In optical films, anti-reflection coatings, and specialty fiber optics, the refractive index, adhesion, and cure performance of a resin directly determine product quality. T-6135 is a two-functional fluorinated acrylate UV resin. With its low refractive index (1.38–1.42), good adhesion to PET/TAC, and fast LED curing capability, it has become a common base resin in low-refractive-index functional films and optical anti-reflection coatings.
1. Key Technical Specifications
The following data are based on manufacturer technical datasheets. Actual values may vary slightly depending on formulation and process conditions.
| Property | Typical Value |
|---|---|
| Refractive index | 1.38 – 1.42 |
| Curing shrinkage | < 3% |
| Elongation at break | 55% |
| Glass transition temperature (Tg) | 35°C |
| Viscosity (25°C) | ~15,000 mPa·s |
| Recommended curing | 365nm LED, <10–30 seconds |
| Heat resistance | Up to 200°C |
2. Key Features
2.1 Low Refractive Index (1.38–1.42)
The fluorinated molecular structure of T-6135 gives it a refractive index significantly lower than conventional acrylate resins (typically >1.5). This property makes it well suited for anti-reflection (AR) coatings, optical anti-reflection films, and low-index matching layers where light path control is required.
2.2 Ultra-low Curing Shrinkage (<3%)
Low curing shrinkage means the coating volume changes only minimally during UV curing. This helps maintain dimensional stability on thin film substrates such as PET and TAC, reducing the risk of cracking or delamination. For multi-layer optical film structures, this feature is particularly important.
2.3 Good Flexibility (Elongation at break 55%)
Cured T-6135 films are relatively soft (Tg ~35°C) with an elongation at break of 55%. This allows the coating to accommodate bending, rolling, and other mechanical deformations of the film substrate, making it suitable for flexible optical devices or applications requiring certain bending resistance.
2.4 Good Adhesion to PET/TAC and Other Substrates
Thanks to its two-functional acrylate groups, T-6135 forms strong chemical bonding with PET, TAC and similar surfaces during UV curing. Reliable adhesion can be achieved without a separate primer. This is a key reason why it is widely used in LCD protective films and polarizer coatings.
2.5 Fast LED Curing and Heat Resistance
T-6135 responds well to 365nm LED light sources, with curing time typically under 30 seconds, and in some formulations as short as 10 seconds. In addition, its heat resistance reaches up to 200°C, meeting the requirements of short-term high-temperature processes (e.g., sputtering, baking) in downstream manufacturing.
3. Typical Applications
Optical functional film coatings: Low-index coatings on PET or TAC substrates, such as LCD screen protective films and polarizer anti-glare layers.
Anti-reflection (AR) and anti-reflection films: Used as the low-index layer in multi-layer AR stacks.
Specialty optical fiber coatings: Suitable for fiber coatings in military, medical, and other applications requiring specific refractive index and environmental resistance.
UV inks and adhesives: Can be used as a base resin in UV-curable inks or optical adhesives where low refractive index is required.
4. Formulation and Handling Recommendations
4.1 Solvent compatibility
T-6135 is compatible with esters (e.g., ethyl acetate, butyl acetate), ketones (e.g., MEK, cyclohexanone), and aromatic hydrocarbons (e.g., toluene, xylene). Avoid using alcohols alone, as this may cause compatibility issues.
4.2 Formulation design
With a viscosity of approximately 15,000 mPa·s, the resin has good flow and coating adaptability. To maintain low shrinkage and low gloss, the amount of reactive diluent monomers should be minimized to avoid unnecessary increases in refractive index and shrinkage.
4.3 Curing process
A 365nm LED light source is recommended. The actual energy density required depends on film thickness and formulation. Stepwise testing is advised to determine the optimal curing parameters.
5. Comparison with Conventional UV Resins
| Property | T-6135 (fluorinated) | Conventional acrylate UV resins |
|---|---|---|
| Refractive index | 1.38–1.42 (low) | 1.48–1.52 (moderate to high) |
| Surface energy | Low (due to fluorine) | Normal |
| Curing shrinkage | <3% (very low) | 5–10% (moderate to high) |
| Adhesion to PET/TAC | Good (no primer needed) | Often requires primer or corona |
| Flexibility | Good (elongation 55%) | Varies, often brittle or rigid |
6. Limitations
T-6135 has a Tg of 35°C, so the cured film is flexible at room temperature. If the application requires higher hardness or scratch resistance at elevated temperatures (e.g., >80°C), blending with other high-Tg resins or crosslinkers may be necessary. Also, fluorinated resins are generally more expensive than conventional acrylates, so cost–performance balance should be considered.
Conclusion
T-6135 is a specialty UV resin designed for low-refractive-index optical coating applications. It offers a balanced combination of low refractive index, low curing shrinkage, good flexibility, strong adhesion to PET/TAC, and fast LED curing. For formulation engineers working on anti-reflection films, low-index functional films, or specialty fiber coatings, T-6135 provides a proven base resin option. Pilot testing is recommended to verify compatibility with specific substrates, additives, and curing conditions before full-scale production.