractive index of air, interfering with the display effect. However, when using OCA, the air layer is removed, and the refractive index of OCA is similar to that of each material layer, significantly reducing light reflection and loss, thus enhancing the display effect.

In addition to its optical performance and adhesion capabilities, OCA also focuses on enhancing the bending performance of the screen to achieve better bending capability and longer bending life. When the screen is in a bent state, the outer side bears significant tensile stress, while the inner side experiences substantial compressive stress, and shear stress also occurs between the layers. OCA effectively reduces these internal stresses.

Currently, the global OCA market is mainly dominated by overseas giants, with brands such as 3M, Mitsubishi, Tesa, and Nitto Denko occupying the primary market. These companies hold the core technologies and related patents for OCA optical adhesives.

In recent years, domestic manufacturers have been catching up to international levels by introducing technical teams and strengthening R&D. A few companies’ products have already entered the high-end market of OCA optical adhesives, including Xinlun New Materials, Vancet, and Sidik.

Key domestic companies involved in OCA include Jiangsu Sidik, Jinghua New Materials, Suzhou Vancet, Changzhou Xinlun, Nanjing Huixin, Guangzhou Huigu, Anhui Fuyin, Shenzhen Jiayun, Dongguan Zhengxian, Shenzhen Baoli, Suzhou Saiwu, Zhejiang Rijiu, Guangdong Crown, Jiangyin Tongli, Hengshan Jiacheng, Zhongshan Liwang, Dongguan Chuyin, Shenzhen Meixin, and Lushan New Materials.

Sidik

Jiangsu Sidik New Material Technology Co., Ltd. was established in 2006, and its main products include functional film materials, electronic-grade adhesive materials, thermal management composite materials, and film packaging materials. The company has established long-term stable partnerships with internationally renowned enterprises such as Foxconn, Tesla, Facebook, Lingyi, and Bourns, making it a leading supplier of functional coating composite materials in China.

Sidik’s functional film materials and electronic adhesive materials both include OCA products, and it has achieved technological breakthroughs in OCA optical adhesives, with products featuring high cleanliness, high light transmittance, and low haze. According to the incoPat database, Sidik has 73 patents related to OCA adhesives, of which 9 pertain to folding effectiveness, including: dual-curable high-adhesion foldable OCA adhesive, adhesive film and preparation method, impact-resistant flexible OCA adhesive, adhesive, its preparation method and application, flexible OCA optical adhesive, foldable mobile phone outer screen and its preparation method, OCA adhesive with high adhesion characteristics for UTG materials, adhesive film and its preparation method, high-adhesion bend-resistant OCA adhesive, adhesive, its preparation method and application, radiation-curable flexible OCA optical adhesive, foldable screen protective film and its preparation method, addition-type impact-resistant foldable protective film and its preparation method, and foldable screen low-modulus OCA adhesive and its preparation method.

On September 3rd, Sidik added the concept of “flexible screens (foldable screens)” and applied for a patent for a dual-curable high-adhesion foldable OCA adhesive in April, improving the creep performance of the adhesive. The adhesive sheet produced has high light transmittance, good adhesive performance, creep recovery performance, excellent moisture resistance, and weather resistance, making it widely applicable in the foldable smartphone field. Based on Sidik’s technological expansion, it can participate more in the layered design of foldable products, achieving an extension from producing OCA optical adhesive films to designing OCA modules.

Jinghua New Materials

Jinghua New Materials has achieved breakthroughs in polymerization technologies such as thermal bulk polymerization, UV bulk polymerization, and solution polymerization for OCA products, realizing technological breakthroughs in fields such as full lamination OCA, blind hole OCA, OLED 3D OCA, foldable OCA, and automotive OCA. Jinghua New Materials’ foldable OCA products have been utilized by leading domestic smartphone companies in their latest foldable phones, successfully achieving domestic substitution.

In terms of OCA production capacity, Jiangsu Jinghua has 3 OCA optical adhesive coating lines, with a designed capacity of 12 million square meters per year, while Anhui Jinghua has a designed annual production capacity of 26 million m² for OCA optical film adhesive tape.

Lushan New Materials

Lushan New Materials has stated that its OCA optical adhesive films include OCA for touch screens, full lamination OCA for LCDs, NCF products for polarizer bonding, and OCA for automotive and foldable screens, meeting the general performance requirements for consumer electronics. The optical adhesive film product TOCF and OCA materials have already achieved mass shipments. Among them, the foldable screen and flexible screen OCA optical adhesive films have undergone systematic verification at BOE and OPPO, receiving positive feedback and leading performance among domestic products; automotive OCA for client applications has been verified and meets testing requirements.

Vancet

Suzhou Vancet Material Technology Co., Ltd. was established in August 2016 and is a high-tech enterprise focused on the R&D, production, and sales of OCA optical adhesives and electronic adhesive tapes. The core product, OCA optical adhesive, is widely used in the displays of terminals such as mobile phones, laptops, tablets, and automotive displays to improve the reliability, transparency, and clarity of touch screens; various electronic adhesive tapes are primarily applied in wafer thinning processes and to eliminate 5G electromagnetic interference.

In 2016, Vancet acquired the optical adhesive division of Hitachi Chemical, mastering complete OCA technology and patents, continuously developing optical adhesive products for new applications, and has successfully entered international well-known terminals such as Amazon, Huawei, and OPPO, becoming a leading domestic OCA optical adhesive enterprise.

Xinlun New Materials

Xinlun New Materials has stated that its foldable optical adhesive OCA and foldable protective films have already achieved mass production. In addition to well-known domestic clients such as Xiaomi and OPPO, it has also established stable cooperation with Google in the foldable phone business.

Local optical adhesive companies are making significant breakthroughs in process technology, successfully entering downstream application markets and promoting the domestic substitution process.

OCA in mobile display applications has gone through flat OLED touch displays, curved flexible OLED touch displays, and foldable flexible OLED touch displays. In addition to upgrades in OCA process technology and performance, the demand for OCA in foldable screens is increasing, and the future increase in foldable screen penetration will drive overall demand growth.

In addition to foldable devices, in-car displays have also become a new growth point for OCA optical adhesives.With the trend of in-car displays moving towards larger and multi-screen setups, most new models on the market are equipped with dual or triple screens.In the future development trend of smart cockpits, the utilization rate of in-car displays will further increase.

As in-car displays upgrade, the performance requirements for OCA are also increasing. On one hand, in-car displays need to operate stably in high-temperature environments inside the car and maintain clear display effects under direct sunlight; thus, OCA optical adhesives need to possess high heat resistance and UV resistance. On the other hand, as in-car touch screens move towards lightweight, high-definition, and diversification, the performance of OCA optical adhesives also needs to be enhanced.

In terms of VR displays, during the period from 2022 to 2023, companies like Sony, Oculus, Pico, and Apple have launched their own head-mounted display devices. Particularly, the release of Apple’s first head-mounted device, Vision Pro, has pushed the popularity of head-mounted devices to a new high, which will also drive the development of the OCA optical adhesive market.