Polarizers, as key "optical switches" for liquid crystal displays (LCDs) and even some OLEDs, directly determine the brightness, contrast, color, and lifespan of the screen based on their performance. This seemingly simple "sandwich" structure (TAC protective layer/PVA polarizing layer/TAC protective layer/functional adhesive/PET release film) actually embodies cutting-edge technologies such as polymer physics, precision coating, optical design, and chemical treatment.
Currently, with the acceleration of domestic substitution and the adjustment of the Japanese supply chain, a deep analysis of the technological differences between China and Japan in the core manufacturing processes of polarizing films - PVA stretch dyeing and TAC film forming - not only concerns the technology itself, but also affects the strategic landscape of the global display materials industry.
The typical structure of polarizing film is a "sandwich" style: two layers of TAC film (protective layer) sandwiching a stretched and dyed PVA film (polarizing core layer), supplemented by functional adhesive and PET release film. It is the manufacturing level of PVA and TAC that determines the polarization efficiency, uniformity, durability, and yield of the final product. The Sino Japanese system presents a sharp contrast here:
PVA stretch dyeing: precision coupling vs flexible decoupling
Japanese philosophy (wet stretching+synchronous dyeing integrated): Stretching, dyeing, and cross-linking are completed in one step in a liquid environment (such as alkaline solution). The advantages lie in the highly uniform and stable molecular chain orientation, ultra-high stretching ratio (5.5-6.5 times), top-notch polarization efficiency, and excellent color cast control, especially suitable for high-end displays such as OLED and VR. Representative manufacturers such as Sumitomo Chemical, Mitsubishi Chemical, etc. But its equipment system is extremely complex (precise tension control, integrated dry wet conversion), with strict dye selection, low process fault tolerance, and high risk.
Chinese path (dry stretching+segmented dyeing): PVA film is dry stretched using a hot air furnace, and dyeing is completed in an independent process (spraying/immersion). The advantages are modular process, low investment threshold, easy to rapidly expand production (especially for large-sized TVs), and strong adaptability to domestic equipment. Represented by Sanlipu, Shengbo Optoelectronics, etc. But the disadvantage is that the polarization efficiency is relatively low, there is axial drift caused by thermal expansion and contraction, color shift control is weaker than wet methods, and it is difficult to meet the strict requirements of OLED/vehicle, with a narrow processing window.
TAC membrane preparation: vertical integration vs import dependence
Japanese Barrier (Raw Material Equipment Formula Collaboration): Mastering the synthesis technology of high-purity cellulose acetate raw material, independently developing precision co extrusion equipment (such as three-layer co extrusion), and synchronously integrating composite functional layers such as UV resistance and scratch resistance. The fluctuation of film thickness can be controlled within ± 1 μ m, and the optical axis consistency is>99.9%. Emphasizing the "vertical integration" control from raw materials to bonding, laying the foundation for cutting-edge applications such as MicroLED and transparent displays.
China bottleneck (dependence on imports and integration challenges): TAC film mainly relies on imports (Eastman, Fujifilm, Mitsubishi). Although some companies have attempted to introduce co extrusion equipment (domestic/Taiwanese), they are not yet mature in terms of core raw material purity, formula dispersion control, temperature consistency management, etc. Functional coatings (anti blue light, anti-static) are mostly purchased externally, and the system integration is not high.
The gap in polarizing film technology between China and Japan appears to be in terms of equipment and formula, but deep down it is a significant difference in manufacturing thinking
Japan follows the system engineering logic of "high coupling, high precision". Pursuing a high degree of integration and collaboration in craftsmanship, with ultimate consistency and stability as the goal, to build an overall barrier that is difficult to replicate.
China has developed a highly decoupled and flexible iterative manufacturing architecture. By decomposing and modularizing the process steps, reducing the threshold of individual links, pursuing fast response and cost efficiency, significant results have been achieved in specific markets such as medium and large-sized TVs.
Analysis of the Breakthrough Path for Domestic Manufacturers
To cross the deep-water zone of "domestic substitution" and challenge the Japanese high-end monopoly, China's polarizer industry needs a systematic upgrade:
Breaking the bottleneck of PVA wet stretching: "Alliance style" research and development
Establish a "Wet PVA Technology Alliance" led by leading enterprises, in collaboration with equipment suppliers, material suppliers, and universities, to establish a small-scale validation production line.
Initially focusing on the high-precision market for small and medium-sized devices (such as smartphones and wearable devices), to verify the feasibility of the technology.
Innovative investment model, adopting a "risk sharing mechanism" to share high upfront investment and process risks.
Localization of TAC film: Building the capability of "material system engineering"
We cannot just focus on introducing extrusion equipment. We must start with the localization of high-purity cellulose acetate raw materials.
Establish an integrated process research and development platform covering "functional layer design - precision co extrusion (such as three-layer) - film thickness control - post-processing system".
Work closely with downstream application providers (such as automotive and industrial display manufacturers) to jointly define and develop functional TAC films that meet specific requirements (anti fog, high weather resistance, anti blue light, etc.).
Opening up a 'new battlefield': marching into the non-traditional display blue ocean
Actively layout emerging fields such as medical displays, vehicle mounted curved HUDs, transparent advertising screens, AR/MR devices, etc. These applications have unique requirements for the flexibility, curved surface adhesion, special optical properties (such as high transparency and low reflection), and accuracy of polarizers, and have not yet been completely monopolized by the Japanese. Utilize the rapid response and customization capabilities of China's industrial chain to seize the opportunity in segmented markets.
Summary
The competition in the polarizing film industry between China and Japan is essentially a collision of two manufacturing philosophies. Japan builds a moat with precision collaboration, while China wins scale with flexible decoupling. However, in order to achieve a qualitative change from "having" to "being excellent", Chinese manufacturers must move towards deeper levels of systematic technological collaboration (from molecular design to process control) and vertical integration of localization. Only in this way can we truly master the core technology and achieve a leap from a "follower" to a "runner" and even a "leader" in the field of high-end polarizing films, completing a magnificent transformation from "capable" to "ultimate".
