In optical coatings and precision electronic packaging, the value of a low refractive index resin is not limited to reducing interfacial reflection. As applications extend from flat optical films to fiber claddings, AR waveguides, and miniaturized electronic devices, materials must also address dielectric performance, surface tension, environmental compliance, and precision processing. A single low refractive index specification is no longer sufficient to describe a resin's suitability for complex optical and electronic structures.
T-61360 is a difunctional fluorine-modified acrylate UV resin developed by Shenzhen U-Sunny Technology. While maintaining a low refractive index, it also offers low dielectric characteristics and low surface tension. It does not contain heavy metals or other harmful substances and is designed to meet RoHS and PFAS-related environmental requirements. The product is suitable for low-film-thickness precision printing and thick-film dispensing processes. This article summarizes its performance characteristics, application areas, and formulation recommendations based on the product TDS and public information on related optical materials.
1. Basic Product Information of T-61360
T-61360 belongs to the fluorine-modified acrylate class of UV resins and has a functionality of 2. Its main technical parameters are listed below:
| Item | Parameter |
|---|---|
| Functionality | 2 |
| Refractive Index | 1.360 |
| Specific Gravity | 1.26 |
| Molecular Weight (GPC) | 2200 |
| Tg | 35°C |
| Elongation at Break | 35% |
| Acid Value | ≤2 mg KOH/g |
| Viscosity at 25°C | 2500–4500 mPa·s |
| Effective Content | 100% |
| Surface Tension | dyn 17.6 |
| Environmental Compliance | Heavy-metal-free; designed to meet RoHS and PFAS requirements |
2. Main Performance Characteristics of T-61360
2.1 Low Refractive Index and Low Dielectric Performance
Conventional acrylate UV resins typically have a refractive index above 1.45. Through its fluorine-modified structure, T-61360 reduces the refractive index to 1.360 while also exhibiting low dielectric characteristics. This combination makes it suitable not only for optical anti-reflection and light-confinement structures, but also as a candidate for interfacial materials in high-frequency communication devices and microelectronic packaging where dielectric loss needs to be controlled.
In fiber coatings, the cladding material must have a lower refractive index than the core to achieve effective light confinement. The refractive index of quartz core is approximately 1.46, and T-61360's 1.360 falls within the range suitable for low refractive index cladding designs.
2.2 Low Surface Tension and Precision Processing Adaptability
T-61360 has a surface tension of dyn 17.6, which is relatively low. The direct benefit of low surface tension is good leveling: it helps form uniform thin layers in low-film-thickness precision printing and assists in controlling adhesive spreading behavior in thick-film dispensing. At the same time, the low surface energy also gives the cured coating a certain hydrophobic and oleophobic tendency, which can contribute to anti-fouling and easy-clean functions.
The TDS explicitly lists "low-film-thickness precision printing" and "thick-film dispensing" as suitable processes for this product, indicating that its viscosity and rheological properties are designed to cover a range from thin layers to thick layers.
2.3 Environmental Compliance
T-61360 does not contain heavy metals or other harmful substances and is designed to meet RoHS and PFAS-related environmental requirements. As UV-curable materials move toward PFAS-free or reduced-fluorine directions, this compliance attribute is practically relevant for export-oriented electronic and optical products. It should be noted that the relationship between fluorine-modified materials and PFAS compliance depends on specific regulatory definitions and product structures. Formulators should still confirm against the requirements of the target market.
2.4 Balance of Curing Speed and Film Properties
The resin cures quickly and has good surface drying, making it suitable for low-energy LED curing scenarios. With a Tg of 35°C and an elongation at break of 35%, the difunctional structure provides a moderate balance between hardness and flexibility. Compared with higher-Tg, higher-hardness grades in the same series, T-61360 leans toward a combination of flexibility and processing adaptability.
2.5 Compatibility and Compounding Considerations
T-61360 has relatively good compatibility with monomers. The TDS recommends dissolving and diluting it with LM-501 or LM-502 fluorine-modified acrylate monomers to adjust for application requirements. For polymer compounding, the TDS notes that fluorine resins generally have limited compatibility, especially high-molecular-weight, high-viscosity products. It is recommended to first mix with low-molecular-weight fluorine monomers or low-viscosity resins at low speed, confirm that there is no turbidity or precipitation, and then add other components. This mixing sequence is particularly important for the formulation stability of fluorine-containing systems.
3. Main Application Areas of T-61360
3.1 Specialty Optical Fiber Coatings
Low refractive index cladding coatings are one of the key application directions for T-61360. In medical fibers, communication fibers, and sensing fibers, the cladding material needs to confine light within the core. T-61360's low refractive index, heat resistance, and chemical resistance make it suitable for coating scenarios with reliability and environmental durability requirements. Public information on related T-6135 resins also shows that fluorine-modified acrylate systems are used in medical and sensing specialty fiber coatings.
3.2 Anti-Reflective Coatings and Anti-Reflection Films
T-61360 can be used in functional films and optical materials requiring low refractive index, with typical applications including anti-reflective coatings and anti-reflection films. On display devices, optical lenses, and transparent substrates, low refractive index layers combined with high refractive index layers form a refractive index gradient, helping to reduce interfacial Fresnel reflection and improve light transmittance.
