High-transmittance B270 window pane, UV-visible light hardened glass lens, optical instrument protective window.

B270 is a "super white" modified soda-lime glass developed by SCHOTT of Germany. It is formed in a single process using the down-draw method and then flame-polished, making it affordable with a smooth surface. It is one of the most commonly used large-area window substrates in the visible to near-infrared range.

1. Optical Performance
   • Transmission range: 330 nm – 2.5 µm, average visible light transmittance ≥ 91%, which can increase to 98% with MgF₂ or VIS-NIR anti-reflection coating on both sides.
   • Refractive index n_d≈1.523, Abbe number ν_d≈60, low dispersion, similar to N-BK7, and can be directly paired with it.
   • No "iron green" color center, does not yellow with long-term sun exposure, suitable for outdoor optical windows.

2. Physical and Mechanical Properties
   • Density: 2.55 g cm⁻³; Knoop hardness: 542, higher than conventional soda-lime glass, offering better scratch resistance.
   • Thermal expansion: 9 × 10⁻⁶ K⁻¹ (20 – 300 ℃), thermal stability superior to ordinary float glass, can withstand thermal shocks of 120 ℃.
   • Thickness series: B270® 0.9 – 10 mm; B270® Thin 0.3 – 1.1 mm, can be directly cut and finely ground, reducing processing requirements.

3. Chemical Properties
   • Made from high-purity raw materials, iron content < 0.01%, ensuring a "crystal-clear" super white appearance.
   • Resistant to moisture, alkali, and cleaning agents, suitable for frequently disinfected applications such as medical touchscreens and countertop glass.

4. Processing Capabilities
   • Can be double-side polished to surface flatness λ/10, surface finish 20-10, parallelism 5″, minimum thickness 0.3 mm, maximum plate size 1676 mm × 711 mm.
   • Capable of slicing, edge grinding, chamfering, drilling, screen printing black borders, and vacuum coating (anti-reflection, reflective, ITO conductive films, etc.).

5. Typical Applications
   • Optical windows: laser rangefinders, barcode scanners, CCD/CMOS protective windows.
   • Consumer electronics: touchscreen cover glass, copier document tables, projector lens protectors.
   • Medical and biological: PCR instruments, microplate readers, microfluidic chip cover glass.
   • Industrial measurement: level gauges, flow meters, outdoor camera front windows.