Birefringence-free plastics

US4544583A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Uwe Claussen · Leverkusen, DE
• Hellmut Hannes · Beedenbostel, DE
• Hans-Leo Weber · Eschenried, DE

Key dates

• Filing date: Sep 27, 1983
• Grant date: Oct 1, 1985
• Expiry date: Sep 27, 2003

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/31507
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Birefringence-free arrangement of plastic foils, characterized in that two plastic foils having a single principal optical axis, said optical axis lying within the plane of the plastic foil, are arranged parallel behind each other so that the optical axes of both plastic foils are forming an angle of 90.degree..+-.7.degree. and the material of the foils with regard to its optical properties and the thickness of the foils being selected in such a manner that the optical path differences .DELTA.n.sub.1 D.sub.1 for the light waves which are associated with the two main refraction indices within the first plastic foil is approximately equal to the optical path difference .DELTA.n.sub.2 d.sub.2 of the second plastic foil, .DELTA.n.sub.1, .DELTA.n.sub.2, being the difference of the main refraction indices in the first and second foil, respectively, and d.sub.1, d.sub.2 standing for their thicknesses, and the use of said arrangement in components and devices in which polarized light is used, especially in liquid crystal displays.