In the premium optical lens, functional film, and high-end display industries, selective light filtering has become
a critical performance metric. Manufacturers of anti-blue light eyeglass lenses, smartphone screen protectors, and automotive displays require chemical additives that block high-energy visible (HEV) blue light (400–420 nm) while maintaining supreme visible clarity.
Traditional light stabilizers and older-generation blue light blockers continuously force manufacturers into a compromise: choosing between poor blue light protection or heavy substrate yellowing.
To break this industry dilemma, Sinocure Chemical Group introduces Sinosorb® BL 326-S (CAS No.: 1877301-52-4). By structurally engineering the classic benzotriazole core with a 5-position aromatic thioether group, we have achieved a pristine "sharp cut-off" boundary that outperforms leading market alternatives in anti-blue light applications.
Sinosorb® BL 326-S is an innovative light absorber derived from the classic benzotriazole skeleton. By replacing the traditional chlorine atom with a p-tolylthio (thioether) group at the 5-position of the core ring, the molecular π-conjugation system is significantly extended. This precise structural modification narrows the HOMO-LUMO bandgap, creating a powerful red-shift effect (λ_max ∼ 365 nm) optimized for HEV light blockage.
Parameter | Technical Details |
Brand Name | Sinosorb® BL 326-S |
Chemical Name | 2-(2-Hydroxy-3-tert-butyl-5-methylphenyl)-5-(p-tolylthio)-2H-benzotriazole |
CAS Registry Number | 1877301-52-4 |
Molecular Formula | C24H25N3OS |
Molecular Weight | 403.54 g/mol |
To understand why Sinosorb® BL 326-S represents a milestone advancement for anti-blue light technology, we must examine its transmittance spectrum against current market standards. As certified by the spectroscopic data below, traditional additives fail to balance high blocking and zero yellowing.
Wavelength | Conventional UVAs | Competitor Eversorb® BL3 | Sinosorb® BL 326-S | Technical Performance Verdict |
390 nm | ~25.0% – 65.0% ❌ | 0.0% | 0.0% (Completely Opaque) ✨ | Traditional UVAs fail here. They leak a massive amount of high-energy light. |
410 nm | ~95.0% – 100.0% | ~45.0% | ~50.0% | Targeted HEV Protection: Both BL3 and Sinosorb® actively trap the most toxic blue light region. |
420 nm | ~99.0% | ~68.0% ❌ | ~88.0% | The Turning Point: Competitor BL3 is trapped in massive absorption, while Sinosorb® rapidly climbs towards full clarity. |
430 nm | ~100.0% | ~82.0% ❌ |
≥98.0%(Nearly Fully Clear) | The Ultimate Divider: BL3 suffers from heavy trailing (forces optical matrix to turn yellow). Sinosorb® instantly recovers total transparency. |
450 nm | ~100.0% | ~95.0% | ~100.0% | Sinosorb® ensures a crystal-clear appearance with an ultra-low Yellowing Index (Y.I.). |
Standard ultraviolet absorbers provide excellent coverage for UV-A and UV-B spectrums, but their absorption boundary cuts off way too early. Right at the critical 390 nm – 400 nm mark, their transmittance spikes. Consequently, they completely leak harmful short-wave blue light (400-420nm), leaving eyes or sensitive electronics entirely unprotected.
Eversorb® BL3 successfully shifts its absorption into the HEV region, but its absorption curve suffers from severe "tailing" (sluggish slope). Even at 420 nm to 430 nm, it continues to strongly absorb light, failing to recover full transparency until past 450 nm. By absorbing beneficial visible blue-violet light, it forces the host matrix into a heavy yellowish appearance (High Yellowing Index, Y.I.), disqualifying it from high-clarity optical applications.
For optical-grade compounding, consistency in product purity and moisture control is vital to prevent bubbles or haze during high-temperature extrusion or casting.
Quality Parameter | Standard Specification | Typical Batch Value | Test Method |
Appearance | Light yellow crystalline powder | Conforms | Visual Inspection |
Purity | ≥98.5% | 99.9% | HPLC Analysis |
Water Content | ≤0.2% | 0.09% | Karl Fischer (KF) |
Rapid Moisture | ≤1.0% | 0.42% | Moisture Analyzer |
Melting Point | 135.0 - 145.0°C | 138.5°C | Capillary Method |
Optical Clarity with Minimal Yellowing: Sinosorb® BL 326-S features a razor-sharp cut-off curve that drops to near-zero absorption immediately after 430 nm. This guarantees that your optical sheets retain a total light transmittance of ≥87% with a pristine, crystal-clear appearance.
High Processing Thermal Stability: Engineering plastics such as Polycarbonate (PC) and PET require melt processing temperatures up to 300°C. Sinosorb® BL 326-S exhibits a 5% weight loss temperature (TGA) of >280°C, preventing degradation during severe melt operations.
Anti-Sublimation Property: Thanks to its high molecular weight (403.54) and the introduction of the aromatic thioether structure, sublimation is heavily suppressed. This drastically minimizes the formation of mold-plate out and pipeline clogging during manufacturing.
Matrix Compatibility: The sterically hindered tert-butyl groups allow excellent solubility in polar engineering resins. This prevents blooming, migration, or surface crystallization (frosting) over extended product lifetimes.
Depending on the thickness of the target substrate, the dosage of Sinosorb® BL 326-S can be adjusted based on the Beer-Lambert law. Thinner coatings or films require a slightly higher percentage by weight to achieve identical HEV filtering performance.
Application Field | Target Resin Matrix | Recommended Dosage |
Anti-blue Light Eyeglasses | PC, CR-39, MR-8 acrylics | 0.3 – 1.2 phr |
Automotive & In-vehicle Screens | PC, PMMA, PET polymers | 0.3 – 1.0 phr |
LED Covers & Diffusion Plates | Polycarbonate, PMMA | 0.2 – 0.8 phr |
High-End Optical Films/Sheets | PET, Optical grade PC | 0.2 – 1.0 phr |
Transparent UV Functional Coatings | Acrylic / Polyurethane UV cure | 1.0% – 3.0% (solid wt) |
*Note: "phr" stands for parts per hundred parts of resin by weight.
Sinosorb® BL 326-S can be seamlessly integrated into existing industrial manufacturing lines through two main methods:
Melt Blending (Extrusion / Injection): Recommended processing temperature range is 240°C – 300°C (depending on the base resin). Dry-blend Sinosorb® BL 326-S powder directly with polymer pellets before feeding into a twin-screw compounding extruder.
Solvent Dissolution (Coatings / Inks): Pre-dissolve the additive completely in common industrial solvents (e.g., Toluene, Xylene, Chloroform, Ethyl Acetate, or Butyl Acetate) before introducing it into the paint/ink liquid system for complete and uniform dispersion.
When it comes to advanced light stabilization, data speaks louder than marketing. The steep, narrow absorption band of Sinosorb® BL 326-S provides an uncompromised solution to the oldest problem in blue-light filtering.
Manufactured in the Shandong Pilot Free Trade Zone, Sinocure Chemical Group supplies optical-grade functional additives globally. Sinosorb® BL 326-S is standardly packaged in 25 kg fiber drums with double PE inner bags, with 1 kg and 5 kg pilot-test foil packs available upon request.
Elevate your material formulations today.
Contact our engineering sales group at Info@sinocurechem.com or call +86 15668330235.
We look forward to providing full TDS, SDS, and testing samples for your R&D validation.