3.3 AR Waveguide Optical Interfaces
In AR optical waveguide devices, a low refractive index layer around the waveguide is needed to achieve total internal reflection confinement. Ultra-low refractive index materials can partially replace the function of an air gap, providing optical isolation and a total reflection layer. Although T-61360's 1.360 refractive index is not in the ultra-low refractive index range, it can be evaluated as a candidate material for AR waveguide interfaces or cladding designs where dielectric performance and processability also need to be considered.
3.4 Low-Film-Thickness Precision Printing and Thick-Film Dispensing
T-61360's viscosity range and low surface tension make it suitable for both low-film-thickness precision printing and thick-film dispensing. In micro optical components, sensor packaging, and electronic device assembly, precision printing requires the resin to spread uniformly in thin layers and cure quickly, while dispensing requires the adhesive to maintain shape stability and cure depth in thick layers. The TDS lists these two processes together as suitable scenarios, reflecting the resin's design consideration for a broad processing window.
3.5 UV Adhesives
T-61360's recommended applications include UV adhesives. In optical component bonding, a low refractive index adhesive layer helps reduce reflection loss at interfaces. Its low dielectric characteristics also provide an additional consideration for bonding interfaces in high-frequency or microelectronic applications. Combined with adhesion adaptability to various substrates, the resin can be used in formulations that need to balance bonding function with optical and electrical performance.
4. Recommended Dosage and Formulation Suggestions
The TDS for T-61360 does not list a fixed recommended dosage. The actual addition level should be determined according to the target refractive index, film thickness, application method, and curing conditions.
Diluent Monomer Selection: The TDS recommends using LM-501 or LM-502 fluorine-modified acrylate monomers for dilution. These low refractive index monomers help adjust viscosity while avoiding a significant increase in refractive index.
Compounding Sequence: Fluorine resins have limited compatibility with high-molecular-weight polymers. It is recommended to first mix T-61360 with low-molecular-weight fluorine monomers or low-viscosity resins at low speed, confirm that the system is uniform without turbidity or precipitation, and then add other components such as polyester, epoxy, or polyurethane.
Photoinitiator Matching: The system is suitable for low-energy LED curing. A free-radical photoinitiator matching the light source wavelength should be selected, and its solubility and compatibility in the fluorine-containing system should be confirmed.
Process Window: For low-film-thickness precision printing, attention should be paid to leveling and surface drying speed. For thick-film dispensing, attention should be paid to cure depth and internal stress. Gradient exposure tests under the target film thickness and light source conditions are recommended.
5. FAQ
What is the refractive index of T-61360?
T-61360 has a typical refractive index of 1.360, which is in the lower range of fluorine-modified low refractive index UV resins. It is suitable for fiber claddings, anti-reflective coatings, and other applications requiring controlled refractive index.
What is the difference between T-61360 and T-6135 or T-6139-2?
All three are fluorine-modified low refractive index UV resins from U-Sunny, but they are positioned differently. T-61360 has a refractive index of 1.360, moderate viscosity (2500–4500 mPa·s), and is suitable for both precision printing and thick-film dispensing, with emphasis on low dielectric and low surface tension characteristics. T-6135 has a lower refractive index and very low viscosity, leaning toward ultra-thin films and nanoimprinting. T-6139-2 has a refractive index of 1.38 and a higher Tg, leaning toward applications requiring both hardness and adhesion. Formulation selection should be based on a comprehensive evaluation of target refractive index, film thickness, application method, and curing conditions.
Is T-61360 suitable for LED curing?
Yes. The TDS states that the product cures quickly and is suitable for low-energy curing scenarios. The specific curing energy requirement depends on film thickness, photoinitiator system, and LED wavelength.
Does T-61360 comply with PFAS regulations?
The TDS states that the product does not contain heavy metals or other harmful substances and is designed to meet RoHS and PFAS-related environmental requirements. However, because the scope of PFAS definitions and jurisdictions varies, it is recommended to confirm against the specific regulatory text and supply chain declarations in the target market.
Can T-61360 be used for optical fiber coatings?
Yes. The TDS lists optical fiber coatings as a recommended application. Low refractive index cladding is a typical use of fluorine-modified acrylate resins, but fiber coatings have strict requirements for cure degree, modulus, and long-term reliability. Verification under simulated drawing or coating process conditions is recommended.
6. Summary
T-61360 is a fluorine-modified UV resin characterized by a combination of low refractive index, low dielectric performance, and low surface tension. While maintaining optical function, it also considers environmental compliance and processing adaptability from thin-film printing to thick-film dispensing. It is suitable for specialty optical fiber coatings, anti-reflective/anti-reflection films, AR waveguide interfaces, precision printing and dispensing, and UV adhesives. For material projects that need to address optical performance, interfacial behavior, and process windows in UV-curable formulations, T-61360 can be evaluated as a candidate main resin or functional modifier.