Without using dam‑forming adhesive, how can this optical adhesive be adapted for high‑volume production via slot‑die coating?

I. Slot Coating Process: The Mainstream Process Upgrade Direction for High-End Display Full-Lamination Technology

In the full‑lamination process, dispensing, potting, and slot‑die coating are the three most widely used dispensing techniques in the industry. As automotive displays and large‑format commercial displays place ever‑stricter demands on lamination precision, yield, and mass‑production efficiency, the limitations of conventional dispensing and potting processes have become increasingly apparent. Thanks to its core advantages of high precision, low material loss, and excellent process uniformity, slit coating has gradually become the preferred process for the full‑lamination stage in OCR, fully meeting the production requirements of mid‑ to high‑end display products.

The core operating principle of slot-die coating is both simple and highly precise: the entire process relies on a specialized coating blade to apply the adhesive, with the blade assembly comprising an upper die, a lower die, and a thin, precision‑engineered shim positioned between them. During production, the optical adhesive is uniformly extruded through the precisely controlled gap between the upper and lower dies, forming stable adhesive beads at the bonding interface. These beads are then smoothly transferred onto the substrate surface, creating a flat, uniform, and continuous wet film that ensures the stability of the adhesive layer right from the outset.

Compared with other sizing methods, Slot coating The advantages in mass production are primarily reflected in:

• High precision in adhesive film thickness: Coating thickness can be precisely controlled in both directions via shim specifications and an automated feeding system, ensuring exceptional uniformity across the entire adhesive layer. Thickness variation is maintained within ±8%, effectively eliminating uneven coating and significantly enhancing optical consistency of the display image.

• Excellent batch-to-batch consistency It effectively addresses the issue of inconsistent adhesive layer thickness caused by misalignment and path deviations in conventional dispensing, resulting in an extremely low coefficient of variation for adhesive layer thickness within the same batch and enhanced quality stability for mass-produced products.

• No glue overflow, cost reduction and efficiency improvement : Featuring a closed‑die coating design, it precisely defines the adhesive layer’s boundaries, eliminating edge‑bleed at the process stage, significantly reducing subsequent manual cleaning steps, minimizing optical adhesive consumable waste, and lowering production costs.

• Suitable for large‑size, high‑throughput production. : Achieves one‑step coating and one‑time molding, eliminating the need for repeated adhesive application, perfectly matched Large-size displays, in-vehicle screens Its mass-production pace and capacity efficiency significantly outperform conventional manufacturing processes.

Currently, the slot-die coating process has been widely adopted in high-end applications such as automotive displays, large‑size commercial displays, and industrial‑control displays. According to industry‑validated test data, the slot‑die process outperforms traditional dispensing and potting techniques across key mass‑production metrics—including adhesive layer thickness uniformity, glue‑overflow control, material waste, and yield stability—making it a central trend in the upgrade of full‑lamination display manufacturing.

II. Product Introduction: Betely BTY-5218

In response to the process characteristics and quality requirements of high-end, large-scale production in slit coating applications, Betely New Materials has deeply cultivated the optical adhesive field and independently developed and launched BTY-5218 Single-Component Silicone UV Delay-Curing Optical Adhesive It is primarily used for interlayer bonding in touch‑screen glass and display modules. The product employs a dual‑curing mechanism—UV photocatalytic activation combined with thermal curing—offering exceptional compatibility and flexible integration with both slot‑die coating and conventional dispensing processes, thereby meeting the demands of large‑scale production across diverse applications.

Core Basic Parameters

• Appearance: Colorless and transparent

• Refractive index: 1.404

• Mixed viscosity: 8000 mPa·s

• Density: 0.97 g/cm³

• Component: Single-component

• Gel energy: 4000 mJ

Leveraging mature formulation development and process‑tuning capabilities, BTY‑5218 delivers outstanding performance across optical properties, reliability, process compatibility, and practicality, seamlessly meeting the mass‑production standards for high‑end fully laminated displays.

1. Optical Performance and Bonding Strength

After curing, the product exhibits a light transmittance exceeding 99% and a haze of less than 0.2%, ensuring exceptionally high optical clarity without compromising display transparency or color reproduction. It also demonstrates excellent adhesion to both glass and plastics, with an adhesive strength of 0.38 MPa and a shear strength of 0.19 MPa.

2. Vehicle Reliability

The product formulation has been specially optimized to ensure no corrosion or precipitation on ITO circuits. It has successfully passed multiple automotive‑grade high‑ and low‑temperature as well as damp‑heat reliability tests, fully meeting the stringent performance requirements of in‑vehicle display applications and providing stable compatibility with key in‑vehicle systems such as central control units and touchscreens.

3. Yellowing resistance

It exhibits excellent high-temperature resistance and yellowing resistance; after a 150-hour aging test at 95°C, the yellowing index remains below 0.1. With long-term use, it is unlikely to yellow or become hazy, ensuring lifelong optical stability for display devices.

4. Resistance to poisoning

Addressing the widespread issue of contact‑surface poisoning in OC adhesives, BTY‑5218 has undergone targeted formulation iterations and optimizations, delivering robust resistance to such degradation. Under rigorous test conditions—365 nm LED illumination at 2000 mW/cm², exposure to 6000 mJ/cm², followed by baking in a 60°C oven—and when paired with pre‑cured substrates made from multiple OC adhesive formulations, no signs of poisoning‑induced failure were observed. The interface bonding remains stable, material compatibility is broadened, and production‑line defect rates are effectively reduced.

5. Mechanical Properties and Repair Convenience

The product boasts an elongation at break of up to 620%, and its highly resilient molecular structure effectively dissipates and accommodates various stresses during application, preventing common defects such as bubble formation, adhesive layer cracking, and delamination caused by stress concentration. Moreover, its outstanding mechanical properties reliably withstand process‑induced and environmental stresses arising from high‑pressure degassing and elevated temperatures, ensuring enhanced production‑line stability. In addition, the product is easy and efficient to clean off during rework, minimizing the risk of screen damage during repair.

III. Summary

As the fully laminated display industry evolves toward higher precision, greater efficiency, lower losses, and enhanced reliability, the advantages of slit‑coating technology are becoming increasingly evident. Its core attributes—±8% uniformity in adhesive layer thickness, zero adhesive overflow, and minimal consumable waste—are unmatched by conventional dispensing and potting processes.

Betely BTY‑5218 optical adhesive precisely meets the demands of advanced industry process upgrades, delivering exceptional optical performance, automotive‑grade reliability, resistance to yellowing and contamination, and seamless compatibility with high‑end slot‑die coating for large‑volume production. Combining superior quality with enhanced efficiency, it provides a highly stable, high‑yield, cost‑effective full‑lamination bonding solution for premium applications such as large‑size displays and in‑vehicle touch‑display systems.