The document establishes the rationale for ergonomic requirements for work with visual displays based on flat panels. This part of EN ISO 13406 is applicable to flat-panel technology applied to displays for office work and similiar work. It defines ergonomic requirements and measuring techniques for optical display units based on flat panels. According to the requirements of legibility, legibility when unwanted reflections exist on the display and discriminability of colours this standard gives examples of special flat-panel considerations such as the picture element discretness, slow response time of the elctro-optical effect, panels that electrically vary the reflection properties at the picture element site and optical properties that strongly depend on viewing direction. To guarantee usability including effectiveness, efficiency, comfort and acceptability, it is differed between reflective and transflective flat-panel displays as well as cathode ray tube (CRT) and emissive flat-panel displays. There are seven notes to consider for the coverage of remarkable requirements such as the properties of displays or viewing directions. The document defines the term flat panel.