Abstract: The invention provides a method for improving the contrast ratio of the display image projected on a screen from a liquid crystal projector that comprises at least a light source, an electrode-having, twisted nematic liquid crystal cell comprising at least one nematic liquid crystal, and two polarizers disposed so that the liquid crystal cell is sandwiched between them, which is characterized in that at least two HBLC optical films are so arrayed between the polarizers that the slow axes of the films are approximately perpendicular to each other so as not to cause a retardation in the direction normal to the film surfaces; and provides a liquid crystal projector that uses the improving method.

Abstract: The invention provides a method for improving the contrast ratio of the display image projected on a screen from a liquid crystal projector that comprises at least a light source, an electrode-having, twisted nematic liquid crystal cell comprising at least one nematic liquid crystal, and two polarizers disposed so that the liquid crystal cell is sandwiched between them, which is characterized in that at least two HBLC optical films are so arrayed between the polarizers that the slow axes of the films are approximately perpendicular to each other so as not to cause a retardation in the direction normal to the film surfaces; and provides a liquid crystal projector that uses the improving method.

Abstract: A toner for electrophotography containing a compound represented by the following formula (1) ##STR1## wherein R represents an alkyl group, --A-- represents --O--COCH.dbd.CH-- or --S--CH.sub.2 CH.sub.2 -- and L is an integer of 2 to 10.The toner for electrophotography has a sharp distribution for the charging amount, excellent moisture resistance and stability to aging. As a result, the toner can provide an image of extremely high gradation and shows satisfactory performance of replicate image formation.

Abstract: A toner for an electrophotographic process which comprises a complex salt compound represented by the following formula (1) ##STR1## wherein X represents Cl, Br, So.sub.2 NH.sub.2, So.sub.2 CH.sub.3 or So.sub.2 C.sub.2 H.sub.5 and A.sym. represents an alkenyl or alkylammonium ion of 17-28 carbon atoms. The complex salt compound of the formula (1) acts as a negative charge control agent in the toner and is good in compatibility with a binder and the toner prepared using it is excellent in specific chargeability and durability of charge.