General Specification for Jungbecker Micro Prisms and Fresnel Lenses

jungbecker pic


Polymethylmetacrylate (PMMA), (identification “A“), refractive index 1.49

• PMMA, clear, 92 % transmission (without further identification)

• PMMA, light grey, 89 ± 1 % transmission (add. identification “N“)

• PMMA, light grey, 86 ± 1 % transmission (add. identification “M“)

• PMMA, grey, 72 ± 2 % transmission (add. identification “G“)

Polycarbonate (PC), (identification „B“), refractive index 1.59

• PC, clear, 88 % transmission (without further identification)

(All transmission ratios refer to light rays entering the prism sheet perpendicularly to the surface and to a thickness of the sheets of 3mm. Due to Fresnel reflection 8 % is reflected by the prism sheets, but can be re-reflected by the fixture to enter the prism sheets a second time. This information does not specify the efficiency of a luminaire)

Cut Sheets:

The actual dimensions will be cut according to the customer drawings. Tighter tolerances than listed below might not be practice oriented, due to the expansion of the material on temperature and humidity changes. Dimensions given without tolerances will be cut with our standard tolerances below:


Tolerance of thickness for trimmed edges: +/- 0.2 mm

Maximum curvature of a solidly seated sheet: 0.8 mm

Uncut Sheets: Dimensions of uncut sheets are approximate to mentioned size. Borders may not be straight and prism structure may be of less quality within the outer range. Thus the usable optical area is 30 mm smaller both in length and width than the original size of the sheet.
Thickness: The specified material thickness shows the nominal value, which has to be calculated +0.2 to 0.5 mm depending on the type of structure.
Temperature Range:

PMMA: - 40 to 80 °C;

PC: - 40 to 110 °C

Expansion due to Temperature Change: The expansion ratio upon temperature change is for PMMA: 7 x 10-5/K; and for PC: 7 x 10-5/K. This corresponds to the expansion of a prism sheet of 1500 mm nominal length by ca. 1 mm per 10 Kelvin temperature increase.
Expansion due to Humidity Change: The actual dimensions may vary slightly depending on the humidity of the material, in practice it may vary ca. +/1 mm for a prism sheet of 1500 mm nominal length.
Fire Rating:

PMMA: class B2 (DIN 4102), rating info for other countries available upon request

PC: class B1 (DIN 4102), rating info for other countries available upon request glow wire temperature: 850oC (3mm), 960oC (4mm)


PMMA: almost unlimited

PC: some tendency to yellow, may be stabilized by material additives or coating

Cleaning: PMMA and PC sheets may be cleaned with water and some adds of dishwashing detergent. Plastics underlie static charge and attract dust. Never apply dry cleaning.
Our products are listed under commodity code 90029000, and are RoHS 2002/95/EG compliant, including the changes dd. 01.07.2008.